WO2023233452A1

WO2023233452A1 - Outdoor unit and refrigeration cycle device

Info

Publication number: WO2023233452A1
Application number: PCT/JP2022/021891
Authority: WO
Inventors: 素早坂; 隆池田; 悠介有井; 智隆石川
Original assignee: 三菱電機株式会社
Priority date: 2022-05-30
Filing date: 2022-05-30
Publication date: 2023-12-07

Abstract

This outdoor unit is configured to be connected to a load device including a first expansion valve and an evaporator. The outdoor unit comprises: a compressor having a suction port and a discharge port; a condenser; a heat exchanger that has a first passage and a second passage and exchanges heat between a refrigerant flowing in the first passage and a refrigerant flowing in the second passage; and a control device. The compressor, the condenser, the first passage of the heat exchanger, the first expansion valve of the load device, and the evaporator of the load device form a circulation flow path in which the refrigerant circulates. Further provided is a bypass flow path which allows the refrigerant to flow from a first branch section disposed between an outlet of the condenser and the load device in the circulation flow path to a first connection section disposed between the suction port and the load device. The bypass flow path has a suction on-off valve that switches whether the refrigerant flows into the first connection section. The control device controls the compressor and the suction on-off valve. If the control device executes an oil recovery operation to recover refrigerating machine oil that remains in the circulation flow path, the control device, before starting the oil recovery operation, opens the suction on-off valve to allow the refrigerant to flow into the first connection section from the bypass flow path.

Description

Outdoor unit and refrigeration cycle equipment

The present disclosure relates to an outdoor unit and a refrigeration cycle device.

Patent Document 1 discloses a refrigeration system that includes a compressor, a condenser, a liquid receiver, an expansion valve, an accumulator, a circulation passage through which a refrigerant circulates through an evaporator, and an injection passage branching from the circulation passage. is disclosed. In the refrigeration system described in Patent Document 1, a part of the refrigerant flowing from the condenser toward the expansion valve is merged with the intermediate-pressure refrigerant of the compressor using an injection flow path, thereby adjusting the discharge temperature of the compressor. It is possible to reduce the

Furthermore, the refrigeration apparatus described in Patent Document 1 includes an economizer that performs heat exchange between the refrigerant flowing in the circulation channel from the condenser toward the expansion valve and the refrigerant flowing in the injection channel. An economizer is a type of heat exchanger. By using the economizer, the refrigerant flowing from the condenser toward the expansion valve is cooled by the refrigerant flowing through the injection flow path, thereby ensuring supercooling. At this time, if the intermediate injection pressure becomes higher than the desired degree of supercooling, supercooling cannot be ensured. Therefore, the refrigeration system described in Patent Document 1 further includes a suction injection and performs injection into the low-pressure piping on the suction side of the compressor to reduce the pressure in the injection flow path and ensure supercooling. There is.

Here, the accumulator has a function of not directly returning the liquid refrigerant to the compressor, and an oil return mechanism that returns only the refrigerating machine oil taken out from the compressor to the compressor. The oil return mechanism of the accumulator is composed of U-shaped piping. One end of the U-shaped pipe is an outflow pipe that returns refrigerating machine oil to the compressor side. The outflow pipe is inserted into and fixed to the upper part of the container of the accumulator. Further, the bent portion of the U-shaped pipe is configured to be disposed below the container of the accumulator. An oil return hole is provided at the bottom of the bent portion of the U-shaped pipe.

International Publication No. 2021/048898

As mentioned above, the refrigerating machine oil taken out from the compressor accumulates in the evaporator or in the suction pipe connecting the outdoor unit and the load device. If the refrigerating machine oil does not return to the compressor, the compressor may run out of oil, which may cause wear or failure of the compressor.

In the refrigeration system described in Patent Document 1, an accumulator is provided before the compressor. The accumulator temporarily stores therein the liquid refrigerant and refrigerating machine oil that return from the load device to the compressor. The accumulator mainly returns the refrigerating machine oil to the compressor through the oil return hole, thereby preventing the compressor from running out of oil.

However, in order to collect the refrigerating machine oil on the load equipment side into the accumulator, it is necessary to collect the refrigerating machine oil that has accumulated in each pipe due to the viscosity of the refrigerating machine oil by using the flow rate of the refrigerant. This can be achieved by speeding up. However, in general, compressors use the evaporation temperature as a target value to control the capacity to send out refrigerant per unit time. The evaporation pressure value (that is, the low pressure value) is reached, and the refrigeration system enters the thermo-off state. As a result, it is not possible to secure sufficient time to recover refrigerating machine oil. Note that the term "thermo OFF" refers to a state in which when the controlled value reaches the target value, the compressor stops operating and only air is blown to the air-conditioned space.

Therefore, in a typical refrigeration system, the operation of the outdoor unit is temporarily stopped when recovering refrigeration oil from the load device. Then, after confirming that the evaporation temperature has risen, the compressor is started, and an oil recovery operation is periodically performed in which the compressor is operated at a frequency higher than a certain level. Therefore, the operational efficiency of the refrigeration system deteriorates due to losses caused by starting and stopping the oil recovery operation.

Furthermore, when the accumulator operates the oil return mechanism in a state where liquid refrigerant and refrigerating machine oil are mixed in the accumulator, the internal state of the accumulator is in one of the following cases. In other words, the internal state of the accumulator is either a state in which the refrigerating machine oil and the refrigerant are dissolved, or a state in which the refrigerating machine oil and the refrigerant are separated into two phases with the density of the refrigerating machine oil being higher than that of the refrigerant and the refrigerating machine oil being accumulated at the bottom. It is one of the following states. When the refrigerating machine oil and refrigerant are dissolved, the oil return mechanism of the accumulator works well. On the other hand, when the refrigerating machine oil and the refrigerant are separated into two phases, the oil return mechanism of the accumulator may not function and the refrigerating machine oil may accumulate in the accumulator. In this way, when the accumulator operates the oil return mechanism, the operation of the oil return mechanism largely depends on physical property values such as the viscosity and solubility of the refrigerating machine oil. However, depending on the combination of refrigerant and refrigerant oil, the refrigerant oil and refrigerant may separate into two phases within the operating range of the refrigeration system. Therefore, within the operating range of the refrigeration system, not all combinations of refrigerant and refrigeration oil satisfy favorable conditions for the operation of the oil return mechanism.

The present disclosure has been made to solve such problems, and utilizes the characteristics of refrigerating machine oil to control whether or not refrigerant flows from the injection flow path into the circulation flow path, thereby ensuring sufficient return. The object is to obtain an outdoor unit and a refrigeration cycle device that can ensure oil capacity.

An outdoor unit according to the present disclosure is an outdoor unit configured to be connected to a load device including a first expansion valve and an evaporator, and includes a compressor having a suction port and a discharge port, and a condenser. a heat exchanger having a first passage and a second passage and performing heat exchange between a refrigerant flowing in the first passage and a refrigerant flowing in the second passage, and a control device, The compressor, the condenser, the first passage of the heat exchanger, the first expansion valve of the load device, and the evaporator of the load device form a circulation flow path in which refrigerant circulates, and the a bypass that allows refrigerant to flow from a first branch located between the outlet of the condenser and the load device in the circulation flow path to a first connection located between the suction port and the load device; The bypass flow path further includes a suction on-off valve that switches whether or not refrigerant flows into the first connection portion, and the control device controls the compressor and the suction on-off valve. When performing an oil recovery operation to recover refrigerating machine oil remaining in the circulation flow path, the control device opens the suction on-off valve before starting the oil recovery operation. , the refrigerant is caused to flow into the first connection portion from the bypass flow path.

A refrigeration cycle device according to the present disclosure includes the outdoor unit described above and the load device connected to the outdoor unit.

According to the outdoor unit and refrigeration cycle device according to the present disclosure, an injection flow path that bypasses the high pressure side and the low pressure side is provided. When performing oil recovery operation to recover refrigerating machine oil accumulated in the circulation flow path, the control device opens the suction on-off valve and disconnects the suction port and load from the injection flow path before starting the oil recovery operation. A refrigerant is introduced into a first connection disposed between the refrigerant and the device. As a result, the pressure of the refrigerant in the circulation path between the load device and the suction port increases, and the viscosity, which is one of the characteristics of refrigerating machine oil, decreases. As a result, refrigerating machine oil can be easily recovered. In this way, by utilizing the characteristics of refrigerating machine oil to control whether or not refrigerant flows into the circulation flow path from the injection flow path, sufficient oil return capacity can be achieved according to the conditions of the refrigerant and refrigerating machine oil. can be secured.

1 is a configuration diagram showing the overall configuration of a refrigeration cycle device 1 according to Embodiment 1. FIG. 2 is a configuration diagram showing various sensors and a control device 100 arranged in the refrigeration cycle device 1 shown in FIG. 1. FIG. This is a Daniel chart showing the characteristics of refrigeration oil and refrigerant. This is a Daniel chart showing the characteristics of refrigeration oil and refrigerant. 2 is a flowchart showing a procedure for transitioning from normal operation to oil recovery operation in the refrigeration cycle device 1 according to the first embodiment. 2 is a flowchart showing a processing procedure of an oil recovery operation under first control in the refrigeration cycle device 1 according to the first embodiment. 7 is a flowchart showing a processing procedure for oil recovery operation under second control in the refrigeration cycle device 1 according to the first embodiment. It is a control flowchart when the compressor 10 is started during normal operation in the refrigeration cycle device 1 according to the first embodiment. FIG. 2 is a configuration diagram showing the overall configuration of a refrigeration cycle device 1 according to a second embodiment. 10 is a configuration diagram showing various sensors and a control device 100 arranged in the refrigeration cycle device 1 shown in FIG. 9. FIG. It is a control flowchart when the compressor 10 is started during normal operation in the refrigeration cycle device 1 according to the second embodiment. FIG. 7 is a diagram schematically showing a configuration of an accumulator 40 provided in a refrigeration cycle device 1 according to a third embodiment.

