Refrigeration system and oil return method therefor

Abstract

A refrigeration system includes a compressor, a condenser, a throttling device, and an evaporator connected in series to form a refrigeration circuit, wherein the refrigeration system further includes an oil recovery system including an operating chamber having a first port communicating with an oil-containing location in the refrigeration system through a first line and a second port communicating with a bearing chamber or a bearing lubrication line of the compressor through a second line, and a main piston in the operating chamber reciprocating in the operating chamber to perform a suction stroke in which oil-containing refrigerant from the oil-containing location in the refrigeration system is drawn into the operating chamber and a discharge stroke in which the oil-containing refrigerant in the operating chamber is delivered to the bearing chamber or the bearing lubrication line of the compressor. The apparatus and method according to embodiments of the present invention can provide refrigerant having sufficient oil content to the bearing chamber or the bearing lubrication line of the compressor.

Description

Technical Field

[0001] This invention relates to a refrigeration system, and more specifically, to an oil return device and method in a refrigeration system. Background Technology

[0002] In refrigeration systems, compressor components such as bearings require oil lubrication. In essentially oil-free compressors, the refrigeration system itself does not have an oil separator; the system delivers the liquid refrigerant from the condenser to the compressor's bearing housing or bearing lubrication lines. Due to the characteristics of lubricating oil, it does not accumulate in the condenser but rather in areas such as the bottom of the evaporator or the bottom of the compressor's internal casing. To improve the reliability of the compressor bearings, this oil-rich refrigerant layer (also known as the gas-liquid two-phase layer) needs to be delivered to the compressor bearing housing or bearing lubrication lines. In these systems, there are specific requirements for the amount and pressure of the returned refrigerant to ensure that sufficient oil reaches the desired lubrication points in the compressor bearing housing or bearing lubrication lines. Summary of the Invention

[0003] The purpose of this invention is to solve or at least alleviate the problems existing in the prior art.

[0004] According to one aspect, a refrigeration system is provided, comprising: a compressor, a condenser, a throttling device, and an evaporator connected in sequence to form a refrigeration circuit, wherein the refrigeration system further comprises an oil recovery system, the oil recovery system comprising: The control room includes a first port connected to an oil-containing location in the refrigeration system via a first pipe, and a second port connected to the bearing housing or bearing lubrication line of the compressor via a second pipe; and The main piston in the operating chamber reciprocates within the operating chamber to perform a draw-in stroke and a discharge stroke. During the draw-in stroke, oil-containing refrigerant from the oil-containing location in the refrigeration system is drawn into the operating chamber. During the discharge stroke, the oil-containing refrigerant in the operating chamber is delivered to the bearing chamber of the compressor or the bearing lubrication line.

[0005] Optionally, in an embodiment of the refrigeration system, the oil-containing location in the refrigeration system is either the oil collection chamber inside the compressor or the evaporator.

[0006] Optionally, in an embodiment of the refrigeration system, a first check valve is provided on the end cap of the first pipeline or at one end of the operating chamber, allowing fluid to flow only from the oil-containing position to the first port, and a second check valve is provided on the second pipeline or the end cap, allowing fluid to flow only from the second port to the bearing chamber or bearing lubrication pipeline of the compressor.

[0007] Alternatively, in an embodiment of the refrigeration system, the main piston is driven by an electric actuator.

[0008] Optionally, in an embodiment of the refrigeration system, the main piston is connected to a first side of the control piston via a connecting rod. The first side of the control piston has a first control chamber, and the second side of the control piston has a second control chamber. The first control chamber and the second control chamber are alternately connected to a first pressure fluid source and a second pressure fluid source. The first pressure fluid source and the second pressure fluid source have a sufficient pressure difference, thereby driving the control piston to reciprocate together with the main piston to perform the extraction stroke and the discharge stroke.

[0009] Optionally, in an embodiment of the refrigeration system, the first control chamber is located between the back side of the main piston and the first side of the control piston, and the control piston has a larger working area than the main piston.

[0010] Optionally, in an embodiment of the refrigeration system, the first pressure fluid source is from the evaporator, and the second pressure fluid source is from the condenser.

