Refrigeration cycle device

Abstract

This refrigeration cycle device constitutes a main refrigerant circuit in which a compressor, a condenser, a first throttle device, and an evaporator are connected by piping, and in which a refrigerant circulates. In a configuration including: bypass piping connecting a first branching / merging part that is between a discharge side of the compressor and the condenser, and a second branching / merging part that is on an inflow side of the evaporator; and a second throttle device that has a valve and adjusts the pressure and the flow rate of the refrigerant flowing through the bypass piping, the refrigeration cycle device has a bypass configuration in which, from among the refrigerant discharged from the compressor, refrigerant containing more liquid phase than gas phase flows toward the evaporator via the bypass piping when the compressor is started.

Description

Refrigeration cycle device

[0005]

[0001] The present disclosure relates to a refrigeration cycle device. In particular, it aims to shorten the warm-up operation of a compressor.

[0002] Conventionally, there is a refrigeration cycle device provided with a refrigerant circuit that supplies a heat load to the air in a target space, an object, etc. and performs heating, cooling, etc. by utilizing evaporation, condensation, etc. of a refrigerant. The refrigeration cycle device has a heat exchanger. The heat exchanger is mounted, for example, in an indoor unit and functions as a condenser or an evaporator. When the heat exchanger becomes a condenser, in the refrigeration cycle device, the liquid refrigerant condensed by the heat exchanger is depressurized by an expansion device and becomes a gas-liquid two-phase refrigerant in a gas-liquid two-phase state in which gaseous refrigerant, which is a gaseous phase refrigerant, and liquid refrigerant, which is a liquid phase refrigerant, are mixed. Then, in the heat exchanger that functions as an evaporator mounted in an outdoor unit, the liquid refrigerant among the gas-liquid two-phase refrigerant evaporates and becomes a low-pressure gaseous refrigerant. After that, the low-pressure gaseous refrigerant further flows into a compressor, is compressed by the compressor to become a high-temperature and high-pressure gaseous refrigerant, and is discharged again from the compressor. The refrigeration cycle device heats a load by repeating this cycle. ​​​​​​​The technology described in Patent Document 1, mentioned above, is a technique for warming up the compressor using only the input heat during the warm-up operation. As a result, it takes time to warm up the compressor, and during the gas-liquid two-phase state from startup until the discharged refrigerant becomes superheated refrigerant, refrigerant oil continues to flow out of the compressor along with the liquid refrigerant. Also, when the compressor starts up, the pressure at the compressor's intake port decreases, causing the liquid refrigerant remaining in the refrigerant circuit to flow towards the compressor's intake side. As a result, in refrigerant circuits equipped with a refrigerant tank, the amount of liquid stored in the refrigerant tank increases, causing an overflow where the liquid volume exceeds a certain specified value and overflows, resulting in an excessive supply of liquid refrigerant to the compressor and becoming a cause of compressor failure. Even in refrigerant circuits without a refrigerant tank, liquid refrigerant is supplied directly to the compressor, which can also cause compressor failure.

[0006] On the other hand, to avoid compressor failure, increasing the size of the gas-liquid separation mechanism and refrigerant tank within the compressor can suppress the leakage of refrigerant oil from the compressor and overflow from the refrigerant tank. However, increasing the size of the compressor and refrigerant tank will increase the size of the housing that houses the compressor or refrigerant tank, or require miniaturization of the heat exchanger, blower, and piping installed within the housing. As a result, the efficiency of the refrigerant circuit cannot be improved, the energy efficiency of the refrigeration cycle system is compromised, and the performance deteriorates.

[0007] This disclosure aims to provide a refrigeration cycle system that can achieve both quality improvement and performance improvement in order to solve the problems described above.

[0008] The refrigeration cycle apparatus according to this disclosure is a refrigeration cycle apparatus comprising a compressor, a condenser, a first throttling device, and an evaporator connected by piping to constitute a main refrigerant circuit through which a refrigerant circulates, and comprises a bypass pipe connecting a first branch junction between the discharge side of the compressor and the condenser and a second branch junction on the inlet side of the evaporator, and a second throttling device having a valve for adjusting the pressure and flow rate of the refrigerant flowing through the bypass pipe, wherein, when the compressor is started, the refrigerant discharged from the compressor, which contains more liquid phase than gas phase, flows through the bypass pipe toward the evaporator.

[0009] The refrigeration cycle device described herein allows for both improved device quality through failure avoidance and improved performance through energy savings, by shortening the time until the refrigerant discharged by the compressor overheats and suppressing the reduction of refrigerant oil in the compressor.

[0010] This is a diagram showing an example of the configuration of the refrigeration cycle device 100 according to Embodiment 1. This is a diagram illustrating the configuration of the refrigerant tank 114 according to Embodiment 1. This is a diagram illustrating an example of the first branch / junction section 131 according to Embodiment 1. This is a diagram illustrating the arrangement of the first branch / junction section 131 according to Embodiment 1. This is a diagram illustrating another example of the configuration of the first branch / junction section 131 according to Embodiment 1. This is a diagram illustrating the control flow when the refrigeration cycle device 100 according to Embodiment 1 is started up. This is a diagram illustrating the effect of the compressor 111 of the refrigeration cycle device 100 according to Embodiment 1. This is a diagram illustrating the effect of the liquid refrigerant of the refrigeration cycle device 100 according to Embodiment 1. This is a diagram showing the equipment configuration of the refrigeration cycle device 100 according to Embodiment 2. This is a diagram showing the equipment configuration of the refrigeration cycle device 100 according to Embodiment 3. This is a diagram showing the configuration of the gas-liquid separator 134A which becomes the third branch / junction section 134 according to Embodiment 3. This is a diagram showing the equipment configuration of the refrigeration cycle device 100 according to Embodiment 4. This is a diagram illustrating the control flow when the refrigeration cycle device 100 according to Embodiment 4 is started up. This is a diagram showing the equipment configuration of the refrigeration cycle device 100 according to Embodiment 5. This is a diagram illustrating the relationship between the outdoor air temperature T and the opening degree υ of the outdoor throttle device 117 according to Embodiment 5. This is a diagram illustrating the control flow during startup of the refrigeration cycle device 100 according to Embodiment 5. This is a diagram illustrating another example of the control flow during startup of the refrigeration cycle device 100 according to Embodiment 5. This is a diagram showing another example of the relationship between the outdoor air temperature T and the opening degree υ of the outdoor throttle device 117 according to Embodiment 5. This is a diagram showing the relationship between the elapsed time t from startup and the discharge refrigerant saturation temperature according to Embodiment 5. This is a diagram illustrating the relationship between the outdoor air temperature T and the opening degree ω of the return throttle device 115 according to Embodiment 6. This is a diagram showing another example of the relationship between the outdoor air temperature T and the opening degree ω of the return throttle device 115 according to Embodiment 6. This is a diagram illustrating the relationship between the outdoor air temperature T and the opening degree ξ of the indoor throttle device 122 according to Embodiment 6. This is a diagram showing another example of the relationship between the outdoor air temperature T and the opening degree ξ of the indoor throttle device 122 according to Embodiment 6. This is a diagram showing the equipment configuration of the refrigeration cycle device 100 according to Embodiment 7. This figure illustrates an example of a second branching and merging section 132 according to Embodiment 8.This is a diagram illustrating the arrangement of the second branch / junction section 132 according to Embodiment 8. This is a diagram illustrating another example of the structure of the second branch / junction section 132 according to Embodiment 8. This is a diagram illustrating the effect of the compressor 111 of the refrigeration cycle device 100 according to Embodiment 8. This is a diagram showing the equipment configuration of the refrigeration cycle device 100 according to Embodiment 9. This is a diagram showing the equipment configuration of the refrigeration cycle device 100 according to Embodiment 10. This is a diagram illustrating the relationship between the number of operating indoor units 120 and the drive frequency of the compressor 111 when the compressor 111 is started up according to Embodiment 10. This is a diagram illustrating the operation of the outdoor fan 116 from the start-up of the compressor 111 according to Embodiment 10.

[0011] In the following, a refrigeration cycle device according to an embodiment will be described with reference to the drawings. In each drawing, components with the same reference numerals are the same or equivalent and will be common throughout the entire text of the embodiments described below. Also, the size relationships of the components in the drawings may differ from those in reality. Furthermore, the forms of the components shown throughout the specification are merely examples and are not limited to the forms described in the specification. It may not be necessary to include all the equipment described in the specification. In particular, the combination of components is not limited to the combination in each embodiment, and components described in other embodiments can be applied to other embodiments. Furthermore, the high and low values ​​of pressure and temperature are not determined in relation to absolute values, but rather are determined relatively in relation to the state and operation of the device, etc. Also, for multiple similar devices that are distinguished by subscripts, if there is no need to distinguish or specify them, the reference numerals and subscripts may be omitted.

[0012] Embodiment 1. <Configuration of Refrigeration Cycle Device 100> Figure 1 is a diagram showing an example of the configuration of the refrigeration cycle device 100 according to Embodiment 1. The refrigeration cycle device 100 is a compression-type refrigeration cycle device in which a refrigerant circulates through a main refrigerant circuit in which a compressor 111, a condenser, a first throttling device, and an evaporator are connected by refrigerant piping 130. The refrigeration cycle device 100 is a device used for refrigeration or air conditioning purposes, such as a refrigerator or freezer, a vending machine, an air conditioning system, a refrigeration system, and a water heater. Here, the refrigeration cycle device 100 will be described as an air conditioning system that supplies a heat load by an indoor unit 120 installed in a room which is the space to be air-conditioned, and performs air conditioning by heating or cooling the room.

[0013] As shown in Figure 1, the refrigeration cycle device 100 in Embodiment 1 comprises an outdoor unit 110 and an indoor unit 120. The equipment in the outdoor unit 110 and the indoor unit 120 are connected by refrigerant piping 130, forming a refrigerant circuit through which the refrigerant, which is the working fluid, circulates. The outdoor unit 110 is equipped with an outdoor heat exchanger 113 that performs heat exchange between the outdoor air and the refrigerant, and the indoor unit 120 is equipped with an indoor heat exchanger 121 that performs heat exchange between the indoor air and the refrigerant. The main refrigerant circuit has a flow path switching device 112 that switches the direction of refrigerant circulation between heating operation and cooling operation. In heating operation, the indoor heat exchanger 121 functions as a refrigerant condenser, and the outdoor heat exchanger 113 functions as a refrigerant evaporator. In cooling operation, the outdoor heat exchanger 113 functions as a refrigerant condenser, and the indoor heat exchanger 121 functions as a refrigerant evaporator.

[0014] The refrigerant circuit in Embodiment 1 has a main refrigerant circuit through which the refrigerant contributing to heating and cooling circulates during heating and cooling operations, and a bypass circuit through which the refrigerant related to the warm-up operation when the compressor 111 is started in Embodiment 1 flows. The main refrigerant circuit passes through a first path 141. The first path 141 is the path through which the refrigerant circulates through the compressor 111, the first branch / junction 131, the flow path switching device 112, the indoor heat exchanger 121, the indoor throttling device 122, the second branch / junction 132, the outdoor heat exchanger 113, the flow path switching device 112, and the compressor 111 when performing heating operations. The indoor throttling device 122 is a first throttling device that functions as an expansion valve for the refrigeration cycle device 100. The first throttling device may be installed in the outdoor unit 110, or in both the indoor unit 120 and the outdoor unit 110. The bypass circuit also has a second path 142. The second path 142 is the path through which the refrigerant circulates through the compressor 111, the first branch / junction 131, the return throttling device 115, the second branch / junction 132, the outdoor heat exchanger 113, the flow path switching device 112, and the compressor 111. The return throttling device 115 is a second throttling device that has a valve and adjusts the pressure and flow rate of the refrigerant flowing through the bypass piping 133. The second path 142 is a bypass path that circulates through a bypass circuit that shortens the path length for returning the refrigerant oil to the compressor 111. In particular, the first branch / junction 131 and the second branch / junction 132 are connected by the bypass piping 133. Here, the first branch / junction 131 is the part in the refrigerant circuit where the refrigerant branches into the main refrigerant circuit side and the bypass circuit side. The second branch / junction 132 is the part in the refrigerant circuit where the refrigerant flowing in the main refrigerant circuit and the refrigerant flowing in the bypass circuit merge. The first branch junction 131 and the second branch junction 132 have branch pipes which are part of the piping that connects the equipment.

