GB1380360A - Rack and pinion power assisted steering - Google Patents

Abstract

1380360 Power steering CAM GEARS Ltd 10 July 1973 [20 July 1972] 34039/72 Heading B7H In an hydraulic power assisted steering system including a valve spool 17 actuated axially in response to relative rotational and axial movement of two members 13, 22 interconnected by helically disposed resilient elements 24, the valve spool 17 is adapted to be urged against the actuation by a servomotor pressure resulting from the actuation. In a preferred embodiment steering torque from splined connection 21 is transmitted via helical spring wires or beams 24 to lower element 22 coupled by a pin 23 to column part 3. Relative rotation between connection 21 and part 3 causes rod 15, locked with element 13 and connected by pin 16, to move valve spool 17 axially. The ends of the spool 17, i.e. 17A and 17B, are sealed by 0-rings in body 18 thus forming pressure chambers 18A, 18B connected by ducts 20 to connections 19C, 19D which supply one or other ends of the servomotor cylinder 8 formed on a rack bar 6. The part 3 has a pinion which engages a rack on bar 6. When one of the connections, e.g. 19D, is pressurized from an accumulator via connection 19A, like pressure is applied in chamber 18B to the end of the spool which is urged in this case upwards tending to return the spool to its centre position. The rod 15 having a slot 15A is screwed in element 13 and locked by a grubscrew 15B which arrangement affords adjustment of spool 17 in its body 18. Parallel pins 14 act as cotter pins to provide torque between parts 13, 3 in the event of hydraulic failure. In an alternative arrangement an open centre valve arrangement, in which the supply of pressure fluid is of continuous nature such as an engine driven pump, is employed.