Evaluation of Torque Characteristics of Rack and Pinion Steering Gear Using ADAMS Model

The Rack and Pinion Steering (RPS) gear differs from the conventional rack and pinion gear arrangement. In Rack and Pinion Steering gear, the pinion has smaller diameter with fewer numbers of teeth. The steering gear has crossed helical gearing arrangement with the rack having circular cross section. A preloaded spring is used to keep the gears in constant mesh. While the rack and pinion is in motion, the rack shows undesirable motions like rolling. Center distance between the rack and pinion also varies. These introduce variation in the torque required to rotate the pinion. The power loss in the gear box due to torque variation cannot be estimated easily due to unpredictable motions of the rack. To estimate the torque required to rotate the pinion, it is necessary to consider various frictional interfaces and their behaviors. The RPS is modeled in commercially available simulation software, ADAMS (Automatic Dynamic Analysis of Mechanical Systems) on the component level, where involute profile of the gear and non-standard meshing conditions like crossed helical gear joint with spring preload, flexible mounting of the rack are modeled to reproduce the actual behavior. Validation of ADAMS results with those available from the experiments, makes the virtual prototype suitable to study the RPS in depth and test several possible improvements before a real prototype is attempted.