Refrigeration cycle device

Abstract

This refrigeration cycle device comprises: a refrigerant circuit; a low-pressure sensor; and a control device. The refrigerant circuit includes a compressor. The low-pressure sensor measures a low pressure, which is the pressure of a refrigerant sucked into the compressor. In a start-stop repetition period, which is a period during which the compressor repeats starting and stopping, the control device executes an upper limit adjustment process for adjusting an upper limit operation frequency of the compressor in a first period, which is a period until the compressor stops after starting. If a first reduction condition and a second reduction condition are satisfied, the control device reduces the upper limit operation frequency in the first period to below an upper limit operation frequency in the preceding period in the start-stop repetition period. If the number of executions of upper limit reduction control reaches a threshold number, the control device stops the upper limit reduction control, such that the upper limit operation frequency in the first period is equal to the upper limit operation frequency in the preceding period. The preceding period is a period from the starting to the stopping of the compressor immediately before the first period. The first reduction condition is a condition that the speed of change of the low pressure in the preceding period is at least a first pressure change speed. The second reduction condition is a condition that the low pressure in the preceding period falls below a target low pressure, and the absolute value of the difference between the low pressure in the preceding period and a target low pressure is greater than the value of a first pressure difference.

Description

Refrigeration Cycle Equipment

[0001] The present disclosure relates to a refrigeration cycle device including a compressor with a variable operating frequency.

[0002] Conventionally, there are refrigeration cycle devices in which the start and stop of a compressor is controlled based on the measured low-pressure pressure. In such refrigeration cycle devices, abrupt changes in the low-pressure pressure can cause the compressor to repeatedly start and stop in a short period of time. Specifically, while the compressor is stopped, the low-pressure pressure, which is the pressure of the refrigerant drawn into the compressor, increases. Then, when the compressor starts, and immediately thereafter, if the load is light and the compressor operates at its upper limit operating frequency, the low-pressure pressure drops rapidly. Then, when the low-pressure pressure value falls below a set low-pressure cutoff value, the compressor stops again. In this way, the compressor may repeatedly start and stop under low load conditions. This increases the compressor's power consumption and shortens its lifespan.

[0003] Here, Patent Document 1 discloses a refrigeration cycle device that quickly obtains the required refrigeration capacity by determining the operating frequency of the compressor based on information such as the low-pressure pressure, the rate of change of the low-pressure pressure, and the deviation between the target low-pressure pressure and the low-pressure pressure. According to the refrigeration cycle device described in Patent Document 1, when the required refrigeration capacity is small, the operating frequency of the compressor is reduced by control based on the low-pressure pressure, etc., making it possible to reduce the frequency of starting and stopping the compressor.

[0004] Japanese Patent Application Laid-Open No. 2008-39200

[0005] However, when the load is low, excessively lowering the operating frequency of the compressor at startup may actually increase the amount of power consumed by the compressor.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a refrigeration cycle device that reduces the frequency of starting and stopping the compressor while reducing the amount of power consumed by the compressor.

[0007] A refrigeration cycle apparatus according to the present disclosure includes a refrigerant circuit in which a compressor, a heat source heat exchanger, an expansion valve, and a load heat exchanger are sequentially connected by refrigerant piping to circulate a refrigerant; a low-pressure pressure sensor that measures a low-pressure pressure that is the pressure of the refrigerant drawn into the compressor; and a control device that executes upper limit adjustment processing to adjust an upper limit operating frequency of the compressor in a first period that is a period from when the compressor is started to when the compressor is stopped during a start-stop repeating period in which the compressor repeatedly starts and stops, and when a first reduction condition and a second reduction condition are satisfied, the control device performs upper limit reduction control to reduce the upper limit operating frequency in the first period to be lower than the upper limit operating frequency in a preceding period of the start-stop repeating period. and when the number of times the upper limit reduction control has been executed reaches a predetermined threshold number of times, the upper limit reduction control is stopped and the upper limit operating frequency in the first period is made equal to the upper limit operating frequency in the preceding period, the preceding period being a period from when the compressor is started immediately before the first period to when it is stopped, the first reduction condition being a condition that the rate of change of the low-pressure pressure in the preceding period is equal to or greater than a predetermined first rate of pressure change, and the second reduction condition being a condition that the low-pressure pressure in the preceding period is lower than a predetermined target low-pressure pressure and the absolute value of the difference between the low-pressure pressure in the preceding period and the target low-pressure pressure is greater than a predetermined first pressure difference value.

