JPH05209627A - Rolling bearing for semiconductor manufacturing equipment - Google Patents

Abstract

PURPOSE:To enhance durability of a lubricating film by forming the lubricating film made of PTFE(polytetrafluoroethylene) having a specific average molecular weight on a surface where rolling friction or slide friction is generated, and forming numerous fine recesses on at least the surface where slide friction is generated. CONSTITUTION:Lubricating films 1a-3a made of PTFE having an average molecular weight of 5000 or lower (PTFE of a low molecular weight) are formed on the rolling surfaces of an inner race 1 and an outer race 2, the flange surface of the inner race 1, and the whole surface of a roller 3 in a cylindrical rolling bearing or the like. Numerous fine recesses 31 are randomly formed in the maximum depth of about 1.0-2.0mum at the rolling surface and flange surface of the inner race 1 by barreling so that the lubricating film 1a is formed into an island shape. Consequently, when a load is applied to the lubricating film 1a from a mating surface, a part of the film la is deeply inserted into the recess 31 so as to prevent the lubricating film 1a from being unnecessarily peeled off owing to an anchor effect of the inserted portion of the film.

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 for semiconductor manufacturing equipment.

[0002]

2. Description of the Related Art Since bearings used in semiconductor manufacturing equipment are operated under a sealed vacuum which requires high cleanliness, generally, a layered material such as molybdenum disulfide is used for lubrication thereof.
Solid lubricants such as soft metals such as gold, silver and lead, polymer materials such as PTFE and polyimide are used.

By the way, in recent years, in the field of semiconductor manufacturing, the line width of circuit patterns has become finer as the degree of integration of semiconductors has increased, and if the abrasion powder of the solid lubricant discharged from the bearing adheres to the pattern, various adverse effects are caused. Because of the possibility of causing it, solid lubricants are required to have particularly low dusting property in addition to the original lubricity and durability.

In view of the above situation, the applicant of the present invention has found that polytetrafluoroethylene having an average molecular weight of 5,000 or less (hereinafter, for the sake of simplicity, on the surface of at least rolling friction or sliding friction among the components constituting the rolling bearing). , Which is abbreviated as low molecular weight PTFE), has already filed an application for a solid lubrication rolling bearing having a lubricating film formed thereon (Japanese Patent Application No. 3-190150, etc.). Conventionally, PTFE used as a solid lubricant for bearings has an average molecular weight of 1 ×.
10 ⁵ or more, mainly 1 × 10 ⁶ to 1 × 10 ⁷ , but by forming a lubricating film using low molecular weight PTFE, excellent lubricity, durability, low dust generation, etc. It has been shown in the above application that a lubricating coating can be obtained. These effects were due to the fact that low-molecular-weight PTFE has remarkably small shear strength and excellent transferability as compared with PTFE conventionally used as a solid lubricant.

[0005]

In recent years, in the field of semiconductor manufacturing, there is a marked tendency toward in-line and compact manufacturing facilities, and it is desired to use the bearing under high load and to reduce the bearing space. There is a strong demand. Such a case can be dealt with by using a roller bearing as the bearing, for example.

However, when a roller bearing having a lubricating coating of low molecular weight PTFE formed thereon was tested for durability and low dust generation, it was found that the characteristics were slightly inferior to the ball bearing. This is considered to be due to the effect of sliding frictional force generated between the end surface of the roller and the collar surface of the bearing ring. That is, in the roller bearing, since the end surface of the roller is contact-guided by the flange surfaces of the inner ring and the outer ring, simply forming a lubricating film on this contact surface causes the lubricating film to be scraped off by sliding friction force, It causes local dropout and early wear. It is considered that this leads to poor lubrication and an increase in the amount of dust generation. As mentioned above, low molecular weight PT
The FE lubricating film is excellent in lubricity and low dust generation, but for these reasons, it is difficult for the roller bearing to sufficiently exhibit its original excellent characteristics.

On the other hand, the ball bearing does not have the above-mentioned problems, but some bearings used in semiconductor manufacturing equipment require maintenance-free use. In such a case, Further improvement of durability is required.

Therefore, an object of the present invention is to provide a low molecular weight PTF.
By exhibiting the excellent characteristics of the lubricating coating made of E in the roller bearing as well, it is possible to expand the applicable bearing types and achieve maintenance-free ball bearings.