Hereinafter, embodiments of an outdoor unit and a refrigeration cycle device according to the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments, and can be variously modified without departing from the gist of the present disclosure. Furthermore, the present disclosure includes all combinations of configurations that can be combined among the configurations shown in the following embodiments and modifications thereof. Furthermore, in each figure, the same reference numerals are the same or equivalent, and this is common throughout the entire specification. Identical or equivalent configurations are indicated by the same reference numerals, and their descriptions will not be repeated. Note that in each drawing, the relative dimensional relationship or shape of each component may differ from the actual one.

Embodiment 1.
(Configuration of refrigeration cycle device 1)
FIG. 1 is a configuration diagram showing the overall configuration of a refrigeration cycle device 1 according to the first embodiment. Note that FIG. 1 functionally shows the connection relationship and arrangement of each device in the refrigeration cycle device 1, and does not necessarily show the arrangement in a physical space.

As shown in FIG. 1, the refrigeration cycle device 1 includes an outdoor unit 2, a load device 3, a first extension pipe 88, and a second extension pipe 84. The outdoor unit 2 and the load device 3 are connected via a first extension pipe 88 and a second extension pipe 84.

The outdoor unit 2 is an outdoor unit of the refrigeration cycle device 1 configured to be connected to the load device 3. The outdoor unit 2 is installed outdoors. On the other hand, the load device 3 is a load device of the refrigeration cycle device 1, and is installed in the space to be cooled. The space to be cooled is, for example, an indoor space.

The outdoor unit 2 includes a compressor 10, a condenser 20, a fan 22, a liquid receiver 73, a heat exchanger 30, an accumulator 40, and piping 80 to 83 and 89. The heat exchanger 30 has a first passage H1 and a second passage H2, and performs heat exchange between the refrigerant flowing through the first passage H1 and the refrigerant flowing through the second passage H2. Heat exchanger 30 is sometimes called an economizer.

The load device 3 includes a first expansion valve 50, an evaporator 60, and piping 85 to 87. Evaporator 60 performs heat exchange between air and refrigerant. The evaporator 60 is, for example, a fin-and-tube heat exchanger having heat exchanger tubes and fins. In the refrigeration cycle device 1, the evaporator 60 evaporates the refrigerant by absorbing heat from the air in the space to be cooled. The first expansion valve 50 is, for example, an electronic expansion valve that reduces the pressure of the refrigerant. Further, the first expansion valve 50 may be a temperature expansion valve that is controlled independently of the outdoor unit 2, for example. The piping 85 has one end connected to the second extension piping 84 and the other end connected to the inlet of the first expansion valve 50 . The piping 86 has one end connected to the outlet of the first expansion valve 50 and the other end connected to the inlet of the evaporator 60. The piping 87 has one end connected to the outlet of the evaporator 60 and the other end connected to the first extension piping 88 . The load device 3 also includes an on-off valve 28 that operates to prevent the object to be cooled from becoming too cold. By detecting the temperature of the object to be cooled (temperature inside the refrigerator, etc.) and closing the on-off valve 28, it is possible to prevent excessive cooling and adjust the temperature of the object to be cooled. In addition, for periodic defrosting operation, the operation of closing the on-off valve 28 and turning off the thermostat is also carried out.

The accumulator 40, the compressor 10, the condenser 20, the liquid receiver 73, the first passage H1 of the heat exchanger 30, the first expansion valve 50 of the load device 3, and the evaporator 60 of the load device 3 are connected to the refrigerant. Forms a "main refrigerant circuit" that circulates in sequence. The "main refrigerant circuit" is sometimes called the "circulation flow path" of the refrigeration cycle.

In the accumulator 40 , refrigerant flows into the pipe 89 and flows out into the pipe 97 . Piping 89 is a piping arranged between first extension piping 88 and accumulator 40 . Further, the pipe 97 is a pipe arranged between the accumulator 40 and the compressor 10.

The compressor 10 has a suction port G1, a discharge port G2, and an intermediate pressure port G3. The compressor 10 compresses the refrigerant sucked through the

pipes

97 and 96 and discharges it to the pipe 80. The pipe 96 is a pipe that constitutes a part of an injection flow path 101, which will be described later, and is connected to an intermediate pressure port G3 of the compressor 10. Piping 97 connects accumulator 40 and suction port G1 of compressor 10. The compressor 10 is, for example, an inverter compressor whose driving frequency can be arbitrarily changed by inverter control. As described above, the compressor 10 is provided with the intermediate pressure port G3, and the refrigerant from the intermediate pressure port G3 can be made to flow into the middle part of the compression process. Compressor 10 is configured to adjust its rotational speed according to a control signal from control device 100 (see FIG. 2). By adjusting the rotational speed of the compressor 10, the amount of refrigerant circulated can be adjusted, and the capacity of the refrigeration cycle device 1 can be adjusted. The compressor 10 can be of various types, such as a scroll type, a rotary type, a screw type, or a two-stage compression type of each of these types. In addition, in the compressor 10, the operation of the compressor 10 is performed according to the air conditioning load of the space to be cooled within the control value range of "minimum frequency" and "maximum frequency" set for control by the control device 100. The frequency is determined and operation is carried out. "Minimum frequency" is sometimes referred to as the minimum operating frequency or minimum allowable frequency. The "highest frequency" is sometimes referred to as the maximum operating frequency or the maximum allowed frequency. In addition, in the following explanation, the "minimum frequency" set during normal operation will be referred to as "first minimum frequency", and the "minimum frequency" set during oil recovery operation for recovering refrigerating machine oil will be referred to as "second minimum frequency". ”.

The inlet of the condenser 20 is connected to a pipe 80, into which the high-temperature, high-pressure gas refrigerant discharged from the compressor 10 flows. The condenser 20 is configured so that the high temperature, high pressure gas refrigerant discharged from the discharge port G2 of the compressor 10 and the outside air exchange heat (radiate heat). The condenser 20 is, for example, a fin-and-tube heat exchanger having heat exchanger tubes and fins. Through heat exchange in the condenser 20, the refrigerant is condensed and changed from a gas phase to a liquid phase. In this way, the refrigerant discharged from the compressor 10 to the pipe 80 is condensed and liquefied in the condenser 20 and flows out to the pipe 81. Further, a fan 22 for feeding outside air is attached to the condenser 20 in order to increase the efficiency of heat exchange in the condenser 20. The fan 22 supplies outside air to the condenser 20 with which the refrigerant exchanges heat in the condenser 20 . By adjusting the rotational speed of the fan 22, the refrigerant pressure (high pressure side pressure) on the discharge side of the compressor 10 can be adjusted. The rotation speed of fan 22 is controlled by control device 100.

The liquid receiver 73 is connected between the piping 81 and the piping 82. The liquid receiver 73 is a container that stores the refrigerant that has been condensed into a liquid phase in the condenser 20 as a surplus amount of refrigerant with respect to the main refrigerant circuit. The pipe 81 is a pipe that connects the outlet of the condenser 20 and the inlet of the liquid receiver 73. The pipe 82 is a pipe that connects the outlet of the liquid receiver 73 and the inlet of the first passage H1 of the heat exchanger 30.

The outdoor unit 2 further includes an "injection passage 101" that branches from the main refrigerant circuit and sends refrigerant to the compressor 10 via the second passage H2. Injection channel 101 is composed of pipes 91 to 92, pipe 96, and pipe 98. Note that the "injection flow path 101" is sometimes referred to as a "bypass flow path."

The injection flow path 101 is provided between the first branch portion P1 and the first connection portion P2. The first branch P1 is arranged between the outlet of the condenser 20 and the load device 3 in the main refrigerant circuit. More specifically, the first branch P1 is arranged between the outlet of the first passage H1 in the main refrigerant circuit and the load device 3. On the other hand, the first connecting portion P2 is arranged upstream of the suction port G1 of the compressor 10. More specifically, the first connection portion P2 is arranged between the load device 3 and the accumulator 40.

The injection flow path 101 includes a "first refrigerant flow path" made up of a pipe 91, a "second refrigerant flow path" made up of a pipe 92 and a pipe 98, and a "third refrigerant flow path" made of a pipe 96. ``Route''.

The "first refrigerant flow path" (piping 91) is a refrigerant flow path for flowing the refrigerant from the pipe 83, which is the high-pressure part of the main refrigerant circuit, to the inlet of the second passage H2 of the heat exchanger 30. One end of the pipe 91 is connected to the pipe 83, and the other end of the pipe 91 is connected to the entrance of the second passage H2.

The "third refrigerant flow path" (piping 96) is a refrigerant flow path branched from the "second refrigerant flow path" (pipes 92, 98). One end of the "third refrigerant flow path" (piping 96) is connected to the piping 92, and the other end is connected to the intermediate pressure port G3 of the compressor 10. The "third refrigerant flow path" is a refrigerant flow path for flowing refrigerant from the outlet of the second passage H2 of the heat exchanger 30 to the intermediate pressure port G3 of the compressor 10. Piping 96 is arranged between piping 92 and intermediate pressure port G3.

The "second refrigerant flow path" (pipes 92, 98) is connected at one end to the outlet of the second passage H2 of the heat exchanger 30 and at the other end to the first connection part P2 arranged in the piping 89. There is. The "second refrigerant flow path" (piping 92, 98) is a refrigerant flow path for flowing the refrigerant from the outlet of the second passage H2 of the heat exchanger 30 to the first connection portion P2. Piping 92 is arranged between the outlet of second passage H2 and piping 96. Piping 98 is arranged between piping 92 and first connection portion P2. The piping 89 is a piping connected between the first extension piping 88 and the accumulator 40, as shown in FIG.

