JP7195449B2 - Outdoor unit and refrigeration cycle equipment - Google Patents

Description

The present invention relates to an outdoor unit and a refrigerating cycle device.

Japanese Patent Laying-Open No. 2014-01917 (Patent Document 1) discloses a refrigeration system having an intermediate injection channel and a suction injection channel. In this refrigeration system, part of the refrigerant flowing from the condenser to the evaporator can be combined with the intermediate pressure refrigerant in the compressor using the intermediate injection channel, or the suction injection channel can be used to join the suction channel. It is also possible to join the low-pressure refrigerant sucked into the compressor at . Therefore, when the use of the intermediate injection flow path deteriorates the operating efficiency, the suction injection flow path can be used to lower the discharge temperature of the compressor.

JP 2014-01917 A

In the refrigeration system described in Japanese Patent Application Laid-Open No. 2014-01917 (Patent Document 1), the operation of the load device is stopped, etc., and the flow of the refrigerant is interrupted on the indoor unit side, and the load device side performs the pump-down operation. When started, the pressure in the liquid pipe of the outdoor unit rises. For example, with a CO2 refrigerant that uses supercriticality, the discharge pressure of the compressor is high, so the pressure in a part of the liquid pipe may exceed the design pressure.

SUMMARY OF THE INVENTION An object of the present invention is to provide an outdoor unit and a refrigeration cycle apparatus improved so that pressure exceeding the design pressure is not applied to piping.

The present disclosure relates to an outdoor unit of a refrigeration cycle apparatus configured to be connected to a load device including a first expansion device and an evaporator. The outdoor unit includes a refrigerant outlet port and a refrigerant inlet port for connecting to the load device, and a flow path from the refrigerant inlet port to the refrigerant outlet port, which forms a circulation flow path in which the refrigerant circulates together with the load device. a flow path, a compressor, a condenser and a second expansion device disposed in the first flow path, and branching from a portion of the first flow path between the condenser and the second expansion device and passing through the condenser a second flow path configured to return the depressurized refrigerant to the compressor; and a third expansion device and a liquid receiver disposed in the second flow path in order from the branch point of the second flow path from the first flow path. a third flow path connecting a portion of the first flow path between the second expansion device and the refrigerant outlet port and the refrigerant inlet of the liquid receiver; and an on-off valve disposed in the third flow path. .

According to the outdoor unit of the present disclosure and the refrigeration cycle device including the same, even if the pressure rises suddenly due to interruption of the refrigerant flow on the load device side, the pressure in the piping can be prevented from exceeding the design pressure. .

1 is an overall configuration diagram of a refrigeration cycle apparatus according to an embodiment; FIG. 7 is a flowchart for explaining control of a third expansion valve 71; 7 is a flowchart for explaining control of a flow rate adjustment valve 72; 4 is a flowchart for explaining control of a second expansion valve 40; 4 is a flowchart for explaining control of an on-off valve 78;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. A plurality of embodiments will be described below, but appropriate combinations of the configurations described in the respective embodiments have been planned since the filing of the application. The same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated.

FIG. 1 is an overall configuration diagram of a refrigeration cycle apparatus according to this embodiment. Note that FIG. 1 functionally shows the connection relationship and arrangement configuration of each device in the refrigeration cycle apparatus, and does not necessarily show the arrangement in a physical space.

Referring to FIG. 1, the refrigeration cycle device 1 includes an outdoor unit 2, a load device 3, and pipes 84,88. The outdoor unit 2 has a refrigerant outlet port PO2 and a refrigerant inlet port PI2 for connecting with the load device 3 . The load device 3 has a refrigerant outlet port PO3 and a refrigerant inlet port PI3 for connecting with the outdoor unit 2 . A pipe 84 connects the refrigerant outlet port PO2 of the outdoor unit 2 and the refrigerant inlet port PI3 of the load device 3 . A pipe 88 connects the refrigerant outlet port PO3 of the load device 3 and the refrigerant inlet port PI2 of the outdoor unit 2 .

