Refrigeration cycle apparatus

A refrigeration cycle apparatus capable of performing pump down operation while suppressing degradation in performance is provided. The refrigeration cycle apparatus includes an outdoor heat exchanger, a compressor including an inlet side and an outlet side, at least one indoor heat exchanger, a four-way valve, a check valve including an inlet side and an outlet side, a pipe serving as a first flow path connecting the outlet side of the check valve to the inlet side of the compressor, a first on-off valve, and a refrigerant leak detection device. The refrigeration cycle apparatus is configured such that, when a refrigerant leak is detected by the refrigerant leak detection device, pump down operation is performed as refrigerant transfer operation of transferring the refrigerant from the indoor heat exchanger to the outdoor heat exchanger.

CROSS REFERENCE TO RELATED APPLICATION

This application is a U.S. national stage application of International Application PCT/JP2016/081639, filed on Oct. 25, 2016, the contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to refrigeration cycle apparatuses, and more particularly to a refrigeration cycle apparatus configured to perform pump down operation when a refrigerant leak occurs.

BACKGROUND

Pump down operation is an operation intended to transfer refrigerant in an indoor unit and in pipes between the indoor unit and an outdoor unit into the outdoor unit by operating a compressor by closing a liquid shutoff valve. Generally, the pump down operation is often performed in existing equipment at the time of renewal or relocation of an air conditioner and a refrigerator.

Japanese Patent Laying-Open No. 5-118720 (PTL 1) discloses a refrigeration apparatus that minimizes the amount of refrigerant released into the room or into the atmosphere when a refrigerant leak occurs due to a failure of the refrigeration apparatus. This refrigeration apparatus is provided with a leak detection device for detecting a refrigerant leak, and on-off valves at portions of two pipes connecting an indoor unit and an outdoor unit. In this refrigeration apparatus, pump down operation is performed when the leak detection device detects a refrigerant leak. In the pump down operation, one of the on-off valves provided at portions of the pipes is closed first, and the other on-off valve is closed after refrigerant recovery operation has been performed.

PATENT LITERATURE

However, the two on-off valves disposed at portions of the two pipes described above, which are required to perform the pump down operation as described above, are not required during normal operation, and are generally not installed. The installation of such on-off valves may cause an increase in flow path resistance of the pipes, resulting in degraded performance of a refrigeration cycle apparatus.

SUMMARY

An object of the present invention is to provide a refrigeration cycle apparatus capable of performing pump down operation while suppressing degradation in performance.

A refrigeration cycle apparatus according to the present embodiment includes an outdoor heat exchanger, a compressor including an inlet side and an outlet side, at least one indoor heat exchanger, a four-way valve, a check valve including an inlet side and an outlet side, a first flow path connecting the outlet side of the check valve to the inlet side of the compressor, a first on-off valve, and a refrigerant leak detection device. The refrigerant leak detection device is configured to detect a refrigerant leak from a refrigerant circuit. The refrigerant circuit is configured to cause at least refrigerant to circulate through the compressor, the outdoor heat exchanger, the first on-off valve, the at least one indoor heat exchanger, the four-way valve, and the check valve. The refrigerant circuit is configured, by operation of the four-way valve, such that the refrigerant circulates successively through the compressor, the outdoor heat exchanger, the first on-off valve, the at least one indoor heat exchanger, the check valve, and the first flow path in a cooling operation state. The refrigerant circuit is also configured such that the refrigerant circulates successively through the compressor, the at least one indoor heat exchanger, the first on-off valve, the outdoor heat exchanger, the check valve, and the first flow path in a heating operation state. The refrigeration cycle apparatus is configured such that, when a refrigerant leak is detected by the refrigerant leak detection device, refrigerant transfer operation of transferring the refrigerant from the indoor heat exchanger to the outdoor heat exchanger is performed. In the refrigerant transfer operation, when the refrigerant leak is detected by the refrigerant leak detection device in the cooling operation state, the compressor is operated with the first on-off valve being closed. In the refrigerant transfer operation, when the refrigerant leak is detected by the refrigerant leak detection device in the heating operation state, the compressor is operated with the first on-off valve being closed, after an operation state of the refrigerant circuit is changed from the heating operation state to the cooling operation state.