[0009]

A rolling bearing for semiconductor manufacturing equipment according to the present invention is made of polytetrafluoroethylene having an average molecular weight of 5000 or less on at least a surface of rolling bearings which causes rolling friction or sliding friction. A lubricating film is formed, which is characterized in that at least the surface of the above-mentioned component that causes sliding friction has a large number of minute recesses.

[0010]

By forming a lubricating film using low molecular weight PTFE, a lubricating film having excellent lubricity and low dust generation can be obtained. This lubricating film is scraped off by the frictional force due to the contact with the mating surface to become lubricating powder. The lubricating powder transfers to the mating surface or the like to form a film again. In this way, the lubricating film performs a lubricating action by repeatedly peeling and transferring.

On the other hand, when sliding friction occurs, a large shearing force acts on the lubricating coating, so that means for limiting the peeling of the lubricating coating to the limit necessary for lubrication is required. In the rolling bearing of the present invention, a large number of minute recesses are formed at least on the surface that causes sliding friction, and when the lubricating film receives a load from the mating surface, a part of the recess enters deeply into the recesses, and this recess enters. Due to the anchor effect, the sub-film portion prevents unnecessary peeling of the lubricating film.

[0012]

EXAMPLES Examples of the present invention will be described below.

FIG. 1 illustrates an embodiment in which the present invention is applied to a cylindrical roller bearing. This bearing includes an inner ring 1, an outer ring 2, a plurality of rollers 3 interposed between the inner and outer rings 1, 2, and a roller 3.
Is constituted by a bearing component such as a retainer 4 for holding at equal intervals around the circumference. Collar portions 1b are provided at both ends of the inner ring 1, and the end surfaces of the rollers 3 are guided in contact with the collar surfaces of the collar portion 1b. The rolling surfaces of the inner and outer races 1 and 2, the rib surface of the inner race 1, and the entire surface of the rollers 3 each have a PTFE (low molecular weight PTFE) lubricant film 1a, 2 having an average molecular weight of 5000 or less.
a and 3a are formed. These lubricating coatings are made of low molecular weight PTFE (for example, ARC7 manufactured by Nippon Acheson),
It was sprayed and adhered to the film forming surface from a position 25 cm apart, and the average film thickness in this case was about 0.6 μm. However, in the figure, the film thickness is exaggerated considerably. As a film coating method of low molecular weight PTFE, there is a dipping method in addition to the above-mentioned spraying method. In the figure, the lubricating coatings 1a, 2 are formed on the entire outer surfaces of the inner and outer races 1, 2.
Although a is formed, as shown in FIG. 2, the parts such as the fitting surface where the lubricating film is not originally required are not subjected to the film treatment by masking, or are removed before the final product. Good to do.

On the rolling surface and the flange surface of the inner ring 1, a large number of minute depressions 31 as shown in an enlarged scale in FIG. 3 are randomly formed, and a lubricating coating 1a is further formed in an island shape. The recess 31 is formed by subjecting the rolling surface and the flange surface to barrel processing or the like, and the maximum depth thereof is approximately 1.0 to 2.0 μm, and the shape thereof is a wedge facing the inside of the base material. It is in a shape. As shown in FIG. 3B, when the lubricating coating 1a receives a load from the rollers 3, the coating portion 1a1 near the recess 31 deeply penetrates into the recess 31. When the lubricating film 1a receives a frictional force due to the contact with the roller 3, the film portion 1a1 deeply entering the recess 31 serves as a kind of anchor to hold the lubricating film 1a. Therefore, the lubricating film 1a does not easily fall off even if it receives a relatively large rolling frictional force or sliding frictional force, and exhibits good lubricity and low dust generation. In particular, a sliding frictional force is generated between the flange surface 3 and the end surface of the inner ring 1, so that the lubricating coating 1a at this portion is particularly likely to fall off, but this can be prevented by forming the recess 31. it can. Further, as shown in FIG. 7C, the lubricating powder 1a3 scraped from the surface of the lubricating coating 1a is the island 1a.
2 and the island 1a2 are trapped in the base material portion, and the transfer film 1a4 is formed in that portion. Also on this transfer film 1a4,
Similarly, the anchor effect of the recess 31 extends and does not fall off easily.

