GB855578A - Improvements in and relating to valve control mechanism for hydraulic servo-steeringsystems - Google Patents

Abstract

855,578. Steering motor vehicles. ZAHNRADFABRIK FRIEDRICHSHAFEN A.G. July 24, 1958 [July 24, 1957], No. 23927/58. Class 79(5). A hydraulic servo-steering system, e.g. for motor vehicles, wherein a two-part steering spindle, one part of which carries a thread and steering nut, is provided with a servo-piston acting upon the steering nut and a control member for control of the pressure medium which is displaceable by a member under the influence of the axial spindle force, and is characterized in that the two parts of the steering spindle are provided with inter-engaging ends, rocking bolts being mounted in apertures in the ends and engage and displace the control member which is concentric to the steering spindle. In the steering assembly, Fig. 1, a pump 1 supplies fluid under pressure to a valve 6 through a supply 5, a relief valve 3 and flow regulating valve 4 being provided. A steering nut 23 operating on a worm 22 is disposed rockably within a piston 83. Fluid is admitted to the pressure cylinders 12 and 11 through the conduits 9 and 10 respectively. A return line 7 connects the valve 6 to the reservoir 8. The piston 83 is connected to the steering linkage through a crank drive, not shown. The steering spindle comprises the parts 14 and 22, Fig. 2, having concentric engaging parts 14<SP>1</SP> and 22<SP>1</SP> respectively, rocker bolts 15 being provided, fitted without clearance in recesses in the part 14<SP>1</SP> and apertures in the part 22'. A concentric member 17 is rigidly attached to the member 14 and is provided with apertures through which the bolts 15 pass and which limit the rocking motion thereof by the amount of the clearance provided. The axial movement of bolts 15 is transmitted through bearings 24 to an axially displaceable valve member 25. The pressure fluid enters the valve 6 through the conduit 5 and when in the neutral position, shown in Fig. 2, passes between the valve members 25 and 26, through apertures 33 and 34 and through the space 35 and return line 7. Rotation of the steering wheel causes axial displacement of the member 25 through the rocker bolts 15, according to its direction of rotation. A movement of the member 25 to the left (Fig. 2) closes the control slots 37, 38, so that fluid passes through a bore 39 and groove 40 into line 9 and fluid displaced from chamber 11 returns through line 10, groove 41, bore 42, grooves 29 and 31 and return line 7. Lateral adjustment of valve portion 26 may be effected with the aid of conical-ended screws 48 and 49 engaging conical apertures in the members 26. Bearing adjustment may be provided by a nut 80. Reaction pistons may be fitted to provide a steering resistance at the steering wheel. The valve bush 25 is returned to a neutral position by springs 54, 55. Friction in the transmission of movement between the parts 14, 22 and member 25 is minimised by the bolts 15 rotating whilst transmitting the rocking motion. Pressure in the chamber 21 of the piston 83 upon the worm 22 is neutralised by admitting fluid to the space 74 via ducts 77<SP>1</SP> and 77, a sealing ring 73 being provided. In a modification, Fig. 4, one part, 104, of the steering spindle, engages by its forked end 105 an extension 107 of the other part 106. The inner faces of the fork 105 or alternatively, the outer faces of the extension 107 are spherically shaped. Two hollow rocker bolts 131 and 132 are provided spaced apart by a member 109. The bolts have spherical portions 112, 113, 112<SP>1</SP> and 113<SP>1</SP> by means of which they are mounted without clearance in bores 108, 111 and 110 in the ends of the spindle parts, one bore, 110 in the forked member being larger than the other, 108. Axial movement of the member 106 is transmitted through the rocking bolts and rollers 129, 129<SP>1</SP> mounted upon needle bearings upon the ends thereof to the valve control member 103. Specification 855,579 is referred to.