Refrigeration cycle equipment

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

Technical Field

[0005] , , ,

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

Background Art

[0002] Conventionally, there has been a refrigeration cycle apparatus in which the start and stop of a compressor are controlled based on the measured low-pressure. In such a refrigeration cycle apparatus, due to a rapid change in the low-pressure, the start and stop of the compressor may be repeated in a short time. Specifically, during the stop of the compressor, the low-pressure, which is the pressure of the refrigerant sucked by the compressor, rises. Thereafter, when the compressor starts and immediately operates at the upper limit operating frequency in a case where the load is small, the low-pressure rapidly decreases. And when the value of the low-pressure falls below the set low-pressure cut-off value, the compressor stops again. In this way, the compressor may repeatedly start and stop under low load. As a result, the power consumption of the compressor increases and the life of the compressor is shortened.

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

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, at low loads, lowering the compressor's operating frequency too much during startup can actually increase the compressor's power consumption.

[0006] This disclosure is made to solve the above-mentioned problems and aims to provide a refrigeration cycle device that reduces the power consumption of the compressor while reducing the frequency of compressor start-stopping. [Means for solving the problem]

[0007] The refrigeration cycle apparatus according to this disclosure comprises a refrigerant circuit through which a compressor, a heat source heat exchanger, an expansion valve, and a load heat exchanger are sequentially connected by refrigerant piping and a refrigerant circulates; a low-pressure sensor for measuring the low-pressure pressure, which is the pressure of the refrigerant drawn into the compressor; and a control device that performs an upper limit adjustment process to adjust the upper limit operating frequency of the compressor during a first period, which is the period from when the compressor starts until it stops, during a start-stop repetition period, which is the period during which the compressor repeatedly starts and stops. The control device performs an upper limit reduction control to reduce the upper limit operating frequency in the first period to the upper limit operating frequency in the preceding period of the start-stop repetition period if the first reduction condition and the second reduction condition are met. When the execution of the upper limit reduction control reaches a predetermined threshold number of executions, the upper limit reduction control is stopped 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 is the period from when the compressor is started immediately before the first period until it is stopped, the first reduction condition is that the rate of change of the low pressure in the preceding period is equal to or greater than a predetermined first rate of change, and the second reduction condition is that the low pressure in the preceding period is below 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. [Effects of the Invention]

[0008] According to the refrigeration cycle device described herein, when the first reduction condition and the second reduction condition are met, the control device lowers the upper limit operating frequency of the compressor in the first period to a lower level than the upper limit operating frequency of the compressor in the preceding period. This reduces the frequency of compressor starts and stops. When the number of executions of the upper limit reduction control reaches a threshold number, the control device does not reduce the upper limit operating frequency of the compressor in the first period to a level lower than the upper limit operating frequency of the compressor in the preceding period, but instead sets it to be equal to the upper limit operating frequency of the preceding period. This suppresses the increase in compressor power consumption due to a decrease in compressor operating efficiency. Therefore, the refrigeration cycle device can achieve both a reduction in the frequency of compressor starts and stops and a reduction in compressor power consumption. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic refrigerant circuit diagram showing an example of the configuration of a refrigeration cycle device 100 according to an embodiment. [Figure 2] This figure illustrates the time variation of the operating frequency of the compressor of a refrigeration cycle system in a comparative example under low load conditions. [Figure 3] This figure illustrates the time variation of power consumption of a compressor in a refrigeration cycle system under low load conditions, as shown in the comparative example. [Figure 4] This figure illustrates the time change in internal temperature under low load conditions in a comparative example of a refrigeration cycle system. [Figure 5] This is a diagram illustrating the reduction conditions of the embodiment. [Figure 6] This figure illustrates the operating frequency of the compressor controlled by the control device in the embodiment. [Figure 7] This flowchart illustrates the flow of the upper limit adjustment process by the control device in the embodiment. [Modes for carrying out the invention]

[0010] The following description details a refrigeration cycle device according to an embodiment, with reference to the drawings. This disclosure is not limited to the following embodiments, and various modifications are possible without departing from the spirit of this disclosure.

