Oil separation mechanism and refrigeration apparatus

Abstract

To provide an oil separation mechanism capable of suppressing a temperature drop of a refrigerant in a mechanism for separating oil from the refrigerant discharged from a compressor, and a refrigerating device.SOLUTION: The oil separation mechanism 3 includes the oil separator 14 that separates the oil from the refrigerant discharged from the compressors, the oil storage device that stores the oil separated by the oil separator 14, and the oil pipe 17 that connects the oil separator 14 and the oil storage device to each other. The lower end of the oil separator 14 is located higher than the first connecting portion 17a where the oil pipe 17 is connected to the oil storage device. The oil moves from the oil separator 14 to the oil storage device by its own weight through the oil pipe 17, and at least a part of the flow passage of the oil pipe 17 is located at a position lower than the oil separator 14 and lower than the first connecting part 17a.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an oil separation mechanism and a refrigeration device. [Background technology]

[0002] Patent Document 1 discloses a refrigeration circuit having a configuration in which oil contained in refrigerant discharged from a plurality of compressors is separated from the refrigerant by an oil separator, stored, and returned to each compressor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-133209 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides an oil separation mechanism that can suppress a decrease in the temperature of a refrigerant in a mechanism that separates oil from a refrigerant discharged from a compressor, and a refrigeration device. [Means for solving the problem]

[0005] The oil separation mechanism of the present disclosure is provided in a refrigeration circuit formed by connecting a compressor, a heat source side heat exchanger, and a user side heat exchanger, and includes an oil separator that separates oil from the refrigerant discharged from the compressor, an oil storage device that stores the oil separated by the oil separator, and an oil pipe that connects the oil separator to the oil storage device, wherein the lower end of the oil separator is located higher than a first connection part that connects the oil pipe to the oil storage device, and the oil moves from the oil separator to the oil storage device through the oil pipe by its own weight, and at least a portion of the flow path of the oil pipe is located lower than the oil separator and the first connection part.

[0006] The refrigeration device disclosed herein is a refrigeration device including a refrigeration circuit connecting a compressor, a heat source side heat exchanger, and a user side heat exchanger, and includes an oil separator that separates oil from the refrigerant discharged from the compressor, an oil storage device that stores the oil separated by the oil separator, and an oil pipe that connects the oil separator and the oil storage device, wherein the lower end of the oil separator is located higher than a first connection part that connects the oil pipe to the oil storage device, and the oil moves from the oil separator to the oil storage device through the oil pipe by its own weight, and at least a portion of the flow path of the oil pipe is located lower than the oil separator and the first connection part. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to suppress a decrease in the temperature of the refrigerant in a mechanism that separates oil from the refrigerant discharged from the compressor. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing the configuration of a refrigeration device according to a first embodiment. [Figure 2] FIG. 1 is a diagram showing the configuration of a refrigeration device according to a first embodiment. [Figure 3] FIG. 1 is a diagram showing the configuration of a refrigeration device according to a first embodiment. [Figure 4] Perspective view of the oil separation mechanism [Figure 5] Partially broken side view of the oil separation mechanism [Figure 6] Enlarged view of the main part of the oil separation mechanism [Figure 7] Enlarged view of the main part of the oil separation mechanism DETAILED DESCRIPTION OF THE INVENTION

[0009] (Findings that formed the basis of this disclosure) At the time the inventors came up with the idea for the present disclosure, there was a technology in place that used an oil separator to separate oil contained in a refrigerant discharged from a compressor in a refrigeration system and return the oil to the compressor. Inside the oil separator, the flow of the refrigerant is dispersed and its flow velocity is reduced, raising concerns about heat loss from the refrigerant. In particular, refrigeration systems that use a large amount of oil require large oil separators, and the inventors discovered a problem in that the heat lost by the refrigerant during the process of separating the oil from the refrigerant was not negligible. The subject matter of the present disclosure was created to solve this problem. Therefore, the present disclosure provides an oil separation mechanism that can suppress a decrease in the temperature of a refrigerant in a mechanism that separates oil from a refrigerant discharged from a compressor, and a refrigeration device.

[0010] Hereinafter, embodiments will be described in detail with reference to the drawings. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters or redundant description of substantially the same configuration may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0011] (Embodiment 1) Hereinafter, the first embodiment will be described with reference to the drawings. [1-1. Configuration of refrigeration equipment] [1-1-1. Refrigeration circuit configuration] 1, 2, and 3 are circuit diagrams showing the refrigeration system 1 in embodiment 1, where FIG. 1 shows the state of the refrigeration system 1 in cooling mode, and FIGS. 2 and 3 show the state of the refrigeration system 1 in heating mode. In FIGS. 1, 2, and 3, for ease of explanation, an open opening / closing device is shown in white, and a closed opening / closing device and an expansion mechanism are shown in black. In addition, of the refrigerant piping shown in the figures, piping through which refrigerant flows is shown in thick lines, piping through which refrigerant does not flow is shown in thin lines, and the direction of refrigerant flow in the main piping is indicated by arrows. An opening / closing device is a device that can close the piping through which refrigerant flows in the refrigeration system 1, and specifically refers to a shutoff valve, a throttling mechanism, an expansion mechanism, etc.

[0012] As shown in each of Figures 1 to 3, the refrigeration device 1 comprises an outdoor unit 10, an indoor unit 20, and a cooling equipment 30, which are connected to each other by refrigerant piping to form a refrigeration circuit 2 that functions as a flow path through which the refrigerant flows. In this embodiment, the refrigerant used in the refrigeration circuit 2 is, for example, carbon dioxide refrigerant (R744), which is a natural refrigerant that is non-flammable and non-toxic.

[0013] The indoor unit 20 includes an indoor heat exchanger 22. The indoor unit 20 conditions the interior of a store, which is a space to be conditioned, based on a temperature setting set by a user in a store such as a convenience store or supermarket. The refrigeration equipment 30 includes a refrigeration heat exchanger 32. The refrigeration equipment 30 cools the interior of a refrigerated showcase or a freezer showcase, which serves as refrigerated storage equipment installed in the store, based on a temperature setting set by a user. The indoor heat exchanger 22 and the refrigeration heat exchanger 32 correspond to "use-side heat exchangers" in this disclosure, and the indoor heat exchanger 22 can also be called an air-conditioning heat exchanger. The refrigeration heat exchanger 32 may also function as a heat source-side heat exchanger in the heating mode, which will be described later.

[0014] The refrigeration device 1 has the function of heating and cooling the space to be conditioned by the indoor unit 20. The refrigeration device 1 can switch between a plurality of operating modes, which include a cooling mode and a heating mode for the space to be conditioned. In the cooling mode, cooling is performed by the indoor unit 20, and in the heating mode, heating is performed by the indoor unit 20. In this embodiment, the refrigeration heat exchanger 32 cools the refrigeration equipment 30 but does not heat the refrigeration equipment 30.

[0015] The refrigeration apparatus 1 includes a controller 100 that controls the operation of the refrigeration apparatus 1. The controller 100 controls the compressor and opening / closing devices included in the refrigeration apparatus 1, and adjusts the opening / closing and opening degrees of each opening / closing device. In this way, the controller 100 switches the operation mode of the refrigeration apparatus 1 and performs cooling and heating in the cooling mode and the heating mode. The opening / closing devices controlled by the controller 100 include, for example, an indoor expansion mechanism 21, an opening / closing valve 23, a cooling inlet expansion mechanism 31, a cooling outlet pressure adjustment mechanism 33, pressure adjustment mechanisms 47 and 48, a first cooling valve 51, a first heating valve 52, an outdoor refrigerant return valve 53, a refrigerant return expansion mechanism 58, a gas refrigerant flow control valve 61, and a liquid refrigerant flow adjustment valve 65.

[0016] Although not shown in FIGS. 1, 2 and 3, the outdoor heat exchanger 15, the indoor heat exchanger 22 and the cooling heat exchanger 32 are each provided with a blower for promoting heat exchange.

[0017] The outdoor unit 10 functions as a so-called heat source device. The outdoor unit 10 is formed by sequentially connecting multiple compressors, a first switching mechanism 50, an outdoor heat exchanger 15, a second switching mechanism 54, and a gas-liquid separator 16. The outdoor heat exchanger 15 corresponds to the "heat source-side heat exchanger" of the present disclosure.

[0018] The outdoor unit 10 is equipped with a two-stage compressor including a low-stage compressor 11 and two high-stage compressors 12, 12. This two-stage compressor is configured by connecting the low-stage compressor 11 and the high-stage compressors 12, 12 in series, and the two high-stage compressors 12, 12 are connected in parallel to the discharge side of the low-stage compressor 11. The low-stage compressor 11 and the high-stage compressor 12 are rotary compressors whose compression mechanisms are driven by, for example, a motor. The high-stage compressor 12 discharges refrigerant at a higher discharge pressure than the low-stage compressor 11.

[0019] An accumulator 13 is arranged between the discharge side of the low-stage compressor 11 and the high-stage compressor 12. The refrigerant compressed by the low-stage compressor 11 is sent to the high-stage compressor 12 via the accumulator 13.

[0020] An oil separator 14 is connected to the discharge side of the high-stage compressor 12. A first switching mechanism 50 is connected to the oil separator 14. That is, the first switching mechanism 50 is connected to the discharge pipe of the high-stage compressor 12 via the oil separator 14.

[0021] The oil separator 14, together with the oil pipe 17 and the reserve tank 18, constitutes the oil separation mechanism 3. The oil separation mechanism 3 is a mechanism that separates oil contained in the refrigerant discharged by the high-stage compressor 12 from the refrigerant, stores the separated oil, and returns the stored oil to the low-stage compressor 11 and the high-stage compressor 12. The reserve tank 18 corresponds to the "oil storage device" in this disclosure.

