| 摘要 |
812,207. Vehicle power steering. BISHOP, A. E. Nov. 5, 1956 [Nov. 10, 1955], No. 33712/56. Class 79(5) [Also in Groups XXIV and XXIX] In a variable ratio steering mechanism employing an eccentric or cam-shaped toothed pinion 15, Fig. 1, on the steering wheel shaft 14 meshing with a corresponddngly shaped rack 17 or with a straight rack suitably supported or guided for actuating the dirigible wheels through tierods coupled to ball studs 24, 25, power operation is provided by the admission of hydraulic pressure fluid to chambers 28, 29 on either side of a fixed pinion 26 in a cylinder 21 secured to the track 17. The hydraulic fluid is supplied to the chambers 28, 29 through a tubular supporting rod 18 and a conduit 31 respectively from ports 32, 33 in the gear housing 12 under control of a valve mechanism 16, Fig. 4. This valve comprises a piston member 53 with a central land 54 controlling the exhaust from chambers 28, 29 through conduits 61, 62. The member 53 is centralized in a neutral position by a spring 85 to relieve both chambers 28, 29 but an axial movement one way or the other by a rod 51 the exhaust of one chamber is closed and one of balanced poppet valves 67 at the ends of the cylinder is actuated to supply pressure fluid through an inlet 69 to that chamber to provide power actuation of the steering. Control and followup of the power drive is effected through a coupling 40 (see also Fig. 5) between the steering wheel section 14a of the shaft 14 and the power section, comprising rollers 42 on shaft section 14a operating in inclined slots 43 in a drum 44 on the other section. Initial rotation of the steering wheel causes the rollers 42 to ride up the inclines 43 to effect an axial movement of shaft section 14a and control rod 51 coupled thereto. The control piston 53 is thus actuated to effect power operation and follow-up is effected through rack and pinion 17, 15 to centralize rollers 42 in slots 43 again and thereby centralize piston 53. During power operation "feel" is provided by the hydraulic pressure acting on the end faces 66, 76 of the piston 53 through restricted orifices 70, 80 but this "feel" is limited by relief valves 72, 83 to reduce the force necessary on the steering wheel under conditions such as during parking operations. |