The outdoor unit 2 of the refrigeration cycle device 1 is configured to be connected to the load device 3 . The outdoor unit 2 includes a compressor 10 having a suction port G1, a discharge port G2, and an intermediate pressure port G3, a condenser 20, a fan 22, a heat exchanger 30, a second expansion valve 40, and pipes 80 to 83. , 89. The heat exchanger 30 has a first passage H1 and a second passage H2, and is configured to exchange heat between the refrigerant flowing through the first passage H1 and the refrigerant flowing through the second passage H2.

The load device 3 includes a first expansion valve 50 , an evaporator 60 , pipes 85 , 86 and 87 and an on-off valve 28 . Evaporator 60 is configured to exchange heat between the air and the refrigerant. In the refrigeration cycle device 1, the evaporator 60 evaporates the refrigerant by absorbing heat from the air in the space to be cooled. The first expansion valve 50 is, for example, a temperature expansion valve controlled independently of the outdoor unit 2 . Note that the first expansion valve 50 may be an electronic expansion valve capable of reducing the pressure of the refrigerant. The on-off valve 28 is closed to shut off the refrigerant when the load device 3 stops operating.

The compressor 10 compresses the refrigerant sucked from the pipe 89 and discharges it to the pipe 80 . Compressor 10 can arbitrarily change the driving frequency by inverter control. In addition, the compressor 10 is provided with an intermediate pressure port G3, and the refrigerant from the intermediate pressure port G3 can flow into the intermediate portion of the compression process. Compressor 10 is configured to adjust its rotational speed according to a control signal from control device 100 . By adjusting the rotational speed of the compressor 10, the circulation amount of the refrigerant is adjusted, and the capacity of the refrigeration cycle device 1 can be adjusted. Various types can be adopted for the compressor 10, for example, a scroll type, a rotary type, a screw type, etc. can be adopted.

Condenser 20 is configured such that the high-temperature, high-pressure gas refrigerant discharged from compressor 10 exchanges heat (radiates heat) with the outside air. This heat exchange causes the refrigerant to condense and change to a liquid phase. Refrigerant discharged from compressor 10 to pipe 80 is condensed and liquefied in condenser 20 and flows out to pipe 81 . A fan 22 is attached to the condenser 20 to send outside air to increase the efficiency of heat exchange. The fan 22 supplies outside air to the condenser 20 with which the refrigerant exchanges heat in the condenser 20 . By adjusting the rotational speed of the fan 22, the pressure of the refrigerant on the discharge side of the compressor 10 (high-pressure side pressure) can be adjusted. The second expansion valve 40 is an electronic expansion valve that can reduce the pressure of the refrigerant that has passed through the condenser 20 and the first passage H1 of the heat exchanger 30 .

Here, the refrigerant used in the refrigerant circuit of the refrigeration cycle device 1 is CO ₂ , but other refrigerants may be used if a state occurs in which it is difficult to secure the degree of supercooling.

In this specification, for ease of explanation, the condenser 20 is also used when cooling a refrigerant such as CO ₂ in a supercritical state. Further, in this specification, for ease of explanation, the amount of decrease from the reference temperature of the refrigerant in the supercritical state is also referred to as the degree of supercooling.

A first flow path F1 from the refrigerant inlet port PI2 to the refrigerant outlet port PO2 via the first passage H1 of the compressor 10, the condenser 20, the heat exchanger 30, and the second expansion valve 40 is the first flow path of the load device 3. Together with the flow path in which the 1 expansion valve 50 and the evaporator 60 are arranged, a circulation flow path through which the refrigerant circulates is formed. Hereinafter, this circulation flow path is also referred to as the "main refrigerant circuit" of the refrigeration cycle.

The outdoor unit 2 includes pipes 91, 92, and 94 for flowing the refrigerant from the portion between the outlet of the first passage H1 of the circulation flow path and the second expansion valve 40 to the inlet of the second passage H2, and the second passage H2. Pipes 96 to 98 for flowing the refrigerant from the outlet of the compressor 10 to the suction port G1 or the intermediate pressure port G3, and either the suction port G1 or the intermediate pressure port G3 as the destination of the refrigerant flowing out from the outlet of the second passage H2 and a channel switching unit 74 that can select the . Hereinafter, the second flow path F2 that branches from the main refrigerant circuit and sends the refrigerant to the compressor 10 via the second passage H2 is also referred to as an "injection flow path".

