Refrigeration cycle apparatus

Abstract

To suppress lowering of high pressure of a refrigerating cycle device having a PFC heat exchanger while avoiding excessive rise of the high pressure.SOLUTION: The refrigeration cycle apparatus includes a compressor configured to compress a refrigerant, a heat-source-side heat exchanger configured to exchange heat between the refrigerant discharged from the compressor and air, an expansion device configured to expand the refrigerant flowing out of the heat-source-side heat exchanger, a load-side heat exchanger configured to exchange heat between the refrigerant flowing out of the expansion device and air, a bypass expansion device connected to the compressor in parallel with the heat-source-side heat exchanger and having an adjustable opening degree, and a controller configured to control the opening degree of the bypass expansion device based on a high pressure of the refrigerant discharged from the compressor. The heat source-side heat exchanger includes a pair of headers, a plurality of flat tubes disposed between the pair of headers, and a corrugated fin disposed between the plurality of flat tubes.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] It is known that in conventional refrigeration cycle devices, in order to ensure the compression ratio of the compressor, control is performed to prevent the high-pressure from decreasing too much. Incidentally, Patent Document 1 discloses a technology in which a movable plate is provided inside the header of a parallel flow condenser heat exchanger (hereinafter referred to as a PFC heat exchanger) to increase or decrease the number of heat transfer tubes through which the refrigerant flows, thereby adjusting the heat transfer area. Patent Document 1 aims to maintain the differential pressure before and after the expansion section provided downstream of the heat exchanger, but it is generally considered possible to increase the high-pressure by limiting the heat transfer area of ​​the heat exchanger. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-124401 Summary of the Invention [Problem to be solved by the invention]

[0004] However, because PFC heat exchangers generally use flat tubes, they have a small internal volume and large pressure loss. Therefore, when attempting to increase the high-pressure pressure by limiting the heat transfer area of ​​the heat exchanger to a portion of the entire heat exchanger, as in the technology disclosed in Patent Document 1, the internal volume becomes excessively small relative to the refrigerant flow rate, and the high-pressure pressure may rise excessively. If the high-pressure pressure rises excessively, it may go outside the operating range of the compressor or cause damage to components that make up the refrigeration cycle.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to prevent excessive increase and suppress excessive decrease in the high-pressure of a refrigeration cycle device having a PFC heat exchanger. [Means for solving the problem]

[0006] The refrigeration cycle device of the present disclosure includes a compressor that compresses a refrigerant, a heat source side heat exchanger that performs heat exchange between the refrigerant discharged from the compressor and air, a throttling device that expands the refrigerant that has flowed out of the heat source side heat exchanger, a load side heat exchanger that performs heat exchange between the refrigerant that has flowed out of the throttling device and air, a bypass throttling device that is connected to the compressor in parallel with the heat source side heat exchanger and has an adjustable opening, and a control device that controls the opening of the bypass throttling device based on the high pressure of the refrigerant discharged from the compressor, and the heat source side heat exchanger has a pair of headers, a plurality of flat tubes arranged between the pair of headers, and corrugated fins arranged between the plurality of flat tubes. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to prevent an excessive increase in the high pressure of a refrigeration cycle device having a PFC heat exchanger, and also to suppress an excessive decrease in the high pressure. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a circuit diagram showing a refrigeration cycle device according to a first embodiment. [Figure 2] 1 is a hardware configuration diagram showing a control device according to a first embodiment. [Figure 3] 1 is a hardware configuration diagram showing a control device according to a first embodiment. [Figure 4] 1 is a block diagram showing a refrigeration cycle device according to a first embodiment. [Figure 5] 4 is a flowchart showing the operation of the control device according to the first embodiment. [Figure 6] 4 is a flowchart showing the operation of the control device according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Embodiment 1 A refrigeration cycle apparatus 1 according to a first embodiment will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing the refrigeration cycle apparatus 1 according to the first embodiment. The refrigeration cycle apparatus 1 is an apparatus that controls the temperature of a target space by a refrigeration cycle that circulates a refrigerant. Here, the refrigeration cycle apparatus 1 will be described as an air conditioner that conditions indoor air. When the refrigeration cycle apparatus 1 is an air conditioner, the refrigeration cycle apparatus 1 can at least perform cooling operation. Note that the refrigeration cycle apparatus 1 may also be another apparatus that configures a refrigeration cycle using a refrigeration cycle, such as a refrigerator. As shown in FIG. 1, the refrigeration cycle apparatus 1 has an outdoor unit 2 and two indoor units 3a and 3b. Note that while FIG. 1 illustrates one outdoor unit 2, the number of outdoor units 2 may be two or more. Also, while FIG. 1 illustrates two indoor units 3a and 3b, the number of indoor units may be one or three or more.

