Twin-screw main unit

Abstract

This application provides a twin-screw compressor. The twin-screw compressor includes a housing, a rotor assembly, a bearing assembly, and an oil supply system. A chamber is provided within the housing, and the rotor assembly is located within the chamber. The bearing assembly is located at both ends of the rotor assembly. The chamber has a low-pressure side and a high-pressure side arranged opposite to each other. The oil supply system is integrated within the housing and includes an oil chamber located near the high-pressure side, and rotor oil passages and bearing oil passages respectively connected to the oil chamber for supplying oil to the rotor assembly and bearing assembly. By integrating the oil supply system within the housing, this application simplifies the external oil supply pipeline, achieves high integration, and saves installation space. Simultaneously, by providing heat exchange and cooling for the rotor assembly and bearing assembly through the rotor oil passages and bearing oil passages, the housing achieves high heat dissipation efficiency and avoids cylinder rubbing caused by high-temperature expansion of the rotor assembly against the housing, resulting in high reliability.

Description

Technical Field

[0001] This application relates to the field of compressors, and more particularly to twin-screw compressors. Background Technology

[0002] Oil-injected screw compressors require the injection of cooled and filtered lubricating oil during operation. The amount of oil injected affects the performance and reliability of the compressor, and also directly impacts the configuration of the entire system that relies on pressure differential for lubrication. Higher injection pressure and larger injection volume result in greater reliability; conversely, lower injection pressure and smaller injection volume can easily lead to high-temperature seizure of the compressor rotor. When oil-injected screw compressors are extended to low-pressure and vacuum applications, the system pressure drops significantly, weakening the oil supply capacity to the compressor. This necessitates the use of auxiliary oil pumps to achieve lubrication and cooling functions for the compressor.

[0003] Existing twin-screw compressor oil supply systems mostly employ external piping or decentralized oil circuit designs, resulting in low integration between the oil supply system and the casing. This leads to a complex overall structure and high installation costs for the twin-screw compressor. Furthermore, traditional oil supply systems, in pursuit of high performance, deflect rotor oil injection towards high internal pressure points in an attempt to reduce oil churning power consumption. This results in a high risk of thermal deformation of the casing and rotor components, making cylinder rubbing more likely and compromising reliability.

[0004] Therefore, it is necessary to provide an improved twin-screw compressor to solve the above problems. Utility Model Content

[0005] This application provides a highly integrated and reliable twin-screw compressor.

[0006] This application provides a twin-screw compressor, comprising: a housing, a rotor assembly, a bearing assembly, and an oil supply system. The housing has a chamber, the rotor assembly is located within the chamber, and the bearing assembly is disposed at both ends of the rotor assembly. The chamber has a low-pressure side and a high-pressure side disposed opposite to each other. The oil supply system is integrated within the housing and includes an oil chamber located near the high-pressure side and rotor oil passages and bearing oil passages respectively communicating with the oil chamber and used to supply oil to the rotor assembly and the bearing assembly.

[0007] Furthermore, the oil cavity is located at the bottom of the housing and below the chamber; a partition wall is provided between the oil cavity and the chamber, and the rotor oil passage includes a male rotor oil supply hole and a female rotor oil supply hole that penetrate the partition wall.

[0008] Furthermore, the bearing assembly includes a front bearing disposed at one end of the rotor assembly and close to the low-pressure side; the bearing oil passage includes a front oil passage extending horizontally along the axial direction from the oil chamber to the low-pressure side and an upper oil passage extending upward from the front oil passage, the upper oil passage being located at the end of the housing.

[0009] Furthermore, the bearing oil circuit also includes a first throttling orifice and a second throttling orifice that are connected to the upper oil passage for spraying oil onto the front bearing.

[0010] Furthermore, the housing also includes an exhaust seat disposed on the high-pressure side; the chamber is provided with an air inlet and an exhaust outlet, the air inlet is disposed on the low-pressure side and located at the top of the chamber, and the exhaust outlet is disposed inside the exhaust seat.

[0011] Furthermore, the bearing assembly includes a rear bearing disposed within the exhaust seat; the bearing oil passage includes a rear oil passage extending horizontally along the axial direction from the oil chamber to the high-pressure side and a collection tank communicating with the rear oil passage.

