JP7150148B2 - Outdoor unit, refrigeration cycle device and refrigerator - Google Patents

Description

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

Japanese Patent Application Laid-Open No. 2017-187189 (Patent Document 1) discloses that the temperature of the refrigerant discharged from the compressor is prevented from becoming excessively high by controlling the torque of the motor built into the compressor. A refrigeration system is disclosed.

JP 2017-187189 A

In recent years, natural refrigerants such as _CO2 have attracted attention as refrigerants. Since the critical temperature of CO ₂ is low at 31° C., the condensation process of a refrigeration cycle apparatus using CO ₂ is carried out in a supercritical pressure state in summer when the outside air becomes hot. Therefore, there is a problem that the whole system becomes high pressure. Designing the entire system to withstand high pressure increases the cost over conventional CFC or alternative CFC systems. In order to reduce costs, it is desirable that conventionally used devices can be used as they are, even for load devices.

However, if the design pressure of the load device is lowered, it is necessary to reduce the pressure in advance by an expansion valve in the liquid pipe that sends the liquid refrigerant from the outdoor unit to the load device. At this time, if the gas refrigerant mixes with the liquid refrigerant before the expansion valve of the load device, the flow rate of the expansion valve will drop significantly, so it is necessary to secure a sufficient degree of supercooling (SC: subcool) to avoid a decline in performance. is necessary.

Also, in order to improve performance, it is conceivable to install an internal heat exchanger to increase the degree of subcooling and adopt an intermediate pressure injection circuit that returns the refrigerant on the cooling side to the intermediate pressure port of the compressor, but the evaporation temperature is high. In some cases, the intermediate pressure is also high, making it difficult to ensure the degree of supercooling in the internal heat exchanger. For this reason, there is a possibility that the performance of the refrigeration cycle device will decrease.

SUMMARY OF THE INVENTION An object of the present invention is to provide an outdoor unit, a refrigerating cycle device, and a refrigerator capable of ensuring the degree of supercooling of the refrigerant at the inlet portion of the load device even when the evaporation temperature is high.

An outdoor unit of the present disclosure is an outdoor unit of a refrigeration cycle apparatus configured to be connected to a load device including a first expansion valve and an evaporator. The outdoor unit includes a compressor having a suction port, a discharge port and an intermediate pressure port, a condenser, a heat exchanger and a second expansion valve. The heat exchanger has a first passageway and a second passageway, and is configured to exchange heat between refrigerant flowing through the first passageway and refrigerant flowing through the second passageway. 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 for switching the destination of the air to either the suction port or the intermediate pressure port.

According to the outdoor unit and the refrigerating cycle device and the refrigerator including the outdoor unit of the present disclosure, even if the evaporation temperature changes, the degree of supercooling of the liquid refrigerant sent from the outdoor unit to the load device can be ensured, so the refrigerating capacity decreases. can be prevented.

1 is an overall configuration diagram of a refrigeration cycle apparatus according to Embodiment 1 of the present disclosure; FIG. 7 is a flowchart for explaining control of a flow path switching unit 74; 7 is a flowchart for explaining control of a third expansion valve 71; 7 is a flowchart for explaining control of a fourth expansion valve 72; 4 is a flowchart for explaining control of a second expansion valve 40;

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 an embodiment of the present disclosure. 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 . The first expansion valve 50 is, for example, a temperature expansion valve 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 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, and the like can be adopted.

The condenser 20 condenses the refrigerant discharged from the compressor 10 to the pipe 80 and flows it to the pipe 81 . 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 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.

In this specification, for ease of explanation, the condenser 20 is also used to cool the refrigerant in the 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 of the load device 3 and the evaporator 60 are arranged. , form a circulation flow path through which the coolant circulates. Hereinafter, this circulation flow path is also referred to as the "main 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; and a flow path switching unit 74 for switching the destination of the refrigerant flowing out from the intake port G1 to either the suction port G1 or the intermediate pressure port G3. Hereinafter, this channel that branches off from the main circuit and sends the refrigerant to the compressor 10 via the second channel H2 is referred to as an "injection channel".

The outdoor unit 2 further includes a liquid receiver (receiver) 73 that is arranged in the first refrigerant flow path and stores the refrigerant, and a portion between the outlet of the first passage H1 of the circulation flow path and the second expansion valve 40. and the third expansion valve 71 arranged in the pipe 91 between the liquid receiver 73 and the inlet of the liquid receiver 73; A gas vent passage 93 for discharging refrigerant gas in the vessel 73 and a fourth expansion valve 72 arranged in the gas vent passage 93 are provided.

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.