[0022] Oil separator 14 separates oil from the refrigerant discharged from high-stage compressor 12. The oil separated in oil separator 14 is sent to reserve tank 18 through oil pipe 17 and stored in reserve tank 18. In addition, oil separator 14 sends the refrigerant from which the oil has been separated to first switching mechanism 50 through discharge pipe 25.

[0023] An oil return pipe 46 is connected to the reserve tank 18. The oil return pipe 46 is connected to the low-stage compressor 11 and the accumulator 13. In the low-stage compressor 11, the oil return pipe 46 is connected, for example, to the suction pipe of the low-stage compressor 11 or to the case of the low-stage compressor 11. The oil accumulated in the reserve tank 18 is sent to the accumulator 13 together with the refrigerant through the oil return pipe 46 due to the pressure difference between the inside of the reserve tank 18 and the accumulator 13. In addition, the oil in the reserve tank 18 is sent to the low-stage compressor 11 together with the refrigerant due to the pressure difference with the inside of the reserve tank 18.

[0024] The oil return pipe 46 is provided with pressure adjustment mechanisms 47 and 48. The opening degrees of the pressure adjustment mechanisms 47 and 48 are adjusted under the control of the controller 100. The pressure adjustment mechanism 47 adjusts the pressure and flow rate of the refrigerant containing oil sent from the oil return pipe 46 to the accumulator 13. The pressure adjustment mechanism 48 adjusts the pressure and flow rate of the refrigerant containing oil sent from the oil return pipe 46 to the low-stage compressor 11. The pressure adjustment mechanisms 47, 48 are, for example, expansion valves.

[0025] The two high-stage compressors 12 are connected in parallel to the accumulator 13. The accumulator 13 functions as a flow divider that distributes the oil returned from the reserve tank 18 to each of the high-stage compressors 12 approximately equally.

[0026] The first switching mechanism 50 has a pipe 40 and a first heating pipe 41 as refrigerant flow paths connected to the discharge pipe 25. A first cooling valve 51 is provided in the pipe 40. A first heating valve 52 is provided in the first heating pipe 41. In the present embodiment, the first cooling valve 51 and the first heating valve 52 are on-off valves that are opened and closed under the control of the controller 100. The first cooling valve 51 switches the pipe 40 between an open state in which the refrigerant can flow and a closed state in which the flow of the refrigerant is blocked. The first heating valve 52 switches the first heating pipe 41 between an open state in which the refrigerant can flow and a closed state in which the flow of the refrigerant is blocked. In this way, the first switching mechanism 50 switches the flow path of the refrigerant discharged from the high-stage compressor 12 between the pipe 40 and the first heating pipe 41 by opening and closing the first cooling valve 51 and the first heating valve 52.

[0027] The pipe 40 is connected to the discharge pipe 25 and the outdoor heat exchanger 15, and supplies the refrigerant to the outdoor heat exchanger 15 when the first cooling valve 51 is open.

[0028] One end of the first heating pipe 41 is connected to the discharge pipe 25, and the other end of the first heating pipe 41 is connected to a pipe 71 that connects the indoor heat exchanger 22 of the indoor unit 20 and the suction side of the high-stage compressor 12. An on-off valve 23 that opens and closes the pipe 71 is provided in the pipe 71 between the point where the other end of the first heating pipe 41 is connected and the accumulator 13.

[0029] With the first heating valve 52 open, the first heating pipe 41 supplies the refrigerant discharged from the high-stage compressor 12 to the pipe 71. In this case, the high-pressure refrigerant that has flowed into the pipe 71 is supplied to the indoor heat exchanger 22, causing the indoor heat exchanger 22 to operate as a gas cooler. Here, when the on-off valve 23 is closed, the high-pressure refrigerant is supplied in its entirety to the indoor heat exchanger 22 without returning to the accumulator 13.

[0030] In the piping 40, one end of a first outdoor return piping 42 is connected between the first cooling valve 51 and the outdoor heat exchanger 15. The other end of the first outdoor return piping 42 is connected to the piping 72. An outdoor refrigerant return valve 53 is provided in the first outdoor return piping 42. In the present embodiment, the outdoor refrigerant return valve 53 is an on-off valve that is opened and closed under the control of the controller 100. The outdoor refrigerant return valve 53 switches the first outdoor return piping 42 between an open state, which allows the refrigerant to flow, and a closed state, which blocks the flow of refrigerant.

[0031] The piping 72 connects the chilled-unit heat exchanger 32 and the suction side of the low-stage compressor 11. A chilled-unit outlet pressure adjustment mechanism 33 is provided in the piping 72 between the point where the other end of the first outdoor return piping 42 is connected and the chilled-unit heat exchanger 32. The chilled-unit outlet pressure adjustment mechanism 33 is an opening / closing device that can change its opening degree from fully closed to fully open under the control of the controller 100. By adjusting the opening degree of the chilled-unit outlet pressure adjustment mechanism 33, the pressure of the refrigerant flowing through the piping 72 can be adjusted, and the chilled-unit outlet pressure adjustment mechanism 33 functions as a so-called throttle valve.

[0032] In this way, the first switching mechanism 50 is connected to the outdoor heat exchanger 15, the indoor heat exchanger 22, the chilled heat exchanger 32, and the low-stage compressor 11. The first switching mechanism 50 switches the refrigerant flow path in the refrigeration circuit 2 by opening and closing the first cooling valve 51, the first heating valve 52, and the outdoor refrigerant return valve 53. The first cooling valve 51, the first heating valve 52, and the outdoor refrigerant return valve 53 may be valves whose opening degrees can be adjusted from fully closed to fully open.

[0033] The piping 40 is connected to a second switching mechanism 54. The second switching mechanism 54 is arranged on the opposite side of the piping 40 from the first switching mechanism 50, with the outdoor heat exchanger 15 sandwiched between them. The second switching mechanism 54 is a mechanism that connects the outdoor heat exchanger 15, the indoor heat exchanger 22, the chilled heat exchanger 32, and the gas-liquid separator 16 to one another, and switches the flow of refrigerant to multiple flow paths connected to these.

[0034] The second switching mechanism 54 is formed by connecting a first pipe 73, a second pipe 74, a third pipe 75, and a fourth pipe 76 in a ring shape at connection parts A, B, C, and D. A check valve 59 is provided in each of the first pipe 73, the third pipe 75, and the fourth pipe 76. A refrigerant return expansion mechanism 58 is provided in the second pipe 74. The check valve 59 is a so-called self-acting automatic valve that opens and closes depending on the flow of refrigerant. The first pipe 73 is a pipe connecting connection part A and connection part D, and refrigerant can flow from connection part A to connection part D, with the check valve 59 preventing the flow in the reverse direction. The third pipe 75 is a pipe connecting connection part B and connection part C, and refrigerant can flow from connection part B to connection part C, with the check valve 59 preventing the flow in the reverse direction. The fourth pipe 76 is a pipe that connects the connection part C and the connection part D, and allows the refrigerant to flow from the connection part C to the connection part D, with the flow in the reverse direction being stopped by the check valve 59 .

[0035] The refrigerant return expansion mechanism 58 is a flow control valve whose opening can be changed from fully closed to fully open under the control of the controller 100. The second pipe 74 is a pipe that connects the connection part A and the connection part B. The refrigerant return expansion mechanism 58 functions as a so-called throttle valve that can change the pressure of the refrigerant flowing through the second pipe 74.

[0036] Pipe 40 is connected to connection part A. Connection part B is connected to pipe 77. Pipe 77 is a pipe that connects gas-liquid separator 16 and chilled-use heat exchanger 32, and connection part B is located midway along pipe 77. In pipe 77, a chilled-use inlet-side expansion mechanism 31 is provided between connection part B and chilled-use heat exchanger 32.

[0037] One end of the pipe 78 is connected to the connection part C, and the other end of the pipe 78 is connected to the indoor heat exchanger 22. An indoor expansion mechanism 21 is provided in the pipe 78 between the connection part C and the indoor heat exchanger 22. The indoor expansion mechanism 21 is a valve whose opening degree can be changed from fully closed to fully open. The controller 100 can adjust the opening degree of the indoor expansion mechanism 21, and the indoor expansion mechanism 21 functions as a so-called throttle valve that can change the pressure of the refrigerant flowing through the pipe 78. Connection part D is connected to gas-liquid separator 16 via piping 69. In second switching mechanism 54, the refrigerant flowing from connection part A toward connection part D and the refrigerant flowing from connection part C toward connection part D flow into gas-liquid separator 16 via piping 69.

[0038] The gas-liquid separator 16 is a so-called flash tank that separates the gas-liquid two-phase refrigerant that has passed through the gas cooler into liquid refrigerant and gas refrigerant. The gas-liquid separator 16 is connected to the outdoor heat exchanger 15, the indoor heat exchanger 22, and the cooling heat exchanger 32 via a second switching mechanism 54. A pressure reducing valve 19 is provided in a pipe 69 that connects the second switching mechanism 54 and the gas-liquid separator 16. The pressure reducing valve 19 adjusts the pressure of the refrigerant flowing into the gas-liquid separator 16. This causes the refrigerant inside the gas-liquid separator 16 to be in a gas-liquid two-phase state.

[0039] A pipe 77 is connected to the gas-liquid separator 16. The pipe 77 connects the gas-liquid separator 16 and the cold-set heat exchanger 32, and is connected to a connection point B at a midpoint of the pipe 77.

