Development of an Inexpensive, Highly Wear-Resistant Ceramic Cam Follower - Part 2 Brazing Technology

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. (1)
   Parts are only three.
   -A thin ceramic disc, a steel body, and an active brazing foil.
2. (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. (3)
   No hardening is necessary after brazing.
   -The steel body is hardened by the heat treatment of brazing.

Ceramic cam followers manufactured by the direct brazing were evaluated using a heat cycle tester and a cam motoring tester which could apply repeated impacts, to verify reliability and durability. Neither cracks nor break-away problems occurred after these endurance tests.

This paper describes the direct brazing technology for the ceramic cam followers, which were first adopted for the mass-produced engines in 1993.