[0012] Furthermore, the liquid collection tank is disposed on the vent seat, and the bearing oil circuit further includes a first oil supply hole and a second oil supply hole disposed on the vent seat, communicating with the liquid collection tank and used to supply oil to the rear bearing.

[0013] Furthermore, the twin-screw compressor also includes a gear located near the low-pressure side, and the oil supply system includes a gear hole that communicates with the upper oil passage and is used to supply oil to the gear.

[0014] Furthermore, the chamber has an exhaust end face and an intake end face located on the high-pressure side and the low-pressure side, respectively; the front part of the oil chamber is close to the lower part of the center line of the intake port, and the rear part of the oil chamber is spaced a certain distance from the exhaust end face; the width of the oil chamber is close to the width of the chamber; the male rotor oil supply hole and the female rotor oil supply hole are arranged directly above the oil chamber.

[0015] Further, the distance between the male rotor oil supply hole or the female rotor oil supply hole and the exhaust end face is defined as L1, and the distance between the exhaust end face and the intake end face is defined as L. The ratio of L1 to L ranges from 30% to 60%. The range of the injection volume ratio of the male rotor oil supply hole and the female rotor oil supply hole is 1.05 to 2.05.

[0016] Furthermore, the twin-screw compressor also includes an oil return system, which includes a front bearing and gear oil return channel located at the bottom of the housing and near the low-pressure side, and the front bearing and gear oil return channel communicates with the chamber; the oil return system also includes a rear bearing oil return channel located in the exhaust seat and communicating with the chamber.

[0017] This application simplifies external piping by integrating the oil supply system within the housing, achieving a high degree of integration and saving installation space. Simultaneously, by setting up rotor and bearing oil circuits for heat exchange and cooling of the rotor and bearing assemblies, the heat dissipation efficiency is high, and it avoids the rotor assembly's high-temperature expansion from rubbing against the housing, thus ensuring high reliability. Attached Figure Description

[0018] Figure 1 This is a perspective view of the twin-screw main unit of this application.

[0019] Figure 2 yes Figure 1 One of the cross-sectional views of the twin-screw main unit shown.

[0020] Figure 3 yes Figure 1 The second sectional view of the twin-screw compressor shown.

[0021] Figure 4 yes Figure 1 The third sectional view of the twin-screw compressor shown.

[0022] Figure 5 yes Figure 1 The fourth sectional view of the twin-screw main unit shown.

[0023] Figure 6 yes Figure 1 The diagram shows a cross-sectional view of the twin-screw compressor at the rear bearing.

[0024] Figure 7 yes Figure 1 The fifth sectional view of the twin-screw main unit shown.

[0025] Explanation of icon numbers

[0026] 10. Housing; 101. Chamber; 1011. Intake chamber; 1012. Compression chamber; 1013. Butterfly inlet; 102. Partition wall; 103. Air inlet; 104. Exhaust port; 11. Low-pressure side; 111. Inlet end face; 12. High-pressure side; 121. Exhaust end face; 20. Rotor assembly; 21. Male rotor; 22. Female rotor; 30. Bearing assembly; 31. Front bearing; 32. Rear bearing; 321. Rear cylindrical roller bearing; 322. Angular contact bearing; 40. Oil supply system; 41. Oil chamber; 410. Main oil inlet; 42. Rotor oil passage; 421, Male rotor oil supply hole; 422, Female rotor oil supply hole; 43, Bearing oil passage; 431, Front oil passage; 432, Upper oil passage; 4321, First throttling orifice; 4322, Second throttling orifice; 433, Rear oil passage; 434, Liquid collection tank; 4341, First oil supply hole; 4342, Second oil supply hole; 44, Gear hole; 50, Exhaust seat; 60, Oil return system; 61, Front bearing and gear oil return channel; 62, Rear bearing oil return channel; 70, Rotor seat; C, Center line; M, Vertical center axis; N, Vertical center axis. Detailed Implementation

[0027] The technical solutions in the embodiments (or "implementations") of this application will be clearly and completely described herein with reference to the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements.