[0010] As shown in Fig. 1, the outdoor unit 2 is mainly installed outdoors and has the function of supplying cold energy to the indoor unit 3. The outdoor unit 2 has a compressor 11, a heat source side heat exchanger 12, an accumulator 13, and an outdoor fan 14. The indoor units 3a and 3b are installed, for example, indoors and have the function of cooling a target space using the cold energy supplied from the outdoor unit 2. The indoor unit 3a has a load side heat exchanger 31a and a load side throttle device 32a. The indoor unit 3b has a load side heat exchanger 31b and a load side throttle device 32b.

[0011] The discharge side of the compressor 11 and the heat source side heat exchanger 12 are connected by a high-pressure gas pipe 21. The high-pressure gas pipe 21 is a pipe through which high-pressure gaseous refrigerant flows. The heat source side heat exchanger 12 is connected to the load side throttling device 32a of the indoor unit 3a and the load side throttling device 32b of the indoor unit 3b by a high-pressure liquid pipe 22. The high-pressure liquid pipe 22 is a pipe through which high-pressure liquid refrigerant flows. The load side heat exchanger 31a of the indoor unit 3a and the load side heat exchanger 31b of the indoor unit 3b are connected to the suction side of the compressor 11 by a low-pressure gas pipe 23 via the accumulator 13. The low-pressure gas pipe 23 is a pipe through which low-pressure gaseous refrigerant flows.

[0012] The compressor 11, the heat source side heat exchanger 12, the load side throttle devices 32a and 32b, the load side heat exchangers 31a and 31b, and the accumulator 13 are connected by piping to form a refrigeration cycle.

[0013] In the following explanation, when there is no particular need to distinguish between the indoor units 3a and 3b, the indoor units 3a and 3b will be described with the "a" and "b" omitted, as in the indoor unit 3. Furthermore, although the components mounted on the indoor units 3a and 3b respectively have "a" and "b" added to the end of their reference numerals, when there is no particular need to distinguish between them, they will be described with the "a" and "b" omitted.

[0014] The compressor 11 draws in low-temperature, low-pressure refrigerant that has flowed in through the accumulator 13, compresses the drawn refrigerant, and discharges it as high-temperature, high-pressure gas refrigerant. The compressor 11 can be configured, for example, as a rotary compressor, a scroll compressor, a screw compressor, or a reciprocating compressor. The compressor 11 may also be configured as a capacity-controllable inverter compressor.

[0015] The heat source-side heat exchanger 12 is a heat exchanger that exchanges heat between outdoor air and a refrigerant and functions as a condenser during cooling operation. The heat source-side heat exchanger 12 is an air-cooled PFC heat exchanger. The PFC heat exchanger is a heat exchanger configured with a pair of headers, multiple flat tubes arranged between the pair of headers, and corrugated fins arranged between two adjacent flat tubes. PFC heat exchangers are known for their compact size and high performance. The flat tubes have a flat outer shape when viewed from the tube axis direction and have a multi-hole tube structure with multiple refrigerant flow paths formed therein. The corrugated fins are fins that are bent to form a wave shape by connecting multiple arc-shaped, triangular, or rectangular shapes.

[0016] The accumulator 13 is provided on the suction side of the compressor 11 and stores excess refrigerant, excess refrigerant due to transient operational changes, or excess refrigerant generated by load fluctuations. The accumulator 13 separates liquid refrigerant from gas refrigerant and supplies only the gas refrigerant to the compressor 11. Transient operational changes occur, for example, when the number of operating indoor units 3 changes, when the refrigeration cycle apparatus 1 starts up, or when oil recovery operation is being performed. Furthermore, if the indoor unit 3 is provided with a fan for blowing air to the load-side heat exchanger 31, transient operational changes also occur when the fan's wind speed changes. The oil recovery operation is an operation in which the frequency is increased to recover refrigeration oil taken from the outdoor unit 2 to the outdoor unit 2 when the compressor 11 continues to operate at or below a predetermined frequency.

[0017] The outdoor fan 14 is provided near the heat source-side heat exchanger 12. The outdoor fan 14 supplies outdoor air to the heat source-side heat exchanger 12. The rotation speed of the outdoor fan 14 is controlled by the control device 60, thereby adjusting the condensation capacity of the heat source-side heat exchanger 12.

