JP2006153285A - Bearing unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To greatly reduce the maintenance and inspection frequency of a bearing. <P>SOLUTION: A cap 3 having a flange portion 3A is integrally fixed to the front end face of a rotating shaft 1 in the rotating direction. The end face of a backing ring 5A abuts on the face of the flange portion 3A directed to the side of the bearing 2 and the other end face of the backing ring 5A abuts on the end face of an inner ring 2c. On the other hand, closer to a central portion of the rotating shaft 1 than to the position of the rotating shaft 1 where the bearing 2 is fixed, a tapered portion 1A whose diameter is enlarged at the side of the central portion and a large diameter portion 1B are formed. The backing ring 5B is externally fitted to the tapered portion 1A, and the inner end of the backing rind 5B abuts on a front end side stepped portion 1C of the large diameter portion 1B and the front end face of the backing ring 5B abuts on the end face of an inner ring 2d. On each of the end face 5a of the backing ring 5B abutting on the end face of the inner ring 2c and the end face 5b of the backing ring 5B abutting on the end face of the inner ring 2d membranes are formed for absorbing axial stress fluctuations in the respective end faces 5a and 5b. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a bearing unit, and in particular, in a bearing unit having a backing ring that abuts against an end surface of the bearing and fixes the bearing to a rotating shaft, wear of contact surfaces between the bearing end surface and the backing ring can be reduced. It is a thing.

In recent years, with the increase in speed of land transportation, there is a demand for extending the continuous use time of axle bearings also in a railway vehicle. In other words, there is a demand for developing a bearing unit that can reduce the frequency of maintenance and inspection.
In response to such demands, conventionally, the seal structure has been improved to prevent entry of foreign matter from the outside of the bearing as much as possible, or the housing end surface to which the bearing is fixed is made of the same material as the bearing and is subjected to quenching treatment. In order to improve the hardness, the generation of fine powder due to minute wear is suppressed and deterioration of grease as a lubricant is prevented.

Certainly, if measures such as those mentioned above are taken, the mixing of metal powder into the bearing and grease can be reduced accordingly, but a dramatic reduction in the frequency of maintenance and inspection of the bearing unit has not been achieved. is the current situation.
That is, for example, double-row cylindrical roller bearings and back-side conical roller bearings are applied to bearings that require high rigidity and impact resistance, such as bearings for railway vehicle axles. Two sets are used for one axle. Since each axle has a radial load of about 10 tons, a so-called bending phenomenon occurs in which the axle itself rotates while being bent in a direction perpendicular to the axis.

Then, in order to fix the bearing to the axle, the stress on the contact surface between the backing ring that contacts the end surface of the bearing inner ring or the like and the end surface of the inner ring fluctuates periodically due to the effect of bending. This causes minute wear (fretting). On the other hand, since the seal of the bearing is disposed outside the contact surface where minute wear occurs, it is impossible to prevent the metal wear powder generated by fretting from entering the inside of the bearing. If a state where a large amount of the wear powder is mixed in the bearing is left unattended, the surface of the raceway becomes rough and the grease deteriorates, so that smooth rotation cannot be maintained. For this reason, frequent maintenance inspections are necessary.
The present invention has been made paying attention to such an unsolved problem of the conventional technology, and an object of the present invention is to provide a bearing unit that can greatly reduce the frequency of maintenance and inspection.

In order to achieve the above object, the present invention provides a bearing unit comprising: a bearing that supports a rotating shaft; and a backing ring that abuts against an end surface of the bearing and fixes the bearing to the rotating shaft. A stress fluctuation effect reducing structure for reducing the influence of the stress fluctuation between the end face of the substrate and the backing ring is provided.
In addition, as the said stress fluctuation influence reduction structure, it is possible to interpose the stress fluctuation absorption layer which absorbs the stress fluctuation which arises between them, for example between the end surface of a bearing and a backing ring. That is, the stress fluctuation absorbing layer interposed between the bearing end face and the backing ring absorbs the stress fluctuation on the contact surface between the bearing end face and the backing ring, and thus the occurrence of fretting is suppressed.

Here, as a specific example of the stress fluctuation absorbing layer, a layer made of a material having lower hardness than both the material of the bearing and the material of the backing ring can be considered. As such a low hardness material, soft metals such as silver, lead, zinc and tin can be applied.
As another specific example of the stress fluctuation absorbing layer, a layer made of a material having a lower 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 such a small elastic force and a yield point, a polymer elastomer represented by rubber or plastic can be used.

