JP3361158B2 - Rolling bearing for vacuum equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in an environment where heat resistance and electrical conductivity are required at the same time in a vacuum atmosphere, such as a rolling bearing used in an ion plating or sputtering processing apparatus. Regarding rolling bearings.

[0002]

2. Description of the Related Art Ion plating and sputtering treatment devices are used for semiconductor manufacturing, and as surface treatment devices, for example, hard film treatment (Ti) on jigs and tools such as drills.
N film treatment, TiC film treatment). In general, such a hard coating treatment is often carried out while heating the work (drill or the like) to a high temperature in order to enhance the adhesion of the coating, and the work surface temperature may reach up to about 500 ° C.

By the way, in the above-mentioned ion plating processing apparatus and the like, a mechanism for rotating the workpiece is installed in the processing tank, but the bearing used in this mechanism is exposed to a high temperature for the reason described above. Therefore, heat resistance is required as its characteristic. On the other hand, during the coating treatment, since it is necessary for the current to flow on the work side as a cathode electrode, the bearing that serves as the current-carrying path is required to have conductivity.

[0004]

As a means for ensuring the heat resistance of the bearing, it may be considered that the bearing is made of all-ceramic. However, since the cost is too high, rolling elements are generally used. Often, a hybrid type is used in which ceramics and bearing rings are made of a heat-resistant metal material.
In addition, since the hybrid type can avoid the adhesion phenomenon due to contact between metals, there is also an advantage that it can be used without lubrication in a vacuum. On the other hand, in such a hybrid type bearing, since the metal and the ceramic are in contact with each other, it is not possible to ensure the electrical conductivity.

Therefore, the present invention is to provide a rolling bearing having both heat resistance and conductivity in a vacuum atmosphere.

[0006]

According to a first aspect of the present invention, there is provided a rolling bearing for vacuum equipment, comprising a plurality of ceramics which are interposed between an inner ring and an outer ring made of an iron-based material and raceway surfaces of the inner ring and the outer ring to load bearing loads. a load rolling elements, there is provided with a plurality of metallic non-loaded rolling element without loading the bearing load, and a metallic cage holding the loaded rolling member and the non-loaded rolling member, in the axial direction By applying a preload, the orbit of the loaded rolling element and the orbit of the unloaded rolling element are forcibly made different.

According to a second aspect of the present invention, in the rolling bearing for vacuum equipment according to the first aspect, a non-load rolling element is provided with a metal coating of good electric conductivity on its surface. Here, the good-electricity metal coating refers to a coating made of a metal material having higher electrical conductivity than the material for forming the unloaded rolling element.

According to a third aspect of the present invention, there is provided a rolling bearing for vacuum equipment according to the first or second aspect, in which a solid lubricating coating having no conductivity is formed on the surface of the load rolling element.

According to a fourth aspect of the present invention, in the rolling bearing for vacuum equipment according to the first aspect, a lubricating coating of molybdenum disulfide or PTFE is formed on the surface of the loaded rolling element, and a silver coating is formed on the surface of the unloaded rolling element. It was formed.

[0010]

[Function] By forming the inner ring and the outer ring of an iron-based material and the load rolling element of a ceramic material, the heat resistance of the bearing can be improved, and at the same time, the adhesion phenomenon due to contact between metals is avoided. Therefore, it is possible to allow non-lubricated use in a vacuum. Further, by forming the unloaded rolling element with a metal material, through the unloaded rolling element,
Alternatively, since the energization path is formed between the inner and outer races through the unloaded rolling element and the metal cage, it is possible to ensure the energization of the bearing. Furthermore, by forcibly making the orbit of the loaded rolling element different from the orbit of the unloaded rolling element, the surface condition of the unloaded rolling element orbit is maintained in a healthy state, so that a good energized state can be maintained for a long time. can do.

By forming a metal coating of good electric conductivity on the surface of the unloaded rolling element, the electrical conductivity between the inner and outer races and the unloaded rolling element and between the unloaded rolling element and the cage is improved. The conductivity of the bearing can be further improved.

By forming the solid lubricating coating on the surface of the load rolling element, lubrication between the raceways of the inner and outer rings and the load rolling element is performed, so that the durability of the bearing can be improved. Generally, as solid lubricants, soft metals such as gold, silver and lead, layered substances such as molybdenum disulfide, polyimides and polymer materials such as PTFE are used. Among them, molybdenum disulfide and PTFE are used. When a solid lubricant having no conductivity such as is used, there is a concern that the insulating transfer coating formed on the raceway surface may insulate the inner and outer races from the unloaded rolling element. However, in the present invention, the orbit of the loaded rolling element and the orbit of the unloaded rolling element are forcibly made different, so an insulating transfer coating is not formed on the orbit of the unloaded rolling element, and the electrical conductivity is Reserved.

