JP2014228063A - Sliding member, retainer, and rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sliding member having a film of which abrasion quantity is small even in a mixed lubrication condition on a sliding surface and excellent in abrasion resistance, and a rolling bearing having the sliding member as a retainer and exhibiting the long service life.SOLUTION: In a deep groove ball bearing 1, an inner ring 2 having an inner ring rolling surface 2a on an outer peripheral surface and an outer ring 3 having an outer ring rolling surface 3a on an inner peripheral surface are concentrically disposed, and a plurality of rolling elements 4 are disposed between the inner ring rolling surface 2a and the outer ring rolling surface 3a. A retainer 5 is provided for retaining the rolling elements 4, and a tin-zinc alloy film is formed at least in a surface area of a surface of the retainer 5 slidably abutted to the rolling elements 4, and a thickness of the film is within a range of 10-25 μm, and a weight ratio of zinc to the total of tin and zinc is within a range of 20% or more and 80% or less in the film.

Description

  The present invention relates to a sliding member having a sliding surface formed with a coating of an alloy of tin and zinc, and more particularly to a cage for a rolling bearing. Moreover, it is related with the rolling bearing provided with this.

  In recent years, the conditions under which sliding members are used in various machines have become increasingly severe, such as an increase in load surface pressure due to downsizing of various machines and an increase in sliding speed due to an increase in speed. Therefore, various surface treatments capable of imparting wear resistance to sliding members of various machines have been studied. For example, Ni in which fine particle spraying treatment is applied to the sliding portion of the sliding member. A method for improving wear resistance by forming a -P plating film has been reported (see Patent Document 1).

  In addition, a rolling device has been reported in which a metal film is formed as a thin film by shot blasting an alloy powder of zinc and tin on a sliding surface (see Patent Document 2). By forming a metal film by a method using shot blasting, it is said that reliability is superior to a method by electroplating.

JP-A-8-39432 Republished patent WO2007 / 139197

  However, the method disclosed in Patent Document 1 may have an effect under a low surface pressure condition, but there is a concern that the wear may increase when exposed to a higher surface pressure condition. . As such a case, for example, there is a phenomenon of delayed advance occurring during the rotation of the bearing, which is seen in a cage of a rolling bearing. Due to this phenomenon, the contact between the pocket surface of the cage and the rolling element may become larger than expected. The higher the rotation of the bearing, the greater the contact force. Also, in the case of grease lubrication, it is difficult for grease to enter between the pocket surface of the cage and the rolling elements, so that sufficient lubrication may not be obtained, resulting in a mixed lubrication state, and even higher wear resistance. The demanding situation will be severe.

  In addition, even when using an alloy coating of zinc and tin by shot blasting disclosed in Patent Document 2, sufficient wear resistance is ensured depending on the composition distribution and film thickness of zinc and tin in the coating. There are cases where it is not possible.

  The present invention has been made to cope with such problems, and a sliding member having excellent wear resistance, in which a coating with a small amount of wear is formed on the sliding surface even in a mixed lubrication state, and An object of the present invention is to provide a rolling bearing having a long life provided with a sliding member as a cage.

  The sliding member of the present invention is a sliding member in which a tin-zinc alloy coating composed of tin and zinc is formed on a sliding surface, and the thickness of the coating is 10 to 25 μm. The weight ratio of the zinc to the whole of the tin and the zinc is 20% or more and 80% or less. In particular, the weight ratio is more than 35% and not more than 80%.

  The coating film is a plating film formed by electroplating.

  The cage of the present invention is a cage for a rolling bearing that holds a plurality of rolling elements, and the cage is a sliding member of the present invention, and at least a surface that is in sliding contact with the rolling elements of the cage. The above tin-zinc alloy film is formed on the surface.

  The rolling bearing of the present invention is a rolling bearing comprising a plurality of rolling elements and a cage that holds the rolling elements, and the cage is the cage of the present invention. .

