JP2002227848A - Rolling bearing retainer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling bearing retainer capable of stably maintaining a rotation of a conveying roller or the like for a long period of time even under an environment that a condition of use is severe such as a high temperature. SOLUTION: A cylindrical rolling element retaining part 21 for retaining a rolling element of the rolling bearing is constituted of a mixed sintering material of a solid lubricant and a metal. Reinforcement parts 22 are provided at both ends of the rolling element retaining part 21 and are constituted from a metal material containing at least one of metal components of the mixed sintering material as a main component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cage for a rolling bearing used as a cage for a rolling bearing for supporting a conveying roller of a semiconductor manufacturing facility or a main shaft of an anode rotating X-ray tube.

[0002]

2. Description of the Related Art For example, in a facility for forming a semiconductor layer on the surface of a silicon wafer, processes such as thin film formation on the wafer surface, lithography or etching are performed in a vacuum atmosphere. In addition, such a vacuum process in the semiconductor manufacturing process is performed in a batch process in which a batch of products is collectively processed, and in order to increase production efficiency, each process is connected by a transport line, and the entire transport line is vacuumed. There are cases where in-line production is performed as an atmosphere.In such in-line production, a number of transfer rollers are installed in an apparatus that performs high-temperature processes such as forward / reverse sputtering and vapor deposition on wafers, and these rollers are rotated. In order to transport the product to each process, the bearing supporting the transport roller is required to have a performance capable of stably maintaining the rotation of the roller even under extremely severe conditions of high temperature and vacuum atmosphere.

On the other hand, as shown in FIG. 7, an anode rotating type X-ray tube used in medical and industrial X-ray devices comprises a cathode filament 72 provided in a vacuum vessel 71 and a cathode filament 72 provided in the vacuum vessel 71. An anode target 73 provided in the vacuum vessel 71 so as to face the anode target 72;
And a rolling bearing 74 rotatably supporting the main shaft of No. 3 so that electrons emitted from the cathode filament 72 collide with the anode target 73 to generate X-rays. At this time, the inside of the X-ray tube is maintained in a high vacuum state in order to secure the mean free path of the thermally emitted electrons. Further, when electrons collide with the anode target 73, heat is generated by the kinetic energy of the electrons, so that the inside of the X-ray tube has a high temperature of 300 ° C. or more. Therefore, the bearing 74 that supports the main shaft of the anode target 73 is also exposed to a high temperature of 300 ° C. or more, and such a bearing is required to have the same performance as described above.

[0004] Conventionally, as a bearing for supporting the above-mentioned conveying roller and the main shaft of the X-ray tube, for example, the inner and outer wheels and rolling elements of the bearing are made of a heat-resistant steel material such as stainless steel or tool steel. Ag, Pb, Sn, C on at least one of the raceway surfaces of the inner and outer wheels or the rolling member surface that comes into contact with the moving body
rolling bearings and which gave the lubricating effect by forming a coating of soft metal or MoS _2, WS ₂ such as a single layer or a laminated structure made of a solid lubricant of u like, Ag on the surface of the rolling element, Pb
Rolling bearings in which a coating made of a soft metal such as a metal is formed by a PVD (Physical Vapor Deposition) method such as ion plating are often used.

[0005]

However, the above-described rolling bearings generally wear out quickly, and when such bearings are used as the bearings of the above-described transport rollers, the production line is stopped in a short period of time. The problem arises that the bearing has to be replaced. Further, in the case of an anode rotating type X-ray tube in which bearing replacement is structurally impossible, the life of the bearing becomes the usable time of the tube as it is. Therefore, it is necessary to replace the tube itself, which increases the running cost. It becomes a factor.

In the case of a bearing structure in which lubricant is supplied in the form of a film to the raceway surfaces of the inner and outer wheels, the rolling element surface, the cage, and the like, the film thickness is very small, on the order of submicron or several microns at most. It is thin and the lubricating film may be easily worn depending on the rotation condition of the bearing. If the bearing member is brought into direct contact with the portion where the lubricating film is not formed, it may cause torque fluctuation and may also be a seizure source. That is, in the type of bearing in which such a lubricant is supplied by a film, the bearing life is limited during a period in which the lubricant film is maintained.