[0011] Optionally, in an embodiment of the refrigeration system, the evaporator is connected to the first control chamber via a first valve and to the second control chamber via a second valve, and the condenser is connected to the first control chamber via a third valve and to the second control chamber via a fourth valve, or... The evaporator is connected to the first control chamber and the second control chamber respectively via a first three-way valve, and the condenser is connected to the first control chamber and the second control chamber respectively via a second three-way valve, or... The evaporator, the condenser, the first control chamber, and the second control chamber are connected by a four-way valve.

[0012] Optionally, in an embodiment of the refrigeration system, the refrigeration system further includes: Sensor, the sensor being used to sense the position of the control piston or the main piston; and A controller that communicates with the sensor operates at least one valve based on the position of the control piston or main piston provided by the sensor, so that the first control chamber and the second control chamber are alternately connected to a first pressure fluid source and a second pressure fluid source.

[0013] Optionally, in an embodiment of the refrigeration system, the oil recovery system further includes an auxiliary control chamber, the auxiliary control chamber comprising a first port connected to an oil-containing location in the refrigeration system via a third pipeline, and a second port connected to the bearing chamber or bearing lubrication pipeline of the compressor via a fourth pipeline; and The auxiliary main piston in the auxiliary operating chamber is connected to the second side of the control piston via a connecting rod. The second control chamber is located between the back side of the auxiliary main piston and the second side of the control piston. The control piston has a larger working area than the auxiliary main piston. During the extraction stroke of the main piston, the auxiliary main piston performs a discharge stroke to deliver oil-containing refrigerant from the auxiliary operating chamber to the compressor bearing chamber or bearing lubrication line. During the discharge stroke of the main piston, the auxiliary main piston performs an extraction stroke to extract oil-containing refrigerant from the oil-containing location in the refrigeration system to the auxiliary operating chamber.

[0014] According to another aspect, a method for oil return in a refrigeration system is also provided, the method comprising: The main piston in the operating chamber is moved by an electric actuator or the pressure difference between a first pressure fluid source and a second pressure fluid source in the refrigeration system to draw oil-containing refrigerant from an oil-containing location in the refrigeration system into the operating chamber; and The main piston in the operating chamber is driven to move by an electric actuator or the pressure difference between the first and second pressure fluid sources in the refrigeration system to deliver the oil-containing refrigerant in the operating chamber to the bearing chamber or bearing lubrication line of the compressor.

[0015] The apparatus and method according to embodiments of the present invention can provide refrigerant with sufficient oil content to the bearing chamber of the compressor or the bearing lubrication line. Attached Figure Description

[0016] The disclosure of this invention will become more readily understood with reference to the accompanying drawings. It will be readily understood by those skilled in the art that these drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. Furthermore, similar numbers in the drawings are used to denote similar components, wherein: Figure 1 A schematic diagram of a refrigeration system according to an embodiment of the present invention is shown; Figure 2 A schematic diagram of a refrigeration system according to another embodiment of the present invention is shown; Figure 3 A schematic diagram of a refrigeration system according to another embodiment of the present invention is shown; Figure 4 A schematic diagram of a refrigeration system according to another embodiment of the present invention is shown; and Figure 5 A schematic diagram of a refrigeration system according to another embodiment of the present invention is shown. Detailed Implementation

