Brake Friction Pad Assembly

This invention relates generally to brake systems of the type used in domestic road vehicles, and particularly concerns an improved brake friction pad assembly having an elastomeric noise-damping material incorporated into the assembly only after complete material thermal curing.

Various elastomeric materials have been knowingly incorporated into vehicular brake friction pad assemblies for the purpose of reducing the squeal-type noise that often is otherwise generated in the incorporating brake system during vehicle braking. Other elastomeric materials in such assemblies have been used as adhesives to bond brake friction pad elements to a metallic backing plate.

None of the prior art brake assembly teachings disclose or suggest that improved brake assembly squeal and other noise reductions can be realized if an elastomeric adhesive film applied to the brake friction material pad is completely thermally cured prior to subsequent assembly of the friction material pad to its backing member, and that the subsequent assembly be accomplished not by relying on the adhesive strength of the elastomeric film but by using mechanical fasteners instead.

The present invention, which may be utilized in either disc brake or drum brake applications, involves the sequential steps of applying a uniform thin film of elastomeric adhesive to the mating surface of a brake friction pad element, air-drying the elastomeric adhesive film to remove entrained solvent-like constituents, heating the friction pad element and elastomeric film at an elevated temperature in the range of 350 to 400 degrees Fahrenheit for a sufficient time to thermally cure the elastomeric adhesive film, and, after cooling, joining the friction pad element and cured film to the mating surface of the assembly backing plate element with either rivets, threaded fasteners, or the like.

FIG. 1 is a perspective view of a preferred embodiment of the improved brake friction pad assembly of our invention; and

FIG. 2 is a view along line 2--2 of FIG. 1.

In FIGS. 1 and 2 we illustrate a disc brake friction pad assembly (10) comprised of a molded friction pad element (12), a thermally cured elastomeric adhesive film (14) adhered to the mating surface of element (12), a metal backing plate element (16) for mounting the assembly in a cooperating vehicle brake system, and rivet fasteners (18) utilized to mechanically join friction pad element (12) to backing plate element (16) with film (14) being located in an intermediate position.

Friction pad element (12) in the preferred embodiment is molded of a semi-metallic friction-generating material. A typical composition for such material is comprised of a mixture of 57 parts metallic particles such as iron powder and steel wool fiber particles, 12 parts straight or modified phenolic resin binder particles, 21 parts carbonaceous particles such as graphite particles or coke particles, 5 parts filler particles such as barytes particles, 4 parts abrasive particles such as magnesia or alumina particles, and 1 part friction particles such as rubber peel particles, all parts proportions being on a percentage volume basis. The friction-generating material mixture, with an included curative for the resin binder particles, normally is compressed in a pre-heated mold to an isostatic pressure as high as approximately 6000 pounds per square inch. After compaction, the friction pad is thermally cured by slow linear heating to a temperature of approximately 400 degrees Fahrenheit and maintained at that temperature for up to 24 hours to complete the thermal curing cycle.

After cooling, the cured friction pad element (12) is provided with a thin film of an elastomeric adhesive (14) such as the commercially-available synthetic rubber elastomeric adhesives marketed in the United States under the names "Cycle Weld" and "Plastilock" by B. F. Goodrich Company of Akron, Ohio. We prefer that the film be distributed evenly over element (12) and that it have a thickness that will result in a finally-cured thickness of from approximately 0.003 inch to approximately 0.015 inch. Following application of the elastomeric adhesive film to cured friction pad assembly (12) the film is air-dried or oven dried for up to 24 hours to remove entrained volatile constituents and then subjected to thermal curing. Thermal curing normally involves heating the air-dried film and the friction pad element combination to a temperature in the range of approximately from 350 degrees Fahrenheit to 400 degrees Fahrenheit for a period of from 1/4 hour to 3 hours. After subsequent cooling the friction pad/elastomeric film combination is readied for assembly to metal backing plate element (16).

Lastly, we preferably assemble element (12) and its elastomeric film (14) to element (16) by means of mechanical fasteners such as rivets (18) as shown in FIG. 1. Other mechanical fasteners such as threaded bolts and the like may be substituted for rivets (18). It should be noted that the substitution of a further adhesive for fasteners (18) is not acceptable if the noise and squeal reduction advantages of our invention are to be realized.

Other friction-generating material compositions, elastomeric adhesive compositions, and component shapes and sizes may be utilized in the practice of our claimed invention.