JP3036987B2 - Rolling bearing - Google Patents

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 so-called hybrid rolling bearing in which a rolling element is made of ceramics and a race is made of steel.

[0002]

2. Description of the Related Art The hybrid rolling bearings described above are conventionally used under the operating conditions of high speed and small temperature rise as in a machine tool spindle.

[0003]

However, a large tensile stress acts on a raceway (for example, an inner race) of a rolling bearing that rotates at high speed due to expansion due to centrifugal force. General S
For UJ2 material, the limit of hoop stress is 15kg for safety.
f / mm ² is said to less is, dn the product (d: bearing bore, n: number of revolutions rpm) at 2.5 million or more, beyond the limits, leading to burst the minute surface damage or the like is emitted There is a risk.

On the other hand, considering the effect of heat generation due to rolling contact of a hybrid rolling bearing, the hardness of a ceramic rolling element hardly decreases due to heat generation, whereas the hardness of a steel bearing ring decreases at high temperature due to heat generation. Come. For this reason, the hardness difference between the ceramic rolling element and the steel race is further increased, and as a result, the life of the steel race may be shortened.

Accordingly, an object of the present invention is to improve the hoop stress resistance and reduce the decrease in high-temperature hardness during rolling, thereby extending the life of a hybrid rolling bearing.

[0006]

In order to solve the above-mentioned problems, the present invention relates to a rolling bearing in which the rolling element is made of ceramic and at least the rotating raceway of the races is made of steel. At least the raceway surface of the race is subjected to carburizing and quenching and then nitriding.

[0007]

[Examples] Table 1 shows the results of point contact life tests on a ceramic rolling element and a cylindrical test piece obtained by carburizing a case ring steel as a bearing ring and further performing a nitriding treatment together with a comparative example. Show.

[0008]

[Table 1]

Test conditions Ceramic ball: φ7 / 16 inch Various material cylindrical specimen: (diameter) 25 mm × (length) 22 mm Hertz contact surface pressure: Pmax 667 kgf / mm ² Load frequency (cylindrical specimen): 22195 c. p. m Lubrication: Turbine oil As can be seen from the above test results, in the case of the example, the peel life is 10 times that of the comparative example 1 and about 6 times that of the comparative example 2. Also, compared to the hoop resistance of the SUJ2 inner ring,
The inner ring of the carburized and quenched product is excellent, approximately double the 25kgf
It is possible to use up to / mm ^2.

[0010]

As described above, the present invention provides a hybrid rolling bearing having a carburizing and quenching at least a raceway surface of a steel rotating raceway, and then performing a nitriding treatment. A rolling bearing having a high hoop stress, that is, a rolling bearing suitable for high-speed rotation can be provided.

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Claims (1)

(57) [Claims] In a rolling bearing in which a rolling element is made of ceramics and at least a rotating raceway is made of steel, at least at least a raceway surface of the steel race is subjected to carburizing and quenching, followed by nitriding treatment. Rolling bearing characterized by having been subjected to the following.