The outdoor unit 2 further includes a liquid receiver (receiver) 73 that is arranged in the second flow path F2 and stores the refrigerant. The third expansion valve 71 is located between a pipe 91 branched from a portion between the outlet of the first passage H1 of the circulation flow path and the second expansion valve 40 and a pipe 92 connected to the inlet of the liquid receiver 73. placed. The outdoor unit 2 further includes a gas vent pipe 93 that connects the gas discharge port of the liquid receiver 73 and the second passage H2 and discharges the refrigerant gas in the liquid receiver 73, the gas vent pipe 93 and the second passage H2. and a flow control valve 72 for adjusting the flow rate of the refrigerant in the pipe 94 connected to the liquid refrigerant discharge port of the liquid receiver 73 .

A pipe 91 is a pipe that branches off from the main refrigerant circuit and allows the refrigerant to flow into the liquid receiver 73 . The third expansion valve 71 is an electronic expansion valve capable of reducing the pressure of the refrigerant in the high pressure section of the main refrigerant circuit to an intermediate pressure. The liquid receiver 73 is a container capable of separating the vapor phase and the liquid phase of the pressure-reduced two-phase refrigerant in the container, storing the refrigerant, and adjusting the circulation amount of the refrigerant in the main refrigerant circuit. A degassing pipe 93 connected to the upper part of the liquid receiver 73 and a pipe 94 connected to the lower part of the liquid receiver 73 separate the gas refrigerant and the liquid refrigerant in the liquid receiver 73 from each other. It is a pipe for taking out. The flow control valve 72 can adjust the amount of refrigerant in the liquid receiver 73 by adjusting the amount of liquid refrigerant discharged from the pipe 94 .

By providing the liquid receiver 73 in the injection flow path in this way, it becomes easy to ensure the degree of supercooling in the pipes 82 and 83 which are liquid pipes. This is because gas refrigerant generally exists in the liquid receiver 73, and the temperature of the refrigerant reaches the saturation temperature.

Further, if the liquid receiver 73 is provided in the intermediate pressure portion, even when the pressure in the high pressure portion of the main refrigerant circuit is high and the refrigerant is in a supercritical state, the intermediate pressure liquid refrigerant can be stored inside the liquid receiver 73. It becomes possible. Therefore, the design pressure of the container of the liquid receiver 73 can be made lower than that of the high-pressure part, and cost reduction can be achieved by making the container thinner.

The outdoor unit 2 further controls the pressure sensors 110 to 112, the temperature sensors 120 to 122, the compressor 10, the second expansion valve 40, the third expansion valve 71, the flow control valve 72, and the flow path switching section 74. and a control device 100 that

Pressure sensor 110 detects pressure PL at the suction port of compressor 10 and outputs the detected value to control device 100 . Pressure sensor 111 detects the discharge pressure PH of compressor 10 and outputs the detected value to control device 100 . Pressure sensor 112 detects pressure P<b>1 in pipe 83 at the outlet of second expansion valve 40 and outputs the detected value to control device 100 .

By providing the second expansion valve 40 in the liquid pipe, the outdoor unit 2 can reduce the pressure of the refrigerant below the design pressure of the load device 3 (for example, 4 MPa) and then send the refrigerant to the load device 3 . As a result, even if a supercritical refrigerant such as CO ₂ is used, a general-purpose product having the same design pressure as the conventional one can be used as the load device 3 .

Temperature sensor 120 detects a discharge temperature TH of compressor 10 and outputs the detected value to control device 100 . Temperature sensor 121 detects refrigerant temperature T<b>1 in piping 81 at the outlet of condenser 20 and outputs the detected value to control device 100 . Temperature sensor 122 detects refrigerant temperature T<b>2 at the outlet of first passage H<b>1 on the cooled side of heat exchanger 30 and outputs the detected value to control device 100 .

