Refrigeration cycle system

Abstract

To provide a refrigeration cycle system that can appropriately detect abnormalities in the refrigerant circuit. [Solution] The refrigeration cycle system according to this disclosure includes measuring means for measuring relevant physical quantities related to the state of the refrigerant circuit. When the abnormality determination mode is started, the control means sets the depressurization device to a first depressurization state, measures the value of the relevant physical quantity as a first measurement value by the measuring means when a first time has elapsed, then switches from the first depressurization state to a second depressurization state and measures the value of the relevant physical quantity as a second measurement value by the measuring means. If the value obtained by subtracting the first measurement value from the second measurement value is less than or equal to the first abnormality determination value, and the value obtained by subtracting the second measurement value from the first measurement value is less than or equal to the second abnormality determination value which is smaller than the first abnormality determination value, it is counted as an abnormality count, and when the cumulative count of abnormality counts exceeds a predetermined number of determination counts, it is determined that there is an abnormality in the refrigerant circuit.

Description

Technical Field

[0001] The present disclosure relates to a refrigeration cycle system.

Background Art

[0002] In Patent Document 1 below, as a technique for determining an abnormality in the refrigerant circuit of a heat pump water heater, a decompression device is set to a first decompression amount state, a compressor is operated at a first speed, and from the current value when a first time has elapsed, when the value obtained by subtracting the current value measured after the decompression amount is switched to the second decompression amount state is greater than the first abnormality determination value, a technique for stopping the operation of the compressor is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above-described conventional system, the measured value of the current changes according to differences in outside air temperature and other environmental conditions, the refrigerant distribution in the refrigerant circuit, the temperature of the compressor, and the like. Therefore, there is a possibility that an abnormality in the refrigerant circuit cannot be appropriately detected.

[0005] The present disclosure has been made to solve the above problems. The object of the present disclosure is to provide a refrigeration cycle system capable of appropriately detecting an abnormality in a refrigerant circuit.

Means for Solving the Problems

[0006] The refrigeration cycle system according to this disclosure comprises a refrigerant circuit having a compressor for compressing a refrigerant, a cooler for cooling the refrigerant compressed by the compressor, a pressure reducing device for reducing the pressure of the refrigerant that has passed through the cooler, and an evaporator for evaporating the refrigerant that has passed through the pressure reducing device; measuring means for measuring related physical quantities, which are physical quantities related to the state of the refrigerant circuit; and control means for executing an abnormality determination mode to detect an abnormality in the refrigerant circuit when starting operation of the refrigeration cycle by the refrigerant circuit. The pressure reducing device is switchable between a first pressure reduction state and a second pressure reduction state in which the pressure reduction is smaller than that of the first pressure reduction state. When the abnormality determination mode is started, the control means sets the pressure reducing device to the first pressure reduction state and operates the compressor at a first speed. The control means measures the value of the related physical quantity as the first measured value by the measuring means when a first hour has elapsed since the start of the abnormality determination mode. After setting the pressure, the pressure reducing device is switched from the first pressure reduction state to the second pressure reduction state. After the pressure reducing device is switched from the first pressure reduction state to the second pressure reduction state, the value of the relevant physical quantity is measured by the measuring means as the second measured value. If the value obtained by subtracting the first measured value from the second measured value is greater than the first abnormality judgment value, it is determined that there is an abnormality in the refrigerant circuit, and the operation of the compressor is stopped. If the value obtained by subtracting the first measured value from the second measured value is less than or equal to the first abnormality judgment value, and the value obtained by subtracting the second measured value from the first measured value is less than or equal to the second abnormality judgment value which is smaller than the first abnormality judgment value, it is counted as an abnormality, the pressure reducing device is returned to the first pressure reduction state, and the system returns to the start of the abnormality judgment mode and continues the operation of the compressor. When the cumulative count of the number of abnormalities exceeds a predetermined judgment count, it is determined that there is an abnormality in the refrigerant circuit, and the operation of the compressor is stopped. Furthermore, the refrigeration cycle system according to this disclosure comprises a refrigerant circuit having a compressor for compressing a refrigerant, a cooler for cooling the refrigerant compressed by the compressor, a pressure reducing device for reducing the pressure of the refrigerant that has passed through the cooler, an evaporator for evaporating the refrigerant that has passed through the pressure reducing device, and a fluid actuator for flowing air through the evaporator; measuring means for measuring related physical quantities, which are physical quantities related to the state of the refrigerant circuit; and control means for executing an abnormality determination mode to detect an abnormality in the refrigerant circuit when starting operation of the refrigeration cycle by the refrigerant circuit, wherein the pressure reducing device is switchable between a first pressure reduction state and a second pressure reduction state in which the pressure reduction is smaller than that of the first pressure reduction state, and when the abnormality determination mode starts, the control means sets the pressure reducing device to the first pressure reduction state, operates the fluid actuator at the second speed, and measures the compressor temperature after the first hour has elapsed from the start of the abnormality determination mode, and then measures the pressure The compressor is operated at a first speed. The control means measures the value of the relevant physical quantity as the first measured value by the measuring means when two hours have elapsed since the start of the abnormality determination mode. Then, the pressure reducing device is switched from the first pressure reduction state to the second pressure reduction state. After the pressure reducing device is switched from the first pressure reduction state to the second pressure reduction state, the measuring means measures the value of the relevant physical quantity as the second measured value. If the value obtained by subtracting the first measured value from the second measured value is greater than the first abnormality determination value, it is determined that there is an abnormality in the refrigerant circuit, and the operation of the compressor is stopped. If the value obtained by subtracting the first measured value from the second measured value is less than or equal to the first abnormality determination value, and the value obtained by subtracting the second measured value from the first measured value is less than or equal to the second abnormality determination value which is smaller than the first abnormality determination value, the operation of the compressor is stopped. The second abnormality determination value is determined from the compressor temperature measured when one hour has elapsed since the start of the abnormality determination mode. [Effects of the Invention]

