Clothes dryer

Abstract

 A clothes dryer includes a water-receiving tub (4), a wash tub (7) rotated by a washing motor (5), a ventilation path (26) including the water-receiving tub (4) as a part so that air in the water-receiving tub (4) is circulated, an evaporator (27) disposed in the ventilation path (26), a condenser (30) disposed in the ventilation path (26) and applying heat to air flowing along the ventilation path (26) downstream relative to the evaporator (27), a compressor (33) supplying a refrigerant into first and second refrigerant pipes (28, 31), a decompressor (35) throttling the refrigerant, and a motor drive unit (51) rotating a compressor motor (34) in a drying processing when a result of detection by an outside temperature sensor (40) has been determined to be larger than a first threshold. The motor drive unit (51) rotates the compressor motor (34) in the drying processing based on a result of setting by a second speed setting unit (47) when the result of detection by the outside temperature sensor (40) has been determined not to be larger than the first threshold.

Description

[0001] The present invention relates to a clothes dryer provided with a heat-pump drying function.

[0002] Japanese patent application publication, JP-A-2006-87484 (first publication) discloses a clothes dryer provided with an annular ventilation path including a part constituted by a water-receiving tub. Air in the water-receiving tub is circulated through the ventilation path. On the other hand, Japanese patent application publication, JP-A-H10-148416 (second publication) discloses a dehumidifier provided with a heat pump including an evaporator (cooler) and a condenser. In the clothes dryer disclosed by the above-mentioned first publication, an evaporator of the heat pump is mounted in the ventilation path. When undried laundry containing water is put in the water-receiving tub, air flowing through the ventilation path is cooled by the evaporator thereby to be dehumidified. A condenser of the heat pump is provided in the ventilation path so as to be located at the downstream of the air flow. When undried laundry containing water is put in the water-receiving tub, dehumidified air is heated by the condenser so that warm air with a low humidity is produced. The warm air with the low humidity is supplied into the water-receiving tub, thereby enhancing the drying of the laundry. When a compressor motor of a compressor in a stopped state is driven under the condition where an ambient temperature is at such low temperature as about 5°C, the temperature of the evaporator becomes to 0°C or below. The evaporator comprises a plurality of fins joined together on the surface of a refrigerant pipe. In a case where the temperature of the evaporator is decreased to 0°C or below, moisture adheres as frost to surfaces of the fins when air is dehumidified by the evaporator. As a result, the cooling performance of the evaporator is reduced since gaps between the fins of the evaporator are closed.

[0003] An electronic valve serving as a decompressor throttling a flow of refrigerant is provided between the condenser and the evaporator in the conventional clothes dryer. When the compressor motor in the stopped state is driven, an opening degree of the electronic valve is electrically controlled so that frost can be prevented from adhering to the fins of the evaporator. As a result, the weight of the clothes dryer tends to be increased.

[0004] Therefore, an object of the present invention is to provide a clothes dryer which includes a pipe-shaped decompressor with a fixed opening degree instead of the electronic valve but can prevent frost from adhering to the fins of the evaporator when the compressor motor in the stopped state is driven.

[0005] According to one aspect of the present invention, there is provided a clothes dryer comprising a water-receiving tub receiving water for washing laundry; a wash tub which is provided inside the water-receiving tub and into which the laundry is put, the wash tub being rotated by a washing motor serving as a drive source; an outer casing which is hollow and encloses the water-receiving tub, the outer casing having an opening through which the laundry is put into and taken out of the wash tub; a ventilation path which is formed into an annular shape and includes the water-receiving tub as a part thereof so that air in the water-receiving tub is circulated; a blower which includes a fan motor serving as a drive source and circulates air in the water-receiving tub along the ventilation path; an evaporator provided in the ventilation path so as to be located outside the water-receiving tub, the evaporator including a first refrigerant pipe through which a refrigerant flows and a plurality of fins joined to an outer circumferential surface of the first refrigerant pipe, thereby cooling air flowing along the ventilation path; a condenser provided in the ventilation path so as to be located outside the water-receiving tub and having a second refrigerant pipe connected to the first refrigerant pipe, thereby applying heat to air flowing along the ventilation path downstream relative to the evaporator; a compressor supplying a refrigerant into the first and second refrigerant pipes in turn and including a speed-controllable compressor motor serving as a drive source; a decompressor which throttles the refrigerant flowing between the first and second refrigerant pipes, the decompressor including a pipe having a fixed degree of opening; an outside temperature sensor which detects a temperature outside the outer casing; an evaporator temperature sensor which detects a temperature of the evaporator; an operation course setting unit which sets an operation course to wash the laundry in the wash tub, the operation course including an operation course with a drying processing, in which the compressor motor and the fan motor are operated so that air which has been cooled by the evaporator and to which heat has been applied by the condenser is supplied into the wash tub; a comparison unit which determines whether a result of detection by the outside temperature sensor is larger than a predetermined first threshold when the compressor motor in a stopped state is operated in the drying processing, the first threshold being used as a temperature on which whether frost adheres to the fins of the evaporator when the compressor motor in the stopped state is accelerated by a predetermined normal pattern; a first speed setting unit which sets a rotational speed of the compressor motor when a result of detection by the outside temperature sensor has been determined to be larger than the first threshold, the first speed setting unit increasing the rotational speed of the compressor motor by the normal pattern when the compressor motor in the stopped state is operated; a second speed setting unit which sets a rotational speed of the compressor motor when the result of detection by the outside temperature sensor has been determined not to be larger than the first threshold, the second speed setting unit setting the rotational speed of the compressor motor so that a result of detection by the evaporator temperature sensor is lower than the first threshold and is higher than a second threshold at which frost adheres to the fins of the evaporator, when the compressor motor in the stopped state is operated in the drying processing; and a motor drive unit which rotates the compressor motor in the drying processing based on a result of setting by the first speed setting unit, when the result of detection by the outside temperature sensor has been determined to be larger than the first threshold, the motor drive unit rotating the compressor motor in the drying processing based on a result of setting by the second speed setting unit when the result of detection by the outside temperature sensor has been determined not to be larger than the first threshold.

[0006] According to the above-described clothes dryer, it is determined that the result of detection by the outside temperature sensor is not larger than the first threshold in such a low condition that the temperature of the evaporator becomes equal to or lower than 0°C when the compressor motor is accelerated from the stopped state in a normal pattern in the drying processing. In this case, when the compressor in the stopped state is operated, a rotational speed of the compressor motor is set according to the result of detection by the evaporator temperature sensor. The compressor motor is thus rotated based on the result of setting of the rotational speed. The rotational speed of the compressor motor is set so that the result of detection by the evaporator temperature sensor is lower than the first threshold and exceeds the second threshold at which frost adheres to the fins of the evaporator. Accordingly, frost can be prevented from adhering to the surfaces of the fins of the evaporator when the compressor motor in the stopped state is operated in the drying processing. Consequently, the cooling performance of the evaporator can be prevented from being lowered while the pipe-shaped decompressor having the fixed opening degree is used.

[0007] The invention will be described, merely by way of example, with reference to the accompanying drawing, in which:

FIG. 1 is a longitudinal section of a clothes dryer in accordance with a first embodiment of the present invention, showing an inner construction;

FIG. 2 is a block diagram showing an electrical arrangement of the clothes dryer;

FIG. 3 is a schematic block diagram showing a heat pump employed in the clothes dryer;

FIG. 4 is a flowchart showing the contents to be processed by a main control circuit;

FIG. 5 is a flowchart showing a washing process executed by the main control circuit;

FIG. 6 is a flowchart showing a timer interrupt process executed by the main control circuit;

FIG. 7 is a flowchart showing a rinse process executed by the main control circuit;

FIG. 8 is a flowchart showing a dehydration process executed by the main control circuit;

FIG. 9 is a flowchart showing a drying process executed by the main control circuit;

FIG. 10 is a flowchart showing a drying process executed by the main control circuit;

FIG. 11 is a flowchart showing a dehydration process executed by the main control circuit in the clothes dryer in accordance with a second embodiment;

FIG. 12 is a flowchart showing the dehydration process executed by the main control circuit;

FIGS. 13A and 13B show a heat pump and a heater employed in the clothes dryer in accordance with a third embodiment respectively;

FIG. 14 is a flowchart similar to FIG. 10;

FIG. 15 is a flowchart similar to FIG. 5, showing a fourth embodiment;

FIG. 16 is a flowchart similar to FIG. 7;

FIG. 17 is a flowchart similar to FIG. 8;

FIG. 18 is a flowchart showing a compressor heating process executed by the main control circuit;

FIGS. 19A and 19B are flowcharts similar to FIG. 10, showing a fifth embodiment;

FIGS. 20A and 20B show a heat pump and a heater respectively, showing a sixth embodiment;

FIGS. 21A and 21B are flowcharts similar to FIGS. 19A and 19B;

FIG. 22 is a flowchart showing a refrigerant recovery process by the main control circuit; and

FIGS. 23A and 23B show a heat pump and a suction pipe both employed in the clothes dryer in accordance with a seventh embodiment, respectively.

[0008] Several embodiments will be described with reference to the accompanying drawings. A first embodiment will now be described with reference to FIGS. 1 to 10. Referring to FIG. 1, a clothes dryer includes an outer casing 1 constituting a housing thereof. The outer casing 1 includes a front panel, a rear panel, a left side panel, a right side panel, a bottom plate and a ceiling panel and is hollow. The front panel of the outer casing 1 has a through access opening 2 formed therethrough. A door 3 is pivotally mounted on the front panel of the outer casing 1. The door 3 is operable between a closed state and an open state by a user standing in front of the clothes dryer. The access opening 2 is closed and opened by the door 3. A water-receiving tub 4 is enclosed by the outer casing 1 and mounted in position. The water-receiving tub 4 is formed into a cylindrical shape and has a closed rear. The water-receiving tub 4 is disposed in an inclined state and thus, a central axis line CL extends rearwardly downward. The water-receiving tub 4 has a front opening which is airtightly closed by the door 3 when the door 3 is closed.

[0009] The water-receiving tub 4 includes a rear plate to which a drum motor 5 located outside the tub 4 is mounted. The drum motor 5 is a speed-controllable three-phase brushless DC motor, for example. The drum motor 5 has a rotational shaft 6 protruding through the rear plate into an interior of the water-receiving tub 4. The rotational shaft 6 is aligned with the central axis line CL. A drum 7 is enclosed in the water-receiving tub 4 and mounted to the rotational shaft 6 in the water-receiving tub 4. The drum 7 is formed into a cylindrical shape and has a closed rear. The drum 7 is rotated with the rotational shaft 6 when the drum motor 5 is driven. The drum 7 has a front opening opposed via the front opening of the water-receiving tub 4 to the access opening 2 from behind. When the door 3 is open, laundry is put through the access opening 2, the front openings of the water-receiving tub 4 and the drum 7 into an interior of the drum 7. The drum 7 corresponds to a wash tub, and the drum motor 5 serves as a washing motor.

[0010] The drum 7 has a number of small through holes 8 formed through a circumferential wall thereof. The interior of the drum 7 communicates through the holes 8 with the interior of the water-receiving tub 4. The drum 7 has a plurality of baffles 9 mounted to the inner circumferential wall thereof. The baffles 9 are moved circumferentially about the central axis line CL with rotation of the drum 7. The laundry put into the drum 7 is moved circumferentially while being caught by the baffles and thereafter falls by gravity, whereby the laundry is agitated in the drum 7.

[0011] A water-supply valve 10 is fixedly mounted in an upper interior of the outer casing 1. The water-supply valve 10 has an inlet connected to a faucet (not shown) of the water system. A water-supply valve motor 11 (see FIG. 2) serves as a drive source of the water-supply valve 10. The outlet of the water-supply valve 10 is switched between an open state and a closed state according to an amount of rotation of the water-supply motor 11. The outlet of the water-supply valve 10 is connected to a water filling case 12 as shown in FIG. 1. Tap water is supplied through the water-supply valve 10 into the water filling case 12 when the water-supply valve 10 is open. When the water-supply valve 10 is closed, tap water is not supplied into the water filling case 12. The water filling case 12 is mounted in the outer casing 1 so as to be located higher than the water-receiving tub 4. The tap water supplied through the water-supply valve 10 into the water case 12 is further supplied through a filling port 13 into the water-receiving tub 4.

