Axial force balance structure and two-stage screw compressor using the same
By setting oil holes and oil passages on both sides of the rotor and an axial force balancing structure with a balance piston, the axial force problem of coaxial direct drive and single-unit two-stage screw compressors is solved, achieving effective balance of rotor axial force and compressor compactness, and reducing power consumption.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GREE ELECTRIC APPLIANCE INC OF ZHUHAI
- Filing Date
- 2022-12-05
- Publication Date
- 2026-06-23
AI Technical Summary
Existing technologies cannot simultaneously meet the axial force balance requirements of coaxial direct drive and single-unit two-stage screw compressors, resulting in limitations on bearing size and increased power consumption.
An axial force balancing structure is adopted, which achieves axial force balancing by setting exhaust side oil holes and intake side oil holes on both sides of the rotor and setting oil passages inside the rotor, combined with a balancing piston.
Reduce the axial force on the rotor, broaden the high-pressure application range of the compressor, reduce the number of bearings, reduce oil pump power consumption, and improve working efficiency.
Smart Images
Figure CN116066366B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of compressor technology, and more particularly to an axial force balancing structure and a two-stage screw compressor using the same structure. Background Technology
[0002] Screw compressors are widely used in many fields due to their simple structure, high reliability, and ability to transport mixed liquids. To expand the applicable pressure range of twin-screw compressors, single-unit two-stage screw compressors and the latest coaxial direct-drive two-stage screw compressors have been proposed (coaxial direct drive means that the two-stage screw rotors share a single main shaft, achieving linkage through the main shaft; there are no cylindrical roller bearings to withstand radial forces or angular contact ball bearings to withstand axial forces between the two stages). However, the conventional structures of both are subject to axial forces from the high-pressure stage to the low-pressure stage. Larger axial forces require larger bearings, and the bearing size is limited by the rotor center distance.
[0003] An existing invention patent with authorization announcement number CN112746958B discloses a twin-screw compressor-expander integrated machine for fuel cells. High-pressure ports are located near the center of the machine body, while low-pressure ports are located at both ends. The compressor's female rotor and the expander's male rotor are coaxially connected and fixed. The compressor's male rotor and the expander's female rotor are also connected via a rotor shaft, but the compressor's male rotor is fixed to the rotor shaft, while the expander's female rotor has a clearance fit with the rotor shaft, allowing for mutual sliding. The low-pressure side of the expander is connected to a motor. This technical solution utilizes the force balancing effect between the compressor rotor and the expander rotor, effectively reducing the bearing load and power loss, and solving the problem of low power recovery under low load conditions. However, although this technical solution can balance axial forces, it is only applicable to integrated compressor-expander machines.
[0004] Another invention patent, CN110206729B, discloses a self-balancing axial force four-screw mechanical device with gas thrust bearings. This device employs four symmetrically arranged screws with opposite thread directions. Screws within the same housing mesh in pairs, while screws on the same shaft in different housings have opposite thread directions. This ensures that during normal operation, the axial forces on the two rotors are essentially canceled out, achieving self-balancing of the axial forces. Each shaft is equipped with two symmetrical thrust bearings, allowing the remaining axial force on each shaft to be borne by these two bearings, handling smaller, incompletely self-balancing axial forces. However, this technical solution uses the same two pairs of rotors to balance the axial force and is not suitable for coaxial direct-drive or single-unit two-stage screw compressors.
[0005] Furthermore, utility model patent CN205937114U discloses a screw compressor with symmetrically arranged male rotors, comprising: two male rotors and two female rotors, the two male rotors being coaxially and fixedly connected, each having an intake end and an exhaust end, the intake ends of the two male rotors being interconnected or their exhaust ends being interconnected, so that the forces generated on the two male rotors in the axial direction during the operation of the screw compressor cancel each other out; and two female rotors, each correspondingly meshing with one of the two male rotors. This technical solution can only balance the axial force of the male rotors, but cannot balance the axial force of the female rotors.
[0006] As can be seen from the above, how to simultaneously meet the axial force balance requirements of coaxial direct drive and single-unit two-stage screw compressors is a technical problem that urgently needs to be solved. Summary of the Invention
[0007] This invention provides an axial force balancing structure and a two-stage screw compressor using this structure to solve the problem of axial force balancing, thereby meeting the usage requirements of both coaxial direct drive and single-unit two-stage screw compressors.
