TECHNICAL FIELD
[0001] The present invention relates to an air conditioner, and particularly to an air conditioner
provided with a receiver for collecting surplus refrigerant.
BACKGROUND ART
[0002] A refrigerant circuit of an air conditioner is formed of a refrigerant pipe structure
connecting an accumulator, a compressor, a four-way valve and an outdoor heat exchanger,
which are arranged in an outdoor unit, as well as an indoor heat exchanger arranged
in an indoor unit, and provides a circulation path of refrigerant.
[0003] When the refrigerant circuit of the air conditioner operate for cooling, the dour-way
valve controls a refrigerant circulating direction such that the outdoor heat exchanger
functions as a condenser, and the indoor heat exchanger functions as an evaporator.
In a heating operation, the four-way valve controls the refrigerant circulating direction
such that the outdoor heat exchanger functions as an evaporator, and the indoor heat
exchanger functions as a condenser.
[0004] In the above air conditioner, it is desired in view of ease of installation that
the refrigerant circuit on the outdoor unit side is filled with an appropriate amount
of refrigerant containing an additional amount of refrigerant, which is required for
a connection pipe of a maximum length. However, the appropriate amount of refrigerant,
which is required during an operation, significantly changes depending on an operation
mode, a capacity of the indoor unit and a length of the connection pipe used for actual
installation. Therefore, surplus refrigerant may be present in the refrigerant circuit,
and this may cause abnormal rising of a pressure when it remains in the condenser,
and may lower the operation efficiency.
[0005] For deal with such surplus refrigerant, it has been proposed to arrange a receiver
between the outdoor heat exchanger and a liquid shut-off valve for collecting the
surplus refrigerant.
[0006] In a conventional receiver circuit, a receiver is arranged in a pipe portion on a
liquid pipe side between the outdoor heat exchanger and the liquid shut-off valve,
and is located in series thereto. Therefore, the amount of refrigerant in the receiver
increases or decreases merely in accordance with a degree of opening of a motor-operated
valve located downstream from the receiver. This motor-operated value corresponds
to each room motor-operated value in a cooling operation, and corresponds to a main
pressure reducing value, and the degree of opening thereof is controlled based on
a degree of super-heating. Therefore, it is difficult to control or adjust precisely
the amount of liquid refrigerant in the receiver, and particularly, it is impossible
to control the amount of liquid refrigerant in the receiver when a special operation
such as an operation with a low outside-air temperature or with an excessive load.
[0007] For example, when a cooling operation is performed when the outside-air temperature
is extremely low, the outdoor heat exchanger has an excessively large capacity so
that the pressure on the high-pressure side lowers. Therefore, a difference between
the high and low pressures of the compressor decreases, which lowers reliability of
the compressor. If the surplus refrigerant, which is collected in the receiver, can
be transferred to the outdoor heat exchanger, a portion of the outdoor heat exchanger
can be filled with the surplus refrigerant. Thereby, the capacity of the outdoor heat
exchanger lowers, and the pressure on the high-pressure side rises so that a sufficient
pressure difference can be ensured.
[0008] Further,
JP 60-114669 A discloses an air-conditioner having the features of the preamble of claim 1.
JP 2000-146 322 A discloses an air-conditioner using a temperature sensor and a pressure sensor downstream
of the evaporator to calculate the super-cooling degree based on the measured values.
Based on the calculated super-cooling degree the circulating flow rate of the refrigerant
is changed.
DISCLOSURE OF THE INVENTION
[0009] An object of the invention is to control surplus refrigerant in accordance with operation
situations such as a cooling operation at a lower outside-air temperature and an operation
with an excessive load.
[0010] An air conditioner according to the invention is defined in claim 1. Embodiments
are named in the dependent claims.
[0011] The presence/absence of the surplus refrigerant is determined in the heating operation
by comparing a high-pressure corresponding saturation temperature with a target value
of the high-pressure corresponding saturation temperature.
[0012] In the heating operation, the target temperature of the high-pressure corresponding
saturation temperature may be determined from an amount of circulated refrigerant
and a room temperature, or may be determined from an operation frequency of the compressor
and the room temperature.
