Dynamic Modeling of Ratcheting Devices in Transmissions 2004-01-1327

Ratcheting Devices are often used in automatic transmissions to provide a unidirectional power flow to achieve specific gear functions. These devices consist of two members that rotate relative to each other and a locking mechanism between these two rotating parts. In order to meet certain gearshift needs, the ratcheting device performs a combined overrun and engagement function. In both modes the components experience high-speed rotation and are subjected to significant impact forces. The high impact forces between the components may cause damage on the parts and the device may fail to function as intended. It is important to understand the dynamic behaviors of these ratcheting devices and the key design factors affecting their performances under various operating conditions. Vehicle tests and/or laboratory tests are often conducted to investigate the dynamic performance of these devices. However, these tests are costly and time consuming and sometimes impossible to simulate the real world situations. It makes dynamic modeling essential to help better understand the dynamic characteristics of the ratcheting device, and to provide design engineers with physical insights and direction for problem resolution. In this paper we describe the development of a dynamic model with ADAMS to simulate a ratcheting device in automatic transmission systems. The dynamic behaviors of the ratcheting device are investigated under various operating conditions. The mechanism consists of two rotating parts, namely, the notch plate and pocket plate. A locking component called strut sits in the pocket plate with a preloaded spring located in the pocket underneath to provide the necessary engaging force. In the dynamic modeling, all the rotating inertias of the connecting parts are lumped into the notch plate and the pocket plate. The strut is modeled as a solid body with 6-degree of freedom, governed entirely by contact, impact, fluid damping, and spring forces. Real world operating situations are taken as the input loading conditions. The key design parameters that affect the dynamic behaviors of the mechanism are investigated in this study.