[0011] Embodiment. Figure 1 is a schematic refrigerant circuit diagram showing an example configuration of a refrigeration cycle device 100 according to an embodiment. The refrigeration cycle device 100 has a heat source device 1 and a load device 2. The heat source device 1 includes a compressor 10, a heat source heat exchanger 11, and a control device 12 within a first housing 1A that forms the outer casing. The load device 2 includes an expansion valve 20 and a load heat exchanger 21 within a second housing 2A that forms the outer casing. 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 the refrigerant flows, forming a refrigerant circuit 4 through which the refrigerant circulates. The expansion valve 20 may be provided inside the first housing 1A of the heat source device 1 instead of in the load device 2, or it may be provided outside the heat source device 1 and the load device 2.

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

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

[0014] The expansion valve 20 is, for example, an electronic expansion valve whose opening degree can be adjusted. The expansion valve 20 depressurizes and expands the liquid refrigerant from the heat source heat exchanger 11. The liquid refrigerant, depressurized by the expansion valve 20, flows to the load heat exchanger 21.

[0015] The load heat exchanger 21 is, for example, a fin-tube type heat exchanger, which exchanges heat between the air in the 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 this embodiment, the target space is described using the interior space of a refrigerator or freezer as an example. In the load heat exchanger 21, the refrigerant absorbs heat from the air inside the compartment and cools the air. The refrigerant that flows out of the load heat exchanger 21 flows to the compressor 10.

[0016] Here, the refrigeration cycle device 100 has a low-pressure sensor 5 that measures the low-pressure level, which is the pressure of the refrigerant drawn in by the compressor 10. The low-pressure sensor 5 is installed in the refrigerant piping 3 on the side where the compressor 10 draws in the refrigerant. In addition to the low-pressure sensor 5, the refrigeration cycle device 100 also has sensors (not shown) that measure various physical quantities. Hereafter, multiple sensors in the refrigeration cycle device 100, including the low-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, or a current sensor. The refrigerant temperature sensor measures the temperature of the refrigerant drawn in by the compressor 10. The compressor sensor measures the temperature of the compressor 10's casing, or the temperature of the refrigerant oil accumulating inside the compressor 10's casing. 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 composed of a CPU (Central Processing Unit) 12A, a memory 12B, an input / output interface circuit (not shown) for inputting and outputting various signals, etc. The memory 12B includes a ROM (Read Only Memory) and a RAM (Random Access Memory). A program indicating the processing procedure of the control device 12 is stored in the ROM. By the CPU 12A expanding and executing the program in the RAM, the control device 12 executes various processes such as the control of the compressor 10. Note that all or some of the functions of the control device 12 may be obtained by dedicated hardware such as a CPLD (Complex Programmable Logic Device), an FPGA (Field Programmable Gate Array), or an ASIC (Application Specific Integrated Circuit).

[0018] Here, conventionally, when the low-pressure pressure changes rapidly at the start of the compressor, the compressor may start and stop, that is, repeat starting and stopping, within a short period of time. Specifically, first, the low-pressure pressure rises during the stop of the compressor. Then, when the compressor starts and the load is small such that the compressor operates at the upper limit operating frequency immediately after starting, the low-pressure pressure drops rapidly. When the value of the low-pressure pressure falls below the set low-pressure cut-off value, the compressor stops again, and thus, the start and stop of the compressor in a short time have been repeated. By the repeated start and stop of the compressor, the power consumption of the compressor increases, and the life of the compressor is shortened.

