JP7531736B2 - Air conditioner and control method - Google Patents

Description

The present disclosure relates to an air conditioner and a control method.

In recent years, air conditioners have begun circulating slightly flammable or flammable refrigerants with low Global Warming Potential (GWP) in their refrigerant circuits to prevent global warming. As a safety measure, such air conditioners are equipped with a shut-off valve in the refrigerant circuit that cuts off the flow of refrigerant when a refrigerant leak is detected. This shut-off valve is often a solenoid valve that remains closed when not energized and opens when energized. In this solenoid valve, the built-in solenoid valve coil remains open when energized.

The shutoff valves used in the refrigerant circuit are a gas side shutoff valve arranged in the gas side refrigerant piping through which refrigerant flows from the user side heat exchanger to the heat source side heat exchanger during cooling operation, and a liquid side shutoff valve arranged in the liquid side refrigerant piping through which refrigerant flows from the heat source side heat exchanger to the user side heat exchanger during cooling operation (see, for example, Patent Document 1).

JP 2017-9268 A

The problem to be solved is that the gas side shut-off valve and the liquid side shut-off valve must always be energized and in the open state while the air conditioner is operating.

The present disclosure has been made to solve the above-mentioned problems, and one aspect of the present disclosure is an air conditioner including a user-side heat exchanger and a heat-source-side heat exchanger, and equipped with a refrigerant circuit through which a refrigerant circulates, the air conditioner including a gas-side refrigerant pipe connecting the user-side heat exchanger and the heat-source-side heat exchanger, a liquid-side refrigerant pipe connecting the user-side heat exchanger and the heat-source-side heat exchanger, a gas-side shutoff mechanism disposed in the gas-side refrigerant pipe, a liquid-side shutoff mechanism disposed in the liquid-side refrigerant pipe, and a shutoff mechanism for preventing leakage of the refrigerant from the refrigerant circuit or a pressure difference of the refrigerant. and a control unit that performs a refrigerant recovery operation when a normal state is detected, wherein the gas-side shut-off mechanism, when powered, allows bidirectional refrigerant flow, and, when powered off, only allows refrigerant flow from the user-side heat exchanger to the heat source-side heat exchanger, and the liquid-side shut-off mechanism, when powered, allows bidirectional refrigerant flow, and, when powered off, only allows refrigerant flow from the user-side heat exchanger to the heat source-side heat exchanger, and the control unit sets the gas-side shut-off mechanism to a non-powered state during the refrigerant recovery operation.

Another aspect of the present disclosure is the air conditioner described above, which is provided with a user-side expansion valve arranged in the liquid-side refrigerant piping closer to the user-side heat exchanger than the liquid-side shutoff mechanism, and the control unit closes the user-side expansion valve and energizes the liquid-side shutoff mechanism during the refrigerant recovery operation.

Further, another aspect of the present disclosure is the air conditioner described above, further comprising a user-side expansion valve disposed in the liquid-side refrigerant piping on the user-side heat exchanger side relative to the liquid-side shutoff mechanism,
The control unit opens the utilization side expansion valve and de-energizes the liquid side cutoff mechanism during the refrigerant recovery operation.

Another aspect of the present disclosure is the air conditioner described above, wherein the control unit, during cooling operation, sets the liquid side shut-off mechanism in an energized state and the gas side shut-off mechanism in a de-energized state, and, at the end of cooling operation, sets the liquid side shut-off mechanism in a de-energized state after a predetermined time has elapsed since stopping the compressor that compresses the refrigerant.

Another aspect of the present disclosure is the air conditioner described above, wherein the control unit, during heating operation, sets the gas-side shut-off mechanism to an energized state and the liquid-side shut-off mechanism to a de-energized state, and, at the end of the heating operation, sets the gas-side shut-off mechanism to a de-energized state when the compressor that compresses the refrigerant is stopped or after a time shorter than the predetermined time has elapsed since the compressor was stopped.

Another aspect of the present disclosure is the air conditioner described above, wherein each of the liquid side shutoff mechanism and the gas side shutoff mechanism is a mechanism having a function equivalent to a circuit configuration in which a solenoid valve that is open when energized and closed when de-energized is connected in parallel with a check valve.

Another aspect of the present disclosure is a control method for an air conditioner having a refrigerant circuit including a user-side heat exchanger and a heat source-side heat exchanger, in which a refrigerant circulates, the method comprising: a liquid-side shutoff mechanism disposed in a liquid-side refrigerant piping connecting the user-side heat exchanger and the heat source-side heat exchanger during cooling operation, the liquid-side shutoff mechanism being in an energized state, which allows refrigerant to flow in both directions when energized, and only allows refrigerant to flow from the user-side heat exchanger to the heat source-side heat exchanger when de-energized; and a gas-side shutoff mechanism disposed in a gas-side refrigerant piping connecting the user-side heat exchanger and the heat source-side heat exchanger, which being in an energized state, the gas-side shutoff mechanism being de-energized during heating operation; the gas-side shutoff mechanism being energized and the liquid-side shutoff mechanism being de-energized during heating operation; when leakage of the refrigerant from the refrigerant circuit or an abnormality in the pressure of the refrigerant is detected, performing a refrigerant recovery operation to recover refrigerant from a user-side unit having the user-side heat exchanger; and during the refrigerant recovery operation, the gas-side shutoff mechanism being de-energized.

The air conditioner disclosed herein has the advantage that only one of the gas side shutoff mechanism and the liquid side shutoff mechanism needs to be energized and left in the open state during operation.

1 is a refrigerant circuit diagram showing the configuration of an air conditioner 1 according to a first embodiment of the present disclosure. 2 is a cross-sectional view showing the configuration of an electromagnetic valve 50 in the embodiment. 2 is a refrigerant circuit diagram showing a state during cooling operation of the air conditioner 1 in the embodiment. FIG. FIG. 2 is a refrigerant circuit diagram showing a state during heating operation of the air conditioner 1 in the embodiment. 10 is a schematic diagram showing a refrigerant flow when a gas-side cutoff mechanism 108 and a liquid-side cutoff mechanism 109 in the embodiment are energized. FIG. 10 is a schematic diagram showing a refrigerant flow when a gas-side cutoff mechanism 108 and a liquid-side cutoff mechanism 109 in the embodiment are not energized. FIG. 4 is a refrigerant circuit diagram showing the function of a blocking mechanism 700 in the same embodiment. FIG. 2 is a refrigerant circuit diagram showing the configuration of a blocking mechanism 800 in the same embodiment. FIG. 4 is a flowchart illustrating control during cooling operation by a control unit 114 in the embodiment. 5 is a flowchart illustrating control during heating operation by a control unit 114 in the embodiment. 4 is a flowchart illustrating control for transitioning the air conditioner 1 in the embodiment from a cooling operation to a refrigerant recovery operation. 4 is a flowchart illustrating control for transitioning the air conditioner 1 in the embodiment from a heating operation to a refrigerant recovery operation. 4 is a flowchart illustrating control for transitioning from a stopped state of the air conditioner 1 in the embodiment to a refrigerant recovery operation. FIG. 4 is a refrigerant circuit diagram showing the configuration of an air conditioner 1 according to a second embodiment of the present disclosure. 4 is a refrigerant circuit diagram showing another configuration example of the air conditioner 1 in the same embodiment. FIG. 13 is a flowchart illustrating control for transitioning from a cooling operation to a refrigerant recovery operation in an air conditioner 1 according to a third embodiment of the present disclosure. 4 is a flowchart illustrating control for transitioning the air conditioner 1 in the embodiment from a heating operation to a refrigerant recovery operation. 4 is a flowchart illustrating control for transitioning from a stopped state of the air conditioner 1 in the embodiment to a refrigerant recovery operation. 13 is a flowchart illustrating control for transitioning from a heating operation to a refrigerant recovery operation in an air conditioner 1 according to a fourth embodiment of the present disclosure. 4 is a flowchart illustrating control for transitioning from a stopped state of the air conditioner 1 in the embodiment to a refrigerant recovery operation. 4 is a flowchart illustrating control for transitioning the air conditioner 1 in the embodiment from a cooling operation to a refrigerant recovery operation.

