Double-layer protection bearing

Abstract

The utility model belongs to the technical field of bearings, and particularly relates to a double-layer protection bearing which comprises an outer-layer bearing and an inner-layer bearing, the outer-layer bearing is composed of an outer ring, outer-layer balls and an outer circle of a middle ring, the inner-layer bearing is composed of an inner circle of the middle ring, inner-layer balls and an inner ring, a plurality of outer-layer balls are arranged in an annular cavity between the outer ring and the outer circle of the middle ring, and a plurality of inner-layer balls are arranged in the annular cavity between the outer ring and the outer circle of the middle ring. And a plurality of inner-layer balls are arranged in an annular cavity between the inner ring and the inner circle of the middle ring. According to the utility model, by adopting the structure that the adaptation degree of the inner-layer bearing is reduced, the adaptation degree of the outer-layer bearing is increased, the inner-layer bearing adopts a dry-type lubricant with a larger friction coefficient, and the outer-layer bearing adopts a dry-type lubricant with a smaller friction coefficient, the problem that the dragging friction torque of the inner-layer bearing to the outer-layer bearing is insufficient is solved; the outer-layer bearing can rotate faster, and the purposes of improving the limit rotating speed of the whole double-layer bearing and providing better and safer protection for the magnetic suspension bearing are achieved.

Description

Technical Field

[0001] The utility model belongs to the technical field of bearings, and specifically relates to a double-layer protected bearing, especially a double-layer protected bearing based on a magnetic levitation bearing system. Background Art

[0002] Although the architecture of the double-layer protected bearing applied in the magnetic levitation bearing system has been proposed in the engineering field for many years, its core design defect - the imbalance of the dynamic rotational speed matching between the inner and outer layer bearings has not been effectively solved. The specific manifestations are as follows: Under normal working conditions, the rotational speed of the outer layer bearing can only reach the range of 15% - 20% of that of the inner layer bearing. Even with the design of an enhanced inner layer bearing with a double-row raceway structure, its speed ratio is still difficult to break through the critical value of 30%. This significant drop in transmission efficiency directly leads to a performance redundancy of up to 65% in the peak rotational speed bearing capacity of the outer layer bearing (usually 1.8 - 2.2 times that of the inner layer bearing), not only causing low resource utilization rate of the mechanical energy transmission system, but also forming a bottleneck effect that restricts the rotational speed threshold of the entire composite bearing system. Experimental data shows that this structural defect causes the overall ultimate rotational speed of the double-layer bearing to drop by about 40% compared with the theoretically calculated value, severely weakening its application potential in the field of high-speed rotating machinery.

[0003] Different from the traditional oil / grease lubricated bearing system, the magnetic levitation protected bearing needs to follow the dry friction boundary conditions when the non-contact suspension fails. The layered solid lubricants (such as graphite and molybdenum disulfide) used in it will form a transfer film with anisotropic friction characteristics in the boundary lubrication state, resulting in an atypical evolution law of the Stribeck curve. This makes the prediction error of the classical friction torque calculation formula (such as the Petrushevich equation) based on the hydrodynamic lubrication theory reach 47% - 62% under dry friction working conditions.

[0004] The core root cause restricting the dynamic transmission efficiency loss of the outer layer bearing lies in the insufficient effective friction driving torque generated at the inner layer bearing-rotor interface, which is unable to establish sufficient tangential traction force to overcome the inertial resistance torque of the outer layer bearing system. When the friction coefficient of the inner layer bearing is lower than 0.15, its torque transmission efficiency will show an exponential decay, resulting in the rotational speed of the outer layer bearing unable to break through the critical coupling threshold. Summary of the Utility Model

[0005] Aiming at the defects in the prior art, the purpose of the utility model is to provide a double-layer protected bearing.

[0006] A double-layer protected bearing provided by the present utility model includes an outer bearing and an inner bearing. The outer bearing is composed of an outer ring, outer-layer balls, and the outer circle of a middle ring. The inner bearing is composed of the inner circle of the middle ring, inner-layer balls, and an inner ring. A number of outer-layer balls are arranged in the annular cavity between the outer ring and the outer circle of the middle ring, and a number of inner-layer balls are arranged in the annular cavity between the inner ring and the inner circle of the middle ring.

[0007] The tightness parameters of the outer bearing and the inner bearing are inconsistent. The inner bearing structure uses a dry lubricant with a high coefficient of friction to perform gradient coating on the contact interfaces between the inner circle of the middle ring, the raceway of the inner ring, and the inner-layer balls. The outer bearing structure uses a dry lubricant with a low coefficient of friction to treat the contact interfaces between the outer ring, the outer circle of the middle ring, and the surfaces of the outer-layer balls respectively.