[0017] First refer to Figure 1The structure of a refrigeration system according to an embodiment of the present invention is described below. The refrigeration system includes: a compressor 1, a condenser 2, a throttling device 3, and an evaporator 4, connected sequentially to form a refrigeration loop. The compressor 1 includes a compressor inlet 13, a compressor outlet 12, and a compressor bearing chamber or bearing lubrication line 11. The compressor outlet 12 is connected to the condenser 2 via a pipe, the condenser 2 is connected to the throttling device 3 via a pipe, the throttling device 3 being, for example, an expansion valve, the throttling device 3 is connected to the evaporator 4, and finally the evaporator 4 is connected to the compressor inlet 13 to form a refrigeration loop. In the refrigeration system according to an embodiment of the present invention, the compressor 1 can be an oil-free or substantially oil-free compressor, which itself does not include an oil circuit; therefore, the refrigeration system also provides an oil recovery system. The oil recovery system includes: an operating chamber 5, the operating chamber 5 including a first port 51 and a second port 52, the first port 51 being connected to an oil-containing location in the refrigeration system via a first pipe 61, and the second port 52 being connected to the bearing chamber or bearing lubrication line 11 of the compressor 1 via a second pipe 62. In the illustrated embodiment, the operating chamber 5 is defined by a cylinder 59 and an end cap 58 at one end of the cylinder 59, with a first port 51 and a second port 52 provided on the end cap 58. A main piston 531 is arranged in the operating chamber 5, reciprocating to perform a draw-in stroke and a discharge stroke. During the draw-in stroke, oil-containing refrigerant from the oil-containing location in the refrigeration system is drawn into the operating chamber 5. During the discharge stroke, the oil-containing refrigerant in the operating chamber 5 is delivered to the compressor bearing chamber or bearing lubrication line 11, thereby delivering refrigerant with a certain oil concentration and pressure to the compressor bearing chamber or bearing lubrication line 11 for lubrication, corrosion protection, and cooling. It should be understood that the draw-in stroke and discharge stroke are repeated periodically with the reciprocating motion of the main piston 531. In the illustrated embodiment, the first port 51 of the operating chamber 5 is connected to port 42 of the evaporator 4 via a first conduit 61. Port 42 may be an additional port of the evaporator 4, not an inlet or outlet connecting the evaporator 4 to the throttling device 3 or the compressor inlet 13. In some embodiments, port 42 of the evaporator 4 may be located at the bottom of the evaporator 4 to recover the oil-rich refrigerant layer (also known as the gas-liquid two-phase) at the bottom of the evaporator to the compressor 1. The term "extraction stroke" refers to the stroke in which the main piston 531 moves to the left to extract the refrigerant from the evaporator 4 into the operating chamber 5, and the term "discharge stroke" refers to the stroke in which the main piston 531 moves to the right to discharge the refrigerant from the operating chamber 5 into the compressor bearing housing or bearing lubrication line.

[0018] An oil-containing location refers to a location in the refrigeration system where refrigerant with a certain oil content exists. Although the embodiments shown use the interior of the evaporator 4 as a specific example of an oil-containing location, it should be understood that there are many other options for oil-containing locations in the refrigeration system, such as the oil collection chamber inside the compressor 1, the economizer (if present) of the refrigeration system, or other evaporators, as long as refrigerant with a certain oil content exists at that location.

[0019] In some embodiments, a first check valve 63 is provided on the first pipeline 61 or the first port 51, allowing fluid to flow only from the oil-containing location, i.e., inside the evaporator 4, to the first port 51 of the operating chamber 5, and a second check valve 64 is provided on the second pipeline 62 or the second port 52, allowing fluid to flow only from the second port 52 of the operating chamber 5 to the bearing chamber of the compressor 1 or the bearing lubrication pipeline 11, thereby preventing reverse flow of refrigerant fluid. In an alternative embodiment, openable and closable valves, such as solenoid valves, may also be provided on the first pipeline 61 and the second pipeline 62, with the valve on the first pipeline opening and the valve on the second pipeline closing during the extraction stroke, and the valve on the second pipeline opening and the valve on the first pipeline closing during the discharge stroke. Figure 1 In this embodiment, the main piston 531 is connected to the electric actuator 91 via a connecting rod 534, thereby being driven by the electric actuator 91 to perform the extraction and discharge strokes. The electric actuator 91 may be, for example, a linear motor or similar device.

