Drum type washing machine

Abstract

 A washing machine includes a water tub (8), a rotating tub (10) rotatably mounted in the water tub (8) so that laundry is put into the rotating tub (10), a water supply unit (53) for supplying water into the water tub (8), and a foam detector (37, 46, 47) for detecting foam produced in the rotating tub (10). The washing machine may further include a determining unit (92) for determining whether an amount of foam produced in the rotating tub (10) is abnormal, on the basis of a result of detection by the foam detector (37, 46, 47) and a foam restricting unit (92) for restricting the amount of foam produced in the rotating tub (10) when the determining unit (92) has determined that the amount of foam produced in the rotating tub (10) is abnormal.

Description

[0001] This invention relates generally to automatic washing machines comprising a water tub and a rotating tub rotatably mounted in the water tub, and more particularly to drum type washing machines.

[0002] Low foaming detergents have been recommended for use with conventional drum type washing machines. An amount of foam produced in a wash step is relatively smaller in the case of low foaming detergents than in the case of non-low-foaming or ordinary synthetic detergents. A rotating tub is rotated at a relatively low speed in the wash step so that laundry falls from an upper interior of the rotating tub to a lower interior of the rotating tub in the wash step. In this case, a large amount of foam produced in the rotating tub moderates an impact due to fall of laundry, thereby reducing a washing effect.

[0003] Furthermore, when a large amount of foam is produced in the wash step, the foam enters a space between the rotating tub and a water tub during a dehydration step, thereby preventing the rotating tub from rotation. As a result, since the rotational speed of the rotating tub is not sufficiently increased, the laundry is insufficiently dehydrated or rotation of the rotating tub is interrupted.

[0004] The non-low-foaming detergents or ordinary synthetic detergents are more available and less expensive and have more types than the aforesaid low foaming detergents. Accordingly, a drum type washing machine with which the ordinary synthetic detergents can be used have been desired.

[0005] Therefore, an object of the present invention is to provide a washing machine from which a desired washing effect can be achieved without interruption of rotation of the rotating tub even when a non-low-foaming detergent is used.

[0006] The present invention provides a washing machine which comprises a wash tub, a rotating tub rotatably mounted in the wash tub so that laundry is put into the rotating tub, and water supply means for supplying water into the water tub, characterized by foam detecting means for detecting foam produced in the rotating tub.

[0007] According to the above-described construction, the foam detecting means detects an amount of foam produced in the rotating tub during the washing operation. Accordingly, since an abnormal condition is quickly found thereby to be coped with suitably, a sufficient washing effect can be achieved when either the low-foaming detergent or the non-low-foaming detergent is used.

[0008] In a preferred form, the washing machine is further characterized by determining means for determining whether an amount of foam produced in the rotating tub is abnormal on a basis of a result of detection by the foam detecting means, and foam restricting means for restricting the amount of foam produced in the rotating tub when the determining means has determined that the amount of foam produced in the rotating tub is abnormal. Since an amount of foam in the rotating tub is restricted to a small value, the rotating tub can be prevented from being blocked by the foam produced therein.

[0009] In another preferred form, the washing machine is further characterized by an outer casing in which the water tub and the rotating tub are mounted. In this construction, the rotating tub has a front formed with an opening, the water tub has a front formed with an opening, and the outer casing has a front formed with an access opening communicating with the opening of the water tub. The washing machine is further characterized by a door mounted on the front of the outer casing so as to close and open the access opening, locking means for locking the door in a closed state, interrupt instructing means operable to interrupt a washing operation, and lock control means for causing the locking means to unlock the door. The lock control means prevents the locking means from unlocking the door when the interrupt instructing means has been operated under a condition where the determining means has determined that the amount of foam produced is abnormal. Consequently, when a large amount of foam is produced in the rotating tub, the foam can be prevented from overflowing from the access opening.

[0010] In further another preferred form, the washing machine is further characterized by drying means for drying the laundry in the rotating tub, the drying means including a heat exchanger having a duct communicating with an interior of the water tub. The foam detecting means includes an air trap communicating with the duct and a pressure sensor for detecting a pressure in the air trap.

[0011] The invention will be described, merely by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a longitudinally sectional side view of a drum type washing machine of a first embodiment in accordance with the present invention;

FIG. 2 is a front view of the washing machine;

FIG. 3 illustrates an operation panel;

FIG. 4 is a plan view of the washing machine with an upper panel of an outer cabinet being eliminated;

FIG. 5 is a rear view of the washing machine with a rear panel of the outer cabinet being eliminated;

FIG. 6 is a rear view of an air trap of a heat exchanger;

FIG. 7 is a view taken along line 7-7 in FIG. 6;

FIG. 8 is a schematic block diagram showing an electrical arrangement of the washing machine;

FIG. 9 is a graph showing the relationship between an output frequency of a pressure sensor and pressure in the air trap;

FIG. 10 is a flowchart showing a STANDARD course;

FIG. 11 is a flowchart showing a wash step;

FIGS. 12A and 12B are timing charts showing operations of a water-supply valve and a rotating tub in the wash step;

FIG. 13 is a flowchart showing a water supplying operation in the wash step;

FIG. 14 is a graph showing changes in the output of the pressure sensor during an agitating operation in the wash step;

FIG. 15 illustrates an error code indicating that a door locking device is inoperative;

FIG. 16 is a flowchart showing a rinse step;

FIG. 17 is a flowchart showing a final draining operation of the rinse step in the washing machine of a second embodiment in accordance with the invention;

FIG. 18 illustrates the air trap to which water has been supplied under the condition where a connecting member between the air trap and a duct is clogged with lint;

FIG. 19 is a graph showing changes in the output of the pressure sensor when water has been supplied into the air trap under the condition where the connecting member is clogged with lint;

FIG. 20 is a flowchart showing a water supplying operation of the rinse step in the washing machine of a third embodiment in accordance with the invention;

FIGS. 21A, 21B and 21C are timing charts showing operations of a water-supply valve, heating element and rotating tub in the washing machine of a fourth embodiment in accordance with the invention;

FIG. 22 illustrates an error code indicating that operation has been interrupted due to abnormal occurrence of foam;

FIG. 23 is a view similar to FIG. 5, showing the washing machine of a fifth embodiment in accordance with the invention;

FIG. 24 is a view similar to FIG. 4;

FIG. 25 is a view similar to FIG. 6;

FIG. 26 is a view taken along line 26-26 in FIG. 25;

FIG. 27 is a graph showing the relationship between a ratio of an amount of water supplied into the duct to an amount of water supplied into the air trap and a dehumidifying performance of the heat exchanger;

FIG. 28 is a view similar to FIG. 7, showing the duct and air trap of the washing machine of a sixth embodiment in accordance with the invention;

FIG. 29 is a view similar to FIG. 7, showing the duct and air trap of the washing machine of a seventh embodiment in accordance with the invention;

FIG. 30 is a view similar to FIG. 7, showing the duct and air trap of the washing machine of an eighth embodiment in accordance with the invention;

FIG. 31 is a view similar to FIG. 7, showing the duct and air trap of the washing machine of a ninth embodiment in accordance with the invention; and

FIG. 32 is a view similar to FIG. 7, showing the duct and air trap of the washing machine of a tenth embodiment in accordance with the invention.