[0007] This disclosure makes it possible to provide a refrigeration cycle system that can appropriately detect abnormalities in the refrigerant circuit. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows a refrigeration cycle system according to Embodiment 1. [Figure 2]This flowchart shows an example of the processing performed by the control unit in the abnormality detection mode of Embodiment 1. [Figure 3] This figure shows an example of a graph illustrating the time-dependent changes in related physical quantities after a compressor has been started. [Figure 4] This figure shows examples of graphs illustrating the time-dependent changes in related physical quantities under conditions where the compressor drive load is likely to be high and under conditions where the compressor drive load is unlikely to be high. [Figure 5] This flowchart shows an example of the processing performed by the control unit in the abnormality detection mode of Embodiment 4. [Figure 6] This figure shows a refrigeration cycle system according to Embodiment 4. [Modes for carrying out the invention]

[0009] The embodiments will be described below with reference to the drawings. Common or corresponding elements in each drawing are denoted by the same reference numerals, and their descriptions are simplified or omitted.

[0010] Embodiment 1. Figure 1 shows a refrigeration cycle system according to Embodiment 1. As shown in Figure 1, the refrigeration cycle system 1 comprises a refrigerant circuit 2, a measuring unit 7, and a control unit 8. The refrigerant circuit 2 comprises a compressor 3 for compressing the refrigerant, a cooler 4 for cooling the high-pressure refrigerant compressed by the compressor 3, a pressure reducing device 5 for reducing the pressure of the high-pressure refrigerant that has passed through the cooler 4, and an evaporator 6 for evaporating the low-pressure refrigerant reduced in pressure by the pressure reducing device 5. The compressor 3, cooler 4, pressure reducing device 5, and evaporator 6 are connected via refrigerant piping to form a ring-shaped circuit. The low-pressure refrigerant gas flowing out of the evaporator 6 is drawn into the compressor 3 and circulates again through the refrigerant circuit 2. The refrigerant circuit 2 is operated by electricity.

[0011] The refrigerant sealed in the refrigerant circuit 2 is not particularly limited, but may be, for example, carbon dioxide, ammonia, propane, isobutane, fluorocarbons such as HFCs, HFO-1123, or HFO-1234yf.

[0012] Cooler 4 corresponds to a heat exchanger that exchanges heat between the high-pressure refrigerant discharged from compressor 3 and a first fluid that is at a lower temperature than the high-pressure refrigerant. In cooler 4, the temperature of the first fluid rises as it is heated by the high-pressure refrigerant. The first fluid may be a liquid, such as water or other liquid heat transfer medium, or a gas, such as outdoor or indoor air. The refrigeration cycle system 1 may be equipped with a first fluid actuator (not shown), such as a pump or blower, for flowing the first fluid to cooler 4.

[0013] The pressure reducing device 5 expands the high-pressure refrigerant to convert it into a low-pressure refrigerant. The pressure reducing device 5 may also be an expansion valve with adjustable refrigerant passage opening. The low-pressure refrigerant that has passed through the pressure reducing device 5 becomes a two-phase gas-liquid state.

[0014] The evaporator 6 corresponds to a heat exchanger that exchanges heat between the low-pressure refrigerant, which has been reduced in pressure by the depressurization device 5, and a second fluid that is at a higher temperature than the low-pressure refrigerant. The refrigerant in the evaporator 6 evaporates by absorbing heat from the second fluid. The second fluid may be a gas, such as outdoor or indoor air, or a liquid, such as water or another liquid heat transfer medium. The refrigeration cycle system 1 may be equipped with a second fluid actuator (not shown), such as a blower or pump, for flowing the second fluid to the evaporator 6.

[0015] The refrigeration cycle system 1 may be used to heat a first fluid with a cooler 4, or to cool a second fluid with an evaporator 6. For example, the refrigeration cycle system 1 may be used in at least one of a heat pump hot water supply system, a heat pump heating system, or an air conditioning system.

[0016] The physical quantities related to the state of the refrigerant circuit 2 are hereinafter referred to as "related physical quantities". The measuring unit 7 corresponds to measuring means for measuring related physical quantities. The measuring unit 7 in the present embodiment measures the compressor current, which is the current that drives the electric motor included in the compressor 3, as a related physical quantity. The compressor current is correlated with the driving load of the compressor 3. The higher the pressure on the high-pressure side of the refrigerant circuit 2, the more likely the driving load of the compressor 3 is to increase, and the more likely the compressor current is to increase. Therefore, by using the compressor current as a related physical quantity, it becomes possible to appropriately determine the state of the refrigerant circuit 2.