[0040] The pipe 77 allows the liquid refrigerant to flow from the gas-liquid separator 16 into the chilled-set heat exchanger 32. The refrigerant flowing into the chilled-set heat exchanger 32 passes through the chilled-set inlet-side expansion mechanism 31. The opening degree of the chilled-set inlet-side expansion mechanism 31 can be adjusted under the control of the controller 100. The chilled-set inlet-side expansion mechanism 31 functions as a so-called throttle valve that can change the pressure of the refrigerant entering the chilled-set heat exchanger 32, and controls the evaporation temperature in the chilled-set heat exchanger 32.

[0041] A gas refrigerant return pipe 60 is connected to the gas-liquid separator 16. The gas refrigerant return pipe 60 is connected to the accumulator 13 via a pipe 71.

[0042] A gas refrigerant flow rate control valve 61 is provided in the gas refrigerant return pipe 60. The gas refrigerant flow rate control valve 61 is a valve whose opening can be changed from fully closed to fully open under the control of the controller 100. The controller 100 adjusts the opening of the gas refrigerant flow rate control valve 61 to control the flow rate of gas refrigerant flowing through the gas refrigerant return pipe 60.

[0043] A portion of the gas refrigerant separated in the gas-liquid separator 16 passes through a pipe 60, has its flow rate adjusted by a gas refrigerant flow control valve 61, and is sent to the accumulator 13. This refrigerant is returned from the accumulator 13 to the suction side of the high-stage compressor 12.

[0044] In the gas-liquid separator 16, a portion of the gas refrigerant separated in the gas-liquid separator 16 is separated from the liquid refrigerant and flows out of the gas-liquid separator 16. As the gas refrigerant flows out in this manner, the liquid refrigerant inside the gas-liquid separator 16 is cooled to a saturation temperature corresponding to the pressure of the gas-liquid separator 16. Therefore, the gas-liquid separator 16 functions as a heat exchanger that cools the liquid refrigerant, and it is possible to increase the refrigeration capacity of the refrigeration device 1.

[0045] An internal heat exchanger 64 is provided in the piping 60. The piping 60 and the piping 77 pass through the internal heat exchanger 64. The internal heat exchanger 64 is a so-called economizer heat exchanger that exchanges heat between the liquid refrigerant flowing through the piping 77 from the gas-liquid separator 16 toward the connection part B and the gas refrigerant flowing through the piping 60 from the gas-liquid separator 16 toward the accumulator 13.

[0046] The internal heat exchanger 64 has the effect of cooling the liquid refrigerant with the gas refrigerant. This ensures that the liquid refrigerant flowing through the pipe 77 toward the chilled heat exchanger 32 is in a subcooled state, increasing the degree of subcooling. This ensures a high degree of subcooling of the liquid refrigerant supplied to the chilled heat exchanger 32 operating as an evaporator, achieving higher operating efficiency.

[0047] The refrigeration device 1 includes a connection pipe 66 that bypasses the pipe 77 and the pipe 60. One end of the connection pipe 66 is connected to the pipe 77 on the outlet side of the internal heat exchanger 64, and the other end of the connection pipe 66 is connected to the connection pipe 66 on the inlet side of the internal heat exchanger 64. A portion of the liquid refrigerant that has passed through the pipe 77 and exchanged heat in the internal heat exchanger 64 passes through the connection pipe 66, flows from the pipe 77 into the pipe 60, and is mixed with the gas refrigerant that has not yet exchanged heat in the internal heat exchanger 64.

[0048] Therefore, the gas refrigerant mixed with the liquid refrigerant passes through the pipe 60 and is mixed in the internal heat exchanger 64, and this mixed refrigerant exchanges heat with the liquid refrigerant flowing through the pipe 77. Therefore, the degree of subcooling of the liquid refrigerant can be increased in the internal heat exchanger 64, enabling further improvement in operating efficiency.

[0049] A liquid refrigerant flow rate adjustment valve 65 is provided on the connection pipe 66. The liquid refrigerant flow rate adjustment valve 65 is a valve whose opening degree can be changed from fully closed to fully open, and adjusts the flow rate of the liquid refrigerant flowing through the connection pipe 66.

[0050] Refrigerant pressure sensors 80 that detect refrigerant pressure are installed in each component of the refrigeration circuit 2. For example, refrigerant pressure sensors 80 are installed in the refrigerant pipe 24 through which the refrigerant discharged from the high-stage compressor 12 flows, in the pipe 71 between the indoor heat exchanger 22 and the on-off valve 23, in the pipe 72 downstream of the chiller outlet pressure adjustment mechanism 33, and in the pipe 77. Each refrigerant pressure sensor 80 is connected to the controller 100 and outputs the detected refrigerant pressure to the controller 100. Based on the refrigerant pressure detected by the refrigerant pressure sensor 80, the controller 100 controls the rotation speed of the low-stage compressor 11 and the high-stage compressor 12 and controls the on-off and opening of each opening / closing device and adjusts the opening degree. Each component of the refrigeration circuit 2 may also be provided with a temperature sensor that detects the temperature of the refrigerant and the temperature sensor that detects the temperature of the heat exchanger. These temperature sensors are connected to the controller 100, and the controller 100 may reflect the temperatures detected by the temperature sensors in the control of the refrigeration system 1.

[0051] [1-1-2. Oil separation mechanism configuration] The configuration of the oil separation mechanism 3 will be described with reference to Figures 4, 5, 6, and 7. In these figures, the up, down, left, and right directions of the oil separator 14 and the reserve tank 18 are illustrated as mutually perpendicular X, Y, and Z axes. The X axis corresponds to the left-right direction, with the positive direction of the X axis being the left. The Y axis corresponds to the front-rear direction, with the positive direction of the Y axis being the front. The Z axis corresponds to the up and down direction, and corresponds to the vertical direction when the oil separation mechanism 3 is installed. The positive direction of the Z axis is the up.

[0052] Fig. 4 is a perspective view of the oil separation mechanism 3. Fig. 5 is a partially cutaway side view of the oil separation mechanism 3, showing the reserve tank 18 and part of the oil pipe 17 in a cross section taken along line AA in Fig. 4.

[0053] 4, the oil separation mechanism 3 is configured by connecting an oil separator 14 and a reserve tank 18 by an oil pipe 17. There is no limit to the number of oil separators 14 and the number of reserve tanks 18 that configure the oil separation mechanism 3. The oil separation mechanism 3 described in this embodiment is an example configuration having one reserve tank 18 and two oil separators 14A, 14B.

[0054] The oil separator 14A and the oil separator 14B shown in this embodiment have the same shape and structure. The oil separator 14A and the oil separator 14B may differ, for example, in size and capacity. In this specification, when there is no need to distinguish between the oil separator 14A and the oil separator 14B, they will be referred to as the oil separator 14. The oil separator 14B corresponds to the "terminal oil separator" in the present disclosure, and the oil separator 14A corresponds to the "oil separator different from the terminal oil separator."

[0055] The oil separator 14 includes a refrigerant pipe connection 142 through which the refrigerant flows into the oil separator 14, and a discharge pipe connection 143 through which the refrigerant flows out of the oil separator 14. The refrigerant pipe connection 142 and the discharge pipe connection 143 communicate with a separation section 141a (FIG. 5), which is the internal space of the main body 141 of the oil separator 14. This configuration is common to the oil separator 14A and the oil separator 14B. The discharge pipe connection 143 corresponds to the "discharge port" in this disclosure.

[0056] A refrigerant pipe 24 and a discharge pipe 25 are connected to the oil separator 14. A base end 24a of the refrigerant pipe 24 is connected to the discharge pipe of the high-stage compressor 12, and the refrigerant discharged from the high-stage compressor 12 flows into the refrigerant pipe 24 in the direction indicated by the arrow F1 in the figure.

[0057] Refrigerant pipe 24 has branch portion 24b where the pipe branches, and inflow branch pipe 24c branches in a T-shape at branch portion 24b. In addition, inflow pipe 24e is connected to terminal end 24d of refrigerant pipe 24. Inflow branch pipe 24c is connected to refrigerant pipe connecting portion 142 of oil separator 14A, and inflow pipe 24e is connected to refrigerant pipe connecting portion 142 of oil separator 14B.

[0058] A portion of the refrigerant that flows into the refrigerant pipe 24 from the base end 24a branches at the branching portion 24b and flows into the oil separator 14A, while the remaining refrigerant strikes the end 24d and flows into the oil separator 14B. Because the refrigerant that strikes the end 24d flows into the oil separator 14B, more refrigerant tends to flow into the oil separator 14B. This tendency becomes more pronounced as the refrigerant flow velocity in the F1 direction increases. Furthermore, when the flow rate of the refrigerant in the refrigerant pipe 24 exceeds a predetermined amount, the amounts of refrigerant flowing into the oil separator 14A and the oil separator 14B become approximately equal.

[0059] In this way, the multiple oil separators 14 are connected to the refrigerant pipe 24 so as to cause a bias in the amount of refrigerant flowing into each oil separator 14. Specifically, some of the multiple oil separators 14 are connected to terminal end 24d of refrigerant pipe 24, and the other oil separators 14 are connected to inlet branch pipe 24c that branches off from the middle of refrigerant pipe 24. For this reason, the smaller the refrigerant flow rate, the more refrigerant flows into oil separator 14B, and as the refrigerant flow rate increases, the more refrigerant flows into oil separator 14A.

