JP2934697B2 - Anti-corrosion 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 an anti-corrosion type rolling bearing in which grease is sealed.

[0002]

2. Description of the Related Art For example, in a bearing used for an electric motor of a railway vehicle, an electric current sometimes flows from the electric motor into a bearing steel bearing, and a current passing through the inside of the bearing causes a contact portion between a rolling element of the bearing and inner and outer rings. Electrolytic corrosion occurs and the life is shortened. Therefore, in this type of bearing, it has been conventionally practiced to prevent the occurrence of electrolytic corrosion by forming an insulating film on the outer surfaces of the inner and outer rings.

[0003]

In the above conventional example, when the coating is made of a synthetic resin, the bearing is elastically deformed when a load is applied, so that the axis of the bearing itself tends to fluctuate or shrink with time. It has been pointed out that creep may be caused, and if the coating is made of a hard material such as ceramics, the ceramic coating may be partially peeled off, such as chipping, when it is installed in the required places. It is pointed out that a certain insulating function cannot be exhibited.

Further, even with these insulating coatings, the insulating properties of the bearing portion are not absolute, that is, wear powder such as iron powder and copper powder generated between the rolling element and the bearing ring or the cage is greased. The grease may be scattered into the inside or water entering from the outside may be mixed into the grease, and these abrasion powders and water may serve as a medium for electric charge and destroy the insulation between the adjacent housing and the outer ring. is there.

[0005] In view of such circumstances, it is an object of the present invention to provide a structure having an excellent insulating function and having no problems at the time of assembling or assembling as in the related art.

[0006]

According to the present invention, there is provided an anti-corrosion type rolling bearing in which grease is sealed therein, wherein at least a rolling element interposed between an inner ring and an outer ring mainly comprises silicon nitride. as formed by pressure sintering, and at least its roughness of the rolling surface is less 0.2Z, inner and outer
The configuration was such that the wheels were electrically insulated .

[0007]

A large space between the inner and outer rings including the retainer is electrically insulated by the rolling elements made of an insulating material, so that no electrolytic corrosion occurs 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 rings, there is a problem that occurs when a conventional bearing is assembled or assembled. Does not occur. In addition, since the rolling elements are formed by pressure sintering mainly using silicon nitride, the crystal bonding is strong and the strength is excellent, and the generation rate of bubbles and cracks is extremely low and moisture is absorbed. It is hard to be done. In addition, since the surface roughness is specified to be small to make it difficult for metal abrasion powder or moisture to adhere thereto, current passing using metal abrasion powder or moisture as a medium does not occur.
Further, since the absolute amount of the metal wear powder itself is reduced, the possibility of dielectric breakdown due to the reduction is also reduced.

Further, since the rolling elements have a smaller specific gravity than those made of metal, they are effective in reducing the inertial force of the rolling elements.
The burden on the retainer can be reduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be explained 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 formed of a cylindrical roller, and 4 is a retainer. Although not shown, grease is sealed inside 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 elements 3 are made of ceramics mainly made of silicon nitride and formed by pressure sintering. The roughness of the rolling surface that can be a path is set to 0.2Z or less. As this pressure sintering, for example, a technique called HIP (hot isostatic press) is adopted.

The retainer 4 is divided into two parts in the axial direction, and has a structure in which portions between a plurality of pockets 5 that rotatably hold the rolling elements 3 are connected by rivets 6.
It is formed of a metal such as a copper alloy. This cage 4
It is designed to be a so-called rolling element guide.
Since a relatively large gap exists in the radial direction with respect to each of the outer rings 1 and 2, the facing gap between the inner / outer rings 1 and the cage 4 is larger than that of the outer ring guide type or the inner ring guide type. Lubricant such as hegrease can be easily added without unevenness. The generation of abrasion powder due to contact with the inner and outer rings is smaller than that of the outer ring guide type or inner ring guide type.

