JP2013079720A - Solid lubrication roller bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid lubrication roller bearing having superior long-term durability even when used under a high surface pressure and a high temperature vacuum of at least 250°C and a vacuum of no greater than 10Pa.SOLUTION: A solid lubrication roller bearing 1 includes: an inner race 2 and an outer race 3; a plurality of rolling bodies 4 interposed between the inner race 2 and the outer race 3; and at least one ball 5 comprising a solid lubrication composite material assembled between the inner race 2 and the outer race 3. The rolling bodies 4 are balls comprising silicon nitride, the ball 5 comprising the solid lubrication composite material is a smaller-diameter ball than the balls comprising silicon nitride, and the solid lubrication composite material is a sintered material in which tungsten disulfide is dispersed in an alloy.

Description

  The present invention relates to a solid lubricated rolling bearing for vacuum and high temperature that can be used in film forming apparatuses such as electronic components, optical systems, liquid crystal glass, and semiconductor manufacturing apparatuses, and thin film manufacturing apparatuses for solar cells.

A film forming apparatus such as an electronic component, an optical system, liquid crystal glass, or a semiconductor manufacturing apparatus, or a thin film manufacturing apparatus for a solar cell requires a manufacturing process for performing an organic or inorganic thin film forming process. A surface treatment apparatus such as a sputtering apparatus or a vapor deposition apparatus (PVD, CVD) is used for the film formation process, and an in-line apparatus using a belt conveyance or a multi-chamber apparatus using a robot conveyance is used to move a processed product. In these apparatuses, there are movable parts in the vacuum processing chamber, and solid lubricated rolling bearings used for the movable parts are required to be usable in either air or vacuum, and have low dust generation and durability. In particular, the demand for durability at high vacuum temperatures is the greatest. These solid-lubricated rolling bearings are specifically used in a vacuum high temperature environment of about 250 to 400 ° C. and a degree of vacuum of about 10 ⁻⁴ Pa or less.

  Conventionally, as a solid lubricated rolling bearing for vacuum high temperature, there is one in which a fluorine resin film such as an ion plating film of silver (Ag) or polytetrafluoroethylene (PTFE) is formed on the surface of the ball, but only the film The lubrication source has poor durability.

Further, the plurality of rolling elements incorporated in the rolling bearing include a load rolling element to which a bearing load is applied and a non-loading rolling element to which the bearing load is not applied, and at least one or more non-loading rolling elements are formed of PTFE resin. A solid-lubricated rolling bearing is proposed that has a surface roughness of 1.0 μm or less and a diameter ratio of an unloaded rolling element to a loaded rolling element within a predetermined range (see Patent Document 1). Also proposed is a solid-lubricated rolling bearing in which at least one solid-lubricated composite ball made of a sintered material in which tungsten disulfide (WS ₂ ) is dispersed in a tungsten (W) alloy with high blending is incorporated between the rolling elements. (See Patent Document 2).

JP 2002-250350 A JP 2005-48852 A

  However, since the solid lubricated rolling bearing of Patent Document 1 uses PTFE resin balls, it is difficult to use in a high temperature of 250 ° C. or higher, an environment under a high surface pressure, and is inferior in vacuum high temperature durability. Further, the solid lubricated rolling bearing of Patent Document 2 is excellent in vacuum high temperature durability as compared with that of Patent Document 1, but further improvement in durability is desired. Particularly in recent years, semiconductors and thin films for solar cells are rapidly advancing in related technologies, and the cost reduction in the market is remarkable, and it is important to improve the reliability and durability of rolling bearings, which are the basic components incorporated in the manufacturing equipment. It is a difficult task.

The present invention has been made in order to cope with such a problem, and is a solid lubricated rolling bearing excellent in long-term durability even when used at a high temperature and high surface pressure at a vacuum of not less than 250 ° C. and a vacuum degree of 10 ⁻⁴ Pa or less. The purpose is to provide.

The solid lubrication rolling bearing of the present invention is a solid lubrication rolling bearing used in a vacuum high temperature environment of 250 ° C. or higher and a vacuum degree of 10 ⁻⁴ Pa or less, and is interposed between the inner ring and the outer ring and the inner ring and the outer ring. A plurality of rolling elements, and balls made of at least one solid lubricating composite material incorporated between the inner ring and the outer ring, wherein the rolling elements are balls made of silicon nitride, and made of the solid lubricating composite material. The ball is a ball having a diameter smaller than that of the silicon nitride ball, and the solid lubricating composite material is a sintered material in which tungsten disulfide is dispersed in an alloy.

