Power steering casing capable of operating in a power-assist mode and also capable of operating in a strictly mechanical mode

摘要

A power steering casing capable of operating in a power-assist mode and also capable of operating in a strictly mechanical mode. The power steering casing includes an inner cylinder where there is disposed a piston affixed to an end of a rack bar. The rack bar projects outside of the steering casing for connection to steering linkage of the vehicle. The steering casing is in communication with a valve which controls the passage of a power-assistance fluid in response to turning of a steering wheel. The valve comprises a jacket and a valvular nucleus. The valvular nucleus is connected to the vehicle's steering column, while the jacket is connected to a bushing on the pinion. The pinion meshes with the rack bar. The bushing is connected, via an anchorage piece and pin, to a torque bar that coaxially extend through the valvular nucleus from the bushing to the steering column. Relative rotation of the valvular nucleus with respect to the valvular jacket permits hydraulic fluid to flow through the casing and thereby provides power assistance to the steering effort. Such relative rotation between the valvular nucleus and the jacket is selectively prevented by a blocking dowel which selectively locks the torque bar, via its anchorage piece, to the bushing and valvular nucleus so that all of these elements rotate together for direct transmission of steering wheel rotation to the pinion of the rack bar. The blocking dowel selectively prevents the relative rotation in response to vehicle speed and the amount of torque on the steering wheel.