Elastically supported foil hydrodynamic gas bearing with inherent structural pre-wedge space

Abstract

The present invention discloses an elastic support foil dynamic pressure gas bearing with an inherent structural pre-wedge space, comprising a bearing and a rotating shaft located in the bearing; an elastic support element is arranged on the inner side of the bearing, a top flat foil is arranged between the elastic support element and the rotating shaft, a smooth shaft section is arranged in the axial middle area of ​​the rotating shaft surface, a row of inclined grooves are arranged on the rotating shaft surface and on both sides of the smooth shaft section, and the inner side of the top flat foil surrounds and wraps the rotating shaft and forms a pre-gap between the top flat foil and the rotating shaft, and at the same time, one end of the elastic support element and the top flat foil is fixed at the same position of the bearing and the other end is free; the present invention has the advantage that a dynamic pressure gas film can be formed at a relatively low rotation speed and small foil deformation, the rotating shaft and the bearing are in uniform contact during the start and stop stages, the contact friction time and wear between the rotating shaft and the bearing are reduced, and the operation stability and reliability of the system are improved.

Description

Technical Field

[0001] The invention relates to an elastically supported foil dynamic pressure gas bearing with an inherent structural pre-wedge-shaped space. Background Art

[0002] Gas bearings are non-contact sliding bearings that use viscous gas as a lubricant. According to the different mechanisms for generating air film pressure, gas bearings can be divided into static pressure gas bearings and dynamic pressure gas bearings. Static pressure gas bearings use an external gas source to provide high-pressure gas, which requires an additional gas supply system, increasing the complexity of the overall system. At the same time, the gas supply system compresses and generates high-pressure gas, which reduces the economy of the system and limits the application scope of static pressure gas bearings. Dynamic pressure gas bearings use the air film pressure generated by the viscous gas in the wedge-shaped gap of the bearing when the shaft moves to support the load. Its biggest feature is that it does not require an additional gas supply system and has a simple structure, which expands the application field of gas bearings, especially in aerospace fields such as turbochargers, aviation gas turbines, and space turbine expanders.

[0003] According to whether the bearing surface is deformed, hydrodynamic gas bearings can be divided into rigid surface gas bearings and flexible surface gas bearings. The main disadvantage of rigid surface gas bearings is that they have poor stability when running at high speeds, and because the air film gap of the bearing is small, the processing accuracy and assembly method of the bearing and the shaft are required to be high. Flexible surface gas bearings, namely foil gas bearings, generally use metal foil as the bearing support surface, and their flexible surface is conducive to the formation of the air film gap. When the shaft load changes, the flexible surface gas bearing will undergo adaptive deformation to adjust the air film gap, establish an air film thickness that matches the load, and make the bearing have better high-speed stability. At the same time, this characteristic of the flexible surface gas bearing causes the shaft and the bearing housing to have certain thermal deformation, mechanical deformation and misalignment, which reduces the processing accuracy and assembly accuracy of the bearing and the shaft. Therefore, flexible surface gas bearings are widely used in high-speed rotating machinery.

[0004] For foil dynamic pressure gas bearings, during the shaft startup phase, since the bearing clearance has not yet established an effective dynamic pressure gas film, the shaft surface and the top flat foil surface of the bearing will inevitably come into contact and wear, which will reduce the service life of the shaft and the bearing. At the same time, the worn shaft surface and the top flat foil surface of the bearing are not conducive to the establishment and stability of the dynamic pressure gas film, resulting in an increase in the shaft floating time and a decrease in the stability and reliability of the bearing. Summary of the invention

[0005] The purpose of the present invention is to provide an elastically supported foil dynamic pressure gas bearing with an inherent structural pre-wedge space, which can form a dynamic pressure gas film at a relatively low rotation speed and small foil deformation, make the contact between the rotating shaft and the bearing uniform during the start and stop stages, reduce the contact friction time and wear between the rotating shaft and the bearing, and improve the operating stability and reliability of the system. At the same time, it also has good stiffness and damping characteristics, can be applied to a variety of load conditions, and effectively suppress the vortex of the rotating shaft.

[0006] The technical solution of the present invention is: an elastic support foil dynamic pressure gas bearing with an inherent structural pre-wedge space, comprising a bearing and a rotating shaft located in the bearing; an elastic support element is arranged on the inner side of the bearing, a top layer of flat foil is arranged between the elastic support element and the rotating shaft, a smooth shaft section is arranged in the axial middle area of ​​the rotating shaft surface, a row of inclined grooves are arranged on the rotating shaft surface and on both sides of the smooth shaft section, and the inner side of the top layer of flat foil surrounds and wraps the rotating shaft and forms a pre-gap between the top layer of flat foil and the rotating shaft, and at the same time, one end of the elastic support element and the top layer of flat foil is fixed at the same position of the bearing and the other end is free.

