JPH0712129A - Electrolytic corrosion preventing type rolling bearing - Google Patents

Abstract

PURPOSE:To form an electrolytic corrosion preventing type rolling bearing into such structure as to be excellent in the insulating function without an ill condition heretofore generated at the built-in time and in the built-in state. CONSTITUTION:In a grease-filled electrolytic corrosion preventing type rolling bearing, a rolling element interposed between an inner and an outer rings made of steel is formed of silicon nitride as a main body by pressure-sintering, and the roughness of at least the rolling surface is to be 0.2Z or less. The inner and outer rings 1, 2 are thus insulated electrically by the rolling element 3 formed of insulating material. Also, since the manufacturing method and surface roughness of the rolling element 3 are specified, moisture absorption, moisture adhesion to the surface and the adhesion of metal abrasion powder can be prevented. Moreover, since a coat as in the existing method is not formed at the inner and outer rings 1, 2, no ill condition is generated at the built-in time and in the built-in state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic corrosion-prevention type rolling bearing in which grease is enclosed.

[0002]

2. Description of the Related Art For example, in a bearing used for an electric motor of a railway vehicle, an electric current may flow from the electric motor to the inside of a bearing steel bearing, and the contact portion between the rolling element of the bearing and the inner / outer ring is caused by the electric current passing through the inside of the bearing. Electrolytic corrosion occurs and shortens the service life. Therefore, in this type of bearing, it has been conventionally practiced to prevent the occurrence of electrolytic corrosion by forming an insulating coating on the outer surfaces of the inner and outer races.

[0003]

By the way, in the above-mentioned conventional example, when the coating is made of synthetic resin, the shaft center of the bearing itself tends to fluctuate due to elastic deformation when a load is applied, or due to shrinkage over time. It has been pointed out that this may lead to creep, and if the coating is made of a hard material such as ceramics, the ceramic coating may be partially peeled off when it is installed in the required place, and for the original purpose. It is pointed out that a certain insulating function cannot be exerted.

Furthermore, even if these insulating coatings are used, the insulating property of the bearing is not absolute, that is, abrasion powder such as iron powder and copper powder generated between the rolling element and the bearing ring or the cage causes grease. It may scatter inside, or water that has entered from the outside may mix into the grease, and these abrasion powder and water can act as a charge medium and destroy the insulation between the housing and the outer ring that are in close proximity. is there.

In view of such circumstances, it is an object of the present invention to provide a structure which is excellent in an insulating function and which does not have a problem in the conventional assembling or assembled state.

[0006]

SUMMARY OF THE INVENTION According to the present invention, in an electrolytic corrosion preventing type rolling bearing in which grease is enclosed, at least the rolling element interposed between the inner and outer rings is mainly made of silicon nitride. Is formed by pressure sintering, and at least the rolling surface has a roughness of 0.2Z or less.

[0007]

The wide space between the inner and outer rings, including the cage, is electrically insulated by the rolling elements made of an insulating material, so that electrolytic corrosion does not occur inside the bearing.

Since the existing bearing components are made of an insulating material without forming a coating on the outer surfaces of the inner and outer races, there is a problem in the conventional assembling or mounting state of the bearing. Does not happen. Moreover, since the rolling elements are formed by pressure sintering with silicon nitride as the main constituent, the crystal bond is strong and the strength is excellent, and the occurrence rate of bubbles and cracks is extremely low and moisture is absorbed. It becomes difficult to be played. Further, by specifying the surface roughness to be small, it is possible to prevent the metal abrasion powder and the water from adhering to each other, so that the electric current passing through the metal abrasion powder and the water does not occur.
Moreover, since the absolute amount of the metal abrasion powder itself is reduced, the possibility of dielectric breakdown due to it is reduced.

Further, since the rolling element has a smaller specific gravity than that made of metal, it is effective in reducing the inertial force of the rolling element.
The load on the cage can be reduced.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described with reference to an embodiment shown in FIGS. In the figure, 1 is an inner ring, 2 is an outer ring, 3 is a rolling element made of cylindrical rollers, and 4 is a cage. Although not shown, grease is sealed in the bearing by a sealing device or the like.

The inner and outer rings 1 and 2 are made of metal such as bearing steel, and the rolling element 3 is made of ceramics which is mainly formed of silicon nitride by pressure sintering. The roughness of the rolling surface that can serve as a path is set to 0.2Z or less. As the pressure sintering, for example, a method called HIP (Hot Isostatic Press) is adopted.