An intermediate on-off valve 75 is arranged in the "third refrigerant flow path" (piping 96) of the injection flow path 101. By opening and closing the intermediate on-off valve 75, it is possible to switch whether or not refrigerant flows from the third refrigerant flow path to the intermediate pressure port G3 of the compressor 10. In addition, in FIG. 1, the intermediate on-off valve 75 does not necessarily need to be provided. If the intermediate opening/closing valve 75 is not provided, the second expansion valve 71 controls the amount of refrigerant flowing into the intermediate pressure port G3 or controls whether or not the refrigerant flows into the intermediate pressure port G3.

Furthermore, a suction on-off valve 76 is arranged in the "second refrigerant flow path" (pipes 92, 98) of the injection flow path 101. More specifically, the suction on-off valve 76 is arranged in the pipe 98 of the second refrigerant flow path. By opening and closing the suction on-off valve 76, it is possible to switch whether or not the refrigerant flows from the second refrigerant flow path to the first connection portion P2.

In this way, the intermediate on-off valve 75 and the suction on-off valve 76 function as a flow path switching device that switches the destination of the refrigerant flowing out from the outlet of the second passage H2. Specifically, when the suction on-off valve 76 is in the open state, the refrigerant flowing out from the outlet of the second passage H2 flows into the pipe 89. On the other hand, when the intermediate on-off valve 75 is open and the suction on-off valve 76 is closed, the refrigerant flowing out from the outlet of the second passage H2 flows to the intermediate pressure port G3. The opening and closing operations of the intermediate on-off valve 75 and the suction on-off valve 76 cause the refrigerant from the injection flow path 101 to flow into at least one of the intermediate pressure port G3 and the first connection portion P2 of the compressor 10.

Further, a second expansion valve 71 is arranged in the pipe 91. The second expansion valve 71 is an electronic expansion valve that can reduce the pressure of the refrigerant flowing from the pipe 83, which is a high pressure section in the main refrigerant circuit, to an intermediate pressure PM. Therefore, the pressure of the refrigerant flowing through the "second refrigerant flow path" and the "third refrigerant flow path" is the intermediate pressure PM.

As described above, in the first embodiment, by providing the injection flow path 101 and the heat exchanger 30, it becomes easy to ensure the degree of supercooling in the pipe 83, which is the liquid pipe of the main refrigerant circuit.

The heat exchanger 30 has a first passage H1 and a second passage H2, and is configured to exchange heat between the refrigerant flowing through the first passage H1 and the refrigerant flowing through the second passage H2. The heat exchanger 30 performs heat exchange between the refrigerant flowing through the first passage H1, which is a part of the main refrigerant circuit, and the refrigerant flowing through the second passage H2, which is a part of the injection passage 101. At this time, the refrigerant flowing through the first passage H1 is on the side to be cooled. The first passage H1 has an inlet connected to the pipe 82 and an outlet connected to the pipe 83. The second passage H2 has an inlet connected to the pipe 91 and an outlet connected to the pipe 92.

FIG. 2 is a configuration diagram showing various sensors and the control device 100 arranged in the refrigeration cycle device 1 shown in FIG. As shown in FIG. 2, the outdoor unit 2 includes pressure sensors 110 to 112, temperature sensors 120 to 125, and a control device 100. Further, as shown in FIG. 2, the load device 3 includes a temperature sensor 126.

The pressure sensor 110 detects the pressure PL at the suction port G1 of the compressor 10 and outputs the detected value to the control device 100. Pressure PL is sometimes referred to as "low pressure" or "evaporation pressure." The pressure sensor 111 detects the discharge pressure PH of the refrigerant discharged from the discharge port G2 of the compressor 10, and outputs the detected value to the control device 100. Discharge pressure PH is sometimes referred to as "high pressure" or "condensing pressure." Further, the pressure sensor 112 detects the intermediate pressure PM of the refrigerant flowing out from the outlet of the second passage H2 and flowing through the pipe 92, and outputs the detected value to the control device 100. Intermediate pressure PM is lower than discharge pressure PH and higher than pressure PL.

In the following description, in the direction in which the refrigerant of the refrigeration cycle device 1 flows, the area from the discharge port G2 of the compressor 10 to the inlet of the first expansion valve 50 will be referred to as the "high pressure side", and the outlet of the first expansion valve 50 will be referred to as the "high pressure side". The area from the air to the suction port G1 of the compressor 10 is referred to as the "low pressure side." Furthermore, the injection flow path 101 is referred to as an "intermediate pressure section."

The temperature sensor 120 detects the discharge temperature TH of the refrigerant discharged from the compressor 10 and outputs the detected value to the control device 100. The temperature sensor 121 detects the refrigerant temperature T1 of the pipe 81 at the outlet of the condenser 20 and outputs the detected value to the control device 100. The temperature sensor 122 detects the refrigerant temperature at the outlet of the first passage H1 of the heat exchanger 30 as the outlet temperature T2 of the heat exchanger 30, and outputs the detected value to the control device 100.

The temperature sensor 123 detects the ambient temperature of the outdoor unit 2 as the outside air temperature TA, and outputs the detected value to the control device 100. The temperature sensor 123 is placed, for example, near the condenser 20, but may be placed on the casing of the outdoor unit 2, and the placement position is not limited. The temperature sensor 124 detects the temperature TL of the pipe 97 connected to the suction port G1 of the compressor 10 and outputs the detected value to the control device 100. The temperature sensor 125 detects the temperature at the outlet of the second passage H2 of the heat exchanger 30 and outputs the detected value to the control device 100.

The temperature sensor 126 detects the outlet temperature of the evaporator 60 and automatically adjusts the first expansion valve 50.

The control device 100 includes a CPU (Central Processing Unit) 102, a memory 104, an input/output buffer (not shown) for inputting and outputting various signals, and the like. The memory 104 includes a ROM (Read Only Memory) and a RAM (Random Access Memory). The CPU 102 expands the program stored in the ROM into a RAM or the like and executes the program. The program stored in the ROM is a program in which the processing procedure of the control device 100 is written. The control device 100 executes control of each device in the outdoor unit 2 according to these programs. This control is not limited to processing by software, but can also be performed by dedicated hardware (electronic circuit).

The control device 100 controls the operations of the compressor 10, the second expansion valve 71, the intermediate on-off valve 75, and the suction on-off valve 76. Further, the control device 100 may also control the first expansion valve 50.

(Characteristics of refrigeration oil)
3 and 4 are Daniel charts representing the characteristics of refrigerating machine oil and refrigerant. In FIGS. 3 and 4, the horizontal axis represents temperature, and the vertical axis represents oil viscosity. Each diagonal line in FIGS. 3 and 4 indicates the solubility between the refrigerant and the refrigerant in the refrigerating machine oil, and each curve indicates an isobaric line.

As shown in FIGS. 3 and 4, it can be seen that as a characteristic of the refrigerant and the refrigerating machine oil, when the pressure is increased, the viscosity of the refrigerating machine oil tends to decrease.

(Control of discharge temperature TH by second expansion valve 71)
During normal operation, the control device 100 opens the intermediate on-off valve 75 and closes the suction on-off valve 76, and controls the second temperature so that the discharge temperature TH of the compressor 10 matches a preset target temperature. The opening degree of the expansion valve 71 is feedback-controlled. Specifically, the control device 100 acquires the discharge temperature TH of the compressor 10 from the temperature sensor 120. When the discharge temperature TH of the compressor 10 is higher than the target temperature, the control device 100 increases the opening degree of the second expansion valve 71. As a result, the amount of refrigerant flowing into the intermediate pressure port G3 via the liquid receiver 73 increases, so that the discharge temperature TH decreases.

On the other hand, if the discharge temperature TH of the compressor 10 is lower than the target temperature, the control device 100 reduces the opening degree of the second expansion valve 71. As a result, the amount of refrigerant flowing into the intermediate pressure port G3 via the liquid receiver 73 decreases, so that the discharge temperature TH increases.

When the discharge temperature TH is the target temperature, the control device 100 maintains the opening degree of the second expansion valve 71 at the current state.

In this way, the control device 100 controls the opening degree of the second expansion valve 71 so that the discharge temperature TH of the compressor 10 approaches the target temperature.

(Oil recovery operation control)
In the refrigeration cycle device 1 according to the first embodiment, it is necessary to appropriately collect refrigeration oil that has accumulated in the main refrigerant circuit, for example, in the load device 3 or the first extension pipe 88 due to continuous operation. Periodic oil recovery operation is performed depending on the operating state of the compressor 10. The reason why the refrigerating machine oil accumulates in the load device 3 or the first extension pipe 88 is that the flow rate of the refrigerant in the pipe falls below a certain threshold value, causing the refrigerant oil to accumulate due to the viscosity of the oil. Therefore, the control device 100 determines the timing to perform the oil recovery operation based on the operating frequency of the compressor 10. Then, the control device 100 increases the speed of the compressor 10 at the determined appropriate timing and increases the amount of refrigerant circulating through the refrigeration cycle device 1, thereby increasing the flow rate of the refrigerant in the pipes and causing the refrigerant to accumulate. Collect the refrigerating machine oil.

As mentioned above, FIGS. 3 and 4 show Daniel charts representing characteristics depending on the combination of refrigerating machine oil and refrigerant. From the Daniel charts of FIGS. 3 and 4, it can be seen that the viscosity of refrigerating machine oil tends to decrease as the pressure increases. Utilizing this characteristic of refrigerating machine oil, in the first embodiment, as a means to increase the pressure on the low pressure side of the compressor 10, the opening and closing of the suction on-off valve 76 is controlled to perform an oil recovery operation using suction injection. do.

FIG. 5 is a flowchart showing a procedure for transitioning from normal operation to oil recovery operation in the refrigeration cycle device 1 according to the first embodiment.

