JP7155440B2 - 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

A refrigeration system described in Japanese Patent Application Laid-Open No. 2014-01917 (Patent Document 1) switches an intermediate injection flow path to a suction injection flow path when it is necessary to lower the discharge temperature of the compressor. At this time, if the flow path is switched by the on-off valve during the operation of the compressor, the pressure fluctuation causes the compressor to vibrate. Therefore, in order to suppress vibration, it is necessary to switch the flow path after stopping the compressor. For this reason, it takes time to stop and restart the compressor, and this is a factor that deteriorates the operating efficiency.

An object of the present invention is to provide an outdoor unit and a refrigeration cycle apparatus with improved operating efficiency.

The present disclosure relates to an outdoor unit of a refrigeration cycle apparatus. The outdoor unit is configured to be connected to a load including a first expansion valve and an evaporator. The outdoor unit has a compressor having a suction port, a discharge port and an intermediate pressure port, a condenser, a first passage and a second passage, and between the refrigerant flowing through the first passage and the refrigerant flowing through the second passage. and a second expansion valve. A flow path from the compressor to the condenser, the first passage of the heat exchanger, and the second expansion valve forms a circulation flow path in which the refrigerant circulates together with the load device. The outdoor unit is arranged in a first refrigerant flow path through which the refrigerant flows from a portion of the circulation flow path between the outlet of the first passage and the second expansion valve to the inlet of the second passage, and the first refrigerant flow path. a third expansion valve; a second refrigerant passage that flows refrigerant from an outlet of the second passage to a suction port or an intermediate pressure port of the compressor; refrigerant arranged in the second refrigerant passage and flowing out from the outlet of the second passage; a flow path switching unit capable of selecting either one of the suction port and the intermediate pressure port as a destination of the air. The flow path switching unit includes a first on-off valve provided between the outlet of the second passage and the intermediate pressure port, and a pressure reducing device and the second valve arranged in series between the outlet of the second passage and the suction port. On-off valves.

According to the outdoor unit of the present disclosure and the refrigerating cycle device and the refrigerator including the same, it is possible to switch the injection flow path without stopping the compressor, so that the operating efficiency of the refrigerating cycle can be improved. can.

1 is an overall configuration diagram of a refrigeration cycle apparatus according to Embodiment 1. FIG. It is the figure which showed the various sensors and control apparatus which are arrange|positioned at the refrigerating-cycle apparatus 1 shown in FIG. 7 is a flowchart for explaining control of a flow path switching unit 74; 4 is a flowchart for explaining control during pump-down operation; 4 is a flowchart for explaining control during oil recovery operation; FIG. 6 is a diagram showing the configuration of a refrigeration cycle apparatus according to Embodiment 2; 7 is a flowchart for explaining control of a flow path switching unit 74A; FIG. 3 is a diagram showing the configuration of a refrigeration cycle device 201 of Modification 1; FIG. 10 is a diagram showing the configuration of a refrigeration cycle device 201A of Modification 2; FIG. 11 is a diagram showing the configuration of a refrigeration cycle device 201B of Modification 3;

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.

Embodiment 1.
FIG. 1 is an overall configuration diagram of a refrigeration cycle apparatus according to Embodiment 1. FIG. 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 , refrigeration cycle device 1 includes an outdoor unit 2 , a load device 3 , and extension pipes 84 and 88 .

The outdoor unit 2 is an outdoor unit of the refrigeration cycle device 1 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.

Load device 3 includes first expansion valve 50 , evaporator 60 , and pipes 85 , 86 , 87 . Evaporator 60 performs heat exchange between air and 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 an electronic expansion valve that can reduce the pressure of the refrigerant. Note that the first expansion valve 50 may be, for example, a temperature expansion valve that is controlled independently of the outdoor unit 2 .

Compressor 10 compresses the refrigerant sucked from pipes 89 and 97 and discharges it to 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. The refrigerant discharged from the compressor 10 to the pipe 80 is condensed and liquefied in the condenser 20 and flows out to the 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 coming out of the condenser 20 .

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

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.

