Importance

Loading Importance Indicators...

Abstract

Disclosed is a shim or a valve lifter for an automotive engine valve driving system that slides against a cam lobe of a camshaft to drive an intake/exhaust valve of an internal combustion engine. The shim or lifter has the top of a sliding surface thereof opposing the cam lobe and being coated with a hard carbon film. The hard carbon film has a surface hardness of 1500 to 4500 kg/mm.sup.2 in terms of Knoop hardness, a thickness of 0.3 to 2.0 .mu.m and a surface roughness Ry (.mu.m) satisfying the following equation (A): Ry<{(0.75-Hk/8000).times.h+0.07/0.8} (A) where h is the thickness (.mu.m) of the hard carbon film; and Hk is the knoop hardness (kg/mm.sup.2) of the hard carbon film. By imparting durability, reliability and a low friction coefficient to the hard carbon film that is said to be low in ductility to prevent the hard carbon film from becoming cracked and separated when applied to the sliding portion.

Loading the Abstract Image...

First Claim