[0007] As a preferred technical solution, the outer end of the inclined groove is flush with the bearing end surface on its corresponding side or extends out of the bearing end surface.

[0008] As a preferred technical solution, two rows of inclined grooves are arranged axially symmetrically on the rotating shaft, and when transitioning to the middle area of ​​the rotating shaft, the depth and width of the inclined grooves are equal or gradually decrease.

[0009] As a preferred technical solution, the circumferential inclination direction of the inclined groove is opposite to the rotation direction of the shaft.

[0010] As a preferred technical solution, the inclined groove adopts a rectangular cross-section groove, a triangular cross-section groove, a trapezoidal cross-section groove, a stepped groove, a horizontal semi-cylindrical groove or a tapered semi-conical groove, etc.

[0011] As a preferred technical solution, the elastic support element has uniform overall stiffness or has a large stiffness in the axial middle region and a small stiffness on both edge sides.

[0012] As a preferred technical solution, one end of the elastic supporting element and the top flat foil are fixed to the bearing by welding or fixing elements, and the rotation direction of the elastic supporting element and the top flat foil from the fixed end to the free end is opposite to the rotation direction of the rotating shaft.

[0013] As a preferred technical solution, the elastic supporting element is an elastic supporting foil of a cantilever, a corrugated foil, a bubble or other structures.

[0014] The advantages of the present invention are:

[0015] 1. The present invention can form a dynamic pressure gas film at a relatively low rotation speed and small foil deformation, and provide a certain stiffness support and buffer damping for the rotating shaft in advance, absorb the vibration energy of the rotating shaft, effectively weaken the shaking of the rotating shaft, make the rotating shaft and the bearing contact evenly during the start and stop stages, reduce the contact friction time and wear between the rotating shaft and the bearing, improve the operation stability and reliability of the system, and also have good stiffness and damping characteristics, can be applied to a variety of load conditions, and effectively suppress the vortex of the rotating shaft;

[0016] 2. In the present invention, when the rotation speed and foil deformation are relatively small, the bearing capacity is provided by the dynamic pressure air film between the inclined groove and the top flat foil, and between the smooth shaft section and the top flat foil; while at high rotation speed, the bearing capacity is mainly provided by the dynamic pressure air film between the smooth shaft section and the top flat foil, ensuring that when the load changes greatly, the bearing can provide sufficient bearing capacity for high-speed operation and heavy-load conditions of the rotating shaft;

[0017] 3. The present invention can adjust the air film stiffness between the shaft and the bearing by changing the ratio of the length of the smooth shaft section and the axial length of the inclined groove, the arrangement density of the inclined groove in the circumferential direction of the shaft, and the shape of the inclined groove, thereby improving the operating characteristics and load-bearing performance of the system during the start, stop and normal operation of the shaft and promoting the stable operation of the system;

[0018] 4. The present invention sets a smooth shaft section in the axial middle area of ​​the rotating shaft surface, which is conducive to the formation and pressure distribution of the high-pressure area, reduces the pressure drop gradient from the high-pressure area to the low-pressure area, has a pressure-maintaining effect on the high-pressure area, and further improves the stability of the bearing;

[0019] 5. The present invention adopts elastic support foil and top flat foil to provide elastic support for the bearing, which is coupled with the dynamic pressure effect of the pre-wedge space of the inherent structure, has good structural damping and multiple adaptive stiffness, can absorb the impact load of the rotating shaft in time, increase the bearing capacity variation range of the bearing, improve the stability and start and stop performance of the bearing, and the elastic support foil structure in the middle of the bearing has good self-centering performance, which is convenient for the processing and installation of the bearing and the rotating shaft. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0021] Figure 1 It is a structural cross-sectional view of the present invention;

[0022] Figure 2 is a transverse cross-sectional view of the present invention;

[0023] Among them: 1 bearing, 2 rotating shaft, 3 elastic supporting element, 4 top flat foil, 5 smooth shaft section, 6 inclined groove, 7 fixing element. DETAILED DESCRIPTION

[0024] Example: Refer to Figure 1and 2 As shown, an elastic support foil dynamic pressure gas bearing with an inherent structural pre-wedge space includes a bearing 1 and a rotating shaft 2 located in the bearing 1; an elastic support element 3 is arranged on the inner side of the bearing 1, a top layer flat foil 4 is arranged between the elastic support element 3 and the rotating shaft 2, a smooth shaft section 5 is arranged in the axial middle area of ​​the surface of the rotating shaft 2, a row of inclined grooves 6 are arranged on the surface of the rotating shaft 2 and on both sides of the smooth shaft section 5, and the inner side of the top layer flat foil 4 surrounds and wraps the rotating shaft 2 and forms a pre-gap between the top layer flat foil 4 and the rotating shaft 2, and at the same time, one end of the elastic support element 3 and the top layer flat foil 4 is fixed at the same position of the bearing 1 and the other end is free.

