JPH06229423A - Solid lubricating rolling bearing - Google Patents

Abstract

PURPOSE:To improve the durability and low dusting characteristics in a solid lubricating rolling bearing. CONSTITUTION:Microscopic projecting and recessed parts 1b1 and 1b2 created by mechanical work exist on a rolling travel surface and a collar surface of an inner ring 1, and among them, the projecting part 1b1 has a smooth tip part. The recessed part 1b2 is formed in a wedge shape turning inside a base material. These projecting and recessed parts 1b1 and 1b2 run in a stripe shape on the rolling travel surface and the collar surface. A lubricating coat 1a is formed in an island shape on a surface (rolling travel surface and collar surface) of the inner ring 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid lubrication rolling bearing used in semiconductor manufacturing equipment and the like.

[0002]

2. Description of the Related Art For example, a bearing used in a semiconductor manufacturing facility is operated under a sealed vacuum which requires high cleanliness. Therefore, for lubrication, a layered substance such as molybdenum disulfide, gold, Solid lubricants such as soft metals such as 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). , Abbreviated as low molecular weight PTFE) has already been filed (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 the roller bearing on which the lubricating coating of low molecular weight PTFE was formed 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 would cause the lubricating film to be scraped off by sliding frictional force. It causes local drop-off and early wear. It is considered that this leads to poor lubrication and an increase in the amount of dust generation. As described above, the low molecular weight PTFE lubricating coating is excellent in lubricity and low dust generation, but for the above reasons, it is necessary for the roller bearing to fully exhibit its original excellent characteristics. Is difficult. Of course, such a problem is more remarkable in the rolling bearing using the solid lubricant other than the low molecular weight PTFE. On the other hand, in ball bearings, the above-mentioned problems are unlikely to occur, but among bearings used in semiconductor manufacturing equipment, etc.
In some cases, maintenance-free use is required, and in such a case, further improvement in durability is required.

Therefore, an object of the present invention is to solve the problems such as local dropout of the solid lubricating coating and early wear, and to further improve the durability and low dust generation of the solid lubricating rolling bearing.

[0008]

A rolling bearing for semiconductor manufacturing equipment according to the present invention has a solid lubricating coating formed on at least a surface of rolling bearing or sliding friction that causes rolling friction or sliding friction. The surface is one in which the convex portions of the minute irregularities on the surface produced by machining are smooth.

[0009]

The surface that causes rolling friction or sliding friction has a surface shape in which the convex portion of the minute irregularities generated by machining is smooth. Although this surface has a larger surface roughness than a mirror-like surface such as a rolling surface or a flange surface of a general bearing component, the convex portion is smooth. When the solid lubricating coating formed on this surface receives a load from the mating surface, a part of it penetrates deeply into the recess, and the entered coating portion enhances the adhesion to the surface of the solid lubricating coating due to the anchor effect, Prevents unnecessary peeling and wear. The reason why the convex portion is made smooth is to reduce the contact pressure at the tip of the convex portion caused by the load from the mating surface and to avoid the adverse effects caused by increasing the surface roughness.

[0010]

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. The inner ring 1 has a flange portion 1b at both ends thereof, and the end surface of the roller 3 is contact-guided by the flange surface of the flange portion 1b when the bearing rotates. Then, for example, PTFE (low molecular weight PT) having an average molecular weight of 5000 or less is formed on the rolling surfaces of the inner and outer races 1 and 2, the collar surface of the collar portion 1b of the inner race 1, and the entire surface of the roller 3.
FE) lubricating coatings 1a, 2a, 3a are formed.
These lubricating coatings are obtained by spraying and adhering low molecular weight PTFE (for example, ARC7 manufactured by Nippon Acheson) on the coating surface from a position 25 cm away. 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, 2a are formed on the entire outer surfaces of the inner and outer races 1, 2, but as shown in FIG. It is advisable to perform no masking treatment by masking or to remove it before the final product.

As shown in FIG. 3, on the rolling surface and the flange surface of the inner ring 1, minute uneven portions 1b1 formed by machining,
1b2, of which the tip of the convex portion 1b1 is smooth. The recess 1b2 has a wedge shape facing the inside of the base material. The concave and convex portions 1b1 and 1b2 run along the rolling surface and the brim surface in a streak pattern. The height of the convex portion 1b1 (the depth of the concave portion 1b2) is about 1 to 2 μm at the maximum.
After grinding, it is mirror-finished by superfinishing and has a surface roughness of about 0.2 to 0.5 μm. The surface roughness is larger than that of

The surface having the above-mentioned surface shape can be formed, for example, by performing superfinishing up to an intermediate stage after grinding. FIG. 5 shows the surface of the inner ring 1 after completion of grinding. The grinding process performed is the same as that performed as a pre-process for superfinishing in a general bearing manufacturing process. The surface after the completion of grinding is covered with a large number of grinds produced by being ground off by the grindstones, and the cross section thereof has minute irregularities. In the stage of grinding, a machining allowance for the subsequent superfinishing is left, so the surface irregularities 1b1 and 1b2 caused by grinding are left.
Is the final surface finish level (for normal bearing parts)
Compared with, it is considerably large (about 2 to 3 μm). Then, in the superfinishing after grinding, by finishing the machining before finishing the machining for the planned machining allowance, as shown in FIG. Only the portion 1b1 can be made smooth. Not only the inner race 1, but also the rolling surface of the outer race 1 and the surface of the ball 3 may be similarly provided. still,
The ball 3 is usually lapped, but it is preferable to process it according to the above.