[0012] A first embodiment of the present invention will be described with reference to FIGS. 1 to 16. In the first embodiment, the invention is applied to a drum type washer-drier. Referring to FIGS. 1 and 2, an overall construction of the washer-drier is shown. A generally rectangular box-shaped outer cabinet 1 has a front formed with a circular access opening 5. A door 2 is hingedly mounted on the front of the cabinet 1 for opening and closing the access opening 5. An operation panel 3 is provided on an upper front of the cabinet 1. An operation circuit unit 6 is provided in the cabinet 1 so as to be located in the rear of the operation panel 3. A control circuit unit 7 is also provided in the cabinet 1 so as to be located in the rear of a lower front of the cabinet 1.

[0013] A drum-like water tub 8 is mounted in the cabinet 1 so as to be inclined rearwardly downward. The water tub 8 is supported by two suspension mechanisms 9 and has a front formed with a circular opening 13. An elastic member such as a rubber bellows 15 connects the opening 13 to the access opening 5 of the cabinet 1 with watertightness. A drum-like rotating tub 10 is rotatably mounted in the water tub 8. The rotating tub 10 is also inclined rearwardly downward so as to be substantially coaxial with the water tub 8. The rotating tub 10 serves as a dehydration tub, wash tub and drying tub. The rotating tub 10 has a front formed with a circular opening 14 and includes a circumferential wall and a rear end panel each formed with a number of through holes 11 serving to cause water or air to pass therethrough. The rotating tub 10 has a plurality of baffles 12 formed on an inner surface of the circumferential wall thereof.

[0014] An electric motor 16 is mounted on a generally central part of the rear end panel of the water tub 8 for driving the rotating tub 10. The motor 16 is of the outer rotor type in which a rotor is disposed outside a stator. The motor 16 includes a stator 16a, a rotor 16b and a rotational shaft 16c. A bearing support for supporting a bearing is fixed on a generally central part of the rear end panel of the water tub 8 though none of them are shown. The stator 16a is mounted on an outer circumference of the bearing support. The rotational shaft 16c is rotatably mounted on the bearing. The rotational shaft 16c has a front end extending through the rear end panel of the water tub 8, being secured to a generally central portion of the rear end panel of the rotating tub 10. The rotating tub 10 is thus directly rotated by the motor 16.

[0015] An outwardly protruding water reservoir 17 is formed on a lowermost portion of the circumferential wall of the water tub 8 so as to be integral with the circumferential wall. A heating element 18 for heating washing liquid is enclosed in the water reservoir 17. A drain hole 17a is formed in a rear end of the bottom of the water reservoir 17. A drain valve 19 and a drain hose 20 both serving as draining means are connected to the drain hole 17a.

[0016] Referring to FIGS. 1, 4 and 5, a drier 33 serving as drying means is provided over the rear, upper and upper front portions of the water tub 8. More specifically, a heater 22 and blower 21 are disposed before and behind on the upper portion of the water tub 8. The blower 21 includes a casing 23, a blowing blade 24 provided in the casing 23, and an electric motor 25 fixed to an outer part of the casing 23 for driving the blowing blade 24. A belt transmission mechanism 26 connects the motor 25 to the blowing blade 24. The heater 22 includes a casing 27 and a heating element 28 disposed in the casing 27. The casing 27 has a rear end connected to a discharge side of the casing 23. A duct 29 has one of two ends connected to the front end of the casing 27. The other end of the duct 29 is connected to an upper front circumferential wall of the water tub 8.

[0017] A heat exchanger 30 is provided in the rear of the water tub 8 in the casing 1. The heat exchanger 30 comprises a duct 30a provided on the left hand of the rear end panel of the water tub 8 as viewed in FIG. 5. The duct 30a is curved along the outer circumference of the rear end panel. The rear end panel of the water tub 8 has an air inlet 31 formed to correspond to a lower portion of the duct 30a. The air inlet 31 also serves as a water inlet. The duct 30a has an air outlet 32 formed in an upper portion thereof. The duct 30a is connected through the air outlet 32 to a suction side of the casing 23. A water feed conduit 34 extends horizontally in the upper interior of the duct 30a as shown in FIG. 5. The conduit 34 has a number of spraying holes 34a formed in a lower portion thereof. A right-hand end of the conduit 34 projects out of the duct 30a as viewed in FIG. 5. A projecting portion of the conduit is provided with a connecting member 34b, which is connected via a water feed conduit 35 to a water supply unit 53. The water supply unit 53 serves as dehumidifying water supply means. Each of the conduits 34 and 35 serves as a dehumidifying water supply passage. The conduit 35 also serves as a dehumidifying water supply tube. The water supply unit 53 will be described in detail later. Heat exchange is caused between air in the duct 30a and water supplied through the spraying holes 34a in the above-described heat exchanger 30. The air in the duct 30a is thus cooled to be dehumidified. Accordingly, the heat exchanger 30 is of the water cooling type. The above-described blower 21, heater 22 and heat exchanger 30 constitute a drier 33.

[0018] Referring further to FIG. 5, a temperature sensor 67 is mounted on a lower portion of the rear end plate of the water tub 8. The temperature sensor 67 comprises a thermistor, for example and detects a water temperature and an air temperature in the water tub 8. A pressure sensor 47 and a water level sensor 49 are provided in an upper rear interior of the cabinet 1. The water level sensor 49 is connected via an air conduit 50 to an air trap (not shown) to detect a water level in the water tub 8. The pressure sensor 47 is connected via an air conduit 46 to another air trap 37 to detect pressure in the air trap 37. The pressure sensor 47 has a sensitivity about ten times higher than the water level sensor 49, designed to be capable of detecting a small pressure in an order of several hundreds [Pa].