[0013] The target value of the high-pressure corresponding saturation temperature may be
corrected based on a deviation in super-heat control or target discharge pipe temperature
control.
[0014] The target value of the high-pressure corresponding saturation temperature may be
equal to or lower than a sum of a high-pressure saturation temperature and a predetermined
value, and may be equal to or higher than a sum of a room temperature and a predetermined
value.
[0015] Further, the air conditioner may be configured such that the gas pipe motor-operated
valve operates in the heating operation to open when the high-pressure corresponding
saturation temperature is lower than the target temperature, and to close when the
high-pressure corresponding saturation temperature is higher than the target temperature.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016]
Fig. 1 schematically shows a refrigerant circuit of an air conditioner employing an
embodiment of the invention;
Figs. 2 to 5 are control flowcharts depicting control of surplus refrigerant in cooling
operation;
Figs. 6 to 9 are control flowcharts depicting control of surplus refrigerant in cooling
operation;
Figs. 10 to 13 are control flowcharts depicting control of surplus refrigerant in
heating operation;
Figs. 14 to 17 are control flowcharts depicting control of surplus refrigerant according
to the present invention;
Fig. 18 is a control block diagram;
Fig. 19 is a control block diagram of a compressor drive circuit;
Fig. 20 is a flowchart showing a manner of estimating a high-pressure corresponding
saturation temperature; and
Fig. 21 shows a table for calculating a saturation temperature.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
(Schematic Structure)
[0017] An air conditioner employing a first embodiment of the invention has a refrigerant
circuit shown in Fig. 1.
[0018] An outdoor unit 100 includes an outdoor refrigerant circuit provided with a compressor
101, a four-way valve 102, an outdoor heat exchanger 103 and an accumulator 105. A
discharge-side pressure protection switch 108 is arranged on the discharge side of
the compressor 101 for detecting abnormal rising of the discharge pressure. An intake-side
pressure sensor 110 is arranged on the intake side of the compressor 101 for detecting
an intake pressure.
[0019] An oil separator 107 is arranged on the discharge side of the compressor 101 for
separating and returning lubricating oil contained in the refrigerant to the accumulator
105. The oil separator 107 is provided with a discharge pipe thermistor 109 for detecting
a temperature on the discharge side of the compressor 101.
[0020] An oil return pie 197 of the oil separator 107 is provided with a discharge bypass
circuit 194, which is branched from the oil return pipe 197, and is connected to an
inlet side of the accumulator 105. This discharge bypass circuit 194 is provided with
a heat exchanger pipe portion 196 arranged within the accumulator 105 and a discharge-intake
motor-operated valve 142 for capacity control. The oil return pipe 197 of the oil
separator 107 is provided with a capillary 141, which is also connected to the intake
side of the accumulator 105.
[0021] The outdoor unit 100 is also provided with an outside-air thermistor 111 for detecting
an outside-air temperature, an outdoor heat exchange thermistor 112 for detecting
an outlet temperature of the outdoor heat exchanger 103, and an heat exchange intermediate
thermistor 113 for detecting an heat exchanger intermediate temperature. The outdoor
unit 100 is further provided with a fan 106 for performing heat exchange between the
outside air taken into the unit 100 and the refrigerant flowing within the outdoor
heat exchanger 103, and a fan motor 104 for driving the fan 106.
[0022] The refrigerant pipe extending from the outdoor unit 100 toward the indoor unit is
provided with a liquid pipe connection port 114 connected to the outdoor heat exchanger
103, and a gas pipe connection port 115 connected to the outdoor heat exchanger 103
via the four-way valve 102. The ports 114 and 115 are internally provided with a liquid
pipe shut-off valve 116 and a gas pipe shut-off valve 117, respectively.