The flow path from the compressor 10 to the condenser 20, the first passage H1 of the heat exchanger 30, and the second expansion valve 40 is the flow path in which the first expansion valve 50 and the evaporator 60 of the load device 3 are arranged. , form a circulation flow path through which the coolant circulates. Hereinafter, this circulation flow path is also referred to as the "main refrigerant circuit" of the refrigeration cycle.

The outdoor unit 2 includes first refrigerant passages (91 to 94) that flow refrigerant from a portion of the circulation passage between the outlet of the first passage H1 and the second expansion valve 40 to the inlet of the second passage H2; Second refrigerant passages (96 to 98) that flow refrigerant from the outlet of the second passage H2 to the suction port G1 or the intermediate pressure port G3 of the compressor 10; It further includes a channel switching portion 74 that can select either one of the suction port G1 and the intermediate pressure port G3 as the destination of the refrigerant flowing out of the port. Hereinafter, this flow path that branches off from the main refrigerant circuit and sends the refrigerant to the compressor 10 via the second passage H2 is referred to as an "injection flow path" 101. As shown in FIG.

The outdoor unit 2 further includes a liquid receiver (receiver) 73 that is arranged in the first refrigerant channel and stores the refrigerant. The third expansion valve 71 is arranged between pipes 91 and 92 between the inlet of the liquid receiver 73 and the portion between the outlet of the first passage H1 and the second expansion valve 40 of the circulation flow path. The outdoor unit 2 further comprises a flow control valve 72 disposed between a pipe 93 at the outlet of the liquid receiver 73 and a pipe 94 leading to the second passage H2, a gas discharge port of the liquid receiver 73 and the second passage. A gas vent passage 95 for connecting H2 and discharging the refrigerant gas in the liquid receiver 73 is provided.

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 that separates the pressure-reduced two-phase refrigerant into gas and liquid in the container, stores the refrigerant, and adjusts the amount of refrigerant in the main refrigerant circuit. A gas venting passage 95 connected to the upper part of the liquid receiver 73 and a pipe 93 connected to the lower part of the liquid receiver 73 separate the gas refrigerant and the liquid refrigerant in the liquid receiver 73 in a state of separation. 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 93 .

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 the liquid receiver 73 generally contains a gas refrigerant, and the refrigerant temperature reaches the saturation temperature.

The heat exchanger 30 exchanges heat between the refrigerant flowing through the first passage H<b>1 that is part of the main refrigerant circuit and the refrigerant flowing through the second passage H<b>2 that is part of the injection passage 101 .

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.

FIG. 2 is a diagram showing various sensors and a control device arranged in the refrigeration cycle apparatus 1 shown in FIG. Referring to FIG. 2, the outdoor unit 2 further includes pressure sensors 110 to 113, temperature sensors 120 to 125, and a control device 100 that controls the flow path switching section 74. As shown in FIG.

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 . Also, the pressure sensor 113 detects the intermediate pressure PM of the pipe 92 after the third expansion valve 71 and outputs the detected value to the 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 .

Temperature sensor 123 detects ambient temperature TA of outdoor unit 2 and outputs the detected value to control device 100 . Temperature sensor 125 detects the temperature at the outlet of second passage H2 of heat exchanger 30 and outputs the detected value to control device 100 . Temperature sensor 124 detects temperature TL of the suction pipe of compressor 10 and outputs the detected value to control device 100 .

The second refrigerant flow path includes a pipe 96 connecting between the outlet of the second passage H2 of the heat exchanger 30 and the flow path switching section 74 and the flow path switching section 74 . 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.

The on-off valve 75 is provided between the outlet of the second passage H2 and the intermediate pressure port G3. 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.

A pipe 97 is connected between the pipe 96 and the intermediate pressure port G3. The injection destination of the refrigerant 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 injection passage 101 controls the discharge temperature TH of the compressor 10 by causing the pressure-reduced two-phase refrigerant to flow into the compressor 10 . In addition, the amount of refrigerant in the main refrigerant circuit can be adjusted by the liquid receiver 73 installed on the injection flow path 101 . Furthermore, the injection flow path 101 also ensures supercooling of the refrigerant in the main refrigerant circuit through heat exchange by the heat exchanger 30 . The control device 100 performs switching of injection by the on-off valve 75 and the on-off valve 76 so that each purpose can be achieved under each operating condition.

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.