First Embodiment
1 is a refrigerant circuit diagram showing the configuration of an air conditioner 1 according to a first embodiment of the present disclosure. The air conditioner 1 includes a heat source unit 10, a user unit 20, and refrigerant piping 30.

The heat source unit 10 serves as a hot heat source during heating operation and as a cold heat source during cooling operation. The heat source unit 10 has a casing 100, a compressor 101, a four-way valve (four-way switching valve) 110, a heat source side heat exchanger 102, a fan 103, a heat source side expansion valve 113, a double pipe 111, a liquid side shutoff mechanism 109, a gas side shutoff mechanism 108, a pressure vessel 112, a control unit 114, a refrigerant pressure acquisition unit 115, and piping connecting the components.

The casing 100 houses the components of the heat source unit 10. The compressor 101 compresses low-pressure gas refrigerant and discharges high-pressure gas refrigerant. The low-pressure gas refrigerant flows from the pressure vessel 112 toward the compressor 101. The high-pressure gas refrigerant flows from the compressor 101 toward the four-way valve 110.

The four-way valve 110 switches between a refrigerant circuit configuration for cooling operation and a refrigerant circuit configuration for heating operation. During cooling operation, the four-way valve 110 makes the connection shown by the solid line in FIG. 3. As a result, the refrigerant flows in the direction of the arrow in FIG. 3. That is, during cooling operation, the refrigerant discharged from the compressor 101 flows toward the heat source side heat exchanger 102. On the other hand, during heating operation, the four-way valve 110 makes the connection shown by the solid line in FIG. 4. As a result, the refrigerant flows in the direction of the arrow in FIG. 4. That is, during heating operation, the refrigerant discharged from the compressor 101 flows toward the gas side cutoff mechanism 108. In this embodiment, the four-way valve 110 has a refrigerant circuit configuration for heating operation when it is energized, and a refrigerant circuit configuration for cooling operation when it is deenergized, but it may be reversed.

The heat source side heat exchanger 102 exchanges heat between the refrigerant and the air (outside air). The heat source side heat exchanger 102 dissipates heat into the air during cooling operation to become a hot heat source, and absorbs heat from the air during heating operation to become a cold heat source. The fan 103 promotes the heat exchange between the refrigerant and the air by the heat source side heat exchanger 102.

The heat source side expansion valve 113 is a valve whose opening degree can be adjusted. The double pipe 111 is, for example, a tube made by processing a copper plate into a double pipe shape. The double pipe 111 promotes heat exchange between the refrigerant flowing through the outer pipe and the refrigerant flowing through the inner pipe.

The liquid-side shutoff mechanism 109 is disposed in the liquid-side refrigerant piping 32, and in the energized state, it allows the refrigerant to flow in both directions, and in the de-energized state, it allows the refrigerant to flow only from the user-side unit 20 (user-side heat exchanger 201) side to the heat source-side unit 10 (heat source-side heat exchanger 102) side. The liquid-side shutoff mechanism 109 may be configured as shown in FIG. 1 in which the liquid-side check valve 106 and the liquid-side solenoid valve 107 are arranged in parallel. The liquid-side shutoff mechanism 109 may be any shutoff mechanism 700 having a function equivalent to that of the check valve 701 and the solenoid valve 702 arranged in parallel as shown in FIG. 7. For example, the liquid-side shutoff mechanism 109 may be a single solenoid valve having an equivalent function, or may be a shutoff mechanism 800 shown in FIG. 8 in which the check valve 801, the check valve 802, and the solenoid valve 803 are arranged in parallel. In this case, the direction of flow permitted by check valve 801 is opposite to the direction of flow permitted by check valve 802 .

The liquid-side shutoff mechanism 109 is for opening or closing the refrigerant path. When the air conditioner 1 is installed, the liquid-side shutoff mechanism 109 seals the refrigerant sealed in the heat source unit 10 to prevent the refrigerant from leaking, for example, to the user unit 20 and to the outside. The liquid-side solenoid valve 107 constituting the liquid-side shutoff mechanism 109 is a normally closed type solenoid valve. The liquid-side solenoid valve 107 constituting the liquid-side shutoff mechanism 109 has, for example, a coil 501, a magnet 502, a needle 503, a valve seat 504, and pipes 505 and 506 as shown in the solenoid valve (shutoff valve) 50 in FIG. 2.

When the control unit 114 energizes the coil 501 of the liquid side solenoid valve 107, the needle 503 is maintained away from the valve seat 504 by the coil 501. This allows the refrigerant to flow between the pipes 505 and 506. Therefore, as shown in Figure 5, the refrigerant flows from the heat source side unit 10 through the liquid side solenoid valve 107 constituting the liquid side cutoff mechanism 109 to the user side unit 20, realizing the refrigerant path during cooling operation as shown by the arrow in Figure 3.

On the other hand, when the control unit 114 is not energizing the coil of the liquid side solenoid valve 107, the needle 503 is maintained in a state of close contact with the valve seat 504. This prevents the refrigerant from flowing between the pipes 505 and 506. Therefore, as shown in Figure 6, the refrigerant flows from the user side unit 20 through the liquid side check valve 106 that constitutes the liquid side cutoff mechanism 109 to the heat source side unit 10, realizing the refrigerant path during heating operation as shown by the arrow in Figure 4.

The gas-side shutoff mechanism 108 is disposed in the gas-side refrigerant piping 31, and in the energized state, it allows the refrigerant to flow in both directions, and in the de-energized state, it allows the refrigerant to flow only from the user-side unit 20 (user-side heat exchanger 201) side to the heat source-side unit 10 (heat source-side heat exchanger 102) side. The gas-side shutoff mechanism 108 may be configured as shown in FIG. 1 in which the gas-side check valve 104 and the gas-side solenoid valve 105 are arranged in parallel. In addition, the gas-side shutoff mechanism 108 may be any shutoff mechanism 700 having a function equivalent to that of the check valve 701 and the solenoid valve 702 arranged in parallel as shown in FIG. 7. For example, the gas-side shutoff mechanism 108 may be a single solenoid valve having an equivalent function, or may be a shutoff mechanism 800 shown in FIG. 8 in which the check valve 801, the check valve 802, and the solenoid valve 803 are arranged in parallel. In this case, the direction of flow permitted by check valve 801 is opposite to the direction of flow permitted by check valve 802 .

The gas-side shutoff mechanism 108 is for opening or closing the refrigerant path. When the air conditioner 1 is installed, the gas-side shutoff mechanism 108 seals off the refrigerant so that the refrigerant sealed in the heat source unit 10 does not leak, for example, to the user unit 20 or to the outside. The gas-side solenoid valve 105 constituting the gas-side shutoff mechanism 108 is a normally closed type solenoid valve. The gas-side solenoid valve 105 constituting the gas-side shutoff mechanism 108 has, for example, a coil 501, a magnet 502, a needle 503, a valve seat 504, and pipes 505 and 506 as shown in FIG. 2.

When the control unit 114 energizes the coil of the gas side solenoid valve 105, the needle 503 is maintained away from the valve seat 504 by the coil 501. This allows the refrigerant to flow between the pipes 505 and 506. Therefore, as shown in Figure 5, the refrigerant flows from the heat source side unit 10 through the gas side solenoid valve 105 that constitutes the gas side cutoff mechanism 108 to the user side unit 20, realizing the refrigerant path during heating operation as shown by the arrow in Figure 4.

On the other hand, when the control unit 114 is not energizing the coil of the gas-side solenoid valve 105, the needle 503 is maintained in a state of close contact with the valve seat 504. This prevents the refrigerant from flowing between the pipes 505 and 506. Therefore, as shown in Figure 6, the refrigerant flows from the user side unit 20 through the gas side check valve 104 constituting the gas side shutoff mechanism 108 to the heat source side unit 10, realizing the refrigerant path during cooling operation as shown by the arrow in Figure 3.