[0017] The measuring unit 7 may measure the current that drives only the compressor 3 as the compressor current, or may measure the current that drives the compressor 3 and other devices (for example, the first fluid actuator, the second fluid actuator) as the compressor current. Since the current that drives the other device is smaller than the current that drives the compressor 3, it can be substantially ignored. In the case of alternating current, the measuring unit 7 may measure the effective value of the current as the compressor current.

[0018] The control unit 8 corresponds to control means for controlling the operation of the refrigeration cycle system 1. Each actuator and each sensor included in the refrigeration cycle system 1 are electrically connected to the control unit 8. The control unit 8 has a timer function for managing time. The control unit 8 may be communicable with a user interface device (not shown).

[0019] Each function of the control unit 8 may be realized by a processing circuit. The processing circuit of the control unit 8 may include at least one processor 8a and at least one memory 8b. At least one processor 8a may realize each function of the control unit 8 by reading and executing a program stored in at least one memory 8b. Each processing circuit of the control unit 8 may include at least one dedicated hardware. The configuration is not limited to being controlled by a single control unit 8 as in the illustrated example, and may be a configuration in which a plurality of control devices cooperate to control the operation.

[0020] The control unit 8 controls the operations of the compressor 3 and the decompression device 5. The control unit 8 may control, for example, by inverter control, so that the operating speed of the compressor 3 is variable. Further, the control unit 8 may control, for example, by inverter control, so that the operating speed of at least one of the first fluid actuator and the second fluid actuator is variable.

[0021] The decompression device 5 can be switched between a first decompression amount state and a second decompression amount state in which the decompression amount is smaller than the first decompression amount state. The first decompression amount state corresponds to, for example, a state where the opening degree of the decompression device 5 is small. The second decompression amount state corresponds to, for example, a state where the opening degree of the decompression device 5 is large.

[0022] The control unit 8 can execute a normal operation mode in which the refrigeration cycle operation by the refrigerant circuit 2 is performed. In the normal operation mode, it may be as follows. The control unit 8 may control the operating speed of the compressor 3 according to the target heating capacity or cooling capacity. The control unit 8 may adjust the opening degree of the decompression device 5 according to the temperature or pressure of the refrigerant discharged from the compressor 3. The control unit 8 may control the operating speed of the first fluid actuator according to at least one of the temperature of the first fluid flowing into the cooler 4 and the temperature of the first fluid flowing out of the cooler 4. The control unit 8 may control the operating speed of the second fluid actuator according to at least one of the temperature of the second fluid flowing into the evaporator 6 and the temperature of the second fluid flowing out of the evaporator 6.

[0023] When starting the operation of the refrigeration cycle, the control unit 8 executes an abnormality determination mode to detect an abnormality in the refrigerant circuit 2. In the abnormality determination mode, the control unit 8 operates the compressor 3 at a predetermined first speed. By keeping the operating speed of the compressor 3 constant, an abnormality in the refrigerant circuit 2 can be detected more appropriately. Further, in the abnormality determination mode, it is desirable that the control unit 8 keeps the operating speed of the first fluid actuator at a predetermined constant speed or stops the first fluid actuator, and it is desirable that the control unit 8 keeps the operating speed of the second fluid actuator at a predetermined constant speed or stops the second fluid actuator. By doing so, an abnormality in the refrigerant circuit 2 can be detected more appropriately.

[0024] Figure 2 is a flowchart showing an example of the processing performed by the control unit 8 in the abnormality detection mode. Figure 3 is a diagram showing an example of a graph of the time-dependent change of related physical quantities after the compressor 3 is started. In this embodiment, the time-dependent change of related physical quantities shown in Figure 3 corresponds to the time-dependent change of the compressor current. In Figure 3, the abnormality detection mode starts at time t0. The time when the operation of the compressor 3 is started can be considered as the time when the abnormality detection mode starts. In Figure 3, solid line 11 is a graph when the refrigerant circuit 2 is blocked, solid line 12 is a graph when the refrigerant circuit 2 is normal, and solid line 13 is a graph when the refrigerant in the refrigerant circuit 2 is leaking out. Figure 4 is a diagram showing an example of a graph of the time-dependent change of related physical quantities after the compressor 3 is started in a state where the drive load of the compressor 3 is likely to be high. In this embodiment, the time-dependent change of related physical quantities shown in Figure 4 corresponds to the time-dependent change of the compressor current. In Figure 4, the abnormality detection mode starts at time t0. The moment when the compressor 3 starts operating can be considered the moment when the abnormality detection mode starts. In Figure 4, solid line 16 is a graph of a state where the refrigerant circuit 2 is normal and the drive load of the compressor 3 is likely to be high, and solid line 17 is a graph of a state where the refrigerant circuit 2 is normal and the drive load of the compressor 3 is unlikely to be high. The drive load of the compressor 3 tends to be high when the refrigerant is not evenly distributed in the refrigerant circuit and is mostly distributed on the high-pressure side of the refrigerant circuit 2, and when the temperature of the compressor 3 is high when the abnormality detection mode starts.

