JPH06159373A - Self-lubricant coating roller bearing - Google Patents

Abstract

PURPOSE:To carry out the uniform coating of rolling body surfaces as well as transfer surfaces and facilitate mass production by conducting the coating of surfaces where at least rolling or sliding contact is made by means of a self-lubricant, conducting this coating by means of mechanical energy. CONSTITUTION:In the case of a roller bearing between whose inner rim 2 and whose outer rim 1 plural rolling bodies 3 are inserted, surfaces where at least rolling or sliding contact is made are coated by means of a self-lubricant selected from graphite, lead, gold, silver, boron nitride, molybdenum disulfide or polyterafluoroethylene of the like. A coating film is formed by joining solid lubricant micropowder to processed matter surfaces by utilizing energy obtained from a mechanical energy means for example, a ball mill, barrel processing, shot peening or the like. As solid lubricant micropowder is coated on processed matter surfaces by means of a physical science reaction, a roller bearing whose coating film thickness is uniform and whose mass production is possible and whose cost is low, can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling bearing, and more particularly, to a rolling bearing which is used in a special environment such as vacuum, high temperature, in liquid metal, in organic solvent, in water, where lubricating oil or grease cannot be used, Alternatively, the present invention relates to a self-lubricant-coated rolling bearing that can be suitably applied when an oil film cannot be formed on a rolling contact portion or a sliding contact portion due to poor lubrication with oil or grease.

[0002]

2. Description of the Related Art Conventionally, there is a self-lubricant coated rolling bearing as a rolling bearing used in an environment where lubrication with oil or grease is inappropriate. This is one in which molybdenum disulfide (MoS ₂ ) or a lubricative film of gold, silver, lead or the like is coated on the component surface of the outer ring, the inner ring, the rolling element, etc. by various means. For example, Japanese Patent Laid-Open No. 2-245514 discloses a technique using sputtering as a coating means. Further, Japanese Patent Application Laid-Open No. 51-42847 discloses a technique for plating the surface of rolling elements with a lubricating metal such as gold or silver.

[0003]

In the conventional self-lubricant coated rolling bearing, when the surface of the rolling element is coated by, for example, sputtering, it is coated only in the direction facing the target, and the back side thereof is not coated. Therefore, the direction is changed again and sputtering is performed with the uncoated surface facing the target. However, even in this case, there is a problem that the coating film thickness becomes thicker on the surface of the rolling element surface closer to the target and becomes thinner at the portion corresponding to the equator, which eventually causes the coating film thickness to become uneven. .

In the case of coating by electroplating, the plating thickness is greatly affected by the distance from the metal electrode, and the electrode must be installed on the rolling element, so that the electrode installation portion is not plated. There was a point. Furthermore, the conventional vapor coating technology has a problem in that the product bearing is expensive because the amount of treatment per batch is small and mass production is difficult and the treatment cost is high.

Therefore, the present invention has been made by paying attention to the above-mentioned conventional problems, and is a means which is uniform not only on the surface of rolling elements but also on the transfer surfaces of the inner ring and the outer ring, and which is easy to mass produce. It is an object of the present invention to provide a low-cost self-lubricant coated rolling bearing coated with a self-lubricant.

[0006]

Means for Solving the Problems The present invention to achieve the above object is to provide a rolling bearing in which a plurality of rolling elements are inserted between an inner ring and an outer ring, at least a surface of which rolling or sliding contact is made of graphite, lead, It is characterized in that it is coated with a self-lubricating agent selected from gold, silver, boron nitride, molybdenum disulfide, polytetrafluoroethylene or the like, and the coating is made by mechanical energy.

[0007]

The self-lubricating coating film of the present invention is formed by binding the solid lubricant fine powder to the surface of the workpiece by utilizing the energy obtained by mechanical energy means such as ball milling, barrel machining, shot peening and the like. Has been formed. That is, by utilizing the impact energy and friction energy generated between the workpieces or between the workpiece and the processing medium (ceramic ball etc.),
The solid lubricant fine powder is coated on the surface of the workpiece by a physicochemical reaction. Therefore, it is possible to provide a low-cost self-lubricant-coated rolling bearing which has a uniform coating film thickness, can be mass-produced.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a cross-sectional view of a ball bearing to which the present invention is applied, in which 1 is an outer ring, 2 is an inner ring, and 3 is a plurality of balls rotatably inserted between an outer ring 1 and an inner ring 2. Rolling element (ball), 4 is ball 3
Is a holder that holds each of them at equal intervals in the circumferential direction. In the above ball bearing, the ball 3 is made of silicon nitride, and the surface thereof is coated with a graphite film as a self-lubricating coating film.

