Single-circuit power steering in left steer, function

W46.25-1002-05

Diagram of single circuit power steering in left steer (left-hand drive vehicle steering gear)

1 Pressure reduction valve

2 Adjustment screw for limiter

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 Operating piston

11 Stabilizer bar

12 Valve pressure limiting valve

13 Suction valve

14 Rotor

15 Adjustment screw for limiter

W46.20-1002-05

Pressure reduction valve in left steer (left-hand drive vehicle steering gear)

1 Pressure reduction valve

2 Adjustment screw

15 Adjustment screw

A Lower working chamber

B Upper working chamber

Function

When steering to the left the working piston (10) with a left-hand recirculating ball thread (left-hand drive vehicle steering systems) is shifted mechanically towards the upper working chamber (B).

The oil must be lead into the lower working chamber (A) in order to assist the mechanical movement of the working piston (10) hydraulically.

When torque is transmitted from the steering shaft to the primary shaft (5) of the steering or vice versa, the torsion bar (11) of the steering gear (3) is deformed in the elastic area (torsion) so that a relative movement takes place between the rotor (14) and the control covers (4 and 6). As a result the control edges of the rotor (14) are moved out of the center position (neutral position) in relation to the control edges of the control covers (4 and 6).

The resultant control gap for the oil feed of the lower working chamber (A) is opened when the steering is turned to the left (left-hand drive vehicle) depending on the steering wheel angle and causes the oil to flow into the lower working chamber (A). Simultaneously the control gap

for the oil return of the lower working chamber (A) is reduced or closed depending on the steering wheel angle in order to build up the required pressure in the lower working chamber (A).

The oil from the upper working chamber (B) is driven out by the working piston movement over the open control gap for the oil return of the upper working chamber (B) and reaches the oil reservoir (8) via the return.

The arising pressure differential on the working piston (10) causes the hydraulic steering assistance.

When the piston moves towards the upper working chamber (B) (left steer-LHD) the pressure reduction valve (1) is operated corresponding to the adjustment screw setting, as a result of which oil can flow from the lower working chamber (A) into the upper working chamber (B) and is lead via the star valve (7) into the return.

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