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. Specifically, the control device 100 increases the degree of opening of the third expansion valve 71 when the discharge temperature TH of the compressor 10 is higher than the target temperature. 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, the controller 100 reduces the degree of opening of the third expansion valve 71 . 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 the discharge temperature TH=target temperature, the control device 100 maintains the current opening of the third expansion valve 71 .

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. Specifically, 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 greater than the target value, the control device 100 Decrease the degree of opening. As a result, the amount of liquid refrigerant passing through 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, the control device 100 adjusts the opening of the flow control valve 72 to increase. As a result, the amount of gas refrigerant in the liquid receiver 73 increases and the amount of liquid refrigerant decreases, so the amount of refrigerant circulating in the main refrigerant circuit increases and the refrigerant temperature T1 decreases, thereby increasing the degree of supercooling SC.

If the degree of subcooling SC=the target value, the control device 100 maintains the current opening of the flow control valve 72 .

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. In this case, the pressure in the high pressure section of the main refrigerant circuit increases. A second expansion valve 40 reduces the pressure so that the load device 3 can be used with devices that are normally used with 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. Specifically, when the pressure P1 is higher than the target pressure, the control device 100 reduces the degree of opening of the second expansion valve 40 . As a result, the amount of pressure reduction by the second expansion valve 40 increases, so the pressure P1 decreases.

On the other hand, when the pressure P1 is lower than the target pressure, the controller 100 increases the degree of opening of the second expansion valve 40 . 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, 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 in the injection passage 101 can be merged, and the intermediate pressure PM can be lowered to ensure the temperature difference in the heat exchanger 30 .

Since each device such as the liquid receiver 73 arranged in the injection flow path 101 is decompressed by the third expansion valve 71 with respect to the main refrigerant circuit, the design pressure can be lowered, so that 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.

FIG. 3 is a flowchart for explaining the control of the channel switching section 74. As shown in FIG. 2 and 3, control device 100 determines in step S1 whether on-off valve 75 is open and on-off valve 76 is closed. If the on-off valve 75 is open and the on-off valve 76 is closed (YES in S1), the intermediate pressure port G3 is selected as the destination of the refrigerant flowing through the injection flow path 101 . Conversely, when the suction port G1 is selected as the destination of the refrigerant flowing through the injection flow path, the on-off valve 75 is closed and the on-off valve 76 is open.

When the on-off valve 75 is open (YES in S1), in step S2, the control device 100 determines whether the refrigerant temperature T2 at the outlet of the first passage H1 of the heat exchanger 30 is equal to or higher than the first temperature Tth1. to judge. Based on this, it is determined whether or not the degree of supercooling of the refrigerant passing through the pipe 82 is ensured.

When the refrigerant temperature T2 at the outlet of the first passage H1 of the heat exchanger 30 is higher than the first temperature Tth1 (YES in S2), the controller 100 controls the intake refrigerant temperature TL to reach the threshold value TLth1 in step S3. determine whether it is higher than Control device 100 similarly executes the process of step S3 when refrigerant temperature T2 at the outlet of first passage H1 of heat exchanger 30=first temperature Tth1 (YES in S2).

When the on-off valve 76 is opened and the injection passage 101 is connected to the low-pressure side of the extended pipe 88 on the gas side, the liquid refrigerant in the liquid receiver 73 may flow into the compressor 10 in a liquid back state. In step S<b>3 , in such a case, switching of the flow path to the on-off valve 76 is stopped to prevent the liquid refrigerant from flowing into the compressor 10 .

When the refrigerant temperature TL is lower than the saturation temperature at the pressure PL of the refrigerant sucked by the compressor 10 , liquid refrigerant may be sucked into the compressor 10 . At this time, since the compressor 10 breaks down due to liquid compression, control is performed to keep the on-off valve 76 closed when the suction of the liquid refrigerant is detected. The on-off valve 75 may also be closed when liquid refrigerant is sucked. Whether or not the compressor 10 sucks the liquid refrigerant is determined by checking that the degree of superheat, which is the difference between the saturation temperature at the pressure PL detected by the pressure sensor 110 and the temperature TL detected by the temperature sensor 124, has disappeared. can.

