Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Physical dimension specified
Patent
1990-02-27
1992-01-14
Herbert, Jr., Thomas J.
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Physical dimension specified
428457, 528211, B32B 1508, B32B 2700
Patent
active
050809709
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to plain bearings and materials for plain bearings.
High performance, crystalline, aromatic thermoplastic polymers such as poly aryl ether ketones are known for use in plain bearing applications. One polymer, poly ether ether ketone (PEEK), whilst possessing excellent mechanical strength properties and resistance to oil degradation at high temperatures has shown less than ideal surface properties in marginally lubricated applications in the unmodified condition. To overcome these problems various fillers and dry lubricant materials have been added to improve the surface properties. The result of this is a weakening of the matrix and an increase in the processing complexity which leads to economic disadvantages.
We have now found a polymer which possesses inherently superior surface properties and overcomes the above disadvantages.
According to a first aspect of the present invention a material for the working surface of a plain bearing operated in the presence of a lubricant comprises poly cyano aryl ether (PCAE).
We have found that the surface properties of PCAE are particularly suited to lubricated bearing applications because of the highly active polar nitrile (--CN) groups. These groups have a strong affinity for both the base oil and the boundary lubricant additives in lubricating oils. Thus, retention of oil film characteristics are good which leads to improved life in marginally lubricated conditions where rubbing contact between the bearing surface and the counterface may occur such as, for example, at start up in an automotive engine.
PCAE may be used as a solid bearing material, i.e. where the bearing material layer is comprised exclusively of the polymer. In this case the polymer layer thickness may lie between 0.1 to 1 mm, a preferred range maybe 0.2 to 0.4 mm.
PCAE may alternatively be used as a thin overlay layer on top of another bearing material such as, for example, an aluminum-tin alloy. The metallic bearing material may itself have a stronger backing material such as steel. In this case where PCAE is used as an overlay the metallic bearing layer contributes to a high overall fatigue strength and the polymer contributes improved surface properties in boundary lubricated conditions. A PCAE overlay may have a thickness in the range from 0.01 to 0.05 mm and a preferred thickness range between 0.02 and 0.03 mm.
PCAE may be bonded to steel either directly or via a bonding interlayer such as sintered bronze or sprayed aluminium bronze, for example.
Other backing materials to which PCAE may be bonded include stainless steel, aluminium alloys and various copper based alloys.
According to a second aspect of the present invention there is provided a plain machinery bearing for operation in the presence of a lubricant, the bearing having a working surface comprising poly cyano aryl ether.
Such bearings may include thin-wall half bearings, thrust washers and wrapped bushes, for example. Lubrication may be by oil or grease.
The polymer matrix material may be modified by the inclusion of other materials such as reinforcing additives or friction and wear reducing agents.
Reinforcing additives may include mica, carbon fibre, aramid fibre, e.g. Kevlar (trade name), metallic or mineral fibres, for example.
Friction and wear reducing agents may include alumina, antimony oxide, aramid fibre, asbestos, barium sulphate, boron nitride, cadmium sulphide, calcium fluoride, carbon fibres, ceramic powders (fine), clay, chromic oxide, coke, copper oxide, ferric oxide, glass, graphite, graphite fluoride, lead fluoride, lead iodide, lead oxides, lead sulphide, manganese ammonium phosphate, metal fibre, metal flake, metal powders, mica, molybdenum disulphide, phthaloycyanines, polyoxybenzoate, PPS, PTFE, silicon carbide, silicon, talc, wollastonite, zinc sulphide.
PCAE may be processed by any conventional techniques such as compounding and tape extrusion, compounding and moulding, powder coating, solvent casting and injection moulding for example.
In order that the present invention may be
REFERENCES:
patent: 4640975 (1987-02-01), Matsuo et al.
Herbert, Jr. Thomas J.
Hinds William R.
T&N Technology Limited
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