REFRIGERATION CYCLE DEVICE

Description

CROSS-REFERENCE TO RELATED APPLICATION

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.

FIELD

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

BACKGROUND

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)

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a circuit diagram showing a refrigeration cycle device according to an embodiment.

FIG. 2 is a circuit diagram showing a refrigeration cycle device according to a first modified example of the embodiment.

FIG. 3 is a circuit diagram showing a refrigeration cycle device according to a second modified example of the embodiment.

DESCRIPTION OF EMBODIMENTS

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.

FIG. 1 is a circuit diagram showing a refrigeration cycle device 1 of the embodiment. The refrigeration cycle device 1 includes an outdoor unit 11, an indoor unit 10, and a main circuit 5. The main circuit 5 allows a refrigerant to flow between the outdoor unit 11 and the indoor unit 10. 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 device 1 contains a refrigerant such as R410A, R32, R1123, R454B, R466A, or carbon dioxide (CO₂). The refrigerant circulates through the refrigeration cycle device 1 while changing the phase thereof.

The outdoor unit 11 includes a compressor 2, a check valve 3, a four-way valve 18, an outdoor heat exchanger 8, and an outdoor expansion valve 6b.

The indoor unit 10 includes an indoor heat exchanger 4 and an indoor expansion valve 6a.

A case in which the refrigeration cycle device 1 performs a cooling operation will be described.

The compressor 2 compresses a low-pressure gaseous refrigerant taken into the inside into a high-temperature and high-pressure gaseous refrigerant. The refrigerant discharged from the compressor 2 is supplied to the four-way valve 18 via an oil separator 2b and the check valve 3. When the refrigeration cycle device 1 performs a cooling operation, the refrigerant is supplied from the four-way valve 18 to the outdoor heat exchanger 8 of the outdoor unit 11.

The outdoor heat exchanger 8 functions as a condenser (radiator, first heat exchanger). The condenser dissipates heat from a high-temperature and high-pressure gaseous refrigerant discharged from the compressor 2 to convert the high-temperature and high-pressure gaseous refrigerant into a high-pressure liquid refrigerant. The outdoor heat exchanger 8 is accompanied by an outdoor fan (fan) 8f. The outdoor fan 8f causes outdoor air to flow through the outdoor heat exchanger 8.

The refrigeration cycle device 1 includes, as an expansion device 6, the outdoor expansion valve 6b and the indoor expansion valve 6a. When the refrigeration cycle device 1 performs a cooling operation, the refrigerant discharged from the outdoor heat exchanger 8 flows through the outdoor expansion valve (first expansion device) 6b and the indoor expansion valve (second expansion device) 6a in this order. The outdoor expansion valve 6b and the indoor expansion valve 6a reduce a pressure of the high-pressure liquid refrigerant supplied from the outdoor heat exchanger 8 and 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 valve 6a is supplied to the indoor heat exchanger 4.

The indoor heat exchanger 4 functions as an evaporator (heat absorber, second heat exchanger). The evaporator converts the gas-liquid two-phase refrigerant discharged from the indoor expansion valve 6a into a low-pressure gaseous refrigerant. The refrigerant discharged from the indoor heat exchanger 4 is supplied to the four-way valve 18. The refrigerant discharged from the four-way valve 18 is supplied to the compressor 2 via an accumulator (gas-liquid separator) 2a.

The refrigeration cycle device 1 performs the cooling operation as described above. In the main circuit 5, the compressor 2, the outdoor heat exchanger 8 (first heat exchanger), the expansion device 6, and the indoor heat exchanger 4 (second heat exchanger) are connected in a loop in this order. The main circuit 5 causes the refrigerant to flow through the compressor 2, the outdoor heat exchanger 8, the expansion device 6, and the indoor heat exchanger 4. In the main circuit 5, a flow path in the flow direction of the refrigerant from the downstream side of the compressor 2 to the indoor expansion valve 6a of the expansion device 6 is referred to as a high-pressure circuit 5a. A pressure of the refrigerant in the high-pressure circuit 5a is high. In the main circuit 5, a flow path in the flow direction of the refrigerant from the indoor expansion valve 6a of the expansion device 6 to the upstream side of the compressor 2 is referred to as a low-pressure circuit 5b. A pressure of the refrigerant in the low-pressure circuit 5b is low.