According to the above, since the check valve is disposed at the inlet side of the compressor, backflow of the refrigerant to the indoor unit can be suppressed by this check valve after the refrigerant has been transferred to the outdoor heat exchanger by the refrigerant transfer operation. In addition, the check valve increases flow path resistance of a pipe to a lesser extent than the on-off valve. Accordingly, a refrigeration cycle apparatus can be obtained that is capable of performing refrigerant transfer operation, that is, pump down operation, without causing degradation in performance resulting from an increase in flow path resistance.

DETAILED DESCRIPTION

In the following, embodiments of the present invention will be described in detail with reference to the drawings. Although a plurality of embodiments are described below, it has been intended from the time of filing of the present application to appropriately combine configurations described in the respective embodiments. The same or corresponding parts are designated by the same symbols in the drawings and will not be described repeatedly.

First Embodiment

<Configuration of Refrigeration Cycle Apparatus>

FIG. 1shows a refrigerant circuit of a refrigeration cycle apparatus1according to a first embodiment. Refrigeration cycle apparatus1shown inFIG. 1is an air conditioning apparatus, and includes an outdoor unit2and a plurality of indoor units3a,3b. Although two indoor units3a,3bare disclosed inFIG. 1, there may be three or more indoor units, or there may be one indoor unit. Outdoor unit2is connected to indoor units3a,3bby pipes21,30,32b,33b.

Outdoor unit2mainly includes a four-way valve6, a check valve4, a compressor5, an outdoor heat exchanger7, a high pressure receiver corresponding to a first receiver, a first on-off valve9, a pressure sensor10, and a controller17. Indoor unit3amainly includes an indoor heat exchanger12a, a second on-off valve11a, and a refrigerant leak detection device13a. Indoor unit3bmainly includes an indoor heat exchanger12b, a second on-off valve11b, and a refrigerant leak detection device13b. Each of first on-off valve9and second on-off valves11a,11bis an expansion valve, for example, a liner expansion valve (LEV). The degree of opening of each of first on-off valve9and second on-off valves11a,11bis controlled such that the valve is fully opened, performs SH (superheat) control, SC (subcool) control, or is closed, depending on a control signal received from controller17to be described later.

In outdoor unit2, a first port of four-way valve6is connected to an inlet side of check valve4through a pipe23. Pressure sensor10is installed at pipe23. An outlet side of check valve4is connected to an inlet side of compressor5through a pipe24corresponding to a first flow path. An outlet side of compressor5is connected to a second port of four-way valve6through a pipe25. The third port of four-way valve6is connected to outdoor heat exchanger7through a pipe26. Outdoor heat exchanger7is connected to a high pressure receiver8through a pipe27. High pressure receiver8is connected to first on-off valve9through a pipe28. First on-off valve9is connected to a third on-off valve14through a pipe29.

A fourth port of four-way valve6is connected to a fourth on-off valve15through a pipe22. Four-way valve6is configured to switch between a state in which the first port is connected to the third port and a state in which the first port is connected to the fourth port. Four-way valve6is also configured to switch between a state in which the second port is connected to the third port and a state in which the second port is connected to the fourth port. As to the connection state of each port of four-way valve6inFIG. 1, the connection state indicated by dotted lines is a state during cooling operation, and the connection state indicated by solid lines is a state during heating operation. That is, during the cooling operation, the second port and the third port are connected and the first port and the fourth port are connected in four-way valve6. During the heating operation, the first port and the third port are connected and the second port and the fourth port are connected in four-way valve6.

In indoor unit3a, second on-off valve11ais connected to indoor heat exchanger12athrough a pipe31a. Indoor heat exchanger12ais connected to fourth on-off valve15through pipes33a,21. Second on-off valve11ais connected to third on-off valve14through pipes32a,30. Refrigerant leak detection device13ais installed within a casing of indoor unit3a, for example.

