Bearings – Rotary bearing – Plain bearing
Reexamination Certificate
1999-09-08
2001-02-06
Footland, Lenard A. (Department: 3682)
Bearings
Rotary bearing
Plain bearing
C384S908000, C384S909000, C384S911000, C384S913000
Reexamination Certificate
active
06183137
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a bearing structure, which comprises a shaft and a bearing for supporting the shaft, the shaft and the bearing having a resin layer formed on the respective sliding surfaces.
2. Related Art
Bearings having a resin layer formed on their sliding surfaces by coating are well known, and it is also well known that addition of polytetrafluoroethylene (which will be hereinafter referred to as PTFE) to the resin can reduce the coefficient of friction and also can improve the wear resistance, but their development has been based on a bearing structure comprising a metallic shaft and a resin-coated bearing.
Recent bearings have a tendency to be used in a severer condition, therefore they are required to have bearing structures with a higher wear resistance, etc. However, bearings having the resin layer on the sliding surfaces still have such problems as an unsatisfactory wear resistance and easy wear.
SUMMARY OF THE INVENTION
The present inventors have found that further reduction in the coefficient of friction and further improvement of wear resistance can be attained by coating both of the shaft sliding surface and the bearing sliding surface with resin and adding a specific amount of PTFE to the resin, and have established the present invention.
The first aspect of the present invention provides a bearing structure, which comprises a shaft and a bearing for supporting the shaft, the shaft and the bearing having a resin layer formed on the respective sliding surfaces, the resin layer on the shaft sliding surface being made from a resin composition comprising at least one member selected from the group consisting of epoxy resin, phenol resin, polyamideimide resin, polyimide resin, polyacetal resin, polyamide resin, polyphenylene sulfide resin, polyether ether ketone resin and tetrafluoroethylene-perfluoroalkylvinyl ether copolymer resin and 5 to 50% by weight of PTFE based on total resin composition, and the resin layer on the bearing sliding surface being made from at least one member selected from the group consisting of epoxy resin, phenol resin, polyamideimide resin, polyimide resin, polyacetal resin, polyamide resin, polyphenylene sulfide resin, polyether ether ketone resin and tetrafluoroethylene-perfluoroalkylvinyl ether copolymer resin and not more than 50% by weight of PTFE based on total resin composition.
DETAILED DESCRIPTION OF THE INVENTION
The resin for use in the resin layer on the shaft and bearing sliding surfaces includes, for example, epoxy resin, phenol resin, polyamideimide resin, polyimide resin, polyacetal resin, polyamide resin, polyphenylene sulfide resin, polyether ether ketone resin and tetrafluoroethylene-perfluoroalkylvinyl ether copolymer resin, which are all distinguished in wear resistance.
In the ordinary bearing structure, shaft exchange is hard to be made, whereas bearing exchange is easy to be done. Thus, it is desired to make the wear resistance of shaft sliding surface higher than that of bearing sliding surface, thereby making the wear rate of shaft sliding surface as low as possible. To this effect, it is desirable that the resin layer on the shaft sliding surface is made from a thermosetting resin having a high hardness and that on the bearing sliding surface from a thermoplastic resin having a relatively low hardness and a low friction property (the second aspect of the present invention).
The thermosetting resin for use in the resin layer on the shaft sliding surface includes, for example, epoxy resin, phenol resin, polyamideimide resin and polyimide resin. When at least one of these resins contains PTFE, the friction resistance can be lowered and the wear resistance can be improved. Less than 5% by weight of PTFE, no satisfactory effects can be obtained, whereas more than 50% by weight of PTFE the wear resistance is lowered on the contrary. Thus, the PTFE content must be 5 to 50% by weight and particularly a content of 10 to 30% by weight thereof is preferable because of their more remarkable effects.
The thermoplastic resin for use in the resin layer on the bearing sliding surface includes, for example, polyacetal resin, polyamide resin, polyphenylene sulfide resin, polyether ether ketone resin, thermoplastic polyamideimide resin, thermoplastic polyimide resin and tetrafluoroethylene-perfluoroalkylvinyl ether copolymer resin. When at least one of these resins contains PTFE, the friction resistance can be further lowered and the wear resistance can be improved. More than 50% by weight of PTFE the wear resistance is lowered on the contrary. Thus, the PTFE content must be not more than 50% by weight, and particularly a content of 10 to 30% by weight thereof is preferable because of their more remarkable effects.
When the shaft or the backing metal of bearing is made of a metal, and the resin may be bonded directly to the shaft or the bearing surface, the bonding force between the shaft or the bearing surface and the resin is not satisfactory in some cases. As disclosed in JP-A-57(1982)-74153, it has been already established as a technique to set a metallic mesh or bronze powder to the backing metal surface of the bearing by sintering and cover the metallic mesh or bronze powder layer with a resin by filling or impregnation, thereby assuring the bonding force. This means that, for further improvement of bearing sliding surface, it will be possible to use various means, for example, addition of a lead compound to the resin layer (the fourth aspect of the present invention), addition of short fibers, such as potassium titanate whiskers (the third aspect of the present invention), etc., and a solid lubricant, etc., thereby further improving the coefficient of friction and wear resistance.
On the other hand, application of such means to the shaft sliding surface is generally difficult, except for ordinary mere spraying or coating of the resin. If the bonding force between the shaft sliding surface and the resin layer can be improved, it will be also possible to add a solid lubricant or additives such as short fibers, etc., for example, potassium titanate whiskers, etc. to the resin layer on the shaft sliding surface. Therefore a thermosetting resin having superior bonding force is preferably used for the resin on the shaft (the second aspect of the present invention).
Preferable application example of a bearing structure comprising the shaft and the bearing is an application to a continuously variable transmission (the fifth aspect of the present invention).
According to the first aspect of the present invention, a bearing structure comprises a shaft and a bearing for supporting the shaft, the shaft and the bearing having a resin layer formed on the respective sliding surfaces, where the resin layer on the shaft sliding surface is made from a resin composition comprising at least one member selected from the group consisting of epoxy resin, phenol resin, polyamideimide resin, polyimide resin, polyacetal resin, polyamide resin, polyphenylene sulfide resin, polyether ether ketone resin and tetrafluoroethylene-perfluoroalkylvinyl ether copolymer resin and 5 to 50% by weight of PTFE based on the total resin composition, and the resin layer on the bearing sliding surface is made from at least one member selected from the group consisting of epoxy resin, phenol resin, polyamideimide resin, polyimide resin, polyacetal resin, polyamide resin, polyphenylene sulfide resin, polyether ether ketone resin and tetrafluoroethylene-perfluoroalkylvinyl ether copolymer resin and not more than 50% by weight of PTFE based on the total resin composition. The bearing structure can be given a lower coefficient of friction and a distinguished wear resistance thereby.
According to the second aspect of the present invention, the resin layer on the shaft sliding surface is made from a thermosetting resin, and the resin layer on the bearing sliding surface is made from a thermoplastic resin in the bearing structure according to the first aspect of the present invention. Particularly the resi
Hiramatsu Nobutaka
Kojima Akira
Ogawa Yukitoshi
Ono Akira
Shibayama Takayuki
Browdy and Neimark
Daido Metal Company
Footland Lenard A.
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