GB1460257A - Power-assisted steering gear particularly but not exclusively for motor vehicles - Google Patents

Abstract

1460257 Power-assisted steering apparatus ZAHNRADFABRIK FRIEDRICHSHAFEN AG 27 March 1975 [29 March 1974] 12930/75 Heading B7H The steering gear of a power-assisted steering system for a motor vehicle is of the type in which a spindle 5, Fig. 1, coupled by recirculatory balls 3 to a nut 4 acting on an output shaft 6, moves axially against the biasing force of a spring device 13 to operate a control valve device 7 controlling fluid flow to a power-assistance servomotor 27, the steering gear being characterized in that the control valve device 7 comprises a first reaction chamber 18, Fig. 2, connected by a bore 25 to a connection 26 for the servomotor, a second reaction chamber 19 which is disposed adjacent a collar 20 of a spool valve member 10 and which is connected by a bore 28 to a further connection 29 for the servomotor, an elastic sealing ring 17 providing a seal between the first reaction chamber 18 and an annular chamber 14 communicating with a reservoir return connection 15 and formed between the valve member 10 and an axial extension 8 of the spindle 5, and seal members 21, 22 providing a seal between the second reaction chamber 19 and chambers 23, 24 communicating with the reservoir return connection 15. The illustrated construction of the steering gear is intended to minimize friction forces occurring during operation of the steering gear. Axial movement of the extension 8 of the spindle 5 are transmitted to the spool valve member 10 through thrust bearings 11 and 12.