JPH07145820A - Rolling bearing for vacuum apparatus - Google Patents

Abstract

PURPOSE:To enhance corner corrosion resistance and durability under vacuum and atmospheric environment by forming a PTFE lubricating film on the surface where produces rolling friction or sliding friction of rolling bearing, and interposing no load rolling elements made of a PTFE base polymer material between an inner ring and outer ring. CONSTITUTION:A deep groove ball bearing uses about half load rolls 31 to which bearing load is applied and the rest no-load balls to which bearing load is not applied, of a plurality of balls 3, and the load balls 31 and no-load balls 32 are alternately arranged. The load ball 31 is made of a metallic material and the no-load ball 32 is made of PTFE base polymer material having self- lubricating capability, and the diameter of the no-load ball 32 is slightly smaller than that of the load ball 31. Lubricating films 1a, 2a, 3a made of crystalline PTFE are formed on the surfaces of the raceway of the inner and outer rings 1, 2 and the surface of the load ball 31 respectively. The lubricating films 1a-3a displays excellent lubricating performance, enhances the durability of the bearing, protects the surface of a base material from a corrosive environment, and increases the corrosion resistance of the bearing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling bearing used in vacuum equipment such as etching equipment and CVD coating equipment in semiconductor manufacturing equipment, carrier equipment in hard disk manufacturing equipment and the like.

[0002]

2. Description of the Related Art In a semiconductor etching process or a CVD (chemical vapor deposition) film treatment process, a reactive gas such as silane, fluorine or chlorine is used. It may come into contact with the reactive gas that it has. For example, in the etching apparatus, since the bearing is rarely used in the processing chamber and is mainly used in the wafer cassette chamber, it does not come into direct contact with the reactive gas, but the wafer is exchanged between the chambers. At this time, the reactive gas may flow into the cassette chamber and come into contact with the bearing. The reactive gas that has flowed in reacts with moisture in the atmosphere that has flowed into the cassette chamber during the exchange with the outside to generate an acid, which corrodes the bearing base material. In particular, if the device is stopped for a long time (about one week), as shown in FIG. 3, the corner corrosion A occurs at the contact portion between the ball 13 and the raceway surface 11a.
May occur, and if the starting torque increases or the corrosion is severe, the starting may be impossible.

On the other hand, in mass-production equipment for hard disks, at present, the vacuum equipment is mainly used in an in-line form, and work is exchanged between the vacuum equipment by a dolly called a carrier. Since this trolley moves alternately in a vacuum and the atmosphere, the bearings incorporated therein are required to have characteristics capable of withstanding operation in both a vacuum and an atmosphere.

[0004]

In order to lubricate bearings used in vacuum equipment, layered substances such as molybdenum disulfide, soft metals such as gold, silver and lead, and polymers such as PTFE and polyimide are generally used. Solid lubricants such as materials are often used. Among these, the layered material and the soft metal are easily attacked by the reactive gas, and are not suitable for use in the above corrosive atmosphere. In addition, silver is severely worn and deteriorated in the atmosphere, and molybdenum disulfide is severely deteriorated by moisture absorption in the atmosphere, and therefore cannot be used in both vacuum and atmospheric atmospheres. On the other hand, PTFE is a chemically stable substance, which is relatively resistant to invasion by reactive gases, and is also excellent in durability in both vacuum and atmospheric atmospheres.

However, when the PTFE lubricating coating is repeatedly peeled and transferred, the coating thickness changes, and the reactive gas permeates from the thinned coating portion to invade the bearing base material, or the coating thickness is reduced. There is a possibility that the lubrication performance will be deteriorated due to the decrease of. Therefore, forming the PTFE coating on the surface of the bearing which causes rolling friction or sliding friction may not be sufficient for preventing corner corrosion and ensuring good durability.

Therefore, an object of the present invention is to provide an effective countermeasure against the above-mentioned corner corrosion, and to provide a rolling bearing having good durability in both vacuum and atmospheric atmospheres.

[0007]

According to the present invention, a lubricating coating made of crystalline PTFE is formed on at least the surface of a rolling bearing which causes rolling or sliding friction, and the inner and outer rings have self-lubricating properties. One or a plurality of unloaded rolling elements made of a PTFE polymer material were interposed.