  The solid lubricating composite material is characterized by containing 80% by volume or more of the tungsten disulfide with respect to the total volume of the composite material. It is particularly preferable that the tungsten disulfide is contained in an amount of 95% by volume or more based on the total volume of the composite material.

  Two balls made of the above-mentioned solid lubricating composite material are incorporated. Further, the alloy is a tungsten alloy.

  The transfer amount of the tungsten disulfide to the inner ring rolling surface is larger than that of a solid lubricated rolling bearing having the same configuration except that the rolling elements are balls made of stainless steel.

  The solid lubricated rolling bearing is a bearing used for a CVD apparatus or a solar cell thin film manufacturing apparatus.

A solid lubricated rolling bearing of the present invention includes an inner ring and an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, and a ball made of at least one solid lubricating composite material incorporated between the inner ring and the outer ring. The rolling element is a ball made of silicon nitride, the ball made of the solid lubricating composite material is a ball having a smaller diameter than the ball made of the silicon nitride, and the solid lubricating composite material is made of tungsten disulfide. Because it is a sintered material dispersed in an alloy, it is used in a vacuum high temperature environment of 250 ° C. or higher and a vacuum degree of 10 ⁻⁴ Pa or lower, and it rolls inner and outer rings from a ball made of a solid lubricating composite material for a long time. The solid lubricating component is sufficiently transferred to the surface and the durability can be improved.

  In addition, since the solid lubricating composite material used in the present invention has a lower hardness than a ball made of a conventional solid lubricating composite material, the processing time is shortened for processing into a spherical ball, leading to cost reduction. By incorporating a ball made of at least one solid lubricant composite material, it is possible to achieve a long life at a high vacuum temperature, so that the function can be improved at low cost.

It is an axial sectional view of the solid lubricated rolling bearing of the present invention. It is a partially cutaway perspective view of the solid lubricated rolling bearing of the present invention. It is the schematic of the barrel processing machine used for processing of a solid lubrication composite material ball.

The solid lubricated rolling bearing of the present invention will be described with reference to FIGS. FIG. 1 is an axial sectional view of a solid lubricated rolling bearing of the present invention, and FIG. 2 is a partially cutaway perspective view of the solid lubricated rolling bearing of the present invention. These bearings are deep groove ball bearings. As shown in FIGS. 1 and 2, the solid lubricated rolling bearing 1 of the present invention includes an inner ring 2 and an outer ring 3, a plurality of rolling elements 4 interposed between the inner ring 2 and the outer ring 3, and the inner ring 2 and the outer ring 3. And a ball (hereinafter also referred to as a “solid lubricant composite ball”) 5 made of at least one solid lubricant composite material interposed therebetween. The rolling element 4 is a ball made of silicon nitride (Si ₃ N ₄ ) (hereinafter also referred to as “silicon nitride ball”). As shown in FIG. 2, the solid lubricated rolling bearing of the present invention has a configuration in which one or more of the plurality of rolling elements 4 are replaced with solid lubricated composite balls 5 from the rolling bearing of the normal mode. . In each bearing, a plurality of silicon nitride balls 4 and solid lubricating composite material balls 5 are held by a cage 6.

  The solid lubricating composite ball 5 has a smaller diameter than the silicon nitride ball 4. For this reason, the silicon nitride ball 4 receives the bearing load, and the solid lubricant composite ball 5 becomes an unloaded ball. Since the solid lubricated composite ball 5 is an unloaded ball, it makes a light frictional contact with the cage surface and the rolling surface of the inner and outer rings while rotating at a lower speed or intermittently than the loaded silicon nitride ball 4. To do. At that time, the ball surface is worn little by little, and the solid lubricating component held on the surface of the cage as the contact surface and the rolling surface of the inner and outer rings is transferred.

In order to improve the durability (lubrication life) of solid lubricated rolling bearings under severe conditions of 250 ° C. or higher (for example, 250 to 400 ° C.) and high vacuum (for example, 10 ⁻⁴ Pa or lower), It is important to secure the amount of solid lubricating component transferred to the outer ring raceway over a long period of time. As a result of intensive studies, the present inventors have found that the amount of transfer depends not only on the composition of the solid-lubricated composite ball but also on the material of other rolling elements that serve as load balls. Specifically, in a conventional configuration in which a part of an existing SUS440C ball (load ball) is replaced with a solid lubricant composite ball (non-load ball) highly blended with tungsten disulfide, the ball made of SUS440C is a load ball. By changing to a silicon nitride ball, the amount of solid lubricating component transferred to the inner ring rolling surface can be greatly increased, and the solid lubricating component can be transferred and supplied to the rolling surface over a long period of time. As a result, it was found that a significant improvement in durability was achieved. The present invention is based on such knowledge.