[0008] According to the refrigeration cycle apparatus of the present disclosure, when the first reduction condition and the second reduction condition are satisfied, the control device lowers the upper limit operating frequency of the compressor in the first period below the upper limit operating frequency of the compressor in the preceding period. This reduces the frequency of on / off switching of the compressor. When the number of executions of the upper limit reduction control reaches a threshold number, the control device does not lower the upper limit operating frequency of the compressor in the first period below the upper limit operating frequency of the compressor in the preceding period, but sets it equal to the upper limit operating frequency in the preceding period. This makes it possible to suppress an increase in the amount of power consumed by the compressor due to a decrease in compressor operating efficiency. Therefore, the refrigeration cycle apparatus can achieve both a reduction in the frequency of on / off switching of the compressor and a reduction in the amount of power consumed by the compressor.

[0009] 1 is a refrigerant circuit diagram schematically showing an example of the configuration of a refrigeration cycle device 100 according to an embodiment; FIG. 2 is a diagram illustrating an example of a change over time in the operating frequency of a compressor of a refrigeration cycle device according to a comparative example when the compressor is under low load; FIG. 3 is a diagram illustrating an example of a change over time in the amount of power consumed by a compressor of a refrigeration cycle device according to a comparative example when the compressor is under low load; FIG. 4 is a diagram illustrating an example of a change over time in the internal temperature of a refrigeration cycle device according to a comparative example when the compressor is under low load; FIG. 5 is a diagram for explaining reduction conditions according to an embodiment; FIG. 6 is a diagram illustrating an example of an operating frequency of a compressor controlled by a control device according to an embodiment; and FIG. 7 is a flowchart illustrating an example of a flow of an upper limit adjustment process by a control device according to an embodiment.

[0010] Hereinafter, a refrigeration cycle apparatus according to an embodiment will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the following embodiment, and various modifications can be made without departing from the spirit and scope of the present disclosure.

[0011] 1 is a refrigerant circuit diagram schematically illustrating an example configuration of a refrigeration cycle apparatus 100 according to an embodiment. The refrigeration cycle apparatus 100 includes a heat source apparatus 1 and a load apparatus 2. The heat source apparatus 1 includes a compressor 10, a heat source heat exchanger 11, and a control device 12 in a first housing 1A that forms an outer shell. The load apparatus 2 includes an expansion valve 20 and a load heat exchanger 21 in a second housing 2A that forms the outer shell. The compressor 10, the heat source heat exchanger 11, the expansion valve 20, and the load heat exchanger 21 are sequentially connected by refrigerant piping 3 through which a refrigerant flows, forming a refrigerant circuit 4 through which the refrigerant circulates. The expansion valve 20 may be provided in the first housing 1A of the heat source apparatus 1 instead of the load apparatus 2, or may be provided external to the heat source apparatus 1 and the load apparatus 2.

[0012] The compressor 10 is a scroll, rotary, reciprocating, screw, or other type of compressor, and is an inverter compressor whose capacity can be controlled by an inverter. The compressor 10 draws in low-temperature, low-pressure gas refrigerant from the refrigerant pipe 3, compresses it, and discharges it into the refrigerant pipe 3 as high-temperature, high-pressure gas refrigerant. The refrigerant discharged from the compressor 10 flows into the heat source heat exchanger 11.

[0013] The heat source heat exchanger 11 is, for example, a fin-tube heat exchanger, and performs heat exchange between the refrigerant and air supplied by a heat source blower (not shown), including a fan, to cool and condense the refrigerant. The heat source heat exchanger 11 may be an air-cooled heat exchanger or a water-cooled heat exchanger, such as a plate heat exchanger. In this case, the heat source heat exchanger 11 performs heat exchange between the refrigerant and water supplied by a water pump (not shown). The refrigerant from the compressor 10 becomes a low-temperature, high-pressure liquid refrigerant in the heat source heat exchanger 11, flows out of the heat source heat exchanger 11, and then flows to the expansion valve 20.

[0014] The expansion valve 20 is, for example, an electronic expansion valve whose opening degree is adjustable. The expansion valve 20 reduces the pressure of the liquid refrigerant from the heat source heat exchanger 11 to expand it. The liquid refrigerant reduced in pressure by the expansion valve 20 flows to the load heat exchanger 21.

[0015] The load heat exchanger 21 is, for example, a fin-tube heat exchanger, and performs heat exchange between air in a target space supplied by a load blower (not shown) including a fan and the refrigerant from the expansion valve 20, thereby evaporating the refrigerant. In the embodiment, the target space will be described as an interior space of a refrigerator, freezer, or the like. In the load heat exchanger 21, the refrigerant absorbs heat from the air inside the compartment and cools the air. The refrigerant flowing out of the load heat exchanger 21 flows to the compressor 10.

