JPH0972344A - Bearing unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remarkably reduce the frequency of maintenance inspection by providing a stress variation effect reduction construction reducing the effect of stress variation between the end face of a bearing and a packing ring. SOLUTION: Because a radial load of about 10 ton is loaded on the axle 1 of a railway rolling stock, bending is generated on the rotating axle 1. Then stress between the end face of an inner ring 2c and the end face 5a of a packing ring 5A and stress between the end face of an inner ring 2d and the end face 5b of a packing ring 5B are periodically varied synchronizing with rotation of the axle 1. But, because the end faces 5a, 5b of the packing rings 5A, 5B are formed with films for absorbing the stress variation, fretting due to such stress variation is prevented from generating on the end faces of the inner rings 2c, 2d, the end faces 5a, 5b of the packing rings 5A, 5B, and the like. As a result, mixing of abrasion powder of metal into the bearing is avoided, and hence the raceway surface can be prevented from chapping and the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing unit, and more particularly to a bearing unit provided with a backing ring that abuts an end face of the bearing to fix the bearing to a rotary shaft, and the contact between the bearing end face and the backing ring. This is to reduce the wear of the surface.

[0002]

2. Description of the Related Art In recent years, with the increase in speed of land transportation, there is a demand for extending the continuous use time of bearings for axles even in railway vehicles. That is, there is a demand for development of a bearing unit that can reduce the frequency of maintenance and inspection.

In order to meet such demands, conventionally, by improving the seal structure, foreign matter from the outside of the bearing is prevented as much as possible, or the housing end face to which the bearing is fixed is made of the same material as the bearing. In order to prevent the deterioration of grease as a lubricant by suppressing the generation of fine powder due to minute wear, it was attempted to improve the hardness by hardening it to increase its hardness.

[0004]

Certainly, if the above measures are taken, it is possible to reduce the mixing of metal powder or the like into the bearing and grease, but the frequency of maintenance and inspection of the bearing unit is reduced. The current situation is that no dramatic reduction has been achieved.

That is, for example, a double row cylindrical roller bearing or a rear combination tapered roller bearing is applied to a bearing which is required to have high rigidity and impact resistance, such as a bearing for a railroad vehicle axle. Two sets of different bearings are used for one axle. Further, since a radial load of about 10 tons is applied to each axle, a phenomenon called so-called bending occurs in which the axle itself rotates while bending in a direction perpendicular to the axle.

Then, the stress of the contact surface between the backing ring that abuts on the end surface of the bearing inner ring or the like for fixing the bearing to the axle and the end surface of the inner ring periodically fluctuates due to the effect of bending, and the stress fluctuation. This causes minute wear (fretting) on the contact surface. On the other hand, since the bearing seal is arranged outside the contact surface where minute wear occurs, it is not possible to prevent the metal abrasion powder generated by fretting from entering the inside of the bearing. If a large amount of the abrasion powder is left in the bearing, the surface roughness of the raceway surface and the deterioration of grease will be caused, and smooth rotation cannot be maintained. Therefore, frequent maintenance inspections are necessary.

The present invention has been made by paying attention to the unsolved problems of the conventional technique, and an object thereof is to provide a bearing unit capable of greatly reducing the frequency of maintenance and inspection. I am trying.

[0008]

In order to achieve the above object, the present invention provides a bearing for supporting a rotating shaft, and a backing ring for abutting an end surface of the bearing to fix the bearing to the rotating shaft. In the bearing unit including, a stress fluctuation influence reducing structure for reducing the influence of stress fluctuation between the end surface of the bearing and the backing ring is provided.

As the structure for reducing the influence of stress fluctuation, for example, between the end surface of the bearing and the backing ring,
It is conceivable to interpose a stress fluctuation absorbing layer that absorbs stress fluctuations occurring between them. That is, since the stress fluctuation absorbing layer interposed between the bearing end surface and the backing ring absorbs the stress fluctuation at the contact surface between the bearing end surface and the backing ring, the occurrence of fretting is suppressed.

Here, as a specific example of the stress fluctuation absorbing layer, a layer made of a material having a hardness lower than that of both the bearing material and the backing ring material can be considered. As such a material having low hardness, a soft metal such as silver, lead, zinc or tin can be applied.

As another specific example of the stress fluctuation absorbing layer, a layer made of a material having a smaller elastic force and a yield point than both the material of the bearing and the material of the backing ring can be considered.
As a material having a small elastic force and a yield point, a polymer elastomer represented by rubber or plastic can be applied.

As another specific example of the stress fluctuation absorbing layer, a layer made of a material having self-lubricating property can be considered. As the material having such self-lubricating property, a slidable resin containing a solid lubricant can be applied, and for example, a solid lubricant such as ethylene tetrafluoride, molybdenum disulfide, polyethylene, etc., or slidability is imparted. A polymer elastomer or the like can be applied.

The stress fluctuation absorbing layer as described above is
It can be provided as a coating on the surface of the portion of the backing ring that abuts the bearing end surface. For example, the soft metal as described above can be provided by plating.

