Heat pump system and method for controlling the same

Abstract

A heat pump system (100) is provided, the heat pump system comprising: a first bypass pipe (331) provided with a first bypass valve (341) and connecting a liquid refrigerant pipe (322) with a low-pressure refrigerant pipe (324); a refrigerant heat exchanger (314) configured to perform heat exchange between the refrigerant flowing in the liquid refrigerant pipe and the refrigerant flowing in the first bypass pipe; a second bypass pipe (332) provided with a second bypass valve (342) and connecting the liquid refrigerant pipe with the low-pressure refrigerant pipe; and a controller (400). The controller is configured to control the opening of the first bypass valve based on the detected superheat temperature of the refrigerant flowing in the first bypass pipe and the detected discharge temperature of the compressor (311), and to control the opening of the second bypass valve based on the detected discharge temperature.

Description

Technical Field

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

[0002] WO2018 / 062177A1 proposes a heat pump system with a subcooling system and an injection system. The subcooling system includes a first bypass pipe, a refrigerant heat exchanger and a first bypass valve. The injection system includes a second bypass pipe and a second bypass valve.

[0003] The first bypass pipe of the above-mentioned supercooling system connects the liquid refrigerant pipe of the heat pump system with the low-pressure refrigerant pipe. The above-mentioned refrigerant heat exchanger is configured to perform heat exchange between the refrigerant flowing in the liquid refrigerant pipe and the refrigerant flowing in the first bypass pipe. The refrigerant flowing in the first bypass pipe is decompressed and expanded by a first bypass valve arranged in the first bypass pipe, so that the refrigerant becomes colder than the refrigerant flowing in the liquid refrigerant pipe. Therefore, the refrigerant flowing in the liquid refrigerant pipe is cooled when flowing through the heat exchanger. The opening of the first bypass valve is controlled so that the temperature of the refrigerant flowing in the liquid refrigerant pipe is cooled to a predetermined target temperature. Therefore, the cooling efficiency in the heat exchanger arranged on the downstream side of the liquid refrigerant pipe can be improved.

[0004] The second bypass pipe of the injection system also connects the liquid refrigerant pipe with the low-pressure refrigerant pipe. The refrigerant in the second bypass pipe flows to the low-pressure refrigerant pipe without passing through the heat exchanger, and merges with the refrigerant flowing through the heat exchanger. In addition, the refrigerant flowing in the second bypass pipe is decompressed and expanded by a second bypass valve arranged in the second bypass pipe, so that the refrigerant becomes colder than the refrigerant flowing in the low-pressure refrigerant pipe. Therefore, the refrigerant sucked in by the refrigerant compressor is cooled, and the temperature of the refrigerant discharged from the refrigerant compressor (hereinafter referred to as the "discharge temperature") is thereby reduced. The opening of the second bypass valve is controlled so that the discharge temperature is cooled to another predetermined target temperature. Therefore, the reliability and safety of the heat pump system can be improved.

[0005] However, there is a situation where the above-mentioned injection system cannot sufficiently reduce the discharge temperature due to its insufficient flow capacity of the refrigerant. At the same time, the increase in the thickness and / or number of the second bypass pipe will lead to an increase in the production cost and / or size of the heat pump system. In addition, if the amount of refrigerant bypassing the second bypass pipe is simply increased in order to further reduce the discharge temperature, the amount of refrigerant delivered to the heat exchanger will be reduced. As a result, the performance of the heat pump system will become quite poor.

[0006] Reference List

[0007] Patent Literature

[0008] Patent Document 1: WO2018 / 062177A1 Summary of the invention

[0009] The object of the present invention is to improve the efficiency, reliability and safety of a heat pump system while preventing an increase in the production cost and / or size of the system as much as possible.

[0010] A first aspect of the present invention provides a heat pump system, comprising: a refrigerant compressor; a high-pressure refrigerant pipe, the high-pressure refrigerant pipe being connected to a discharge port of the refrigerant compressor; a low-pressure refrigerant pipe, the low-pressure refrigerant pipe being connected to a suction port of the refrigerant compressor; a heat source side heat exchanger, the heat source side heat exchanger being connected to any one of the high-pressure refrigerant pipe and the low-pressure refrigerant pipe and being configured to perform heat exchange between the refrigerant flowing in the heat source side heat exchanger and a fluid passing through the heat source side heat exchanger; and a liquid refrigerant pipe, the liquid refrigerant pipe being connected to the heat source side heat exchanger , and is configured to be connected to a utilization-side heat exchanger, the 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 gas refrigerant pipe, the gas refrigerant pipe being connected to the other of the high-pressure refrigerant pipe and the low-pressure refrigerant pipe, and being configured to be connected to the utilization-side heat exchanger; a main expansion mechanism, the main expansion mechanism being arranged in the liquid refrigerant pipe; a first bypass pipe, the first bypass pipe being connected to the liquid refrigerant pipe at a position point between the main expansion mechanism and the utilization-side heat exchanger, and being connected to the low-pressure refrigerant pipe; a refrigerant heat exchanger configured to exchange heat between the refrigerant flowing in the liquid refrigerant pipe and the refrigerant flowing in the first bypass pipe; a first bypass valve, the first bypass valve being arranged in the first bypass pipe at a position between the liquid refrigerant pipe and the refrigerant heat exchanger; a second bypass pipe, the second bypass pipe being connected to the liquid refrigerant pipe at a position between the main expansion mechanism and the utilization side heat exchanger, and being connected to the low-pressure refrigerant pipe; a second bypass valve, the second bypass valve being arranged in the second bypass pipe ; an overheat temperature detector configured to detect a parameter representing the overheat temperature of the refrigerant flowing in the first bypass pipe; a discharge side sensor configured to detect the temperature of the refrigerant flowing in the high-pressure refrigerant pipe between the refrigerant compressor and any one of the heat source side heat exchanger and the utilization side heat exchanger as a discharge temperature; and a controller configured to control the opening of the first bypass valve based on the overheat temperature and the discharge temperature represented by the detected parameters, and to control the opening of the second bypass valve based on the discharge temperature.

[0011] By this configuration, the opening of the first bypass valve is controlled not only based on the superheat temperature but also based on the discharge temperature. Therefore, in addition to the second bypass pipe, the first bypass pipe originally provided for the subcooling system can also be used to support the injection system to reduce the discharge temperature. Therefore, the flow capacity of the refrigerant bypassing the utilization side heat exchanger can be increased so as to reduce the discharge temperature without increasing the thickness and / or number of the second bypass pipe. Therefore, the increase in the production cost and / or size of the system can be prevented as much as possible while improving the efficiency, reliability and safety of the heat pump system.

[0012] According to a preferred embodiment of the heat pump system as described above, the first bypass pipe is connected to the low-pressure refrigerant pipe, and the overheat temperature detector includes a bypass sensor and a suction side sensor, the bypass sensor is configured to detect the temperature of the refrigerant flowing in the first bypass pipe at the downstream side of the refrigerant heat exchanger, and the suction side sensor is configured to detect the pressure of the refrigerant flowing in the low-pressure refrigerant pipe.

[0013] By this configuration, the refrigerant flowing in the first bypass pipe can be guided to the low-pressure refrigerant pipe. Therefore, even in the case where the refrigerant compressor does not have an injection port, the discharge temperature can be reduced by using the first bypass pipe. In addition, the superheat temperature can be detected by using a temperature sensor and a pressure sensor that are easily and reasonably available. Therefore, the efficiency of the heat pump system can be improved while avoiding increasing the production cost of the system.

[0014] According to another preferred embodiment of any one of the heat pump systems as described above, the first bypass pipe is connected to the injection port of the compressor, and the overheat temperature detector includes: a first bypass sensor, which is configured to detect the temperature of the refrigerant flowing in the first bypass pipe at the downstream side of the refrigerant heat exchanger; and a second bypass sensor, which is configured to detect the temperature of the refrigerant flowing in the first bypass pipe between the first bypass valve and the refrigerant heat exchanger, or, the overheat temperature detector includes: a first bypass sensor, which is configured to detect the temperature of the refrigerant flowing in the first bypass pipe at the downstream side of the refrigerant heat exchanger; and a second bypass sensor, which is configured to detect the pressure of the refrigerant flowing in the first bypass pipe at the downstream side of the first bypass valve.

[0015] By this configuration, the refrigerant flowing in the first bypass pipe can be guided to the injection port of the refrigerant compressor. Therefore, the efficiency of the refrigerant compressor can be improved while the discharge temperature is reduced by using the first bypass pipe. In addition, the superheat temperature can be detected by using a temperature sensor and a pressure sensor or other temperature sensors that are easily and reasonably available. Therefore, the production cost of the system can be avoided from being increased while the efficiency of the heat pump system is improved. When two temperature sensors are used and one of the sensors is arranged between the first bypass valve and the refrigerant heat exchanger, the superheat temperature can be more easily obtained.