In indoor unit3b, second on-off valve11bis connected to indoor heat exchanger12bthrough a pipe31b. Indoor heat exchanger12bis connected to fourth on-off valve15through pipes33b,21. Second on-off valve11bis connected to third on-off valve14through pipes32b,30. Refrigerant leak detection device13bis installed within a casing of indoor unit3b, for example. Depending on the type of refrigerant to be detected, any mechanism can be employed for the refrigerant leak detection devices (or refrigerant leak detectors)13a,13b. Here, stated from a different perspective, second on-off valves11a,11bare disposed at pipes29,30,32a,31a,32b,31bserving as a third flow path connecting first on-off valve9to at least one indoor heat exchangers12a,12b.

Controller17installed in outdoor unit2is connected to pressure sensor10, compressor5, first on-off valve9, second on-off valves11a,11b, four-way valve6, and refrigerant leak detection devices13a,13b. Controller17controls each device of outdoor unit2and indoor units3a,3bduring pump down operation to be described later. It should be noted that controller17includes a CPU (Central Processing Unit), a memory, an input/output buffer and the like (neither shown). The control in controller17is not limited to processing by software, but can also be processed by dedicated hardware (electronic circuit).

<Action of Refrigeration Cycle Apparatus>

Refrigeration cycle apparatus1is configured to switch its operation state between a cooling operation state and a heating operation state. The action of refrigeration cycle apparatus1in each operation state is described below.

(1) Cooling Operation State

High-temperature and high-pressure gas refrigerant compressed at compressor5flows into the second port of four-way valve6. In four-way valve6, a flow path connecting the second port and the third port is formed as indicated by the dotted lines inFIG. 1. Thus, the gas refrigerant flows to outdoor heat exchanger7through pipe26. Outdoor heat exchanger7serves as a condenser. The gas refrigerant is cooled at outdoor heat exchanger7by air blown by an outdoor fan not shown in the figure. Thus, the gas refrigerant undergoes a phase change into a two-phase refrigerant state in which gas refrigerant and liquid refrigerant are present in a mixed manner, or into a single-phase state of liquid refrigerant. Subsequently, the refrigerant flows in the refrigerant circuit through high pressure receiver8and first on-off valve9to indoor units3a,3b. The refrigerant that has flown to indoor units3a,3bflows to indoor heat exchangers12a,12bthrough second on-off valves11a,11b. Indoor heat exchangers12a,12beach serve as an evaporator. Thus, the liquid refrigerant in the refrigerant in indoor heat exchangers12a,12bis evaporated and gasified by air blown by an indoor fan (not shown). The gasified refrigerant flows into the fourth port of four-way valve6through pipes33a,33b,21,22. Since the fourth port and the first port have been connected in four-way valve6as described above, the gasified refrigerant returns from the first port to compressor5through pipe23, check valve4and pipe24. This cycle allows cooling operation of cooling indoor air.

(2) Heating Operation State

High-temperature and high-pressure gas refrigerant compressed at compressor5flows into the second port of four-way valve6. In four-way valve6, a flow path connecting the second port and the fourth port is formed as indicated by the solid lines inFIG. 1. Thus, the gas refrigerant that has passed through the fourth port of four-way valve6flows to indoor units3a,3bthrough pipe22, fourth on-off valve15and pipe21. The refrigerant that has flown to indoor units3a,3bpasses through indoor heat exchangers12a,12bof respective indoor units3a,3b. Here, indoor heat exchangers12a,12beach serve as a condenser. Thus, the gas refrigerant in indoor heat exchangers12a,12bis cooled and liquefied by air supplied to indoor heat exchangers12a,12bby the indoor fan (not shown). In addition, air warmed by heat from the gas refrigerant in indoor heat exchangers12a,12bis supplied into a room to be heated.

The liquefied liquid refrigerant passes through second on-off valves11a,11beach of which is a linear expansion valve (LEV), to thereby enter a two-phase refrigerant state in which low-temperature and low-pressure gas refrigerant and liquid refrigerant are present in a mixed manner, and returns to the outdoor unit through pipes32a,32b,30. Subsequently, the refrigerant that has entered a two-phase refrigerant state (also referred to as two-phase refrigerant) flows to outdoor heat exchanger7through first on-off valve9which is an expansion valve. Outdoor heat exchanger7serves as an evaporator. In outdoor heat exchanger7, the two-phase refrigerant is heated by air blown by the outdoor fan (not shown). As a result, the now-gasified refrigerant flows into the third port of four-way valve6. The third port and the first port are connected in four-way valve6. Thus, the gas refrigerant supplied to the third port returns to compressor5through the first port, pipe23, check valve4and pipe24. This cycle allows heating operation of heating indoor air.