[0019] The air trap 37 is mounted on a rear wall of the duct 30a and has three tabs 41, and the rear wall of the duct is formed with three bosses 43 corresponding to the tabs 41 respectively, as shown in FIGS. 6 and 7. Screws 45 are screwed through the tabs 41 and bosses 43 respectively so that the air trap 37 is mounted to the duct 30a. The air trap 37 has front, upper and side connecting members 38, 39 and 40. The rear wall of the duct 30a has a connecting member formed to correspond to a lower portion of the air trap 37 and projecting rearward. The connection has an opening 42. The connecting member 38 is inserted into the opening 42 with a sealing member such as an O-ring 44 being interposed therebetween. Thus, the air trap 37 is connected to the duct 30 airtightly and watertightly. In this case, a distal end of the connecting member 38 is adapted to be coplanar with the inner face of the duct 30a. The pressure sensor 47 is connected through the conduit 46 to the connecting member 39. The connecting member 40 is connected through a water feed conduit 51 to the water supply unit 53. Accordingly, the water supply unit 53 serves as air trap water-supply means, and the conduit 51 serves as an air trap water-supply passage.

[0020] When a detergent and water are supplied into the water tub 8 and foam is produced in the rotating tub 10, part of the foam enters the water tub 8 through the holes 11 and opening 14. The foam further enters the duct 30a through the air inlet 31. When an amount of foam is large, the foam having entered the duct 30a further enters the air trap 37 through the connecting member 38, whereupon a pressure in the air trap 37 varies. Accordingly. the air trap 37, conduit 46, pressure sensor 47 constitute a foam detector 48 serving as foam detecting means. The pressure sensor 47 delivers a frequency signal according to the detected pressure. FIG. 9 shows the relationship between an output frequency of a pressure sensor and pressure in the air trap 37.

[0021] A pump 57 for supply of bathwater is provided in the left-hand upper rear interior of the cabinet 1 as shown in FIGS. 1, 4 and 5. The pump 57 has a priming hole 58, a water inlet 59 and a water outlet 60. A hose (not shown) is connected to the water inlet 59 so that bathwater is pumped up from a bathtub (not shown).

[0022] A water-feeding case 61 is provided in an upper left-hand front interior of the casing 1. The water-feeding case 61 is connected to the water tub 8 through a water-supply conduit 62 connected to the underside of the case. The water outlet 60 and priming hole 58 of the pump 57 are connected through respective conduits 63 and 64 to the water-feeding case 61. A detergent case 4 (see FIG. 2) is accommodated in the water-feeding case 61. The detergent case 4 has a detergent reserving section and a softener reserving section neither of which is shown.

[0023] The water supply unit 53 is disposed on the right of the pump 57 in the cabinet 1. The pump 57 and water supply unit 53 serve as water supply means. The water supply unit 53 has one water inlet 56 and four water outlets, none of which are shown. Water-supply valves 36, 52, 54 and 55 are mounted on the water outlets respectively. The water inlet 56 is connected via a hose (not shown) to a faucet of a water service. The conduit 35 is connected to the water supply valve 36. The conduit 51 is connected to the water supply valve 52. The water supply valves 54 and 55 are connected via conduits 65 and 66 to the water feed case 61 respectively.

[0024] Bathwater supplied through the conduit 63 into the water feed case 61 passes through the detergent reserving section of the detergent case 4 and is thereafter supplied into the water tub 8. Tap water supplied through the conduit 65 into the water feed case 61 also passes through the detergent reserving section of the detergent case 4 and is thereafter supplied into the water tub 8. On the other hand, tap water supplied through the conduit 66 into the water feed case 61 passes through the softener reserving section of the detergent case 4 and is thereafter supplied into the water tub 8.

[0025] The operation panel 3 will now be described in detail with reference to FIG. 3. The operation panel 3 includes various operation switches such as a power supply switch 68, START/INTERRUPT switch 69 serving both as a start switch and as an interrupt switch, COURSE switch 72, WARM WATER mode switch 73, and DETERGENT switch 75. The START/INTERRUPT switch 69 serves as interrupt indicating means. The COURSE switch 72 is operated to set various courses of a washing operation and a drying operation. The WARM WATER mode switch 73 is operated to set a WARM WATER mode in which warm water is used in a washing operation. The DETERGENT switch 75 is operated to set either normal detergent (non-low-foaming detergent) or low foaming detergent as a type of detergent to be used in the washing operation. In the following description, an ORDINARY SYNTHETIC DETERGENT mode refers to a mode in which an ordinary synthetic detergent is used in the washing operation, and a LOW FOAMING DETERGENT mode refers to a mode in which a low foaming detergent is used in the washing operation.

[0026] The operation panel 3 further includes various display sections such as a COURSE display section 77, DETERGENT MODE display section 83, and detergent quantity display section 81. The COURSE display section 77 displays a washing course set by the COURSE switch 72. The DETERGENT MODE display section 83 includes a single light-emitting diode (LED), which is turned on when the ORDINARY SYNTHETIC DETERGENT mode has been set by the DETERGENT switch 75. The detergent quantity display section 81 displays a quantity of detergent, a remaining time of the washing operation and an error code indicative of the contents of an error upon occurrence of the error.

[0027] FIG. 8 shows an electrical arrangement of the washer-drier. A control circuit 92 serving as control means comprises a microcomputer and stores a control program for controlling an overall washing operation and an overall drying operation. An input circuit 93 delivers an operation signal to the control circuit 92. The water level sensor 49, rotation sensor 94 and turbidity sensor 95 also deliver respective signals to the control circuit 92. Furthermore, the dryness sensor 96, pressure sensor 47 and temperature sensor 67 also deliver respective signals to the control circuit 92.

[0028] The input circuit 93 delivers a signal in response to operation of each of the switches except the power supply switch 68 on the operation panel 3. The rotation sensor 94 delivers a signal according to a rotational position of the motor 16. The turbidity sensor 95 comprises a photosensor detecting a turbidity of wash liquid in the water tub 8, for example and delivers a signal according to a detected turbidity of the wash liquid. The dryness sensor 96 delivers a signal according to a dryness of the laundry (dryness factor) and comprises a thermistor detecting a temperature in the duct 30a of the heat exchanger 30 and another thermistor detecting a temperature in the water tub 8.