The load rolling element is made of a ceramic material.

[0009]

The lubricating coating made of crystalline PTFE has a lubricating effect on the surface that causes rolling friction or sliding friction, and at the same time protects the base material surface from reactive gas. Further, the lubricating coating made of PTFE exhibits good durability in both vacuum and air atmospheres. Moreover, even when the lubricating coating is reduced due to wear or the like, the PTFE lubricating powder supplied from the unloaded rolling element can be expected to be transferred, so that the corrosion resistance and durability of the bearing are maintained for a long period of time. Further, even if the bearing is corroded, the number of loaded rolling elements is smaller than that of a normal bearing (because the non-loaded rolling elements are incorporated), so that adverse effects such as increase in starting torque and inability to start are less likely to occur. By forming the load rolling element with a ceramic material, the corrosion resistance is further improved. Further, even if the lubricating coating is worn, the load rolling element and the bearing ring are in contact with each other by ceramic and metal, so that the adhesion phenomenon does not occur and there is no fear of becoming unrotatable.

[0010]

EXAMPLES Examples in which the present invention is applied to a deep groove ball bearing will be described below.

The deep groove ball bearing shown in FIG. 1 is suitable for use in an etching processing apparatus or a CVD coating processing apparatus in a semiconductor manufacturing facility.
It is composed of a plurality of (for example, eight) balls 3 interposed between the outer rings 1 and 2, and a cage 4 for holding the balls 3 at equal intervals around the circumference.

Of the plurality of balls 3, for example, half (4
The number of loaded balls 31 bears the bearing load, and the other half (4) is the unloaded balls 32 that do not load the bearing load. The loaded balls 31 and the unloaded balls 32 are arranged alternately. Load ball 31 is a metal material, non-load ball 32
Is a PTFE-based polymer material (polyimide-based PTFE
In addition, the diameter of the non-loaded ball 32 is slightly smaller than that of the loaded ball 31 in this embodiment. In FIG. 1, the load ball 31
The difference in diameter between the unloaded ball 32 and the unloaded ball 32 is shown in a much exaggerated manner.

In this embodiment, the inner and outer rings 1, 2 are
The lubricating coatings 1a, 2a, and 3a made of crystalline PTFE are formed on the raceway surface and the surface of the load ball 31, respectively. Here, the "lubricating film made of crystalline PTFE" means a PTF like a so-called sputtering film.
A crystal structure (molecular structure) of E is not subdivided, and is formed by, for example, spraying a treatment liquid of PTFE onto a treatment object or immersing the treatment object in the treatment liquid. be able to.

Lubricating coatings 1a, 2a, 3a as described above
Exhibits excellent lubricating properties inherent in PTFE, enhances the durability of the bearing, and at the same time protects the surface of the base material from corrosive atmosphere and enhances the corrosion resistance of the bearing. In addition, these lubricating coatings 1
Even if a, 2a, and 3a decrease due to wear or the like, the PTFE lubricating powder supplied from the unloaded balls 32 (the unloaded balls 32 due to contact with the raceways of the inner and outer rings 1 and 2 and the cage 4). The reduced amount of the film thickness is compensated by the transfer of (generated by scraping from the surface of) and the above effect is maintained for a long time. Further, even if the bearing is corroded, since the number of the load balls 31 is smaller than that of the normal bearing (8) (4), adverse effects such as increase in starting torque and inability to start are less likely to occur. Moreover,
In this embodiment, since the non-loaded balls 32 have a smaller diameter than the loaded balls 31, the adverse effects of corner corrosion are further suppressed. As a means for ensuring the corrosion resistance of the bearing, it is conceivable that the bearing is made of all-ceramic or made of a food material, but there is a problem that the cost becomes too high. In this respect, the configuration of this embodiment is also advantageous in terms of cost.

In FIG. 1, a lubricating coating is formed on the entire outer surfaces of the inner and outer races 1 and 2, but as shown in FIG. 2, a portion such as a fitting surface where the lubricating coating is unnecessary is masked or the like. The film may not be formed from the beginning, or may be removed after the film is formed.