[0016] According to another preferred embodiment of any heat pump system in which the first bypass pipe is connected to the low-pressure refrigerant pipe as described above, the above-mentioned heat pump system also includes a storage tank arranged in the low-pressure refrigerant pipe, wherein the first bypass pipe is connected to the low-pressure refrigerant pipe at a position point between the storage tank and any one of the heat source side heat exchanger and the utilization side heat exchanger, any one of which is connected to the low-pressure refrigerant pipe, and the second bypass pipe is connected to the low-pressure refrigerant pipe at a position point between the storage tank and the refrigerant compressor.

[0017] With this configuration, the accumulator receives the refrigerant that has flowed through the first bypass pipe, while the accumulator does not receive the refrigerant that has flowed through the second bypass pipe. Due to heat exchange in the refrigerant heat exchanger, the refrigerant flowing through the first bypass pipe tends to contain less liquid refrigerant, while the refrigerant flowing through the second bypass pipe tends to contain more liquid refrigerant. Therefore, the refrigerant in the liquid phase or gas-liquid two-phase form can be delivered to the low-pressure refrigerant pipe so that the so-called liquid injection can be effectively performed.

[0018] According to another preferred embodiment of any heat pump system in which the first bypass pipe is connected to the injection port of the compressor as described above, the above-mentioned heat pump system also includes a storage tank arranged in the low-pressure refrigerant pipe, wherein the second bypass pipe is connected to the low-pressure refrigerant pipe at a position point between the storage tank and the refrigerant compressor.

[0019] With this configuration, the receiver does not receive the refrigerant that has flowed through the second bypass pipe. The refrigerant that has flowed through the second bypass pipe tends to contain more liquid refrigerant. Therefore, the refrigerant in the liquid phase or gas-liquid two-phase form can be delivered to the low-pressure refrigerant pipe so as to effectively perform the so-called liquid injection.

[0020] According to another preferred embodiment of any of the heat pump systems described above, the controller is configured to increase the opening of the first bypass valve at least when the opening of the second bypass valve has reached a first opening threshold.

[0021] With this configuration, an increase in the opening of the second bypass valve triggers an increase in the opening of the first bypass valve. Therefore, the opening of the first bypass valve can be quickly increased before the exhaust temperature rises excessively. Therefore, the exhaust temperature can be quickly reduced and effectively prevented from becoming too high. In addition, there may be a situation where the second bypass valve is still capable of reducing the exhaust temperature despite the high exhaust temperature. Therefore, the opening of the first bypass valve can be prevented from being unnecessarily increased.

[0022] According to another preferred embodiment of any one of the heat pump systems described above, the controller is configured to increase the opening degree of the first bypass valve at least when the discharge temperature has reached a discharge temperature threshold.

[0023] With this configuration, an increase in the exhaust temperature triggers an increase in the opening of the first bypass valve. When the exhaust temperature is high, the second bypass valve may have been opened to a greater extent. Therefore, by the above triggering, the exhaust temperature can be more reliably reduced. In addition, there may be a situation where the exhaust temperature is not high when the second bypass valve is opened to a greater extent. Therefore, it is possible to prevent the opening of the first bypass valve from being increased unnecessarily.

[0024] According to another preferred embodiment of any one of the heat pump systems as described above, the controller is configured to control the opening of the first bypass valve so that when the discharge temperature is lower than or equal to the first target discharge temperature, the superheat temperature is close to the target superheat temperature, and when the discharge temperature is higher than the first target discharge temperature, the discharge temperature is close to the first target discharge temperature.

[0025] With this construction, the first bypass pipe is used to adjust the superheat temperature when the discharge temperature remains low, and is used to adjust the discharge temperature when the discharge temperature rises to the first target discharge temperature. Therefore, while the first bypass pipe is used to prevent the discharge temperature from being too high, the function of the first bypass pipe as a supercooling system can be maximized to improve the efficiency of the heat pump system. In addition, the first bypass valve can be opened when the second bypass valve is still capable of lowering the discharge temperature. The overall effect of the second bypass valve in lowering the discharge temperature is greater than that of the first bypass valve. Therefore, the discharge temperature can be quickly lowered. In addition, there may be a situation where the discharge temperature is not high when the second bypass valve is opened to a large extent. Therefore, the opening of the first bypass valve can be prevented from being increased unnecessarily.

[0026] According to another preferred embodiment of the heat pump system as described above, the controller is configured to control the opening of the first bypass valve so that when the discharge temperature is higher than the first target discharge temperature, the discharge temperature is close to the first target discharge temperature, and the above-mentioned controller is configured to reduce the value of the first target discharge temperature when the opening of the second bypass valve has reached the first opening threshold.

[0027] With this configuration, the more the second bypass valve is opened, the more likely it is that the opening degree of the first bypass valve will be controlled based on the exhaust temperature. Therefore, the exhaust temperature can be lowered more reliably.

[0028] According to another preferred embodiment of the heat pump system as described above, the controller is configured to reduce the value of the first target discharge temperature when the opening of the second bypass valve reaches a first opening threshold, and the controller is configured to increase the value of the first target discharge temperature when the opening of the second bypass valve decreases to a second opening threshold that is lower than or equal to the first opening threshold.

[0029] With this configuration, when the first bypass pipe is no longer needed to adjust the discharge temperature, the first bypass pipe resumes the function of adjusting the superheat temperature. Therefore, the first bypass pipe can play the role of the supercooling system as much as possible to improve the efficiency of the heat pump system.

[0030] According to another preferred embodiment of any one of the heat pump systems as described above, the controller is configured to control the opening of the first bypass valve so that when the opening of the second bypass valve is lower than a first opening threshold, the superheat temperature approaches the target superheat temperature, and when the opening of the second bypass valve is higher than the first opening threshold, the discharge temperature approaches the first target discharge temperature.

[0031] By the above-mentioned construction, the first bypass pipe is used to adjust the superheat temperature when the opening of the second bypass valve remains low, and is used to adjust the discharge temperature when the opening of the second bypass valve has increased. Therefore, while the first bypass pipe is used to prevent the discharge temperature from being too high, the function of the first bypass pipe as a supercooling system can be exerted as much as possible to improve the efficiency of the heat pump system. In addition, after the greater potential of the second bypass valve has been used to reduce the discharge temperature, the opening of the first bypass valve is opened. It is possible that the second bypass valve is still capable of reducing the discharge temperature despite the high discharge temperature. Therefore, the opening of the first bypass valve can be prevented from being increased unnecessarily. In addition, the opening of the first bypass valve can be quickly increased before the discharge temperature rises excessively. Therefore, the discharge temperature can be quickly reduced and the discharge temperature can be effectively prevented from becoming too high.

[0032] According to another preferred embodiment of any heat pump system using the first target discharge temperature as described above, the controller is configured to switch from a first control in which the opening of the first bypass valve is controlled so that the discharge temperature approaches the first target discharge temperature to a second control in which the opening of the first bypass valve is controlled so that the superheat temperature approaches the target superheat temperature when the discharge temperature has dropped to a second target discharge temperature that is lower than or equal to the first target discharge temperature, and / or the opening of the second bypass valve has dropped to a second opening threshold that is lower than or equal to the first opening threshold.

[0033] With this configuration, when the first bypass pipe is no longer needed to adjust the discharge temperature, the first bypass pipe resumes the function of adjusting the superheat temperature. Therefore, the first bypass pipe can play the role of the supercooling system as much as possible to improve the efficiency of the heat pump system.

[0034] According to another preferred embodiment of any one of the heat pump systems described above, the heat pump system is configured to use R32 refrigerant.

[0035] R32 refrigerant is also called HFC-32 refrigerant or difluoromethane refrigerant, and its chemical formula is CH 2 F 2 , having the characteristics of zero ozone depletion potential and low global warming potential. Meanwhile, when using R32 refrigerant, the discharge temperature tends to become higher. In this regard, the heat pump system according to any one of the heat pump systems described above can reduce the discharge temperature. Therefore, it is possible to ensure high reliability and safety while realizing an environmentally friendly heat pump system.

[0036] According to another preferred embodiment of any one of the heat pump systems described above, the heat pump system further includes: a mode switching mechanism, the mode switching mechanism being configured to switch the state of the heat pump system between a cooling operation mode and a heating operation mode, in which, in the cooling operation mode, the heat source side heat exchanger is connected to the high-pressure refrigerant pipe, and the gas refrigerant pipe is connected to the low-pressure refrigerant pipe, and in the heating operation mode, the heat source side heat exchanger is connected to the low-pressure refrigerant pipe, and the gas refrigerant pipe is connected to the high-pressure refrigerant pipe; and a connection switching mechanism, the connection switching mechanism being configured to switch between a first connection mode and a second connection mode. The state of the second bypass pipe is switched between connection modes, in the above-mentioned first connection mode, the second bypass pipe is connected to the liquid refrigerant pipe at a position point between the refrigerant heat exchanger and the utilization side heat exchanger, and in the above-mentioned second connection mode, the second bypass pipe is connected to the liquid refrigerant pipe at a position point between the main expansion mechanism and the refrigerant heat exchanger, wherein the controller is also configured to control the connection switching mechanism so that when the heat pump system is in the cooling operation mode, the second bypass pipe is in the first connection mode, and when the heat pump system is in the heating operation mode, the second bypass pipe is in the second connection mode.

