Bearing cage and rolling bearing having the same

Details Bearing cage and rolling bearing having the same Bearing cage and rolling bearing having the same

2002-03-25

2004-01-27

Hannon, Thomas R. (Department: 3682)

Bearings

Rotary bearing

Antifriction bearing

C384S908000

Reexamination Certificate

active

06682224

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates to a bearing cage comprising thermoplastic resin as base material, and to a rolling bearing having the bearing cage.
2. Description of the Related Art
The rolling bearing has a cage interposed between an inner ring and an outer ring. The cage holds a plurality of rolling elements. In such a rolling bearing, generally, lubricant is not used under environment of severe lubricating condition such as high temperature and high pressure. Instead the cage itself has lubricating ability. As one of techniques for providing the cage itself with lubricating ability, it is proposed that the cage is made of resin.
The present inventors have selected and used polytetrafluoroethylene (PTFE) as base material of the cage. Polytetrafluoroethylene has excellent lubricating performance and excellent out gas ability.
However the cage using polytetrafluoroethylene as the base material can not be formed by injection molding and is required to be formed by shaving. As a result, it takes a long time to manufacture the cage, which increases the manufacturing cost of the whole rolling bearing.
There are various kinds of thermoplastic resins as resins which can be injection molded. The thermoplastic resins may be used as the base material of the cage. The cage is, however, brought into contact with the rolling elements or the like. Therefore the thermoplastic resins, when used as the base material of the cage, causes wearing amount or torque of the cage to increase at early stage of use of the rolling. Thus, the performance of the cage is deteriorated at the early stage, and life of the rolling bearing having the cage is affected.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to make it possible to easily manufacture a cage using thermoplastic resin as its base material and to make it possible to prevent the wearing amount or torque of the cage from increasing at early stage of use of the rolling bearing having the cage.
To achieve the above object, a rolling bearing of the present invention comprises an inner ring, an outer ring concentric with the inner ring, a cage interposed between the inner ring and the outer ring and a plurality of rolling elements held by the cage. The cage comprises base material, reinforced fiber and solid lubricant. The base material is thermoplastic resin. The reinforced fiber and solid lubricant are mixed into the base material. The reinforced fiber of 5 to 30 wt % is mixed with the base material. As the solid lubricant three kinds of materials, i.e., polytetrafluoroethylene of 5 to 30 wt %, molybdenum disulfide (MoS
2
) of 3 to 15 wt % and graphite (C) of 3 to 15 wt % are mixed with the base material.
In the case of the rolling bearing of the present invention, since thermoplastic resin is used as the base material of the cage, the cage can be formed by injection molding. Thus, manufacturing time of the cage can be shortened, and the manufacturing cost of the rolling bearing having the cage can be reduced. In this cage, the reinforced fiber and solid lubricant are mixed into the thermoplastic resin.
With the above wt % polytetrafluoroethylene, molybdenum disulfide and graphite are included in the solid lubricant. Nevertheless the thermoplastic resin is, therefore, used as the base material of the cage, wear resistance is enhanced, the dust-generating properties are reduced and life of the cage is elongated.
Being configured by the base material using thermoplastic resin, the cage of the present invention can be easily manufactured by working easiness which is a feature of thermoplastic resin. Since the cage of the present invention includes the reinforced fiber and solid lubricant in the base material, a defect of the cage using thermoplastic resin as the base material, such as wear resistance, can be overcome. Thereby the life of the rolling bearing using the cage can be elongated.
In the rolling bearing of the present invention, it is preferable that the thermoplastic resin is selected from either one of ethylene tetrafluoroethylene (ETFE), polyether ether ketone (PEEK), polyamidimide (PAI) alloy and thermoplastic polyimide (TPI). Such thermoplastic resin is excellent in out gas characteristics. Mixed amounts of the reinforced fiber and solid lubricant are specified with respect to the thermoplastic resin. Thereby the environment contamination caused by the out gas can be suppressed and excellent lubricating ability can be exhibited for a long term.
Preferably, in the rolling bearing of the present invention, potassium titanate whisker is selected as the reinforced fiber. If the potassium titanate whisker is used as the reinforced fiber, strength of the cage is enhanced, a mating member which is brought into contact with the cage is less prone to be damaged, and dust-generating suppressing effect is especially enhanced.


REFERENCES:
patent: 5988891 (1999-11-01), Yamamoto et al.
patent: 6203207 (2001-03-01), Yamamoto et al.
patent: 6332717 (2001-12-01), Oohira et al.
patent: 6367981 (2002-04-01), Yamamoto et al.
patent: 05032989 (1993-02-01), None
patent: 11125257 (1999-05-01), None

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