[0029] The motor 16 is connected via an inverter circuit 97 to the control circuit 92. A buzzer 98 and a display circuit 99 are connected via a drive circuit 101 to the control circuit 92. The heating elements 18 and 28, drain valve 19 and motor 25 are also connected via the drive circuit 101 to the control circuit 92. Furthermore, the pump 57, water supply valves 36, 52, 54 and 55 and door locking device 100 are also connected via the drive circuit 101 to the control circuit 92. The display circuit 99 is connected to one of the display sections on the operation panel 3. The door locking device 101 serves as locking means for locking the door 2 in a closed state and comprises an electromagnet, for example.

[0030] The control circuit 92 and motor 16 constitute driving means. The control circuit 92 constitutes determining means, foam restricting means, rinsing executing means and lock control means.

[0031] The operation of the washer-drier will be described with reference to FIGS. 10 to 16. The following describes the operation in a STANDARD course in washing and drying courses. In the STANDARD course, the control circuit 92 carries out an initial setting (step S1) on the basis of operation of the START/INTERRUPT switch 69 and sets a water level in the water tub 8 (step S2), as shown in FIG. 10. Thereafter, the control circuit 92 carries out a wash step (step S3), a first dehydration step (step S4), a rinse step (step S5), a second dehydration step (step S6) and a drying step (step S7) sequentially in this order. The control circuit 92 incorporates a RAM onto which data of the numbers of times of an agitating operation and a dehydrating operation in a rinse step is written in the initial setting. Furthermore, the flag F is set at "0" in the initial setting. The flag F shows whether the door locking device is operable to unlock the door. The flag F is set at "0" when the door locking device is operable to unlock the door. The flag F is set at "1" when the door locking device is inoperable to unlock the door. The flag F will be described in detail later. The water level in the water tub 8 is determined on the basis of an amount of laundry in the rotating tub 10. The amount of laundry in the rotating tub 10 is detected on the basis of a rotational speed of the motor 16 and accordingly, a rotational speed of the rotating tub 10 in a case where a predetermined input current is supplied to the motor so that the latter is driven.

[0032] Referring to FIGS. 11 to 13, water supply is first executed in the wash step (step S31). The water-supply valve 54 is opened in the wash step (S311). Tap water is supplied through the conduit 65 and the water feed case 61 into the water tub 8 together with the detergent. The control circuit 92 then inputs an output frequency of the pressure sensor 47 to determine whether the output frequency is equal to or lower than a threshold X (kHz) (step S312). The threshold X was experimentally obtained on the basis of foam in the rotating tub 10 and output of the pressure sensor 47. An amount of foam is abnormally large when the output frequency of the pressure sensor 47 is equal to or lower than the threshold X. This abnormal condition occurs when an ordinary synthetic detergent is erroneously used even though the washer-drier is set at a LOW-FOAMING DETERGENT mode or an amount of detergent is erroneous.

[0033] When the output frequency of the pressure sensor 47 is higher than the threshold X (NO at step S312) or when an amount of foam is normal, the control circuit 92 advances to step S313 to determine whether the water level in the water tub 8 has reached a starting level for the preliminary agitation on the basis of the output of the water level sensor 49. When the starting water level has been reached in the tub 8 (YES at step S313), the control circuit 92 advances to step S314 to start the preliminary agitation. In the preliminary agitation, the rotating tub 10 is intermittently driven so that tap water and the detergent are mixed together. More specifically, the motor 16 is energized to be rotated in the normal direction at 50 rpm for 5 seconds, deenergized for 2 seconds, energized to be rotated in the reverse direction at 50 rpm for 5 seconds and deenergized for 2 seconds repeatedly sequentially in this order, as shown in FIG. 11.

[0034] The control circuit 92 then advances to step S315 to determine whether a water level in the tub 8 has reached the set level. When the water level in the tub 8 has reached the set level (YES at step S315), the control circuit 92 finishes the preliminary agitation and closes the water-supply valve 54 thereby to finish the water supply (steps S316 and S317). On the other hand, the control circuit 92 returns to step S312 when the set water level has not been reached in the tub 8 (NO at step S315). Furthermore, when the output frequency of the pressure sensor 47 is equal to or lower than the threshold X (YES at step S312), the control circuit 92 advances to step S316 to finish the preliminary agitation and to close the water-supply valve 54 thereby to finish the water supply. Upon finish of the water supply, the control circuit 92 actuates the door locking device so that the door 2 is locked in the closed state (step S32). The control circuit 92 then drives the rotating tub 10 so that the tub is rotated in both directions continuously alternately (agitating operation). More specifically, the motor 16 is energized to be rotated in the normal direction at 60 rpm for 20 seconds, deenergized for 2 seconds, energized to be rotated in the reverse direction at 60 rpm for 20 seconds and deenergized for 2 seconds repeatedly sequentially in this order, as shown in FIG. 12.

[0035] The control circuit 92 then determines whether the output frequency of the pressure sensor 47 is equal to or lower than the threshold Z (step S34). In a case where the output frequency of the pressure sensor 47 is equal to or lower than the threshold Z, foam leaks out of the access opening 5 when the door 2 has been closed. The threshold Z is set so as to be larger than the threshold X. In a case where the output frequency of the pressure sensor 47 is higher than the threshold Z (NO at step S34), there is no possibility that foam leaks out of the access opening 5 when the door 2 has been opened. Accordingly, the control circuit 92 determines that the door locking device 100 is operable to release the door 2 from the locked state, setting the flag F at "0" (step S35). On the other hand, in a case where the output frequency of the pressure sensor 47 is equal to or lower than the threshold Z (YES at step S34), there is a possibility that foam leaks out of the access opening 5 when the door 2 has been opened. Accordingly, the control circuit 92 determines that the door locking device 100 is inoperable to release the door 2 from the locked state, setting the flag F at "1" (step S36).

[0036] The control circuit 92 then determines whether the output frequency of the pressure sensor 47 is equal to or lower that the threshold X (step S37). The control circuit 92 advances to step S39 when the output frequency of the pressure sensor 47 is higher than the threshold X (NO at step S37). On the other hand, when the output frequency of the pressure sensor 47 is equal to or lower than the threshold X (YES at step S37), the control circuit 92 opens the drain valve 19 for a predetermined time so that part of the wash liquid in the water tub 8 is discharged (step S38), thereafter advancing to step S39. As a result, the level of the foam is reduced such that a space used for the foam in the wash tub 8 can be increased, and an amount of foam produced with the washing operation can be reduced.