[0008] The present invention provides an axial force balancing structure, including an exhaust-side bearing housing, a body, and a rotor. The exhaust-side bearing housing is provided with an oil supply hole, and the body is provided with an air intake port. An exhaust-side oil hole and an air intake oil hole are respectively provided on both sides of the rotor along its axial direction. The exhaust-side oil hole and the air intake oil hole are respectively connected to the oil supply hole and the air intake port. Furthermore, an internal oil passage is provided inside the rotor to connect the exhaust-side oil hole and the air intake oil hole.
[0009] In one embodiment, the rotor includes a male rotor and a female rotor; the exhaust side oil port includes:
[0010] An exhaust side oil port for the male rotor is provided on the male rotor and communicates with the oil supply port; and
[0011] An oil hole on the exhaust side of the female rotor is provided on the female rotor and is connected to the oil supply hole.
[0012] In one embodiment, the oil supply port includes:
[0013] The male-side oil supply port is connected to the male rotor exhaust-side oil port; and
[0014] The oil supply hole on the female side is connected to the oil outlet hole on the female rotor side.
[0015] In one embodiment, the internal oil passage includes:
[0016] An internal oil passage for the male rotor is located inside the male rotor and communicates with the exhaust side oil port of the male rotor; and
[0017] An internal oil passage for the female rotor is located inside the female rotor and is connected to the oil hole on the exhaust side of the female rotor.
[0018] In one embodiment, the intake-side oil port includes:
[0019] An oil port on the intake side of the male rotor is provided on the male rotor and connects to the internal oil passage of the male rotor; and
[0020] The female rotor has an oil hole on its intake side, which is located on the female rotor and connects to the internal oil passage of the female rotor.
[0021] In one embodiment, both the male rotor intake side oil hole and the female rotor intake side oil hole are connected to the intake port.
[0022] In one embodiment, a balance piston is fitted onto the rotor, and the side of the balance piston near the machine body is connected to the inter-tooth volume of the male and female rotors of the radial exhaust port.
[0023] In one embodiment, the balancing piston includes:
[0024] A male rotor balance piston is sleeved on the male rotor and located on the side of the male rotor exhaust-side bearing near the machine body; and
[0025] The female rotor balance piston is sleeved on the female rotor and located on the side of the female rotor exhaust side bearing close to the machine body.
[0026] In one embodiment, both the male rotor balance piston and the female rotor balance piston are provided with a sealing portion for sealing the gap between them and the exhaust-side bearing housing.
[0027] Another aspect of the present invention provides a two-stage screw compressor, including the above-described axial force balancing structure.
[0028] In summary, compared with the prior art, the beneficial technical effects of the present invention are as follows: by using this axial force balancing structure, the axial force on the rotor is reduced, which not only broadens the high-pressure application range of the compressor, enabling it to simultaneously meet the application requirements of coaxial direct drive and single-unit two-stage screw compressors, but also reduces the number of axial bearings, which helps to make the compressor structure more compact and saves compressor costs. In addition, it also reduces the power consumption of the compressor oil pump and improves the compressor's working efficiency. Attached Figure Description
[0029] The invention will now be described in more detail with reference to embodiments and the accompanying drawings.
[0030] Figure 1 This is an overall schematic diagram of the axial force balance structure in one embodiment of the present invention;
[0031] Figure 2 This is a schematic diagram of the male rotor balance piston in one embodiment of the present invention;
[0032] Figure 3 This is a schematic diagram of the force analysis of the rotor in one embodiment of the present invention.
[0033] Reference numerals: 1. Exhaust side bearing housing; 2. Machine body; 3. Male rotor; 4. Female rotor; 5. Male rotor exhaust side bearing; 6. Female rotor exhaust side bearing; 7. Male rotor intake side bearing; 8. Female rotor intake side bearing; 9. Male side oil supply hole; 10. Female side oil supply hole; 11. Male rotor exhaust side oil hole; 12. Female rotor exhaust side oil hole; 13. Male rotor internal oil passage; 14. Female rotor internal oil passage; 15. Male rotor balance piston; 16. Female rotor balance piston; 17. Sealing part; 18. Male rotor intake side oil hole; 19. Female rotor intake side oil hole. Detailed Implementation
[0034] The present invention will now be described clearly and completely with reference to the accompanying drawings.