[0015] In some cases, the compressor 111 may be started under conditions where the outdoor air temperature is low (low-temperature outdoor start). At this time, the refrigerant being compressed inside the compressor 111 is cooled by the components that make up the compressor 111 and becomes liquid refrigerant, which is a liquid-phase refrigerant. The refrigerant oil that lubricates the components inside the compressor 111 is then diluted by the liquid refrigerant and may flow out of the compressor 111 along with the liquid refrigerant. If the refrigerant oil inside the compressor 111 is depleted due to this outflow, it can cause the compressor 111 to fail due to excessive friction and reduce the air conditioning performance. Therefore, the refrigeration cycle device 100 according to Embodiment 1 has a bypass configuration such that, when the compressor 111 is started, the refrigerant discharged by the compressor 111, which contains more liquid phase than gas phase by mass, mainly flows towards the evaporator via the bypass piping 133.

[0016] The bypass piping 133 is connected at the second branch junction 132 so that when the compressor 111 discharges a gas-liquid two-phase refrigerant in which a gaseous refrigerant and a liquid refrigerant are mixed, the liquid refrigerant, which mainly contains refrigerant oil and has a larger liquid component than gaseous component, flows toward the evaporator. Furthermore, at the first branch junction 131, the bypass piping 133 is configured so that the refrigerant, which has a larger gaseous component than liquid component in terms of mass, and contains more gaseous phase than liquid phase, flows toward the condenser. In heating operation, the evaporator becomes the outdoor heat exchanger 113, and the condenser becomes the indoor heat exchanger 121.

[0017] Here, it is desirable that the first branch / junction 131 has a configuration that allows liquid refrigerant to flow more easily toward the evaporator than gaseous refrigerant, and that the second branch / junction 132 has a configuration that allows liquid refrigerant to flow more easily toward the evaporator. However, if only one of the first branch / junction 131 or the second branch / junction 132 has such a connection configuration, then each branch / junction can be said to be a connection that allows for the flow described above.

[0018] In the first embodiment, the first branch and junction section 131 has a gas-liquid separation structure that separates gas and liquid in order to flow the liquid refrigerant mixed with refrigerant oil into the second path 142. The first branch and junction section 131 will be described later.

[0019] The refrigerant is a pure or mixed refrigerant containing one or more of the following: an olefin-based refrigerant such as tetrafluoropropene, an ethylene-based refrigerant such as difluoroethylene, an ethane-based refrigerant such as tetrafluoroethane, propane, or DME (dimethyl ether). Here, examples of olefin-based refrigerants include HFO1234yf or HFO1234ze(E).

[0020] The outdoor unit 110 is, for example, installed outdoors, outside the space to be air-conditioned, and is a heat source unit that sends heat from the outdoor air to the indoor unit 120. The outdoor unit 110 is equipped with a compressor 111, a flow path switching device 112, an outdoor heat exchanger 113, a return throttling device 115, a refrigerant tank 114, and an outdoor fan 116. The compressor 111 draws in refrigerant, compresses it, and discharges it in a high-temperature and high-pressure state. The refrigerant compressed and discharged by the compressor 111 is sent to the flow path switching device 112. Here, the type of compressor 111 in Embodiment 1 is not particularly limited. For example, the compressor 111 may be a rotary compressor, a scroll compressor, a screw compressor, or a reciprocating compressor. Also, the shell type of the compressor 111 in Embodiment 1 is not particularly limited. The compressor 111 has an effect of suppressing the outflow of refrigerant oil, which serves as lubricant, regardless of whether it is a high-pressure shell type or a low-pressure shell type, but the effect is particularly great in the high-pressure shell type. Furthermore, the refrigeration cycle device 100 in Embodiment 1 has, for example, an inverter device (not shown) that can arbitrarily change the drive frequency of the power supplied to the compressor 111. Therefore, based on instructions from the control device 200, which will be described later, the inverter device changes the drive frequency, which in turn changes the rotational speed of the motor (not shown) in the compressor 111 and changes the drive capacity.

[0021] The flow path switching device 112 is a device in the refrigerant circuit that switches the direction in which the refrigerant flows during heating operation and the direction in which the refrigerant flows during cooling operation. The flow path switching device 112 has, for example, a four-way valve and switches the flow of the refrigerant by switching the valve.

[0022] During heating operation, the outdoor heat exchanger 113 acts as an evaporator, exchanging heat between the refrigerant flowing into it and the outdoor air, causing the refrigerant to evaporate and vaporize. During cooling operation, the outdoor heat exchanger 113 acts as a condenser, exchanging heat between the refrigerant flowing into it and the outdoor air, causing the refrigerant to condense and liquefy. To improve the efficiency of heat exchange between the refrigerant and the outdoor air, an outdoor fan 116 is positioned adjacent to the outdoor heat exchanger 113. The outdoor heat exchanger 113 can be composed of, for example, a fin-and-tube heat exchanger, a microchannel heat exchanger, a shell-and-tube heat exchanger, a heat pipe heat exchanger, a double-tube heat exchanger, or a plate heat exchanger.

[0023] The outdoor fan 116 is a blower that facilitates heat exchange by passing outdoor air through the outdoor heat exchanger 113. The outdoor fan 116 can be, for example, a propeller fan or a multi-blade centrifugal fan. Here, the explanation assumes that the outdoor fan 116 passes air through the outdoor heat exchanger 113, but it may also pass a fluid such as water through it.

[0024] The return throttling device 115, which serves as the second throttling device, is installed in the bypass piping 133 and is a device having a valve that acts as a second valve to adjust the expansion and pressure of the refrigerant based on instructions from the control device 200, which will be described later. The return throttling device 115 has, for example, an electrically operated expansion valve that can adjust the flow rate of the refrigerant. In particular, the return throttling device 115 adjusts the flow rate and pressure of the refrigerant passing through the bypass piping 133 in the second path 142. Here, the return throttling device 115 is not limited to an electrically operated expansion valve, but may be a mechanical expansion valve with a diaphragm in the pressure-receiving part, or a device in which part is a capillary tube, etc.

[0025] Figure 2 is a diagram illustrating the configuration of a refrigerant tank 114 according to Embodiment 1. For example, a refrigerant tank 114 such as an accumulator is a container that stores excess refrigerant in a refrigerant circuit. For example, in the refrigerant tank 114 shown in Figure 2, if the liquid refrigerant to be stored reaches a height H1 or higher than the outlet of the container outlet pipe 1141, an overflow occurs in which the liquid flows directly out from the outlet. For this reason, the refrigerant tank 114 is usually designed so that the stored liquid refrigerant does not reach a height H1 or higher.

[0026] Furthermore, the indoor unit 120 is a unit that is installed indoors and supplies a heat load to the indoor air by a heat source supplied from the outdoor unit 110. The indoor unit 120 includes an indoor heat exchanger 121, an indoor throttling device 122, and an indoor fan 123. During heating operation, the indoor heat exchanger 121 acts as a condenser, exchanging heat between the refrigerant flowing into it and the indoor air that becomes the room, condensing and liquefying the refrigerant. During cooling operation, the indoor heat exchanger 121 acts as an evaporator, exchanging heat between the refrigerant flowing into it and the indoor air, evaporating and vaporizing the refrigerant. To improve the efficiency of heat exchange between the refrigerant and the outdoor air, the indoor fan 123 is positioned adjacent to the indoor heat exchanger 121. The indoor heat exchanger 121 is composed of, for example, a fin-and-tube type heat exchanger. Here, the indoor heat exchanger 121 may supply hot water or cold water by exchanging heat with water or the like, instead of exchanging heat with air.

[0027] The indoor fan 123 is a blower that facilitates heat exchange by passing indoor air through the indoor heat exchanger 121. The indoor fan 123 is composed of, for example, a centrifugal fan or a cross-flow fan driven by a motor (not shown).

[0028] The first throttling device, the indoor throttling device 122, is a device having a valve that acts as a first valve to adjust the expansion and pressure of the refrigerant based on instructions from the control device 200, which will be described later. Similar to the return throttling device 115, the indoor throttling device 122 has, for example, an electrically operated expansion valve that can adjust the flow rate of the refrigerant. The indoor throttling device 122 mainly adjusts the flow rate and pressure of the refrigerant passing through the first path 141. Here, the indoor throttling device 122 is not limited to an electrically operated expansion valve, but may be a mechanical expansion valve with a diaphragm in the pressure-receiving part, or a device in which part is a capillary tube, etc.

[0029] Furthermore, the refrigeration cycle device 100 in Embodiment 1 includes a control device 200. Here, the outdoor unit 110 is assumed to have the control device 200, but it is not limited to this. The control device 200 sends signals to the equipment within the refrigeration cycle device 100 and controls the overall operation of the refrigeration cycle device 100, such as cooling operation or heating operation. For example, the control device 200 controls the direction of refrigerant flow in the flow path switching device 112. The control device 200 also controls the discharge amount of compressed refrigerant by, for example, the rotation speed of the motor (not shown) of the compressor 111. Furthermore, the control device 200 controls the airflow by, for example, the rotation speed of the motors (not shown) of the outdoor fan 116 and the indoor fan 123. Finally, the control device 200 controls the opening degree of the indoor throttling device 122 and the return throttling device 115. In this case, the control device 200 specifically controls the opening degree of the return throttle device 115 during the warm-up operation performed when starting the compressor 111 in the refrigeration cycle device 100.

[0030] The control device 200 includes, for example, a microcomputer. The microcomputer includes a control unit 201, a storage unit 202, and a timing unit 203. The control unit 201 includes, for example, a control arithmetic processing unit such as a CPU (Central Processing Unit).

[0031] Furthermore, the storage unit 202 includes, for example, a volatile storage device (not shown) such as a random access memory (RAM) that can temporarily store data, and a non-volatile auxiliary storage device (not shown) such as flash memory. The storage unit 202 stores, for example, numerical values ​​and set values ​​that serve as criteria when the control unit 201 makes a decision. The storage unit 202 also has, for example, data that is a program of the processing procedures to be performed by the control arithmetic processing unit. The control unit 201 then executes processing based on the program data. However, it is not limited to this, and the control device 200 may be a device (hardware) dedicated to control. The timing unit 203 has a device such as a timer and performs timing.

[0032] The outdoor air temperature sensor 210 is installed, for example, at the outdoor air inlet portion of the outdoor heat exchanger 113. The outdoor air temperature sensor 210 detects the outdoor air temperature T, which is the temperature around the installation location, and sends an outdoor air temperature signal.

[0033] <Operation of the Refrigeration Cycle System 100> Next, the operation of the refrigeration cycle system 100 will be explained based on the flow of the refrigerant. First, normal cooling operation will be explained. The dotted arrows in Figure 1 show the flow of the refrigerant during cooling operation. In the refrigeration cycle system 100, when the compressor 111 is driven, high-temperature and high-pressure gaseous refrigerant is discharged from the compressor 111. The high-temperature and high-pressure gaseous refrigerant discharged from the compressor 111 flows into the outdoor heat exchanger 113, which functions as a condenser, via the first branch / junction section 131 and the flow path switching device 112.

[0034] The high-temperature, high-pressure gaseous refrigerant flowing into the outdoor heat exchanger 113 exchanges heat with the air supplied by the outdoor fan 116. Through heat exchange in the outdoor heat exchanger 113, the refrigerant condenses into a high-pressure liquid phase liquid refrigerant or a gas-liquid two-phase refrigerant mixture of gaseous and liquid refrigerants, and flows out of the outdoor heat exchanger 113. The refrigerant that has flowed out of the outdoor heat exchanger 113 flows out of the outdoor unit 110, passes through the refrigerant piping 130, flows into the indoor unit 120, and passes through the indoor throttling device 122.

