Single-circuit power steering at left full lock function

W46.25-1002-05

Diagram of single-circuit power steering at left full lock (LHS power steering)

1 End limiting valve

2 End limiting adjusting screw

3 Steering gear

4 Control cover (bottom)

5 Primary shaft

6 Control cover (top)

7 Star valve

8 Oil reservoir

9 Power steering pump

10 Working piston

11 Torsion bar

12 Pressure limiting valve

13 Suction valve (replenishing valve)

14 Rotor

15 End limiting adjusting screw

W46.20-1002-05

End limiting valve at left full lock (LHS power steering)

1 End limiting valve

2 Adjusting screw

15 Adjusting screw

A Lower working chamber

B Upper working chamber

Function

When the steering is turned to left full lock, the working piston (10) with the left-hand-rotating circulating ball thread (LHS steering) is moved mechanically in the direction of the upper working chamber (B). The oil has to be passed into the lower working chamber (A) in order to hydraulically assist the mechanical movement of the working piston (10).

When a torque is transmitted by the steering shaft to the primary shaft (5) of the steering, or vice versa, the torsion (11) of the steering gear (3) is misshapen in the elastic range (torsion) so that a relative motion takes place between rotor (14) and the control covers (4 and 6). As a result, the control edges of the rotor (14) are moved out of the middle position (neutral position) vis-à-vis the control edges of the control covers (4 and 6).

The resulting control gap for the oil feed of the lower working chamber (A) is opened when the steering is turned to left full lock, depending on the steering wheel angle, and results in oil flowing into the lower working chamber (A). At the same time the control gap for the oil return flow of the lower working chamber (A) is reduced or closed, depending on the steering wheel angle, in order to build up the necessary pressure in the lower working chamber (A).

As a result of the movement of the working piston, the oil is forced out of the upper working chamber (B) through the opened control gap for the oil return flow of the upper working chamber (B) and flows along the return flow into the oil reservoir (8).

The pressure difference which is produced at the working piston (10) acts on the hydraulic steering assistance. When the piston moves in the direction of the upper working chamber (B) (left full lock of LHS), the end limiting valve (1) is operated in accordance with the setting of the adjusting screw, as a result of which oil is able to flow off from the lower working chamber (A) into the upper working chamber (B) and is passed through the star valve (7) into return flow.

The oil pressure in the lower working chamber (A) is reduced accordingly.