[0025] As shown in Figure 2, when the refrigeration cycle starts operation, the control unit 8 first starts the abnormality detection mode. When the abnormality detection mode starts, the control unit 8 sets the pressure reducing device 5 to the first pressure reduction state (step S1). Next, the control unit 8 starts the compressor 3 and operates the compressor 3 at the first speed (step S2). Subsequently, the control unit 8 determines whether the first time has elapsed since the start of the abnormality detection mode (step S3), and if the first time has elapsed since the start of the abnormality detection mode, the measurement unit 7 measures the relevant physical quantity (step S4). The control unit 8 stores the value of this measured relevant physical quantity as the first measurement value PQ1. After that, the control unit 8 switches the pressure reducing device 5 from the first pressure reduction state to the second pressure reduction state (step S5).

[0026] After the pressure reducing device 5 is switched from the first pressure reduction state to the second pressure reduction state, the control unit 8 measures the relevant physical quantity using the measuring unit 7 (step S6). The control unit 8 stores the value of this measured relevant physical quantity as the second measurement value PQ2. The control unit 8 compares the value obtained by subtracting the first measurement value PQ1 from the second measurement value PQ2 with the first abnormality determination value (step S7). If the value obtained by subtracting the first measurement value PQ1 from the second measurement value PQ2 is greater than the first abnormality determination value, the control unit 8 determines that there is an abnormality in the refrigerant circuit 2 and stops the operation of the compressor 3 (step S8).

[0027] As shown in Figure 3, when the refrigerant circuit 2 is functioning normally, the value of the relevant physical quantity increases after the start of the abnormality detection mode, as shown by the solid line 12. The first time is set to be shorter than the time required for the value of the relevant physical quantity to stabilize when the refrigerant circuit 2 is functioning normally. For example, time t1 in Figure 3 may correspond to the first time. When the refrigerant circuit 2 is functioning normally, at time t1, after the first time has elapsed since the start of the abnormality detection mode, the value of the relevant physical quantity shown by the solid line 12 is still increasing. When the refrigerant circuit 2 is functioning normally, at time t2 in Figure 3, the increase in the value of the relevant physical quantity shown by the solid line 12 is nearing completion.

[0028] The dashed line 14 in Figure 3 is a graph showing the case when the pressure reducing device 5 is switched from the first pressure reduction state to the second pressure reduction state at time t1, assuming the refrigerant circuit 2 is functioning normally. The dashed line 15 in Figure 3 is a graph showing the case when the pressure reducing device 5 is switched from the first pressure reduction state to the second pressure reduction state at time t2, assuming the refrigerant circuit 2 is functioning normally. When the refrigerant circuit 2 is functioning normally, as shown by dashed line 14 or dashed line 15, when the pressure reducing device 5 is switched from the first pressure reduction state to the second pressure reduction state, the load on the compressor 3 decreases, and the value of the related physical quantity, the compressor current, decreases. Therefore, when the refrigerant circuit 2 is functioning normally, the second measured value PQ2 will be lower than the first measured value PQ1.

[0029] In contrast, if there is a blockage somewhere in the refrigerant circuit 2, the refrigerant downstream of the compressor 3 will stagnate even after the pressure reducing device 5 switches from the first pressure reduction state to the second pressure reduction state at time t1, causing the load on the compressor 3 to continue to increase. As a result, the value of the compressor current, which is a related physical quantity, will continue to rise. Therefore, in this case, the second measured value PQ2 will be higher than the first measured value PQ1. Thus, if the value obtained by subtracting the first measured value PQ1 from the second measured value PQ2 is greater than the first abnormality determination value, it is considered that the refrigerant circuit 2 is blocked. In this embodiment, the control unit 8 can determine that there is an abnormality in the refrigerant circuit 2 in this case and stop the operation of the compressor 3, thereby reliably protecting the refrigerant circuit 2.

[0030] In general, measuring instruments that measure physical quantities have variations in characteristics due to individual differences. Therefore, there is some error in the values ​​of the relevant physical quantities measured by the measuring unit 7. In addition, the values ​​of the relevant physical quantities change depending on the ambient temperature and other environmental conditions. If the measured value of the relevant physical quantity itself were compared with the abnormality judgment value, there is a possibility of misjudgment due to the influence of the variation in the measured value caused by the above factors. In contrast, in this embodiment, by comparing the value obtained by subtracting the first measured value PQ1 from the second measured value PQ2 with the first abnormality judgment value, the variation contained in the first measured value PQ1 and the variation contained in the second measured value PQ2 cancel each other out. Therefore, in this embodiment, the influence of the variation in the measured value is less likely to occur, and misjudgment can be reliably prevented.

[0031] Furthermore, in this embodiment, the control unit 8 can detect blockage of the refrigerant circuit 2 before the values ​​of the relevant physical quantities stabilize after the abnormality detection mode has started. Therefore, the abnormality detection mode can be terminated in a short amount of time.

