Solid anti-friction devices – materials therefor – lubricant or se – Solid anti-friction device – article or material therefor – Silicon compound
Reexamination Certificate
2001-08-13
2003-05-27
Howard, Jacqueline V. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Solid anti-friction device, article or material therefor
Silicon compound
C508S100000, C508S136000
Reexamination Certificate
active
06569816
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a composition having lubricity and a product comprising the composition (hereinafter referred to as slide product). Particularly, the present invention relates to a composition having lubricity such as a lubricating resinous composition, lubricating elastomer composition, and a lubricating coating film composition capable of continuously oozing a lubricant to a slide interface little by little; an additive imparting lubricity to a base material; and a slide product using these compositions. Representative slide products are a slide bearing, a retainer for a holding a roll of a rolling bearing, and a seismically isolated apparatus.
Among demands growing year by year for the composition having lubricity such as a resinous slide member obtained by molding the lubricating resinous composition, a material having rubber elasticity, and a lubricating coating film, the strong demands are that they have low degree of friction and wear in an initial time and they maintain their initial sliding property for a long time. For low degree of friction and wear, a solid lubricant such as graphite, polytetrafluoroethylene (hereinafter referred to as PTFE), molybdenum disulfide (MoS
2
), boron nitride (BN) or the like is added to resin or a reinforcing material such as glass fiber and carbon fiber is added thereto to impart slide characteristic to the composition having lubricity. However, only the addition of the solid lubricant has a limitation in lowering the friction characteristic. Under these circumstances, a method of adding lubricating oil or the like has been carried out.
As the additive imparting lubricity to a base material, solid lubricants such as graphite, PTFE, molybdenum disulfide, boron nitride and the like are known. Base materials improve lubricity by adding the solid lubricants to the base materials such as resin, rubber, and the coating film. However, only the addition of the solid lubricant has a limitation in lowering a coefficient of friction and is incapable of allowing materials to have lower degree of friction. For achieving lower degree of friction, boundary lubrication by means of oil is generally adopted. For example, if a state in which the lubricating oil is always present on a slide interface can be maintained by adding the lubricating oil to a material, the material is allowed to have a lower degree of friction.
But the addition of only the lubricant to the resinous material or the like causes the following problems: In the case where only the lubricating oil is dispersed in the resinous material as the lubricant, the dispersion unit of the oil changes owing to kneading. Thus it is difficult to reliably manufacture a material having uniform slide characteristic.
To improve the slide characteristic of the resinous material such as the friction characteristic thereof, it is preferable that the addition amount of the lubricating oil is large. However, if the addition amount of the lubricating oil is large, a screw slip in a kneading time and metering time period is not uniform, which causes a cycle time to be long. Thus stable manufacturing is difficult. In addition, oil attaches to a die and a size accuracy is unstable. Further, if the lubricating oil and the base material are not compatible with each other, the lubricating oil cannot be dispersed into the base material, depending on the combination thereof.
In the lubricating oil-containing resinous material, a resinous layer of the base is worn little by little at a slide time and a lubricating oil layer appears on the slide portion. That is, the lubricating oil oozes on the surface of the slide portion. It is difficult to control the oozing condition of the lubricating oil. Thus there is a possibility that a pore from which the lubricating oil has oozed causes reduction of strength of the resinous layer.
In the case where a filler is added to the base material to improve the mechanical strength and wear resistance of the composition having lubricity, oil is locally present on the interface of the filler. Thus a sufficient reinforcing effect cannot be obtained.
The slide product obtained by molding the composition includes a slide bearing, a retainer for a rolling bearing, a seismically isolated apparatus, and the like.
The conventional retainer for a rolling bearing is made from metal, polyamide resin, polyacetal resin, polybutylene terephthalate resin, and the like. In molding synthetic resin, injection-moldable synthetic resin or a synthetic resinous composition reinforced with glass fiber, carbon fiber or organic fiber added to a molding material of the synthetic resin has been used. Semi-solid lubricant such as lubricating oil or grease has been used to lubricate the retainer-incorporated rolling bearing.
In the case where the semi-solid lubricant such as grease is used, resistance to stirring is generated by the consistency of the lubricant. Therefore, when a rotary shaft supported by the bearing rotates, a required torque is applied and a torque fluctuation is generated. In the conventional bearing incorporating the retainer owing to grease lubrication, when the rotational speed of the inner ring or the outer ring is as high as about 10,000 rpm, the resistance to stirring generated by the consistency of the grease causes a required torque for rotating the rotary shaft supported by the bearing to be high and a torque fluctuation to occur. Further, owing to the presence of the grease, a comparatively large amount of dust floats in the periphery of the bearing. Owing to such an increase and fluctuation of torque, generation of dust, and generation of noise caused by the rotation of the bearing, there is reduction of the performance of a bearing, especially a bearing having a diameter not more than 6 mm, which is incorporated in office appliances such as an HDD, a VTR, a DAT, a LBP and audio appliances, peripheral appliances, and the like.
To improve these problems, there are proposed a retainer, for a rolling bearing, composed of a material having a lubricating function. In Japanese Patent Application Laid-Open No.61-6429, there is disclosed the bearing containing polyamide-imide resin porously compression-molded and impregnated with fluorinated oil. According to Japanese Patent Application Laid-Open No.1-93623, the retainer formed by molding oil-containing plastic consisting of the oil-containing binder and the matrix is impregnated with lubricating oil. According to Japanese Patent Application Laid-Open No.8-21450, the mixture of polyolefin resin and the lubricating oil is molded into the configuration of the retainer. According to Japanese Patent Application Laid-Open No.2000-97241, the mixture of synthetic resin and the inorganic porous particulate matter is molded into the configuration of the retainer.
However, the retainer disclosed in Japanese Patent Application Laid-Open No.61-6429 is inferior to a retainer composed of a precise porous material in its mechanical strength. Thus depending on a use condition, the retainer lacks strength. Further because interconnected pores are formed, powdery resin is compression-molded, sintered, and then machined. Thus a large number of manufacturing processes are required.
In the case of the retainer disclosed in Japanese Patent Application Laid-Open No.1-93623, to increase oil absorption capacity, it is necessary to immerse the retainer in the lubricating oil at a high temperature (120° C.-130° C.) for a long time (about seven days). Therefore, there is a possibility that the lubricating oil and the resin forming the retainer deteriorate and dimensions change greatly. That is, the method is inferior in the stability of products. Another disadvantage is that the lubricating oil oozes at a comparatively early time. Thus the retainer is incapable of maintaining stable lubricity for a long time.
In the case of the retainer disclosed in Japanese Patent Application Laid-Open No.8-21450, the lubricating oil is held by polyolefin resin because the polyolefin resin is highly absorbent of oil. Thus little oil ooz
Egami Masaki
Oohira Kouya
Shimazu Eiichirou
Tsutsui Hideyuki
Hedman & Costigan ,P.C.
Howard Jacqueline V.
NTN Corporation
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