[0037] With this configuration, the operation mode of the heat pump system can be switched between a cooling operation mode in which the utilization side heat exchanger is used as an evaporator and a heating operation mode in which the utilization side heat exchanger is used as a condenser. In addition, regardless of the operation mode, the second bypass pipe can always be connected to the downstream side of the refrigerant heat exchanger for bypassing the refrigerant with a lower temperature. Therefore, the discharge temperature can be more effectively reduced during both the cooling operation mode and the heating operation mode.

[0038] A second aspect of the present invention provides a method for controlling a heat pump system according to any one of the heat pump systems described above, comprising: controlling the opening of a first bypass valve so that when the discharge temperature is lower than or equal to a first target discharge temperature, the superheat temperature is close to a target superheat temperature, and when the discharge temperature is higher than the first target discharge temperature, the discharge temperature is close to the first target discharge temperature; and when the opening of the second bypass valve has reached a first opening threshold, reducing the value of the first target discharge temperature.

[0039] By the above method, the first bypass pipe plays a role in adjusting the superheat temperature when the discharge temperature is kept low, and plays a role in adjusting the discharge temperature when the discharge temperature increases. Therefore, the efficiency of the heat pump system can be improved as much as possible while preventing the discharge temperature from becoming too high. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a schematic configuration diagram of a heat pump system according to a first embodiment of the present invention;

[0041] Figure 2 Yes means Figure 1 A block diagram of the functional composition of the controller shown;

[0042] Figure 3 is a flow chart representing a process performed by a controller;

[0043] Figure 4 is a schematic configuration diagram of a heat pump system according to a second embodiment of the present invention;

[0044] Figure 5 is a schematic configuration diagram of a heat pump system according to a third embodiment of the present invention;

[0045] Figure 6 Yes means Figure 5 A block diagram of the functional configuration of the controller shown; and

[0046] Figure 7 is a flowchart showing a process executed by the controller. DETAILED DESCRIPTION

[0047] <First Embodiment>

[0048] A preferred embodiment of a heat pump system according to the present invention (hereinafter referred to as a "first embodiment") is described with reference to the drawings. The heat pump system according to the first embodiment is a refrigeration system for cooling a target space by using, for example, R32 refrigerant.

[0049] -System circuit structure-

[0050] Figure 1 is a schematic configuration diagram of a heat pump system according to a first embodiment.

[0051] like Figure 1 As shown, the heat pump system 100 according to the first embodiment includes a utilization side unit 200 and a heat source side unit 300 forming a heat pump loop. For example, the utilization side unit 200 is configured in the target space, and the heat source side unit 300 is configured outside the target space. The utilization side unit 200 and the heat source side unit 300 can be produced separately and then connected to each other by the pipes described later. Alternatively, the utilization side unit 200 and the heat source side unit 300 can be integrated into a single unit. A plurality of utilization side units 200 can be connected to one or more heat source side units 300.

[0052] The utilization-side unit 200 includes a utilization-side expansion mechanism 211 and a utilization-side HEX (heat exchanger) 212. The elements of the utilization-side unit 200 may be accommodated in a casing (not shown).

[0053] The utilization side expansion mechanism 211 is arranged in the liquid refrigerant pipe 322 described later extending from the heat source side unit 300, and is configured to decompress the refrigerant flowing in the liquid refrigerant pipe from the heat source side unit 300 to expand it. The utilization side expansion mechanism 211 may be an electric expansion valve. The utilization side HEX 212 is connected to one end of the liquid refrigerant pipe 322, and is also connected to one end of the gas refrigerant pipe 323 described later extending from the heat source side unit 300. The utilization side HEX 212 is configured to exchange heat between the refrigerant flowing into the utilization side HEX from the liquid refrigerant pipe 322 and the gas refrigerant pipe 323 and the fluid passing through the utilization side HEX. When the refrigerant in the liquid refrigerant pipe 322 flows to the utilization side HEX 212, the refrigerant is decompressed and expanded by the utilization side expansion mechanism 211. The fluid passing through the utilization side HEX 212 may be air, water or other refrigerants. The utilization-side HEX 212 may be provided with a fan, a pump, etc. to facilitate fluid flow.

[0054] The heat source side unit 300 includes a refrigerant compressor 311, a heat source side HEX 312, a main expansion mechanism 313, a refrigerant HEX (heat exchanger) 314, a liquid side stop valve 315, a gas side stop valve 316, and a storage tank 317. The heat source side unit 300 also includes a high-pressure refrigerant pipe 321, a liquid refrigerant pipe 322, a gas refrigerant pipe 323, a low-pressure refrigerant pipe 324, a first bypass pipe 331, and a second bypass pipe 332. The heat source side unit 300 also includes a first bypass valve 341, a second bypass valve 342, a bypass sensor 351, a suction side sensor 352, a discharge side sensor 353, and a controller 400. The elements of the heat source side unit 300 may be accommodated in a housing (not shown).

[0055] The refrigerant compressor 311 has a suction port and a discharge port (not shown), and is configured to suck refrigerant through the suction port, compress the sucked refrigerant, and discharge the compressed refrigerant from the discharge port. One end of the low-pressure refrigerant pipe 324 is connected to the suction port, and one end of the high-pressure refrigerant pipe 321 is connected to the discharge port.

[0056] The heat source side HEX 312 is connected to the other end of the high pressure refrigerant pipe 321, and is also connected to the other end of the liquid refrigerant pipe 322. The heat source side HEX 312 is configured to exchange heat between the refrigerant flowing into the heat source side HEX from the high pressure refrigerant pipe 321 to the liquid refrigerant pipe 322 and the fluid passing through the heat source side HEX. The refrigerant flowing into the heat source side HEX 312 is the refrigerant compressed by the refrigerant compressor 311. The fluid passing through the heat source side HEX 312 may be air, water or other refrigerants. The heat source side HEX 312 may be provided with a fan, a pump, etc. to facilitate the flow of fluid.

[0057] The main expansion mechanism 313 is disposed in the liquid refrigerant pipe 322, and is configured to decompress and expand the refrigerant flowing in the liquid refrigerant pipe 322 from the heat source side HEX 312. The main expansion mechanism 313 may be an electric expansion valve.

[0058] The refrigerant HEX 314 is configured to exchange heat between the refrigerant flowing in the liquid refrigerant pipe 322 and the refrigerant flowing in the first bypass pipe 331. The refrigerant HEX 314 may have two flow channels, and heat conduction exists between the two flow channels. The two flow channels form a part of the liquid refrigerant pipe 322 and a part of the first bypass pipe 331, respectively.

[0059] The liquid stop valve 315 is disposed in the heat source side unit 300 at the portion of the liquid refrigerant pipe 322 farthest from the refrigerant compressor 311, and can prevent the refrigerant from flowing out of the heat source side unit 300 through the liquid refrigerant pipe 322. The liquid stop valve 315 may be an electric expansion valve.

[0060] The other end of the gas refrigerant pipe 323 is connected to the other end of the low-pressure refrigerant pipe 324. Therefore, the usage-side HEX 212 of the usage-side unit 200 is connected to the refrigerant compressor 311 via the gas refrigerant pipe 323 and the low-pressure refrigerant pipe 324.

[0061] The gas-side stop valve 316 is disposed in the heat source-side unit 300 at the portion of the gas refrigerant pipe 323 farthest from the refrigerant compressor 311, and can prevent the refrigerant from flowing into the heat source-side unit 300 through the gas refrigerant pipe 323. The gas-side stop valve 316 may be an electric expansion valve.

[0062] The storage tank 317 is disposed in the low-pressure refrigerant pipe 324 and is configured to accumulate excess refrigerant in the heat pump circuit. The storage tank 317 is also configured to separate gas refrigerant from the refrigerant flowing into the storage tank 317 and deliver the separated gas refrigerant to the refrigerant compressor 311.

[0063] One end of the first bypass pipe 331 is connected to the liquid refrigerant pipe at a point P1 between the main expansion mechanism 313 and the refrigerant HEX 314. The other end of the first bypass pipe 331 is connected to the low-pressure refrigerant pipe 324 at a point P2 between the accumulator 317 and the utilization-side HEX 212, that is, between the accumulator 317 and the gas refrigerant pipe 323.

[0064] The first bypass valve 341 (EVT) is arranged in the first bypass pipe 331 at a position point between the position point P1 and the refrigerant HEX 314, and is configured to decompress the refrigerant flowing in the first bypass pipe 331 from the liquid refrigerant pipe 322 to expand it. Therefore, the first bypass valve 341 is configured to supply a gas-liquid two-phase refrigerant having a lower temperature than the refrigerant flowing in the liquid refrigerant pipe 322 to the refrigerant HEX 314. Therefore, the refrigerant flowing in the liquid refrigerant pipe 322 is cooled when passing through the refrigerant HEX 314. The first bypass valve 341 can also block the refrigerant flow. The first bypass valve 341 may be an electric expansion valve.

