JP2563923Y2 - Protective bearing for magnetic bearing device - Google Patents

Description

[Detailed description of the invention]

[0001]

The present invention relates to a magnetic bearing device which is mounted on a magnetic bearing device such as a turbo-molecular pump or the like which supports a rotating portion rotating at a high speed in a non-contact state, and causes the rotating portion to be so-called touch-down. The present invention relates to protective bearings for vehicles.

[0002]

2. Description of the Related Art A magnetic bearing device is, for example, a radial magnetic bearing and an axial magnetic bearing fixed to a fixed shaft.
The rotor which is rotated at a high speed of about m is supported in a non-contact state. When the rotation of the rotor is stopped, if the rotor rotating at a high speed contacts the magnetic bearing, the magnetic bearing is damaged. Therefore,
To avoid this, the fixed shaft is provided with a protective bearing for so-called touch-down of the rotor.
Touchdown refers to an operation in which the rotor is stopped by being received by the protective bearing.

[0003] Normally, all ball bearings are used as protective bearings in order to increase the load capacity. One race of the full ball bearing is fixed to a fixed shaft. In a state where the rotor is rotating normally, a predetermined gap (for example, about 0.2 to 0.3 mm) is provided between the other bearing ring and the rotor. The touchdown is performed by the other race contacting the rotor. In this touchdown, when the rotor gradually decelerates and comes into contact with the protective bearing after the rotor rotates at low speed, the load on the protective bearing is relatively small, but the rotor remains at high speed due to power failure or the like. In the case of contact with the protection bearing, the load on the protection bearing becomes very large.

[0004]

Generally, a deep groove type full ball bearing used as a protective bearing is provided with a pair of raceways 91, 92 in a circumferential direction of raceways 91, 92 as shown in FIG. Ball insertion grooves 94, 9 for inserting balls 93 between 92
5 are provided. For this reason, the raceway surfaces 91a and 92a
The ball insertion grooves 94 and 95 are exposed.

On the other hand, since the predetermined gap is provided between the bearing ring 91 for receiving the rotor and the rotor 90 as described above, during touchdown, the bearing ring is inclined while the axis of the rotor 90 is inclined. 91 is often contacted. In this case, the end of the race 91 in the axial direction is a contact portion P with the rotor 90, and the race 91 is also inclined following the rotor 90. And the ball 93 and the raceway surface 91a are liable to be worn, resulting in a problem that durability is reduced.

This invention solves the above technical problem,
Prevents the movement of the ball from being hindered by the ball insertion groove,
An object of the present invention is to realize a protective bearing for a magnetic bearing device having excellent durability.

[0007]

According to a first aspect of the present invention, there is provided a protective bearing for a magnetic bearing device, wherein the rotating portion is supported in a non-contact state with respect to a fixed portion. In a protective bearing comprising a deep groove type full ball bearing provided on a portion and receiving the rotating portion when the rotating portion is stopped, a bearing ring which is brought into contact with the rotating portion when the rotating portion is stopped has a shaft, The crowning is provided along the direction.

[0008]

According to the above arrangement, even when the rotating portion is in contact with the bearing ring in a tilted state at the time of touchdown, the contacted surface is crowned. The part can be located closer to the center in the axial direction. Therefore, the moment for tilting the bearing ring at the time of touchdown can be reduced, and the inclination of the bearing ring can be suppressed.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 2 shows a magnetic bearing device including a protective bearing as one embodiment of the present invention. Referring to the figure, on the inner peripheral side of a cylindrical casing 1 as a fixed portion,
A rotating shaft 2 as a rotating part is arranged. Rotary axis 2
Is supported in a non-contact state by a pair of radial magnetic bearings 3 and a pair of axial magnetic bearings 4 provided in the casing 1, and rotates at a high speed of, for example, about 30000 to 40000 rpm. Protective bearings 5 and 6 are provided at two upper and lower portions of the casing 1 to receive the rotating shaft 2 when the rotating shaft 2 stops. The upper protective bearing is the deep groove type full ball bearing 5 according to the present invention. The lower protective bearing 6 has two oblique contact ball bearings arranged face to face so that a load in the axial direction can be received. The races of the protective bearings 5, 6 are, for example, S
The ball is made of a ceramic material such as silicon nitride or SUS440C material. The surface of the ball is preferably covered with a coating film such as silver.