[0023] The outdoor unit 100 includes a receiver 121 for temporarily storing surplus refrigerant
liquid, which flows from the outdoor heat exchanger 103 serving as a condenser in
the cooling operation. The receiver 121 is provided with a liquid pipe connection
pipe 122 and a gas pipe connection pipe 123. The liquid pipe connection pipe 122 is
connected to a liquid-side pipe portion 131 between the outdoor heat exchanger 103
and the liquid pipe shut-off valve 116. The gas pipe connection pipe 123 is connected
to a gas-side pipe portion 132 between the four-way valve 102 and the gas pipe shut-off
valve 117.
[0024] The liquid pipe connection pipe 122 of the receiver 121 is provided with a liquid
pipe motor-operated valve (EVL) 128 having a pressure reducing function and a refrigerant
shut-off function. The gas pipe connection pipe 123 is provided with a gas pipe motor-operated
valve (EVG) 129.
[0025] An auxiliary heat exchanger 133 is arranged between the gas pipe motor-operated valve
129 and a connection to the gas-side pipe portion 132. A sub-cool heat exchanger 134
is arranged in a liquid-side outlet of the outdoor heat exchanger 103.
[0026] A gas vent capillary 130 is directed toward a portion of the gas-side pipe portion
132 between the four-way valve 102 and the gas pipe shut-off valve 117 for collecting
a refrigerant gas from the receiver 121.
[0027] A plurality of branch units 300A, 300B,
··· are connected to each of the liquid pipe connection port 114 and the gas pipe connection
port 115 of the outdoor unit 100. Since these branch units 300A, 300B, ... have the
same structures, the description will now be given on only the branch unit 300A, and
the others will not be described.
[0028] The branch unit 300A includes an outdoor side liquid pipe connection port 301 connected
to the liquid pipe connection port 114 of the outdoor unit 100 and an indoor side
gas pipe connection port 303 connected to the gas pipe connection port 115 of the
outdoor unit 100. The branch unit 300A has liquid-side branches divided within the
outdoor side connection port 301, and ends of these branches form a plurality of indoor
side liquid pipe connection ports 302 equal in number to the indoor units connected
thereto. The branch unit 300A also has gas-side branches divided within the outdoor
side gas pipe connection port 303, and ends of these branches form indoor side gas
pipe connection ports 304 equal in number to the indoor units connected thereto. In
the following description, it is assumed that the indoor units connected to the ports
are three in number, and indoor side liquid pipe connection ports 302A, 302B and 302C
as well as indoor side gas pipe connection ports 304A, 304B and 304C are employed.
A motor-operated valve 308 for bypass is arranged between the outdoor side liquid
pipe connection port 301 and the outdoor side gas pipe connection port 303.
[0029] The branches, which extend from the outdoor side liquid pipe connection port 301
within the branch unit 300A to the indoor side liquid pipe connection ports 302A -
302C, respectively, are provided with motor-operated valves 305A - 305C for reducing
the pressures of the refrigerant flowing therethrough as well as liquid pipe thermistors
306A - 306C for detecting temperatures of the refrigerant flowing therethrough, respectively.
The branches, which extend from the outdoor side gas pipe connection port 303 within
the branch unit 300A to the indoor side gas pipe connection ports 304A - 304C, respectively,
are provided with gas pipe thermistors 307A - 307C for detecting the temperatures
of the refrigerant flowing therethrough, respectively.
[0030] Each of the branch units 300A, 300B, ... is connected to a plurality of outdoor units
200. It is assumed in the structure shown in Fig. 1 that three outdoor units can be
connected to each of the branch units 300A, 300B, ... so that outdoor units 200A -
200C are connected to the branch unit 300A, and outdoor units 200D - 200F are connected
to the branch unit 300B. Each of the indoor units 200A - 200F can be used in the indoor
unit of either a multi-unit type or a pair-unit type. In the following description,
the indoor unit 200A is of the pair-unit type.
[0031] The indoor unit 200A is provided with an indoor heat exchanger 201, which is connected
to a refrigerant pipe extending toward the outdoor unit through a liquid pipe connection
port 204 and a gas pipe connection port 205. The indoor unit 200A is provided with
a room temperature thermistor 202 for detecting a room temperature and an indoor heat
exchange thermistor 203 for detecting a temperature of the indoor heat exchanger 201.
