VALVOLA ROTATIVA PER IL CONTROLLO DI MECCANISMI DI STERZATURA SERVO ASSISTITI

摘要

A rotary valve for controlling fluid to a power assistance device of a steering gear. A rotor 6 is mounted in the bore 5 of a relatively rotatable sleeve 3 so that displacement of control regions 12 to 15 on the rotor relative to ports 42 to 45 controls fluid flow through two pairs of supply ports 38 to 41. Of the eight ports in the sleeve and rotor assembly two pressure ports 42 and 43 are circumferentially spaced in the sleeve bore and disposed alternately with respect to two low pressure return ports 44 and 45 to be controlled one by each of the four control regions to direct fluid to the power assistance device 26 (for actuation of that device to assist in a steering manoeuvre which imparts the relative displacement between the sleeve and rotor). Each of the return ports 44, 45 is formed by a slot 50 which extends axially in the sleeve bore to open into a radially extending end face of the sleeve and therethrough be in constant communication with a fluid return chamber in the valve. Both slots 44 and 45 can open into a common fluid return chamber or into fluid return chambers at opposite axial ends of the valve. Preferably both return ports 44 and 45 are in the form of slots which extend axially through the bore 6 of the valve sleeve so that they each open into chambers at opposite axial ends of the valve sleeve.