Refrigeration cycle device

Abstract

To provide a refrigeration cycle device capable of preventing heating capacity of a utilization-side heat exchanger from being fluctuated when changing an injection flow rate of refrigerant to an injection port of a compressor.SOLUTION: A refrigeration cycle device includes: a main refrigerant circuit where a compressor having an injection port communicating with a compression chamber, a utilization-side heat exchanger, a first expansion valve and a heat source-side heat exchanger are successively connected and the refrigerant is circulated; a bypass refrigerant circuit which is branched from the main refrigerant circuit between the utilization-side heat exchanger and the first expansion valve and communicates with the injection port of the compressor, and in which a second expansion valve and the utilization-side heat exchanger are successively connected from the side of the main refrigerant circuit; and a controller for controlling an operation frequency of the compressor and an aperture of the second expansion valve. The controller executes compressor operation control changing the operation frequency of the compressor according to the aperture of the second expansion valve.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a refrigeration cycle device. [Background technology]

[0002] Patent Document 1 discloses a configuration in an air conditioner that conditions indoor air using a refrigeration cycle with a two-stage compressor, in which when the outdoor air temperature falls below a predetermined temperature, a target discharge superheat is calculated based on the compressor frequency and high / low pressure ratio, and the flow rate of refrigerant flowing into the injection port of the two-stage compressor through an injection pipe branched off from a main pipe connecting an indoor heat exchanger and an outdoor heat exchanger is controlled by an expansion valve provided in the injection pipe so as to achieve the target discharge superheat. In the above configuration, when the high / low pressure ratio of the two-stage compressor is low, the expansion valve is controlled to reduce the target discharge superheat, improving efficiency. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] European Patent Application Publication No. 3730875 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a refrigeration cycle device that can suppress fluctuations in the heating capacity of a utilization-side heat exchanger when the injection flow rate of a refrigerant into an injection port of a compressor is changed. [Means for solving the problem]

[0005] The refrigeration cycle device of the present disclosure includes a compressor having an injection port communicating with a compression chamber, a main refrigerant circuit in which a utilization side heat exchanger, a first expansion valve, and a heat source side heat exchanger are connected in sequence to allow a refrigerant to circulate, a bypass refrigerant circuit that branches off from the main refrigerant circuit between the utilization side heat exchanger and the first expansion valve, communicates with the injection port of the compressor, and in which a second expansion valve and the utilization side heat exchanger are connected in sequence from the main refrigerant circuit side, and a controller that controls the operating frequency of the compressor and the aperture of the second expansion valve, and the controller executes compressor operation control that changes the operating frequency of the compressor in accordance with the aperture of the second expansion valve. The operating frequency of a compressor corresponds to the rotational speed of a rotor in a compressor that pumps refrigerant by the rotational motion of a rotor, and corresponds to the reciprocating speed of a piston in a compressor that pumps refrigerant by the reciprocating motion of a piston. Effect of the Invention

[0006] The refrigeration cycle device of the present disclosure has a configuration in which refrigerant is injected into the compressor through a bypass refrigerant circuit, and the operating frequency of the compressor is changed according to the opening degree of a second expansion valve provided in the bypass refrigerant circuit, so that the fluctuation of the heating capacity of the utilization side heat exchanger, which changes according to the injection flow rate of the refrigerant, can be suppressed. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a configuration diagram of a refrigeration cycle device according to an embodiment. [Diagram 2] Control block diagram of a refrigeration cycle device according to an embodiment [Diagram 3] Pressure-enthalpy diagram (Ph diagram) in the refrigeration cycle device in the embodiment [Figure 4] Graph showing the heating capacity improvement rate vs. outside air temperature in a refrigeration cycle device according to an embodiment [Diagram 5] A graph showing the relationship between the change rate of the compressor operating frequency and the outside air temperature in a refrigeration cycle device according to an embodiment. [Figure 6]Timing chart of start-up and injection control of the refrigeration cycle device in the embodiment [Figure 7] A timing chart of a modified version of the start-up and injection control of the refrigeration cycle device in the embodiment. [Figure 8] 1 is a first flowchart of a control process for a compressor, a first expansion valve, and a second expansion valve of a refrigeration cycle device according to an embodiment. [Figure 9] 2 is a second flowchart of the control process of the compressor, the first expansion valve, and the second expansion valve of the refrigeration cycle device in the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] (The knowledge and other information that formed the basis of this disclosure)

