JPH0988975A - Bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent any peeling damage and frosting from occurring as well as to make improvements in bearing acoustic performance by forming a hard carbon film at least either surface of a rolling body or bearing ring. SOLUTION: In this bearing, its form base material of a rolling body and a bearing ring is made of steel, and lubricating oil and grease or the like are interposed between the rolling body and the bearing ring, and in this constitution, a hard carbon film (diamondlike carbon film) is formed in at least either surface of the rolling body or bearing ring. Hardness of this hard carbon film is 2000 to 4000 at Hv, and excellent in wear resistance as a friction factor is about 2.0. This carbon film is formable by means of a physical evaporation of ion plating or the like. With this constitution, even if surface roughness in the rolling body or the bearing ring is large enough, all jog parts of the counterpart surface roughness are crushed at the initial stage of rolling motion, while if there is a nonmetallic interposition, any projection on the surface is also crushed, so that any peeling damage and frosting due to the effect of the surface roughness and the interposition is thus preventable. In addition, sound degradation will not occur for a long period of time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing in which a base material for forming rolling elements and races is steel, and a lubricant such as lubricating oil or grease is interposed between the rolling elements and races.

[0002]

2. Description of the Related Art When a base material for forming rolling elements and races is steel, lubricating performance is improved by interposing a lubricant such as lubricating oil or grease between the rolling elements and races. .

However, when the surface roughness of the mating component is large, or when the lubrication performance deteriorates due to oil film breakage, grease deterioration, etc., the race surface of the races and the rolling element surface are damaged by minute peeling called dense peeling. There is a problem that streak-shaped scratches called frosting occur and the bearing sound is deteriorated.

Conventionally, as countermeasures against these peeling damage and frosting, measures such as changing the lubricating oil and grease and making the surface roughness of the mating object finer have been taken. The demands for downsizing, weight reduction, and high-speed use cannot be met.

In view of this, the present invention prevents peeling damage and frosting by forming a new film having excellent wear resistance and a good friction coefficient on the surface of rolling elements or races made of steel or the like. It is intended to improve the bearing acoustic performance.

[0006]

In order to solve the above problems, the present invention forms a hard carbon film (diamond-like carbon film) on at least one of the surface of rolling elements such as steel and the surface of races. It was done.

The hardness of the hard carbon film is 20 at Hv.
The friction coefficient is about 0.2, which is extremely good as compared with the abrasion coefficient of 0.6 or more when the hard carbon film treatment is not performed.

Therefore, even if the surface roughness of the rolling element or the bearing ring is large, the projections of the mating surface roughness are crushed at the initial stage of rolling, and the projections on the surface are crushed even if there are non-metallic inclusions. Therefore, peeling damage and frosting due to the influence of surface roughness and inclusions can be prevented, and peeling damage due to poor lubrication hardly occurs.

The hard carbon film can be formed on the surface of the steel material by physical vapor deposition such as ion plating.

For example, in ion plating, a hydrocarbon-based gas is introduced into a vacuum container, a DC voltage is applied to a target bearing material to generate glow discharge, and the surface of the bearing material is hardened under the discharge. This is a method of forming a carbon film. In this method, the hard carbon film thickness is about 0.4 to
Since it is 0.6 μm and can be used for most steel materials,
There is no need to change the material or design of the bearing itself. In addition, this method does not require an expensive ion gun or the like and is easy to operate, so that a hard carbon film can be obtained at low cost.

As the steel material forming the rolling elements or races, martensitic stainless steel, precipitation hardening stainless steel, or steel such as SUJ2 or M50 can be used.

In order to improve the peel strength between the steel base material and the hard carbon film on the surface, a SiC-based coating of about 0.1 μm may be interposed between the steel base material and the hard carbon film.

[0013]

[Example] A ring sample made of SUJ2 and M50 materials (superfinish surface roughness Rmax ≈ 0.1 to 0.2 μm, φ
(53 x 11 mm) surface, a hard carbon film was directly formed by ion plating without an intermediate layer.
Under the test conditions shown in Fig. 1, a peeling test was performed between metals of the same type (superfinishing-grinding finish), and the results are shown in Fig. 1.
Shown in (a) and (b).