Further, the lubrication method using a soft metal PVD coating, which is mainly used at present, does not sufficiently soften the soft metal when the bearing is rotated at a low temperature, and exhibits a brittle behavior. It is difficult for a soft metal to form a lubricating film between the bearing and the raceway surface, and it is easy to cause a decrease in lubricity. Further, when the soft metal is exposed to the air due to a device trouble or the like, it may be oxidized and deteriorated, thereby shortening the life of the bearing. Further, in a high-temperature and low-vacuum environment, such deterioration of the soft metal due to oxidation proceeds sequentially, and the required life may not be sufficiently satisfied. Such deterioration of the lubricant may not only limit the life of the bearing, but also cause a rotational failure such as an increase in bearing torque, causing slippage between the conveyed product and the roller, and possibly damaging the product. In addition, in a bearing for an anode rotary type X-ray tube, these deteriorations in lubricity may cause bearing vibration to increase the operating noise of the device. In particular, quietness is required for medical X-ray diagnostic devices and the like. Can be problematic in certain applications.

In order to solve the above-mentioned problem, Japanese Patent Application Laid-Open No. 63-247507 discloses an arrangement in which a cage for holding a rolling element is made of a solid lubricant. However, since the cage disclosed in the above publication is composed entirely of a solid lubricant, the strength is weak, and cracks and cracks may occur in the cage during rotation.
There is a problem that the rotation of the bearing is hindered or the vibration is remarkably increased due to cracks or cracks generated in the cage.

In order to improve the strength of a cage made of a solid lubricant as described above, Japanese Utility Model Laid-Open No. 2-87121 discloses a highly lubricating graphite material and a high-strength graphite as constituent materials of the cage. A technique has been disclosed in which a material is used, and a portion in contact with a rolling element is formed of a graphite material having good lubricity, and other portions are formed of a high-strength graphite material. However, the strength of graphite is limited.

Further, Japanese Patent Application Laid-Open No. 63-282239 discloses that a holding portion for holding a rolling element is formed of a sintered material having excellent lubricity, and the other portions are formed of a high-strength reinforcing material. A reinforced cage is disclosed. However, in the above-described cage, since the holding portion for holding the rolling element and the reinforcing portion are made of independent materials,
The interface strength between the holding portion and the reinforcing portion is low, and the reinforcing portion may fall off from the holding portion when the bearing rotates. In addition, when a thermal cycle is applied, an interface stress is generated due to a difference in thermal expansion coefficient between the two, and the cage may be decomposed at an interface between the holding unit and the reinforcing unit. Furthermore, if the rolling element contact portion of the cage is made of a solid lubricant, it is difficult to guide the cage as a rolling element due to its strength, and the cage can be either the outer ring inner diameter surface or the inner ring outer diameter surface during bearing rotation. Contact. In this case, if only the contact portion with the rolling element is made of the solid lubricant, excessive shear stress acts in the circumferential direction of the retainer, so that higher strength is required and bearing vibration is generated. It becomes a factor.

An object of the present invention is to solve the above problems,
An object of the present invention is to provide a cage for a rolling bearing which can stably maintain the rotation of a transport roller or the like for a long period of time even under severe use conditions such as high temperature.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides reinforcing members at both ends or one end of a cylindrical rolling element holding portion made of a mixed sintering material of a solid lubricant and a metal. In the provided rolling bearing cage, the reinforcing portion is made of a metal material containing at least one of the metal components of the mixed sintering material as a main component.

[0013] With this configuration, the strength of adhesion between the rolling element holding portion and the reinforcing portion is improved, so that the reinforcing portion does not fall off from the rolling element holding portion during rotation. The rotation of the transport roller and the like can be stably maintained over a long period of time even under severe environment. In particular,
In this case, by forming the reinforcing portion with a metal material having the same composition as the metal component of the mixed sintering material, the adhesion strength between the rolling element holding portion and the reinforcing portion can be further increased.

Further, the cage according to the present invention can be incorporated in a bearing and used for a special environment.
Preferably, the rolling elements of the bearing are formed of a heat-resistant material such as ceramics. When the retainer is guided by the outer ring inner diameter surface or the inner ring outer diameter surface (hereinafter, the former is referred to as the outer ring guide, and the latter is referred to as the inner ring guide), the reinforcing portion ( By adding a solid lubricant to the constituent material of the metal part, the shear stress acting on the cage can be effectively reduced, and the generation of rotational vibration due to the contact between the cage and the inner and outer wheels is effectively suppressed. it can.
Here, if the addition amount of the solid lubricant added to the constituent material (metal material) of the reinforcing portion exceeds 30 vol%, the strength of the solid lubricant is reduced because the strength is weak. The amount is desirably 30 vol% or less. When the amount of the solid lubricant added to the constituent material of the reinforcing portion is 5 to 20 vol%, the adhesion between the rolling element holding portion and the reinforcing portion can be effectively improved, and the inner and outer wheels and the cage can be effectively improved. Since the lubricating property at the contact surface can be reduced, the amount of the solid lubricant added to the constituent material of the reinforcing portion is 5 to 20
vol% is preferred.

