Reduction of Friction Loss by Arrangement of the Segment of the Polyimide Arms & Guides for Timing Chains in Automobile Engines

Abstract

The world cannot counter climate change without the automobile industry becoming far more environmentally sustainable than it is today. With the realization that electrified mobility will take decades, not years, and that internal combustion engines (ICE) will continue to power vehicles in the near future, we need to step up the focus on improving fuel efficiency of ICE vehicles. In this report, we have confirmed that, in timing chains for automobile engines, the sliding area can be reduced by changing the arrangement of the arms & guides from continuous contact to a segmented one and by using an aromatic polyimide (PI) that can withstand the high contact surface pressure, thereby reducing friction loss. Through bench test monitoring, we confirmed that the friction loss was reduced in comparison to that by the conventional arms & guides in ICEs. The conventional arms & guides in the layout of the timing chains are placed with a curvature of ~ R2000 mm (at least R500 mm). In this study, the layout of the arms & guides was investigated. Each arm or guide is divided into two or three segments in the direction of travel and each curvature is reduced to about R100 mm. In addition, the material has been changed from polyamide (PA66) to PI. By these changes, the contact surface is decreased, and the surface pressure is increased. This means that on the Stribeck diagram, the lubrication conditions move in the direction of the smaller Sommerfeld number and the friction loss decreases. The use of the high compressive modulus material reduces the amount of deformation of the arms & guides contact surface, leading to the reduction of the friction loss.