[0019] In order to reduce the number of start / stop operations of such a compressor, when the refrigerating capacity required by the load device is small, there are methods such as reducing the operating frequency of the compressor. However, if the operating frequency of the compressor is reduced too much, the operating efficiency of the compressor may decrease, which may in turn increase the power consumption of the compressor 10. In addition, after the compressor is started, the difference between the indoor temperature, which is the temperature of the air in the room that exchanges heat with the load heat exchanger 21, and the target indoor temperature, which is the target indoor temperature, may increase. Hereinafter, with reference to FIGS. 2 to 4, the operating conditions of the refrigeration cycle device for each operating frequency of the compressor when the required refrigerating capacity is small will be described. FIG. 2 is a diagram illustrating the time change of the operating frequency of the compressor at low load of the refrigeration cycle device according to the comparative example. FIG. 3 is a diagram illustrating the time change of the power consumption of the compressor at low load of the refrigeration cycle device according to the comparative example. FIG. 4 is a diagram illustrating the time change of the indoor temperature at low load in the refrigeration cycle device according to the comparative example.

[0020] In (a) of FIG. 2, the time change of the operating frequency of the compressor when the upper limit operating frequency of the compressor is 100 [Hz] is shown. In (b) of FIG. 2, the time change of the operating frequency of the compressor when the upper limit operating frequency of the compressor is 55 [Hz] is shown. In (c) of FIG. 2, the time change of the operating frequency of the compressor when the upper limit operating frequency of the compressor is 40 [Hz] is shown.

[0021] As shown in Figure 2(a), 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 minutes, and the compressor starts and stops 8 times between 0 minutes (when it first starts) and 60 minutes (when it first starts). As shown in Figure 2(b), 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 minutes, and the compressor starts and stops 6 times between 60 minutes (when it first starts). As shown in Figure 2(c), 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 minutes, and the compressor stops once, starts again, and then stops again between 0 minutes (when it first starts) and 60 minutes (when it first starts). Therefore, when the compressor's upper limit operating frequency is the lowest at 40 Hz (out of 40 Hz, 55 Hz, and 100 Hz), the number of compressor starts and stops is minimized, and when it is the highest at 100 Hz, the number of compressor starts and stops is maximized. Thus, it can be inferred that under low load conditions, the number of compressor starts and stops increases as the compressor's upper limit operating frequency increases.

[0022] Figure 3(a) shows the time variation of the power consumption of compressor 10 when the upper limit operating frequency of the compressor is set to 100 [Hz]. Figure 3(b) shows the time variation of the power consumption of compressor 10 when the upper limit operating frequency of the compressor is set to 55 [Hz]. Figure 3(c) shows the time variation of the power consumption of compressor 10 when the upper limit operating frequency of the compressor is set to 40 [Hz].

[0023] As shown in Figure 3(a), 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 Figure 3(b), 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 Figure 3(c), 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]. In other words, of the upper limit operating frequency of the compressor, out of 40[Hz], 55[Hz], and 100[Hz], the power consumption of the compressor 10 is minimum when it is 55[Hz], and maximum when it is 100[Hz]. From this, it can be inferred that, under low load conditions, the power consumption of a compressor operating at an upper limit operating frequency higher than the standard upper limit operating frequency (such as 55 Hz) will be greater than the power consumption of a compressor operating at the standard upper limit operating frequency. Furthermore, it can be inferred that the power consumption of a compressor operating at an upper limit operating frequency lower than the standard will be greater than the power consumption of a compressor operating at the standard upper limit operating frequency.

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

[0025] As shown in Figure 4(a), 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 Figure 4(b), 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 Figure 4(c), 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 compressor's upper limit operating frequency is the lowest of 40Hz (out of 40Hz, 55Hz, and 100Hz), the peak internal temperature is highest, resulting in a large internal temperature difference. Conversely, when the compressor's upper limit operating frequency is the highest of 100Hz (out of 40Hz, 55Hz, and 100Hz), the peak internal temperature is lowest, resulting in a small internal temperature difference. This suggests that, under low load conditions, the lower the compressor's upper limit operating frequency, the larger the internal temperature difference becomes, potentially failing to meet user requirements.