[0032] Unlike this embodiment, if we assume a configuration where the abnormality of the refrigerant circuit 2 is detected only after the values ​​of the relevant physical quantities have stabilized, a long time will be required to determine the abnormality. In such a configuration, it is not possible to determine the abnormality during normal operation, and a dedicated mode must be provided. In such a configuration, it is only possible to determine the abnormality when there is a suspicion of an abnormality, and it is not possible to diagnose abnormalities in the refrigerant circuit 2 on a daily basis. In contrast, with this embodiment, the abnormality determination mode can be terminated in a short time, making it possible to diagnose abnormalities in the refrigerant circuit 2 on a daily basis.

[0033] In step S7 of Figure 2, if the value obtained by subtracting the first measurement value PQ1 from the second measurement value PQ2 is less than or equal to the first abnormality determination value, the control unit 8 proceeds to step S9 to determine whether the second time has elapsed since the start of the abnormality determination mode. The second time is longer than the first time. In step S9, if the second time has not yet elapsed since the start of the abnormality determination mode, the control unit 8 repeats the processing from step S6 onwards. That is, in step S6, the control unit 8 measures the relevant physical quantity again using the measurement unit 7 and stores the remeasured value as the second measurement value PQ2. In other words, the control unit 8 updates the second measurement value PQ2. Next, in step S7, the control unit 8 compares the value obtained by subtracting the first measurement value PQ1 from the updated second measurement value PQ2 with the first abnormality determination value again. If the value obtained by subtracting the first measurement value PQ1 from the second measurement value PQ2 is greater than the first abnormality determination value, the control unit 8 determines that there is an abnormality in the refrigerant circuit 2 and stops the operation of the compressor 3. Thus, when the control unit 8 is configured to repeatedly execute the processes of steps S6 and S7, the blockage of the refrigerant circuit 2 can be detected more reliably.

[0034] If, in step S9, the control unit 8 has already elapsed two hours since the start of the abnormality detection mode, it proceeds to step S10 and compares the value obtained by subtracting the second measurement value PQ2 from the first measurement value PQ1 with the second abnormality detection value. As mentioned above, if the refrigerant circuit 2 is normal, the second measurement value PQ2 will be lower than the first measurement value PQ1. Therefore, if the value obtained by subtracting the second measurement value PQ2 from the first measurement value PQ1 is greater than the second abnormality detection value, the refrigerant circuit 2 is considered to be normal. For this reason, if the control unit 8 finds in step S10 that the value obtained by subtracting the second measurement value PQ2 from the first measurement value PQ1 is greater than the second abnormality detection value, it proceeds to step S11 and terminates the abnormality detection mode to start the normal operation mode. In this way, if the control unit 8 is configured to compare the value obtained by subtracting the second measurement value PQ2 from the first measurement value PQ1 with the second abnormality detection value, it becomes possible to start the normal operation mode earlier. The second abnormality detection value is a value smaller than the first abnormality detection value.

[0035] If, in step S10, the control unit 8 determines whether the value obtained by subtracting the second measurement value PQ2 from the first measurement value PQ1 is less than or equal to the second abnormality determination value, it proceeds to step S12 to determine whether the third time has elapsed since the start of the abnormality determination mode. The third time is longer than the second time. For example, time t2 in Figure 3 may correspond to the third time. If, in step S12, the third time has not yet elapsed since the start of the abnormality determination mode, the control unit 8 repeats the process from step S6 onwards. If, in step S12, the third time has already elapsed since the start of the abnormality determination mode, the control unit 8 proceeds to step S13, increments the abnormality count by 1, and proceeds to step S14. If the cumulative count of the abnormality count exceeds a predetermined number of determinations, it determines that there is an abnormality in the refrigerant circuit 2 and stops the operation of the compressor 3. If the cumulative count of the abnormality count does not exceed the predetermined number of determinations, the control unit 8 proceeds to step S15, changes the pressure reducing device to the first pressure reduction state, and repeats the process from step S3 onwards again. When repeating the process from step S3 onward, the first, second, and third hours are not the time from the start of the abnormality detection mode, but rather the time from proceeding to step S15 and changing the depressurization device to the first depressurization state.

[0036] As shown by the solid line 13 in Figure 3, when refrigerant leaks out of refrigerant circuit 2, the load on compressor 3 is low, so the value of the related physical quantity is lower compared to when refrigerant circuit 2 is functioning normally. If refrigerant circuit 2 is functioning normally, when the pressure reducing device 5 is switched from the first pressure reduction state to the second pressure reduction state at time t2 in Figure 3, the value of the related physical quantity decreases as shown by the dashed line 15. In contrast, when refrigerant leaks out of refrigerant circuit 2, the load on compressor 3 does not change even when the pressure reducing device 5 is switched from the first pressure reduction state to the second pressure reduction state, so the value of the related physical quantity does not change. Therefore, when refrigerant leaks out of refrigerant circuit 2, the difference between the first measured value PQ1 and the second measured value PQ2 is small, so in step S10, the value obtained by subtracting the second measured value PQ2 from the first measured value PQ1 is less than or equal to the second abnormality judgment value.