[0035] The refrigerant, having passed through the indoor throttling device 122 and been depressurized to a gas-liquid two-phase state, then passes through the indoor heat exchanger 121. In the indoor heat exchanger 121, the liquid refrigerant evaporates through heat exchange with indoor air supplied by, for example, an indoor fan 123, becoming low-pressure gaseous refrigerant. At this time, the indoor air is cooled. The low-pressure gaseous refrigerant flows out of the indoor unit 120, passes through the refrigerant piping 130, and flows into the outdoor unit 110. The low-pressure gaseous refrigerant that flows into the outdoor unit 110 is drawn into the compressor 111 via the flow path switching device 112 and the refrigerant tank 114, where it is compressed again and discharged. This cycle is repeated during the cooling operation of the refrigeration cycle device 100.

[0036] Next, we will explain the heating operation. The solid arrows in Figure 1 indicate the flow of refrigerant in the first path 141 during heating operation. Here, we will explain the flow of refrigerant in the first path 141 that circulates through the main refrigerant circuit. In the refrigeration cycle device 100, when the compressor 111 is driven, high-temperature and high-pressure gaseous refrigerant is discharged from the compressor 111. The high-temperature and high-pressure gaseous refrigerant discharged from the compressor 111 flows out of the outdoor heat exchanger 113 via the first branch junction 131 and the flow path switching device 112. The refrigerant that has flowed out of the outdoor heat exchanger 113 flows out of the outdoor unit 110, passes through the refrigerant piping 130, and flows into the indoor unit 120.

[0037] The high-temperature and high-pressure gaseous refrigerant flowing into the indoor unit 120 flows into the indoor heat exchanger 121, which functions as a condenser. The high-temperature and high-pressure gaseous refrigerant flowing into the indoor heat exchanger 121 exchanges heat with the indoor air supplied by the indoor fan 123. The high-temperature and high-pressure gaseous refrigerant is cooled while supplying heat to the indoor air, and flows out of the indoor heat exchanger 121 as a low-temperature liquid refrigerant. At this time, the indoor air is heated. The liquid refrigerant flowing out of the indoor heat exchanger 121 passes through the indoor throttling device 122, is depressurized, and flows out of the indoor unit 120 as a low-temperature and low-pressure gas-liquid two-phase refrigerant, passes through the refrigerant piping 130, and flows into the outdoor unit 110.

[0038] The low-temperature, low-pressure gaseous-liquid two-phase refrigerant flowing into the outdoor unit 110 flows into the outdoor heat exchanger 113 via the second branch junction 132. In the outdoor heat exchanger 113, the liquid refrigerant evaporates by exchanging heat with outdoor air supplied, for example, by the outdoor fan 116, becoming a low-pressure gaseous refrigerant. The low-pressure gaseous refrigerant flowing out of the outdoor heat exchanger 113 is drawn into the compressor 111 via the flow path switching device 112 and the refrigerant tank 114, where it is compressed again and discharged. This cycle is repeated during the heating operation of the refrigeration cycle device 100.

[0039] Here, we will explain the flow of refrigerant in the second path 142 circulating through the bypass circuit when the return throttling device 115 is open. In particular, we will explain the flow of refrigerant during heating operation. The dashed arrow in Figure 1 indicates the flow of refrigerant in the second path 142. When the valve of the return throttling device 115 is open, the refrigerant discharged from the compressor 111 separates at the first branch junction 131. As described above, a portion passes through the flow path switching device 112 on the main refrigerant circuit side, while the remainder passes through the bypass piping 133 on the bypass circuit side.

[0040] The refrigerant that flows from the first branch / junction 131 through the bypass piping 133 and into the return throttling device 115 is depressurized in the return throttling device 115, becoming a low-pressure gas-liquid two-phase refrigerant, which flows into the second branch / junction 132 and merges with the refrigerant passing through the first path 141. The merged refrigerant flows into the outdoor heat exchanger 113, where it exchanges heat with the outdoor air, causing the liquid refrigerant to evaporate and become a low-pressure gaseous refrigerant. The low-pressure gaseous refrigerant that flows out of the outdoor heat exchanger 113 is drawn into the compressor 111 via the flow path switching device 112 and the refrigerant tank 114, where it is compressed again and discharged.

[0041] Here, the outdoor unit 110 is installed outdoors. As time passes, the compressor 111 during drive stop reaches the same temperature as the outdoor air. Therefore, when the outdoor air is at a low temperature, before starting the normal heating operation or cooling operation, during the preheating operation performed, until the compressor 111 warms up, inside the compressor 111, the refrigerant being compressed is cooled by the components of the compressor 111 and a part of it becomes liquid refrigerant. Then, the refrigerating machine oil inside the compressor 111 diluted by the liquid refrigerant is mixed with the refrigerant and discharged from the compressor 111. Here, hereinafter, in the refrigerant circuit, including the refrigerating machine oil mixed with the refrigerant, it may sometimes be described as the refrigerant.

[0042] When the refrigerating machine oil flows out from the compressor 111, the amount of refrigerating machine oil inside the compressor 111 decreases, and the components are subject to excessive friction, leading to problems such as failure of the compressor 111 and reduction of air conditioning performance. Since the path length of the first path 141 which is the path of the main refrigerant circuit is long, when the refrigerating machine oil flows through the first path 141, it takes a long time to return to the compressor 111. Therefore, when the preheating operation becomes long, there is a possibility that the refrigerating machine oil inside the compressor 111 runs out before the refrigerating machine oil returns to the compressor 111.

[0043] Therefore, in the refrigeration cycle device 100 in the first embodiment, during the preheating operation when the compressor 111 is started, the valve of the return throttle device 115 installed on the second path 142 is opened so that the refrigerant containing a large amount of refrigerating machine oil flows through the second path 142. Thereby, the time until the refrigerating machine oil returns to the compressor 111 is shortened.

[0044] FIG. 3 is a diagram for explaining an example of the first branch - merging portion 131 according to the first embodiment. The first branch - merging portion 131 according to the first embodiment is assumed to have a configuration with a T - shaped pipe as shown in FIG. 3. In the first branch - merging portion 131, the refrigerant discharged from the compressor 111 flows in from the inlet 1311 and can flow out from the first - path - side outlet 1312 and the second - path - side outlet 1313.

[0045] Figure 4 is a diagram illustrating the arrangement of the first branch junction 131 according to Embodiment 1. As described above, the first branch junction 131 allows liquid refrigerant mixed with refrigerant oil to flow into the second path 142. For this reason, the T-shaped pipe that forms the first branch junction 131 in Embodiment 1 is arranged such that the angle θ that the second path side outlet 1313, which is the direction of refrigerant outflow to the second path 142, makes with respect to gravity is -30° < θ < 30°. The liquid refrigerant collides with the pipe wall at the end of the extension of the pipe from the inlet 1311, falls in the direction of gravity, and flows into the second path side outlet 1313. On the other hand, the indoor throttling device 122, which is an expansion valve, is open so that the refrigerant can be circulated. For this reason, gaseous refrigerant, which is hardly affected by gravity, can flow through the first path side outlet 1312 toward the condenser, circulating through the main refrigerant circuit. Here, in the main refrigerant circuit, for a short period immediately after startup when the pressure on the condenser side is lower than the discharge pressure of the compressor 111, gaseous refrigerant can flow out from the first branch junction 131 even if the expansion valve is closed, so the indoor throttling device 122, which is the expansion valve, may be kept closed. After that, when the pressure on the condenser side becomes equal to the discharge pressure of the compressor 111, the expansion valve may be opened.

[0046] Therefore, the first branch junction 131 in Embodiment 1 functions as a gravity-based gas-liquid separation mechanism that uses gravity to separate gas and liquid. The gravity-based separation method is a method that has high separation efficiency when the refrigerant flow velocity is relatively low. In the outdoor unit 110, the first branch junction 131 is arranged such that the outlet on the gravity-down side becomes the second path side outlet 1313, so that the refrigerant and liquid mixed with refrigerant oil preferentially flow to the second path 142 side.

[0047] Figure 5 illustrates another example of the configuration of the first branch junction 131 according to Embodiment 1. In the first branch junction 131 of Figure 5, a pipe having a first route-side outlet 1312 is connected to the inside of the L-shaped piping in the bending direction. Therefore, the first branch junction 131 of Figure 5 is an F-shaped piping. Furthermore, the first branch junction 131 is arranged such that the outlet on the gravity-down side becomes the second route-side outlet 1313.

[0048] In the first branch and confluence section 131, the refrigerant flowing in from the inlet 1311 flows along the outer wall inside the pipe due to centrifugal force, making it easier for the liquid to flow. Therefore, a large amount of liquid refrigerant containing refrigerating machine oil flows out from the outlet 1313 on the second path side, and a large amount of gas refrigerant flows out from the outlet 131 on the first path side.

[0049] The liquid refrigerant mixed with the refrigerating machine oil flowing through the second path 142 flows to the outdoor heat exchanger 113 through the second branch and confluence section 132. The pressure of the refrigerant flowing into the outdoor heat exchanger 113 is reduced by the resistance of the bypass pipe 133 or the return throttle device 115 so that it can evaporate at the temperature of the outside air. Then, through heat exchange in the outdoor heat exchanger 113, the liquid refrigerant absorbs heat from the outdoor air and evaporates, becoming a fluid in which the gas-phase-dominated gas-liquid two-phase refrigerant and the refrigerating machine oil are mixed. The refrigerant passes through the flow path switching device 112 and the refrigerant tank 114 and flows into the compressor 111.

[0050] Thereby, at the time of starting the compressor 111, it is possible to execute a warm-up operation that suppresses the outflow of the refrigerating machine oil to the indoor unit 120 side flowing through the first path 141. The control device 200 controls the refrigerant discharged from the compressor 111 to become a superheated gas refrigerant, and after the warm-up operation is completed, controls to close or reduce the opening degree of the return throttle device 115 so that the flow rate of the refrigerant flowing through the first path 141 on the main refrigerant circuit side increases.

[0051] The control device 200 opens the return throttle device 115 (the second throttle device) while the refrigerant discharged from the compressor 111 contains both a gas phase and a liquid phase at the time of starting the compressor 111. After that, when the temperature of the compressor 111 rises and the compressor 111 starts to discharge only gas refrigerant, the control device 200 controls to close the return throttle device 115. Here, during normal heating operation or cooling operation, etc., the control device 200 controls to close the return throttle device 115, but the return throttle device 115 may be opened in addition to the control immediately after startup described above. For example, when removing frost adhering to the outdoor heat exchanger 113 that functions as an evaporator, the control device 200 may control to open the return throttle device 115.

[0052] Figure 6 is a diagram illustrating the control flow during startup of the refrigeration cycle device 100 according to Embodiment 1. Although the process shown in Figure 6 is essentially mainly executed by the control unit 201, it will be described here as being executed by the control device 200. When operating the refrigeration cycle device 100, the control device 200 sends a start signal to the compressor 111 to start the compressor 111 (step S1). It determines whether the outdoor air temperature T detected by the outdoor air temperature sensor 210 is lower than a preset temperature T0 (step S2). Here, setting the preset temperature T0 to a large value can suppress the outflow of refrigerant oil, thereby improving reliability and quality. On the other hand, setting the preset temperature T0 to a small value leads to a reduction in the number of warm-up operations and the warm-up operation time, which shortens the time until transitioning to normal operation, improves the capacity per unit of heat input, and saves energy.

[0053] When the control device 200 determines that the outdoor air temperature T is lower than the set temperature T0, it controls the valve opening ω in the return throttling device 115 to the set opening ω1 (step S3). Here, the opening ω1 which is the initial first set opening is 0 < ω1. The control device 200 then determines whether the elapsed time t since the compressor 111 was started has exceeded the pre-set opening setting time τ (step S4), and sets the valve opening ω in the return throttling device 115 to opening ω1 until it determines that the opening setting time τ has been exceeded.

[0054] If the control device 200 determines in step S4 that the elapsed time t has exceeded the opening degree setting time τ, or if it determines in step S2 that the outdoor air temperature T is equal to or greater than the set temperature T0, it controls the opening degree ω of the return throttling device 115 to opening degree ω2 (step S5). Here, the opening degree ω2 is a smaller opening degree (including closing) than the opening degree ω1 mentioned above, and 0 ≤ ω2 < ω1. The opening degree ω2 is set based on, for example, the performance of the return throttling device 115 (the same applies hereafter). Then, the refrigeration cycle device 100 transitions to normal operation and continues operation (step S6).

