Refrigeration Cycle Device

This application is a continuation of International Application No. PCT/JP2024/005055, filed Feb. 14, 2024, which is based upon and claims the benefit of priority from Japanese Patent Application No. 2023-021787 filed in Japan on Feb. 15, 2023; the entire contents of which are incorporated herein by reference.

An embodiment of the present invention relates to a refrigeration cycle device.

A refrigeration cycle device includes a main circuit. In the main circuit, a compressor, a first heat exchanger, an expansion device, and a second heat exchanger are connected in a loop. The main circuit allows a refrigerant to flow through the compressor, the first heat exchanger, the expansion device, and the second heat exchanger. A check valve may be provided in the main circuit of the refrigeration cycle device. The check valve is disposed downstream of the compressor in a flow direction of the refrigerant. There are cases in which the compressor is stopped while the main circuit positioned downstream of the compressor is in a high-pressure state. A refrigeration cycle device capable of stably restarting the compressor is required (for example, PCT International Publication No. WO 2022/059054)

Hereinafter, a refrigeration cycle device according to an embodiment will be described with reference to the drawings.

A refrigeration cycle device according to an embodiment includes a main circuit, a check valve, and a control unit. The main circuit connects a compressor, a first heat exchanger, an expansion device, and a second heat exchanger in a loop to allow a refrigerant to flow thereto. A downstream side in a flow direction of the refrigerant is defined as a first side and an upstream side in the flow direction of the refrigerant is defined as a second side. The check valve is provided in the main circuit on the first side of the compressor. The control unit controls execution of a pressure reduction operation when a predetermined condition is satisfied and an operation of the compressor is stopped. The pressure reduction operation is an operation of reducing a first pressure of the main circuit on the first side of the check valve.

is a circuit diagram showing a refrigeration cycle deviceof the embodiment. The refrigeration cycle deviceincludes an outdoor unit, an indoor unit, and a main circuit. The main circuitallows a refrigerant to flow between the outdoor unitand the indoor unit. In the present embodiment, a downstream side (first side) in a flow direction of the refrigerant may be simply referred to as a “downstream side,” and an upstream side (second side) in the flow direction of the refrigerant may be simply referred to as an “upstream side”. In the present embodiment, a pipe through which the refrigerant flows may be referred to as a “circuit”.

The refrigeration cycle devicecontains a refrigerant such as R410A, R32, R1123, R454B, R466A, or carbon dioxide (CO). The refrigerant circulates through the refrigeration cycle devicewhile changing the phase thereof.

The outdoor unitincludes a compressor, a check valve, a four-way valve, an outdoor heat exchanger, and an outdoor expansion valve

The indoor unitincludes an indoor heat exchangerand an indoor expansion valve

A case in which the refrigeration cycle deviceperforms a cooling operation will be described.

The compressorcompresses a low-pressure gaseous refrigerant taken into the inside into a high-temperature and high-pressure gaseous refrigerant. The refrigerant discharged from the compressoris supplied to the four-way valvevia an oil separatorand the check valve. When the refrigeration cycle deviceperforms a cooling operation, the refrigerant is supplied from the four-way valveto the outdoor heat exchangerof the outdoor unit.

The outdoor heat exchangerfunctions as a condenser (radiator, first heat exchanger). The condenser dissipates heat from a high-temperature and high-pressure gaseous refrigerant discharged from the compressorto convert the high-temperature and high-pressure gaseous refrigerant into a high-pressure liquid refrigerant. The outdoor heat exchangeris accompanied by an outdoor fan (fan). The outdoor fancauses outdoor air to flow through the outdoor heat exchanger.

The refrigeration cycle deviceincludes, as an expansion device, the outdoor expansion valveand the indoor expansion valve. When the refrigeration cycle deviceperforms a cooling operation, the refrigerant discharged from the outdoor heat exchangerflows through the outdoor expansion valve (first expansion device)and the indoor expansion valve (second expansion device)in this order. The outdoor expansion valveand the indoor expansion valvereduce a pressure of the high-pressure liquid refrigerant supplied from the outdoor heat exchangerand convert the high-pressure liquid refrigerant into a low-temperature and low-pressure gas-liquid two-phase refrigerant. The refrigerant discharged from the indoor expansion valveis supplied to the indoor heat exchanger.