Further, as another specific example of the stress fluctuation absorbing layer, a sheet in which a fluorine compound such as tetrafluoroethylene is used as a matrix (matrix) and abrasion resistant particles are mixed therein is conceivable. By bonding such a sheet to the end surface of the bearing or the metal surface of the backing ring, a structure that reduces the influence of stress fluctuations can be realized.

Here, as the abrasion resistant particles, for example, Econor (trade name) manufactured by Sumitomo Chemical Co., Ltd., Unibex (trade name) manufactured by Unitika Co., Ltd., Bell Pearl (trade name) manufactured by Kanebo Co., Ltd., DuPont. Polyimide, spherical carbon made by Nippon Carbon Co., and calcium carbonate,
Any material, such as graphite, that is harder than the matrix layer that surrounds these materials is applicable.

The blending ratio of the wear resistant particles to the matrix layer is preferably 2 to 60 wt%, and more preferably 5 to 60 wt%.
40 wt%, and more preferably 10 to 30 wt%. The thickness of the sheet is preferably 10 to 1000 μm. If the thickness is less than 10 μm, the effect of absorbing the stress fluctuation is insufficient, and the time until the occurrence of fretting cannot be made sufficiently long. On the other hand, if it exceeds 1000 μm, the influence on the dimensional tolerance of the bearing unit cannot be ignored.

As another structure for reducing the effect of stress fluctuation in the present invention, for example, it is conceivable to increase the hardness of the backing ring end surface that abuts the end surface of the bearing.
More specifically, the hardness of the backing ring end surface is
By setting the hardness to be equal to or higher than the hardness of the bearing end surface contacting with this, a stress fluctuation influence reducing structure can be obtained. That is, if the hardness of the backing ring end surface is increased, the resistance to stress fluctuation is increased, so that the influence of the stress fluctuation on the backing ring end surface is reduced, and the occurrence of fretting on the backing ring is suppressed.

Specific examples of increasing the hardness of the backing ring end surface include chrome plating on the backing ring end surface and coating with a titanium compound or the like, but TiC (titanium carbon) having particularly excellent slidability. Coating is also excellent in terms of preventing fretting. The chrome plating may be electrolysis at low temperature to form black chrome oxide on the surface of the backing ring. Further, as the titanium compound, T
It may be a compound such as iN (titanium nitride) or TiCN (titanium carbon nitride). In addition to plating, these high hardness layers include ion plating, C
It can be formed by various methods such as VD and sputtering. Further, a composite layer of tetrafluoroethylene, difluoroethylene or the like may be formed on the high hardness thin layer.

The thickness of this high hardness layer is 0.3 to 20 μm.
Is preferable from the viewpoint of preventing fretting of the end surface of the backing ring. For example, if the TiC layer is formed by ion plating or CVD, 0.3
.About.3 .mu.m is particularly desirable.
5 to 20 μm is desirable. When the thickness of these high hardness layers is less than the lower limit of the desirable range, the time until the occurrence of fretting cannot be made sufficiently long. On the other hand, if the upper limit is exceeded, another adverse effect such as peeling will occur.

As another specific example of increasing the hardness of the backing ring end surface, it is conceivable to increase the hardness of the backing ring end surface itself. For example, for the backing ring surface, carbonitriding treatment, carburizing treatment,
The hardness of the surface can be increased by performing a sulfurizing treatment, a bath nitriding treatment, or the like. These carbonitriding treatments and the like can form a high hardness layer up to a depth of about 200 μm.

Further, as another structure for reducing the influence of the stress fluctuation in the present invention, for example, the backing ring end surface which abuts the end surface of the bearing is processed into an edge non-contact shape so as not to contact the edge portion of the end surface of the bearing. It is possible to do it. That is, the stress between the bearing end surface and the backing ring is mainly concentrated on the edge portion of the bearing end surface,
Since the part of the backing ring end face that contacts the edge of the bearing end face becomes the starting point for fretting, eliminating the contact between the edge and the backing ring reduces the effect of stress fluctuations on the backing ring end face. The occurrence of fretting on the backing ring is suppressed.

As a specific example of the edge non-contact shape, it is conceivable that the backing ring end surface is subjected to crowning so that the backing ring is rounded so that the central portion in the thickness direction rises. That is, it is usual that chamfers (chamfered portions) are formed on the inner peripheral side and the outer peripheral side of the end surface of the inner ring of the bearing, and the edge portion is formed at the boundary between the flat portion of the end surface and the chamfer. Therefore, if the backing ring end surface is rounded so as to escape the edge portion, the above edge non-contact shape can be obtained.

As another specific example of the edge non-contact shape, it is conceivable that the backing ring end surface is tapered so as to escape the edge portion of the bearing end surface. That is, the central portion in the thickness direction of the backing ring end surface is a flat portion that abuts on the bearing end surface, and a part of the backing ring end surface from the central portion side to the end portion slightly from the portion facing the bearing end surface edge portion ( That is, the above edge non-contact shape can be obtained by making the backing ring end surface slightly inclined from the portion facing the bearing end surface chamfer portion) away from the bearing end surface as it approaches the end portion.