[0055] <Effects of Embodiment 1> Figure 7 is a diagram illustrating the effects of the compressor 111 of the refrigeration cycle device 100 according to Embodiment 1. Figure 7(a) shows the degree of superheating of the discharged refrigerant during warm-up operation when gas-liquid separation is not performed at the first branch-junction section 131, and Figure 7(b) shows the degree of superheating of the discharged refrigerant during warm-up operation when gas-liquid separation is performed at the first branch-junction section 131. The refrigeration cycle device 100 in Embodiment 1 includes a first branch-junction section 131 that can branch the refrigerant discharged from the compressor 111 into a first path 141, which is the main refrigerant circuit path, and a second path 142, which is the bypass circuit path. At this time, the first branch-junction section 131 has a gas-liquid separation structure such that gaseous refrigerant mainly flows into the first path 141 and liquid refrigerant mainly flows into the second path 142. Furthermore, the refrigeration cycle device 100 has a return throttling device 115 on the second path 142, and the return throttling device 115 is configured to adjust the amount of liquid refrigerant that branches off at the first branch / junction 131 and passes through the second path 142. In addition, the refrigeration cycle device 100 in Embodiment 1 is configured so that the refrigerant that has passed through the return throttling device 115 flows into an outdoor heat exchanger 113 which functions as an evaporator.

[0056] During the warm-up operation when the compressor 111 is started, the liquid refrigerant mixed with the refrigerant oil that has leaked out of the compressor 111 is separated from the gaseous refrigerant at the first branch junction 131 and flows through the second path 142. This allows the refrigerant oil that has leaked out of the compressor 111 to be quickly returned to the compressor 111. Therefore, the reduction of refrigerant oil inside the compressor 111 can be suppressed. In addition, in the outdoor heat exchanger 113, the refrigerant that has absorbed heat and evaporated through heat exchange with the outdoor air is drawn into the compressor 111, so that the heat absorbed from the outdoor air can be used to heat the compressor 111. As a result, energy saving can be achieved efficiently, and the time it takes for the refrigerant discharged from the compressor 111 to go from a gas-liquid two-phase state to a superheated state can be shortened, thereby improving performance.

[0057] Figure 8 is a diagram illustrating the effects of the liquid refrigerant in the refrigeration cycle device 100 according to Embodiment 1. Figure 8(a) shows the liquid level in the refrigerant tank 114 during warm-up operation when gas-liquid separation is not performed at the first branch-junction 131, and Figure 8(b) shows the liquid level in the refrigerant tank 114 during warm-up operation when gas-liquid separation is performed at the first branch-junction 131. In the refrigeration cycle device 100 according to Embodiment 1, during warm-up operation when the compressor 111 is started, the amount of refrigerant flowing through the main refrigerant circuit (first path 141) can be reduced by flowing liquid refrigerant containing refrigerant oil through the second path 142 via the first branch-junction 131. Therefore, when the refrigeration cycle device 100 is stopped, the amount of refrigerant accumulated in the indoor unit 120 and refrigerant piping 130 that flows into the outdoor unit 110 can be reduced. Furthermore, in the second path 142, the liquid refrigerant that has passed through the second branch junction 132 flows into the outdoor heat exchanger 113, where a portion evaporates due to heat exchange. As a result, the amount of liquid refrigerant decreases after passing through the outdoor heat exchanger 113, reducing the amount of liquid refrigerant that accumulates in the refrigerant tank 114. Therefore, even if the storage volume of the refrigerant tank 114 is small, overflow in the refrigerant tank 114 can be avoided, liquid back flow of liquid refrigerant into the compressor 111 can be suppressed, and compressor 111 failure can be avoided. Consequently, in the outdoor unit 110, energy saving can be achieved without reducing the size of the outdoor heat exchanger 113 or other components and without compromising performance, and the reliability and quality of the refrigeration cycle device 100 can be improved. Based on the above, the refrigeration cycle device 100 in Embodiment 1 is equipped with a first branch junction 131 having a gravity separation type gas-liquid separation mechanism, and by performing gas-liquid separation during warm-up operation, it is possible to achieve both quality improvement and performance improvement. The opening degree setting time τ is a design variable selected based on a trade-off between quality and performance. By setting the opening degree setting time τ to a longer duration, the components related to the outdoor unit 110, including the compressor 111, are preferentially warmed up during startup, which suppresses the outflow of refrigerant oil from the compressor extension piping and improves quality.Furthermore, by setting the opening time τ to a shorter duration, the refrigerant piping 130 from the outdoor unit 110 to the indoor unit 120 and the indoor heat exchanger 121 can heat up quickly, enabling a faster start-up of heating and improving operating performance.

[0058] Embodiment 2. <Configuration of Embodiment 2> Figure 9 is a diagram showing the equipment configuration of the refrigeration cycle device 100 according to Embodiment 2. Next, the refrigeration cycle device 100 according to Embodiment 2 will be described using Figure 9. The refrigeration cycle device 100 according to Embodiment 2 has some modifications to the configuration of the refrigeration cycle device 100 according to Embodiment 1, and the basic overall configuration is the same as that of the refrigeration cycle device 100 in Embodiment 1. Here, in Figure 9, equipment and the like that are denoted by the same reference numerals as in Figure 1 perform the same functions and operations as those described in Embodiment 1.

[0059] The refrigerant circuit in the refrigeration cycle device 100 according to Embodiment 2 has a return circuit. The return circuit passes through a third path 143. The third path 143 is a path that passes through the compressor 111, the third branch / junction 134, the fourth branch / junction 135, and the compressor 111. In particular, the third branch / junction 134 and the fourth branch / junction 135 are connected by a return pipe 136.

[0060] The third branch junction 134 is the part that branches the refrigerant discharged from the compressor 111. In Embodiment 2, the third branch junction 134 has a gas-liquid separator 134A. During warm-up, the gas-liquid separator 134A separates the refrigerant discharged from the compressor 111 into gaseous refrigerant and liquid refrigerant containing refrigerant oil. The gas-liquid separator 134A has an inlet into which the gaseous and liquid mixed refrigerant flows, a gaseous refrigerant outlet from which the gaseous and liquid are separated and mainly the gaseous component flows out, and a liquid refrigerant outlet from which mainly the liquid component flows out. In addition, during normal operation after warm-up, the gas-liquid separator 134A functions as an oil separator, separating the refrigerant discharged from the compressor 111 into gaseous refrigerant and refrigerant oil. The first branch junction 131 of the bypass piping 133 is provided in the refrigerant flow between the gaseous refrigerant outlet of the gas-liquid separator 134A and the heat exchanger which functions as a refrigerant evaporator. The liquid refrigerant containing refrigerant oil separated by the gas-liquid separator 134A mainly flows through the third path 143. On the other hand, the gaseous refrigerant mainly flows towards the first branch-junction 131. During warm-up, the gaseous two-phase refrigerant discharged by the compressor 111 contains a large amount of liquid refrigerant, and liquid refrigerant is also present on the first branch-junction 131 side from the gas-liquid separator 134A. Therefore, the first branch-junction 131 separates the gaseous refrigerant and the liquid refrigerant containing refrigerant oil that could not be separated at the third branch-junction 134, for example, during warm-up, in the same manner as described in Embodiment 1. Thus, in the refrigeration cycle device 100 of Embodiment 2, gas-liquid separation can be performed in two stages.

[0061] Furthermore, the refrigeration cycle device 100 has a fourth branch junction 135 between the outdoor heat exchanger 113 and the compressor 111. The fourth branch junction 135 is the part on the suction side of the compressor 111 where the refrigerant flowing through the main refrigerant circuit and the refrigerant containing refrigerant oil that has passed through the return pipe 136 merge. In Embodiment 2, the fourth branch junction 135 has a branch pipe which is part of the piping. Therefore, at the fourth branch junction 135, the liquid refrigerant containing refrigerant oil separated in the gas-liquid separator 134A returns to the suction side of the compressor 111.

[0062] <Effects of Embodiment 2> For example, after the warm-up operation of the refrigeration cycle device 100, the opening of the return throttle device 115 is fully closed. In the case where the refrigeration cycle device 100 does not have a third path 143, the refrigerant oil that flows out of the compressor 111 together with the gaseous refrigerant will flow into the indoor unit 120. As a result, the time it takes for the refrigerant oil to return to the compressor 111 becomes longer, and the amount of refrigerant oil in the compressor 111 may decrease. On the other hand, if the return throttle device 115 is left open and the refrigerant oil flows into the second path 142, there is a concern that the refrigerant oil will accumulate in the outdoor heat exchanger 113 if the system is operated for a long time. If the amount of refrigerant oil filled into the compressor 111 is increased in order to maintain the amount of refrigerant oil in the compressor 111, the proportion of the compressor 111's drive that contributes to the compression of the refrigerant decreases, which reduces the efficiency of the compressor 111 and reduces energy saving.

[0063] Therefore, in the refrigeration cycle device 100 of Embodiment 2, the gas-liquid separator 134A of the third branch-junction section 134 is configured to function as an oil separator. This configuration allows the refrigeration cycle device 100 to perform both oil return during warm-up operation by the first branch-junction section 131 and oil return after warm-up operation by the first branch-junction section 131. For example, during warm-up operation, as described in Embodiment 1, the control device 200 controls the opening degree ω of the return throttle device 115, thereby mainly performing oil return from the second path 142. At this time, the refrigerant absorbs heat in the outdoor heat exchanger 113 for a short time, which promotes heating of the compressor 111. On the other hand, after warm-up operation, the return throttle device 115 is closed, and oil return is mainly performed from the third path 143. By returning the refrigerant oil contained in the refrigerant discharged by the compressor 111 directly to the compressor 111 without passing through the outdoor heat exchanger 113, refrigerant oil does not accumulate in the outdoor heat exchanger 113. Therefore, the refrigeration cycle device 100 in Embodiment 1 improves oil return during and after warm-up operation, achieving both improved quality and improved performance.

[0064] Embodiment 3. <Configuration of Embodiment 3> Figure 10 is a diagram showing the equipment configuration of the refrigeration cycle device 100 according to Embodiment 3. Next, the refrigeration cycle device 100 according to Embodiment 3 will be described using Figure 10. The refrigeration cycle device 100 according to Embodiment 3 is a modification of the configuration of the refrigeration cycle device 100 according to Embodiment 2, and the basic overall configuration is the same as that of the refrigeration cycle device 100 in Embodiment 2. Here, in Figure 10, equipment and the like that are denoted by the same reference numerals as in Figure 9 perform the same functions and operations as those described in Embodiment 2. The refrigeration cycle device 100 in Embodiment 3 shown in Figure 10 has a configuration in which a refrigerant tank 114 is not installed in the refrigerant circuit. However, Embodiment 3 is not limited to this configuration, and may have a configuration with a refrigerant tank 114, as in the refrigeration cycle device 100 in Embodiment 2. The refrigeration cycle device 100 in Embodiment 3 has a configuration that includes a second path 142 and a third path 143, similar to Embodiment 2, and the gas-liquid separator 134A in the third branching / merging section 134 is of the centrifugal separation type.

[0065] Figure 11 shows the configuration of the gas-liquid separator 134A in the third branch / junction section 134 according to Embodiment 3. In Figure 11, the first branch / junction section 131 is also shown in order to explain the piping connection relationship.

[0066] The gas-liquid separator 134A shown in Figure 11 has a container 1341, an inlet 1342, a refrigerant outlet 1343, and a refrigerant oil outlet 1344. The container 1341 is cylindrical in shape so that the gaseous refrigerant containing refrigerant oil flows as a swirling flow within the container 1341. The inlet 1342 is an opening on the upper side of the container 1341 that communicates with the discharge side piping of the compressor 111. The refrigerant outlet 1343 is installed on the top surface of the container 1341 and is an opening that communicates with the piping connected to the first branch junction 131. The refrigerant oil outlet 1344 is installed on the bottom surface of the container 1341 and is an opening that communicates with the piping connected to the fourth branch junction 135.

[0067] <Effects of Embodiment 3> The refrigeration cycle device 100 according to Embodiment 3 comprises a first branch-to-confluence section 131 using gravity separation and a third branch-to-confluence section 134 having a gas-liquid separator 134A using centrifugal separation. The first branch-to-confluence section 131 has high separation efficiency when the fluid velocity is low, and the third branch-to-confluence section 134 has high separation efficiency at high fluid velocity when the fluid velocity is high.