As shown in FIG. 5, the control device 100 determines whether the compressor 10 is in the activated state (step S1). If the compressor 10 is not started (YES in step S1), start-up control of the compressor 10 is performed using control of the intermediate on-off valve 75 and the suction on-off valve 76, which are flow path switching devices (step S2). . The startup control of the compressor 10 performed in step S2 will be described later using FIG. 8.

On the other hand, if the compressor 10 is activated (NO in step S1), the control device 100 determines whether the current operating frequency of the compressor 10 is lower than a preset second minimum frequency. (Step S3). The second lowest frequency is the lowest frequency used by the control device 100 to control the compressor 10 when performing the oil recovery operation.

If the current operating frequency of the compressor 10 is lower than the second minimum frequency (YES in step S3), the control device 100 proceeds to the process of step S4. On the other hand, if the current operating frequency of the compressor 10 is equal to or higher than the second lowest frequency, the flow in FIG. 5 is directly ended.

In step S4, the control device 100 determines whether the operating frequency of the compressor 10 continues to be lower than the second minimum frequency for a preset first period or more. That is, the control device 100 determines whether or not a first period or more has elapsed since the operating frequency of the compressor 10 was determined to be lower than the second minimum frequency in step S3. Note that the first period is, for example, one hour, but is not limited thereto.

If it is determined that the operating frequency of the compressor 10 is lower than the second minimum frequency for the first period or longer (YES in step S4), the control device 100 performs the oil recovery operation in step S6 or step S7. do.

The control device 100 determines whether or not the suction port G1 of the compressor 10 is in a liquid back state in step S5 to determine which of step S6 and step S7 to select. That is, before starting the oil recovery operation, the control device 100 determines whether the state of the suction port G1 of the compressor 10 is in a liquid back state, and controls the oil recovery operation based on the presence or absence of the liquid back state. The type of control is switched (step S5). Here, an example will be described in which the control device 100 has first control and second control as types of control for oil recovery operation. Note that the liquid back state means that the refrigerant sucked into the compressor 10 is not completely evaporated in the evaporator 60, and liquid refrigerant is continuously sucked into the compressor 10 together with the gas refrigerant. Note that when the suction port G1 of the compressor 10 is in a liquid back state, the following conditions are satisfied.

(Saturation temperature at pressure PL) - (temperature TL) <first threshold (1)

That is, in step S5, the control device 100 determines the presence or absence of liquid back by determining whether the above conditions are satisfied. Therefore, the control device 100 acquires the pressure PL at the suction port G1 portion of the compressor 10 from the pressure sensor 110. Then, the control device 100 calculates the saturation temperature of the refrigerant at the pressure PL based on the pressure PL. The control device 100 also acquires the temperature TL of the suction pipe of the compressor 10 from the temperature sensor 124. Then, the control device 100 determines whether the difference DL between the saturation temperature of the refrigerant at the pressure PL and the temperature TL is less than a first threshold value set in advance. Note that the first threshold is, for example, 5K (Kelvin), but is not limited to this.

If the difference DL is less than the first threshold, the control device 100 determines that the compressor 10 is in a liquid back state (NO in step S5), and performs the oil recovery operation under the second control in step S7.

On the other hand, if the difference DL is greater than or equal to the first threshold value, the control device 100 determines that the compressor 10 is not in the liquid back state (YES in step S5), and performs the oil recovery operation according to the first control in step S6.

Note that in the first embodiment, since the compressor 10 is an inverter compressor, the operating frequency of the compressor 10 varies. Therefore, as shown in the flowchart of FIG. 5, the control device 100 determines the timing to perform the oil recovery operation based on the operating frequency of the compressor 10. However, the first embodiment is not limited to that case. For example, if the compressor 10 is not an inverter compressor but a constant-speed compressor, there is no frequency fluctuation, so regular oil recovery operation may be performed at a preset cycle. In that case, instead of steps S3 and S4 in the flow of FIG. 5, the control device 100 determines whether the integrated value of the operating time of the compressor 10 is equal to or greater than a preset threshold. If the integrated value of the operating time of the compressor 10 is equal to or greater than the threshold value, the process proceeds to step S5, and if the integrated value of the operating time of the compressor 10 is less than the threshold value, the flow of FIG. 5 is directly ended.

(Oil recovery operation when there is no liquid back)
FIG. 6 is a flowchart showing the processing procedure of the oil recovery operation under the first control in the refrigeration cycle device 1 according to the first embodiment. In FIG. 6, the control device 100 determines that there is no liquid back in step S5 of FIG. It shows the flow.

When the control device 100 moves to step S6 in FIG. 5, as shown in FIG. 6, the control device 100 opens the suction on-off valve 76 (step S11). Thereby, the high pressure side and the low pressure side of the refrigeration cycle device 1 are bypassed, so that the pressure PL of the low pressure portion detected by the pressure sensor 110 can be increased.

Next, the control device 100 determines whether the pressure PL exceeds a preset second threshold (step S12). If the pressure PL exceeds the second threshold, the process advances to step S13. On the other hand, if the pressure PL is less than or equal to the second threshold, the process advances to step S16. In step S16, the control device 100 determines whether a preset second period or more has elapsed since the first determination in step S12. The second period is, for example, 3 minutes, but is not limited thereto. If it is determined in step S16 that the second period or more has not elapsed (NO in step S16), the control device 100 returns to the process in step S12. On the other hand, if it is determined in step S16 that the second period or more has elapsed (YES in step S16), the control device 100 proceeds to the process in step S13.

In this way, when the pressure PL has been sufficiently increased in steps S12 and S16 by opening the suction on-off valve 76, the suction on-off valve 76 is closed (step S13). Note that the reason for performing the process in step S16 is as follows. If the mode is such that the pressure PL cannot rise completely and the suction on-off valve 76 is kept open, the amount of refrigerant circulating to the evaporator 60 will decrease during that period. In that case, the refrigeration capacity of the refrigeration cycle device 1 becomes insufficient, and the space to be cooled becomes uncooled. Therefore, it is desirable to close the suction on-off valve 76 when the viscosity of the refrigerating machine oil can be reduced to some extent, that is, after the second period has elapsed.

Next, the control device 100 changes the lowest frequency from the first lowest frequency during normal operation to the second lowest frequency during oil recovery operation (step S14). Note that the second lowest frequency is set to a higher frequency than the first lowest frequency.

In this way, in step S14, by changing the setting of the lowest frequency of the compressor 10 to the second lowest frequency necessary for the oil recovery operation, the operation continues at the second lowest frequency or higher in subsequent operations. be able to.

Next, the control device 100 determines whether the operation at the second lowest frequency or higher continues for a preset third period or longer (step S15). The third period is, for example, 5 minutes, but is not limited to this. If the operation at the second lowest frequency or higher has not continued for the third period or longer (NO in step S15), the control device 100 returns to the process in step S14. On the other hand, if the operation at the second lowest frequency or higher continues for a third period or longer (YES in step S15), the control device 100 returns the lowest frequency to the original first lowest frequency (step S17) and shifts to normal operation. .

As described above, in the flow of FIG. 6, the low pressure side pressure PL detected by the pressure sensor 110 is increased by opening the suction on-off valve 76. Thereby, there is an advantage that the viscosity, which is a characteristic of refrigerating machine oil, described above using the Daniel charts of FIGS. 3 and 4 can be reduced. Furthermore, in order to recover the refrigerating machine oil accumulated in the load device 3, it is necessary to increase the speed of the compressor 10. However, if the speed of the compressor 10 is increased for oil recovery operation with the target evaporation temperature set during normal operation, the evaporation temperature will immediately fall below the target evaporation temperature and the thermostat will be turned off, causing the Oil recovery operations may not be able to continue. Therefore, in the flow of FIG. 6, the saturation temperature of the pressure PL detected by the pressure sensor 110 is increased by opening the suction on-off valve 76. Thereby, the operating frequency of the compressor 10 is naturally increased by the capacity control of the compressor 10 by the control device 100, and the oil recovery operation can be continued at a sufficiently high operating frequency. In Patent Document 1 mentioned above, thermo-off is avoided by stopping operation for a certain period of time, but in that case, the operating efficiency of the refrigeration cycle apparatus deteriorates due to the start and stop of the refrigeration cycle apparatus. On the other hand, in the first embodiment, by opening the suction on-off valve 76, it is possible to avoid turning off the thermostat and continue the oil recovery operation for a sufficient period of time. The number of stops can be reduced. As a result, the operating efficiency of the refrigeration cycle device can be improved. Furthermore, by opening the suction on-off valve 76, oil recovery operation can be performed with the viscosity, which is a characteristic of refrigerating machine oil, reduced.

(Oil recovery operation when there is liquid back)
FIG. 7 is a flowchart showing the processing procedure of the oil recovery operation under the second control in the refrigeration cycle device 1 according to the first embodiment. In FIG. 7, the control device 100 determines that there is a liquid back in step S5 of FIG. It shows the flow.

The second control in FIG. 7 is performed when it is determined in step S5 in FIG. 5 that there is liquid back. When the suction on-off valve 76 is opened in a liquid back state, the refrigerant in the liquid state from the pipe 83 is injected into the first connection part P2, which promotes a tendency for the suction port G1 of the compressor 10 to become slightly damp. There is a risk of Therefore, due to the condition of the load device 3, if oil recovery operation is performed with the suction on-off valve 76 opened while the operation is already in liquid back mode, liquid back up will be promoted and the accumulator 40 will overflow. This may lead to failure of the compressor 10.

Therefore, in the first embodiment, when the control device 100 detects the liquid back state based on the detected values of the pressure sensor 110 and the temperature sensor 124, the compressor 10 is first stopped as shown in FIG. (Step S21).

Then, with the compressor 10 stopped, the suction on-off valve 76 is opened (step S22).