[0009] At the time when the inventors arrived at the present disclosure, there was a technique in a refrigeration cycle device in which, under a predetermined condition such as when the outside air temperature is low, a part of the refrigerant discharged from the compressor and subjected to heat exchange in the utilization side heat exchanger is injected into the compressor through a bypass circuit. This technique can improve the heating capacity of the utilization side heat exchanger.

[0010] However, when switching from injection of refrigerant to the compressor to injection, there is a disadvantage that the discharge temperature of the refrigerant from the compressor overshoots, increasing the load on the compressor. In addition, when switching from injection to injection, there is a disadvantage that the heating capacity of the user-side heat exchanger is significantly reduced, causing a decrease in the temperature of the heat medium supplied from the user-side heat exchanger. The inventors have discovered a problem of how to avoid the occurrence of these problems, and have come to constitute the subject of the present disclosure in order to solve the problem. In view of the above, the present disclosure provides a refrigeration cycle device that can suppress fluctuations in the heating capacity of a utilization side heat exchanger when the injection flow rate of a refrigerant into an injection port of a compressor is changed.

[0011] Hereinafter, the embodiments will be described in detail with reference to the drawings. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of already well-known matters or duplicate explanation of substantially the same configuration may be omitted. This is to avoid the following explanation becoming more redundant than necessary and to facilitate understanding by those skilled in the art. It should be noted that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0012] (Embodiment) Hereinafter, the embodiment will be described with reference to FIGS. 1 to 7. FIG. [1. Configuration] 1 is a configuration diagram of a refrigeration cycle apparatus 1 according to the present embodiment. The refrigeration cycle apparatus 1 is a vapor compression type refrigeration cycle apparatus, and includes a main refrigerant circuit 10, a bypass refrigerant circuit 20, and a controller 50.

[0013] The main refrigerant circuit 10 is configured by sequentially connecting a compressor 11 that compresses the refrigerant, a utilization side heat exchanger 12 that functions as a radiator, an intermediate heat exchanger 13 that functions as an economizer, a first expansion valve 14, and a heat source side heat exchanger 15 that functions as an evaporator, through refrigerant piping 16. The first expansion valve 14 is an opening adjustment valve whose opening can be changed by a stepping motor or the like. In this embodiment, a four-way valve 17 is provided in the refrigerant piping 16 between the compressor 11 and the utilization side heat exchanger 12. The four-way valve 17 switches the flow direction of the refrigerant discharged from the compressor 11.

[0014] That is, the four-way valve 17 switches between a first direction state in which the refrigerant discharged from the compressor 11 flows in the direction of the compressor 11 → the four-way valve 17 → the use-side heat exchanger 12 → the intermediate heat exchanger 13 → the first expansion valve 14 → the heat source-side heat exchanger 15 → the four-way valve 17 → the compressor 11, as shown by the dashed arrow in Fig. 1, and a second direction state in which the refrigerant flows in the direction of the compressor 11 → the four-way valve 17 → the heat source-side heat exchanger 15 → the first expansion valve 14 → the intermediate heat exchanger 13 → the use-side heat exchanger 12 → the four-way valve 17 → the compressor 11, which is opposite to the first direction state. In the second direction state, the heat source-side heat exchanger 15 functions as a radiator, and the use-side heat exchanger 12 functions as an evaporator. In this embodiment, a case will be described in which the refrigeration cycle device 1 is operated in the first direction state and the use-side heat exchanger 12 functions as a radiator.

[0015] The bypass refrigerant circuit 20 branches off from the refrigerant pipe 16 between the utilization side heat exchanger 12 and the first expansion valve 14, and communicates with an injection port 11a provided in a compression chamber of the compressor 11. A second expansion valve 21 and an intermediate heat exchanger 13 are connected to the bypass refrigerant circuit 20, in this order from the upstream side. The second expansion valve 21 is an opening / closing valve that can be switched between an open state and a closed state. The opening degree of the second expansion valve 21 in the closed state corresponds to the first opening degree in the present disclosure, and the opening degree of the second expansion valve 21 in the open state corresponds to the second opening degree in the present disclosure.