Also, in the injection passage 101, when it is detected that the temperature of the temperature sensor 125 is lower than the saturation pressure of the pressure sensor 113 and the degree of superheat is not obtained, the on-off valve 76 is closed and the liquid refrigerant is supplied to the compressor 10. Inhalation may be prevented.

Specifically, when the temperature TL of the refrigerant drawn into the compressor 10 is equal to or higher than the threshold value TLth1 (YES in S3), the control device 100 sequentially executes the processes of steps S4 to S5 to set the destination of the refrigerant to the suction port. The channel switching unit 74 is controlled so as to be G1. After closing the on-off valve 75 in step S4 and opening the on-off valve 76 in step S5, the control device 100 returns to the main routine in step S10.

In the present embodiment, since the decompression device 77 is provided between the on-off valve 75 and the on-off valve 76 , the pressure fluctuation when switching the flow path in the flow path switching section 74 is alleviated and transmitted to the compressor 10 . Therefore, since the vibration at the time of flow passage switching is reduced, the opening and closing of the on-off valves 75 and 76 can be performed without stopping the operation of the compressor 10 . Therefore, the switching of the flow path can be completed in a short time, and the energy loss associated with the stopping and restarting of the compressor 10 can be avoided.

When the refrigerant temperature T2 is lower than the first temperature Tth1 (NO in S2), the degree of subcooling is ensured, and when the refrigerant temperature TL sucked into the compressor 10 is lower than the threshold value TLth1 (in S3 NO), the liquid refrigerant may be sucked into the compressor 10, so the control device 100 returns the process to the main routine in step S10 without switching the flow path switching unit 74 in steps S4 to S5. .

On the other hand, when the on-off valve 75 is closed (NO in S1), the control device 100 performs steps S8 to S9 when the refrigerant temperature TL taken into the compressor 10 is lower than the threshold value TLth2 (NO in S6). The flow switching unit 74 is controlled so that the process is sequentially executed and the destination of the refrigerant is the intermediate pressure port G3. Note that TLth1>TLth2.

When the temperature TL of the refrigerant drawn into the compressor 10 is equal to or higher than the threshold value TLth2 (YES in S6), the controller 100 controls the temperature T2 of the refrigerant at the outlet of the first passage H1 of the heat exchanger 30 to reach the second temperature Tth2. The degree of supercooling of the refrigerant in the pipe 82 is determined depending on whether or not the above is satisfied.

When the coolant temperature T2 is equal to or higher than the second temperature Tth2 (YES in S7), the degree of supercooling cannot be ensured. In this case, the current state in which the on-off valve 75 is closed and the on-off valve 76 is open is maintained, and the process proceeds to step S10. Note that Tth1>Tth2.

On the other hand, if the coolant temperature T2 is lower than the second temperature Tth2 (NO in S7), the degree of subcooling is ensured, and the on-off valve 76 is closed in step S8 in order to restore the normal injection flow path state. After the on-off valve 75 is opened in step S9, the process proceeds to step S10.

As described above, when the pressure difference between the pipes 82 and 94 is small, the control device 100 controls the flow path switching unit 74 so as to increase the pressure difference so that the refrigerant is transferred from the intermediate pressure port G3 to the suction port G1. switch destinations. Therefore, the amount of pressure reduction in the third expansion valve 71 can be ensured, so the amount of temperature decrease in the third expansion valve 71 increases. Thereby, the temperature difference between the refrigerant temperature in the first passage H1 and the refrigerant temperature in the second passage H2 of the heat exchanger 30 can be ensured. Therefore, the amount of heat exchanged in the heat exchanger 30 is increased, and the refrigerant temperature T2 can be lowered.

Furthermore, since the decompression device 77 is arranged between the on-off valve 75 and the on-off valve 76, even if the flow path is switched without stopping the compressor 10, the behavior of the compressor 10 is stabilized. Higher speed can be achieved.

(Control during pump-down operation)
Next, control during pump-down operation will be described. By installing an on-off valve 28 or the like in the pipe 84 or 85 through which the liquid refrigerant flows in the main refrigerant circuit and operating the compressor 10 with the pipe 83 cut off, the refrigerant is moved from the load device 3 to the outdoor unit 2, Storing is called pump-down operation. The pump-down operation is performed, for example, by operating the compressor 10 after closing the second expansion valve 40 or closing the on-off valve 28 before stopping the operation or at the time of relocation.