As described above, the inner and outer rings 1 and 2 are electrically insulated by the rolling elements 3 made of an insulating material, so that no electrolytic corrosion occurs inside the bearing.

In addition, since the rolling element 3 is 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 element 3 is made of metal, so that the inertial force due to the rotational centrifugal force can be reduced. Thus, the impact load of the rolling element 3 on the inner wall of the pocket 5 of the retainer 4 can be reduced. This has been confirmed by the bearing rotational 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 rotating shaft that is cantilevered, 9 is a supporting bearing, 10
Numerals 12 to 12 are positioning spacers and pedestals, and 13 is a positioning nut. The test conditions were as follows: vibration acceleration: 50
G, vibration frequency: 60 Hz (sine wave), amplitude: 3.45
mm, number of revolutions: 1000 rpm, load: only the shaft's own weight (2.0 Kgf), lubrication: Multi-knock NO. 2, the number of vibrations: rivet breakage or looseness is set. Test bearing A is
The product of this embodiment having the above-described structure, and a comparative product in which all of the constituent elements are made of bearing steel (SUJ2) (JIS model number N)
U219FY). As a result, vibration 7
The rivet of the cage was broken after 500,000 times, whereas the rivet of the cage was loosened after 23 million vibrations in the product of the present embodiment. Is shown. In this manner, the ceramics of the rolling elements 3 can make the retainer 4 secondary to the rolling element guide type, and can use a two-part structure with riveting, which is advantageous in terms of cost. Becomes Furthermore, since the rolling element has a small inertial force, contact wear between the rolling element and the rolling element is reduced, the generation of wear powder is reduced, and the possibility of dielectric breakdown is reduced.

In the above embodiment, the inner and outer races 1, 2
Is made of bearing steel, but at least the outer ring 2 on the upstream side of the conduction path, and also the inner ring 1 may be formed of ceramics mainly composed of silicon nitride, like the rolling elements 3. In addition, 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-described embodiment, the inner ring 1 on the upstream side of the conduction path is made of ceramics mainly composed of silicon nitride. May be formed. Furthermore, rolling elements 3
Although only the roughness of the rolling surface is specified to be 0.2Z or less,
The axial end face of the rolling element 3 may have a roughness of 0.2Z or less from the viewpoint of completely preventing adhesion of moisture and wear powder. The rolling element 3 may be a ball in addition to the rollers shown in the drawing. Further, a full roller bearing or a full ball bearing without a cage may be used.

[0016]

According to the present invention, the rolling elements, which are the existing bearing components, are made of specific ceramics so as to provide electrical insulation between the inner and outer races. There is no waste such as no need for processing,
There is no problem when the bearing is assembled or in a state where the bearing is assembled as in the related art, and the reliability of electrical insulation is high. In addition, by specifying the manufacturing method and surface roughness of this rolling element, it suppresses the generation of bubbles and cracks that may absorb moisture, prevents moisture from adhering to the surface, and also prevents the adhesion of metal abrasion powder. Since it is made possible, the reliability of the electrical insulation is also high in that the occurrence of electrical continuity due to uncertain factors such as moisture and metal abrasion powder can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is a longitudinal 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 apparatus according to the present embodiment.

[Explanation of symbols]

 Reference Signs List 1 inner ring 2 outer ring 3 rolling element 4 cage

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor: Miyoshi, 3-5-8, Minamisenba, Chuo-ku, Osaka-shi Koyo Seiko Co., Ltd. (56) References JP-A-61-92322 (JP, A) 60-29921 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) F16C 33/32

Claims (1)

(57) [Claims] 1. An anti-corrosion type rolling bearing in which grease is sealed inside, wherein at least a rolling element interposed between an inner ring and an outer ring is made of silicon nitride as a main component by pressure sintering. It is formed, and at least its roughness of the rolling surface is less 0.2Z, between the inner and outer rings
A rolling bearing of an anti-corrosion type, wherein the rolling bearing is electrically insulated .