Experimental Study of Torque Characteristics of Rack and Pinion Steering System

In case of power steering system, the torque applied by the driver is enhanced with additional power supplied in electrical or hydraulic form. Improvement in power steering system is always aimed at reducing the amount of auxiliary power. This paper aims at reducing the resistance of steering system itself instead of incorporating auxiliary power. The amount of steering effort for a stand-alone steering system depends upon a damping force provided by means of spring, which keeps the rack and pinion of the manual steering system (RPS) in constant mesh. Plunger force due to the spring preload being the major source of normal load on gear teeth pair, its variation during operation leads to non-uniform steering effort. This variation can be controlled to obtain desired torque characteristics of the steering system. A series of experiments are conducted where the plunger force is varied to respond to two major modes of vehicle motion namely, straight-ahead and turning. A modified steering system is proposed to obtain desired dual torque characteristic showing high and low torque value for straight-ahead and turning movement respectively.