  In the sliding member of the present invention, a tin-zinc alloy coating composed of tin and zinc is formed on the sliding surface, and the thickness of this coating is 10 to 25 μm. In this coating, the weight of zinc relative to the entire tin and zinc Since the ratio is 20% or more and 80% or less, it is possible to reduce the amount of wear even when the sliding portion is in a harsh state such as a mixed lubrication state. Is unlikely to occur. Therefore, the sliding member can contribute to extending the life of various machines provided with the sliding member.

  Since the rolling bearing of the present invention includes this sliding member as a cage, wear on the cage sliding surface, in particular, the cage pocket surface sliding with the rolling element can be prevented over a long period of time, and seizure can also be prevented.

It is sectional drawing of a deep groove ball bearing. It is a figure which shows a sliding test machine. It is a figure showing the result of the sliding test which shows the influence with respect to the specific wear amount of the composition in a tin-zinc alloy film.

  Examples of the sliding member of the present invention include sliding members used in various machines such as aircraft, railway vehicles, construction machines, automobile electrical accessories, and automobile hubs, and in particular, rolling bearings that hold a plurality of rolling elements. For example.

  The sliding member of the present invention has a sliding surface including a surface that is in sliding contact with other members in the machine that it constitutes. A tin-zinc alloy coating is formed on part or all of the sliding surface of the sliding member of the present invention. The tin-zinc alloy coating is not formed as an underlayer of another coating, but is formed on the outermost surface of the sliding member.

  In the case of a rolling bearing retainer that holds a rolling element, the sliding surface on which the coating is formed includes a surface in which the cage is in sliding contact with the rolling element, and a surface in which the cage is in sliding contact with other bearing components. Can be mentioned. Other bearing constituent members include an inner ring and an outer ring. The coating is preferably formed on the surface where the cage is in sliding contact with the rolling element and the surface where the cage is in sliding contact with other bearing components. Furthermore, it is preferable to form the coating film on the entire outermost surface of the cage because it is easy to manufacture.

  In the tin-zinc alloy coating in the present invention, the weight ratio of tin and zinc is (tin: zinc) = (20:80) to (80:20). That is, in the tin-zinc alloy coating according to the present invention, the weight ratio of zinc to the entire tin and zinc is 20% or more and 80% or less. In addition, the weight ratio of tin to the entire tin and zinc is also 20% or more and 80% or less. In sliding members that are subjected to harsh usage conditions such as mixed lubrication conditions, if the weight ratio of zinc is less than 20%, the amount of tin will be relatively large, and it will be close to a single tin coating, and will be used for a long time. There is a risk of causing delamination during operation. On the other hand, if the weight ratio of zinc exceeds 80%, the surface free energy of the entire alloy film tends to increase, and the wear amount may increase particularly in the early stage of sliding. Further, it is more preferable that the weight ratio of zinc exceeds 35% and is 80% or less, and further preferably 40% or more and 80% or less.

In a metal film, generally, the smaller the surface free energy, the less the adsorption and the wear suppression effect can be expected. When the surface free energy of tin is about 500 mJ / m ² and the surface free energy of zinc is about 800 mJ / m ² , when using a tin-zinc alloy coating, the wear resistance is improved from the above viewpoint alone. For this reason, it may be necessary to simply increase the amount of tin. However, in the tin-zinc alloy coating formed on the sliding member used under the above severe conditions, due to concerns such as in-layer peeling and insufficient adhesion to the substrate of the coating, this is as expected. In other words, the composition determination is not easy. As shown in an example (FIG. 3) to be described later, the present inventor has made various studies on the tin-zinc alloy coating formed on the sliding member, in particular, the weight ratio of tin and zinc within the specific range described above. It has been found that the specific wear amount under severe conditions can be significantly reduced. The present invention is based on such knowledge.

  As a method for forming a tin-zinc alloy film on the surface of the sliding member, physical vapor deposition (PVD) such as electroplating, electroless plating, vacuum deposition, ion plating, sputtering, cold spray method, spraying method, chemical vapor deposition (CVD) ) And other known film forming methods can be employed. Since the surface roughness and shape of the coating can be reduced, the film thickness can be easily adjusted, and an alloy coating can be easily formed at low cost, an electroplating coating formed by electroplating is preferable. Since it is excellent in productivity especially, forming by barrel electroplating is preferable.