  Usually, since the load ball is not in direct contact with the solid lubricant composite material ball, it cannot be assumed that the material of the load ball affects the amount of transfer of the solid lubricant component to the rolling surfaces of the inner and outer rings. Although it is not clear about the above action, the load ball of silicon nitride is inactive as compared with that made of SUS440C, the transfer of the solid lubricating component to the load ball is suppressed, and the inner and outer rings are relatively It is thought that the amount transferred to the rolling surface increased. The above transfer amount is the amount of the solid lubricating component present on the rolling surface at an arbitrary time after the operation, and in order to increase this amount, the supply amount from the solid lubricating composite ball is increased. Of course, it is also important that the solid lubricant component once transferred does not desorb.

  The number of solid lubricant composite material balls to be incorporated, that is, the number replaced with load balls is at least one. As the number of solid lubricating composite balls increases, the amount of transfer of the solid lubricating component can be ensured, but at the same time, the number of load balls decreases and the load resistance of the bearing decreases. Although depending on the total number of rolling elements of the solid lubricated rolling bearing (loaded ball + unloaded ball), the number of solid lubricated composite balls incorporated is preferably 1 or 2, and most preferably 2.

  When the diameter of the silicon nitride ball is A, the diameter B of the solid lubricating composite ball is preferably 0.8A ≦ B <A. In the case of B <0.8A, the solid lubricating composite ball is too small to hold the absolute amount of the solid lubricating component, and the amount of wear and transfer when friction contact is made with the cage surface and the inner / outer ring rolling surface. There is a risk that the amount of wearing will be reduced, resulting in insufficient lubrication and poor durability.

  The material of the inner ring 2, the outer ring 3, and the cage 6 is not particularly limited, and an iron-based metal material or the like can be used. Examples of ferrous metal materials include bearing steel, case-hardened steel, cold-rolled steel, hot-rolled steel, carbon steel, stainless steel, and mild steel.

The solid lubricating composite material forming the solid lubricating composite ball in the present invention is a sintered material in which tungsten disulfide (WS ₂ ) is dispersed in a high blend in an alloy having a binder. The alloy used as the binder can be any alloy such as a tungsten (W) alloy or a Cu—Sn alloy. It is preferable to use a W alloy because it has excellent adhesion to tungsten disulfide (WS ₂ ) and can form a solid lubricating composite ball even with a small amount. Further, it may be a sintered material combined with carbon. As a commercial product of the sintered material (solid lubricant composite material) forming the solid lubricant composite ball, for example, NF metal (W + WS ₂ composite material, Cu-Sn + WS ₂ composite material, Cu-Sn + C + WS ₂ composite product) manufactured by Fuji Dice Co., Ltd. Material). After sintering using these sintered materials to form a polyhedral solid lubricating composite material such as a cubic shape, it is processed into a ball shape by barrel processing or the like to be described later.

The solid lubricating composite material preferably contains 80% by volume or more of tungsten disulfide (WS ₂ ) with respect to the total volume of the composite material. By setting it as this range, durability can be improved as compared with a case where an existing SUS440C ball is used as the load ball and a composite material containing 95% by volume of tungsten disulfide (WS ₂ ) is used. Further, it is particularly preferable that 95% by volume or more of tungsten disulfide (WS ₂ ) is included with respect to the total volume of the composite material. By setting this range, the amount of solid lubricant components transferred to the inner raceway can be greatly increased, and solid lubricant components can be transferred to the raceway for a long period of time. Improved durability can be achieved.

On the other hand, in the case where an existing SUS440C ball is used as the load ball, even when the compounding amount of tungsten disulfide (WS ₂ ) in the composite material is equal (95% by volume), such a significant improvement in durability is achieved. I can't hope. In addition, when a composite material containing a high content of molybdenum disulfide (MoS ₂ ) instead of tungsten disulfide (WS ₂ ) is used, the durability is significantly inferior even if silicon nitride balls are used as load balls. From these, it is considered that the above-described effects of the present invention are obtained by a synergistic effect of using silicon nitride balls and using a composite material containing a high blend of tungsten disulfide (WS ₂ ).