[0012] A drain pipe 14 has an upper end connected to a lowermost part of the bottom of the water-receiving tub 4. The drain pipe 14 is provided with a drain valve 15 including a drain valve motor 16 (see FIG. 2) serving as a drive source. The drain valve 15 is switchable between an open state and a closed state according to an amount of rotation of the drain valve motor 16. The tap water supplied through the filling port 13 into the water-receiving tub 4 is stored in the tub 4 when the drain valve 15 is closed. When the drain valve 15 is opened, water is discharged out of the water-receiving tub 4 through the drain pipe 14.

[0013] A main duct 17 is fixed to the bottom plate of the outer casing 1 so as to be located below the water-receiving tub 4. The main duct 17 is formed into a cylindrical shape and extends in the front-back direction. The main duct 17 has a front end to which a lower end of a front duct 18 is connected. The front duct 18 is formed into a cylindrical shape and extends vertically. An upper end of the front duct 18 is connected to a front lower end of the water-receiving tub 4 so as to communicate with the interior of the tub 4. The main duct 17 has a rear end to which a fan casing 19 is mounted. The fan casing 19 has a through hole or an air inlet 20 and a cylindrical air outlet 21. An interior of the fan casing 19 communicates through the air inlet 20 with the interior of the main duct 17.

[0014] A fan motor 22 is mounted to an outer wall of the fan casing 19. The fan motor 22 has a rotational shaft 23 protruding into the fan casing 19. A fan 24 is mounted to the rotational shaft 23 so as to be located in the fan casing 19. The fan 24 is of the centrifugal type that axially sucks air and radially discharges air. The air inlet 20 of the fan casing 19 is opposed to the fan 24 axially with respect to the fan 24. The air outlet 21 of the fan casing 19 is opposed to the fan 24 radially with respect to the fan 24. The fan 24 serves as a blower.

[0015] A rear duct 25 has a lower end connected to the air outlet 21 of the fan casing 19. The rear duct 25 is formed into a cylindrical shape and extends vertically. The rear duct 25 has an upper end communicating with the interior of the water-receiving tub 4 at the rear end of the tub 4. As a result, an annular circulation duct 26 is constituted by the rear duct 25, fan casing 19, main duct 17, front duct 18 and water-receiving tub 4. The circulation duct 26 has a starting point and a terminal point both in the interior of the water-receiving tub 4. When the fan motor 22 is in operation in the closed state of the door 3, the fan 24 is rotated in a predetermined direction, so that air in the water-receiving tub 4 is drawn through the front duct 18 and the main duct 17 into the fan casing 19. The air drawn into the fan casing 19 is returned from the fan casing 19 through the rear duct 25 into the water-receiving tub 4. The circulation duct 26 serves as a ventilation path.

[0016] An evaporator 27 is mounted in the main duct 17 for cooling air. The evaporator 27 comprises a meandering refrigerant pipe 28 and a plurality of plate-shaped fins 29 joined to an outer circumferential surface of the refrigerant pipe 28. A condenser 30 is mounted in the duct 17 to apply heat to air. The condenser 30 is located downstream of an air flow path relative to the evaporator 27. The condenser 30 comprises a meandering refrigerant pipe 31 and a plurality of plate-shaped fins 32 joined to an outer circumferential surface of the refrigerant pipe 31. The refrigerant pipe 28 of the evaporator 27 communicates with the refrigerant pipe 31 of the condenser 30.

[0017] A compressor 33 is mounted in the outer casing 1 so as to be disposed outside the circulation duct 26. The compressor 33 has an outlet through which a refrigerant is discharged and an inlet through which the refrigerant is drawn. A compressor motor 34 (see FIG. 2) is a drive source for the compressor 33. The compressor motor 34 is a speed-controllable three-phase brushless DC motor, for example. A flow rate of the refrigerant discharged through the outlet of the compressor 33 is increased in proportion to an increase in the rotational speed of the compressor motor 34. The refrigerant pipe 31 of the condenser 30 is connected to the outlet of the compressor 33, and the refrigerant pipe 28 of the evaporator 27 is connected to the outlet of the compressor 33. When the compressor motor 34 is in operation, the refrigerant discharged through the outlet of the compressor 33 is returned through the refrigerant pipe 31 of the condenser 30 and the refrigerant pipe 28 in turn into the compressor 33.

[0018] A capillary tube 35 is mounted in the outer casing 1 and serves as a decompressor. The capillary tube 35 is interposed between the refrigerant pipe 28 of the evaporator 27 and the refrigerant pipe 31 of the condenser 30, so as to be disposed outside the circulation duct 26. The capillary tube 35 is made of a steel pipe having a larger inner diameter than the refrigerant pipes 28 and 31. An accumulator 36 is mounted in the outer casing 1 and interposed between the refrigerant pipe 28 of the evaporator 27 and the inlet of the compressor 33, so as to be disposed outside the circulation duct 26. The accumulator 36 separates a gas phase and a liquid phase from the refrigerant. The liquid phase of the refrigerant separated by the accumulator 36 is returned to the inlet of the compressor 33.

[0019] The above-described evaporator 27, condenser 30, capillary tube 35 and accumulator 36 constitute a heat pump. When both the fan motor 22 and the compressor motor 34 are in operation with the door 3 being closed, air in the water-receiving tub 4 is brought into contact with the evaporator 27 thereby to be changed into cold air. The cold air is further brought into the condenser 30 thereby to be changed into warm air, which is returned into the water-receiving tub 4. Accordingly, when undried laundry containing water is put in the drum 7, the evaporator 27 cools air supplied from the water-receiving tub 4 thereby to dehumidify the air and the condenser 30 applies heat to the dehumidified air. As a result, a low-temperature warm air is supplied into the water-receiving tub 4 from the condenser 30, whereby the drying of laundry in the drum 7 is enhanced.

[0020] An outside air fan motor 37 is provided in the outer casing 1 as shown in FIG. 1. The fan motor 37 has a rotational shaft fixed to an outside air fan 38. The front panel of the outer casing 1 is formed with an outside air inlet 39 located in front of the fan motor 37 and fan 38. The outside air inlet 39 comprises a number of through holes. When the outside air fan motor 37 is in operation, the outside air fan 38 is rotated in a predetermined direction so that air outside the outer casing. 1 is sucked through the outside air inlet 39 into the outer casing 1. A room temperature sensor 40 comprising a thermistor is provided in the outer casing 1 so as to be located downstream of the air flow relative to the outside air fan 38. When the outside air fan motor 37 is in operation, air outside the outer casing 1 is blown against the room temperature sensor 40 from the outside air fan 38. The room temperature sensor 40 detects a temperature of outside air in the outer casing 1, delivering a temperature signal indicative of the result of detection. The room temperature sensor 40 serves as an outside air sensor.

[0021] A drum inlet temperature sensor 41, drum outlet temperature sensor 42 and condenser temperature sensor 43 are provided in the circulation duct 26 as shown in FIG. 3. The drum inlet temperature sensor 41 comprises a thermistor located downstream of the air flow relative to the condenser 30 and is spaced away from the condenser 30. The drum inlet temperature sensor 41 detects a temperature of air flowing in the circulation duct 26 at a location downstream of the condenser 30, delivering a temperature signal according to the result of temperature detection. The drum outlet temperature sensor 42 comprises a thermistor disposed upstream of the air flow relative to the evaporator 27 and is spaced away from the evaporator 27. The drum outlet temperature sensor 42 detects a temperature of air flowing in the circulation duct 26 at a location upstream relative to the evaporator 27, delivering a temperature signal according to the result of temperature detection. The condenser temperature sensor 43 comprises a thermistor including a part located in the center of the flow of refrigerant. The part of the condenser temperature sensor 43 is brought into contact with the surface of the condenser 30. The condenser temperature sensor 43 detects a surface temperature of the condenser 30, delivering a temperature signal according to the result of temperature detection.

[0022] An outlet temperature sensor 44, evaporator inlet temperature sensor 45 and evaporator outlet temperature sensor 46 are provided in the outer casing 1 so as to be located outside the circulation duct 26. The outlet temperature sensor 44 comprises a thermistor brought into contact with the surface of outlet of the compressor 33. The outlet temperature sensor 44 detects a surface temperature of the outlet of the compressor 33, delivering a temperature signal according to the result of temperature detection. The evaporator inlet temperature sensor 45 comprises a thermistor in contact with the surface of the inlet side of the refrigerant pipe 28 of the evaporator 27. The evaporator temperature sensor 45 detects a surface temperature of the refrigerant pipe 28 of the evaporator 27, delivering a temperature signal according to the result of temperature detection. The evaporator outlet temperature sensor 46 comprises a thermistor brought into contact with an outlet side surface of the refrigerant pipe 28 of the evaporator 27. The evaporator outlet temperature sensor 46 detects an outlet side surface temperature of the refrigerant pipe 28, delivering a temperature signal according to the result of temperature detection. These temperature sensors 45 and 46 serve as an evaporator temperature sensor.

[0023] A main control circuit 47 as shown in FIG. 2 is mainly composed of a microcomputer and includes a central processing unit (CPU), a read only memory (ROM) and a random access memory (RAM). The main control circuit 47 is mounted in the outer casing 1 and detects a room temperature T_r or a temperature of air outside the outer casing 1 based on the temperature signal delivered by the room temperature sensor 40. The main control circuit 47 also detects a drum inlet temperature T_di or a temperature of air returned from the rear duct 25 into the water-receiving tub 4 based on the temperature signal delivered by the drum inlet temperature sensor 41. The main control circuit 47 further detects a drum outlet temperature T_do or a temperature of air supplied from the water-receiving tub 4 into the front duct 18 based on the temperature signal delivered by the drum outlet temperature sensor 42. The main control circuit 47 further detects a condenser temperature T_c or a surface temperature of the condenser 30 based on the temperature signal delivered by the condenser temperature sensor 43. The main control circuit 47 further detects an outlet temperature Tt or a temperature of the outlet of the compressor 33 based on the temperature signal delivered by the outlet temperature sensor 44. The main control circuit 47 further detects an evaporator inlet temperature T_ei or an inlet side temperature of the evaporator 27 based on the temperature signal delivered by the evaporator inlet temperature sensor 45. The main control circuit 47 further detects an evaporator outlet temperature T_eo or an outlet side temperature of the evaporator 27 based on the temperature signal delivered by the evaporator outlet temperature sensor 46. The main control circuit 47 serves as an operation course setting unit, a comparison unit, a first speed setting unit and a second speed setting unit.

[0024] An operation course switch 48 and a start switch 49 are mounted on the front panel of the outer casing 1 so as to be operable by the user in front of the clothes dryer. Each of the operation course switch 48 and a start switch 49 is switched between an on-state and an off-state, thereby changing an electrical state thereof. The main control circuit 47 determines whether the operation course switch 48 has been operated, based on the change in the electrical state of the operation course switch 48. The main control circuit 47 also determines whether the start switch 49 has been operated, based on the change in the electrical state of the start switch 49. A water level sensor 50 delivers a water level signal according to a water level in the water-receiving tub 4. The main control circuit 47 detects the water level in the water-receiving tub 4 based on the water level signal delivered by the water level sensor 50.

[0025] An inverter control circuit 51 is mainly composed of a microcomputer and includes a CPU, a ROM and a RAM. A speed sensor 52 comprises a Hall IC fixed to a stator of the drum motor 5. The speed sensor 52 changes an electrical state thereof when subjected to magnetic field from rotor magnets of the drum motor 5. The inverter control circuit 51 measures an amount of change per time in the electrical state of the speed sensor 52 when the drum motor 5 is in operation, thereby detecting a rotational speed f_d (Hz) of the drum motor 5. The speed sensor 53 comprises a Hall IC fixed to a stator of the compressor motor 34. The speed sensor 53 changes an electrical state thereof when subjected to magnetic field from rotor magnets of the compressor motor 34. The inverter circuit 51 measures an amount of change per time in the electrical state of the speed sensor 53 when the compressor motor 34 is in operation, thereby detecting a rotational speed f_c (Hz) of the compressor motor 34. The inverter control circuit 51 serves as a motor drive unit.