[0035] See appendix Figure 1 An axial force balancing structure is mainly used for axial force balancing of the rotor inside a compressor. It includes an exhaust-side bearing housing 1, a housing 2, and a rotor disposed between the exhaust-side bearing housing 1 and the housing 2. The rotor has bearings at both ends that form rotational engagements with the exhaust-side bearing housing 1 and the housing 2, respectively.
[0036] The exhaust-side bearing housing 1 is provided with an oil supply hole, and the machine body 2 is provided with an air intake port (not shown in the figure, but can be consistent with the air intake port on a conventional compressor); an exhaust-side oil hole and an air intake-side oil hole are provided on both sides of the rotor axis, respectively, and the exhaust-side oil hole and the air intake-side oil hole are respectively connected to the above-mentioned oil supply hole and air intake port, and an internal oil passage for connecting the exhaust-side oil hole and the air intake-side oil hole is also provided inside the rotor.
[0037] In actual operation, lubricating oil is injected through the oil supply port. A portion of this oil is used to lubricate the exhaust-side bearing and flows out through the return oil passage. The other portion enters the exhaust-side oil port and then flows through the aforementioned internal oil passage to the intake-side bearing. It is then compressed along with the intake airflow into the rotor and finally discharged from the compressor's exhaust side with the gas. It should be noted that the internal return oil passage of the compressor is prior art and not the focus of this invention, and will not be elaborated upon here.
[0038] See appendix Figure 1In this embodiment, the rotor includes a male rotor 3 and a female rotor 4. One end of the male rotor 3 is rotatably connected to the exhaust-side bearing seat 1 via a male rotor exhaust-side bearing 5, and the other end is rotatably connected to the machine body 2 via a female rotor intake-side bearing 8. Similarly, both ends of the female rotor 4 are respectively provided with a female rotor exhaust-side bearing 6 and a female rotor intake-side bearing 8 for mounting the female rotor 4 and enabling its flexible rotation.
[0039] Two oil supply holes can be provided, namely a male side oil supply hole 9 and a female side oil supply hole 10. Correspondingly, two exhaust side oil holes are also provided, including a male rotor exhaust side oil hole 11 provided on the male rotor 3 and a female rotor exhaust side oil hole 12 provided on the female rotor 4. The male rotor exhaust side oil hole 11 is connected to the male side oil supply hole 9, and the female rotor exhaust side oil hole 12 is connected to the female side oil supply hole 10. In this way, part of the lubricating oil is injected through the male side oil supply hole 9 and enters the male rotor exhaust side oil hole 11; the other part is injected through the female side oil supply hole 10 and enters the female rotor exhaust side oil hole 12.
[0040] In another embodiment, only one oil supply hole may be provided, so that the lubricating oil is split at the oil supply hole and then flows into the male rotor exhaust side oil hole 11 and the female rotor exhaust side oil hole 12 respectively.
[0041] Meanwhile, the aforementioned internal oil passages include an internal oil passage 13 for the male rotor 3 and an internal oil passage 14 for the female rotor 4. Correspondingly, the aforementioned suction-side oil holes include a male rotor suction-side oil hole 18 for the male rotor 3 and a female rotor suction-side oil hole 19 for the female rotor 4.
[0042] In this embodiment, the internal oil passage 13 of the male rotor extends axially along the male rotor 3, with its two ends connected to the aforementioned male rotor exhaust side oil hole 11 and male rotor intake side oil hole 18, respectively. Thus, after the lubricating oil enters the male rotor exhaust side oil hole 11 through the male side oil supply hole 9, it flows along the internal oil passage 13 to the male rotor intake side oil hole 18. Similarly, the internal oil passage 14 of the female rotor extends axially along the female rotor 4, with its two ends connected to the female rotor exhaust side oil hole 12 and female rotor intake side oil hole 19, respectively. This allows the lubricating oil, after being injected through the female side oil supply hole 10, to flow through the female rotor exhaust side oil hole 12 and the internal oil passage 14 to the female rotor intake side oil hole 19.
[0043] In another embodiment, the internal oil passage 13 of the male rotor and the internal oil passage 14 of the female rotor can also be provided on the compressor body. It is only necessary to ensure that the lubricating oil can flow to the oil hole 18 on the suction side of the male rotor and the oil hole 19 on the suction side of the female rotor, that is, it is only necessary to ensure that the lubricating oil can flow to the suction port position.
