Sliding bearing material

Details Sliding bearing material Sliding bearing material

1994-02-02

1996-03-12

Szekely, Peter A.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

At least one aryl ring which is part of a fused or bridged...

524495, 524496, 524513, 524546, 525165, 252511, C08K 322, C08K 304, C08L 6703, C08L 2712

Patent

active

054986540

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention is related to sliding bearing material, more particularly to the polytetrafluoroethylene-based sliding bearing material with improved resistance against fretting wear.


PRIOR ART

Polytetrafluoroethylene (hereinafter referred to as "PTFE") is used as the sliding bearing material of auxiliary machinery or the like of an automobile. Since the wear-resistance of PTFE is not exceptional, generally, metal or metal oxide is added to strengthen PTFE, lubricant such as MoS.sub.2 or graphite is added to improve the frictional and wear properties, or additives to improve the sliding characteristics are added in the PTFE based sliding bearing material. These additives are uniformly dispersed in the matrix material consisting of PTFE. These sliding bearing materials are used as the solid material, or are used as baked and are bonded in the clearances of the layer of the bearing-alloy such as lead bronze sintered on the backing metal.
The additives are utilized in the above PTFE-based sliding bearing materials mentioned above with the following aim. That is, in the initial period of sliding, the PTFE wears out slightly on the sliding surface so that the additive concentration on the sliding surface increases. The wear-resistance effect of the additive is thus utilized and hence the wear is suppressed. When the sliding advances further, the additive concentration increases further, so that the wear at the sliding surface considerably decreases. Thus wear doesn't advance any further under a sliding condition.
Lead or lead-alloy, whose lubrication property or compatibility is excellent, is a suitable additive for PTFE which is used in a general dry sliding condition. However, lead from the PTFE sliding bearing with a lead- or lead-alloy additive occasionally coheres on the opposing material and incurs abnormal wear in the accompanying sliding and fretting. These cohesive additives wear out in such a manner that they are transferred from the sliding material to the opposing material and form a thick film on the latter material. The cohesion is therefore very likely to occur. In addition, these additives may roughen the surface of the opposed material.
PTFE-based sliding bearing material with the addition of lead or lead alloy and aromatic polyester particles is also known. It involves however a problem that wear due to cohesion is also likely to occur.
A sliding condition, under which cohesion is particularly likely to occur, is a minute vibration of a sliding bearing, which causes fretting wear. A specific case is vibration in a direction intersecting with the rotational, main sliding direction, and is realized in such a sliding bearing for a frequently vibrating rotary axis. Since the lead or lead alloy grows on the opposed surface, the sliding thus realized is the one between the cohesive materials of the same kind and hence cohesion is likely to occur.


DISCLOSURE OF THE INVENTION

It is therefore an object of the present invention to provide a PTFE based sliding bearing material having improved cohesive wear.
The present inventors considered the following points in developing the PTFE-based sliding material. First, since lead or lead-alloy is a soft material and coheres on the opposed material under the sliding condition with incidental fretting, the additive must therefore be free of lead or lead-alloy. Next, it was discovered that such additives as aromatic polyester, spherical carbon and zinc oxide whisker exhibited essentially no cohesion with the opposed material, and, further, the wear-resistance of PTFE was considerably enhanced by the combination of two or more of them. It was further confirmed that the bearing performance equivalent with that of conventional materials was also provided in the general sliding condition. Sliding bearing-material having improved resistance against fretting wear could thus be provided.
Therefore, the sliding bearing material according to the present invention is characterized by dispersing at least two kinds of aromatic polyester-resin par

REFERENCES:
patent: 5124397 (1992-01-01), Kanazawa et al.
patent: 5183594 (1993-02-01), Yoshinaka et al.
patent: 5276080 (1994-01-01), Oku

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