[0026] A motor drive circuit 54 supplies a drive power to the water-supply valve motor 11. The main control circuit 47 electrically controls the motor drive circuit 54 thereby to turn on and off the water-supply valve motor 11. The main control circuit 47 further adjusts an amount of rotation of the water-supply valve motor 11 according to a length of turn-on time, thereby opening and closing the water-supply valve 10. A motor drive circuit 55 supplies drive power to the drain valve motor 16. The main control circuit 47 electrically controls the motor drive circuit 55 thereby to turn on and off the drain valve motor 16. The main control circuit 47 adjusts an amount of rotation of the drain motor 16 according to a length of on-time, thereby opening and closing the drain valve 15. A motor drive circuit 56 supplies a drive power to the fan motor 22. The main control circuit 47 electrically controls the motor drive circuit 56 thereby to turn on and off the fan motor 22. The main control circuit 47 controls the fan 24 between an operating state in which the fan 24 is rotated at a predetermined speed in a predetermined direction and a stopped state in which the fan 24 remains at rest. A motor drive circuit 57 supplies drive power to the outside air fan motor 37. The main control circuit 47 controls the motor drive circuit 57 thereby to turn on and off the outside air fan motor 37. The main control circuit 47 controls the outside air fan 38 between an operating state in which the outside air fan 37 is rotated at a predetermined speed in a predetermined direction and a stopped state in which the outside air fan 37 remains at rest.

[0027] An inverter circuit 58 converts a DC power to an AC power to generate a drive power for the drum motor 5. The inverter control circuit 51 calculates a deviation Δf_d between a target speed f and a rotational speed f_d of the drum motor 5. The inverter control circuit 51 controls the inverter circuit 58 according to a result of calculation of the deviation Δf_d, thereby rotate the drum motor 5 at the target speed f. An inverter circuit 59 converts DC power to AC power to generate drive power for the compressor motor 34. The inverter control circuit 51 calculates a deviation Δf_c between a target speed f and a rotational speed f_c of the compressor motor 34. The inverter control circuit 51 controls the inverter circuit 59 according to a result of calculation of the deviation Δf_c, thereby rotate the compressor motor 34 at the target speed f. The main control circuit 47 transmits the target speeds f of the drum motor 5 and the compressor motor 34 as operation frequencies f (Hz) to the inverter control circuit 51. Rotational speeds of the drum motor 5 and the compressor motor 34 are increased with increase in the respective operating frequencies f.

[0028] When determining that the operation course switch 48 has been operated, the main control circuit 47 sets an operation course according to operation contents of the operation course switch 48. The main control circuit 47 sets an operation control program according to a result of setting of the operation course when determining that the start switch 49 has been operated with the operation course having been set. The main control circuit 47 executes a result of setting of the operation control program with the RAM serving as a work area. The ROM of the main control circuit 47 stores a plurality of operation control programs including an operation control program for a standard course. The main control circuit 47 selects one of the plural operation control programs stored in the ROM according to the operation contents of the operation course switch 48, thereby setting the operation control program.

[0029] The operation control program for the standard course includes a weight determination processing at step S1, an operation information setting processing at step S2, a water supply processing at step S3, a wash processing at step S4, a drain processing 1 at step S5, a water supply processing at step S6, a rinse processing at step S7, a drain processing 1 at step S8, a dehydration processing at step S9, and a drying processing at step S10. The aforesaid processings at steps S1 to S10 will be described in detail as follows.

1. Weight determination processing

[0030] The main control circuit 47 transmits a sensing start command and a sensing stop command to the inverter control circuit 51 in turn when proceeding to the weight determination processing at step S1. The sensing stop command is transmitted upon lapse of a predetermined time recorded on the ROM on the basis of transmission of the sensing start command. When receiving the sensing start command, the inverter control circuit 51 starts the control of the inverter circuit 58 with the use of a predetermined sensing pattern. This sensing pattern is used to rotate the drum motor 5 from the rest state in a predetermined direction. When receiving the sensing stop command, the inverter control circuit 51 detects the rotational speed f_d of the drum motor 5 and thereafter stops the drum motor 5, transmitting a result of detection of the rotational speed f_d to the main control circuit 47.

[0031] When receiving the result of detection of the rotational speed f_d, the main control circuit 47 compares the detection result with a high weight determination range and a middle weight determination range. Data of the high and low weight determination ranges is previously stored on the ROM of the main control circuit f_d. When determining that the received result of the rotational speed f_d is within the high weight determination range, the main control circuit 47 determines that the weight of laundry in the drum 7 is high. Furthermore, when determining that the received result of the rotational speed f_d is within the middle weight range, the main control circuit 47 determines that the weight of laundry in the drum 7 is middle (<high weight) . When determining that the received result of the rotational speed f_d belongs to neither high weight range not middle weight range, the main control circuit 47 determines that the weight of laundry in the drum 7 is low (<middle weight) . Thus, in the weight determination processing, the weight of laundry in the drum 7 is determined in a stepwise manner on the basis of the rotational speed f_d of the drum 7 upon lapse of a predetermined time after operation start of the drum motor 5.

2. Operation information setting processing

[0032] When proceeding to the operation information setting processing at step S2, the main control circuit 47 sets a water level, a wash time, a rinse time, a dehydration time and a drying time. The water level refers to a level of tap water stored in the water-receiving tub 4 in the water supply processing 1 at step S3 and in the water supply processing 2 at step S6. The main control circuit 47 selects and sets one of plural water levels recorded on the ROM, according to the result of weight detection. The wash time refers to a necessary time from operation start to stop of the drum motor 5 in the wash processing at step S4. The main control circuit 47 selects and sets one of plural wash times recorded on the ROM, according to the result of weight detection.

[0033] The rinse time refers to a necessary time from operation start to stop of the drum motor 5 in the rinse processing at step S7. The main control circuit 47 selects and sets one of plural rinse times recorded on the ROM, according to the result of weight detection. The dehydration time refers to a necessary time from operation start to stop of the drum motor 5 in the dehydration processing at step S9. The main control circuit 47 selects and sets one of plural dehydration times recorded on the ROM, according to the result of weight detection. The drying time refers to a necessary time from operation start to stop of the compressor motor 34 in the drying processing at step S10. The main control circuit 47 selects and sets one of plural drying times recorded on the ROM, according to the result of weight detection.

3. Water supply processing 1

[0034] When proceeding to the water supply processing 1 at step S3, the main control circuit 47 controls the water supply valve motor 11 to switch the water supply valve 10 from the closed state to the open state. Furthermore, the main control circuit 47 controls the drain valve motor 16 to switch the drain valve 15 from the open state to the closed state. The main control circuit 47 then controls so that tap water is supplied from a faucet of the water system through the water case 12 into the water-receiving tub 4. When the water supply valve 10 is open, the main control circuit 47 detects a water level in the water-receiving tub 4 based on a water level signal from the water level sensor 50. When determining that a result of water level detection has reached the result of set water level at step S2, the main control circuit 47 controls the water supply valve motor 11 to switch the water supply valve 10 from the open state to the closed state. Thus, an amount of tap water according to the result of water level setting is stored in the water-receiving tub 4 in the water supply processing 1. Detergent is previously put into the water case 12 in the water supply processing. The detergent in the water case 12 is supplied into the water-receiving tub 4 together with the tap water.

4. Wash processing

[0035] FIG. 5 shows the details of the wash processing at step S4 in FIG. 4. The main control circuit 47 sets an initial value T₀ (0, for example) recorded on the ROM to a timer T of the RAM. The timer T is provided for measuring the lapse of time in a timer interrupt processing. FIG. 6 shows the timer interrupt processing. The main control circuit 47 interrupt a current processing every time a predetermined time (1 second, for example) elapses thereby to start up the timer interrupt processing as shown in FIG. 6. When the timer interrupt processing has been started up, the main control circuit 47 adds a predetermined value T₁ (1, for example) recorded on the ROM to the timer T of the RAM at step S21, thereafter returning to the state immediately before startup of the timer interrupt processing to restart the processing.

[0036] When the timer T is reset at step S11 in FIG. 5, the main control circuit 47 transmits an operation frequency f of the drum motor 5 for the wash processing to the inverter control circuit 51 at step S12 and further transmits a drum motor 5 operation start command to the inverter control circuit 51 at step S13. The operation frequency f for the wash processing is recorded on the ROM of the main control circuit 47. When receiving an operation start command regarding the drum motor 5, the inverter circuit 51 controls the inverter circuit 58 based on the result of calculation of the deviation Δf_d, thereby controlling the drum motor 5 so that the drum motor 5 is rotated at the received result of the operation frequency f. When the drum motor 5 is operated in this mode, laundry in the drum 7 is circumferentially moved together with the baffles 9 so as to be lifted up. The laundry is then caused to fall from the baffles 9 into the stored wash liquid containing the detergent in the water-receiving tub 4. The above-described operation of the drum motor 5 is carried out while the compressor motor 34 is stopped. The laundry is caused to fall into the stored wash liquid such that a beat washing is carried out.

[0037] When transmitting an operation start command at step S13 in FIG. 5, the main control circuit 47 proceeds to step S14 to compare the result of addition of the timer T with the result of setting of the wash time. When determining that T=the wash time, the main control circuit 47 proceeds to step S15 to transmit an operation stop command regarding the drum motor 5 to the inverter control circuit 51. When receiving the operation stop command, the inverter control circuit 51 stops the operation of the drum motor 5, completing the wash processing.

5. Drain processing 1

[0038] When proceeding to the drain processing 1 at step S5, the main control circuit 47 controls the drain valve motor 16 so that the drain valve 15 is switched from the closed state to the open state, thereby discharging the wash liquid used in the wash processing through the drain pipe 14.

6. Water supply processing 2

[0039] When proceeding to the water supply processing at step S6, the main control circuit 47 controls the water-supply motor 11 to switch the drain valve 15 from the open state to the closed state. The CPU of the main control circuit 4 controls so that tap water is supplied from the faucet of the water system through the water case 12 into the water-receiving tub 4. When the water-supply valve 10 is open, the main control circuit 47 detects the water level in the water-receiving tub 4 based on a water level signal from the water level sensor 50. When determining that the result of the water level detection has reached the result of setting of the water level at step S2, the main control circuit 47 controls the water-supply motor 11 to switch the water-supply valve 10 from the open state to the closed state.

7. Rinse processing

[0040] FIG. 7 shows a rinse processing at step S7 in FIG. 4. The main control circuit 47 proceeds to step S31 to reset the timer T. The main control circuit 47 proceeds to step S32 to transmit an operation frequency f of the drum motor 5 for the rinse processing to the inverter control circuit 51. The main control circuit 47 further proceeds to step S33 to transmit an operation start command for the drum motor 5 to the inverter control circuit 51. The operation frequency f for the rinse processing is recorded on the ROM of the main control circuit 47. When receiving the operation start command for the drum motor 5, the inverter control circuit 51 controls the inverter circuit 51 based on the result of calculation of the deviation Δf_d, thereby rotating the drum motor 5 at the operational frequency f for the rinse processing. When the drum motor 5 is in operation, the laundry in the drum 7 is caused to fall into the water stored in the wash-receiving tub 4 and not containing a detergent component, whereby the detergent component is eliminated from the laundry in the drum 7. The above-mentioned operation of the drum motor 5 is carried out while the compressor motor 34 in the operation stop state. When transmitting the operation start command at step S33, the main control circuit 47 proceeds to step S34 to compare the result of addition of timer T with the result of setting of the rinse time. When determining that T=rinse time, the main control circuit 47 proceeds to step S35 to transmit the operation stop command regarding the drum motor 5 to the inverter control circuit 51 thereby to stop the operation of the drum motor 5, thereby completing the rinse processing.

8. Drain processing 2

[0041] When proceeding to the drain processing 2 at step S8, the main control circuit 47 controls the drain valve motor 16 to switch the drain valve 15 from the closed state to the open state, thereby discharging the wash liquid stored in the water-receiving tub 4 and used in the rinse processing.