When the amount of the solid lubricant added to the constituent material of the reinforcing portion is 0 to 5% by volume, the cage 14 is used as a rolling element guide in consideration of lubricity, and 5 to 20 vol. %
In the case of, the retainer 14 should be a rolling element guide, an inner ring guide and an outer ring guide in consideration of lubricity and strength, and in the case of 20 to 30 vol%, the retainer 14 should be an inner ring and outer ring guide in consideration of strength. Is preferred.

Further, by incorporating such a cage into a bearing and forming the inner and outer wheels and the rolling elements of the bearing with a heat-resistant material such as heat-resistant steel or ceramics, the inner and outer wheels may be deformed even in a high temperature atmosphere, or the inner and outer wheels may be deformed. Is more preferable because it does not soften and can maintain stable rotation. In particular, it is preferable that the rolling element is made of a ceramic material because it hardly adheres to the constituent materials of the inner and outer wheels even at a high temperature. The heat-resistant steel used here is at least a steel material such as bearing steel, stainless steel, M50 material, high-speed tool steel, etc. tempered at an abnormal operating temperature, or a ceramic material such as silicon nitride, zirconia, or aluminum oxide. No. In particular, when the inner and outer wheels are made of steel material,
It is desirable that the rolling elements are made of silicon nitride because of excellent seizure resistance.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an embodiment in which the present invention is applied to a kneaded cage, and FIG. 2 is a cross-sectional view of a rolling bearing provided with the cage of FIG. In FIG. 2, a rolling bearing 10 includes an inner ring 11 that is externally fitted to a shaft body to be supported (for example, a roller shaft of a conveying roller, a main shaft of an anode rotating X-ray tube, and the like), and a concentric circle on the outer periphery of the inner ring 11. When the inner ring 11 rotates integrally with a shaft to be supported, a plurality of (for example, eight) spherical rolling elements 13 disposed between the inner ring 11 and the outer ring 12 are provided. Is the inner and outer ring 1
It rolls in the circumferential direction of 1 and 12.

The rolling elements 13 are held by a retainer 14. On both sides of the retainer 14, foreign matter such as dust enters between the inner ring 11 and the outer ring 12 and scattering of abrasion powder generated from inside the bearing is prevented. A seal ring 15 is provided for passing through. As shown in FIG. 1, the retainer 14 includes a solid lubricant (for example, WS ₂ , C and BN) and a metal (for example, Cu, N).
i and Sn) and a cylindrical rolling element holding portion 21 (for example, inner diameter: 17.5 mm, outer diameter: 21 m) made of a sintered material mixed with
m, width: 5 mm) and an annular reinforcing portion 22 (for example, inner diameter: 17.5 mm, outer diameter:
21 mm, width: 1 mm).
A plurality of (for example, eight) pocket holes 23 for holding the rolling elements (diameter: 4.7625 mm) 13 in a rolling manner.
Are formed at equal intervals along the circumferential direction of the rolling element holding portion 21.

The reinforcing portion 22 is made of a metal material (for example, a Cu-Ni-Sn-based alloy) having the same composition as the constituent material of the rolling element holding portion 21, that is, the metal component of the mixed sintering material. It is formed integrally. The mixing ratio of the solid lubricant and the metal of the mixed sintering material constituting the rolling element holding portion 21 is 70 vol% of solid lubricant and 30 vol% of metal in volume ratio. The mixed sintering material obtained is molded with a compressive strength of 100 MPa or more.

Table 1 shows examples and comparative examples of a rolling bearing (inner diameter: 12 mm, outer diameter: 28 mm, ball diameter: 4.7625 mm) based on such a configuration.