Further, the edge non-contact shape may be formed on the bearing side instead of being formed on the backing ring side.
That is, the end surface of the bearing may be rounded by, for example, crowning so that the edge portion of the end surface of the bearing does not contact the end surface of the backing ring. Similarly, the end surface of the bearing may be tapered so that the edge portion of the end surface of the bearing does not contact the end surface of the backing ring. When the bearing end surface has a tapered shape, it is desirable that the portion where the tapered surface starts be smoothly bent.

Further, as another stress fluctuation influence reducing structure in the present invention, the stress fluctuation absorbing layer,
It may be a combination of both of the above edge non-contact shapes. That is, while processing the shape of the backing ring end surface or the bearing end surface into an edge non-contact shape such that the edge part of the end surface of the bearing does not contact the backing ring end surface, one or both of the end surface of the backing ring or the bearing end surface, By forming the stress fluctuation absorbing layer as described above, the advantages of both the stress fluctuation absorbing layer and the edge non-contact shape are exhibited, and the occurrence of fretting is more reliably suppressed.

Further, as another structure for reducing the influence of stress fluctuation in the present invention, a structure in which both the structure for increasing the hardness of the end surface of the backing ring and the non-edge contact shape are combined may be used. That is, the backing ring end surface or the bearing end surface is processed into an edge non-contact shape so that the edge portion of the bearing end surface does not contact the backing ring end surface, and the hardness of the backing ring end surface is increased as described above. If this is the case, the advantages of both the point where the end surface hardness is increased and the edge non-contact shape are exhibited, and the occurrence of fretting is more reliably suppressed.

[0027]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a bearing unit showing a configuration of a first embodiment of the present invention. First, the configuration will be described. This bearing unit is a bearing unit for an axle of a railroad vehicle and serves as a rotary shaft. It has a bearing 2 that rotatably supports the axle 1. In addition, the bearing 2 is a double row tapered roller bearing of a back combination having two rows of tapered rollers as the rolling elements 2a, and is provided for each row of the rolling elements 2a and has two rows with a spacer 2b interposed therebetween. Inner rings 2c, 2d
An outer ring 2e common to each row of rolling elements 2a, and rolling elements 2a
And a retainer 2f provided for each row, and inner rings 2c and 2d sandwiching the spacer 2b are externally fitted to the tip portion of the axle 1. A grease supply port 2g is formed at a proper position in the axial center of the outer ring 2e.

A cap 3 having a flange portion 3A protruding outward in the circumferential direction is integrally fixed to the tip end surface of the axle 1 in the rotational direction by a plurality of bolts 4, and the bearing 2 of the flange portion 3A is fixed. The end surface of one backing ring 5A comes into contact with the surface facing the side, and the backing ring 5A
The other end surface of A is in contact with the end surface of one inner ring 2c as a bearing end surface.

On the other hand, a tapered portion 1A and a large-diameter portion 1B whose central portion expands in diameter are formed closer to the central portion of the axle 1 than the position where the bearing 2 of the axle 1 is fixed, and the taper portion 1A has the other backing. The ring 5B is fitted on the outside, and the inner end portion of the backing ring 5B abuts on the tip side step portion 1C of the large diameter portion 1B, and the tip surface of the backing ring 5B serves as a bearing end surface. The other inner ring 2d
Is in contact with the end surface of.

Further, on each of the end surface of the outer ring 2e on the side of the cap 3 and the end surface on the side of the large diameter portion 1B, a thin-walled cylindrical guide member 6 whose diameter gradually decreases as the distance from the outer ring 2e increases.
A and 6B are fixed, the tip of one guide member 6A surrounds the outer peripheral surface of the flange 3A with a very small gap, and the tip of the other guide member 6B has a very small gap. Is opened to surround the outer peripheral surface of the backing ring 5B.

An oil seal 7A is provided between the outer peripheral surface of the central portion of the backing ring 5A and the inner peripheral surface of the central portion of the guide member 6A, and the outer peripheral surface of the central portion of the backing ring 5B and the central portion of the guide member 6B are arranged. An oil seal 7B is disposed between the oil seal 7B and the peripheral surface. Such oil seal 7
A and 7B prevent intrusion of fine powder and the like from the outside to the inside of the bearing 2.

To mount the bearing 2 on the axle 1, the backing ring 5B, the bearing 2 and the backing ring 5A are fitted in this order from the tip side of the axle 1, and then the cap 3 is attached to the tip surface of the axle 1. , Bolt 4 is tightened. This is an axle bearing unit, and since a large radial load is applied to the bearing 2 to support the weight of the vehicle, the bearing 2 is attached to the bolt 4, the cap 3 and both end surfaces of the bearing 2. A pressure input of several tons is applied in the axial direction via the rings 5A and 5B, and the bearing 2 is fixed to the axle 1 by the pressure input.

In the bearing unit of this embodiment, the end surface 5a of the backing ring 5A which abuts the end surface of the inner ring 2c and the end surface 5b of the backing ring 5B which abuts the end surface of the inner ring 2d are respectively attached to the shafts. A film is formed as a stress fluctuation absorbing layer that absorbs stress fluctuations along the direction.