[0016] A portion of the high-pressure refrigerant that has passed through the user-side heat exchanger 12 flows into the bypass refrigerant circuit 20 and is reduced in pressure by the second expansion valve 21 to become an intermediate-pressure refrigerant. The intermediate-pressure refrigerant exchanges heat with the high-pressure refrigerant flowing through the main refrigerant circuit 10 in the intermediate heat exchanger 13, and is then injected into the compressor 11. The refrigerant injected into the compressor 11 merges with the refrigerant being compressed in the compression chamber of the compressor 11. The compressor 11 recompresses the refrigerant by merging the injected refrigerant with the refrigerant being compressed.

[0017] The utilization side heat medium circuit 30 is configured by connecting the utilization side heat exchanger 12, a transfer pump 31, and a heating terminal or a hot water tank (not shown) via a heat medium pipe 32. Water or antifreeze can be used as the heat medium flowing through the utilization side heat medium circuit 30. The utilization side heat exchanger 12 heats the heat medium flowing through the heat medium pipe 32 by performing heat exchange between the heat medium flowing through the heat medium pipe 32 and the refrigerant discharged from the compressor 11 to the main refrigerant circuit 10.

[0018] When the heat medium piping 32 is connected to the heating terminal, the heat medium heated in the user-side heat exchanger 12 is used for heating by heat radiation from the heating terminal, and the heat medium cooled by heat radiation from the heating terminal is heated again in the user-side heat exchanger 12. When the heat medium piping 32 is connected to the top and bottom of the hot water storage tank and the heat medium is water stored in the hot water storage tank, the water heated in the user-side heat exchanger 12 is supplied from the top of the hot water storage tank into the hot water storage tank by the heat medium piping 32, and low-temperature water from the bottom of the hot water storage tank is supplied to the heat medium piping 32 and heated in the user-side heat exchanger 12.

[0019] A discharge pressure sensor 41 is provided on the refrigerant piping 16 on the discharge side of the compressor 11 to detect the pressure of the refrigerant discharged from the compressor 11. A pre-heating temperature sensor 43 is provided on the heat medium piping 32 on the inlet side of the use-side heat exchanger 12 to detect the temperature of the heat medium near the inlet of the use-side heat exchanger 12. An outside air temperature sensor 44 is provided near the heat source-side heat exchanger 15 to detect the outside air temperature.

[0020] The refrigeration cycle apparatus 1 includes a controller 50 for controlling the operation of the compressor 11, the first expansion valve 14, the second expansion valve 21, the four-way valve 17, the conveying pump 31, etc., and a remote control 60 for performing operations such as starting and stopping the operation of the refrigeration cycle apparatus 1. Fig. 2 is a control block diagram of the refrigeration cycle apparatus 1. Referring to Fig. 2, the controller 50 is connected to a discharge pressure sensor 41, a pre-heating temperature sensor 43, and an outside air temperature sensor 44, and detection signals from these sensors are input to the controller 50.

[0021] The controller 50 is also connected to the compressor 11, the first expansion valve 14, the four-way valve 17, the second expansion valve 21, and the conveying pump 31, and the operation of these actuators is controlled by a control signal output from the controller 50. The controller 50 is also connected to a remote control 60. The remote control 60 has a switch and a display unit, and an operation signal of the switch is input to the controller 50, and the operating state of the refrigeration cycle apparatus 1 is displayed on the display unit of the remote control 60 in response to a display signal output from the controller 50.

[0022] The controller 50 includes a processor 51, a memory 52, etc., and the memory 52 stores a program 53 for controlling the refrigeration cycle apparatus 1 and control data 54 for determining control conditions for the compressor 11 and the first expansion valve 14. The processor 51 controls the operation of the refrigeration cycle apparatus 1 by reading and executing the program 53.