[0065] One end of the second bypass pipe 332 is connected to the liquid refrigerant pipe 322 at a position point P3. In this embodiment, the position point P3 is located between the refrigerant HEX 314 and the liquid-side stop valve 315. The other end of the second bypass pipe 332 is connected to the low-pressure refrigerant pipe at a position point P4 between the storage tank 317 and the refrigerant compressor 311.

[0066] The second bypass valve 342 (EVL) is arranged in the second bypass pipe 332, and is configured to decompress the refrigerant flowing in the second bypass pipe 332 from the liquid refrigerant pipe 322 to expand it. Therefore, the second bypass valve 341 is configured to supply a gas-liquid two-phase refrigerant having a lower temperature than the refrigerant flowing from the gas refrigerant pipe 323 to the low-pressure refrigerant pipe 324. The refrigerant with a lower temperature is combined with the refrigerant discharged from the storage tank 317 to reduce the temperature of the refrigerant to be sucked by the refrigerant compressor 311. The second bypass valve 342 can also block the refrigerant flow. The second bypass valve 342 can be an electric expansion valve.

[0067] The bypass sensor 351 is attached to the first bypass pipe 331 at a position point between the refrigerant HEX 314 and the position point P2. The bypass sensor 351 is configured to detect the temperature of the refrigerant flowing in the first bypass pipe 331 at the downstream side of the refrigerant HEX 314 (hereinafter, referred to as "bypass refrigerant temperature Tsh") and output a signal indicating the detected bypass refrigerant temperature Tsh to the controller 400. The bypass sensor 351 may be a thermistor.

[0068] The suction side sensor 352 is attached to the low-pressure refrigerant pipe 324 on the upstream side of the position point P2. The suction side sensor 352 is configured to detect the pressure of the refrigerant flowing in the low-pressure refrigerant pipe 324 (hereinafter, referred to as "suction side pressure Psu") and output a signal indicating the detected suction side pressure Psu to the controller 400. The suction side sensor 352 may be a capacitive pressure sensor.

[0069] When the refrigerant used is known, the saturation temperature Teg of the refrigerant flowing in the low-pressure refrigerant pipe can be identified based on the suction side pressure Psu. The superheat temperature SH of the refrigerant flowing in the first bypass pipe 331 can be identified based on the difference of the bypass refrigerant temperature Tsh relative to the saturation temperature Teg. Therefore, it can be said that the bypass sensor 351 and the suction side sensor 352 form a superheat temperature detector, which is configured to detect the bypass refrigerant temperature Tsh and the suction side pressure Psu as a parameter representing the superheat temperature SH of the refrigerant flowing in the first bypass pipe 331.

[0070] The discharge side sensor 353 is attached to the high pressure refrigerant pipe 321. The discharge side sensor 353 is configured to detect the temperature of the refrigerant flowing in the high pressure refrigerant pipe 321 (hereinafter, referred to as "discharge temperature Tdi") and output a signal indicating the detected discharge temperature Tdi to the controller 400.

[0071] The controller 400 includes: an operation circuit, such as a CPU (central processing unit); a working memory used by the CPU, such as a RAM (random access memory); and a recording medium, such as a ROM (read-only memory), which stores a control program and information used by the CPU, although they are not shown. The controller 400 is configured to perform information processing and signal processing by the CPU executing the control program to control the operation of the heat pump system 100. In particular, the controller 400 is configured to control the opening of the first bypass valve 341 and the second bypass valve 342.

[0072] By this configuration, when the refrigerant compressor 311 is operated, the heat source side HEX 312 and the utilization side HEX 212 are used as the condenser and evaporator of the heat pump circuit, respectively. Therefore, the target space can be cooled. In addition, when the first bypass valve 341 is opened to a certain extent, the first bypass pipe 331 is used as a supercooling system for reducing the temperature of the refrigerant flowing in the liquid refrigerant pipe 322. Therefore, the refrigerant flowing in the liquid refrigerant pipe can be cooled by refrigerant heat exchange to improve the cooling efficiency in the refrigerant HEX 314.

[0073] This structure can be more effective when the piping length between the heat source side unit 300 and the utilization side unit 200 is relatively long. In the case of a long piping length, the pressure loss of the refrigerant in the liquid refrigerant pipe 322 tends to increase. In this regard, by opening the first bypass valve 341, the degree of supercooling of the refrigerant can be increased. As a result, although the refrigerant circulation amount in the liquid refrigerant pipe 322 is reduced, the cooling performance in the utilization side unit 200 can be maintained.

[0074] In addition, when the second bypass valve 342 is opened to a certain extent, the second bypass pipe 332 functions as an injection system to reduce the temperature of the refrigerant flowing in the low-pressure refrigerant pipe 324. Therefore, the discharge temperature Tdi can be reduced to improve the reliability and safety of the heat pump system 100. This configuration is more effective when using R32 refrigerant.

[0075] The opening degrees of the first bypass valve 341 and the second bypass valve 342 are controlled by the controller 400 based on signals from the bypass sensor 351 , the suction-side sensor 352 , and the discharge-side sensor 353 (hereinafter referred to as “sensors” as necessary).

[0076] -Functional structure of the controller-

[0077] Figure 2 It is a block diagram showing the functional configuration of the controller 400 .

[0078] like Figure 2 As shown, the controller 400 includes a storage unit 410 , an information input unit 420 , an operation unit 430 , an information output unit 440 , and a valve control unit 450 .

[0079] The storage unit 410 stores information in a format readable by the valve control unit 450. The stored information includes saturation temperature information and valve control information prepared in advance based on experiments or the like.

[0080] The saturation temperature information indicates the correlation between the pressure and the saturation temperature of the refrigerant used in the heat pump system 100. According to the saturation temperature information, if the suction-side pressure Psu of the refrigerant has been detected, the saturation temperature Teg thereof can be identified.

[0081] The valve control information indicates a predetermined standard for determining the value of the target superheat temperature SH_tgt. For example, the target superheat temperature SH_tgt is 5K (Kelvin). The target superheat temperature SH_tgt can be determined in such a way that the refrigerant flowing in the first bypass pipe 331 located on the downstream side of the refrigerant HEX 314 is kept in gas form and the temperature is kept as low as possible. Therefore, the full potential of the refrigerant HEX 314 can be utilized to generate a supercooled liquid refrigerant in the liquid refrigerant pipe 322, while avoiding a negative impact on the discharge temperature due to excessively high superheat temperature.

[0082] The valve control information also indicates a first temperature value T1 and a third temperature value T3 of a first target exhaust temperature Tdi_tgt1. The target superheat temperature SH_tgt and the first target exhaust temperature Tdi_tgt1 are reference values ​​used by the valve control portion 450 to control the opening of the first bypass valve 341. The valve control information also indicates a second temperature value T2 of a second target exhaust temperature Tdi_tgt2. The second target exhaust temperature Tdi_tgt2 is a reference value used by the valve control portion 450 to control the opening of the second bypass valve 342.

[0083] Here, the first temperature value T1 is greater than any one of the second temperature value T2 and the third temperature value T3. Preferably, the second temperature value T2 is less than the third temperature value T3. For example, when using R32 refrigerant, the first temperature T1 is 115, the second temperature T2 is 95, and the third temperature T3 is 90 (degrees Celsius). However, one or more of the first temperature value T1, the second temperature value T2, and the third temperature value T3 may vary according to conditions such as the operating state of the heat pump system 100. In this case, the valve control information represents a predetermined standard for determining the first temperature value T1, the second temperature value T2, and / or the third temperature value T3. These temperature values ​​T1, T2, and T3 may be determined in a manner that prevents the deterioration of the oil used in the refrigerant compressor 311 and / or the insulating material of the motor coil.

[0084] In addition, the valve control information indicates an opening threshold value ODth. The opening threshold value ODth is a reference value used by the valve control unit 450 to switch between the first temperature value T1 and the third temperature value T3.

[0085] The information input unit 420 is configured to input information required for controlling the operation of the heat pump system 100. The information to be input includes signals output from sensors. The information input unit 420 is configured to output the bypass refrigerant temperature Tsh, the suction side pressure Psu and the discharge temperature Tdi represented by the input signals to the valve control unit 450 (hereinafter referred to as "sensing results" as needed). The information input unit 420 obtains and outputs the sensing results regularly or when the sensing results change. The information input unit 420 can be a wired / wireless communication interface for communicating with the sensor (signal line not shown).

[0086] The operation part 430 is configured to operate the heat pump system 100 to perform heat pump operation by operating the refrigerant compressor 311, the utilization-side expansion mechanism 211, the fan, etc. In addition, the operation part 430 is configured to operate the first bypass valve 341 and the second bypass valve 342 according to a command from the valve control part 450. The operation part 430 may be a wired / wireless communication interface for communicating with the above mechanisms, and may include a power supply unit for the above mechanisms.

[0087] The information output unit 440 is configured to output information to a user of the heat pump system 100 according to a command from the valve control unit 450. The information output unit 440 may be a display device, a lamp, a speaker, a wired / wireless communication interface for sending information to the information output device, etc.