It should be noted that, in reality, one axle 1 is shown in FIG.
Bearings 2 as shown in are arranged at both ends,
Since it has the same structure, its illustration and description are omitted. Next, the operation of the present embodiment will be described.

That is, since a radial load of about 10 tons is applied to the axle 1, bending occurs on the rotating axle 1. Then, the stress between the end surface of the inner ring 2c and the end surface 5a of the backing ring 5A and the stress between the end surface of the inner ring 2d and the end surface 5b of the backing ring 5B periodically fluctuate in synchronization with the rotation of the axle 1.

However, since the end faces 5a and 5b of the backing rings 5A and 5B are coated with a film for absorbing the stress variation, the inner ring 2 is caused by the stress variation.
End surfaces 5c and 2d and end surfaces 5 of backing rings 5A and 5B
Fretting on a, 5b, etc. is prevented. As a result, a large amount of metal abrasion powder is prevented from entering the bearing, so that the inner rings 2c and 2d and the outer ring 2e are prevented.
Therefore, the frequency of maintenance and inspection is reduced as compared with the conventional bearing unit without causing surface roughness of the track surface and deterioration of grease.

FIG. 2 is a sectional view showing the structure of a bearing unit according to the second embodiment of the present invention. The same members and parts as those in the structure shown in FIG. 1 are designated by the same reference numerals.
That is, the bearing unit shown in FIG. 2 has substantially the same structure as that shown in FIG.
B is thinner than in the case of FIG. Even in the bearing unit having such a configuration, the fretting prevention effect can be obtained by forming the stress fluctuation absorbing layer on the end surfaces 5a and 5b of the backing rings 5A and 5B.

FIG. 3 is a view showing a third embodiment of the present invention and is an enlarged sectional view of a main part. The overall configuration is the same as in the first embodiment, and the same members and parts as those in the first embodiment are designated by the same reference numerals. The configuration on the backing ring 5A side is shown in FIG.
The configuration is the same as that of FIG.

That is, in the present embodiment, the high hardness layer 10 having an increased hardness is formed on the surface of the end surface 5b of the backing ring 5B, and the high hardness layer 10 is brought into contact with the end surface of the inner ring 2d. . The high-hardness layer 10 is a layer having a hardness equal to or higher than that of the end surface of the inner ring 2d that is in contact with the high-hardness layer 10, and is formed by the above-described plating treatment, coating treatment, carbonitriding treatment or the like.

Even with such a structure, the resistance of the end surface 5b to the stress fluctuation between the inner ring 2d and the backing ring 5B is improved by forming the high hardness layer 10, so that the end surface 5b is fretting. Is less likely to occur. Therefore, as in the first embodiment,
There is an advantage that the frequency of maintenance and inspection is reduced as compared with the conventional bearing unit.

FIG. 4 is a view showing a fourth embodiment of the present invention and is an enlarged sectional view of a main part. The overall configuration is the same as in the first embodiment, and the same members and parts as those in the first embodiment are designated by the same reference numerals. The structure on the backing ring 5A side is shown in FIG.
The configuration is the same as that of FIG.

That is, in this embodiment, the end face 5b of the backing ring 5B is not provided with a stress fluctuation absorbing layer or the like,
By processing the end surface 5b into a predetermined shape, the influence of stress fluctuation can be reduced.

In other words, in this embodiment, the end surface 5b of the backing ring 5B is crowned so that the end surface 5b is rounded so that the center portion in the thickness direction is higher than the end portion. . This prevents the edge portion 13 formed between the chamfer portion 11 and the flat surface portion 12 on the end surface of the inner ring 2d from contacting the end surface 5b of the backing ring 5B.

With this structure, the edge portion 13 where the stress between the inner ring 2d and the backing ring 5B is concentrated.
Does not come into contact with the end surface 5b, so that even if the stress changes, it is possible to prevent the edge portion 13 from becoming the starting point of fretting occurrence, so that the influence of the stress change on the end surface 5b is reduced. The occurrence of fretting on the end surface 5b is suppressed. Therefore, as in the first embodiment, there is an advantage that the frequency of maintenance and inspection is reduced as compared with the conventional bearing unit.

The crowning shape of the end surface 5b is not particularly limited as long as the edge 13 and the end surface 5b can be kept in non-contact with each other, and the reference radius and the like are arbitrary. Also,
Processing such as barrel and shot peening may be applied to the portion subjected to the crowning processing. Furthermore, even if the edge portion 13 does not come into contact with the end surface 5b by performing the crowning process on the end surface side of the inner ring 2d, the same effect as that of the present embodiment can be obtained.

FIG. 5 is a view showing a fifth embodiment of the present invention and is an enlarged sectional view of a main part. The overall configuration is the same as in the first embodiment, and the same members and parts as those in the first embodiment are designated by the same reference numerals. The structure on the backing ring 5A side is shown in FIG.
The configuration is the same as that of FIG.

