Browse Publications Technical Papers 2019-28-0111

Design Optimization of Trunk Lid Torsion Bar Type Trunk Lid Pop Up Mechanism 2019-28-0111

Trunk lid can be opened using hydraulic/pneumatic balancers, coil springs, torsion bars or combination of the above. Trunk Lid Opening Mechanism specific to Trunk Lid Torsion Bar (TLTB) is being discussed in the paper. After de-latching, trunk lid should open smoothly and stop at such a height that it is visible from driver seat. The system consists of a four bar linkage mechanism, in which the fixed link is formed by BIW Bracket. Connecting link, Trunk lid Hinge Arm and Torsion bar form the other three links. Hinge has its one end attached to trunk lid and the other end to BIW bracket. Torsion bar transfers torque to Trunk lid hinge through the connecting link. Major challenges in designing TLTB mechanism are part tolerances, C.G position and Weight variations in individual parts, Torsion bar Raw Material variation, uncertain friction in the system etc. If above challenges are not addressed properly, then issues like Trunk Lid not popping up to desired level consistently and smoothly and hard closing may occur. Trunk Lid pops up when torque due to torsion bar is greater than the combination of torque due to trunk lid weight and friction at linkages. Considering the above challenges and drop in elasticity of TLTB with time, upper and lower values of torques are derived. When lower tolerance torque of torsion bar is greater than the upper tolerance torque of trunk lid weight, trunk lid always opens. When effects of these tolerances are not considered, pop up of trunk lid is uncertain. The difference between these torques should be as low as possible so as to ensure smooth pop up. This paper outlines the design optimization of Trunk Lid Pop up Mechanism while addressing afore mentioned challenges.


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