JP2000087986A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling bearing suitable for use under an ultra-high vacuum of 10 ^-5 Pa or less, in which the amount of generated dust is small and vacuum evacuation can be performed efficiently. SOLUTION: A plurality of rolling elements 3 are rotatably held between an inner ring 1 and an outer ring 2 via a retainer 4,
In a rolling bearing sealed with a shield plate 5, a solid lubricant film is formed on at least one of the inner raceway surface of the inner ring 1, the outer raceway surface of the outer ring 2, the surface of the rolling element 3 and the inner peripheral surface of the pocket of the cage 4. A rolling bearing, wherein a plurality of through holes are formed so as to occupy 20% or less of the surface area of the seal member in the shield plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rolling bearing,
More specifically, the present invention relates to a rolling bearing used under a vacuum, particularly, an ultra-high vacuum of 10 ⁻⁵ Pa or less.

[0002]

2. Description of the Related Art For example, in the manufacture of semiconductor elements, liquid crystal panels, hard disks (HD), etc., rolling bearings used in film forming processes such as sputtering and plasma CVD are used in an environment where vacuum or air and vacuum are repeated. Grease etc. cannot be used because it contaminates the vacuum chamber by evaporation, and a solid lubricating film is formed on the rolling elements, the raceway surfaces of the inner and outer rings, and the inner peripheral surface of the cage pocket for lubrication. . Further, in these film forming apparatuses, it is required to minimize dust generation due to abrasion friction of the solid lubricating film, but at the same time, in order to suppress impurities taken into the film as low as possible, the outgas from the bearing should be reduced. It is important to control. The demand for the suppression of the outgassing tends to increase more and more. As a countermeasure, for example, Japanese Patent Application Laid-Open No. Hei 6-280881 proposes a rolling bearing in which a sliding portion is coated with a lubricating film in which a hydrocarbon gas is degassed. ing.

[0003]

By the way, in the above-mentioned film-forming process, exhaust is performed to evacuate the film-forming chamber and the like. At that time, the bearing is also exhausted. However, bearings are generally sealed, for example, by fixing a shield plate to the outer ring so that dust such as a solid lubricating film or metal powder that has separated does not contaminate the external environment. The gap is very small. For this reason, the conductance becomes small, and it becomes difficult to exhaust the gas. In some cases, the gas may be accumulated. If the number of bearings incorporated in the device is several, this does not cause a serious problem, but if the number is several tens, the effect of the conductance cannot be ignored. In recent years, for example, a film forming process is often performed under an ultra-high vacuum of, for example, 10 ⁻⁵ Pa or less.
When evacuating to such an ultra-high vacuum, there is a problem that the bearing itself is a source of outgassing and it takes time to evacuate. In particular, in a use environment where vacuum and atmosphere are repeated, evacuation is frequently performed, so that shortening the evacuation time has a great effect on production efficiency.

[0004] The present invention has been made in view of such a situation, has a small amount of dust generation, can efficiently perform evacuation, and can be used particularly under an ultra-high vacuum of 10 ^-5 Pa or less. It is an object of the present invention to provide a suitable rolling bearing.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to hold a plurality of rolling elements between an inner ring and an outer ring so as to roll freely through a retainer, and to seal the rolling elements with a shield plate. A solid lubricant film is formed on at least one of the inner ring raceway surface of the inner ring, the outer ring raceway surface of the outer ring, the rolling element surface, and the pocket inner peripheral surface of the cage,
The rolling bearing is characterized in that a plurality of through holes are formed in the shield plate so as to occupy 20% or less of the surface area of the sealing member.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of a main part showing an embodiment of the rolling bearing of the present invention.
This rolling bearing holds a plurality of rolling elements, ie, balls 3, between an inner ring 1 and an outer ring 2 via a retainer 4 so as to roll freely, and also fixes shield plates 5 to both ends of the outer ring 2. It is schematically configured. Further, the gap between the shield plate 5 and the inner ring 1 is extremely small.

In the above, the material of each member is not limited, but the inner ring 1, the outer ring 2 and the balls 3 are preferably formed of a non-magnetic material such as non-magnetic stainless steel or ceramics. For example, in an electron beam lithography system, when a magnetic material is used for transportation or the like, residual magnetism may be generated, which may adversely affect the resolution of the electron beam and the like. Can be. Cr-Ni as non-magnetic stainless steel
, Cr-Mn-N and austenitic precipitation hardened steels are known, and all of them can be suitably used in the present invention. Cr-Ni type is 18
The base material is SUS304, which is -8 stainless steel, and the amount of Ni is increased. In addition, Cr-Mn-N-based is a completely austenitic Cr-Ni stainless steel of N
It is a high Mn-high N steel in which i is replaced with Mn, N, etc., and has high strength. In addition, austenitic precipitation hardening steel is austenitic stainless steel, precipitation hardening element C,
Ceramics to which P, Ti, Al, Nb, V, etc. are added, and these precipitated phases, carbides, phosphides and other intermetallic compounds are precipitated by aging treatment, include sintering aids such as yttria, alumina, and nitride. Alumina, silicon carbide, zirconia, aluminum nitride, and the like can be used in addition to those mainly containing silicon nitride using aluminum, titanium nitride, or the like.