That is, also in the present embodiment, as in the fourth embodiment, the end face 5b is processed into a predetermined shape so that the influence of stress fluctuation can be reduced. That is, in this embodiment, the inner ring 2d of the end surface 5b is
A taper surface 14 is formed at a portion of the end face facing the chamfered portion 11 so as to separate from the inner ring 2d as it approaches the end. However, the position where the taper surface 14 begins to tilt is slightly closer to the center than the edge 13,
The edge portion 13 does not contact the end surface 5b of the backing ring 5B.

Even with such a configuration, the edge portion 13
Does not come into contact with the end surface 5b, the same effect as that of the fourth embodiment can be obtained. In particular, according to the present embodiment, it is sufficient to form the tapered surface 14 on the end surface 5b, which is advantageous in cost as compared with the above-mentioned respective embodiments, particularly the above-mentioned fourth embodiment.

The angle of formation of the tapered surface 14 is not particularly limited, and the point is that the edge 13 and the end surface 5b need not be in contact with each other. Further, even if the edge portion 13 is prevented from coming into contact with the end surface 5b by forming the tapered shape on the inner ring 2d side, the same operational effect as in the present embodiment can be obtained.

FIG. 6 is a view showing a sixth embodiment of the present invention and is an enlarged sectional view of a main part. The overall configuration is the same as in the first embodiment, and the same members and parts as those in the first embodiment are designated by the same reference numerals. The structure on the backing ring 5A side is shown in FIG.
The configuration is the same as that of FIG.

That is, in this embodiment, the end surface 5b of the backing ring 5B has the same shape as that of the fourth embodiment, and the end surface 5b has the same stress as that of the first embodiment. The fluctuation absorbing layer 20 is formed.

With such a configuration, the effects of both the first and fourth embodiments described above are exhibited, and the influence of stress fluctuations becomes extremely small, so that the occurrence of fretting is suppressed. There is an advantage that the effect becomes remarkable and the frequency of maintenance and inspection is greatly reduced as compared with the conventional bearing unit.

FIG. 7 is a view showing a seventh embodiment of the present invention and is an enlarged sectional view of a main part. The overall configuration is the same as in the first embodiment, and the same members and parts as those in the first embodiment are designated by the same reference numerals. The configuration on the backing ring 5A side is shown in FIG.
The configuration is the same as that of FIG.

That is, in this embodiment, the end surface 5b of the backing ring 5B has the same shape as that of the fifth embodiment, and the end surface 5b has the same stress as that of the first embodiment. The fluctuation absorbing layer 20 is formed, and with such a configuration, the effects of both the first embodiment and the fifth embodiment are exhibited, and thus the sixth embodiment. The same effects and advantages can be obtained, and the cost is more advantageous than that of the sixth embodiment.

In each of the above embodiments, the case where the bearing unit according to the present invention is applied to a bearing unit having a double row tapered roller bearing with a combination of back surfaces has been described, but the application of the present invention is not limited to this. However, other bearings such as double-row cylindrical roller bearings may be used.

In the first, second, sixth and seventh embodiments, the case where the stress fluctuation absorbing layer is formed mainly on the end surfaces 5a and 5b of the backing rings 5A and 5B has been described. Inner ring 2 with which the end surfaces 5a, 5b abut
A stress fluctuation absorbing layer may be formed on the end faces of c and 2d,
Alternatively, both may be formed. That is, in the sixth and seventh embodiments, the end faces 5a, 5b of the backing rings 5A, 5B or the end faces of the inner rings 2c, 2d have the crowning shape or the tapered shape as described above, and the backing ring 5A , 5B end surfaces 5a, 5b or inner ring 2c,
The stress fluctuation absorbing layer may be formed on one or both of the 2d end faces.

Further, in the sixth and seventh embodiments, the stress fluctuation absorbing layer 20 is formed on the end faces 5a and 5b, but instead of this, the high hardness as in the third embodiment is provided. The layer 10 may be formed.

[0058]

EXAMPLES Examples of the present invention will be described below in detail with the results of experiments conducted by the present inventors.

In Experimental Examples 1 to 3 described below, the bearing unit having the same structure as that of FIG. 1 in the above-mentioned embodiment is used, and the axle 2 is rotated by the motor drive while the bearing 2 is loaded with the radial load. As a result, the axle 1 is forcibly bent, and the inner ring 2c, and the inner ring 2c, are regenerated every time a predetermined time (50 hours, 100 hours, 200 hours, 300 hours, 400 hours, 500 hours, 1000 hours) elapses.
2d end surface and backing ring 5A, 5B end surface 5
The occurrence of fretting was evaluated by observing a and 5b, and after 1,000 hours, the surface profile of the end faces of the inner rings 2c and 2d was measured for wear depth with a roughness measuring instrument (manufactured by Tokyo Seimitsu Co., Ltd.). Further, as a comparative example, the same experiment was conducted for the bearing 2 in which the stress fluctuation absorbing layer was not formed on the end faces 5a and 5b. The experimental conditions were: radial load: 5000 kgf, axial load: 1500 kgf, rotation speed: 2000 rpm, load load interval: 5 seconds on, 25 seconds off. Part of the surface observation results is shown in Table 1, part of the wear depth measurement results is shown in Table 2, and the relationship between the film thickness of the stress fluctuation absorbing layer and the durability time of the bearing 2 is shown in FIG. Indicated by. [Experimental Example 1] The material of the backing rings 5A and 5B is S4.
5C and the size of each part is 120m inside diameter
m, outer diameter 170 mm, length 70 mm, inner rings 2c, 2
The contact area with the d end surface was set to about 2300 mm ² .