The pressure vessel 112 functions as a vessel for storing, for example, low-pressure refrigerant flowing through the air conditioner 1. The control unit 114 receives output signals from various sensors and the refrigerant leakage detection unit 204 provided in the heat source side unit 10 and the user side unit 20. These various sensors may include sensors not shown. The control unit 114 drives the compressor 101, the four-way valve 110, the fan 103, the heat source side expansion valve 113, and other actuators not shown.

The refrigerant piping 30 includes piping that connects the heat source side unit 10 and the user side unit 20, and connects the heat source side heat exchanger 102 and the user side heat exchanger 201. The refrigerant piping 30 has a gas side refrigerant piping 31 and a liquid side refrigerant piping 32. A gas side shutoff mechanism 108 is arranged in the gas side refrigerant piping 31. A liquid side shutoff mechanism 109 is arranged in the liquid side refrigerant piping 32. In FIG. 1, the gas side shutoff mechanism 108 and the liquid side shutoff mechanism 109 are arranged in the heat source side unit 10, but may be arranged in the user side unit 20.

The user side unit 20 provides cold energy during cooling and hot energy during heating. The user side unit 20 constituting the air conditioner 1 generates cold or hot air to adjust the indoor temperature. The user side unit 20 has a casing 200, a user side heat exchanger 201, a fan 202, and a user side expansion valve 203. The casing 200 houses the components of the user side unit 20. The user side heat exchanger 201 exchanges heat between the refrigerant and air. The user side heat exchanger 201 absorbs heat during cooling operation to become a cold heat source, and releases heat during heating operation to become a hot heat source. The fan 202 promotes the heat exchange between the refrigerant and air by the user side heat exchanger 201. The fan 202 blows the air that has completed the heat exchange from the casing 200 into the room. The user side expansion valve 203 is a valve whose opening degree can be adjusted.

The refrigerant leak detection unit 204 is a sensor that detects refrigerant leaks. The refrigerant leak detection unit 204 is installed in the air-conditioned space of the user unit 20, but may also be provided inside the casing 200.

The refrigerant used in the air conditioner 1 may be a fluorine-based refrigerant or a hydrocarbon-based refrigerant with a low global warming potential (GWP). For example, a single refrigerant selected from R1234yf, R1234ze, R32, and R290, or a mixture of two or more of these, or a mixture of these with other refrigerants, a mixture containing R1132(E), or a mixture containing R1123. Other examples include a mixture of R516A, R445A, R444A, R454C, R444B, R454A, R455A, R457A, R459B, R452B, R454B, R447B, R447A, R446A, and R459A.

Below, we explain the basic operation of the refrigeration cycle of the air conditioner 1. For simplicity, we will explain it as if the refrigerant undergoes a reaction accompanied by a phase change such as condensation and evaporation, but as long as heat exchange occurs, it does not necessarily have to involve a phase change.

<Cooling operation>
During cooling operation, the four-way valve 110 of the heat source side unit 10 is connected as shown by the solid lines in Fig. 3. The liquid side solenoid valve 107 is open, and the gas side solenoid valve 105 is closed. The high-pressure gas refrigerant discharged from the compressor 101 passes through the four-way valve 110, dissipates heat and condenses in the heat source side heat exchanger 102 to become high-pressure liquid refrigerant. The high-pressure liquid refrigerant passes through the heat source side expansion valve 113 and the double pipe 111 to reach the liquid side shutoff mechanism 109. The high-pressure liquid refrigerant passes through the liquid side solenoid valve 107 of the liquid side shutoff mechanism 109 and the liquid side refrigerant piping 32 and enters the user side unit 20.

The high-pressure liquid refrigerant is decompressed by the user-side expansion valve 203 to become a low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant absorbs heat and evaporates in the user-side heat exchanger 201 to become a low-pressure gas refrigerant. The low-pressure gas refrigerant enters the heat source side unit 10 via the gas-side refrigerant piping 31, passes through the gas-side check valve 104, four-way valve 110, and pressure vessel 112 of the gas-side shutoff mechanism 108, and is sucked into the compressor 101.

Figure 9 is a flowchart explaining the control during cooling operation by the control unit 114 in this embodiment. At the start of this flowchart, the control unit 114 has both the liquid side shutoff mechanism 109 and the gas side shutoff mechanism 108 in a non-energized state. In step Sa1, the control unit 114 starts the compressor 101. In step Sa2, the control unit 114 starts energizing the coil of the liquid side solenoid valve 107 that constitutes the liquid side shutoff mechanism 109, opening the liquid side solenoid valve 107. This realizes a refrigerant circuit as shown in Figure 3. Steps Sa1 and Sa2 may be performed at the same time, or in the reverse order.

In step Sa3, the control unit 114 checks whether or not a cooling operation stop signal has been received. If the control unit 114 has not received a cooling operation stop signal (step Sa3-No), it performs step Sa3 again. When the control unit 114 receives a cooling operation stop signal, i.e., when the cooling operation is finished (step Sa3-Yes), it proceeds to step Sa4. In step Sa4, the control unit 114 stops the compressor 101. In step Sa5, the control unit 114 acquires the time T since receiving the cooling operation stop signal.

In step Sa6, the control unit 114 determines the elapsed time. The control unit 114 compares the time T since receiving the acquired cooling operation stop signal with a predetermined threshold value T1. If the time T is less than the threshold value T1 (step Sa6-No), the control unit 114 performs step Sa5 again. If the time T is equal to or greater than the threshold value T1 (step Sa6-Yes), the control unit 114 proceeds to step Sa7.

In step Sa7, the control unit 114 stops the power supply to the coil of the liquid-side solenoid valve 107 constituting the liquid-side cutoff mechanism 109, and closes the liquid-side solenoid valve 107. This stops the supply of refrigerant to the user-side unit 20.

<Heating operation>
During heating operation, the four-way valve 110 of the heat source side unit 10 is connected as shown by the solid lines in Fig. 4. Furthermore, the liquid side solenoid valve 107 is closed, and the gas side solenoid valve 105 is open. The high-pressure gas refrigerant discharged from the compressor 101 passes through the four-way valve 110 and reaches the gas side shutoff mechanism 108. The high-pressure gas refrigerant passes through the gas side solenoid valve 105 of the gas side shutoff mechanism 108 and the gas side refrigerant piping 31 and enters the user side unit 20, where it dissipates heat and is condensed in the user side heat exchanger 201 to become a high-pressure liquid refrigerant.

The high-pressure liquid refrigerant passes through the user-side expansion valve 203, the liquid-side refrigerant piping 32, the liquid-side check valve 106 of the liquid-side shutoff mechanism 109, and the double pipe 111, and reaches the heat-source-side expansion valve 113. The high-pressure liquid refrigerant is reduced in pressure by the user-side expansion valve 203, the heat-source-side expansion valve 113, or by both the user-side expansion valve 203 and the heat-source-side expansion valve 113 to become a low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant absorbs heat and evaporates in the heat-source-side heat exchanger 102 to become a low-pressure gas refrigerant. The low-pressure gas refrigerant passes through the four-way valve 110 and is sucked into the compressor 101.

Figure 10 is a flowchart explaining the control during heating operation by the control unit 114 in this embodiment. At the start of this flowchart, the control unit 114 has both the liquid side shut-off mechanism 109 and the gas side shut-off mechanism 108 in a non-energized state. In step Sb1, the control unit 114 starts the compressor 101. In step Sb2, the control unit 114 energizes the four-way valve 110 to open it. As a result, the four-way valve 110 is in the state shown by the solid lines in Figure 4, and the refrigerant discharged from the compressor 101 flows through the four-way valve 110 to the gas side shut-off mechanism 108.

In step Sb3, the control unit 114 starts energizing the coil of the gas side solenoid valve 105 constituting the gas side shutoff mechanism 108, and opens the gas side solenoid valve 105. This realizes the refrigerant circuit as shown in Figure 4. Steps Sb1 to Sb3 may be performed at the same time, or may be performed in a different order than that shown in Figure 10.