[0088] The valve control portion 450 is configured to increase the opening of the first bypass valve 341 at least when the opening of the second bypass valve 332 has reached the opening threshold ODth. The valve control portion 450 includes a first valve control portion 451 , a second valve control portion 452 , and a mode control portion 453 .

[0089] The first valve control section 451 is configured to control the opening of the first bypass valve 341 so that when the discharge temperature Tdi is lower than or equal to the first target discharge temperature Tdi_tgt1, the superheat temperature SH approaches the target superheat temperature SH_tgt (second control). The first valve control section 451 is also configured to control the opening of the first bypass valve 341 so that when the discharge temperature Tdi is higher than the first target discharge temperature Tdi_tgt1, the discharge temperature Tdi approaches the first target discharge temperature Tdi_tgt1 (first control). As described later, the temperature value of the first target discharge temperature Tdi_tgt1 is determined by the mode control section 453. The first valve control section 451 controls the opening of the first bypass valve 341 by outputting a command to the operation section 430.

[0090] The second valve control section 452 is configured to control the opening of the second bypass valve 342 so that when the exhaust temperature Tdi is lower than or equal to the second target exhaust temperature Tdi_tgt2, the second bypass valve 342 is closed. This may include a state where the second bypass valve 342 is at a minimum opening but not completely closed. The second valve control section 452 is also configured to control the opening of the first bypass valve 342 so that when the exhaust temperature Tdi is higher than the second target exhaust temperature Tdi_tgt2, the exhaust temperature Tdi approaches the second target exhaust temperature Tdi_tgt2. The temperature value of the second target exhaust temperature Tdi_tgt2 is fixed to the second temperature value T2. However, the temperature value can be changed by the mode control section 453. The second valve control section 452 controls the opening of the second bypass valve 342 by outputting a command to the operating section 430.

[0091] The mode control portion 453 is configured to reduce the value of the first target exhaust temperature Tdi_tgt1 when the opening degree of the second bypass valve 342 has reached the opening degree threshold value ODth. More specifically, the mode control portion 453 is configured to switch the first target exhaust temperature Tdi_tgt1 from the first temperature value T1 to the third temperature value T3 when the opening degree of the second bypass valve 342 has exceeded the opening degree threshold value ODth.

[0092] By the above configuration, when the second bypass valve 342 is largely opened, the controller 400 relaxes the condition for controlling the first bypass valve 341 based on the exhaust temperature Tdi. Therefore, the controller 400 can make the opening of the first bypass valve 341, which is usually controlled based on the superheat temperature SH, more likely to be controlled based on the exhaust temperature Tdi to reduce the exhaust temperature Tdi when there is a possibility that the exhaust temperature becomes too high.

[0093] -Operation by controller-

[0094] Figure 3 is a flowchart showing the processing executed by the controller 450 .

[0095] In step S1100, the mode control portion 453 first sets the first temperature value T1 as the first target exhaust temperature Tdi_tgt1, and sets the second temperature value T2 as the second target exhaust temperature Tdi_tgt2. As described above, the first temperature value T1 is higher than the second temperature value T2. Preferably, the first temperature value T1 is a value that the exhaust temperature Tdi will not reach when the exhaust temperature Tdi can be lowered by increasing the opening of the second bypass valve 342.

[0096] In step S1200, the valve control part 450 acquires the discharge temperature Tdi and the superheat temperature SH. More specifically, the valve control part 450 acquires the bypass refrigerant temperature Tsh, the suction side pressure Psu and the discharge temperature Tdi from the bypass sensor 351, the suction side sensor 352 and the discharge side sensor 353 via the information input part 420. Then, the valve control part 450 identifies the saturation temperature Teg according to the suction side pressure Psu by referring to the saturation temperature information. The valve control part 450 identifies the value obtained by subtracting the identified saturation temperature Teg from the bypass refrigerant temperature Tsh as the superheat temperature SH. The valve control part 450 can use a moving average of each sensing result.

[0097] In step S1300, the second valve control unit 452 determines whether the acquired exhaust temperature Tdi is higher than the second target exhaust temperature Tdi_tgt2 (i.e., the second temperature value T2). If the exhaust temperature Tdi is lower than or equal to the second target exhaust temperature Tdi_tgt2 (S1300: No), the second valve control unit 452 proceeds to step S1400. If the exhaust temperature Tdi is higher than the second target exhaust temperature Tdi_tgt2 (S1300: Yes), the second valve control unit 452 proceeds to step S1500.

[0098] In step S1400 , the second valve control unit 452 controls the second bypass valve 342 to be closed. If the second bypass valve 342 is already closed, the second valve control unit 452 maintains the closed state. If the second bypass valve 342 is open, the second valve control unit 452 closes the second bypass valve 342 .

[0099] In step S1500, as described above, the second valve control unit 452 controls the second bypass valve 342 to be open, and controls the opening degree of the second bypass valve 342 based on the exhaust temperature Tdi. More specifically, the second valve control unit 452 controls the second bypass valve 342 to reduce the exhaust temperature Tdi to (approach) the second target exhaust temperature Tdi_tgt2 (i.e., the second temperature value T2) as much as possible.

[0100] When the second bypass valve 342 is largely opened, it is difficult to further reduce the exhaust temperature Tdi.

[0101] Therefore, in step S1600, the mode control unit 453 determines whether the opening of the second bypass valve 342 is higher than the opening threshold value Odth. If the opening of the second bypass valve 342 is lower than or equal to the opening threshold value ODth (S1600: No), the mode control unit 453 proceeds to step S1700. If the opening of the second bypass valve 342 is higher than the opening threshold value ODth (S1600: Yes), the mode control unit 453 proceeds to step S1800.

[0102] In step S1700, the mode control part 453 maintains the first target exhaust temperature Tdi_tgt1 as the initial value (ie, the first temperature value T1). If the third temperature value T3 has been set in step S1800 described later in the previous processing cycle, the mode control part 453 sets the first temperature value T1 as the first target exhaust temperature Tdi_tgt1.

[0103] In step S1800, the mode control portion 453 sets the third temperature value T3 as the first target exhaust temperature Tdi_tgt1. Therefore, the value of the first target exhaust temperature Tdi_tgt1 is reduced from the first temperature value T1 to the third temperature value T3 when the opening degree of the second bypass valve 342 has reached the opening degree threshold value ODth. If the third temperature value T3 has been set in the previous processing cycle, the mode control portion 453 maintains the first target exhaust temperature Tdi_tgt1 unchanged.

[0104] When the opening of the second bypass valve 332 is reduced to the opening threshold ODth and the first target exhaust temperature Tdi_tgt1 is the third temperature value T3, the mode control portion 453 increases the value of the first target exhaust temperature Tdi_tgt1 from the third temperature value T3 to the first temperature value T1 in step S1700. However, the opening threshold ODth (first opening threshold) used when the first target exhaust temperature Tdi_tgt1 is the first temperature value T1 may be different from the opening threshold ODth (second opening threshold) used when the first target exhaust temperature Tdi_tgt1 is the third temperature value T3. In this case, it is preferred that the second opening threshold is lower than the first opening threshold to prevent the first target exhaust temperature Tdi_tgt1 from changing frequently in a short time.

[0105] In step S1900, the first valve control part 451 determines whether the exhaust temperature Tdi is higher than the first target exhaust temperature Tdi_tgt1. As described above, according to the determination result in step S1600, the first target exhaust temperature Tdi_tgt1 is one of the first temperature value T1 and the third temperature value T3. If the exhaust temperature Tdi is lower than or equal to the first target exhaust temperature Tdi_tgt1 (S1900: No), the first valve control part 451 proceeds to step S2000. If the exhaust temperature Tdi is higher than the first target exhaust temperature Tdi_tgt1 (S1900: Yes), the first valve control part 451 proceeds to step S2100.

[0106] In step S2000, as described above, the first valve control unit 451 controls the opening of the first bypass valve 341 based on the superheat temperature SH. More specifically, the first valve control unit 451 determines the target superheat temperature SH_tgt based on the valve control information, and controls the opening of the first bypass valve 341 so that the superheat temperature SH is as close to the target superheat temperature SH_tgt as possible.

[0107] In step S2100, as described above, the first valve control unit 451 controls the opening of the first bypass valve 341 based on the exhaust temperature Tdi. More specifically, the first valve control unit 451 controls the first bypass valve 341 so that the exhaust temperature Tdi is reduced to (close to) the first target exhaust temperature Tdi_tgt1 (i.e., the first temperature value T1 or the third temperature value T3) as much as possible.

[0108] Therefore, when the second bypass valve 342 is opened more and exceeds the opening threshold ODth, the first target discharge temperature Tdi_tgt1 decreases, and the second valve control section 452 becomes more likely to control the opening of the first bypass valve 341 to reduce the discharge temperature Tdi. In other words, the operation of the first bypass valve 341 is switched from an operation mainly used to achieve a supercooling system to another operation mainly used to reduce the discharge temperature. The increase in the opening of the first bypass valve 341 causes the refrigerant flowing in the liquid refrigerant pipe 322 to be more supercooled, thereby enhancing the cooling effect achieved by the second bypass pipe 332.