Further, when the liquid receiver 73 is provided in the intermediate pressure portion, it becomes possible to store the intermediate pressure liquid refrigerant inside the liquid receiver 73 even when the high pressure portion of the main circuit is in a supercritical state. 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 includes pressure sensors 110 , 111 , 112 , temperature sensors 120 , 121 , 122 and a control device 100 that controls the flow path switching section 74 .

Pressure sensor 110 detects a suction pressure PL 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 CO2 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 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 channel switching unit 74 includes pipes 97 and 98 obtained by branching the pipe 96 into two, and on-off valves 75 and 76 arranged in the pipes 97 and 98, respectively. A pipe 97 is connected between the pipe 96 and the intermediate pressure port G3. A pipe 98 is connected between the pipe 96 and the suction port G1. By selectively opening one of the on-off valves 75 and 76, the destination of the coolant flowing through the injection flow path is switched.

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 develops 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.

FIG. 2 is a flowchart for explaining the control of the channel switching section 74. As shown in FIG. 1 and 2, 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 passage. Conversely, when the suction port G1 is selected as the destination of the refrigerant flowing through the injection channel, 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.

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 determines the destination of the refrigerant in the processing of steps S3 to S7. The flow switching unit 74 is controlled so as to switch to the port G1. Even when the refrigerant temperature T2 at the outlet of the first passage H1 of the heat exchanger 30=the first temperature Tth1 (YES in S2), the control device 100 sets the destination of the refrigerant to the suction port G1 in the processing of steps S3 to S7. The channel switching unit 74 is controlled such that

Specifically, when the intake air temperature TL of 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 S7 to determine the destination of the refrigerant to the suction port G1. The channel switching unit 74 is controlled such that The intake air temperature TL of the compressor 10 can be obtained by converting the intake pressure PL detected by the pressure sensor 110 . The operation of the compressor 10 is stopped in step S4, the on-off valve 75 is closed in step S5, the on-off valve 76 is opened in step S6, and the operation of the compressor 10 is restarted in step S7.

When the refrigerant temperature T2 is lower than the first temperature Tth1 (NO in S2), the degree of subcooling is ensured, and when the intake air temperature TL of the compressor 10 is lower than the threshold value TLth1 (NO in S3) ), since the evaporation temperature is low and the intermediate pressure is also low, control device 100 does not switch flow path switching unit 74 in steps S4 to S7.

On the other hand, when the on-off valve 75 is closed (NO in S1), if the refrigerant temperature T2 at the outlet of the first passage H1 of the heat exchanger 30 is lower than the second temperature Tth2 (YES in S8), In the processing of steps S9 to S13, the control device 100 controls the flow path switching section 74 so that the destination of the refrigerant is the intermediate pressure port G3. The control device 100 controls the flow path switching unit 74 so that the destination of the refrigerant is the intermediate pressure port G3 even when the refrigerant temperature T2=the second temperature Tth2 ( YES in S8). Note that Tth1>Tth2.

Specifically, when the intake air temperature TL of the compressor 10 is equal to or lower than the threshold value TLth 2 (YES in S9), the control device 100 sequentially executes the processes of steps S10 to S13 to change the destination of the refrigerant to the intermediate pressure. The flow switching unit 74 is controlled to switch to port G3. Note that TLth1>TLth2. The operation of the compressor 10 is stopped in step S10, the on-off valve 76 is closed in step S11, the on-off valve 75 is opened in step S12, and the operation of the compressor 10 is restarted in step S13.

When the refrigerant temperature T2 is higher than the second temperature Tth2 (NO in S8), the degree of subcooling cannot be ensured, and when the intake air temperature TL of the compressor 10 is higher than the threshold value TLth2 (in S9 NO) has a high evaporation temperature and a high intermediate pressure. Therefore, the controller 100 maintains the destination of the refrigerant in the flow path switching unit 74 as the suction port G1 and does not switch the flow path.

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.

As shown in the flowchart of FIG. 2, it is preferable to switch the flow path while the operation is stopped because the behavior is stabilized. The flow chart may be modified so as to switch the flow path. Similarly, the flow chart may be modified so that the flow paths are switched during operation without performing steps S10 and S13 among the processes of steps S10 to S13.

FIG. 3 is a flowchart for explaining control of the third expansion valve 71. As shown in FIG. 1 and 3, the third expansion valve 71 is feedback-controlled so that the discharge temperature TH of the compressor 10 matches the target temperature. Specifically, when the discharge temperature TH of the compressor 10 is higher than the target temperature in step S21 (YES in S21), the controller 100 increases the opening degree of the third expansion valve 71 in step 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 controller 100 reduces the opening degree of the third expansion valve 71 in step 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 the discharge temperature TH=the target temperature (NO in S21 and NO in S23), the degree of opening of the third expansion valve 71 is maintained at its 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.