[0060] Discharge pipe 25 is a refrigerant pipe connected to first switching mechanism 50 at tip end 25a. Discharge pipe 25 has branch portion 25b where the pipe branches, and at branch portion 25b, branched discharge pipe 25c branches in a T-shape. Discharge pipe 25e is connected to base end 25d of discharge pipe 25. Branched discharge pipe 25c is connected to discharge pipe connecting portion 143 of oil separator 14B, and discharge pipe 25e is connected to discharge pipe connecting portion 143 of oil separator 14A. Discharge pipe 25 flows the refrigerant from which oil has been separated in oil separator 14 in the direction indicated by arrow F2 in the figure.

[0061] The arrangement of the multiple oil separators 14 relative to the discharge pipe 25 is opposite to the arrangement of the oil separators 14 relative to the refrigerant pipe 24. That is, oil separator 14A is connected to a base end 25d of discharge pipe 25, and oil separator 14B is connected to a middle portion of discharge pipe 25. Therefore, more refrigerant flows into oil separator 14B from the refrigerant pipe 24 than into oil separator 14A, and the resistance to the refrigerant flowing from oil separator 14B to discharge pipe 25 is greater than that of oil separator 14A. This has the effect of reducing the flow rate of the refrigerant inside oil separator 14B, allowing for more reliable separation of oil from the refrigerant.

[0062] The oil separator 14 separates the oil contained in the refrigerant into a liquid state by diffusing, colliding, and swirling the refrigerant flowing in from the refrigerant pipe connecting portion 142 in the separation portion 141a. The oil separated from the refrigerant moves downward due to its own weight inside the separation portion 141a and accumulates at the bottom of the separation portion 141a.

[0063] The internal mechanism of the oil separator 14 for separating oil from the refrigerant is not limited, and various configurations can be employed. For example, as shown in FIG. 5, the refrigerant pipe connection portion 142 is connected to an inner pipe 142a disposed in the separation portion 141a. The inner pipe 142a has holes on its side, and as the refrigerant passes through the holes, the oil contained in the refrigerant is separated into mist and falls downward. To separate as much oil as possible from the refrigerant, the inner pipe 142a extends vertically to at least halfway below the separation portion 141a. This configuration is merely an example, and a mesh-like inner pipe 142a may also be used. Alternatively, a so-called cyclone-type configuration may be employed in which the refrigerant flowing in from the refrigerant pipe connection portion 142 flows in a swirling manner in the separation portion 141a to separate the oil. Alternatively, the refrigerant flowing in from the refrigerant pipe connection portion 142 may collide with the inner wall of the main body 141 to reduce the flow rate and separate the oil.

[0064] 4, an oil pipe connection part 144 is provided at the bottom of the oil separator 14. The oil pipe connection part 144 is connected to the separation part 141a and discharges oil that has accumulated at the bottom of the separation part 141a. This configuration is common to the oil separator 14A and the oil separator 14B.

[0065] Oil pipe connection portion 144 of oil separator 14A is connected to branch pipe 172. Oil pipe connection portion 144 of oil separator 14B is connected to branch pipe 173. Branch pipes 172 and 173 are connected to main pipe 171 via connector 174. Main pipe 171 is connected to oil pipe connection portion 182 of reserve tank 18.

[0066] The reserve tank 18 is a storage tank that stores the oil separated by the oil separator 14, and the tank body 181 of the reserve tank 18 has a capacity sufficient for the amount of oil used in the refrigeration circuit 2. A bottom plate 184 is attached to the bottom of the tank body 181. The bottom plate 184 is fixed to the ground surface S (FIG. 5) when the reserve tank 18 is installed.

[0067] The reserve tank 18 is provided with an oil pipe connection part 182 through which oil flows in from the oil separator 14, and a connection part 183 through which oil is discharged from the reserve tank 18. The oil pipe connection part 182 and the connection part 183 communicate with the internal space of the tank body 181 of the reserve tank 18. The connection part 183 is connected to the oil return pipe 46 shown in FIGS. 1 to 3, and the oil is returned from the connection part 183 to the low-stage compressor 11 and the accumulator 13.

[0068] Oil pipe connecting portion 182 is provided above connecting portion 183. Oil that flows into tank main body 181 from oil pipe connecting portion 182 accumulates at the bottom of tank main body 181 due to its own weight and is discharged from connecting portion 183 provided at the bottom of tank main body 181.

[0069] The reserve tank 18 is located below the oil separators 14. Specifically, at least a portion of the tank body 181 is located below the separation portions 141a of all the oil separators 14. Preferably, at least a portion of the tank body 181 is located below the oil pipe connection portions 144 of all the oil separators 14.

[0070] The oil separated from the refrigerant in separation section 141a moves downward due to its own weight and flows into branch pipes 172 and 173. Branch pipes 172 and 173 join at connector 174 and are connected to main pipe 171. Therefore, the oil flowing out from oil pipe connection sections 144 of multiple oil separators 14 joins together, flows through main pipe 171, and flows into oil pipe connection section 182. Because reserve tank 18 is located below oil separator 14, the oil moves from branch pipes 172 and 173 through main pipe 171 to reserve tank 18 due to its own weight. Therefore, no power is required to transport the oil from oil separator 14 to reserve tank 18, and the oil separated from the refrigerant can be efficiently collected in reserve tank 18.

[0071] 5, an oil pipe connection portion 144 is provided at the lower end of a main body 141 of an oil separator 14B. A branch pipe 173 extending directly downward is connected to the oil pipe connection portion 144, and the branch pipe 173 is connected to a connector 174. In this configuration example, the connector 174 is located at the lowest position among the main pipe 171, the branch pipes 172 and 173, and the connector 174 that form the oil pipe 17. In other words, the oil reservoir portion 17b, which is the space inside the connector 174 where the oil flows and is stored, is located at the lowest position in the oil pipe 17.

[0072] The main pipe 171 connecting the connector 174 and the oil pipe connecting portion 182 can be configured to be bent, for example, as shown in Fig. 5. This makes it possible to realize a configuration in which the height of the oil pipe connecting portion 182 and the height of the connector 174 are different.

[0073] As shown in FIG. 5, when at least a part of the tank body 181 is located lower than the separation part 141a, the oil inside the separation part 141a moves to the reserve tank 18 through the oil pipe 17 due to the oil's own weight.

[0074] [1-1-3. Positional relationship of each part of the oil separation mechanism] In the oil separation mechanism 3, by appropriately adjusting the relationship between the height of the oil pipe connection part 182, the height of the main body 141, and the height of the oil pipe 17, it is expected that the operating efficiency of the refrigeration device 1 can be improved.

[0075] For example, if the oil separator 14 and the reserve tank 18 are connected by a space while oil movement is stopped, the refrigerant may move between the oil separator 14 and the reserve tank 18 due to the internal pressure difference between them. The internal pressure difference may be caused by, for example, a temperature difference between the oil separator 14 and the reserve tank 18, or fluctuations in the amount of refrigerant flowing into the oil separator 14. Such refrigerant movement causes heat to diffuse from the oil separator 14 to the reserve tank 18, resulting in an increase in the heat removed from the refrigerant in the oil separation mechanism 3.

[0076] Here, even when oil is not moving through oil pipe 17, if oil blocks the space in oil pipe 17 through which the refrigerant moves, the movement of refrigerant between oil separator 14 and reserve tank 18. This reduces the heat removed from the refrigerant discharged from high-stage compressor 12 in oil separation mechanism 3, suppresses a drop in the temperature of the refrigerant, and maintains the amount of heat dissipated from the heat exchanger.

[0077] If the oil separated from the refrigerant is configured to move from oil separator 14 to reserve tank 18 without accumulating in large amounts in main body 141, the capacity of oil separator 14 can be further reduced. Also, this is expected to have the effect of increasing the efficiency of oil separation in oil separator 14. Specifically, because oil separator 14 does not need to have the function of storing oil, the capacity of main body 141 can be set to the minimum capacity necessary to separate oil from the refrigerant. This reduces the space in oil separator 14 where the refrigerant diffuses, collides, swirls, etc., and therefore suppresses a drop in the temperature of the refrigerant in oil separator 14. Furthermore, the miniaturization of oil separator 14 brings various advantages, such as a smaller size, lighter weight, easier installation, and lower costs for refrigeration equipment 1.

[0078] The conditions under which such an advantageous configuration can be realized can be defined, for example, as the relationship between the height H1 of the oil pipe connecting portion 182, the height H2 of the connector 174, and the height H3 of the bottom of the separating portion 141a. In this embodiment, for convenience, the ground surface S to which the bottom plate 184 is fixed is used as the reference height, but this is just one example. In this explanation, the heights of each portion in the vertical direction are defined as heights H1, H2, and H3 to explain that oil moves under its own weight, so the reference height may be at any position.

[0079] Height H1 is the height from the ground surface S to the bottom of oil pipe connecting portion 182, and more specifically, the height of the upper end of oil remaining in oil pipe connecting portion 182. As shown in Fig. 5, for example, if the lower end of the inner surface of main pipe 171 at the portion where main pipe 171 is joined to oil pipe connecting portion 182 is defined as first connecting portion 17a, height H1 is the height from the ground surface S to first connecting portion 17a.

[0080] Height H2 is the height of the oil accumulated in oil reservoir 17b, more specifically, the height of the upper end of the oil accumulated in oil reservoir 17b. Height H2 can also be said to be the height of the upper end of the internal space of connector 174.

[0081] Height H3 is the height of the lowest point in separation portion 141a, and this position is designated as second connection portion 17d. In this embodiment, second connection portion 17d is a portion where separation portion 141a is connected to oil flow path 17c, which straddles the interior of branch pipe 172 and oil pipe connection portion 144, and may also be referred to as a discharge position where oil is discharged from separation portion 141a. Second connection portion 17d corresponds to the lower end of oil separator 14, and more specifically, corresponds to the lower end of main body 141, which serves as an oil storage portion in oil separator 14, where oil is stored.