[0026] In this 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 when under low load. The upper limit adjustment process will be described in detail below. The control device 12 determines whether the first reduction condition and the second reduction condition are met when the compressor 10 repeatedly starts and stops. If the first reduction condition and the second reduction condition are met, the control device 12 performs an upper limit reduction control to reduce 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. Here, the first period refers to the period in the start-stop repeating period, from when the compressor 10 starts up until it stops. The preceding period refers to the period in the start-stop repeating period, from when the compressor 10 starts up immediately before the first period until it stops. The start-stop repeating period refers to the period during which the compressor 10 repeatedly starts up and stops. Note that there is a preceding period before the first period, and the period from when the compressor 10 first starts up until it stops in the start-stop repeating period is omitted from the first period. The first reduction condition is that the rate of change of low pressure during the preceding period is equal to or greater than the first pressure change rate. The second reduction condition is that the low pressure during the preceding period is below the target low pressure, and the absolute value of the difference between the low pressure during the preceding period and the target low pressure is greater than the value of the first pressure difference. The first pressure change rate and the first pressure difference are physical quantities based on either or both of the target low pressure value and the low pressure cutoff value, and are predetermined by experimentation or other means. In the following, the combination of the first and second reduction conditions may also be referred to as the reduction condition.

[0027] If the reduction conditions are not met, the control device 12 sets the upper limit operating frequency of the compressor 10 in the first period to be equal to the upper limit operating frequency of the compressor 10 in the preceding period. Even if the reduction conditions are met, if the amount of power consumed by the compressor 10 from the start of the upper limit adjustment process exceeds a predetermined first amount of power, the control device 12 sets the upper limit operating frequency of the compressor 10 in the first period to be equal to the upper limit operating frequency of the compressor 10 in the preceding period. Hereinafter, the control that sets the upper limit operating frequency of the compressor 10 in the first period to be equal to the upper limit operating frequency of the compressor 10 in the preceding period, that is, the control that sets the upper limit operating frequency in the first period to be equal to the upper limit operating frequency in the preceding period and causes the compressor 10 to operate, may also be referred to as upper limit maintenance control.

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

[0029] In the 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 of the refrigeration cycle device 100 at the time of shipment. C is the number of changes, which is the number of times the control device 12 has reduced the upper limit operating frequency of the compressor 10, if the number of changes is less than or equal to a predetermined threshold number. On the other hand, if the number of changes exceeds the threshold number, C is the threshold number. Note that C may be an arbitrarily set value other than the number of changes and the threshold number. Here, the threshold number may be determined based on the above power consumption, for example, by experimentation or learning. Specifically, the threshold number may be determined by learning the number of changes at which the above power consumption becomes equal to or equal to the first power amount. In this case, the determination process of whether the above power consumption is equal to or equal to the first power amount in the upper limit adjustment process may be replaced with the determination process of whether the number of changes is equal to or equal to the threshold number. Note that below, the process by which the control device 12 determines the upper limit operating frequency of the compressor 10 may also be referred to as the 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 an upper limit determination process.

[0030] The reduction conditions will be described in detail below with reference to Figure 5. Figure 5 is a diagram illustrating the reduction conditions of the embodiment. In Figure 5, the target evaporation temperature of the refrigerant in the load heat exchanger 21 is on the horizontal axis, and temperature is on the vertical axis. The dashed line α in Figure 5 has a slope of 1 and represents the target evaporation temperature. The solid line β in Figure 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 sensor 5. Furthermore, the target evaporation temperature is uniquely determined by the target low-pressure pressure. The dashed line γ in Figure 5 represents the evaporation temperature of the refrigerant at the low-pressure cutoff value described above. Hereafter, the evaporation temperature of the refrigerant at the low-pressure cutoff value may also be referred to as the cutoff temperature.