As shown in FIG. 4, the lubricating coating 1a is the inner ring 1
Is formed like an island on the surface (rolling surface, brim surface). When the lubricating coating 1a receives a load from the rollers 3, the coating portion 1a1 near the wedge-shaped recess 1b2 deeply penetrates into the recess 1b2. Then, when the lubricating coating 1a receives a frictional force due to the contact with the rollers 3, the coating portion 1a1 deeply entering the recess 1b2 serves as a kind of anchor to hold the lubricating coating 1a on the surface. This action is due to the fact that the surface roughness is increased to some extent. However, this structure alone rather promotes the slippage and wear of the lubricating coating 1a. That is, the convex portion 1b1 generated on the surface after grinding shown in FIG. 5 has an acute angle, and if the lubricating coating 1a is formed directly on this surface, the tip of the convex portion 1b1 is in high contact with the load applied from the roller 3. This is because a pressure is generated and the lubricating coating 1a around the convex portion 1b1 is locally dropped and worn. And as this progresses,
The convex portion 1b1 may protrude from the surface of the lubricating coating 1a and may come into direct contact with the rollers 3. In this embodiment, the convex portion 1b1 is made smooth so as to reduce the contact pressure generated at the tip of the convex portion 1b1 and avoid such an adverse effect. As described above, the lubricating coating 1a has high adhesion to the surface, does not easily fall off even when subjected to a relatively large rolling frictional force or sliding frictional force, and exhibits good lubricity and low dust generation for a long period of time. To do. Especially inner ring 1
Since a sliding frictional force is generated between the rib surface and the end surface of the rib surface 3, the lubricating coating 1a in this portion is particularly likely to fall off, but the rib surface should have a surface shape as shown in FIGS. 3 and 4. This can effectively prevent this. The above effects can be made more remarkable by inclining the lines of the uneven portions 1b1 and 1b2 with respect to the movement direction of the roller 3 (including the case of intersecting the lines).

In the present embodiment, the lubricating coating 1a has an island-shaped distribution for the following reason. That is, the island-shaped distribution allows the lubricant powder 1a3 scraped from the surface of the lubricating coating 1a to be trapped in the base metal portion between the islands 1a2 and 1a2 and form the transfer coating on that portion. , Not only the lubricity is further improved, but also the lubricating powder 1
This is because a3 is less likely to be discharged to the outside of the bearing, and the low dust generation property is further improved.

FIG. 6 shows a rolling bearing (smooth surface of convex portion: bearing A) having the above structure and a low molecular weight P in a standard bearing part.
The results of a durability test conducted on a cylindrical roller bearing (specular surface: bearing B) on which a TFE lubricating film is formed are shown. In the durability test, two test bearings supporting the shaft were rotated under the conditions of room temperature, vacuum degree of 10 ^-6 Torr or less, thrust load of 10 N, and rotation speed of 2500 rpm.
The life was defined as the time point when the total friction torque of the individual test bearings reached 10 ^-2 Nm. As shown in the figure, bearing A is bearing B
2 times more durable than that of However, the durability of the bearing B is considerably higher than that of a bearing using molybdenum disulfide as a solid lubricant.

FIG. 7 shows the results of the dust generation 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.

The lubricating coating is not limited to the island-shaped distribution, and may have a continuous island-shaped distribution (islands in which the thin coating portions are continuous) or a uniform distribution. Further, the solid lubricant is not limited to the exemplified low molecular weight PTFE, but may be a general PTF.
E, molybdenum disulfide or the like may be used. Even in that case, the same effect can be obtained. Further, the bearing type is not limited to the cylindrical roller bearings shown in FIGS. 1 and 2, but can be applied to roller bearings such as tapered roller bearings and self-aligning roller bearings, as well as rolling bearings including ball bearings in general. it can. When the present invention is applied to a ball bearing, at least the surface of the ball has the surface shape shown in FIG. Since the adhesion of the lubricating coating to the surface is improved and good lubricity and low dust generation are maintained for a long period of time, it is possible to achieve maintenance-free ball bearings in semiconductor manufacturing equipment.

[0019]

As described above, the solid lubrication rolling bearing of the present invention has a structure in which the convex portions of the surface that cause rolling friction or sliding friction are smooth, and therefore the solid lubrication formed on this surface is Even if the coating film receives rolling friction and sliding frictional force, it does not easily fall off or wear, maintaining good lubricity and durability for a long period of time. Therefore, according to the present invention, it is possible to further improve the durability and low dust generation of the solid lubrication rolling bearing, and in the case of the roller bearing, the application to semiconductor manufacturing equipment and the like, and in the case of the ball bearing, Maintenance-free can be achieved by improving durability.

[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 coating such as a fitting surface is removed in FIG.

FIG. 3 is an enlarged sectional view schematically showing the surface of the inner ring.

FIG. 4 is an enlarged sectional view schematically showing a lubricating coating formed on the surface of the inner ring.

FIG. 5 is an enlarged plan view (FIG. A) and an enlarged sectional view (FIG.) Showing the surface of the inner ring after grinding.

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 Lubricating film 1b1 Convex part 1b2 Recessed part 2 Outer ring 2a Lubricating film 3 Roller 3a Lubricating film 4 Cage

Claims (1)

[Claims] 1. A solid lubricating coating is formed on at least a surface of rolling bearings that causes rolling friction or sliding friction, and the surface has a minute uneven portion formed by machining. The solid lubrication rolling bearing is characterized in that the convex portion is smooth.