[0109] In step S2100, the valve control unit 450 may also output alarm information in the form of images, light, sound, communication signals, etc. via the information output unit 440 by outputting a command thereto to inform the user of a possible excessively high exhaust temperature. The valve control unit 450 may output alarm information based on other conditions, for example, when the exhaust temperature Tdi has reached a predetermined threshold, or when the opening of the second bypass valve 342 has exceeded a predetermined opening threshold.

[0110] The valve control part 450 may also output a command to the operation part 430 to stop the operation of the refrigerant compressor 311 when the discharge temperature Tdi is higher than a predetermined threshold value higher than the first target discharge temperature Tdi_tgt1.

[0111] In step S2200, the controller 400 determines whether the termination of the operation has been specified. The specification may be performed by a user operation, another device, or the controller 400 itself. If the termination of the operation has not been specified (S2200: No), the controller 400 returns to step S1200. If the termination of the operation has been specified (S2200: Yes), the controller 400 terminates its operation.

[0112] Through the above operation of the controller 400 , the heat pump system 100 can quickly support the injection function of the second bypass pipe 332 by using the first bypass pipe 331 provided for the supercooling system when the injection function is insufficient.

[0113] It should be noted that the execution order of steps S1300 to S1500, steps S1600 to S1800, and steps S1900 to S2100 as described above may be changed. In addition, the step of obtaining the discharge temperature Tdi in step S1200 may be performed at another timing before at least steps S1300 and S1900, and the step of obtaining the superheat temperature SH in step S1200 may be performed at another timing before at least step S2000.

[0114] -Beneficial Effects-

[0115] According to the first embodiment, by utilizing the first bypass pipe 331 and the first bypass valve 341 initially set for the subcooling of the refrigerant flowing in the liquid refrigerant pipe 322, the flow capacity of the refrigerant bypassing the utilization side HEX 212 can be improved. Therefore, the discharge temperature Tdi can be effectively reduced to prevent it from becoming too high. In addition, this effect can be achieved without increasing the thickness and / or number of the second bypass pipe 332. Therefore, while improving the efficiency, reliability and safety of the heat pump system 100, the increase in the production cost and / or size of the system can be prevented as much as possible.

[0116] When the heat pump circuit is relatively long and / or a specific refrigerant such as R32 is used, the discharge temperature Tdi tends to become higher. Therefore, the above configuration is suitable for such a heat pump system with a long circuit. In other words, the discharge temperature can be controlled within an acceptable range regardless of the piping conditions.

[0117] If the thickness and / or number of the second bypass pipe 332 are simply increased to improve the flow capacity of the second bypass pipe 332, the production cost and / or size of the heat source side unit 300 will be increased. Therefore, it is possible to prevent the increase in the production cost and / or size of the system as much as possible while providing a heat pump system 100 with high efficiency, reliability and safety.

[0118] <Variation of First Embodiment>

[0119] In the above embodiment, the trigger factor for switching the value of the first target exhaust temperature Tdi_tgt1 is that the opening of the second bypass valve 342 has exceeded the opening threshold ODth. However, the trigger factor may be that the exhaust temperature Tdi has reached the exhaust temperature threshold. Therefore, the controller 400 may be configured to increase the opening of the first bypass valve 341 when the opening of the second bypass valve 342 has reached the opening threshold ODth and / or the exhaust temperature Tdi has reached the exhaust temperature threshold. Therefore, the exhaust temperature Tdi can also be effectively reduced to prevent it from becoming too high.

[0120] In addition, in the above-mentioned embodiment, the high-pressure refrigerant pipe 321 is connected to the heat source side HEX 312, and the low-pressure refrigerant pipe 324 is connected to the utilization side HEX 212 via the gas refrigerant pipe 323. However, the high-pressure refrigerant pipe 321 may be connected to the utilization side HEX 212 via the gas refrigerant pipe 323, and the low-pressure refrigerant pipe 324 may be connected to the heat source side HEX 312. In this configuration, the heat source side HEX 312 and the utilization side HEX 212 are used as an evaporator and a condenser of the heat pump circuit, respectively. Preferably, the connection point P3 of the second bypass pipe 332 is located on the downstream side of the refrigerant HEX 314.

[0121] <Second Embodiment>

[0122] Referring to the accompanying drawings, another preferred embodiment of the heat pump system according to the present invention (hereinafter referred to as the "second embodiment") is described. The heat pump system according to the second embodiment has substantially the same features as the heat pump system 100 according to the above-mentioned first embodiment, except for the features described below.

[0123] Figure 4 is a schematic configuration diagram of a heat pump system according to a second embodiment.

[0124] like Figure 4 As shown, in the heat source side unit 300a of the heat pump system 100a according to the present embodiment, the first bypass pipe 331a is not connected to the low-pressure refrigerant pipe 324, but is connected to the injection port (position point P5) of the refrigerant compressor 311. The injection port is connected to the medium-pressure chamber of the refrigerant compressor 311.

[0125] To the first bypass pipe 331a, a bypass sensor (hereinafter, referred to as "first bypass sensor 351") and another bypass sensor (hereinafter, referred to as "second bypass sensor 351a") which are the same as the bypass sensor 351 of the first embodiment are attached. There are two modes of sensor types of the first bypass sensor 351 and the second bypass sensor 351a.

[0126] In the first mode, the first bypass sensor 351 is configured to detect the temperature of the refrigerant flowing in the first bypass pipe 331a located at the downstream side of the refrigerant HEX 314, and the second bypass sensor 351a is configured to detect the temperature of the refrigerant flowing in the first bypass pipe 331a located between the first bypass valve 341 and the refrigerant HEX 314.

[0127] In the second mode, the first bypass sensor 351 is configured to detect the temperature of the refrigerant flowing in the first bypass pipe 331a at the downstream side of the first bypass valve 341, and the second bypass sensor 351a is configured to detect the pressure of the refrigerant flowing in the first bypass pipe 331a at the downstream side of the first bypass valve 341. Therefore, in the second mode, the second bypass sensor 351a does not need to be positioned between the first bypass valve 341 and the refrigerant HEX 314.

[0128] The refrigerant flowing in the first bypass pipe 331a from the first bypass valve 341 to the refrigerant HEX 314 is in gas-liquid two-phase. Therefore, the second bypass sensor 351a in the first mode can detect the saturation temperature Ts of the refrigerant flowing in the first bypass pipe 331a. Therefore, in the case of the first mode, the controller 400 can easily obtain the superheat temperature SH of the refrigerant flowing in the first bypass pipe 331a by simply subtracting the temperature detected by the second bypass sensor 351a from the temperature detected by the first bypass sensor 351.

[0129] In the second mode, the pressure detected by the second bypass sensor 351a can be used in the same manner as the suction side pressure Psu of the present embodiment. Therefore, the superheat temperature SH of the refrigerant flowing in the first bypass pipe 331a can be obtained in the same manner as the first embodiment.

[0130] Since the refrigerant used in the refrigerant HEX 314 is injected to the injection port of the refrigerant compressor 311, the efficiency of the refrigerant compressor 311 can be improved. In addition, by controlling the first bypass valve 341 based on the discharge temperature Tdi, the discharge temperature Tdi can be effectively lowered.

[0131] <Third Embodiment>

[0132] In addition, with reference to the accompanying drawings, another preferred embodiment of the heat pump system according to the present invention (hereinafter referred to as the "third embodiment") is described. The heat pump system according to the third embodiment has substantially the same features as the heat pump system 100 according to the above-mentioned first embodiment, except for the features described below.

[0133] Figure 5is a schematic configuration diagram of a heat pump system according to a third embodiment.

[0134] like Figure 5 As shown, the heat source side unit 300b of the heat pump system 100b according to the present embodiment further includes a mode switching mechanism 325b and a connection switching mechanism 333b.

[0135] The mode switching mechanism 325b is configured to switch the state of the heat pump system 100b between the cooling operation mode and the heating operation mode. In the cooling operation mode, the heat source side HEX 312 is connected to the high pressure refrigerant pipe 321, and the gas refrigerant pipe 323 is connected to the low pressure refrigerant pipe 324. This connection state corresponds to Figure 1 The first embodiment of the present invention is constructed by Figure 5 In the heating operation mode, the heat source side HEX is connected to the low-pressure refrigerant pipe 324, and the gas refrigerant pipe 323 is connected to the high-pressure refrigerant pipe 321. This connection state is indicated by Figure 5 The solid line in the mode switching mechanism 325b is shown. The mode switching mechanism 325b can be a four-way reversing valve, or a combination of a branch pipe and a reversing valve.

[0136] The connection switching mechanism 333b is configured to switch the state of the second bypass pipe between the first connection mode and the second connection mode. In the first connection mode, the second bypass pipe 332 is connected to the liquid refrigerant pipe 322 at the position point P3 as in the first embodiment. In the second connection mode, the second bypass pipe 332 is connected to the liquid refrigerant pipe 322 at the position point P6 between the main expansion mechanism 313 and the refrigerant HEX 314. The connection state of the first connection mode is determined by Figure 5 The connection state of the second connection mode is represented by the dotted line in the connection switching mechanism 333b. Figure 5 The connection switching mechanism 333b is indicated by a solid line. The connection switching mechanism 333b may be two connection pipes branched from the second bypass pipe 332 and two shutoff valves, such as solenoid valves, disposed in the two connection pipes.