As another specific example of the stress fluctuation absorbing layer, a layer made of a material having self-lubricating property can be considered. As such a self-lubricating material, a slidable resin containing a solid lubricant can be applied. For example, a solid lubricant such as ethylene tetrafluoride, molybdenum disulfide, and polyethylene, and slidability are imparted. A polymer elastomer or the like can be applied.
The stress fluctuation absorbing layer as described above can be provided as a coating on the surface of the portion that contacts the bearing end surface of the backing ring. For example, the soft metal as described above can be provided by plating.

Furthermore, as another specific example of the stress fluctuation absorbing layer, a sheet in which a fluorine compound such as ethylene tetrafluoride is used as a matrix (matrix) and wear-resistant particles are blended therein can be considered. The structure for reducing the effect of stress fluctuations can be realized by bonding to the end face of the bearing or the metal surface of the backing ring.
Here, as the wear-resistant particles, for example, Econol (trade name) manufactured by Sumitomo Chemical Co., Ltd., Universex (trade name) manufactured by Unitika Co., Ltd., Bell Pearl (trade name) manufactured by Kanebo Co., Ltd., DuPont As long as it is harder than the matrix layer surrounding these, such as polyimide, spherical carbon made by Nippon Carbon Co., Ltd., calcium carbonate, graphite, etc., it is applicable.

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

  In addition, as another structure for reducing the influence of stress fluctuation in the present invention, for example, it is conceivable to increase the hardness of the end surface of the backing ring that contacts the end surface of the bearing. More specifically, the stress fluctuation effect reducing structure can be obtained by setting the hardness of the end surface of the backing ring to be equal to or higher than the hardness of the bearing end surface in contact therewith. That is, if the hardness of the end face of the backing ring is increased, resistance to stress fluctuations is increased, so that the influence of the stress fluctuations on the end face of the backing ring is reduced, and the occurrence of fretting in the backing ring is suppressed.

  Specific examples of increasing the hardness of the end surface of the backing ring include chrome plating on the end surface of the backing ring and coating with a titanium compound, etc., but coating with TiC (titanium carbon) that is particularly excellent in slidability. This is also excellent in terms of preventing fretting. The chromium plating may be performed by electrolysis at a low temperature to form black chromium oxide on the surface of the backing ring. Moreover, as a titanium compound, composites, such as TiN (titanium nitride) and TiCN (titanium carbon nitride), may be sufficient. These high hardness layers can be formed by various methods such as ion plating, CVD, and sputtering in addition to plating. Furthermore, a composite layer such as tetrafluoroethylene and ethylene difluoride may be formed on the high hardness thin layer.

  The thickness of the high hardness layer is preferably 0.3 to 20 μm from the viewpoint of preventing fretting of the end surface of the backing ring. For example, 0.3 to 3 μm is particularly desirable for a TiC layer formed by ion plating or CVD, and 0.5 to 20 μm is desirable for chrome plating. If the thickness of these high hardness layers is less than the lower limit of the desired range, the time until the occurrence of fretting cannot be made sufficiently long. Conversely, if the upper limit is exceeded, other adverse effects such as peeling will occur.

  As another specific example of increasing the hardness of the backing ring end face, or increasing the hardness of the backing ring end face itself can be considered. For example, the surface hardness can be increased by subjecting the backing ring surface to carbonitriding, carburizing, sulfurizing, or bath nitriding. These carbonitriding treatments and the like can form a high hardness layer to a depth of about 200 μm.

  In addition, as another structure for reducing the influence of stress fluctuation in the present invention, for example, the backing ring end face that contacts the end face of the bearing is processed into an edge non-contact shape that does not contact the edge portion of the end face of the bearing. Conceivable. 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, and the portion of the backing ring end surface that contacts the edge portion of the bearing end surface becomes the starting point of fretting. If the contact between the portion and the backing ring is eliminated, the influence of the stress fluctuation on the end surface of the backing ring is reduced, and the occurrence of fretting in the backing ring is suppressed.

  As a specific example of the edge non-contact shape, it can be considered that the end surface of the backing ring is crowned so that the central portion in the thickness direction of the backing ring is raised. That is, chamfers (chamfered portions) are usually formed on the inner peripheral side and the outer peripheral side of the end surface of the inner ring or the like 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 face is rounded so as to escape the edge portion, the above-mentioned edge non-contact shape can be obtained.