In step Sb4, the control unit 114 checks whether or not a signal to stop heating operation has been received. If the control unit 114 has not received a signal to stop heating operation (step Sb4-No), it performs step Sb4 again. When the control unit 114 receives a signal to stop heating operation, i.e., when the heating operation is finished (step Sb4-Yes), it proceeds to step Sb5. In step Sb5, the control unit 114 stops the compressor 101. In step Sb6, the control unit 114 acquires the time T since the signal to stop heating operation was received.

In step Sb7, the elapsed time is determined. The control unit 114 compares the time T from when the acquired heating operation stop signal was received with a predetermined threshold value T2. If the time T is less than the threshold value T2 (step Sb7-No), the control unit 114 performs step Sb6 again. If the time T is equal to or greater than the threshold value T2 (step Sb7-Yes), the control unit 114 proceeds to step Sb8. Note that the threshold value T2 (≧0) may be a time shorter than the threshold value T1 at the end of the cooling operation. In addition, the flowchart in FIG. 10 may not include steps Sb6 and Sb7, and the control unit 114 may proceed to step Sb8 after stopping the compressor 101 in step Sb5.

In step Sb8, the control unit 114 stops the flow of electricity to the coil of the gas side solenoid valve 105 that constitutes the gas side shutoff mechanism 108, and closes the gas side solenoid valve 105. This stops the supply of refrigerant to the user side unit 20. In step Sb9, the control unit 114 stops the flow of electricity to the four-way valve 110, and closes it. This causes the four-way valve 110 to enter the state shown by the solid lines in Figure 3. Steps Sb8 and Sb9 may be performed at the same time, or may be performed in an order different from that shown in Figure 10.

<When stopped>
When the air conditioner 1 is stopped, power is cut off to the gas side shutoff mechanism 108 and the liquid side shutoff mechanism 109. As a result, the refrigerant does not reach the user side unit 20 from the heat source side unit 10. Furthermore, if power is not supplied to the actuator due to a power outage or the like, power is cut off to the gas side shutoff mechanism 108 and the liquid side shutoff mechanism 109, and the refrigerant does not reach the user side unit 20 from the heat source side unit 10. The above is the basic operation.

<In the event of an abnormality: Refrigerant recovery operation>
When the control unit 114 receives information about a refrigerant leak from a refrigerant leak detection unit 204 installed in the air-conditioned space of the user side unit 20, it switches the four-way valve 110 to a refrigerant circuit configuration for cooling operation, opens the liquid side shut-off mechanism 109 (energized state) and closes the gas side shut-off mechanism 108 (de-energized state) to perform refrigerant recovery operation to recover refrigerant from the user side unit 20.

In refrigerant recovery operation, the four-way valve 110 of the heat source unit 10 is connected as shown by the solid lines in FIG. 3. The high-pressure gas refrigerant discharged from the compressor 101 passes through the four-way valve 110 and is condensed and released heat in the heat source heat exchanger 102 to become a high-pressure liquid refrigerant. The high-pressure liquid refrigerant passes through the heat source expansion valve 113 and the double pipe 111 to reach the liquid side shutoff mechanism 109. The high-pressure liquid refrigerant passes through the liquid side solenoid valve 107 of the liquid side shutoff mechanism 109 and the liquid side refrigerant piping 32 to enter the user side unit 20. The high-pressure liquid refrigerant is decompressed by the user side expansion valve 203 to become a low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant absorbs heat and evaporates in the user side heat exchanger 201 to become a low-pressure gas refrigerant. The low-pressure gas refrigerant enters the heat source side unit 10 through the gas side refrigerant piping 31 , passes through the gas side check valve 104 of the gas side shutoff mechanism 108 , the four-way valve 110 , and the pressure vessel 112 , and is sucked into the compressor 101 .

Figure 11 is a flowchart explaining the control of the air conditioner 1 in this embodiment to transition from cooling operation to refrigerant recovery operation. In step Sc1, the control unit 114 checks whether the refrigerant leakage detection unit 204 has detected a refrigerant leakage. When the refrigerant leakage detection unit 204 has not detected a refrigerant leakage (step Sc1-No), the control unit 114 performs step Sc1 again. When the refrigerant leakage detection unit 204 has detected a refrigerant leakage or when the control unit 114 has determined that a refrigerant leakage has occurred (step Sc1-Yes), the control unit 114 proceeds to step Sc2. In step Sc2, the control unit 114 closes the user side expansion valve 203. The closed state of the user side expansion valve 203 is a state in which the user side expansion valve 203 does not allow refrigerant to pass through.

Step Sc3 is an end determination process. In step Sc3, the control unit 114 determines whether or not to end the refrigerant recovery operation. If it has not been determined that the refrigerant recovery operation should be ended (step Sc3-No), the control unit 114 performs step Sc3 again. If it has been determined that the refrigerant recovery operation should be ended (step Sc3-Yes), the control unit 114 proceeds to step Sc4.

In step Sc4, the control unit 114 stops the compressor 101. In step Sc5, the control unit 114 stops the supply of electricity to the coil of the liquid side solenoid valve 107 that constitutes the liquid side cut-off mechanism 109, and closes the liquid side solenoid valve 107. This stops the supply of refrigerant to the user side unit 20. Steps Sc4 to Sc5 may be performed at the same time, or may be performed in an order different from that shown in FIG. 11.

Figure 12 is a flowchart explaining the control of the air conditioner 1 in this embodiment to transition from heating operation to refrigerant recovery operation. In step Sd1, the control unit 114 checks whether the refrigerant leak detection unit 204 has detected a refrigerant leak. When the refrigerant leak detection unit 204 has not detected a refrigerant leak (step Sd1-No), the control unit 114 performs step Sd1 again. When the refrigerant leak detection unit 204 has detected a refrigerant leak or when the control unit 114 has determined that there is a refrigerant leak (step Sd1-Yes), the control unit 114 proceeds to step Sd2.

In step Sd2, the control unit 114 closes the user side expansion valve 203. In step Sd3, the control unit 114 stops the flow of electricity to the four-way valve 110, closing it. In step Sd4, the control unit 114 starts the flow of electricity to the coil of the liquid side solenoid valve 107 that constitutes the liquid side shutoff mechanism 109, opening the liquid side solenoid valve 107. In step Sd5, the control unit 114 stops the flow of electricity to the coil of the gas side solenoid valve 105 that constitutes the gas side shutoff mechanism 108, closing the gas side solenoid valve 105. Steps Sd2 to Sd5 may be performed at the same time, or may be performed in a different order than that shown in FIG. 12.

Step Sd6 is an end determination process. In step Sd6, the control unit 114 determines whether or not to end the refrigerant recovery operation. If it has not been determined that the refrigerant recovery operation should be ended (step Sd6-No), the control unit 114 performs step Sd6 again. If it has been determined that the refrigerant recovery operation should be ended (step Sd6-Yes), the control unit 114 proceeds to step Sd7.

In step Sd7, the control unit 114 stops the compressor 101. In step Sd8, the control unit 114 stops the supply of electricity to the coil of the liquid side solenoid valve 107 that constitutes the liquid side cut-off mechanism 109, and closes the liquid side solenoid valve 107. This stops the supply of refrigerant to the user side unit 20. Steps Sd7 to Sd8 may be performed at the same time, or may be performed in an order different from that shown in FIG. 12.

Figure 13 is a flowchart explaining the control of the air conditioner 1 in this embodiment to transition from stopped to refrigerant recovery operation. In step Se1, the control unit 114 checks whether the refrigerant leak detection unit 204 has detected a refrigerant leak. When the refrigerant leak detection unit 204 has not detected a refrigerant leak (step Se1-No), the control unit 114 performs step Se1 again. When the refrigerant leak detection unit 204 has detected a refrigerant leak or when the control unit 114 has determined that there is a refrigerant leak (step Se1-Yes), the control unit 114 proceeds to step Se2.

In step Se2, the control unit 114 starts the compressor 101. In step Se3, the control unit 114 closes the user side expansion valve 203. In step Se4, the control unit 114 stops the supply of electricity to the four-way valve 110, and sets the refrigerant circuit configuration for cooling operation. In step Se5, the control unit 114 starts supplying electricity to the coil of the liquid side solenoid valve 107 constituting the liquid side cutoff mechanism 109, and opens the liquid side solenoid valve 107. In step Se6, the control unit 114 stops supplying electricity to the coil of the gas side solenoid valve 105 constituting the gas side cutoff mechanism 108, and closes the gas side solenoid valve 105. Steps Se2 to Se6 may be performed at the same timing, or may be performed in an order different from that shown in FIG. 13.