The flow path switching unit 74 includes pipes 97 and 98 obtained by bifurcating the pipe 96, a decompression device 77 arranged between the pipes 97 and 98, and opening/closing valves 75 and 76 arranged in the pipes 97 and 98, respectively. include.

A pipe 97 is connected between the pipe 96 and the intermediate pressure port G<b>3 , and the on-off valve 75 is provided in the pipe 97 . The pressure reducing device 77 and the on-off valve 76 are arranged in series between the outlet of the second passage H2 and the intake port G1.

The destination of the refrigerant in the second flow path F2 can be switched between the intermediate pressure port G3 of the compressor 10 and the suction port G1 by the on-off valve 75 and the on-off valve 76 .

In the present embodiment, the second flow path F2 controls the discharge temperature TH of the compressor 10 by causing the two-phase refrigerant to flow into the compressor 10 after being decompressed. In addition, the amount of refrigerant in the main refrigerant circuit can be adjusted by the liquid receiver 73 installed on the second flow path F2. Furthermore, the second flow path F2 also ensures supercooling of the refrigerant in the main refrigerant circuit by heat exchange by the heat exchanger 30 . The control device 100 switches the destination of the refrigerant by the on-off valve 75 and the on-off valve 76 so that each purpose can be achieved under each operating condition.

The outdoor unit 2 further includes a third flow path F3 that connects the pipes 83 and 92, and an on-off valve 78 provided in the third flow path F3. The on-off valve 78 is provided to avoid a sudden rise in the pressure P1 in the pipe 83 at the start of the pump-down operation, which will be described later.

The control device 100 includes a CPU (Central Processing Unit) 102, a memory 104 (ROM (Read Only Memory) and RAM (Random Access Memory)), an input/output buffer (not shown) for inputting and outputting various signals, and the like. Consists of The CPU 102 expands a program stored in the ROM into the RAM or the like and executes it. The program stored in the ROM is a program in which processing procedures of the control device 100 are described. The control device 100 controls each device in the outdoor unit 2 according to these programs. This control is not limited to processing by software, and processing by dedicated hardware (electronic circuit) is also possible.

(Control during normal operation of refrigeration cycle device)
The control device 100 feedback-controls the third expansion valve 71 so that the discharge temperature TH of the compressor 10 matches the target temperature.

FIG. 2 is a flow chart for explaining the control of the third expansion valve 71. As shown in FIG. When the discharge temperature TH of the compressor 10 is higher than the target temperature (YES in S21), the controller 100 increases the degree of opening of the third expansion valve 71 (S22). As a result, the amount of refrigerant flowing into the intermediate pressure port G3 or the suction port G1 via the liquid receiver 73 increases, so the discharge temperature TH decreases.

On the other hand, when the discharge temperature TH of the compressor 10 is lower than the target temperature (NO in S21 and YES in S23), the control device 100 reduces the degree of opening of the third expansion valve 71 (S24). As a result, the amount of refrigerant flowing into the intermediate pressure port G3 or the suction port G1 via the liquid receiver 73 is reduced, and the discharge temperature TH rises.

If discharge temperature TH=target temperature (NO in S21 and NO in S23), control device 100 maintains the opening degree of third expansion valve 71 at the current state.

In this manner, the control device 100 controls the degree of opening of the third expansion valve 71 so that the discharge temperature TH of the compressor 10 approaches the target temperature.

In addition, in order to ensure the subcooling degree SC of the refrigerant at the outlet of the condenser 20, the control device 100 feedback-controls the flow control valve 72 so that the refrigerant temperature T1 at the outlet of the condenser 20 matches the target temperature.

FIG. 3 is a flow chart for explaining the control of the flow regulating valve 72. As shown in FIG. If the degree of supercooling SC determined by the refrigerant temperature T1 at the outlet of the condenser 20 and the pressure (approximate by PH) of the condenser 20 is greater than the target value (YES in S31), the control device 100 closes the flow regulating valve 72 is decreased (S32). As a result, the amount of liquid refrigerant discharged from the liquid receiver 73 decreases and the amount of liquid refrigerant in the liquid receiver 73 increases, so the amount of refrigerant circulating in the main refrigerant circuit decreases and the refrigerant temperature T1 rises. Therefore, the degree of supercooling SC decreases.