[0031] The above first reduction condition is equivalent to the condition that, in the preceding period, the evaporation temperature of the refrigerant in the load heat exchanger 21 drops to a first temperature or higher within a predetermined first specified time elapsed after the compressor 10 is started. Here, the first specified time is predetermined by experimentation, for example, 7 minutes. The first temperature is a quantity determined based on the product of the first temperature change rate and the first specified time. The first temperature change rate is determined from the first pressure change rate. The first temperature exemplified in Figure 5 is 20°C when the target evaporation temperature is -45°C or higher and less than -5°C. Also, the first temperature exemplified in Figure 5 is 25°C higher than the target evaporation temperature when the target evaporation temperature is -5°C or higher and less than 10°C, and is 35°C when the target evaporation temperature is, for example, 10°C.

[0032] The second reduction condition described above is equivalent to the 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 said 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 described above. The first temperature difference is, for example, 5 [°C].

[0033] The evaporation temperature in the first and second reduction conditions may be replaced with the internal temperature. That is, the first reduction condition may be that the internal temperature drops to a first temperature or higher within a first specified time elapsed from the start of the compressor 10 during the preceding period. The second reduction condition may be that the internal temperature during the preceding 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 value of the first temperature difference. In this case, the refrigeration cycle device 100 may have a load temperature sensor (not shown) that measures the temperature of the air flowing into the load heat exchanger 21 or the temperature of the air flowing out of the load heat exchanger 21, in place of the low-pressure sensor 5, or together with the low-pressure sensor 5, and the control device 12 may obtain the internal temperature from the load temperature sensor.

[0034] Figure 6 is a diagram illustrating the operating frequency of the compressor 10 controlled by the control device 12 in the embodiment. Figure 6 shows the operating frequency of the compressor 10 during the start-stop cycle period, from 0 seconds, when the compressor 10 is first started by user operation, until 60 seconds have elapsed. In Figure 6, if the first period is "b", then "a" is the preceding period; if the first period is "c", then "b" is the preceding period; if the first period is "d", then "c" is the preceding period; if the first period is "e", then "d" is the preceding period; and if the first period is "f", then "e" is the preceding period. As shown in Figure 6, from 0 [min] to 40 [min], the upper limit operating frequency decreases with each start of the compressor 10. In other words, in Figure 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 start-up of the compressor 10 at "e", the power consumption of the compressor 10 has reached the first power consumption, the reduction condition has not been met, or the number of changes has reached the threshold number, and the upper limit operating frequency of the compressor 10 from "f" onward is maintained at approximately 40 [Hz].

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

[0036] If the reduction condition is met (step S1: YES), in step S2, the control device 12 determines whether the amount of power consumed since the start of the upper limit adjustment process has reached the first amount of power. If the amount of power consumed has reached the first amount of power (step S2: YES), the control device 12 moves to step S3. If the amount of power consumed has not reached the first amount of power (step S2: NO), the control device 12 moves to step S4. In step S2, the control device 12 may, instead of determining whether the amount of power consumed has reached the first amount of power, or together with determining whether the amount of power consumed has reached the first amount of power, determine whether the number of changes has reached a threshold number of changes. In this case, the control device 12 moves to step S3 if the number of changes has reached a threshold number of changes. Also, if the amount of power consumed is less than the first amount of power, the control device 12 moves to step S4 if the number of changes is less than a threshold number of changes. In step S3, the control device 12 performs upper limit maintenance control. After the processing in step S3, the control device 12 moves to step S6.

[0037] Steps S1 and S2 may be executed in reverse order or in parallel. If step S2 is executed before step S1, step S1 is executed if the power consumption in step S2 has not reached the first power consumption, and step S4 is executed if the reduction condition is met in step S1. If step S2 precedes step S1, and step S2 determines whether the number of changes is equal to or greater than the threshold number, step S1 is executed if the power consumption is less than the first power consumption and the number of changes is less than the threshold number, and step S4 is executed if the reduction condition is met in step S1. On the other hand, step S3 is executed if at least one of the following conditions is met in step S2: the number of changes is equal to or greater than the threshold number, and the power consumption is equal to or greater than the first power consumption.