The indoor heat exchangerfunctions as an evaporator (heat absorber, second heat exchanger). The evaporator converts the gas-liquid two-phase refrigerant discharged from the indoor expansion valveinto a low-pressure gaseous refrigerant. The refrigerant discharged from the indoor heat exchangeris supplied to the four-way valve. The refrigerant discharged from the four-way valveis supplied to the compressorvia an accumulator (gas-liquid separator)

The refrigeration cycle deviceperforms the cooling operation as described above. In the main circuit, the compressor, the outdoor heat exchanger(first heat exchanger), the expansion device, and the indoor heat exchanger(second heat exchanger) are connected in a loop in this order. The main circuitcauses the refrigerant to flow through the compressor, the outdoor heat exchanger, the expansion device, and the indoor heat exchanger. In the main circuit, a flow path in the flow direction of the refrigerant from the downstream side of the compressorto the indoor expansion valveof the expansion deviceis referred to as a high-pressure circuit. A pressure of the refrigerant in the high-pressure circuitis high. In the main circuit, a flow path in the flow direction of the refrigerant from the indoor expansion valveof the expansion deviceto the upstream side of the compressoris referred to as a low-pressure circuit. A pressure of the refrigerant in the low-pressure circuitis low.

When the refrigeration cycle deviceperforms a heating operation, a state of the four-way valveis switched from the state shown in. Due to the switching operation of the four-way valve, the refrigerant discharged from the compressorflows through the four-way valve, the indoor heat exchanger, the expansion device, the outdoor heat exchanger, the four-way valve, and the compressorin this order. In this case, the indoor heat exchangerfunctions as an evaporator (radiator, first heat exchanger), and the outdoor heat exchangerfunctions as a condenser (heat absorber, second heat exchanger).

The refrigeration cycle deviceperforms the heating operation as described above. In the main circuit, the compressor, the indoor heat exchanger(first heat exchanger), the expansion device, and the outdoor heat exchanger(second heat exchanger) are connected in a loop in this order. The main circuitcauses the refrigerant to flow through the compressor, the indoor heat exchanger, the expansion device, and the outdoor heat exchanger. The refrigerant discharged from the indoor heat exchangerflows through the indoor expansion valve (first expansion device)and the outdoor expansion valve (second expansion device)in this order. In the main circuit, a flow path in the flow direction of the refrigerant from the downstream side of the compressorto the outdoor expansion valveof the expansion deviceis referred to as the high-pressure circuit. In the main circuit, a flow path in the flow direction of the refrigerant from the outdoor expansion valveof the expansion deviceto the upstream side of the compressoris referred to as the low-pressure circuit

In the present embodiment, of the outdoor heat exchangerand the indoor heat exchanger, a heat exchanger that functions as a condenser (radiator) may be referred to as the first heat exchanger, and a heat exchanger that functions as an evaporator (heat absorber) may be referred to as the second heat exchanger. In the present embodiment, of the outdoor expansion valveand the indoor expansion valve, an expansion valve positioned upstream in the flow direction of the refrigerant may be referred to as the first expansion device, and an expansion valve positioned downstream may be referred to as the second expansion device.

The outdoor unitincludes a discharge pressure sensor, a suction pressure sensor, and an outside air temperature sensor. The discharge pressure sensoris provided in the high-pressure circuit. The discharge pressure sensoroutputs a discharge pressure signal corresponding to a discharge pressure of the refrigerant by the compressor. The suction pressure sensoris disposed in the low-pressure circuit. The suction pressure sensoroutputs a suction pressure signal corresponding to a suction pressure of the refrigerant by the compressor. The outdoor air temperature sensoris provided at a location on the outdoor unitthat comes into contact with outside air. The outdoor air temperature sensoris provided near the outdoor heat exchanger. The outside air temperature sensoroutputs an outside air temperature signal corresponding to an outside air temperature.

The outdoor unitincludes a pressure equalization circuitand a pressure equalization circuit valve. The pressure equalization circuitconnects the high-pressure circuitupstream of the check valveand the low-pressure circuit. The pressure equalization circuit valveis provided in the pressure equalization circuitto open and close the pressure equalization circuit. The pressure equalization circuit valveis opened while the compressoris stopped. The pressure equalization circuitequalizes a pressure of the high-pressure circuitupstream of the check valveand a pressure of the low-pressure circuit. The pressure equalization circuitreduces the pressure of the high-pressure circuitupstream of the check valve.

The outdoor unitincludes a subcooling heat exchanger, a subcooling circuit (bypass circuit), and a subcooling circuit expansion valve (bypass circuit opening-closing device).

The subcooling heat exchangeris provided in the main circuitbetween the outdoor expansion valveand the indoor expansion valve

The subcooling circuitconnects a first positionof the high-pressure circuitdownstream of the check valveand a second positionof the low-pressure circuitupstream of the compressor. When the refrigeration cycle deviceperforms the cooling operation, the first positionis downstream of the outdoor heat exchangerand downstream of the subcooling heat exchanger. The second positionis downstream of the indoor heat exchanger. When the refrigeration cycle deviceperforms the heating operation, the first positionis downstream of the indoor heat exchangerand upstream of the subcooling heat exchanger. The second positionis downstream of the outdoor heat exchanger.