Here, the graphite coating of the ball 3 will be described. First, a 3/8 inch silicon nitride ball was degreased and cleaned in acetone with an ultrasonic cleaner.
Put about half of this in a ball mill container (80 mm diameter, 100 mm height). Next, graphite (graphite CLX manufactured by Chuetsu Graphite Co., average particle size 4 μm, scale-like) was placed in the same container.
And add 30 g to seal the container. As shown in FIG. 2, the container 5 was set on a rotating roll 7 of a ball mill rotating device 6, and a motor 9 was used to pass 500 rpm through a belt 8.
It was rotated for 6 hours. During this rotation, the balls collide with each other in the container 5. Due to the impact energy and the friction energy, graphite existing between the balls is coated on the surface of the silicon nitride ball. Since graphite has no cohesive property, it was finely crushed and coated on the surface of the ball with a thickness of about 1 μm. (Example 2) The ball 3 in the ball bearing shown in Fig. 1 was made by quenching and hardening balls made of SUS440C coated with polytetrafluoroethylene (PTFE).

Explaining the coating in this case, similarly to the above, first, a 3/8 inch SUS440C ball was degreased and washed in acetone with an ultrasonic cleaner. This is a container for ball mill (diameter 80mm, height 100mm)
Put about half of it into the same container and put PTFE (TLP-10F manufactured by Mitsui DuPont Fluorochemicals Co., Ltd., particle size 0.8 μm) into 2
Add 0 g and seal the container. The container was set in a ball mill rotating device and rotated at 500 rpm for 6 hours. Due to the impact energy and the friction energy caused by the collision between the rotating balls, the PTFE interposed between the balls was coated on the surface of the balls. However, PTFE has a cohesive property and is coated thickly and unevenly on the ball surface. The coated balls may be directly incorporated into the bearing and used, but excess PTFE is discharged to the outside of the bearing by the rotation of the bearing. As a result, on the surface of the ball 3 and the rolling contact surfaces of the outer ring 1 and the inner ring 2,
A uniform PTFE coating film having a thickness of 2 μm or less is left and acts as a self-lubricating agent.

In addition, in the case where the solid lubricant such as PTFE is discharged to the outside of the bearing and the surroundings of the bearing are disliked, or in order to further extend the durable life of the bearing, the seal 11 as shown in FIG. 3 is used. It is desirable to use a bearing with a seal attached. In this case, PTF excessively attached to the surface of the ball 3
Since the solid lubricant such as E is blown off by the centrifugal force of the rotation of the bearing, it does not necessarily have to have a closed structure in which the inner ring 2 and the seal 11 are in contact with each other. Further, in order to extend the durable life of the bearing, a plastic cage containing PTFE may be used as the cage 4.

Coated balls 3 obtained in Examples 1 and 2 above
A bearing rotation test was performed using the above, and the difference in torque increase due to the presence or absence of self-lubricant coating was observed. The outline of the test apparatus is shown in FIG. The rolling bearing ball 3 of the DUT is set on the test stand 13 having the air bearing 12 built therein, and the thrust load Fa is applied from the lower part of the stand to drive the rotary shaft 14 to rotate, while the torque is measured by the torque measuring load cell 15. It was measured. FIG. 5 shows the results of comparison by recording the time taken for the torque to rise and reach 100 g · cm or more. The test conditions were as follows.

Rotation speed: 500 rpm, load Fa: 35
kgf, no cage, balls: use 3/8 inch 12 pieces, race surface (transfer surface): same size as thrust ball bearing # 51305, lubrication: coating film only. No wear was observed in either the graphite coating or the PTFE coating, and the torque increase was markedly smaller than that in the case without coating. In addition, the results of the same test performed on the conventional coating by molybdenum disulfide (MoS ₂ ) WO sputtering are also shown in FIG.
It took 34 hours to reach the above torque value. (Embodiment 3) Both the outer ring 1 and the inner ring 2 are made of SUS440C, the balls 3 are coated with PTFE by the same means as in Example 2, and the applicant of the present application filed Japanese Patent Application Laid-Open No. 63-175065. A radial ball bearing # 6206 using the plastic cage 4 made of the polyphenylene sulfide resin composition disclosed in the publication was produced.
The polyphenylene sulfide resin composition comprises 30 to 85% by weight of linear polyphenylene sulfide resin, 5 to 30% by weight of oxybenzoyl polyester, and 10 to 60% by weight of fluororesin. The content of PTFE as a resin was set to 50% by weight.

A rotation test was carried out using this radial ball bearing, and the effect of self-lubricant coating and the effect of sealing were examined in comparison with those of the conventional one. Figure 6 shows the schematic of the test equipment.
It shows in FIG. The bearing 20 to be tested is mounted on a rotary shaft 22 rotatably supported by a supporting bearing 21, and a radial load Fr is applied to the bearing 20 to be tested via an upper lever type pressure device 23.
Was rotated while loading downward. The vibration detector 24 detects the vibration of the test object and the thermocouple 25 detects the temperature rise, and the durability times are compared. The durability life was judged based on the degree of increase in bearing temperature and vibration acceleration. The test conditions were as follows. Number of revolutions:
500 rpm, radial load Fr: 80 kgf, DUT: radial ball bearing # 6206.

