Heat pump system and controller for controlling operation thereof

Abstract

A heat pump system (100) is provided, the heat pump system comprising a liquid-side on-off valve (420), a gas-side on-off valve (460), an ambient temperature detector (520) configured to detect the temperature of a fluid passing through a heat source-side heat exchanger (230), and a controller (600). The controller is configured to, when the liquid-side on-off valve is closed and the gas-side on-off valve is open, operate a compressor (210) to perform a refrigerant recovery operation for recovering refrigerant from a utilization-side pipe section to a heat source-side pipe section (101), and to control the compressor so that an increase rate (S1800) of the compressor speed when the ambient temperature is higher than or equal to a predetermined value (S1600: No) is lower than an increase rate (S1700) of the compressor speed when the ambient temperature is lower than the predetermined value.

Description

Technical Field

[0001] The present invention relates to a heat pump system and a controller for controlling the operation of the heat pump system. Background Art

[0002] EP 3 115 714 A1 proposes a heat pump system configured to perform a refrigerant recovery operation. In this refrigerant recovery operation, when an on-off valve provided in a liquid refrigerant pipe is closed and an on-off valve provided in a gas refrigerant pipe is opened, the compressor is operated to recover refrigerant from a utilization-side pipe section to a heat source-side pipe section.

[0003] However, during the refrigerant recovery operation, the pressure of the refrigerant discharged from the compressor often becomes too high. As a result, the compressor may need to be stopped due to this high pressure before the refrigerant recovery operation is completed. Furthermore, if the compressor speed is simply reduced to prevent this high pressure, the compressor's suction power will be insufficient to complete the refrigerant recovery operation.

[0004] Reference List

[0005] Patent Literature

[0006] [Patent Document 1] EP 3 115 714 A1 Summary of the Invention

[0007] An object of the present invention is to provide a heat pump system and a controller for controlling the operation of the heat pump system capable of performing a refrigerant recovery operation.

[0008] A first aspect of the present invention provides a heat pump system, which includes: a compressor; a heat source side heat exchanger, the heat source side heat exchanger being configured to perform heat exchange between the refrigerant flowing in the heat source side heat exchanger and the fluid passing through the heat source side heat exchanger; a utilization side heat exchanger being configured to perform heat exchange between the refrigerant flowing in the utilization side heat exchanger and the fluid passing through the utilization side heat exchanger; a high-pressure refrigerant pipe connected to each of the discharge port of the compressor and the heat source side heat exchanger; a liquid refrigerant pipe connected to each of the heat source side heat exchanger and the utilization side heat exchanger; a low-pressure refrigerant pipe connected to each of the utilization side heat exchanger and the suction port of the compressor; a liquid side switching valve, the liquid side switching valve being arranged in the liquid refrigerant pipe; an expansion mechanism, the expansion mechanism being arranged in the liquid refrigerant pipe; a gas side switching valve, which is arranged in the low-pressure refrigerant pipeline; an ambient temperature detector, which is configured to detect the temperature of the fluid passing through the heat source side heat exchanger as the ambient temperature; and a controller, which is configured to control the heat pump system to perform a refrigerant recovery operation by operating the compressor when the liquid side switching valve is closed and the gas side switching valve is opened, so as to recover the refrigerant from the utilization side pipeline section to the heat source side pipeline section, the utilization side pipeline section extending between the liquid side switching valve and the gas side switching valve and including at least the utilization side heat exchanger, the heat source side pipeline section extending between the gas side switching valve and the liquid side switching valve and including at least the compressor, wherein the controller is configured to control the compressor in the refrigerant recovery operation so that the increase rate of the compressor speed when the ambient temperature is higher than or equal to the predetermined ambient temperature value is lower than the increase rate of the compressor speed when the ambient temperature is lower than the predetermined ambient temperature value.

[0009] In this heat pump system, as the temperature of the fluid exchanging heat with the refrigerant at the heat source-side heat exchanger increases, the pressure of the refrigerant discharged from the compressor tends to increase. At the same time, during refrigerant recovery operation, the pressure of the refrigerant discharged from the compressor reaches a peak at the start of operation. If the temperature of the fluid is high, the peak pressure of the discharged refrigerant will become too high, necessitating a protective control to stop the compressor for safety reasons. In this regard, the above-described configuration suppresses the rate of increase in the compressor speed during refrigerant recovery operation when the temperature of the fluid passing through the heat source-side heat exchanger is relatively high. This suppresses the peak pressure of the discharged refrigerant when it could exceed the permissible upper limit due to the fluid temperature, and prevents the compressor from shutting down. Even if the rate of increase in the compressor speed is suppressed, the compressor speed will eventually reach the same desired compressor speed, albeit over a longer period of time. Therefore, the refrigerant recovery operation can be completed more reliably.

[0010] According to a preferred embodiment of the above-mentioned heat pump system, the heat pump system also includes a refrigerant leakage detector, which is configured to detect the occurrence of refrigerant leakage in the utilization-side pipe section, wherein the controller is configured to control the heat pump system to perform a refrigerant recovery operation when a refrigerant leakage has been detected.

[0011] With the above configuration, when refrigerant leakage has occurred in the usage-side pipe section, the refrigerant can be evacuated from the usage-side pipe section, thereby preventing further refrigerant leakage and safely repairing the leaking point.

[0012] According to another preferred embodiment of any of the above heat pump systems, the heat source-side heat exchanger is configured to allow outdoor air to pass therethrough.

[0013] Outdoor air is a simple and inexpensive source of heat and cooling in heat pump systems. However, the temperature of outdoor air often varies significantly depending on the region, season, and time of day. As described above, the refrigerant recovery operation according to the present invention can be performed even when the fluid temperature is relatively high. Therefore, the above-described configuration provides a heat pump system capable of performing a low-cost refrigerant recovery operation.

[0014] According to another preferred embodiment of any one of the above-mentioned heat pump systems, the heat pump system further includes: a bypass pipe connected to a position between the heat source side heat exchanger and the liquid side switching valve in the liquid refrigerant pipe, and connected to a position between the gas side switching valve and the compressor in the low-pressure refrigerant pipe; a bypass expansion mechanism arranged in the bypass pipe; and a storage tank inserted in the low-pressure refrigerant pipe at a position between the bypass pipe and the compressor, wherein the controller is configured to control the bypass expansion mechanism to open during the refrigerant recovery operation.

[0015] This configuration allows refrigerant to be pumped from the utilization-side piping section to the heat-source-side piping section, while simultaneously circulating within the heat-source-side piping section. Furthermore, refrigerant can accumulate not only in the heat-source-side heat exchanger but also in the storage tank. This increases the amount of refrigerant to be recovered while preventing the pressure of the discharged refrigerant from becoming excessively high. Furthermore, the capacity of the heat-source-side heat exchanger can be determined based on its required heat exchange capacity, regardless of the amount of refrigerant to be recovered. This allows the size and design of the heat-source-side heat exchanger to be optimized.

[0016] According to another preferred embodiment of any of the above-mentioned heat pump systems with a bypass pipe, the heat pump system also includes a refrigerant heat exchanger, which is configured to exchange heat between the refrigerant flowing in the liquid refrigerant pipe and the refrigerant flowing in the bypass pipe, wherein the bypass expansion mechanism is arranged at a point in the bypass pipe between the liquid refrigerant pipe and the refrigerant heat exchanger.

[0017] With the above-described structure, the refrigerant heat exchanger, bypass pipe, and bypass expansion mechanism function as a so-called subcooling system, which is widely used in heat pump systems. Therefore, the bypass pipe and bypass expansion mechanism of the subcooling system can be used to circulate refrigerant within the heat source-side piping section. This allows for a low-cost heat pump system capable of refrigerant recovery operation.

[0018] According to another preferred embodiment of any of the above-mentioned heat pump systems, the heat pump system further comprises: a discharge-side refrigerant pipe, the discharge-side refrigerant pipe being connected to the discharge port of the compressor; a suction-side refrigerant pipe, the suction-side refrigerant pipe being connected to the suction port of the compressor; a first gas refrigerant pipe, the first gas refrigerant pipe being connected to the heat source-side heat exchanger; a second gas refrigerant pipe, the second gas refrigerant pipe being connected to the utilization-side heat exchanger; and a mode switching mechanism, the mode switching mechanism being configured to switch between a cooling mode connection and a heating mode connection, through which the discharge-side refrigerant pipe is connected The discharge-side refrigerant pipe and the first gas refrigerant pipe are connected to each other to form a high-pressure refrigerant pipe, and through the cooling mode connection, the suction-side refrigerant pipe and the second gas refrigerant pipe are connected to each other to form a low-pressure refrigerant pipe, while through the heating mode connection, the discharge-side refrigerant pipe and the second gas refrigerant pipe are connected to each other to form a high-pressure refrigerant pipe, and through the heating mode connection, the suction-side refrigerant pipe and the first gas refrigerant pipe are connected to each other to form a low-pressure refrigerant pipe, wherein the controller is configured to operate with the cooling mode connection when performing the refrigerant recovery operation.

[0019] The mode switching mechanism allows the heat pump system to perform both cooling and heating operations. However, for refrigerant recovery operation, the mode switching mechanism should be in the connected state for cooling operation. This configuration allows the refrigerant recovery operation to be properly performed even in a heat pump system that has both cooling and heating functions.

[0020] According to another preferred embodiment of any of the above-mentioned heat pump systems, the heat pump system also includes an evaporation temperature detector, which is configured to detect the evaporation temperature of the refrigerant flowing in the low-pressure refrigerant pipeline, wherein: the compressor is configured to control the compressor speed so that the evaporation temperature is close to a target evaporation temperature value; and the controller is configured to lower the target evaporation temperature value compared to the target evaporation temperature value used in conventional refrigeration operation when the refrigerant recovery operation is started.

[0021] By controlling the compressor speed based on the target evaporation temperature value, the performance of the heat pump system can be optimized. With the above configuration, the compressor can be easily kept running during the refrigerant recovery operation simply by changing the target evaporation temperature value.