Step Se7 is an end determination process. In step Se7, the control unit 114 determines whether or not to end the refrigerant recovery operation. If it has not been determined that the refrigerant recovery operation should be ended (step Se7-No), the control unit 114 performs step Se7 again. If it has been determined that the refrigerant recovery operation should be ended (step Se7-Yes), the control unit 114 proceeds to step Se8.

In step Se8, the control unit 114 stops the compressor 101. In step Se9, the control unit 114 stops the power supply to the coil of the liquid side solenoid valve 107 constituting the liquid side cutoff mechanism 109, and closes the liquid side solenoid valve 107. This stops the supply of refrigerant to the user side unit 20. Steps Se8 to Se9 may be performed at the same time, or may be performed in an order different from that shown in FIG. 13.

In this way, the air conditioner 1 in this embodiment does not need to have both the gas side solenoid valve 105 and the liquid side solenoid valve 107 energized during normal cooling or heating operation, and can circulate the refrigerant in the refrigerant circuit by energizing only one of them. Therefore, compared to the case of solenoid valves that need to be constantly energized during operation to be in the open state, the time that each solenoid valve is energized is shorter, and the number of times it is switched from the open state to the closed state is reduced. This makes it possible to suppress a shortening of the lifespan of the coils and valve seats of the gas side solenoid valve 105 and the liquid side solenoid valve 107.

In addition, the gas side solenoid valve 105 constituting the gas side shutoff mechanism 108 and the liquid side solenoid valve 107 constituting the liquid side shutoff mechanism 109 are normally closed type solenoid valves. They have the function of closing the refrigerant path when in a non-energized state such as when operation is stopped or during a power outage. Therefore, the gas side solenoid valve 105 and the liquid side solenoid valve 107 can block the movement of refrigerant from the heat source side unit 10 to the user side unit 20.

Second Embodiment
A plurality of user side units 20 may be connected to the heat source side unit 10. Fig. 14 is a refrigerant circuit diagram showing the configuration of an air conditioner 1 in a second embodiment of this disclosure. The air conditioner 1 has a heat source side unit 10, user side units 20, 20-a, refrigerant piping 30, and a valve unit 40. Note that, although two user side units 20, 20-a are connected in Fig. 14, three or more user side units may be connected to the valve unit 40.

The valve unit 40 has a casing 400 and user side expansion valves 203, 203-a. The heat source side unit 10 has the same configuration as in FIG. 1, so a description thereof will be omitted. The user side unit 20 is the same as in FIG. 1 except that the user side expansion valve 203 is provided in the valve unit 40, so a description thereof will be omitted. The user side unit 20-a has the same configuration as the user side unit 20, so a description thereof will be omitted. The basic operation of the refrigeration cycle of the air conditioner 1 in this embodiment is the same as in the first embodiment. The user side expansion valves 203, 203-a may have their openings adjusted individually to correspond to the respective user side units 20, 20-a.

Regarding the operation of the air conditioner 1 in the present embodiment during an abnormality, if the refrigerant leakage detection unit 204 of the user side unit 20 detects a refrigerant, the refrigerant is shut off and the refrigerant recovery operation is performed in the same manner as in the first embodiment. Note that the same operation may also be performed if the refrigerant leakage detection unit 204-a of the user side unit 20-a detects a refrigerant.

Figure 15 is a refrigerant circuit diagram showing another example of the configuration of the air conditioner 1 in this embodiment. In Figure 15, the air conditioner 1 does not include a valve unit 40, and the user side expansion valves 203, 203-a are provided in the user side units 20, 20-a, respectively, which is different from Figure 14, but otherwise is the same.

In this manner, in this embodiment, as in the first embodiment, there is no need to energize both the gas side solenoid valve 105 and the liquid side solenoid valve 107 during normal cooling or heating operation, and the refrigerant can be circulated in the refrigerant circuit by energizing only one of them. Therefore, compared to the case of solenoid valves that need to be constantly energized during operation to be in the open state, the shortening of the life span of the coils and valve seats of the gas side solenoid valve 105 and the liquid side solenoid valve 107 can be suppressed.

In addition, the gas side solenoid valve 105 constituting the gas side shutoff mechanism 108 and the liquid side solenoid valve 107 constituting the liquid side shutoff mechanism 109 are normally closed type solenoid valves. They have the function of closing the refrigerant path when in a non-energized state such as when operation is stopped or during a power outage. Therefore, the gas side solenoid valve 105 and the liquid side solenoid valve 107 can block the movement of refrigerant from the heat source side unit 10 to the user side units 20, 20-a.

Third Embodiment
In the third embodiment, the transition to refrigerant recovery operation is determined using the pressure of the refrigerant sucked into the compressor 101, acquired by the refrigerant pressure acquisition unit 115. The configuration of the air conditioner 1 in this embodiment is similar to that in Fig. 1, and therefore a description thereof will be omitted. The configuration of the air conditioner 1 may also be similar to that in Figs. 14 and 15. In that case, the control unit 114 may perform the same control on the utilization side expansion valve 203-a as on the utilization side expansion valve 203. Furthermore, the basic operation of the refrigeration cycle of the air conditioner 1 is similar to that in the first embodiment, and therefore a description thereof will be omitted.

In this embodiment, the control unit 114 compares the pressure P acquired by the refrigerant pressure acquisition unit 115 with a predetermined threshold value P1, and when the pressure P is less than the threshold value P1, determines that the pressure is abnormal and transitions to refrigerant recovery operation. Note that the control unit 114 may also determine that the operation is abnormal using a value acquired from a sensor (not shown) and transition to refrigerant recovery operation.

Figure 16 is a flowchart explaining the control of the air conditioner 1 in the third embodiment of this disclosure to transition from cooling operation to refrigerant recovery operation. In step Sf1, the control unit 114 determines whether there is a pressure abnormality. The control unit 114 compares the pressure P acquired by the refrigerant pressure acquisition unit 115 with a threshold value P1. When the pressure P is equal to or greater than the threshold value P1 (step Sf1-No), the control unit 114 performs step Sf1 again. When the pressure P is less than the threshold value P1 (step Sf1-Yes), the control unit 114 proceeds to step Sf2. In step Sf2, the control unit 114 closes the utilization side expansion valve 203.

Step Sf3 is a termination determination process. In step Sf3, the control unit 114 determines whether or not to terminate the refrigerant recovery operation. When it is not determined that the refrigerant recovery operation is to be terminated (step Sf3-No), the control unit 114 performs step Sf3 again. When it is determined that the refrigerant recovery operation is to be terminated (step Sf3-Yes), the control unit 114 proceeds to step Sf4. In step Sf4, the control unit 114 stops the compressor 101. In step Sf5, the control unit 114 stops the power supply to the coil of the liquid side solenoid valve 107 that constitutes the liquid side cutoff mechanism 109, and closes the liquid side solenoid valve 107. This stops the supply of refrigerant to the user side unit 20. Steps Sf4 to Sf5 may be performed at the same timing, or may be performed in a different order from that shown in FIG. 16.

Figure 17 is a flowchart explaining the control of the air conditioner 1 in this embodiment to transition from heating operation to refrigerant recovery operation. In step Sg1, the control unit 114 determines whether there is a pressure abnormality. The control unit 114 compares the pressure P acquired by the refrigerant pressure acquisition unit 115 with a threshold value P1. When the pressure P is equal to or greater than the threshold value P1 (step Sg1-No), the control unit 114 performs step Sg1 again. When the pressure P is less than the threshold value P1 (step Sg1-Yes), the control unit 114 proceeds to step Sg2.