When the outdoor unit 2 is stopped during pump-down operation, if the on-off valve 76 is opened to connect the injection flow path 101 to the low-pressure portion, the suction port (low-pressure side) and discharge port (high-pressure side) of the compressor 10 are connected. Therefore, even if the compressor 10 is operated, the pressure (low pressure) of the load device 3 does not decrease and the outdoor unit 2 cannot be stopped.

Control device 100 is configured to control compressor 10 and on-off valve 75 and on-off valve 76 . The control device 100 is configured to close the on-off valve 76 while operating the compressor 10 when executing the pump-down operation for collecting the refrigerant in the liquid receiver 73 .

The control for stopping the outdoor unit 2 by closing the on-off valve 76 during pump-down will be described below.

FIG. 4 is a flowchart for explaining control during pump-down operation. 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, under certain conditions, if supercooling is prioritized, the pump will be pumped down with the on-off valve 76 open, and the pressure PL may not drop completely and the outdoor unit may not stop. PL may rise immediately, and the compressor 10 may repeat starting and stopping in a short period of time.

Therefore, when the control device 100 detects in step S21 that the pressure PL in the low-pressure section has suddenly dropped below the set value, the control device 100 executes the processing of steps S22 to S25, and the opening/closing valve in the injection flow path 101 when the pump is down. By closing 76, the bypass to the high pressure or intermediate pressure can be cut off and the pump down can be stably performed.

Specifically, in step S22, the control device 100 closes the on-off valve 76 to cut off the bypass path between the load device 3 and the high pressure section.

Then, the control device 100 opens the on-off valve 75 in step S23, increases the opening degree of the third expansion valve 71 in step S24, and increases the opening degree of the flow rate adjustment valve 72 in step S25. is decreased, the amount of refrigerant stored in the liquid receiver 73 is increased.

In the above description, the on-off valve 75 is opened during the pump-down operation, but the on-off valve 75 may be closed.

In the above description, the on-off valve 76 is closed during the pump-down operation. However, if the pressure sensor 111 or 113 detects an excessive increase in pressure due to refrigerant overfilling, the on-off valve 76 is temporarily opened. By doing so, the pressure in the reservoir 73 may be temporarily released to the intake side of the compressor. As a result, the compressor 10 can be stopped after recovering as much refrigerant as possible in the liquid receiver 73 in the pump-down operation.

(Control of oil recovery operation)
When the liquid receiver 73 is arranged in the injection flow path 101 as in the configuration shown in FIGS. As a result, it becomes difficult for the refrigerating machine oil to return to the compressor 10 . Therefore, in the present embodiment, the oil recovery operation is executed.

Regarding the oil recovery operation, the outdoor unit 2 includes a gas vent passage 95 provided between the outlet of the liquid receiver 73 and the liquid receiver 73 for discharging the refrigerant gas in the liquid receiver 73 and a liquid in the liquid receiver 73. and a flow control valve 72 positioned at the refrigerant outlet. The outdoor unit 2 also includes a control device 100 configured to control the compressor 10 and the flow control valve 72 . The control device 100 is configured to increase the degree of opening of the third expansion valve 71 and decrease the degree of opening of the flow control valve 72 when the oil recovery condition for reducing the amount of refrigerating machine oil in the compressor 10 is satisfied. be.

FIG. 5 is a flow chart for explaining the control during the oil recovery operation. In step S31, the control device 100 determines whether or not the oil recovery condition is satisfied. The oil recovery condition is satisfied, for example, when the operating time has passed for a certain period of time, or when the low-speed operation of the compressor 10 has continued for a certain period of time or more.

If the oil recovery condition is not satisfied (NO in S31), control device 100 once returns to the main routine in step S35, and again monitors whether the oil recovery condition is satisfied in step S31.

On the other hand, if the oil recovery condition is satisfied (YES in S31), the control device 100 closes the on-off valve 76 in step S32, opens the on-off valve 75 in step S33, and adjusts the opening degree of the flow control valve 72 in step S34. decrease. As a result, the amount of refrigerant flowing out from the liquid refrigerant outlet of the liquid receiver 73 is reduced, the amount of liquid refrigerant stored in the liquid receiver 73 is increased, and the liquid refrigerant is separated and stored above the liquid refrigerant through the gas vent passage 95 . Refrigerant oil will start to flow out.