  As a method for producing a solid lubricant composite material ball, there is a method in which a sintered polyhedral solid lubricant composite material is processed into a spherical ball by a barrel processing machine and finished to a required size. By barrel processing, a ball having a required size can be obtained, and costs can be reduced in terms of materials and material processing. As a method for forming a ball shape, barrel processing is considered to be the most effective method, which is a mass-productive and low-cost processing method. The solid lubricating composite material is processed into a ball shape while the surface is cut with hard particles. The configuration of the barrel processing machine can include a rotating disk, a fixed disk, a through-hole provided in the fixed disk, and a ball pop-out preventing plate removably fixed to the upper surface of the fixed disk.

  The method for producing the solid lubricating composite ball will be described in detail with reference to FIG. FIG. 3 is a schematic view of a barrel processing machine used for processing a solid lubricating composite ball. This barrel processing machine has a rotating disk 7 and a fixed disk 9. The rotating disk 7 is rotationally driven by driving means (not shown) such as an electric motor. Diamond paper 8 is pasted on the upper surface of the rotating disk 7. A fixed disk 9 is located above the rotating disk 7. The fixed disk 9 has a plurality of through holes 10 distributed in the circumferential direction. The lower end of the through hole 10 is opened, and the upper end is closed by attaching a ball jumping prevention plate 11 to the upper surface of the fixed disk 9. There is a clearance between the upper surface of the rotating disk 7 and the lower surface of the fixed disk 9 so that the finished solid lubricant composite ball does not pass through.

  The material of the fixed disk 9 is an iron-based material or the like. Instead of attaching the diamond paper 8 to the rotating disk 7, a layer containing diamond, silicon carbide, alumina or other hard particles may be provided. At the time of processing, the solid lubricating composite material 12 is put into the through hole 10 with the ball pop-out prevention plate 11 removed. After the ball jumping prevention plate 11 is attached, the driving means is activated to rotate the rotating disk 7. Then, as indicated by the dotted line arrow in the figure, the solid lubricating composite material 12 jumps between the diamond paper 8 and the wall of the fixed disk 9 made of an iron-based material, and repeatedly collides with the diamond paper 8 to cut round corners. Then, the surface is gradually evenly cut into a ball shape.

  By barrel processing, solid lubricated composite balls of the required dimensions can be obtained. In addition, with the barrel processing machine, when # 100 diamond paper with the coarsest particle is used, the particle is coarse, so there is no noticeable clogging when processing solid lubricated composite balls, and the processing time is shortened. Thus, a lubricating ball having a required size can be obtained. Furthermore, with a barrel processing machine, if the processing time is set, lubricating balls of the required dimensions can be obtained, and maintenance of the processing machine is relatively easy.

Examples 1 to 4 and Comparative Examples 1 to 8
As the solid lubricating composite material, a sintered material in which tungsten disulfide (WS ₂ ) or molybdenum disulfide (MoS ₂ ) was dispersed in a tungsten (W) alloy was employed. A sintered body (cube shape with a side of 4 mm) was obtained using a sintered material in which the addition amount of tungsten disulfide (WS ₂ ) or molybdenum disulfide (MoS ₂ ) was changed in various proportions as shown in Table 1. This was finished into a spherical ball by a barrel processing machine shown in FIG. 3 to obtain a solid lubricating composite ball. For barrel polishing, a diamond paper (# 100) manufactured by Marto was used, and a rotating disk was rotated at 85 rpm, and processed into a ball of a size that could be incorporated into a nominal number 608 of a JISB1521 deep groove ball bearing.

  As many solid lubricant composite balls as shown in Table 1 were incorporated into SUS440C deep groove ball bearing SEB08 (claw bending cage), and other rolling elements were used as balls made of SUS440C or silicon nitride to obtain test bearings. The solid lubricating composite material ball (ball diameter: 3.92 mm) was smaller in diameter than the other rolling elements (ball diameter: 4 mm). The following long-term durability tests 1 and 2 were performed on the obtained test bearing. Moreover, the element ratio in the transfer film was measured by the following method. These results are also shown in Table 1.

<Long-term durability test 1 (250 ° C)>
A high-temperature vacuum bearing durability tester was used as a tester, and the degree of vacuum was 10 ⁻⁴ to 10 ⁻⁵ Pa, and the bearings were attached in sets of two. The test conditions were a bearing outer ring temperature of 250 ° C., an axial load of 150 N, a rotation speed of 2000 rpm, and the life judgment was performed when the friction torque of the two bearings reached 152 mN · m.