[0022] According to another preferred embodiment of any of the above-mentioned heat pump systems, the heat pump system has a refrigerant leakage detector, and when the occurrence of refrigerant leakage has been detected during the period when the compressor is not operating, the controller is configured to control the heat pump system in the refrigerant recovery operation so that the liquid-side switching valve is closed, and to start the operation of the compressor after the liquid-side switching valve has been closed.

[0023] When the compressor is operating, closing the liquid-side on-off valve creates a pressure differential across the valve, making complete closure more difficult. In this regard, the above configuration allows the compressor to begin operating to recover refrigerant with the liquid-side on-off valve closed. This allows for quick and efficient refrigerant recovery, while also properly shutting off refrigerant flow at the liquid-side on-off valve.

[0024] According to another preferred embodiment of any of the above-mentioned heat pump systems, the heat pump system has a refrigerant leakage detector, and when the occurrence of refrigerant leakage has been detected while the compressor is operating, the controller is configured to control the heat pump system in the refrigerant recovery operation, so that the operation of the compressor is stopped, and then the operation of the compressor is started to recover the refrigerant after a first predetermined time has passed after the operation of the compressor is stopped, and the liquid-side switching valve is closed during the period when the operation of the compressor is stopped.

[0025] When the compressor is operating, closing the liquid-side on-off valve creates a pressure differential across the valve, making complete closure more difficult. In this regard, the above configuration allows the compressor to begin operating to recover refrigerant with the liquid-side on-off valve closed. Therefore, even if a refrigerant leak is detected during compressor operation, refrigerant flow can be properly shut off at the liquid-side on-off valve. Furthermore, because the compressor remains stopped for the first predetermined time, the liquid-side on-off valve can be completely closed before the compressor begins operating.

[0026] According to another preferred embodiment of any one of the above-mentioned heat pump systems, the heat pump system has a bypass expansion mechanism, and the controller is configured to control the bypass expansion mechanism to open during the period when the compressor is stopped in the refrigerant recovery operation, and if the expansion mechanism includes a heat source side expansion mechanism arranged at a point between the heat source side heat exchanger and the bypass pipe, the heat source side expansion mechanism is controlled to open.

[0027] According to the above configuration, the operation of the compressor is started to recover the refrigerant with the bypass expansion mechanism and the heat source side expansion mechanism open. Therefore, the circulation of the refrigerant in the heat source side pipe section can be started quickly and efficiently.

[0028] According to another preferred embodiment of any one of the above-mentioned heat pump systems, the heat pump system further includes: a suction pressure detector, which is configured to detect the pressure of the refrigerant flowing in the low-pressure refrigerant pipeline, wherein the controller is configured to control the heat pump system during the refrigerant recovery operation so that while the compressor is running to recover the refrigerant, the gas-side switching valve begins to close when a predetermined valve closing condition is met, and the predetermined valve closing condition includes that while the compressor is running to recover the refrigerant, the pressure of the refrigerant flowing in the low-pressure refrigerant pipeline remains lower than a first predetermined suction pressure value for a second predetermined time.

[0029] With this configuration, when the pressure in the low-pressure refrigerant pipe has dropped sufficiently, meaning that refrigerant has been fully recovered from the utilization-side pipe section to the heat-source-side pipe section, the flow of refrigerant in the low-pressure refrigerant pipe can be shut off. This allows for the gas-side on-off valve to be closed earlier, while refrigerant is fully recovered, thereby stopping the compressor operation earlier.

[0030] According to another preferred embodiment of any one of the above-mentioned heat pump systems, the controller is configured to control the compressor in the refrigerant recovery operation so that the operation of the compressor stops when a predetermined compressor stop condition is met, and the predetermined compressor stop condition includes at least one of the following: a first condition, namely, the rate of change of the pressure of the refrigerant flowing in the high-pressure refrigerant pipe is lower than a predetermined discharge pressure change rate value, and the rate of change of the pressure of the refrigerant flowing in the low-pressure refrigerant pipe is lower than a predetermined suction pressure change rate value, and the predetermined suction pressure change rate value is equal to or different from the predetermined discharge pressure change rate value; a second condition, namely, the rate of change of the refrigerant flowing in the low-pressure refrigerant pipe is lower than a predetermined discharge pressure change rate value; pressure is lower than a second predetermined suction pressure value, which is lower than the first predetermined suction pressure value; a third condition, that is, a third predetermined time has passed after the compressor starts to run to recover the refrigerant; a fourth condition, that is, a fourth predetermined time has passed after the closing of the gas side switching valve has been completed; a fifth condition, that is, the current discharge temperature of the compressor is lower than the previous discharge temperature of the compressor, and the discharge superheat temperature of the compressor is lower than the predetermined superheat temperature value; a sixth condition, that is, the discharge temperature of the compressor is higher than the predetermined discharge temperature value; and a seventh condition, that is, a fifth predetermined time has passed after the closing of the gas side switching valve starts.

[0031] The above configuration enables the compressor to be stopped at an appropriate time to complete the refrigerant recovery operation. For example, the compressor can be stopped when the heat pump system is in a state that prevents refrigerant from flowing back from the heat source-side pipe section via the low-pressure refrigerant pipe to the utilization-side pipe section, and / or when it is necessary to stop the compressor for safety reasons or the like.

[0032] 14. The heat pump system of claim 13, wherein the heat pump system further comprises a first heat exchanger configured to heat the refrigerant flowing in the heat source side heat exchanger to a fluid passing through the heat source side heat exchanger; a second heat exchanger configured to heat the refrigerant flowing in the heat source side heat exchanger to a fluid passing through the heat source side heat exchanger; a third heat exchanger configured to heat the refrigerant flowing in the heat source side heat exchanger to a fluid passing through the heat source side heat exchanger; a fourth heat exchanger configured to heat the refrigerant flowing in the heat source side heat exchanger to a fluid passing through the heat source side heat exchanger; a fifth heat exchanger configured to heat the refrigerant flowing in the heat source side heat exchanger to a fluid passing through the heat source side heat exchanger; a fifth heat exchanger configured to heat the refrigerant flowing in the heat source side heat exchanger to a fluid passing through the heat source side heat exchanger; a fifth heat exchanger configured to heat the refrigerant at a point between the heat source side heat exchanger and the liquid side switch valve in the refrigerant pipeline, and connected to a point between the gas side switch valve and the compressor in the low-pressure refrigerant pipeline; a bypass expansion mechanism, which is arranged in the bypass pipeline; and an ambient temperature detector, which is configured to detect the temperature of the fluid passing through the heat source side heat exchanger as the ambient temperature, the controller being configured to control the heat pump system to perform a refrigerant recovery operation by operating the compressor when the liquid side switch valve is closed and the gas side switch valve is open, so as to recover the refrigerant from the utilization side pipeline section to the heat source side pipeline section, the utilization side pipeline section extending between the liquid side switch valve and the gas side switch valve and including at least the utilization side heat exchanger, the heat source side pipeline section extending between the gas side switch valve and the liquid side switch valve and including at least the compressor, wherein the controller is configured to control the compressor in the refrigerant recovery operation so that the increase rate of the compressor speed when the ambient temperature is higher than or equal to a predetermined ambient temperature value is lower than the increase rate of the compressor speed when the ambient temperature is lower than the predetermined ambient temperature value.

[0033] In this heat pump system, as the temperature of the fluid exchanging heat with the refrigerant at the heat source-side heat exchanger increases, the pressure of the refrigerant discharged from the compressor tends to increase. Furthermore, during refrigerant recovery operation, the pressure of the refrigerant discharged from the compressor reaches a peak at the start of operation. If the fluid temperature is high, the peak pressure of the discharged refrigerant will become too high, necessitating a protective control to stop the compressor for safety reasons. In this regard, the above-described configuration enables control of the heat pump system to suppress the rate of increase in the compressor speed during refrigerant recovery operation when the temperature of the fluid passing through the heat source-side heat exchanger is relatively high. This suppresses the peak pressure of the discharged refrigerant when it could exceed the upper limit allowed by the fluid temperature, and prevents the compressor from stopping. Even if the rate of increase in the compressor speed is suppressed, the compressor speed can eventually reach the same desired speed, albeit over a longer period of time. Consequently, the refrigerant recovery operation of the heat pump system can be completed more reliably. Furthermore, simply by applying the controller according to the present invention to an existing heat pump system, the above-described effects can also be achieved in existing heat pump systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] [ Figure 1 ] Figure 1 is a schematic structural diagram of a heat pump system according to a preferred embodiment of the present invention;

[0035] [ Figure 2 ] Figure 2 Yes Figure 1 A block diagram of the functional structure of the controller shown;

[0036] [ Figure 3 ] Figure 3 is the first part of a flowchart showing the process of a refrigerant recovery operation performed by the controller;

[0037] [ Figure 4 ] Figure 4 It is the second part of the flow chart showing the process of the refrigerant recovery operation;

[0038] [ Figure 5 ] Figure 5 is a table showing examples of conditions used as compressor stop conditions;

[0039] [ Figure 6 ] Figure 6 is a schematic configuration diagram of a first modified example of the heat pump system according to the preferred embodiment; and

[0040] [ Figure 7 ] Figure 7 is a schematic configuration diagram of a second modified example of the heat pump system according to the preferred embodiment. DETAILED DESCRIPTION

[0041] A preferred embodiment of a heat pump system according to the present invention (hereinafter referred to as "this embodiment") will be described with reference to the accompanying drawings. For example, the heat pump system according to this embodiment is an air conditioning system capable of performing cooling and heating operations using R32 refrigerant.

[0042] <System Circuit Structure>

[0043] Figure 1 is a schematic configuration diagram of a heat pump system according to this embodiment.

[0044] like Figure 1 As shown, the heat pump system 100 includes a compressor 210, a mode switching mechanism 220, a heat source side heat exchanger 230, a utilization side heat exchanger 240, and a storage tank 250. The heat source side heat exchanger 230 may be provided with a heat source side fan 231, and the utilization side heat exchanger 240 may be provided with a utilization side fan 241.