  Further, as another specific example of the edge non-contact shape, it is conceivable that the backing ring end face is tapered so as to escape the edge portion of the bearing end face. That is, the central portion in the thickness direction of the backing ring end surface is a flat portion that abuts the bearing end surface, and is slightly closer to the end portion from the central side than the portion facing the bearing end surface edge portion of the backing ring end surface ( That is, the edge non-contact shape described above can be obtained if the portion of the backing ring end surface that is slightly picked up from the portion facing the bearing end surface chamfer portion is inclined so as to move 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 without 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 bearing end surface does not contact the backing ring end surface. Similarly, the end surface of the bearing may be tapered so that the edge portion of the bearing end surface does not come into contact with the backing ring end surface. When the end face of the bearing is tapered, it is desirable to have a smooth bend where the tapered surface begins.

  Furthermore, as another stress fluctuation effect reducing structure in the present invention, a combination of both the stress fluctuation absorbing layer and the edge non-contact shape may be used. That is, the shape of the backing ring end face or the bearing end face is processed into an edge non-contact shape such that the edge portion of the bearing end face does not contact the backing ring end face, and one or both of the backing ring end face and the bearing end face are The stress fluctuation absorbing layer as described above is formed. According to this, 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.

  In addition, as another structure for reducing the effect of stress fluctuation in the present invention, a structure that increases the hardness of the backing ring end face and the edge non-contact shape may be combined. In other words, the shape of the backing ring end face or the bearing end face is processed into an edge non-contact shape so that the edge portion of the end face of the bearing does not contact the backing ring end face, and the hardness of the end face of the backing ring can be increased as described above. For example, the advantages of both the increased end face hardness and the edge non-contact shape are exhibited, and the occurrence of fretting is more reliably suppressed.

  As described above, according to the present invention, since the stress fluctuation effect reducing structure for reducing the influence of the stress fluctuation between the bearing end face and the backing ring is provided, the stress on the contact face between the bearing end face and the backing ring is reduced. Since the influence of fluctuations can be reduced and the occurrence of fretting is suppressed, there is an effect that the frequency of maintenance and inspection can be reduced without causing roughening of the raceway surface of the raceway or deterioration of grease. Therefore, the bearing unit according to the present invention is suitable for an axle bearing.

Hereinafter, embodiments of the present invention will be described 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 railway vehicle, and serves as a rotating shaft. A bearing 2 that rotatably supports the axle 1 is provided. The bearing 2 is a double-row tapered roller bearing of a back surface 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. The inner ring 2c, 2d, the outer ring 2e common to each row of the rolling elements 2a, and the cage 2f provided for each row of the rolling elements 2a, the inner ring in a state of sandwiching the spacer 2b 2c and 2d are fitted on the front end portion of the axle 1. In addition, a grease supply port 2g is formed at an appropriate position in the central portion in the axial direction of the outer ring 2e.

And the cap 3 provided with the flange part 3A which protrudes on the outer peripheral direction is integrally fixed to the front end surface of the axle shaft 1 by the some volt | bolt 4, and faces the bearing 2 side of the flange part 3A. The end surface of one backing ring 5A is in contact with the surface, and the other end surface of the backing ring 5A is in contact with the end surface of one inner ring 2c as a bearing end surface.
On the other hand, a taper portion 1A and a large-diameter portion 1B whose diameter increases at the center portion side are formed closer to the center portion of the axle 1 than a position where the bearing 2 of the axle shaft 1 is fixed, and the other backing ring 5B is formed on the taper portion 1A. The outer ring is fitted and the inner end of the backing ring 5B is in contact with the front end side step portion 1C of the large diameter portion 1B, and the front end surface of the backing ring 5B is the other inner ring as the bearing end surface. 2d is in contact with the end face.

  Further, thin cylindrical guide members 6A and 6B that are gradually reduced in diameter as they move away from the outer ring 2e are fixed to the end face on the cap 3 side and the end face on the large diameter portion 1B side of the outer ring 2e, respectively. The front end of the guide member 6A surrounds the outer peripheral surface of the flange portion 3A with a very small gap, and the front end of the other guide member 6B opens the outer peripheral surface of the backing ring 5B with a very small gap. Besieged.