<Pump Down Operation in Cooling Operation State of Refrigeration Cycle Apparatus>

Referring now toFIGS. 2 and 3, pump down operation when a refrigerant leak is detected by one of refrigerant leak detection devices13a,13bin the above-described cooling operation state is described.FIG. 2is a flowchart illustrating the pump down operation in refrigeration cycle apparatus1shown inFIG. 1.FIG. 3is a flowchart illustrating specific action of a pump down operation step (S20) inFIG. 2during the cooling operation. It should be noted that control with regard to the pump down operation as described below is performed by controller17controlling first on-off valve9, second on-off valves11a,11b, compressor5and the like.

As shown inFIG. 2, in refrigeration cycle apparatus1, a step of confirming whether a refrigerant leak has been detected (S10) is performed. When a refrigerant leak is not detected in this step (S10), this step (S10) is repeated at regular intervals, for example. A method of detecting a refrigerant leak may be such that, when a refrigerant leak is detected by refrigerant leak detection devices13a,13b, a signal is transmitted from refrigerant leak detection devices13a,13bto controller17, for example.

When a refrigerant leak is detected in the step (S10), the pump down operation step (S20) is performed. In this step (S20), as shown inFIG. 3, after the pump down operation step is started (S21), a step of fully closing first on-off valve9(S22) is performed first. Specifically, first on-off valve9is fully closed by a control signal from controller17. Next, a step of fully opening second on-off valves11a,11b(S23) is performed. Specifically, second on-off valves11a,11bare fully opened by a control signal from controller17. The operation of compressor5is continued in this state. As a result, the refrigerant in indoor units3a,3bis transferred to outdoor unit2. The transferred refrigerant cannot return to indoor units3a,3bthrough pipes29,30, because first on-off valve9has been fully closed. As a result, in outdoor unit2, the refrigerant is accumulated in a refrigerant circuit portion from first on-off valve9, pipe28, high pressure receiver8, pipe27, outdoor heat exchanger7, pipes26,25, compressor5to pipe24. In addition, because check valve4is disposed, the refrigerant transferred to the outlet side of check valve4cannot return to the inlet side of check valve4.

Next, a step of confirming whether a condition for stopping the pump down operation has been satisfied (S24) is performed. Any condition can be employed as the condition for stopping the pump down operation. Any condition can be used as this condition, as long as the condition indicates that the amount of refrigerant in indoor units3a,3bhas reached an amount equal to or lower than a prescribed amount. For example, a condition that pressure at the inlet side of check valve4has reached a value equal to or lower than a prescribed value, or that a prescribed period of time has elapsed since the start of the pump down operation can be employed as this condition. The pressure at the inlet side of check valve4can be detected by pressure sensor10, for example. In this step (S24), the confirmation of whether this condition has been satisfied is repeated until this condition is satisfied.

When it is confirmed in the step (S24) that the condition for stopping the pump down operation has been satisfied, a step of stopping the compressor (S25) is performed. In this step, the operation of compressor5is stopped by a control signal from controller17. The pump down operation ends in this manner (S26).

<Pump Down Operation in Heating Operation State of Refrigeration Cycle Apparatus>

Referring now toFIGS. 2 and 4, pump down operation when a refrigerant leak is detected by one of refrigerant leak detection devices13a,13bin the above-described heating operation state is described.FIG. 4is a flowchart illustrating specific action of the pump down operation step (S20) inFIG. 2during the heating operation.

The step (S10) shown inFIG. 2is similar to that during the cooling operation described above. Then, when a refrigerant leak is detected during the heating operation, the steps shown inFIG. 4are performed as the pump down operation step (S20).