[0082] The relationship between the heights H1, H2, and H3 will be described with reference to FIGS. FIG. 6 is an enlarged view of a main part showing an example of the configuration of the oil separation mechanism 3, and is an explanatory diagram of the conditions relating to the height of the oil pipe 17.

[0083] 6 shows a state in which oil has stopped moving from the oil separator 14 to the reserve tank 18. In this state, residual oil RO has accumulated in the main pipe 171 and the connector 174. Furthermore, residual oil DO has accumulated at the bottom of the oil pipe connecting portion 182.

[0084] The height of the oil level SO, which is the upper end of the residual oil DO, is the height H1 of the first connecting portion 17a. This is because oil that is lower than the first connecting portion 17a flows down from the oil pipe connecting portion 182 to the tank main body 181 after the movement of the oil stops.

[0085] If the height of the oil level SO is equal to or greater than the height H2 of the top of the oil reservoir 17b, the oil reservoir 17b will be filled with the residual oil RO. In contrast, if the height of the oil level SO is lower than the height H2, a space will be created above the oil reservoir 17b. This space will become a flow path for the refrigerant to move between the oil separator 14 and the reserve tank 18.

[0086] That is, the condition for the structure that can prevent or suppress the flow of refrigerant between the oil separator 14 and the reserve tank 18 is the following formula (1). H2

[0087] Height H1 is the height of first connecting portion 17a, the height of the oil surface SO, and the lower end of the connection position where oil pipe 17 is connected to oil pipe connecting portion 182. Height H2 is the lowest position of oil pipe 17 and the upper end of oil reservoir portion 17b, which is the lowest position in the space in oil pipe 17 through which oil flows.

[0088] In other words, by providing a portion in oil pipe 17 that satisfies the above formula (1), such as connector 174, it is possible to prevent or suppress the movement of refrigerant between oil separator 14 and reserve tank 18. In a configuration in which oil pipe 17 connects one reserve tank 18 and one oil separator 14, a portion that satisfies the above formula (1) can be provided in oil pipe 17 instead of connector 174.

[0089] FIG. 7 is an enlarged view of a main part showing an example of the configuration of the oil separation mechanism 3, and is an explanatory diagram of the conditions relating to the heights of the oil separator 14 and the reserve tank 18.

[0090] ​7 shows a state in which oil has stopped moving from the oil separator 14 to the reserve tank 18. In this state, residual oil RO has accumulated in the oil pipe 17, and residual oil DO has accumulated at the bottom of the oil pipe connection part 182.

[0091] As in the example of FIG. 6, the height of the oil surface SO of the residual oil DO is the height H1 of the first connecting portion 17a.

[0092] Furthermore, when the inside of oil pipe 17 is filled with oil and the pressure inside tank main body 181 and the pressure inside main body 141 are in equilibrium, the height of oil level SO is equal to the height of the oil level in separation part 141a. Therefore, if height H1 of first connection part 17a is higher than height H3, which is the lower end of separation part 141a, oil will accumulate inside main body 141. In other words, if height H1 is lower than height H3, oil is less likely to accumulate in main body 141.

[0093] That is, the preferable condition for a structure that can prevent or suppress oil from accumulating inside the oil separator 14 is the following formula (2). H1 <H3 ···(2)

[0094] Even if the above formula (2) is not satisfied, there is no major problem as long as the amount of oil that accumulates in the main body 141 is small, but as mentioned above, it is useful to reduce the capacity of the main body 141. Therefore, the condition of the above formula (2) can be said to be a condition for a preferable structure of the oil separation mechanism 3.

[0095] Regarding the conditions of the above formulas (1) and (2), the height of the highest point in the oil pipe 17 is not limited, but if the oil pipe 17 is configured to pass through a position significantly higher than heights H1 and H2, it becomes difficult for the oil to move through the oil pipe 17 by its own weight. For this reason, it is preferable that the entire oil pipe 17 be located lower than at least one of the oil pipe connecting portion 182 and the oil pipe connecting portion 144. More specifically, it is preferable that the highest point in the oil pipe 17 be lower than at least one of the highest point of the oil pipe connecting portion 182 and the second connecting portion 17d.

[0096] The configuration of the oil separation mechanism 3 can be changed as appropriate. For example, three or more oil separators 14 may be connected to one reserve tank 18 by oil pipes 17, or multiple reserve tanks 18 may be provided. Also, one oil separator 14 may be connected to one reserve tank 18. Furthermore, the temperature drop of the refrigerant in the oil separator 14 may be further reduced by surrounding the oil separator 14 with a heat insulating material.

[0097] [1-2. Operation of refrigeration equipment] [1-2-1. Operation of refrigeration equipment] Next, the operation of the refrigeration device 1 will be described. As described above, the refrigeration device 1 switches between the cooling mode and the heating mode. The cooling equipment 30 is operated so that the cooling equipment 30 is cooled by the cooling heat exchanger 32 in both the cooling mode and the heating mode.

[0098] In both the cooling mode and the heating mode, liquid refrigerant is supplied to the cooling-set heat exchanger 32 from the gas-liquid separator 16 through a pipe 77. This liquid refrigerant is the refrigerant that has undergone heat exchange with the gas refrigerant passing through the pipe 60 in the internal heat exchanger 64. Furthermore, with regard to the heat exchange in the internal heat exchanger 64, the opening of the liquid refrigerant flow rate control valve 65 is adjusted by the control of the controller 100.

[0099] The liquid refrigerant flowing from gas-liquid separator 16 through pipe 77 is decompressed by chiller inlet side expansion mechanism 31 and flows into chiller heat exchanger 32. Chiller heat exchanger 32 operates as an evaporator, and cools the interior of, for example, a refrigerated showcase or a freezer showcase. The refrigerant evaporated in chiller heat exchanger 32 has its pressure adjusted by chiller outlet side pressure adjustment mechanism 33, then passes through pipe 72 and flows to the suction side of low-stage compressor 11.

[0100] The evaporation temperature of the refrigeration heat exchanger 32 is determined by the opening degree of the refrigeration inlet-side expansion mechanism 31. The controller 100 adjusts the opening degree of the refrigeration inlet-side expansion mechanism 31 in accordance with the target temperature set in the refrigeration equipment 30 and the inside temperature detected by a temperature sensor (not shown).

[0101] The refrigeration equipment 30 can select and set the temperature range inside the cabinet from, for example, a refrigeration temperature range (3°C to 6°C), a temperature range slightly higher than the refrigeration temperature range (3°C to 8°C), a partial temperature range (-3°C to -1°C), and a freezing temperature range (-20°C to -18°C). Therefore, the evaporation temperature range of the refrigeration heat exchanger 32 is set lower than the temperature range inside the cabinet.

[0102] When the refrigeration equipment 30 is set to the refrigeration temperature range, the evaporating temperature range of the refrigeration heat exchanger 32 is, for example, -5°C to 0°C. When the refrigeration equipment 30 is set to the partial temperature range, the evaporating temperature range of the refrigeration heat exchanger 32 is, for example, -12°C to -8°C. When the refrigeration equipment 30 is set to the freezing temperature range, the evaporating temperature range of the refrigeration heat exchanger 32 is, for example, -40°C to 20°C.

[0103] On the other hand, when the refrigeration device 1 is operated in cooling mode, the indoor heat exchanger 22 acts as a utilization-side heat exchanger to cool the space to be conditioned. At this time, multiple utilization-side heat exchangers are operating in the refrigeration circuit 2. Since the indoor heat exchanger 22 is operated for the purpose of air conditioning the space to be conditioned, the evaporation temperature range of the indoor heat exchanger 22 is, for example, 3°C to 6°C.

[0104] In this way, when the refrigeration device 1 operates in cooling mode, the refrigeration device 1 has two user-side heat exchangers with different evaporation temperature ranges. The refrigerant discharged from the cold-service heat exchanger 32 with a lower evaporation temperature flows into the low-stage compressor 11, while the refrigerant discharged from the indoor heat exchanger 22 with a higher evaporation temperature flows into the high-stage compressor 12 via the accumulator 13. In other words, in the refrigeration circuit 2 equipped with a two-stage compressor consisting of the low-stage compressor 11 and the high-stage compressor 12, the refrigerant evaporated in the two user-side heat exchangers with different evaporation temperature ranges flows separately into the low-pressure section and the medium-pressure section of the two-stage compressor. This allows the refrigeration device 1 to operate with high operating efficiency.

[0105] [1-2-2. Cooling mode] In the cooling mode, the refrigeration device 1 cools the space to be conditioned by the indoor unit 20 and performs cooling by the cooling equipment 30. In the cooling mode, the indoor heat exchanger 22 and the cooling heat exchanger 32 operate as evaporators, and the outdoor heat exchanger 15 operates as a gas cooler.

[0106] 1, in the cooling mode, the controller 100 opens the on-off valve 23 and the first cooling valve 51, and closes the first heating valve 52 and the outdoor refrigerant return valve 53. In addition, the controller 100 fully closes the refrigerant return expansion mechanism 58.

[0107] The controller 100 adjusts the aperture of the indoor expansion mechanism 21 to control the evaporation temperature in the indoor heat exchanger 22. Similarly, the controller 100 adjusts the aperture of the cooling-unit inlet-side expansion mechanism 31 to control the evaporation temperature in the cooling-unit heat exchanger 32. The controller 100 fully opens the cooling-unit outlet-side pressure adjustment mechanism 33, for example, and appropriately adjusts the apertures of the gas refrigerant flow control valve 61 and the liquid refrigerant flow adjustment valve 65 as described above.

