A combined bearing

Abstract

This invention discloses a combined bearing, comprising a radial parallel bearing and a thrust bearing. The parallel bearing includes a shaft bearing and a stator bearing. The shaft bearing is a contact bearing, and the stator bearing is a non-contact bearing. The stator bearing is sleeved on the shaft bearing, with a gap between the inner wall of the stator bearing and the outer wall of the shaft bearing. The thrust bearing includes foil, an elastomer, and a thrust bearing housing. The thrust bearing housing is a disc-shaped housing with a central through hole, and at least one end face of the housing is fixed with foil by the elastomer. An air inlet for the thrust bearing is formed on its side wall. This invention solves the technical problems of high dependence on lubricants in existing contact bearings and excessive friction between existing non-contact bearings and high-speed rotating shafts.

Description

Technical Field

[0001] The invention relates to the technical field of bearings, and in particular to a combined bearing. Background Art

[0002] Theoretically, the thicker the shaft diameter, the greater the load and critical speed it can withstand. However, this will increase the DN value of the bearing that matches it, and a higher performance lubricant will be required, otherwise it will cause bearing wear, shaft jamming and other faults. The DN value is a reference value for selecting rolling bearing lubricants, where D is the bearing diameter and N is the relative speed of the inner and outer rings of the bearing. Bearings with high DN values ​​have higher requirements for the adhesion, service life and operating temperature of grease or lubricant, and the price of such grease or lubricant is usually higher.

[0003] For non-contact bearings, such as radial air bearings, the support function is achieved by compressed air between the shaft and the inner ring of the bearing. Usually, a rubber ring is installed between the outer diameter of the bearing and the bearing seat, and the friction between the rubber ring and the outer diameter of the bearing is used to fix the bearing to prevent it from rotating in the circumferential direction. However, in the actual use of air bearings, when the rotation speed of the rotating shaft reaches about 100,000 revolutions or more, there will be air friction between the compressed air film and the rotating shaft, and this friction will also increase with the increase of the rotation speed of the rotating shaft. The torque generated by this friction makes the air bearing rotate more obviously and frequently with the rotating shaft. And as the rotation speed of the rotating shaft is further increased or the diameter of the rotating shaft is increased, the friction between the air film and the inner diameter of the radial air bearing is further increased, the rotation speed of the radial air bearing relative to the bearing seat increases, and the rubber ring will be easily worn and damaged. Summary of the invention

[0004] In order to overcome the above defects of the prior art, the present invention provides a combined bearing which can solve the technical problems that the existing contact bearings are highly dependent on lubricants and the friction between the existing non-contact bearings and the high-speed rotating shaft is too large.

[0005] The parallel bearing involved in the present invention is defined as: comprising at least two bearings of different diameters, each bearing being nested in sequence from outside to inside or from inside to outside, and each bearing axis in the parallel bearing being parallel to each other during operation, and each bearing being fully nested or partially nested.

[0006] In order to achieve the above object, the present invention adopts the following technical solution.

[0007] A combined bearing comprises a radial parallel bearing and a thrust bearing.

[0008] The parallel bearing comprises a rotating shaft bearing and a stator bearing; the rotating shaft bearing is a contact bearing, and the stator bearing is a non-contact bearing; the stator bearing is sleeved on the rotating shaft bearing, and a gap is left between the inner wall of the stator bearing and the outer wall of the rotating shaft bearing;

[0009] The thrust bearing comprises a foil, an elastomer and a thrust bearing housing; the thrust bearing housing is a disc-type housing with a central through hole, at least one end face of which is fixed with a foil through an elastomer, and a thrust bearing air inlet is provided on the side wall.

[0010] The shaft bearing is sleeved on the shaft and tightly fit with the shaft, and the shaft is driven to rotate by a driving device; the stator bearing is fixed on the stator; a thrust plate is provided on the shaft and is integrally formed or fixed therewith; the thrust bearing housing is covered outside the thrust plate and sleeved on the shaft, and a gap is left between the foil and the thrust plate; the thrust bearing housing is fixed to the stator.

[0011] The driving device is a motor.

[0012] The rotating shaft bearing is a ball bearing, and the stator bearing is an air bearing.

[0013] The air bearing is annularly cylindrical, and its outer wall is parallel to the end surface and is provided with at least one annular groove, and a damper is nested in the annular groove, and the damper is an annular rubber ring, and the top of the rubber ring protrudes from the outer wall of the air bearing.

