GB945318A - Improvements in or relating to motor vehicle steering mechanisms - Google Patents

Abstract

945,318. Motor vehicle power assisted steering. ZAHNRADFABRIK FRIEDRICHSHAFEN A.G. Feb. 9, 1961 [Feb. 13, 1960], No. 4864/61. Heading B7H. In a power-assisted worm and nut steering mechanism wherein the power-assistance valve is controlled by relatively moving parts haying a screw thread connection, spring means are provided to maintain contact between co-operating flanks of the engaging screw parts. As shown in Fig. 1 the steering spindle 2 is provided with a worm 3 engaged by a nut 6 by means of which rotary movement of the steering wheel is transmitted to the steering linkage through a crank drive 10a, 10b, 10c, 10d, and power assistance is provided by a double acting piston 10, the control of the power fluid being provided by valve elements provided by grooves formed in the interior of the piston 10 co-operating with grooves or control edges formed on a cylindrical extension of the nut 6, there being permitted tolerance to provide the appropriate relative movement between the nut 6 and the piston 10. The nut 6 comprises, within the cylindrical extension, a threaded member 24, Fig. 2, located against rotation by a pin 45 and retained by a ring 40. A spring 26 is located between the member 22 and a shoulder 29 and maintains contact between the flanks 34<SP>1</SP> and 35 of the threaded members 24 and 3. Alternatively the spring 26 may be located between the member 22 and a washer which bears against the retaining ring 40 or may be replaced by a corrugated spring washer. In a modification, Fig. 5, the steering shaft comprises two parts 61, 62 having a flanged connection 64, the part 62 having a forked extension 65 having a tongue and groove connection (Fig. 6) with a sleeve member 66 axially slidable in a steering worm 63 on which is mounted, by means of recirculating balls, a steering nut 64<SP>1</SP> conventionally connected to the steering linkage, to which a double acting power piston 107, 108 is also connected, the supply of pressure fluid to which is controlled by a valve spool 80. A member 70 having a slot 71 is connected to the sleeve 66 and one arm of a lever 75 engages the slot, its other arm engaging the valve spool 80 acted upon by a spring 86. A torsion bar 67 is connected to one end of the shaft portion 62 and has a splined connection 67<SP>1</SP> with the steering worm, and a threaded extension 68 engaging a corresponding thread 69 in the sleeve 66. On operation of the steering shaft, if the resistance encountered is sufficient to twist the torsion bar 67, relative rotation is produced between the sleeve 66 and the extension of the torsion bar, whereby, because of the threads 68, 691 axial movement of the sleeve and consequential operation of the valve 80 takes place. The spring 86 maintains the flanks 95, 96 of the threaded portions 68, 69 (Fig. 7) in contact.