[0023] The operation of the refrigeration cycle apparatus 1 will be described with reference to Fig. 1 and Fig. 3. Fig. 3 is a pressure-enthalpy diagram (Ph diagram) when refrigerant is injected into the compressor 11 in the refrigeration cycle apparatus 1. Points (a) to (g) and (a)' to (g)' in Fig. 3 correspond to the points (a) to (g) shown in Fig. 1, respectively. Also, (a) to (g) in Fig. 3 show a case where the outlet water temperature from the use-side heat exchanger 12 (the temperature of water, which is a heat medium flowing from the use-side heat exchanger 12 to the use-side piping 32) is 20°C, and (a)' to (g)' show a case where the outlet water temperature from the use-side heat exchanger 12 is 70°C.

[0024] First, the high-pressure refrigerant (a) discharged from the compressor 11 dissipates heat in the utilization-side heat exchanger 12, then branches off from the main refrigerant circuit 10 to the bypass refrigerant circuit 20 at (e), and is reduced in pressure to an intermediate pressure by the second expansion valve 21 to become intermediate-pressure refrigerant (f), which exchanges heat with the refrigerant flowing through the main refrigerant circuit 10 in the intermediate heat exchanger 13. The high-pressure refrigerant flowing through the main refrigerant circuit 10 after dissipating heat in the utilization-side heat exchanger 12 is cooled by the intermediate-pressure refrigerant (f) flowing through the bypass refrigerant circuit 20, and becomes a reduced-enthalpy state (b) and a reduced-pressure state (c) by the first expansion valve 14.

[0025] The refrigerant (c) decompressed by the first expansion valve 14 has a lower refrigerant dryness (weight ratio of gas phase components to the total refrigerant) when it flows into the heat source side heat exchanger 15, and the liquid component of the refrigerant increases, and the refrigerant evaporates in the heat source side heat exchanger 15 and returns to the suction side (d) of the compressor 11. Meanwhile, the intermediate pressure refrigerant (f) decompressed to an intermediate pressure by the second expansion valve 21 is heated by the high pressure refrigerant flowing through the main refrigerant circuit 10 in the intermediate heat exchanger 13, and merges with the refrigerant being compressed in the compressor 11 from the injection port 11a of the compressor 11 with increased enthalpy (g). The same applies to (a)' to (g)'.

[0026] 3, as the outlet water temperature from the utilization side heat exchanger 12 increases (20° C. outlet water → 70° C. outlet water), the temperature of the refrigerant discharged from the compressor 11 must be increased, and the pressure of the refrigerant rises. When injection is performed, by operating to increase the injection amount as the outlet water temperature from the utilization side heat exchanger 12 increases, the circulating amount of the refrigerant increases and the heating capacity of the utilization side heat exchanger 12 increases.

[0027] This makes it possible to reduce the operating frequency of the compressor 11. This is because, as shown in Fig. 3, when the pressure of the high-pressure refrigerant discharged from the compressor 11 increases, the pressure of the intermediate-pressure refrigerant flowing into the bypass refrigerant circuit 20 also increases, increasing the density of the intermediate-pressure refrigerant, thereby increasing the flow rate of the refrigerant injected into the compressor 11 and making it possible to increase the circulating flow rate of the refrigerant in the main refrigerant circuit 10.

[0028] Furthermore, when the pressure of the high-pressure refrigerant discharged from the compressor 11 increases, the temperature difference between the high-pressure refrigerant and the intermediate-pressure refrigerant that perform heat exchange in the intermediate heat exchanger 13 increases. This increases the temperature difference between the inlet (e') and outlet (b') of the high-pressure refrigerant in the intermediate heat exchanger 13, and the degree of decrease in the outlet temperature in the intermediate heat exchanger 13 can be increased, thereby decreasing the degree of decrease in the enthalpy difference.

[0029] Here, Fig. 4 is a graph showing the effect of improving the heating capacity (heating capacity of the utilization-side heat exchanger 12) by performing injection. In Fig. 4, the vertical axis is set to the improvement rate of the heating capacity with injection (second expansion valve 21 open) compared to without injection (second expansion valve 21 closed) under the condition that the operating frequency of the compressor 11 is the same, and the horizontal axis is set to the outside air temperature. Fig. 4 shows that when the outside air temperature is low, the improvement rate of the heating capacity by performing injection is high.