[0014] A plurality of protrusions are evenly distributed axially around the annular end surface of the air bearing, an anti-rotation end cover is provided at one end of the air bearing where the protrusions are provided, an anti-rotation hole is provided on the anti-rotation end cover corresponding to the protrusion, the protrusion is embedded in the anti-rotation hole and the anti-rotation end cover is fixed to the stator end surface by screws.

[0015] A cross-shaped hole is arranged on the anti-rotation end cover, including four anti-rotation holes vertically connected to each other, and four protrusions are correspondingly arranged, each of which is respectively embedded in each anti-rotation hole, and a screw hole is arranged between two adjacent anti-rotation holes. A screw hole 1 is arranged on the stator end face, and the screw hole is aligned with screw hole 1 and then fastened with screws.

[0016] The rotating shaft bearing is a pair of angular contact ball bearings arranged opposite to each other, and a preload spring is arranged between the outer rings of the two angular contact ball bearings; the two ends of the preload spring are respectively fixed to the ends of the outer rings of the two angular contact ball bearings.

[0017] The parallel bearing also includes at least one intermediate bearing, which is a contact bearing. The intermediate bearing is sleeved between the rotating shaft bearing and the stator bearing, and a gap is left between the stator bearing and the intermediate bearing.

[0018] The intermediate bearing is a ball bearing.

[0019] The surface of the shaft section of the rotating shaft sleeved in the rotating shaft bearing is coated with a tetrafluoroethylene anti-wear coating.

[0020] The rotating shaft bearing is a ball bearing, a roller bearing, a ceramic bearing or a tetrafluoroethylene bearing.

[0021] The ball bearing, roller bearing, ceramic bearing or tetrafluoroethylene bearing is single-row, double-row or multi-row.

[0022] The ball bearing, roller bearing, ceramic bearing or tetrafluoroethylene bearing is single-layer, double-layer or multi-layer.

[0023] The stator bearing is an air bearing, an oil film floating ring bearing or a tilting pad bearing.

[0024] The beneficial effects of the present invention are:

[0025] (1) The combined bearing of the present invention is low-cost and can support the bearing in the radial direction and limit the displacement of the rotating shaft in the axial direction; the thrust foil bearing surface is flexible and has the advantages of high load-bearing capacity, low friction power consumption, high stability, allowable bearing clearance loss, and resistance to vibration and impact; the radial parallel bearing is low-cost, the relative speed of each level of bearing is reduced, it is not limited by the theoretical DN value, and has low dependence on lubricating oil.

[0026] (2) In the prior art, an air film exists between the rotating shaft and the air bearing. As the rotation speed of the rotating shaft further increases or the diameter of the rotating shaft increases, the friction force further increases. After adopting the parallel bearing of the present invention, an air film exists between the outer ring of the ball bearing and the air bearing. Since the rotation speed of the outer ring of the ball bearing is relatively low, the relative rotation speed between the air film and the air bearing is relatively low, the friction force is small, and the rotation speed relative to the bearing seat is also small. Therefore, the rubber ring between the air bearing and the bearing housing is not easy to wear and has a long service life.

[0027] (3) The speed of multiple combined bearings on the same shaft can be adaptively adjusted without the need for manual setting or adjustment of the speed, and the effect of synchronous rotation can be achieved.

[0028] (4) It can be used not only at low speeds, but also at high speeds, and can be used for rotors with speeds ranging from tens of thousands to hundreds of thousands of revolutions.

[0029] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the parallel bearing structure of the first embodiment of the present invention.

[0031] Figure 2It is a schematic diagram of the parallel bearing structure of the second embodiment of the present invention.

[0032] Figure 3 It is a schematic diagram of the parallel bearing structure of embodiment 3 of the present invention.

[0033] Figure 4 It is a schematic diagram of the parallel bearing structure of embodiment 4 of the present invention.

[0034] Figure 5 It is a schematic diagram of the structure in which the parallel bearings of the present invention are arranged at both ends of the shaft.

[0035] Figure 6 It is a schematic diagram of a fixing method of the parallel bearing of the present invention.

[0036] Figure 7 It is a side view of the parallel bearing with a projection according to the present invention.

[0037] Figure 8 It is a structural schematic diagram of the anti-rotation end cover of the present invention.

[0038] Fig. 9 FIG. 1 is a side view of an air bearing with a protrusion according to the present invention.