[0045] The heat pump system 100 further includes a discharge-side refrigerant pipe 310, a first gas refrigerant pipe 320, a liquid refrigerant pipe 330, a second gas refrigerant pipe 340, and a suction-side refrigerant pipe 350. The discharge-side refrigerant pipe 310 is connected to each of the discharge port of the compressor 210 and the mode switching mechanism 220. The first gas refrigerant pipe 320 is connected to each of the mode switching mechanism 220 and the heat source-side heat exchanger 230. The liquid refrigerant pipe 330 is connected to each of the heat source-side heat exchanger 230 and the utilization-side heat exchanger 240. The second gas refrigerant pipe 340 is connected to each of the utilization-side heat exchanger 240 and the mode switching mechanism 220. The suction-side refrigerant pipe 350 is connected to each of the mode switching mechanism 220 and the suction port of the compressor 210. The accumulator 250 is interposed in the suction-side refrigerant pipe 350.

[0046] The heat pump system 100 further includes a heat source-side expansion mechanism 410, a liquid-side on-off valve 420, a liquid-side stop valve 430, a utilization-side expansion mechanism 440, a gas-side stop valve 450, and a gas-side on-off valve 460. The heat source-side expansion mechanism 410, the liquid-side on-off valve 420, the liquid-side stop valve 430, and the utilization-side expansion mechanism 440 are sequentially arranged in the liquid refrigerant pipe 330 from the heat source-side heat exchanger 230 toward the utilization-side heat exchanger 240. The gas-side stop valve 450 and the gas-side on-off valve 460 are sequentially arranged in the second gas refrigerant pipe 340 from the utilization-side heat exchanger 240 toward the mode switching mechanism 220. The heat source-side expansion mechanism 410 and the utilization-side expansion mechanism 440 each correspond to an expansion mechanism according to the present invention.

[0047] The heat pump system 100 also includes a refrigerant heat exchanger 260, a bypass pipe 360, and a bypass expansion mechanism 470. The refrigerant heat exchanger 260 is arranged in the liquid refrigerant pipe 330 at a position between the heat source-side expansion mechanism 410 and the liquid-side on-off valve 420. The bypass pipe 360 ​​is connected to each of the liquid refrigerant pipe 330 and the suction-side refrigerant pipe 350 in parallel with the utilization-side heat exchanger 240. More specifically, the bypass pipe 360 ​​is connected to the liquid refrigerant pipe 330 at a point between the heat source-side expansion mechanism 410 and the refrigerant heat exchanger 260, and to the suction-side refrigerant pipe 350 at a point between the mode switching mechanism 220 and the accumulator 250. A portion of the bypass pipe 360 ​​is arranged in the refrigerant heat exchanger 260. The bypass expansion mechanism 470 is provided in the bypass pipe 360 ​​at a point between the liquid refrigerant pipe 330 and the refrigerant heat exchanger 260.

[0048] The heat pump system 100 further includes a discharge-side refrigerant state detector 510, an ambient temperature detector 520, a refrigerant leak detector 530, and a suction-side refrigerant state detector 540. The discharge-side refrigerant state detector 510 is attached to the discharge-side refrigerant pipe 310. The ambient temperature detector 520 is disposed near the heat source-side heat exchanger 230. The refrigerant leak detector 530 is disposed near the utilization-side heat exchanger 240. The suction-side refrigerant state detector 540 is attached to the suction-side refrigerant pipe 350 at a point between the accumulator 250 and the compressor 210. The suction-side refrigerant state detector 540 corresponds to each of the evaporation temperature detector and the suction pressure detector according to the present invention.

[0049] The heat pump system 100 further includes a controller 600. The controller 600 is connected to each of the above-mentioned mechanical devices through a wired / wireless communication path (not shown).

[0050] The heat pump system 100 may include a heat source unit 110 and a utilization unit 120 as separate units. For example, the heat source unit 110 may be located externally, while the utilization unit 120 may be located within or near the target space to be air-conditioned. In this case, at least the compressor 210, the gas-side on / off valve 460, the liquid-side on / off valve 420, and the controller 600 are located within the heat source unit 110, and at least the utilization-side heat exchanger 240 is located within the utilization unit 120.

[0051] In this embodiment, the liquid refrigerant pipe 330 and the second gas refrigerant pipe 340 extend between the heat source-side unit 110 and the utilization-side unit 120. The utilization-side expansion mechanism 440, the utilization-side heat exchanger 240, the utilization-side fan 241, and the refrigerant leak detector 530, among the aforementioned mechanical devices, are disposed in the utilization-side unit 120, while the other mechanical devices are disposed in the heat source-side unit 110. The controller 600 can be connected to the mechanical devices in the utilization-side unit 120 via a sub-controller (not shown) disposed in the utilization-side unit 120. It can be said that the sub-controller in the utilization-side unit 120 is part of the controller 600.

[0052] <Functions of the Organization>

[0053] The compressor 210 has a suction port and a discharge port, and is configured to suck refrigerant through the suction port, internally compress the sucked refrigerant, and discharge the compressed refrigerant from the discharge port.

[0054] The mode switching mechanism 220 is configured to switch between a cooling mode connection and a heating mode connection. In the cooling mode connection, the mode switching mechanism 220 interconnects the discharge-side refrigerant pipe 310 and the first gas refrigerant pipe 320 to form a high-pressure refrigerant pipe, and interconnects the suction-side refrigerant pipe 350 and the second gas refrigerant pipe 340 to form a low-pressure refrigerant pipe. In the heating mode connection, the mode switching mechanism 220 interconnects the discharge-side refrigerant pipe 310 and the second gas refrigerant pipe 340 to form a high-pressure refrigerant pipe, and interconnects the suction-side refrigerant pipe 350 and the first gas refrigerant pipe 320 to form a low-pressure refrigerant pipe. Here, the high-pressure refrigerant pipe is the pipe (flow path) connected to each of the discharge port of the compressor 210 and the heat source-side heat exchanger 230, while the low-pressure refrigerant pipe is the pipe connected to each of the utilization-side heat exchanger 240 and the suction port of the compressor 210. The mode switching mechanism 220 may be a four-way selector valve.

[0055] The heat source side heat exchanger 230 is configured to allow refrigerant to flow from the first gas refrigerant pipe 320 to the liquid refrigerant pipe 330, and vice versa. The heat source side heat exchanger 230 is also configured to exchange heat between the refrigerant flowing therein and the fluid passing therethrough. In this embodiment, the heat source side heat exchanger 230 is configured to allow outdoor air to pass therethrough. The heat source side fan 231 is configured to promote the flow of air passing through the heat source side heat exchanger 230.

[0056] The utilization-side heat exchanger 240 is configured to allow refrigerant to flow from the liquid refrigerant pipe 330 to the second gas refrigerant pipe 340, and vice versa. The utilization-side heat exchanger 240 is also configured to exchange heat between the refrigerant flowing therein and a fluid passing therethrough. In this embodiment, the utilization-side heat exchanger 240 is configured to allow indoor air and / or outdoor air in the target space to pass therethrough. A utilization-side fan 241 is configured to facilitate the flow of air passing through the utilization-side heat exchanger 240. The air that has passed through the utilization-side heat exchanger 240 is supplied to the target space.

[0057] The storage tank 250 is configured to separate the gas refrigerant from the refrigerant flowing into the storage tank 260 and to advance the separated gas refrigerant. The storage tank 250 is also configured to accumulate excess refrigerant in the heat pump circuit of the heat pump system 100.

[0058] The refrigerant heat exchanger 260 is configured to perform heat exchange between the refrigerant flowing in the liquid refrigerant pipe 330 and the refrigerant that has flowed into the bypass pipe 360 ​​and has been decompressed and expanded by the bypass expansion mechanism 470. The refrigerant heat exchanger 260 may have two flow channels that respectively form a portion of the liquid refrigerant pipe 330 and a portion of the bypass pipe 360, and have thermal conductivity between the two.

[0059] The heat source-side expansion mechanism 410 is configured to decompress and expand the refrigerant flowing therethrough when the heat source-side expansion mechanism 410 is partially opened. More specifically, under the control of the controller 600, the heat source-side expansion mechanism 410 is configured to decompress and expand the refrigerant flowing from the utilization-side heat exchanger 240 to the heat source-side heat exchanger 230 in the liquid refrigerant pipe 330 during heating operation of the heat pump system 100. The heat source-side expansion mechanism 410 may be an electric expansion valve.

[0060] The liquid-side on-off valve 420 is configured to regulate the flow of refrigerant therethrough. More specifically, the liquid-side on-off valve 420 is configured to shut off the flow of refrigerant in at least a portion of the liquid refrigerant pipe 330 when the liquid-side on-off valve 420 is fully closed under the control of the controller 600. The liquid-side on-off valve 420 may be an electric expansion valve.

[0061] The liquid-side shutoff valve 430 is configured to block refrigerant flow therethrough when manually closed. The liquid-side shutoff valve 430 remains fully open unless manually closed. The liquid-side shutoff valve 430 may be a service valve configured to switch between an open state and a closed state while allowing refrigerant to pass therethrough for charging into and discharging from the heat pump circuit.

[0062] The utilization-side expansion mechanism 440 is configured to decompress and expand the refrigerant flowing therethrough when the utilization-side expansion mechanism 440 is partially opened. More specifically, under the control of the controller 600, the utilization-side expansion mechanism 440 is configured to decompress and expand the refrigerant flowing from the heat source-side heat exchanger 230 to the utilization-side heat exchanger 240 in the liquid refrigerant pipe 330 during cooling operation of the heat pump system 100. The utilization-side expansion mechanism 440 may be an electric expansion valve.

[0063] The gas-side shutoff valve 450 is configured to block the flow of refrigerant therethrough when manually closed. The gas-side shutoff valve 450 remains fully open unless manually closed. The liquid-side shutoff valve 430 may be a service valve configured to switch between an open state and a closed state while allowing refrigerant to pass therethrough for charging into and discharging from the heat pump circuit.