[0018] The load-side heat exchanger 31 is a heat exchanger that exchanges heat between indoor air and a refrigerant and functions as an evaporator during cooling operation. The load-side heat exchanger 31 generates cool air to be supplied to the space to be air-conditioned. The load-side heat exchanger 31 can be configured, for example, as a fin-and-tube heat exchanger, a microchannel heat exchanger, a shell-and-tube heat exchanger, a heat pipe heat exchanger, a double-pipe heat exchanger, or a plate heat exchanger. In the first embodiment, a case where the load-side heat exchanger 31 is a fin-and-tube heat exchanger will be described as an example.

[0019] The load-side throttle device 32 expands and reduces the pressure of the refrigerant supplied from the outdoor unit 2. In Fig. 1, the load-side throttle device 32 is provided in each indoor unit 3 between the outdoor unit 2 and the load-side heat exchanger 31. The load-side throttle device 32 is, for example, an electronic expansion valve that can adjust the flow rate of the refrigerant. Note that instead of using an electronic expansion valve, the load-side throttle device 32 may be a mechanical expansion valve that uses a diaphragm in the pressure-receiving section, or a capillary tube, etc.

[0020] The refrigeration cycle apparatus 1 also has a bypass piping 71 and a bypass throttle device 72. The bypass piping 71 connects the high-pressure gas pipe 21 and the high-pressure liquid pipe 22. The bypass throttling device 72 is provided in the bypass piping 71 and is thereby connected to the compressor 11 in parallel with the heat source-side heat exchanger 12. The bypass throttling device 72 is, for example, an electronic expansion valve with an adjustable opening, and the opening is controlled by the control device 60. When the opening of the bypass throttling device 72 is 0, that is, when the bypass throttling device 72 is closed, all of the refrigerant discharged from the compressor 11 and flowing through the high-pressure gas pipe 21 flows to the heat source-side heat exchanger 12. When the bypass throttling device 72 is open, a portion of the refrigerant discharged from the compressor 11 and flowing through the high-pressure gas pipe 21 bypasses the high-pressure gas pipe 21 and flows into the bypass piping 71. When the bypass throttling device 72 is open, the amount of refrigerant bypassing the high-pressure gas pipe 21 and flowing into the bypass piping 71 is controlled according to the opening of the bypass throttling device 72. The larger the opening of the bypass throttle device 72, the more refrigerant is bypassed from the high-pressure gas pipe 21 and flows into the bypass piping 71. In this way, the bypass throttle device 72 has the function of adjusting the amount of refrigerant flowing into the heat source side heat exchanger 12.

[0021] Here, the operation modes performed by the refrigeration cycle apparatus 1 will be described together with the flow of refrigerant. The refrigeration cycle apparatus 1 is configured to be able to start and stop at least the cooling operation based on instructions from, for example, a remote control (not shown) installed indoors. The refrigeration cycle apparatus 1 can perform the cooling operation in all the indoor units 3 connected to the outdoor unit 2.

[0022] (Cooling operation mode) The cooling operation performed by the refrigeration cycle apparatus 1 will now be described. When the refrigeration cycle apparatus 1 performs the cooling operation, the outdoor unit 2 causes the refrigerant discharged from the compressor 11 to flow into the indoor unit 3 via the heat source-side heat exchanger 12. First, a case where the bypass throttle device 72 is closed will be described. In this case, the refrigerant circulates through the refrigeration cycle along the path indicated by the solid arrows in FIG. 1. Specifically, the compressor 11 compresses low-temperature, low-pressure refrigerant and discharges it as high-temperature, high-pressure gas refrigerant. The high-temperature, high-pressure gas refrigerant discharged from the compressor 11 flows into the heat source-side heat exchanger 12 via the high-pressure gas pipe 21. The refrigerant that flows into the heat source-side heat exchanger 12 exchanges heat with air supplied by the outdoor fan 14, becoming high-temperature, high-pressure liquid refrigerant and flowing out of the heat source-side heat exchanger 12. The high-temperature, high-pressure liquid refrigerant that flows out of the heat source-side heat exchanger 12 flows into the indoor unit 3 via the high-pressure liquid pipe 22. The high-temperature, high-pressure liquid refrigerant that flows into the indoor unit 3 is converted into low-temperature, low-pressure liquid refrigerant or two-phase refrigerant by the load-side throttle device 32, and flows into the load-side heat exchanger 31. The refrigerant that flows into the load-side heat exchanger 31 exchanges heat with the air and becomes low-temperature, low-pressure gas refrigerant, which flows out of the load-side heat exchanger 31. The refrigerant absorbs heat from the air in the load-side heat exchanger 31, thereby cooling the room, which is the space to be air-conditioned. The refrigerant that flows out of the load-side heat exchanger 31 passes through the low-pressure gas piping 33 and flows into the outdoor unit 2. The refrigerant that flows into the outdoor unit 2 is sucked back into the compressor 11 via the accumulator 13. The above cycle is then repeated.