  In general, a tin-zinc alloy plating film is used for base treatment or the like as corrosion-resistant plating that combines the sacrificial corrosion resistance of zinc and the excellent corrosion resistance of tin, which has a low ionization tendency with respect to iron. The present invention is characterized in that the tin-zinc alloy plating film is formed on the outermost surface of the cage and the surface that is actually in sliding contact with the rolling elements and other members. The tin-zinc alloy plating film in the present invention is preferably formed directly on the surface of the base material without forming another base film by plating or the like.

  As a method of forming a tin-zinc alloy plating film having a predetermined weight ratio by electroplating, a silicofluoride bath, a borofluoride bath, a sulfonate bath, a phenol sulfonic acid bath, an alkanol sulfonic acid bath, an alkane sulfonic acid bath It is possible to adopt a known method such as immersing the sliding member base material in the process.

  The film thickness of the tin-zinc alloy film formed on the sliding member surface is 10 to 25 μm. If it is less than 10 μm, there is a risk that the substrate is exposed due to initial wear. Even if the thickness exceeds 25 μm, the function is exhibited, but no further improvement in the function is recognized. The film thickness is preferably 10 to 20 μm, more preferably 15 to 20 μm, and still more preferably 18 to 20 μm.

  In the sliding member of the present invention, examples of the material of the sliding member main body include iron-based metal materials. As the ferrous metal material, bearing steel, carburized steel, carbon steel for machine structure, cold rolled steel, or hot rolled steel can be used. For example, in the cage for rolling bearings of the present invention, use of cold rolled steel SPCC as the material of the cage body can be mentioned.

  The rolling bearing of the present invention is a rolling bearing including a plurality of rolling elements and the above-described cage that holds the rolling elements. As the rolling bearing of the present invention, a ball bearing whose rolling element is a ball is mainly mentioned. Examples of this ball bearing include radial ball bearings such as deep groove ball bearings and angular ball bearings, and thrust ball bearings.

  An example of the rolling bearing of the present invention is shown in FIG. FIG. 1 is a cross-sectional view of a deep groove ball bearing in which a grease composition is enclosed. In the deep groove ball bearing 1, an inner ring 2 having an inner ring rolling surface 2a on the outer peripheral surface and an outer ring 3 having an outer ring rolling surface 3a on the inner peripheral surface are arranged concentrically, and the inner ring rolling surface 2a and the outer ring rolling surface 3a. A plurality of rolling elements 4 are arranged between the two. Sealers 6 that are fixed to the cage 5, the outer ring 3, and the like that hold the plurality of rolling elements 4 are provided in the axially opposite end openings 8a, 8b of the inner ring 2 and the outer ring 3, respectively. Grease 7 is sealed at least around the rolling element 4. A tin-zinc alloy coating is formed on the surface of the cage 5 on the surface where the cage 5 is in sliding contact with the rolling element 4 and on the surface where the cage 5 is in sliding contact with other bearing constituent members. In the coating film, the weight ratio of zinc to the whole of tin and zinc is 20% or more and 80% or less.

  As the grease, any grease used for rolling bearings can be used. The sliding surface is protected by the tin-zinc alloy coating even when the cage is in a mixed lubrication state because it is difficult for grease to enter between the surface (pocket surface) in sliding contact with the rolling element and the rolling element. And prevent wear and seizure. In addition, even when this tin-zinc alloy coating contains a sulfur-based additive such as zinc dialkyldithiophosphate in the grease, it is difficult for the alloy coating components to elute into the grease.

Example 1 to Example 3, Comparative Example 1 to Comparative Example 6
In order to compare the wear resistance of the coating, the coating shown in Table 1 was formed on a SPCC 30 mm × 30 mm flat plate to prepare a plate-like test piece, and the following sliding test was performed on this to perform the specific wear of the coating. The amount was measured. The results are shown in Table 1. FIG. 3 shows the relationship between the tin content and the specific wear amount in the tin-zinc alloy coating.

