Patent ID: 6896093

Claim:
An integral power steering apparatus comprising: a housing; an input shaft for being connected to a steering wheel for rotation therewith; a piston mounted in the housing for longitudinal motion and defining a pair of hydraulic chambers including a first hydraulic chamber and a second hydraulic chamber in cooperation with the housing; a first motion transmission mechanism coupling the input shaft and the piston for transmission between rotary motion of the input shaft and longitudinal motion of the piston; a control valve disposed between a hydraulic pressure source and the pair of hydraulic chambers for variably regulating fluid flow to each of the first hydraulic chamber and the second hydraulic chamber; a second motion transmission mechanism coupling the piston and a steerable wheel for transmission between longitudinal motion of the piston and swinging motion of the steerable wheel; a communicating passage; a first valve disposed between the first hydraulic chamber and the communicating passage for fluid communication therebetween during hydraulic pressure in the first hydraulic chamber being greater than or equal to a predetermined threshold pressure and during displacement of the piston being greater than or equal to a predetermined threshold distance in a direction to decrease volumetric capacity of the first hydraulic chamber; and a second valve disposed between the second hydraulic chamber and the communicating passage for fluid communication therebetween during hydraulic pressure in the second hydraulic chamber being greater than or equal to a predetermined threshold pressure and during displacement of the piston being greater than or equal to a predetermined threshold distance in a direction to decrease volumetric capacity of the second hydraulic chamber.