[0023] 1. Specifically, a portion of the high-temperature, high-pressure gas refrigerant discharged from the compressor 11 flows through the bypass piping 71 without flowing into the heat source-side heat exchanger 12. The high-temperature, high-pressure gas refrigerant flowing through the bypass piping 71 flows into the high-pressure liquid pipe 22, where it merges with the high-temperature, high-pressure liquid refrigerant that has flowed into the heat source-side heat exchanger 12 and flows toward the indoor unit 3.

[0024] The refrigeration cycle apparatus 1 has indoor temperature sensors 81a and 81b, an outdoor temperature sensor 91, a high-pressure sensor 51, and a control device 60. The indoor temperature sensor 81a is provided, for example, at an air intake (not shown) of the indoor unit 3a, and measures the temperature of the air in the room where the indoor unit 3a is provided. The indoor temperature sensor 81a transmits the measurement results to the control device 60. The indoor temperature sensor 81b is provided, for example, at an air intake (not shown) of the indoor unit 3b, and measures the temperature of the air in the room where the indoor unit 3b is provided. The indoor temperature sensor 81b transmits the measurement results to the control device 60. The outdoor temperature sensor 91 is provided, for example, inside the outdoor unit 2, and measures the outdoor temperature. The outdoor temperature sensor 91 transmits the measurement results to the control device 60.

[0025] The high-pressure pressure sensor 51 is provided in the high-pressure gas pipe 21. The high-pressure pressure sensor 51 measures the pressure of the refrigerant discharged from the compressor 11 and flowing through the high-pressure gas pipe 21 (hereinafter sometimes referred to as the high-pressure pressure), and transmits the measurement result to the control device 60. Note that, if it is possible to estimate the pressure of the refrigerant discharged from the compressor 11 and flowing through the high-pressure gas pipe 21, the measurement result of a sensor provided at another location may be used.

[0026] The control device 60 is housed inside the outdoor unit 2. The control device 60 may be provided in a location other than the indoor unit 3, or the outdoor unit 2 and the indoor unit 3. The control device 60 controls each actuator of the refrigeration cycle device 1 based on the detection results received from each sensor. In the first embodiment, the actuators are, for example, the compressor 11, the outdoor fan 14, the load-side throttle device 32, and the bypass throttle device 72.

[0027] In particular, when the outdoor temperature is low (e.g., 10°C or lower) during cooling operation, it is known that the volume of the heat source-side heat exchanger 12 becomes excessively large relative to the refrigerant flow rate, causing a decrease in condenser efficiency and a drop in the high-pressure pressure of the refrigeration cycle apparatus 1. Furthermore, when a transient operational change occurs in the refrigeration cycle apparatus 1, the condenser efficiency may also decrease, causing a drop in the high-pressure pressure of the refrigeration cycle apparatus 1. If the high-pressure pressure of the refrigeration cycle apparatus 1 drops, the compression ratio may not be maintained at a normal value. The normal value of the compression ratio is set to ensure the reliability of the compressor and is, for example, a value of 2 or more. The control device 60 of the first embodiment has a function of suppressing a drop in the high-pressure pressure by controlling the outdoor fan 14 and the bypass throttle device 72 of the refrigeration cycle apparatus 1 to reduce the heat transfer performance of the heat source-side heat exchanger 12.

[0028] 2 and 3 are hardware configuration diagrams showing the control device 60 according to the first embodiment. When each function of the control device 60 is executed by hardware, the control device 60 is configured by a processing circuit 101, as shown in Fig. 2. When each function is executed by hardware, the processing circuit 101 corresponds to, for example, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof.