The cage 4 is divided into two parts in the axial direction and has a structure in which a part between a plurality of pockets 5 for rotatably holding the rolling element 3 is connected by a rivet 6.
It is made of metal such as copper alloy. This cage 4
It is designed to be a so-called rolling element guide,
Since there is a relatively large radial gap with respect to both the outer rings 1 and 2, the facing gap between the inner / outer rings 1 and 2 and the cage 4 is larger than that of the outer ring guide type or the inner ring guide type. It becomes easier to add grease and other lubricants without bias. Compared to the outer ring guide type and inner ring guide type, less abrasion powder is generated due to contact with the inner and outer rings.

Since the rolling elements 3 made of an insulating material electrically insulate the inner and outer rings 1 and 2 from each other in this manner, electrolytic corrosion does not occur inside the bearing.

In addition, since the rolling elements 3 are made of ceramics, the specific gravity is greatly reduced from about 7.8 to about 3.2 as compared with the case where the rolling elements 3 are made of metal. The impact load of the rolling element 3 on the inner wall of the pocket 5 of the cage 4 can be reduced. This can be confirmed by the bearing rotation vibration test described below.
This bearing rotational vibration test is performed using an apparatus as shown in FIG. In FIG. 2, A is a test bearing, 7 is a housing, 8 is a cantilevered rotary shaft, 9 is a support bearing, and 10 is a bearing.
Numeral 12 is a pedestal or pedestal for preload adjustment, and 13 is a nut for preload adjustment. And the test condition is vibration acceleration: 50
G, vibration frequency: 60 Hz (sine wave), amplitude: 3.45
mm, rotation speed: 1000 rpm, load: shaft own weight only (2.0 Kgf), lubrication: Nippon Oil Co., Ltd., trade name Multi Knock NO. 2. Vibration frequency: Rivet breakage or looseness is set respectively. The test bearing A is
The product of this embodiment having the above-described structure and the product of comparison which has all the constituent elements made of bearing steel (SUJ2) (JIS model number N
U219 FY). As a result, the comparison product vibrates 7
The rivet of the cage was broken after 500,000 cycles, whereas the rivet of the cage was loosened after vibration of 23 million cycles in the product of this example. Is shown. As described above, by making the rolling elements 3 ceramic, the cage 4 can be secondarily formed into a rolling element guide type, and a two-part structure with riveting can be used, which is advantageous in terms of cost. Becomes Further, since the rolling element has a small inertial force, contact wear between the rolling element and the rolling element is reduced even in the rolling element guide, the generation of abrasion powder is reduced, and the risk of dielectric breakdown is reduced.

In the above embodiment, the inner and outer bearing rings 1, 2 are
Is made of bearing steel, but at least the outer ring 2 on the upstream side of the conduction path, as well as the inner ring 1, may be formed of ceramics mainly composed of silicon nitride, like the rolling elements 3. Further, in order to prevent electrolytic corrosion of a main shaft bearing of a machine tool or the like, in addition to the rolling element 3 as in the above embodiment, the inner ring 1 on the upstream side of the conduction path is made of a ceramic mainly composed of silicon nitride. You may form with. Furthermore, rolling element 3
Although only the roughness of the rolling surface of is specified as 0.2Z or less,
The roughness of the axial end surface of the rolling element 3 may be 0.2Z or less from the viewpoint of completely preventing the adhesion of water and abrasion powder. The rolling elements 3 may be balls instead of the illustrated ones. Further, it may be a full roller bearing or a full ball bearing without a cage.

[0016]

According to the present invention, the rolling element, which is an existing bearing component, is made of a specific ceramic to electrically insulate between the inner and outer rings. There is no waste such as processing is unnecessary,
There is no problem when the bearing is assembled or in the assembled state as in the past, and the electrical insulation is highly reliable. In addition, by specifying the manufacturing method and surface roughness of this rolling element, we suppress the occurrence of bubbles and cracks that may absorb water, and prevent the adhesion of water to the surface, and also the adhesion of metal abrasion powder. Therefore, the reliability of the electrical insulation is high in that the electrical conduction due to uncertain factors such as moisture and metal abrasion powder can be surely prevented.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an upper half of an embodiment of an electrolytic corrosion type rolling bearing of the present invention.

FIG. 2 is a side view of an upper half section showing a schematic configuration of a bearing rotational vibration test device according to the present embodiment.

[Explanation of symbols]

 1 Inner ring 2 Outer ring 3 Rolling element 4 Cage

Front page continuation (72) Inventor Miyoshi 3-5-8 Minamisenba, Chuo-ku, Osaka City Koyo Seiko Co., Ltd.

Claims (1)

[Claims] 1. A rolling bearing of an electrolytic corrosion prevention type in which grease is sealed inside, wherein at least the rolling element interposed between the inner and outer rings is mainly made of silicon nitride by pressure sintering. An electrolytic corrosion-preventing rolling bearing, which is formed and has a roughness of at least its rolling surface of 0.2Z or less.