[0037] FIG. 14 shows changes in the output of the pressure sensor 47 during an agitating operation in the wash step. Curves D1, D2 and D3 in FIG. 14 designate a case where an amount of foam is large, a case where an amount of foam is normal, and a case where an amount of foam is small, respectively. Foam is gradually produced in the rotating tub 10 with the agitation. When an amount of foam is large, the foam reaches near the opening 42 (connecting member 38) in the duct 30a at an early stage after start of the agitation, whereupon pressure in the air trap 37 starts rising. The output of the pressure sensor 47 starts lowering according to the pressure increase. On the other hand, when a foam amount is normal, the output of the pressure sensor 47 starts lowering a short time after start of the agitation. Furthermore, in a case where a foam amount is small, foam does not almost reach near the opening 42 even when the agitation is carried out. Accordingly, the output of the pressure sensor 47 does not almost change.

[0038] The control circuit 92 further determines at step S39 whether the START/INTERRUPT switch 69 has been operated for interrupt. When the START/INTERRUPT switch 69 has not been operated, the control circuit 92 determines whether an agitating time has expired (step S40). When the agitating time has not expired (NO at step S40), the control circuit 92 returns to step S34, repeating the foregoing processing. On the other hand, when the agitating time has expired (YES at step S40), the control circuit 92 deenergizes the motor 16 to finish the agitation (step S41). Thereafter, the control circuit 92 opens the drain valve 19 so that an overall wash liquid is discharged from the water tub 8 (step S42).

[0039] On the other hand, when the START/INTERRUPT switch 96 has been operated (YES at step S39), the control circuit 92 deenergizes the motor 16 to interrupt the agitation (step S43). The control circuit 92 then advances to step S44 to determine whether the flag F is set at "1." When the flag F is set at "0" (NO at step S44), the door 2 is released from the locked state (step S45). Thereafter, the control circuit 92 advances to step S46 to be on standby for re-operation of the START/INTERRUPT switch 69. On the other hand, when the flag F is set at "1" (YES at step S44), the control circuit 92 advances to step S46. Accordingly, the user cannot open the door 2 even though he or she wishes to add laundry during the agitation. Consequently, the door 2 can be prevented from being opened in the condition where a foam amount in the rotating tub 10 is large, whereby foam can be prevented from leaking out of the access opening 5. Furthermore, the control circuit 92 operates the display section 81 so that an error code, "E: -d" as shown in FIG. 15 is displayed thereon. The error code indicates that the door 2 cannot be released from the locked state due to a large amount of foam in the rotating tub 10.

[0040] When the START/INTERRUPT switch 69 has been operated (YES at step S46), the control circuit 92 advances again to step S32 to operate the door locking device 100 so that the door 2 is locked in the closed state. Thereafter, the control circuit 92 restarts the agitation. The control circuit 92 advances to a first dehydration step of step S4 in FIG. 10 when the foregoing wash step has been finished. The control circuit 92 drives the motor 16 (and accordingly the rotating tub 10) so that the motor is rotated at high speeds in one direction with the drain valve 19 remaining open.

[0041] The control circuit 16 then advances to the rinse step of step S5. In the rinse step, the water-supply valve 55 is first opened so that water is supplied up to a set level, as shown in FIG. 16 (step S51). When the set level has been reached, agitation is carried out in which the motor 16 is rotated in both directions alternately repeatedly with the water-supply valve 55 remaining open (step S52). In this case, a drive timing of the motor 16 is the same as that of the agitation in the wash step. Upon start of the agitation, the control circuit 92 determines whether the output frequency of the pressure sensor 47 is equal to or lower than a threshold Y (step S53). The threshold Y is set so as to be approximately equal to or slightly larger than the threshold X. When the output of the pressure sensor is larger than the threshold Y (NO at step S53), the control circuit 92 advances to step S54 to determine whether an agitating time has expired. When the agitating time has not expired yet (NO at step S54), the control circuit 92 returns to step S53. When the agitating time has expired (YES at step S54), the control circuit 92 deenergizes the motor 16 thereby to finish the agitation (step S55).

[0042] Upon finish of the agitation, the control circuit 92 opens the drain valve 19 so that an overall wash liquid is discharged from the water tub 8 (step S56). The control circuit 92 then advances to step S57 in which "1" is added to the number N of times of the agitating and draining operation. The control circuit 92 then advances to step S58 to determine the number N has reached a predetermined number M. When the number N has not reached the number M, the control circuit 92 returns to step S51. On the other hand, the control circuit 92 finishes the rinse step when the number N has reached the number M. The number M is set at "1" or "3" on the basis of a result of detection by the turbidity sensor 90 in the LOW-FOAMING-DETERGENT mode, whereas the number M is set at "4" in the ORDINARY SYNTHETIC DETRGENT mode.

[0043] Upon finish of the rinse step, the control circuit 92 advances to step S6 to carry out a second dehydration step in FIG. 10. The control circuit 92 drives the motor 16 so that the motor is rotated at high speeds in one direction with the drain valve 19 remaining open. Upon finish of the dehydration step, the control circuit 92 advances to step S7 to carry out a drying step. In the drying step, the control circuit 92 drives the motor 16 (and accordingly the rotating tub 10) so that the motor is rotated at low speeds in both directions alternately repeatedly. Furthermore, the control circuit 92 drives the blower 21. The control circuit 92 further energizes the heating element 28 of the heater 22 and opens the water-supply valves 36 and 52. As a result, humid air in the rotating tub 10 is caused to flow through the holes 11 as shown by arrows A in FIGS. 1 and 5 to be sucked through the air inlet 31 into the duct 30a. Furthermore, water is sprayed from the spraying holes 34a into the duct 30a as shown by arrows B in FIGS. 1 and 5. Additionally, water is supplied through the connecting member 40 into the duct 30a as shown by arrows C in FIG. 7. Consequently, the air sucked into the duct 30a is condensed by the water sprayed from the spraying holes 34a to be dehumidified. The dehumidified air is caused to flow through the air outlet 32 into the casing 23 of the blower 21. The dehumidified air is further caused to flow through the case 27 of the heater 22 and duct 29 in turn to be returned into the water tub 8 and accordingly the rotating tub 10. Thus, the air in the rotating tub 10 is rendered warm by the foregoing circulation and is dehumidified, whereupon the laundry is dried.