[0025] The outer end of the inclined groove 6 of the present invention is flush with the end face of the bearing 1 on its corresponding side or extends out of the end face of the bearing, and the two rows of inclined grooves 6 are arranged axially symmetrically on the rotating shaft. The inclined groove 6 can form an effective wedge-shaped dynamic pressure area due to its inherent groove structure and has a pumping effect, so that the working gas on both sides is pumped into the axial middle area between the two rows of inclined grooves 6 to form a high-pressure area, which is conducive to the establishment of a dynamic pressure air film. At the same time, during the start and stop stages, the dynamic pressure air film can provide the rotating shaft 2 with symmetrically distributed stiffness support and buffer damping at both ends of the bearing 1, so that the rotating shaft 2 and the top flat foil 4 are in full and uniform contact, the effective contact area is increased, and the violent collision between the rotating shaft 2 and the bearing 1 can be significantly reduced or even avoided, the wear between the rotating shaft 2 and the top flat foil 4 is reduced, and the rotating shaft 2 floats smoothly and quickly transitions to a stable working speed. And for the parking stage, the bearing 1 has the same operating characteristics, so it has good stability and friction reduction characteristics in the starting and stopping stages, and when transitioning to the middle area of ​​the rotating shaft 2, the depth and width of the inclined groove 6 are equal or gradually decrease, so as to facilitate the formation of the dynamic pressure air film and the maintenance of the high-pressure area of ​​the dynamic pressure air film at the smooth shaft section 5.

[0026] The inclined groove 6 of the present invention has a circumferential inclination direction opposite to the rotation direction of the rotating shaft 2 to effectively form a dynamic pressure air film, and the inclined groove 6 can be a rectangular cross-section groove, a triangular cross-section groove, a trapezoidal cross-section groove, a stepped groove, a horizontal semi-cylindrical groove or a tapered semi-conical groove, etc.

[0027] The elastic supporting element 3 and one end of the top flat foil 4 of the present invention are fixed to the bearing 1 by welding or fixing elements 7, and the overall stiffness of the elastic supporting element 3 is uniform or the stiffness in the axial middle region is large and the stiffness on both edge sides is small. Therefore, in the startup phase, the smaller stiffness at the edge of the bearing 1 makes it easy for the edge of the foil to deform. At the same time, combined with the pre-clearance generated by the inherent structure of the edges of the rotating shaft 2 and the bearing 1 on both sides, it further promotes the establishment of a dynamic pressure air film under low speed / small foil deformation.

[0028] The elastic supporting element 3 and the top flat foil 4 of the present invention are arranged in a rotation direction from the fixed end to the free end opposite to the rotation direction of the rotating shaft 2 to effectively form a dynamic pressure air film, and the elastic supporting element 3 can be an elastic supporting foil of a cantilever, corrugated foil, bubble or other structure.

[0029] The working principle of the present invention is as follows: an inclined groove 6 is arranged on the surface of the rotating shaft 2, and an elastic supporting foil with uniform overall stiffness or large stiffness in the middle axial region and small stiffness on the edge side is used, which is conducive to the formation of a dynamic pressure wedge-shaped air film gap. At a relatively low speed in the startup stage of the rotating shaft 2, an effective dynamic pressure air film is preferentially formed near the inclined groove 6. As the speed increases, a dynamic pressure air film is further formed between the smooth shaft section 5 and the top flat foil 4, and finally the entire rotating shaft 2 floats. The inherent structure of the inclined groove 6 accelerates the establishment of the dynamic pressure air film, so that the rotating shaft 2 can float at a relatively low speed / small foil deformation, reducing the friction time between the rotating shaft 2 and the bearing 1. During the normal operation stage of the rotating shaft 2 and the bearing 1, when the load is small, the dynamic pressure air film between the inclined groove 6 and the top flat foil 4 and between the smooth shaft section 5 and the top flat foil 4 jointly provides the bearing capacity. When the load is large, the dynamic pressure air film between the smooth shaft section 5 and the top flat foil 4 mainly provides the bearing capacity. During the parking stage of the shaft 2, as the speed decreases, the dynamic pressure air film between the smooth shaft section 5 and the top flat foil 4 fails first. As the speed further decreases, the dynamic pressure air film near the inclined groove 6 fails, and the shaft 2 and the top flat foil 4 begin to contact and rub. At this time, the speed of the shaft 2 is relatively low, which reduces the friction time between the shaft 2 and the bearing 1 during the parking stage. Therefore, during the starting and parking stages, the contact friction time between the shaft 2 and the bearing 1 is reduced, thereby extending the service life of the shaft 2 and the bearing 1.