Next, the control device 100 changes the lowest frequency from the first lowest frequency during normal operation to the second lowest frequency during oil recovery operation, and then restarts the compressor 10 with the suction on-off valve 76 closed. (Step S23). Note that when moving from step S22 to step S23, processing similar to step S12 and step S16 in FIG. 6 may be performed.

Next, the control device 100 increases the operating frequency of the compressor 10 to the second lowest frequency (step S24). Then, the control device 100 determines whether the operation at the second lowest frequency or higher continues for a preset fourth period or longer (step S25). The fourth period is, for example, 5 minutes, but is not limited to this. If the operation at the second lowest frequency or higher has not continued for the fourth period or longer (NO in step S25), the control device 100 returns to the process in step S24. On the other hand, if the operation at the second lowest frequency or higher continues for a fourth period or longer (YES in step S25), the control device 100 returns the lowest frequency to the first lowest frequency during normal operation (step S26) and returns to normal operation. Transition.

As described above, in the flow of FIG. 7, by bringing the compressor 10 into a stopped state and opening the suction on-off valve 76, it is possible to suppress the flow of wet refrigerant into the suction port G1 side of the compressor 10. can. In addition, in the oil recovery control in Patent Document 1 mentioned above, after the compressor is stopped, the compressor is restarted after a certain period of time has passed in order to sufficiently increase the low pressure detected by the pressure sensor. . On the other hand, in the first embodiment, by opening the suction on-off valve 76, the pressure PL on the low pressure side can be immediately increased. Therefore, the pressure PL can be increased in the flow of FIG. 7 as well as in the flow of FIG. 7 when the suction on-off valve 76 is opened while the compressor 10 is operating as in the flow of FIG. As a result, even in the flow of FIG. 7, it is possible to avoid turning off the thermostat and continue the oil recovery operation for a sufficient period of time, so the number of times the refrigeration cycle device 1 starts and stops can be reduced. Thereby, the operating efficiency of the refrigeration cycle device can be improved. Furthermore, by opening the suction on-off valve 76, oil recovery operation can be performed with the viscosity, which is a characteristic of refrigerating machine oil, reduced.

(Control flow when starting the compressor 10 during normal operation)
FIG. 8 is a control flowchart when the compressor 10 is started during normal operation in the refrigeration cycle device 1 according to the first embodiment. The control flow in FIG. 8 is the control flow executed in step S2 in FIG.

As shown in FIG. 8, when the operation of the compressor 10 is stopped in the steady state during normal operation, the control device 100 closes the intermediate on-off valve 75 and the suction on-off valve 76 (step S31).

Next, the control device 100 starts the compressor 10 (step S32) and increases the operating frequency of the compressor 10 (step S33).

Next, the control device 100 determines whether the current operating frequency of the compressor 10 has become equal to or higher than the first lowest frequency during normal operation (step S34).

If the current operating frequency of the compressor 10 is less than the first lowest frequency during normal operation (NO in step S34), the control device 100 returns to the process in step S33. On the other hand, if it is confirmed that the current operating frequency of the compressor 10 has increased to the first lowest frequency during normal operation (YES in step S34), the control device 100 proceeds to the process of step S35.

In step S35, the control device 100 opens the intermediate on-off valve 75 and performs normal operation. In normal operation, the discharge temperature TH is controlled by the second expansion valve 71 described above.

As described above, in the first embodiment, when the control device 100 performs the oil recovery operation, the suction on-off valve 76 is opened. As a result, the high-pressure side and the low-pressure side are bypassed, and the refrigerant flows from the first branch part P1 arranged in the pipe 83 to the first connecting part P2 arranged upstream of the accumulator 40. As a result, the pressure PL on the low pressure side increases. Refrigerating machine oil has a property that its viscosity decreases as the pressure increases. Therefore, as the pressure PL increases, the viscosity of the refrigerating machine oil remaining in the main refrigerant circuit decreases. Thereby, the refrigerating machine oil in each pipe of the main refrigerant circuit can be easily recovered depending on the flow rate of the refrigerant. As described above, in the first embodiment, the refrigerant and the refrigerant oil are controlled by controlling whether or not the refrigerant flows into the main refrigerant circuit, which is the circulation flow path, from the injection flow path 101 by utilizing the characteristics of the refrigerant oil. Sufficient oil return capacity can be ensured according to the conditions.

Furthermore, in the first embodiment, the control device 100 determines the timing to perform the oil recovery operation according to the control flow shown in FIG. That is, the control device 100 determines to perform the oil recovery operation when the compressor 10 is in operation and the current operating frequency of the compressor 10 is lower than the second minimum frequency that requires the oil recovery operation. do. Thereby, the oil recovery operation can be performed at appropriate timing compared to the case where the oil recovery operation is performed periodically at a fixed period. As a result, the oil recovery operation is not performed at an unnecessary timing, so it is possible to suppress a decrease in operating efficiency due to starting and stopping of the oil recovery operation.

Further, in the first embodiment, when performing the oil recovery operation, the control device 100 sets the lowest frequency of the compressor 10 to a second lowest frequency higher than the first lowest frequency, which is the lowest frequency during normal operation. Set. As described above, when the frequency of the compressor 10 is increased, the evaporation pressure decreases and falls below the target evaporation pressure. Therefore, in the first embodiment, after the pressure PL on the low pressure side is increased by opening the suction on-off valve 76, the frequency of the compressor 10 is increased to the second lowest frequency, and the suction on-off valve 76 is opened. The frequency of turning off the thermostat can be reduced compared to the case without it. As a result, it is possible to prevent the oil recovery operation from being interrupted due to the thermostat being turned off, and thus it is possible to secure time to recover the refrigerating machine oil.

Further, in the first embodiment, the control device 100 determines whether or not the state of the suction port G1 of the compressor 10 is in a liquid back state before performing the oil recovery operation according to the control flow shown in FIG. are doing. The control device 100 switches the type of oil recovery operation control based on the presence or absence of liquid back. That is, if there is no liquid back, the oil recovery operation is performed using the first control according to the control flow shown in FIG. On the other hand, if there is liquid back, oil recovery operation is performed using the second control according to the control flow shown in FIG. If the suction on-off valve 76 is opened in a state where liquid back is already present, liquid back will be promoted. Therefore, in the second control, the suction on-off valve 76 is opened while the compressor 10 is stopped. Thereby, the pressure PL on the low pressure side can be increased without being affected by liquid back.

Embodiment 2.
FIG. 9 is a configuration diagram showing the overall configuration of the refrigeration cycle device 1 according to the second embodiment. FIG. 10 is a configuration diagram showing various sensors and a control device 100 arranged in the refrigeration cycle device 1 shown in FIG. Note that FIG. 9 functionally shows the connection relationship and arrangement of each device in the refrigeration cycle device 1, and does not necessarily show the arrangement in a physical space.

The difference between the first embodiment and the second embodiment is that in the refrigeration cycle device 1 according to the second embodiment, an outdoor unit 2A is provided instead of the outdoor unit 2 shown in FIG. In the outdoor unit 2A, a liquid receiver 73A is arranged in the injection flow path 101. Further, a flow rate adjustment valve 72,

pipes

93 and 94, and a gas vent passage 95 are added to the injection flow path 101. Furthermore, a check valve 77 is added to the piping 89 disposed upstream of the accumulator 40. The check valve 77 is a valve that prevents refrigerant from flowing in a direction opposite to the flow of refrigerant in the main refrigerant circuit. Since the other configurations are the same as those in FIG. 1, they are denoted by the same reference numerals, and the explanation thereof will be omitted here. In addition, in FIG. 9, the intermediate on-off valve 75 does not necessarily need to be provided. If the intermediate opening/closing valve 75 is not provided, the second expansion valve 71 controls the amount of refrigerant flowing into the intermediate pressure port G3, or controls whether or not the refrigerant flows into the intermediate pressure port G3.

As shown in FIGS. 9 and 10, in the second embodiment, an embodiment will be described in which a liquid receiver 73A is provided in the injection flow path 101.

In the second embodiment, the injection flow path 101 is provided between the first branch portion P1A and the first connection portion P2A. The first branch P1A is arranged between the condenser 20 and the load device 3 in the main refrigerant circuit. More specifically, the first branch P1A is arranged between the outlet of the condenser 20 and the inlet of the first passage H1 in the main refrigerant circuit. On the other hand, the first connection portion P2A is arranged upstream of the suction port G1 of the compressor 10. More specifically, the first connecting portion P2A is connected to an injection pipe 44 of the accumulator 40, which will be described later. However, the present invention is not limited to this, and in the second embodiment, the first connection part P2A is disposed between the load device 3 and the accumulator 40, similarly to the first connection part P2 of the first embodiment. Good too.

The injection flow path 101 is comprised of a "first refrigerant flow path" comprised of

pipes

91A, 91B, 93, and 94, a "third refrigerant flow path" comprised of pipe 96, and

pipes

92, 98. and a "second refrigerant flow path."

The "first refrigerant flow path" (

pipes

91A, 91B, 93, 94) is a refrigerant flow path for flowing the refrigerant from the high-pressure part of the main refrigerant circuit, ie, the pipe 81, to the inlet of the second passage H2 of the heat exchanger 30. It is a road. One end of the "first refrigerant flow path" is connected to the pipe 81, and the other end of the "first refrigerant flow path" is connected to the entrance of the second passage H2. The pipe 91A is a pipe between the first branch part P1A arranged in the pipe 81 and the second expansion valve 71. The pipe 91B is a pipe between the second expansion valve 71 and the inlet of the liquid receiver 73A. The pipe 93 is a pipe connected between the outlet of the liquid receiver 73A and the flow rate adjustment valve 72. The pipe 94 is a pipe connected between the flow rate regulating valve 72 and the inlet of the second passage H2.

