Rotary valve for power steering system

摘要

A rotary valve for a power steering system includes a valve sleeve in which a rotor is rotatably carried for controlling fluid flow from a supply pump to a cylinder of the power steering system. A plurality of lands are formed on the outer periphery of the rotor, at least three of which have the same configuration. A plurality of lands are formed on the inner periphery of the valve sleeve, at least two of which have the same configuration to thereby vary the areas of two orifices formed between the three lands of the rotor and the two lands of the valve sleeve at the same rate during relative rotation therebetween. Further, the edge portions of the three lands of the rotor are formed with two longitudinally curved slopes so as to provide an optimum two-step valving characteristic. Furthermore, two of lands formed on the rotor have at each side edge portion thereof a longitudinaly curved and radially extending wall so as to form additional orifice areas to provide an optimum valving characteristic by combining the same with the above two orifice areas.