In step Sg2, the control unit 114 closes the user side expansion valve 203. In step Sg3, the control unit 114 stops the flow of electricity to the four-way valve 110, and sets the refrigerant circuit configuration for cooling operation. In step Sg4, the control unit 114 starts the flow of electricity to the coil of the liquid side solenoid valve 107 that constitutes the liquid side shutoff mechanism 109, and opens the liquid side solenoid valve 107. In step Sg5, the control unit 114 stops the flow of electricity to the coil of the gas side solenoid valve 105 that constitutes the gas side shutoff mechanism 108, and closes the gas side solenoid valve 105. Steps Sg2 to Sg5 may be performed at the same timing, or may be performed in an order different from that shown in FIG. 17.

Step Sg6 is an end determination process. In step Sg6, the control unit 114 determines whether or not to end the refrigerant recovery operation. If it has not been determined that the refrigerant recovery operation should be ended (step Sg6-No), the control unit 114 performs step Sg6 again. If it has been determined that the refrigerant recovery operation should be ended (step Sg6-Yes), the control unit 114 proceeds to step Sg7.

In step Sg7, the control unit 114 stops the compressor 101. In step Sg8, the control unit 114 stops the supply of electricity to the coil of the liquid side solenoid valve 107 that constitutes the liquid side cut-off mechanism 109, and closes the liquid side solenoid valve 107. This stops the supply of refrigerant to the user side unit 20. Steps Sg7 to Sg8 may be performed at the same time, or may be performed in an order different from that shown in FIG. 17.

Figure 18 is a flowchart explaining the control of the air conditioner 1 in this embodiment to transition from shutdown to refrigerant recovery operation. In step Sh1, the control unit 114 determines whether there is a pressure abnormality. The control unit 114 compares the pressure P acquired by the refrigerant pressure acquisition unit 115 with a threshold value P1. When the pressure P is equal to or greater than the threshold value P1 (step Sh1-No), the control unit 114 performs step Sh1 again. When the pressure P is less than the threshold value P1 (step Sh1-No), the control unit 114 proceeds to step Sh2.

In step Sh2, the control unit 114 starts the compressor 101. In step Sh3, the control unit 114 closes the user side expansion valve 203. In step Sh4, the control unit 114 stops the supply of electricity to the four-way valve 110, and sets the refrigerant circuit configuration for cooling operation. In step Sh5, the control unit 114 starts the supply of electricity to the coil of the liquid side solenoid valve 107 that constitutes the liquid side shutoff mechanism 109, and opens the liquid side solenoid valve 107. In step Sh6, the control unit 114 stops the supply of electricity to the coil of the gas side solenoid valve 105 that constitutes the gas side shutoff mechanism 108, and closes the gas side solenoid valve 105. Steps Sh2 to Sh6 may be performed at the same timing, or may be performed in an order different from that shown in FIG. 17.

Step Sh7 is an end determination process. In step Sh7, the control unit 114 determines whether or not to end the refrigerant recovery operation. If it has not been determined that the refrigerant recovery operation is to be ended (step Sh7-No), the control unit 114 performs step Sh6 again. If it has been determined that the refrigerant recovery operation is to be ended (step Sh7-Yes), the control unit 114 proceeds to step Sh8.

In step Sh8, the control unit 114 stops the compressor 101. In step Sh9, the control unit 114 stops the supply of electricity to the coil of the liquid side solenoid valve 107 that constitutes the liquid side cut-off mechanism 109, and closes the liquid side solenoid valve 107. This stops the supply of refrigerant to the user side unit 20. Steps Sh8 to Sh9 may be performed at the same time, or may be performed in an order different from that shown in FIG. 17.

In this embodiment, as in the first embodiment, the air conditioner 1 does not need to have both the gas side solenoid valve 105 and the liquid side solenoid valve 107 energized during normal cooling or heating operation, and can circulate the refrigerant in the refrigerant circuit by energizing only one of them. Therefore, compared to the case of solenoid valves that need to be constantly energized during operation to be in the open state, it is possible to suppress shortening of the life of the coils and valve seats of the gas side solenoid valve 105 and the liquid side solenoid valve 107.

In addition, the gas side solenoid valve 105 constituting the gas side shutoff mechanism 108 and the liquid side solenoid valve 107 constituting the liquid side shutoff mechanism 109 are normally closed type solenoid valves. They have the function of closing the refrigerant path when in a non-energized state such as when operation is stopped or during a power outage. Therefore, the gas side solenoid valve 105 and the liquid side solenoid valve 107 can block the movement of refrigerant from the heat source side unit 10 to the user side unit 20.

Fourth Embodiment
In the first embodiment, when a refrigerant leak is detected, the user side expansion valve 203 is closed to perform a refrigerant recovery operation, and the recovered refrigerant is also stored in the liquid side refrigerant pipe 32. In the fourth embodiment, when a refrigerant leak is detected, the user side expansion valve 203 is opened, and refrigerant is also recovered from the liquid side refrigerant pipe 32. The configuration of the air conditioner 1 in this embodiment is the same as that in FIG. 1, so a description thereof will be omitted. The configuration of the air conditioner 1 may be the same as that in FIG. 14 and FIG. 15. In that case, the control unit 114 may perform the same control as that for the user side expansion valve 203 on the user side expansion valve 203-a. In addition, the basic operation of the refrigeration cycle of the air conditioner 1 is the same as that in the first embodiment, so a description thereof will be omitted.

Figure 19 is a flowchart explaining the control of the air conditioner 1 in this embodiment to transition from heating operation to refrigerant recovery operation. In step Si1, the control unit 114 checks whether the refrigerant leak detection unit 204 has detected a refrigerant leak. When the refrigerant leak detection unit 204 has not detected a refrigerant leak (step Si1-No), the control unit 114 performs step Si1 again. When the refrigerant leak detection unit 204 has detected a refrigerant leak or when the control unit 114 has determined that there is a refrigerant leak (step Si1-Yes), the control unit 114 proceeds to step Si2.

In step Si2, the control unit 114 opens the user-side expansion valve 203 fully. The fully open state is an open state in which the pressure change of the refrigerant is the smallest before and after the user-side expansion valve 203. Although the fully open state is preferable, the fully open state may be changed to an open state in which the refrigerant has a predetermined pressure change before and after the user-side expansion valve 203. In step Si3, the control unit 114 stops the supply of electricity to the coil of the liquid-side solenoid valve 107 constituting the liquid-side cutoff mechanism 109, and closes the liquid-side solenoid valve 107. In step Si4, the control unit 114 stops the supply of electricity to the four-way valve 110, and closes it. In step Si5, the control unit 114 stops the supply of electricity to the coil of the gas-side solenoid valve 105 constituting the gas-side cutoff mechanism 108, and closes the gas-side solenoid valve 105. Steps Si2 to Si5 may be performed at the same timing, or may be performed in a different order from that shown in FIG. 19.

Step Si6 is an end determination process. In step Si6, the control unit 114 determines whether or not to end the refrigerant recovery operation. If it has not been determined that the refrigerant recovery operation is to be ended (step Si6-No), the control unit 114 performs step Si6 again. If it has been determined that the refrigerant recovery operation is to be ended (step Si6-Yes), the control unit 114 proceeds to step Si7.

In step Si7, the control unit 114 stops the compressor 101. In step Si8, the control unit 114 closes the user-side expansion valve. Steps Si7 to Si8 may be performed at the same time, or may be performed in an order different from that shown in FIG. 19.

Figure 20 is a flowchart explaining the control of the air conditioner 1 in this embodiment to transition from shutdown to refrigerant recovery operation. In step Sj1, the control unit 114 checks whether the refrigerant leak detection unit 204 has detected a refrigerant leak. When the refrigerant leak detection unit 204 has not detected a refrigerant leak (step Sj1-No), the control unit 114 performs step Sj1 again. When the refrigerant leak detection unit 204 has detected a refrigerant leak or when the control unit 114 has determined that there is a refrigerant leak (step Sj1-Yes), the control unit 114 proceeds to step Sj2.