The results are shown in FIG. Conventional outer ring, inner ring,
A bearing with balls made of SUS440C and a cage made of SUS304 without seals seized in 4 hours. On the contrary,
Each of the bearings of the present invention exhibited long-term durability. That is, the beads are coated with PTFE and the PT
The FE-containing plastic cage without a seal exhibited a durable life of 530 hours, and the one having the seal 11 further attached exhibited a durable life of 700 hours or more. (Example 4) The PTFE coating of the present invention was applied to each transfer surface of the outer ring and the inner ring made of SUS440C.
In this case, an alumina ball having a diameter of 6 mm was used as a coating medium to be put in the ball mill container together with the outer ring (or inner ring). Below, P in the container of the ball mill
The step of introducing TFE and rotating the container with a ball mill rotating device to apply PTFE coating to the transfer surface may be the same as in the case of coating PTFE on the surface of the ball in Example 2.

On the other hand, uncoated radial ball bearings 620 using uncoated silicon nitride balls as the balls and the above-mentioned PTFE-containing plastic cage as the cage.
6 was prepared and the same durability life test as in Example 3 was conducted.
The test results are also shown in FIG. The durable life in this case is 7
It was over 00 hours. In addition, in the above-mentioned Examples 3 and 4, the combination of the PTFE coating and the PTFE-containing plastic cage was shown, but the graphite coating and the graphite-containing cage may be used. Also, a combination thereof may be used. (Embodiment 5) In this embodiment, a self-lubricant coated rolling bearing of the present invention was obtained by coating the inner race surface of a tapered roller bearing with graphite using the mechanical energy of shot peening.

The outline of the coating process will be described with reference to FIG. The inner ring 30 of the tapered roller bearing having an inner diameter of 55 mm is supported so that its race surface 30a is located on the side surface, and is axially rotated at a rotation speed of, for example, 2 rpm. A graphite tank 31 is arranged above the race surface 30a, and a shot peening material tank 32 is provided side by side with the shot material 3 by compressed air 34 through a pipe 33.
5 is sprayed onto the race surface 30a. The shot material 35 has a hardness of HRC50 or more and a particle size of 200.
Shot material speed is 100
m / sec. As the graphite 36, a scaly one having an average particle diameter of 4 μm is used, and the shot material 3 is dropped at a falling rate of 3 g / sec.
5 was continuously supplied and sprayed onto the race surface 30a. The shot peening time was set while observing the coating film thickness.

The coating means of this embodiment can be applied not only to the roller transfer surface but also to the inner ring flange surface which makes sliding contact with the roller head, and is not limited to solid lubrication bearings and grease lubrication bearings. In oil-lubricated bearings,
It can be applied to prevent seizure on the brim surface. In the self-lubricating coating rolling bearing of the present invention, the coating means is not limited to the ball mill shown in FIG. 2 and the tumbler or barrel may be used for similar coating.

Further, the rollers and the needles can be coated in the same manner as the balls. Furthermore, by coating balls such as alumina and silicon nitride in a ball mill container, the surfaces of the inner and outer rings and the transfer surface are coated. be able to. In that case, the transfer surface can be effectively coated by selecting the ball diameter according to the bearing type and the sizes of the inner and outer rings.

[0020]

As described above, according to the present invention,
At least the surface of the rolling bearing that is in rolling or sliding contact,
A self-lubricating agent selected from graphite, lead, gold, silver, boron nitride, molybdenum disulfide, polytetrafluoroethylene, etc., which was coated using mechanical energy, so that the coating film thickness is uniform and self-lubricating. There is an effect that a lubricant-coated rolling bearing can be provided at low cost.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of a self-lubricating coating rolling bearing of the present invention.

FIG. 2 is a schematic view showing an example of a self-lubricant coating device.

FIG. 3 is a cross-sectional view of another embodiment of the self-lubricating coated rolling bearing of the present invention.

FIG. 4 is a schematic diagram of a rotation test device for a thrust rolling bearing.

FIG. 5 is a graph showing the rotation test results of the product of the present invention and the comparative product.

FIG. 6 is a front view of a durability test apparatus for a radial rolling bearing.

7 is a cross-sectional view of the test device of FIG.

FIG. 8 is a graph showing the results of durability tests of the product of the present invention and the comparative product.

FIG. 9 is a schematic view of a coating application example of the present invention on the inner race surface of the tapered roller bearing.

[Explanation of symbols]

 1 outer ring 2 inner ring 3 rolling element

Claims (1)

[Claims] 1. A rolling bearing in which a plurality of rolling elements are interposed between an inner ring and an outer ring, at least a surface in rolling or sliding contact is coated with a self-lubricant.
A self-lubricating coated rolling bearing whose coating is made by mechanical energy.