[0044] In this embodiment, unlike conventional compressors, neither the male rotor suction side oil hole 18 nor the female rotor suction side oil hole 19 has a sealing structure, allowing both to be connected to the suction port on the housing 2. Thus, the lubricating oil flowing to the male rotor suction side oil hole 18 and the female rotor suction side oil hole 19 will leak directly into the suction port. As the compressor operates and draws in air, the lubricating oil will enter the rotor along with the suction airflow and be compressed, ultimately being discharged from the compressor's exhaust side along with the suction airflow.
[0045] See appendix Figure 1-2 To further achieve axial force balance, a balancing piston is also provided on the rotor. Specifically, the balancing piston includes a male rotor balancing piston 15 and a female rotor balancing piston 16. The male rotor balancing piston 15 is fitted onto the male rotor 3 and located on the side of the male rotor exhaust-side bearing 5 near the machine body 2, and the side of the male rotor balancing piston 15 near the machine body 2 is connected to the inter-tooth volume of the male and female rotors at the radial exhaust port (not shown in the figure). Similarly, the female rotor balancing piston 16 is fitted onto the female rotor 4 and located on the side of the female rotor exhaust-side bearing 6 near the machine body 2, and the side of the female rotor balancing piston 16 near the machine body 2 is also connected to the aforementioned inter-tooth volume of the male and female rotors.
[0046] In this embodiment, taking the male rotor balance piston 15 as an example, since the left side of the male rotor balance piston 15 is connected to the chamber where the male rotor exhaust side bearing 5 is located, and the right side is connected to the inter-tooth volume of the male and female rotors, the pressure on the left side of the male rotor balance piston 15 is equivalent to the oil pressure at the male rotor exhaust side bearing 5, while the pressure on its right side is equivalent to the air pressure in the aforementioned inter-tooth volume of the male and female rotors, i.e., the exhaust pressure. Similarly, the pressures on the left and right sides of the female rotor balance piston 16 are also oil pressure and exhaust pressure, respectively.
[0047] Meanwhile, to ensure that the pressures on both sides of the male rotor balance piston 15 and the female rotor balance piston 16 are oil pressure and exhaust pressure respectively, a sealing part 17 is provided on both the male rotor balance piston 15 and the female rotor balance piston 16.
[0048] In this embodiment, the sealing portions 17 on the male rotor balance piston 15 and the female rotor balance piston 16 can adopt the same structure. Taking the male rotor balance piston 15 as an example, the sealing portion 17 can adopt a comb-tooth sealing structure directly formed on the periphery of the male rotor balance piston 15, and the number of comb teeth is at least 3 to ensure the sealing effect.
[0049] In another embodiment, the sealing part 17 may also be an O-ring that is separately provided from the male rotor balance piston 15 and the female rotor balance piston 16. That is, the sealing is achieved by providing an O-ring in the gap between the male rotor balance piston 15, the female rotor balance piston 16 and the inner wall of the exhaust side bearing seat 1.
[0050] In this way, the sealing part 17 can effectively seal the gap between the inner wall of the exhaust side bearing housing 1 and the male rotor balance piston 15 and the female rotor balance piston 16, preventing the gas on the right side of the male rotor balance piston 15 and the female rotor balance piston 16 from leaking to the corresponding bearing position.
[0051] To verify the balancing effect of the axial force on the rotor in this embodiment, a force analysis was performed on the axial force borne by the rotor during operation.
[0052] like Figure 3 As shown, in this embodiment, the rotor (including the male rotor 3 and the female rotor 4) is subjected to a total of 6 axial forces; F1 is the leftward thrust of the high-pressure gas (exhaust pressure) on the right side of the balance piston (male rotor balance piston 15 and female rotor balance piston 16); F2 is the rightward thrust of the low-pressure oil at the exhaust-side bearing (including the male rotor exhaust-side bearing 5 and the female rotor exhaust-side bearing 6); F3 is the rightward thrust of the high-pressure gas on the rotor during the exhaust process; F4 is the leftward thrust of the gas in the inter-tooth volume of the male and female rotors on the male rotor 3; F5 is the rightward thrust of the gas in the inter-tooth volume of the male and female rotors on the female rotor 4. F4 and F5 are similar in magnitude but opposite in direction, and can be considered to cancel each other out; F6 is the leftward thrust of the intake gas on the rotor. Therefore, the axial force on the rotor in this model is F2 + F3 - F1 - F6.
[0053] Similarly, in a conventional compressor without a balancing piston, the axial force on the rotor is F2+F3-F6, meaning that compared to a conventional compressor without a balancing piston, the axial force on the rotor in this embodiment is reduced by F1.
