Power steering apparatus for vehicles

Abstract

Power steering apparatus for a vehicle comprising a rack rod operatively connected to a steering wheel and supported in a steering gear casing, the rack rod being drivable by a power cylinder consisting of an outer cylinder fixed to the steering gear casing, an inner cylinder disposed in the outer cylinder and fitted into the steering gear casing, and a piston mounted on the rack rod to divide the interior of the inner cylinder into first and second oil chambers. A control valve is mounted on the lower surface of the steering gear casing for controlling the operation of the power cylinder. The second oil chamber is in communication with the outer cylinder via the spaces between the coils of a coil spring, the inner cylinder being supported in floating state on the outer cylinder by the coil spring. A pair of parallel, annular or semi-annular oil passages are provided in that portion of the steering gear casing which is engaged with the inner cylinder. The oil passages are respectively in communication with a pair of output ports of the control valve. The oil passages are also in communication at respective upper portions thereof with the outer cylinder and the first oil chamber separately. Due to these internally provided oil passages, the number of parts and assembly steps of the apparatus can be minimized. Because the inner cylinder is supported in floating state by the coil spring on the outer cylinder, it can be kept concentric therewith so that the piston can be operated smoothly at all times. The mounting of the control valve under the gear casing leaves a large space above the gear casing for the installation of the engine.