Additional steered axle steer angle, function

W46.60-1007-05

Schematic of auxiliary steered axle

(Leading axle, left steering direction)

1 Front axle steering gear

2 Drag links

3 Idler lever

4 Hydraulic lines

5 Steering cylinder

5.1 Cylinder chamber (auxiliary steered axle, right steering angle)

5.2 Cylinder chamber (auxiliary steered axle, left steering angle)

6 Hydraulic pump

7 Electric cables

A54 ZL control unit

B86 Front axle steering angle sensor

B87 Auxiliary axle steering angle sensor

Y67 Auxiliary steered axle hydraulic control block

W46.60-1006-05

Schematic of auxiliary steered axle

(Trailing axle, left steering direction)

1 Front axle steering gear

2 Drag links

3 Idler lever

4 Hydraulic lines

5 Steering cylinder

5.1 Cylinder chamber (auxiliary steered axle, right steering angle)

5.2 Cylinder chamber (auxiliary steered axle, left steering angle)

6 Hydraulic pump

7 Electric cables

A54 ZL control unit

B86 Front axle steering angle sensor

B87 Auxiliary axle steering angle sensor

Y67 Auxiliary steered axle hydraulic control block

Function

For steering angle the front axle steering angle sensor (B86) on the steering linkage of the front axle records the current steering angle and the steering direction.

The auxiliary axle steering angle sensor (B87) simultaneously records the current position of the auxiliary steered axle (steering direction and steering angle).

These measured values are processed by the ZL control unit (A54), together with the vehicle speed, giving the specified steering angle and the steering direction of the auxiliary steered axle.

The hydraulic control reacts depending on the steering direction calculated and the deviating angle. The proportioning valve in the auxiliary steered axle hydraulic control block (Y67) is actuated, pressure and volume flow is supplied to the cylinder chambers (5.1 or 5.2) of the steering cylinder (5) accordingly.

The steering cylinder (5) operates the steering linkage of the auxiliary steered axle. If the actual steering angle corresponds to the specified steering angle, the proportioning valve returns to the position of rest.

The ZL control unit (A54) constantly compares the current measured values of the front axle and the auxiliary steered axle with the current calculated specified value for the auxiliary steered axle.

If the steering gear (1) is operated again or if the measured values are outside the tolerance window, the control is reactivated.

If the values are in the parameterized tolerance window the hydraulic control remains in the position of rest.

If the vehicle speed increases above a parameterized value the steering angle reduction starts, i.e. the higher the vehicle speed the smaller the steering angle of the auxiliary steered axle in relation to the steering angle of the front axle.

If the vehicle speed is above another parameterized value steering angle suppression starts, i.e. irrespective of how far the front axle is steered, the auxiliary steered axle remains in the straight-ahead position.

If the steering angle of the front axle approaches the end stop when manoeuvring, steering angle increase is active, i.e. the auxiliary steered axle is also brought to its maximum steering angle when the front axle is on maximum steering angle. This function is limited by the steering angle reduction and steering angle suppression.