[0030] During the start and stop phases of the rotating shaft 2, the bearing 1 has a flexible surface, good structural damping, and two rows of inclined grooves 6 are symmetrically arranged on the axis of the rotating shaft 2. Therefore, the edge of the bearing 1 provides symmetrically distributed stiffness support and buffer damping for the rotating shaft 2 at both ends at a relatively low rotation speed, so that the rotating shaft 2 is in uniform contact with the top flat foil 4, increasing the effective contact area, significantly reducing or even avoiding the violent collision between the rotating shaft 2 and the bearing 1, reducing the wear between the bearing 1 and the rotating shaft 2, and making the system have good stability and friction reduction characteristics during the start and stop phases.

[0031] The inclined groove 6 structure provided in the present invention can improve the starting and stopping performance and stable operation of the rotating shaft 2. The air film gap between the smooth shaft section 5 and the top flat foil 4 provides the main bearing capacity, has good structural damping and a large stiffness variation range, and further promotes the high-speed and stable operation of the system.

[0032] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. An elastically supported foil dynamic pressure gas bearing with an inherent structural pre-wedge space, characterized in that: It comprises a bearing (1) and a rotating shaft (2) located in the bearing (1); An elastic support element (3) is arranged on the inner side of the bearing (1), a top flat foil (4) is arranged between the elastic support element (3) and the rotating shaft (2), a smooth shaft section (5) is arranged in the axial middle area of ​​the surface of the rotating shaft (2), a row of inclined grooves (6) are arranged on the surface of the rotating shaft (2) and on both sides of the smooth shaft section (5), and the inner side of the top flat foil (4) surrounds and wraps the rotating shaft (2) and forms a pre-gap between the top flat foil (4) and the rotating shaft (2), and one end of the elastic support element (3) and the top flat foil (4) are fixed at the same position of the bearing (1) and the other end is free; the rotation direction of the elastic support element (3) and the top flat foil (4) from the fixed end to the free end is opposite to the rotation direction of the rotating shaft (2); The two rows of inclined grooves (6) are arranged axially symmetrically on the rotating shaft, and the circumferential inclination direction of the inclined grooves (6) is opposite to the rotation direction of the rotating shaft (2), so that the working gas on both sides is pumped into the axial middle area between the two rows of inclined grooves (6), forming a high-pressure area and establishing a dynamic pressure gas film.

2. The elastically supported foil dynamic pressure gas bearing with inherent structural pre-wedge space according to claim 1, characterized in that: The outer end of the inclined groove (6) is flush with the end surface of the bearing (1) on the corresponding side or extends beyond the end surface of the bearing.

3. The elastically supported foil dynamic pressure gas bearing with inherent structural pre-wedge space according to claim 1, characterized in that: When transitioning to the middle area of ​​the rotating shaft (2), the depth and width of the inclined groove (6) are equal or gradually decrease.

4. The elastically supported foil dynamic pressure gas bearing with inherent structural pre-wedge space according to claim 1, characterized in that: The inclined groove (6) is a rectangular cross-section groove, a triangular cross-section groove, a trapezoidal cross-section groove, a stepped groove, a horizontal semi-cylindrical groove or a tapered semi-conical groove.

5. The elastically supported foil dynamic pressure gas bearing with inherent structural pre-wedge space according to claim 1, characterized in that: The elastic support element (3) has uniform overall stiffness or has a large stiffness in the axial middle region and a small stiffness on both edge sides.

6. The elastically supported foil dynamic pressure gas bearing with inherent structural pre-wedge space according to claim 1, characterized in that: The elastic supporting element (3) and one end of the top flat foil (4) are fixed to the bearing (1) by welding or a fixing element (7).

7. The elastically supported foil dynamic pressure gas bearing with inherent structural pre-wedge space according to claim 1, characterized in that: The elastic supporting element (3) is a cantilever, a corrugated foil, or an elastic supporting foil with a bubbling structure.

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