Solid anti-friction devices – materials therefor – lubricant or se – Solid anti-friction device – article or material therefor – Heavy metal or aluminum compound
Patent
1997-11-03
1999-09-28
Johnson, Jerry D.
Solid anti-friction devices, materials therefor, lubricant or se
Solid anti-friction device, article or material therefor
Heavy metal or aluminum compound
508166, 508167, 423511, C10M12522
Patent
active
059588462
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a solid lubricant, in particular for friction linings, on the basis of metal sulphides, as well as to friction lining mixtures and friction linings containing the same, such as brake or clutch linings.
For instance, MoS.sub.2 being a sulphide has long been known as a solid lubricant for the formation of a solid lubricant film between surfaces intended to glide with regard to each other. MoS.sub.2 and other metal sulphides are also used as components of gliding compositions consisting e.g. primarily of PTFE, i.e. for instance plain bearing half liners or slide bushings, in order to reduce surface friction.
Metal sulphides are also used as solid lubricants in a completely different field, namely in the production of friction elements, such as brake blocks, brake shoes, brake and clutch linings, the purpose of which is not the prevention of friction but the generation of friction.
Thus it is obvious that the aim of using solid lubricants in friction linings is not the reduction of friction, but rather the stabilisation of the frictional behaviour in relation to time, resulting in the reduction of abrasive processes and in a positive effect on wear and vibration characteristics. A highly desirable side effect when using certain solid lubricants is a considerable stabilisation of the coefficient of friction, i.e. the detrimental dependence of the coefficient of friction and thus of braking efficiency on temperature, pressure load and speed, is suppressed to a major extent.
Those best known among the special solid lubricants used in friction linings are graphite and molybdenum disulphide, But there are a number of other metal sulphides used almost exclusively in friction linings, differing from those mentioned above primarily with respect to the stabilisation of the coefficient of friction.
Publications to be mentioned in this context are EP497,751 and AT-399,162, which are concerned with various metal sulphides and combinations thereof, respectively.
One well-known and frequently used solid lubricant for friction linings is lead sulphide, which will however be available for future applications to a constantly reduced extent because of the increasing ecological sensibilization against heavy metals. But according to the present art, the good and favourable characteristics of this material make it practically impossible to use a substitute for lead sulphide without impairing the quality of the friction lining.
For many years there have been attempts to produce synergistic mixtures having extraordinary effects by combining various solid lubricants on the basis of graphites, sulphides, fluorides, phosphates etc. (see DE 25 14 575, DE 35 13 031 or EP-328,514). However, these or similar combinations have so far not been successful in achieving an effect that is satisfactory in every respect.
Even the combinations of AT-399162 on the basis of the sulphides of copper with those of zinc, antimony, molybdenum, tin, tungsten and titanium, in spite of their generally favourable properties, are not fully satisfactory with respect to their effect either. Even less common sulphides, like that of bismuth, are no satisfactory solution.
Now it has surprisingly been found that a number of bimetal and trimetal sulphides, when used as solid lubricants, in particular in friction linings, give excellent results, among others much more favourable results than single-metal sulphide mixtures of analogous composition.
Accordingly, the present invention primarily proposes a solid lubricant, in particular for friction linings that are preferably resin-bound, on the basis of metal sulphides, characterized in that the solid lubricant contains or consists of at least one compound of the formula Fe, Cu, Zn, Mo, W, Sb, Sn and Bi, S denotes sulphur, and the subscripts comprise the ranges of I=1-5, m=1-5, n=0-5 and x=2-8.
Preferably the solid lubricant is a polyphase sulphide mixture, in particular a combination of at least one compound of the formula Bi.
Furthermore the invention proposes the corresponding frictio
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Chemetall Ges. m.b.H.
Johnson Jerry D.
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