[0029] When each function of the control device 60 is executed by software, as shown in Fig. 3, the control device 60 is configured with a CPU or the like including a processor 102 and a memory 103. The processor 102 and the memory 103 are communicatively connected via a bus 104. The software is written as a program and stored in the memory 103. The processor 102 realizes each function of the control device 60 by reading and executing the program stored in the memory 103. For example, a non-volatile semiconductor memory such as a ROM (Read Only Memory) is used as the memory 103. Alternatively, a volatile semiconductor memory such as a RAM (Random Access Memory) may be used as the memory 103.

[0030] The function of the control device 60 will be described in detail with reference to Fig. 4. Fig. 4 is a block diagram showing the refrigeration cycle device 1 according to the first embodiment. As shown in Fig. 4, the control device 60 has a determination unit 61 and an equipment control unit 62.

[0031] The determination unit 61 acquires the high-pressure pressure of the refrigerant indicated by the measurement result of the high-pressure sensor 51 during cooling operation. The determination unit 61 compares the high-pressure pressure of the refrigerant with a target value to determine whether the high-pressure pressure of the refrigerant is higher or lower than the target value. The target value is set in advance to a value that can maintain the compression ratio of the compressor 11 at a normal value and ensure the necessary condensing capacity. For example, when the refrigeration cycle device 1 is to perform at its rated capacity, a high-pressure pressure that will result in a condensing temperature of 50°C is set as the target value. When the refrigeration cycle device 1 is operated with emphasis on energy-saving performance, a high-pressure pressure that will result in a condensing temperature of 45°C is set as the target value.

[0032] The equipment control unit 62 controls each device of the refrigeration cycle apparatus 1. The equipment control unit 62 controls the operating frequency of the compressor 11, the opening degree of the load side throttle device 32, and the rotation speed of the outdoor fan 14 so that the indoor temperature measured by the indoor temperature sensor 81 becomes the set temperature set by the user via a remote control (not shown).

[0033] In particular, when the high-pressure pressure is less than the target value, the equipment control unit 62 controls the outdoor fan 14 and the bypass throttle device 72 to increase the high-pressure pressure. Specifically, when the high-pressure pressure is less than the target value, the equipment control unit 62 reduces the rotation speed of the outdoor fan 14 by a predetermined first rotation speed (e.g., 50 rpm). Here, because a sudden reduction in the rotation speed of the outdoor fan 14 may cause hunting, the equipment control unit 62 reduces the rotation speed of the outdoor fan 14 in stages by the first rotation speed each time it is determined that the high-pressure pressure is less than the target value. Note that the first rotation speed is set to an appropriate value based on the specifications of the outdoor fan 14 and the heat-source-side heat exchanger 12. Reducing the rotation speed of the outdoor fan 14 reduces the condensation capacity of the heat-source-side heat exchanger 12. This increases the condensation temperature, allowing the high-pressure pressure of the refrigeration cycle apparatus 1 to be increased.

[0034] The equipment control unit 62 also acquires information indicating the rotation speed of the outdoor fan 14 from the outdoor fan 14. If the high-pressure pressure is less than the target value even after the rotation speed of the outdoor fan 14 has been reduced to the minimum rotation speed, the equipment control unit 62 increases the opening degree of the bypass throttle device 72 by a predetermined first opening degree (e.g., 50 [pulse]). In other words, if the bypass throttle device 72 is closed when the opening degree of the bypass throttle device 72 is increased, the bypass throttle device 72 is opened. If the opening degree of the bypass throttle device 72 is increased suddenly, hunting may occur. Therefore, the equipment control unit 62 increases the opening degree of the bypass throttle device 72 in stages by the first opening degree each time it is determined that the high-pressure pressure is less than the target value. The first opening degree is set to an appropriate value depending on the specifications of the bypass throttle device 72. By increasing the opening degree of the bypass throttle device 72, the amount of refrigerant flowing through the heat source side heat exchanger 12 functioning as a condenser decreases, thereby reducing the condensing capacity of the heat source side heat exchanger 12. This increases the condensation temperature, allowing the high pressure of the refrigeration cycle apparatus 1 to be increased.

[0035] In particular, when the high-pressure exceeds the target value, the equipment control unit 62 controls the outdoor fan 14 and the bypass throttle device 72 to reduce the high-pressure. Specifically, when the high-pressure exceeds the target value, the equipment control unit 62 increases the rotation speed of the outdoor fan 14 by a predetermined first rotation speed (e.g., 50 rpm). Here, because a sudden increase in the rotation speed of the outdoor fan 14 may cause hunting, the equipment control unit 62 increases the rotation speed of the outdoor fan 14 stepwise by the first rotation speed each time it is determined that the high-pressure exceeds the target value. Increasing the rotation speed of the outdoor fan 14 increases the condensation capacity of the heat source-side heat exchanger 12. This reduces the condensation temperature, allowing the high-pressure of the refrigeration cycle apparatus 1 to be reduced.