The frequency of changing the degree of opening of the third expansion valve 71 may be reduced by setting the target temperature in step S21>the target temperature in step S23.

FIG. 4 is a flowchart for explaining control of the fourth expansion valve 72. As shown in FIG. Referring to FIGS. 1 and 4, the fourth expansion valve 72 adjusts the refrigerant temperature T1 at the outlet of the condenser 20 to match the target temperature in order to ensure the degree of subcooling of the refrigerant at the outlet of the condenser 20. Feedback controlled. Specifically, in step S31, if the degree of supercooling SC determined by the refrigerant temperature T1 at the outlet of the condenser 20 and the pressure of the condenser 20 (approximate by PH) is greater than the target value (YES in S31), the control The device 100 increases the opening degree of the fourth expansion valve 72 in step S32. As a result, the gas refrigerant escapes from the liquid receiver 73 and the amount of liquid refrigerant increases, so the amount of refrigerant circulating in the main circuit decreases, and the refrigerant temperature rises as a whole, causing the refrigerant temperature T1 to rise. The degree of cooling SC decreases.

On the other hand, if the degree of subcooling 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 (YES in S33), the control device 100 in step S34 The degree of opening of the fourth expansion valve 72 is decreased. 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 circuit increases. The degree of cooling SC increases.

If degree of supercooling SC=target value (NO in S31 and NO in S33), the degree of opening of fourth expansion valve 72 is maintained at its current state.

In this manner, the control device 100 controls the opening degree of the fourth expansion valve 72 so that the refrigerant temperature T1 at the outlet of the condenser 20 approaches the target temperature.

The frequency of changing the opening degree of the fourth expansion valve 72 may be reduced by setting the target value of step S31>the target value of step S33.

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 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.

FIG. 5 is a flow chart for explaining the control of the second expansion valve 40. As shown in FIG. 1 and 5, the second expansion valve 40 is feedback-controlled so that the pressure P1 matches the target pressure. Specifically, in step S41, if pressure P1 is higher than the target pressure (YES in S41), control device 100 reduces the degree of opening of second expansion valve 40 in step 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 controller 100 increases the degree of opening of the second expansion valve 40 in step 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 degree of opening of the second expansion valve 40 maintains the current state.

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.

As described above, the present embodiment has been described by exemplifying a refrigerator including the refrigerating cycle device 1, but 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 30 Heat exchanger 40 Second expansion valve 50 First expansion valve 60 Evaporator 71 Third expansion valve , 72 fourth expansion valve, 73 liquid receiver, 74 channel switching unit, 75, 76 on-off valve, 80, 81, 82, 83, 85, 89, 91, 94, 96, 97, 98 piping, 84, 88 Extension piping, 93 degassing passage, 100 control device, 102 CPU, 104 memory, 110, 111, 112 pressure sensor, 120, 121, 122 temperature sensor, G1 suction port, G2 discharge port, G3 intermediate pressure port, H1 first Aisle, H2 Second Aisle.

Claims (8)

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 through which refrigerant flows 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 switching a destination of the refrigerant flowing out from the outlet of the second passage to either the suction port or the intermediate pressure port ;
a liquid receiver arranged in the first refrigerant flow path and storing a refrigerant;
A control device that controls the flow path switching unit,
the third expansion valve is disposed 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;
The control device controls the flow path switching unit so that the destination of the refrigerant is the suction port when the temperature of the outlet of the first passage of the heat exchanger is higher than a first temperature. unit. a gas release passage provided between an outlet of the liquid receiver and the liquid receiver for discharging refrigerant gas in the liquid receiver;
2. The outdoor unit according to claim 1, further comprising a fourth expansion valve arranged in said gas vent passage. When the temperature of the outlet of the first passage of the heat exchanger is lower than a second temperature, the control device controls the flow path switching unit so that the destination of the refrigerant is the intermediate pressure port. The outdoor unit according to claim 1 . 2. The outdoor unit according to claim 1 , wherein said controller controls the degree of opening of said third expansion valve so that the refrigerant temperature at said discharge port of said compressor approaches a target temperature. 3. The outdoor unit according to claim 2 , wherein said control device controls the degree of opening of said fourth expansion valve so that the refrigerant temperature at the outlet of said condenser approaches a target temperature. The outdoor unit according to any one of claims 1 to 5 , wherein the controller controls the compressor and the second expansion valve so as to use the supercritical region of the refrigerant. A refrigeration cycle apparatus comprising the outdoor unit according to any one of claims 1 to 6 and the load device. A refrigerator comprising the refrigeration cycle device according to claim 7 .

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