The subcooling circuitpasses through the subcooling heat exchanger. The subcooling heat exchangerperforms heat exchange between the refrigerant flowing through the main circuitand the refrigerant flowing through the subcooling circuit. The refrigerant flowing through the subcooling circuitabsorbs heat from the refrigerant flowing through the main circuit. The subcooling heat exchangercondenses the refrigerant flowing through the main circuit.

The subcooling circuit expansion valvereduces a pressure of the refrigerant flowing through the subcooling circuit. The subcooling circuit expansion valveadjusts an opening degree of the subcooling circuit.

The refrigeration cycle deviceincludes a central processing unit (CPU), a memory, an auxiliary storage device, or the like. The CPU functions as a control unitby executing a program stored in the memory and the auxiliary storage device. The control unitcontrols an operation of each part of the refrigeration cycle device. The control unitcontrols a current of a motor (sometimes referred to as a drive current of the compressor) that drives the compressor. The control unitreceives a discharge pressure signal output from the discharge pressure sensorand an outside air temperature signal output from the outside air temperature sensor. The control unitcontrols opening and closing of the pressure equalization circuit valveand the subcooling circuit expansion valve.

Hereinafter, a case in which the refrigeration cycle deviceperforms a cooling operation will be described as an example.

During the cooling operation of the refrigeration cycle device, an outside air temperature may become high. In order to increase a temperature of the refrigerant supplied to the outdoor heat exchanger (radiator), the compressoris operated in an overloaded state. A large amount of current flows through the motor of the compressor. The refrigerant in the high-pressure circuitbecomes high in pressure.

There are cases in which the operation of the refrigeration cycle deviceis stopped while the refrigerant in the high-pressure circuitis in a high-pressure state. Along with the stop of the operation of the refrigeration cycle device, an operation of the compressoris stopped, and the outdoor expansion valveand the indoor expansion valveare closed. At this time, the pressure in the high-pressure circuitupstream of the check valvedecreases by opening the pressure equalization circuit valve. The pressure in the high-pressure circuitdownstream of the check valve(sometimes referred to as a first pressure) is maintained at a high level.

When the operation of the refrigeration cycle deviceis resumed, the compressoris restarted. In order to circulate the refrigerant, the compressorincreases the pressure of the refrigerant to a level higher than the first pressure. There is a possibility that the compressorsuddenly enters an overloaded state, causing step-out or the like in the motor. It is difficult to stably restart the compressor.

The control unitcontrols execution of a pressure reduction operation when a predetermined condition is satisfied and the operation of the compressoris stopped. The pressure reduction operation is an operation of reducing the first pressure in the high-pressure circuitdownstream of the check valve.

The pressure reduction operation is an operation of opening the subcooling circuit expansion valve. When the subcooling circuit expansion valveis opened, the refrigerant in the high-pressure circuitflows through the subcooling circuitto the low-pressure circuit. The first pressure in the high-pressure circuitdecreases. Therefore, the compressorcan be restarted stably. The subcooling circuitand the subcooling circuit expansion valveare used as a bypass circuit and a bypass circuit opening-closing device between the high-pressure circuitand the low-pressure circuit. Since there is no need to provide a new bypass circuit and a bypass circuit opening-closing device, an increase in cost of the refrigeration cycle deviceis suppressed.

While the operation of the compressoris stopped, the outdoor expansion valveand the indoor expansion valveare closed. When the subcooling circuit expansion valveis opened in this state, the first pressure on the downstream side of the outdoor expansion valve (first expansion device)decreases, but the first pressure on the upstream side does not decrease. When the compressoris restarted, if the outdoor expansion valveis opened, the first pressure on the upstream side of the outdoor expansion valvedecreases. Therefore, the compressorcan be restarted stably. The control unitmay open the subcooling circuit expansion valveand the outdoor expansion valvewhile the operation of the compressoris stopped.

The pressure reduction operation may be an operation of operating the outdoor fan. The outdoor fancauses outdoor air to flow through the outdoor heat exchanger. A temperature of the refrigerant of the high-pressure circuitpassing through the outdoor heat exchangerdecreases, and the first pressure of the high-pressure circuitdecreases. Therefore, the compressorcan be restarted stably.

As described above, the control unitcontrols execution of the pressure reduction operation when a predetermined condition is satisfied and the operation of the compressoris stopped.

The predetermined condition is a condition in which a drive current of the compressorexceeds a first predetermined value. As described above, the control unitcontrols the drive current of the compressor. The first pressure in the high-pressure circuitincreases as the drive current of the compressorincreases. When the compressoris restarted in a state in which the first pressure of the high-pressure circuitis high, the compressoris driven with a current larger than the drive current when the operation is stopped. If the compressoris suddenly restarted by a large amount of drive current, step-out or the like may occur in the motor. The first predetermined value is a current value that makes the restart of the compressorunstable. The control unitcontrols execution of the pressure reduction operation when the operation of the compressoris stopped in a state in which the drive current of the compressorexceeds the first predetermined value. Therefore, the compressorcan be restarted stably.