[0068] Therefore, in the refrigeration cycle device 100, during the warm-up operation immediately after startup when the refrigerant flow rate is low, the mixed liquid that has not been properly separated at the third branch / junction 134 can be separated into gas and liquid at the first branch / junction 131. Furthermore, when the refrigerant circulates at a high flow rate after the warm-up operation, the gas and liquid separation efficiency can be ensured at the third branch / junction 134. Thus, the refrigeration cycle device 100 in Embodiment 3 can improve oil return during and after the warm-up operation, achieving both improved quality and improved performance.

[0069] Embodiment 4. <Configuration of Embodiment 4> Figure 12 is a diagram showing the equipment configuration of the refrigeration cycle device 100 according to Embodiment 4. Next, the refrigeration cycle device 100 according to Embodiment 4 will be described using Figure 12. The refrigeration cycle device 100 according to Embodiment 4 is a modification of the configuration of the refrigeration cycle device 100 according to Embodiment 2, and the basic overall configuration is the same as that of the refrigeration cycle device 100 in Embodiment 2. Here, in Figure 12, equipment and the like that are denoted by the same reference numerals as in Figure 1 perform the same functions and operations as those described in Embodiment 1.

[0070] The refrigeration cycle device 100 in Embodiment 4 includes a discharge pressure sensor 211 and a discharge temperature sensor 212. The discharge pressure sensor 211 detects the discharge pressure PO of the refrigerant on the discharge side of the compressor 111. The discharge pressure PO detected by the discharge pressure sensor 211 becomes the high pressure on the high-pressure side in the refrigerant circuit. The discharge temperature sensor 212 detects the discharge temperature TO of the refrigerant on the discharge side of the compressor 111. The discharge temperature sensor 212 is a device that includes a thermistor or the like. In the refrigeration cycle device 100 of Embodiment 4, the control device 200 controls the opening degree of the return throttle device 115 based on the discharge temperature TO of the refrigerant after the compressor 111 has been started.

[0071] Figure 13 is a diagram illustrating the control flow during startup of the refrigeration cycle device 100 according to Embodiment 4. The processes shown in Figure 13 will be described as being executed by the control device 200. In Figure 13, the processes of steps S11 to S13 executed by the control device 200 are the same as the processes of steps S1 to S3 described in Embodiment 1. Therefore, the control device 200 controls the opening degree ω of the valve in the return throttling device 115 based on a comparison of the outdoor air temperature T and the set temperature T0.

[0072] The control device 200 calculates the discharge refrigerant superheat temperature Tsh based on the discharge pressure PO detected by the discharge pressure sensor 211 and the discharge temperature TO detected by the discharge temperature sensor 212 (step S14). The control device 200 also determines whether the discharge refrigerant superheat temperature Tsh is greater than a predetermined set superheat degree Tsh0 (step S15). The control device 200 then sets the valve opening ω in the return throttling device 115 to opening ω1 until it determines that the discharge refrigerant superheat temperature Tsh is greater than or equal to the set superheat degree Tsh0. Setting the set superheat degree Tsh0 to a large value can suppress the outflow of refrigerant oil, thereby improving reliability and quality. On the other hand, setting the set superheat degree Tsh0 to a small value can shorten the startup time, improve the capacity per unit of heat input, and save energy.

[0073] If the control device 200 determines in step S15 that the discharge refrigerant superheat temperature Tsh exceeds the set superheat Tsh0, or in step S12 that the outdoor air temperature T is equal to or greater than the set temperature T0, it controls the opening degree ω of the return throttle device 115 to opening degree ω2 (step S16). Here, the opening degree ω2 is a smaller opening degree (including closing) than the aforementioned opening degree ω1, and 0 ≤ ω2 < ω1. Then, the refrigeration cycle device 100 transitions to normal operation and continues operation (step S17).

[0074] <Effects of Embodiment 4> In Embodiment 1, the refrigeration cycle device 100, when controlling the opening of the return throttle device 115 during startup, determined the completion of warm-up operation based on the opening setting time τ. Determining the completion of warm-up operation based on the opening setting time τ may, depending on weather conditions and initial state, result in determining that warm-up operation is complete even if it has not actually been completed. If control is performed to reduce the size of the return throttle device 115 before the completion of warm-up operation, the amount of refrigerant oil in the compressor 111 decreases, or the amount of heating of the compressor 111 during warm-up operation decreases, which may delay normal operation. In Embodiment 4, the refrigeration cycle device 100 is able to perform control based on the refrigerant state (superheated state) on the discharge side of the compressor 111, thereby maintaining robustness against weather conditions and initial state. For this reason, the refrigeration cycle device 100 in Embodiment 4 can achieve both quality improvement and performance improvement.

[0075] Here, the discharge refrigerant superheat temperature Tsh was calculated based on the discharge pressure P detected by the discharge pressure sensor 211 and the discharge temperature TO detected by the discharge temperature sensor 212, but this is not the only method. For example, the discharge refrigerant superheat temperature Tsh may be calculated by calculating or detecting the condensation saturation temperature in a heat exchanger that functions as a condenser.

[0076] Embodiment 5. <Configuration of Embodiment 5> Figure 14 is a diagram showing the equipment configuration of the refrigeration cycle device 100 according to Embodiment 5. Next, the refrigeration cycle device 100 according to Embodiment 5 will be described using Figure 14. The refrigeration cycle device 100 according to Embodiment 5 is a modification of the configuration of the refrigeration cycle device 100 according to Embodiment 1, and the basic overall configuration is the same as that of the refrigeration cycle device 100 in Embodiment 1. Here, in Figure 14, equipment and the like that are denoted by the same reference numerals as in Figure 1 perform the same functions and operations as those described in Embodiment 1.

[0077] The refrigeration cycle device 100 according to Embodiment 5 has an outdoor throttling device 117 between the second branch / junction section 132 and the outdoor heat exchanger 113. The outdoor throttling device 117, which is a third throttling device, has a valve that acts as a third valve and functions as a pressure reducing valve or expansion valve, similar to the indoor throttling device 122, and adjusts the expansion and depressurization of the refrigerant by adjusting the opening degree υ based on a signal from the control device 200.

[0078] For the refrigeration cycle system 100 to perform efficient heating operation, the discharge saturation temperature of the refrigerant must be equal to or higher than the room air temperature. When the return throttle device 115 is opened in the refrigeration cycle system 100, the flow resistance between the high-pressure and low-pressure refrigerant in the refrigerant circuit is reduced compared to when it is not opened. As a result, the time it takes for the discharge saturation temperature to reach the room air temperature after startup is increased. In particular, when the outdoor air temperature T is low, the time it takes for the discharge saturation temperature to reach the room air temperature becomes even longer.

[0079] Therefore, in Embodiment 5, the control device 200 restricts the opening degree υ of the outdoor throttle device 117 during the warm-up operation when the compressor 111 is started, thereby widening the pressure difference between the suction side and the discharge side of the compressor 111 and ensuring flow resistance. Then, when the opening degree setting time τ has elapsed, the control device 200 controls the opening degree υ of the outdoor throttle device 117 to widen it.

[0080] Figure 15 is a diagram illustrating the relationship between the outdoor air temperature T and the opening degree υ of the outdoor throttle device 117 according to Embodiment 5. As shown in Figure 15, the opening degree υ of the outdoor throttle device 117 is set as follows: an opening degree υ1 for startup operation under a specific outdoor air temperature T1 environment, and an opening degree υ1' for startup operation under an outdoor air temperature T2 environment that is lower than the outdoor air temperature T1. At this time, the opening degree υ of the outdoor throttle device 117 is set so that opening degree υ1 > opening degree υ1'. By setting the opening degree υ of the outdoor throttle device 117 based on the outdoor air temperature T, it is possible to secure the flow resistance necessary to improve the discharge saturation temperature even in low outdoor air environments.

[0081] Figure 16 is a diagram illustrating the control flow during startup of the refrigeration cycle device 100 according to Embodiment 5. The process shown in Figure 16 will be described as being executed by the control device 200. Here, the control device 200 performs the process shown in Figure 16, as well as the process shown in Figure 6, which was described in Embodiment 1. Here, the criteria for determining the outdoor air temperature T and the elapsed time t after startup will be described as being the same as in the case of the return throttle device 115 described in Embodiment 1, etc., but the criteria may be different (the same applies below).

[0082] When operating the refrigeration cycle unit 100, the control device 200 sends a start signal to the compressor 111 to start the compressor 111 (step S21). It determines whether the outdoor air temperature T detected by the outdoor air temperature sensor 210 is lower than a preset temperature T0 (step S22).

[0083] When the control device 200 determines that the outdoor air temperature T is lower than the set temperature T0, it controls the valve opening degree υ in the outdoor throttle device 117 to opening degree υ1 (step S23). Here, the opening degree υ1, which is the initially set second set opening degree, is 0 < υ1. The control device 200 then determines whether the elapsed time t since the compressor 111 was started has exceeded the pre-set opening degree setting time τ (step S24), and sets the valve opening degree υ in the outdoor throttle device 117 to opening degree υ1 until it determines that the opening degree setting time τ has been exceeded.

[0084] If the control device 200 determines in step S24 that the elapsed time t has exceeded the opening degree setting time τ, or if it determines in step S22 that the outdoor air temperature T is equal to or greater than the set temperature T0, it controls the opening degree υ of the valve in the outdoor throttle device 117 to opening degree υ2 (step S25). Here, opening degree υ2 is a larger opening degree than the aforementioned opening degree υ1, so υ1 < υ2. Then, the refrigeration cycle device 100 switches to normal operation and continues operation (step S26).

[0085] Figure 17 is a diagram illustrating another example of the control flow during startup of the refrigeration cycle device 100 according to Embodiment 5. The processes shown in Figure 17 will be described as being executed by the control device 200. For processes in Figure 17 that have the same step numbers as in Figure 16, the same processes as in Figure 16 are performed. For steps S21 to S23, similar to Embodiment 1, the control device 200 controls the valve opening degree υ in the outdoor throttle device 117 based on a comparison between the outdoor air temperature T1 and the set temperature T0.

[0086] The control device 200 calculates the discharge refrigerant superheat temperature Tsh based on the discharge pressure PO detected by the discharge pressure sensor 211 and the discharge temperature TO detected by the discharge temperature sensor 212 (step S31). The control device 200 also determines whether the discharge refrigerant superheat temperature Tsh is greater than a predetermined set superheat degree Tsh0 (step S32). The control device 200 then sets the valve opening degree υ in the outdoor throttle device 117 to opening degree υ1 until it determines that the discharge refrigerant superheat temperature Tsh has exceeded the set superheat degree Tsh0.

[0087] If the control device 200 determines in step S32 that the discharge refrigerant superheating temperature Tsh exceeds the set superheating degree Tsh0, or in step S22 that the outdoor air temperature T is equal to or greater than the set temperature T0, it controls the opening degree υ of the valve of the outdoor throttle device 117 to opening degree υ2 (step S25). The refrigeration cycle device 100 then continues operation (step S26).

[0088] Figure 18 shows another example of the relationship between the outdoor air temperature T and the opening degree υ of the outdoor throttle device 117 according to Embodiment 5. In Figure 15, the outdoor air temperature T and the opening degree υ of the outdoor throttle device 117 were set to change linearly, but this is not the only option, and the opening degree υ of the outdoor throttle device 117 may be set to change in accordance with the outdoor air temperature T. For example, in the example shown in Figure 18, the opening degree υ of the outdoor throttle device 117 is set to change in multiple stages in accordance with the outdoor air temperature T, while satisfying the condition υ1 > υ1', as described above.

[0089] Furthermore, the opening degree υ of the outdoor throttle device 117 may be changed during warm-up based on time τ1, as shown in equation (1) below. Here, τ1 is defined as the time from startup until the discharged refrigerant becomes superheated vapor.