On the other hand, when the degree of supercooling SC determined by the refrigerant temperature T1 at the outlet of the condenser 20 and the pressure (approximate by PH) of the condenser 20 is smaller than the target value (NO in S31 and YES in S33), the control device 100 , the opening degree of the flow control valve 72 is increased (S34). As a result, the amount of liquid refrigerant discharged from the liquid receiver 73 increases and the amount of liquid refrigerant stored in the liquid receiver 73 decreases. Since it decreases, the degree of supercooling SC increases.

If the degree of supercooling SC=the target value (NO in S31 and NO in S33), the control device 100 maintains the opening degree of the flow control valve 72 at the current state.

Thus, the control device 100 controls the degree of opening of the flow control valve 72 so that the refrigerant temperature T1 at the outlet of the condenser 20 approaches the target temperature.

Further, when CO ₂ is used as the refrigerant, control device 100 controls compressor 10 and second expansion valve 40 so as to use the supercritical region of the refrigerant. For example, when the outside air temperature is higher than the supercritical temperature of the refrigerant, such as in summer, the control device 100 increases the rotation speed of the compressor 10 more than in spring or autumn to increase the pressure of the high pressure section of the main refrigerant circuit. Since the pressure is reduced by the second expansion valve 40, the load device 3 can be used in common with a device that uses normal refrigerant. At this time, the second expansion valve 40 is controlled as follows.

The control device 100 feedback-controls the second expansion valve 40 so that the pressure P1 matches the target pressure. This target pressure is set to the same level as the pressure when using a normal refrigerant such as R410.

FIG. 4 is a flow chart for explaining the control of the second expansion valve 40. As shown in FIG. If the pressure P1 is higher than the target pressure (YES in S41), the controller 100 reduces the degree of opening of the second expansion valve 40 (S42). As a result, the amount of pressure reduction by the second expansion valve 40 increases, so the pressure P1 decreases.

On the other hand, if the pressure P1 is lower than the target pressure (NO in S41 and YES in S43), the control device 100 increases the degree of opening of the second expansion valve 40 (S44). As a result, the amount of pressure reduction by the second expansion valve 40 is reduced, so the pressure P1 increases.

If the pressure P1=the target pressure (NO in S41 and NO in S43), the control device 100 maintains the current opening of the second expansion valve 40 .

Since the pressure P1 is controlled in this way, the pressure in the load device 3 can be kept below the design pressure of a device that uses a normal refrigerant. becomes possible.

(Switching control of injection flow path)
When the temperature sensor 120 detects an excessive rise in the discharge temperature TH of the compressor 10, the control device 100 opens the on-off valve 75 and closes the on-off valve 76 to increase the amount of injection to the compressor 10 and discharge. Prevent further temperature rise.

At this time, if the intermediate pressure PM rises due to, for example, an increase in the evaporation temperature while the on-off valve 75 is open, the saturation temperature of the refrigerant rises. Since the cooling in the heat exchanger 30 becomes insufficient, the degree of subcooling of the refrigerant in the second expansion valve 40 may not be ensured.

Therefore, the control device 100 monitors the refrigerant temperature T2 with the temperature sensor 122 while the on-off valve 75 is open, and closes the on-off valve 75 when it detects that the degree of supercooling of the refrigerant cannot be ensured. , the on-off valve 76 is opened. As a result, the refrigerant on the low-pressure side and the refrigerant on the second flow path F<b>2 are allowed to merge, thereby reducing the intermediate pressure PM and ensuring the temperature difference in the heat exchanger 30 .

Since each device such as the liquid receiver 73 arranged in the second flow path F2 is depressurized by the third expansion valve 71 with respect to the main refrigerant circuit, the design pressure can be lowered, so the manufacturing cost can be reduced. . Even if the design pressure is lowered, if the pressure sensor 113 detects an increase in the intermediate pressure PM during operation due to overfilling of the refrigerant or an increase in the outside air temperature, the on-off valve 76 is opened to release the pressure to the low pressure side. Countermeasures can be taken.