9. Dehydration processing

[0042] FIG. 8 shows a dehydration processing executed at step S9 in FIG. 4. The main control circuit 47 resets the timer T at step S41. The main control circuit 47 transmits an operation frequency of the drum 5 for the dehydration processing to inverter control circuit 51. The main control circuit 47 then proceeds to step S43 to transmit an operation start command for the drum motor 5 to the inverter circuit 51. The operation frequency for the dehydration processing is previously stored on the main control circuit. The operation frequency f for the dehydration processing is recorded on the ROM of the main control circuit 47. When receiving the operation start signal regarding the drum motor 5, the inverter control circuit 51 controls the inverter circuit 58 based on the result of calculation of the deviation Δf_d, thereby rotating the drum motor 5 at an operation frequency f for the dehydration processing. When the drum motor 5 is in operation, the laundry in the drum 7 is circumferentially moved without disengaging from the baffles 9, whereupon water content is centrifugally extracted from the laundry in the drum 7. The aforesaid dehydration processing is carried out with the drain valve 15 being open. The water content extracted from the laundry is discharged through the drain pipe 14 outside the water-receiving tub 4.

[0043] When transmitting the operation start command at step S43, the main control circuit 47 proceeds to step S44 to compare the result of addition by the timer T with the result of setting of a dehydration time. When determining that T=the dehydration time, the main control circuit 47 proceeds to step S45 to transmit the operation stop command regarding the drum motor 5 to stop the operation of the drum motor 5, thereby completing the dehydration processing.

10. Drying processing

[0044] FIGS. 9 and 10 show the drying processing at step S10 of FIG. 4. The main control circuit 47 switches the outside air fan motor 37 from an off-state to an on-state so that air outside the outer casing 1 is blown against the room temperature sensor 40. The main control circuit 47 further proceeds to step S52 to reset the timer T. The main control circuit 47 further proceeds to step S53 to switch the fan motor 22 from an off-state to an on-state, thereby starting an operation of the fan 24. As a result, air is circulated through the circulation duct 26. The main control circuit 47 further proceeds to step S54 to set an initial value f₀ (20 Hz, for example) recorded on the ROM to the operation frequency f on the RAM. The main control circuit 47 further proceeds to step S55 to transmit the result of initial setting of the operation frequency f to the inverter control circuit 51. The main control circuit 47 further proceeds to step S56 to transmit an operation start command regarding the compressor motor 34 to the inverter control circuit 51. When receiving the operation start command regarding the compressor motor 34, the inverter control circuit 51 controls the inverter circuit 59 based on the result of calculation of a deviation Δf_c so that the compressor motor 34 is rotated at an initially set operating frequency f.

[0045] When transmitting the operation start command regarding the compressor motor 34 at step S56, the main control circuit 47 proceeds to step S57 to detect a room temperature T_r based on a temperature signal delivered by the temperature sensor 40 and further to step S58 to compare the result of detection of the room temperature T_r with a frost formation estimation temperature T_f (10°C, for example) recorded on the ROM. When the compressor motor 34 is normally accelerated by a normal acceleration processing at step S59, whether frost adheres to the fins 29 of the evaporator 27 is determined based on the aforesaid frost formation estimation temperature T_f. The frost formation estimation temperature T_f serves as a first threshold.

[0046] When the room temperature is such that frost does not adhere to the fins 29 of the evaporator 27, the main control circuit 47 proceeds to step S58 to determine that T_r>T_f, thereafter proceeding to step S59 for the normal acceleration processing. In the normal acceleration processing, the main control circuit 47 determines whether a predetermined time (1 second, for example) has elapsed, based on the result of addition by the timer T. When determining that the predetermined time has elapsed, the main control circuit 47 adds a predetermined unit value f₁ (1 Hz, for example) recorded on the ROM to the operation frequency f of the RAM, transmitting the result of addition of the operation frequency f to the inverter control circuit 51. The inverter control circuit 51 controls the inverter circuit 59 based on the received result so that the inverter circuit 59 is accelerated at a speed change rate Δf₁ (1 Hz/second) corresponding to the normal pattern. The result of addition of the operation frequency f is compared with an acceleration interrupt value 1 (45 Hz, for example) and an acceleration interrupt value 2 (60 Hz, for example) both recorded on the ROM. When it is determined that the result of addition of the operation frequency f equals to the acceleration interrupt value 1 or 2, the addition of operation frequency is interrupted for a predetermined hold time (1 minute, for example) recorded on the ROM. As a result, when the compressor motor 34 is accelerated from the initial value f₀ at the speed change rate Δf₁, the operation frequency f of the compressor motor 34 is mounted to the acceleration interrupt value 1 or 2 for the hold time.

[0047] Upon completion of the normal acceleration processing at step S59, the main control circuit 47 proceeds to step S60 to compare the result of addition of the operation frequency f with a maximum frequency f_max1 (110 Hz, for example) recorded on the ROM. When determining that f=f_max1, the main control circuit 47 proceeds to step S61 for a superheat processing. In the superheat processing, the main control circuit 47 detects an evaporator inlet temperature T_ei based on a temperature signal delivered by the evaporator inlet temperature sensor 45 and an evaporator outlet temperature T_eo based on a temperature signal delivered by the evaporator outlet temperature sensor 46. The main control circuit 47 sets an operation frequency f of the compressor motor 34 so that the difference between the results of detection of evaporator inlet and outlet temperatures T_ei and T_eo falls within a predetermined range, thereafter transmitting a result of setting of the operation frequency f to the inverter control circuit 51. The inverter control circuit 51 controls the inverter circuit 59 based on the result of calculation of the deviation Δf_c, whereby the compressor motor 34 is rotated at a received operation frequency f.

[0048] Upon completion of the superheat processing at step S61, the main control circuit 47 proceeds to step S62 to detect an outlet temperature T_t of the compressor 33 based on a temperature signal delivered by the outlet temperature sensor 44 and further to step S63 to compare a result of detection of the outlet temperature T_t with a forced deceleration value Down1 recorded on the ROM. When determining that T_t≥Down1, the main control circuit 47 proceeds to step S66. The main control circuit 47 proceeds to step S64 when determining that T_t<Down1.

[0049] When proceeding to step S64, the main control circuit 47 detects a condenser temperature T_c of the condenser 30 based on a temperature signal delivered by the condenser temperature sensor 43. The main control circuit 47 then proceeds to step S65 to compare a result of detection of the condenser temperature T_c with a forced deceleration value Down2 recorded on the ROM. When determining that T_c≥Down2, the main control circuit 47 proceeds to step S66. When determining that T_c<Down2, the main control circuit 47 proceeds to step S69.

[0050] When proceeding to step S66, the main control circuit 47 compares the result of setting of the operation frequency f at step S61 with a minimum frequency f_min (40 Hz, for example) recorded on the ROM. When determining that f>f_min, the main control circuit 47 proceeds to step S67 to subtract a unit value f₂ recorded on the ROM from the result of setting of the operation frequency f at the superheat processing. The main control circuit 47 further proceeds to step S68 to transmit a result of subtraction of the operation frequency f to the inverter control circuit 51, thereafter proceeding to step S69. More specifically, when the result of detection of the outlet temperature T_t is equal to or larger than the forced deceleration value Down1 or the result of detection of the condenser temperature T_c is equal to or larger than the forced deceleration value Down2, the operation frequency f of the compressor motor 34 at the superheat processing is subtracted on condition that the result of setting is higher than the minimum frequency f_min. Consequently, the compressor motor 34 is operated at a lower speed than the result of setting at the superheat processing. In this case, a flow rate of refrigerant flowing through each of the condenser 30, the capillary tube 35 and the evaporator 27 becomes lower than a flow rate at the superheat processing, whereupon the temperature of the condenser 30 is decreased.

[0051] When proceeding to step S69, the main control circuit 47 compares the result of addition of timer T with the result of setting of the drying time. When determining that T=the drying time, the main control circuit 47 proceeds to step S70 to switch the outside air fan motor 37 from an on-state to an off-state thereby to stop the operation of the outside air fan motor 37. Furthermore, the main control circuit 47 proceeds to step S71 to switch the fan motor 22 from an on-state to an off-state thereby to stop the operation of the fan motor 22. The main control circuit 47 further proceeds to step S72 to transmit an operation stop command to the compressor motor 34 to stop the operation of the compressor motor 34. Consequently, the main control circuit 47 completes the drying processing.

[0052] When determining at step S58 that the result of detection of the room temperature T_r is equal to or lower than the frost formation estimation temperature T_f, the main control circuit 47 proceeds to step S73 (FIG. 10) to determine whether a predetermined time T₂ (60 seconds, for example) recorded on the ROM has elapsed, based on the result of addition by the timer T. The main control circuit 47 detects the evaporator inlet temperature T_ei based on a temperature signal delivered by the evaporator inlet temperature sensor 45 every time determining that the predetermined time T₂ has elapsed, at step S74. The main control circuit 47 further proceeds to step S75 to detect the evaporator outlet temperature T_eo based on a temperature signal delivered by the evaporator outlet temperature sensor 46. The main control circuit 47 further proceeds to step S76 to detect the current result of setting of the operation frequency f of the compressor motor 34 from the RAM. The operation frequency f of the compressor motor 34 serves as a rotational speed.

[0053] When detecting the result of setting of the operational frequency f at step S76, the main control circuit 47 proceeds to step S77 to compare the result of detection of the evaporator inlet temperature T_ei with a frost formation determination value T_i (0°C, for example) recorded on the ROM. The frost formation determination temperature T_i denotes a temperature at which frost adheres to the fins 29 of the evaporator 27 and is set to be higher than the frost formation anticipation temperature T_f. The frost formation determination temperature T_i serves as a second threshold. When determining at step S77 that T_ei≤T_i, the main control circuit 47 proceeds to step S78 to compare the result of detection of the evaporator outlet temperature T_eo with the frost formation determination temperature T_i. When determining that T_eo≤T_i, the main control circuit 47 proceeds to step S79 to compare the result of detection of the operation frequency f with a lower limit value f_low1 (25 Hz, for example) recorded on the ROM.

[0054] When determining at step S79 that f<f_low1, the main control circuit 47 proceeds to step S87. The main control circuit 47 proceeds to step S80 when determining at step S79 that f≥f_low1. The main control circuit 47 subtracts a unit value f₃ (5 Hz, for example) from the result of detection of the operation frequency f. The main control circuit 47 proceeds to step S86 to transmit a result of subtraction of the operation frequency f to the inverter control circuit 51. When receiving the result of subtraction of the operation frequency f, the inverter control circuit 51 controls the inverter circuit 59 based on a result of calculation of the deviation Δf_c thereby to rotate the compressor motor 34 at the received operation frequency f.

[0055] When determining at step S78 that T_eo>T_i, the main control circuit 47 proceeds to step S84 to compare the result of detection of the operation frequency f with an upper limit value f_hi1 (108 Hz, for example) recorded on the ROM. When determining that f>f_hi1, the main control circuit 47 proceeds to the superheat processing at S61 (FIG. 9) to rotate the compressor motor 34 so that the difference between the result of detection of the evaporator inlet temperature T_ei and the result of detection of the evaporator outlet temperature T_eo falls within a predetermined range.

[0056] When determining at step S84 (FIG. 10) that f≤f_hi1. the main control circuit 47 proceeds to step S85 to add a unit value f₄ (2 Hz, for example) recorded on the ROM to the result of detection of the operation frequency f, transmitting a result of addition of the operation frequency f to the inverter control circuit 51. When receiving the result of addition of the operation frequency f, the inverter control circuit 51 controls the inverter circuit 59 based on the result of calculation of the deviation Δf_c to rotate the compressor motor 34 at the received operation frequency f.

[0057] When determining at step S77 that T_ei>T_i, the main control circuit 47 proceeds to step S81 to compare the result of detection of the evaporator outlet temperature T_eo with the frost formation value T_i. When determining that T_eo>T_i, the main control circuit 47 proceeds to step S82 to compare the result of detection of the operation frequency f with a predetermined upper limit value f_hi2 (105 Hz, for example). When determining that f>f_hi2, the main control circuit 47 proceeds to step S61 for the superheat processing to rotate the compressor motor 34 so that the difference between the result of detection of the evaporator inlet temperature T_ei and the result of detection of the evaporator outlet temperature T_eo falls within a predetermined range.

