JP2002130279A - Touchdown bearing for magnetic bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve durability that can withstand a number of touchdowns without corroding a bearing itself even in a corrosive circumstance, and to obtain a touchdown bearing capable of stabilizing the performance of a magnetic bearing device and improving its operational efficiency. SOLUTION: A holder 24 is made from a metal of a lead-containing copper family, and the whole or a part of the surface, other than the surface for rolls of an internal ring 21 and an external ring 22, is coated with a material represented by zinc and having high tendency for ionization. An important part can be well protected by utilizing the material having a high tendency to be ionized as a sacrificial positive-pole member 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a touch-down bearing for supporting a rotating member when a magnetic bearing device cannot be controlled.

[0002]

2. Description of the Related Art In a conventional magnetic bearing device, as shown in FIG. 1, touch-down bearings 3 and 4 are disposed at both ends of a rotating shaft 2 which is supported in a non-contact manner by a magnetic bearing 1, so that sudden disconnection or disconnection may occur. When the magnetic bearing 1 becomes uncontrollable due to a power failure or the like, the touchdown bearings 3 and 4 support the rotating shaft 2 to prevent the magnetic bearing 1 and the rotating shaft 2 from being damaged.

FIG. 2 shows the structure of the lower touch-down bearing 3 in the above-mentioned device. This bearing 3 is a front combination of two angular ball bearings 5 and 6, both of a radial load and an axial load. I am receiving it.
Each of the angular ball bearings 5, 6 is formed by incorporating a plurality of balls 10 held by a retainer 9 between an inner ring 7 and an outer ring 8. Is provided so that a preload is not applied to the bearing due to thermal expansion of the inner ring.

In the touch-down bearing 3 having the above structure, the inner ring 7 faces the rotating shaft 2 and the inner diameter surface thereof is the touch-down surface 1.
It becomes 2. On the other hand, in FIG. 1, in a structure in which the housing 15 is rotated and the housing 15 is supported by a magnetic bearing provided on a central shaft, the outer ring 8 of the touch-down bearing faces the housing 15 which is a rotating member, Touch down on the outer diameter surface.

[0005]

Incidentally, the above-mentioned touchdown bearing has been conventionally considered as an emergency use, so that even if the bearing becomes unusable by one or two touchdowns, it is unavoidable. I was But,
To replace the unusable touchdown bearing, disassemble the magnetic bearing device, replace the bearing, and then adjust the touchdown clearance between the inner ring or outer ring and the rotating member to the bearing clearance of the magnetic bearing. Since it is necessary to perform an operation of assembling the bearing device while adjusting with high accuracy, there is a problem that the operation is extremely troublesome. For this reason, recently, there has been a demand for a structure capable of increasing the durability of the touch-down bearing and enduring a large number of touch-downs.

However, in the conventional touchdown bearing, the ball rolling surface and the sliding surface are combined with a ball and a cage material that does not cause seizure, and a solid lubricant is used for lubrication in a vacuum. Although a lubricating structure has been adopted, a bearing structure that can be used in an environment containing a corrosive gas therein in a vacuum environment has not been studied.

In recent years, magnetic bearing devices are often used in semiconductor manufacturing devices, and their use environment has been required to have durability in a highly corrosive gas such as chlorine gas. At present, the problem that the bearing itself corrodes and the internal lubrication performance cannot be exerted even when not used for touchdown due to the corrosive gas has been highlighted.

Accordingly, an object of the present invention is to provide a touch-down bearing having an optimum touch-down performance in which the bearing is prevented from being corroded even in a corrosive environment.

[0009]

In order to solve the above-mentioned problems, the present invention comprises an inner ring, an outer ring, and a ball held by a retainer incorporated between the inner ring and the outer ring. Or, in the touch-down bearing of a magnetic bearing device in which one of the outer rings is arranged to face a rotating member supported by a magnetic bearing, the retainer is formed of a lead-containing copper-based metal,
The sacrificial anode member is formed on the entire surface or a part of the surface other than the rolling surfaces of the inner ring and the outer ring.

That is, the retainer is formed of a lead-containing copper-based metal,
On the entire surface or a part of the surface other than the rolling surface of the inner and outer rings,
A material having a high ionization tendency, such as zinc, is coated, and the material having a high ionization tendency is used as a sacrificial anode member of the bearing itself, thereby protecting a portion important for lubrication.

As the sacrificial anode member, zinc or a zinc alloy can be used, and the coating can be formed by plating or ion plating. As the lubricating film formed on the ball rolling surface, a lead film,
There is a coating of molybdenum disulfide, and three types of lead bronze are preferable as the lead-containing copper-based metal forming the cage.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic structure of a touch-down bearing according to the present invention is the same as the conventional structure shown in FIG. 2, and as shown in each embodiment of FIGS. A plurality of balls 23 are interposed between the balls 23
Is held by the holder 24.

As shown in FIG. 3, the retainer 24 is made of a lead-containing copper-based metal such as lead bronze (for example, three types of lead bronze).
Is formed by machining a pocket hole 14 into which the ball 23 fits. Since a lead-containing copper-based metal such as lead bronze emits a smaller amount of gas under vacuum and high temperature conditions than other heat-resistant polymer materials, it does not adversely affect the degree of vacuum even when used in a high vacuum.

As shown in FIG. 4, zinc (Zn) is applied to the inner and outer ring surfaces other than the rolling surface 25 of the inner ring 21 and the rolling surface 26 of the outer ring 22 facing the rotating shaft 2 by ion plating or plating. Alternatively, a coating 17 of a zinc alloy is formed. With this configuration, the lead contained in the cage 24 is transferred to the rolling surface and the ball surface by the rotation of the inner and outer races and the ball, and an excellent lubrication effect can be obtained.