[0108] When the controller 100 operates the low-stage compressor 11 and the high-stage compressor 12, the high-temperature, high-pressure refrigerant discharged from the high-stage compressor 12 flows into the piping 40 through the discharge pipe 25. This high-pressure refrigerant does not flow into the first heating piping 41 and the first outdoor return piping 42 because the first heating valve 52 and the outdoor refrigerant return valve 53 are closed.

[0109] The high-pressure refrigerant discharged from the high-stage compressor 12 flows through the pipe 40 into the outdoor heat exchanger 15, where it exchanges heat with outside air and is condensed. Furthermore, the refrigerant condensed in the outdoor heat exchanger 15 reaches the connection part A of the second switching mechanism 54. Since the refrigerant return expansion mechanism 58 is fully closed, the refrigerant that has reached the connection part A passes through the first pipe 73 to reach the connection part D, and then passes through the pipe 69 to flow into the gas-liquid separator 16 .

[0110] The liquid refrigerant in the gas-liquid separator 16 is supplied to the chilled-unit heat exchanger 32 and the indoor heat exchanger 22 through the pipe 77. That is, the liquid refrigerant that flows from the pipe 77 to the connection part B of the second switching mechanism 54 branches at the connection part B. One of the branched refrigerants flows through the pipe 77 to the chilled-unit inlet-side expansion mechanism 31, and the other flows through the third pipe 75 and the pipe 78 to the indoor expansion mechanism 21. As a result, the indoor heat exchanger 22 and the chilled-unit heat exchanger 32 operate as evaporators.

[0111] The refrigerant evaporated in the indoor heat exchanger 22 flows into the accumulator 13 through a pipe 71. The refrigerant evaporated in the cold-set heat exchanger 32 flows into the suction side of the low-stage compressor 11 through a pipe 72.

[0112] [1-2-3. Heating mode (excessive heat)] In the heating mode, the refrigeration device 1 performs heating of the space to be conditioned by the indoor unit 20 and cooling by the cooling equipment 30.

[0113] When the indoor unit 20 heats the target space, the controller 100 operates the indoor heat exchanger 22 as a cooler or a radiator. The controller 100 also operates the cooling heat exchanger 32 as an evaporator regardless of whether the indoor unit 20 is cooling or heating. The controller 100 operates the outdoor heat exchanger 15 as either an evaporator or a gas cooler depending on the balance between the amount of heat required by the indoor unit 20 and the amount of heat obtained by the cooling heat exchanger 32 as an evaporator.

[0114] Specifically, when the amount of heat obtained by the cooling-type heat exchanger 32 is equal to or greater than the amount of heat required by the indoor unit 20 for heating, the outdoor heat exchanger 15 functions as a gas cooler. This state is called an excess heat state. In contrast, when the amount of heat obtained by the cooling-type heat exchanger 32 as an evaporator is less than the amount of heat required by the indoor unit 20 for heating, the outdoor heat exchanger 15 functions as an evaporator. This state is called a heat shortage state. In a heat shortage state, the amount of heat required by the indoor unit 20 is obtained from both the outdoor heat exchanger 15 and the cooling-type heat exchanger 32, making it possible to heat the target space.

[0115] FIG. 2 shows the state of each switching device and the flow of refrigerant in heating mode when the amount of heat is excessive. In this heating mode, the controller 100 opens the first heating valve 52 and closes the on-off valve 23, the first cooling valve 51, and the outdoor refrigerant return valve 53. The controller 100 also fully closes the refrigerant return expansion mechanism 58 and fully opens the indoor expansion mechanism 21.

[0116] The controller 100 adjusts the aperture of the chiller-use inlet-side expansion mechanism 31 to control the evaporation temperature in the chiller-use heat exchanger 32. The controller 100, for example, fully opens the chiller-use outlet-side pressure adjustment mechanism 33, and appropriately adjusts the apertures of the gas refrigerant flow control valve 61 and the liquid refrigerant flow adjustment valve 65 as described above.

[0117] When the controller 100 operates the low-stage compressor 11 and the high-stage compressor 12, the high-temperature, high-pressure refrigerant discharged from the high-stage compressor 12 flows into the first heating pipe 41 through the discharge pipe 25. This high-pressure refrigerant does not flow into the first heating pipe 41 or the first outdoor return pipe 42 because the first cooling valve 51 is closed.

[0118] The high-pressure refrigerant discharged from the high-stage compressor 12 flows through the first heating pipe 41 into the indoor heat exchanger 22, where it exchanges heat with the air in the space to be conditioned and condenses. This heats the air in the space to be conditioned. The refrigerant condensed in the indoor heat exchanger 22 flows through pipe 78 to reach connection C of the second switching mechanism 54. Due to the action of the check valve 59 provided in the third pipe 75, the refrigerant that has reached connection C does not flow into the third pipe 75, but instead passes through the fourth pipe 76 to reach connection D, and then further flows through pipe 69 into the gas-liquid separator 16.

[0119] The liquid refrigerant in the gas-liquid separator 16 is supplied to the chilled-unit heat exchanger 32 through the pipe 77. That is, the liquid refrigerant that flows from the pipe 77 to the connection part B of the second switching mechanism 54 flows from the connection part B through the pipe 77 to the chilled-unit inlet-side expansion mechanism 31. This causes the chilled-unit heat exchanger 32 to operate as an evaporator. Here, due to the pressure difference between the refrigerant flowing from the indoor heat exchanger 22 to the connection part C and the connection part B, the refrigerant does not flow from the connection part B to the connection part C. The refrigerant evaporated in the chilled-unit heat exchanger 32 flows through the pipe 72 to the suction side of the low-stage compressor 11, just like in the cooling mode.

[0120] [1-2-4. Heating mode (insufficient heat)] FIG. 3 shows the state of each switching device and the flow of refrigerant in the heating mode when there is a heat shortage. In this heating mode, the controller 100 opens the first heating valve 52 and the outdoor refrigerant return valve 53, and closes the on-off valve 23 and the first cooling valve 51. The controller 100 also fully opens the indoor expansion mechanism 21.

[0121] The controller 100 adjusts the aperture of the chiller-use inlet-side expansion mechanism 31 to control the evaporation temperature in the chiller-use heat exchanger 32. The controller 100, for example, fully opens the chiller-use outlet-side pressure adjustment mechanism 33, and appropriately adjusts the apertures of the gas refrigerant flow control valve 61 and the liquid refrigerant flow adjustment valve 65 as described above.

[0122] When the controller 100 operates the low-stage compressor 11 and the high-stage compressor 12, the high-temperature, high-pressure refrigerant discharged from the high-stage compressor 12 flows into the first heating pipe 41 through the discharge pipe 25. This high-pressure refrigerant does not flow into the first heating pipe 41 or the first outdoor return pipe 42 because the first cooling valve 51 is closed.

[0123] The high-pressure refrigerant discharged from the high-stage compressor 12 flows through the first heating pipe 41 into the indoor heat exchanger 22, where it exchanges heat with the air in the space to be conditioned and condenses. This heats the air in the space to be conditioned. The refrigerant condensed in the indoor heat exchanger 22 flows through pipe 78 to reach connection C of the second switching mechanism 54. Due to the action of the check valve 59 provided in the third pipe 75, the refrigerant that has reached connection C does not flow into the third pipe 75, but instead passes through the fourth pipe 76 to reach connection D, and then further flows through pipe 69 into the gas-liquid separator 16.

[0124] The liquid refrigerant in the gas-liquid separator 16 is supplied to the chiller heat exchanger 32 and the outdoor heat exchanger 15 through the pipe 77. That is, the liquid refrigerant that flows from the pipe 77 to the connection part B of the second switching mechanism 54 branches at the connection part B. One of the branched refrigerants flows through the pipe 77 to the chiller inlet side expansion mechanism 31, and the other flows through the second pipe 74 to the connection part A, and then flows from the connection part A through the pipe 40 to the outdoor heat exchanger 15.

[0125] 3, the outdoor heat exchanger 15 functions as an evaporator. In this case, the refrigerant return expansion mechanism 58 functions as a throttling mechanism that adjusts the pressure of the refrigerant flowing into the outdoor heat exchanger 15 through the second pipe 74. The refrigerant that flows into the outdoor heat exchanger 15 through the refrigerant return expansion mechanism 58 has its pressure adjusted by the throttling mechanism, so it evaporates in the outdoor heat exchanger 15 and exchanges heat with the outside air. In this heating mode, the controller 100 controls the evaporation temperature in the outdoor heat exchanger 15 by adjusting the opening degree of the refrigerant return expansion mechanism 58.

[0126] In the second switching mechanism 54, the refrigerant that has reached the connection part B from the pipe 77 does not flow into the third pipe 75 due to the pressure difference between the connection parts C and B.

[0127] The refrigerant that has exchanged heat in the outdoor heat exchanger 15 flows into the first outdoor return pipe 42 because the first cooling valve 51 is closed. This refrigerant flows from the first outdoor return pipe 42 into the pipe 72, and flows to the suction side of the low-stage compressor 11 together with the refrigerant that has exchanged heat in the cooling heat exchanger 32.