[0058] When determining at step S82 (FIG. 10) that f≤fhi2, the main control circuit 47 proceeds to step S83 to add a unit value f₃ to the result of detection of the operation frequency f. The main control circuit 47 further proceeds to step S86 to transmit a result of addition of the operation frequency f to the inverter control circuit 51. When receiving the result of addition of the operation frequency f, the inverter control circuit 51 controls the inverter circuit 59 so that the compressor motor 34 is rotated at the received operation frequency f.

[0059] When determining at step S81 that T_eo≤T_i, the main control circuit 47 proceeds to step S84 to compare the result of detection of the operation frequency f with the upper limit value f_hi1. When determining f>f_hi1, the main control circuit 47 proceeds to step S61 (FIG. 9) for the superheat processing to rotate the compressor motor 34 so that the difference between the result of detection of the evaporator inlet temperature T_ei and the result of detection of the evaporator outlet temperature T_eo falls within a predetermined range.

[0060] When determining at step S84 (FIG. 10) that f≤f_hi1, the main control circuit 47 proceeds to step S85 to add a unit value f₄ to the result of detection of the operation frequency f. The main control circuit 47 further proceeds to step S86 to transmit a result of addition to the operation frequency f to the inverter control circuit 51. When receiving the result of addition to the operation frequency f, the inverter control circuit 51 controls the inverter circuit 59 so that the compressor motor 34 is rotated at the received operation frequency f.

[0061] When transmitting the result of addition to or subtraction from the operation frequency f to the inverter control circuit 51, the main control circuit 47 proceeds to step S87 to detect the outlet temperature T_t based on a temperature signal delivered by the outlet temperature sensor 44. The main control circuit 47 further proceeds to step S88 to detect the compressor temperature T_c based on a temperature signal delivered by the compressor temperature sensor 43. The main control circuit 47 further proceeds to step S89 to calculate a difference (T_t-T_c) between the result of detection of outlet temperature T_t and the result of detection of condenser temperature T_c, comparing a result of calculation of the difference (T_t-T_c) with an operation change value T_ch (10°C, for example) recorded on the ROM. The operation change value T_ch is provided for determining whether the heat pump is in a normal operation state where air is heated by the condenser 30. When determining at step S89 that T_t-T_c>T_ch, the main control circuit 47 proceeds to step S59 (FIG. 9) of the normal acceleration processing to increase the operation frequency f of the compressor motor 34 from the current value to a maximum frequency f_max at the normal speed change rate Δf₁ (1 Hz/sec), at step S60. Subsequently, the main control circuit 47 proceeds to step S61 for the superheat processing.

[0062] When determining at step S89 (FIG. 10) that T_i-T_c≤T_ch, the main control circuit 47 proceeds to step S90 to compare the result of addition of the Timer T with the result of setting of the drying time. When determining that T<the drying time, the main control circuit 47 returns to step S73. The main control circuit 47 proceeds to step S74 when determining that a predetermined time T₂ has further elapsed based on the result of addition of timer T with reference to the previous determination of elapse of the predetermined time T₂. When determining at step S90 that T=the drying time, the main control circuit 47 proceeds to step S70 (FIG. 9) to switch the outside air fan motor 37 to the off-state, and further advance to the step S71 to switch the fan motor 22 to the off-state. The main control circuit 47 further proceeds to step S72 to transmit an operation stop command for the compressor motor 34 to the inverter control circuit 51, completing the drying processing.

[0063] When the compressor motor 34 has started at the normal speed change rate (Δf₁) and the heat pump is exposed to a temperature zone (T_r<T_f), the operation frequency f of the compressor motor 34 is set as an initial value f₀, so that the compressor motor 34 is operated for a predetermined time T₂ at the initially set operation frequency f. Upon expiration of the predetermined time T₂, the evaporator inlet and outlet temperatures T_ei and T_eo are detected, and each of the results of detection of the temperatures T_ei and T_eo is compared with the frost formation determination value T_i. As a result, when the compressor motor 34 is accelerated, the possibility of frost formation on the fins 29 of the evaporator 27 is determined in a stepwise manner as described below.

First step:

[0064] The possibility of frost formation on the fins 29 of the evaporator 27 is lowest when each of detection results of the evaporator inlet and outlet temperatures T_ei and T_eo is larger than the frost formation determination value T_i. In this case, a unit value f₃ (5 Hz, for example) is added to the operation frequency f every lapse of the predetermined time T₂ so that the operation frequency f does not exceed the maximum frequency f_max1 (110 Hz, for example) . As a result, the compressor motor 34 is accelerated at a lower speed change rate Δf₃ (5 Hz/60 sec) than the normal speed change rate Δf₁.

Second step

[0065] When either one of detection results of evaporator inlet and outlet temperatures T_ei and T_eo is equal to or smaller than the frost formation determination value Ti and the other is larger the frost formation determination value T_i, the possibility of frost formation on the fins 29 of the evaporator 27 with acceleration of the compressor motor 34 is second lowest. In this case, a unit value f₄ (2 Hz, for example) is added to the operation frequency f every lapse of the predetermined time T₂ so that the operation frequency f does not exceed the maximum frequency f_max1 (110 Hz, for example). As a result, the compressor motor 34 is accelerated at a lower speed change rate Δf₄ (2 Hz/60 sec) than the normal speed change rate Δf₃.

Third step

[0066] When each of detection results of the evaporator inlet and outlet temperatures T_ei and T_eo is equal to or smaller than the frost formation determination value T_i, the possibility of frost formation between the fins 29 of the evaporator 27 with acceleration of the compressor motor 34 is highest. In this case, the unit value f₃ (5 Hz, for example) is subtracted from the operation frequency f every lapse of the predetermined time T₂ so that the operation frequency f is not reduced to or below the minimum frequency f_min (40 Hz, for example), whereby the compressor motor 34 is decelerated at the speed change rate Δf₃ (5 Hz/60 sec).

[0067] The following effects can be achieved from the foregoing embodiment. The main control circuit 47 sets the operation frequency f of the compressor motor 34 according to the evaporator inlet temperature T_ei and starts the compressor motor 34 at the set operation frequency f when the compressor motor 34 has started at the normal speed change rate Δf₁ and the heat pump is exposed to the temperature zone in which frost is formed on the fins 29 of the evaporator 27. Accordingly, frost is prevented from being formed between the fins 29 of the evaporator 27 when the compressor motor 34 starts up at the drying processing. Consequently, the cooling performance of the evaporator 27 can be prevented from being reduced although the pipe-shaped capillary tube 35 having a fixed degree of opening is used in the clothes dryer. The same effect can be achieved with respect to the evaporator outlet temperature T_eo. Moreover, the main control circuit 47 changes a flow rate of the refrigerant flowing through each of the condenser 30, the capillary tube 35 and the evaporator 37. In this case, the flow rate is changed at the rate according to the possibility of frost adhering to the fins 29 of the evaporator 27. Consequently, the drying performance of the heat pump can quickly be improved without frost formation on the fins 29 of the evaporator 27.

[0068] A speedy drying operation can be carried out at the normal acceleration processing without deterioration of cooling performance when the result of detection of the room temperature T_r is equal to or higher than 10°C. Air can be dehumidified even when the detected room temperature T_r is about 5°C. More specifically, when the laundry in the drum 7 has reached an approximate temperature of 10°C, air can be dehumidified by sensible heat of about 10°C possessed by the air at the inlet side of the evaporator 27 even without reduction in the temperature of the evaporator 27 to or below 0°C. For example, energy of about 12 Wh is necessitated in order that 6 kg of standard laundry in a dried state with the dewatering ratio of 80% may be increased from 5°C to 10°C. Accordingly, when the compressor motor 34 is operated at the operation frequency of about 30 Hz which frequency increases the compressor temperature T_c upon startup thereof, an amount of heat ranging from 100 to 200 W is obtained in a refrigerating cycle with displacement capacity of about 7 cc. Consequently, the drum outlet temperature T_do can be increased to or above 10°C in 10 to 20 minutes without stagnation of liquefied refrigerant or the like theoretically.

[0069] FIGS. 11 and 12 illustrate a second embodiment. The main control circuit 47 executes the dehydration processing as shown in FIGS. 11 and 12, instead of the dehydration processing of FIG. 8. When transmitting an operation start command for the drum motor 5 to the inverter control circuit 51 at step S43 in FIG. 11, the main control circuit 47 proceeds to step S101 to switch the fan motor 37 from the off-state to the on-state. The main control circuit 47 proceeds to step S102 to switch the fan motor 22 from the off-state to the on-state and further to step S103 to set the initial value f₀ to the operation frequency f of the compressor motor 34. Subsequently, the main control circuit 47 proceeds to step S104 to transmit a result of setting of the initial value of operation frequency f of the compressor motor 34 to the inverter control circuit 51. Upon receipt of the operation start command for the compressor motor 34, the inverter control circuit 51 rotates the compressor motor 34 at the initial setting of the operation frequency f.

[0070] When transmitting the operation start command for the compressor motor 34 at step S105, the main control circuit 47 proceeds to step S106 to detect the room temperature T_r based on the temperature signal delivered by the room temperature sensor 40 and further to step S107 to compare the result of detection of the room temperature T_r with the frost formation estimation value T_f. When determining that T_r>T_f, the main control circuit 47 proceeds to step S108 for the normal acceleration processing. In the normal acceleration processing, the main control circuit 47 sets the operation frequency f of the compressor motor 34 in the same process as the normal acceleration processing at step S59 in FIG. 9, transmitting a result of setting of the operation frequency f of the compressor motor 34 to the inverter control circuit 51. The inverter control circuit 51 controls the inverter circuit 59 so that the compressor motor 34 is accelerated at the speed change rate Δf₁ (1 Hz/sec).

[0071] When completing the normal acceleration processing at step S108, the main control circuit 47 proceeds to step S109 to compare the result of addition to the operation frequency f with the maximum frequency f_max2 (60 Hz, for example) recorded on the ROM. When determining that f=f_max2, the main control circuit 47 proceeds to step 110 of superheat processing. In the superheat processing, the main control circuit 47 sets the operation frequency f of the compressor motor 34 in the same process as the superheat processing at step S61 in FIG. 9, transmitting the result of setting of the operation frequency f to the inverter control circuit 51. The inverter control circuit 51 controls the inverter circuit 59 so that the compressor motor 34 is rotated at the received operation frequency f.

[0072] Upon completion of the superheat processing at step S110 in FIG. 11, the main control circuit 47 proceeds to step S111 to detect the outlet temperature T_t of the compressor 33 based on the temperature signal delivered by the outlet temperature sensor 44, comparing a result of detection of the outlet temperature T_t with the forced deceleration value Down1. When determining that T_t≥Down1, the main control circuit 47 proceeds to step S115. The main control circuit 47 proceeds to step S113 when having determined that T_t<Down1.

[0073] When having advanced to step S113, the main control circuit 47 detects the condenser temperature T_c of the condenser 30 based on the temperature signal delivered by the condenser temperature sensor 43 and further compares a result of detection of the condenser temperature signal T_c with the forced deceleration value Down2 at step S114. When having determined that T_c≥Down2, the main control circuit 47 proceeds to step S115. The main control circuit 47 proceeds to step S118 when having determined that T_c<Down2.

[0074] The main control circuit 47 proceeds to step S115 to compare, with the minimum frequency f_min, a result of setting of the operation frequency f in the superheat processing at step S110. When determining that f>f_min, the main control circuit 47 proceeds to step S116 to subtract the unit value f2 from the setting result of operation frequency f. The main control circuit 47 proceeds to step S117 to transmit the result of subtraction of the operation frequency f to the inverter circuit 51, thereafter proceeding to step S118.

[0075] The main control circuit 47 compares the result of addition of time T with the result of setting of the dehydration time at step S118. When determining that T=the dehydration time, the main control circuit 47 proceeds to step S119 to transmit an operation stop command for the drum motor 5 to the inverter control circuit 51, thereby stopping the operation of the drum motor 5. The main control circuit 47 then stops the operation of the outside air fan motor 37 at step S120 and the operation of the fan motor 22 at step S121. The main control circuit 47 further transmits an operation stop command for the compressor motor 34 to the inverter control circuit 51 at step S122, thereby stopping the operation of the compressor motor 34 and completing the dehydration processing.