[0016] The refrigeration cycle apparatus 100 includes a low-pressure pressure sensor 5 that measures the low-pressure pressure, which is the pressure of the refrigerant drawn into the compressor 10. The low-pressure pressure sensor 5 is provided in the refrigerant pipe 3 on the side where the compressor 10 draws the refrigerant. In addition to the low-pressure pressure sensor 5, the refrigeration cycle apparatus 100 also includes sensors (not shown) that measure various physical quantities. Hereinafter, the multiple sensors in the refrigeration cycle apparatus 100, including the low-pressure pressure sensor 5, may be referred to as a sensor group. Examples of sensors included in the sensor group include a refrigerant temperature sensor, a compressor temperature sensor, and a current sensor. The refrigerant temperature sensor measures the temperature of the refrigerant drawn into the compressor 10. The compressor sensor measures the temperature of the housing of the compressor 10 or the temperature of refrigeration oil remaining in the housing of the compressor 10. The current sensor detects overcurrent.

[0017] The control device 12 controls the operating frequency of the compressor 10 and the opening degree of the expansion valve 20 based on the measurement results of all or some of the sensors in the sensor group. The control device 12 can be configured with a central processing unit (CPU) 12A, a memory 12B, and an input / output interface circuit (not shown) for inputting and outputting various signals. The memory 12B includes a read-only memory (ROM) and a random access memory (RAM). The ROM stores a program that describes the processing procedures of the control device 12. The CPU 12A loads and executes the program in the RAM, causing the control device 12 to perform various processes, such as control of the compressor 10. Some or all of the functions of the control device 12 may be achieved by dedicated hardware such as a complex programmable logic device (CPLD), a field programmable gate array (FPGA), or an application specific integrated circuit (ASIC).

[0018] Here, in the past, when a compressor was started, the low-pressure pressure would suddenly change, causing the compressor to start and stop repeatedly within a short period of time. Specifically, the low-pressure pressure would first rise while the compressor was stopped. Then, immediately after the compressor started, if the load was so light that the compressor operated at its upper limit operating frequency, the low-pressure pressure would suddenly drop. When the low-pressure pressure value fell below the set low-pressure cutoff value, the compressor stopped again, causing the compressor to start and stop repeatedly within a short period of time. The repeated start and stop of the compressor increased the compressor's power consumption and shortened its lifespan.

[0019] To reduce the number of compressor starts and stops, methods such as reducing the compressor's operating frequency can be used when the refrigeration capacity required by the load device is low. However, reducing the compressor's operating frequency too much can reduce the compressor's operating efficiency and increase the amount of power consumed by the compressor 10. Furthermore, after the compressor is started, the difference between the internal temperature (the temperature of the air inside the refrigerator that exchanges heat with the load heat exchanger 21) and the target internal temperature (the target internal temperature) can become large. Below, with reference to Figures 2 to 4, we will explain the operating conditions of the refrigeration cycle device for each compressor operating frequency when the required refrigeration capacity is low. Figure 2 illustrates the time variation of the operating frequency of the compressor of a comparative example when the compressor is operating at a low load. Figure 3 illustrates the time variation of the power consumption of the compressor of a comparative example when the compressor is operating at a low load. Figure 4 illustrates the time variation of the internal temperature of a comparative example when the compressor is operating at a low load.

[0020] Fig. 2(a) shows the change over time of the operating frequency of the compressor when the upper limit of the operating frequency of the compressor is set to 100 [Hz], Fig. 2(b) shows the change over time of the operating frequency of the compressor when the upper limit of the operating frequency of the compressor is set to 55 [Hz], and Fig. 2(c) shows the change over time of the operating frequency of the compressor when the upper limit of the operating frequency of the compressor is set to 40 [Hz].

[0021] As shown in Figure 2A, when the upper limit operating frequency of the compressor is 100 Hz, the time from start to stop of the compressor is approximately 5.1 min. The compressor starts and stops eight times between 0 min, when the compressor is first started, and 60 min. As shown in Figure 2B, when the upper limit operating frequency of the compressor is 55 Hz, the time from start to stop of the compressor is approximately 7.4 min. The compressor starts and stops six times between 0 min and 60 min. As shown in Figure 2C, when the upper limit operating frequency of the compressor is 40 Hz, the time from start to stop of the compressor is approximately 36.1 min. The compressor stops once, starts again, and then stops again between 0 min and 60 min. Therefore, when the upper limit operating frequency of the compressor is the minimum of 40 [Hz] among 40 [Hz], 55 [Hz], and 100 [Hz], the number of starts and stops of the compressor is minimum, and when it is the maximum of 100 [Hz], the number of starts and stops of the compressor is maximum. Therefore, it is estimated that under low load, the number of starts and stops of the compressor will increase as the upper limit operating frequency of the compressor is higher.

[0022] Fig. 3(a) shows the change over time in the amount of power consumed by the compressor 10 when the upper limit of the operating frequency of the compressor is set to 100 Hz. Fig. 3(b) shows the change over time in the amount of power consumed by the compressor 10 when the upper limit of the operating frequency of the compressor is set to 55 Hz. Fig. 3(c) shows the change over time in the amount of power consumed by the compressor 10 when the upper limit of the operating frequency of the compressor is set to 40 Hz.