[0128] When the amount of heat is excessive during heating operation, the refrigeration device 1 of the present disclosure causes the cooling heat exchanger 32 to function as a heat source and does not use the outdoor heat exchanger 15. That is, the refrigeration device 1 can operate without using the outdoor heat exchanger 15 by performing heat exchange in the cooling heat exchanger 32 using the refrigerant dissipated in the indoor heat exchanger 22. Furthermore, when the amount of heat is insufficient during heating operation, heating is performed by the indoor heat exchanger 22 by using the outdoor heat exchanger 15 and the cooling heat exchanger 32 as heat sources. In this way, the refrigeration device 1 can efficiently perform heating according to the operating state of the cooling equipment 30 and the heating load of the indoor heat exchanger 22.

[0129] [1-3. Effects, etc.] As described above, the oil separation mechanism 3 is provided in the refrigeration system 1 including the refrigeration circuit 2 connecting the compressor, the heat source-side heat exchanger, and the user-side heat exchanger. The oil separation mechanism 3 includes the oil separator 14 that separates oil from the refrigerant discharged from the compressor, the reserve tank 18 that stores the oil separated by the oil separator 14, and the oil pipe 17 that connects the oil separator 14 and the reserve tank 18. The second connection portion 17d at the lower end of the oil separator 14 is located higher than the first connection portion 17a at which the oil pipe 17 is connected to the reserve tank 18, and is configured so that oil moves from the oil separator 14 to the reserve tank 18 through the oil pipe 17 by its own weight. The oil reservoir portion 17b, which is at least a part of the flow path of the oil pipe 17, is located lower than the oil separator 14 and also lower than the first connection portion 17a.

[0130] As a result, the oil separator 14 does not need to have a function for storing oil, and therefore the capacity of the oil separator 14 can be reduced, allowing for a more compact oil separator 14. This reduces the volume of the space in which the refrigerant diffuses in the oil separator 14, thereby suppressing a drop in the temperature of the refrigerant in the oil separator 14. This improves the operating efficiency, for example, when the refrigerant discharged from the compressor is sent to the indoor heat exchanger 22 and used for heating by the indoor heat exchanger 22. Furthermore, the smaller size of the oil separator 14 offers various advantages, such as a more compact, lightweight, easier to install, and lower costs for the refrigeration system 1. Furthermore, the oil separated from the refrigerant in the oil separator 14 can be sent to the reserve tank 18 by its own weight, allowing the oil to be transported to the reserve tank 18 without using refrigerant pressure or a power source. Furthermore, because oil reservoir 17b is located lower than oil separator 14 and lower than first connecting portion 17a, at least a portion of oil pipe 17 is blocked by oil without oil moving. This prevents refrigerant from moving between oil separator 14 and reserve tank 18, thereby suppressing heat transfer from oil separator 14 to reserve tank 18. This further reduces the temperature drop of the refrigerant in oil separation mechanism 3. Moreover, the above-mentioned effects can also be obtained in the refrigeration device 1 equipped with the oil separation mechanism 3.

[0131] The oil separation mechanism 3 may be provided in a refrigeration system 1 including a refrigeration circuit 2 connecting multiple compressors, a heat source-side heat exchanger, and multiple user-side heat exchangers. The refrigeration system 1 may be capable of switching the operation of at least one of the multiple user-side heat exchangers between a cooling mode and a heating mode. In a configuration such as the refrigeration device 1 that includes multiple compressors consisting of a low-stage compressor 11 and a high-stage compressor 12, there is a tendency for a large amount of oil to be required by the refrigeration circuit 2. Even in such a configuration, the configuration of the present disclosure is expected to reduce the size of the oil separator 14 and improve the operating efficiency of the refrigeration device 1.

[0132] In the oil separation mechanism 3, the oil pipe 17 has an oil reservoir 17b where oil is stored, and the upper end of the oil reservoir 17b is located at a position lower than the first connection portion 17a.

[0133] This more reliably blocks a portion of the oil pipe 17 with oil without oil moving from the oil separator 14 to the reserve tank 18. This prevents the refrigerant from moving between the oil separator 14 and the reserve tank 18, further reducing the heat removed from the refrigerant in the oil separation mechanism 3.

[0134] In the oil separation mechanism 3, the second connection portion 17d where the oil pipe 17 is connected to the oil separator 14 is located higher than the first connection portion 17a.

[0135] This makes it possible to reduce the amount of oil remaining inside the oil separator 14, thereby enabling the oil separator 14 to be made even more compact.

[0136] In the oil separation mechanism 3, the second connection portion 17d is a portion where the oil flow path 17c in the oil pipe 17, through which the oil flows, is connected to the separation portion 141a, which is the internal space of the oil separator .

[0137] This makes it possible to reduce the amount of oil remaining inside the oil separator 14, thereby enabling the oil separator 14 to be made even more compact.

[0138] The oil separation mechanism 3 includes a plurality of oil separators 14 and refrigerant pipes 24 that branch the refrigerant discharged from the compressor and supply it to each of the plurality of oil separators 14. Each oil separator 14 and refrigerant pipe 24 are connected so that the refrigerant supplied from the refrigerant pipe 24 flows unevenly through the plurality of oil separators 14.

[0139] This allows for a configuration including multiple oil separators 14 in which a large amount of refrigerant flows unevenly through some of the oil separators 14. Therefore, when the amount of refrigerant flowing into the oil separators 14 is small, the refrigerant is unevenly distributed through some of the oil separators 14, thereby reducing the volume of refrigerant diffusion. This reduces the amount of heat removed from the refrigerant as the refrigerant diffuses, thereby improving the operating efficiency of the refrigeration system 1. Furthermore, by using multiple oil separators 14, oil can be separated from the refrigerant in the refrigeration circuit 2 through which a larger amount of refrigerant flows. Therefore, in a large-scale refrigeration circuit 2, the amount of heat removed from the refrigerant by the oil separation mechanism 3 can be reduced, improving operating efficiency.

[0140] In the oil separation mechanism 3, the refrigerant pipe 24 is configured so that the refrigerant flowing into the base end 24a of the refrigerant pipe 24 flows toward the terminal end 24d of the refrigerant pipe 24. At least some of the multiple oil separators 14 are terminal oil separators 14B connected to the terminal end 24d of the refrigerant pipe 24. An oil separator 14A different from the terminal oil separator 14B is connected to an inlet branch pipe 24c branching off from between the terminal end 24d and the base end 24a of the refrigerant pipe 24.

[0141] As a result, in an oil separation mechanism 3 including multiple oil separators 14, a configuration in which more refrigerant flows into oil separator 14B, which is the terminal oil separator, than into the other oil separators 14A can be realized by the configuration of oil pipe 17. Therefore, without providing a mechanism for managing and adjusting the amount of refrigerant flowing into the multiple oil separators 14, it is possible to suppress a decrease in the temperature of the refrigerant in the oil separation mechanism 3 and improve operating efficiency.

[0142] In the oil separation mechanism 3, each oil separator 14 is provided with a discharge pipe connection portion 143 through which the refrigerant separated from the oil in the oil separator 14 is discharged. The oil separation mechanism 3 is provided with discharge pipes 25 connected to the discharge pipe connection portions 143 of the multiple oil separators 14. The discharge pipes 25 are configured so that the refrigerant flows from the base end portion 25d of the discharge pipe 25 toward the tip end portion 25a. The base end portion 25d of the discharge pipe 25 is connected to the discharge pipe connection portion 143 of an oil separator 14A that is different from the terminal oil separator 14. The discharge pipe connection portion 143 of the terminal oil separator 14B is connected to a discharge branch pipe 25c that branches off from between the tip end portion 25a and the tip end portion 25d of the discharge pipe 25.

[0143] This allows the refrigerant to flow efficiently in a configuration in which the refrigerant discharged from the compressor flows into the plurality of oil separators 14 and the refrigerant from which the oil has been separated in the plurality of oil separators 14 is discharged through the single discharge pipe 25. This reduces the resistance that the oil separation mechanism 3 imparts to the flow of the refrigerant, thereby improving the operating efficiency of the refrigeration device 1. Furthermore, in the terminal oil separator, a larger amount of refrigerant flows in unevenly from the refrigerant pipe 24, while the resistance when the refrigerant flows out from the terminal oil separator to the discharge pipe 25 is larger than that of the oil separator 14A. This has the effect of reducing the flow rate of the refrigerant inside the oil separator 14B, and allows for more reliable separation of oil from the refrigerant.

[0144] It should be noted that the above-described embodiments are intended to illustrate the technology of the present disclosure, and various modifications, substitutions, additions, omissions, etc. may be made within the scope of the claims or their equivalents.

[0145] (Addendum) The above description of the embodiments discloses the following techniques.

[0146] (Technology 1) An oil separation mechanism provided in a refrigeration circuit formed by connecting a compressor, a heat source side heat exchanger, and a user side heat exchanger, the oil separation mechanism comprising: an oil separator that separates oil from the refrigerant discharged from the compressor; an oil storage device that stores the oil separated by the oil separator; and an oil pipe that connects the oil separator and the oil storage device, wherein a lower end of the oil separator is positioned higher than a first connection part that connects the oil pipe to the oil storage device, and the oil is configured to move from the oil separator to the oil storage device through the oil pipe by its own weight, and at least a portion of a flow path of the oil pipe is positioned lower than the oil separator and the first connection part. This eliminates the need for the oil separator to store oil, thereby reducing the volume of the space in the oil separator where the refrigerant diffuses, thereby reducing the heat lost from the refrigerant. Furthermore, the smaller oil separator provides advantages such as a smaller, lighter, easier installation, and lower costs for the refrigeration system. The oil separated from the refrigerant in the oil separator can be transported to the oil storage device by its own weight without using refrigerant pressure or a power source. Furthermore, since at least a portion of the oil pipe is blocked by oil when the oil is not moving, the movement of refrigerant between the oil separator and the oil storage device is prevented, thereby suppressing heat transfer. Therefore, the oil separation mechanism effectively reduces the temperature drop of the refrigerant discharged from the compressor.

