Modeling and analysis of clutch engagement judder in commercial vehicle powertrain systems 2019-01-0784
Transient events in a vehicle drivetrain such as tip in-out, clutch engagement-disengagement, engine start, etc. are very important considering NVH characteristics and hence comfort of a vehicle system overall. Clutch engagement (especially during vehicle launch from a rest) is one of the most important transient events in heavy vehicles utilizing automated manual transmissions (AMTs).
This paper presents common NVH issues observed during vehicle launch in a commercial heavy duty truck. One of the most important NVH issues is clutch judder. Judder is seen when torque fluctuations are generated in a slipping clutch which induces undesired driveline vibrations. This paper concentrates on friction judder as well as geometric judder. The ceramic and organic friction materials are compared for their performance against friction judder. Also performance of friction materials with respect to slip speed, temperature, pressure, and wear is studied. Organic friction materials are much stable as compared to ceramic friction materials and show better characteristics against judder. Geometric judder and how cushion discs can be effectively used as counter measure against geometric judder is also discussed in the later part of paper. Cushion disc stiffness comes out to be a very important parameter considering performance of clutch against geometrical judder. Both simulation and vehicle test results show the importance of friction material selection and cushion disc design for better design of clutches against judder.
Apart from clutch judder, few other issues during vehicle launch like inconsistent launch due to driveline backlash, impact of AMT controls are also presented with their mitigations actions.
Keywords: Clutch engagement, AMTs, NVH, Judder, friction coefficient, cushion disc, clutch
Tejas Paygude, Rohit Ravindra Joshi
Eaton India Innovation Center, Eaton India Engineering Center