(Control during pump-down operation)
Next, control during pump-down operation will be described. An on-off valve 28 or the like is installed in the pipe 85 through which the liquid refrigerant flows in the main refrigerant circuit, and the compressor 10 is operated with the pipe 85 cut off to move the refrigerant from the load device 3 to the outdoor unit 2 and store it. This is called pump-down operation. The pump-down operation is performed by, for example, operating the compressor 10 after closing the second expansion valve 40 or closing the on-off valve 28 before stopping the operation.

In general, the signal instructing the start of the pump-down operation is not particularly transmitted from the load device 3 side to the outdoor unit 2, and the pump-down operation is executed by continuing normal operation in the outdoor unit 2. .

In the pump-down operation, when the on-off valve 28 is closed and the pressure PL of the low-pressure portion detected by the pressure sensor 110 drops to the set value, the control device 100 stops the compressor 10 to stop the pump-down. ing. Since the compressor 10 is configured so that the refrigerant does not pass through it in the stopped state, the refrigerant does not flow back to the load device 3 .

However, when the first expansion valve 50 or the on-off valve 28 is closed during normal operation, the pressure P1 in the pipes 83, 84, 85 rises sharply. If the pressure P1 exceeds the design pressure of the pipes 83, 84, 85 and the load device 3, problems such as refrigerant leakage may occur, and it is necessary to control the pressure P1 within a range that does not exceed the design pressure.

Therefore, the control device 100 temporarily opens the on-off valve 78 to prevent a sudden rise in the pressure P1.

The control of the on-off valve 78 executed during pump-down will be described below. FIG. 5 is a flowchart for explaining control of the on-off valve 78. As shown in FIG.

In step S51, the control device 100 determines whether the pressure P1 has exceeded the design pressure. The design pressure here is a pressure that can be endured for a short period of time, and may be set slightly lower than the actual design pressure.

In step S51, if the pressure P1 does not exceed the design pressure (NO in S51), there is no need to reduce the pressure P1, so the control device 100 closes the on-off valve 78 in step S56, and proceeds to step S57. Proceed with processing.

On the other hand, when it is detected in step S51 that pressure P1 has exceeded the design pressure (YES in S51), control device 100 executes the processes of steps S52 to S55 to prevent pressure P1 from suddenly rising.

In step S52, the control device 100 determines whether the pressure P1 of the pipe 83 is higher than the pressure P2 of the pipe 92 of the injection flow path.

Unless P1>P2 (NO in S52), the pressure P1 in the pipe 83 does not decrease even if the on-off valve 78 is opened. , to reduce the pressure in the second flow path F2. Then, the process proceeds to step S54.

If P1>P2 (YES in S52), the pressure P1 in the pipe 83 can be lowered by opening the on-off valve 78, so the process proceeds to step S54 without executing the process of step S53.

It should be noted that the pipe 96 and the intermediate pressure port G3 may be directly connected without the flow path switching unit 74, but in this case, the processes of steps S52 and S53 are not executed, and it is determined as YES in step S51. In this case, the process proceeds to step S54 immediately.

In step S54, the control device 100 opens the on-off valve 78 and closes the flow control valve 72 to introduce the intermediate pressure of the second flow path F2 into the pipe 83 and reduce the pressure P1. This can prevent the pressure P1 from exceeding the design pressure of the pipes 83 and 84 and the load device 3 .

Although not necessarily performed, preferably, control device 100 further reduces the rotational speed of compressor 10 in step S55 to prevent pressure P1 in pipe 83 from further increasing. If the process of step S55 is executed when the pressure P1 suddenly rises temporarily, and if the pressure P1 subsequently drops, the pump-down operation time is shortened following the process of step S56. For this reason, processing may be performed to return the rotational speed of the compressor 10 to its original state.

Then, in step S57, the process is once returned to the main routine, and then the process of the flowchart of FIG. 5 is repeatedly executed.