[0137] The heat source side unit 300b further includes a controller 400b having other functions in addition to the functions of the controller 400 of the first embodiment.

[0138] Figure 6 It is a block diagram showing the functional configuration of the controller 400b.

[0139] like Figure 6As shown, the controller 400b includes an operation unit 430b, and the valve control unit 450b of the controller 400b further includes a connection control unit 454b. The operation unit 430b has other functions in addition to the functions of the operation unit 430 of the first embodiment.

[0140] The operation part 430b is also configured to operate the mode switching mechanism 325b to switch the state of the heat pump system 100b between the above-mentioned cooling operation mode and the heating operation mode. The operation part 430b is configured to switch the above-mentioned state according to a command from the valve control part 450b, a judgment made by the operation part 430b itself, or a user operation. The operation part 430b is also configured to operate the connection switching mechanism 333b according to a command from the valve control part 450b.

[0141] The connection control unit 454b is configured to control the connection switching mechanism 325b via the operation unit 430b. The connection control unit 454b is configured to control the connection switching mechanism 325b so that when the heat pump system 100b is in the cooling operation mode, the second bypass pipe 332 is in the first connection mode, and when the heat pump system 100b is in the heating operation mode, the second bypass pipe 332 is in the second connection mode.

[0142] Figure 7 is a flowchart showing the processing executed by the controller 400b.

[0143] First, the controller 400b executes Figure 3 Step S1100 of the first embodiment shown in FIG. Then, in steps S1110a and S1120b, the connection control unit 454b determines whether the heat pump system 100b is to be operated in the cooling operation mode or the heating operation mode. If the heat pump system 100b is to be operated in the cooling operation mode (S1100b: Yes), the connection control unit 454b proceeds to step S1130b. If the heat pump system 100b is to be operated in the heating operation mode (S1120b: Yes), the connection control unit 454b proceeds to step S1140b. The determination steps S1110a and S1120b may be repeated (S1110a: No, S1120b: No).

[0144] In step S1130b, the connection control unit 454b controls the connection switching mechanism 333b so that the second bypass pipe 332 is connected to the position point P3. Then, the controller 400b executes Figure 3 The first embodiment shown is steps S1200 to S2100.

[0145] In step S2110b, the controller 400b determines whether the termination of the operation has been specified. If the termination of the operation has not been specified (S2110b: No), the controller 400b returns to step S1130b. If the termination of the operation has been specified (S2110b: Yes), the controller 400b terminates its operation. The termination of the operation may include changing the operation mode between the cooling operation mode and the heating operation mode.

[0146] On the other hand, in step S1140b, the connection control unit 454b controls the connection switching mechanism 333b so that the second bypass pipe 332 is connected to the position point P6. Then, the controller 400b executes Figure 3 The first embodiment shown in FIG. 1 shows steps S1200 to S2100. However, step S2000 is replaced with step S2000b in which the first valve control unit 451 closes the first bypass valve 341. This may include a state in which the first bypass valve 341 is at a minimum opening but not completely closed.

[0147] In step S2120b, the controller 400b determines whether the operation termination has been specified. If the operation termination has not been specified (S2120b: No), the controller 400b returns to step S1140b. If the operation termination has been specified (S2120b: Yes), the controller 400b terminates its operation.

[0148] By the above configuration, the operation mode of the heat pump system 100b can be switched between the cooling operation mode and the heating operation mode while the second bypass pipe 332 is always connected to the downstream side of the refrigerant HEX 314. The temperature of the refrigerant flowing in the liquid refrigerant pipe 322 is lowered by the refrigerant HEX 314. Therefore, the temperature of the refrigerant flowing in the second bypass pipe 332 can be lowered during both the cooling operation mode and the heating operation mode to more effectively lower the discharge temperature Tdi.

[0149] <Other variations>

[0150] While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made without departing from the scope of the present disclosure as defined in the appended claims.

[0151] The controller 400, 400b may be configured to increase the opening of the first bypass valve 341 only when the opening of the second bypass valve 332 has reached the opening threshold ODth, without performing the Figure 3 and Figure 7Alternatively, or additionally, the controller 400, 400b may be configured to increase the opening of the first bypass valve 341 only when the exhaust temperature Tdi has reached the exhaust temperature threshold, without performing the Figure 3 and Figure 7 Steps S1700 to S2100 shown in .

[0152] The arrangement of the elements of the heat source side unit 300 and the utilization side unit 200 is not limited to the arrangement as described above. For example, the heat source side HEX 312 can be configured outside the shell of the heat source side unit 300. In addition, the heat pump system 100 of the first embodiment and the heat pump system 100a of the second embodiment can be configured so that the heat source side HEX 312 is used as an evaporator and the utilization side HEX 212 is used as a condenser. In this case, the piping connection of the heat pump system 100b of the third embodiment in the heating operation mode can be applied. Therefore, heat can be provided to the utilization side unit 200 by refrigerant.

[0153] Two or more configurations of the first to third embodiments may be combined. For example, the mode switching mechanism 325b of the third embodiment may be applied to the first or second embodiment. The first bypass pipe 331a of the second embodiment may be applied to the third embodiment.

[0154] For example, unless otherwise specifically stated, the size, shape, position or orientation of various parts can be changed as needed and / or desired, as long as these changes do not substantially affect its intended function. Unless otherwise specifically stated, the parts directly connected or in contact with each other shown can have an intermediate structure configured between them, as long as these changes do not substantially affect its intended function. Unless otherwise specifically stated, the function of an element can be performed by two elements, and vice versa. The structure and function of an embodiment can be adopted in another embodiment. All advantages do not need to appear in a specific embodiment at the same time. Thus, the foregoing description according to the embodiment of the present invention provided is only for illustration.

[0155] Reference numerals list

[0156] 100, 100a, 100b: heat pump system;

[0157] 200: using the side unit;

[0158] 211: Utilizing side expansion mechanism;

[0159] 212: Utilization side HEX;

[0160] 300, 300a: heat source side unit;

[0161] 311: Refrigerant compressor;

[0162] 312: heat source side HEX;

[0163] 313: main expansion mechanism;

[0164] 314: Refrigerant HEX;

[0165] 315: Liquid side stop valve;

[0166] 316: Gas side stop valve;

[0167] 317: Storage tank;

[0168] 321: High-pressure refrigerant pipe;

[0169] 322: Liquid refrigerant pipe;

[0170] 323: gas refrigerant pipe;

[0171] 324: low pressure refrigerant pipe;

[0172] 325b: mode switching mechanism;

[0173] 331, 331a: first bypass pipe;

[0174] 332: second bypass pipe;

[0175] 333b: connection switching mechanism;

[0176] 341: first bypass valve;

[0177] 342: second bypass valve;

[0178] 351: bypass sensor (first bypass sensor);

[0179] 351a: Second bypass sensor;

[0180] 352: Suction side sensor;

[0181] 353: discharge side sensor;

[0182] 400, 400b: controller;

[0183] 410: storage unit;

[0184] 420: information input unit;

[0185] 430, 430B: operation unit;

[0186] 440: information output unit;

[0187] 450, 450b: valve control unit;

[0188] 451: first valve control unit;

[0189] 452: second valve control unit;

[0190] 453: mode control unit;

[0191] 454b: Connection control unit.

Claims

1. A heat pump system, include: Refrigerant compressor; a high-pressure refrigerant pipe connected to a discharge port of the refrigerant compressor; a low-pressure refrigerant pipe connected to a suction port of the refrigerant compressor; a heat source side heat exchanger connected to any one of the high-pressure refrigerant pipe and the low-pressure refrigerant pipe and configured to perform heat exchange between the refrigerant flowing in the heat source side heat exchanger and a fluid passing through the heat source side heat exchanger; a liquid refrigerant pipe connected to the heat source side heat exchanger and configured to be connected to a utilization side heat exchanger configured to perform heat exchange between the refrigerant flowing in the utilization side heat exchanger and a fluid passing through the utilization side heat exchanger; a gas refrigerant pipe connected to the other of the high-pressure refrigerant pipe and the low-pressure refrigerant pipe and configured to be connected to the utilization-side heat exchanger; a main expansion mechanism, the main expansion mechanism being disposed in the liquid refrigerant pipe; a first bypass pipe connected to the liquid refrigerant pipe at a point between the main expansion mechanism and the refrigerant heat exchanger and connected to the low-pressure refrigerant pipe or an injection port of the compressor; the refrigerant heat exchanger configured to perform heat exchange between the refrigerant flowing in the liquid refrigerant pipe and the refrigerant flowing in the first bypass pipe; a first bypass valve disposed in the first bypass pipe at a point between the liquid refrigerant pipe and the refrigerant heat exchanger; a second bypass pipe connected to the liquid refrigerant pipe at a point between the main expansion mechanism and the utilization-side heat exchanger and connected to the low-pressure refrigerant pipe; a second bypass valve, the second bypass valve being disposed in the second bypass pipe; a superheat temperature detector configured to detect a parameter indicating a superheat temperature of the refrigerant flowing in the first bypass pipe; a discharge-side sensor configured to detect, as a discharge temperature, a temperature of the refrigerant flowing in the high-pressure refrigerant pipe between the refrigerant compressor and any one of the heat source-side heat exchanger and the utilization-side heat exchanger; as well as a controller configured to control the opening degree of the first bypass valve based on the superheat temperature and the discharge temperature represented by the detected parameter, and to control the opening degree of the second bypass valve based on the discharge temperature, The controller is configured to increase the opening degree of the first bypass valve at least when the opening degree of the second bypass valve has reached a first opening degree threshold.

