JP3395988B2 - Corrosion resistant ball bearings - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing used in a corrosive atmosphere.

[0002]

2. Description of the Related Art For example, in a semiconductor etching process or a CVD (chemical vapor deposition) process, a silane-based, fluorine-based, or chlorine-based reactive gas is used. It may come into contact with a reactive gas having properties. Taking an etching processing device as an example, 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. When performing, the reactive gas may flow into the cassette chamber and come into contact with the bearing. Therefore, particularly high corrosion resistance is required for the bearing used in such an atmosphere.

By the way, for lubrication of bearings used in the above vacuum equipment, layered substances such as molybdenum disulfide, soft metals such as gold, silver and lead, polymer materials such as PTFE and polyimide are generally used. Often solid lubricants are 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, P
When the TFE lubricant film is repeatedly peeled and transferred, the film thickness changes, and reactive gas permeates from the thinned film part to attack the bearing base material, and the lubrication performance is reduced by decreasing the film thickness. May cause a decline in Therefore, forming the PTFE coating on the surface of the bearing that causes rolling friction or sliding friction may not be sufficient to ensure good durability.

In view of the above points, the applicant of the present invention has at least an inner ring and an outer ring made of Ni30 as a rolling bearing suitable for use in the above-mentioned vacuum / atmosphere and corrosive atmosphere.
Of 35% Cr, 19-23% Cr, and the balance of Fe and a high-nickel iron-based alloy, and lubrication of crystalline PTFE on the surface of at least rolling friction or sliding friction among the components of the rolling bearing. We have already proposed a rolling bearing with a coating (Japanese Patent Application No. 4-1727).
22).

[0005]

[Problems to be Solved by the Invention]
No. 172722) rolling bearings are
Although it showed excellent corrosion resistance, durability, and low dust generation in a corrosive atmosphere, for example, a strong corrosive atmosphere in which a high concentration of reactive substances (reactive gas) etc. exist in the atmosphere. Further consideration may be needed to improve corrosion resistance, such as under-use or when long-term no-maintenance use is expected. That is, the cage in this type of corrosion-resistant bearing has a SU
Although it is often formed of austenitic stainless steel represented by S304 (note that the material of the cage is not particularly limited in the above proposal), the corrosion resistance of these materials is higher than that of high nickel alloys. This is because there is concern that the bearing function may deteriorate due to corrosion resistance deterioration of the cage when the usage conditions become severe. On the other hand, a means for forming the retainer with a polymer material is conceivable, but there are problems such as high cost, difficulty in obtaining required strength, and difficulty in processing.

In view of the above problems, it is an object of the present invention to further improve the corrosion resistance and durability of bearings in a corrosive atmosphere.

[0007]

According to the present invention, at least the inner ring and the outer ring are made of a high nickel alloy, and the cage, which becomes a neck in improving the corrosion resistance, is eliminated, and a full ball type is adopted. Then, in order to enable the insertion of the balls between the raceways, the inner ring or the outer ring is provided with an insertion hole for inserting the ball between the raceways of the inner and outer rings, and the insertion hole can be sealed. The member was equipped. In addition, at least rolling
From crystalline PTFE on the surface that causes rubbing or sliding friction
Forming a lubricating coating of
Made of E-based polymer

The balls are made of ceramic.

[0009]

The good corrosion resistance can be ensured by forming at least the inner ring and the outer ring with a high nickel alloy. Furthermore, by eliminating the cage, which becomes a bottleneck in improving corrosion resistance, and adopting a full ball type, there is no concern about deterioration of bearing function due to deterioration of corrosion resistance of the cage, so bearing durability in corrosive atmosphere is further improved. improves. The plurality of balls are inserted between the raceways through the insertion holes provided in the inner ring or the outer ring. The insertion hole is sealed by the sealing member after the ball is completely inserted.

By forming a lubricating coating made of crystalline PTFE on at least the surface of the bearing where rolling or sliding friction occurs, use in vacuum becomes possible. 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,
It also acts to protect the surface of the base material from reactive gases.
Further, the lubricating coating made of PTFE exhibits good durability in both vacuum and air atmospheres.

By forming the sealing member from a PTFE-based polymer material, even if the lubricating coating of PTFE is reduced due to wear or the like, P supplied from the sealing member
Since transfer of TFE lubricant powder can be expected, the corrosion resistance of the bearing,
Durability is maintained for a long time.

By forming the balls of ceramic, the corrosion resistance of the bearing is further improved.

[0013]

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 vacuum equipment such as etching processing equipment and CVD processing equipment in semiconductor manufacturing equipment. This bearing is a full ball bearing consisting of a plurality of balls 3 interposed between the raceways of the inner ring 1, the outer ring 2, and the inner / outer rings 1, 2 and has no cage. The inner ring 1 and the outer ring 2 are made of high nickel alloy, and the balls 3 are made of ceramic. here,
"High nickel alloy" is based on nickel,
It includes both a mixture of this with other materials (metal, metal and non-metal) and a mixture of this with other metal materials such as iron as a base material and nickel. As the former, Hastelloy C-276 (manufactured by Mitsubishi Materials Corporation: Cr
16%, Mo16%, W4%, Fe4%, Ni balance),
Hastelloy C-22 (Mitsubishi Materials Corporation: Cr
22%, Mo13%, W3%, Fe3%, Ni balance),
MA Plasthard-C (manufactured by Mitsubishi Materials Corporation)
(Hereinafter referred to as a high nickel-based alloy), and the latter includes Ni 30 to 35%, Cr 19 to 23%, Fe.
The rest is iron-based alloys (hereinafter referred to as high-nickel iron-based alloys).