[0032] If the indoor units connected to the branch units 300A and 300B is of the multi-unit
type, the liquid-side pipe portion may be provided with a liquid pipe thermistor for
detecting the temperature of the refrigerant flowing therethrough, in which case the
liquid pipe thermistors in the branch units 300A and 300B may be eliminated.
(Surplus Refrigerant Control in Cooling Operation)
[0033] In the cooling operation, the surplus refrigerant is controlled in accordance with
a liquid pipe temperature. This will be described below with reference to a flowchart
of Fig. 2.
[0034] In a step S11, it is determined whether a surplus refrigerant control sampling time
TSCSET has elapsed or not. When it is determined that an elapsed time counted by a
timer has reached the surplus refrigerant control sampling time TSCSET, the processing
moves to a step S12.
[0035] In the step S12, the target liquid pipe temperature is calculated.
[0036] The processing of calculating the target liquid pipe temperature will now be described
with reference to a flowchart of Fig. 3.
[0037] In a step S21, a variable DOATD is calculated in accordance with the following formula
using target liquid pipe temperature calculation coefficients KSCC1, KSCC2, KSCC3
and EDOSC, a target frequency FMK of the compressor 101, a discharge pipe temperature
deviation EDO and others.
[0038] In a step S22, it is determined whether the variable DQATD is larger than a lower
limit DQMTMIN of the target liquid pipe temperature or not. When it is determined
that the variable DOATD is not larger than the lower limit DOATDMIN of the target
liquid pipe temperature, the processing moves to a step S23. In the step S23, the
value of variable DOATD is set to the lower limit DOATDMIN of the target liquid pipe
temperature.
[0039] In a step S24, it is determined whether the variable DOATD is equal to or smaller
than ((upper limit DOATDMAX of target liquid pipe temperature) - (outside air temperature
DOA)) or not. When it is determined that the variable DOATD is larger than ((upper
limit DQATDMAX of target liquid pipe temperature) - (outside air temperature DOA)),
the processing moves to a step S25. In the step S25, the value of variable DQATD is
set to ((upper limit DQATDMAX of target liquid pipe temperature) - (outside air temperature
DOA)).
[0040] In a step S26, a target liquid pipe temperature DELSET is calculated. In this embodiment,
the following formula is employed for this calculation.
[0041] In a step S13, a liquid pipe temperature deviation ΔDEL is calculated from the target
liquid pipe temperature DELSET and the outdoor heat exchanger outlet temperature DEL
in accordance with the following formula.
[0042] In a step S14, processing is performed to calculate an amount or degree, by which
the motor-operated valve is to be operated.
[0043] This processing of calculating the motor-operated valve operation amount is shown
in a flowchart of Fig. 4.
[0044] In a step S31, a motor-operated valve operation amount POSC is calculated in accordance
with the following formula using coefficients KOSCA1 and KOSCA, which are coefficients
for calculating the motor-operated valve operation amount, the liquid pipe temperature
deviation ΔDEL, the last liquid pipe temperature deviation ΔDELZ and others.
[0045] In a step S15, the motor-operated valve is operated in accordance with the operation
amount determined in the step S14.
[0046] Processing of operating the motor-operated valve is shown in a flowchart of Fig.
5.
[0047] It is assumed that a degree EVL of opening of the liquid pipe motor-operated valve
128 is defined by ((current degree EVL) + (motor-operated valve operation amount POSC)).
At the same time, a degree EVG of opening of the gas pipe motor-operated valve 129
is controlled to attain ((current degree EVG) + (operation amount POSC) x KPOSC1).
[0048] The liquid pipe temperature during the cooling operation can be determined from a
value detected by the outdoor heat exchange thermistor 112 arranged at the vicinity
of the outlet of the outdoor heat exchanger 103. Based on the liquid pipe temperature,
it is possible to control the amount of the surplus refrigerant in the receiver 121.
[0049] Therefore, even when the cooling operation is performed while an outside-air temperature
is low, the amount of the surplus refrigerant is controlled to ensure a difference
between high and low pressures in the compressor 101.