[0076] When determining at step S107 that the result of detection of the room temperature T_r is at or below the frost formation estimation value T_f, the main control circuit 47 proceeds to step S123 to determine whether the predetermined time T₂ has elapsed, based on the result of addition of the timer T. When determining that the predetermined time T₂ has elapsed, the main control circuit 47 proceeds to step S124 to detect the evaporator inlet temperature T_ei based on the temperature signal delivered by the evaporator inlet temperature sensor 46 and further proceeds to step S125 to detect the evaporator outlet temperature T_eo based on the temperature signal delivered by the evaporator outlet temperature sensor 46. The main control circuit 47 further proceeds to step S126 to detect a current result of setting of the operation frequency f of the compressor motor 34 from the RAM.

[0077] When detecting the result of setting of the operation frequency f at step S126, the main control circuit 47 proceeds to step S127 to compare the result of evaporator inlet temperature T_ei with the result of detection of the frost formation determination value T_i. When determining that T_ei≤T_i, the main control circuit 47 proceeds to step S128 to compare the result of evaporator outlet temperature T_eo with the result of detection of the frost formation determination value T_i. When determining that T_eo>T_i, at step S128, the main control circuit 47 proceeds to step S137. When determining that T_eo>T_i, the main control circuit 47 proceeds to step S129.

[0078] The main control circuit 47 compares the result of detection of the operation frequency f of the compressor motor 34 with a lower limit value f_low1 at step S129. When determining that f<f_low1, the main control circuit 47 proceeds to step S137. When determining that f≥f_low1, the main control circuit 47 proceeds to step S130. The main control circuit 47 subtracts a unit value f₃ from the result of detection of the operation frequency f. The main control circuit 47 then proceeds to step S136 to transmit the result of subtraction of the operation frequency f to the inverter control circuit 51. When receiving the result of subtraction of the operation frequency f, the inverter control circuit 51 controls the inverter circuit 59 to rotate the compressor motor 34 at the received operation frequency f.

[0079] When determining at step S127 that T_ei>T_i, the main control circuit 47 proceeds to step S131 to compare the result of detection of the evaporator outlet temperature T_eo with the frost formation determination value Ti. When determining that T_eo≤T_i, the main control circuit 47 proceeds to step S132 to compare the result of detection of the operation frequency f with an upper limit value f_hi3 (55 Hz, for example) recorded on the ROM. When determining at S132 that f>f_hi3, the main control circuit 47 proceeds to step S137.

[0080] When determining at step S132 that f≤f_hi3, the main control circuit 47 proceeds to step S133 to detect a drum outlet temperature T_do based on the temperature signal delivered by the drum outlet temperature sensor 42. The main control circuit 47 further proceeds to step S134 to compare the result of detection of the drum outlet temperature Td with a predetermined target value T_b (15°C, for example) recorded on the ROM. When determining that T_do>T_b, the main control circuit 47 proceeds to step S137. When determining that T_do≤T_b, the main control circuit 47 proceeds to step S135 to add the unit value f₃ to the result of detection of the operation frequency f. The main control circuit 47 transmits the result of addition to the inverter control circuit 51 at step S136. When receiving the result of addition of the operation frequency f, the inverter control circuit 51 controls the inverter circuit 59 so that the compressor motor 34 is rotated at the result of reception of the operation frequency f.

[0081] The main control circuit 47 then proceeds to step S137 to detect an outlet temperature T_t based on a temperature signal delivered by the outlet temperature sensor 44. The main control circuit 47 further proceeds to step S138 to detect a condenser temperature T_c based on a temperature signal delivered by the condenser temperature sensor 44. The main control circuit 47 further proceeds to step S139 to compare the difference (T_t-T_c) between the detection results of the outlet temperature T_t and the condenser temperature T_c with an operation change value T_ch. When determining that T_c>T_ch, the main control circuit 47 proceeds to step S108 of a normal acceleration processing (FIG. 11) thereby to increase the operation frequency f from the current value to the maximum frequency f_max2 at the normal speed change rate Δf₁.

[0082] When determining at step S139 that T_t-T_c≤T_ch, the main control circuit 47 proceeds to step S140 to compare the result of addition by the timer T with the result of setting of the dehydration time. When determining that T<the dehydration time, the main control circuit 47 returns to step S123. The main control circuit 47 proceeds to step S124 every elapse of the predetermined time T₂. When determining at step S140 that T=the dehydration time, the main control circuit 47 proceeds to steps S119, S120, S121 and S122 in FIG. 11 thereby to stop operation of the drum motor 5, the outside air fan motor 37, the fan motor 22 and the compressor motor 34 respectively.

[0083] The second embodiment can achieve the following advantages. The compressor motor 34 and the fan motor 29 are operated in the dehydration processing individually. Consequently, influences of liquefied refrigerant stagnation are reduced before start of the drying processing. The liquefied refrigerant stagnation refers to refrigerant blending into the lubricant of the compressor 3. The drum inlet temperature T_d1 is rapidly increased in the drying processing since the influences of the liquefied refrigerant stagnation is previously reduced. Accordingly, the normal acceleration processing can be carried out promptly even when the result of detection of the room temperature T_r is at or lower than the frost formation estimation value T_f.

[0084] FIGS. 13A to 14 illustrate a third embodiment. A heater 60 serving as an auxiliary electrical heater is mounted in the interior of the rear duct 25 as shown in FIG. 13A. The heater 60 comprises a nichrome wire wound into a coil and is connected via a heater drive circuit to the main control circuit 47 as shown in FIG. 13B. The heater drive circuit applies a drive power to the heater 60 to turn on the heater 60 and cuts off the drive power to turn off the heater 60. The main control circuit 47 controls the heater drive circuit thereby to turn on and off the heater 60.

[0085] The main control circuit 47 executes a drying processing as shown in FIG. 14, instead of the drying processing in the first and second embodiments as shown in FIG. 10. When determining that the result of detection of the room temperature T_r is at or below the frost formation estimation value T_f, the main control circuit 47 proceeds from step S73 in FIG. 14 to steps 74 to 76 sequentially and to step S91 to turn on the heater 60. The heater 60 is adapted to be operated so that a duty cycle (a ratio of on-time to unit time) takes a value recorded on the ROM. When turning on the heater 60 at step S91, the main control circuit 47 proceeds to step S92 to set the heater flag of the RAM to on-state. When the heater 60 is in on-state, air circulated along the circulation duct 26 is heated downstream of the condenser 30, whereupon air heated by the condenser 30 and the heater 60 in turn is returned into the water-receiving tub 4.

[0086] The main control circuit 47 then proceeds to step 93 to detect a drum outlet temperature T_do based on a temperature signal delivered by the drum outside temperature sensor 42. Step S93 is carried out in the following cases 1 to 5. The main control circuit 47 proceeds to step S94 when having detected the drum outlet temperature T_do at step S93.

1. Case where the main control circuit 47 determines at step S77 that T_ei≤T_i and at step S78 that T_eo>T_i;

2. Case where the main control circuit 47 determines at step S77 that T_ei>T_i and at step S81 that T_eo≤T_i;

3. Case where the main control circuit 47 determines at step S78 that T_eo≤T_i and at step S79 that f<f_low1;

4. Case where the main control circuit 47 determines at step S78 that T_eo≤T_i and at step S79 that f≥f_low1, in which case the main control circuit 47 executes steps S80, S86 and S93 sequentially; and

5. Case where the main control circuit 47 determines at step S77 that T_ei>T_i and at step S81 that T_eo>T_i, in which case the main control circuit 47 executes steps S83, S86 and S93 sequentially when determining at step S82 that f≤f_hi2.

[0087] The main control circuit 47 proceeds to step S94 to determine whether the heater flag of the RAM is set to on-state. For example, when the heater 60 is in on-state, the main control circuit 47 determines that the heater flag is set to on-state, proceeding to step S95 to compare the result of detection of the drum outlet temperature T_do with a predetermined operation stop value T_p (20°C, for example). When determining that T_do>T_p, the main control circuit 47 turns off the heater 60 at step S96 and resets the heater flag to off-state at step S97, proceeding to step S87. More specifically, the heater 60 is turned off when the result of detection of the drum outlet temperature T_do becomes larger than the operation stop value T_p during on-state of the heater 60.

[0088] When the heater 60 is in off-sate, the main control circuit 47 determines at step S94 that the heater flag of the RAM is reset to off-state, proceeding to step S98 to compare the result of detection of the drum outlet temperature T_do with an operation restart value T_rp (10°C, for example) recorded on the ROM. When determining that T_do≤T_rp, the main control circuit 47 proceeds to step S99 to restart the operation of the heater 60. The operation restart of the heater 60 is executed in order that the duty cycle may take a value recorded on the ROM. When the operation of the heater 60 has been restarted at step S99, the main control circuit 47 proceeds to step S100 to set the heater flag to on-state, further proceeding to step S87. More specifically, the heater 60 is restarted when the result of detection of the drum outlet temperature T_do is at or below the operation restart value T_rp with the heater 60 in the off-state.

[0089] The third embodiment can achieve the following advantages. When determining that the result of detection of the room temperature T_r is at or below the frost formation estimation value T_f, the main control circuit 47 operates the heater 60 so that air flowing along the circulation duct is heated downstream of the evaporator 27. This can compensate for a reduction in the heating performance of the heat pump due to stagnation of liquefied refrigerant during startup of the compressor motor 34. Accordingly, the drum outlet temperature T_do is increased more rapidly than in the first embodiment when the result of detection of the room temperature T_r is at or below the frost formation estimation value T_f. Consequently, the normal acceleration processing can be more rapidly than in the first embodiment.

[0090] FIGS. 15 to 18 illustrate a fourth embodiment. A wash processing as shown in FIG. 15 is executed by the main control circuit 47 instead of the wash processing as shown in FIG. 5 in the first to third embodiments. When having transmitted an operation start command for the drum motor 5 to the inverter control circuit 51 at step S13, the main control circuit 47 proceeds to step S151 to start the operation of the outside air fan motor 37 and further to step S152 to detect a room temperature based on the result of detection of the room temperature T_r. The main control circuit 47 further proceeds to step 153 to compare the result of detection of the room temperature T_r with the frost formation estimation value T_f. When determining that T_r>T_f, the main control circuit 47 proceeds to step S154 to reset a compressor heating flag to off-state and further to step S159 to compare the result of addition of the timer T with the result of setting of the wash time.

[0091] When determining at step S153 that T_r≤T_f, the main control circuit 47 proceeds to step S155 to set an initial value C₀ recorded on the ROM to the duty cycle C of the RAM, and further to step S156 to transmit the result of initial setting of the duty cycle to the inverter control circuit 51. The duty cycle C informs how long specified two of the phase coils (phase U and V coils, for example) of the compressor motor 34 should be turned on per unit time. When transmitting the result of initial setting of the duty cycle C to the inverter control circuit 51 at step S156, the main control circuit 47 proceeds to step S157 to transmit the energization start command to the inverter control circuit 51 and further to step S158 to set the compressor heating flag to on-state. When receiving the energization start command, the inverter control circuit 51 controls the inverter circuit 59 so that energization of the specified two phase coils of the compressor 34 is started based on the result of initial setting. In this state, each of the specified coils generates heat while the rotational shaft of the compressor motor 34, whereupon heat is applied to the lubrication oil in the compressor motor 34. The lubrication oil contains the refrigerant, which is evaporated when heat is applied to the lubrication oil.

[0092] When setting the compressor heating flag to on-state, the main control circuit 47 proceeds to step S159 to compare the result of addition of the timer T with the result of setting of the wash time. When determining that the result of addition of the timer T has not reached the result of setting of a wash time, the main control circuit 47 proceeds to step S160 to determine whether the compressor heating flag is set to on-state. When determining that the compressor heating flag is set to on-state, the main control circuit 47 proceeds to step S161 for a compressor heating processing. In the compressor heating processing, the specified two phase coils of the compressor motor 34 are energized so that the compressor motor 34 generates heat without generation of rotating magnetic field. When the compressor heating flag is set to on-state, the main control circuit 47 also executes the compressor heating processing in each of the dehydration processing 1 at step S5, the water supply processing 2 at step S6, the rinse processing at step S7, the drain processing 2 at step S8 and the dehydration processing at step S9.

