JPH0469406A - Ball bearing - Google Patents

Abstract

PURPOSE:To decrease fear of rupture due to hoop force by forming the outer race of a bearing out of a ceramic material, and assembling a metal ring on its outer circumferential surface by means of shrinkage fitting to give prestress. CONSTITUTION:This ball bearing 10 is constructed to have hybrid structure which consists of two kinds of materials; the one is a race main body 20 wherein an outer race 14 is formed out of ceramic material and the other is a metal ring 22 that is integrally formed on its outer circumference by means of shrinkage fitting. As the ceramic material, silicon nitride, zirconia, etc. are used, and the metal ring 22 is made of cold-finished steel of SUS material. Although hoop force that runs parallel with the circumferential direction generates in the outer race 14 as outward force in the radial direction acts on the outer race 14 through a steel ball 16 in the rotation supporting state, or by assembling the outer race while axial center of the bearing and the axial center of a mounting hole remain discordant in mounting to the side of a case, tensil stress that results in rupture is reduced, and momentary rupture can be prevented.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to ball bearings, and more particularly to improvements in bearings constructed using ceramic materials.

[Conventional technology]

A ball bearing has steel balls interposed between an inner race and an outer race, and rolling contact allows the inner race and outer race to rotate smoothly relative to each other. In such ball bearings, attempts have been made to form members other than steel balls from ceramic materials to obtain the advantages of ceramics, such as weight reduction, wear resistance, and heat resistance. This has a structure in which the inner race and outer race are made of a ceramic material, and a steel ball is sandwiched between the two races.By making the main structural members made of ceramic, the material's characteristics are effectively utilized. be.

[Problem to be solved by the invention]

However, in conventional ball bearings that use ceramic materials, the ceramic material itself is extremely susceptible to cracking, so if hoop stress occurs, there is a risk that the ceramic race will break instantly, resulting in a lack of reliability. was there. This is especially a problem on the outer race side,
When assembling the bearing into the case, if the axis of the mounting hole on the case side and the axis of the bearing are not aligned, excessive hoop stress will be generated due to the twisting caused by forcefully assembling the bearing, leading to instantaneous breakage of the outer race. This has become a problem. The present invention has focused on the above-mentioned conventional problems, and has developed a ball bearing that uses ceramic materials to achieve weight reduction, wear resistance, heat resistance, etc., while significantly reducing the risk of breakage and improving reliability. The purpose is to provide.

[Means to solve the problem]

In order to achieve the above object, the ball bearing according to the present invention has an outer race of the bearing formed of a ceramic material, a metal ring shrink-fitted to the outer peripheral surface of the ceramic outer race, and a prestressed ceramic outer race. It has a configuration in which it is attached and assembled.

[Effect]

According to the above configuration, the outer race is formed of a ceramic material, but since a metal ring is shrink-fitted to the outer circumferential surface of the outer race to give prestress, the hoop stress of an external force acts on the outer race. Also, the stresses are offset and the ceramic outer race can be prevented from breaking. Therefore, even if the bearing mounts in a case where it twists, it can absorb the instantaneous excessive stress caused by this and prevent the ceramic race from breaking, resulting in a highly reliable structure. It is possible.

【Example】

Hereinafter, specific embodiments of the ball bearing according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view of a main part of a ball bearing according to an embodiment. As shown in the figure, this ball bearing 10 has a structure including an inner race 12 as an annular ring and an outer race 14 having a larger diameter than the inner race 12, with a plurality of steel balls 16 interposed between them. The steel balls 16 are held in a regular position by a retainer 18, and the inner race 12 and the outer race 14 are caused to rotate relative to each other through rolling contact. In this embodiment of the ball bearing 10, the outer race 14 is configured as a hybrid structure made of two materials: a race body 20 made of a ceramic material and a metal ring 22 fitted and integrated around the outer periphery of the race body 20. ing. As the ceramic material forming the outer race main body 20, well-known ceramic materials such as silicon nitride and zirconia are used, and this is molded into the shape of a desired outer race. On the other hand, the metal ring 22 attached to the outer periphery of the outer race body 20 is made of SO8 material, particularly polished steel, and is attached to the outer race body 2 by shrink fitting.
The ceramic lace body 20 is fitted onto the outer circumferential surface of the ceramic lace body 20 and is coupled to the ceramic lace body 20 so as to apply pre-compression stress. In this case, when the total thickness of the outer race 14 is t, the wall thickness sio of the metal ring 22 is i~0.3t.
In particular, the shrink fit allowance is set to 25/100.
00-35/110000 (■) The name is formed by fitting and connecting the two. Shrink fitting can be done using a normal method, and can be easily assembled by heating the metal ring 22, which is subject to large thermal deformation, to give it thermal expansion, fitting it onto the outer periphery of the ceramic lace body 20, and cooling it. . Note that the inner race 12 may be formed of only a ceramic material since the risk of breakage due to hoop stress is of little concern. In the ball bearing 10 configured in this way, a rotating shaft or the like is inserted through the inner race 12, and the outer race 1 is attached to the inner race 12.
The attachment provided on the case on the supporting member side provides rotational support by fitting and attaching 4 to the hole. At this time, an outward force in the radial direction as shown in FIG. 2 is applied to the outer race 14 through the steel balls 16 in the rotationally supported state, or when the bearing axis is attached to the case side, the axis of the mounting hole is By assembling the outer race 14 with the centers mismatched, a hoop force is generated in the outer race 14 along the circumferential direction. This acts on the outer race 14 as a breaking force along the generatrix line, but in the embodiment, the metal ring 22 applies prestress to the outer race body 20 to counter the hoop stress, so the hoop force is supported by the metal ring 22. . As a result, the pre-applied compressive stress in the ceramic lace main body 20 is only relaxed by the hoop stress, and the generation of tensile stress that can lead to breakage is reduced. Therefore, even if the inner race 12 and the outer race 14 are formed using a ceramic material, instantaneous breakage due to external hoop stress can be prevented, and the advantages of ceramic, such as light weight, wear resistance, heat resistance, and no need for lubrication, can be prevented. It is possible to create a ball bearing with effective functions and high reliability. In addition, in the above embodiment, an example was shown in which SUS material was used as the metal ring 22, but other metal materials can also be used, and not only ferrous materials but also non-ferrous metals can be used. Any material that can apply prestress to 20 may be used.

【Effect of the invention】

As explained above, according to the present invention, the outer race of the bearing is formed of a ceramic material, a metal ring is shrink-fitted to the outer peripheral surface of the ceramic outer race, and a prestress is applied to the ceramic outer race. Since it is assembled, it is possible to obtain a ball hair ring with improved reliability by significantly reducing the risk of breakage due to hoop force while taking advantage of the characteristics of the ceramic material.

[Brief explanation of drawings]

Fig. 1 is a sectional view of the ball bearing according to the embodiment, Fig. 2 is a sectional view of the ball bearing according to the embodiment;
The figure is an explanatory diagram of hoop force. 10...Ball hair ring, 12...Inner lace, 14...Outer lace, 16...
... Steel ball, 18 ... Retainer, 20 ...
Ceramic lace body, 22...Metal ring.

Claims (1)

[Claims] 1) A ball bearing characterized in that the outer race of the bearing is formed of a ceramic material, a metal ring is shrink-fitted to the outer peripheral surface of the ceramic outer race, and the ceramic outer race is assembled by applying prestress. .