In step Sj2, the control unit 114 starts the compressor 101. In step Sj3, the control unit 114 opens the user-side expansion valve 203 fully. As in step Si2, it is desirable to open the user-side expansion valve 203 fully, but it may be changed to an open state in which there is a predetermined pressure change in the refrigerant before and after the user-side expansion valve 203 instead of the fully open state. In step Sj4, the control unit 114 stops the supply of electricity to the coil of the liquid-side solenoid valve 107 constituting the liquid-side shutoff mechanism 109, and closes the liquid-side solenoid valve 107. In step Sj5, the control unit 114 stops the supply of electricity to the four-way valve 110, and sets the refrigerant circuit configuration for cooling operation. In step Sj6, the control unit 114 stops the supply of electricity to the coil of the gas-side solenoid valve 105 constituting the gas-side shutoff mechanism 108, and closes the gas-side solenoid valve 105. Steps Sj2 to Sj6 may be performed at the same timing, or may be performed in a different order from that shown in FIG. 20.

Step Sj7 is an end determination process. In step Sj7, the control unit 114 determines whether or not to end the refrigerant recovery operation. If it has not been determined that the refrigerant recovery operation should be ended (step Sj7-No), the control unit 114 performs step Sj7 again. If it has been determined that the refrigerant recovery operation should be ended (step Sj7-Yes), the control unit 114 proceeds to step Sj8.

In step Sj8, the control unit 114 stops the compressor 101. In step Sj9, the control unit 114 closes the user-side expansion valve 203. This stops the supply of refrigerant to the user-side unit 20. Steps Sj8 to Sj9 may be performed at the same time, or may be performed in an order different from that shown in FIG. 20.

Figure 21 is a flowchart explaining the control of the air conditioner 1 in this embodiment to transition from cooling operation to refrigerant recovery operation. In step Sk1, the control unit 114 checks whether the refrigerant leakage detection unit 204 has detected a refrigerant leakage. When the refrigerant leakage detection unit 204 has not detected a refrigerant leakage (step Sk1-No), the control unit 114 performs step Sk1 again. When the refrigerant leakage detection unit 204 has detected a refrigerant leakage or when the control unit 114 has determined that a refrigerant leakage has occurred (step Sk1-Yes), the control unit 114 proceeds to step Sk2. In step Sk2, the control unit 114 stops the supply of electricity to the coil of the liquid side solenoid valve 107 that constitutes the liquid side cutoff mechanism 109, and closes the liquid side solenoid valve 107. This stops the supply of refrigerant to the user side unit 20.

Step Sk3 is an end determination process. In step Sk3, the control unit 114 determines whether or not to end the refrigerant recovery operation. If it has not been determined that the refrigerant recovery operation is to be ended (step Sk3-No), the control unit 114 performs step Sk3 again. If it has been determined that the refrigerant recovery operation is to be ended (step Sk3-Yes), the control unit 114 proceeds to step Sk4.

In step Sk4, the control unit 114 stops the compressor 101. In step Sk5, the control unit 114 closes the utilization side expansion valve 203. The closed state of the utilization side expansion valve 203 is a state in which the utilization side expansion valve 203 does not allow refrigerant to pass through. Steps Sk4 to Sk5 may be performed at the same time, or may be performed in an order different from that shown in FIG. 21.

In addition, in Figures 19, 20, and 21, refrigerant recovery operation is performed when a refrigerant leak is detected, but even when a pressure abnormality is detected, refrigerant recovery operation may be performed by opening the user side expansion valve 203 and closing the liquid side shut-off mechanism 109 and the gas side shut-off mechanism 108.

The following embodiment may also be adopted.
(1) One embodiment is an air conditioner including a user side heat exchanger and a heat source side heat exchanger, and equipped with a refrigerant circuit in which a refrigerant circulates, the air conditioner including a gas side refrigerant piping connecting the user side heat exchanger and the heat source side heat exchanger, a liquid side refrigerant piping connecting the user side heat exchanger and the heat source side heat exchanger, a gas side shutoff mechanism disposed in the gas side refrigerant piping, and a liquid side shutoff mechanism disposed in the liquid side refrigerant piping, and a refrigerant recovery mechanism that detects leakage of the refrigerant from the refrigerant circuit or an abnormality in the pressure of the refrigerant. and a control unit that operates the air conditioner, wherein the gas-side shut-off mechanism, when powered, allows bidirectional refrigerant flow, and, when de-powered, only allows refrigerant flow from the user-side heat exchanger to the heat source-side heat exchanger, and the liquid-side shut-off mechanism, when powered, allows bidirectional refrigerant flow, and, when de-powered, only allows refrigerant flow from the user-side heat exchanger to the heat source-side heat exchanger, and the control unit sets the gas-side shut-off mechanism to a de-powered state during the refrigerant recovery operation.

This eliminates the need to energize both the gas-side shutoff mechanism and the liquid-side shutoff mechanism during normal cooling or heating operation, and allows the refrigerant to circulate through the refrigerant circuit by energizing only one of them. Therefore, the coil life of the gas-side shutoff mechanism and the liquid-side shutoff mechanism can be suppressed from being shortened compared to when they are constantly energized during operation.
In addition, the number of times the valve body is opened and closed can be reduced by half, which reduces wear on the valve seats of the gas side shutoff mechanism and liquid side shutoff mechanism and also reduces the shortening of the valve body's lifespan.
The gas-side shutoff mechanism and the liquid-side shutoff mechanism do not shut off the flow of refrigerant from the user-side unit to the heat-source-side unit, and therefore the refrigerant can be recovered efficiently.

(2) Another embodiment is an air conditioner as described in (1), which is provided with a user side expansion valve arranged in the liquid side refrigerant piping closer to the user side heat exchanger than the liquid side shut-off mechanism, and the control unit closes the user side expansion valve and switches the liquid side shut-off mechanism to an energized state during the refrigerant recovery operation.

The refrigerant recovered during refrigerant recovery operation can be stored in the heat source unit and liquid side refrigerant piping. Since refrigerant can be stored in the heat source unit as well as the liquid side refrigerant piping, this is particularly effective for air conditioners that require a large amount of refrigerant to be sealed in.

(3) Another embodiment is an air conditioner as described in (1), which is provided with a user side expansion valve arranged in the liquid side refrigerant piping closer to the user side heat exchanger than the liquid side shut-off mechanism, and the control unit opens the user side expansion valve and de-energizes the liquid side shut-off mechanism during the refrigerant recovery operation.

The refrigerant recovered during refrigerant recovery operation can be stored in the heat source unit. Since the refrigerant can be stored in a location separate from the user unit via liquid refrigerant piping and gas refrigerant piping, the risk of refrigerant leaking into the room can be reduced.

(4) Another embodiment is an air conditioner described in any of (1) to (3), wherein the control unit, during cooling operation, sets the liquid side shut-off mechanism to an energized state and the gas side shut-off mechanism to a de-energized state, and at the end of the cooling operation, sets the liquid side shut-off mechanism to a de-energized state after a predetermined time has elapsed since stopping the compressor that compresses the refrigerant.

By maintaining the flow of refrigerant from the high pressure side to the low pressure side when cooling operation is terminated, the pressure on the suction side and discharge side of the compressor can be equalized quickly.

(5) Another embodiment is the air conditioner described in (4), in which the control unit, during heating operation, sets the gas side shut-off mechanism to an energized state and sets the liquid side shut-off mechanism to a de-energized state, and at the end of heating operation, sets the gas side shut-off mechanism to a de-energized state when the compressor compressing the refrigerant is stopped or after a time shorter than the predetermined time has elapsed since the compressor was stopped.

Even when the compressor is stopped and the gas side shut-off mechanism and liquid side shut-off mechanism are closed, the flow of refrigerant from the user unit to the heat source unit is not blocked, so the pressure on the suction side and discharge side of the compressor can be equalized quickly.

(6) Another embodiment is an air conditioner described in any of (1) to (5), wherein each of the liquid side shut-off mechanism and the gas side shut-off mechanism is a mechanism having a function equivalent to a circuit configuration in which a solenoid valve that is open when energized and closed when de-energized is connected in parallel with a check valve.

This makes it possible to make the liquid side shut-off mechanism and gas side shut-off mechanism more compact, and prevents the configuration of the air conditioner's refrigerant circuit from becoming too complicated.