(Control of Surplus Refrigerant in Cooling Operation)
[0050] Referring to a flowchart of Fig. 6, description will now be given on control of surplus
refrigerant performed with a high-pressure corresponding saturation temperature in
the cooling operation. It is assumed that the same refrigerant circuit as that in
the first embodiment is used for controlling the surplus refrigerant in the cooling
operation.
[0051] In a step S51, it is determined whether a surplus refrigerant control sampling time
TSCSET has elapsed or not. When it is determined that an elapsed time counted by the
timer has reached the surplus refrigerant control sampling time TSCSET, the processing
moves to a step S52.
[0052] In the step S52, the target high-pressure corresponding saturation temperature is
calculated.
[0053] The processing of calculating the target high-pressure corresponding saturation temperature
will now be described with reference to a flowchart of Fig. 7.
[0054] In a step S61, the variable DQATD is calculated in accordance with the following
formula using the target high-pressure corresponding saturation temperature calculation
coefficients KSCC1, KSCC2, KSCC3 and EDOSC, the target frequency EMK of the compressor
101, the discharge pipe temperature deviation EDO and others.
[0055] In a step S62, it is determined whether the variable DOATD is larger than a lower
limit DOATDMIN of the target high-pressure corresponding saturation temperature or
not. When it is determined that the variable DOATD is not larger than the lower limit
DOATDMIN of the target high-pressure corresponding saturation temperature, the processing
moves to a step S63. In the step S63, the value of variable DOATD is set to the lower
limit DOATDMIN of the target high-pressure corresponding saturation temperature.
[0056] In a step S64, it is determined whether the variable DOATD is equal to or smaller
than the upper limit DOATDMAX of the target high-pressure corresponding saturation
temperature or not. When it is determined that the variable DOATD is larger than the
upper limit DQATDMAX of the target high-pressure corresponding saturation temperature,
the processing moves to a step S65. In the step S65, the value of variable DOATD is
set to the upper limit DOATDMAX of the target high-pressure corresponding saturation
temperature.
[0057] In a step S66, the target high-pressure corresponding saturation temperature TDSSET
is calculated. In this embodiment, the following formula is employed for this calculation.
[0058] In a step S53, a high-pressure corresponding saturation temperature deviation ΔTDS
is calculated from the high-pressure corresponding saturation temperature TDSSET and
the target high-pressure corresponding saturation temperature TDSSET TDS in accordance
with the following formula.
[0059] In a step S54, processing is performed to calculate an amount or degree, by which
the motor-operated valve is to be operated.
[0060] This processing of calculating the motor-operated valve operation amount is shown
in a flowchart of Fig. 8.
[0061] In a step S71, the motor-operated valve operation amount POSC is calculated in accordance
with the following formula using the coefficients KOSCA1 and KOSCA, which are coefficients
for calculating the motor-operated valve operation amount, the high-pressure corresponding
saturation temperature deviation TDS, the last high-pressure corresponding saturation
temperature deviation TDSZ and others.
[0062] In a step S55, the motor-operated valve is operated in accordance with the operation
amount determined in the step S54.
[0063] Processing of operating the motor-operated valve is shown in a flowchart of Fig.
9.
[0064] It is assumed that the degree EVL of opening of the liquid pipe motor-operated valve
128 is defined by ((current degree EVL) + (motor-operated valve operation amount POSC)).
At the same time, the degree EVG of opening of the gas pipe motor-operated valve 129
is controlled to attain ((current degree EVG) + (operation amount POSC) x KPOSC1).
[0065] Referring to a flowchart of Fig. 10, description will now be given on control of
surplus refrigerant performed with a liquid pipe temperature in the heating operation.
[0066] In a step S91, it is determined whether a surplus refrigerant control sampling time
TSCSET has elapsed or not. When it is determined that an elapsed time counted by the
timer has reached the surplus refrigerant control sampling time TSCSET, the processing
moves to a step S92.
[0067] In the step S92, the target liquid pipe temperature is calculated.
[0068] The processing of calculating the target liquid pipe temperature will now be described
with reference to a flowchart of Fig. 11.
