Applicability of Convex and Concave Shaped Surface Texturing to Improve Damping Performance of Mechanical Tensioner for Timing Chain of Internal Combustion Engine

Abstract

The present study describes an improvement of damping performance of a mechanical tensioner driven by friction force at the power spring interface, used for the timing chain system for an internal combustion engine. The mechanical tensioner consists of a power spring subjected to face-to-face contact with a reciprocal motion and a leaf spring to apply the reaction load. The concave and convex surface texture was fabricated with an electrochemical etching on the power spring surfaces. Since the reaction load is affected by the friction force at the power spring interface, the damping performance is evaluated from a hysteresis loop resulting in the reaction load and the plunger displacement trajectory. Superior stabilization of the reaction load and a remarkable decrease of the wear loss including the restriction of the oxidation was found on the convex textured tensioner in lubricated condition. The tensioner performance was also evaluated in staved lubricating conditions. Results showed that the change of the reaction load of the convex textured tensioner was small just before the stiction occurrence. In contrast, the reaction load of the concave textured tensioner increased with the increase in the number of cycles. Therefore, the applicability of the convex surface texture to the power spring surface of the tensioner was confirmed. It was also estimated that the discharge of the wear debris is an important factor in maintaining the tensioner performance.