[0030] Moreover, Fig. 5 is a graph showing the rate of change in the operating frequency of compressor 11 required to obtain the same heating capacity depending on whether or not injection is performed. The graph in Fig. 5 shows the ratio of the operating frequency with injection (second expansion valve 21 open) to the operating frequency without injection (second expansion valve 21 closed) on the vertical axis, and the outdoor air temperature on the horizontal axis. Fig. 5 shows that when the outdoor air temperature is low, the effect of lowering the operating frequency of compressor 11 by performing injection becomes greater.

[0031] 4 and 5, when heating is performed by the refrigeration cycle device 1, the lower the outdoor air temperature, the greater the effect of improving the heating capacity by performing injection. Therefore, the controller 50 executes control to open the second expansion valve 21 to perform injection when the outdoor air temperature detected by the outdoor air temperature sensor 44 is equal to or lower than a predetermined temperature, and to close the second expansion valve 21 to perform no injection when the outdoor air temperature exceeds the predetermined temperature.

[0032] 4, when the operating frequency of the compressor 11 is the same, the heating capacity differs greatly between the state with injection and the state without injection. Therefore, when switching from no injection to the state with injection, or from the state with injection to the state without injection, without changing the operating frequency of the compressor 11, the fluctuation in the heating capacity of the utilization side heat exchanger 12 becomes large. Therefore, when switching from no injection to the state with injection, or from the state with injection to the state without injection, the controller 50 executes control (compressor operation control) to suppress the fluctuation in the heating capacity of the utilization side heat exchanger 12 by changing the operating frequency of the compressor 11.

[0033] 6 and 7 are timing charts of the start-up control and relative control of the refrigeration cycle apparatus 1 by the controller 50, and show transitions of the bypass flag and the operation frequency of the compressor 11 against the time axis t. The relative control is a control that applies the discharge pressure of the refrigerant from the compressor 11 detected by the discharge pressure sensor 41, the temperature of the water (heat medium) flowing into the use-side heat exchanger 12 detected by the pre-heating temperature sensor 43, the outside air temperature detected by the outside air temperature sensor 44, etc. to the control conditions based on the control data 54, and sets the presence or absence of injection, the operation frequency of the compressor 11, the opening degree of the first expansion valve 14, the rotation speed of the conveying pump 31, etc.

[0034] The bypass flag corresponds to the presence or absence of injection, and when the bypass flag is ON, the second expansion valve 21 is controlled to an open state with injection, and when the bypass flag is OFF, the second expansion valve 21 is controlled to a closed state with no injection. The control at the start-up of the refrigeration cycle device 1 shown in Figures 6 and 7 is an example of control of the timing of switching the bypass flag from OFF to ON (switching from no injection to with injection).

[0035] In FIG. 6, when an operation start operation (remote control ON) is performed by the remote control 60 at t1, the controller 50 starts the operation of the refrigeration cycle device 1, and starts the operation of the compressor 11 at t2 (compressor ON) in a bypass flag OFF (no injection) state. The controller 50 increases the operating frequency of the compressor 11 stepwise from f1 to f2 to f3 to f4 to fa from t2 to t3. Then, the controller 50 turns the bypass flag ON at t4 and switches to injection (injection ON). In this case, when switching from no injection to injection at t4, the heating capacity of the use-side heat exchanger 12 increases as described above. Therefore, there is a risk of overshooting the discharge temperature of the refrigerant from the compressor 11. In addition, the temperature of hot water discharged from the use-side heat exchanger 12 rises, increasing the amount of heat released from the heating terminal, or unnecessarily high-temperature hot water is circulated to the hot water storage tank, thereby impairing the thermal efficiency of the use-side heat exchanger 12.