[0023] As shown in Fig. 3A, when the upper limit operating frequency of the compressor is 100 Hz, the power consumption from 0 min to 60 min is 3.694 kWh. As shown in Fig. 3B, when the upper limit operating frequency of the compressor is 55 Hz, the power consumption from 0 min to 60 min is 3.196 kWh. As shown in Fig. 3C, when the upper limit operating frequency of the compressor is 40 Hz, the power consumption from 0 min to 60 min is 3.339 kWh. That is, when the upper limit operating frequency of the compressor is 55 Hz among 40 Hz, 55 Hz, and 100 Hz, the power consumption of the compressor 10 is minimum when the upper limit operating frequency is 55 Hz, and maximum when the upper limit operating frequency is 100 Hz. From this, it is presumed that, under low load, the power consumption of a compressor operating at an upper limit operating frequency higher than a reference upper limit operating frequency such as 55 Hz will be greater than the power consumption of a compressor operating at the reference upper limit operating frequency. It is also presumed that the power consumption of a compressor operating at an upper limit operating frequency lower than the reference will be greater than the power consumption of a compressor operating at the reference upper limit operating frequency.

[0024] Figure 4(a) shows the change in the temperature inside the refrigerator over time when the upper limit operating frequency of the compressor is set to 100 [Hz]. Figure 4(b) shows the change in the temperature inside the refrigerator over time when the upper limit operating frequency of the compressor is set to 55 [Hz]. Figure 4(c) shows the change in the temperature inside the refrigerator over time when the upper limit operating frequency of the compressor is set to 40 [Hz]. In the example shown in Figure 4, the target temperature inside the refrigerator is -24 [°C].

[0025] As shown in (a) of FIG. 4, when the upper limit operating frequency of the compressor is 100 [Hz], the peak internal temperature from 0 [min] to 60 [min] is approximately −21.6 [°C], and the internal temperature difference at that time is 2.4 [°C]. The internal temperature difference is the difference between the internal temperature and the target internal temperature. As shown in (b) of FIG. 4, when the upper limit operating frequency of the compressor is 55 [Hz], the peak internal temperature from 0 [min] to 60 [min] is approximately −21.4 [°C], and the internal temperature difference at that time is 2.6 [°C]. As shown in (c) of FIG. 4, when the upper limit operating frequency of the compressor is 40 [Hz], the peak internal temperature from 0 [min] to 60 [min] is approximately −20.6 [°C], and the internal temperature difference at that time is 3.4 [°C]. Therefore, when the upper limit operating frequency of the compressor is the minimum of 40 Hz, 55 Hz, and 100 Hz, the peak temperature inside the refrigerator is the highest, resulting in a large temperature difference inside the refrigerator. Also, when the upper limit operating frequency of the compressor is the maximum of 100 Hz, the peak temperature inside the refrigerator is the lowest, resulting in a small temperature difference inside the refrigerator. Therefore, under low load conditions, the lower the upper limit operating frequency of the compressor, the larger the temperature difference inside the refrigerator, potentially failing to meet user needs.

[0026] In the embodiment, the control device 12 performs an upper limit adjustment process to adjust the upper limit operating frequency of the compressor 10 immediately after startup during low load operation. The upper limit adjustment process will be described in detail below. When the compressor 10 repeatedly starts and stops, the control device 12 determines whether a first reduction condition and a second reduction condition are satisfied. If the first reduction condition and the second reduction condition are satisfied, the control device 12 executes upper limit reduction control to reduce the upper limit operating frequency of the compressor 10 during the first period to a value lower than the upper limit operating frequency of the compressor 10 during the preceding period. Here, the first period refers to a period during the on-stop repeating period from startup to shutdown of the compressor 10. The preceding period refers to a period during the on-stop repeating period from startup of the compressor 10 immediately before the first period to shutdown of the compressor 10. The on-stop repeating period refers to a period during which the compressor 10 repeatedly starts and stops. Note that the preceding period precedes the first period, and the first period excludes the period during the on-stop repeating period from the initial startup of the compressor 10 to shutdown. The first reduction condition is a condition that the rate of change of the low pressure in the preceding period is equal to or greater than a first pressure change rate. The second reduction condition is a condition that the low pressure in the preceding period is lower than the target low pressure, and the absolute value of the difference between the low pressure in the preceding period and the target low pressure is greater than a first pressure difference. Note that the first pressure change rate and the first pressure difference are physical quantities based on both or either the target low pressure and the low pressure cutoff value, and are determined in advance by experiment or the like. Hereinafter, the combination of the first reduction condition and the second reduction condition may also be referred to as a reduction condition.