When the refrigeration cycle device 1 performs a heating operation, a state of the four-way valve 18 is switched from the state shown in FIG. 1. Due to the switching operation of the four-way valve 18, the refrigerant discharged from the compressor 2 flows through the four-way valve 18, the indoor heat exchanger 4, the expansion device 6, the outdoor heat exchanger 8, the four-way valve 18, and the compressor 2 in this order. In this case, the indoor heat exchanger 4 functions as an evaporator (radiator, first heat exchanger), and the outdoor heat exchanger 8 functions as a condenser (heat absorber, second heat exchanger).

The refrigeration cycle device 1 performs the heating operation as described above. In the main circuit 5, the compressor 2, the indoor heat exchanger 4 (first heat exchanger), the expansion device 6, and the outdoor heat exchanger 8 (second heat exchanger) are connected in a loop in this order. The main circuit 5 causes the refrigerant to flow through the compressor 2, the indoor heat exchanger 4, the expansion device 6, and the outdoor heat exchanger 8. The refrigerant discharged from the indoor heat exchanger 4 flows through the indoor expansion valve (first expansion device) 6a and the outdoor expansion valve (second expansion device) 6b in this order. In the main circuit 5, a flow path in the flow direction of the refrigerant from the downstream side of the compressor 2 to the outdoor expansion valve 6b of the expansion device 6 is referred to as the high-pressure circuit 5a. In the main circuit 5, a flow path in the flow direction of the refrigerant from the outdoor expansion valve 6b of the expansion device 6 to the upstream side of the compressor 2 is referred to as the low-pressure circuit 5b.

In the present embodiment, of the outdoor heat exchanger 8 and the indoor heat exchanger 4, 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 valve 6b and the indoor expansion valve 6a, 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 unit 11 includes a discharge pressure sensor 14, a suction pressure sensor 15, and an outside air temperature sensor 17. The discharge pressure sensor 14 is provided in the high-pressure circuit 5a. The discharge pressure sensor 14 outputs a discharge pressure signal corresponding to a discharge pressure of the refrigerant by the compressor 2. The suction pressure sensor 15 is disposed in the low-pressure circuit 5b. The suction pressure sensor 15 outputs a suction pressure signal corresponding to a suction pressure of the refrigerant by the compressor 2. The outdoor air temperature sensor 17 is provided at a location on the outdoor unit 11 that comes into contact with outside air. The outdoor air temperature sensor 17 is provided near the outdoor heat exchanger 8. The outside air temperature sensor 17 outputs an outside air temperature signal corresponding to an outside air temperature.

The outdoor unit 11 includes a pressure equalization circuit 26 and a pressure equalization circuit valve 27. The pressure equalization circuit 26 connects the high-pressure circuit 5a upstream of the check valve 3 and the low-pressure circuit 5b. The pressure equalization circuit valve 27 is provided in the pressure equalization circuit 26 to open and close the pressure equalization circuit 26. The pressure equalization circuit valve 27 is opened while the compressor 2 is stopped. The pressure equalization circuit 26 equalizes a pressure of the high-pressure circuit 5a upstream of the check valve 3 and a pressure of the low-pressure circuit 5b. The pressure equalization circuit 26 reduces the pressure of the high-pressure circuit 5a upstream of the check valve 3.

The outdoor unit 11 includes a subcooling heat exchanger 20, a subcooling circuit (bypass circuit) 21, and a subcooling circuit expansion valve (bypass circuit opening-closing device) 22.

The subcooling heat exchanger 20 is provided in the main circuit 5 between the outdoor expansion valve 6b and the indoor expansion valve 6a.

The subcooling circuit 21 connects a first position 21a of the high-pressure circuit 5a downstream of the check valve 3 and a second position 21b of the low-pressure circuit 5b upstream of the compressor 2. When the refrigeration cycle device 1 performs the cooling operation, the first position 21a is downstream of the outdoor heat exchanger 8 and downstream of the subcooling heat exchanger 20. The second position 21b is downstream of the indoor heat exchanger 4. When the refrigeration cycle device 1 performs the heating operation, the first position 21a is downstream of the indoor heat exchanger 4 and upstream of the subcooling heat exchanger 20. The second position 21b is downstream of the outdoor heat exchanger 8.