[0093] The rinse processing as shown in FIG. 16 is executed by the main control circuit 47 instead of the rinse processing in each of the first to third embodiments. When determining at step S36 that the compressor heating flag is set to on-state, the main control circuit 47 proceeds to step S37 for a compressor heating processing. A dehydration processing as shown in FIG. 17 is executed by the main control circuit 47 instead of the dehydration processing in each of the first to third embodiments. When determining at step S46 that the compressor heating flag is set to on-state, the main control circuit 47 proceeds to step S47 for the compressor heating processing. When transmitting an operation stop command for the drum motor 5 to the inverter control circuit 51 at step S45, the main control circuit 47 proceeds to step S48 to reset the compressor heating flag of the RAM to off-state.

[0094] When determining at step S159 in FIG. 15 that the result of addition of the timer T has reached the result of setting of the wash time, the main control circuit 47 proceeds to step S162. The main control circuit 47 transmits an operation stop command for the drum motor 5 to the inverter control circuit 51 at step S162, stopping the operation of the drum motor 5. The main control circuit 47 then proceeds to step S163 to stop the operation of the outside air fan motor 37, thereby completing the wash processing.

[0095] FIG. 18 shows the compressor heating processing executed by the main control circuit 47 at steps S161, S37 and S47. The main control circuit 47 determines at step S171 whether the predetermined time T₂ has elapsed, based on the result of addition of the timer T. At step S171, the main control circuit 47 determines whether the predetermined time T₂ has further elapsed on the basis of the previous affirmative determination of lapse of the predetermined time T₂. When determining at step S171 that the predetermined time T₂ has elapsed, the main control circuit 47 proceeds to step S172 to detect an outlet temperature T_t based on the temperature signal delivered by the outlet temperature sensor 44, further proceeding to step S173 to detect the current result of setting of duty cycle C from the RAM.

[0096] Upon detection of the result of setting of the duty cycle C at step S173, the main control circuit 47 proceeds to step S174 to compare the result of detection of the outlet temperature T_t with an upper limit value T_u (40°C, for example) recorded on the ROM. When determining that T_t>T_u, the main control circuit 47 proceeds to step S175 to compare the result of detection of duty cycle C with a lower limit value C_low recorded on the ROM. When determining that C≥C_low, the main control circuit 47 proceeds to step S176 to subtract a predetermined unit value C1 recorded on the ROM from the result of detection of the duty cycle C. The main control circuit 47 then proceeds to step S180 to transmit the result of subtraction of the duty cycle C to the inverter control circuit 51. When receiving the result of subtraction of the duty cycle C, the inverter control circuit 51 energizes the specified two phase coils at the result of subtraction of the duty cycle C. More specifically, the main control circuit 47 reduces the current value of the duty cycle C of the specified two phase coils by the unit value C₁, thereby reducing the heating level of the compressor 33.

[0097] When determining at step S174 that T_t≤T_u, the main control circuit 47 proceeds to step S177 to compare the result of detection of the outlet temperature T_t with a lower limit temperature T_d (20°C, for example) recorded on the ROM. When determining that T_t≤T_d, the main control circuit 47 proceeds to step S178 to compare the result of detection of the duty cycle C with the upper limit value C_hi recorded on the ROM. When determining at step S178 that C≤C_hi, the main control circuit 47 adds the unit value C1 to the result of detection of the duty cycle C at step S179. The main control circuit 47 further proceeds to step S180 to transmit the result of addition of the duty cycle C to the inverter control circuit 51. When receiving the result of addition of the duty cycle C, the inverter control circuit 51 energizes the specified two phase coils of the compressor motor 34 at the result of reception of the duty cycle C. More specifically, the main control circuit 47 increases the current value of the duty cycle C by the unit value C₁ thereby to intensify the heating level of the compressor 34. Thus, in the compressor heating processing, the duty cycle is controlled so that the result of detection of the outlet temperature T_t falls within the range of the lower and upper limit values T_d and T_u.

[0098] The fourth embodiment can achieve the following advantages. The stator coil of the compressor motor 34 is energized at the wash processing so that the rotational shaft of the compressor motor 34 is not rotated. As a result, the influences of stagnation of liquefied refrigerant can be reduced before start of a drying processing. Accordingly, the drum inlet temperature T_di is increased rapidly in the drying processing. Consequently, the normal acceleration processing can be executed rapidly even when the result of detection of the room temperature T_r is at or below the frost formation estimation value T_f.

[0099] FIGS. 19A and 19B illustrate a fifth embodiment. A drying processing as shown in FIGS. 19A and 19B is executed by the main control circuit 47 instead of the drying processing in each of the first, second and fourth embodiments as shown in FIG. 10 and the drying processing in the third fourth embodiment as shown in FIG. 14. The main control circuit 47 proceeds to step S192 to compare the result of detection of the evaporator inlet temperature T_ei with an operation interrupt value T_c (-5°C, for example) recorded on the ROM. Step S192 is executed in each of the following cases 1 to 4. When determining at step S192 that T_ei≤T_c, the main control circuit 47 proceeds to step S193.

1. The case where the main control circuit 47 determines at step S77 that the result of detection of the evaporator inlet temperature T_ei is at or below the frost formation determination value T_i and at step S78 that the result of detection of the evaporator outlet temperature T_eo is at or below the frost formation determination value T_i;

2. The case where the main control circuit 47 determines at step S77 that the result of detection of the evaporator inlet temperature T_ei is at or below the frost formation determination value T_i, at step S78 that the result of detection of the evaporator outlet temperature T_eo is at or below the frost formation determination value T_i, and at step S79 that the result of detection of the operation frequency f of the compressor motor 34 is below the lower limit value flow;

3. The case where the main control circuit 47 determines at step S77 that the result of detection of the evaporator inlet temperature T_ei is at or below the frost formation determination value T_i, at step S78 that the result of detection of the evaporator outlet temperature T_eo is at or below the frost formation determination value T_i and at step S79 that the result of detection of the operation frequency f of the compressor motor 34 is below the lower limit value flow, and the main control circuit 47 subtracts a unit value f₃ from the result of detection of the operation frequency f at step S80 and transmits the result of subtraction of the operation frequency f to the inverter control circuit 51; and

4. The case where the main control circuit 47 determines at step S77 that the result of detection of the evaporator inlet temperature T_ei is above the frost formation determination value T_i and at step S81 that the result of detection of the evaporator outlet temperature T_eo is at or below the frost formation determination value T_i.

[0100] On proceeding step S193, the main control circuit 47 compares the result of detection of the evaporator outlet temperature T_eo with the operation interrupt value T_c. When determining that T_eo>T_c, the main control circuit 47 proceeds to step S87. When determining that T_eo≤T_c, the main control circuit 47 proceeds to step S194. The operation interrupt valve T_c serves as a third threshold used to determine whether frost is adherent to the fins 29 of the evaporator 27. The operation interrupt value T_f is set to be smaller than the frost formation estimation value T_f and the frost formation determination value T_i. When frost is adherent to the fins 29 of the evaporator 27, the main control circuit 47 determines that either detection result of the evaporator inlet temperature T_ei or detection result of the evaporator outlet temperature T_eo is lower than the operation interrupt value T_c, executing step S194.

[0101] On proceeding to step S194, the main control circuit 47 stops the operation of the fan motor 22. The main control circuit 47 then proceeds to step S195 to transmit an operation stop command for the compressor motor 34 to the inverter control circuit 51, whereby the operation of the compressor motor 34 is stopped. The main control circuit 47 further proceeds to step S196 to set the timer Ts to the initial value T₀. A predetermined value T₁ is to be added to the timer Ts in a timer interrupt processing as shown in FIG. 6. The main control circuit 47 resets the timer Ts at step C196, thereby starting an interrupt time measurement processing on the basis of operation stop of each of the fan motor 22 and the compressor motor 34.

[0102] When resetting the timer Ts at step S196, the main control circuit 47 proceeds to step S197 to compare the result of addition of the timer Ts with a constant value T₃ (60) recorded on the ROM. When determining that Ts=T₃, the main control circuit 47 proceeds to step S198 to detect the evaporator inlet temperature T_ei based on a temperature signal delivered by the evaporator inlet temperature sensor 45. Furthermore, the main control circuit 47 detects the evaporator outlet temperature T_eo based on a temperature signal delivered by the evaporator outlet temperature sensor 46 at step S199. The main control circuit 47 then compares the result of detection of the evaporator inlet temperature T_ei with an operation restart value T_k (1°C, for example) recorded on the ROM. The main control circuit 47 also compares the evaporator outlet temperature T_eo with the operation restart value T_k at step S201. The operation restart value T_k is used to determine whether frost adherent to the fins 29 of the evaporator 27 has melted and serves as a fourth threshold. When frost adherent to the fins 29 has not been melted, the main control circuit 47 determines that either result of detection of the evaporator inlet or outlet temperature T_ei or T_eo is at or below the operation restart value, returning to step S198. When frost adherent to the fins 29 has been melted, the main control circuit 47 determines that both results of detection of the evaporator inlet and outlet temperatures T_ei and T_eo are above the operation restart value T_k, proceeding to step S202.

[0103] On proceeding to step S202, the main control circuit 47 restarts the operation of the fan motor 22. The main control circuit 47 then proceeds to step S203 to set the operation frequency f to the initial value f₀, further to step S204 to transmit the result of initial setting of the operation frequency f to the inverter control circuit 51, and further to step S205 to transmit an operation restart command for the compressor motor 34 to the inverter control circuit 51. More specifically, when the operation of the fan motor 22 and the compressor motor 34 is stopped such that the results of detection of the evaporator inlet and outlet temperatures T_ei and T_eo are above the operation restart value T_k, the main control circuit 47 restarts the operation of the fan motor 22 and further restarts the operation of the compressor motor 34 from the initial value f₀.

[0104] When transmitting the operation restart command at step S205, the main control circuit 47 proceeds to step S206 to detect the result of addition of the timer Ts, further to step S207 to add the result of detection of the timer Ts to the result of setting of a drying time. This processing extends the result of the drying time by interrupt times of the respective fan motor 22 and compressor motor 34. When the result of setting of the drying time has been extended at step S207, the main control circuit detects the room temperature T_r based on the temperature signal delivered by the room temperature sensor 40 at step S208. The main control circuit 47 further compares the result of detection of the room temperature T_r with the frost formation estimation value T_f at step S209. When determining that T_r>T_f, the main control circuit 47 proceeds to step S59 in FIG. 9. When determining at step S209 that T_r<T_f, the main control circuit 47 proceeds to step S73 in FIG. 19A.

[0105] The fifth embodiment achieves the following advantages. When determining that the detection result of the room temperature T_r is at or below the frost formation estimation value T_f in the drying processing, the main control circuit 47 compares each of the detection results of evaporator inlet and outlet temperatures T_ei and T_eo with the operation interrupt value T_c. When determining that either result of detection of the evaporator inlet or outlet temperature T_ei or T_eo is at or below the operation interrupt value T_c, the main control circuit 47 stops the operation of each of the fan motor 22 and compressor motor 34. Accordingly, the main control circuit 47 stops the operation of the compressor motor 34 when frost has adhered to the fins 29 of the evaporator 27 even though the compressor motor 34 is being accelerated or decelerated both at the speed change rate f₃ or accelerated at the speed change rate f₄. As a result, the high-temperature refrigerant in the condenser 30 flows into the evaporator 27, whereupon frost adherent to the fins 29 can be melted by the heat of the refrigerant. Moreover, the main control circuit 47 compares the detection results of the evaporator inlet and outlet temperatures T_ei and T_eo with the operation restart value T_k while the fan motor 22 and compressor motor 34 are in off-state. When determining that both detection results of the evaporator inlet and outlet temperatures T_ei and T_eo are above the operation restart value T_k, the main control circuit 47 restarts the operation of the fan motor 22 and compressor motor 34. As a result, the hot air supply processing can be restarted in synchronization with meltdown of the frost adherent to the fins 29.