[0021]

[Table 1]

In Table 1, Examples 1 to 4 of the present invention
The rolling element holding part 21 of the cage 14 is made of a mixed sintering material composed of three kinds of solid lubricants of WS ₂ , C and BN and three kinds of metals of Cu, Ni and Sn.
With the same metal material (Cu
-Ni-Sn-based alloy), but the metal material constituting the reinforcing portion 22 of Examples 2 to 4 improves the adhesion between the lubricating portion and the reinforcing portion, and improves the inner and outer wheels 11, 1
In order to suppress the occurrence of rotational vibration due to contact with
Solid lubricants of S ₂ , C and BN are added in an amount of 5 vol% by volume. In the first to third embodiments of the present invention, the inner ring 11, the outer ring 12, and the rolling elements 13 of the bearing are made of SUS440C. However, the rolling elements 13 of the fourth example are formed by nitriding to improve seizure resistance. It is made of silicon.

On the other hand, in Comparative Example 1, as in Embodiment 4, SUS440C was used as a material for the inner ring 11 and the outer ring 12.
The rolling element 13 is made of silicon nitride, and the rolling element holding portion 22 of the cage 14 is made of a mixed sintered material of a solid lubricant and a metal.
This is an example in which the reinforcing portions 22 are not provided at both ends of the first. In Comparative Example 2, the same material as in Examples 2 and 3 was used as a material for forming the reinforcing portion 22 of the cage 14, but the inner ring 11,
SUJ2 is used as a material for forming the outer race 12 and the rolling elements 13.
This is a bearing which is tempered at a lower temperature than that of the embodiment 2 by using. Comparative Example 3 is an example in which a stainless steel press retainer is used as the retainer. A film made of Ag is formed on the surface of the rolling element 13 of Comparative Example 3 by ion plating.

FIG. 3 shows the results obtained by performing a compressive strength test on the cages of Examples 1 to 4 and Comparative Examples 1 and 2 and measuring the breaking load at that time. In the compression strength test at this time, as shown in FIG. 4, the cage 14 was installed with the pocket hole 23 facing downward, and the load cell was compressed from above by a hydraulic press to measure the breaking load of the cage 14. .

In FIG. 3, Examples 1-4 and Comparative Example 2
The compression strength of each of the cages is shown with the measured value of Comparative Example 1 as 1. As shown in FIG. 3, in Examples 1 to 4 of the present invention, it can be seen that the compression strength of the cage is 2.9 to 3.8 times that of Comparative Example 1. Next, a bearing rotation test was performed on each of the bearings in Table 1 using a test device as shown in FIG. 5, and the results of evaluating the life of the bearings are shown in FIG. In the bearing rotation test, the axial load 98
N, the rotation speed was 500 rpm, the outer ring temperature was 300 ° C., and the degree of vacuum was 4 × 10 ⁻⁴ Pa or less. The time when the bearing vibration value became twice the initial value was evaluated as the bearing life. Also,
In FIG. 5, reference numeral 51 denotes a bearing as a specimen, 52 denotes a rotating shaft, 53 denotes a bearing housing, and 54 denotes a coil spring for applying a load (98).
N), 55 are joints, 56 is an AC servomotor, 57 is a vacuum chamber, 58 is a magnetic seal unit, 59 is a heater, 60 is a thermocouple for measuring bearing temperature, and 61 is a dust sensor.

The bearing life evaluation results shown in FIG. 6 show the bearing life of Comparative Example 3 as 1. Examples 1 to 3 are 2.5 to 2.5 of Comparative Example 3 which are all conventional technologies.
It can be seen that the bearing life is 2.9 times as long and that the embodiment 4 in which the rolling elements are made of silicon nitride has a life of 4 times or more. As can be seen from the test results shown in FIGS. 3 and 4, by forming the reinforcing portion 22 with the same metal material as the metal component of the mixed sintering material forming the rolling element holding portion 21,
The adhesion strength between the rolling element holding portion 21 and the reinforcing portion 22 is improved. Therefore, the reinforcing portion 22 does not fall off from the rolling element holding portion 21 during rotation, and the rotation of the transport roller and the like can be stably maintained for a long period of time even under severe use conditions such as high temperature.