[0036] Therefore, as shown in Fig. 7, the controller 50 sets the operating frequency of the compressor 11 in the state without injection from t3 to t4 to fb, and executes control to lower the operating frequency of the compressor 11 to fa when switching from no injection to injection at t4. Here, the reduction width xa of the operating frequency is set so as to offset the fluctuation in the heating capacity of the utilization side heat exchanger 12 due to the presence or absence of injection as shown in Figs. 4 and 5.

[0037] In this way, when switching from no injection to injection, the operating frequency of the compressor 11 is controlled to be lowered so as to offset the fluctuation in the heating capacity of the user-side heat exchanger 12, thereby making it possible to suppress an increase in the temperature of the heat medium flowing out from the user-side heat exchanger 12 to the heat medium pipe 32. In addition, it is possible to suppress a decrease in the reliability of the compressor 11 due to an increase in the temperature of the refrigerant discharged from the compressor 11.

[0038] Furthermore, when switching from with injection to without injection, the controller 50 controls to increase the operation frequency of the compressor 11. In this case, the controller 50 sets the increase in the operation frequency so as to offset the reduction in the heating capacity of the utilization side heat exchanger 12 due to the presence or absence of injection.

[0039] [2. Control processing] The control process of the compressor 11, the first expansion valve 14, and the second expansion valve 21 executed by the controller 50 will be described with reference to the flowcharts shown in Figures 8 and 9. The controller 50 repeatedly executes the process according to the flowcharts shown in Figures 8 and 9 during operation of the refrigeration cycle apparatus 1.

[0040] 8, the controller 50 recognizes the outside air temperature based on the detection signal of the outside air temperature sensor 44. In the following step S2, the controller 50 determines whether the outside air temperature is equal to or lower than a predetermined temperature Tth, and if the outside air temperature is equal to or lower than Tth, proceeds to step S3, and if the outside air temperature is higher than Tth, proceeds to step S20 in FIG.

[0041] In step S3, the controller 50 determines whether the second expansion valve 21 is already in an open state (with injection). If the second expansion valve 21 is in an open state, the controller 50 advances the process to step S7, and if the second expansion valve 21 is in a closed state, the controller 50 advances the process to step S4.

[0042] In step S4, the controller 50 reduces the operating frequency of the compressor 11 so as to offset the increase in the heating capacity of the utilization side heat exchanger 12 caused by switching from no injection to injection, as described above. In the next step S5, the controller 50 reduces the opening of the first expansion valve 14 to reduce the flow rate of the refrigerant flowing through the main refrigerant circuit 10. By reducing the flow rate of the refrigerant flowing through the main refrigerant circuit 10, it is possible to suppress the increase in the heating capacity of the utilization side heat exchanger 12 caused by switching from no injection to injection.

[0043] In the next step S6, the controller 50 switches the second expansion valve 21 to an open state to enable injection. In the next step S7, the controller 50 uses a control map included in the control data 54 to control the operating frequency of the compressor 11 so that the temperature of the heat medium flowing from the use-side heat exchanger 12 to the use-side heat medium circuit 30 becomes the set temperature.

[0044] 9, the controller 50 determines whether the second expansion valve 21 is already in a closed state (no injection). If the second expansion valve 21 is in a closed state, the controller 50 advances the process to step S24, and if the second expansion valve 21 is in an open state, the controller 50 advances the process to step S21.

[0045] In step S21, the controller 50 increases the operating frequency of the compressor 11 so as to offset the decrease in the heating capacity of the utilization side heat exchanger 12 caused by switching from with injection to without injection, as described above. In the next step S22, the controller 50 increases the opening of the first expansion valve 14 to increase the flow rate of the refrigerant flowing through the main refrigerant circuit 10. By increasing the flow rate of the refrigerant flowing through the main refrigerant circuit 10, it is possible to suppress the decrease in the heating capacity of the utilization side heat exchanger 12 caused by switching from with injection to without injection.

[0046] In the next step S23, the controller 50 switches the second expansion valve 21 out of the closed valve field to disable injection. In the next step S24, the controller 50 uses a control map included in the control data 54 to control the operation frequency of the compressor 11 so that the temperature of the heat medium flowing from the use-side heat exchanger 12 to the use-side heat medium circuit 30 becomes the set temperature.

