JP2000009146A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling bearing provided with ceramic rolling elements, the production costs of which are lowered down though its performance is nearly as high as that of a bearing provided with ceramic rolling elements high in grade as shown by a conventional example. SOLUTION: It is discontinued that each ceramic rolling element 3 is formed into a conventional configuration high in grade in such a way that there exists almost no pore, on the contrary, it is formed into a configuration that there exist at least 100 pores of 3 μm to 30 μm per 1 mm2 on the surface and the inside of the rolling element 3, or into the other configuration classified as a middle class in grade permitting the number of pores to exist therein. Thus, the manufacturing process of each ceramic rolling element 3 can be simplified in process as compared with a conventional one, and its pressure withstanding strength can be sufficiently increased even though processing pressure is dropped down in a sintering process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rolling bearing having a ceramic rolling element.

[0002]

2. Description of the Related Art Conventionally, there is a rolling element formed of ceramics. This ceramic rolling element is usually
It is manufactured by sintering ceramic material powder at high pressure and high temperature. Conventionally, various studies have been made in the direction of preventing bubbles or pores from being formed inside during sintering.

For example, Japanese Patent Application Laid-Open No. 63-101519 discloses a rolling element made of ceramics containing silicon nitride as a main component, and the internal pore size can be reduced to 3 μm or less. I try to make it smaller.

[0004] In this gazette technology, it is manufactured in the following procedure. First, silicon nitride powder and a sintering aid are pulverized to, for example, an average particle size of 1.0 μm or less, mixed, and a solvent is added thereto and kneaded to obtain an average particle size of 150 to 10 μm.
Granulate to 0 μm. The outer shape is adjusted by a die press using the granulated powder. After degreased, the compact is sintered under normal pressure and further subjected to isotropic pressure sintering (HIP). Thereafter, the sintered body is finished by barrel polishing or the like.

[0005]

In the above conventional example, it is pointed out that although a high-quality, high-strength structure having few pores therein can be manufactured, the manufacturing cost is extremely high. This has resulted in limited use.

[0006] In other words, in applications where the pressure resistance is important, such as when the load conditions are high, the above-mentioned high-grade ceramic rolling elements must be used. In applications where the strength is not so important, the use of the above-mentioned high-grade ceramic rolling element remains unsatisfactory in terms of price.

[0007] In view of the above, the present applicant proposes the present invention for the purpose of providing a rolling bearing having a ceramic rolling element having a performance close to that of the above-mentioned conventional example while keeping manufacturing costs low. .

[0008]

[SUMMARY OF] according to the invention of claim 1 rolling bearing, rolling elements intended to be formed of ceramics mainly containing silicon nitride, the surface and inside of the rolling elements, 1 mm ² It is set in a form in which there are 100 or more average distributions of pores of 3 μm to 30 μm per hit.

According to a second aspect of the present invention, in the rolling bearing according to the first aspect, the race is formed of a metal material.

As described above, according to the present invention, rather than forming almost no pores inside as in the prior art, it is possible to allow a relatively large pore to be formed, thereby enabling easy manufacture. In short, the inventor of the present application believes that even a rolling element manufactured by a manufacturing method with a simplified process, that is, one in which a somewhat large pore exists, has a certain degree of pressure resistance, and can be sufficiently used depending on the intended use. Therefore, the present invention was proposed based on this finding.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described based on embodiments shown in FIGS.

1 to 5 relate to an embodiment of the present invention. FIG. 1 is a longitudinal sectional side view of a rolling bearing, FIG. 2 is a process diagram showing a manufacturing process of a ceramic rolling element, and FIG. FIG. 4 is a schematic configuration diagram of a test device used for a load test of a rolling element, FIG. 4 is a table showing test results, and FIG. 5 is an enlarged cross-sectional photograph of a test sample.

In the figure, A indicates the entire rolling bearing such as a deep groove ball bearing. The rolling bearing A includes an inner ring 1, an outer ring 2, a plurality of rolling elements 3, and a retainer 4. The inner / outer rings 1 and 2 are formed of a metal material such as bearing steel or stainless steel as required. The rolling elements 3 are formed of ceramics containing silicon nitride as a main component. The surface and inside of the rolling element 3 are set so that there are 100 or more average distributions of pores of 3 μm to 30 μm per 1 mm ² .

Next, a method of manufacturing the ceramic rolling element 3 will be described. As shown in FIG. 2, first, a silicon nitride powder and a sintering aid are mixed, for example, with an average particle size of 1.0 μm.
The mixture is pulverized and mixed as follows, and a solvent is added to the mixture, followed by kneading to granulate to an average particle size of 150 to 100 μm. The outer shape is adjusted by a die press using the granulated powder. The molded body is degreased and then sintered. In this sintering process,
The heat treatment is performed at about 1800 ° C. in a nitrogen gas atmosphere at a pressure of less than 10 atm for 4 hours. Thereafter, the sintered body is finished by barrel polishing or the like.