[0027] When the reduction condition is not satisfied, the control device 12 equalizes the upper limit operating frequency of the compressor 10 in the first period to the upper limit operating frequency of the compressor 10 in the preceding period. Even when the reduction condition is satisfied, when the amount of power consumed by the compressor 10 from the start of the upper limit adjustment process becomes equal to or exceeds a predetermined first amount of power, the control device 12 equalizes the upper limit operating frequency of the compressor 10 in the first period to the upper limit operating frequency of the compressor 10 in the preceding period. Hereinafter, control of equalizing the upper limit operating frequency of the compressor 10 in the first period to the upper limit operating frequency of the compressor 10 in the preceding period, that is, control of operating the compressor 10 by equalizing the upper limit operating frequency in the first period to the upper limit operating frequency in the preceding period, may also be referred to as upper limit maintenance control.

[0028] The control device 12 performs a process of determining whether a reduction condition is satisfied, a process of determining whether the power consumption is equal to or greater than a first power amount, and upper limit reduction control or upper limit maintenance control until at least one of the following first and second termination conditions is satisfied. Here, the first termination condition is a condition that the control device 12 continuously performs the upper limit reduction control for a predetermined first specified termination time. The second termination condition is a condition that a predetermined second specified termination time has elapsed since the control device 12 started the upper limit adjustment process or since the compressor 10 was first started by a user's operation on the refrigeration cycle apparatus 100. Note that the upper limit adjustment process refers to a process that includes a process of determining whether a reduction condition is satisfied, a process of determining whether the power consumption is equal to or greater than a first power amount, and upper limit reduction control or upper limit maintenance control.

[0029] In this embodiment, the control device 12 determines the upper limit operating frequency to be reduced in the upper limit reduction control based on the following equation (1): Fmax = Fmax_o - (Fmax_o × 0.1 × C) (1) Here, Fmax is the upper limit operating frequency of the compressor 10 during the first period, and Fmax_o is the upper limit operating frequency at the time of shipment of the refrigeration cycle apparatus 100. If the number of changes, which is the number of times the control device 12 reduces the upper limit operating frequency of the compressor 10, is equal to or less than a predetermined threshold number, C is the number of changes. On the other hand, if the number of changes exceeds the threshold number, C is the threshold number. Note that C may be any value other than the number of changes and the threshold number. Here, the threshold number may be determined based on the power consumption, for example, by experimentation or learning. Specifically, the threshold number may be determined by learning the number of changes at which the power consumption becomes equal to or greater than a first amount of power. In this case, the process of determining whether the power consumption amount is equal to or greater than the first power amount in the upper limit adjustment process may be replaced with a process of determining whether the number of changes is equal to or greater than the threshold number. Note that, hereinafter, the process by which the control device 12 determines the upper limit operating frequency of the compressor 10 may also be referred to as an upper limit determination process. The process by which the control device 12 determines the upper limit operating frequency of the compressor 10 based on equation (1) is an example of the upper limit determination process.

[0030] The reduction conditions will be described in detail below with reference to FIG. 5 . FIG. 5 is a diagram for explaining the reduction conditions according to an embodiment. In FIG. 5 , the horizontal axis represents the target evaporation temperature of the refrigerant in the load heat exchanger 21, and the vertical axis represents the temperature. The dashed line α in FIG. 5 has a slope of 1 and represents the target evaporation temperature. The solid line β in FIG. 5 represents the evaporation temperature of the refrigerant in the load heat exchanger 21. This evaporation temperature is obtained from the measurement results of the low-pressure pressure sensor 5. The target evaporation temperature is uniquely determined by the target low-pressure pressure. The dashed-dotted line γ in FIG. 5 represents the evaporation temperature of the refrigerant at the above-mentioned low-pressure cutoff value. Hereinafter, the evaporation temperature of the refrigerant at the low-pressure cutoff value may also be referred to as the cutoff temperature.

[0031] The first reduction condition is equivalent to a condition that the evaporation temperature of the refrigerant in the load heat exchanger 21 decreases by a first temperature or more within a first specified time period after the compressor 10 is started during the advance period. The first specified time period is determined in advance through experiments or the like, e.g., 7 minutes. The first temperature is a quantity determined based on the product of the first temperature change rate and the first specified time period. The first temperature change rate is determined from the first pressure change rate. The first temperature illustrated in FIG. 5 is 20°C when the target evaporation temperature is equal to or greater than −45°C and less than −5°C. The first temperature illustrated in FIG. 5 is 25°C higher than the target evaporation temperature when the target evaporation temperature is equal to or greater than −5°C and less than 10°C, and is 35°C when the target evaporation temperature is, for example, 10°C.

[0032] The second reduction condition is equivalent to a condition that the evaporation temperature of the refrigerant in the load heat exchanger 21 during the preceding period is lower than the target evaporation temperature, and the absolute value of the difference between the evaporation temperature and the target evaporation temperature is greater than a predetermined first temperature difference. The first temperature difference is determined from the first pressure difference. The first temperature difference is, for example, 5°C.