[0064] The gas-side switching valve 460 is configured to regulate the flow of refrigerant therethrough. More specifically, the gas-side switching valve 460 is configured to cut off the flow of refrigerant in at least a portion of the liquid refrigerant pipe 330 when the gas-side switching valve 460 is fully closed under the control of the controller 600. The gas-side switching valve 460 may be an electric expansion valve.

[0065] Typically, the diameter of the second gas refrigerant pipe 340 is larger than the diameter of the liquid refrigerant pipe 330. Therefore, the Cv value of the gas-side on-off valve 460 is greater than the Cv value of the liquid-side on-off valve 420. For example, the Cv value of the gas-side on-off valve 460 is at least five times the Cv value of the liquid-side on-off valve 420. The Cv value of the gas-side on-off valve 460 may be 5, and the Cv value of the liquid-side on-off valve 420 may be 0.6. In this case, the Cv value of the heat source-side expansion mechanism 410 may be 0.3.

[0066] The bypass expansion mechanism 470 is configured to decompress and expand the refrigerant flowing therethrough when the bypass expansion mechanism 470 is partially opened. More specifically, under the control of the controller 600, the bypass expansion mechanism 470 is configured to decompress and expand the refrigerant flowing from the liquid refrigerant pipe 330 to the suction-side refrigerant pipe 350 in the bypass pipe 360 ​​while the heat pump system 100 is operating in cooling operation and refrigerant recovery operation (described later). The bypass expansion mechanism 470 may be an electric expansion valve.

[0067] In the following description, the heat source-side expansion mechanism 410 , the liquid-side on-off valve 420 , the utilization-side expansion mechanism 440 , the gas-side on-off valve 460 , and the bypass expansion mechanism 470 are collectively referred to as “control valves” as needed.

[0068] The discharge-side refrigerant state detector 510 is configured to detect the pressure and / or temperature of the refrigerant flowing in the discharge-side refrigerant pipe 310 and continuously or periodically transmit discharge-side refrigerant information indicating the detected pressure (hereinafter referred to as "discharge pressure Pc") and / or the detected temperature (hereinafter referred to as "discharge temperature Tdi") to the controller 600. Alternatively or additionally, the discharge-side refrigerant state detector 510 may transmit the discharge-side refrigerant information when the detected discharge pressure Pc and / or discharge temperature Tdi has changed by a predetermined amount and / or upon receiving a request from the controller 600. The discharge-side refrigerant state detector 510 may be a capacitive pressure sensor and / or a thermistor.

[0069] The ambient temperature detector 520 is configured to detect the temperature of the fluid (outdoor air) passing through the heat source side heat exchanger 230 and continuously or periodically transmit ambient temperature information indicating the detected temperature (hereinafter referred to as "ambient temperature Ta") to the controller 600. Alternatively or additionally, the ambient temperature detector 520 may transmit the ambient temperature information when the detected temperature Ta has changed by a predetermined amount and / or when a request is received from the controller 600. The ambient temperature detector 520 may be a thermistor provided on the upstream side of the heat source side heat exchanger 230 in the air flow path of the outdoor air flowing through the heat source side heat exchanger 230. In other words, the ambient temperature detector 520 is configured to detect the temperature of the fluid that exchanges heat with the refrigerant in the heat source side heat exchanger 230.

[0070] The refrigerant leak detector 530 is configured to detect the occurrence of a refrigerant leak in the utilization-side unit 120 and continuously or periodically transmit refrigerant leak information to the controller 600. The refrigerant leak information is information indicating whether a refrigerant leak (hereinafter referred to as "refrigerant leak") has occurred in the utilization-side unit 120. Alternatively or additionally, the refrigerant leak detector 530 may transmit the refrigerant leak information when a refrigerant leak has occurred.

[0071] The refrigerant leak detector 530 may be a semiconductor gas sensor that reacts to the refrigerant used in the heat pump system 100. In this case, the refrigerant leak detector 530 detects the refrigerant concentration in the air surrounding the refrigerant leak detector 530 and outputs a detection value indicating the detected concentration as refrigerant leak information. Whether the detection value is greater than a predetermined threshold value indicates whether a refrigerant leak has occurred. The refrigerant leak detector 530 is disposed in the utilization-side unit 120 or the target space. In the case of a refrigerant heavier than air, such as R32 refrigerant, the refrigerant leak detector 530 is preferably disposed on or near the inner bottom surface of the air chamber (not shown) in which the utilization-side heat exchanger 240 is disposed.

[0072] The suction-side refrigerant state detector 540 is configured to detect the pressure of the refrigerant flowing in the suction-side refrigerant pipe 350 and to detect the evaporation temperature of the refrigerant flowing in the suction-side refrigerant pipe 350. The suction-side refrigerant state detector 540 is also configured to continuously or periodically transmit suction-side refrigerant information indicating the detected pressure (hereinafter referred to as "suction pressure Pe") and the detected evaporation temperature TeS to the controller 600. Alternatively or additionally, the suction-side refrigerant state detector 540 may transmit the suction-side refrigerant information when the detected suction pressure Pe and / or evaporation temperature TeS have changed by a predetermined amount and / or upon receiving a request from the controller 600.

[0073] The suction-side refrigerant state detector 540 may include a capacitive pressure sensor configured to detect the pressure of the refrigerant flowing in the suction-side refrigerant pipe 350, and a thermistor configured to detect the temperature of the refrigerant flowing in the suction-side refrigerant pipe 350. The suction-side refrigerant state detector 540 may also include a storage medium and a calculator. In this case, the storage medium pre-stores table information indicating a known correlation between the refrigerant pressure and the refrigerant's evaporation temperature TeS at that pressure. The calculator calculates the refrigerant's evaporation temperature TeS based on the detected pressure and the table. However, this calculation may be performed by the controller 600.

[0074] In the following description, the discharge-side refrigerant state detector 510 , the ambient temperature detector 520 , the refrigerant leakage detector 530 , and the suction-side refrigerant state detector 540 are collectively referred to as “sensors” as needed.

[0075] The controller 600 is configured to switch the mode switching mechanism 220 between the cooling mode connection and the heating mode connection according to an instruction made by a user or an external controller, and control the cooling operation and the heating operation of the heat pump system 100 .

[0076] During cooling operation, the controller 600 controls the mechanical devices of the heat pump system 100 so that the refrigerant discharged from the compressor 210 flows through each of the heat source side heat exchanger 230, the utilization side heat exchanger 240 and the bypass pipe 360 ​​and the storage tank 250 in sequence and is sucked into the compressor 210. Figure 1 The arrows shown in represent the flow direction of the refrigerant during the cooling operation of the heat pump system 100. In the cooling operation, the heat source side unit 110 functions as a condenser, and the utilization side unit 120 functions as an evaporator.

[0077] During heating operation, controller 600 controls the mechanical equipment so that refrigerant discharged from compressor 210 flows sequentially through utilization-side heat exchanger 240, heat source-side heat exchanger 230, and accumulator 250, and is drawn into compressor 210. It can be said that when mode switching mechanism 220 is in heating mode, first gas refrigerant pipe 320 is part of suction-side refrigerant pipe 350, and second gas refrigerant pipe 340 is part of discharge-side refrigerant pipe 310. During heating operation, heat source-side unit 110 functions as an evaporator, and utilization-side unit 120 functions as a condenser.

[0078] The controller 600 is further configured to control the heat pump system 100 to perform a refrigerant recovery operation when a refrigerant leak is detected. The refrigerant recovery operation involves operating the compressor 210 while the liquid-side on-off valve 420 is closed and the gas-side on-off valve 460 is open, thereby recovering refrigerant from the utilization-side pipe section 102 to the heat-source-side pipe section 101. The heat-source-side pipe section 101 extends between the gas-side on-off valve 460 and the liquid-side on-off valve 420 and includes at least the compressor 210. The heat-source-side pipe section 101 also includes the heat-source-side heat exchanger 230. The utilization-side pipe section 102 extends between the liquid-side on-off valve 420 and the gas-side on-off valve 460 and includes at least the utilization-side heat exchanger 240.

[0079] In this embodiment, the heat source-side piping section 101 includes a portion of the second gas refrigerant piping 340 connected to the mode switching mechanism 220, the mode switching mechanism 220, the suction-side refrigerant piping 350, the accumulator 250, the compressor 210, the discharge-side refrigerant piping 310, the first gas refrigerant piping 320, the heat source-side heat exchanger 230, a portion of the liquid refrigerant piping 330 connected to the heat source-side heat exchanger 230, the heat source-side expansion mechanism 410, the refrigerant heat exchanger 260, the bypass piping 360, and the bypass expansion mechanism 470. The utilization-side piping section 102 includes a portion of the liquid refrigerant piping 330 connected to the utilization-side heat exchanger 240, the liquid-side stop valve 430, the utilization-side expansion mechanism 440, a portion of the second gas refrigerant piping 340 connected to the utilization-side heat exchanger 240, and the gas-side stop valve 450.

[0080] During the refrigerant recovery operation, the controller 600 controls the mechanical equipment of the heat pump system 100 so that the refrigerant in the utilization-side pipe section 102 is directed to the suction port of the compressor 210 via the second gas refrigerant pipe 340. The refrigerant then flows through the heat source-side heat exchanger 230, the bypass pipe 360, and the accumulator 250 within the heat source-side pipe section 101. While circulating within the heat source-side pipe section 101, the refrigerant primarily accumulates in the accumulator 250 and the heat source-side heat exchanger 230.

[0081] The controller 600 is further configured to control the compressor 210 during the refrigerant recovery operation so that the rate of increase in the compressor speed is lower when the ambient temperature Ta is greater than or equal to a predetermined ambient temperature value Ta_th than when the ambient temperature Ta is less than the predetermined ambient temperature value Ta_th. Here, "compressor speed" refers to the speed of the compressor 210, which is expressed, for example, in revolutions per minute. The rate of increase in the compressor speed is, for example, the amount of increase in the compressor speed per unit time.