2. The heat pump system according to claim 1, It is characterized in that The first bypass pipe is connected to the low-pressure refrigerant pipe, The overheat temperature detector includes a bypass sensor and a suction side sensor, wherein the bypass sensor is configured to detect the temperature of the refrigerant flowing in the first bypass pipe located on the downstream side of the refrigerant heat exchanger, and the suction side sensor is configured to detect the pressure of the refrigerant flowing in the low-pressure refrigerant pipe.

3. The heat pump system according to claim 1, It is characterized in that The first bypass pipe is connected to the injection port of the compressor, and The overheat temperature detector comprising: a first bypass sensor configured to detect the temperature of the refrigerant flowing in the first bypass pipe at a downstream side of the refrigerant heat exchanger; and a second bypass sensor configured to detect the temperature of the refrigerant flowing in the first bypass pipe between the first bypass valve and the refrigerant heat exchanger, or The invention comprises: a first bypass sensor, which is configured to detect the temperature of the refrigerant flowing in the first bypass pipe at the downstream side of the refrigerant heat exchanger; and a second bypass sensor, which is configured to detect the pressure of the refrigerant flowing in the first bypass pipe at the downstream side of the first bypass valve.

4. The heat pump system according to claim 2, It is characterized in that It also includes a storage tank arranged in the low-pressure refrigerant pipe, wherein: The first bypass pipe is connected to the low-pressure refrigerant pipe at a position between the storage tank and any one of the heat source side heat exchanger and the utilization side heat exchanger, and any one of the heat source side heat exchangers is connected to the low-pressure refrigerant pipe, and The second bypass pipe is connected to the low-pressure refrigerant pipe at a point between the storage tank and the refrigerant compressor.

5. The heat pump system according to claim 3, It is characterized in that It also includes a storage tank arranged in the low-pressure refrigerant pipe, wherein: The second bypass pipe is connected to the low-pressure refrigerant pipe at a point between the storage tank and the refrigerant compressor.

6. The heat pump system according to any one of claims 1 to 5, It is characterized in that The controller is configured to increase the opening of the first bypass valve at least when the exhaust temperature has reached an exhaust temperature threshold.

7. The heat pump system according to any one of claims 1 to 5, It is characterized in that The controller is configured to control the opening degree of the first bypass valve so that When the discharge temperature is lower than or equal to the first target discharge temperature, the superheat temperature approaches the target superheat temperature, and When the exhaust temperature is higher than the first target exhaust temperature, the exhaust temperature approaches the first target exhaust temperature.

8. The heat pump system according to claim 7, It is characterized in that The controller is configured to reduce a value of the first target exhaust temperature when the opening degree of the second bypass valve has reached a first opening degree threshold.

9. The heat pump system according to claim 8, It is characterized in that The controller is configured to increase the value of the first target exhaust temperature when the opening degree of the second bypass valve has decreased to a second opening degree threshold value that is lower than or equal to the first opening degree threshold value.

10. The heat pump system according to any one of claims 1 to 5, It is characterized in that The controller is configured to control the opening degree of the first bypass valve so that When the opening degree of the second bypass valve is lower than a first opening degree threshold, the superheat temperature approaches a target superheat temperature, and When the opening degree of the second bypass valve is higher than the first opening degree threshold, the exhaust temperature approaches a first target exhaust temperature.

11. The heat pump system according to claim 7, It is characterized in that The controller is configured to When the discharge temperature has been reduced to a second target discharge temperature that is lower than or equal to the first target discharge temperature, and / or When the opening degree of the second bypass valve has decreased to a second opening degree threshold value that is lower than or equal to the first opening degree threshold value, Switching from a first control in which the opening of the first bypass valve is controlled so that the exhaust temperature approaches the first target exhaust temperature to a second control in which the opening of the first bypass valve is controlled so that the superheat temperature approaches the target superheat temperature.

12. The heat pump system according to claim 10, It is characterized in that The controller is configured to When the discharge temperature has been reduced to a second target discharge temperature that is lower than or equal to the first target discharge temperature, and / or When the opening degree of the second bypass valve has decreased to a second opening degree threshold value that is lower than or equal to the first opening degree threshold value, Switching from a first control in which the opening of the first bypass valve is controlled so that the exhaust temperature approaches the first target exhaust temperature to a second control in which the opening of the first bypass valve is controlled so that the superheat temperature approaches the target superheat temperature.

13. The heat pump system according to any one of claims 1 to 5, It is characterized in that The heat pump system is configured to use R32 refrigerant.

14. The heat pump system according to any one of claims 1 to 5, It is characterized in that Also includes: a mode switching mechanism configured to switch the state of the heat pump system between a cooling operation mode and a heating operation mode, In the cooling operation mode, the heat source side heat exchanger is connected to the high-pressure refrigerant pipe, the gas refrigerant pipe is connected to the low-pressure refrigerant pipe, and In the heating operation mode, the heat source side heat exchanger is connected to the low-pressure refrigerant pipe, and the gas refrigerant pipe is connected to the high-pressure refrigerant pipe; as well as A connection switching mechanism, the connection switching mechanism is configured to switch the state of the second bypass pipe between a first connection mode and a second connection mode, in which in the first connection mode, the second bypass pipe is connected to the liquid refrigerant pipe at a position point between the refrigerant heat exchanger and the utilization side heat exchanger, and in the second connection mode, the second bypass pipe is connected to the liquid refrigerant pipe at a position point between the main expansion mechanism and the refrigerant heat exchanger, wherein The controller is further configured to control the connection switching mechanism so that when the heat pump system is in the cooling operation mode, the second bypass pipe is in the first connection mode, and when the heat pump system is in the heating operation mode, the second bypass pipe is in the second connection mode.

15. A method for controlling a heat pump system, The heat pump system include: Refrigerant compressor; a high-pressure refrigerant pipe connected to a discharge port of the refrigerant compressor; a low-pressure refrigerant pipe connected to a suction port of the refrigerant compressor; a heat source side heat exchanger connected to any one of the high-pressure refrigerant pipe and the low-pressure refrigerant pipe and configured to perform heat exchange between the refrigerant flowing in the heat source side heat exchanger and a fluid passing through the heat source side heat exchanger; a liquid refrigerant pipe connected to the heat source side heat exchanger and configured to be connected to a utilization side heat exchanger configured to perform heat exchange between the refrigerant flowing in the utilization side heat exchanger and a fluid passing through the utilization side heat exchanger; a gas refrigerant pipe connected to the other of the high-pressure refrigerant pipe and the low-pressure refrigerant pipe and configured to be connected to the utilization-side heat exchanger; a main expansion mechanism, the main expansion mechanism being disposed in the liquid refrigerant pipe; a first bypass pipe connected to the liquid refrigerant pipe at a point between the main expansion mechanism and the refrigerant heat exchanger and connected to the low-pressure refrigerant pipe or an injection port of the compressor; the refrigerant heat exchanger configured to perform heat exchange between the refrigerant flowing in the liquid refrigerant pipe and the refrigerant flowing in the first bypass pipe; a first bypass valve disposed in the first bypass pipe at a point between the liquid refrigerant pipe and the refrigerant heat exchanger; a second bypass pipe connected to the liquid refrigerant pipe at a point between the main expansion mechanism and the utilization-side heat exchanger and connected to the low-pressure refrigerant pipe; a second bypass valve, the second bypass valve being disposed in the second bypass pipe; a superheat temperature detector configured to detect a parameter indicating a superheat temperature of the refrigerant flowing in the first bypass pipe; a discharge-side sensor configured to detect, as a discharge temperature, a temperature of the refrigerant flowing in the high-pressure refrigerant pipe between the refrigerant compressor and any one of the heat source-side heat exchanger and the utilization-side heat exchanger; as well as a controller configured to control the opening degree of the first bypass valve based on the superheat temperature and the discharge temperature represented by the detected parameter, and to control the opening degree of the second bypass valve based on the discharge temperature, The method comprises: controlling the opening of the first bypass valve so that when the discharge temperature is lower than or equal to a first target discharge temperature, the superheat temperature approaches a target superheat temperature, and when the discharge temperature is higher than the first target discharge temperature, the discharge temperature approaches the first target discharge temperature; as well as When the opening degree of the second bypass valve has reached a first opening degree threshold, the value of the first target exhaust temperature is reduced.

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