[0028] If the embodiments of this application contain terms relating to directional indications or positional relationships (such as up, down, left, right, front, back, inside, outside, top, bottom, center, vertical, horizontal, longitudinal, transverse, length, width, counterclockwise, clockwise, axial, radial, circumferential, etc.), such terms are only used to explain the relative positional relationships and movements between components in a specific posture (as shown in the attached figures); if the specific posture changes, the directional indications or positional relationships will also change accordingly. Furthermore, the terms "first" and "second" used in the embodiments of this application are only for descriptive convenience and should not be construed as indicating or implying relative importance.

[0029] See Figures 1 to 3 As shown, this application provides a twin-screw compressor, including a housing 10, a rotor assembly 20, a bearing assembly 30, an oil supply system 40, and an oil return system 60. The rotor assembly 20 is disposed within the housing 10. The bearing assemblies 30 are disposed at both ends of the rotor assembly 20. The oil supply system 40 is integrated within the housing 10 and is used to supply oil to the rotor assembly 20 and the bearing assembly 30. The housing 10 includes an exhaust seat 50 and a rotor seat 70 fixed together. The oil return system 60 is used to collect the returned oil from the rotor assembly 20 and the bearing assembly 30.

[0030] The housing 10 contains a chamber 101, which has a low-pressure side 11 and a high-pressure side 12 arranged opposite to each other. The chamber 101 has an air inlet 103 and an air outlet 104. The air inlet 103 is located on the low-pressure side 11 and at the top of the chamber 101, while the air outlet 104 is located within the exhaust seat 50. The chamber 101 has an exhaust end face 121 located on the high-pressure side 12 and an air inlet end face 111 located on the low-pressure side 11. This top-intake and exhaust-out structure of the rotor seat 70 optimizes the airflow path, improves compression efficiency, and simplifies the integration of the oil supply system 40, eliminating the need for additional machining holes and reducing cost.

[0031] Chamber 101 includes an intake chamber 1011, a compression chamber 1012, and a butterfly port 1013. The intake chamber 1011 communicates with the inlet 103 and the compression chamber 1012. The compression chamber 1012 is formed between the rotor base 70 and the rotor assembly 20. The butterfly port 1013 is located on the high-pressure side 12 and communicates with the compression chamber 1012 and the exhaust port 104.

[0032] According to an embodiment of this application, a pneumatic flow channel is formed inside the twin-screw compressor. The pneumatic flow channel adopts an upper intake and bottom exhaust layout. Specifically, the working fluid enters the intake chamber 1011 radially downward from the intake port 103. As the rotation angle of the rotor assembly 20 changes, the medium is pushed into the compression chamber 1012 to begin compression. When the designed internal pressure ratio is reached, the compression chamber 1012 connects with the butterfly port 1013 and begins exhaust. The compressed gas enters the subsequent process through the exhaust port 104.

[0033] See Figure 4 and Figure 5 As shown, the rotor assembly 20 is located within the chamber 101. The rotor assembly 20 includes a male rotor 21 and a female rotor 22 that mesh with each other. The male rotor 21 and the female rotor 22 are arranged symmetrically within the chamber 101 along the length of the housing 10. According to an embodiment of this application, the male rotor 21 has four teeth, and the female rotor 22 has six teeth. The space between the teeth of the male rotor 21 and the female rotor 22 forms a compression chamber 1012.

[0034] The bearing assembly 30 includes a front bearing 31 located at one end of the rotor assembly 20 and near the low-pressure side 11, and a rear bearing 32 located within the exhaust seat 50. There are two front bearings 31, located at the front ends of the male rotor 21 and the female rotor 22, respectively. The front bearings 31 are cylindrical roller bearings, which bear the radial force of the gas within the pneumatic flow channel.

[0035] The rear bearing 32 includes a rear cylindrical roller bearing 321 and an angular contact bearing 322 that bears the axial force of the gas. The angular contact bearing 322 is located outside the rear cylindrical roller bearing 321. There are two rear cylindrical roller bearings 321, respectively located at the rear ends of the male rotor 21 and the female rotor 22. There are three angular contact bearings 322, two located at the rear ends of the male rotor 21 and the remaining one located at the rear end of the female rotor 22. In the embodiment of this application, the front end is the end of the rotor assembly 20 near the intake end face 111, and the rear end is the end of the rotor assembly 20 near the exhaust end face 121.