The subcooling circuit 21 passes through the subcooling heat exchanger 20. The subcooling heat exchanger 20 performs heat exchange between the refrigerant flowing through the main circuit 5 and the refrigerant flowing through the subcooling circuit 21. The refrigerant flowing through the subcooling circuit 21 absorbs heat from the refrigerant flowing through the main circuit 5. The subcooling heat exchanger 20 condenses the refrigerant flowing through the main circuit 5.

The subcooling circuit expansion valve 22 reduces a pressure of the refrigerant flowing through the subcooling circuit 21. The subcooling circuit expansion valve 22 adjusts an opening degree of the subcooling circuit 21.

The refrigeration cycle device 1 includes a central processing unit (CPU), a memory, an auxiliary storage device, or the like. The CPU functions as a control unit 13 by executing a program stored in the memory and the auxiliary storage device. The control unit 13 controls an operation of each part of the refrigeration cycle device 1. The control unit 13 controls a current of a motor (sometimes referred to as a drive current of the compressor) that drives the compressor 2. The control unit 13 receives a discharge pressure signal output from the discharge pressure sensor 14 and an outside air temperature signal output from the outside air temperature sensor 17. The control unit 13 controls opening and closing of the pressure equalization circuit valve 27 and the subcooling circuit expansion valve 22.

Hereinafter, a case in which the refrigeration cycle device 1 performs a cooling operation will be described as an example.

During the cooling operation of the refrigeration cycle device 1, an outside air temperature may become high. In order to increase a temperature of the refrigerant supplied to the outdoor heat exchanger (radiator) 8, the compressor 2 is operated in an overloaded state. A large amount of current flows through the motor of the compressor 2. The refrigerant in the high-pressure circuit 5a becomes high in pressure.

There are cases in which the operation of the refrigeration cycle device 1 is stopped while the refrigerant in the high-pressure circuit 5a is in a high-pressure state. Along with the stop of the operation of the refrigeration cycle device 1, an operation of the compressor 2 is stopped, and the outdoor expansion valve 6b and the indoor expansion valve 6a are closed. At this time, the pressure in the high-pressure circuit 5a upstream of the check valve 3 decreases by opening the pressure equalization circuit valve 27. The pressure in the high-pressure circuit 5a downstream of the check valve 3 (sometimes referred to as a first pressure) is maintained at a high level.

When the operation of the refrigeration cycle device 1 is resumed, the compressor 2 is restarted. In order to circulate the refrigerant, the compressor 2 increases the pressure of the refrigerant to a level higher than the first pressure. There is a possibility that the compressor 2 suddenly enters an overloaded state, causing step-out or the like in the motor. It is difficult to stably restart the compressor 2.

The control unit 13 controls execution of a pressure reduction operation when a predetermined condition is satisfied and the operation of the compressor 2 is stopped. The pressure reduction operation is an operation of reducing the first pressure in the high-pressure circuit 5a downstream of the check valve 3.

The pressure reduction operation is an operation of opening the subcooling circuit expansion valve 22. When the subcooling circuit expansion valve 22 is opened, the refrigerant in the high-pressure circuit 5a flows through the subcooling circuit 21 to the low-pressure circuit 5b. The first pressure in the high-pressure circuit 5a decreases. Therefore, the compressor 2 can be restarted stably. The subcooling circuit 21 and the subcooling circuit expansion valve 22 are used as a bypass circuit and a bypass circuit opening-closing device between the high-pressure circuit 5a and the low-pressure circuit 5b. 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 device 1 is suppressed.

While the operation of the compressor 2 is stopped, the outdoor expansion valve 6b and the indoor expansion valve 6a are closed. When the subcooling circuit expansion valve 22 is opened in this state, the first pressure on the downstream side of the outdoor expansion valve (first expansion device) 6b decreases, but the first pressure on the upstream side does not decrease. When the compressor 2 is restarted, if the outdoor expansion valve 6b is opened, the first pressure on the upstream side of the outdoor expansion valve 6b decreases. Therefore, the compressor 2 can be restarted stably. The control unit 13 may open the subcooling circuit expansion valve 22 and the outdoor expansion valve 6b while the operation of the compressor 2 is stopped.