[0037] The dashed lines 18 and 19 in Figure 4 are graphs representing the changes in related physical quantities when the pressure reducing device 5 is switched from the first pressure reduction state to the second pressure reduction state at time t3. The amount of change in related physical quantities differs depending on whether the compressor 3's drive load is likely to be high or low. To reliably detect abnormalities, the second abnormality judgment value should be set high, but if the second abnormality judgment value is set too high, there is a concern that refrigerant leakage may be falsely detected in the state where the compressor 3's drive load is unlikely to be high. Therefore, if the third time has elapsed since the start of the abnormality judgment mode in step S12, the processing from step S3 onwards is repeated again, and when the cumulative count of the number of abnormalities exceeds a predetermined number of judgments, the control unit 8 proceeds to step S16 and confirms the determination that refrigerant is leaking out of the refrigerant circuit 2. By equalizing the refrigerant distribution conditions in the refrigerant circuit 2 and the temperature conditions of the compressor 3, and eliminating the factors that cause fluctuations in the compressor 3's drive load, the control unit 8 can reliably detect that refrigerant is leaking out of the refrigerant circuit 2, and will not falsely detect refrigerant leakage in a normal state.

[0038] Embodiment 2. Next, Embodiment 2 will be described, focusing on the differences from Embodiment 1 described above, and the same or equivalent parts will be simplified or omitted.

[0039] This second embodiment differs from the first embodiment in that it uses compressor temperature as the relevant physical quantity instead of compressor current. The compressor temperature is the temperature of the compressor 3. The measuring unit 7 in this second embodiment measures the compressor temperature. The compressor temperature may also be, for example, the temperature of the shell of the compressor 3. In a high-pressure shell-type compressor 3, the inside of the shell is filled with high-pressure refrigerant before it is discharged from the compressor 3. The higher the pressure on the high-pressure side of the refrigerant circuit 2, the higher the drive load on the compressor 3 tends to be. And the higher the drive load on the compressor 3, the higher the compressor temperature tends to be. Therefore, by using the compressor temperature as the relevant physical quantity, it becomes possible to appropriately determine the state of the refrigerant circuit 2.

[0040] The change in compressor temperature over time after starting compressor 3 shows a similar trend to the graphs in Figures 3 and 4. In this embodiment 2, the control unit 8 performs the same processing as in embodiment 1 by using the compressor temperature value instead of the compressor current value in embodiment 1, thereby obtaining the same effect as in embodiment 1.

[0041] Embodiment 3. Next, Embodiment 3 will be described, focusing on the differences from Embodiment 1 described above, and the same or equivalent parts will be simplified or omitted.

[0042] This third embodiment differs from the first embodiment in that it uses the discharged refrigerant temperature as the relevant physical quantity instead of the compressor current. The discharged refrigerant temperature is the temperature of the refrigerant discharged from the compressor 3. The measuring unit 7 in this third embodiment measures the discharged refrigerant temperature.

[0043] The change in the discharge refrigerant temperature over time after the compressor 3 is started shows a trend similar to that of the graphs in Figures 3 and 4. In this embodiment 3, the control unit 8 performs the same processing as in embodiment 1 by using the value of the discharge refrigerant temperature instead of the value of the compressor current in embodiment 1, thereby obtaining the same effect as in embodiment 1.

[0044] Embodiment 4. Next, Embodiment 4 will be described with reference to Figures 5 and 6, focusing on the differences from Embodiment 1 described above, and simplifying or omitting the explanation of identical or equivalent parts.

[0045] Figure 5 is a flowchart showing an example of the processing performed by the control unit in the abnormality detection mode of Embodiment 4. Figure 6 is a diagram showing the refrigeration cycle system according to Embodiment 4.

[0046] This embodiment 4 differs from embodiment 1 in that the second abnormality determination value is determined from the temperature of the compressor 3, it is equipped with a second fluid actuator 9 as shown in Figure 6, and it does not perform accumulation of counts of abnormalities. As shown in Figure 5, when the abnormality determination mode starts, the control unit 8 sets the pressure reducing device 5 to the first pressure reduction state (step S21). Next, the control unit 8 starts the second fluid actuator 9 and operates it at the second speed (step S22), and after the first time has elapsed (step S23), the measurement unit 7 measures the compressor temperature (step S24) and determines the second abnormality determination value (step S25). The second abnormality determination value is set to second abnormality determination value a if the compressor temperature is below the threshold, and to second abnormality determination value b which is higher than second abnormality determination value a if the compressor temperature is above the threshold. After that, the refrigerant circuit abnormality is determined in the same procedure as in embodiment 1, and the refrigerant circuit abnormality (refrigerant leak) is determined without accumulating counts of abnormalities.

[0047] After step S25, the control unit 8 starts the compressor 3 and operates the compressor 3 at the first speed (step S26). Next, the control unit 8 determines whether the second time has elapsed since the start of the abnormality determination mode (step S27), and if the second time has elapsed since the start of the abnormality determination mode, the measurement unit 7 measures the relevant physical quantity (step S28). The control unit 8 stores the value of this measured relevant physical quantity as the first measurement value PQ1. After that, the control unit 8 switches the pressure reducing device 5 from the first pressure reduction state to the second pressure reduction state (step S29).