(7) Another embodiment is a control method for an air conditioner having a refrigerant circuit including a user side heat exchanger and a heat source side heat exchanger, through which a refrigerant circulates, and during cooling operation, a liquid side shut-off mechanism is arranged in a liquid side refrigerant piping connecting the user side heat exchanger and the heat source side heat exchanger, and in an energized state, the liquid side shut-off mechanism allows refrigerant to flow in both directions, and in a non-energized state, only allows refrigerant to flow from the user side heat exchanger to the heat source side heat exchanger, and a gas side shut-off mechanism is arranged in a gas side refrigerant piping connecting the user side heat exchanger and the heat source side heat exchanger, and in an energized state, This control method includes the steps of: de-energizing a gas-side shut-off mechanism, which allows refrigerant to flow in both directions and, in a de-energized state, allows refrigerant to flow only from the user-side heat exchanger to the heat source-side heat exchanger; energizing the gas-side shut-off mechanism and de-energizing the liquid-side shut-off mechanism during heating operation; performing a refrigerant recovery operation to recover refrigerant from a user-side unit having the user-side heat exchanger when leakage of the refrigerant from the refrigerant circuit or an abnormality in the refrigerant pressure is detected; and de-energizing the gas-side shut-off mechanism during the refrigerant recovery operation.

This eliminates the need to energize both the gas-side shutoff mechanism and the liquid-side shutoff mechanism during normal cooling or heating operation, and allows the refrigerant to circulate through the refrigerant circuit by energizing only one of them. Therefore, the coil life of the gas-side shutoff mechanism and the liquid-side shutoff mechanism can be suppressed from being shortened compared to when they are constantly energized during operation.
In addition, the number of times the valve body is opened and closed can be reduced by half, which reduces wear on the valve seats of the gas side shutoff mechanism and liquid side shutoff mechanism and also reduces the shortening of the valve body's lifespan.
The gas-side shutoff mechanism and the liquid-side shutoff mechanism do not shut off the flow of refrigerant from the user-side unit to the heat-source-side unit, and therefore the refrigerant can be recovered efficiently.

1, 14, and 15 may be integrated into a chip in part or in whole. The integrated circuit may be realized by a dedicated circuit or a general-purpose processor, not limited to an LSI. Either a hybrid or monolithic circuit may be used. Some of the functions may be realized by hardware and some by software.
Furthermore, with the advancement of semiconductor technology, if a technology for integrated circuitry that can replace LSIs emerges, it may be possible to use integrated circuits based on that technology.

The above describes in detail an embodiment of this disclosure with reference to the drawings, but the specific configuration is not limited to this embodiment and also includes design modifications and the like that do not deviate from the gist of this disclosure.

REFERENCE SIGNS LIST 1 Air conditioner 10 Heat source side unit 100 Casing 101 Compressor 102 Heat source side heat exchanger 103 Fan 104 Gas side check valve 105 Gas side solenoid valve 106 Liquid side check valve 107 Liquid side solenoid valve 108 Gas side shutoff mechanism 109 Liquid side shutoff mechanism 110 Four-way valve 111 Double pipe 112 Pressure vessel 113 Heat source side expansion valve 114 Control unit 115 Refrigerant pressure acquisition unit 20 User side unit 200 Casing 201 User side heat exchanger 202 Fan 203 User side expansion valve 204 Refrigerant leak detection unit 20-a User side unit 200-a Casing 201-a User side heat exchanger 202-a Fan 203-a User side expansion valve 204-a Refrigerant leak detection unit 30 Refrigerant piping 31 Gas side refrigerant piping 31-a Gas side refrigerant piping 32 Liquid side refrigerant piping 32-a Liquid side refrigerant piping 40 Valve unit 400 Casing 50 Solenoid valve 501 Coil 502 Magnet 503 Needle 504 Valve seat 505, 506 Pipe 700 Shut-off mechanism 701 Check valve 702 Solenoid valve 801, 802 Check valve 803 Solenoid valve

Claims (7)

An air conditioner including a utilization-side heat exchanger and a heat source-side heat exchanger, and a refrigerant circuit through which a refrigerant circulates,
A gas side refrigerant pipe connecting the utilization side heat exchanger and the heat source side heat exchanger;
A liquid-side refrigerant pipe connecting the utilization-side heat exchanger and the heat source-side heat exchanger;
A gas side shutoff mechanism disposed in the gas side refrigerant piping;
A liquid-side shutoff mechanism disposed in the liquid-side refrigerant piping;
a control unit that performs a refrigerant recovery operation to recover the refrigerant from a user-side unit having the user-side heat exchanger when the control unit detects leakage of the refrigerant from the refrigerant circuit or an abnormality in the pressure of the refrigerant,
the gas-side shutoff mechanism, in an energized state, allows a bidirectional flow of refrigerant, and, in a de-energized state, allows only a flow of refrigerant from the utilization-side heat exchanger to the heat-source-side heat exchanger;
the liquid-side shutoff mechanism, in an energized state, allows a bidirectional flow of refrigerant, and, in a de-energized state, allows only a flow of refrigerant from the utilization-side heat exchanger to the heat-source-side heat exchanger;
The control unit de-energizes the gas-side shutoff mechanism during the refrigerant recovery operation.
Air conditioner. a utilization side expansion valve disposed on the liquid side refrigerant piping closer to the utilization side heat exchanger than the liquid side shutoff mechanism,
The control unit closes the user side expansion valve and energizes the liquid side cutoff mechanism during the refrigerant recovery operation.
The air conditioner according to claim 1. a utilization side expansion valve disposed on the liquid side refrigerant piping closer to the utilization side heat exchanger than the liquid side shutoff mechanism,
The control unit opens the utilization side expansion valve and de-energizes the liquid side cutoff mechanism during the refrigerant recovery operation.
The air conditioner according to claim 1. The air conditioner according to any one of claims 1 to 3, wherein the control unit energizes the liquid-side shutoff mechanism and deenergizes the gas-side shutoff mechanism during cooling operation, and deenergizes the liquid-side shutoff mechanism after a predetermined time has elapsed since the compressor that compresses the refrigerant is stopped when the cooling operation ends. The air conditioner according to claim 4, wherein the control unit energizes the gas-side shutoff mechanism and deenergizes the liquid-side shutoff mechanism during heating operation, and deenergizes the gas-side shutoff mechanism when the compressor compressing the refrigerant is stopped or after a time shorter than the predetermined time has elapsed since the compressor was stopped at the end of heating operation. An air conditioner according to any one of claims 1 to 5, wherein each of the liquid-side shutoff mechanism and the gas-side shutoff mechanism is a mechanism having a function equivalent to a circuit configuration in which a solenoid valve that is open when energized and closed when de-energized is connected in parallel with a check valve. A method for controlling an air conditioner having a refrigerant circuit including a utilization-side heat exchanger and a heat source-side heat exchanger, in which a refrigerant circulates, comprising:
During cooling operation, a liquid-side shutoff mechanism is arranged in a liquid-side refrigerant piping connecting the user-side heat exchanger and the heat source-side heat exchanger, and in an energized state, the liquid-side shutoff mechanism allows refrigerant to flow in both directions and in a non-energized state only allows refrigerant to flow from the user-side heat exchanger to the heat source-side heat exchanger, and a gas-side shutoff mechanism is arranged in a gas-side refrigerant piping connecting the user-side heat exchanger and the heat source-side heat exchanger, and in an energized state, the gas-side shutoff mechanism allows refrigerant to flow in both directions and in a non-energized state only allows refrigerant to flow from the user-side heat exchanger to the heat source-side heat exchanger, and in a non-energized state;
During a heating operation, the gas-side shutoff mechanism is energized and the liquid-side shutoff mechanism is deenergized;
performing a refrigerant recovery operation of recovering refrigerant from a user-side unit having the user-side heat exchanger when leakage of the refrigerant from the refrigerant circuit or an abnormality in the pressure of the refrigerant is detected;
and during the refrigerant recovery operation, bringing the gas-side shutoff mechanism into a non-energized state.

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