JP2001288535A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the service life of a rolling bearing even under a condition in which an oil film of the rolling bearing is not formed sufficiently. SOLUTION: Rolling rings 2, 3 and a rolling element 4 are formed of a carburized steel having the carbon content of 0.15 to 0.4%, a surface hardened layer 5 is provided on the surfaces of the rolling rings 2, 3 and the rolling element 4 by the carburizing, predetermined very small recesses 6 are formed on at least one of the surfaces of the rolling rings 2, 3 and the rolling element 4, and the service life of the rolling bearing 1 used under a condition in which the oil film is not formed sufficiently is prolonged by hardening the surfaces and improving the oil film forming ratio by the predetermined very small recesses 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling bearing used under conditions where formation of an oil film is not sufficient.

[0002]

2. Description of the Related Art In order to extend the life of a rolling bearing used under conditions where the formation of an oil film is not sufficient, the strength and lubricity of the material are important factors.

Conventionally, methods for extending the life of rolling bearings are to use a carburized steel as a material of the bearing components, heat-treat the surface hardness of those components to HRC 58 or higher, and reduce the surface roughness of each component to 0.1 μm Ra. Super finishing was performed to the extent.

[0004] However, the surface structure as described above may cause peeling or flaking in a relatively short time under conditions of use in which the formation of an oil film at the rolling contact portion is not sufficient.

[0005] As a remedy for such a problem,
In addition to the surface hardness of carburized steel, a method of increasing the material hardness by increasing the internal hardness and defining the depth of the surface hardened layer, or randomly distributing recesses with a depth of about 1 μm on the surface of the rolling element and rolling Methods for extending the life by increasing the ability of the contact surface to form an oil film have been proposed.

[0006]

However, none of the above conventional methods is still sufficient to extend the life of a rolling bearing used under conditions where the formation of an oil film is not sufficient. Particularly, in recent years, due to demands for downsizing industrial machines and automobile parts, expectations for rolling bearings used under conditions where oil film formation is not sufficient have been further increased.

Accordingly, an object of the present invention is to extend the life of a rolling bearing used under conditions where the formation of an oil film is not sufficient.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a rolling bearing used under conditions where the formation of an oil film is not sufficient, and a rolling element interposed between the inner and outer races. Is configured as follows.

That is, the present invention relates to a rolling bearing used under conditions in which the formation of an oil film is not sufficient, wherein the inner and outer races and the rolling elements interposed therebetween have a carbon content of 0.15 to 0.4%. Made of carburized steel, the hardness of the hardened surface layer is HRC
58 or more, and the depth of the surface hardened layer / depth of the surface hardened layer of the bearing ring / rolling element diameter is 0.05 or more, and the depth of the surface hardened layer of the rolling element / rolling element diameter is 0. 07 or more, and at least one of the bearing ring and the rolling element is RMS 0.10 μm or more on the surface of the surface hardened layer when indicated by the parameter RMS of roughness, and is negative when indicated by the parameter SK value. A minute concave portion is formed on the substrate.

[0010]

According to the rolling bearing of the present invention which is used under the condition that the oil film is not sufficiently formed, the material strength of the inner and outer races and the rolling elements interposed therebetween is increased, and at least one of the races and the rolling elements is provided. A minute recess is formed on the surface, and the finished surface roughness of the minute recess is determined by the parameter R
MS is set to 0.10 μm or more, and the parameter S
Since the K value is set to a negative value, the oil film formation rate on the rolling contact surface is improved. Therefore, even when lubrication conditions are poor due to a synergistic effect of both, peeling and flaking do not occur early, and a long life can be obtained.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, a rolling bearing 1 according to the present invention comprises inner and outer races 2, 3 made of carburized steel having a carbon content of 0.15 to 0.4% and a rolling bearing interposed therebetween. The surface rings 2 and 3 and the rolling elements 4 are carburized to form a surface hardened layer 5.
In addition to the above, each core hardness is set in a range of HRC 48 or more and less than 58.

