GB1410956A - Power directing system - Google Patents

Abstract

1410956 Power-assisted steering mechanism A G FONDA 28 Nov 1972 54864/72 Heading B7H [Also in Division G3] A power-assisted steering mechanism comprises an input member, an output member, gear mechanism operatively connecting the input and output members, power actuating means for displacing a reaction element of the gear mechanism to increase the movement of the output member in response to a movement of the input member, and power control means responsive to a movement of the input member for controlling the power actuating means. As shown, a manually operable input shaft 71 terminates in a worm 73 engaged through recirculating balls 77 with a nut 78 rotatably mounted in a rack 81 meshing with a sector gear 82 on a pitman shaft 83. So that the nut 78 can be displaced to a greater extent than corresponds purely to rotation of the worm 73, the nut 78 is rotated by an irreversible hydraulic or electric rotary actuator 75<SP>1</SP> connected to a shaft 75 which has a non-circular end portion 74 received in a non-circular portion 79 of the nut. Operation of the actuator 75<SP>1</SP> is controlled in response to relative rotation between an inner control member 97 which roates with the shaft 71 and an outer control member 96 which rotates with a gear 95 meshing with a gear 94 on a threaded member 92 engaging a local extension 91 of the rack 81. The pitch of the threaded member 92 is greater than that of the worm 73 so that total movement of the rack 81 is, for example, twice as great as would be produced solely by rotation of the input shaft 71, and the pitch may vary along the length of the member 92 to provide a varying amplification factor. The gear 94 is frictionally engaged with a hub 93 on the member 92 so that the gear can slip to permit manual operation of the mechanism in the event of power failure. The threaded member 92 may be moved axially with consequent rotation by an actuator 99 which may be controlled automatically in response to lateral acceleration, yaw velocity, or speed of the vehicle. In other embodiments, the reaction element displaced by the power actuating means is the fulcrum of a lever, a wedge, the annulus of an epicyclic gear train, the worm of a worm and nut gear, or the rack of a rack and pinion gear.