Then, the backing rings 5A, 5
On the end faces 5a and 5b of B, a silver film as a stress fluctuation absorbing layer was formed by plating to a thickness of 2 μm to 50 μm. Specifically, the portions other than the end faces 5a and 5b are covered with a chloroprene-based masking agent, alkali degreasing and acid cleaning are performed, and then copper strike plating is applied to 1 μm, and then the end faces 5a and 5b are electroplated. To provide a silver coating. The thickness of the silver coating was controlled by controlling the electrolysis current per unit area and the electrolysis time to form silver coatings having different thicknesses. [Experimental Example 2] Commercially available urethane-based elastomers having different thicknesses were coated on the end surfaces 5a and 5b of the backing rings 5A and 5B having the same material and dimensions as in Experimental Example 1. [Experimental Example 3] Manganese phosphate chemical conversion treatment was previously applied to the end surfaces 5a and 5b of the backing rings 5A and 5B having the same material and dimensions as those in Experimental Example 1, and then tetrafluoroethylene and a thermosetting resin were used. The mixture was coated. The chemical conversion treatment is performed with a film weight of about 5.0 g / m ² (film thickness: about 4 μm
˜5 μm) manganese phosphate treatment. The upper resin coating layer is a coating layer in which the ratio of polyamideimide 4 to tetrafluoroethylene 1 is 4, and the coating method uses a mixture of tetrafluoroethylene and polyamideimide in the above ratio. Form a coating layer with a spray gun using air using the same weight ratio of organic solvent as a dispersion.
This is a method in which the end faces 5a and 5b are covered by heat treatment at 00 degrees for 1 hour. A plurality of types of film thickness were formed.

[0061]

[Table 1]

The meaning of each symbol in Table 1 is as follows. ○: No fretting occurred △: Partially fretting occurred ×: Full surface fretting occurred

[0063]

[Table 2]

As is clear from Table 1 and Table 2,
It was confirmed that any of Experimental Examples 1 to 3 had an effect of preventing fretting as compared with Comparative Example. The effect of preventing fretting in the configuration of Experimental Example 1 is that the stress fluctuation acts on the plating layer of silver or the like having a low hardness, and the plating layer is abraded to cause the inner rings 2c and 2d end surfaces and the backing rings 5A and 5B. This is because fretting does not occur on the end surfaces 5a and 5b.

In the structure of Experimental Example 2, the effect of preventing fretting can be obtained if the interposing material has a small elastic force and a yield point exists, the end faces 5a of the inner rings 2c and 2d and the end faces 5a of the backing rings 5A and 5B. , 5b is absorbed. Further, it is considered that since the gap is not formed between the end faces due to the plastic deformation of the intervening substance, the impact is further mitigated, and as a result, the fretting prevention effect is improved as compared with the case of Experimental Example 1.

The effect of preventing fretting can be obtained with the structure of Experimental Example 3 as in the case of Experimental Example 2, but the intervening substance has a self-lubricating property, so that a particularly remarkable fretting effect is obtained. Anti-tinging effect is obtained. In other words, the structure of Experimental Example 3 in which the matrix resin layer containing the solid lubricant particles was formed on the metal surface by chemical conversion treatment was used to prevent fretting in Experimental Examples 1 to 3 above. Most preferred.

The endurance time until the wear amount of the untreated backing ring in the comparative example due to fretting reaches 150 μm, which is a tentative limit value, is 450 hours. Therefore, stress fluctuation absorption that can clear the endurance time is absorbed. Assuming that the film thickness of the layer is effective for preventing fretting, the lower limit of film thickness in the structure of Experimental Example 1 is 50 μm, the lower limit of film thickness in the structure of Experimental Example 2 is 30 μm, and the structure of Experimental Example 3 is It can be said that the lower limit of the film thickness is preferable to be 5 μm.

On the other hand, in any of the structures, if the stress fluctuation absorbing layer exceeds 100 μm, cracks or peeling easily occur in the stress fluctuation absorbing layer, which adversely affects fretting prevention. It has been confirmed. Therefore, the upper limit of the film thickness of the stress fluctuation absorbing layer is 100 μm.
Is preferred.

In the structure of Experimental Example 3 in which the effect of preventing fretting is particularly remarkable, the thickness of the stress fluctuation absorbing layer considered to be effective for the above reason is 5 μm to 100 μm.
More preferably, it is in the range of 20 μm to 100 μm.

It has been confirmed that, among the various conditions of Experimental Example 1, the strike plating is not limited to copper, and the same effect can be obtained with other metals such as nickel. Also, the thickness of the strike plating is
It has been confirmed that the same effect can be obtained in the range of 0.5 μm to 5.0 μm. In addition to silver, it has been confirmed that other soft metals such as lead and tin have substantially the same effect as in the case of silver. Therefore, even if a metal other than silver is plated on the end faces 5a and 5b. Often, these silver, lead, zinc, tin, etc. are effective in preventing fretting. In short, the same effect as in Experimental Example 1 can be obtained if the coating is made of a material having a hardness lower than that of both the materials of the inner rings 2c and 2d and the backing rings 5A and 5B.

