Power steering apparatus for vehicle

Claim 1

A power steering apparatus for a vehicle comprising a valve housing provided with a rotary valve body arranged to be turned in one direction or the other by a turning operation of a steering shaft; an oil pressure pump; a power cylinder; an oil supply port connected to said oil pressure pump and selectively connectible with either of two cylinder ports connected to respective left and right chambers of said power cylinder; said valve housing being provided with an arcuate oil pressure reaction chamber, an intermediate partition plate extending from said valve body into said oil pressure reaction chamber to divide said chamber into two areas, each of said areas of said chamber extending on one side and the other of said plate in the turning direction of said valve body and being in respective communication with said cylinder ports, said partition plate dividing said chamber so that said areas are equal in a neutral position of said valve body in said housing, said partition plate tuning with said valve body from said neutral position to travel in said oil pressure reaction chamber during a steering operation to decrease the area on one side of the chamber while increasing the area on the other side of the chamber, the area of the reaction chamber which is decreased by the movement of said valve body and the plate therewith being connected to the cylinder port which is placed into communication with the supply port and thereby pressurized whereas said other area of the reaction chamber is connected to tank and depressurized whereby a differential pressure is established on said plate urging the valve body to return to its initial position.