The predetermined condition may be a condition in which the first pressure in the high-pressure circuitexceeds a second predetermined value. The control unitreceives a discharge pressure signal output from the discharge pressure sensorto detect the first pressure of the high-pressure circuit. The control unitcontrols execution of the pressure reduction operation when the operation of the compressoris stopped in a state in which the first pressure of the high-pressure circuitexceeds the second predetermined value. Therefore, the compressorcan be restarted stably.

The predetermined condition may be a condition in which an outside air temperature exceeds a third predetermined value during the cooling operation of the refrigeration cycle device. The control unitreceives an outside air temperature signal output from the outside air temperature sensorto detect the outside air temperature. As the outside air temperature increases, the drive current of the compressorincreases, and the first pressure in the high-pressure circuitincreases. The control unitcontrols execution of the pressure reduction operation when the operation of the compressoris stopped in a state in which the outside air temperature exceeds the third predetermined value during the cooling operation of the refrigeration cycle device. Therefore, the compressorcan be restarted stably.

As described above in detail, the refrigeration cycle deviceof the embodiment includes the main circuit, the check valve, and the control unit. The check valveis provided in the main circuitdownstream of the compressor. The control unitcontrols execution of the pressure reduction operation when the predetermined condition is satisfied and the operation of the compressoris stopped. The pressure reduction operation is an operation of reducing the first pressure in the main circuitdownstream of the check valve.

When the first pressure of the main circuitdownstream of the check valveis reduced, a sudden overload during restart of the compressoris suppressed. Therefore, the compressorcan be restarted stably.

is a circuit diagram showing a refrigeration cycle deviceB in a first modified example of the embodiment. The refrigeration cycle deviceB of the first modified example is different from the refrigeration cycle deviceof the embodiment in that a plurality of outdoor unitsandconnected in parallel to the indoor unitare provided. Description of the first modified example that is the same as that in the embodiment may be omitted.

The plurality of outdoor unitsandinclude a first outdoor unitand a second outdoor unit. The plurality of outdoor units may include three or more outdoor units. The first outdoor unitincludes the compressor, the check valve, the four-way valve, the outdoor heat exchanger, and the outdoor expansion valve. The second outdoor unithas the same configuration as that of the first outdoor unit. The indoor unitincludes the indoor heat exchangerand the indoor expansion valve

The control unitadjusts the number of outdoor unitsandin operation based on an indoor temperature and an outdoor temperature. Among the plurality of outdoor unitsand, only some of the outdoor units may be operated, and the remaining outdoor units may be stopped. For example, in the heating operation state shown in, only the first outdoor unitis operated, and the second outdoor unitis stopped. A high-pressure refrigerant discharged from the compressorof the first outdoor unitenters not only the indoor unitbut also the second outdoor unitwhich is in a stopped state. The check valveof the second outdoor unitprevents the high-pressure refrigerant from entering the second outdoor unit, which is in a stopped state, from the first outdoor unitin operation.

When the refrigeration cycle deviceB performs a cooling operation, a state of the four-way valveis switched from the state shown in. As in the embodiment, there are cases in which an operation of the compressoris stopped while the refrigerant in the high-pressure circuitis in a high-pressure state. It is difficult to stably restart the compressor.

The control unitcontrols execution of a pressure reduction operation when a predetermined condition is satisfied and the operation of the compressoris stopped. As in the embodiment, the pressure reduction operation is an operation of opening the subcooling circuit expansion valveor the like. The predetermined condition is a condition in which a drive current of the compressorexceeds a first predetermined value or the like. Therefore, the compressorcan be restarted stably.

is a circuit diagram showing a refrigeration cycle deviceC in a second modified example of the embodiment. The refrigeration cycle deviceC of the second modified example is different from the refrigeration cycle deviceof the embodiment in that a plurality of indoor unitsconnected in parallel to the outdoor unitvia a switching unitare provided. Description of the second modified example that is the same as that in the embodiment may be omitted.

The refrigeration cycle deviceC is a heat recovery type air conditioning system capable of simultaneously performing cooling and heating operations in the plurality of indoor units. The refrigeration cycle deviceC includes the outdoor unit, the plurality of indoor units, a first circuit, a second circuit, a third circuit, and a switching unit.

The outdoor unitincludes the compressor, the check valve, the four-way valve, an outdoor heat exchanger, and the outdoor expansion valve. The plurality of indoor unitseach include the indoor expansion valveand the indoor heat exchanger.

The first circuitcauses a refrigerant to flow between the outdoor heat exchangerand the indoor heat exchanger.

The second circuitcauses the refrigerant discharged from the compressorto flow into the indoor heat exchanger.