Engagement behaviour of a paper-based wet clutch Part 1: Influence of drive torque

Abstract

Owing to increasing demands when designing wet clutches for automatic transmissions, more knowledge about their behaviour is needed. In cars with power shifting automatic transmissions, an engine torque is continuously transmitted through the gear box. Most experimental and theoretical work concerning investigations of wet clutches today uses the inertia type of test apparatus, e.g. the SAE test machine 2. However, this type of test machine has no possibility of investigating the influence of a drive torque from the power supply. In order to investigate the influence of drive torque on wet clutch engagements, a new type of apparatus was built, which can operate with different combinations of inertia and drive torque. This apparatus can perform engagements more similar to those in automatic transmissions. The aim of this paper was to compare experimental outputs obtained using these principles of testing, concerning the influence of drive torque. It was found that the friction characteristics of wet clutches are independent of how the input energy is produced. This means that friction can be investigated with both principles. It was also found that an apparatus using only inertia gives shorter engagement times and higher temperatures than an apparatus including a drive torque at the same level of input energy. This can be explained by different power characteristics. Therefore, when investigating temperatures of wet clutch engagements, one must be careful when translating the results into reality.