[0036] The equipment control unit 62 also acquires information indicating the rotation speed of the outdoor fan 14 from the outdoor fan 14. If the high-pressure pressure exceeds a target value even when the rotation speed of the outdoor fan 14 is increased to the maximum rotation speed, the equipment control unit 62 reduces the opening degree of the bypass throttle device 72 by a predetermined first opening degree (e.g., 50 [pulses]). When reducing the opening degree of the bypass throttle device 72, if the opening degree of the bypass throttle device 72 is the minimum opening degree, the equipment control unit 62 closes the bypass throttle device 72. Because a sudden reduction in the opening degree of the bypass throttle device 72 may cause hunting, the equipment control unit 62 reduces the opening degree of the bypass throttle device 72 in stages by the first opening degree each time it is determined that the high-pressure pressure exceeds the target value. By reducing the opening degree of the bypass throttle device 72, the amount of refrigerant flowing through the heat-source-side heat exchanger 12, which functions as a condenser, increases, thereby improving the condensing capacity of the heat-source-side heat exchanger 12. This reduces the condensation temperature, allowing the high pressure in the refrigeration cycle device 1 to be reduced.

[0037] If the high-pressure pressure is equal to the target value, the equipment control unit 62 determines that there is no need to adjust the high-pressure pressure, and maintains the rotation speed of the outdoor fan 14 and the opening of the bypass throttle device 72. Note that the high-pressure pressure being equal to the target value does not necessarily mean that the two exactly match. If the high-pressure pressure is within a certain range based on the target value plus an error, etc., the high-pressure pressure can be considered to be equal to the target value.

[0038] The operation of the control device 60 according to the first embodiment will be described using a flowchart. Here, the operation for suppressing a drop in the high-pressure will be described. FIGS. 5 and 6 are flowcharts showing the operation of the control device 60 according to the first embodiment. In FIGS. 5 and 6, it is assumed that the refrigeration cycle device 1 is performing cooling operation. Also, FIGS. 5 and 6 show continuous processing. First, as shown in FIG. 5, the determination unit 61 determines whether the high-pressure of the refrigerant is less than a target value (step S1). If the high-pressure is less than the target value (step S1: YES), the equipment control unit 62 determines whether the rotation speed of the outdoor fan 14 is the minimum rotation speed (step S2). If the rotation speed of the outdoor fan 14 is greater than the minimum rotation speed (step S2: NO), the equipment control unit 62 reduces the rotation speed of the outdoor fan 14 by a first rotation speed (step S3). If the rotation speed of the outdoor fan 14 is the minimum rotation speed (step S2: YES), the equipment control unit 62 increases the opening degree of the bypass throttle device 72 by a first opening degree (step S4). When the processing of step S3 or S4 is completed, the control device 60 waits for a predetermined time (e.g., 30 seconds) (step S5) and then repeats the processing from step S1. The wait time in step S5 is set to avoid hunting, taking into consideration the time lag between adjusting the rotation speed of the outdoor fan 14 and the opening degree of the bypass throttle device 72 and reflecting the adjustment in the condensing capacity.

[0039] If the high-pressure pressure is equal to or greater than the target value (step S1: NO), as shown in FIG. 6, the determination unit 61 determines whether the high-pressure pressure exceeds the target value (step S6). If the high-pressure pressure exceeds the target value (step S6: YES), the equipment control unit 62 determines whether the rotation speed of the outdoor fan 14 is the maximum rotation speed (step S7). If the rotation speed of the outdoor fan 14 is lower than the maximum rotation speed (step S7: NO), the equipment control unit 62 increases the rotation speed of the outdoor fan 14 by a first rotation speed (step S8). If the rotation speed of the outdoor fan 14 is the maximum rotation speed (step S7: YES), the equipment control unit 62 decreases the opening degree of the bypass throttle device 72 by a first opening degree (step S9). When the processing of step S8 or S9 is completed, the control device 60 waits for a predetermined time (e.g., 30 seconds) (step S10) and repeats the processing from step S1. The waiting time in step S5 is set to avoid hunting, taking into consideration the time lag between adjusting the rotation speed of the outdoor fan 14 and the opening degree of the bypass throttle device 72 and reflecting the adjustment in the condensing capacity.