[0039] Fig.10 Graph showing the relationship between the friction torque of the air bearing of the present invention and time.

[0040] Fig.11 Graph showing the relationship between the friction torque of the ball bearing of the present invention and time.

[0041] Figure numbers: 1-rotating shaft bearing, 2-stator bearing, 21-rubber ring, 22-bump, 4-stator, 41-screw hole one, 5-anti-rotation end cover, 51-anti-rotation hole, 52-screw hole, 6-intermediate bearing, 100-rotating shaft, 210-thrust plate, 800-thrust bearing, 801-foil, 802-elastomer, 803-thrust bearing housing. DETAILED DESCRIPTION

[0042] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0043] The present invention provides a parallel bearing, which is used to be installed on a rotating shaft 100 to support the rotating shaft 100 in a radial direction.

[0044] A combined bearing, see Figure 1-4 , including radial parallel bearings and thrust bearings 800,

[0045] The parallel bearing comprises a rotating shaft bearing 1 and a stator bearing 2; the rotating shaft bearing 1 is a contact bearing; the stator bearing 2 is a non-contact bearing, and the stator bearing 2 is sleeved on the rotating shaft bearing 1, with a gap between the inner wall of the stator bearing 2 and the outer wall of the rotating shaft bearing 1.

[0046] The thrust bearing 800 includes a foil 801, an elastomer 802 and a thrust bearing housing 803; the thrust bearing housing 803 is a disc-type housing with a central through hole, at least one end face of which is fixed with a foil 801 through the elastomer 802, and a thrust bearing air inlet is opened on the side wall.

[0047] The rotating shaft bearing 1 is sleeved on the rotating shaft 100 and tightly fits with the rotating shaft 100, and the rotating shaft 100 is driven to rotate by a driving device; the stator bearing 2 is fixed on the stator 4; a thrust plate 210 is provided on the rotating shaft 100 and is integrally formed or fixed thereto; the thrust bearing housing 803 is covered outside the thrust plate 210 and sleeved on the rotating shaft 100, and a gap is left between the foil 801 and the thrust plate 210; the thrust bearing housing 803 is fixed to the stator 4.

[0048] In the present invention, the parallel bearing has the following four implementation modes:

[0049] Embodiment 1

[0050] The rotating shaft bearing 1 is a ball bearing, and the stator bearing 2 is an air bearing.

[0051] See also Figure 1 In this embodiment, the parallel bearing includes a rotating shaft bearing 1 and a stator bearing 2. The rotating shaft bearing 1 is sleeved on the rotating shaft 100, and the stator bearing 2 is sleeved outside the rotating shaft bearing 1 and maintains a certain gap with the outer wall of the rotating shaft bearing 1.

[0052] The air bearing is an annular cylinder, and its outer wall is parallel to the end surface and is provided with at least one annular groove, and a damper is nested in the annular groove, and the damper is an annular rubber ring 21, and the top of the rubber ring 21 protrudes from the outer wall of the air bearing.

[0053] See also Figure 6 , 7 , 8, 9, a plurality of protrusions 22 are axially and evenly arranged on the annular end surface of the air bearing, an anti-rotation end cover 5 is arranged at one end of the air bearing where the protrusion 22 is arranged, an anti-rotation hole 51 is arranged on the anti-rotation end cover 5 corresponding to the protrusion 22, the protrusion 22 is embedded in the anti-rotation hole 51 and the anti-rotation end cover 5 is fixed to the end surface of the stator 4 by screws.

[0054] Furthermore, a cross-shaped hole is provided on the anti-rotation end cover 5, including four anti-rotation holes 51 vertically connected to each other, and the protrusions 22 are correspondingly provided in four, each protrusion 22 is respectively embedded in each anti-rotation hole 51, a screw hole 52 is provided between two adjacent anti-rotation holes 51, and a screw hole 41 is provided on the end face of the stator 4, and the screw hole 52 is aligned with the screw hole 41 and fastened with screws.

[0055] Embodiment 2

[0056] See also Figure 2 The parallel bearing also includes at least one intermediate bearing 6, which is a contact bearing. The intermediate bearing 6 is sleeved between the rotating shaft bearing 1 and the stator bearing 2, and a gap is left between the stator bearing 2 and the intermediate bearing 6.

[0057] The intermediate bearing 6 is a ball bearing.