In addition, the end surfaces 5a, 5
When the stress fluctuation absorbing layer is coated on b to form the stress fluctuation absorbing layer, the substance forming the stress fluctuation absorbing layer is not limited to the elastomer, and if it is a viscoelastic body, it may be thermoplastic, thermosetting, or rubber. Even if you use a thermoplastic elastomer, which is a polymer of
It has been confirmed that the same effect as in Experimental Example 2 can be obtained. Further, such a substance is formed in a sheet shape and is sandwiched between the end faces of the inner rings 2c, 2d and the end faces 5a, 5b, or such a sheet form is fixed to at least one end face. Also, the same effect as that of Experimental Example 2 can be obtained. In short, the inner rings 2c, 2d are placed between the end faces.
The same effect as in Experimental Example 2 can be obtained by interposing a layer made of a material having a smaller elastic coefficient and a yield point than both the material of No. 1 and the materials of the backing rings 5A and 5B.

Further, the chemical conversion treatment film in Experimental Example 3 is not limited to manganese phosphate salt, and salts such as zinc phosphate, calcium phosphate, iron phosphate, etc. can be applied, and the film weight is 1.0 g / g. If m ² or more, the same effect can be obtained. Further, it has been confirmed that even if the solid lubricant particles in the resin coating film are particles having self-lubricating properties, other solid lubricant particles can prevent fretting. In addition to the polyamide-imide, the upper resin layer may be any viscoelastic body such as epoxy, urethane, and phenol, which has a smaller elastic coefficient than metal.

Next, another experimental example conducted by the present inventors will be described. The experimental conditions and the experimental method are the same as in Experimental Examples 1 to 3 above, unless otherwise specified. [Experimental Example 4] 70 wt% of tetrafluoroethylene and 30 wt% of Econol (trade name) manufactured by Sumitomo Chemical Co., Ltd. were mixed,
The sintered material was made into a sheet having a thickness of 0.3 mm, and the sheet was adhered to the end surfaces 5a and 5b of the backing rings 5A and 5B. A two-component curing type epoxy made by ThreeBond Co., Ltd. was used as the adhesive, and the adhesive was applied to the entire surface of the sheet and cured at 80 ° C.

It should be noted that the back surfaces 5a and 5B of the backing rings 5A and 5B were previously coated with a manganese phosphate salt film of 5 μm, and the above-mentioned sheet was activated with a sodium naphthalene solution. [Experimental Example 5] 85 wt% of tetrafluoroethylene and 15 wt% of polyimide manufactured by DuPont were mixed and sintered into a sheet having a thickness of 0.6 mm, and the sheet was used as a backing for each inner ring 2c, 2d of the bearing 2. It was adhered to the end faces of the rings 5A and 5B. A two-component curing type epoxy made by ThreeBond Co., Ltd. was used as an adhesive, and the sheet was dry-etched with argon gas and then adhered to the end faces of the inner rings 2c and 2d.

Table 3 shows a part of the results of observing the surface in Experimental Examples 4 and 5. The meanings of the symbols in Table 3 are the same as in Table 1. In addition, the elapsed time is from the above Experimental Examples 1 to
Different from 3, it was set to 500 to 3500 hours.

[0076]

[Table 3]

From these Experimental Examples 4 and 5, it was found that the use of a mixture of a wear resistant material and a sheet material of tetrafluoroethylene as the stress fluctuation absorbing layer makes the effect of preventing fretting extremely remarkable. . Also, the stress fluctuation absorbing layer is
It was also found that the same fretting prevention effect can be obtained by the end faces 5a, 5b of the backing rings 5A, 5B and the end faces on the inner rings 2a, 2d side. Furthermore, on the sheet surface,
It was also confirmed that the chemical or physical activation treatment improves the adhesion to the backing rings 5A and 5B and the inner rings 2a and 2d. In particular, unlike the coating material, the sheet material has excellent durability against fretting, even if the thickness of the sheet increases, cracks and cracks due to stress fluctuations do not occur.

Next, another experimental example conducted by the present inventors will be described. The experimental conditions and the experimental method are the same as in Experimental Examples 1 to 3 above, unless otherwise specified. [Experimental Example 6] End surfaces 5a of the backing rings 5A and 5B,
A chromium layer was formed as a high hardness layer 10 on 5b by 1 to 20 μm by plating, and the surface hardness of the end faces 5a and 5b was 1100 Hv (see FIG. 3). [Experimental Example 7] End surfaces 5a of the backing rings 5A and 5B,
A TiC film as the high hardness layer 10 is formed on the surface 5b by ion plating to have a thickness of 2 μm.
The surface hardness was set to 2300 Hv (see FIG. 3). [Experimental Example 8] The backing rings 5A and 5B are made of the same steel carbon chrome steel as the bearing material, and the end surfaces 5 thereof are
Carbonized and nitrided a and 5b were formed to form the high hardness layer 10, and the hardness of the end faces 5a and 5b was made equal to or higher than the hardness of the end faces of the inner rings 2a and 2d (see FIG. 3).

