JP2006242261A - Rolling bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of surface originating separation leading to a very short life resulting from metal contact of poor lubrication. <P>SOLUTION: This rolling bearing comprises a plurality of rolling elements laid between the raceway surfaces of an inner ring and an outer ring and rotatably held by a cage. A phosphoric acid metal salt coating is formed on at least either the raceway surface or the rolling element. The total thickness of the coating on the raceway surface or the rolling element is 10 nm or greater. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rolling bearing used for, for example, a shaft support portion of an automobile transmission.

  For example, in a rolling bearing used for a shaft support part of an automobile transmission, as a means for preventing damage caused by poor lubrication such as peeling damage, the surface of the rolling element or the raceway surface of the inner and outer rings is made into a random minute rough surface. There is one formed so as to keep the roughness of the minute rough surface within a certain range (for example, see Patent Documents 1 and 2). However, since the sound deteriorates, it is difficult to adopt means as disclosed in Patent Documents 1 and 2 for the ball bearing. In addition, a dedicated processing facility is required for forming the dimples, which increases the cost.

On the other hand, by forming a compound reaction film layer with a thickness of 0.05 to 0.5 μm under the surface of the rolling element or under the raceway surface of the inner and outer rings, the load resistance and seizure resistance can be sufficiently improved with low wear. There is a rolling bearing (for example, refer to Patent Document 3). However, the effect of peeling life due to poor lubrication such as peeling damage is not clearly disclosed.
Japanese Patent Publication No. 5-87688 No. 6-20900 Japanese Patent No. 2969700

  By the way, in recent years, low-viscosity oil tends to be used for automobile transmissions for the purpose of AT / CVT missions and fuel efficiency reductions, and the use environment has been reduced due to the miniaturization and high output of missions. There is a tendency for high loads and high temperatures.

  For this reason, the bearing has changed to a harsh lubricating environment, and surface-origin separation with a very short life due to the occurrence of metal contact due to poor lubrication is becoming more likely to occur on the raceway surface of the inner and outer rings. is the current situation.

  Therefore, the present invention has been proposed in view of the above-mentioned problems, and its object is to prevent the occurrence of surface-origin separation in a very short life due to the occurrence of metal contact due to poor lubrication. It is to provide a rolling bearing that can be used.

  As a technical means for achieving the above-mentioned object, the present invention provides a rolling bearing in which a plurality of rolling elements rotatably held by a cage are interposed between both raceway surfaces of an inner member and an outer member. The metal phosphate film is formed on at least one of the raceway surface and the rolling element, and the total film thickness of the raceway surface and the rolling element is 10 nm or more.

  In the present invention, the oil film forming ability of the bearing raceway surface in a lean lubrication environment is obtained by forming a highly lipophilic metal phosphate salt film on the raceway surface of the inner and outer members or at least one bearing metal surface of the rolling element. Since the rate of occurrence of metal contact can be increased and the occurrence of metal contact due to poor lubrication can be prevented, it is possible to prevent occurrence of surface-origin separation with a very short life. Further, the total film thickness of the raceway surface and the rolling element needs to be 10 nm or more. When the total film thickness is smaller than 10 nm, the oil film forming ability of the bearing raceway surface in a lean lubrication environment is enhanced. This makes it difficult to achieve the desired effect.

  The aforementioned metal phosphate salt film can be formed by immersing the inner and outer members or rolling elements in a phosphate triester solution containing tricresyl phosphate. The phosphate triester solution containing tricresyl phosphate means that tricresyl phosphate is used as a representative example of the phosphate triester solution. Further, in the formation of the metal phosphate salt film, it is difficult to form a metal phosphate salt film having a thickness larger than 70 nm in consideration of the dimensional change of the bearing and the number of processing steps. The thickness of the coating is desirably 70 nm or less.

  As is well known, a rolling bearing is a mechanical element that supports a shaft that rotates or swings by a rolling motion of a rolling element (ball or roller). Usually, the rolling element is movably interposed between the raceway surface of the inner ring and the raceway surface of the outer ring, but the type having no inner ring, such as the inner circumference of a gear, in which the outer peripheral surface of the shaft is directly the raceway surface. There is also a type that does not have an outer ring with the surface as a direct raceway surface. Therefore, the above-described inner member and outer member are not limited to the inner ring and outer ring, but do not exclude shafts and gears having a raceway surface.

  According to the present invention, a highly lipophilic metal phosphate salt film is formed on at least one bearing metal surface of the raceway surface or rolling element of the inner and outer members, and the total film thickness of the raceway surface and rolling element Is 10 nm or more, so that the oil film forming ability of the bearing raceway surface in a dilute lubrication environment can be increased and the metal contact occurrence rate can be lowered. Therefore, the occurrence of metal contact due to poor lubrication is extremely short. It is possible to prevent the occurrence of surface-origin separation at the end of life. As a result, a highly reliable long-life rolling bearing can be provided.