[0044] In the above-described case, lint L1 resulting from the laundry is circulated with air. There is a possibility that the lint L1 may be caught by the connecting member 38 between the duct 30a and the air trap 37. This would change the relationship between an amount of foam produced in the rotating tub 10 and pressure in the air trap 37. As a result, the state of foam could not be detected accurately. In the embodiment, however, water is supplied through the tube 51 and the connecting member 40 into the duct 30a as shown by arrows C in FIG. 7. Accordingly, the lint L1 caught by the connecting member 38 can be caused to fall into the duct 30a with the water.

[0045] FIGS. 17 to 19 illustrate a second embodiment of the invention. Only the differences of the second embodiment from the first embodiment will be described. Identical parts in the second embodiment are labeled by the same reference symbols as those in the first embodiment. The second embodiment differs from the first embodiment in the final draining in the rinse step (the M-th draining). Referring to FIG. 17, processing for the final draining is shown. The control circuit 92 opens the drain valve 19 so that wash liquid is discharged from the wash tub 8 (step S201). The control circuit 92 then determines whether a water level in the tub 8 is equal to or lower than a reset level (step S202). The reset level refers to a lowermost water level the water level sensor 49 can detect. When the water level in the wash tub 8 is equal to or lower than the reset level (YES at step S202), the control circuit 92 opens the water-supply valve 52 so that water is supplied into the air trap 37 (step S203).

[0046] The control circuit 92 then inputs the output frequency of the pressure sensor 47 to determine whether the output frequency is equal to or lower than a threshold P (step S204). In step S204, the control circuit 92 determines whether the connecting member 38 is clogged with lint. For example, in a case where water is supplied into the air trap 37 when the connecting member 38 has been clogged with lint as the result of the previous drying, the water W remains in the air trap 38 as shown in FIG. 18. The remaining water raises pressure in the air trap 37. FIG. 19 shows changes in the output frequency of the pressure sensor 47 when water has been supplied into the air trap under the condition where the connecting member 38 is clogged with lint. As obvious from FIG. 19, the output frequency of the pressure sensor 47 is rapidly reduced with lapse of time or as an amount of water remaining in the air trap 37 increases. The output frequency is finally reduced to about 36 kHz. In the embodiment:, the threshold P is set at, for example, 37 kHz which value is much lower than the output of the pressure sensor 47 upon occurrence of foam.

[0047] When determining that the output frequency of the pressure sensor 47 is larger than the threshold P (NO at step S204), the control circuit 92 advances to step S205 to determine whether a predetermined time for the examining process has expired. When determining that the predetermined time has not expired yet (NO at step S205), the control circuit 92 returns to step S204. When determining that the predetermined time has expired (YES at step S205), the control circuit 92 closes the water-supply valve 52 so that water supply to the air trap 37 is interrupted (step S206). On the other hand, when determining that the output frequency of the pressure sensor 47 is equal to or lower than the threshold P (YES at step S204), the control circuit 92 starts a timing operation of a timer which is not shown (step S207). When the condition where the output is equal to or lower than the threshold P continues for 5 seconds (YES at step S208), the control circuit 92 determines that the connecting member 38 has been clogged with lint and stores data of the determination (step S209). The control circuit 92 then advances to step S206 to close the water-supply valve 52 so that the water supply to the air trap 37 is interrupted.

[0048] The rinse step is completed upon finish of the above-described final draining. The second dehydration step and drying step are successively carried out in turn. When storing data of determination that the connecting member 38 has been clogged with lint, at step S209, the control circuit 92 activates the buzzer 98 upon finish of the drying step and displays an error code (not shown) on the display section 81. Consequently, the user can find that the connecting member 38 has been clogged with lint. Thus, that the connecting member 38 is clogged with lint is informed of when the overall operation has been finished. The reason for this is that a foam amount is detected by the pressure sensor 47 in neither dehydration step nor drying step. Furthermore, the dehydration or drying step need not be interrupted.

[0049] FIG. 20 illustrates a third embodiment of the invention. Only the differences of the third embodiment from the first embodiment will be described. In the third embodiment, the control circuit 92 determines, during water supply in the rinse step, whether the connecting member 38 of the air trap 37 has been clogged with lint. Referring to FIG. 20, processing for a water supplying operation of the rinse step is shown. The control circuit 92 opens the water-supply valve 52 so that water supply to the air trap 37 starts (step S301). The control circuit 92 further opens the water-supply valve 54 so that water supply to the water tub 8 starts (step S302).

[0050] The control circuit 92 then inputs the output frequency of the pressure sensor 47 to determine whether the output frequency is equal to or lower than the threshold P (step S303). In step S303, the control circuit 92 determines whether the connecting member 38 is clogged with lint in the same manner as in step S204. When determining that the output frequency of the pressure sensor 47 is higher than the threshold P (YES at step S303), the control circuit 92 advances to step S304 to determine whether the set water level has been reached in the water tub 8. When determining that the set water level has not been reached (NO at step S304), the control circuit 92 returns to step S303. On the other hand, when determining that the set water level has been reached (YES at step S304), the control circuit 92 closes the water-supply valve 52 to stop water supply to the air trap 37 (step S305), advancing to the agitation.

[0051] On the other hand, when determining that the output frequency of the pressure sensor 47 is equal to or lower than the threshold P (YES at step S303), the control circuit 92 starts a timing operation of a timer which is not shown (step S308). When the condition where the output is equal to or lower than the threshold P continues for 5 seconds (YES at step S309), the control circuit 92 determines that the connecting member 38 has been clogged with lint and stores data of the determination (step S310). The control circuit 92 then advances to step S305 to close the water-supply valve 52 so that the water supply to the air trap 37 is interrupted. Consequently, the same effect can be achieved from the third embodiment as from the second embodiment.

[0052] FIGS. 21A to 22 illustrate a fourth embodiment of the invention. Only the differences of the third embodiment from the first embodiment will be described. FIGS. 21A, 21B and 21C show operations of a water-supply valve, heating element and rotating tub in the wash step under a WARM WATER mode, respectively. The WARM WATER mode is set by the WARM WATER mode switch 73. In the WARM WATER mode, the heating element 18 is energized when the set water level is reached in the water tub 8. Energization to the heating element 18 is continued until the temperature detected by the temperature sensor 98 increases to 60°C.