As described above, the sintering process is completed once and the process is simplified, and the sintering process is performed at a pressure lower than 10 atm, which is much lower than that of the conventional isotropic pressure sintering process. Thus, a simple and inexpensive sintering apparatus can be used. As a result, the manufacturing cost can be greatly reduced as compared with the conventional example, which can greatly contribute to the reduction of the product price.

Then, the pressure resistance of the ceramic rolling element 3 manufactured in the above-described form was examined and will be described.

Here, three samples, a product of the present invention, a comparative product, and a conventional product were prepared as samples. The product of the present invention is formed by the above manufacturing method, and as shown in the cross-sectional photograph of FIG. 5 (a), 3 μm to 30 μm per 1 mm ² .
Has an average distribution of 100 or more pores.
As shown in the cross-sectional photograph of FIG.
There are pores exceeding μm. What is a conventional product?
This is a high-grade product having almost no pores as described in the conventional example. As shown in the cross-sectional photograph of FIG.
The following pores are slightly present. FIG.
The cross-sectional photograph shown in the figure is the optical microscope
The photograph was taken at a magnification of 400 times using.

The sample has an outer diameter of 60 mm and an inner diameter of 25 m
m, an annular plate having a thickness of 5 mm.

The test apparatus shown in FIG. 3 was used. The test device of the example shown in FIG.
The grooved thrust trace 12 and the above-described sample 13 are arranged, and a plurality of (three) rolling elements 14 are interposed between the thrust trace 12 and the sample 13. The rolling element 14 is formed of 、 ３ ″ JIS standard SUJ2. Then, the rotating shaft 10 is rotated while the receiving member 11 is pressed against the rotating shaft 10.

As conditions, lubrication using spindle oil is used, the number of revolutions of the rotating shaft 10 is set to 1200 rpm, and the load is increased stepwise. The load is increased every 1.08 × 10 ⁷ repetitions of the load.

As a result, as shown in FIG. 4, in the case of the comparative product, the peeling occurred at the load of 500 N or more, which was considered to be a starting point. No damage occurred when increased.

Based on the test results, it is not necessary for the ceramic rolling element 3 to almost eliminate the presence of pores as in the prior art. It turned out that it can withstand use sufficiently even under the condition where a load acts. However, rolling bearing A
The inner and outer rings 1 and 2 are preferably made of general bearing steel or other various metal materials having higher toughness than ceramics. In such a combination,
Since the load on the ceramic rolling element 3 can be reduced due to the bending of the outer races 1 and 2, the problem that the ceramic rolling element 3 peels or cracks for a long time does not occur.

[0023]

According to the present invention, a ceramic rolling element can be manufactured by a simple manufacturing process that allows the presence of a certain amount of pores, instead of a high-grade ceramic having almost no pores as in the conventional example. Although it is inexpensive, it can be made sufficiently practical by only slightly limiting the load conditions.

Further, if the bearing ring of the rolling bearing is made of a general bearing steel or other various metal materials having better toughness than ceramics, a somewhat excessive radial load is applied. Even in such a situation, the load on the ceramic rolling element can be reduced by bending of the bearing ring, so that the problem that the ceramic rolling element peels or cracks for a long time does not occur.

[Brief description of the drawings]

FIG. 1 is a longitudinal side view of a rolling bearing according to an embodiment of the present invention.

FIG. 2 is a process diagram showing a manufacturing process of a ceramic rolling element.

FIG. 3 is a schematic configuration diagram of a test device used for a load test of a ceramic rolling element.

FIG. 4 is a table showing test results.

FIG. 5 is an enlarged photograph of a cross section of a test sample.

[Explanation of symbols]

 A Rolling bearing 1 Inner ring 2 Outer ring 3 Rolling element 4 Cage

Continued on the front page (72) Inventor Hiroaki Takebayashi 3-5-8 Minamisenba, Chuo-ku, Osaka-shi F-term (reference) in Koyo Seiko Co., Ltd. 3J101 AA01 AA32 AA62 BA10 BA70 DA09 DA11 DA20 EA03 EA06 EA44 FA31 FA44

Claims (2)

[Claims] 1. A rolling bearing in which a rolling element is formed of ceramics containing silicon nitride as a main component, wherein the average distribution of pores of 3 μm to 30 μm per 1 mm ² is 100 or less on the surface and inside of the rolling element. A rolling bearing, wherein the rolling bearing is set in a form in which at least one rolling bearing exists. 2. The rolling bearing according to claim 1, wherein the race is formed of a metal material.