[0020] Now continue with the reference. Figures 2 to 4 This section introduces some modifications to the refrigeration system according to embodiments of the present invention. Figure 2In this structure, instead of the electric actuator 91, two fluids with a pressure difference are used to drive the main piston 531. Specifically, the main piston 531 is connected to a first side of the control piston 532 via a connecting rod 534. The first side of the control piston 532 has a first control chamber 54, and the second side of the control piston 532 has a second control chamber 55. The main piston 531, connecting rod 534, and control piston 532 form a whole, referred to as piston assembly 53. The first control chamber 54 and the second control chamber 55 are alternately connected to a first pressure fluid source and a second pressure fluid source, which have a sufficient pressure difference to drive the control piston 532 to reciprocate together with the main piston 531 (i.e., piston assembly 53) to perform the extraction stroke and the discharge stroke. More specifically, for example, during the extraction stroke, a first pressure fluid source with greater pressure is supplied to the first control chamber 54, and a second pressure fluid source is supplied to the second control chamber 55, causing the control piston 532 to move the main piston 531 to the left, thereby extracting oil-containing refrigerant from the evaporator 4 to the operating chamber 5. During the discharge stroke, a first pressure fluid source with greater pressure is supplied to the second control chamber 55, and a second pressure fluid source is supplied to the first control chamber 54, causing the control piston 532 to move the main piston 531 to the right, thereby discharging oil-containing refrigerant from the operating chamber 5 to the compressor bearing chamber or the bearing lubrication line 11. In the illustrated embodiment, the operating chamber 5, the first control chamber 54, and the second control chamber 55 are defined by the same cylinder 59, which includes a smaller cross-sectional area near the operating chamber 5 and a larger cross-sectional area near the second control chamber. The end of cylinder 59 near the operating chamber 5 is covered by a first cylinder head 581, which has a first port 51 and a second port 52. The end of cylinder 59 near the second control chamber is covered by a second cylinder head 582. The first control chamber 54 is located between the back side of the main piston 531 and the first side of the control piston 532, with the control piston 532 having a larger working area (fluid pressure working area) than the main piston 531. During the extraction and discharge strokes, the main piston 531 is located in the smaller portion of the cylinder's cross-section, while the control piston 532 is located in the larger portion of the cylinder's cross-section. In an alternative embodiment, the operating chamber 5 and the first control chamber 54, and the second control chamber 55 can be separated and defined by different cylinders, and the first control chamber 54 may not be in communication with the back side of the main piston 531. The first and second pressure fluid sources can be selected from any location within the refrigeration system, provided there is a sufficient pressure difference between them. Alternatively, the first and second pressure fluid sources can also be external fluid sources independent of the refrigeration system itself. In the illustrated embodiment, the first pressure fluid source is from the evaporator 4, and the second pressure fluid source is from the condenser 2.Specifically, the auxiliary port 21 of condenser 2 is connected to port 551 of the second control chamber 55 via condenser first pipe 22, and to port 541 of the first control chamber 54 via condenser second pipe 23. A first control valve 81 and a second control valve 82 are respectively installed on condenser first pipe 22 and condenser second pipe 23. On the other hand, the auxiliary port 41 of evaporator 4 is connected to port 541 of the first control chamber 54 via evaporator first pipe 43, and to port 551 of the second control chamber 55 via evaporator second pipe 44. A third control valve 83 and a fourth control valve 84 are respectively installed on evaporator first pipe 43 and evaporator second pipe 44. The first control valve 81, second control valve 82, third control valve 83, and fourth control valve 84 communicate with the controller. The controller is configured to, during the extraction stroke, open the second control valve 82 and the fourth control valve 84, and close the first control valve 81 and the third control valve 83, thereby introducing fluid from the condenser 2 into the first control chamber 54 and fluid from the evaporator 4 into the second control chamber 55, thereby driving the piston assembly 53, consisting of the main piston 531, connecting rod 534, and control piston 532, to move to the left. The controller is also configured to, during the discharge stroke, open the first control valve 81 and the third control valve 83, and close the second control valve 82 and the fourth control valve 84, thereby introducing fluid from the condenser 2 into the second control chamber 55 and fluid from the evaporator 4 into the first control chamber 54, thereby driving the piston assembly 53 to move to the right, and repeating this cycle sequentially.

[0021] Continue to refer to Figure 3 In this embodiment, with Figure 2 The difference in the illustrated embodiment is that two three-way valves 85 and 86 are used instead of Figure 2 The system comprises four control valves. Specifically, the evaporator 4 is connected to the first control chamber 54 and the second control chamber 55 via a first three-way valve 86, and the condenser 2 is connected to both the first and second control chambers 54 and 55 via a second three-way valve 85. Both valves are connected to a controller. During the extraction stroke, the first three-way valve 86 is adjusted to connect the evaporator 4 to the second control chamber 55, and the second three-way valve 85 is adjusted to connect the condenser 2 to the first control chamber 54. During the discharge stroke, the first three-way valve 86 is adjusted to connect the evaporator 4 to the first control chamber 54, and the second three-way valve 85 is adjusted to connect the condenser 2 to the second control chamber 55.

[0022] Continue to refer to Figure 4 In this embodiment, with Figure 2 The difference in the illustrated embodiment is that a four-way valve 87 is used instead of... Figure 2The system comprises four control valves. Specifically, the evaporator 4, condenser 2, first control chamber 54, and second control chamber 55 are connected via a four-way valve 87. During the extraction stroke, the four-way valve 87 is adjusted to connect the evaporator 4 to the second control chamber 55 and the condenser 2 to the first control chamber 54. During the discharge stroke, the four-way valve 87 is adjusted to connect the evaporator 4 to the first control chamber 54 and the condenser 2 to the second control chamber 55.