The deep groove ball bearing shown in FIG. 4 is suitable for use as a carrier device in a hard disk manufacturing facility. The basic configuration is similar to that shown in FIG. 1, but one of the plurality of balls 3 is the unloaded ball 3
2 ', the rest is the loaded ball 31, the unloaded ball 3
The difference is that 2 ′ has the same diameter as the load ball 31 or slightly larger than it. The reason why the number of the load balls 31 is increased is that this type of bearing (the bearing used in the carrier device or the like) does not cause the problem of corner corrosion. Therefore, by increasing the number of the load balls 31, the bearing load capacity is increased. This is because it is desirable to improve the durability of the bearing. In addition, the unloaded ball 32 ′ is replaced with the loaded ball 31.
The diameter is made the same as or slightly larger than that in order to more effectively exert the role of the unloaded balls 32 'as a lubricant supply source and further improve the durability of the bearing. . That is, as compared with that shown in FIG. 1, the frictional force between the unloaded balls 32 ′ and the inner and outer rings 1, 2 is increased, so that the amount of PTFE lubricating powder supplied from the unloaded balls 32 ′ is increased, As a result, the lubricating coatings 1a, 2
The decrease of a and 3a is more effectively compensated. as a result,
The good lubrication performance of the lubricating coatings 1a, 2a, 3a is maintained for a long period of time, and the durability of the bearing is significantly improved.
Since the linear expansion coefficient of the PTFE-based polymer material is larger than that of the metal material, the unloaded ball 32 ′ is the loaded ball 31.
Even if the diameter is the same as the bearing operating (bearing temperature rises)
Due to the thermal expansion of, it comes into contact with the inner and outer rings 1 and 2 with a tight margin, and plays a role as a supply source of PTFE lubricating powder.
Although the number of the unloaded balls 32 'is one in this embodiment, the number may be appropriately increased depending on the usage conditions. It goes without saying that the lubricating performance is improved if the number of the unloaded balls 32 'as the lubricant supply source is increased.

The present invention can be applied not only to deep groove ball bearings but also to rolling bearings including roller bearings in general.

[0018]

As described above, according to the present invention,
The lubricating coating made of crystalline PTFE has a lubricating effect on the surface that causes rolling friction or sliding friction, and at the same time protects the surface of the base material from reactive gas, etc. Corrosion resistance and durability can be secured. Further, even when the lubricating coating is reduced due to wear or the like, the PTFE lubricating powder supplied from the unloaded rolling element can be expected to be transferred, so that the corrosion resistance and the durability are maintained for a long time. Further, even if the bearing is corroded, the number of loaded rolling elements is smaller than that of a normal bearing (because the non-loaded rolling elements are incorporated), so that adverse effects such as increase in starting torque and inability to start are less likely to occur.

By forming the load rolling element from a ceramic material, the corrosion resistance and durability of the bearing can be further improved.

[Brief description of drawings]

FIG. 1 is a sectional view (FIG. A) showing an embodiment of the present invention, a bb sectional view (FIG. B) and a cc sectional view (FIG. C) in FIG.

2 is a cross-sectional view showing a state in which a lubricating coating is not formed on a fitting surface or the like in the bearing shown in FIG.

FIG. 3 is a diagram showing corner corrosion.

FIG. 4 is a sectional view (FIG. A) showing another embodiment of the present invention, a bb sectional view (FIG. B) and a cc sectional view (FIG. C) in FIG.

[Explanation of symbols]

 1 Inner ring 1a Lubricating film 2 Outer ring 2a Lubricating film 3 Rolling element 31 Loaded rolling element 3a Lubricating film 32 Unloaded rolling element 32 'Unloaded rolling element

Claims (2)

[Claims] 1. A rolling bearing, wherein a lubricating coating made of crystalline PTFE is formed on at least the surface that causes rolling friction or sliding friction, and a plurality of load rolling elements for bearing load and bearing load are applied. A rolling bearing for vacuum equipment, characterized in that one or a plurality of unloaded rolling elements are interposed between the inner and outer rings, and the unloaded rolling elements are formed of a PTFE polymer material having self-lubricating properties. 2. The rolling bearing for vacuum equipment according to claim 1, wherein the load rolling element is formed of a ceramic material.