[0047] [3. Effects, etc.] As described above, in this embodiment, the refrigeration cycle device 1 includes the compressor 11 having the injection port 11a communicating with the compressor chamber, the utilization side heat exchanger 12, the first expansion valve 14, and the heat source side heat exchanger 15 connected in sequence to form a main refrigerant circuit 10 in which the refrigerant circulates, the bypass refrigerant circuit 20 branching off from the main refrigerant circuit 10 between the utilization side heat exchanger 12 and the first expansion valve 14, communicating with the injection port 11a of the compressor 11, and connecting the second expansion valve 21 and the utilization side heat exchanger 12 in sequence from the main refrigerant circuit 10 side, and the controller 50 for controlling the operating frequency of the compressor 11 and the opening degree of the second expansion valve 21. The controller 50 changes the operating frequency of the compressor 11 according to the opening degree of the second expansion valve 21. In the refrigeration cycle apparatus 1, the amount of refrigerant injected into the compressor 11 changes depending on the opening of the second expansion valve 21, which causes the heating capacity of the utilization side heat exchanger to vary. Therefore, by changing the operating frequency of the compressor 11 depending on the opening of the second expansion valve 21 using the controller 50, it is possible to suppress the fluctuation in the temperature of the heat medium flowing out from the utilization side heat exchanger 12 to the heat medium pipe 32.

[0048] (Other embodiments) As described above, the above embodiment has been described as an example of the technology disclosed in the present application. However, the technology in the present disclosure is not limited to this, and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made.

[0049] In the above embodiment, an on-off valve that can be switched between an open state and a closed state has been exemplified as the second expansion valve 21, but the second expansion valve 21 may be an opening adjustment valve that can change the opening degree. In this case, the injection flow rate of the refrigerant to the compressor 11 is adjusted by the opening degree of the second expansion valve 21, and the heating capacity of the use-side heat exchanger 12 is changed. Therefore, by changing the operating frequency of the compressor 11 according to the opening degree of the second expansion valve 21 by the controller 50, it is possible to suppress fluctuations in the temperature of the heat medium flowing out from the use-side heat exchanger 12 to the heat medium pipe 32.

[0050] Specifically, when the opening degree of the second expansion valve 21 is changed from a first opening degree to a second opening degree larger than the first opening degree by the controller 50, the operation frequency of the compressor 11 is controlled to be lowered. Also, when the opening degree of the second expansion valve 21 is changed from a third opening degree to a fourth opening degree smaller than the third opening degree by the controller 50, the operation frequency of the compressor 11 is controlled to be increased.

[0051] In the above embodiment, the controller 50 performs control to reduce the opening degree of the first expansion valve 14 when switching from no injection to with injection in step S5 of FIG. 8, but this control may be omitted.

[0052] In the above embodiment, the controller 50 performs control to increase the opening degree of the first expansion valve 14 when switching from with injection to without injection in step S22 of FIG. 9, but this control may be omitted.

[0053] In the above embodiment, the controller 50 switches between the presence or absence of injection depending on whether the outdoor air temperature detected by the outdoor air temperature sensor 44 is equal to or lower than the predetermined temperature Tth in steps S1 and S2 of Fig. 8. In another embodiment, the presence or absence of injection may be switched depending on the outdoor air temperature detected by the outdoor air temperature sensor 44, the temperature of the heat medium near the inlet of the use-side heat exchanger 12 detected by the pre-heating temperature sensor 43 (inlet water temperature), and the state of the refrigeration cycle.

