Effect of Pinion Profile Modification on Rack and Pinion Steering Gear

Low rack gain and high reduction gear ratio in the case of Rack and Pinion Steering (RPS) gear of an automobile puts a limit on pinion diameter. The tooth strength for small diameter pinion is achieved by reducing the number of teeth. Undercutting is avoided by resorting to a pinion profile shift. The profile shift has effect on frictional characteristics of the steering gear. Considerable higher tooth load makes it important to consider the friction variation. This variation in friction is responsible for variation in steering effort. In order to reduce the undesirable torque variation, contribution of pinion profile modification to the variation in torque is analyzed by taking into account the friction variation and sliding velocities.