The metal material constituting the reinforcing portion 22 is made of W
By adding solid lubricants such as S ₂ , C and BN,
The shear stress acting on the cage 14 can be effectively reduced, and the occurrence of rotational vibration due to the contact between the cage 14 and the inner and outer wheels 11, 12 can be effectively suppressed. The amount of the solid lubricant to be added is 30 vol% or less, preferably 5 vol.
-20% by volume is desirable, and the addition amount of the solid lubricant is 5-2
By setting the volume to 0 vol%, the adhesion between the rolling element holding portion 21 and the reinforcing portion 22 can be effectively improved, and the inner and outer wheels 1
Lubricity at the contact surfaces between the cages 1 and 12 and the cage 14 can be reduced. Further, the addition amount of the solid lubricant is 0 to 5 vol% in volume ratio when the cage 14 is a rolling element guide, and 5 to 2 vol% when the cage 14 is a rolling element guide, an inner ring guide and an outer ring guide.
0 vol%, 2 when cage 14 is inner ring and outer ring guide
It is preferable to set it to 0 to 30 vol%.

Further, the above-mentioned cage 14 is incorporated in the bearing, and the inner and outer wheels 11 and 12 and the rolling elements 13 of the bearing are made of a heat-resistant material such as heat-resistant steel or ceramics. Deformation does not occur, and the inner and outer wheels 11, 12 are not softened, so that stable rotation can be maintained. In particular, when the rolling element 13 is made of a ceramic material, an effect is obtained that it is difficult to adhere to the constituent materials of the inner and outer wheels even at a high temperature.

In the above-described embodiment, the rolling element holding portion 2
Although the case where the present invention is applied to the retainer provided with the reinforcing portions 22 at both ends has been described, the present invention is not limited to this. For example, the reinforcing portions 22 are provided at both ends of the rolling element holding portion 21. The present invention can also be applied to a retainer that is used. In the embodiment described above, WS ₂ , C and BN, Cu and N are used as the mixed sintering material constituting the rolling element holding portion 21.
Although the mixed sintering material with i and Sn was used, the present invention is not limited to this. For example, MoS ₂ or the like may be used as the solid lubricant component of the mixed sintering material. In addition, as a metal serving as a matrix, Fe, Cu, Ni, Cr, M
If at least one selected from the group consisting of o, W, Ta, Co, and Sn is selected, a strong bond can be easily obtained with the solid lubricant component, and the strength of the lubricant portion can be improved.

Further, in the above-mentioned embodiment, the reinforcing portion 22 is made of a metal material having the same composition as the metal component of the mixed sintering material. However, it is not necessary to make the composition up to the alloy composition. Can be obtained. Further, in the above-described embodiment, the normal pressure sintering is used as a method of forming the rolling element holding portion 22. However, even when the HIP sintering is performed after the temporary sintering or the temporary sintering is not performed, the discharge plasma that applies a potential to both ends is used. Higher strength can be obtained by sintering by the sintering method.

In the above-described embodiment, a cylindrical mold is used, and a cage is obtained by machining from a center cylindrical material. However, the mold has an outer diameter and an inner diameter of a predetermined cage shape.
The post-process can be shortened by obtaining a cylindrical material.
Further, as in the third embodiment shown in Table 1, by reducing the number of the rolling elements 13, although the allowable load is reduced, the column portion between the pocket holes 23 can be designed to be thick, so that the strength of the retainer 14 is reduced. Can be more enhanced.

[0032]

As described above, according to the present invention,
It is possible to obtain a rolling bearing retainer and a rolling bearing that can stably maintain the rotation of the transport roller and the like for a long period of time even under severe use conditions such as high temperature.

[Brief description of the drawings]

FIG. 1 is a perspective view of a rolling bearing retainer according to one embodiment of the present invention.

FIG. 2 is a diagram showing a structure of a rolling bearing provided with a cage.

FIG. 3 is a diagram showing the compressive strength of a cage in an embodiment of the present invention and a comparison with a comparative example.

FIG. 4 is a diagram showing a method for test-evaluating the compressive strength of a cage.

FIG. 5 is a view showing a configuration of a test device for testing and evaluating the rotational life of a rolling bearing provided with a cage.

FIG. 6 is a diagram showing the rotational life of a rolling bearing in an example of the present invention in comparison with a comparative example.

FIG. 7 is a diagram showing a configuration of an anode rotating X-ray tube.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Rolling bearing 11 Inner ring 12 Outer ring 13 Rolling element 14 Cage 15 Seal ring 21 Rolling element holding part 22 Reinforcement part 23 Pocket hole

Claims (1)

[Claims] 1. A rolling bearing cage in which reinforcing members are provided at both ends or at one end of a cylindrical rolling element holding portion made of a mixed sintering material of a solid lubricant and a metal. A rolling bearing retainer comprising a metal material containing at least one of the metal components of the material as a main component.