[0008] In a preferred embodiment: The outer ring, the middle ring, and the inner ring are concentrically arranged.

[0009] In a preferred embodiment: The groove curvature coefficient of the inner bearing is greater than that of the outer bearing, and the tightness of the inner bearing is less than that of the outer bearing.

[0010] In a preferred embodiment: The inner-layer balls are in a stepped interference fit in the raceway between the inner circle of the middle ring and the inner ring, and the outer-layer balls are in a stepped clearance fit in the raceway between the outer ring and the outer circle of the middle ring.

[0011] In a preferred embodiment: The contact stress of the inner-layer balls in the raceway between the inner circle of the middle ring and the inner ring is less than the contact stress of the outer-layer balls in the raceway between the outer ring and the outer circle of the middle ring.

[0012] In a preferred embodiment: The surface of the inner-layer balls is subjected to homogeneous lubrication modification using a dry lubricant with a high coefficient of friction.

[0013] In a preferred embodiment: The surface of the outer-layer balls is subjected to homogeneous lubrication modification using a dry lubricant with a low coefficient of friction.

[0014] Compared with the prior art, the present utility model has the following beneficial effects:

[0015] By adopting a structure of reducing the tightness of the inner bearing, increasing the tightness of the outer bearing, selecting a dry lubricant with a larger coefficient of friction for the inner bearing, and selecting a dry lubricant with a smaller coefficient of friction for the outer bearing, the present utility model solves the problem of insufficient drag friction torque of the inner bearing on the outer bearing, enables the outer bearing to rotate faster, and achieves the purpose of increasing the limiting speed of the entire double-layer bearing and providing better and safer protection for the magnetic levitation bearing. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Other features, objects, and advantages of the present utility model will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0017] Figure 1 It is a schematic structural diagram of the present utility model;

[0018] In the figure: 1. Outer ring; 2. Outer layer of rolling balls; 3. Middle ring; 4. Inner layer of rolling balls; 5. Inner ring. Specific embodiments

[0019] The present utility model will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present utility model, but do not limit the present utility model in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present utility model, several changes and improvements can still be made. These all belong to the protection scope of the present utility model.

[0020] As Figure 1 shown, the present utility model discloses a double-layer protection bearing, including an outer bearing and an inner bearing. The outer bearing is composed of the outer ring 1, the outer layer of rolling balls 2, and the outer circle of the middle ring 3. The inner bearing is composed of the inner circle of the middle ring 3, the inner layer of rolling balls 4, and the inner ring 5. The outer ring 1, the middle ring 3, and the inner ring 5 are concentrically arranged. A number of outer layer of rolling balls 2 are arranged in the annular cavity between the outer ring 1 and the outer circle of the middle ring 3, and a number of inner layer of rolling balls 4 are arranged in the annular cavity between the inner ring 5 and the inner circle of the middle ring 3.

[0021] The tightness parameters of the outer bearing and the inner bearing are inconsistent. The groove curvature coefficient of the inner bearing is greater than that of the outer bearing, and the tightness of the inner bearing is less than that of the outer bearing, so that the rolling contact stress of the inner layer of rolling balls 4 between the inner circle of the middle ring 3 and the inner ring 5 is less than the rolling contact stress of the outer layer of rolling balls 2 between the outer ring 1 and the outer circle of the middle ring 3. By adopting a larger groove curvature coefficient for the inner bearing to reduce the contact stress, and at the same time reducing the rigidity through a smaller tightness, the inner friction torque is increased due to the differential slip effect. The outer bearing improves the rigidity through a smaller groove curvature coefficient and a larger preload (tightness), optimizing the overall load-bearing and energy consumption distribution.

[0022] For the inner bearing structure, a dry lubricant with a high coefficient of friction is used to perform gradient coating on the inner circle of the middle ring 3 and the contact interfaces between the raceways of the inner ring 5 and the inner-layer balls 4. Through interface friction strengthening, the damping characteristics of the movement are improved. For the outer bearing structure, a dry lubricant with a low coefficient of friction is used to synchronously treat the contact interfaces between the outer ring 1, the outer circle of the middle ring 3 and the surfaces of the outer-layer balls 2 respectively, and homogeneous lubrication modification is implemented on the surfaces of the outer-layer balls 2, so as to reduce friction loss and optimize the transmission efficiency of the system, strengthen the dragging effect on the outer bearing, and accelerate the rotation speed of the outer bearing, so as to achieve the purpose of increasing the limiting speed of the entire double-layer bearing and providing better and safer protection for the magnetic levitation bearing.