[0069] In a step S101, the variable DOATD is calculated in accordance with the following
formula using target liquid pipe temperature calculation coefficients KSCC1 and KSCC2,
the target frequency EMK of the compressor 101 and others.
[0070] In a step S102, it is determined whether the variable DQATD is larger than the lower
limit DOATIMIN of the target liquid pipe temperature or not. When it is determined
that the variable DOATD is not larger than the lower limit DQATDMIN of the target
liquid pipe temperature, the processing moves to a step S103. In the step S103, the
value of variable DOATD is set to the lower limit DQATDMIN of the target liquid pipe
temperature.
[0071] In a step S104, it is determined whether the variable DOATD is equal to or smaller
than ((upper limit DQATDMAX of target liquid pipe temperature) - room temperature
DA) or not. When it is determined that the variable DOATD is larger than ((upper limit
DOATDMAX of target liquid pipe temperature) - room temperature DA), the processing
moves to a step S105. In the step S105, the value of variable DOATD is set to ((upper
limit DOATDMAX of target liquid pipe temperature) - room temperature DA).
[0072] In a step S106, a target liquid pipe temperature DLSET is calculated. In this embodiment,
the following formula is employed for this calculation.
[0073] In a step S93, a liquid pipe temperature deviation ΔDL is calculated. For the indoor
heat exchanger 201 having the lowest liquid pipe temperature in the indoor unit 200,
which is operating, the liquid pipe temperature deviation ΔDL is calculated from a
representative value DL of the liquid pipe temperature and the target liquid pipe
temperature DLSET in accordance with the following formula.
[0074] In a step S94, processing is performed to calculate an amount or degree, by which
the motor-operated valve is to be operated.
[0075] This processing of calculating the motor-operated valve operation amount is shown
in a flowchart of Fig. 12.
[0076] In a step S111, the motor-operated valve operation amount POSC is calculated in accordance
with the following formula using the coefficients KOSCA1 and KOSCA, which are coefficients
for calculating the motor-operated valve operation amount, the liquid pipe temperature
deviation ΔDL, the last liquid pipe temperature deviation ΔDLZ and others.
[0077] In a step S95, the motor-operated valve is operated in accordance with the operation
amount determined in the step S94.
[0078] Processing of operating the motor-operated valve is shown in a flowchart of Fig.
13.
[0079] It is assumed that the degree EVG of opening of the gas pipe motor-operated valve
129 is defined by ((current degree EVG) + (motor-operated valve operation amount POSC)).
Likewise, the degree EVL of opening of the liquid pipe motor-operated valve 128 is
controlled to attain ((current degree EVL) + (operation amount POSC) x KPOSC1).
[0080] In the heating operation, the lowest liquid pipe temperature in the indoor unit 200,
which is being operating, is used as the representative value of the liquid pipe temperature,
and the amount of the surplus refrigerant in the receiver 121 can be controlled with
this representative value of the liquid pipe temperature.
[0081] Referring to a flowchart of Fig. 14, description will now be given on control of
surplus refrigerant performed with a high-pressure corresponding saturation temperature
in the heating operation.
[0082] In a step S131, it is determined whether a surplus refrigerant control sampling time
TSCSET has elapsed or not. When it is determined that an elapsed time counted by the
timer has reached the surplus refrigerant control sampling time TSCSET, the processing
moves to a step S132.
[0083] In the step S132, the target high-pressure corresponding saturation temperature is
calculated.
[0084] The processing of calculating the target high-pressure corresponding saturation temperature
will now be described with reference to a flowchart of Fig. 15.
[0085] In a step S141, the variable DQATD is calculated in accordance with the following
formula using the target high-pressure corresponding saturation temperature calculation
coefficients KSCC1 and KSCC2, the target frequency FMK of the compressor 101 and others.
[0086] In a step S142, it is determined whether the variable DQATD is larger than the lower
limit DQATIMIN of the target high-pressure corresponding saturation temperature or
not. When it is determined that the variable DQATD is not larger than the lower limit
DQATIMIN of the target high-pressure corresponding saturation temperature, the processing
moves to a step S143. In the step S143, the value of variable DQATD is set to the
lower limit DQATIMIN of the target high-pressure corresponding saturation temperature.