[0040] If the high-pressure is neither less than nor greater than the target value, that is, if the high-pressure is equal to the target value (step S1: NO and step S6: NO), the equipment control unit 62 determines that there is no need to adjust the high-pressure. In this case, the equipment control unit 62 maintains the rotation speed of the outdoor fan 14 and the opening degree of the bypass throttle device 72, and repeats the process from step S1.

[0041] One possible method for suppressing a drop in the high-pressure is to use a technique for limiting the heat transfer area of ​​the heat exchanger to a portion of the entire heat exchanger by providing a movable plate inside the heat exchanger header. If the heat exchanger in the refrigeration cycle apparatus 1 is a type other than a PFC heat exchanger, limiting the heat transfer area to a portion of the entire heat exchanger is unlikely to result in an excessive increase in the high-pressure to the extent that the compression ratio of the compressor significantly deviates from the normal value. However, if the heat exchanger in the refrigeration cycle apparatus 1 is a PFC heat exchanger, restricting the heat transfer area may result in an excessively small internal volume relative to the refrigerant flow rate, causing an excessive increase in the high-pressure. In contrast, according to the first embodiment, the control device 60 controls the aperture of the bypass throttle device 72 based on the high-pressure. This prevents an excessive increase in the high-pressure of the refrigeration cycle apparatus 1 having a PFC heat exchanger and suppresses an excessive decrease.

[0042] Furthermore, according to the first embodiment, the drop in the high-pressure is suppressed by controlling the opening of the bypass throttle device 72 without restricting the heat transfer area of ​​the heat exchanger. This makes it possible to suppress an excessive increase in pressure loss caused by restricting the heat transfer area in the PFC heat exchanger, which would otherwise cause a significant drop in heat exchange performance.

[0043] Furthermore, in the first embodiment, even if the rotation speed of the outdoor fan 14 is reduced to the minimum rotation speed, if the high-pressure pressure is less than the target value, the opening degree of the bypass throttle device 72 is increased by the first opening degree. Adjusting the opening degree of the bypass throttle device 72 has a greater impact on the condensation capacity than adjusting the rotation speed of the outdoor fan 14. Therefore, by prioritizing control of the rotation speed of the outdoor fan 14 over the opening degree of the bypass throttle device 72, a significant decrease in condensation capacity can be suppressed. However, regardless of the rotation speed of the outdoor fan 14, if the high-pressure pressure is less than the target value, the opening degree of the bypass throttle device 72 may be increased by the first opening degree. With this control, the high-pressure pressure of the refrigeration cycle apparatus 1 can be increased more quickly than with control in which the opening degree of the bypass throttle device 72 is increased by the first opening degree if the high-pressure pressure is less than the target value, even if the rotation speed of the outdoor fan 14 is reduced to the minimum rotation speed.

[0044] Furthermore, when the heat transfer area of ​​the heat exchanger is limited to a portion of the entire heat exchanger by providing a movable plate inside the heat exchanger header, the condensation capacity can only be adjusted when the heat transfer area is limited or not. In contrast, according to the first embodiment, the aperture of the bypass throttle device 72 is controlled in stages to suppress a drop in the high-pressure. Therefore, the aperture of the bypass throttle device 72 can be controlled to the minimum aperture that allows the high-pressure pressure to reach the target value, thereby preventing the condensation capacity from dropping more than necessary.

[0045] Furthermore, according to the first embodiment, when the high-side pressure exceeds the target value, the rotation speed of the outdoor fan 14 is increased or the opening of the bypass throttle device 72 is decreased. Therefore, the high-side pressure of the refrigeration cycle apparatus 1 can be prevented from rising excessively.

[0046] When the high-pressure is lower than the target value, a part of the refrigerant is bypassed to the bypass pipe 71, thereby reducing the cooling capacity of the refrigeration cycle device 1. However, since the required cooling capacity is small when performing cooling operation when the outside air temperature is low, the required condensing capacity of the heat exchanger is ensured even in this case.

[0047] Although the above is a description of the embodiments of the present disclosure, the present disclosure is not limited to the configurations of the above embodiments, and various modifications or combinations are possible within the scope of the technical concept. For example, in the first embodiment, the refrigeration cycle device 1 is an apparatus that performs only cooling operation, but the refrigeration cycle device 1 may have a flow path switching valve or the like for switching the flow direction of the refrigerant and may also perform heating operation.