[0058] Specifically, the parallel bearing includes a rotating shaft bearing 1 , a stator bearing 2 and an intermediate bearing 6 .

[0059] This embodiment is based on the first embodiment, in which an intermediate bearing 6 is sleeved on the rotating shaft bearing 1 (or multiple intermediate bearings 6 are sleeved in sequence and the intermediate bearings 6 are coaxial), and the stator bearing 2 is sleeved outside the outermost intermediate bearing 6 and maintains a certain gap with the outer wall of the outermost intermediate bearing 6.

[0060] Embodiment 3

[0061] Furthermore, the ball bearing, roller bearing, ceramic bearing or tetrafluoroethylene bearing is single-layer, double-layer or multi-layer. The ball bearing or roller bearing of the rotating shaft bearing 1 in the first and second embodiments of the present invention can be an integrated multi-layer bearing, and the ball layer or roller layer is set to be multi-layer, see Figure 3 The multi-layer ball bearing or roller bearing comprises an inner ring, a middle ring and an outer ring which are nested with each other, and balls or rollers are embedded between the inner ring and the middle ring, and between the middle ring and the outer ring, respectively.

[0062] Embodiment 4

[0063] When the shaft bearing 1 of the present invention uses an angular contact ball bearing, since the inner ring of the bearing is fixed on the shaft 100, relative displacement will occur between the outer ring, the retaining frame and the balls. Generally speaking, this means that the balls inside the bearing are too loose and appropriate treatment measures need to be taken.

[0064] See also Figure 4 The shaft bearing 1 is a pair of angular contact ball bearings arranged opposite to each other, and a preload spring is arranged between the outer rings of the two angular contact ball bearings; the two ends of the preload spring are respectively fixed to the ends of the outer rings of the two angular contact ball bearings.

[0065] By adjusting the preload force of the spring, the balls and the cage can be moved closer or further away, that is, the internal friction of the bearing can be increased or decreased to achieve the friction force suitable for the required working conditions.

[0066] Furthermore, the surface of the shaft section of the rotating shaft 100 sleeved in the rotating shaft bearing is coated with a tetrafluoroethylene anti-wear coating.

[0067] Furthermore, the stator bearing 2 is fixed to the stator 4 by a key connection, a pin connection, a dowel connection, or a bolt connection.

[0068] Furthermore, the rotating shaft bearing 1 is a ball bearing, a roller bearing, a ceramic bearing or a tetrafluoroethylene bearing.

[0069] Furthermore, the stator bearing 2 is an air bearing, an oil film floating ring bearing or a tilting pad bearing.

[0070] Furthermore, the ball bearing, roller bearing, ceramic bearing or tetrafluoroethylene bearing is single-row, double-row or multi-row.

[0071] The starting process of the parallel bearing of the present invention is:

[0072] When the rotating shaft 100 is started, the rotating shaft bearing 1 on the outer sleeve of the rotating shaft 100 contacts the bottom of the stator bearing 2. As the rotating shaft 100 rotates, the inner ring of the rotating shaft bearing 1 is driven to rotate. At the same time, the stator bearing 2 and the outer ring of the rotating shaft bearing 1 are gradually separated due to the effect of the air film or oil film, and the rotating shaft bearing 1 rotates eccentrically in the stator bearing 2. When the rotating shaft 100 runs stably at a high speed, the rotating shaft 100 and the rotating shaft bearing 1 are coaxial and rotate eccentrically around a circle in the stator bearing 2. At the same time, the outer ring of the rotating shaft bearing 1 rotates.

[0073] Further, see Figure 1 The present invention uses a ball bearing as the rotating shaft bearing 1 and an air bearing as the stator bearing 2. The following is a description of the working principle:

[0074] When the shaft diameter is constant, for a traditional ball bearing, when the shaft 100 rotates, assuming that the speed of the inner ring of the ball bearing is V2 and the speed of the outer ring is V0, since the outer ring is fixed on the stator 4, V0 is approximately 0, so the relative speed of the outer ring of the ball bearing is n=V2-V0.

[0075] After adopting the parallel bearing of the present invention, when the rotating shaft 100 rotates, the speed of the inner ring of the ball bearing is V2, the speed of the outer ring is V1, the speed of the air bearing is V0, the air bearing is fixed on the stator 4, V0 is approximately 0, the speed difference of the outer ring of the ball bearing relative to the inner ring is a=V2-V1, and the speed difference relative to the air bearing is b=V1-V0, and both a and b are less than n. It can be seen that the relative speed of the inner and outer rings of the rolling bearing is reduced, that is, under the same conditions, the actual DN value is reduced, and the selection of ordinary grease can meet the needs.