[0147] (Technology 2) The oil separation mechanism according to Technology 1, wherein the oil pipe has an oil reservoir in which oil is collected, and the upper end of the oil reservoir is located lower than the first connecting portion. This prevents the movement of refrigerant between the oil separator and the oil storage device while the movement of oil is stopped, thereby further reducing the temperature drop of the refrigerant in the oil separation mechanism.

[0148] (Technical Aspect 3) The oil separation mechanism according to Technical Aspect 1 or Technical Aspect 2, wherein a second connection portion where the oil pipe is connected to the oil separator is located at a higher position than the first connection portion. This reduces the amount of oil remaining inside the oil separator, allowing the oil separator to be made even more compact.

[0149] (Technical Aspect 4) The oil separation mechanism according to Technical Aspect 3, wherein the second connection portion is a portion where a flow path through which oil flows in the oil pipe is connected to an internal space of the oil separator. This reduces the amount of oil remaining inside the oil separator, allowing the oil separator to be made even more compact.

[0150] (Technology 5) An oil separation mechanism according to any one of Technology 1 to Technology 4, comprising a plurality of the oil separators and a refrigerant pipe that branches the refrigerant discharged from the compressor and supplies the refrigerant to each of the plurality of oil separators, wherein each of the oil separators and the refrigerant pipes are connected such that the refrigerant supplied from the refrigerant pipe flows unevenly into the plurality of oil separators. This configuration allows a large amount of refrigerant to flow through some of the oil separators, thereby reducing the volume of refrigerant that diffuses and suppressing the temperature drop that accompanies refrigerant diffusion. Furthermore, by using multiple oil separators, oil can be separated from refrigerant in a refrigeration circuit where a large amount of refrigerant flows.

[0151] (Technology 6) The refrigerant pipe is configured so that refrigerant flowing into the base end of the refrigerant pipe flows toward the terminal end of the refrigerant pipe, at least some of the multiple oil separators are terminal oil separators connected to the terminal ends of the refrigerant pipes, and the oil separators different from the terminal oil separators are connected to an inflow branch pipe that branches off from between the terminal end and the base end of the refrigerant pipe. This allows a configuration in which more refrigerant flows into the terminal oil separator than into the other oil separators without using a mechanism for managing and adjusting the amount of refrigerant flowing into each oil separator.

[0152] (Technology 7) An oil separation mechanism according to Technology 6, wherein each of the oil separators has an outlet through which the refrigerant separated from the oil in the oil separator is discharged, and the oil separators are provided with discharge pipes connected to the outlets of a plurality of the oil separators, the discharge pipes are configured so that the refrigerant flows from the base end to the tip end of the discharge pipe, the base end of the discharge pipe is connected to the outlet of an oil separator different from the terminal oil separator, and the outlet of the terminal oil separator is connected to a discharge branch pipe branching off from between the base end and tip end of the discharge pipe. This allows the refrigerant to flow efficiently in a configuration where multiple oil separators are used to separate oil from the refrigerant, thereby improving the operating efficiency of the refrigeration unit.Furthermore, by reducing the flow rate of the refrigerant inside the terminal oil separator, the oil can be separated from the refrigerant more reliably.

[0153] (Technology 8) A refrigeration system having a refrigeration circuit connecting a compressor, a heat source side heat exchanger, and a user side heat exchanger, the refrigeration system further comprising: an oil separator that separates oil from the refrigerant discharged from the compressor; an oil storage device that stores the oil separated by the oil separator; and an oil pipe that connects the oil separator and the oil storage device, wherein a lower end of the oil separator is positioned higher than a first connection part that connects the oil pipe to the oil storage device, and the refrigeration system is configured such that oil moves from the oil separator to the oil storage device through the oil pipe by its own weight, and at least a portion of a flow path of the oil pipe is positioned lower than the oil separator and lower than the first connection part. This provides the same effect as the oil separation mechanism of Technology 1. [Industrial Applicability]

[0154] The present disclosure is suitably applicable to an oil separation mechanism that can suppress a decrease in refrigerant temperature in a mechanism that separates oil from refrigerant discharged from a compressor, and to a refrigeration device that includes this oil separation mechanism. [Explanation of symbols]

[0155] 1 Refrigeration equipment 2 Refrigeration circuit 3 Oil separation mechanism 10 Outdoor unit 11 Low-stage compressor 12 High-stage compressor 13 Accumulator 14, 14A Oil Separator 14B Oil separator (terminal oil separator) 15 Outdoor heat exchanger (heat source side heat exchanger) 16 Gas-liquid separator 17 Oil pipe 17a First connection part 17b Oil reservoir 17c Oil flow path 17d Second connection part 18 Reserve tank (oil storage device) 19 Pressure reducing valve 20 Indoor unit 21 Indoor expansion mechanism 22 Indoor heat exchanger (user side heat exchanger) 23 On-off valve 24 Refrigerant pipe 24a Proximal end 24b Branch 24c Inlet branch piping 24d Termination 24e Inflow pipe 25 Discharge pipe 25a Tip 25b Branch 25c Exhaust branch piping 25d proximal end 25e discharge pipe 30 Refrigeration equipment 31 Inlet expansion mechanism for refrigeration 32 Refrigeration heat exchanger (user side heat exchanger) 33 Refrigeration outlet pressure adjustment mechanism 41 First heating pipe 42 First outdoor return pipe 46 Oil return pipe 47, 48 Pressure adjustment mechanism 50 First switching mechanism 51 First cooling valve 52 First heating valve 53 Outdoor refrigerant return valve 54 Second switching mechanism 58 Refrigerant return expansion mechanism 59 Check valve 40, 60, 69, 71, 72, 77, 78 Piping 61 Gas refrigerant flow control valve 64 Internal heat exchanger 65 Liquid refrigerant flow control valve 66 Connecting piping 73 First Pipe 74 Second Pipe 75 Third Pipe 76 Fourth Pipe 80 Refrigerant pressure sensor 100 Controllers 141 Main Unit 141a Separation part (internal space) 142 Refrigerant pipe connection 142a Inner tube 143 Discharge pipe connection (discharge port) 144 Oil pipe connection 171 Main Tube 172 Branch Pipe 173 Branch Pipe 174 Connector 181 Tank body 182 Oil pipe connection 183 Connection 184 Bottom plate DO residual oil RO residual oil S ground plane SO Oil level

Claims

1. The refrigeration circuit is provided by connecting a compressor, a heat source side heat exchanger, and a user side heat exchanger, an oil separator that separates oil from the refrigerant discharged from the compressor; an oil storage device that stores the oil separated by the oil separator; an oil pipe connecting the oil separator and the oil storage device, a lower end of the oil separator located at a position higher than a first connection portion where the oil pipe is connected to the oil reservoir device, and configured so that oil moves by its own weight from the oil separator to the oil reservoir device through the oil pipe; an oil separation mechanism, wherein at least a portion of the flow path of the oil pipe is located lower than the oil separator and lower than the first connecting portion;

2. 2. The oil separation mechanism according to claim 1, wherein the oil pipe has an oil reservoir in which oil is collected, and the upper end of the oil reservoir is located lower than the first connecting portion.

3. 2. The oil separation mechanism according to claim 1, wherein a second connection portion at which the oil pipe is connected to the oil separator is located at a higher position than the first connection portion.

4. The oil separation mechanism according to claim 3 , wherein the second connection portion is a portion where a flow path through which oil flows in the oil pipe is connected to an internal space of the oil separator.

5. a plurality of the oil separators; a refrigerant pipe that branches the refrigerant discharged from the compressor and supplies the refrigerant to each of the plurality of oil separators, 2. The oil separation mechanism according to claim 1, wherein each of the oil separators and the refrigerant pipes are connected such that the refrigerant supplied from the refrigerant pipes flows unevenly through the plurality of oil separators.

6. The refrigerant pipe is configured so that the refrigerant flowing into the base end portion of the refrigerant pipe flows toward the terminal end portion of the refrigerant pipe, At least some of the plurality of oil separators are terminal oil separators connected to terminal ends of the refrigerant pipes, 6. The oil separation mechanism according to claim 5, wherein the oil separator different from the terminal oil separator is connected to an inlet branch pipe that branches off from between the terminal end and the base end of the refrigerant pipe.

7. Each of the oil separators has an outlet through which the refrigerant separated from the oil in the oil separator is discharged, a discharge pipe connected to the discharge ports of the plurality of oil separators; The discharge pipe is configured so that the refrigerant flows from the base end to the tip end of the discharge pipe, a base end of the discharge pipe is connected to a discharge port of the oil separator different from the terminal oil separator; 7. The oil separation mechanism according to claim 6, wherein the discharge port of the terminal oil separator is connected to a branch discharge pipe that branches off from between the base end and the tip end of the discharge pipe.

8. A refrigeration device including a refrigeration circuit connecting a compressor, a heat source side heat exchanger, and a user side heat exchanger, an oil separator that separates oil from the refrigerant discharged from the compressor; an oil storage device that stores the oil separated by the oil separator; an oil pipe connecting the oil separator and the oil storage device, a lower end of the oil separator located at a position higher than a first connection portion where the oil pipe is connected to the oil reservoir device, and configured so that oil moves by its own weight from the oil separator to the oil reservoir device through the oil pipe; A refrigeration apparatus, wherein at least a portion of the flow path of the oil pipe is located lower than the oil separator and lower than the first connecting portion.

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