As shown inFIG. 4, in the pump down operation when a refrigerant leak is detected during the heating operation, a step of switching the state of the four-way valve to the state for cooling (S27) is performed first. Specifically, the internal flow path of four-way valve6is switched from the path indicated by the solid lines to the path indicated by the dotted lines inFIG. 1by a control signal from controller17.

Subsequently, the steps (S22) to (S26) are performed, as with the pump down operation in the cooling operation state.

<Function and Effect of Refrigeration Cycle Apparatus>

To summarize the configuration of refrigeration cycle apparatus1according to the present embodiment, refrigeration cycle apparatus1includes outdoor heat exchanger7, compressor5including the inlet side and the outlet side, at least one indoor heat exchangers12a,12b, four-way valve6, check valve4including the inlet side and the outlet side, pipe24serving as the first flow path connecting the outlet side of check valve4to the inlet side of compressor5, first on-off valve9, and refrigerant leak detection devices13a,13b. Refrigerant leak detection devices13a,13bare configured to detect a refrigerant leak from the refrigerant circuit. The refrigerant circuit is configured to cause at least refrigerant to circulate through compressor5, outdoor heat exchanger7, first on-off valve9, at least one indoor heat exchangers12a,12b, four-way valve6, and check valve4. The refrigerant circuit is configured, by operation of four-way valve6, such that the refrigerant circulates successively through compressor5, outdoor heat exchanger7, first on-off valve9, at least one indoor heat exchangers12a,12b, check valve4, and pipe24serving as the first flow path in the cooling operation state. The refrigerant circuit is also configured such that the refrigerant circulates successively through compressor5, at least one indoor heat exchangers12a,12b, first on-off valve9, outdoor heat exchanger7, check valve4, and pipe24serving as the first flow path in the heating operation state. Refrigeration cycle apparatus1is configured such that, when a refrigerant leak is detected by refrigerant leak detection devices13a,13b, pump down operation is performed as refrigerant transfer operation of transferring the refrigerant from indoor heat exchangers12a,12bto outdoor heat exchanger7. In the pump down operation, when the refrigerant leak is detected by refrigerant leak detection devices13a,13bin the cooling operation state, compressor5is operated with first on-off valve9being closed. In the pump down operation, when the refrigerant leak is detected by refrigerant leak detection devices13a,13bin the heating operation state, compressor5is operated with first on-off valve9being closed, after the operation state of the refrigerant circuit is changed from the heating operation state to the cooling operation state.

As a result, when a refrigerant leak occurs, the pump down operation of transferring the refrigerant from indoor units3a,3bto outdoor unit2can be performed, to thereby reduce the amount of the refrigerant leak in the room. Moreover, the use of check valve4can reduce the possibility that the refrigerant transferred to outdoor unit2by the pump down operation will return to indoor units3a,3bthrough pipe22and the like, without installing an on-off valve at the inlet side of compressor5. Moreover, an adverse increase in flow path resistance that occurs when an on-off valve is disposed at the inlet side of compressor5does not occur, so that degradation in performance of refrigeration cycle apparatus1caused by this increase in flow path resistance can be suppressed.

Refrigeration cycle apparatus1described above includes high pressure receiver8serving as the first receiver which is disposed at pipes27,28serving as a second flow path connecting outdoor heat exchanger7to first on-off valve9.

In refrigeration cycle apparatus1described above, at least one indoor heat exchangers12a,12bmay include two or more heat exchangers. In this case, the plurality of indoor units3a,3beach having a heat exchanger mounted thereon are disposed. Such existence of the plurality of indoor units3a,3bincreases the probability of a refrigerant leak in indoor units3a,3b. It is thus effective to employ refrigeration cycle apparatus1capable of performing the pump down operation according to the present embodiment.