As in the first embodiment, the "third refrigerant flow path" (piping 96) branches from the "second refrigerant flow path" and connects from the outlet of the second passage H2 to the intermediate pressure port G3 of the compressor 10. This is a refrigerant flow path through which refrigerant flows.

The "second refrigerant flow path" (piping 92, 98) is connected to the first connection part P2A, as in the first embodiment. The "second refrigerant flow path" (piping 92, 98) is a refrigerant flow path that allows the refrigerant to flow from the outlet of the second passage H2 to the first connection portion P2A.

(Configuration of outdoor unit 2A)
As shown in FIG. 9, in the outdoor unit 2A, a liquid receiver 73A for storing refrigerant and a second expansion valve 71 are arranged in the "first refrigerant flow path" of the injection flow path 101. . Note that the liquid receiver 73A is sometimes called a receiver. The inlet of liquid receiver 73A is connected to piping 81 via

piping

91A and 91B. The pipe 81 is a pipe connected between the outlet of the condenser 20 and the inlet of the first passage H1. Further, the second expansion valve 71 is arranged between the pipe 91A and the pipe 91B.

In the "first refrigerant flow path" of the injection flow path 101, a flow rate adjustment valve 72 and a gas vent passage 95 are further arranged. The flow rate adjustment valve 72 is an expansion valve arranged between a pipe 93 connected to the outlet of the liquid receiver 73A and a pipe 94 connected to the second passage H2. Further, the gas vent passage 95 is a pipe that connects the gas discharge port of the liquid receiver 73A and the inlet of the second passage H2, and discharges the refrigerant gas in the liquid receiver 73A.

A two-phase refrigerant that has been depressurized by the second expansion valve 71 flows into the liquid receiver 73A. The liquid receiver 73A is a container that internally separates the two-phase refrigerant into gas and liquid, stores the refrigerant, and can adjust the amount of refrigerant in the main refrigerant circuit. A gas vent passage 95 connected to the upper part of the liquid receiver 73A and a pipe 93 connected to the lower part of the liquid receiver 73A separate the refrigerant into gas refrigerant and liquid refrigerant in the liquid receiver 73A. This is a pipe for taking out the product in a separated state. That is, the gas vent passage 95 is a pipe for taking out gas refrigerant, and the pipe 93 is a pipe for taking out liquid refrigerant. The flow rate adjustment valve 72 is a valve that adjusts the amount of circulating liquid refrigerant discharged from the liquid receiver 73A. By adjusting the circulating amount of liquid refrigerant discharged from the pipe 93 using the flow rate adjustment valve 72, the amount of refrigerant in the liquid receiver 73A can be adjusted. The opening degree of the flow rate adjustment valve 72 is controlled by the control device 100.

Generally, depending on the type of refrigerant, such as _CO2 , the discharge pressure PH from the compressor 10 may exceed the critical pressure of the refrigerant. When such a high-pressure supercritical refrigerant is used, if the receiver 73A is provided in the

pipes

91A and 91B, which are the high-pressure parts of the main refrigerant circuit, the refrigerant in the

pipes

91A and 91B becomes supercritical, and the receiver Liquid refrigerant cannot be stored in the container 73A. In that case, the buffer function of the excess refrigerant amount by the liquid receiver 73A is lost.

In contrast, in the second embodiment, a second expansion valve 71 is provided on the inlet side of the liquid receiver 73A. The second expansion valve 71 reduces the pressure of the refrigerant flowing through the pipe 91A from high pressure to intermediate pressure. Therefore, the pressure of the refrigerant flowing through the pipe 91B is an intermediate pressure. By providing the liquid receiver 73A in the pipe 92, which is an intermediate pressure section, it becomes possible to store liquid refrigerant in the liquid receiver 73A even in operation in a supercritical state. As a result, the buffer function of the surplus refrigerant amount by the liquid receiver 73A is maintained, and the amount of refrigerant can be adjusted.

In this manner, in the second embodiment, the dryness of the refrigerant in the injection flow path 101 can be controlled by the second expansion valve 71. Therefore, if the dryness of the refrigerant is controlled so that liquid back does not occur, it is sufficient to perform only the oil recovery operation according to the first control in the case of no liquid back shown in FIG. 6 described above. In this case, since the compressor 10 is not stopped for oil recovery operation, starting and stopping during oil recovery operation can be completely eliminated.

(Oil recovery operation control)
In the second embodiment, similarly to the first embodiment, the normal operation is shifted to the oil recovery operation according to the control flow shown in FIG. 5 described above. Since the control flow in FIG. 5 is the same as that described in Embodiment 1, the description thereof will be omitted here. However, in the second embodiment, the content of the "compressor start control" process in step S2 in FIG. 5 is different from the first embodiment. The process of "compressor start control" in step S2 in FIG. 5 in the second embodiment will be described later using FIG. 11. Further, regarding the process of "oil recovery operation using first control" in step S6 of FIG. 5 and the process of "oil recovery operation using second control" of step S7, FIGS. Since this is the same as described above, the explanation thereof will be omitted here.

(Control flow when starting the compressor 10 during normal operation)
FIG. 11 is a control flowchart when the compressor 10 is started during normal operation in the refrigeration cycle device 1 according to the second embodiment. FIG. 11 shows a control flow when starting up the compressor 10 when the check valve 77 is installed in the pipe 89.

Depending on the compressor 10, if the pressure on the high pressure side and the pressure on the low pressure side are not equal at the time of startup, a load will be applied to the compressor 10, which may cause deterioration in the startup performance of the compressor 10. Therefore, in the second embodiment, a check valve 77 is installed in the pipe 89. Further, the first connection portion P2A to which the suction on-off valve 76 of the injection flow path 101 is connected is installed downstream of the check valve 77. As a result, by opening the suction on-off valve 76 when starting the compressor 10, the pressure on the high pressure side and the pressure at the suction port G1 portion of the compressor 10 become the same pressure value, ensuring the startability of the compressor 10. can do. Hereinafter, control at startup of the compressor 10 during normal operation in Embodiment 2 will be described using FIG. 11.

As shown in FIG. 11, when the operation of the compressor 10 is stopped in the steady state during normal operation, the control device 100 closes the intermediate on-off valve 75 and the suction on-off valve 76 (step S41).

Next, the control device 100 starts the compressor 10 (step S42).

Next, the control device 100 opens the suction on-off valve 76 while the compressor 10 continues to operate (step S43).

Next, the control device 100 increases the operating frequency of the compressor 10 (step S44).

Next, the control device 100 determines whether the current operating frequency of the compressor 10 has become equal to or higher than the first minimum frequency during normal operation (step S45).

If the current operating frequency of the compressor 10 is less than the first lowest frequency during normal operation (NO in step S45), the control device 100 returns to the process in step S44. On the other hand, if it is confirmed that the current operating frequency of the compressor 10 has increased to the first lowest frequency during normal operation (YES in step S45), the control device 100 proceeds to the process of step S46.

In step S46, the control device 100 closes the suction on-off valve 76, opens the intermediate on-off valve 75, and performs normal operation. In normal operation, the discharge temperature TH is controlled by the second expansion valve 71 described in the first embodiment. Since the content of the control is the same as described in Embodiment 1, the description thereof will be omitted here.

In the second embodiment, by providing the check valve 77 downstream of the load device 3, the suction on-off valve 76 can be opened every time the compressor 10 is started. With this configuration, when the compressor 10 is started, the effect of increasing the pressure PL is brought about, so that the viscosity, which is a characteristic of refrigerating machine oil, can be reduced. Therefore, oil can be recovered even when the compressor 10 is started during normal operation, and the efficiency of oil recovery can be further improved.

As described above, in the second embodiment, similarly to the first embodiment, the suction on-off valve 76 is opened when the control device 100 performs the oil recovery operation. As a result, the high pressure side and the low pressure side are bypassed, and the refrigerant flows from the first branch part P1A arranged in the pipe 81 to the first connection part P2A arranged upstream of the suction port G1 of the compressor 10. As a result, the pressure PL on the low pressure side increases. Refrigerating machine oil has a property that its viscosity decreases as the pressure increases. Therefore, as the pressure PL increases, the viscosity of the refrigerating machine oil remaining in the main refrigerant circuit decreases. Thereby, the refrigerating machine oil in each pipe of the main refrigerant circuit can be easily recovered depending on the flow rate of the refrigerant. As described above, in the second embodiment, similarly to the first embodiment, the characteristics of refrigerating machine oil are used to control whether or not refrigerant flows into the main refrigerant circuit, which is a circulation flow path, from the injection flow path 101. are doing. By allowing the refrigerant to flow into the first connection portion P2A from the injection flow path 101, sufficient oil return capacity is ensured in accordance with the conditions of the refrigerant and refrigerating machine oil.

Furthermore, in the second embodiment, similarly to the first embodiment, the control device 100 determines the timing to perform the oil recovery operation according to the control flow shown in FIG. That is, the control device 100 determines to perform the oil recovery operation when the compressor 10 is in operation and the current operating frequency of the compressor 10 is lower than the second minimum frequency that requires the oil recovery operation. do. Thereby, the oil recovery operation can be performed at appropriate timing compared to the case where the oil recovery operation is performed periodically at a fixed period. As a result, the oil recovery operation is not performed at an unnecessary timing, so it is possible to suppress a decrease in operating efficiency due to starting and stopping of the oil recovery operation.

Further, in the second embodiment, as in the first embodiment, the control device 100 sets the lowest frequency of the compressor 10 to the first lowest frequency, which is the lowest frequency during normal operation, when performing the oil recovery operation. The second lowest frequency is set higher than the frequency. In this manner, in the second embodiment, as in the first embodiment, the frequency of the compressor 10 is increased to the second lowest frequency after the pressure PL on the low pressure side is increased by opening the suction on-off valve 76. speed up Thereby, the frequency of thermo-off can be reduced compared to the case where the suction on-off valve 76 is not opened. As a result, it is possible to prevent the oil recovery operation from being interrupted due to the thermostat being turned off, and thus it is possible to secure time to recover the refrigerating machine oil.