[0106] FIGS. 20A to 22 illustrate a sixth embodiment. Referring to FIGS. 20A and 20B, a heater 70 serving as a decompressor heater is mounted to the capillary tube 35. The heater 70 is used to apply heat to the capillary tube 35 and comprises a silicon film heater wound on the surface of the capillary tube 35. The heater 70 is connected via a heater drive circuit to the main control circuit 47. The heater drive circuit supplies a drive power to the heater 70 to electrically turn on the heater 70 and cuts off the drive power to turn off the heater 70. The main control circuit 47 controls the drive circuit thereby to turn on and off the heater 70.

[0107] FIGS. 21A and 21B show a drying processing executed by the main control circuit 47 instead of the drying processing of FIGS. 19A and 19B. The main control circuit 47 proceeds to a refrigerant recovery processing at step S210 when determining at step S192 in FIG. 21B that the result of detection of the evaporator inlet or outlet temperature T_ei or T_eo is at or below the operation interrupt value T_c. FIG. 22 shows the refrigerant recovery processing at step S210. The main control circuit 47 turns on the heater 70 at step S211. Te heater 70 is adapted to be operated with a duty cycle recorded on the ROM. When the heater 70 is in on-state, heat is applied to the capillary tube 35 such that the refrigerant is gasified in the capillary tube 35, which results in pressure loss. Accordingly, the gas acts as a wall in the capillary tube 35, thereby holding the flow of a liquefied high-pressure refrigerant. As a result, liquefied low-temperature refrigerant is moved through the compressor 33 into the condenser 30.

[0108] When turning on the heater 70 at step S211, the main control circuit 47 proceeds to step S21 to reset the timer Ts and further to step S213 to set the operation frequency f to a maximum frequency f_max (110 Hz). The main control circuit 47 further proceeds to step S214 to transmit the result of setting of the operation frequency f to the inverter control circuit 51, operating the compressor motor 32 at the maximum frequency f_maxl. The main control circuit 47 further proceeds to step S215 to control a motor drive circuit 56 so that the rotational speed of the fan motor 22 is increased to a maximum speed (4300 rpm, for example). The motor drive circuit 56 increases the voltage level of the drive power of the fan motor 22 to vary a rotational speed of the fan motor 22. The main control circuit 47 proceeds to step S216 when increasing the rotational speed of the fan motor 22 to the maximum speed at step S215.

[0109] On proceeding to the step S216, the main control circuit 47 compares the result of addition of the timer Ts with a predetermined value T₂ (120). When determining that T_s=T₂, the main control circuit 47 proceeds to step S217 to turn off the heater 70. The main control circuit 47 proceeds to step S194 to stop the operation of the fan motor 22 and further to step S195 to stop the operation of the compressor motor 34. Since the capillary tube 35 is cooled when the heater 70 is in off-state, the pressure difference causes high-temperature refrigerant in the condenser 30 to flow toward the evaporator 27. No refrigerant flows in the evaporator 27 such that the evaporator 27 is empty. Heat of the refrigerant is consumed to melt down the frost adherent to the fins 29 of the evaporator.

[0110] The sixth embodiment can achieve the following advantages. When determining that the detection result of evaporator inlet or outlet temperature T_ei or T_eo is at or below the operation interrupt value T_c, the main control circuit 47 turns on the heater 70 while both fan motor 22 and compressor motor 35 are in operation. In this operation of the heater 70, heat is applied to the capillary tube 35 such that the refrigerant is gasified in the capillary tube 35. The gas acts as a wall in the capillary tube 35, thereby holding the flow of a liquefied high-pressure refrigerant. As a result, the liquefied low-temperature refrigerant is moved through the compressor 33 into the condenser 30. The main control circuit 47 turns off the heater 70 at a predetermined time when a predetermined time has elapsed from turn-on of the heater 70, thereby stopping the operation of the fan motor 22 and the compressor motor 34. When the operation of the heater 70 is stopped, the pressure difference causes high-temperature refrigerant in the condenser 30 to flow toward the evaporator 27. Consequently, the frost adherent to the fins 29 can be melted by the heat of the refrigerant.

[0111] FIGS. 23A and 23B illustrate a seventh embodiment. As shown, the capillary tube 35 is wound on the surface of a suction pipe 80 in a contact state. The suction pipe 80 connects between the refrigerant pipes of the capacitor 30 and evaporator 72. Heat exchange takes place between the capillary tube 35 and the suction pipe 80 when the fan motor 22 and the compressor motor 34 are in operation.

[0112] The seventh embodiment achieves the following advantages. In the case where it is determined that the result of detection of the room temperature Tr is at or below the frost formation estimation value T_f in the drying processing, the high-temperature and high-pressure refrigerant discharged out of the compressor 33 flows into the capillary tube 35 while heat is being applied to the compressor motor 34 at the speed change rates Δf₃ and Δf₄. As a result, heat of the refrigerant is applied to the suction pipe 80. Accordingly, the temperature of the refrigerant is increased by the suction pipe 80, whereupon a saturation temperature of the evaporator 27 can be suppressed so as to be reduced below 0°C. Consequently, the normal acceleration processing can be executed more rapidly since the compressor motor 34 is accelerated at the speed variation Δf₃

[0113] In each of the foregoing embodiments 1 to 7, the operation frequency f of the compressor motor 34 may be set so that the detection results of the evaporator inlet and outlet temperatures T_ei and T_eo are above the frost formation determination value T_i.

[0114] In each of the foregoing embodiments, either evaporator inlet or outlet temperature sensors 45 or 46 may be eliminated.

[0115] In each of the foregoing embodiments, a first temperature sensor may be provided for detecting the temperature of the evaporator 27 may be provided, instead of the evaporator inlet temperature sensor 45, and a second temperature sensor may be provided for detecting the temperature of the evaporator 27, instead of the evaporator outlet temperature sensor 46. In this case, the second temperature sensor detects the temperature downstream of the refrigerant flow relative to the first temperature sensor.

Claims

1. A clothes dryer comprising:

a water-receiving tub (4) receiving water for washing laundry;

a wash tub (7) which is provided inside the water-receiving tub (4) and into which the laundry is put, the wash tub (7) being rotated by a washing motor (5) serving as a drive source;

an outer casing (1) which is hollow and encloses the water-receiving tub (4), the outer casing (1) having an opening (2) through which the laundry is put into and taken out of the wash tub (7);

a ventilation path (26) which is formed into an annular shape and includes the water-receiving tub (4) as a part thereof so that air in the water-receiving tub (4) is circulated;

a blower (24) which includes a fan motor (22) serving as a drive source and circulates air in the water-receiving tub (4) along the ventilation path (26);

an evaporator (27) provided in the ventilation path (26) so as to be located outside the water-receiving tub (4), the evaporator (27) including a first refrigerant pipe (28) through which a refrigerant flows and a plurality of fins (29) joined to an outer circumferential surface of the first refrigerant pipe (28), thereby cooling air flowing along the ventilation path (26) ;

a condenser (30) provided in the ventilation path (26) so as to be located outside the water-receiving tub (4) and having a second refrigerant pipe (31) connected to the first refrigerant pipe (28), thereby applying heat to air flowing along the ventilation path (26) downstream relative to the evaporator (27) ;

a compressor (33) supplying a refrigerant into the first and second refrigerant pipes (28, 31) in turn and including a speed-controllable compressor motor (34) serving as a drive source;

a decompressor (35) which throttles the refrigerant flowing between the first and second refrigerant pipes (28, 31), the decompressor (35) including a pipe having a fixed degree of opening;

an outside temperature sensor (40) which detects a temperature outside the outer casing (1);

an evaporator temperature sensor (45, 46) which detects a temperature of the evaporator (27);

an operation course setting unit (47) which sets an operation course to wash the laundry in the wash tub (7), the operation course including an operation course with a drying processing, in which the compressor motor (34) and the fan motor (22) are operated so that air which has been cooled by the evaporator (27) and to which heat has been applied by the condenser (30) is supplied into the wash tub (7);

a comparison unit (47) which determines whether a result of detection by the outside temperature sensor (40) is larger than a predetermined first threshold when the compressor motor (34) in a stopped state is operated in the drying processing, the first threshold being used as a temperature on which whether frost adheres to the fins (29) of the evaporator (27) when the compressor motor (34) in the stopped state is accelerated by a predetermined normal pattern;

a first speed setting unit (47) which sets a rotational speed of the compressor motor (34) when a result of detection by the outside temperature sensor (40) has been determined to be larger than the first threshold, the first speed setting unit (47) increasing the rotational speed of the compressor motor (34) by the normal pattern when the compressor motor (34) in the stopped state is operated;

a second speed setting unit (47) which sets a rotational speed of the compressor motor (34) when the result of detection by the outside temperature sensor (40) has been determined not to be larger than the first threshold, the second speed setting unit (47) setting the rotational speed of the compressor motor (40) so that a result of detection by the evaporator temperature sensor (45, 46) is lower than the first threshold and is higher than a second threshold at which frost adheres to the fins (29) of the evaporator (27), when the compressor motor (34) in the stopped state is operated in the drying processing; and

a motor drive unit (51) which rotates the compressor motor (34) in the drying processing based on a result of setting by the first speed setting unit (47), when the result of detection by the outside temperature sensor (40) has been determined to be larger than the first threshold, the motor drive unit (51) rotating the compressor motor (34) in the drying processing based on a result of setting by the second speed setting unit (47) when the result of detection by the outside temperature sensor (40) has been determined not to be larger than the first threshold.

2. The clothes dryer according to claim 1, wherein the operation course setting unit (47) sets an operation course in which a dehydration processing is carried out before the drying processing, the dehydration processing including rotating the washing motor (5) so that water is centrifugally extracted from the laundry in the wash tub (7), and both of the compressor motor (34) and the fan motor (22) are operated in the dehydration processing so that air which has been cooled by the evaporator (27) and to which heat has been applied by the condenser (30) is supplied into the wash tub (7).

3. The clothes dryer according to claim 1 or 2, further comprising an auxiliary electrical heater (60) provided in the ventilation path (26) so as to be located outside the water-receiving tub (4), thereby applying heat to air flowing along the ventilation path (26) downstream relative to the evaporator (27), the auxiliary electrical heater (60) being operated when the compressor motor (34) is rotated based on a result of setting by the second speed setting unit (47).

4. The clothes dryer according to any one of claims 1 to 3, wherein the operation course setting unit (47) sets an operation course in which a wash processing is carried out before the drying processing, the wash processing including rotating the washing motor (5) so that the laundry in the wash tub (7) is washed with water containing a detergent, and a coil of the compressor motor (34) is energized in the wash processing so that a rotational shaft of the compressor motor (34) is not rotated.

5. The clothes dryer according to any one of claims 1 to 4, wherein:

while the compressor motor (34) is being rotated based on a result of setting by the second speed setting unit (47) in the drying processing, the operation course setting unit (47) compares a result of detection by the evaporator temperature sensor (45, 46) with a third threshold to determine whether frost has adhered to the evaporator (27), the third threshold being lower than the first and second thresholds;

the operation course setting unit (47) stops the fan motor (22) and the compressor motor (34) both in operation when determining that a result of detection by the evaporator temperature sensor (45, 46) is equal to or lower than the third threshold;

the operation course setting unit (47) compares a result of detection by the evaporator temperature sensor (45, 46) with a predetermined fourth threshold when both the fan motor (22) and the compressor motor (34) are stopped, the fourth threshold being used to determine whether frost adherent to the evaporator (27) has melted down or not; and

the operation course setting unit (47) restarts operation of the fan motor (22) and the compressor motor (34) when determining that a result of detection by the evaporator temperature sensor (45, 46) is larger than the fourth threshold.

6. The clothes dryer according to claim 5, further comprising a decompressor electrical heater (70) which applies heat to the decompressor (35), wherein when having determined that the result of detection by the evaporator temperature sensor (45, 46) is equal to or lower than the third threshold, the operation course setting unit (47) switches the decompressor heater (70) from a stopped state to an operating state before both of the fan motor (22) and the compressor motor (34) are stopped, and the operation course setting unit (47) stops the operating state of the decompressor heater (70) when a predetermined time has elapsed from the operating state of the decompressor heater (70).

Drawing