Auxiliary power steering gear for motor vehicles having a common

Abstract

A double acting power boost cylinder comprising a movable servo piston for vehicle steering purposes is provided with means comprising a fixed piston protruding into a bore of the servo piston so as to reduce the effective end surface pressure receiving areas of the servo piston. Thus, the total forces acting to drive the servo piston are reduced to avoid overload or damage to a steering mechanism driven by the servo power piston. The invention has its utility in vehicles where a common hydraulic source is used for various purposes such as steering, brakes, vehicle level and the like where pressures required may vary and where the pressure required for steering is not as great as required for other purposes. Usually accumulators are used and the invention is of particular utility since it permits the use of small pumping devices. In particular, however, the conventional booster steering gear arrangements comprising double acting power cylinders have dimensions and diameters determined by the geometry of gear sectors, within the housing, engaging rack teeth cut into the surface of the servo piston, as well as various other mechanical parts in the housing. Accordingly, the invention permits the reduction in the overall driving force of the servo piston without need for redesign of the overall dimensions of a conventional double acting cylinder arrangement.