<Sliding test>
The sliding tester (Sabang type friction and wear tester) shown in FIG. 2 was used. 2A shows a front view, and FIG. 2B shows a side view. A ring-shaped mating member 9 is attached to the rotating shaft 10, and the plate-shaped test piece 12 is fixed to the air slider 13 of the arm portion 11. The ring-shaped mating member 9 rotates and contacts the plate-shaped test piece 12 while applying a predetermined load 14 from above, and the lubricating oil is supplied to the outer peripheral surface of the ring-shaped mating member 9 from the felt pad 16 impregnated with the lubricating oil. Is done. The frictional force generated when the ring-shaped mating member 9 is rotated is detected by the load cell 15. The ring-shaped mating member 9 is a SUJ2 ring having an outer diameter of 40 mm × width of 10 mm (subcurvature R60 mm) subjected to quenching and tempering treatment. is there. The load is 4.9 N (the surface pressure at the contact between the plate-shaped test piece 12 and the ring-shaped mating member 9 is 224 MPa), the sliding speed is 1 m / s, and the sliding time is 5 minutes. The lubrication between the plate-shaped test piece 12 and the ring-shaped mating member 9 is a mixed lubrication state.

The specific wear amount is a value obtained by dividing the wear volume by the sliding distance and the load, and its unit is mm ³ / N · m. The wear volume was calculated from the short diameter of the formed wear scar and the shape of the ring-shaped mating material (outer diameter 40 mm and sub-curvature R60 mm).

  As is clear from the results shown in Table 1, the tin coating of Comparative Example 1, the zinc coating of Comparative Example 4, and the nickel coating of Comparative Example 5 resulted in a large amount of specific wear. In the tin-zinc alloy coatings of Examples 1 to 3, the weight ratio of tin and zinc is within a predetermined range, and the film thickness is within a predetermined range. It was found to be excellent in abrasion. The tin-zinc alloy coatings of Comparative Example 2 and Comparative Example 3 resulted in a large amount of specific wear because the weight ratio of one of tin and zinc was considerably large. In the tin-zinc alloy coating of Comparative Example 6, the weight ratio of tin and zinc was the same as in Example 2, but since the film thickness was thin, the substrate was exposed.

  As shown in FIG. 3, in the tin-zinc alloy coating, when the tin content exceeds 80% (zinc is less than 20%) and when the tin content is less than 20% (zinc exceeds 80%). ), It was found that the specific wear amount was remarkably increased as compared with the case of other ranges. In particular, when the tin content exceeded 80% (zinc was less than 20%), the specific wear amount suddenly increased.

  The sliding member of the present invention has a coating on the sliding surface that can reduce the amount of wear even under severe usage conditions such as a mixed lubrication state and can prevent the substrate from being exposed due to wear. The machine provided with the sliding member is preferably used as a machine having a long life.

DESCRIPTION OF SYMBOLS 1 Deep groove ball bearing 2 Inner ring 3 Outer ring 4 Rolling body 5 Cage 6 Seal member 7 Grease composition 8a, 8b Opening 9 Ring-shaped mating member 10 Rotating shaft 11 Arm 12 Plate-shaped test piece 13 Air slider 14 Load 15 Load cell 16 Felt pad

Claims (5)

  A sliding member in which a tin-zinc alloy coating composed of tin and zinc is formed on a sliding surface, wherein the coating has a thickness of 10 to 25 μm, and in the coating, the tin and the zinc as a whole A sliding member, wherein a weight ratio of zinc is 20% or more and 80% or less.   2. The sliding member according to claim 1, wherein in the coating, the weight ratio of the zinc to the tin and the entire zinc exceeds 35% and is 80% or less.   The sliding member according to claim 1 or 2, wherein the coating is a plating coating formed by electroplating. A cage for a rolling bearing that holds a plurality of rolling elements,
The cage is a sliding member according to claim 1, claim 2, or claim 3, wherein the tin-zinc alloy coating is formed on at least a surface of the cage that is in sliding contact with the rolling element. And cage.   A rolling bearing comprising a plurality of rolling elements and a cage for holding the rolling elements, wherein the cage is the cage according to claim 4.

Images