JPH05302621A - Protection bearing for magnetic bearing device - Google Patents

Abstract

PURPOSE:To remarkably improve the durability by applying pre-load to balls at a plurality of positions in an orbit direction, thereby generating autorotation on the balls with certainty and further causing revolution of the balls on the orbits. CONSTITUTION:A full type ball bearing is provided on a magnetic bearing device wherein a rotor 1 is supported in a non-contact condition to a fixed shaft 2, receiving the rotor 1 when the rotor is stopped. An orbit 4a of an outer ring 4 fixed to the side of the fixed shaft 2 has a distorsion 4b where curvature is changed in respect to a true circle P. In the distorsion 4b, pre-load is applied between balls 4 and orbits 3a, 4a. An orbit 3a of an inner ring 3 is a true circle. Frictional force is generated between the balls which pass portions receiving the pre-load and the orbits due to a contact pressure. Autorotation is forcibly generated on the pre-loaded balls 5 which accordingly roll on the orbits. The balls 5 are liable to perform normal rolling movement at the time of touch down.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic bearing device mounted on a magnetic bearing device for supporting a rotating part rotating at a high speed such as a turbo molecular pump in a non-contact state and for so-called touching down the rotating part. Protective bearings for automobiles.

[0002]

2. Description of the Related Art A magnetic bearing device is, for example, a radial magnetic bearing and an axial magnetic bearing which are fixed to a fixed shaft, so that 30,000 to 40,000 rp is applied to the fixed shaft.
The rotor, which is rotated at a high speed of about m, is supported in a non-contact state. If the rotor rotating at a high speed comes into contact with the magnetic bearing when the rotation of the rotor is stopped, the magnetic bearing is damaged. Therefore,
In order to avoid this, the fixed shaft is provided with a protective bearing for so-called touchdown of the rotor.
Touchdown is an operation in which the rotor is stopped by being received by the protective bearing.

Generally, a full ball bearing is used as the protective bearing in order to increase the load capacity. One of the races of this full ball bearing is fixed to a fixed shaft. When the rotor is rotating normally, a predetermined gap is provided between the other bearing ring and the rotor, and when the rotor stops, the other bearing ring contacts the rotor. Thus, the touchdown is performed. In this touchdown, if the rotor gradually slows down and contacts the protective bearing after the rotor starts to rotate at low speed, the load on the protective bearing is relatively small, but the rotor remains at high speed due to a power failure or the like. When contacting the protective bearing, the load on the protective bearing becomes very large.

[0004]

However, among a plurality of balls, the balls that are actually loaded at the time of touchdown are limited, and only some balls rotate. The remaining balls slide against each other while controlling their rotations, causing early wear and seizure at an early stage, which causes locking, which is problematic in terms of durability.

The present invention solves the above technical problems,
It is an object of the present invention to realize a protective bearing for a magnetic bearing device, which can prevent balls from slipping during touchdown and has excellent durability.

[0006]

According to a first aspect of the present invention, there is provided a protective bearing for a magnetic bearing device, comprising: a magnetic bearing device for supporting a rotating portion in a non-contact state with respect to a fixed portion; In a protective bearing for a magnetic bearing device, which is provided in a portion and receives a rotating portion when the rotating portion is stopped, a bearing ring for receiving the rotating portion is a perfect circle, and a fixed portion side The curvature of the orbit of the bearing ring fixed to is changed so as to apply a preload to the balls at a plurality of positions along the orbit direction.

[0007]

According to the above construction, a frictional force due to the contact pressure is generated between the balls and the orbits which pass through the portions to which the preload is applied at a plurality of positions. Therefore, the balls in the preload portion are forcibly subjected to the rotation motion, and thus roll on the orbit. Balls pass one after another in the preload section, so that all balls are subjected to rotation motion. This allows the ball to approach normal rolling motion during touchdown.

[0008]

Embodiments will be described in detail below with reference to the accompanying drawings showing embodiments. FIG. 1 shows a protective bearing according to an embodiment of the present invention. Referring to the figure, this protective bearing is composed of a full ball bearing A, and a rotor 1 consisting of a shaft as a rotating portion is inserted with a predetermined play, and the rotor 1 comes into contact with this when the rotor 1 is stopped. The inner ring 3 is provided with an inner ring 3, an outer ring 4 fixed to a cylindrical fixed shaft 2 as a fixed portion, and a plurality of balls 5 interposed between the tracks 3a, 4a of the inner and outer rings 3, 4.