[0023] In some embodiments, the refrigeration system further includes: a sensor for sensing the position of the control piston 532 or the main piston 531; and a controller in communication with the sensor, the controller operating at least one valve (e.g., based on the position of the control piston 532 or the main piston 531 provided by the sensor). Figure 2 Control valves 81, 82, 83, 84 in the embodiments, or Figure 3 The three-way valves 85 and 86 in the embodiments, or Figure 4 The four-way valve 87 in the embodiment allows the first and second control chambers to be alternately connected to the first and second pressure fluid sources, thereby performing the extraction and discharge strokes. Various types of proximity or contact sensors can be used, such as optical sensors, magnetic sensors, etc. The sensors can be mounted, for example, on the cylinder wall, end cap, and / or piston assembly 53.

[0024] Continue to refer to Figure 5 Let's introduce another embodiment of the refrigeration system. Figure 5In the illustrated embodiment, the oil recovery system further includes an auxiliary operating chamber 50, which includes a third port 501 connected to an oil-containing location in the refrigeration system (e.g., evaporator 4) via a third pipe 65, and a fourth port 502 connected to the compressor bearing chamber or bearing lubrication line 11 via a fourth pipe 67. Similarly, a third check valve 66 is provided on the third pipe 65 or the third port 501, allowing only fluid from the evaporator 4 to the auxiliary operating chamber 50 to pass through, and a fourth check valve 68 is provided on the fourth pipe 67 or the fourth port 502, allowing only fluid from the auxiliary operating chamber 50 to pass through the compressor bearing chamber or bearing lubrication line 11. The auxiliary operating chamber 50 has an auxiliary main piston 533, which is connected to the second side of a control piston 532 via a connecting rod 535. A second control chamber 55 is located between the back side of the auxiliary main piston 50 and the second side of the control piston 532. In the illustrated embodiment, the cylinder body 59 defines portions with smaller cross-sections at both ends and a portion with a larger cross-section in the middle. The cylinder block 59 is covered at both ends by a first cylinder head 581 and a second cylinder head 582, the second cylinder head 582 including a first port 501 and a second port 502. During the extraction and discharge strokes, the main piston 531 and the auxiliary main piston 533 move in the portions with smaller cross-sections at both ends of the cylinder block, while the control piston 532 moves in the portion with a larger cross-section in the middle. The control piston 532 has a larger working area (i.e., cross-sectional area) than the main piston 531 and the auxiliary main piston 533; in the illustrated embodiment, the working areas of the main piston 531 and the auxiliary main piston 533 are substantially equal. With this arrangement, when the main piston 531 performs the extraction stroke, the auxiliary main piston 533 performs the discharge stroke to deliver oil-containing refrigerant from the auxiliary operating chamber 50 to the compressor bearing chamber or bearing lubrication line 11, and when the main piston 531 performs the discharge stroke, the auxiliary main piston 533 performs the extraction stroke to extract oil-containing refrigerant from the oil-containing location in the refrigeration system to the auxiliary operating chamber 50. Therefore, unlike... Figures 1 to 4 The structure, wherein only during the discharge stroke is oil-containing refrigerant delivered to the compressor bearing housing or bearing lubrication line 11, Figure 5 In the embodiment shown, oil-containing refrigerant is continuously supplied to the compressor bearing chamber or bearing lubrication line 11.

[0025] The specific embodiments described above are merely for the purpose of more clearly illustrating the principles of the present invention, wherein the various components are clearly shown or described to make the principles of the present invention easier to understand. Various modifications or variations can be readily made to the present invention by those skilled in the art without departing from the scope of the invention. Therefore, it should be understood that all such modifications or variations should be included within the patent protection scope of the present invention.