In this way, when the refrigerating machine oil and the refrigerant are incompatible and separated in the liquid receiver 73, the amount of refrigerant in the liquid receiver 73 is increased by the pump-down operation to raise the liquid level, thereby The refrigerating machine oil located at 1 can be recovered from the gas vent passage 95 to the compressor 10 .

Embodiment 2.
Embodiment 2 will explain a refrigeration cycle apparatus that switches circuits according to conditions when an accumulator is installed in a main refrigerant circuit.

FIG. 6 is a diagram showing the configuration of a refrigeration cycle apparatus according to Embodiment 2. FIG. A refrigeration cycle apparatus 1A shown in FIG. 6 includes an outdoor unit 2A instead of the outdoor unit 2 in the configuration of the refrigeration cycle apparatus 1 shown in FIGS. Since load device 3 has the same configuration, description thereof will not be repeated. Also, the arrangement of the pressure sensor and the temperature sensor is the same as in FIG. 2, so the description will not be repeated.

The outdoor unit 2A, in the configuration of the outdoor unit 2, includes a flow path switching section 74A instead of the flow path switching section 74, and further includes an accumulator 89B.

The accumulator 89B is configured to temporarily accumulate the refrigerant flowing from the load device 3 to the suction port G1 of the compressor 10 in the circulation flow path.

In addition to the structure of the flow path switching part 74 in FIG. 1, the flow path switching part 74A is an on-off valve that opens and closes the flow path connecting the outlet of the second passage H2 and the refrigerant inlet of the accumulator 89B with the decompression device 77 interposed. 78 is further included.

With such a configuration, the connection destination of the injection flow path 101 is three patterns of the intermediate pressure port G3 of the compressor 10, the suction port G1, and the upstream piping 89A of the accumulator 89B.

FIG. 7 is a flowchart for explaining the control of the channel switching section 74A.
6 and 7, control device 100 determines in step S31 whether on-off valve 75 is open and on-off valves 76 and 78 are closed. If the on-off valve 75 is open and the on-off valves 76 and 78 are closed (YES in S31), the intermediate pressure port G3 is selected as the destination of the refrigerant flowing through the injection passage 101. FIG.

If the on-off valve 75 is open (YES in S31), in step S32, the control device 100 determines whether the refrigerant temperature T2 at the outlet of the first passage H1 of the heat exchanger 30 is equal to or higher than the first temperature Tth1. to judge. Based on this, it is determined whether or not the degree of supercooling of the refrigerant passing through the pipe 82 is ensured.

When the refrigerant temperature T2 at the outlet of the first passage H1 of the heat exchanger 30 is higher than the first temperature Tth1 (YES in S32), the controller 100 controls the intake refrigerant temperature TL to reach the threshold value TLth1 in step S33. determine whether it is higher than Control device 100 similarly executes the process of step S33 when refrigerant temperature T2 at the outlet of first passage H1 of heat exchanger 30=first temperature Tth1 (YES in S32).

When the refrigerant suction temperature TL of the compressor 10 is equal to or higher than the threshold value TLth1 (YES in S33), the control device 100 determines in step S34 whether or not the discharge temperature TH is equal to or higher than the target temperature THth1.

When the discharge temperature TH is equal to or higher than the target temperature THth1 (YES in S34), the control device 100 sequentially executes the processes of steps S35 and S36 to direct the refrigerant to the suction port G1. to control. After closing the on-off valves 75 and 78 in step S35 and opening the on-off valve 76 in step S36, the control device 100 returns to the main routine in step S48.

When the discharge temperature TH is lower than the target temperature THth1 (NO in S34), the control device 100 sequentially executes the processes of steps S37 and S38 to switch the flow path so that the destination of the refrigerant is the pipe 89A at the inlet of the accumulator 89B. It controls the section 74A. After closing the on-off valves 75 and 76 in step S37 and opening the on-off valve 78 in step S38, the control device 100 returns to the main routine in step S48.

