Detection of Land Area Wear in Automotive Synchronous Belts

A common way of driving the camshafts of an internal combustion engine is by synchronous belt. One of the major drawbacks is their limited durability. Several failure modes may appear. This paper considers land area wear failures. The area between two teeth on a synchronous belt is called the land area. Most of the semicircular belt profiles, used in automotive cambelt drives today, have a small backlash, i.e. the pulley groove is a little wider than the belt tooth. This allows for a relative motion between belt and pulley teeth. In a cambelt drive, in which torques are oscillating, this is the case. The movement causes wear to the land area that eventually will lead to breakage of the facing fabric, forcing the belt-pulley contact to run on the belt cord which will quickly lead to belt failure. This paper describes a method to detect the wear of land areas of synchronous belts. From surface topology measurements of the land areas at different wear stages, well-known roughness parameters are used to determine the degree of wear. The roughness parameters variations are explained by a physical wear procedure. In addition to this formerly known land area wear originating from complete meshing, another wear mechanism was discovered present near the tooth roots. The newly discovered land area wear type can be explained by seating and unseating effects.Copyright © 2003 by ASME