Development of new groove design for reduction of drag torque or spin loss of disengaged wet clutches in high speed region

Paper #:
  • 2018-01-1300

Published:
  • 2018-04-03
Abstract:
The ordinary graph of a drag torque or spin loss vs. speed of disengaged wet clutch of automotive transmission shows 4 types of trends. First increasing until a peak level, next decreasing and goes to the lowest level, next saturating or no change, and last one is again increasing. If the absolute value of drag torque at high speed (6000rpm-20,000rpm) is high, then fluttering of friction disk, chipping and delamination from friction disk will be observed. Therefore, it is important to understand the physics behind the torque jump up at high speed region and reduce the absolute value of drag torque. In our previous research, we have developed a model to predict the drag torque characteristics for high speed region. In this research we have improved our model and proposed new groove design to reduce the drag torque magnitude at high speed range. We have conducted real time visualization tests and obtained that at higher speed ( ~6000rpm), plate and disk come close to each other and contact and the temp. of separator plate rises. Next, we have conducted test with fixed separator plates with screws. Result shows that when the separator plates are fixed with screws, no drag torque jump is observed and temperature was not increased. From the various test data investigations, we concluded that vacuum formation is one of the possible reasons of high speed torque rising. In order to suppress the torque and temp rise at high speed, we have developed a special groove design which improves the static pressure at high speed range. We have conducted test with new groove design and result shows at certain test conditions, a significant amount of drag torque reduction was achieved at high speed range.
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