FIG. 6 shows the results of a durability test carried out on the rolling bearing (bearing A) having the above construction and the cylindrical roller bearing (bearing B) in which the recess 31 is not formed in the above construction. .. The durability test was carried out by using two test bearings supporting the shaft at room temperature and a vacuum degree of 10 ^-6 Torr or less,
Rotate under the conditions of thrust load 10N and rotation speed 2500 rpm, and the total friction torque of the two test bearings is 10 ^-2.
The time when it reached Nm was defined as the life. As shown in the figure, the bearing A showed durability twice or more that of the bearing B.

FIG. 7 shows the results of a dusting test conducted on the bearing A and the bearing B. Dust generation test, rotation speed: 50r
pm, thrust load: 10 N, vacuum degree: 10 ^-6 Tor
r, temperature: The test bearing was rotated under the conditions of room temperature, and the amount of dust generated was measured by a dust detector arranged directly below the test bearing. As shown in the figure, the amount of dust generated by bearing A is 1 / the amount of dust generated by bearing B.
It was 2 or less, and the bearing A showed extremely low dust generation. However, the amount of dust generated on the bearing B is considerably smaller than that of a bearing using molybdenum disulfide as a solid lubricant.

In this embodiment, the recess 31 is formed on the rolling surface and the flange surface of the inner ring 1, but the recess 3 is formed.
Reference numeral 1 denotes a surface that causes at least sliding friction, that is, the inner ring 1
It suffices to form it on the end face of the brim surface 3 and not necessarily on both sides, but it may be formed on at least one side. In addition, in FIG. 1 and FIG.
A lubricating film is formed on the rolling surfaces of the outer rings 1 and 2, the flange surface of the inner ring 1, and the entire surface of the roller 3. The lubricating film forms at least the rolling surface of the roller 3, and the end surface of the roller 3 and the inner ring. 1
It may be formed on at least the surface on the side where the recess 31 is formed, of the rib surface. Further, the lubricating film may have a continuous island distribution as shown in FIG. 4 or a uniform distribution as shown in FIG. 5, and the bearing type is a cylindrical roller bearing as shown in FIGS. 1 and 2. The present invention can be applied not only to roller bearings such as tapered roller bearings and self-aligning roller bearings but also to rolling bearings including ball bearings in general. When the present invention is applied to a ball bearing, at least the surface of the ball is formed with a depression, and a low molecular weight PTFE lubricating film is formed on this surface. As described above, since the adhesion of the low molecular weight PTFE lubricating film is improved and the original good lubricity and low dust generation are maintained for a long period of time, it can be used as a maintenance-free bearing in a semiconductor manufacturing facility. it can.

[0018]

As described above, since the rolling bearing of the present invention has a large number of minute recesses on at least the surface of the bearing component where sliding friction occurs, the lubricating film of low molecular weight PTFE formed on this surface has Even if it receives sliding frictional force, it does not easily fall off the surface. Therefore, according to the present invention, the excellent characteristics of the low molecular weight PTFE lubricating film can be sufficiently exerted also in the roller bearing.

Further, although the present invention can be applied to a ball bearing, in this case, the durability is particularly improved, and it is possible to provide a maintenance-free rolling bearing in the field of semiconductor manufacturing equipment.

[Brief description of drawings]

FIG. 1 is a sectional view showing a cylindrical roller bearing according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a state in which a lubricating film on a fitting surface or the like has been removed in FIG.

FIG. 3 is an enlarged cross-sectional view (FIGS. A, b, c) showing a lubricating film.

FIG. 4 is an enlarged sectional view showing a lubricating film according to another embodiment of the present invention.

FIG. 5 is an enlarged sectional view showing a lubricating film according to another embodiment of the present invention.

FIG. 6 is a diagram showing a result of a durability test.

FIG. 7 is a diagram showing results of a dusting test.

[Explanation of symbols]

 1 Inner ring 1a Lubrication film 1b Collar 2 Outer ring 2a Lubrication film 3 Rolling element 3a Lubrication film 4 Cage

Claims (1)

[Claims] 1. A rolling bearing comprising at least a surface on which rolling friction or sliding friction is formed, on which a lubricating film made of polytetrafluoroethylene having an average molecular weight of 5000 or less is formed, and at least A rolling bearing for a semiconductor manufacturing facility, which has a large number of minute recesses on a surface which causes sliding friction.