GB1329410A - Control valves for controlling the pressure medium of power- assisted steering gear - Google Patents

Abstract

1329410 Power assisted steering mechanisms ZAHNRADFABRIK FRIEDRICHSHAFEN AG 19 April 1972 [29 April 1971] 18120/72 Heading B7H A power assisted steering-gear control valve comprises damping pistons 27, 28 each slidably arranged in axial bores in reaction pistons 23, 24, fixed in relation to valve cylinder 19, and associated outer and inner damping chambers, e.g. 29, 33 connected with a feed chamber 3 and with an annular groove 10 of the valve piston 2 respectively via choke bores 31, 35 which lead into outer and inner annular chambers 47, 49. In the central position of valve piston 2 annular grooves 10, 11 are connected with feed chambers 3 4 respectively and with the central return groove 7. Holes 45, 46 in valve cylinder 9 connect annular grooves 10, 11 with cylinder chambers 14, 15 of servomotor 16. Piston 17 together with steering gear housing 18 forms the servomotor 16. As piston 2 is moved out by pin 20 according to the rotation of a steering wheel (not shown) feed chamber 3 is placed into communication via groove 10, bore 45 and pipe 12 with cylinder chamber 14 and the other chamber 15 is connected via pipe 13 with central return groove 7 via bore 46. The outer damping chamber 29 of reaction piston 23 is connected via choke bore 31 and annular chamber 47 with feed chamber 3, and the inner damping chamber 33 is connected via annular chamber 49, and choke bore 35 with feed chamber 3. The choking action of choke bores 31, 35 and annular chambers 47, 49 provide damping to the movement of valve piston 2. Outer and inner damping chambers 30, 34 are connected with feed chamber 4 and return groove 7 respectively, thus pressure medium which is sucked in as a result of the enlargement of chambers 30, 34 can flow therein without any increased resistance. When the valve piston 2 is moved in the opposite direction the converse effects are obtained. The outer annular chambers 47, 48 advantageously have a smaller radial dimension than the inner annular chambers 49, 50.