GB1254673A - Improvements in or relating to power-assisted steering mechanisms, particularly for motor vehicles - Google Patents

Abstract

1,254,673. Power-assisted steering mechanism. ZAHNRADFABRIK FRIEDRICHSHAFEN A.G. 8 May, 1970 [10 May, 1969], No. 22308/70. Heading B7H. In power-assisted vehicle steering mechanism comprising a steering spindle 2 and worm 3 connected for relative rotation through a torsion bar 1, and two valve pistons 15, 16 slidable in a valve body 4 on the worm 3 and engaged by pins 13, 14 carried by the spindle 2 so that the valve pistons are displaced in opposite directions upon relative rotation of the spindle and worm, pre-stressed centring springs 55, 56 are disposed between the valve pistons 15, 16 and the valve body 4 to supplement the centring effect of the torsion bar 1. Washers 51, 52 carried by adjustable set screws 47, 48 on a supported member 46 on the valve housing 4 limit expansion of the springs 55, 56 to prevent them influencing the valve pistons 15, 16 in their neutral position. Control edges 32, 35, 38, 39 of the valve pistons 15, 16 control communication between grooves 23, 24 connected to a steering motor and pressure fluid supply and return ports 19, 20. One of reaction pistons 40, 41 is subjected through a passage 42, 43 to the pressure at the groove 23 or 24 which communicates with the supply port 19 during a steering manoeuvre. In another embodiment, Fig. 3 (not shown), both centring springs are operative in both steering directions. In a further embodiment, Figs. 4, 5 (not shown), the centring springs are accommodated in hydraulic damping chambers which replace the reaction pistons. Each damping chamber is sealed by a diaphragm spring and vented through a throttle opening. Additional retaining springs coaxial with the centring springs ensure positive engagement between the valve pistons and pins.