[0036] Please also see Figure 6 and Figure 7 As shown, the oil supply system 40 includes an oil chamber 41, a rotor oil passage 42, and a bearing oil passage 43. The oil chamber 41 is located at the bottom of the housing 10 and below the chamber 101. The rotor oil passage 42 communicates with the oil chamber 41 and is used to supply oil to the rotor assembly 20. The bearing oil passage 43 communicates with the oil chamber 41 and is used to supply oil to the bearing assembly 30.

[0037] The oil chamber 41 is located near the high-pressure side 12. The front part of the oil chamber 41 is located below the center line of the air inlet 103, and the rear part of the oil chamber 41 is spaced a certain distance from the exhaust end face 121. The length of the oil chamber 41 is close to the tooth pitch of the male rotor 21 or female rotor 22. The width of the oil chamber 41 is close to the width of the chamber 101. The oil chamber 41 includes a main oil inlet 410, which connects the oil chamber 41 and the oil supply device (not shown). The lubricating oil in the oil supply device enters the oil chamber 41 through the oil inlet 410.

[0038] A partition wall 102 is provided between the oil cavity 41 and the chamber 101, which enhances the bottom strength of the rotor seat 70. The rotor oil passage 42 includes a male rotor oil supply hole 421 and a female rotor oil supply hole 422 that penetrate the partition wall 102. The male rotor oil supply hole 421 is oriented towards the male rotor 21 for injecting oil and exchanging heat for the male rotor 21, and the female rotor oil supply hole 422 is oriented towards the female rotor 22 for injecting oil and exchanging heat for the female rotor 22.

[0039] According to the embodiments of this application, the male rotor oil supply hole 421 and the female rotor oil supply hole 422 are arranged directly above the oil cavity 41. The male rotor 21 has points A1 and A2 along the circumferential direction, with point A1 near the end of the oil cavity 41 and point A2 near the middle of the oil cavity 41. The female rotor 22 has points B1 and B2 along the circumferential direction, with point B1 near the main oil inlet 410 and point B2 near the middle of the oil cavity 41. The male rotor oil supply hole 421 is located outside the vertical central axis M of the male rotor 21, and the female rotor oil supply hole 422 is located outside the vertical central axis N of the female rotor 22.

[0040] In some embodiments, the positions of the male rotor oil supply port 421 and the female rotor oil supply port 422 are adjustable. For example, the male rotor oil supply port 421 can be positioned between points A1 and A2, and the female rotor oil supply port 422 can be positioned between points B1 and B2. When the twin-screw compressor is used in a low-pressure airport or vacuum pump, the male rotor oil supply port 421 and the female rotor oil supply port 422 can be offset towards points A1 and B1 respectively to achieve low-pressure oil supply, eliminating the need for an additional oil pump.

[0041] Points C1 and C2 are provided on the partition wall 102 along the length of the oil cavity 41. Point C1 is close to the intake end face 111, and point C2 is close to the exhaust end face 121. Along the length of the oil cavity 41, points C1 and C2 are respectively close to the two ends of the oil cavity 41. The positions of the male rotor oil supply hole 421 and the female rotor oil supply hole 422 are adjustable between points C1 and C2.

[0042] The distance between the male rotor oil supply port 421 or the female rotor oil supply port 422 and the exhaust end face 121 is defined as L1, and the distance between the exhaust end face 121 and the intake end face 111 is defined as L. The ratio of L1 to L ranges from 30% to 60%. The volume ratio of the male rotor oil supply port 421 and the female rotor oil supply port 422 ranges from 1.05 to 2.05. In the embodiments of this application, the volume ratio is the ratio of the maximum volume that the inter-tooth volume can reach to the volume ratio when the inter-tooth volume is connected to the exhaust port 104, and the fuel injection volume ratio is the volume ratio corresponding to the inter-tooth volume when it is connected to the oil supply port.

[0043] In some embodiments, the position of the male rotor oil supply hole 421 and the female rotor oil supply hole 422 can be flexibly adjusted in the length and width directions of the oil cavity 41, and their size and number can also be adjusted to achieve more uniform heat exchange in the rotor assembly 20, thereby improving performance and reliability.