Although the solid lubricant film 6 is formed only on the surface of the ball 3 in FIG. 1, the inner raceway surface of the inner ring 1, the outer raceway surface of the outer ring 2, the surface of the ball 3, Cage 4
A solid lubricant film is formed on at least one of the inner peripheral surfaces of the pockets. The solid lubricant that can be used in the present invention is not particularly limited. For example, polytetrafluoroethylene (PTFE), MoS ₂ , graphite, Ag, h
-BN, fluorinated graphite and the like. Further, as described in JP-A-6-280881,
A lubricating film obtained by degassing a hydrocarbon gas is also possible. Also, the thickness of the solid lubricant film 6 is not particularly limited, but is a typical thickness of this kind of solid lubricant film, that is, 0.1 mm.
It can be 1 μm to 10 μm.

The shield plate 5 has a plurality of through holes 7 so as to occupy 20% or less of the surface area of the shield plate 5. By providing the through holes 7, the conductance is increased and the exhaust inside the bearing is facilitated. However, as the area ratio of the through holes 7 increases, there is also a problem that the amount of generated dust increases. According to the experiment described later, even if the area ratio of the through-hole 7 exceeds 20%, the exhaust time cannot be further sharply reduced, and the amount of dust generated is not more than 20%. It turned out that there was no significant increase. The present invention is based on this finding. The opening diameter and number of the through holes 7 are not particularly limited as long as the above-mentioned area ratio is satisfied. However, the larger the opening diameter of the through hole 7 is, the larger the amount of dust generated tends to be. Therefore, the opening diameter is preferably 1 mm to 2 mm. Further, the arrangement of the through holes 7 and their intervals are not particularly limited. The shape of the opening of the through hole 7 is not particularly limited, and may be an ellipse, a rectangle, or a polygon in addition to a circle.

(Experiment 1) The vacuum dust test apparatus shown in FIG.
The change in the amount of dust generated when the area ratio of the through hole 7 is changed
I asked. The vacuum dust tester has a test bearing in the vacuum chamber 10.
11 and accommodated in a test bearing by a motor 12 provided outside.
11 from the test bearing 11
Particle generated by laser scattering type particle counter 13
It is measured by: The test bearing 11 has a silver coating
608 ball bearings with shields with different through hole area ratios
The one to which the plate was attached was used. All through holes have a diameter of 1
mm, and the area ratio was changed according to the number. Trial
The test conditions were an axial load of 19.6N and a maximum hertz contact surface.
Pressure 1.0 GPa, normal temperature, inner ring rotation speed 600 rpm, vacuum
Degree 1 × 10 ^-FourPa and dust with a particle size of 0.21 μm or more
Measured. Figure 3 shows the amount of dust generated from the measurement results
This shows the relationship with the area ratio.
If it is less than 20%, it is almost constant, and if it exceeds 20%,
It was found that the number increased rapidly at that time.

(Experiment 2) A 608 ball bearing having shield plates with different through-hole area ratios is set in a vacuum chamber, and evacuated by a vacuum pump. Time required until the degree of vacuum reaches 1 × 10 ^-5 Pa Was measured. FIG. 4 shows the relationship between the evacuation time and the area ratio of the through-hole obtained from the measurement results. As the area ratio of the through-hole increases, the required evacuation time decreases, but the area ratio of the through-hole decreases. It has been found that if it exceeds 20%, no further reduction in the time required for exhaust is observed.

From the above experimental results, it can be seen that if the area ratio of the through holes 7 of the shield plate 5 is 20% or less, it is possible to simultaneously suppress the amount of dust generation and shorten the exhaust time.

[0013]

As described above, the rolling bearing of the present invention has a small amount of dust and is easy to evacuate. It is particularly suitable for devices used under repeated environments.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part showing one embodiment of a rolling bearing of the present invention.

FIG. 2 is a schematic configuration diagram of a vacuum dust test apparatus.

FIG. 3 is a graph showing the relationship between the amount of dust generated and the area ratio of through holes obtained in Experiment 1.

FIG. 4 is a graph showing the relationship between the required exhaust time and the area ratio of through holes obtained in Experiment 2.

[Explanation of symbols]

 Reference Signs List 1 inner ring 2 outer ring 3 ball (rolling element) 4 cage 5 shield plate 6 solid lubricant film 7 through hole

Claims (2)

[Claims] 1. A rolling bearing comprising a plurality of rolling elements rotatably held between an inner ring and an outer ring via a retainer and sealed with a shield plate, wherein an inner ring raceway surface of the inner ring is provided. A solid lubricant film is formed on at least one of the outer raceway surface of the outer race, the rolling element surface, and the inner peripheral surface of the pocket of the cage, and the shield plate has a plurality of surfaces so as to occupy 20% or less of the surface area of the seal member. A rolling bearing characterized in that a through hole is formed. 2. The rolling bearing according to claim 1, wherein the inner ring, the outer ring, and the rolling elements are formed of a non-magnetic material.