[0023] Working principle

[0024] When the present utility model is in use, an inner bearing with a tightness parameter of 0.515 and an outer bearing with a tightness parameter of 0.530 can be selected, so that in the double-layer bearing, the preload of the inner-layer balls 4 in contact with the raceways between the inner circle of the middle ring 3 and the inner ring 5 is reduced, and the preload of the outer-layer balls 2 of the outer bearing between the outer ring 1 and the outer circle of the middle ring 3 is increased, which mechanically ensures that the frictional torque of the inner bearing is larger; in cooperation with the inner bearing, a dry lubricant with a coefficient of friction of 0.05 - 0.10 is selected to perform gradient coating on the inner circle of the middle ring 3 and the contact interfaces between the raceways of the inner ring 5 and the inner-layer balls 4, and a dry lubricant with a coefficient of friction of 0.005 - 0.01 is selected for the outer bearing to treat the contact interfaces between the outer ring 1, the outer circle of the middle ring 3 and the surfaces of the outer-layer balls 2 respectively, and homogeneous lubrication modification is implemented on the surfaces of the outer-layer balls 2, solving the problem of insufficient dragging frictional torque of the inner bearing on the outer bearing, enabling the outer bearing to rotate faster (the rotation speed of the outer bearing can reach 70% or even higher of the rotation speed of the inner bearing), achieving the purpose of increasing the limiting speed of the entire double-layer bearing and providing better and safer protection for the magnetic levitation bearing;

[0025] When the rotor (main shaft) of the magnetic levitation bearing falls out of control, it first forms an impact on the inner ring 5 and drags the inner ring 5 to accelerate. The inner ring 5 drives the inner-layer balls 4 to start rotating, and the inner-layer balls 4 will exert a dragging frictional torque on the middle ring 3 to make the middle ring 3 rotate. In this way, the effect of "inner bearing independent rotation speed + outer bearing independent rotation speed = magnetic levitation rotor rotation speed" can be achieved, protecting the bearing to achieve a significant increase in the superposition of the limiting speeds, providing a more safe, reliable and long-time impact-resistant protection for the magnetic levitation system, and effectively avoiding the impact damage, jamming or overheating damage of the rotor and the main shaft of the magnetic levitation system.

[0026] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0027] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Without conflict, the embodiments of the present application and the features in the embodiments can be combined arbitrarily with each other.

Claims

1. A double-layer protected bearing, characterized in that, It includes an outer bearing and an inner bearing. The outer bearing is composed of an outer ring (1), outer-layer balls (2) and the outer circle of a middle ring (3). The inner bearing is composed of the inner circle of the middle ring (3), inner-layer balls (4) and an inner ring (5). A number of outer-layer balls (2) are arranged in the annular cavity between the outer ring (1) and the outer circle of the middle ring (3). A number of inner-layer balls (4) are arranged in the annular cavity between the inner ring (5) and the inner circle of the middle ring (3). The tightness parameters of the outer bearing and the inner bearing are inconsistent. For the inner bearing structure, a dry lubricant with a high coefficient of friction is used to perform gradient coating on the contact interfaces between the inner circle of the middle ring (3), the raceway of the inner ring (5) and the inner-layer balls (4). For the outer bearing structure, a dry lubricant with a low coefficient of friction is used to treat the contact interfaces between the outer ring (1), the outer circle of the middle ring (3) and the surfaces of the outer-layer balls (2) respectively.

2. The double-layer protected bearing according to claim 1, wherein The outer ring (1), the middle ring (3) and the inner ring (5) are concentrically arranged.

3. The double-layer protected bearing according to claim 2, characterized in that, The groove curvature coefficient of the inner bearing is greater than that of the outer bearing, and the tightness of the inner bearing is less than that of the outer bearing.

4. The double-layer protected bearing according to claim 3, wherein, The inner-layer balls (4) are in a stepped interference fit in the raceway between the inner circle of the middle ring (3) and the inner ring (5), and the outer-layer balls (2) are in a stepped clearance fit in the raceway between the outer ring (1) and the outer circle of the middle ring (3).

5. The double-layer protected bearing according to claim 4, characterized in that, The contact stress of the inner-layer balls (4) in the raceway between the inner circle of the middle ring (3) and the inner ring (5) is less than the contact stress of the outer-layer balls (2) in the raceway between the outer ring (1) and the outer circle of the middle ring (3).

6. The double-layer protected bearing according to claim 5, characterized in that, The surface of the inner-layer balls (4) is subjected to homogeneous lubrication modification using a dry lubricant with a high coefficient of friction.

7. The double-layer protected bearing according to claim 6, characterized in that, The surface of the outer-layer balls (2) is subjected to homogeneous lubrication modification using a dry lubricant with a low coefficient of friction.

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