[0082] The controller 600 is further configured to control the heat pump system 100 during the refrigerant recovery operation so that when a predetermined valve closing condition is satisfied while the compressor 210 is operating to recover refrigerant, the gas-side on-off valve 460 begins closing. The controller 600 is further configured to control the heat pump system 100 so that the operation of the compressor 210 for recovering refrigerant stops after the gas-side on-off valve 460 begins closing. Details regarding the controller 600 are described below.

[0083] <Functional composition of the controller>

[0084] The controller 600 includes an arithmetic circuit, such as a CPU (Central Processing Unit); a working memory used by the CPU, such as RAM (Random Access Memory); a recording medium, such as ROM (Read Only Memory), that stores control programs and information used by the CPU; and a timer, although these are not shown. The controller 600 is configured to control the operation of the heat pump system 100 by executing a control program through the CPU, thereby performing information processing and signal processing. Therefore, the functions of the controller 600 are realized by executing the program.

[0085] Figure 2 It is a block diagram showing the functional configuration of the controller 600 .

[0086] like Figure 2 As shown, the controller 600 includes a storage unit 610 , an information input unit 620 , a normal operation controller 630 , an information output unit 640 , and a refrigerant recovery controller 650 .

[0087] The storage unit 610 stores information in a format readable by the refrigerant recovery controller 650. The stored information may include conditions and values ​​used by the normal operation controller 630 and the refrigerant recovery controller 650. The stored information may be prepared in advance based on experiments or the like.

[0088] The information input unit 620 is configured to acquire information necessary for controlling the operation of the heat pump system 100 from sensors and transmit the acquired information to the refrigerant recovery controller 650. The information input unit 620 may also transmit the acquired information to the normal operation controller 630. The information to be acquired includes the aforementioned discharge-side refrigerant information, ambient temperature information, refrigerant leakage information, and suction-side refrigerant information. The information input unit 620 may include a wired / wireless communication interface for communicating with each sensor. Under the control of the refrigerant recovery controller 650, the information input unit 620 may transmit requests to sensors requesting information.

[0089] The normal operation controller 630 is configured to control the cooling and heating operations of the heat pump system 100. For cooling operation, the normal operation controller 630 is configured to control the mode switching mechanism 220 to switch to or maintain cooling mode, fully open the heat source-side expansion mechanism 410, the liquid-side on / off valve 420, and the gas-side on / off valve 460, and partially open the utilization-side expansion mechanism 440 and the bypass expansion mechanism 470. For heating operation, the normal operation controller 630 is configured to control the mode switching mechanism 220 to switch to or maintain heating mode, fully open the gas-side on / off valve 460, the utilization-side expansion mechanism 440, and the liquid-side on / off valve 420, partially open the heat source-side expansion mechanism 410, and fully close the bypass expansion mechanism 470. The normal operation controller 630 is also configured to control the operation of the compressor 210, the heat source-side fan 231, and the utilization-side fan 241 for both cooling and heating operations. The normal operation controller 630 may include a wired / wireless communication interface for communicating with each of the mode switching mechanism 220 , the control valve, the compressor 210 , the heat source-side fan 231 , and the utilization-side fan 241 .

[0090] Regarding the control of compressor 210, the normal operation controller 630 is configured to control the compressor speed so that the evaporation temperature TeS approaches the target evaporation temperature TeS_tgt. Whether the heat pump system 100 is in cooling operation or refrigerant recovery operation, the target evaporation temperature TeS_tgt is used, but the value of the target evaporation temperature TeS_tgt varies, as explained later. The normal operation controller 630 is also configured to monitor whether the discharge pressure Pc remains below a predetermined threshold and, when the discharge pressure Pc exceeds the predetermined threshold, reduce the compressor speed (i.e., perform droop control).

[0091] The normal operation controller 630 may also be configured to control the heat pump system 100 during the refrigerant recovery operation under the control of the refrigerant recovery controller 650 .

[0092] The information output unit 640 is configured to output information to a user of the heat pump system 100 or an external device such as an information output device under the control of the refrigerant recovery controller 650. The information output unit 640 may include a display device, a light, a speaker, and a wired / wireless communication interface for transmitting information to an external device. Therefore, the information output unit 640 is configured to output information via images, light, sound, communication signals, and the like.

[0093] The refrigerant recovery controller 650 is configured to perform the refrigerant recovery operation, for example, by using the normal operation controller 630. The refrigerant recovery controller 650 has a leakage detection section 651, a temperature detection section 652, an acceleration rate switching section 653, and a timing control section 654.

[0094] The leakage detection unit 651 is configured to detect the occurrence of a refrigerant leak based on the refrigerant leakage information from the refrigerant leakage detector 530. For example, the leakage detection unit 651 is configured to determine that a refrigerant leak has occurred when the refrigerant concentration detected by the refrigerant leakage detector 530 is greater than a predetermined concentration value. However, this determination can be performed by the refrigerant leakage detector 530 or the information input unit 620. A moving average of the time series data of the detected concentration can be used for this determination. The leakage detection unit 651 can passively receive the refrigerant leakage information continuously or periodically transmitted by the refrigerant leakage detector 530, or actively obtain the refrigerant leakage information by periodically sending a request to the refrigerant leakage detector 630.

[0095] The temperature detection unit 652 is configured to obtain ambient temperature information from the ambient temperature detector 520. The temperature detection unit 652 may passively receive the ambient temperature information continuously or periodically transmitted by the ambient temperature detector 520, or actively obtain the ambient temperature information by sending a request to the ambient temperature detector 152 when the leakage detection unit 651 has determined that a refrigerant leak has occurred.

[0096] The acceleration rate switching unit 653 is configured to set the target increase rate value Rv_tgt based on whether the acquired ambient temperature Ta is higher than or equal to a predetermined ambient temperature value Ta_th. More specifically, when the ambient temperature Ta is higher than or equal to the predetermined ambient temperature value Ta_th, the acceleration rate switching unit 653 is configured to set the target increase rate value Rv_tgt so as to be lower than the target increase rate value Rv_tgtt when the ambient temperature Ta is lower than the predetermined ambient temperature value Ta_th.

[0097] Timing control unit 654 is configured to execute a refrigerant recovery operation and control the timing of events during the refrigerant recovery operation. Specifically, timing control unit 654 is configured to control compressor 210 to increase the compressor speed by a set target increase rate value Rv_tgt, control gas-side on-off valve 460 to close, and control compressor 210 to stop operating to recover refrigerant after gas-side on-off valve 460 begins closing. The functions of timing control unit 654 will be described in detail below in the description of operations controlled by controller 600.

[0098] <Operation controlled by controller>

[0099] The leakage detector 651 of the controller 600 repeatedly determines whether refrigerant leakage occurs during the non-operation period, cooling operation period, and heating operation period of the compressor 210. When refrigerant leakage is detected, the controller 600 starts a refrigerant recovery operation.

[0100] If refrigerant leakage is detected while compressor 210 is not operating and mode switching mechanism 220 is not in cooling mode, controller 600 controls mode switching mechanism 110 to switch to cooling mode and then initiates refrigerant recovery operation. If refrigerant leakage is detected during cooling operation, controller 600 controls compressor 210 to stop and then initiates refrigerant recovery operation. If refrigerant leakage is detected during heating operation, controller 600 controls mode switching mechanism 220 to switch to cooling mode, controls compressor 210 to stop, and then initiates refrigerant recovery operation. In any case, controller 600 is configured to control mode switching mechanism 220 to maintain cooling mode during refrigerant recovery operation.

[0101] When a refrigerant leak is detected, the refrigerant recovery controller 650 may output an alarm message via the information output unit 640 to notify the user of the refrigerant leak. Preferably, the refrigerant recovery controller 650 transmits a signal to the utilization unit 120, so that the alarm message is also output from a display device, a light, a speaker, etc. (not shown) of the utilization unit 120.

[0102] Figure 3 This is the first part of the flowchart showing the processing of the refrigerant recovery operation executed by the controller 600. Figure 4 This is the second part of the flowchart.

[0103] In step S1100, the timing control unit 654 of the controller 600 controls the heat source-side expansion mechanism 410 to fully open, and controls the bypass expansion mechanism 470 to fully open. At this point, the gas-side on / off valve 460 should already be open, while the compressor 210 is still stopped. This allows the refrigerant to flow smoothly through the heat source-side pipe segment 101 when the compressor 210 subsequently starts operating.

[0104] In step S1200 , the timing control unit 654 controls the liquid-side on-off valve 420 to close. This prevents the refrigerant from flowing into the usage-side pipe section 102 via the liquid refrigerant pipe 330 when the compressor 210 subsequently starts operating.

[0105] In step S1300, the timing control unit 654 sets the target evaporation temperature TeS_tgt, used to control the compressor speed, to a lower value than the value typically used in cooling operation. More specifically, the timing control unit 654 changes the target evaporation temperature TeS_tgt from a first target evaporation temperature TeS_1 to a second target evaporation temperature TeS_2. The first target evaporation temperature TeS_1 is a default value, while the second target evaporation temperature TeS_2 is a value lower than the first target evaporation temperature TeS1. For example, the first target evaporation temperature TeS_1 is -6 degrees Celsius, used in conventional cooling operation, and the second target evaporation temperature TeS_2 is -30 degrees Celsius. Therefore, even if the evaporation temperature TeS decreases, the compressor 210 can continue to operate during the refrigerant recovery operation. However, the measures for maintaining the operation of the compressor 210 are not limited to this.

[0106] In step S1400, the timing control unit 654 controls the utilization-side expansion mechanism 440 to open. Therefore, when the compressor 210 subsequently starts operating, the refrigerant can smoothly flow out of the utilization-side pipe section 102. Preferably, the utilization-side expansion mechanism 440 opens gradually.

