Search Results

Ceramic materials such as silicon nitride and sialon are known for their excellent wear-resistance and scuffing-resistance even under high contact pressure and poor lubrication1. However, ceramic materials, which have excellent sliding properties, are not widely adopted for valve train components, at present. A main reason for this is their high cost. A ceramic cam follower, newly developed by utilizing the direct brazing technology, has the following features and can be produced at the lowest cost: (1) Parts are only three. -A thin ceramic disc, a steel body, and an active brazing foil. (2) No grinding is necessary after brazing. -A crowning at the cam sliding surface is formed by the difference of the thermal expansion coefficients between silicon nitride and steel. (3) No hardening is necessary after brazing. -The steel body is hardened by the heat treatment of brazing.

This paper describes the development of an inexpensive ceramic cam follower that uses a silicon nitride material and is more wear and scuff resistant than the sinter alloy cam follower. A thin ceramic disk is directly brazed on a steel cam follower body without using any stress-relief materials which makes the grinding for crowning unnecessary, reducing the production cost. We performed a material screening test using an abrasion tester to determine the optimum type of silicon nitride and the optimum surface roughness. Engine endurance tests proved its excellent wear and scuff resistance. Consequently, it has been adopted in the 1993 series production engines as the first ceramic cam follower.