<Long-term durability test 2 (400 ° C)>
A high-temperature vacuum bearing durability tester was used as a tester, and the degree of vacuum was 10 ⁻⁴ to 10 ⁻⁵ Pa, and the bearings were attached in sets of two. The test conditions were a bearing outer ring temperature of 400 ° C., an axial load of 196 N, a rotation speed of 1000 rpm, and the life judgment was performed when the friction torque of the two bearings reached 152 mN · m.

<Transfer film measurement method>
For Comparative Examples 5 and 6, after completion of the long-term durability test 1 (after the life determination), for Examples and Comparative Examples other than Comparative Examples 5 and 6, after completion of the long-term durability test 2 (after the life determination), the bearings The inner ring rolling surface was measured by SEM / EDX surface analysis to measure the weight% of four elements of Fe, W, Mo, and S. The formation ratio of WS ₂ (MoS ₂ ), which is a solid lubricant, was evaluated based on the ratio of W (Mo) and S to Fe.

As shown in Table 1, by using a solid lubricating composite ball using silicon nitride balls and highly blended with tungsten disulfide (WS ₂ ), a vacuum high temperature of 250 ° C. or higher and a vacuum degree of 10 ⁻⁴ Pa or lower. Under the environment, the amount of solid lubricant components transferred to the inner raceway can be greatly increased, and solid lubricant components can be transferred and supplied to the raceway over a long period of time. Improvements were made.

On the other hand, in Comparative Example 1 using an existing ball made of SUS440C and having a compounding amount of tungsten disulfide (WS ₂ ) in the composite material equivalent to that in Example 1 (95% by volume), significant durability as in the Example was achieved. It was not possible to improve. Further, in Comparative Example 8 using a composite material containing a high blend of molybdenum disulfide (MoS ₂ ) instead of tungsten disulfide (WS ₂ ), the durability was remarkably inferior even if a silicon nitride ball was used as the load ball. there were.

The solid-lubricated rolling bearing of the present invention is solid-lubricated from a ball made of a solid-lubricated composite material to the inner and outer ring rolling surfaces over a long period of time while being used in a vacuum high temperature environment of 250 ° C. or higher and a vacuum degree of 10 ⁻⁴ Pa or lower. Since the components are sufficiently transferred and supplied, durability can be improved, so film deposition equipment such as electronic components, optical systems, liquid crystal glass, and semiconductor manufacturing equipment, vapor deposition equipment (PVD, CVD), and solar cell thin film manufacturing equipment It can utilize suitably as a bearing in a movable part.

DESCRIPTION OF SYMBOLS 1 Solid lubrication rolling bearing 2 Inner ring 3 Outer ring 4 Rolling element (silicon nitride ball)
5 Ball made of solid lubricant composite (solid lubricant composite ball)
6 Cage 7 Rotating Disk 8 Diamond Paper 9 Fixed Disk 10 Through Hole 11 Ball Jump-out Prevention Plate 12 Solid Lubricating Composite Material

Claims (7)

It is a solid lubricated rolling bearing used in a vacuum high temperature environment of 250 ° C. or higher and a vacuum degree of 10 ⁻⁴ Pa or lower,
An inner ring and an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, and a ball made of at least one solid lubricating composite material incorporated between the inner ring and the outer ring,
The rolling element is a ball made of silicon nitride, the ball made of the solid lubricating composite material is a ball having a smaller diameter than the ball made of the silicon nitride,
A solid lubricated rolling bearing, wherein the solid lubricated composite material is a sintered material in which tungsten disulfide is dispersed in an alloy.   2. The solid lubricated rolling bearing according to claim 1, wherein the solid lubricant composite material includes 80% by volume or more of the tungsten disulfide with respect to the total volume of the composite material.   The solid lubricated rolling bearing according to claim 2, wherein the solid lubricated composite material contains 95% by volume or more of the tungsten disulfide with respect to the total volume of the composite material.   The solid lubricated rolling bearing according to claim 1, wherein two balls made of the solid lubricated composite material are incorporated.   The solid lubricated rolling bearing according to any one of claims 1 to 4, wherein the alloy is a tungsten alloy.   The amount of transfer of the tungsten disulfide to the inner ring rolling surface is larger than that of a solid lubricated rolling bearing having the same configuration except that the rolling elements are balls made of stainless steel. The solid lubricated rolling bearing according to claim 5.   The solid lubricated rolling bearing according to any one of claims 1 to 6, wherein the solid lubricated rolling bearing is a bearing used in a CVD apparatus or a solar cell thin film manufacturing apparatus.

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