In addition, in the second embodiment, as in the first embodiment, the control device 100 determines whether the state of the suction port G1 of the compressor 10 is liquid before performing the oil recovery operation according to the control flow of FIG. It is determined whether the camera is in the back position or not. The control device 100 switches the type of oil recovery operation control based on the presence or absence of liquid back. That is, if there is no liquid back, the oil recovery operation is performed using the first control according to the control flow shown in FIG. On the other hand, if there is liquid back, oil recovery operation is performed using the second control according to the control flow shown in FIG. In the second control, the suction on-off valve 76 is opened while the compressor 10 is stopped. Thereby, the pressure PL on the low pressure side can be increased without being affected by liquid back.

Furthermore, in the second embodiment, a second expansion valve 71 that reduces the pressure of the refrigerant to an intermediate pressure is provided on the inlet side of the liquid receiver 73A. Therefore, even in operation in a supercritical state, liquid refrigerant can be stored in the liquid receiver 73A. As a result, the buffer function of the surplus refrigerant amount by the liquid receiver 73A is maintained, and the amount of refrigerant can be adjusted.

Furthermore, in the second embodiment, a flow rate adjustment valve 72 is provided on the outlet side of the liquid receiver 73A to adjust the circulation amount of the liquid refrigerant discharged from the liquid receiver 73A. The amount of refrigerant in the liquid receiver 73A can be adjusted by adjusting the circulating amount of liquid refrigerant discharged from the liquid receiver 73A using the flow rate adjustment valve 72. As a result, even in a supercritical state where the discharge pressure PH of the compressor 10 exceeds the critical pressure of the refrigerant, the amount of refrigerant contained in the main refrigerant circuit and the injection flow path 101 is controlled based on the opening degree of the flow rate adjustment valve 72. Can be adjusted.

Embodiment 3.
FIG. 12 is a diagram schematically showing the configuration of an accumulator 40 provided in the refrigeration cycle device 1 according to the third embodiment. As shown in FIG. 12, in the third embodiment, the injection flow path 101 is connected to the lower part of the casing 41 of the accumulator 40. Note that the configuration of the refrigeration cycle device 1 is as described in Embodiment 1 or Embodiment 2, so its connections will be omitted here.

The accumulator 40 includes a casing 41, an inflow pipe 42, an outflow pipe 43, and an injection pipe 44.

The casing 41 is a container that stores refrigerant and refrigerator oil inside. The accumulator 40 has a sealed structure with a casing 41.

The inflow pipe 42 is arranged to pass through the upper part of the casing 41. An upper end 42a of the inflow pipe 42 is arranged outside the casing 41, and a lower end 42b of the inflow pipe 42 is arranged inside the casing 41. The inflow pipe 42 has, for example, an L-shape, but is not limited thereto. The inflow pipe 42 directs the refrigerant flowing from the pipe 89 into the internal space of the casing 41 . Therefore, the inflow pipe 42 passes through the upper part of the casing 41, and the lower end 42b of the inflow pipe 42 is open at the upper part of the internal space of the casing 41.

The outflow pipe 43 is arranged to pass through the upper part of the casing 41. The outflow pipe 43 has a U-shape. The outflow pipe 43 causes the gas refrigerant and refrigerating machine oil separated in the internal space of the casing 41 to flow into the suction port G1 (see FIGS. 1 and 9) of the compressor 10 through the pipe 97. Therefore, the outflow pipe 43 is installed to penetrate the upper part of the casing 41, and one end 43a of the outflow pipe 43 is arranged outside the casing 41. Further, the other end 43b of the outflow pipe 43 is open at the upper part of the internal space of the casing 41. The outflow pipe 43 has a curved pipe portion 43c located below the internal space of the casing 41. An oil return hole 45 is formed at the lowest part of the curved pipe portion 43c. Furthermore, the outflow pipe 43 has a pressure equalizing hole 46 . The pressure equalizing hole 46 is arranged on the one end 43a side of the outflow pipe 43, and is arranged below the upper part of the casing 41. The outflow pipe 43 is arranged near the penetration part where the outflow pipe 43 penetrates the casing 41. The pressure equalizing hole 46 is arranged inside the casing 41.

The injection pipe 44 is arranged to penetrate the lower part of the casing 41. The injection pipe 44 forms the first connection part P2 (see FIG. 1) or the first connection part P2A (see FIG. 9) itself, to which the

pipes

92 and 98, which are the second refrigerant flow paths, are connected. It functions as part P2 or P2A. Alternatively, the injection pipe 44 is connected to the first connection portion P2 (see FIG. 1) or the first connection portion P2A (see FIG. 9). When the suction on-off valve 76 is opened, the refrigerant from the second refrigerant flow path flows into the injection pipe 44. The injection pipe 44 allows the refrigerant to flow into the internal space of the casing 41 . Note that the "injection piping 44" is sometimes called "bypass piping".

As described above, in the third embodiment, the tip of the pipe 98 provided with the suction on-off valve 76 is installed as the injection pipe 44 so as to penetrate through the lower part of the casing 41. Thereby, when the suction on-off valve 76 is opened, the refrigerant from the high pressure side flows into the casing 41 of the accumulator 40 with force.

With this configuration, the refrigerant accumulated in the accumulator 40 and the refrigerating machine oil can be forcibly stirred while lowering the viscosity of the refrigerating machine oil by increasing the pressure PL as described in

Embodiments

1 and 2.

Depending on the combination of refrigerant and refrigerating machine oil, the refrigerant and refrigerating machine oil may separate into two phases, as shown in the left diagram of FIG. In such a case, for example, if the refrigerating machine oil separates into the upper part of the refrigerant, it becomes impossible to recover the refrigerating machine oil to the compressor 10 through the oil return hole 45. Therefore, in the third embodiment, an injection pipe 44 is provided at the lower part of the accumulator 40 to force the refrigerant to flow into the lower part of the internal space of the accumulator 40. By forcefully forcing the refrigerant into the injection pipe 44 in this way, the refrigerant and refrigerating machine oil in the internal space of the accumulator 40 are agitated, as shown in the right diagram of FIG. As a result, the refrigerating machine oil that has been separated above the refrigerant mixes uniformly with the refrigerant through stirring, so that the refrigerating machine oil can be recovered through the oil return hole 45.

In the oil recovery operation described in the first and second embodiments described above, by combining the configuration of the accumulator 40 shown in the third embodiment, when performing the oil recovery operation, the refrigerant and the refrigerating machine oil are always mixed by stirring. can be in a mixed state. In this way, the oil recovery operation can be carried out with the refrigerant and refrigerating machine oil mixed inside the accumulator 40, thereby making it possible to further improve the efficiency of oil recovery.

As described above, in the third embodiment, when the oil recovery operation is performed, by opening the suction on-off valve 76, the inside of the accumulator 40 is agitated by the refrigerant forcefully flowing in from the injection pipe. Thereby, the oil recovery operation can be performed in a state where the refrigerant and the refrigerating machine oil are mixed, so that the efficiency of oil recovery can be further improved.

Further, in the third embodiment, the refrigerant stirred in the accumulator 40 flows into the pipe 97 from the outflow pipe 43. As a result, similarly to

Embodiments

1 and 2, the high pressure side and the low pressure side are bypassed, and the pressure PL on the low pressure side increases. Refrigerating machine oil has a property that its viscosity decreases as the pressure increases. Therefore, as the pressure PL increases, the viscosity of the refrigerating machine oil remaining in the main refrigerant circuit decreases. Thereby, the refrigerating machine oil in each pipe of the main refrigerant circuit can be easily recovered depending on the flow rate of the refrigerant.

Note that in the first to third embodiments described above, a refrigerator including a refrigeration cycle device was described as an example, but the refrigeration cycle device may also be used in an air conditioner or the like.

Further, in the first to third embodiments described above, the case where the compressor 10 has the intermediate pressure port G3 has been described, but the present invention is not limited to that case. That is, the compressor 10 does not need to have the intermediate pressure port G3. In that case, in the refrigeration cycle apparatus 1, the piping 96 and the intermediate on-off valve 75 shown in FIGS. 1 and 9 are also not installed. In this case as well, the operation of the refrigeration cycle device 1 is basically the same as in the first to third embodiments, except that all the refrigerant sucked into the compressor 10 is sucked through the suction port G1. This is the point. Therefore, in this case as well, as in the first to third embodiments, the control device 100 opens the suction on-off valve 76 before performing the oil recovery operation to increase the pressure PL on the low pressure side. Thereby, as in the first to third embodiments described above, sufficient oil return capacity can be ensured.

Embodiments 1 to 3 disclosed herein are illustrative in all respects and should not be considered restrictive. The scope of the present disclosure is indicated by the claims rather than the above description, and it is intended that all changes within the meaning and range equivalent to the claims are included.

Further, in the first to third embodiments, as the refrigerant, for example, an HFC (Hydro Fluoro Carbon) refrigerant such as R32, or an HFO (Hydro Fluoro Orefin) refrigerant such as R1234yf can be used. Furthermore, in Embodiments 1 to 3, it is also possible to use, for example, a high-pressure supercritical refrigerant such as CO ₂ as the refrigerant. Furthermore, in Embodiments 1 to 3, non-azeotropic refrigerants can also be used, and among the non-azeotropic refrigerants, it is also possible to use, in particular, a CO ₂ mixed refrigerant such as R463A.