The depth of the surface hardened layer 5 in the races 2, 3 and the rolling elements 4 is as follows: race ring: depth / rolling element diameter is 0.05 or more Rolling element: depth / rolling element diameter is 0.07 Each is set above.

In the above-mentioned rolling bearing 1, at least one surface of the races 2, 3 and the rolling elements 4 serving as rolling elements is randomly formed with fine concave portions 6 by a special barrel polishing method after carburizing. (See FIG. 1B).

When the surface having the minute concave portions 6 has a surface roughness represented by a parameter RMS, RMS 0.1
0 μm or more, and the parameter SK value is minus, preferably -1.6 in both the axial and circumferential directions.
It is as follows.

The parameter SK value indicates the degree of distortion (SKEWNESS) of the distribution curve of the surface roughness. For a symmetric distribution such as a Gaussian distribution, the SK value is 0. In both cases, the set value of -1.6 or less is a range in which the shape and distribution of the surface concave portions are advantageous for forming an oil film.

Next, several types of tapered roller bearings are manufactured, and test results obtained by using a bearing life tester will be described.

The tapered roller bearing used in the life test has an outer diameter of 45.237 mm and an inner diameter of 19.050 mm. The test conditions were such that a low-viscosity clean lubricating oil was circulated and supplied, and an oil film parameter for which formation of an oil film was difficult was less than 1.

The types of bearings are standard carburized bearings (symbol A),
There are four types of bearings: standard carburized bearings with minute recesses on the roller surface (symbol B), special carburized bearings (symbol C), and special carburized bearings with minute recesses on the roller surface (symbol D).

Table 1 summarizes the test results. FIG. 2 shows a Weibull probability line obtained by drawing a regression line of the failure life.

The life test uses a radial load tester,
The test was performed under the following test conditions.

Life test conditions Radial load: 1400 kgf Rotation speed: 2000 rpm Temperature: 100 ° C. Oil: Hydraulic oil

[0023]

[Table 1]

As is clear from the results of the above life test,
The bearing (symbol D) of the present invention has a several times longer service life than other bearings.

This means that the tapered roller bearing treated according to the present invention has improved material strength by special carburizing,
It is considered that the improvement of the oil film formation rate due to the minute concave portions 6 on the surface greatly affects the extension of the life.

[0026]

As described above, according to the present invention, in a rolling bearing used under conditions where the formation of an oil film is not sufficient, the surfaces of the inner and outer races and rolling elements formed by using carburized steel are carburized. The surface hardened layer is applied to form a specific minute recess on at least one surface of the race and the rolling element, so the strength is improved by the surface hardened layer and the oil film forming ability is improved by the specific minute recess. Due to the synergistic effect of the above, even if lubrication conditions are poor, peeling or flaking does not occur and a long life can be obtained.

[Brief description of the drawings]

FIG. 1A is a sectional view of a rolling bearing according to the present invention,
(B) is an enlarged cross-sectional view in which a concavity is formed in the rolling surface in the above.

FIG. 2 is a graph showing the results of a life test.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rolling bearing 2, 3 Raceway 4 Rolling element 5 Surface hardened layer 6 Depression

Claims (1)

[Claims] In a rolling bearing used under conditions where an oil film is not sufficiently formed, inner and outer races and rolling elements interposed therebetween are formed of carburized steel having a carbon content of 0.15 to 0.4%. The hardness of the hardened surface layer is HRC58 or more, and the depth of the hardened surface layer is the depth of the hardened surface layer of the raceway / the diameter of the rolling element is 0.05 or more, and the depth of the hardened surface layer of the rolling element is 0.05 or more. And the diameter of the rolling element satisfies the condition of 0.07 or more, and at least one of the bearing ring and the rolling element is provided on the surface of the surface hardened layer by RMS when represented by a roughness parameter RMS.
A rolling bearing, characterized in that a minute concave portion is formed so as to be 0.10 μm or more and become negative when indicated by a parameter SK value.