[0076] By analogy, no matter how many ball bearings are sequentially arranged in parallel on the rotating shaft bearing 1, the actual DN value will not become too large, and the shaft diameter D and the bearing speed N have been decoupled. Therefore, the parallel bearing of the present invention is suitable for large shaft diameter and high speed working conditions. And the damping and stiffness of the parallel bearing of the present invention are not lower than the damping and stiffness of a single bearing. Specifically, the damping of the parallel bearing = the damping of the air bearing + the damping of each bearing rubber ring; the stiffness of the parallel bearing = the stiffness of the air bearing.

[0077] In specific applications, the parallel bearings of the present invention can be arranged in pairs on the rotating shaft 100, see Figure 5 When the rotating shaft 100 rotates, the inner ring of the rotating shaft bearing 1 is driven to rotate, and the outer ring of the rotating shaft bearing 1 or the outer ring of the outermost intermediate bearing 6 rotates under the action of the air bearing or the oil film floating ring bearing. And the speed of multiple parallel bearings on the same rotating shaft will be adaptively adjusted according to the force, so as to achieve the effect of synchronous rotation.

[0078] Taking the case where the rotating shaft bearing 1 is a ball bearing and the stator bearing 2 is an air bearing as an example, the working process of the parallel bearing of the present invention is as follows:

[0079] (1) Turning on the starting device of the rotating shaft 100 to rotate the rotating shaft 100 to an initial predetermined speed; the inner ring of the ball bearing is driven by the rotating shaft 100 and rotates synchronously with the rotating shaft 100;

[0080] (2) After the rotation speed of the rotating shaft 100 is accelerated to the working rotation speed, the outer ring of the ball bearing begins to rotate due to the action of the ball, and the air between the outer ring of the ball bearing and the inner wall of the air bearing vortexes. When the outer ring of the ball bearing rotates to a certain speed, the air film gradually stabilizes, and the ball bearing separates from the inner ring of the air bearing.

[0081] The following is a diagram of the relationship between friction torque and time to further explain its working principle. Fig.10 , 11 :

[0082] (1) In the time period from 0 to t1, that is, the rotating shaft 100 has just started, the inner ring of the ball bearing rotates but the outer ring has not yet rotated, and the linear velocity of the outer ring of the ball bearing is 0. Due to the influence of the rotation of the ball, the friction torque of the outer ring of the ball bearing increases; the air bearing is not subjected to force at this time, so the friction torque is 0, and before time t1, the air bearing is in contact with the outer ring of the ball bearing.

[0083] (2) During the time period from t1 to t2, i.e. before the rotating shaft 100 gradually rotates to stable operation, due to the influence of the rotation of the ball, the friction torque of its outer ring increases, and the outer ring of the ball gradually rotates, but does not take off; the friction torque between the air bearing and the ball bearing gradually increases until the critical point;

[0084] (3) At time t2, the friction torque between the air bearing and the ball bearing reaches the critical point. The friction torque of both reaches the critical value. The outer ring of the ball bearing and the air bearing begin to rotate relative to each other and gradually separate. The air film between the outer ring of the ball bearing and the inner wall of the air bearing gradually stabilizes. The friction torque of the ball bearing decreases slightly and then slowly increases as the speed increases. At the same time, the air bearing takes off, and the friction torque of the air bearing also decreases instantaneously, and then slowly increases as the speed increases.

[0085] The thrust bearing 800 of the present invention comprises a foil 801 , an elastic body 802 and a thrust bearing housing 803 ; the thrust bearing housing 803 is disposed outside the thrust plate 300 and sleeved on the rotating shaft 200 .

[0086] The two inner end surfaces of the thrust bearing housing 803 (see Figure 1 ) or / and an inner end face (see Figure 3 ) The foil 801 is fixed by the elastic body 802, and the elastic body 802, the foil 801 and the thrust bearing housing 803 are all bonded.

[0087] The foil 801 is annular, and its outer diameter is larger than that of the thrust disk 300. A gap is left between the foil 801 and the end face of the thrust disk 210. A thrust bearing air inlet is arranged on the thrust bearing housing 803. When air is taken in, the air flows into the gap between the foil 801 and the thrust disk 210 to form an air film, thereby limiting the displacement of the rotating shaft 100 in the axial direction.