The outer ring 2 is provided at one location with an insertion hole 4 penetrating in the radial direction from the outer diameter surface toward the raceway surface.
Through this insertion hole 4, the ball 3 can be inserted between the raceways of the inner and outer races 1, 2. Since the outer ring 2 is made of a high nickel base alloy or a high nickel iron base alloy and has a lower hardness than general bearing steel (SJ2 etc.) (HRC5
0 or less), there is an advantage that the processing of the insertion hole 4 is easy. After the ball 3 is completely inserted, the insertion hole 4 is
It is sealed by the stopper plug 5. The inner surface of the stopper 5 may be machined at the same time as the raceway surface of the outer ring 2 after fitting the stopper 5 into the insertion hole 4, but the stopper 5 is removed from the insertion hole 4 when the ball 3 is inserted. For the purpose of positioning, the stopper 5 and the insertion hole 4 may have an elongated hole-like fitting structure.

Further, in this embodiment, crystalline PT is formed on the raceways of the inner and outer races 1 and 2 and the surface of the ball 3, respectively.
Lubricating coatings 1a, 2a and 3a made of FE are formed. Here, the "lubricating film made of crystalline PTFE" refers to a so-called sputtering film in which the crystal structure (molecular structure) of PTFE is not subdivided,
For example, it can be formed by spraying the treatment liquid of PTFE on the treatment object or by immersing the treatment object in the treatment liquid. Such a lubricating film 1
a, 2a, and 3a exhibit excellent lubricating properties inherent in PTFE, enhance the durability of the bearing, and at the same time protect the surface of the base material from a corrosive atmosphere and enhance the corrosion resistance of the bearing.

In FIG. 2, the stopper 5 is made of a PTFE polymer material (including a polyimide base to which PTFE is added).
An example formed by is shown. Even if the lubricating coatings 1a, 2a, 3a are reduced due to wear or the like, the stopper 5
Since the reduced amount of the film thickness is compensated by the transfer of the PTFE lubricating powder (generated by being scraped from the inner surface of the stopper 5 by contact with the balls 3) supplied from the above, the above effect is maintained for a long time. It In addition, when the ball 3 is used under a light load, the PTFE lubricating powder can be expected to be transferred from the ball 3 by forming the ball 3 with a ceramic material containing PTFE, and the same effect can be obtained.

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

The deep groove ball bearing described above can be used in vacuum (for both atmosphere and vacuum), but when it is used only in the atmosphere, instead of forming the lubricating coatings 1a, 2a, 3a. It is preferable that a fluid lubricant such as grease is enclosed in the bearing, or a solid lubricating composition such as plastic grease is filled and solidified in the bearing.

[0020]

The present invention has the following effects.

(1) By forming at least the inner ring and the outer ring of a high nickel alloy, good corrosion resistance can be ensured, and further, the cage which becomes a neck for improving the corrosion resistance is eliminated and the total ball type is used. By doing so, there is no concern that the bearing function will deteriorate due to the corrosion resistance deterioration of the cage, so that the durability of the bearing in a corrosive atmosphere can be further improved.

(2) By forming a lubricating coating made of crystalline PTFE on at least the surface of the bearing where rolling or sliding friction occurs, use in vacuum becomes possible. In addition, 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 acts to protect the base material surface from reactive gas and the like, so at a relatively low cost, Corrosion resistance and durability of the bearing can be secured.

(3) By forming the sealing member from a PTFE-based polymer material, even if the lubricating film of PTFE is reduced due to wear or the like, the PTFE lubricating powder supplied from the sealing member is transferred. Since good wear can be expected, good corrosion resistance and durability of the bearing can be maintained for a long period of time.

(4) By forming the balls from ceramics, the corrosion resistance of the bearing can be further improved.

[Brief description of drawings]

1 is a cross-sectional view (FIG. A) showing an embodiment of the present invention, and a cross-sectional view (FIG. B) showing a state in which a lubricating coating is not formed on a fitting surface or the like.

FIG. 2 is a cross-sectional view (FIG. A) showing another embodiment of the present invention, and a cross-sectional view (FIG. B) showing a state in which a lubricating coating is not formed on the fitting surface and the like.

[Explanation of symbols]

1 inner ring 1a Lubrication film 2 outer ring 2a Lubricating film Three balls 4 insertion holes 5 Stop plug (sealing member)

─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-3-37414 (JP, A) JP-A-5-39812 (JP, A) JP-A-48-86010 (JP, A) JP-A-63- 303222 (JP, A) JP 63-140120 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F16C 19/00-19/56 F16C 33/30-33/66

Claims (2)

(57) [Claims] 1. At least an inner ring and an outer ring are formed of a high nickel alloy, and an insertion hole for inserting a ball into the inner or outer ring between raceway surfaces of the inner and outer rings, and a seal capable of sealing the insertion hole. With a hole member , at least rolling friction or sliding
Lubricant surface made of crystalline PTFE on the friction surface
Along with forming the membrane, the sealing member is made of PTFE-based high
Corrosion resistant full ball bearing characterized by being made of child material . 2. The corrosion-resistant full ball bearing according to claim 1 , wherein the balls are made of ceramics.