Finally, the present embodiment will be summarized with reference to the drawings again. As shown in FIG. 1, the present disclosure provides an outdoor unit of a refrigeration cycle device 1 configured to be connected to a load device 3 including a first expansion valve 50 and an evaporator 60 corresponding to a "first expansion device". 2. The outdoor unit 2 corresponds to a refrigerant outlet port PO2 and a refrigerant inlet port PI2 for connecting to the load device 3, a first flow path F1, a compressor 10, a condenser 20, and a "second expansion device." A second expansion valve 40 , a second flow path F<b>2 , a third expansion valve 71 corresponding to a “third expansion device”, a liquid receiver 73 , a third flow path F<b>3 , and an on-off valve 78 are provided. The first flow path F1 is a flow path from the refrigerant inlet port PI2 to the refrigerant outlet port PO2, and forms a circulation flow path in which the refrigerant circulates together with the load device 3. Compressor 10, condenser 20 and second expansion valve 40 are arranged in first flow path F1. The second flow path F2 branches from a portion of the first flow path F1 between the condenser 20 and the second expansion valve 40 and is configured to return the refrigerant that has passed through the condenser 20 to the compressor 10 . The third expansion valve 71 and the liquid receiver 73 are arranged in the second flow path F2 in order from the branch point of the second flow path F2 from the first flow path F1. The third flow path F3 connects the portion of the first flow path F1 between the second expansion valve 40 and the refrigerant outlet port PO2 and the refrigerant inlet of the liquid receiver 73 . The on-off valve 78 is arranged in the third flow path F3.

As shown in FIG. 5, the on-off valve 78 is opened when the pressure P1 in the portion between the second expansion valve 40 and the refrigerant outlet port PO2 in the first flow path F1 exceeds a threshold value corresponding to the design pressure (S51 YES).

Since the third flow path F3 and the on-off valve 78 are provided in this way, even if the pressure P1 suddenly rises at the start of the pump-down operation, the pressure P1 can be quickly lowered. As a result, even when using a refrigerant such as CO ₂ that uses a supercritical region in the high-pressure section, it is possible to use piping and the load device 3 with a low design pressure.

Further, by arranging the liquid receiver 73 in the second flow path F2, even a refrigerant such as CO ₂ that uses a supercritical region can be stored in the liquid refrigerant state in the liquid receiver 73 . In addition, supercooling of the piping portion through which the liquid refrigerant flows can be ensured, and the performance of the refrigeration cycle device is improved.

The outdoor unit 2 further includes a flow rate adjustment valve 72 arranged in the second flow path F2 and configured to adjust the flow rate of the liquid refrigerant discharged from the liquid receiver 73 .

The outdoor unit 2 has a first passage H1 and a second passage H2, and a heat exchanger 30 configured to exchange heat between the refrigerant flowing through the first passage H1 and the refrigerant flowing through the second passage H2. further provide. The first passage H1 of the heat exchanger 30 is arranged between the condenser 20 of the first flow passage F1 and the branch point where the pipe 91 branches from the pipe 82, and the second passage H2 of the heat exchanger 30 is arranged between the condenser 20 and the pipe 82. It is arranged between the flow control valve 72 of the second flow path F2 and the compressor 10 .

Compressor 10 has a discharge port G2, a suction port G1, and an intermediate pressure port G3. The outdoor unit 2 further includes a channel switching portion 74 configured to switch the destination of the refrigerant that has passed through the second channel F2 to either the intermediate pressure port G3 or the suction port G1. As shown in FIG. 5, the flow path switching unit 74 switches when the pressure P1 in the portion downstream of the second expansion valve 40 in the first flow path F1 becomes lower than the pressure P2 of the liquid receiver 73 (NO in S52). , to select the intake port G1 as the destination.

With such a configuration, when the pressure of the liquid receiver 73 rises, the pressure of the liquid receiver 73 can be lowered, so that an operating condition in which the pressure of the liquid receiver 73 increases can be tolerated, and the operating range can be expanded. can.

The outdoor unit 2 further includes a pressure sensor 112 that detects the pressure P1 in the portion downstream of the second expansion valve 40 in the first flow path F1, and a control device 100 that controls the compressor 10 and the on-off valve 78. As shown in FIG. 5, when the pressure P1 detected by the pressure sensor 112 changes from being lower than the threshold value to being higher than the threshold value (YES in S51), the controller 100 opens the on-off valve 78 (S54 ) and reduce the rotational speed of the compressor 10 (S55).