[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 has a plurality of balls 3 interposed between the inner ring 1 and the outer ring 2, and the raceways 1a, 2a of the inner and outer rings 1, 2 and a holding member for holding the balls 3 at equal intervals around the circumference. It is composed of a container 4. The inner ring 1 and the outer ring 2 are made of a ferrous material such as a SUS440C material subjected to a heat treatment, and the cage 4 is made of a metal material such as SUS304 material.

Of the plurality of balls 3, half are load balls 31 for bearing load, and the remaining half are load balls 31.
The non-loaded balls 32 are slightly smaller in diameter and do not bear the bearing load, and the loaded balls 31 and the unloaded balls 32 are alternately arranged. The load ball 31 is made of a ceramic material, and the non-load ball 32 is a metal material such as SUS4.
A metal ball 32a made of 40C material is formed (by ion plating or the like) on a surface of a metal ball 32a having good electric conductivity, for example, a silver film 32b made of silver having the highest electric conductivity among metals. In FIG. 1, the difference in diameter between the loaded ball 31 and the non-loaded ball 32 is shown in a much exaggerated manner.

As shown in FIGS. 1b and 1c, the outer ring 2
Is axially pressed by the spring 5 arranged laterally,
Preload is applied to the bearing. Therefore, the load ball 3
No. 1 rolls on a track separated by a contact angle θ from the groove bottoms of the track surfaces 1a and 2a, but the unloaded ball 32 does not receive preload directly, so that the track bottoms the groove bottoms of the track surfaces 1a and 2a. To roll as.

In this bearing, the load ball 31 is made of a ceramic material, and the inner ring 1 and the outer ring 2 are heat-treated.
Since it is made of a 0C material, it has better heat resistance than a bearing made of only an iron-based material. Moreover, since the load ball 31 and the inner ring 1 and the outer ring 2 are in metal / ceramic contact, no adhesion phenomenon occurs in the contact portions of both, and unlubricated use in vacuum is possible. In addition, between the inner ring 1 and the outer ring 2,
Inner ring 1 → unloaded ball 32 → outer ring 2 or inner ring 1
→ unloaded ball 32 → cage 4 → other unloaded ball 32
→ Because an energizing path such as the outer ring 2 is formed, it can be used in a place where electrical conductivity is required. Furthermore, since a preload is applied to the bearing to forcibly make the orbit of the loaded ball 31 and the orbit of the unloaded ball 32 different, the groove bottom portions of the orbital surfaces 1a and 2a which become the orbit of the unloaded ball 32 are The surface condition is kept healthy, so that a good energization state is maintained for a long time. In this embodiment, since the silver coating 32b is formed on the surface of the non-loaded ball 32, the electric conductivity is better than that of the metal ball 32a alone. Moreover, since the silver coating 32b is not directly subjected to the bearing load, damage (wear and peeling) is small, and good electrical conductivity is maintained for a long period of time. Since silver is significantly worn and deteriorated in the atmosphere, it is particularly effective to adopt a structure capable of suppressing damage to the silver coating 32b when rotation in the atmosphere is unavoidable.

In the embodiment shown in FIG. 2, two deep groove ball bearings having the above construction are used in parallel. The two bearings have a nut 9 screwed to a shoulder portion and a shaft end portion of a shaft 8 via an inner ring spacer 7.
Positioned and fixed on the shaft 8 by and. A spring 5 is interposed between the outer races 2 to apply a predetermined amount of preload to the bearing. It is convenient to handle if it is unitized in the form of this embodiment. The structure of this embodiment is a constant pressure preload structure, but a fixed position preload structure in which an outer ring spacer is interposed between the outer rings 2 may be used.

In the embodiment shown in FIG. 3, a lubricating coating 31b made of crystalline PTFE is formed on the surface of the load ball 31. By forming the lubricating coating 31b,
Since the load balls 31 and the raceways 1a, 2a of the inner and outer races 1, 2 are lubricated, the durability of the bearing can be further improved. On the other hand, since PTFE does not have conductivity, the PTFE formed on the raceways 1a, 2a.
Inner / outer rings 1, 2 and unloaded ball 3 by the transfer coating of E
Although there is a concern that it will insulate between the two, as described above, the trajectory of the loaded ball 31 and the trajectory of the unloaded ball 32 are forcibly made different, so that the trajectory of the unloaded ball 32 is Does not form a PTFE transfer coating,
There is no need to worry about insulation. A lubricating coating made of crystalline PTFE is a PTFE coating like a so-called sputtering coating.
A crystal structure (molecular structure) of E is not subdivided, and is formed by, for example, spraying a treatment liquid of PTFE onto a treatment object or immersing the treatment object in the treatment liquid. You can The configuration of this example is particularly effective when the heat-resistant temperature is about 300 ° C. (because the melting point of PTFE is about 300 ° C.), but when heat resistance higher than that is required, the crystallinity is high. PTFE
Instead of molybdenum, molybdenum disulfide may be used. PTFE,
Since both molybdenum disulfides have relatively good durability in the atmosphere, they can be applied to equipment in which operation in the atmosphere is unavoidable.