The rotor 1 is supported in a non-contact state by a radial magnetic bearing and a pair of axial magnetic bearings, which are provided on the fixed shaft 2, in a non-contact state, for example, from 30,000 to 400.
It rotates at a high speed of about 00 rpm. The full ball bearing A is
It is arranged at both ends of the rotor 1. When the rotor 1 is rotating normally, there is a predetermined gap between the inner ring 3 and the rotor 1, and when the rotor 1 is stopped,
The rotor 1 contacts the inner ring 3 and is received by the full ball bearing 5, so that the rotor 1 does not contact the magnetic bearings and damage them.

The bearing ring of the full ball bearing 5 is, for example, SUS44.
The 0C material and the balls are made of a ceramic material such as silicon nitride or a SUS440C material. The surface of the ball is preferably coated with a coating film of silver or the like. The track 3a of the inner ring 3 is set to be a perfect circle. Further, the track 4a of the outer ring 4 has a plurality of strained portions 4b whose curvatures are partially changed with respect to a perfect circle serving as a base, and are equidistantly arranged in the track direction. Then, the shape of the track 4a including these distorted portions 4b is set to be a substantially triangular shape (in the figure, the distortion is shown in an enlarged state for easy understanding of the distorted shape). .. In each strained portion 4b, the balls 5 passing through the strained portion 4b are projected inward with respect to the perfect circle of the base forming the raceway 4a so that preload can be applied from the respective raceways 3a, 4a. The curvature has changed.

The strained portion 4b has only to be provided at least in the assembled state of the bearing. Therefore, the strained portion 4b may be ground into a shape that causes distortion in the state before the assembly, or may be deformed by force in the assembled state. You may make it generate | occur | produce distortion. In the former case, if polishing is performed in a state in which a force is applied and deformed, a desired strained shape in a state in which the force is released can be obtained. Further, it can be deformed by heat treatment.

According to this embodiment, the balls 5 passing through the strained portion 4b are preloaded from the orbits 3a and 4a, and a large contact is made between the balls 5 and the orbits 3a and 4a. A large frictional force is generated due to the pressure. Therefore, it is possible to reliably cause the plurality of balls 5 passing through the plurality of strained portions 4b to rotate, and to revolve on the track. Therefore, at the time of touchdown, the ball 5 can be brought close to a normal rolling motion, and it is possible to prevent the seizure and the lock at an early stage and significantly improve the durability.

The arrangement of the plurality of strained portions 4b is as follows.
The track 4a can be distorted into other polygonal shapes such as the quadrangular shape shown in FIG. In the case of FIG. 1 and FIG. 2 described above, the curvature changes intermittently with respect to the true circle as the base, but as shown in FIG. 3, the trajectory is continuous over the entire circumference of the trajectory. It can also be an elliptical shape that is dynamically changed.

Further, in the case of the protective bearing which receives the touchdown of the rotor 1 arranged along the horizontal direction, the touchdown direction is the vertical downward direction, so that the ball in this portion does not have a distorted portion. However, it is surely rotated. Therefore, in this case, it is sufficient to provide the distorted portions at equal intervals in the track direction except for the portion below the vertical direction. Further, when the inner ring 3 is fixed to the fixed shaft and the cylindrical rotor comes into contact with the outer ring 4 to be touched down, the curvature of the track of the inner ring 3 may be changed to a predetermined value.

Besides, the present invention is not limited to the above-mentioned embodiments, and various modifications can be made without departing from the scope of the present invention.

[0016]

As described above, according to the protective bearing for a magnetic bearing device of the present invention, by preloading the balls at a plurality of positions in the orbit direction, the balls can be surely rotated.
Further, since it can revolve on the orbit, at the time of touchdown, the ball can be brought close to a normal rolling motion, and durability can be greatly improved.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a protective bearing as an embodiment of the present invention.

FIG. 2 is a schematic diagram of a track of a protective bearing according to another embodiment of the present invention.

FIG. 3 is a schematic view of a track of a protective bearing according to still another embodiment of the present invention.

[Explanation of symbols]

 1 rotor (rotating part) 2 fixed shaft (fixed part) 3 inner ring 3a raceway 4 outer ring 4a raceway 5 balls

Claims (1)

[Claims] 1. A magnetic bearing comprising a deep groove type full ball bearing, which is provided in a fixed part of a magnetic bearing device for supporting a rotating part in a non-contact state with respect to a fixed part and receives the rotating part when the rotating part is stopped. In the protective bearing for equipment, the raceway of the raceway ring for receiving the rotating part is a perfect circle, and the curvature of the raceway of the raceway ring fixed to the fixed part side is preloaded against the ball at multiple positions along the raceway direction. A protective bearing for a magnetic bearing device, which is modified so as to provide