[0053] The rotating tub 10 is intermittently rotated alternately in both directions during energization to the heating element 18. More specifically, the motor 16 is driven at 30 rpm in the normal direction for 2 seconds, interrupted for 38 seconds, driven at 30 rpm in the reverse direction for 2 seconds, and interrupted for 38 seconds, repeatedly in this order. When the temperature detected by the temperature sensor 98 has been increased to 60°C, the rotating tub 10 is rotated continuously alternately in both directions (agitation). More specifically, the motor 16 is driven at 60 rpm in the normal direction for 20 seconds, interrupted for 2 seconds, driven at 60 rpm in the reverse direction for 20 seconds, and interrupted for 2 seconds, repeatedly in this order. The agitation is carried out for a set period of time.

[0054] In parallel with the above-described control of the tub 10, the control circuit 92 carries out a process for determining whether an foam amount in the tub 10 is abnormal, on the basis of the output frequency of the pressure sensor 47 at predetermined intervals. This determining process is substantially the same as described in the first embodiment. When determining that the foam amount is abnormal, during energization to the heating element 18, the control circuit 92 deenergizes the heating element 18 and motor 16. The control circuit 92 further causes the display section 81 to display an error code, "E: -U" as shown in FIG. 22.

[0055] When determining that the foam amount is abnormal in the wash step, the control circuit 92 opens the drain valve 19 so that part of wash liquid is discharged from the water tub 8, as described above. Accordingly, there is a possibility of an excessive heating by the heating element 18 since the water level in the water tub 8 is lower than a usual level. However, since the heating element 18 and motor 16 are turned off in the above-described construction, the wash liquid in the water tub 8 can be prevented from being excessively heated.

[0056] FIGS. 23 to 27 illustrate a fifth embodiment of the invention. Only the differences of the fifth embodiment from the first embodiment will be described. A generally Y-shaped joint 111 connects between the connecting member 34b of the water feed pipe 34 of the heat exchanger 30 and the water feed tube 35, as shown in FIG. 23. The joint 111 has a branch 111a to which one end of a conduit 112 is connected. The air trap 37 has a connecting member 113 serving as an inlet port, instead of the connecting member 40, as shown in FIGS. 25 and 26. The connecting member 113 is disposed near the connecting member 38 on one side of the air trap 37. The other end of the conduit 112 is connected to the connecting member 113. The water supply device 53 includes one inlet section 56 (see FIG. 24) and three outlet sections none of which are shown. The water-supply valves 36, 54 and 55 are mounted on the outlet sections respectively. Thus, the water supply unit 53 is not provided with an output section having a water-supply valve 52.

[0057] When the water-supply valve 36 of the water supply unit 53 is opened in the drying step, tap water is supplied through the conduit 35 to be sprayed through the spraying holes 34a of the conduit 34 into the duct 30a. Simultaneously, tap water is supplied through the conduits 35 and 112 and connecting member 113 into the air trap 37. Since the connecting member 113 is disposed near the connecting member 38, the tap water supplied through the connecting member 113 into the air trap 37 efficiently flows to lint caught on the connecting member 38. Consequently, the lint can be eliminated from the connecting member 38 more efficiently.

[0058] A flow rate per hour through the conduit 112 is set so as to be equal to or one half of a flow rate through the conduit 35, so that a reduction in the dehumidifying performance of the heat exchanger 30 can be prevented. The inventors conducted an experiment to examine changes in the dehumidifying performance of the heat exchanger 30 with changes in a ratio of an amount of water supplied into the duct 30a (W1) to an amount of water supplied into the air trap 37 (W2). The experiment was carried out under a water temperature of 10°C. FIG. 27 shows experimental results. As obvious from FIG. 27, the dehumidifying performance is gradually reduced when the amount of water supplied to the air trap 37 exceeds the amount of water supplied into the duct 30a.

[0059] FIG. 28 illustrates a sixth embodiment of the invention. Only the differences of the sixth embodiment from the first embodiment will be described. In the sixth embodiment, the air trap 37 includes a lower inclined face 121 inclined toward the connecting member 38. Consequently, water supplied through the connecting member 40 into the air trap 37 can be caused to smoothly pass through the connecting member 38. Consequently, the: lint can be eliminated from the connecting member 38 more efficiently.

[0060] FIG. 29 illustrates a seventh embodiment of the invention. Only the differences of the seventh embodiment from the first embodiment will be described. Water sprayed through the spraying holes 34a of the conduit 34 is directed to a lower rear interior of the duct 30a as shown by arrows F in FIG. 29. In this construction, too, the lint caught on the connecting member 38 can be removed by the water sprayed from the spraying holes 34a.

[0061] FIG. 30 illustrates an eighth embodiment of the invention. Only the differences of the eighth embodiment from the seventh embodiment will be described. In the eighth embodiment, the rear inner face of the duct 30a is formed into a mirror surface 131. In this construction, the lint having entered the duct 30a is prevented from easily adhering to the rear inner surface of the duct. Further, the lint can easily be removed even when adhering to the rear inner surface. Consequently, lint can be prevented from being caught by the connecting member 38.

[0062] FIG. 31 illustrates a ninth embodiment of the invention. Only the differences of the ninth embodiment from the eighth embodiment will be described. In the ninth embodiment, a water-repellent fluorine-contained resin 141 is coated on the rear inner surface of the duct 30a, instead of the mirror surface 131. Consequently, the same effect can be achieved from the ninth embodiment as from the eighth embodiment.

[0063] FIG. 32 illustrates a tenth embodiment of the invention. Only the differences of the tenth embodiment from the first embodiment will be described. In the tenth embodiment, an inner peripheral edge of the opening 42 is formed into a tapered surface 42a. The distal end of the connecting member 38 is located in the rear of the tapered surface 42a. Consequently, lint can be prevented from being caught by the connecting member 38.

[0064] In the foregoing embodiments, the rotational speed of the motor 16 may be reduced when the control circuit determines that a foam amount in the washing operation is abnormal. Furthermore, part of the wash liquid in the water tub 8 may be discharged and the rotational speed of the motor 16 may be reduced. Consequently, an amount of foam produced during the washing operation after determination can be reduced.

[0065] When determining that the flag F is not set at "0" (step S44), the control circuit may activate the buzzer to inform that the door cannot be released from the locked state. Furthermore, both buzzer activation and error code display may be carried out.