An oil seal 7A is disposed between the central outer peripheral surface of the backing ring 5A and the central inner peripheral surface of the guide member 6A, and the central outer peripheral surface of the backing ring 5B and the central inner peripheral surface of the guide member 6B An oil seal 7B is disposed between the two. The oil seals 7A and 7B prevent entry of fine powder or the like from the outside to the inside of the bearing 2.
The bearing 2 is attached to the axle 1 after the backing ring 5B, the bearing 2, and the backing ring 5A are fitted in this order from the front end side of the axle 1, and then the cap 3 is attached to the front end surface of the axle 1 and the bolt 4 This is done by tightening. This is an axle bearing unit, and a large radial load is applied to the bearing 2 to support the weight of the vehicle. Therefore, the bearing 2 has a backing that abuts against the bolt 4, the cap 3 and both end faces 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 the present embodiment, the direction along the axis of each of the end surface 5a that contacts the end surface of the inner ring 2c of the backing ring 5A and the end surface 5b that contacts the end surface of the inner ring 2d of the backing ring 5B. A film is formed as a stress fluctuation absorbing layer that absorbs the fluctuation of the stress.
In practice, bearings 2 as shown in FIG. 1 are disposed on both ends of a single axle 1, but the illustration and description thereof are omitted because of the same structure.

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 5a of the inner ring 2c and the backing ring 5A and the stress between the end surface 5b of the inner ring 2d and the backing ring 5B periodically vary in synchronization with the rotation of the axle 1.
However, since the coating for absorbing the stress fluctuation is formed on the end faces 5a and 5b of the backing rings 5A and 5B, the end faces of the inner rings 2c and 2d and the backing rings 5A and 5B are caused by the stress fluctuation. It is possible to prevent fretting from occurring on the end faces 5a, 5b and the like. As a result, it is possible to avoid a large amount of metal wear powder from being mixed in the bearing, so that the raceway surfaces of the inner rings 2c and 2d and the outer ring 2e are not roughened and grease is not deteriorated. In comparison, the frequency of maintenance and inspection is reduced.

  FIG. 2 is a cross-sectional view showing the configuration of the bearing unit in the second embodiment of the present invention, and the same members and parts as those in the configuration shown in FIG. That is, the bearing unit shown in FIG. 2 has substantially the same configuration as that shown in FIG. 1, but the backing rings 5A and 5B are thinner than those shown in FIG. And even if it is a bearing unit of such a structure, a fretting prevention effect can be acquired by forming a stress-fluctuation absorption layer in end surface 5a, 5b of backing ring 5A, 5B.

FIG. 3 is a diagram showing a third embodiment of the present invention, and is an enlarged cross-sectional view of a main part. In addition, the whole structure is the same as that of the said 1st Embodiment, and the same code | symbol is attached | subjected to the member and site | part similar to the said 1st Embodiment. Further, since the configuration on the backing ring 5A side is the same as the configuration of FIG. 3, its illustration is omitted.
That is, in the present embodiment, the high hardness layer 10 having a high hardness is formed on the surface of the end surface 5b of the backing ring 5B, and the high hardness layer 10 is in 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 face of the inner ring 2d 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 in such a configuration, since the resistance of the end surface 5b against the stress fluctuation between the inner ring 2d and the backing ring 5B is improved by forming the high hardness layer 10, fretting occurs on the end surface 5b. It has become difficult. For this reason, 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 cross-sectional view of a main part. The overall configuration is the same as that of the first embodiment, and the same members and parts as those of the first embodiment are denoted by the same reference numerals. Also, since the configuration on the backing ring 5A side is the same as the configuration of FIG. 4, its illustration is omitted.

That is, in this embodiment, the end face 5b of the backing ring 5B is not particularly provided with a stress fluctuation absorbing layer or the like, and the end face 5b is processed into a predetermined shape so that the influence of stress fluctuation can be reduced. is there.
That is, in this embodiment, the end surface 5b of the backing ring 5B is subjected to crowning so that the end surface 5b is rounded so that the central portion in the thickness direction is higher than the end portion. Thereby, the edge part 13 formed between the chamfer part 11 and the plane part 12 on the end face of the inner ring 2d is prevented from contacting the end face 5b of the backing ring 5B.

  With such a configuration, 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. Therefore, even if the stress changes, the edge portion 13 is fretting. Since it can be avoided that it becomes the starting point of occurrence, the influence of stress fluctuation on the end face 5b is reduced, and the occurrence of fretting on the end face 5b is suppressed. For this reason, 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 non-contact between the edge 13 and the end surface 5b can be secured, and the reference radius and the like are arbitrary. Moreover, you may give processing, such as a barrel and shot peening, to the site | part which carried out the crowning process. Furthermore, by applying crowning to the end face side of the inner ring 2d, the same effects as in the present embodiment can be obtained even if the edge portion 13 does not contact the end face 5b.