[0033] The evaporation temperature under the first and second reduction conditions may be replaced with the internal temperature. That is, the first reduction condition may be a condition that the internal temperature drops by a first temperature or more during the advance period from the start of the compressor 10 until a first specified time has elapsed. The second reduction condition may be a condition that the internal temperature during the advance period is lower than the target evaporation temperature, and the absolute value of the difference between the internal temperature and the target evaporation temperature is greater than the first temperature difference. In this case, the refrigeration cycle apparatus 100 may include a load temperature sensor (not shown) that measures the temperature of air flowing into the load heat exchanger 21 or the temperature of air flowing out of the load heat exchanger 21, instead of the low-pressure pressure sensor 5 or in addition to the low-pressure pressure sensor 5, and the control device 12 may obtain the internal temperature from the load temperature sensor.

[0034] FIG. 6 is a diagram illustrating an example of the operating frequency of the compressor 10 controlled by the control device 12 in the embodiment. FIG. 6 shows the operating frequency of the compressor 10 during a period during a start-stop repetition period, which is a period from 0 seconds, when the compressor 10 is first started by a user operation, until 60 seconds have elapsed. In FIG. 6 , when the first period is "b," "a" represents the preceding period; when the first period is "c," "b" represents the preceding period; when the first period is "d," "c" represents the preceding period; when the first period is "e," "d" represents the preceding period; and when the first period is "f," "e" represents the preceding period. As shown in FIG. 6 , the upper limit operating frequency decreases each time the compressor 10 is started from 0 min to 40 min. 6, the upper limit operating frequency of the compressor 10 at "b" is lower than the upper limit operating frequency of the compressor 10 at "a", the upper limit operating frequency of the compressor 10 at "c" is lower than the upper limit operating frequency at "b", the upper limit operating frequency of the compressor 10 at "d" is lower than the upper limit operating frequency at "c", and the upper limit operating frequency of the compressor 10 at "e" is lower than the upper limit operating frequency at "d". On the other hand, after the compressor 10 is started at "e", the upper limit operating frequency of the compressor 10 is maintained at approximately 40 Hz from "f" onwards, either because the amount of power consumed by the compressor 10 has reached the first amount of power, the reduction condition is not satisfied, or the number of changes has reached the threshold number of times.

[0035] The flow of the upper limit adjustment process by the control device 12 will be described below with reference to Fig. 7. Fig. 7 is a flowchart illustrating the flow of the upper limit adjustment process by the control device 12 in this embodiment. In step S1, the control device 12 determines whether the reduction condition is satisfied. If the reduction condition is not satisfied (step S1: NO), the control device 12 proceeds to step S3.

[0036] If the reduction condition is satisfied (step S1: YES), in step S2, the control device 12 determines whether the power consumption since the start of the upper limit adjustment process has reached the first power amount. If the power consumption has reached the first power amount (step S2: YES), the control device 12 proceeds to step S3. If the power consumption has not reached the first power amount (step S2: NO), the control device 12 proceeds to step S4. Note that in step S2, the control device 12 may determine whether the number of changes has reached a threshold number, instead of or in addition to determining whether the power consumption has reached the first power amount. In this case, the control device 12 proceeds to step S3 if the number of changes has reached the threshold number. Furthermore, if the power consumption is less than the first power amount, or if the number of changes is less than the threshold number, the control device 12 proceeds to step S4. In step S3, the control device 12 executes upper limit maintenance control. After processing step S3, the control device 12 proceeds to step S6.

[0037] The processes of steps S1 and S2 may be executed in reverse order or in parallel. If the process of step S2 is executed before the process of step S1, the process of step S1 is executed if the power consumption amount does not reach the first power amount in step S2, and the process of step S4 is executed if the reduction condition is satisfied in step S1. If the process of step S2 precedes step S1 and it is determined in step S2 whether the number of changes is equal to or greater than a threshold number, the process of step S1 is executed if the power consumption amount is less than the first power amount and the number of changes is less than the threshold number, and the process of step S4 is executed if the reduction condition is satisfied in step S1. On the other hand, the process of step S3 is executed if the number of changes is equal to or greater than the threshold number in step S2 or if the power consumption is equal to or greater than the first power amount.

[0038] In step S4, the control device 12 performs an upper limit determination process. In step S5, the control device 12 executes upper limit reduction control. That is, the control device 12 causes the compressor 10 to operate at the upper limit operating frequency determined in step S4.

[0039] In step S6, the control device 12 determines whether or not both the first and second termination conditions are satisfied. If neither the first nor the second termination condition is satisfied (step S6: NO), the control device 12 returns the process to step S1.

