GB834761A - Improved fluid pressure power steering mechanism for a motor vehicle - Google Patents

Abstract

834,761. Vehicle power steering. GENERAL MOTORS CORPORATION. Sept. 18, 1958 [Oct. 2, 1957], No. 29901/58. Class 79(5) In a fluid pressure power steering system operating through a screw shaft 48, Fig. 1, and nut 42 the control valve is actuated by the relative movement between the screw shaft 48 and a manually rotated steering member 16 interconnected by a torsion bar spring 78. The steering member 16 is rotated by a steering wheel (not shown) mounted on a steering shaft 12 connected to the member 16 through a flexible coupling 10. The torsion bar spring 78 passes through the valve body 24 and is connected to the screw shaft 48 which has a recirculating ball connection 50 with the nut 42 and operates the steering gear through a rack and pinion 44. The nut 42 is formed ,as a power piston sliding within the cylinder 40. The servo valve mounted within the body 24 is rotary and comprisesan inner sleeve 70, Fig. 2, mounted on the steering member 16 and positively rotated therewith through a pin connection 72. An outer sleeve 30 is coupled for positive rotation with the screw shaft 48 through a pin and slot connection 60, 62 and is positively connected to the torsion shaft 78 through a flanged end plate 90, 94 having pin connections 88, 102 with the shaft 78 and sleeve 30. Lost-motion connection between the steering member 16 and screw shaft 48 is provided by tangs 100 integral with the shaft 48 and extending with slight clearance into slots of a flanged end 17 of the member 16. The outer sleeve 30 has a central peripheral groove 110 communicating with the power supply line 120 and has a pair of peripheral grooves 112, 114 communicating through passages 130, 132 with opposite ends of the power cylinder 40. The supply groove 110 is connected through radial passages 134, Fig. 7, with axial grooves 140 on the inner face of the sleeve 30 and the power cylinder grooves 112, 114 are connected to slanting passages 136, 138 circumferentially spaced around the sleeve 30 and opening in the region of longitudial slots 146, 148 on the outer face of the sleeve 70. Intermediate lands 162 of the sleeve e 70 have passages 150 communicating with the exhaust line 158 through an annular chamber 54 and Belleville spring 32. Lands 160, Fig. 6, between the grooves 146, 148 have chamfered edges 161 to provide for the circulation of pressure fluid when the servo valve is in the neutral position. In operation, steering effort causes initial twisting of the torsion bar spring 78 with a resultant relative movement between the sleeves 30, 70 to create a pressure differential on opposite ends of the piston 42 to balance the steering resistance. The chamfering 161 provides for gradual increase of fluid pressure so that the feel on the steering wheel is proportional to the steering resistance until the full deflection of the torsion bar spring 78 is taken up.