[0038] In step S4, the control device 12 performs an upper limit determination process. In step S5, the control device 12 performs 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 both or either of the first and second termination conditions are met. If neither the first nor the second termination condition is met (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 met (step S6: YES), the control device 12 terminates the upper limit adjustment process. After the upper limit adjustment process is completed, the control device 12 may control the compressor 10 to operate at the upper limit operating frequency set at the time of shipment, or it may control the compressor 10 to operate at the upper limit operating frequency last determined during the upper limit adjustment process. By the control device 12 terminating the upper limit adjustment process when both or either of the first and second termination conditions are met, a decrease in refrigeration capacity due to repeated reductions of the upper limit operating frequency is suppressed. This prevents a situation where 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 met. In this case, the process in step S6 is omitted, and after the processes in steps S3 and S5, the control device 12 returns to the process in step S1.

[0041] In Figure 7, if the reduction condition is not met in step S1, the control device 12 moves the process to step S3. However, the control device 12 may terminate the upper limit adjustment process if the reduction condition is not met 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 also determine the upper limit operating frequency as follows. The control device 12 accumulates and stores information indicating the number of times the compressor 10 is started and stopped, the amount of power consumed by the compressor 10, the low pressure, all or part of the difference between the low pressure and the target low pressure, and the determined upper limit operating frequency over a predetermined information collection time. Hereinafter, the information indicating all or part of the number of times the compressor 10 is started and stopped, the amount of power consumed by the compressor 10, and the low pressure, along with the upper limit operating frequency determined during the information collection time, may be referred to as start-up operation information. The information collection time may be, for example, 3 days, 1 week, or 1 month or more. Based on the accumulated start-up operation information, the control device 12 performs AI (Artificial Intelligence) learning and determines the upper limit operating frequency that reduces the power consumption of the compressor 10 from the learning results. Furthermore, the control device 12 may determine the upper limit operating frequency based on equation (1) or randomly while the accumulated amount of startup operation information does not reach a predetermined amount of information. The process of determining the upper limit operating frequency of the compressor 10 based on AI learning is another example of upper limit determination processing. Also, the control that operates 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 device 100 according to the embodiment will be described below. The refrigeration cycle device 100 according to the embodiment comprises a refrigerant circuit 4, a low-pressure sensor 5, and a control device 12. The refrigerant circuit 4 is configured by sequentially connecting a compressor 10, a heat source heat exchanger 11, an expansion valve 20, and a load heat exchanger 21 with refrigerant piping 3, and circulating refrigerant. The low-pressure sensor 5 measures the low-pressure, which is the pressure of the refrigerant drawn into the compressor 10. The control device 12 performs an upper limit adjustment process to adjust the upper limit operating frequency of the compressor 10 during the first period, which is the period from when the compressor starts until it stops, during the start-stop repetition period, which is the period during which the compressor 10 repeatedly starts and stops. If the first reduction condition and the second reduction condition are met, the control device 12 performs an upper limit reduction control to reduce the upper limit operating frequency in the first period to the upper limit operating frequency in the preceding period during the start-stop repetition period. When the number of times the upper limit reduction control is executed by the control device 12 reaches a predetermined threshold number of times, it 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 up immediately before the first period until it is stopped. The first reduction condition is that the rate of change of low pressure in the preceding period is equal to or greater than a predetermined first rate of change. The second reduction condition is that the low pressure in the preceding period is below 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 conditions are met, the control device 12 lowers the upper limit operating frequency of the compressor 10 in the first period to a lower level than the upper limit operating frequency of the compressor 10 in the preceding period. This reduces the frequency of starting and stopping 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 makes the upper limit operating frequency in the first period equal to the upper limit operating frequency in the preceding period. This suppresses the increase in the power consumption of the compressor 10 due to a decrease in compressor operating efficiency. Therefore, the refrigeration cycle device 100 can achieve both a reduction in the frequency of starting and stopping the compressor 10 and a reduction in the power consumption of the compressor 10. Furthermore, since 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 device 100 can suppress the expansion of the temperature difference inside the chamber.