[0040] If both or either of the first and second termination conditions are satisfied (step S6: YES), the control device 12 terminates the upper limit adjustment process. After the upper limit adjustment process is terminated, the control device 12 may control the compressor 10 to operate at the upper limit operating frequency set at the time of shipment, or may control the compressor 10 to operate at the upper limit operating frequency finally determined in the upper limit adjustment process. By terminating the upper limit adjustment process when both or either of the first and second termination conditions are satisfied, the control device 12 suppresses a decrease in refrigeration capacity due to repeated reductions in the upper limit operating frequency. This also suppresses the occurrence of a situation in which the required refrigeration capacity cannot be obtained in the load device 2. However, the control device 12 may continue the upper limit adjustment process even if both or either of the first and second termination conditions are satisfied. In this case, the process of step S6 is omitted, and the control device 12 returns to step S1 after each of the processes of steps S3 and S5.

[0041] In FIG. 7, if the reduction condition is not satisfied in step S1, the control device 12 transfers the processing to step S3, but the control device 12 may also terminate the upper limit adjustment processing if the reduction condition is not satisfied in step S1.

[0042] In addition to determining the upper limit operating frequency of the compressor 10 based on Equation (1), the control device 12 may determine the upper limit operating frequency as follows. The control device 12 accumulates and stores information indicating all or part of the number of starts and stops of the compressor 10, the power consumption of the compressor 10, the low-pressure pressure, and the difference between the low-pressure pressure and the target low-pressure pressure, as well as the determined upper limit operating frequency, over a predetermined information collection time. Hereinafter, information indicating all or part of the number of starts and stops of the compressor 10, the power consumption of the compressor 10, and the low-pressure pressure over the information collection time, as well as the upper limit operating frequency determined during the information collection time, may also be referred to as startup operation information. The information collection time may be, for example, three days, one week, or one month or more. The control device 12 performs learning using AI (artificial intelligence) based on the accumulated startup operation information, and determines an upper limit operating frequency that reduces the power consumption of the compressor 10 based on the learning results. Note that while the amount of accumulated startup operation information has not reached a predetermined amount, the control device 12 may determine the upper limit operating frequency based on equation (1) or may randomly determine the upper limit operating frequency. The process of determining the upper limit operating frequency of the compressor 10 based on AI learning is another example of upper limit determination process. Furthermore, control of operating the compressor 10 at the upper limit operating frequency determined based on AI learning is an example of upper limit reduction control.

[0043] The effects of the refrigeration cycle apparatus 100 according to the embodiment will be described below. The refrigeration cycle apparatus 100 according to the embodiment includes a refrigerant circuit 4, a low-pressure sensor 5, and a control device 12. The refrigerant circuit 4 includes a compressor 10, a heat-source heat exchanger 11, an expansion valve 20, and a load heat exchanger 21, which are sequentially connected by refrigerant piping 3, through which a refrigerant circulates. The low-pressure sensor 5 measures the low-pressure pressure, which is the pressure of the refrigerant drawn into the compressor 10. The control device 12 executes an upper limit adjustment process to adjust the upper limit operating frequency of the compressor 10 during a start-stop repeating period, which is a period from start to stop of the compressor, during the start-stop repeating period. If the first reduction condition and the second reduction condition are satisfied, the control device 12 executes upper limit reduction control to reduce the upper limit operating frequency during the first period below the upper limit operating frequency during the preceding period of the start-stop repeating period. When the number of executions of the upper limit reduction control reaches a predetermined threshold number, the control device 12 stops the upper limit reduction control and makes the upper limit operating frequency in the first period equal to the upper limit operating frequency in the preceding period. The preceding period is the period from when the compressor 10 is started immediately before the first period to when it is stopped. The first reduction condition is a condition that the rate of change of the low pressure in the preceding period is equal to or greater than a predetermined first rate of pressure change. The second reduction condition is a condition that the low pressure in the preceding period is lower than a predetermined target low pressure, and the absolute value of the difference between the low pressure in the preceding period and the target low pressure is greater than a predetermined first pressure difference value.

[0044] According to the above configuration, when the reduction condition is satisfied, the control device 12 lowers the upper limit operating frequency of the compressor 10 in the first period below the upper limit operating frequency of the compressor 10 in the preceding period. This reduces the frequency of on / off of the compressor 10. When the number of executions of the upper limit reduction control reaches a threshold number, the control device 12 stops the upper limit reduction control and equalizes the upper limit operating frequency in the first period to the upper limit operating frequency in the preceding period. This prevents an increase in the amount of power consumed by the compressor 10 due to a decrease in compressor operating efficiency. Therefore, the refrigeration cycle apparatus 100 can achieve both a reduction in the frequency of on / off of the compressor 10 and a reduction in the amount of power consumed by the compressor 10. Furthermore, because the control device 12 does not reduce the upper limit operating frequency of the compressor 10 in the first period when the number of executions of the upper limit reduction control reaches a threshold number, the refrigeration cycle apparatus 100 can prevent an increase in the temperature difference inside the refrigeration cycle apparatus 100.