FIG. 5 is a view showing a fifth embodiment of the present invention, and is an enlarged cross-sectional view of a main part. In addition, the whole structure is the same as that of the said 1st Embodiment, and the same code | symbol is attached | subjected to the member and site | part similar to the said 1st Embodiment. Further, since the configuration on the backing ring 5A side is the same as the configuration of FIG. 5, its illustration is omitted.
That is, in the present embodiment, similarly to the fourth embodiment, the influence of stress fluctuation can be reduced by processing the end surface 5b into a predetermined shape.

  That is, in this embodiment, a tapered surface 14 is formed at a portion of the end surface 5b opposite to the chamfer portion 11 on the end surface of the inner ring 2d so as to move away from the inner ring 2d as the end is approached. However, the position where the taper surface 14 begins to be inclined is slightly closer to the center than the edge portion 13 so that the edge portion 13 does not contact the end surface 5b of the backing ring 5B.

Even in such a configuration, since the edge portion 13 does not contact the end surface 5b, the same effects as those of the fourth embodiment can be obtained.
In particular, in the present embodiment, it is only necessary to form the tapered surface 14 on the end surface 5b, which is advantageous in terms of cost compared to the above embodiments, particularly the fourth embodiment.
In addition, the formation angle of the taper surface 14 is not particularly limited. In short, it is only necessary to ensure non-contact between the edge 13 and the end surface 5b. Moreover, even if the edge part 13 does not contact the end surface 5b by making the inner ring 2d side into a tapered shape, the same effect as that of the present embodiment can be obtained.

FIG. 6 is a view showing a sixth embodiment of the present invention, and is an enlarged cross-sectional view of the main part. In addition, the whole structure is the same as that of the said 1st Embodiment, and the same code | symbol is attached | subjected to the member and site | part similar to the said 1st Embodiment. Further, since the configuration on the backing ring 5A side is the same as the configuration of FIG. 6, its illustration is omitted.
That is, in the present embodiment, the end surface 5b of the backing ring 5B has the same shape as that of the fourth embodiment, and the stress fluctuation absorbing layer similar to that of the first embodiment is formed on the end surface 5b. 20 is formed.

With such a configuration, since the effects of both the first embodiment and the fourth embodiment are exhibited, the influence of stress fluctuation is extremely small, and thus the effect of suppressing the occurrence of fretting is remarkable. Thus, there is an advantage that 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 cross-sectional view of a main part. The overall configuration is the same as that of the first embodiment, and the same members and parts as those of the first embodiment are denoted by the same reference numerals. Further, since the configuration on the backing ring 5A side is the same as the configuration of FIG. 7, its illustration is omitted.

That is, in the present embodiment, the end surface 5b of the backing ring 5B has the same shape as that of the fifth embodiment, and the stress fluctuation absorbing layer similar to that of the first embodiment is formed on the end surface 5b. 20 is formed, and if it is such a structure, since the effect | action of both the said 1st Embodiment and 5th Embodiment is exhibited, it is the same as that of the said 6th Embodiment. The effect can be obtained, and the cost is more advantageous than 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 of a back combination has been described, but the scope of application of the present invention is limited to this. Instead, other bearings such as a double row cylindrical roller bearing 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 faces 5a and 5b of the backing rings 5A and 5B has been described. , 5b may be formed on the end faces of the inner rings 2c, 2d, or may be formed on both. That is, in the sixth and seventh embodiments, the end faces 5a and 5b of the backing rings 5A and 5B or the end faces of the inner rings 2c and 2d are made the crowning shape or the tapered shape as described above, and the backing ring 5A. 5B, a stress fluctuation absorbing layer may be formed on one or both of the end faces 5a, 5b of the 5B and the end faces of the inner rings 2c, 2d.
Further, in the sixth and seventh embodiments, the stress fluctuation absorbing layer 20 is formed on the end faces 5a and 5b. Instead, the high hardness layer 10 as in the third embodiment is used instead. You may make it form.