[0090]

[0091] <Effects of Embodiment 5> Figure 19 is a diagram showing the relationship between the elapsed time t from startup and the discharge refrigerant saturation temperature according to Embodiment 5. Figure 19(a) shows the relationship when there is no outdoor throttle device 117, as in a conventional device. Figure 19(b) shows the relationship when there is an outdoor throttle device 117 and it is controlled. According to the refrigeration cycle device 100 of Embodiment 5, by controlling the opening degree υ of the outdoor throttle device 117 and widening the pressure difference between the suction side and the discharge side of the compressor 111 to secure flow resistance, the discharge saturation temperature can be increased more quickly and the warm-up time can be shortened.

[0092] Embodiment 6. Figure 20 is a diagram illustrating the relationship between the outdoor air temperature T and the opening degree ω of the return throttling device 115 according to Embodiment 6. Although not specifically mentioned in Embodiment 1, for example, the opening degree ω of the return throttling device 115, as shown in Figure 20, which is the first set opening degree set when the compressor 111 is started, may be set based on the outdoor air temperature T. For example, an opening degree ω1 for startup operation under a specific outdoor air temperature T1 environment and an opening degree ω1' for startup operation under an outdoor air temperature T2 environment lower than the outdoor air temperature T1 are set. In this case, the opening degree ω of the return throttling device 115 is set so that ω1 > ω1'. By setting the opening degree ω of the return throttling device 115 based on the outdoor air temperature T, it is possible to secure flow resistance to improve the discharge saturation temperature even in low outdoor air environments.

[0093] Figure 21 shows another example of the relationship between the outdoor air temperature T and the opening degree ω of the return throttle device 115 according to Embodiment 6. In Figure 20, the outdoor air temperature T and the opening degree ω of the return throttle device 115 were set to change gradually and linearly, but this is not the only option, and the opening degree ω of the return throttle device 115 may be set to change in accordance with the outdoor air temperature T. For example, in the example shown in Figure 21, the opening degree ω of the return throttle device 115 is set to change in multiple stages in accordance with the outdoor air temperature T, while satisfying the condition ω1 > ω1', as described above.

[0094] Furthermore, the opening degree ω of the return throttle device 115 during warm-up may be changed based on time τ1, as shown in the following equation (2). Here, τ1 is defined as the time from startup until the discharged refrigerant becomes superheated vapor.

[0095]

[0096] Figure 22 is a diagram illustrating the relationship between the outdoor air temperature T and the opening degree ξ of the indoor throttling device 122 according to Embodiment 6. As shown in Figure 22, the opening degree ξ1, which is the third set opening degree set when the compressor 111 is started, may be set based on the outdoor air temperature T. For example, an opening degree ξ1 for startup operation under a specific outdoor air temperature T1 environment and an opening degree ξ1' for startup operation under an outdoor air temperature T2 environment lower than the outdoor air temperature T1 are set. In this case, the opening degree ξ of the indoor throttling device 122 is set so that opening degree ξ1 > opening degree ξ1'. By setting the opening degree ξ of the indoor throttling device 122 based on the outdoor air temperature T, it is possible to secure flow resistance to improve the discharge saturation temperature even in low outdoor air environments.

[0097] Figure 23 shows another example of the relationship between the outdoor air temperature T and the opening degree ξ of the indoor throttle device 122 according to Embodiment 6. In Figure 22, the outdoor air temperature T and the opening degree ξ of the indoor throttle device 122 were set to change gradually and linearly, but this is not the only option, and the opening degree ξ of the indoor throttle device 122 may be set to change in accordance with the outdoor air temperature T. For example, in the example shown in Figure 23, the opening degree ξ of the indoor throttle device 122 is set to change in multiple stages in accordance with the outdoor air temperature T, while satisfying the condition ξ1 > ξ1', as described above.

[0098] Furthermore, the opening degree ξ of the indoor throttle device 122 may be changed during warm-up based on time τ1, as shown in equation (3) below. Here, τ1 is defined as the time from startup until the discharged refrigerant becomes superheated vapor.

[0099]

[0100] <Effects of Embodiment 6> According to the refrigeration cycle device 100 of Embodiment 6, the opening degree ω of the return throttle device 115 or the opening degree ξ of the indoor throttle device 122 is controlled to widen the pressure difference between the suction side and the discharge side of the compressor 111 and secure flow resistance. As a result, the discharge saturation temperature is raised more quickly, and the warm-up time can be shortened.

[0101] Embodiment 7. <Configuration of Embodiment 7> Figure 24 is a diagram showing the equipment configuration of the refrigeration cycle device 100 according to Embodiment 7. Next, the refrigeration cycle device 100 according to Embodiment 7 will be described using Figure 24. The refrigeration cycle device 100 according to Embodiment 7 is a modification of the configuration of the refrigeration cycle device 100 according to Embodiment 1, and the basic overall configuration is the same as that of the refrigeration cycle device 100 in Embodiment 1. Here, in Figure 24, equipment and the like that are denoted by the same reference numerals as in Figure 1 perform the same functions and operations as those described in Embodiment 1.

[0102] The refrigeration cycle device 100 according to Embodiment 7 has a heat dissipation section 118 between the first branch / junction section 131 and the second branch / junction section 132. The heat dissipation section 118 has a heat dissipation mechanism that dissipates heat from the refrigerant passing through the second path 142. The heat dissipation section 118 in Embodiment 7 has a heat radiator 1181. The heat radiator 1181 dissipates heat by, for example, a heat exchanger that exchanges heat between a refrigerant containing refrigerant oil and air. However, the heat dissipation of the refrigerant containing refrigerant oil is not limited to this. Heat exchange with water or other refrigerants may also be performed.

[0103] Furthermore, for example, the drain pan (not shown) installed at the bottom of the outdoor heat exchanger 113 and on the outdoor unit 110, which receives condensation water, is prone to frost formation or freezing due to the cooling of moisture. Therefore, the heat dissipation unit 118 may be placed in the flow path on the gravity-down side of the outdoor heat exchanger 113 or near the drain pan, and the heat dissipation unit 118 may dissipate heat to prevent freezing.

[0104] <Effects of Embodiment 7> For example, if the temperature of the mixed liquid flowing through the second path 142 is higher than the intake temperature of the refrigerant drawn into the compressor 111, the outdoor heat exchanger 113 cannot sufficiently absorb heat from the outdoor air and recover heat. In some cases, the refrigerant may re-condense in the outdoor heat exchanger 113 without evaporating. Therefore, the refrigeration cycle device 100 of Embodiment 7 has a heat dissipation section 118 so that heat is released into the mixed liquid before it flows into the outdoor heat exchanger 113. This promotes the evaporation (gasification) of the refrigerant in the outdoor heat exchanger 113, and gaseous refrigerant can flow out to the refrigerant tank 114 and the compressor 111. Consequently, the time until the refrigerant discharged by the compressor 111 is overheated can be shortened without increasing the storage volume of the refrigerant tank 114, thereby achieving both improved quality and improved performance.

[0105] Embodiment 8. In Embodiment 1, the configuration of the first branch junction 131, in which liquid refrigerant flows more easily toward the outdoor heat exchanger 113 which acts as an evaporator than gaseous refrigerant, was described. In Embodiment 8, the configuration of the second branch junction 132, in which liquid refrigerant flows more easily toward the evaporator, will be described. Here, the refrigeration cycle device 100 can have not only one of these configurations, but also both the configuration of the first branch junction 131 described in Embodiment 1 and the configuration of the second branch junction 132 described in Embodiment 8.

[0106] Figure 25 is a diagram illustrating an example of a second branch / junction section 132 according to Embodiment 8. The second branch / junction section 132 according to Embodiment 8 is configured to have a T-shaped pipe, as shown in Figure 25. Here, in the refrigeration cycle device 100, the other configurations other than the second branch / junction section 132 are the same as those described in Embodiment 1. Furthermore, the control related to the operation of the refrigeration cycle device 100 is also the same as that described in Embodiment 1.

[0107] Figure 26 is a diagram illustrating the arrangement of the second branch / junction section 132 according to Embodiment 8. Here, the configuration of the refrigeration cycle device 100 in Embodiment 8 is the same as in Embodiment 1. Therefore, the configuration of the refrigeration cycle device 100 will be explained here with reference to Figure 1. As shown in Figures 25 and 26, in the second branch / junction section 132, the refrigerant that has flowed out of the return throttling device 115 flows in from the second path side inlet 1321, merges with the refrigerant that has flowed in from the first path side inlet 1322, and flows out from the first path side outlet 1323.

[0108] As mentioned above, when the compressor 111 is started, at the second branch junction 132, the liquid refrigerant mixed with the refrigerant oil flowing through the second path 142 and the refrigerant flowing from the indoor unit 120 side in the first path 141 merge. Here, when the compressor 111 is stopped, the indoor unit 120 is at a higher temperature than the outdoor unit 110, so in low outside air startup, the weight ratio of gaseous refrigerant in the refrigerant flowing from the indoor unit 120 side is larger than during stable operation (steady state). Also, when the compressor 111 is started, mainly the liquid refrigerant flowing out from the compressor 111 flows through the second path 142, so the flow rate through the first path 141 decreases. For this reason, depending on the installation configuration of the second branch junction 132, there is a risk that the liquid refrigerant merging in the second path 142 may flow back in the direction of the first path side inlet 1322 (indoor unit 120 side).

[0109] Therefore, as shown in Figure 26, the second branch junction 132 has a T-shaped pipe with a piping connection structure such that the dot product of the inflow direction vector of the refrigerant flowing in from the second path side inlet 1321 and the outflow direction vector of the refrigerant flowing out from the first path side outlet 1323 is 0 or more. Here, it is preferable that the dot product is greater than 0. For this reason, the second branch junction 132 utilizes the inertial force due to the refrigerant flow in the second path 142 to cause the liquid refrigerant to flow to the evaporator (outdoor heat exchanger 113) side, which is downstream in the refrigerant flow. Thus, the second branch junction 132 in Embodiment 8 has a structure in which the liquid refrigerant flows more easily to the evaporator side than to the condenser side after merging with the refrigerant flowing in the main refrigerant circuit. Here, in the refrigerant circuit, if warming up the compressor 111 etc. is prioritized, the indoor throttling device 122 is closed or has a small opening, and if the refrigerant piping 130 is also to be warmed, the indoor throttling device 122 has a large opening.

[0110] Here, in the second branch junction 132 shown in Figure 26, the first path side outlet 1323 of the second branch junction 132 is located lower in the direction of gravity than the second path side inlet 1321 and the second branch junction 132. In this way, it is basically desirable to have a configuration in which the entire pipe through which the refrigerant flows toward the outdoor heat exchanger 113, which is an evaporator, descends from the point where the refrigerants merge (when the direction of gravity is set to 0°, the flow direction is greater than -90° and less than 90° relative to the direction of gravity). Here, the intersection of the center line of the pipe connected to the bypass piping 133 having the second path side inlet 1321 and the center line of the pipe through which the refrigerant of the main refrigerant circuit flows is defined as the junction point A, which is the point where the refrigerants merge.

[0111] Figure 27 illustrates another example of the structure of the second branch junction 132 according to Embodiment 8. For example, in the second branch junction 132 in Figure 27, the pipe through which the refrigerant of the main refrigerant circuit flows is a nearly straight pipe in the vicinity of the junction point A. In the second branch junction 132, the end of the pipe through which the refrigerant of the main refrigerant circuit flows on the first path side inlet 1322 side is bent in an upward horizontal direction, and the end on the first path side outlet 1323 side is bent in an downward horizontal direction. Here, the pipe between the junction point A and the first path side outlet 1323 is designated as the outflow side piping 1324. The pipe between the first path side inlet 1322 and the junction point A is designated as the inflow side piping 1325.

[0112] At this time, the second branch junction 132 is structured such that, in the pipe through which the refrigerant of the main refrigerant circuit (first path 141) flows, the outlet pipe 1324 is positioned such that, as shown in Figure 27, the direction of refrigerant flow is at an angle greater than -90° and less than 90° with respect to the direction of gravity within 10D, which is 10 times the inner diameter D of the outlet pipe 1324. The second branch junction 132 has such a structure so that, before the refrigerant from the second path side inlet 1321 and the refrigerant from the first path side inlet 1322 mix evenly, the difference in gravity causes the refrigerant from the second path side inlet 1321 to flow towards the outdoor heat exchanger 113.