  A rolling bearing according to an embodiment of the present invention has a structure in which a plurality of rolling elements rotatably held by a cage are interposed between both raceway surfaces of an inner ring that is an inner member and an outer ring that is an outer member. To do. This rolling bearing is assembled to a shaft support portion of a transmission of an automobile, for example, by a shaft (not shown) being coaxially inserted into an inner ring and an outer ring being attached to an inner diameter of a housing (not shown).

  This rolling bearing is not particularly limited in its material and type of radial bearing, thrust bearing, etc., but the inner and outer rings and rolling elements are made of metal that can be treated with a phosphoric acid coating. Materials made of hardened steel, stainless steel, plating, white metal and other bearing alloys containing lead and tin are possible.

  In the rolling bearing described above, a highly lipophilic metal phosphate coating is formed on the raceway surfaces of the inner and outer rings or the bearing metal surface of at least one of the rolling elements. As a result, the oil film forming ability of the bearing raceway surface in a dilute lubrication environment can be increased and the incidence of metal contact can be lowered, so that the surface starting point with a very short life resulting from the occurrence of metal contact due to poor lubrication The occurrence of peeling can be prevented.

  Further, the total thickness of the metal phosphate coating formed on the raceway surface and the bearing metal surface of the rolling element is set to 10 nm or more. If the total film thickness is less than 10 nm, it is difficult to increase the oil film forming ability of the bearing raceway surface in a dilute lubrication environment, and a desired effect cannot be exhibited.

This metal phosphate film can be formed by immersing inner and outer rings or rolling elements in a phosphate triester solution containing tricresyl phosphate. This phosphate triester is an organic phosphate compound represented by (RO) ₃ P═O (wherein R represents an aryl group, an aliphatic hydrocarbon group, or an alicyclic hydrocarbon group). Commercially available industrial materials can be used as the agent. A typical example of these phosphate triesters is tricresyl phosphate (CH ₃ C ₆ H ₄ O) ₃ PO.

  Further, in the formation of the metal phosphate salt film, it is difficult to form a metal phosphate salt film having a thickness larger than 70 nm in consideration of the dimensional change of the bearing and the number of processing steps. The thickness of the coating is preferably 70 nm or less. Furthermore, when forming the metal phosphate salt film, it may be performed while heating in order to increase the reaction rate.

  The present applicant dipped the inner and outer rings or rolling elements constituting the rolling bearing in a 100% stock solution of tricresyl phosphate to form a metal phosphate salt film on the surface of the bearing metal.

  Here, as disclosed in Patent Document 3 described above, when a compound reaction film layer having a thickness of 0.05 to 0.5 μm is formed, load resistance and seizure resistance can be improved with low wear. However, in order to form such a thick film, it is necessary to immerse for a long time, and considering the product cost, it is not suitable for a rolling bearing for automobiles.

  Therefore, the processing temperature and processing time in the formation of the metal phosphate film are considered in consideration of the dimensional change of the bearing and the number of processing steps, and a bearing with a metal phosphate film that can be processed at an upper limit of 150 ° C. × 100 h is manufactured. The improvement effect on the surface-origin peeling was confirmed under severe lubrication environment. The maximum thickness of the metal phosphate coating film that can be formed when 150 ° C. × 100 h is the upper limit treatment condition was 70 nm.

  The thickness of the metal phosphate salt film was measured by X-ray photoelectron spectroscopy (XPS analysis) (the same method as the measurement described in FIG. 1 of Patent Document 3). In this XPS analysis, the sample surface is irradiated with X-rays, and the information (qualitative and quantitative) and the binding state of the elements on the sample surface are obtained by analyzing the energy of photoelectrons emitted from the outermost surface of the sample (about several angstroms). Furthermore, by performing measurement while sputtering the sample surface using an argon (Ar) ion gun, the depth direction of the element, that is, the distribution state under the sample surface can be analyzed.

  As a result of conducting a life test under severe lubrication, if the total thickness of the raceway surfaces of the inner and outer rings and the metal phosphate film of the rolling element is 10 nm or more, the oil film forming ability of the bearing raceway surface under severe lubrication environment It has been confirmed that it is possible to prevent the occurrence of surface-origin separation with a very short lifetime due to the occurrence of metal contact due to poor lubrication. The test data is as shown in FIG.

It is a table | surface which shows the lifetime test result under severe lubrication about the thickness of a metal phosphate salt film.

Claims (3)

  In a rolling bearing in which a plurality of rolling elements rotatably held by a cage are interposed between both raceway surfaces of the inner member and the outer member, a metal phosphate coating is provided on at least one of the raceway surface or the rolling elements. The rolling bearing is characterized in that the total thickness of the raceway surface and the rolling element is 10 nm or more.   2. The rolling bearing according to claim 1, wherein the metal phosphate salt film is formed by immersing an inner / outer member or a rolling element in a phosphate triester solution containing tricresyl phosphate. 3.   The rolling bearing according to claim 1 or 2, wherein a thickness of the metal phosphate film is 70 nm or less.

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