In the present embodiment, since the decompression device 77 is provided between the on-off valve 75 and the on-off valve 76 , the pressure fluctuation when switching the flow path in the flow path switching section 74 A is alleviated and transmitted to the compressor 10 . Therefore, since the vibration at the time of flow path switching is reduced, the on-off valves 75 , 76 , 78 can be opened and closed without stopping the operation of the compressor 10 . Therefore, the switching of the flow path can be completed in a short time, and the energy loss associated with the stopping and restarting of the compressor 10 can be avoided.

When the refrigerant temperature T2 is lower than the first temperature Tth1 (NO in S32), the degree of subcooling is ensured, and when the refrigerant temperature TL sucked into the compressor 10 is lower than the threshold value TLth1 (S33 NO), the liquid refrigerant may be sucked into the compressor 10, so the control device 100 does not switch the flow path switching unit 74A in steps S34 to S38, and proceeds to the main routine in step S48 . return.

On the other hand, when the on-off valve 75 is closed (NO in S31), the control device 100 performs steps S46 to S47 when the intake refrigerant temperature TL of the compressor 10 is lower than the threshold value TLth2 (NO in S39). The flow switching unit 74A is controlled so that the processing is executed sequentially and the destination of the refrigerant is the intermediate pressure port G3. Note that TLth1>TLth2.

Further, when the refrigerant temperature TL drawn into the compressor 10 is equal to or higher than the threshold value TLth2 (YES in S39), the control device 100 controls in step S40 that the refrigerant temperature T2 at the outlet of the first passage H1 of the heat exchanger 30 is The degree of subcooling of the refrigerant in the pipe 82 is determined depending on whether or not the temperature is equal to or higher than the second temperature Tth2. Note that Tth1>Tth2.

When the coolant temperature T2 is equal to or higher than the second temperature Tth2 (YES in S40), the degree of supercooling cannot be ensured. In this case, in step S41, the control device 100 determines whether or not the discharge temperature TH is equal to or higher than the target temperature THth2. Note that THth1<THth2.

When the discharge temperature TH is equal to or higher than the target temperature THth2 (YES in S41), the control device 100 sequentially executes the processes of steps S42 to S43 to direct the refrigerant to the suction port G1. to control. After closing the on-off valve 78 in step S42 and opening the on-off valve 76 in step S43, the control device 100 returns to the main routine in step S48.

When the discharge temperature TH is lower than the target temperature THth2 (NO in S41), the control device 100 sequentially executes the processes of steps S44 to S45 to switch the flow path so that the destination of the refrigerant is the pipe 89A at the inlet of the accumulator 89B. It controls the section 74A. After closing the on-off valve 76 in step S44 and opening the on-off valve 78 in step S45, the control device 100 returns to the main routine in step S48.

On the other hand, if the coolant temperature T2 is lower than the second temperature Tth2 (NO in S40), the degree of subcooling is ensured, and the on-off valves 76 and 78 are closed in step S46 in order to restore the normal injection flow path state. After the on-off valve 75 is opened in the closed state and step S47, the process proceeds to step S48.

Since the connection destination can be selected as described above, for example, when it is detected that the liquid refrigerant is sucked into the compressor 10 in a state where the degree of supercooling in the pipe 82 is not ensured, the connection destination of the injection flow path 101 is set to the accumulator 89B. It is possible to ensure both the degree of supercooling and the prevention of liquid refrigerant from being sucked into the compressor 10 by switching to before . Also, when the degree of supercooling is not ensured, the discharge temperature TH can be suppressed by connecting the injection passage 101 to the suction port G1 behind the accumulator 89B and directly feeding the cooled refrigerant.

FIG. 8 is a diagram showing the configuration of a refrigeration cycle device 201 of Modification 1. As shown in FIG. The refrigeration cycle device 201 has a configuration in which the connection destination of the injection flow path is only the suction port G1 alone. FIG. 9 is a diagram showing the configuration of a refrigeration cycle device 201A of Modification 2. As shown in FIG. The refrigerating cycle device 201A has a configuration in which the connection destination of the injection flow path is only the inlet pipe 89A of the accumulator 89B. FIG. 10 is a diagram showing the configuration of a refrigeration cycle device 201B of Modification 3. As shown in FIG. The refrigeration cycle device 201B has a configuration in which the connection destination of the injection flow path is only the intermediate pressure port G3 alone.