[0048] Various aspects of the present disclosure are summarized below as appendices.

[0049] (Appendix 1) a compressor that compresses a refrigerant; a heat source side heat exchanger that performs heat exchange between the refrigerant discharged from the compressor and air; a throttle device that expands the refrigerant that has flowed out of the heat source side heat exchanger; a load-side heat exchanger that exchanges heat between the refrigerant flowing out of the expansion device and air; a bypass throttle device connected to the compressor in parallel with the heat source side heat exchanger and capable of adjusting its opening degree; a control device that controls an opening degree of the bypass throttle device based on a high pressure of the refrigerant discharged from the compressor, The heat source side heat exchanger has a pair of headers, a plurality of flat tubes arranged between the pair of headers, and corrugated fins arranged between the plurality of flat tubes. Refrigeration cycle equipment. (Appendix 2) The control device increases the opening degree of the bypass throttle device when the high-pressure is lower than a target value. 2. The refrigeration cycle device according to claim 1. (Appendix 3) The control device reduces the opening of the bypass throttle device when the high-pressure exceeds the target value. 3. The refrigeration cycle device according to claim 2. (Appendix 4) an outdoor fan for sending air to the heat source-side heat exchanger; The control device If the high pressure is less than the target value and the rotation speed of the outdoor fan is greater than a minimum rotation speed, reduce the rotation speed of the outdoor fan; When the high pressure is less than the target value and the rotation speed of the outdoor fan is the minimum rotation speed, the opening degree of the bypass throttle device is increased. 4. A refrigeration cycle device according to any one of claims 1 to 3. (Appendix 5) The control device If the high-pressure exceeds the target value and the rotation speed of the outdoor fan is lower than the maximum rotation speed, increasing the rotation speed of the outdoor fan; When the high-pressure is less than the target value and the rotation speed of the outdoor fan is the maximum rotation speed, the opening degree of the bypass throttle device is reduced. 5. A refrigeration cycle device according to any one of appendices 1 to 4. [Explanation of symbols]

[0050] 1 refrigeration cycle device, 2 outdoor unit, 3, 3a, 3b indoor units, 11 compressor, 12 heat source side heat exchanger, 13 accumulator, 14 outdoor fan, 21 high pressure gas pipe, 22 high pressure liquid pipe, 23 low pressure gas pipe, 31, 31a, 31b load side heat exchanger, 32, 32a, 32b load side throttle device, 51 high pressure pressure sensor, 60 control device, 61 determination unit, 62 equipment control unit, 71 bypass piping, 72 bypass throttle device, 81, 81a, 81b indoor temperature sensor, 91 outdoor temperature sensor, 101 processing circuit, 102 processor, 103 memory, 104 bus.

Claims

1. a compressor that compresses a refrigerant; a heat source side heat exchanger that performs heat exchange between the refrigerant discharged from the compressor and air; a throttle device that expands the refrigerant that has flowed out of the heat source side heat exchanger; a load-side heat exchanger that exchanges heat between the refrigerant flowing out of the expansion device and air; a bypass throttle device connected to the compressor in parallel with the heat source side heat exchanger and capable of adjusting its opening degree; a control device that controls an opening degree of the bypass throttle device based on a high pressure of the refrigerant discharged from the compressor, The heat source side heat exchanger has a pair of headers, a plurality of flat tubes arranged between the pair of headers, and corrugated fins arranged between the plurality of flat tubes. Refrigeration cycle equipment.

2. The control device increases the opening degree of the bypass throttle device when the high-pressure is lower than a target value. The refrigeration cycle device according to claim 1.

3. The control device reduces the opening of the bypass throttle device when the high-pressure exceeds the target value. The refrigeration cycle device according to claim 2.

4. an outdoor fan for sending air to the heat source-side heat exchanger; The control device If the high pressure is less than the target value and the rotation speed of the outdoor fan is greater than a minimum rotation speed, reduce the rotation speed of the outdoor fan; When the high pressure is less than the target value and the rotation speed of the outdoor fan is the minimum rotation speed, the opening degree of the bypass throttle device is increased. The refrigeration cycle device according to claim 2 or 3.

5. The control device If the high-pressure exceeds the target value and the rotation speed of the outdoor fan is lower than the maximum rotation speed, increasing the rotation speed of the outdoor fan; When the high-pressure is less than the target value and the rotation speed of the outdoor fan is the maximum rotation speed, the opening degree of the bypass throttle device is reduced. The refrigeration cycle device according to claim 4.

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