[0087] In a step S144, it is determined whether the variable DQATD is equal to or smaller
than the upper limit DOATDMAX of the target high-pressure corresponding saturation
temperature or not. When it is determined that the variable DQATD is larger than the
upper limit DQATDMAX of the target high-pressure corresponding saturation temperature,
the processing moves to a step S145. In the step S145, the value of variable DOATD
is set to the upper limit DOATIMAX of the target high-pressure corresponding saturation
temperature.
[0088] In a step S146, a target high-pressure corresponding saturation temperature TDSSET
is calculated. In this embodiment, the following formula is employed for this calculation.
[0089] In a step S133, the high-pressure corresponding saturation temperature deviation
ΔTDS is calculated. The high-pressure corresponding saturation temperature deviation
ΔTDS is calculated from the high-pressure corresponding saturation temperature TDS
and the target high-pressure corresponding saturation temperature TDSSET in accordance
with the following formula.
[0090] In a step S134, processing is performed to calculate an amount or degree, by which
the motor-operated valve is to be operated.
[0091] This processing of calculating the motor-operated valve operation amount is shown
in a flowchart of Fig. 16.
[0092] In a step S151, the motor-operated valve operation amount POSC is calculated in accordance
with the following formula using the coefficients KOSCAL and KO6CA, which are coefficients
for calculating the motor-operated valve operation amount, the high-pressure corresponding
saturation temperature deviation ΔTDS, the last high-pressure corresponding saturation
temperature deviation ΔTDSZ and others.
[0093] In a step S135, the motor-operated valve is operated in accordance with the operation
amount determined in the step S134.
[0094] Processing of operating the motor-operated valve is shown in a flowchart of Fig.
17.
[0095] It is assumed that the degree EVG of opening of the gas pipe motor-operated valve
129 is defined by ((current degree EVG) + (motor-operated valve operation amount POSC)).
Likewise, the degree EVL of opening of the liquid pipe motor-operated valve 128 is
controlled to attain ((current degree EVL) + (operation amount POSC) x KPOSC1).
(Estimation of High-Pressure Corresponding Saturation Temperature)
[0096] Description will now be given on a manner of estimating the high-pressure corresponding
saturation temperature in the second embodiment already described. A control block
for this estimation is shown in Fig. 18.
[0097] A control portion 501 is formed of a microprocessor including a CPU, a ROM, a RAM
and others, and is connected to a ROM 502 storing an operation control program and
various parameters as well as a RAM 503 for temporarily storing work variables.
[0098] The control portion 501 is also connected to various sensor elements including the
intake-side pressure sensor 110, discharge pipe thermistor 109, outside air thermistor
111, outdoor heat exchange thermistor 112 and heat exchange intermediate thermistor
113, which are arranged within an outdoor unit 100, for receiving values detected
by these sensor and thermistors. Further, the discharge-side pressure switch 108 is
connected to the control portion 501.
[0099] An indoor-side communication interface 504 for transmitting various data between
the indoor unit 200 and the branch unit 300 is connected to the control portion 501.
[0100] Further, the control portion 501 is connected to a compressor drive circuit 505 for
controlling the operation frequency of the compressor 101 and a fan motor drive circuit
506 for controlling a frequency of the fan motor 104.
[0101] The control portion 501 is further connected to the liquid and gas pipe motor-operated
valves 128 and 129 arranged on the opposite sides of the receiver 121, and the discharge-intake
motor-operated valve 142 arranged on the discharge bypass circuit 194 of the compressor
101.
[0102] The compressor drive circuit 505 is provided with an active filter circuit, which
will be described later, and a secondary voltage sensor 507 and a secondary current
sensor 508 of the active filter circuit are connected to the control portion 501.
[0103] Fig. 19 is a block diagram showing control of the compressor drive circuit 505 in
Fig. 18.