Second Embodiment

<Configuration and Action of Refrigeration Cycle Apparatus>

FIG. 5shows a refrigerant circuit of refrigeration cycle apparatus1according to a second embodiment. Refrigeration cycle apparatus1shown inFIG. 5is an air conditioning apparatus and basically has a similar configuration to that of refrigeration cycle apparatus1shown inFIG. 1, but is different from refrigeration cycle apparatus1shown inFIG. 1in that it includes an accumulator41, an intermediate pressure receiver42and a fifth on-off valve16. Specifically, in refrigeration cycle apparatus1shown inFIG. 5, accumulator41is disposed at pipe24serving as the first flow path connecting the outlet side of check valve4to the inlet side of compressor5. Intermediate pressure receiver42and fifth on-off valve16are disposed at pipe29forming the third flow path connecting first on-off valve9to at least one indoor heat exchangers12a,12b. Fifth on-off valve16is installed at a pipe connecting intermediate pressure receiver42to third on-off valve14.

<Pump Down Operation of Refrigeration Cycle Apparatus>

Refrigeration cycle apparatus1shown inFIG. 5can basically perform similar action to that of refrigeration cycle apparatus1shown inFIG. 1, and is configured to operate by switching between the cooling operation state and the heating operation state. The actions of the pump down operations in the cooling operation state and the heating operation state are also basically similar to those of refrigeration cycle apparatus1shown inFIG. 1.

<Function and Effect of Refrigeration Cycle Apparatus>

Refrigeration cycle apparatus1shown inFIG. 5can basically obtain similar effects to those of refrigeration cycle apparatus1shown inFIG. 1. Moreover, refrigeration cycle apparatus1shown inFIG. 5, which has accumulator41disposed at the outlet side of check valve4, can utilize this accumulator41as well for accumulating the refrigerant during the pump down operation. Accordingly, the amount of accumulated refrigerant in outdoor unit2during the pump down operation can be increased.

<Modification of Pump Down Operation of Refrigeration Cycle Apparatus>

FIG. 6is a flowchart illustrating a modification of the pump down operation step (S20) in the cooling operation state shown inFIG. 3. The modification of the pump down operation step shown inFIG. 6is basically similar to the steps shown inFIG. 3, and can obtain similar effects. Moreover, the modification of the pump down operation shown inFIG. 6is characterized in that, when a power failure occurs during the pump down operation, control is performed such that a leak of the refrigerant, which has not been recovered from indoor units3a,3b, from indoor units3a,3bis suppressed. A specific description is given below.

When a refrigerant leak is detected in the step (S10) shown inFIG. 2and the pump down operation step (S20) is performed, the step (S22), the step (S23) and the step (S24) are performed in the process shown inFIG. 6as with the process shown inFIG. 3. Then, when the confirmation of whether the condition for stopping the pump down operation has been satisfied is repeated in the step (S24), and it is determined in the step (S24) that the condition has not been satisfied, then a step of determining whether a power failure has occurred (S28) is performed. In this step (S28), any method can be employed as a method of determining whether a power failure has occurred. For example, in the step (S28), whether a power failure has occurred is determined by a method of receiving an abnormality occurrence signal from a management system such as a facility where the refrigeration cycle apparatus has been installed.

Then, when it is determined in the step (S28) that a power failure has not occurred, the step (S24) is performed again. When it is determined in the step (S28) that a power failure has occurred, on the other hand, a step of fully closing second on-off valves11a,11b(S29) is performed. In this case, compressor5is also stopped due to the power failure. Thus, the process proceeds to the step (S26), where the process of the pump down operation shown inFIG. 6ends.

Any method can be used as a method of fully closing second on-off valves11a,11b. For example, refrigeration cycle apparatus1may have an auxiliary power supply, and refrigeration cycle apparatus1may be configured to perform operation of fully closing second on-off valves11a,11bwhen a power failure occurs.

In this manner, refrigeration cycle apparatus1is configured to close second on-off valves11a,11bwhen a power failure occurs during the pump down operation. Thus, when compressor5is stopped due to a power failure or the like during the pump down operation, the refrigerant located in a refrigerant circuit portion from first on-off valve9to pipes29,30,32a,32bcan be confined in this refrigerant circuit portion by fully closing second on-off valves11a,11b. As a result, the possibility of a leak of this refrigerant circuit portion from the indoor units3a,3bside can be reduced.

It should be noted that the step (S28) and the step (S29) of the process described above may be applied to the pump down operation steps in the heating operation state shown inFIG. 4.