[0048] After the pressure reducing device 5 is switched from the first pressure reduction state to the second pressure reduction state, the control unit 8 measures the relevant physical quantity using the measuring unit 7 (step S30). The control unit 8 stores the value of this measured relevant physical quantity as the second measurement value PQ2. The control unit 8 compares the value obtained by subtracting the first measurement value PQ1 from the second measurement value PQ2 with the first abnormality determination value (step S31). If the value obtained by subtracting the first measurement value PQ1 from the second measurement value PQ2 is greater than the first abnormality determination value, the control unit 8 determines that there is an abnormality in the refrigerant circuit 2 and stops the operation of the compressor 3 (step S32).

[0049] In step S31, if the value obtained by subtracting the first measurement value PQ1 from the second measurement value PQ2 is less than or equal to the first abnormality determination value, the control unit 8 proceeds to step S33 to determine whether the third time has elapsed since the start of the abnormality determination mode. The third time is longer than the second time. In step S33, if the third time has not yet elapsed since the start of the abnormality determination mode, the control unit 8 repeats the processing from step S30 onwards. That is, in step S30, the control unit 8 measures the relevant physical quantity again using the measurement unit 7 and stores the remeasured value as the second measurement value PQ2. In other words, the control unit 8 updates the second measurement value PQ2. Next, in step S31, the control unit 8 compares the value obtained by subtracting the first measurement value PQ1 from the updated second measurement value PQ2 with the first abnormality determination value again. If the value obtained by subtracting the first measurement value PQ1 from the second measurement value PQ2 is greater than the first abnormality determination value, the control unit 8 determines that there is an abnormality in the refrigerant circuit 2 and stops the operation of the compressor 3.

[0050] If, in step S33, the third time has already elapsed since the start of the abnormality determination mode, the control unit 8 proceeds to step S34 and compares the value obtained by subtracting the second measurement value PQ2 from the first measurement value PQ1 with the second abnormality determination value. As mentioned above, if the refrigerant circuit 2 is normal, the second measurement value PQ2 will be lower than the first measurement value PQ1. Therefore, if the value obtained by subtracting the second measurement value PQ2 from the first measurement value PQ1 is greater than the second abnormality determination value, the refrigerant circuit 2 is considered to be normal. For this reason, if the value obtained by subtracting the second measurement value PQ2 from the first measurement value PQ1 is greater than the second abnormality determination value in step S34, the control unit 8 proceeds to step S35, ends the abnormality determination mode, and starts the normal operation mode.

[0051] If, in step S34, the control unit 8 determines that the value obtained by subtracting the second measurement value PQ2 from the first measurement value PQ1 is less than or equal to the second abnormality determination value, it proceeds to step S36 to determine whether the fourth time has elapsed since the start of the abnormality determination mode. The fourth time is longer than the third time. If, in step S36, the fourth time has not yet elapsed since the start of the abnormality determination mode, the control unit 8 repeats the processing from step S30 onward. If, in step S34, the fourth time has already elapsed since the start of the abnormality determination mode, the control unit 8 proceeds to step S37, determines that there is an abnormality in the refrigerant circuit 2 due to refrigerant leakage, and stops the operation of the compressor 3.

[0052] The drive load of compressor 3 tends to increase when the abnormality detection mode is activated, if the refrigerant is not evenly distributed in the refrigerant circuit and is concentrated on the high-pressure side of refrigerant circuit 2, and when the temperature of compressor 3 is high. When the second fluid actuator 9 is operated, the temperature and pressure of the refrigerant in evaporator 6 rise due to heat exchange with the outside air, and the volume of refrigerant in evaporator 6 decreases. As a result, the refrigerant distributed on the high-pressure side flows into evaporator 6, and the refrigerant is evenly distributed in the refrigerant circuit. Once the influence of the refrigerant distribution in the refrigerant circuit is eliminated, the likelihood of the drive load of compressor 3 increasing depends on the temperature of compressor 3. Therefore, by determining the second abnormality detection value based on the temperature of compressor 3, it is possible to reliably detect refrigerant leakage in refrigerant circuit 2, and to prevent false detection of refrigerant leakage under normal conditions.

[0053] For example, the control described above takes into account a situation where compressor 3 stops immediately after startup due to a power outage or the like, and then restarts. When compressor 3 stops immediately after startup, the refrigerant is mostly distributed to the high-pressure side of refrigerant circuit 2 due to the operation of compressor 3, but the temperature of compressor 3 may be low. The ease with which the drive load of compressor 3 increases differs depending on whether the refrigerant is mostly distributed to the high-pressure side of refrigerant circuit 2 or evenly distributed within refrigerant circuit 2. Therefore, in addition to determining the second abnormality judgment value from the compressor temperature, it is necessary to operate the second fluid actuator 9 to eliminate fluctuations in the compressor drive load due to the distribution of refrigerant in the refrigerant circuit.

[0054] By maintaining a constant operating speed for the second fluid actuator 9, abnormalities in the refrigerant circuit 2 can be detected more appropriately. The second abnormality detection value b is set to a smaller value than the first abnormality detection value.

