Raising trailing axle, function

W35.50-1023-09

1 Hydraulic cylinder

2 Trailing axle

3 Lift solenoid valve

4 Lowering solenoid valve

5 Motor

A39 Nummek axle

K18 Check indicator relay

K22 End shut-off relay

K23 Lift-lower relay

S97 Lift/lower axle switch

6 Hydraulic pump relay

7 Pressure limiting switch

8 Nummek axle control module

9 Trailing axle display field

The lowered trailing axle can be raised by actuating the lift/lower axle switch (S97).

Function sequence

Function prerequisites:

 Ignition: ON

 Trailing axle lowered

When the ignition is turned on, power is supplied to the lift/lower axle switch (S97).

If the lift/lower axle switch (S97) is pressed up, the switch closes and power is supplied to the lift solenoid valve (3) and to the check indicator relay (K18), end shut-off relay (K22), lift/lower relay (K23) and hydraulic pump relay (6).

The lift/lower relay (K23) picks up and grounds the lift solenoid valve (3) and the hydraulic pump relay (6) via the NC contact of the end shut-off relay (K22). Both the lift solenoid valve and the hydraulic pump relay pick up.

The hydraulic pump relay (6) switches B+ to the motor (5). The motor is switched on and drives the pump component of the hydraulic pump in the hydraulics box. The trailing axle is raised.

At the same time the check indicator relay (K18) picks up and the indicator lamp lights up.

When the pressure in the hydraulic cylinder reaches approx. 140 bar, the pressure limiting switch (7) grounds the end shut-off relay (K22). The relay picks up and remains in its self-holding state. As a result, the grounding of the lift solenoid valve (3) and the hydraulic pump relay (6) is interrupted and both drop out. The motor (5) of the hydraulic pump is switched off.

 If the lift/lower axle switch (S97) is switched to the 0 position before the axle has reached its final position, the power supply is interrupted to the lift solenoid valve (3) and the hydraulic pump relay (6). The trailing axle is not raised completely; it remains at the corresponding height (stepless raising).