[0066] Whether the connecting member 38 is clogged with lint may be determined during the water supply or draining in the wash step, or the draining in the rinse step. The overall inner surface of the duct 30a may be formed into the mirror surface. Furthermore, the overall inner surface of the duct 30a may be coated with the fluorine-contained resin.

[0067] The foregoing description and drawings are merely illustrative of the principles of the present invention and are not to be construed in a limiting sense. Various changes and modifications willl become apparent to those of ordinary skill in the art. All such changes and modifications are seen to fall within the scope of the invention as defined by the appended claims.

Claims

1. A washing machine which comprises a water tub (8), a rotating tub (10) rotatably mounted in the water tub (8) so that laundry is put into the rotating tub (10), and water supply means (53) for supplying water into the water tub (8), characterized by foam detecting means (37, 46, 47) for detecting foam produced in the rotating tub (10).

2. A washing machine according to claim 1, further characterized by determining means (92) for determining whether an amount of foam produced in the rotating tub is abnormal on a basis of a result of detection by the foam detecting means (37, 46, 47) and foam restricting means (92) for restricting the amount of foam produced in the rotating tub (10) when the determining means (92) has determined that the amount of foam produced in the rotating tub (10) is abnormal.

3. A washing machine according to claim 2, further characterized by driving means (16, 92) for driving the rotating tub (10), and characterized in that when during a water supplying operation by the water supply means (53), the determining means (92) has determined that the amount of foam produced is abnormal, the foam restricting means (92) interrupts the water supplying operation by the water supply means (53) and causes the driving means (16, 92) to drive the rotating tub (10).

4. A washing machine according to claim 2, further
characterized by driving means (16, 92) for driving the rotating tub (10), draining means (19) for draining water from the water tub (8), and rinse executing means (92) controlling the water supplymeans (53) and driving means (16, 92) for executing rinsing the laundry, and characterized in that when during a rinsing operation by the rinse executing means (92), the determining means (92) has determined that the amount of foam produced is abnormal, the foam restricting means (92) interrupts drive of the rotating tub (10) and causes the draining means (19) to execute a draining operation.

5. A washing machine according to claim 1, further characterized by an outer casing (1) in which the water tub (8) and the rotating tub (10) are mounted, characterized in that the rotating tub (10) has a front formed with an opening (14), the water tub (8) has a front formed with an opening (13), and the outer casing (1) has a front formed with an access opening (5) communicating with the opening (13) of the water tub (8), further characterized by a door (2) mounted on the front of the outer casing (1) so as to close and open the access opening (5), locking means (100) for locking the door (2) in a closed state, interrupt instructing means (69) operable to interrupt a washing operation, and lock control means (92) for causing the locking means (69) to unlock the door (2), and characterized in that the lock control means (92) prevents the locking means (100) from unlocking the door (2) when the interrupt instructing means (69) has been operated under a condition where the determining means (92) has determined that the amount of foam produced is abnormal.

6. A washing machine according to claim 1, further characterized by drying means (33) for drying the laundry in the rotating tub (10), the drying means (33) including a heat exchanger (30) having a duct (30a) communicating with an interior of the water tub (8), and characterized in that the foam detecting means (37, 46, 47) includes an air trap (37) communicating with the duct (30a) and a pressure sensor (47) for detecting a pressure in the air trap (37).

7. A washing machine according to claim 6, further characterized by air trap water supply means (53) for supplying water into the air trap (37).

8. A washing machine according to claim 6, characterized in that the heat exchanger (30) includes dehumidifying water supply means (53) for supplying water into the duct (30a) so that air in the duct (30a) is dehumidified and a dehumidifying water supply passage (34, 35) through which the water is supplied into the duct (30a), and characterized in that the dehumidifying water supply passage (34, 35) has an en route branch through which water is supplied into the air trap (37).

9. A washing machine according to claim 8, characterized in that an amount of water supplied into the air trap (37) per time is smaller than an amount of water supplied into the duct (30a) per time.

10. A washing machine according to claim 7, characterized in that the air trap (37) has a water inlet (113) through which the water supplied by the air trap water supply means (53) flows into the air trap (37), and the water inlet (113) is located near a junction between the air trap (37) and the duct (30a).

11. A washing machine according to claim 7, further characterized by an air trap water supply passage (51) through which the water is supplied from the air trap water supply means (53) into the air trap (37), the air trap (37) being inclined downward toward the air trap water supply means (53).

12. A washing machine according to claim 7, characterized in that the air trap (37) has a face (121) formed in a lower portion thereof so as to be inclined downward toward a portion thereof communicating with the duct (30a).

13. A washing machine according to claim 6, characterized in that the heat exchanger (30) includes dehumidifying water supply means (53) for supplying water into the duct (30a) so that air in the duct (30a) is dehumidified, a water feed conduit (34) provided in the duct (30a) and having a number of spraying holes (34a), and a dehumidifying water supplying tube (35) connecting between the dehumidifying water supplying means (53) and the water feed conduit (34), and that the water supplied through the spraying holes (34a) into the duct (30a) is adapted to flow toward a portion of the air trap (37) communicating with the duct (30a).

14. A washing machine according to claim 6, characterized in that the duct (30a) has an inner face including at least a portion to which the air trap (37) is connected, said portion being mirror-finished.

15. A washing machine according to claim 6, characterized in that the duct (30a) has an inner face including at least a portion to which the air trap (37) is connected, said portion having water repellency.

16. A washing machine according to claim 6, characterized in that the duct (30a) has a connecting member (38) to which the air trap (37) is connected, said connecting member (38) including a portion located in the duct (30a) and having a chamfered peripheral edge.

17. A washing machine according to claim 7, characterized in that the duct (30a) has a connecting member (38) to which the air trap (37) is connected, and further characterized by clogged lint determining means (92) for determining whether the connecting member (38) is clogged with lint, based on an output of the pressure sensor (47) in a case where water has been supplied by the air trap water supply means (53) into the air trap (37).

18. A washing machine according to claim 17, further characterized by washing operation executing means for sequentially executing a washing operation, a rinsing operation at a plurality of times, and a dehydrating operation, and alarming means (81) actuated at a time of completion of the washing operation when the clogged lint determining means (92) has determined that the connecting member (38) is clogged with lint, during a final rinsing operation.

Drawing