[0107] In step S1500, the timing control unit 654 controls the compressor 210 to start operating. This allows the refrigerant in the utilization-side pipe segment 102 to be directed to the heat-source-side pipe segment 101 via the second gas refrigerant pipe 340. Preferably, the compressor 210 is started only after a first predetermined time T_1 has elapsed since the compressor 210 was stopped. For example, the first predetermined time T_1 is 1 minute. This ensures that the control valve is properly prepared before the compressor 210 starts operating.

[0108] Through steps S1100 to S1500, the compressor can begin operating with the liquid-side on-off valve closed and the heat-source-side expansion mechanism 410, bypass expansion mechanism 470, utilization-side expansion mechanism 440, and gas-side on-off valve 460 open. However, the measures for preparing the control valves for this state are not limited to steps S1100 to S1400.

[0109] In step S1600, the temperature detection unit 652 obtains the ambient temperature Ta, and the acceleration rate switching unit 653 determines whether the obtained ambient temperature Ta is lower than a predetermined ambient temperature value Ta_th. This determination can be made using a moving average of the time series data of the detected ambient temperature Ta. If the ambient temperature Ta is lower than the predetermined ambient temperature value Ta_th (S1600: Yes), the process proceeds to step S1700. If the ambient temperature Ta is higher than or equal to the predetermined ambient temperature value Ta_th (S1600: No), the process proceeds to step S1800. For example, the predetermined ambient temperature value Ta_th is 35 degrees Celsius.

[0110] In step S1700 , the acceleration rate switching unit 653 sets the first predetermined increase rate value Rv_1 as the target increase rate value Rv_tgt.

[0111] In step S1800, the acceleration rate switching unit 653 sets the second predetermined increase rate value Rv_2 as the target increase rate value Rv_tgt. Here, the second predetermined increase rate value Rv_2 is lower than the first predetermined increase rate value Rv_1.

[0112] In step S1900, the timing control unit 654 controls the compressor 210 so that the compressor speed begins to increase at a target increase rate value Rv_tgt having a set value. The timing control unit 654 can control the compressor 210 to start rotating at a predetermined frequency and then increase the compressor speed by increasing the frequency in predetermined steps at predetermined intervals. The predetermined step size can be determined for each interval based on the evaporation temperature TeS, etc. In this case, the target increase rate value Rv_tgt can serve as an upper limit for the step size of the increase in each interval. In other words, the timing control unit 654 can set an upper limit for the step size of the frequency to be increased in each interval in step S1800, while basically not setting an upper limit in step S1700.

[0113] Compressor 210 is controlled to gradually increase its frequency so that evaporation temperature TeS approaches the target evaporation temperature TeS_tgt described above. However, during the refrigerant recovery operation, since target evaporation temperature TeS_tgt has already been lowered in step S1300, evaporation temperature TeS does not reach the target evaporation temperature TeS_tgt. Therefore, compressor 210 continues to operate while increasing its rotational speed. When the process proceeds to step S1800, it takes longer for the compressor rotational speed to reach the same level than when the process proceeds to step S1700.

[0114] Through the above steps S1600 to S1900 , the compressor speed can be increased, and at the same time, the increase rate of the compressor speed can be slowed down when the ambient temperature Ta is relatively high.

[0115] In step S2000 , the timing control unit 654 determines whether a predetermined valve closing condition is satisfied. The predetermined valve closing condition indicates that the refrigerant has been sufficiently recovered from the utilization-side pipe segment 102 to the heat-source-side pipe segment 101 .

[0116] In this embodiment, the predetermined valve closing condition is that, before the gas-side switching valve 460 begins to close, the suction pressure Pe has remained below a first predetermined suction pressure value Pe_1 for a second predetermined time T_2. For this determination, the timing control unit 654 obtains the suction pressure Pe and determines whether the predetermined valve closing condition is met. The moving average of the time series data of the detected suction pressure Pe can be used for the above determination. For example, the first predetermined suction pressure value Pe_1 is 3.0 kPa, and the second predetermined time T_2 is 30 seconds. However, the duration of the second predetermined time T_2 can be excluded from the predetermined valve closing condition. If step S2100 mentioned later has been executed, the closing of the gas-side switching valve 460 should have already begun.

[0117] If the suction pressure Pe has been maintained below the first predetermined suction pressure value Pe_1 for the second predetermined time T_2 and the gas-side switching valve 460 has not yet begun to close (S2000: YES), the process proceeds to step S2100. If the suction pressure Pe is not lower than the first predetermined suction pressure value Pe_1, the suction pressure Pe is lower than the first predetermined suction pressure value Pe_1 but has not been maintained for the second predetermined time T_2, or the gas-side switching valve 460 has begun to close (S2000: NO), the process proceeds to step S2200.

[0118] In step S2100, the timing control unit 654 controls the gas-side on-off valve 460 to begin closing. Thus, the gas-side on-off valve 460 is closed to prevent refrigerant from flowing back from the heat-source-side pipe segment 101 to the utilization-side pipe segment 102 via the second gas refrigerant pipe 340 even if the compressor 210 subsequently stops operating. The gas-side on-off valve 460 preferably closes gradually. For example, the timing control unit 654 controls the gas-side on-off valve 460 to begin closing by sending a shutoff signal to the gas-side on-off valve 460. The shutoff signal can be a pulse signal whose pulse count is reduced to zero.

[0119] In step S2200, the timing control unit 654 determines whether a predetermined compressor stop condition is met. The predetermined compressor stop condition is a condition that prevents refrigerant from flowing back from the heat source-side pipe segment 101 to the utilization-side pipe segment 102 via the second gas refrigerant pipe 340 even if the compressor 210 is stopped, and / or a condition that requires the compressor 210 to stop for safety reasons. If the predetermined compressor stop condition is not met (S2200: No), the process returns to step S2000. If the predetermined compressor stop condition is met (S2200: Yes), the process proceeds to step S2300.

[0120] Figure 5 is a table showing examples of compressor stop conditions. For example, the compressor stop conditions include Figure 5 At least one of the first to seventh conditions shown.

[0121] The first condition is the condition that the rate of change of the discharge pressure Pc (hereinafter referred to as "discharge pressure change rate |Rpc|") is lower than a predetermined discharge pressure change rate value Rpc_th, and the rate of change of the suction pressure Pe (hereinafter referred to as "suction pressure change rate |Rpe|") is lower than a predetermined suction pressure change rate value Rpe_th. The predetermined suction pressure change rate value Rpe_th may be equal to or different from the predetermined discharge pressure change rate value Rpc_th. Here, the discharge pressure change rate |Rpc| may be the absolute value of the amount of change in the discharge pressure Pc per unit time, and the suction pressure change rate |Rpe| may be the absolute value of the amount of change in the suction pressure Pe per unit time. For example, the predetermined discharge pressure change rate value Rpc_th and the predetermined suction pressure change rate value Rpe_th are both 0.2 kgf / cm2 per second. 2 This condition can be determined using a moving average value of the time series data of the detected discharge pressure Pc and a moving average value of the time series data of the detected suction pressure Pe.

[0122] The second condition is that the suction pressure Pe is lower than a second predetermined suction pressure value Pe_2, which is lower than the first predetermined suction pressure value Pe_1 used in step S2000. For example, the second predetermined suction pressure value Pe_2 is 1.0 kPa. This condition can be determined using a moving average of the time series data of the detected suction pressure Pe.

[0123] The third condition is a condition that a third predetermined time T_3 has passed after the compressor 210 starts operating in step S1500. For example, the third predetermined time T_3 is 15 minutes.

[0124] The fourth condition is that a fourth predetermined time T_4 has elapsed after the gas-side switching valve 460 has been closed. For example, the fourth predetermined time T_4 is 2 minutes. However, the fourth predetermined time T_4 may be zero. The timing control unit 654 may detect the completion of the closure of the gas-side switching valve 460 using a sensor.

[0125] The fifth condition is that the current discharge temperature Tdi_n is lower than the previous discharge temperature Tdi_n-1, and the discharge superheat temperature HDSH of the compressor 210 is lower than a predetermined superheat temperature value HDSH_min. Here, the current discharge temperature Tdi_n is the newly acquired discharge temperature of the compressor 210. The previous discharge temperature Tdi_n-1 is the last discharge temperature of the compressor 210 detected before the current discharge temperature Tdi_n, or the discharge temperature detected at a predetermined time period before the current discharge temperature Tdi_n. The discharge superheat temperature HDSH is the superheat temperature of the refrigerant flowing in the discharge-side refrigerant pipe 310. For example, the predetermined superheat temperature value HDSH_min is 10 Kelvin, and the predetermined time period is 10 seconds. The discharge superheat temperature HDSH can be obtained by subtracting the saturation temperature corresponding to the detected discharge pressure Pc from the detected discharge temperature Tdi. In this case, a table indicating the known correlation between refrigerant pressure and refrigerant saturation temperature is stored in advance in the storage unit 610.

[0126] The sixth condition is that the exhaust temperature Tdi is higher than a predetermined exhaust temperature value Tdi_th. For example, the predetermined exhaust temperature value Tdi_th is 108 Kelvin. This condition can be determined using a moving average of the time series data of the detected exhaust temperature Tdi.

[0127] The seventh condition is that a fifth predetermined time T_5 has elapsed after the gas-side switching valve 460 begins closing in step S2100. Preferably, the fifth predetermined time T_5 is longer than the time period required for the gas-side switching valve 460 to close. The time period required for the gas-side switching valve 460 to close can be predetermined through experiments, etc.

[0128] The timing control unit 654 may use only one of the first to seventh conditions described above. Alternatively, the timing control unit 654 may use a combination of any two or more of the first to seventh conditions described above as an AND condition (logical AND) or an OR condition (logical OR). However, the predetermined compressor stop conditions are not limited to these. In any case, the timing control unit 654 is configured to obtain the information necessary to determine the predetermined compressor stop conditions.

[0129] exist Figure 4 In step S2300 , the timing control unit 654 controls the utilization-side expansion mechanism 440 to be closed.