Table 4 shows a part of the observation results of the surface in these Experimental Examples 6 to 8. The meanings of the symbols in Table 4 are the same as in Table 1.

[0080]

[Table 4]

From these Experimental Examples 6 to 8, by forming the high hardness layer 10 on the end surfaces 5a and 5b of the backing rings 5A and 5B in order to reduce the influence of stress fluctuation, a sufficient fretting suppressing effect can be obtained. I found out that

Next, another experimental example conducted by the present inventors will be described. The experimental conditions and the experimental method are the same as in Experimental Examples 1 to 3 above, unless otherwise specified. [Experimental Example 9] End surfaces 5a of the backing rings 5A and 5B,
By crowning 5b, the inner ring 2a,
The edge portion 13 of the end surface of 2b was prevented from contacting the end surfaces 5a and 5b (see FIG. 4). [Experimental Example 10] End surfaces 5 of backing rings 5A and 5B
By forming the tapered surface 14 on a and 5b, the inner ring 2
The edge portions 13 of the end faces of a and 2b were prevented from contacting the end faces 5a and 5b (see FIG. 5).

Table 5 shows a part of the results of observing the surface in Experimental Examples 9 and 10. The meanings of the symbols in Table 5 are shown in Table 1.
Is the same as

[0084]

[Table 5]

From these Experimental Examples 9 and 10, if the end surfaces 5a and 5b of the backing rings 5A and 5B are made into a crowning shape or a taper shape so that the edge portion 13 does not contact the end surfaces 5a and 5b, It was found that a sufficient fretting suppression effect was obtained. Next, another experimental example conducted by the present inventors will be described. In addition,
The experimental conditions and the experimental method are the same as those in the above Experimental Examples 1 to 3 unless otherwise specified. [Experimental Example 11] Experimental Example 1 and Experimental Example 9 were combined (see FIG. 6). [Experimental Example 12] Experimental Example 3 and Experimental Example 10 were combined (see FIG. 7). [Experimental Example 13] Experimental Example 6 and Experimental Example 6 were combined (see FIG. 6). [Experimental Example 14] Experimental Example 8 and Experimental Example 10 were combined (see FIG. 7).

Table 6 shows a part of the results of observing the surface in these Experimental Examples 11 to 14. The meanings of the symbols in Table 6 are the same as in Table 1.

[0087]

[Table 6]

According to these Experimental Examples 11 to 14, the effect of suppressing fretting by the stress fluctuation absorbing layer or the high hardness layer and the suppression of fretting by the crowning shape or taper shape formed on the end surfaces 5a, 5b of the backing rings 5A, 5B. Since both effects are obtained, the time when fretting occurs can be significantly delayed, and the frequency of maintenance and inspection can be significantly reduced.

[0089]

As described above, according to the present invention,
Since a stress fluctuation influence reduction structure that reduces the influence of stress fluctuation between the bearing end surface and the backing ring is provided, the effect of stress fluctuation on the contact surface between the bearing end surface and the backing ring can be reduced and fretting will not occur. Since it is suppressed, the surface of the bearing ring is not roughened, the grease is not deteriorated, and the frequency of maintenance and inspection can be reduced. Therefore, the bearing unit according to the present invention is suitable for an axle bearing.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a sectional view showing a configuration of a second exemplary embodiment of the present invention.

FIG. 3 is a sectional view showing a configuration of a third exemplary embodiment of the present invention.

FIG. 4 is a sectional view showing a configuration of a fourth exemplary embodiment of the present invention.

FIG. 5 is a sectional view showing a configuration of a fifth exemplary embodiment of the present invention.

FIG. 6 is a sectional view showing the configuration of a sixth exemplary embodiment of the present invention.

FIG. 7 is a sectional view showing a configuration of a seventh exemplary embodiment of the present invention.

FIG. 8 is a graph showing the results of an experiment conducted by the present inventors.

[Explanation of symbols]

 1 Axle (rotating shaft) 2 Bearing 2a Rolling elements 2c, 2d Inner ring 2e Outer ring 5A, 5B Backing ring 5a, 5b End face 7A, 7B Oil seal 10 High hardness layer 11 Chamfer part 12 Plane part 13 Edge part 14 Tapered surface 20 Stress fluctuation Absorption layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroji Eto 1-5-50 Kumei Kugenuma, Fujisawa-shi, Kanagawa Nippon Seiko Co., Ltd. (72) Hiromitsu Asai 1-1-5 Shinmei Kugenuma, Fujisawa-shi, Kanagawa No. 50 NSK Ltd.

Claims (1)

[Claims] 1. A bearing unit comprising: a bearing for supporting a rotating shaft; and a backing ring for abutting an end surface of the bearing to fix the bearing to the rotating shaft, the end surface of the bearing and the backing ring. A bearing unit having a stress fluctuation influence reducing structure for reducing the influence of stress fluctuation between the bearing units.