[0113] Therefore, even when the compressor 111 is started and the flow rate through the first path 141 is low, gravity is utilized at the second branch junction 132 to prevent the liquid refrigerant containing refrigerant oil flowing through the bypass pipe 133 from flowing backward, allowing it to flow towards the outdoor heat exchanger 113 on the downstream side. This effect of suppressing backflow by gravity is particularly effective when the refrigerant flow velocity through the main refrigerant circuit is relatively low.

[0114] Similarly, the second branch junction 132 can be structured such that, as shown in Figure 27, the inlet pipe 1325 through which the refrigerant flows before the junction is positioned such that, within 10D, the flow direction of the refrigerant from the first path side inlet 1322 toward the junction point A is greater than -90° and less than 90° relative to the direction of gravity. With the second branch junction 132 having such a structure, the liquid refrigerant and refrigerant oil joining from the bypass pipe 133 at the second branch junction 132 will flow to the downstream outdoor heat exchanger 113 without flowing against gravity in the direction of reverse flow in the main refrigerant circuit.

[0115] The liquid refrigerant, mixed with the refrigerant oil flowing through the second path 142 via the bypass piping 133, flows to the outdoor heat exchanger 113 via the second branch junction 132. By flowing the liquid refrigerant to the outdoor heat exchanger 113, the liquid refrigerant absorbs heat from the outdoor air and evaporates due to heat exchange with the outdoor air in the outdoor heat exchanger 113, becoming a fluid in which a gas-liquid two-phase refrigerant, mainly in the gas phase, is mixed with the refrigerant oil. This suppresses the outflow of refrigerant oil to the indoor unit 120 side flowing through the first path 141 when the compressor 111 is started, and shortens the warm-up operation by heating the compressor 111 and the liquid refrigerant remaining in the refrigerant circuit using heat absorbed from the outdoor air. When the warm-up operation is finished, the control device 200 controls the opening of the return throttle device 115 to close or reduce the opening degree, so that the flow rate of refrigerant flowing through the first path 141 on the main refrigerant circuit side increases.

[0116] <Effects of Embodiment 8> Figure 28 is a diagram illustrating the effects of the compressor 111 of the refrigeration cycle device 100 according to Embodiment 8. Figure 28(a) shows the degree of superheating of the discharged refrigerant during warm-up operation when backflow or stagnation of liquid refrigerant occurs in the second branch junction 132. Figure 28(b) shows the degree of superheating of the discharged refrigerant during warm-up operation when backflow or stagnation of liquid refrigerant is suppressed in the second branch junction 132. As shown in Figure 28, effects with a similar tendency to those when gas-liquid separation is performed by the first branch junction 131 as described in Embodiment 1 can be obtained.

[0117] The refrigeration cycle device 100 in Embodiment 8 includes a first branching and merging section 131 in the refrigerant circuit that can branch the refrigerant discharged from the compressor 111 into a first path 141, which is the main refrigerant circuit path, and a second path 142, which is the bypass circuit path. When the compressor 111 is started, the refrigerant in the second branching and merging section 132 flows with the refrigerant in the first path 141, which contains a large amount of gaseous refrigerant, and the refrigerant in the second path 142, which contains a large amount of liquid refrigerant, thus supplying the refrigerant to the downstream outdoor heat exchanger 113 without backflow.

[0118] Furthermore, by allowing the liquid refrigerant containing refrigerant oil to flow through the second path 142 during the warm-up operation when the compressor 111 is started, the refrigerant oil that has leaked out of the compressor 111 can be quickly returned to the compressor 111. Therefore, the reduction of refrigerant oil inside the compressor 111 can be suppressed. In addition, in the outdoor heat exchanger 113, the refrigerant that has absorbed heat and evaporated through heat exchange with the outdoor air is drawn into the compressor 111, so that the heat absorbed from the outdoor air can be used to heat the compressor 111. Therefore, energy saving can be achieved efficiently, and the time it takes for the refrigerant discharged from the compressor 111 to go from a gas-liquid two-phase state to a superheated state can be shortened, thereby improving performance. Based on the above, the refrigeration cycle device 100 in Embodiment 8 is equipped with a second branch junction 132 that allows the liquid refrigerant and refrigerant oil to flow to the downstream outdoor heat exchanger 113 without backflow when the compressor 111 is started, and gas-liquid separation is performed during the warm-up operation. Therefore, the refrigeration cycle device 100 in Embodiment 8 can achieve both quality improvement and performance improvement.

[0119] Embodiment 9. <Configuration of Embodiment 9> Figure 29 is a diagram showing the equipment configuration of the refrigeration cycle device 100 according to Embodiment 9. Next, the refrigeration cycle device 100 according to Embodiment 9 will be described using Figure 29. The refrigeration cycle device 100 according to Embodiment 9 combines the configuration of the second branch and merge section 132, which is the same as in Embodiment 8, with some of the configuration of the refrigeration cycle device 100 according to Embodiment 2 being changed. The refrigeration cycle device 100 according to Embodiment 9 differs from the configuration of the refrigeration cycle device 100 in Embodiment 2 in that the first branch and merge section 131 is installed in the middle of the return pipe 136 that connects the liquid refrigerant outlet of the gas-liquid separator 134A and the suction side of the compressor 111.

[0120] In the refrigeration cycle device 100 of Embodiment 9, a first branch junction 131 is provided at the liquid-side outlet of the gas-liquid separator 134A of the third branch junction 134. The refrigerant flowing out from the gas-liquid separator 134A is divided into a second path 142 that flows from the first branch junction 131 to the second branch junction 132 via a return throttling device 115, and a third path 143 that flows to the fourth branch junction 135.

[0121] During warm-up operation, the gas-liquid two-phase refrigerant discharged by the compressor 111 contains a large amount of liquid refrigerant. As a result, a large amount of liquid refrigerant and refrigerant oil flows into the gas-liquid separator 134A. Therefore, when the compressor 111 is started, the amount of liquid refrigerant flowing out from the liquid refrigerant outlet in the first stage of gas-liquid separation by the gas-liquid separator 134A is increased to suppress the outflow of liquid refrigerant into the first path 141. In addition, by flowing liquid refrigerant to the outdoor heat exchanger 113 via the second path 142, the overheating of the discharged refrigerant is promoted.

[0122] As described above, the refrigeration cycle device 100 has a fourth branch junction 135 between the outdoor heat exchanger 113 and the compressor 111. The fourth branch junction 135 is the part on the suction side of the compressor 111 where the refrigerant flowing through the main refrigerant circuit and the refrigerant containing refrigerant oil that has passed through the return pipe 136 merge. In Embodiment 9, the fourth branch junction 135 has a branch pipe which is part of the piping. Therefore, at the fourth branch junction 135, the liquid refrigerant containing refrigerant oil separated in the gas-liquid separator 134A returns to the suction side of the compressor 111. Here, a throttling device or a capillary tube may be provided on the third path to form a constant refrigerant differential pressure.

[0123] Furthermore, the configuration of the refrigeration cycle device 100 in Embodiment 2 shown in Figure 9 may be combined with the second branch / junction section 132 of Embodiment 8. For example, as shown in Figure 9, the first branch / junction section 131 is provided at the gas refrigerant outlet of the gas-liquid separator 134A. In this case, the configuration of the fourth branch / junction section 135 is the same as that in Figure 29. As described in Embodiment 2, during warm-up operation, the refrigerant that could not be separated in the gas-liquid separator 134A of the third branch / junction section 134 flows into the first branch / junction section 131 and is separated there. The refrigerant containing liquid refrigerant then passes through the second path 142 and, via the return throttling device 115, merges with the refrigerant in the first path 141 at the second branch / junction section 132 described in Embodiment 8. Therefore, the refrigeration cycle device 100 can perform gas-liquid separation in two stages.

[0124] <Effects of Embodiment 9> In the refrigeration cycle device 100 of Embodiment 9, the gas-liquid separator 134A of the third branch-junction section 134 is configured to function as an oil separator. This allows the refrigeration cycle device 100 to perform both oil return during warm-up operation via the second path 142 through the first branch-junction section 131 and oil return after warm-up operation via the third branch-junction section 134. For example, during warm-up operation, as described in Embodiment 1, the control device 200 controls the opening degree ω of the return throttle device 115, thereby mainly performing oil return from the second path 142. At this time, the refrigerant absorbs heat in the outdoor heat exchanger 113 for a short time, which promotes heating of the compressor 111. On the other hand, after warm-up operation, the return throttle device 115 is closed, and oil return is mainly performed from the third path 143. By returning the refrigerant oil contained in the refrigerant discharged by the compressor 111 directly to the compressor 111 without passing through the outdoor heat exchanger 113, refrigerant oil does not accumulate in the outdoor heat exchanger 113. Therefore, the refrigeration cycle device 100 in Embodiment 9 improves oil return during and after warm-up operation, achieving both improved quality and improved performance.

[0125] Here, it is preferable to have both the second branch junction 132 described in Embodiment 9 and the first branch junction 131 described in Embodiment 1, but it is also acceptable to have only one of them. For example, if the first branch junction 131 has a gas-liquid separation structure, the pipe connected to the heat exchanger that becomes the evaporator of the second branch junction 132 does not necessarily have to be connected facing downwards. Also, if the pipe connected to the heat exchanger that becomes the evaporator of the second branch junction 132 is connected facing downwards, the first branch junction 131 does not necessarily have to have a gas-liquid separation structure.

[0126] Embodiment 10. Figure 30 is a diagram showing the equipment configuration of the refrigeration cycle device 100 according to Embodiment 10. The refrigeration cycle device 100 according to Embodiment 10 has some modifications to the configuration of the refrigeration cycle device 100 according to Embodiment 1, and the basic overall configuration is the same as that of the refrigeration cycle device 100 in Embodiment 1. Here, in Figure 30, equipment and the like that are denoted by the same reference numerals as in Figure 1 perform the same functions and operations as those described in Embodiment 1.

[0127] The refrigeration cycle device 100 in Embodiment 10 is equipped with a plurality of indoor units 120 arranged in parallel. Each indoor unit 120 has an indoor heat exchanger 121 and an indoor throttling device 122, and for example, the control device 200 can individually control the operation or stopping of each unit.

[0128] Figure 31 is a diagram illustrating the relationship between the number of indoor units 120 operating and the drive frequency of the compressor 111 when the compressor 111 is started up according to Embodiment 10. The number of indoor units 120 in the refrigeration cycle device 100 is A. The drive frequency of the compressor 111 when warming up indoor units 120 A is C1 [Hz] when the compressor 111 is started up. For example, if the drive frequency of the compressor 111 when warming up indoor units 120 B with the indoor units 120 stopped is C2 [Hz], the control device 200 drives the compressor 111 at a drive frequency C2 [Hz] such that C2 > C1 * (A - B) / A, and performs the warm-up operation. In Figure 31, the fewer indoor units 120 performing warm-up operation relative to the total number of indoor units 120 in the refrigeration cycle device 100, the higher the drive frequency C2 [Hz] per unit relative to the virtual straight line C = C1・(A-B) / A.

[0129] During normal operation after warm-up, the control device 200 controls the drive frequency of the compressor 111 according to the total required capacity of the operating indoor units 120. In normal operation, if there are indoor units 120 that are stopped, the drive frequency of the compressor 111 may be lower than the drive frequency when all indoor units 120 are operating. For example, the drive frequency of the compressor 111 can be determined based on the number of operating indoor units 120 and the opening degree of each indoor throttle device 122 when stopped.

[0130] Figure 32 is a diagram illustrating the operation of the outdoor fan 116 from the start of the compressor 111 according to Embodiment 10. Furthermore, if there are indoor units 120 that are stopped, the control device 200 drives the outdoor fan 116 at rotational speed ε1 during the warm-up operation when the compressor 111 starts up, and controls it so that the rotational speed becomes ε1', which is lower than rotational speed ε1, after a certain period of time has elapsed. As shown in Figure 32, it is desirable that this certain period of time be the same as the opening degree setting time τ described above, but considering the trade-off between energy saving and quality, it may be set to a shorter time or a longer time than the opening degree setting time τ.