[0054] In a conventional compressor equipped with a balance piston, the axial force on the rotor is F2 + F3 - F1 - F6. However, even with a balance piston, the lubricating oil in the exhaust-side bearing of a conventional compressor will return to the initial compression stage of the male rotor 3, meaning the oil pressure is at least greater than the initial compression pressure of the male rotor 3. This results in a larger F2. Therefore, compared to a conventional compressor equipped with a balance piston, the axial force balancing structure provided in this embodiment can also reduce the axial force on the rotor.
[0055] Therefore, the axial force balancing structure provided in this embodiment not only reduces the oil supply pressure but also balances most of the axial force, and reduces the power consumption of the oil pump. Furthermore, since the lubricating oil enters the inter-tooth volume of the male and female rotors with the intake airflow in this embodiment, the low-pressure oil also has a certain cooling effect on the rotor as it passes through the rotor's interior.
[0056] The present invention also provides a two-stage screw compressor, which includes the above-described axial force balancing structure. Specifically, the two-stage screw compressor can be a single-unit two-stage screw compressor or a coaxial direct-drive two-stage screw compressor.
[0057] In the description of this invention, it should be understood that the terms "upper", "lower", "bottom", "top", "front", "rear", "inner", "outer", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.
[0058] Although the invention has been described with reference to preferred embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the invention. In particular, the technical features mentioned in the various embodiments can be combined in any manner as long as there is no structural conflict. The invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.
Claims
1. A two-stage screw compressor, comprising an exhaust-side bearing housing, a housing, and a rotor, characterized in that, An oil supply hole is provided on the exhaust side bearing seat, and an air intake port is provided on the machine body; an exhaust side oil hole and an air intake side oil hole are respectively provided on both sides of the rotor axial direction, the exhaust side oil hole and the air intake side oil hole are respectively connected to the oil supply hole and the air intake port, and an internal oil passage for connecting the exhaust side oil hole and the air intake side oil hole is also provided inside the rotor. The rotor includes a male rotor and a female rotor; The exhaust side oil hole includes: An exhaust side oil port for the male rotor is provided on the male rotor and communicates with the oil supply port; and An oil outlet on the female rotor is provided on the female rotor and communicates with the oil supply hole; The oil supply port includes: The male-side oil supply port is connected to the male rotor exhaust-side oil port; and The oil supply hole on the female side is connected to the oil outlet hole on the female rotor side. The internal oil passage includes: An internal oil passage for the male rotor is located inside the male rotor and communicates with the exhaust side oil port of the male rotor; and An internal oil passage for the female rotor is located inside the female rotor and is connected to the exhaust side oil hole of the female rotor. The intake-side oil port includes: An oil port on the intake side of the male rotor is provided on the male rotor and connects to the internal oil passage of the male rotor; and An oil hole on the intake side of the female rotor is provided on the female rotor and is connected to the internal oil passage of the female rotor; The oil hole on the intake side of the male rotor is connected to the intake side bearing of the male rotor. The exhaust side oil hole of the male rotor is radially opened on the male rotor, and its two ends are respectively connected to the male side oil supply hole and the internal oil passage of the male rotor; The oil hole on the intake side of the male rotor is radially opened on the male rotor, and its two ends are respectively connected to the internal oil passage of the male rotor and the intake side bearing of the male rotor. The exhaust side oil hole of the female rotor is radially opened on the female rotor, and its two ends are respectively connected to the female side oil supply hole and the internal oil passage of the female rotor.
2. The two-stage screw compressor according to claim 1, characterized in that, Both the oil hole on the intake side of the male rotor and the oil hole on the intake side of the female rotor are connected to the intake port.
3. The two-stage screw compressor according to claim 1, characterized in that, A balance piston is fitted on the rotor, and the side of the balance piston near the machine body is connected to the inter-tooth volume of the male and female rotors of the radial exhaust port.
4. The two-stage screw compressor according to claim 3, characterized in that, The balance piston includes: A male rotor balance piston is sleeved on the male rotor and located on the side of the male rotor exhaust-side bearing near the machine body; and The female rotor balance piston is sleeved on the female rotor and located on the side of the female rotor exhaust side bearing close to the machine body.
5. The two-stage screw compressor according to claim 4, characterized in that, Both the male rotor balance piston and the female rotor balance piston are provided with sealing parts for sealing the gap between them and the exhaust side bearing seat.