By interlocking the on-off valve 78 and the compressor 10 in this manner, it is possible to quickly reduce the pressure P1 even if the pressure P1 suddenly increases.

Although the refrigerator including the refrigerating cycle device 1 has been described above as an example, the refrigerating cycle device 1 may be used in an air conditioner or the like.

The embodiments disclosed this time should be considered as examples and not restrictive in all respects. The scope of the present invention is indicated by the scope of the claims rather than the description of the above-described embodiments, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

REFERENCE SIGNS LIST 1 Refrigeration cycle device 2 Outdoor unit 3 Load device 10 Compressor 20 Condenser 22 Fan 28, 75, 76, 78 On-off valve 30 Heat exchanger 40 Second expansion valve 50 First expansion valve , 60 evaporator, 70 throttle device, 71 third expansion valve, 72 flow control valve, 73 liquid receiver, 74 flow path switching unit, 77 decompression device, 80 to 85, 88, 89, 91, 92, 94, 96 ~ 98 piping, 93 degassing piping, 100 control device, 104 memory, 110 to 113 pressure sensors, 120 to 122 temperature sensors, F1 first flow path, F2 second flow path, F3 third flow path, G1 suction port, G2 discharge port, G3 intermediate pressure port, H1 first passage, H2 second passage, PI2, PI3 refrigerant inlet port, PO2, PO3 refrigerant outlet port.

Claims (7)

An outdoor unit of a refrigeration cycle device configured to be connected to a load device including a first expansion device and an evaporator,
a refrigerant outlet port and a refrigerant inlet port for connecting with the load device;
a first flow path extending from the refrigerant inlet port to the refrigerant outlet port and forming a circulation flow path in which the refrigerant circulates together with the load device;
a compressor, a condenser and a second expansion device disposed in the first flow path;
a second flow path branching from a portion of the first flow path between the condenser and the second expansion device and configured to return refrigerant that has passed through the condenser back to the compressor;
a third expansion device and a liquid receiver arranged in the second flow path in order from a branch point of the second flow path from the first flow path;
a third flow path connecting a portion of the first flow path between the second expansion device and the refrigerant outlet port and a refrigerant inlet of the liquid receiver;
and an on-off valve arranged in the third flow path. 2. The outdoor unit according to claim 1, wherein the on-off valve is configured to open when pressure in a portion of the first flow path between the second expansion device and the refrigerant outlet port exceeds a threshold value. . 2. The outdoor unit according to claim 1, further comprising a flow rate adjustment valve arranged in said second flow path and configured to adjust a flow rate of liquid refrigerant discharged from said liquid receiver. a heat exchanger having a first passage and a second passage and configured to exchange heat between the refrigerant flowing through the first passage and the refrigerant flowing through the second passage;
the first passage of the heat exchanger is disposed between the condenser and the branch point of the first flow path;
4. The outdoor unit according to claim 3, wherein said second passage of said heat exchanger is arranged between said flow control valve of said second flow path and said compressor. The compressor is
a discharge port;
an intake port;
an intermediate pressure port;
The outdoor unit is
further comprising a flow path switching unit configured to be able to switch the destination of the refrigerant that has passed through the second flow path to either the intermediate pressure port or the suction port;
The flow path switching unit is configured to select the suction port as the destination when pressure in a portion of the first flow path downstream of the second expansion device drops below the pressure of the liquid receiver. The outdoor unit according to claim 1, wherein a pressure sensor that detects pressure in a portion of the first flow path downstream of the second expansion device;
A control device that controls the compressor and the on-off valve,
The control device is configured to open the on-off valve and reduce the rotation speed of the compressor when the detected value of the pressure sensor changes from a state lower than a threshold value to a state higher than the threshold value. , The outdoor unit according to claim 1. A refrigeration cycle apparatus comprising the outdoor unit according to any one of claims 1 to 6 and the load device.

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