The pressure reduction operation may be an operation of operating the outdoor fan 8f. The outdoor fan 8f causes outdoor air to flow through the outdoor heat exchanger 8. A temperature of the refrigerant of the high-pressure circuit 5a passing through the outdoor heat exchanger 8 decreases, and the first pressure of the high-pressure circuit 5a decreases. Therefore, the compressor 2 can be restarted stably.

As described above, the control unit 13 controls execution of the pressure reduction operation when a predetermined condition is satisfied and the operation of the compressor 2 is stopped.

The predetermined condition is a condition in which a drive current of the compressor 2 exceeds a first predetermined value. As described above, the control unit 13 controls the drive current of the compressor 2. The first pressure in the high-pressure circuit 5a increases as the drive current of the compressor 2 increases. When the compressor 2 is restarted in a state in which the first pressure of the high-pressure circuit 5a is high, the compressor 2 is driven with a current larger than the drive current when the operation is stopped. If the compressor 2 is 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 compressor 2 unstable. The control unit 13 controls execution of the pressure reduction operation when the operation of the compressor 2 is stopped in a state in which the drive current of the compressor 2 exceeds the first predetermined value. Therefore, the compressor 2 can be restarted stably.

The predetermined condition may be a condition in which the first pressure in the high-pressure circuit 5a exceeds a second predetermined value. The control unit 13 receives a discharge pressure signal output from the discharge pressure sensor 14 to detect the first pressure of the high-pressure circuit 5a. The control unit 13 controls execution of the pressure reduction operation when the operation of the compressor 2 is stopped in a state in which the first pressure of the high-pressure circuit 5a exceeds the second predetermined value. Therefore, the compressor 2 can 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 1. The control unit 13 receives an outside air temperature signal output from the outside air temperature sensor 17 to detect the outside air temperature. As the outside air temperature increases, the drive current of the compressor 2 increases, and the first pressure in the high-pressure circuit 5a increases. The control unit 13 controls execution of the pressure reduction operation when the operation of the compressor 2 is stopped in a state in which the outside air temperature exceeds the third predetermined value during the cooling operation of the refrigeration cycle device 1. Therefore, the compressor 2 can be restarted stably.

As described above in detail, the refrigeration cycle device 1 of the embodiment includes the main circuit 5, the check valve 3, and the control unit 13. The check valve 3 is provided in the main circuit 5 downstream of the compressor 2. The control unit 13 controls execution of the pressure reduction operation when the predetermined condition is satisfied and the operation of the compressor 2 is stopped. The pressure reduction operation is an operation of reducing the first pressure in the main circuit 5 downstream of the check valve 3.

When the first pressure of the main circuit 5 downstream of the check valve 3 is reduced, a sudden overload during restart of the compressor 2 is suppressed. Therefore, the compressor 2 can be restarted stably.

FIG. 2 is a circuit diagram showing a refrigeration cycle device 1B in a first modified example of the embodiment. The refrigeration cycle device 1B of the first modified example is different from the refrigeration cycle device 1 of the embodiment in that a plurality of outdoor units 11 and 12 connected in parallel to the indoor unit 10 are provided. Description of the first modified example that is the same as that in the embodiment may be omitted.

The plurality of outdoor units 11 and 12 include a first outdoor unit 11 and a second outdoor unit 12. The plurality of outdoor units may include three or more outdoor units. The first outdoor unit 11 includes the compressor 2, the check valve 3, the four-way valve 18, the outdoor heat exchanger 8, and the outdoor expansion valve 6b. The second outdoor unit 12 has the same configuration as that of the first outdoor unit 11. The indoor unit 10 includes the indoor heat exchanger 4 and the indoor expansion valve 6a.

The control unit 13 adjusts the number of outdoor units 11 and 12 in operation based on an indoor temperature and an outdoor temperature. Among the plurality of outdoor units 11 and 12, 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 FIG. 2, only the first outdoor unit 11 is operated, and the second outdoor unit 12 is stopped. A high-pressure refrigerant discharged from the compressor 2 of the first outdoor unit 11 enters not only the indoor unit 10 but also the second outdoor unit 12 which is in a stopped state. The check valve 3 of the second outdoor unit 12 prevents the high-pressure refrigerant from entering the second outdoor unit 12, which is in a stopped state, from the first outdoor unit 11 in operation.

