Clutch Plate Surface Treatment for Improved Frictional Characteristics 922099

Separator plates are utilized in clutch or brake packs for transmissions in vehicles. These plates are internally or externally splined to be operatively connected to the rotatable and/or stationary members in a torsional coupling. When pressure is applied during an engagement, separator plates mate against friction assembly plates and generate torque. Improvements can be made in the separator plate processing and finishing which will improve friction characteristics.

The friction coefficients which result when clutch or brake packs are brought into contact are influenced by factors such as type of lining material, type of oil, temperature, velocity, and loading. Traditionally, varying the composition of the friction material on an assembly plate was a means to obtain different friction coefficients and in turn torque capacity. Additionally, there are other factors such as the separator plate surface finish that may affect the friction characteristics. This paper describes a treated separator plate which will increase the resulting friction coefficient of an engaging clutch or brake pack by up to 25% compared to tests with conventional separator plates. Using these modified separator plates compared to conventional separators will not produce any additional assembly wear after testing. Since the tests with modified separator plates will produce higher friction coefficients at lower pressure than conventional separators, the surface condition of both the separator plate and friction material is less damaged after testing.

The separator plate surfaces are prepared with a suitable surface treatment known as lapping, and then coated by a unique reactive sputtering process with titanium nitride or a similar material from Group IVb of the periodic table. Proper topographical preparation of the steel substrate prior to applying a hard thin coating (1.5 μm) is essential. Although the modified separator plate will provide a surface texture that enhances such frictional characteristics as friction level and curve shape, it will not increase the lining wear of the interleaved assembly plates.