[0130] In step S2400, the timing control unit 654 controls the compressor 210 to stop operating and controls the heat source-side expansion mechanism 410 and the bypass expansion mechanism 470 to close. For example, the timing control unit 654 controls the compressor 210 to stop operating by stopping power to the compressor 21. If the predetermined compressor stop conditions in step S2200 are met but the predetermined valve closing conditions in step S2000 are not met, the gas-side on-off valve 460 has not yet begun to close when the process proceeds to steps S2300 and S2400. In this case, the timing control unit 654 controls the gas-side on-off valve 460 to close in step S2400.

[0131] Through steps S2000 to S2400, the compressor 210 is stopped and the control valve is closed when the refrigerant recovery operation can or should be terminated. The refrigerant recovery operation is then terminated. When the refrigerant recovery operation has terminated, the refrigerant recovery controller 650 may output a termination message via the information output unit 640 to notify the user of the termination. Preferably, the refrigerant recovery controller 650 transmits a signal to the utilization-side unit 120, causing the termination message to be also outputted via a display device, light, speaker, etc. of the utilization-side unit 120.

[0132] After the refrigerant recovery operation is terminated, the user or maintenance personnel of the heat pump system 100 can repair the refrigerant leak point of the utilization-side unit 120. Since most of the refrigerant has been evacuated from the utilization-side piping section 102, the repair can be performed safely.

[0133] <Beneficial Effects>

[0134] As described above, the heat pump system 100 is configured to control the compressor 210 during the refrigerant recovery operation so that the rate of increase Rv_tgt of the compressor speed when the ambient temperature Ta is higher than or equal to the predetermined ambient temperature value Ta_th is lower than the rate of increase of the compressor speed when the ambient temperature Ta is lower than the predetermined ambient temperature value Ta_th. Therefore, while increasing the compressor speed, it is possible to prevent the discharge pressure Pc of the compressor 210 from becoming excessively high, thereby more reliably completing the refrigerant recovery operation.

[0135] <Modification>

[0136] The configuration and operation of the heat pump system 100 and / or the configuration and operation of the controller 600 are not limited to the configuration and operation described above, unless departing from the scope of the present invention as defined in the appended claims. For example, some elements of the heat pump system 100 and some operating steps performed by the controller 600 can be omitted.

[0137] For example, in the case of a refrigeration system, that is, when heating operation is not required, the mode switching mechanism 220 and the heat source side expansion mechanism 410 can be omitted. In the case where the required performance of the heat pump system 100 is not high, the refrigerant heat exchanger 260 can be omitted. In the case where no bypass pipe is connected to each of the liquid refrigerant pipe 330 and the suction side refrigerant pipe 350 in parallel with the utilization side heat exchanger 240, the storage tank 250 can be omitted. In the case where sufficient air is ensured to flow through the heat source side heat exchanger 230 and / or the utilization side heat exchanger 240, the heat source side fan 231 and / or the utilization side fan 241 can be omitted. In the case where the heat pump system 100a is formed as a single unit, the liquid side stop valve 430 and the gas side stop valve 450 can be omitted.

[0138] Controller 600 may only determine whether a refrigerant leak has occurred when predetermined conditions are met. For example, controller 600 may only repeat the determination while compressor 210 is not operating. If a user operation indicates the occurrence of a refrigerant leak, refrigerant leak detector 530 may be omitted. Furthermore, the refrigerant recovery operation may be triggered by other events, such as the input of a command requesting the start of the refrigerant recovery operation, regardless of whether a refrigerant leak has occurred. Steps related to omitted components in controller 600 may be omitted. One or more sensors not required for the controller 600 process may be omitted.

[0139] Figure 6 1 is a schematic configuration diagram of a heat pump system as a first modified example of the heat pump system 100 according to the present embodiment.

[0140] like Figure 6As shown, the heat pump system 100a includes a compressor 210, a heat source side heat exchanger 230, a utilization side heat exchanger 240, a storage tank 250 provided at a location between the bypass pipe 360 ​​and the compressor 210, a discharge side refrigerant pipe 310 connected to the heat source side heat exchanger 230, a liquid refrigerant pipe 330, a suction side refrigerant pipe 350 connected to the utilization side heat exchanger 240, a bypass pipe 360, a utilization side expansion mechanism 440, a gas side switching valve 460, a bypass expansion mechanism 470, an ambient temperature detector 520, and a controller 600a corresponding to the controller 600. The utilization side expansion mechanism 440 may be provided at a location between the heat source side heat exchanger 230 and the bypass pipe 360. In this configuration, the discharge side refrigerant pipe 310 corresponds to the high-pressure refrigerant pipe according to the present invention, and the suction side refrigerant pipe 350 corresponds to the low-pressure refrigerant pipe according to the present invention. Meanwhile, as described above, the heat pump system 100a does not necessarily include the use Figure 1 Other elements described in this embodiment. In addition, other elements can also be omitted.

[0141] Figure 7 1 is a schematic configuration diagram of a heat pump system as a second modified example of the heat pump system 100 according to the present embodiment.

[0142] like Figure 7 As shown, compared to the first modification, heat pump system 100b does not include bypass pipe 360, bypass expansion mechanism 470, and accumulator 250. Even with these components omitted, refrigerant can be directed from utilization-side pipe segment 102 to heat source-side pipe segment 101, and the drawn refrigerant can be primarily accumulated in heat source-side heat exchanger 230. The controller 600b of heat pump system 100b, which corresponds to controller 600, needs to execute fewer steps.

[0143] Other variations of this embodiment are also possible. For example, the controller 600 may set three or more different predetermined rate of increase values ​​Rv_1, Rv_2, Rv_3, etc., corresponding to different predetermined ambient temperature values ​​Ta_th1, Ta_th2, etc. The ambient temperature detector 520 may obtain the outdoor air temperature from an external device such as a weather information server via wired or wireless communication. In this case, the ambient temperature detector 520 does not need to be arranged near the heat source side heat exchanger 230.

[0144] The refrigerant leak detector 530 can be configured to detect the occurrence of a refrigerant leak in any portion of the utilization-side piping segment 102. The controller 600 can be located outside the heat source-side piping segment 101. The controller 600 can also be located remotely from other portions of the heat pump system 100. The fluid passing through the heat source-side heat exchanger 230 and the fluid passing through the utilization-side heat exchanger 240 can be a fluid other than air, such as water. Refrigerants other than R32 can also be used.

[0145] Multiple utilization-side units 120 may be connected to the heat source-side unit 110. In this case, a liquid-side on-off valve 420 may be provided for each sub-liquid refrigerant pipe branching from the liquid refrigerant 330 to the utilization-side unit 120, and a gas-side on-off valve 460 may be provided for each sub-gas refrigerant pipe branching from the second gas refrigerant pipe 340 to the utilization-side unit 120. Preferably, the liquid-side on-off valve 420 and the gas-side on-off valve 460 are provided within or near the heat source-side unit 110. When refrigerant leakage is detected in any utilization-side unit 120 or any corresponding utilization-side pipe segment 102, a refrigerant recovery operation is performed. Preferably, during the refrigerant recovery operation, only the gas-side on-off valve 460 corresponding to the utilization-side unit 120 experiencing the refrigerant leakage is opened, of the liquid-side on-off valve 420 and the gas-side on-off valve 460.

[0146] Although only selected embodiments and variations have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from the present invention that various changes and modifications may be made within the scope of the present invention as defined in the appended claims. For example, unless otherwise specifically stated, the size, shape, position or orientation of the various components may be changed as needed and / or desired, as long as these changes do not substantially affect their intended function. Unless otherwise specifically stated, components shown as being directly connected or in contact with each other may have an intermediate structure disposed therebetween, as long as these changes do not substantially affect their intended function. Unless otherwise specifically stated, the function of one element may be performed by two elements, and vice versa. The structure and function of one embodiment may be adopted in another embodiment. All advantages do not need to appear simultaneously in a particular embodiment. Thus, the foregoing description of the embodiments of the present invention provided is for illustration only.

[0147] [Reference Signs List]

[0148] 100,100a,100b:Heat pump system

[0149] 101: Heat source side pipeline section

[0150] 102: Utilize the side pipe section

[0151] 110: Heat source side unit

[0152] 120: Using the side unit

[0153] 210: Compressor

[0154] 220: Mode switching mechanism

[0155] 230: Heat source side heat exchanger

[0156] 231: Heat source side fan

[0157] 240: Utilization side heat exchanger

[0158] 241: Using side fans

[0159] 250: Storage tank

[0160] 260: Refrigerant heat exchanger

[0161] 310: Discharge side refrigerant pipeline (high-pressure refrigerant pipeline)

[0162] 320: First gas refrigerant pipeline (high-pressure refrigerant pipeline, low-pressure refrigerant pipeline)

[0163] 330:Liquid refrigerant pipeline

[0164] 340: Second gas refrigerant pipeline (low-pressure refrigerant pipeline, high-pressure refrigerant pipeline)

[0165] 350: Suction side refrigerant pipeline (low-pressure refrigerant pipeline)

[0166] 360:Bypass pipe

[0167] 410: Heat source side expansion mechanism (expansion mechanism)

[0168] 420: Liquid side switch valve

[0169] 430: Liquid side stop valve

[0170] 440: Utilization side expansion mechanism (expansion mechanism)

[0171] 450: Gas side stop valve

[0172] 460: Gas side switch valve

[0173] 470:Bypass expansion mechanism

[0174] 510: Discharge side refrigerant status detector

[0175] 520: Ambient temperature detector

[0176] 530: Refrigerant leak detector

[0177] 540: Suction side refrigerant status detector (evaporating temperature detector, suction pressure detector)

[0178] 600, 600a, 600b: controller

[0179] 610: Storage

[0180] 620: Information input unit

[0181] 630: Normal operation controller

[0182] 640: Information output unit

[0183] 650: Refrigerant recovery controller

[0184] 651: Leak detection unit

[0185] 652: Temperature detection unit

[0186] 653: Acceleration rate switching unit

[0187] 654: Timing control unit.