[0044] The bearing oil passage 43 includes a front oil passage 431, an upper oil passage 432, a rear oil passage 433, and a collection groove 434. The front oil passage 431 extends horizontally along the axial direction from the oil chamber 41 toward the low-pressure side 11 and extends to the outside of the chamber 101. The upper oil passage 432 is located at the end of the housing 10 and extends upward from the front oil passage 431. The rear oil passage 433 extends horizontally along the axial direction from the oil chamber 41 toward the high-pressure side 12 to the exhaust end face 121. The collection groove 434 is disposed on the exhaust seat 50 and communicates with the rear oil passage 433, and the collection groove 434 extends along the width direction of the housing 10.

[0045] The bearing oil passage 43 also includes a first throttling orifice 4321, a second throttling orifice 4322, a first oil supply orifice 4341, and a second oil supply orifice 4342. The first throttling orifice 4321 and the second throttling orifice 4322 are connected to the upper oil passage 432 and face the front bearing 31, for spraying oil to the front bearing 31 for heat dissipation. The first oil supply orifice 4341 and the second oil supply orifice 4342 are connected to the liquid collection tank 434 and face the rear bearing 32, for spraying oil to the rear bearing 32 for heat dissipation.

[0046] The twin-screw compressor also includes a gear (not shown) located near the low-pressure side 11. The oil supply system 40 also includes a gear hole 44 that communicates with the upper oil passage 432 and is used to supply oil to the gear. The exhaust seat 50 is located on the high-pressure side 12. One side of the exhaust seat 50 is in contact with the exhaust end face 121, with a friendly interface and no external oil passage. The number of interfaces between the exhaust seat 50 and the rotor seat 70 is reduced, thus reducing installation time.

[0047] The oil return system 60 includes a front bearing and gear oil return passage 61 located at the bottom of the housing 10 and near the low-pressure side 11, which communicates with the chamber 101. The oil return system 60 also includes a rear bearing oil return passage 62 located within the exhaust seat 50 and communicating with the chamber 101.

[0048] The flow process of lubricating oil in the oil supply system 40 of this application is as follows: First, the lubricating oil, after being cooled and filtered, flows out from the oil supply device and enters the oil chamber 41 through the main oil inlet 410. In the oil chamber 41, the lubricating oil preferentially passes through the radial direction of the male rotor oil supply hole 421 and the female rotor oil supply hole 422 to spray oil to cool the male rotor 21 and the female rotor 22 respectively.

[0049] Lubricating oil flows along the front oil passage 431 within the oil chamber 41, and then flows into the upper oil passage 432. Within the upper oil passage 432, the lubricating oil first supplies oil to the gears through the gear hole 44. It then continues to flow upwards, achieving oil spray cooling of the front bearing 31 through the first throttling hole 4321 and the second throttling hole 4322, which are connected to the upper oil passage 432.

[0050] Simultaneously, lubricating oil flows along the rear oil passage 433 towards the exhaust end face 121 within the oil chamber 41, and then flows upward from the exhaust end face 121 to the collection tank 434. The rear bearing 32 is cooled by spraying oil through the first oil supply hole 4341 and the second oil supply hole 4342. The oil supply system 40 is mainly arranged at the bottom of the housing 10, enhancing the rigidity of the bottom, reducing thermal deformation caused by temperature, and effectively improving the heat dissipation of the housing 10 and rotor assembly 20, thereby reducing the risk of collision caused by expansion of the housing 10 or rotor assembly 20 due to localized high temperatures.

[0051] The oil return process of the oil return system 60 is as follows: the lubricating oil of the front bearing 31 is thrown onto the housing 10, and the lubricating oil returns to the bottom of the housing 10 due to gravity. At the same time, the return oil from the gears and the return oil from the front bearing 31 gather together at the bottom of the housing 10, and is connected to the chamber 101 through the front bearing and gear return oil channel 61, improving the lubrication condition of the front end of the rotor assembly 20. The return oil from the rear bearing 32 is connected to the chamber 101 through the rear bearing return oil channel 62. All the return oil from the front bearing 31, rear bearing 32, gears and rotor assembly 20 entering the chamber 101 flows towards the exhaust end face 121 with the compression of the gas, and enters the subsequent cylinder for oil-gas separation through the butterfly port 1013 and exhaust seat 50.

[0052] The twin-screw compressor of this application can be used in air compressors, low-pressure compressors, or vacuum pumps, etc.