[0088] The combined bearing of the present invention can be used in a rotor system.

[0089] The combined bearing of the present invention can be used in a motor.

[0090] The application of the combined bearing of the present invention is not limited to the occasions described in the present invention, and those skilled in the art can easily think of applying it to any high-speed rotation occasion. The implementation methods described in the present invention specification are only examples for understanding the present invention and do not constitute a limitation on the application occasions of the present invention.

[0091] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A combined bearing, characterized in that: It includes radial parallel bearings and thrust bearings, wherein the parallel bearings include rotating shaft bearings and stator bearings; the rotating shaft bearings are contact bearings, and the stator bearings are non-contact bearings; the stator bearings are sleeved on the rotating shaft bearings, and a gap is left between the inner wall of the stator bearings and the outer wall of the rotating shaft bearings; The thrust bearing comprises a foil, an elastomer and a thrust bearing housing; the thrust bearing housing is a disc-type housing with a central through hole, at least one end face of which is fixed with a foil through an elastomer, and a thrust bearing air inlet is provided on the side wall; The shaft bearing is sleeved on the shaft and tightly matched with the shaft, and the shaft is driven to rotate by a driving device; the stator bearing is fixed on the stator; a thrust plate integrally formed or fixed with the shaft is provided on the shaft; the thrust bearing housing is covered outside the thrust plate and sleeved on the shaft, and a gap is left between the foil and the thrust plate; the thrust bearing housing is fixed to the stator; The rotating shaft bearing is a ball bearing, and the stator bearing is an air bearing.

2. A combined bearing according to claim 1, characterized in that: The driving device is a motor.

3. A combined bearing according to claim 1, characterized in that: The air bearing is annularly cylindrical, and its outer wall is parallel to the end surface and is provided with at least one annular groove, and a damper is nested in the annular groove, and the damper is an annular rubber ring, and the top of the rubber ring protrudes from the outer wall of the air bearing.

4. A combined bearing according to claim 3, characterized in that: A plurality of protrusions are evenly distributed axially around the annular end surface of the air bearing, an anti-rotation end cover is provided at one end of the air bearing where the protrusions are provided, an anti-rotation hole is provided on the anti-rotation end cover corresponding to the protrusion, the protrusion is embedded in the anti-rotation hole and the anti-rotation end cover is fixed to the stator end surface by screws.

5. A combined bearing according to claim 4, characterized in that: A cross-shaped hole is arranged on the anti-rotation end cover, including four anti-rotation holes vertically connected to each other, and four protrusions are correspondingly arranged, each of which is respectively embedded in each anti-rotation hole, and a screw hole is arranged between two adjacent anti-rotation holes. A screw hole 1 is arranged on the stator end face, and the screw hole is aligned with screw hole 1 and then fastened with screws.

6. A combined bearing according to claim 1, characterized in that: The rotating shaft bearing is a pair of angular contact ball bearings arranged opposite to each other, and a preload spring is arranged between the outer rings of the two angular contact ball bearings; the two ends of the preload spring are respectively fixed to the ends of the outer rings of the two angular contact ball bearings.

7. A combined bearing according to claim 1, characterized in that: The parallel bearing also includes at least one intermediate bearing, which is a contact bearing. The intermediate bearing is sleeved between the rotating shaft bearing and the stator bearing, and a gap is left between the stator bearing and the intermediate bearing.

8. A combined bearing according to claim 7, characterized in that: The intermediate bearing is a ball bearing.

9. A combined bearing according to claim 1, characterized in that: The surface of the shaft section of the rotating shaft sleeved in the rotating shaft bearing is coated with a tetrafluoroethylene anti-wear coating.

10. A combined bearing according to claim 1, characterized in that: The rotating shaft bearing is a ball bearing, a roller bearing, a ceramic bearing or a tetrafluoroethylene bearing.

11. A combined bearing according to claim 10, characterized in that: The ball bearing, roller bearing, ceramic bearing or tetrafluoroethylene bearing is single-row or multi-row.

12. A combined bearing according to claim 10, characterized in that: The ball bearing, roller bearing, ceramic bearing or tetrafluoroethylene bearing is single-layer or multi-layer.

13. A combined bearing according to claim 1, characterized in that: The stator bearing is an air bearing, an oil film floating ring bearing or a tilting pad bearing.

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