Claims

1. A heat pump system comprising: compressor; a heat source side heat exchanger configured to perform heat exchange between a refrigerant flowing through the heat source side heat exchanger and a fluid passing through the heat source side heat exchanger; a utilization-side heat exchanger configured to perform heat exchange between a refrigerant flowing through the utilization-side heat exchanger and a fluid passing through the utilization-side heat exchanger; a high-pressure refrigerant pipe connected to each of a discharge port of the compressor and the heat source-side heat exchanger; a liquid refrigerant pipe connected to each of the heat source side heat exchanger and the utilization side heat exchanger; a low-pressure refrigerant pipe connected to each of the utilization-side heat exchanger and a suction port of the compressor; a liquid-side on-off valve, the liquid-side on-off valve being disposed in the liquid refrigerant pipeline; an expansion mechanism, the expansion mechanism being disposed in the liquid refrigerant pipeline; a gas-side switching valve, the gas-side switching valve being arranged in the low-pressure refrigerant pipeline; an ambient temperature detector configured to detect a temperature of the fluid passing through the heat source-side heat exchanger as an ambient temperature; as well as a controller configured to control the heat pump system to perform a refrigerant recovery operation by operating the compressor when the liquid-side on-off valve is closed and the gas-side on-off valve is open, so as to recover the refrigerant from the utilization-side pipe section to the heat source-side pipe section; The utilization side pipeline section extends between the liquid side switch valve and the gas side switch valve and includes at least the utilization side heat exchanger. The heat source side pipeline section extends between the gas side switch valve and the liquid side switch valve and includes at least the compressor. in, The controller is configured to control the compressor in the refrigerant recovery operation so that an increase rate of the compressor speed when the ambient temperature is higher than or equal to a predetermined ambient temperature value is lower than an increase rate of the compressor speed when the ambient temperature is lower than the predetermined ambient temperature value.

2. The heat pump system according to claim 1, characterized in that further comprising a refrigerant leakage detector configured to detect occurrence of refrigerant leakage in the utilization-side pipe section, in, The controller is configured to control the heat pump system to perform the refrigerant recovery operation when the occurrence of the refrigerant leakage has been detected.

3. The heat pump system according to claim 1 or 2, characterized in that: The heat source side heat exchanger is configured to allow outdoor air to pass therethrough.

4. The heat pump system according to any one of claims 1 to 3, characterized in that: Also includes: a bypass pipe connected to a point in the liquid refrigerant pipe between the heat source side heat exchanger and the liquid side switching valve, and to a point in the low-pressure refrigerant pipe between the gas side switching valve and the compressor; a bypass expansion mechanism, the bypass expansion mechanism being arranged in the bypass pipe; as well as a storage tank, the storage tank being inserted in the low-pressure refrigerant pipeline at a position between the bypass pipeline and the compressor, in, The controller is configured to control the bypass expansion mechanism to open during the refrigerant recovery operation.

5. The heat pump system according to claim 4, characterized in that Also included is a refrigerant heat exchanger configured to exchange heat between the refrigerant flowing in the liquid refrigerant pipe and the refrigerant flowing in the bypass pipe; in, The bypass expansion mechanism is provided at a point in the bypass pipe between the liquid refrigerant pipe and the refrigerant heat exchanger.

6. The heat pump system according to any one of claims 1 to 5, characterized in that: Also includes: a discharge-side refrigerant pipe connected to the discharge port of the compressor; a suction-side refrigerant pipe connected to the suction port of the compressor; a first gas refrigerant pipe connected to the heat source side heat exchanger; a second gas refrigerant pipe connected to the utilization-side heat exchanger; as well as a mode switching mechanism configured to switch between a cooling mode connection and a heating mode connection, The discharge-side refrigerant pipe and the first gas refrigerant pipe are connected to each other to form the high-pressure refrigerant pipe by the cooling mode connection, and the suction-side refrigerant pipe and the second gas refrigerant pipe are connected to each other to form the low-pressure refrigerant pipe by the cooling mode connection, and By the heating mode connection, the discharge-side refrigerant pipe and the second gas refrigerant pipe are connected to each other to form the high-pressure refrigerant pipe, and by the heating mode connection, the suction-side refrigerant pipe and the first gas refrigerant pipe are connected to each other to form the low-pressure refrigerant pipe, in, The controller is configured to operate with the cooling mode connection when performing the refrigerant recovery operation.

7. The heat pump system according to any one of claims 1 to 6, characterized in that: further comprising an evaporation temperature detector configured to detect an evaporation temperature of the refrigerant flowing in the low-pressure refrigerant pipe, in: The compressor is configured to control the compressor speed so that the evaporation temperature approaches a target evaporation temperature value; and The controller is configured to, when starting the refrigerant recovery operation, lower the target evaporation temperature value compared to the target evaporation temperature value used in a normal cooling operation.

8. The heat pump system according to any one of claims 2 to 7, comprising the refrigerant leak detector, wherein: When the occurrence of the refrigerant leakage is detected during non-operation of the compressor, the controller is configured to control the heat pump system in the refrigerant recovery operation so that the liquid-side on-off valve is closed, and to start operation of the compressor after the liquid-side on-off valve has been closed.

9. The heat pump system according to any one of claims 2 to 8, comprising the refrigerant leak detector, wherein: When the occurrence of the refrigerant leakage is detected while the compressor is operating, the controller is configured to control the heat pump system in the refrigerant recovery operation so that the operation of the compressor stops, and then the operation of the compressor starts to recover the refrigerant when a first predetermined time has passed after the operation of the compressor stops, and the liquid-side switching valve is closed during the period when the operation of the compressor is stopped.

10. The heat pump system according to claim 8 or 9, comprising a bypass expansion mechanism, wherein: The controller is configured to control the bypass expansion mechanism to open during a period when the operation of the compressor is stopped in the refrigerant recovery operation, and, if the expansion mechanism includes a heat source side expansion mechanism provided at a point between the heat source side heat exchanger and the bypass pipe, control the heat source side expansion mechanism to open.

11. The heat pump system according to any one of claims 1 to 10, characterized in that: further comprising a suction pressure detector configured to detect the pressure of the refrigerant flowing in the low-pressure refrigerant pipe, in, The controller is configured to control the heat pump system in the refrigerant recovery operation so that the gas-side on-off valve starts closing when a predetermined valve closing condition is satisfied while the compressor is operating to recover refrigerant. The predetermined valve closing condition includes, during the period when the compressor is operating to recover refrigerant, the pressure of the refrigerant flowing in the low-pressure refrigerant pipe remains lower than a first predetermined suction pressure value for a second predetermined time.

12. The heat pump system according to any one of claims 1 to 11, characterized in that: The controller is configured to control the compressor during the refrigerant recovery operation so that the operation of the compressor stops when a predetermined compressor stop condition is satisfied. The predetermined compressor stop condition includes at least one of the following: a first condition, namely, a rate of change of the pressure of the refrigerant flowing in the high-pressure refrigerant pipe is lower than a predetermined discharge pressure change rate value, and a rate of change of the pressure of the refrigerant flowing in the low-pressure refrigerant pipe is lower than a predetermined suction pressure change rate value, the predetermined suction pressure change rate value being equal to or different from the predetermined discharge pressure change rate value; a second condition, namely, the pressure of the refrigerant flowing in the low-pressure refrigerant pipe is lower than a second predetermined suction pressure value, the second predetermined suction pressure value being lower than the first predetermined suction pressure value; a third condition that a third predetermined time has elapsed after the compressor starts operating to recover refrigerant; a fourth condition that a fourth predetermined time has elapsed after the closing of the gas-side on-off valve has been completed; a fifth condition that the current discharge temperature of the compressor is lower than the previous discharge temperature of the compressor, and the discharge superheat temperature of the compressor is lower than a predetermined superheat temperature value; The sixth condition is that the discharge temperature of the compressor is higher than a predetermined discharge temperature value; as well as The seventh condition is that a fifth predetermined time has elapsed after the closing of the gas-side switching valve is started.

13. A controller for controlling the operation of a heat pump system. The heat pump system comprises: compressor; a heat source side heat exchanger configured to perform heat exchange between a refrigerant flowing through the heat source side heat exchanger and a fluid passing through the heat source side heat exchanger; a utilization-side heat exchanger configured to perform heat exchange between a refrigerant flowing through the utilization-side heat exchanger and a fluid passing through the utilization-side heat exchanger; a high-pressure refrigerant pipe connected to each of a discharge port of the compressor and the heat source-side heat exchanger; a liquid refrigerant pipe connected to each of the heat source side heat exchanger and the utilization side heat exchanger; a low-pressure refrigerant pipe connected to each of the utilization-side heat exchanger and a suction port of the compressor; a liquid-side on-off valve, the liquid-side on-off valve being disposed in the liquid refrigerant pipeline; an expansion mechanism, the expansion mechanism being disposed in the liquid refrigerant pipeline; a gas-side switching valve, the gas-side switching valve being arranged in the low-pressure refrigerant pipeline; a bypass pipe connected to a point in the liquid refrigerant pipe between the heat source side heat exchanger and the liquid side switching valve, and to a point in the low-pressure refrigerant pipe between the gas side switching valve and the compressor; a bypass expansion mechanism, the bypass expansion mechanism being arranged in the bypass pipe; as well as an ambient temperature detector configured to detect a temperature of the fluid passing through the heat source side heat exchanger as an ambient temperature, The controller is configured to control the heat pump system to perform a refrigerant recovery operation by operating the compressor when the liquid-side on-off valve is closed and the gas-side on-off valve is open, so as to recover the refrigerant from the utilization-side pipe section to the heat source-side pipe section. The utilization side pipeline section extends between the liquid side switch valve and the gas side switch valve and includes at least the utilization side heat exchanger. The heat source side pipeline section extends between the gas side switch valve and the liquid side switch valve and includes at least the compressor. in, The controller is configured to control the compressor in the refrigerant recovery operation so that an increase rate of the compressor speed when the ambient temperature is higher than or equal to a predetermined ambient temperature value is lower than an increase rate of the compressor speed when the ambient temperature is lower than the predetermined ambient temperature value.

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