In the embodiment shown in FIG. 4, a silver coating 4b is formed on the wall surface of the pocket of the cage 4. In the above-described energizing path, the energization between the non-loaded balls 32 and the cage 4 is improved, which is an effective means when it is expected that the energization will be insufficient.

In the embodiment described above, without forming the silver coating 32b on the surface of the unloaded ball 32,
It is also possible to use a structure in which the metal balls 32a alone are used for energization. In this case, since the metal balls 32a do not apply bearing load, the adhesion phenomenon at the contact portions between the inner and outer rings 1 and 2 does not easily occur. Further, a gold coating, a copper coating, or the like may be formed instead of the silver coating 32b or 4b. Furthermore, the present invention can be applied not only to deep groove ball bearings but also to rolling bearings including roller bearings in general.

[0022]

The present invention has the following effects.

(1) By forming the inner ring and the outer ring from an iron-based material and the load rolling elements from a ceramic material,
The heat resistance of the bearing can be improved, and at the same time, the adhesion phenomenon due to the contact between metals can be avoided, so that it can be used without lubrication in a vacuum. In addition, since the unloaded rolling element is formed of a metal material, an energization path is formed between the inner and outer rings through the unloaded rolling element or between the unloaded rolling element and the cage, so that the bearing Conductivity can be secured. Furthermore, by forcibly making the orbit of the loaded rolling element different from the orbit of the unloaded rolling element, the surface condition of the unloaded rolling element orbit is maintained in a healthy state, so that a good energized state can be maintained for a long time. can do.

(2) By forming a metal coating of good electrical conductivity on the surface of the loaded rolling element, the electrical conductivity between the inner and outer rings and the unloaded rolling element and between the unloaded rolling element and the cage is improved. Therefore, the electrical conductivity of the bearing can be further improved.
Since the metal coating formed on the surface of the unloaded rolling element is not directly subjected to the bearing load, damage (wear etc.) of the metal coating is small and good electrical conductivity is maintained for a long time.

(3) By forming a solid lubricating film having no conductivity on the surface of the load rolling element, lubrication between the raceways of the inner and outer rings and the load rolling element is performed, so that the durability of the bearing is improved. Can be improved. In addition, since the orbits of the loaded rolling elements and the unloaded rolling elements are forcibly made different, an insulating transfer coating made of solid lubricant that does not have conductivity is formed on the unloaded rolling element orbits. Therefore, the electrical conductivity is secured.

(4) Since silver has an extremely high electric conductivity,
By forming a silver coating on the surface of the unloaded rolling element, good electrical conductivity can be ensured.

(5) Crystalline PT on the surface of the unloaded rolling element
By forming a lubricating coating made of FE or molybdenum disulfide, the durability of the bearing can be improved.
Since PTFE and molybdenum disulfide have relatively good durability in the atmosphere, they can be applied to an apparatus in which operation in the atmosphere is inevitable. Further, since the orbit of the loaded rolling element and the orbit of the unloaded rolling element are forcibly made different from each other, an insulating transfer film made of PTFE or molybdenum disulfide is not formed on the orbit of the unloaded rolling element, Conductivity is secured.

[Brief description of drawings]

FIG. 1 is a sectional view (FIG. A) showing an embodiment of the present invention, a bb sectional view (FIG. B) and a cc sectional view (FIG. C) in FIG.

FIG. 2 is a sectional view showing another embodiment of the present invention.

FIG. 3 is a sectional view showing another embodiment of the present invention.

FIG. 4 is a sectional view showing another embodiment of the present invention.

[Explanation of symbols]

1 inner ring 2 outer ring 3 rolling elements 31 load rolling elements 31b Solid lubrication film 32 unloaded rolling elements 32b silver coating 4 cage

Claims (4)

(57) [Claims] 1. An inner ring and an outer ring made of a ferrous material, a plurality of ceramic load rolling elements interposed between the raceways of the inner ring and the outer ring, and bearing load, and a plurality of metal not bearing bearing load. Of the unloaded rolling element and a metal cage for holding the loaded rolling element and the unloaded rolling element, and by applying a preload in the axial direction, the trajectory of the loaded rolling element and the unloaded rolling element A rolling bearing for vacuum equipment characterized in that the orbit of the rolling element is forcibly made different. 2. The rolling bearing for vacuum equipment according to claim 1, wherein a metal coating having good electric property is formed on the surface of the unloaded rolling element. 3. The load lubricating element has a solid lubricating coating having no conductivity formed on the surface thereof.
Rolling bearings for vacuum equipment. 4. A rolling bearing for vacuum equipment according to claim 1, wherein a lubricating coating of molybdenum disulfide or PTFE is formed on the surface of the loaded rolling element and a silver coating is formed on the surface of the unloaded rolling element. .