Friction between pin and roller of a truck’s valvetrain

Abstract

In order to minimize the fuel consumption in internal combustion engines, the frictional losses must be minimized between the moving parts such as the sliding bearings. In this study, the sliding friction between the pin and roller in a heavy duty truck engine’s valvetrain has been investigated. Three combinations of production components with different surface treatment were used: steel pin with steel roller, steel pin with WS2 coating inside the roller and PVD coated steel pin with steel roller.In-house test rig was used, enabling controlled conditions close to the real engine. A new method for alignment using a laser scanner was introduced together with high resolution tactile measurements of radial displacement during test. Surface topography of pins and rollers was measured before test with a mechanical stylus instrument. The WS2 showed 3.1 times and the PVD showed 2.5 times lower friction than the steel type at low speeds. Even though the friction reduction of WS2 over the PVD is not large, the important advantage is that the WS2 can be manufactured at lower costs than the PVD one. Good correlations among the friction, initial roughness and radial displacements were also found.