Examples of the present invention will be described below in detail with the results of experiments conducted by the present inventors.
The following Experimental Examples 1 to 3 use a bearing unit having the same configuration as that in FIG. 1 in the above embodiment, and rotate the axle 1 by driving the motor while a radial load is applied to the bearing 2. Forcibly causing bending to the axle 1 and every end of the predetermined time (50 hours, 100 hours, 200 hours, 300 hours, 400 hours, 500 hours, 1000 hours) and the end faces of the inner rings 2c, 2d and the backing ring 5A , 5B to observe the end faces 5a and 5b to evaluate the occurrence of fretting, and after 1000 hours, the surface profile of the end faces of the inner rings 2c and 2d is measured with a roughness measuring instrument (manufactured by Tokyo Seimitsu Co., Ltd.). Was measured. As a comparative example, the same experiment was performed for the bearing 2 in which the stress fluctuation absorbing layer is not formed on the end faces 5a and 5b. Experimental conditions are
Radial load: 5000kgf
Axial load: 1500kgf
Rotation speed: 2000rpm
Load load interval: 5 seconds on and 25 seconds off. A part of the surface observation result is shown in Table 1, a part of the wear depth measurement result is shown in Table 2, and the relationship between the thickness of the stress fluctuation absorbing layer and the durability time of the bearing 2 is shown in FIG. It showed in.

[Experimental Example 1]
The material of the backing rings 5A and 5B was S45C, the dimensions of each part were an inner diameter of 120 mm, an outer diameter of 170 mm, and a length of 70 mm, and the contact area with the end faces of the inner rings 2c and 2d was about 2300 mm ² .
A silver film as a stress fluctuation absorbing layer was formed on the end faces 5a and 5b of the backing rings 5A and 5B by plating so as to have a thickness of 2 to 50 μm. Specifically, the portions other than the end faces 5a and 5b are coated with a chloroprene-based masking agent, subjected to alkali degreasing and acid cleaning, and then subjected to copper strike plating of 1 μm, and the surfaces of the end faces 5a and 5b are electroplated. Then, a silver coating was applied. In addition, the film thickness of a silver film formed the silver film from which a film thickness differs by controlling the electrolysis current and electrolysis time per unit area.
[Experimental example 2]
On the end faces 5a and 5b of the backing rings 5A and 5B having the same material and dimensions as those of Experimental Example 1, a commercially available urethane-based elastomer was coated in a plurality of thicknesses.

[Experimental Example 3]
The end faces 5a and 5b of the backing rings 5A and 5B having the same material and dimensions as those of Experimental Example 1 are preliminarily subjected to a chemical conversion treatment of manganese phosphate, and a coating treatment of a mixture of tetrafluoroethylene and a thermosetting resin is performed thereon. gave. The chemical conversion treatment is a manganese phosphate salt treatment having a membrane weight of about 5.0 g / m ² (film thickness: about 4 μm to 5 μm). The upper resin coating layer is a coating layer having a ratio of polyamideimide 4 to ethylene tetrafluoride 1, and the coating method is a mixture of tetrafluoroethylene and polyamideimide in the above ratio. A method in which a dispersion liquid is formed with an organic solvent having the same weight ratio, a coating layer is formed with a spray gun using air, and heat treatment is performed at 200 degrees for 1 hour to coat the end faces 5a and 5b. It is. A plurality of types of coating thicknesses were formed.

In addition, the meaning of each symbol in this Table 1 is as follows.
○: No fretting occurred △: Partial fretting occurred ×: Full fretting occurred

As is clear from Tables 1 and 2, it was confirmed that any of Experimental Examples 1 to 3 has an effect of preventing fretting as compared with the comparative example.
In the configuration of Experimental Example 1, the fretting prevention effect is obtained because the stress fluctuation acts on a plated layer made of silver or the like having a low hardness, and the plated layer is worn, and the inner ring 2c, 2d end face or the backing rings 5A, 5B. This is because fretting does not occur on the end faces 5a and 5b.

  In the configuration of Experimental Example 2, the fretting prevention effect can be obtained when the elastic force of the intervening substance is small and there is a yield point, on the end faces 5a and 5b of the inner rings 2c and 2d and the end faces 5a and 5b of the backing rings 5A and 5B. This is because the working stress is absorbed. In addition, since there is no gap between the end faces due to the plastic deformation of the intervening substance, it is considered that the fretting prevention effect is improved as compared with the case of Experimental Example 1 as a result of further mitigating the impact.

  In the configuration of Experimental Example 3, the fretting prevention effect is obtained in the same manner as in Experimental Example 2. However, since the intervening substance has self-lubricating properties, a particularly remarkable fretting prevention effect is obtained. Is obtained. In other words, the structure of Experimental Example 3 in which the metal surface is subjected to chemical conversion treatment and the matrix resin layer containing solid lubricant particles is formed thereon prevents fretting in Experimental Examples 1 to 3 above. Most preferred.