[0131] <Effects of Embodiment 10> In the case of a refrigerant circuit configuration having multiple indoor units 120, the total piping length becomes long, so it takes time for a large amount of refrigerant oil to return. According to the refrigeration cycle device 100 in Embodiment 10, even when there are multiple indoor units 120, the liquid refrigerant mixed with the refrigerant oil that has leaked out of the compressor 111 is separated during the warm-up operation when the compressor 111 is started and configured to flow through the second path 142. As a result, the refrigerant oil that has leaked out of the compressor 111 can be quickly returned to the compressor 111. Therefore, the reduction of refrigerant oil inside the compressor 111 can be suppressed. In addition, since the heat absorbed from the outside air can be used to heat the compressor 111, the warm-up operation time can be shortened while efficiently saving energy, and performance can be improved.

[0132] Furthermore, the outdoor unit 110 of the refrigeration cycle device 100 in Embodiment 10 has a second path 142, which allows the refrigerant to circulate inside the outdoor unit 110. Therefore, even when the number of indoor units 120 in operation is small, the compressor 111 can be started at a relatively high drive frequency without having to suppress the drive frequency at the time of compressor 111 startup due to the number of units in operation, thereby suppressing the reduction in the refrigerant flow rate inside the outdoor unit 110. Consequently, regardless of the number of units in operation, the decrease in the amount of heat absorbed from the outdoor air in the outdoor heat exchanger 113 can be suppressed, and the heat related to heat absorption can be used to heat the compressor 111.

[0133] Furthermore, in the refrigeration cycle device 100 of Embodiment 10, the outdoor fan 116 is driven at a high rotational speed during the warm-up operation when the compressor 111 is started, regardless of the number of units in operation. As a result, the decrease in the amount of heat absorbed from the outdoor air by the outdoor heat exchanger 113 is suppressed, and the heat absorbed can be used to heat the compressor 111. From the above, by suppressing the reduction of refrigerant oil in the compressor 111 and accelerating the heating of the compressor 111 to promote warm-up, it is possible to achieve both quality improvement and performance improvement.

[0134] Embodiment 11. The configuration of the refrigeration cycle device 100 shown in Embodiments 1 to 10 described above is an example of the content of this disclosure, and it is possible to combine it with known technology, and it is also possible to omit or change some of the configuration without departing from the gist of this disclosure.

[0135] The embodiments 1 to 10 described above primarily describe the case where the refrigeration cycle device 100 is performing heating operation, but the invention is not limited to this. For example, the invention can also be applied to other operations, such as when the refrigeration cycle device 100 is performing cooling operation.

[0136] The refrigeration cycle device 100 in Embodiments 2 to 9 described above is configured in which one indoor unit 120 is connected to the outdoor unit 110 by refrigerant piping 130, but it is not limited to this configuration. As in Embodiment 10, the refrigeration cycle device 100 may also be configured in which multiple indoor units 120 are connected to the outdoor unit 110 by piping.

[0137] In the first embodiment described above, the first branch junction 131 is a piping structure that uses a T-shaped pipe to create a gas-liquid separation structure, but it is not limited to this. For example, it may be a piping structure such as a T-shaped pipe or a Y-shaped pipe.

[0138] 100 Refrigeration cycle unit, 110 Outdoor unit, 111 Compressor, 112 Flow path switching device, 113 Outdoor heat exchanger, 114 Refrigerant tank, 115 Return throttling device, 116 Outdoor fan, 117 Outdoor throttling device, 118 Heat dissipation unit, 120 Indoor unit, 121 Indoor heat exchanger, 122 Indoor throttling device, 123 Indoor fan, 130 Refrigerant piping, 131 First branch / junction, 132 Second branch / junction, 133 Bypass piping, 134 Third branch / junction, 134A Gas-liquid separator, 135 Fourth branch / junction, 136 Return piping, 141 First path, 142 Second path, 143 Third path, 200 Control device, 201 Control unit, 202 Memory unit, 203 Timing unit, 210 Outdoor air temperature sensor, 211 Discharge pressure sensor, 212; Discharge temperature sensor, 1141; Container outlet pipe, 1181; Heat radiator, 1311; Inlet, 1312; First path side outlet, 1313; Second path side outlet, 1321; Second path side inlet, 1322; First path side inlet, 1323; First path side outlet, 1324; Outlet side piping, 1325; Inlet side piping, 1341; Container, 1342; Inlet pipe port, 1343; Refrigerant outlet pipe port, 1344; Refrigerator oil outlet pipe port.

Claims

1. A refrigeration cycle device comprising a compressor, a condenser, a first throttling device, and an evaporator connected by piping to form a main refrigerant circuit through which a refrigerant circulates, wherein the device comprises a bypass pipe connecting a first branch junction between the discharge side of the compressor and the condenser and a second branch junction on the inlet side of the evaporator, and a second throttling device having a valve for adjusting the pressure and flow rate of the refrigerant flowing through the bypass pipe, wherein, when the compressor is started, the refrigerant discharged from the compressor, which contains more liquid phase than gas phase, flows through the bypass pipe toward the evaporator, thus having a bypass configuration.

2. A refrigeration cycle device comprising a compressor, a condenser, a first throttling device, and an evaporator connected by piping to constitute a main refrigerant circuit through which a refrigerant circulates, wherein the device comprises a bypass pipe connecting a first branch junction between the discharge side of the compressor and the condenser and a second branch junction on the inlet side of the evaporator, and a second throttling device having a valve for adjusting the pressure and flow rate of the refrigerant flowing through the bypass pipe, wherein the bypass pipe is connected such that when the compressor discharges the refrigerant in which a mixture of gaseous and liquid phases of the refrigerant is present, at the second branch junction, the refrigerant containing more liquid phase than gaseous flows toward the evaporator, and at the first branch junction, the refrigerant containing more gaseous phase than liquid flows toward the condenser.

3. The refrigeration cycle apparatus according to claim 1 or claim 2, wherein the first branch junction has a gas-liquid separation structure in which the refrigerant discharged by the compressor, which contains more gas phase than liquid phase, flows to the main refrigerant circuit side, and the refrigerant, which contains more liquid phase than gas phase, flows through the bypass piping.

4. The refrigeration cycle apparatus according to any one of claims 1 to 3, wherein the second branch junction has a structure that allows the refrigerant discharged by the compressor, which contains more liquid phase than the gas phase that has passed through the bypass piping, to flow more easily towards the evaporator side than towards the condenser side after merging with the refrigerant flowing through the main refrigerant circuit.

5. A refrigeration cycle apparatus according to any one of claims 1 to 4, comprising a control device for controlling the opening and closing of the second throttling device, wherein the control device opens the second throttling device while the refrigerant discharged by the compressor contains a mixture of gaseous and liquid phase refrigerants when the compressor is started, and then closes the second throttling device when the compressor temperature rises and the compressor discharges only gaseous phase refrigerant.

6. A refrigeration cycle device comprising a compressor, a condenser, a first throttling device, and an evaporator connected by piping to constitute a main refrigerant circuit through which a refrigerant circulates, wherein the device comprises a bypass pipe connecting a first branch junction between the discharge side of the compressor and the condenser and a second branch junction on the inlet side of the evaporator, and a second throttling device having a valve for adjusting the pressure and flow rate of the refrigerant flowing through the bypass pipe, wherein the first branch junction has a gas-liquid separation structure such that, in the refrigerant discharged by the compressor, the gaseous phase of the refrigerant flows to the main refrigerant circuit side and the liquid phase of the refrigerant flows through the bypass pipe.

7. The refrigeration cycle apparatus according to any one of claims 1 to 6, wherein the second branch junction has a piping connection structure in which the dot product of the inflow direction vector of the refrigerant flowing in from the bypass piping and the outflow direction vector of the refrigerant flowing out after junctioning is greater than 0.

8. In the second branch junction, the outlet pipe from which the merged refrigerant flows out is arranged such that, with respect to the inner diameter D of the outlet pipe, the angle with respect to the direction of gravity is between -90° and 90° with respect to the direction of gravity when the direction of gravity is set to 0° within a straight-line distance of 10D, the refrigeration cycle apparatus according to any one of claims 1 to 6.

9. In the second branch junction, the inlet pipe through which the refrigerant of the main refrigerant circuit flows before the junction is arranged such that, with respect to the inner diameter D of the outlet pipe through which the merged refrigerant flows, the angle with respect to gravity is between -90° and 90° with respect to the direction of gravity when the direction of gravity is set to 0° in a pipe within a straight-line distance of 10D, the refrigeration cycle apparatus according to any one of claims 1 to 6 or claim 8.

10. A refrigeration cycle apparatus according to any one of claims 1 to 9, comprising a return pipe connecting a third branch junction between the compressor and the first branch junction, and a fourth branch junction between the evaporator and the suction side of the compressor, wherein the third branch junction has a gas-liquid separation structure such that, in the refrigerant discharged by the compressor, the gas phase of the refrigerant flows towards the first branch junction, and the liquid phase of the refrigerant flows through the return pipe.

11. The gas-liquid separation structure in the third branching and merging section is a separation structure using centrifugal force, according to claim 10.

12. The first branch junction has an outlet in the direction of outflow from which the refrigerant flowing through the bypass piping flows out, and the outlet is positioned at an angle of -30° to 30° with respect to the direction of gravity, wherein it is a gravity-based gas-liquid separation structure, as described in any one of claims 1 to 11.

13. A refrigeration cycle apparatus according to any one of claims 1 to 12, comprising an outdoor air temperature sensor for detecting the outdoor air temperature, wherein in the second throttle device, when the outdoor air temperature at the time of starting the compressor is lower than a preset temperature, the valve is opened at a preset first set opening degree.

14. The refrigeration cycle apparatus according to any one of claims 1 to 13, wherein in the second throttling device, after the valve is opened by the start of the compressor and a set opening time has elapsed, the opening of the valve is reduced or the valve is closed.

15. A refrigeration cycle apparatus according to any one of claims 1 to 14, comprising a discharge temperature sensor for detecting the discharge temperature of the refrigerant on the discharge side of the compressor, wherein the second throttling device reduces the opening of the valve that was opened when the compressor was started or closes the valve when the superheating degree of the refrigerant discharged by the compressor becomes higher than a set superheating degree.

16. The refrigeration cycle apparatus according to any one of claims 1 to 15, comprising a third throttling device installed between the second branch confluence and the evaporator, having a valve, for adjusting the pressure and flow rate of the refrigerant passing through the evaporator.

17. The refrigeration cycle apparatus according to claim 16, wherein the third throttling device opens the valve at a second set opening when the compressor is started, and increases the opening of the valve after a preset opening time has elapsed.

18. A refrigeration cycle apparatus according to claim 16, comprising an outdoor air temperature sensor for detecting the outdoor air temperature, wherein the third throttle device opens the valve at a second set opening when the compressor is started, and the second set opening is such that the opening υ1 in startup operation under a specific outdoor air temperature T1 environment and the opening υ1' in startup operation under an outdoor air temperature T2 environment lower than the outdoor air temperature T1 are in the relationship υ1 > υ1'.

19. A refrigeration cycle apparatus according to any one of claims 1 to 12, comprising an outdoor air temperature sensor for detecting the outdoor air temperature, wherein the second throttle device can set the first set opening degree in multiple stages, and the first set opening degree such that the opening degree ω1 in startup operation under a specific outdoor air temperature T1 environment and the opening degree ω1' in startup operation under an outdoor air temperature T2 environment lower than the outdoor air temperature T1 are in the relationship ω1 > ω1'.

20. A refrigeration cycle apparatus according to any one of claims 1 to 19, comprising an outdoor air temperature sensor for detecting the outdoor air temperature, wherein the first throttling device has a valve, and the degree of opening of the valve, which opens when the compressor is started, can be set in multiple stages as a third set opening, and the third set opening is such that the degree of opening ξ1 in startup operation under a certain outdoor air temperature T1 environment and the degree of opening ξ1' in startup operation under an outdoor air temperature T2 environment lower than the outdoor air temperature T1 are in the relationship ξ1 > ξ1'.

21. The refrigeration cycle apparatus according to any one of claims 1 to 20, comprising a heat dissipation mechanism installed between the first branch confluence and the second branch confluence for dissipating heat to the refrigerant.

22. A refrigeration cycle apparatus according to any one of claims 1 to 21, comprising a plurality of condensers, each connected in parallel by piping and capable of individually controlling heat exchange or stopping, wherein the drive frequency of the compressor at startup is controlled based on the number of condensers performing heat exchange.

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