1 Refrigeration cycle device, 2 outdoor unit, 2A outdoor unit, 3 load device, 10 compressor, 20 condenser, 22 fan, 28 on-off valve, 30 heat exchanger, 40 accumulator, 41 casing, 42 inflow pipe, 42a upper end , 42b lower end, 43 outflow pipe, 43a one end, 43b other end, 43c bent pipe section, 44 injection pipe, 45 oil return hole, 46 pressure equalization hole, 50 first expansion valve, 60 evaporator, 71 second expansion valve, 72 Flow rate adjustment valve, 73 Liquid receiver, 73A Liquid receiver, 75 Intermediate on-off valve, 76 Suction on-off valve, 77 Check valve, 80 Piping, 81 Piping, 82 Piping, 83 Piping, 84 Second extension piping, 85 Piping , 86 piping, 87 piping, 88 first extension piping, 89 piping, 91 piping, 91A piping, 91B piping, 92 piping, 93 piping, 94 piping, 95 gas vent passage, 96 piping, 97 piping, 98 piping, 100 control Device, 101 Injection channel, 102 CPU, 104 Memory, 110 Pressure sensor, 111 Pressure sensor, 112 Pressure sensor, 120 Temperature sensor, 121 Temperature sensor, 122 Temperature sensor, 123 Temperature sensor, 124 Temperature sensor, 125 Temperature sensor, 126 Temperature sensor, DL differential, G1 suction port, G2 discharge port, G3 intermediate pressure port, H1 first passage, H2 second passage, P1 first branch, P1A first branch, P2 first connection, P2A first Connection, PH discharge pressure, PL pressure, PM intermediate pressure, T1 refrigerant temperature, T2 outlet temperature, TA outside temperature, TH discharge temperature, TL temperature.

Claims

An outdoor unit configured to be connected to a load device including a first expansion valve and an evaporator,
a compressor having a suction port and a discharge port;
a condenser;
A heat exchanger having a first passage and a second passage, and performing heat exchange between a refrigerant flowing in the first passage and a refrigerant flowing in the second passage;
a control device;
Equipped with
The compressor, the condenser, the first passage of the heat exchanger, the first expansion valve of the load device, and the evaporator of the load device form a circulation flow path in which refrigerant circulates,
flowing a refrigerant from a first branch located between the outlet of the condenser and the load device in the circulation flow path to a first connection located between the suction port and the load device; Further equipped with a bypass flow path,
The bypass flow path is
a suction on-off valve that switches whether or not refrigerant flows into the first connection part;
The control device controls the compressor and the suction on-off valve,
When performing an oil recovery operation to recover refrigerating machine oil remaining in the circulation flow path, the control device opens the suction on-off valve and removes oil from the bypass flow path before starting the oil recovery operation. causing a refrigerant to flow into the first connection part;
outdoor unit.
The control device opens the suction on-off valve to increase the pressure of the refrigerant in the circulation flow path between the load device and the suction port, and then closes the suction on-off valve to increase the pressure of the refrigerant in the circulation flow path between the load device and the suction port. Start recovery operation,
The outdoor unit according to claim 1.
The control device sets the lowest frequency of the compressor to a second lowest frequency higher than the first lowest frequency during normal operation, and performs the oil recovery operation.
The outdoor unit according to claim 1 or 2.
The control device opens the suction on-off valve to allow refrigerant to flow from the bypass flow path to the first connection portion, then closes the suction on-off valve, and then adjusts the lowest frequency of the compressor to the Set to the second lowest frequency,
The outdoor unit according to claim 3.
When the compressor is in operation and the current operating frequency of the compressor is below a second minimum frequency higher than the first minimum frequency during normal operation for a certain period of time, the control device controls the oil Carry out recovery operations;
The outdoor unit according to any one of claims 1 to 4.
Before starting the oil recovery operation, the control device determines whether the state of the suction port of the compressor is in a liquid back condition, and controls the oil recovery operation based on the presence or absence of the liquid back condition. Switch the type of control,
The outdoor unit according to any one of claims 1 to 5.
When the state of the suction port of the compressor is not the liquid back state, the control device opens the suction on-off valve while continuing operation of the compressor, and supplies the air from the bypass flow path to the performing a first control of the oil recovery operation, which increases the pressure of the refrigerant between the load device and the suction port of the compressor by flowing the refrigerant into the first connection;
The outdoor unit according to claim 6.
When the state of the suction port of the compressor is in the liquid back state, the control device opens the suction on-off valve while the compressor is stopped, and drains the first air from the bypass flow path. performing a second control of the oil recovery operation, which increases the pressure of the refrigerant between the load device and the suction port of the compressor by flowing the refrigerant into the connection part;
The outdoor unit according to claim 6 or 7.
The first branch part is arranged between the outlet of the first passage in the circulation flow path and the load device,
The bypass flow path is
a first refrigerant flow path that allows refrigerant to flow from the first branch to the entrance of the second passage;
a second refrigerant flow path that allows refrigerant to flow from the outlet of the second passage to the first connection part;
the suction on-off valve that is disposed in the second refrigerant flow path and switches whether or not refrigerant flows from the second refrigerant flow path to the first connection portion;
has,
The outdoor unit according to any one of claims 1 to 8.
The first branch part is arranged between the outlet of the condenser and the inlet of the first passage in the circulation flow path,
The bypass flow path is
a first refrigerant flow path that allows refrigerant to flow from the first branch to the entrance of the second passage;
a second refrigerant flow path that allows refrigerant to flow from the outlet of the second passage to the first connection part;
the suction on-off valve that is disposed in the second refrigerant flow path and switches whether or not refrigerant flows from the second refrigerant flow path to the first connection portion;
has,
The outdoor unit according to any one of claims 1 to 8.
The bypass flow path is
a liquid receiver disposed in the first refrigerant flow path;
It is disposed between the first branch part in the first refrigerant flow path and the inlet of the liquid receiver, and reduces the pressure of the refrigerant flowing from the first refrigerant flow path to an intermediate pressure, and reduces the pressure of the refrigerant flowing into the liquid receiver to an intermediate pressure. a second expansion valve that allows the flow to flow into the vessel;
a flow rate adjustment valve that is disposed between the outlet of the liquid receiver and the inlet of the second passage in the first refrigerant flow path and adjusts the amount of refrigerant flowing into the second passage;
has
The control device controls the compressor, the suction on-off valve, the second expansion valve, and the flow rate adjustment valve,
The control device is included in the circulation flow path and the bypass flow path based on the opening degree of the flow rate adjustment valve when the discharge pressure of the compressor is in a supercritical state exceeding the critical pressure of the refrigerant. Adjust the amount of refrigerant,
The outdoor unit according to claim 10.
The compressor has an intermediate pressure port,
The bypass flow path is
a second expansion valve that is disposed between the first branch part and the intermediate pressure port and adjusts the amount of refrigerant flowing into the intermediate pressure port;
The outdoor unit according to any one of claims 1 to 8.
The first branch part is arranged between the outlet of the first passage in the circulation flow path and the load device,
The bypass flow path is
a first refrigerant flow path that allows refrigerant to flow from the first branch to the entrance of the second passage;
a second refrigerant flow path that allows refrigerant to flow from the outlet of the second passage to the first connection part;
a third refrigerant flow path branching from the second refrigerant flow path and connected to the intermediate pressure port;
has,
The outdoor unit according to claim 12.
The first branch part is arranged between the outlet of the condenser and the inlet of the first passage in the circulation flow path,
The bypass flow path is
a first refrigerant flow path that allows refrigerant to flow from the first branch to the entrance of the second passage;
a second refrigerant flow path that allows refrigerant to flow from the outlet of the second passage to the first connection part;
a third refrigerant flow path branching from the second refrigerant flow path and connected to the intermediate pressure port;
a liquid receiver disposed in the first refrigerant flow path;
It is disposed between the first branch part in the first refrigerant flow path and the inlet of the liquid receiver, and reduces the pressure of the refrigerant flowing from the first refrigerant flow path to an intermediate pressure, and reduces the pressure of the refrigerant flowing into the liquid receiver to an intermediate pressure. the second expansion valve that allows the flow into the vessel;
a flow rate adjustment valve that is disposed between the outlet of the liquid receiver and the inlet of the second passage in the first refrigerant flow path and adjusts the amount of refrigerant flowing into the second passage;
has
The control device controls the compressor, the suction on-off valve, the second expansion valve, and the flow rate adjustment valve,
The control device is included in the circulation flow path and the bypass flow path based on the opening degree of the flow rate adjustment valve when the discharge pressure of the compressor is in a supercritical state exceeding the critical pressure of the refrigerant. Adjust the amount of refrigerant,
The outdoor unit according to claim 12.
comprising a check valve disposed upstream of the first connection part in the circulation flow path to prevent the refrigerant from flowing in a direction opposite to the flow of the refrigerant in the circulation flow path;
The control device opens the suction on-off valve and causes refrigerant to flow from the second refrigerant flow path to the first connection portion when the compressor is started, so that the high pressure side and the low pressure side of the circulation flow path are connected to each other. bypassing the side and increasing the pressure of the refrigerant in the circulation flow path between the load device and the suction port to the same pressure value as the high pressure side by the action of the check valve;
The outdoor unit according to claim 14.
an accumulator connected to the suction port of the compressor;
The accumulator is
a casing that stores refrigerant and refrigeration oil inside;
an inflow pipe that is disposed through an upper part of the casing and allows refrigerant from the load device to flow into the inside of the casing;
It has a U-shape, one end passing through the upper part of the casing and disposed outside the casing, and the other end disposed inside the casing, and the refrigerant is supplied from the one end to the suction port of the compressor. an outflow pipe for outflowing;
a bypass pipe that functions as the first connection part and is disposed to penetrate a lower part of the casing;
has
The bypass piping allows the refrigerant from the bypass passage to flow into the casing when the suction on-off valve is opened.
The outdoor unit according to any one of claims 1 to 15.
The outdoor unit according to any one of claims 1 to 16,
the load device connected to the outdoor unit;
A refrigeration cycle device equipped with