As shown in FIGS. 8 to 10, it is also possible to have a structure of each connecting point alone depending on the conditions of use of the refrigeration cycle apparatus.

For example, when the refrigeration cycle device is used under limited conditions such as refrigeration conditions, the intermediate pressure can be sufficiently lowered. 10 may be the only connection of the intermediate pressure port G3. Similarly, when the use is limited to the condition that the discharge temperature does not rise, it is possible to configure only the connection to the pipe 89A as shown in FIG.

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, 1A, 201, 201A, 201B refrigeration cycle device, 2, 2A outdoor unit, 3 load device, 10 compressor, 20 condenser, 22 fan, 28, 75, 76, 78 on-off valve, 30 heat exchanger, 40 2nd expansion valve 50 1st expansion valve 60 evaporator 71 3rd expansion valve 72 flow control valve 73 liquid receiver 74, 74A flow path switching unit 80 to 85, 89, 89A, 91 to 94 , 96 to 98 piping, 77 decompression device, 84, 88 extension piping, 89B accumulator, 95 degassing passage, 100 control device, 101 injection flow path, 102 CPU, 104 memory, 110 to 113 pressure sensor, 120 to 125 temperature sensor , G1 suction port, G2 discharge port, G3 intermediate pressure port, H1 first passage, H2 second passage.

Claims (6)

An outdoor unit of a refrigeration cycle apparatus configured to be connected to a load device including a first expansion valve and an evaporator,
a compressor having a suction port, a discharge port and an intermediate pressure port;
a condenser;
a heat exchanger having a first passage and a second passage, configured to exchange heat between the refrigerant flowing through the first passage and the refrigerant flowing through the second passage;
a second expansion valve,
A flow path from the compressor to the condenser, the first passage of the heat exchanger, and the second expansion valve forms a circulation flow path in which refrigerant circulates together with the load device,
a first refrigerant flow path through which refrigerant flows from a portion of the circulation flow path between the outlet of the first passage and the second expansion valve to the inlet of the second passage;
a third expansion valve arranged in the first refrigerant flow path;
a second refrigerant passage for flowing refrigerant from the outlet of the second passage to the suction port or the intermediate pressure port of the compressor;
a flow path switching unit arranged in the second refrigerant flow path and capable of selecting either one of the suction port and the intermediate pressure port as a destination of the refrigerant flowing out from the outlet of the second passage,
The flow path switching unit is
a first on-off valve provided between the outlet of the second passage and the intermediate pressure port;
a pressure reducing device and a second on-off valve arranged in series between the outlet of the second passage and the suction port ;
further comprising a liquid receiver arranged in the first refrigerant flow path and storing the refrigerant;
The outdoor unit , wherein the third expansion valve is arranged between a portion of the circulation flow path between the outlet of the first passage and the second expansion valve and an inlet of the liquid receiver . further comprising a control device configured to control the compressor and the first on-off valve and the second on-off valve;
2. The control device according to claim 1 , wherein the control device is configured to close the second on-off valve while operating the compressor when executing a pump-down operation for recovering the refrigerant in the liquid receiver. Outdoor unit as described. a gas release passage provided between the gas discharge port of the liquid receiver and the second passage for discharging refrigerant gas in the liquid receiver;
2. The outdoor unit according to claim 1 , further comprising a flow control valve arranged at a liquid refrigerant outlet of said liquid receiver. further comprising a controller configured to control the compressor and the flow control valve;
The control device is configured to increase the degree of opening of the third expansion valve and decrease the degree of opening of the flow rate control valve when an oil recovery condition for reducing refrigerating machine oil in the compressor is satisfied. 4. The outdoor unit according to claim 3 . The outdoor unit is
with an accumulator,
The accumulator is configured to temporarily accumulate refrigerant directed from the load device to the suction port of the compressor in the circulation flow path,
2. The outdoor unit according to claim 1, wherein the flow path switching section further includes a third on-off valve that opens and closes a flow path that connects an outlet of the second passage and a refrigerant inlet of the accumulator via the pressure reducing device. . A refrigeration cycle apparatus comprising the outdoor unit according to any one of claims 1 to 5 and the load device.

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