  And since the durability time until the amount of wear due to fretting of the untreated backing ring in the comparative example reaches a temporary limit value of 150 μm is 450 hours, the film of the stress fluctuation absorbing layer that can clear the durability time If the thickness is effective for preventing fretting, the lower limit value of the film thickness in the structure of Experimental Example 1 is 50 μm, the lower limit value of the film thickness in the structure of Experimental Example 2 is 30 μm, and the film having the structure of Experimental Example 3 is used. It can be said that the thickness lower limit is preferably 5 μm.

On the other hand, in any structure, if the stress fluctuation absorption layer exceeds 100 μm, cracks and peeling are likely to occur in the stress fluctuation absorption layer, and it has been confirmed that it adversely affects fretting prevention. Yes. Therefore, the upper limit value of the thickness of the stress fluctuation absorbing layer is preferably 100 μm.
In particular, in the structure of Experimental Example 3 in which the effect of preventing fretting is remarkable, the thickness of the stress fluctuation absorbing layer considered to be effective for the above-described reason is 5 μm to 100 μm, but it is further preferable to set the thickness within the range of 20 μm to 100 μm. preferable.

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

  In addition, when the stress fluctuation absorbing layer is formed by coating the end faces 5a and 5b as in Experimental Example 2, the material forming the stress fluctuation absorbing layer is not limited to the elastomer, but is a viscoelastic body. If present, it is confirmed that the same effect as in Experimental Example 2 can be obtained even if a thermoplastic, thermosetting, or a thermoplastic elastomer, which is a polymer of rubber and resin, or a silicon compounded resin is used. . Further, such a substance is formed into a sheet shape, and this 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 in Experimental Example 2 can be obtained. In short, if a layer made of a material having a smaller elastic modulus than that of both the material of the inner rings 2c and 2d and the material of the backing rings 5A and 5B is interposed between these end faces, the same as in Experimental Example 2 The effect is obtained.

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

Next, another experimental example conducted by the present inventors will be described. Note that the experimental conditions and the experimental method are not particularly limited, and are the same as in Experimental Examples 1 to 3 described above.
[Experimental Example 4]
A blend of 70 wt% of tetrafluoroethylene and 30 wt% of Econol (trade name) manufactured by Sumitomo Chemical Co., Ltd., and the sintered material is made into a sheet having a thickness of 0.3 mm, and this sheet is used as the end face 5a of the backing rings 5A and 5B, Adhered to 5b. As the adhesive, a two-part curable epoxy manufactured by Three Bond Co., Ltd. was used, and the adhesive was applied to the entire surface of the sheet and cured at 80 ° C.
The end faces 5a and 5b of the backing rings 5A and 5B were preliminarily coated with a 5 μm manganese phosphate coating, and the sheet was activated with a sodium naphthalene solution.

[Experimental Example 5]
The material obtained by blending 85 wt% of tetrafluoroethylene and 15 wt% of DuPont polyimide and making the sintered material a 0.6 mm thick sheet is used as the backing ring 5A, 5B side of each inner ring 2c, 2d of the bearing 2 Glued to the end face of. As the adhesive, a two-component curable epoxy manufactured by Three Bond Co., Ltd. was used, 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 observation results of the surfaces in Experimental Examples 4 and 5. The meaning of the symbols in Table 3 is the same as in Table 1. The elapsed time was 500 to 3500 hours, unlike the experimental examples 1 to 3.

  From Experimental Examples 4 and 5, it was found that the fretting-preventing effect becomes extremely remarkable when the stress fluctuation absorbing layer is made by mixing a tetrafluoroethylene sheet material with an abrasion resistant material. It was also found that the stress fluctuation absorbing layer can provide the same fretting prevention effect on the end faces 5a, 5b of the backing rings 5A, 5B and the end faces on the inner rings 2a, 2d side. Furthermore, it was confirmed that the adhesion with the backing rings 5A and 5B and the inner rings 2a and 2d is improved by subjecting the sheet surface to a chemical or physical activation treatment. In particular, unlike a coating material, a sheet material does not generate cracks or cracks due to stress fluctuations even when the sheet thickness increases, and has excellent durability against fretting.

Next, another experimental example conducted by the present inventors will be described. Note that the experimental conditions and the experimental method are not particularly limited, and are the same as in Experimental Examples 1 to 3 described above.
[Experimental Example 6]
A chromium layer was formed as a high hardness layer 10 on the end faces 5a and 5b of the backing rings 5A and 5B by plating, and the surface hardness of the end faces 5a and 5b was set to 1100 Hv (see FIG. 3).