Further, as shown in FIG. 5, a coating of lead 27 may be formed on the rolling surface 25 of the inner race 21 or the rolling surface 26 of the outer race 22. In this way, the lead 27
When the coating of
This has an effect on lubrication during the period until lead is transferred to lead, and more stable lubrication performance can be obtained.

Further, as shown in FIG. 6, a coating of molybdenum disulfide 28 may be formed on the rolling surface 25 of the inner race 21 or the rolling surface 26 of the outer race 22 to obtain lubrication performance.

Further, as shown in FIG.
A film of molybdenum disulfide 28 may be formed on the surface of the substrate to obtain lubrication performance.

On the other hand, the inner race 21 and the outer race 22 are made of SUJ2
The ball 23 is formed of hardened steel, ceramics, or the like. In particular, ceramic balls such as SiN
Since the welding with the iron material is extremely small, it is possible to obtain no abrasion and high wear resistance. However, the material is not limited to such a material, and any other material can be selected as long as the combination has high abrasion resistance and hardly causes seizure.

The zinc (Zn) or zinc alloy coating 17 formed on the inner and outer ring surfaces other than the rolling surface 25 of the inner ring 21 and the rolling surface 26 of the outer ring 22 has a high ionization tendency, so that the bearing is corroded. When placed in an environment, the zinc itself is first ionized and eluted, thereby acting as a sacrificial anode member that prevents and protects other parts, that is, the bearing rolling surface, the cage, and the ball from corrosion. . Therefore, the sacrificial anode member may be made of a material having a high ionization tendency, that is, a material that is easily corroded. Depending on the corrosive environment, aluminum or magnesium may be used, or an alloy thereof may be used.

In forming the coating of the sacrificial anode member, a wet plating method may be used in addition to the ion plating. Film formation by ion plating is advantageous in that a thin film can be easily formed and a change in the size of the bearing itself can be suppressed, so that there is no problem in mounting the bearing itself.

The sacrificial anode member may be mounted as a bulk material 29 on the inner race 21 or the outer race 22, as shown in FIG.

[0022]

As described above, the present invention realizes durability that can withstand a large number of touchdowns without corroding the bearing itself even in a corrosive environment, and stabilizes the performance of the magnetic bearing device and improves the operation. This has the effect of improving efficiency.

[Brief description of the drawings]

FIG. 1 is a structural diagram of a magnetic bearing device.

FIG. 2 is a sectional view showing a touch-down bearing.

FIG. 3 is a perspective view showing a part of the retainer according to the first embodiment.

FIG. 4 is a partial cross-sectional view showing one example of a touch-down bearing according to the present invention.

FIG. 5 is a partial sectional view showing another example of the touch-down bearing according to the present invention.

FIG. 6 is a partial sectional view showing another example of the touch-down bearing according to the present invention.

FIG. 7 is a partial sectional view showing another example of the touch-down bearing according to the present invention.

FIG. 8 is a partial sectional view showing another example of the touch-down bearing according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic bearing 2 Rotating shaft 3, 4 Touch-down bearing 5, 6 Angular ball bearing 7 Inner ring 8 Outer ring 9 Cage 10 Ball 12 Touch-down surface 13 Ring member 14 Pocket hole 15 Housing 17 Coating 21 Inner ring 22 Outer ring 23 Ball 24 Cage 25, 26 Rolling surface 27 Lead 28 Molybdenum disulfide 29 Bulk material

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kenichi Suzuki 1578 Higashikaizuka, Iwata-shi, Shizuoka Prefecture F-term in NTN Corporation (reference) 3J101 AA02 AA32 AA42 AA54 AA62 BA34 BA50 BA53 BA54 BA55 BA56 BA70 BA77 DA05 EA13 EA23 EA24 EA55 EA78 FA08 FA31 GA55 GA60 3J102 AA01 BA03 BA17 CA08 CA14 CA18 DA03 DA09 FA02 FA12 FA13 FA29

Claims (9)

[Claims] 1. An inner ring, an outer ring, and a ball held by a retainer incorporated between the inner ring and the outer ring. One of the inner ring and the outer ring is opposed to a rotating member supported by a magnetic bearing. In the touch-down bearing of the magnetic bearing device, the retainer is formed of a lead-containing copper-based metal, and a sacrificial anode member is attached to the entire surface or a part of the surface other than the rolling surfaces of the inner ring and the outer ring. Touchdown bearing of magnetic bearing device. 2. The method according to claim 1, wherein said sacrificial anode member is a coating.
A touch-down bearing for a magnetic bearing device according to claim 1. 3. The touch-down bearing for a magnetic bearing device according to claim 1, wherein the sacrificial anode member is made of zinc or a zinc alloy. 4. The touchdown bearing for a magnetic bearing device according to claim 2, wherein the coating of the sacrificial anode member is formed by plating. 5. The touch-down bearing for a magnetic bearing device according to claim 2, wherein the coating of the sacrificial anode member is formed by ion plating. 6. The touch-down bearing according to claim 1, wherein the sacrificial anode member is made of a bulk material. 7. The touch-down bearing for a magnetic bearing device according to claim 1, wherein a lead coating is formed on the rolling surface. 8. The touch-down bearing for a magnetic bearing device according to claim 1, wherein a coating of molybdenum disulfide is formed on the rolling surface. 9. The touch-down bearing for a magnetic bearing device according to claim 1, wherein the lead-containing copper-based metal forming the cage is of three types of lead bronze.