[0045] In this embodiment, the control device 12 terminates the upper limit reduction control when at least one of a first termination condition and a second termination condition is satisfied. The first termination condition is a condition in which the control device 12 continuously executes the upper limit reduction control for a predetermined first specified termination time. The second termination condition is a condition in which a predetermined second specified termination time has elapsed since the upper limit adjustment process was started. This suppresses a decrease in refrigeration capacity due to repeated reductions in the upper limit operating frequency. Therefore, it is possible to suppress the occurrence of a situation in which the required refrigeration capacity cannot be obtained in the load device 2.

[0046] In this embodiment, the control device 12 executes upper limit reduction control when the first and second reduction conditions are satisfied and the amount of power consumed by the compressor 10 since the start of the upper limit adjustment process is less than a predetermined first amount of power. When the amount of power consumed becomes equal to or greater than the first amount of power, the control device 12 equalizes the upper limit operating frequency in the first period with the upper limit operating frequency in the preceding period. This further suppresses the increase in power consumption.

[0047] In the embodiment, the control device 12 accumulates and stores, over a predetermined information collection time, startup operation information indicating all or part of the number of times the compressor 10 starts and stops, the amount of power consumed by the compressor 10, the low-pressure pressure, and the difference between the low-pressure pressure and the target low-pressure pressure, as well as the determined upper limit operating frequency. The control device 12 determines the upper limit operating frequency that reduces the amount of power consumed by the compressor 10 from the learning results based on the accumulated startup operation information. This makes it possible to reduce the number of starts and stops and suppress an increase in power consumption.

[0048] Although the embodiments have been described above, the contents of the present disclosure are not limited to the embodiments and include conceivable equivalents. Furthermore, the configurations described in the embodiments and their modifications can be combined with each other as long as the functions and operations are not impaired.

[0049] 1 Heat source device, 1A First housing, 2 Load device, 2A Second housing, 3 Refrigerant piping, 4 Refrigerant circuit, 5 Low-pressure pressure sensor, 10 Compressor, 11 Heat source heat exchanger, 12 Control device, 12A CPU, 12B Memory, 20 Expansion valve, 21 Load heat exchanger, 100 Refrigeration cycle device.

Claims

a low-pressure pressure sensor that measures a low-pressure pressure that is the pressure of the refrigerant drawn into the compressor; and a control device that executes an upper limit adjustment process to adjust an upper limit operating frequency of the compressor in a first period that is a period from when the compressor is started to when it is stopped during a start-stop repeating period in which the compressor repeatedly starts and stops, wherein the control device executes an upper limit reduction control to reduce the upper limit operating frequency in the first period to be lower than the upper limit operating frequency in a preceding period of the start-stop repeating period when a first reduction condition and a second reduction condition are satisfied, and when the number of times the upper limit reduction control has been executed reaches a predetermined threshold number of times, stops the upper limit reduction control to make the upper limit operating frequency in the first period equal to the upper limit operating frequency in the preceding period, the preceding period being a period from when the compressor is started immediately before the first period to when it is stopped, and the first reduction condition is a second reduction condition being a condition that the rate of change of the low pressure during the preceding period is equal to or greater than a predetermined first pressure change rate, and the second reduction condition being a condition that the low pressure during the preceding period is lower than a predetermined target low pressure, and an absolute value of a difference between the low pressure during the preceding period and the target low pressure is greater than a predetermined first pressure difference value.

2. The refrigeration cycle apparatus of claim 1, wherein the control device terminates the upper limit reduction control when at least one of a first termination condition and a second termination condition is satisfied, the first termination condition being a condition that the control device continuously performs the upper limit reduction control for a predetermined first specified termination time, and the second termination condition being a condition that a predetermined second specified termination time has elapsed since the upper limit adjustment process was started.

3. A refrigeration cycle apparatus as described in claim 1 or claim 2, wherein the control device executes the upper limit reduction control when the first reduction condition and the second reduction condition are satisfied and the amount of power consumed by the compressor after starting the upper limit adjustment process is less than a predetermined first amount of power, and when the amount of power consumed by the compressor becomes equal to or greater than the first amount of power, makes the upper limit operating frequency in the first period equal to the upper limit operating frequency in the preceding period.

4. A refrigeration cycle device as described in any one of claims 1 to 3, wherein the control device accumulates and stores startup operation information indicating all or part of the number of times the compressor starts and stops, the power consumption of the compressor, the low pressure, and the difference between the low pressure and the target low pressure, as well as the determined upper limit operating frequency, over a predetermined information collection time, and determines the upper limit operating frequency that reduces the power consumption of the compressor from a learning result based on the accumulated startup operation information.

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