Dynamic analysis of powershifts with form-fit clutches in automatic transmissions

Abstract

In automatic transmissions, an important share of losses is caused by disengaged multiple-disc wet clutches that generate drag torque. To minimise said losses, an innovative shifting element, composed of a cone and a dog clutch, was developed and tested in a joint project between HOERBIGER Drive Technology Holding GmbH and FZG (Technical University of Munich). Through the use of a cone clutch instead of a multiple-disc wet clutch, friction surfaces and hence drag losses can be significantly reduced. Moreover, the static torque is transmitted via a dog clutch, dramatically reducing the required actuator force. Additionally, high comfort requirements have to be met during all shifting phases and equal conventional clutches. Dynamic shifting behaviour was investigated through multibody simulation. The main focus was the analysis of the form-fit engagement and the performance rating of different dog clutch designs and geometries. Furthermore, the influence of wear on the shifting behaviour was successfully identified.