When the rotating shaft 2 is rotating normally,
A gap of, for example, about 0.2 to 0.3 mm is formed between an inner ring 51 of the full ball bearing 5 and an inner ring 51 described later, and when the rotating shaft 2 stops, the rotating shaft 2 contacts the inner ring 51. And received by the total ball bearing 5. This prevents the rotating shaft 2 from contacting and damaging the magnetic bearings 3 and 4 during touchdown.

Referring to FIG. 1, these full ball bearings 5 include an outer ring 52 fixed to the casing 1, an inner ring 51 opposed to the outer peripheral surface of the rotating shaft 2, and raceway surfaces 51a of the inner and outer rings 51, 52. It consists of a ball 53 interposed between 52a. Ball insertion grooves 54 and 55 for inserting the balls 53 between the inner and outer rings 51 and 52 are provided in a part of the inner and outer rings 51 and 52 in the circumferential direction, so that the ball surfaces are inserted into the raceway surfaces 51a and 52a. Groove 5
4,55 are exposed. Further, the inner peripheral surface 51b of the inner ring 51, which receives the contact of the rotating shaft 2 at the time of touchdown,
Crowning along the axial direction (for example, when the radius of curvature R is 50
(About 0 to 1000 mm).

According to this embodiment, the inner peripheral surface 51b of the inner ring 51 contacted by the rotating shaft 2 at the time of touchdown has:
Crowned along the axial direction. Therefore, when the rotating shaft 2 is brought into contact with the inner peripheral surface 51b of the inner race 51 in a state where the axis 2a is inclined, the contact of the inner peripheral surface 51b with the rotating shaft 2 is greater than when the crowning is not performed. The part P can be located near the center in the axial direction (see FIGS. 1 and 3). Therefore, the moment for tilting the inner ring 51 can be reduced,
Thereby, at the time of touchdown, the inclination of the inner ring 51 can be suppressed, and the interference of the ball 53 with the ball insertion groove 54 can be avoided. Therefore, at the time of touchdown, the movement of the ball 53 is not hindered by the ball insertion groove 54, and the durability can be improved.

In the above-described embodiment, the rotary shaft 2 that rotates about the vertical casing 1 is received, but the rotor that rotates about a horizontal fixed shaft may be received. Further, in a protective bearing in which the rotating shaft 2 contacts the outer peripheral surface of the outer ring 52 at the time of touchdown, the outer peripheral surface of the outer ring 52 may be crowned.

Various changes can be made without changing the gist of the present invention.

[0015]

As described above, according to the protective bearing for a magnetic bearing device of the present invention, when the rotating part is in contact with the bearing ring while the axis of the rotating part is inclined at the time of touchdown, the contacted part is formed by the shaft. Since it can be located near the center in the direction, the moment for tilting the bearing ring can be reduced. Therefore, it is possible to suppress the inclination of the bearing ring at the time of touchdown, to avoid interference between the ball and the ball insertion groove, and to achieve a unique effect that the durability can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a protective bearing for a magnetic bearing device as one embodiment of the present invention.

FIG. 2 is a schematic longitudinal sectional view of a magnetic bearing device.

FIG. 3 is a sectional view of a conventional protective bearing.

[Explanation of symbols]

 Reference Signs List 1 casing (fixed part) 2 rotating shaft (rotating part) 5 total ball bearing (protection bearing) 51 inner ring 51b inner peripheral surface (contact surface)

Claims (1)

(57) [Scope of request for utility model registration] 1. A magnetic bearing device for supporting a rotating part in a non-contact state with respect to a fixed part. A protective bearing comprising a deep groove type full ball bearing provided on the fixed part and receiving the rotating part when the rotating part stops. 3. The protective bearing for a magnetic bearing according to claim 1, wherein a surface of the bearing ring contacted by the rotating portion when the rotating portion is stopped is crowned along the axial direction on the contact surface.