When the refrigeration cycle device 1B performs a cooling operation, a state of the four-way valve 18 is switched from the state shown in FIG. 2. As in the embodiment, there are cases in which an operation of the compressor 2 is stopped while the refrigerant in the high-pressure circuit 5a is in a high-pressure state. It is difficult to stably restart the compressor 2.

The control unit 13 controls execution of a pressure reduction operation when a predetermined condition is satisfied and the operation of the compressor 2 is stopped. As in the embodiment, the pressure reduction operation is an operation of opening the subcooling circuit expansion valve 22 or the like. The predetermined condition is a condition in which a drive current of the compressor 2 exceeds a first predetermined value or the like. Therefore, the compressor 2 can be restarted stably.

FIG. 3 is a circuit diagram showing a refrigeration cycle device 1C in a second modified example of the embodiment. The refrigeration cycle device 1C of the second modified example is different from the refrigeration cycle device 1 of the embodiment in that a plurality of indoor units 10 connected in parallel to the outdoor unit 11 via a switching unit 40 are provided. Description of the second modified example that is the same as that in the embodiment may be omitted.

The refrigeration cycle device 1C is a heat recovery type air conditioning system capable of simultaneously performing cooling and heating operations in the plurality of indoor units 10. The refrigeration cycle device 1C includes the outdoor unit 11, the plurality of indoor units 10, a first circuit 31, a second circuit 32, a third circuit 33, and a switching unit 40.

The outdoor unit 11 includes the compressor 2, the check valve 3, the four-way valve 18, an outdoor heat exchanger 8, and the outdoor expansion valve 6b. The plurality of indoor units 10 each include the indoor expansion valve 6a and the indoor heat exchanger 4.

The first circuit 31 causes a refrigerant to flow between the outdoor heat exchanger 8 and the indoor heat exchanger 4.

The second circuit 32 causes the refrigerant discharged from the compressor 2 to flow into the indoor heat exchanger 4.

The third circuit 33 causes the refrigerant flowing out of the indoor heat exchanger 4 to flow into the compressor 2.

The switching unit 40 switches connection of the second circuit 32 and the third circuit 33 to the indoor heat exchanger 4 for each of the plurality of indoor units 10. The switching unit 40 includes a second circuit valve 42 and a third circuit valve 43. The second circuit valve 42 opens and closes the second circuit 32. The third circuit valve 43 opens and closes the third circuit 33.

The control unit 13 controls switching of the four-way valve 18 and controls opening and closing of the second circuit valve 42 and the third circuit valve 43 based on a command input by a user. Therefore, it is possible to perform cooling and heating operations simultaneously in the plurality of indoor units 10.

As in the embodiment, there are cases in which an operation of the compressor 2 is stopped while the refrigerant in the high-pressure circuit 5a is in a high-pressure state. It is difficult to stably restart the compressor 2.

The control unit 13 controls execution of a pressure reduction operation when a predetermined condition is satisfied and the operation of the compressor 2 is stopped. As in the embodiment, the pressure reduction operation is an operation of opening the subcooling circuit expansion valve 22 or the like. The predetermined condition is a condition in which a drive current of the compressor 2 exceeds a first predetermined value or the like. Therefore, the compressor 2 can be restarted stably.

In the embodiment, the subcooling circuit 21 and the subcooling circuit expansion valve 22 are used as a bypass circuit and a bypass circuit opening-closing device between the high-pressure circuit 5a and the low-pressure circuit 5b. In contrast, a new bypass circuit and a bypass circuit opening-closing device separate from the subcooling circuit 21 and the subcooling circuit expansion valve 22 may be provided.

At least one of the embodiments described above includes the control unit 13 that controls execution of the pressure reduction operation when a predetermined condition is satisfied and the operation of the compressor 2 is stopped. The pressure reduction operation is an operation of reducing the first pressure in the main circuit 5 downstream of the check valve 3. Therefore, the compressor 2 can be restarted stably.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.