Research and application of variable DOF compliant five-bar mechanism based on novel compliant torsion joint in vehicle side door latch

Abstract

In this paper, a novel compliant joint with torsion spring (CJTS) is proposed in order to realize the power release (Note: The “power release” feature means that the closure system with a latch assembly including a pawl-ratchet release mechanism is controlled by at least one electric actuator.) feature of the vehicle side door latch. A new type of variable degree of freedom (DOF) compliant five-bar mechanism (VDCM) based on the novel compliant joint is constructed. The novel compliant mechanism is characterized by multiple motion modes of planar five-bar mechanism and four-joint, crank-shaper, crank-oscillating block mechanism. These motion modes can be switched through the different choices of driving joints and limiting stoppers. This compliant mechanism is effectively implanted into a vehicle side door latch as a sub-branch to perform power release function. The force-adaptive characteristic of the VDCM ensures compatibility with extant manual release branches. Drifting displacement of the CJTS’s torsion spring rotation center in the groove is proposed as a compliant index to describe the compatibility and force-adaptive characteristics under various working modes. The relationship between torsion spring stiffness and mechanism characteristic point motion trajectory or position recovery time duration or motion accuracy is studied. The results show that the introduction of compatibility and force-adaptive characteristics is able to reduce the shaking forces exerted on the mechanism frame. The shaking forces will be further reduced by changing equivalent mass center position of the component. Furthermore, the practicability of the novel compliant mechanism is experimentally validated on the force-displacement test platform. The work in this paper provides a reference for the multi-mode motion mechanical design in a confined space of the latch.