[0104] The compressor drive circuit 505 includes a rectifier circuit 512 connected to a
commercial power supply 511, an active filter circuit 513 and an inverter circuit
514.
[0105] The rectifier circuit 512 is formed of a diode bridge including four diodes, and
performs full-wave rectification on an AC power supplied from the commercial power
supply 511.
[0106] The active filter circuit 513 includes a reactor 521, a diode 522, a capacitor 523,
a switching element 524 and active filter drive means 525 for performing switching
control of the switching element 524.
[0107] The active filter 513 includes a primary voltage sensor 526 for detecting a primary
voltage, a primary current sensor 527 for detecting a primary current, a secondary
voltage sensor 507 for detecting a secondary voltage and a secondary current sensor
508 for detecting a secondary current. The active filter drive means 525 performs
the switching control on the switching element 524 so that the secondary voltage detected
by the secondary voltage sensor 507 may become equal to a predetermined voltage. At
the same time, the active filter drive means 525 controls the current value detected
by the primary current sensor 527 so that it matches in phase with the primary voltage
detected by the primary voltage sensor 526. This significantly increases a power factor,
and thus increases the accuracy of calculating the power consumption based on the
secondary voltage detected by the secondary voltage sensor 507 and the secondary current
detected by the secondary current sensor 508.
[0108] The inverter circuit 514 produces a pulse signal of a constant voltage from an output
signal of a predetermined voltage sent from the active filter circuit 513. The output
frequency of the inverter circuit 514 in this operation is equal to the operation
frequency of the compressor determined based on the current operation situations.
Therefore, the compressor drive motor 531 is driven in accordance with the output
frequency of the inverter circuit 514.
[0109] The power consumption of the compressor 101 is calculated from the secondary voltage
value and the secondary current value of the active filter 513 of the compressor drive
circuit 505, and a value of the high-pressure corresponding temperature is estimated
based on the power consumption thus calculated. A manner for this estimation will
now be described with reference to a flowchart of Fig. 20.
[0110] In a step 5171, an input voltage VIN and an input current IIN applied to the inverter
circuit 514 are detected. The input voltage VIN and the input current IIN applied
to the inverter circuit 514 can be obtained from the secondary voltage sensor 507
and the secondary current sensor 508, which detect the secondary voltage and current
of the active filter 513, respectively.
[0111] In a step S172, power consumption INPUT of the compressor 101 is calculated based
on the secondary voltage VIN and the secondary current IIN of the active filter 513.
Since the switching element 524 is controlled so that the active filter drive means
525 of the active filter 513 may have an appropriate power factor, it can be considered
that the power factor is equal to one. Therefore, the power consumption of the compressor
can be determined by the following formula.
[0112] In a step S173, processing is performed to determine an output frequency FOUT for
driving the compressor 101 as well as an intake pressure value LP thereof. In this
processing, the output frequency FOUT can be specifically determined from the output
frequency of the inverter 514 driving the compressor drive motor 531. The intake pressure
value LP can be specifically determined from the detected value of the intake pressure
sensor 110.
[0113] In a step S174, a high pressure value is determined based on the power consumption
INPUT, output frequency FOUT and intake pressure value LP. This determination is performed
in accordance with the following formula, which uses high pressure estimation constants
KHPLL, KHPFF, KHPII, KHPLF, KHPFI, KHPLI, KHPL, KHPF, KHPI and KHPC as well as a high
pressure correction value HPHOSEI.
[0114] In a step S157, the high-pressure corresponding saturation transmission TDS is calculated
based on the high pressure value HP calculated in the step S174. For this, the following
formula can be used.
where coefficients A and B for calculating the high-pressure corresponding saturation
temperature are determined by the high pressure value HP in accordance with a table
shown in Fig. 21.
Industrial Applicability
[0115] According to the invention, the amount of surplus refrigerant collected into the
receiver can be controlled in accordance with operation situations, and the degree
of super cooling or super heating within the outdoor heat exchanger can be controlled.
Therefore, an appropriate amount of refrigerant can be used in the refrigerant circuit
system for performing efficient driving.