[0054] The controller in the present disclosure may be any controller capable of controlling the device in the present disclosure. When expressing the subject matter of the invention, the device in the present disclosure may be controlled by a control means, a control unit, or similar terms in addition to the controller. The controller can be realized in various forms. For example, a processor may be used as the controller. If a processor is used as the controller, various processes can be executed by loading a program from a storage medium storing the program into the processor and executing the program by the processor. Therefore, the process contents can be changed by changing the program stored in the storage medium, so that the degree of freedom in changing the control contents can be increased. Examples of the processor include a CPU (Central Processing Unit) and an MPU (Micro-Processing Unit). Examples of the storage medium include a hard disk, a flash memory, and an optical disk. In addition, a wired logic in which the program cannot be rewritten may be used as the controller. Using a wired logic as the controller is effective in improving the processing speed. Examples of the wired logic include an ASIC (Application Specific Integrated Circuit). In addition, the controller may be realized by combining a processor and a wired logic. If the controller is realized by combining a processor and wired logic, it is possible to increase the degree of freedom of software design and improve the processing speed. In addition, the controller and a circuit having a function different from that of the controller may be configured with a single semiconductor element. An example of a circuit having a different function is an A / D-D / A conversion circuit. In addition, the controller may be configured with a single semiconductor element or multiple semiconductor elements. When configured with multiple semiconductor elements, each control described in the claims may be realized with different semiconductor elements. Furthermore, the controller may be configured with a configuration including a semiconductor element and a passive component such as a resistor or a capacitor.

[0055] It should be noted that the above-described embodiments are intended to illustrate the technology of the present disclosure, and various modifications, substitutions, additions, omissions, and the like can be made within the scope of the claims or their equivalents. [Industrial Applicability]

[0056] INDUSTRIAL APPLICABILITY The present disclosure is applicable to applications in which a fluctuation in the heating capacity of a utilization-side heat exchanger caused by a change in the injection flow rate is suppressed in a refrigeration cycle device that injects a refrigerant into a compressor. [Explanation of symbols]

[0057] 1 Refrigeration cycle equipment 10 Main refrigerant circuit 11 Compressor 12 User side heat exchanger 13 Intermediate heat exchanger 14 First expansion valve 15 Heat source side heat exchanger 16 Refrigerant piping 17 Four-way valve 20 Bypass refrigerant circuit 21 Second expansion valve 30 User-side heat carrier circuit 31 Transfer pump 32 Heat medium piping 41 Discharge pressure sensor 43 Pre-heating temperature sensor 44 Outside Air Temperature Sensor 50 Controller 51 Processors 52 Memory 53 Programs 54 Control Data 60 Remote Control

Claims

1. a main refrigerant circuit in which a refrigerant circulates, the main refrigerant circuit including a compressor having an injection port communicating with a compression chamber, a utilization side heat exchanger, a first expansion valve, and a heat source side heat exchanger connected in sequence; a bypass refrigerant circuit that branches off from the main refrigerant circuit between the utilization side heat exchanger and the first expansion valve, communicates with an injection port of the compressor, and has a second expansion valve and the utilization side heat exchanger connected in this order from the main refrigerant circuit side; a controller for controlling an operating frequency of the compressor and an opening degree of the second expansion valve; A refrigeration cycle apparatus comprising: The controller executes compressor operation control to change an operation frequency of the compressor in accordance with an opening degree of the second expansion valve. Refrigeration cycle equipment.

2. The controller executes, as the compressor operation control, a control to reduce an operation frequency of the compressor when changing an opening degree of the second expansion valve from a first opening degree to a second opening degree larger than the first opening degree. The refrigeration cycle device according to claim 1.

3. The controller reduces the opening degree of the first expansion valve when changing the opening degree of the second expansion valve from the first opening degree to the second opening degree. The refrigeration cycle device according to claim 2.

4. The second expansion valve is an opening / closing valve that can be switched between an open state and a closed state, and the first opening degree is an opening degree in the closed state, and the second opening degree is an opening degree in the open state. The refrigeration cycle device according to claim 2 or 3.

5. The controller executes, as the compressor operation control, a control for increasing an operation frequency of the compressor when changing an opening degree of the second expansion valve from a third opening degree to a fourth opening degree smaller than the third opening degree. The refrigeration cycle device according to any one of claims 1 to 3.

6. The controller increases the opening degree of the first expansion valve when changing the opening degree of the second expansion valve from the third opening degree to the fourth opening degree. The refrigeration cycle device according to claim 5.

7. The second expansion valve is an opening / closing valve that can be switched between an open state and a closed state, the third opening degree is an opening degree in the open state, and the fourth opening degree is an opening degree in the open state. The refrigeration cycle device according to claim 5.

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