[0014]

[Table 1]

In this test, the hard carbon film peeled off when the load number was about 2.8 × 10 ⁴ times for both the SUJ2 material and the M50 material. Load count 8 × 10 ^{5 for} both sides
Peeling did not occur by the number of times, peeling occurred at an area ratio of only 5% or less even after 5 × 10 ⁶ times of loading, and almost no frosting was observed.

In the case of the M50 material, the test piece having the hard carbon film did not cause peeling up to 8 × 10 ⁵ times, and the area ratio was only 1% at the load times of 2 × 10 ⁶ times or more. The following peeling occurred. The other test piece generated about 5% after 5 × 10 ⁶ times of loading.

Next, in order to increase the adhesion strength between the steel base material and the hard carbon film, a SiC type intermediate coating is formed on the specimens of SUJ2 material and M50 material with a thickness of about 0.1 μm, 0.4 to 0. by ion plating.
Table 2 shows the results of forming a hard carbon film having a thickness of 6 μm and performing a peeling test similar to the above. As shown in Table 2, with the SUJ2 material, peeling of about 10% in area ratio when the number of loading times is 1 × 10 ⁵ times, but the number of loading times is 5 × 10 ⁵
About 50% of peeling was observed in the number of times. Meanwhile, in the case of M50 material about 10% of the load times 5 × 10 ^5, although the load times 5 × 10 ⁶ times peeling of about 20% was observed, that an intermediate layer is independent of the base material The adhesion strength of the film was obviously improved as compared with the case where the hard carbon film was directly formed. Further, in both the SUJ2 material and the M50 material, no peeling was observed in the test piece and the mating test piece even after the number of loading times reached 5 × 10 ⁶ .

[0018]

[Table 2]

In a peeling test between SUJ2 materials not coated with a hard carbon film, peeling with an area ratio of 5% occurred at a load frequency of 1 × 10 ⁵ times, and the load frequency was 5 × 10 5.
^{After 6} times, the area ratio was 20% or more, and it was confirmed that the peeling strength was obviously improved by applying the hard carbon film.

Next, durability tests were carried out by rotating the balls of the laser beam printer bearings with and without the hard carbon film at 25,000 rpm. The state of acoustic deterioration is as shown in Fig. 2. In the untreated bearing, the acoustic deterioration occurs as the operating time increases, whereas in the bearing where the ball is coated with a hard carbon film, the acoustic deterioration does not occur. It was This is because in the case of untreated bearings, the projections of non-metallic inclusions existing on the rolling surfaces of the inner and outer rings cause frosting on the balls, whereas those with a hard carbon coating on the balls are This is because, as in the case of the manufactured ball, the projections of the non-metallic inclusions are crushed at the beginning of the operation, and frosting is not formed on the surface of the ball even after the operation time has elapsed. Therefore, it can be said that the ball coated with the hard carbon film has the same performance as that of the ceramic ball.

The familiar effect of crushing the surface roughness protrusions of the mating ground surface at the initial stage of operation is also effective in preventing seizure of the bearing collar.

[0022]

As described above, the bearing of the present invention has a hard carbon film formed on at least one of the surface of the rolling element made of steel and the surface of the bearing ring, so that it has a large surface roughness. It is possible to prevent peeling damage and frosting that occur due to metal contact and poor lubrication, and acoustic deterioration does not occur for a long time.

[Brief description of drawings]

1A and 1B are graphs showing the relationship between the number of times of load and the peeling occurrence rate.

FIG. 2 is a graph showing a state of acoustic deterioration.

Claims (2)

[Claims] 1. A bearing having a rolling element such as steel and a bearing ring, wherein a lubricant is interposed between the rolling element and the bearing ring, wherein at least one of the surface of the rolling element or the surface of the bearing ring is
A bearing characterized in that a hard carbon film is formed. 2. The bearing according to claim 1, wherein a SiC coating is interposed between the hard carbon film and the base material for forming the rolling elements and the races.