[Experimental Example 7]
A TiC film having a thickness of 2 μm was formed by ion plating as the high hardness layer 10 on the end faces 5a and 5b of the backing rings 5A and 5B, and the surface hardness of the end faces 5a and 5b was set to 2300 Hv (see FIG. 3).
[Experimental Example 8]
The backing rings 5A and 5B are formed of the same carbon steel as the bearing material, and the end surfaces 5a and 5b are subjected to carbonitriding to form the high hardness layer 10, and the hardness of the end surfaces 5a and 5b is set to the inner ring 2a. The hardness of the end face of 2d is equal to or higher than the hardness (see FIG. 3).
Table 4 shows a part of the observation results of the surfaces in Experimental Examples 6 to 8. The meaning of the symbols in Table 4 is the same as in Table 1.

From these experimental examples 6-8, in order to reduce the influence of stress fluctuation, it is possible to obtain a sufficient fretting suppression effect by forming the high hardness layer 10 on the end faces 5a, 5b of the backing rings 5A, 5B. understood.
Next, another experimental example conducted by the present inventors will be described. Note that the experimental conditions and the experimental method are not particularly limited, and are the same as in Experimental Examples 1 to 3 described above.
[Experimental Example 9]
By applying crowning to the end faces 5a and 5b of the backing rings 5A and 5B, the edge portions 13 of the end faces of the inner rings 2a and 2b were prevented from contacting the end faces 5a and 5b (see FIG. 4).

[Experimental Example 10]
By forming tapered surfaces 14 on the end surfaces 5a and 5b of the backing rings 5A and 5B, the edge portions 13 on the end surfaces of the inner rings 2a and 2b are prevented from contacting the end surfaces 5a and 5b (see FIG. 5).
Table 5 shows some of the observation results of the surfaces in Experimental Examples 9 and 10. The meanings of symbols in Table 5 are the same as those in Table 1.

From these experimental examples 9 and 10, if the end faces 5a and 5b of the backing rings 5A and 5B have a crowning shape or a tapered shape so that the edge portion 13 does not come into contact with the end faces 5a and 5b, sufficient fretting can be achieved. It has been found that an anti-ting effect can be obtained.
Next, another experimental example conducted by the present inventors will be described. Note that the experimental conditions and the experimental method are not particularly limited, and are the same as in Experimental Examples 1 to 3 described above.
[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).
[Experiment 14]
Experimental Example 8 and Experimental Example 10 were combined (see FIG. 7).
Table 6 shows a part of the surface observation results in these experimental examples 11-14. The meanings of symbols in Table 6 are the same as those in Table 1.

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

It is sectional drawing which shows the structure of the 1st Embodiment of this invention. It is sectional drawing which shows the structure of the 2nd Embodiment of this invention. It is sectional drawing which shows the structure of the 3rd Embodiment of this invention. It is sectional drawing which shows the structure of the 4th Embodiment of this invention. It is sectional drawing which shows the structure of the 5th Embodiment of this invention. It is sectional drawing which shows the structure of the 6th Embodiment of this invention. It is sectional drawing which shows the structure of the 7th Embodiment of this invention. It is a graph which shows the result of the experiment which the present inventors conducted.

Explanation of symbols

1 axle (rotating shaft)
2 Bearing 2a Rolling element 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 absorbing layer

Claims (3)

  In a bearing unit comprising: a bearing that supports a rotating shaft; and a backing ring that abuts against the end surface of the bearing and fixes the bearing to the rotating shaft, stress fluctuation between the end surface of the bearing and the backing ring A bearing unit characterized in that a stress fluctuation influence reducing structure for reducing the influence of the bearing is provided, wherein the stress fluctuation influence reducing structure is a structure in which the hardness of the end face of the backing ring in contact with the end face of the bearing is increased.   2. The bearing unit according to claim 1, wherein the stress fluctuation effect reducing structure is a structure in which the hardness is increased by subjecting the end surface of the backing ring to carbonitriding, carburizing, sulfurizing, or bath nitriding.   In a bearing unit comprising: a bearing that supports a rotating shaft; and a backing ring that abuts against the end surface of the bearing and fixes the bearing to the rotating shaft, stress fluctuation between the end surface of the bearing and the backing ring The stress fluctuation influence reduction structure is provided to reduce the influence of the edge, and the stress fluctuation influence reduction structure is an edge non-contact shape that does not contact the edge portion of the end face of the bearing with the backing ring end face contacting the end face of the bearing. Bearing unit characterized by having a structure machined into

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