[0055] The second abnormality detection value may be configured to be determined from the temperature of the refrigerant discharged from the compressor 3. In this case as well, the same effect as described above can be obtained. [Explanation of symbols]

[0056] 1 Refrigeration cycle system, 2 Refrigerant circuit, 3 Compressor, 4 Cooler, 5 Pressure reducing device, 6 Evaporator, 7 Measurement unit, 8 Control unit, 8a Processor, 8b Memory, 9 Second fluid actuator, 11,12,13,16,17 Solid lines, 14,15,18,19 Dashed lines

Claims

1. A compressor that compresses the refrigerant, A cooler for cooling the refrigerant compressed by the compressor, A pressure reducing device for reducing the pressure of the refrigerant that has passed through the cooler, A refrigerant circuit having an evaporator that evaporates the refrigerant that has passed through the pressure reducing device, A measuring means for measuring a related physical quantity which is a physical quantity related to the state of the refrigerant circuit, A control means that executes an abnormality determination mode to detect an abnormality in the refrigerant circuit when starting the operation of the refrigeration cycle using the refrigerant circuit, Equipped with, The pressure reducing device is switchable between a first pressure reduction state and a second pressure reduction state in which the pressure reduction is smaller than that of the first pressure reduction state. When the abnormality detection mode is started, the control means sets the pressure reducing device to the first pressure reduction state and operates the compressor at the first speed. The control means is After the first hour has elapsed since the start of the abnormality determination mode, the measurement means measures the value of the relevant physical quantity as the first measured value, and then the depressurization device is switched from the first depressurization state to the second depressurization state. After the pressure reducing device is switched from the first pressure reduction state to the second pressure reduction state, the value of the related physical quantity is measured by the measuring means as the second measured value. If the value obtained by subtracting the first measurement value from the second measurement value is greater than the first abnormality determination value, it is determined that there is an abnormality in the refrigerant circuit, and the operation of the compressor is stopped. If the value obtained by subtracting the first measurement value from the second measurement value is less than or equal to the first abnormality judgment value, and the value obtained by subtracting the second measurement value from the first measurement value is less than or equal to the second abnormality judgment value which is smaller than the first abnormality judgment value, then it is counted as an abnormality, the pressure reducing device is returned to the first pressure reduction state, and then the operation of the compressor is continued by returning to the start of the abnormality judgment mode. A refrigeration cycle system configured to determine that there is an abnormality in the refrigerant circuit and to stop the operation of the compressor when the cumulative count of the number of abnormalities exceeds a predetermined number of determinations.

2. The refrigeration cycle system according to claim 1, wherein the measuring means measures the current driving the compressor as the relevant physical quantity.

3. The refrigeration cycle system according to claim 1, wherein the measuring means measures the temperature of the compressor as the relevant physical quantity.

4. The refrigeration cycle system according to claim 1, wherein the measuring means measures the temperature of the refrigerant discharged from the compressor as the relevant physical quantity.

5. A compressor that compresses the refrigerant, A cooler for cooling the refrigerant compressed by the compressor, A pressure reducing device for reducing the pressure of the refrigerant that has passed through the cooler, An evaporator for evaporating the refrigerant that has passed through the pressure reducing device, A refrigerant circuit having a fluid actuator that flows air through the evaporator, A measuring means for measuring a related physical quantity which is a physical quantity related to the state of the refrigerant circuit, A control means that executes an abnormality determination mode to detect an abnormality in the refrigerant circuit when starting the operation of the refrigeration cycle using the refrigerant circuit, Equipped with, The pressure reducing device is switchable between a first pressure reduction state and a second pressure reduction state in which the pressure reduction is smaller than that of the first pressure reduction state. When the abnormality detection mode is started, the control means sets the pressure reducing device to the first pressure reduction state and operates the fluid actuator at the second speed. After the first hour has elapsed since the start of the abnormality detection mode, the compressor temperature is measured, and then the compressor is operated at the first speed. The control means is After the second time has elapsed since the start of the abnormality determination mode, the measurement means measures the value of the relevant physical quantity as the first measured value, and then the depressurization device is switched from the first depressurization state to the second depressurization state. After the pressure reducing device is switched from the first pressure reduction state to the second pressure reduction state, the value of the related physical quantity is measured by the measuring means as the second measured value. If the value obtained by subtracting the first measurement value from the second measurement value is greater than the first abnormality determination value, it is determined that there is an abnormality in the refrigerant circuit, and the operation of the compressor is stopped. If the value obtained by subtracting the first measurement value from the second measurement value is less than or equal to the first abnormality judgment value, and the value obtained by subtracting the second measurement value from the first measurement value is less than or equal to the second abnormality judgment value which is smaller than the first abnormality judgment value, then the operation of the compressor shall be stopped. A refrigeration cycle system configured such that the second abnormality determination value is determined from the compressor temperature measured at the time the first time has elapsed since the start of the abnormality determination mode.

6. The refrigeration cycle system according to claim 5, wherein the second abnormality determination value is determined from the temperature of the refrigerant discharged from the compressor.

7. The refrigeration cycle system according to claim 5, wherein the measuring means measures the current driving the compressor as the relevant physical quantity.

8. The refrigeration cycle system according to claim 5, wherein the measuring means measures the temperature of the compressor as the relevant physical quantity.

9. The refrigeration cycle system according to claim 5, wherein the measuring means measures the temperature of the refrigerant discharged from the compressor as the relevant physical quantity.

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