Claims

1. A refrigeration system comprising: A compressor, condenser, throttling device, and evaporator connected in sequence to form a refrigeration circuit, characterized in that the refrigeration system further includes an oil recovery system, the oil recovery system comprising: The control room includes a first port connected to an oil-containing location in the refrigeration system via a first pipe, and a second port connected to the bearing housing or bearing lubrication line of the compressor via a second pipe; and The main piston in the operating chamber reciprocates in the operating chamber to perform a pumping stroke and a discharging stroke. In the pumping stroke, oil-containing refrigerant in the oil-containing position of the refrigeration system is pumped into the operating chamber. In the discharging stroke, the oil-containing refrigerant in the operating chamber is delivered to the bearing chamber or bearing lubrication line of the compressor. The main piston is connected to the first side of the control piston via a connecting rod. The first side of the control piston has a first control chamber and the second side of the control piston has a second control chamber. The first control chamber and the second control chamber are alternately connected to a first pressure fluid source and a second pressure fluid source. The first pressure fluid source and the second pressure fluid source have a sufficient pressure difference, thereby driving the control piston to reciprocate together with the main piston to perform the extraction stroke and the discharge stroke. The first pressure fluid source is from the evaporator, and the second pressure fluid source is from the condenser.

2. The refrigeration system according to claim 1, characterized in that, The oil-containing location in the refrigeration system is either the internal oil collection chamber of the compressor or the evaporator.

3. The refrigeration system according to claim 1, characterized in that, A first check valve is provided on the end cap of the first pipeline or at one end of the operating chamber, which only allows fluid to flow from the oil-containing position to the first port, and a second check valve is provided on the second pipeline or the end cap, which only allows fluid to flow from the second port to the bearing chamber or bearing lubrication pipeline of the compressor.

4. The refrigeration system according to any one of claims 1-3, characterized in that, The main piston is driven by an electric actuator.

5. The refrigeration system according to claim 1, characterized in that, The first control chamber is located between the back side of the main piston and the first side of the control piston, and the control piston has a larger working area than the main piston.

6. The refrigeration system according to claim 1, characterized in that, The evaporator is connected to the first control chamber via a first valve and to the second control chamber via a second valve; the condenser is connected to the first control chamber via a third valve and to the second control chamber via a fourth valve, or... The evaporator is connected to the first control chamber and the second control chamber respectively via a first three-way valve, and the condenser is connected to the first control chamber and the second control chamber respectively via a second three-way valve, or... The evaporator, the condenser, the first control chamber, and the second control chamber are connected by a four-way valve.

7. The refrigeration system according to claim 6, characterized in that, The refrigeration system also includes: Sensor, the sensor being used to sense the position of the control piston or the main piston; and A controller that communicates with the sensor operates at least one valve based on the position of the control piston or main piston provided by the sensor, so that the first control chamber and the second control chamber are alternately connected to a first pressure fluid source and a second pressure fluid source.

8. A refrigeration system comprising: A compressor, condenser, throttling device, and evaporator connected in sequence to form a refrigeration circuit, characterized in that the refrigeration system further includes an oil recovery system, the oil recovery system comprising: The control room includes a first port connected to an oil-containing location in the refrigeration system via a first pipe, and a second port connected to the bearing housing or bearing lubrication line of the compressor via a second pipe; and The main piston in the operating chamber reciprocates in the operating chamber to perform a pumping stroke and a discharging stroke. In the pumping stroke, oil-containing refrigerant in the oil-containing position of the refrigeration system is pumped into the operating chamber. In the discharging stroke, the oil-containing refrigerant in the operating chamber is delivered to the bearing chamber or bearing lubrication line of the compressor. The main piston is connected to the first side of the control piston via a connecting rod. The first side of the control piston has a first control chamber and the second side of the control piston has a second control chamber. The first control chamber and the second control chamber are alternately connected to a first pressure fluid source and a second pressure fluid source. The first pressure fluid source and the second pressure fluid source have a sufficient pressure difference, thereby driving the control piston to reciprocate together with the main piston to perform the extraction stroke and the discharge stroke. The oil recovery system further includes an auxiliary operating chamber, which has a first port connected to an oil-containing location in the refrigeration system via a third pipeline, and a second port connected to the compressor's bearing housing or bearing lubrication pipeline via a fourth pipeline; and The auxiliary main piston in the auxiliary operating chamber is connected to the second side of the control piston via a connecting rod. The second control chamber is located between the back side of the auxiliary main piston and the second side of the control piston. The control piston has a larger working area than the auxiliary main piston. When the main piston performs the extraction stroke, the auxiliary main piston performs the discharge stroke to deliver the oil-containing refrigerant in the auxiliary operating chamber to the compressor bearing chamber or bearing lubrication line. And when the main piston performs the discharge stroke, the auxiliary main piston performs the extraction stroke to extract the oil-containing refrigerant in the oil-containing position of the refrigeration system to the auxiliary operating chamber.

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