Steering: Description and Operation
DESIGN AND DESCRIPTION OF BALL AND NUT POWER STEERINGThe housing contains a complete mechanical steering gear. the control valve and operating cylinder. Steering spindle (1) is connected elastically with worm (3) via torsion bar (2) and with valve pistons (4 and 5) without play. The valve pistons are installed transversely in the worm head. The connection between piston (6) and worm (3) is accomplished with an infinite line of balls. When turning the worm the balls are taken up at one end by circulating tube (7) and put out again at the other end of the balls. Piston (6) and sector shaft (8) are meshed. The special shape of teeth on the sector shaft permits zero-play adjustment with an adjusting screw.
In neutral position of valves (4 and 5) the oil flow delivered by the pump passes through the steering and can flow through the opened feed and return control edges to the cylinder chamber and return flow. Hydraulic support cuts in when valve pistons (4 and 5) are moved out of neutral position. This happens when force is transmitted from the steering wheel of from the steering drop arm via the sector shaft and pistons to the worm. Torsion bar (2) then serves as a link. It deforms itself in the elastic range and returns the valve pistons to neutral position after releasing the steering wheel. Moving valves (4 and 5) will let the oil flow into only one of the operating cylinder chambers and in this manner support the rotating motion of the steering spindle and/or counteract the bit from rough roads.
Steering Wheel in Neutral Position:
Oil flows from the impeller pump into the worm head, through feed grooves (9 and 10) or radial grooves (11 and 12). From here via connecting bores to the right and left cylinder chambers and via opened return flow grooves (13 and 14) back to the oil tank. The valve is also illustrated in cross section
15 = Pump
16 = Oil tank
17 = Safety valve
18 = Control valve
Steering Wheel Turned Clockwise:
Valve piston (4) is displaced to the right and feed groove (91 opened. Valve piston (5) is displaced to the left and feed groove (10) closed. This lets the oil flow into the right cylinder chamber. Oil in the left cylinder chamber is forced out and flows beck into the oil tank.
Steering Wheel Turned Counterclockwise:
Valve piston (5) is displaced to the right and feed groove (10) opened. Valve piston (4) is displaced to the left and feed groove (9) closed. This lets the oil flow into the left cylinder chamber. Oil in the right cylinder chamber is forced Out and flows back into the oil tank.