Patent GB-1006072-A (GB)
Title: Power steering systems
IPC: B62D5/093
Filed: 1964-07-02
Abstract: 1,006,072. Power steering systems. GENERAL MOTORS CORPORATION. July 2, 1964 [July 25, 1963], No. 27338/64. Heading B7H. In a power steering system wherein the sole connection between the steerable wheels of a vehicle and a steering wheel is an hydraulic circuit including a control valve 16 displaceable from a neutral position within a housing 15 upon rotation of the steering wheel 1 to supply oil from a pump 44 to a rotary metering device 23 which forwards to a steering cylinder 68 an amount of oil dependent on the degree of rotation of the steering wheel, a blocking valve 78 prevents oil flow to or from the steering cylinder when the control valve 16 occupies its neutral position. During normal operation of the system and with the control valve 16 in the neutral position shown, the blocking valve 78 is urged against a spring 81 to a position wherein lands 79, 80 block the oil lines to the steering cylinder 68 by oil pressure in a chamber 87 communicating with passages (Figs. 3, 4, not shown), in the housing 15 through which oil supplied by the pump 44 to an inlet port 47 flows to a groove 74 communicating with a groove 71 having a return port 48 connected to a reservoir 45. Upon displacement of the control valve 16 in either direction one of lands 117, 118 thereon co-operates with a land 72 in the housing 15 to prevent oil flow from the groove 74 to the return port 48, and back pressure in the chamber 87 moves the valve 78 to a position wherein grooves 92, 94 are aligned with the oil lines to the cylinder 68. The valve 78 may be retained in this position regardless of the position of the control valve 16 by depression and retension of a pin 79 by a bayonet connection 95, 96. Forces on the steerable wheels are then transmitted through the hydraulic system to the steering wheel 1 and are resisted only if the steering wheel is either constrained against rotation, or, in another embodiment (Fig. 10, not shown), having a single land on the valve 16 in place of the lands 117, 118, if the steering wheel is rotated in opposition to the force thereon. In the event of power failure, steering may be effected manually, the rotary metering device 23 acting as a pump and the blocking valve 78 occupying the position shown with grooves 91, 93 aligned with the oil lines to the power cylinder 68. The steering wheel 1 is mounted on an upper steering shaft 3 secured in an intermediate shaft 4 with provision for axial adjustment by a wedging nut 5 tightened by a knob 7. The intermediate shaft 4 is aplined to a hollow input shaft 14 through which extends a torsion bar 17 connected to the shaft 14 by a pin 18 and to a rotor shaft 20 (Fig. 8) by a pin 19. Splines 26 at the lower end of the input shaft 14 slidably engage splines 27 within an actuator ring 28 connected to the valve 16 by a pin 31, and slots 29 engage projections 30 on the rotor shaft 20 with lost motion. Helical splines 32, 33 connect the rotor shaft 20 and the actuator ring 28 whereby twisting of the torsion rod upon rotating the steering wheel 1 results in axial displacement of the control valve 16 to move one of lands 115, 116 from a land 49 in the housing, so that oil from the inlet port 47 flows by way of a groove 52 or 59 and passages 55, 56 or 62, 63 to cavities 57, 58 or 64, 65 at either end of two metering chambers in an oval housing 41 surrounding a vaned rotor 22 on the rotor shaft 20. The rotor 22 turns under the influence of the incoming oil to forward through the other cavities 64, 65 or 57, 58 and passages 62, 63 or 55, 56 to the other groove 59 or 52 an amount of oil which is proportional to the initial rotation of the steering wheel since rotation of the rotor shaft relieves twisting of the torsion rod 17 and restores the control valve 16 to its neutral position. The oil from the groove 59 or 52 flows to an adjacent port 66 or 67 and thence by way of the blocking valve 78 to one end of the steering cylinder 68, oil from the other end of the cylinder flowing back to the other port 67 or 66 and thence to the return port 48 either directly around the land 117 or by way of a groove 115, the interior of the valve 16 and radial passages 34. The vanes 37 on the rotor 22 are biased outwardly by springs 39 (Fig. 1), and by fluid pressure applied to the inner edge of the vanes from the metering chambers through non-return valves (Fig. 7, not shown), and passages 108, 109 in a rotor pressure plate 43. The steering cylinder 68 contains a piston 69 connected to the steerable wheels by a rack 70.