[0045] In this embodiment, the control device 12 terminates the upper limit reduction control when at least one of the first termination condition and the second termination condition is met. The first termination condition is that the control device 12 continuously performs the upper limit reduction control for a predetermined first termination time. The second termination condition is that a predetermined second termination time has elapsed since the start of the upper limit adjustment process. This suppresses a decrease in refrigeration capacity due to repeated reductions of the upper limit operating frequency. Therefore, the occurrence of a situation where the required refrigeration capacity cannot be obtained in the load device 2 is suppressed.

[0046] In this embodiment, the control device 12 executes upper limit reduction control when the first reduction condition and the second reduction condition are met, and the amount of power consumed by the compressor 10 after the start of the upper limit adjustment process is less than a predetermined first amount of power. If the amount of power consumed becomes equal to or greater than the first amount of power, the control device 12 sets the upper limit operating frequency in the first period to be equal to the upper limit operating frequency in the preceding period. This provides a further suppression effect on the increase in power consumption.

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

[0048] Although embodiments have been described above, the contents of this disclosure are not limited to these embodiments and include the scope of equivalent embodiments. Furthermore, the configurations and modifications described in the embodiments can be combined with each other to the extent that they do not impair function and operation. [Explanation of Symbols]

[0049] 1 Heat source device, 1A First enclosure, 2 Load device, 2A Second enclosure, 3 Refrigerant piping, 4 Refrigerant circuit, 5 Low 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

1. A refrigerant circuit in which a compressor, heat source heat exchanger, expansion valve, and load heat exchanger are sequentially connected by refrigerant piping and the refrigerant circulates, A low-pressure sensor for measuring the low pressure, which is the pressure of the refrigerant drawn into the compressor, A control device that performs an upper limit adjustment process to adjust the upper limit operating frequency of the compressor during a start-stop repetition period, which is the period in which the compressor is started and stopped, during a first period, which is the period from when the compressor is started until when it is stopped. Equipped with, The control device is If the first reduction condition and the second reduction condition are met, an upper limit reduction control is executed to reduce the upper limit operating frequency in the first period to a lower limit operating frequency in the preceding period of the start / stop repetition period. When the number of executions of the upper limit reduction control reaches a predetermined threshold number, 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 aforementioned advance period is The period immediately preceding the first period, from when the compressor is started until it is stopped, The first reduction condition is, The condition is that the rate of change of the low pressure during the preceding period is equal to or greater than a predetermined first rate of pressure change. The second reduction condition is, A refrigeration cycle device in which the low pressure during the preceding period is below a predetermined target low pressure, and the absolute value of the difference between the low pressure during the preceding period and the target low pressure is greater than a predetermined first pressure difference.

2. The control device is If at least one of the first termination condition and the second termination condition is met, the upper limit reduction control is terminated. The first termination condition is that the control device continuously performs the upper limit reduction control for a predetermined first termination time. The second termination condition is, The refrigeration cycle apparatus according to claim 1, wherein the condition is that a predetermined second termination time has elapsed since the start of the upper limit adjustment process.

3. The control device is When the first reduction condition and the second reduction condition are met, and the amount of power consumed by the compressor after the start of the upper limit adjustment process is less than a predetermined first amount of power, the upper limit reduction control is executed. The refrigeration cycle apparatus according to claim 1 or 2, wherein if the power consumption of the compressor exceeds the first power consumption, the upper limit operating frequency in the first period is made equal to the upper limit operating frequency in the preceding period.

4. The control device is The number of times the compressor starts and stops, the amount of power consumed by the compressor, the low pressure, and all or part of the difference between the low pressure and the target low pressure, along with the determined upper limit operating frequency, are accumulated and stored over a predetermined information collection period. A refrigeration cycle apparatus according to claim 1 or claim 2, wherein the upper limit operating frequency for reducing the power consumption of the compressor is determined from the learning results based on the accumulated startup operation information.

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