[0053] This application simplifies external piping by integrating the oil supply system 40 into the housing 10, achieving a high degree of integration and saving installation space. Simultaneously, by setting up rotor oil passages 42, bearing oil passages 43, and gear oil passages for heat exchange and cooling of the rotor assembly 20, bearing assembly 30, and gears, the heat dissipation efficiency is high, and high-temperature cylinder rubbing caused by the expansion of the rotor assembly 20 and bearing assembly 30 is avoided, resulting in high reliability.

[0054] It should be noted that the technical solutions or features described in the above embodiments can be combined or supplemented with each other without conflict. The scope of protection of this application is not limited to the precise structures described in the above embodiments and shown in the accompanying drawings; all modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A twin-screw compressor, characterized in that, include: The system comprises a housing, a rotor assembly, a bearing assembly, and an oil supply system. The housing has a chamber, the rotor assembly is located within the chamber, and the bearing assembly is disposed at both ends of the rotor assembly. The chamber has a low-pressure side and a high-pressure side disposed opposite to each other. The oil supply system is integrated within the housing and includes an oil chamber located near the high-pressure side and rotor oil passages and bearing oil passages respectively communicating with the oil chamber and used to supply oil to the rotor assembly and the bearing assembly.

2. The twin-screw compressor according to claim 1, characterized in that, The oil chamber is located at the bottom of the housing and below the cavity; a partition wall is provided between the oil chamber and the cavity, and the rotor oil passage includes a male rotor oil supply hole and a female rotor oil supply hole that penetrate the partition wall.

3. The twin-screw compressor according to claim 2, characterized in that, The bearing assembly includes a front bearing located at one end of the rotor assembly and close to the low-pressure side; the bearing oil passage includes a front oil passage extending horizontally along the axial direction from the oil chamber to the low-pressure side and an upper oil passage extending upward from the front oil passage, the upper oil passage being located at the end of the housing.

4. The twin-screw compressor according to claim 3, characterized in that, The bearing oil circuit also includes a first throttling orifice and a second throttling orifice that are connected to the upper oil passage for spraying oil onto the front bearing.

5. The twin-screw compressor according to claim 2, characterized in that, The housing also includes an exhaust seat disposed on the high-pressure side; the chamber is provided with an air inlet and an exhaust outlet, the air inlet is disposed on the low-pressure side and located at the top of the chamber, and the exhaust outlet is disposed inside the exhaust seat.

6. The twin-screw compressor according to claim 5, characterized in that, The bearing assembly includes a rear bearing disposed within the exhaust seat; the bearing oil passage includes a rear oil passage extending horizontally along the axial direction from the oil chamber to the high-pressure side and a collection tank communicating with the rear oil passage.

7. The twin-screw compressor according to claim 6, characterized in that, The liquid collection tank is disposed on the vent seat, and the bearing oil circuit further includes a first oil supply hole and a second oil supply hole disposed on the vent seat, communicating with the liquid collection tank and used to supply oil to the rear bearing.

8. The twin-screw compressor according to claim 3, characterized in that, The twin-screw compressor also includes a gear located near the low-pressure side, and the oil supply system includes a gear hole that communicates with the upper oil passage and is used to supply oil to the gear.

9. The twin-screw compressor according to claim 5, characterized in that, The chamber has an exhaust end face and an intake end face located on the high-pressure side and the low-pressure side, respectively; the front part of the oil chamber is close to the lower part of the center line of the intake port, and the rear part of the oil chamber is spaced a certain distance from the exhaust end face; the width of the oil chamber is close to the width of the chamber; the male rotor oil supply hole and the female rotor oil supply hole are arranged directly above the oil chamber.

10. The twin-screw compressor according to claim 9, characterized in that, The distance between the male rotor oil supply hole or the female rotor oil supply hole and the exhaust end face is defined as L1, and the distance between the exhaust end face and the intake end face is defined as L. The ratio of L1 to L ranges from 30% to 60%. The range of the injection volume ratio of the male rotor oil supply hole and the female rotor oil supply hole is 1.05 to 2.

05.

11. The twin-screw compressor according to claim 5, characterized in that, The twin-screw compressor also includes an oil return system, which includes a front bearing and gear oil return channel located at the bottom of the housing and near the low-pressure side, and the front bearing and gear oil return channel communicates with the chamber; the oil return system also includes a rear bearing oil return channel located in the exhaust seat and communicating with the chamber.

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