Lowering trailing axle, function

W35.50-1019-09

1 Hydraulic cylinder

2 Trailing axle

3 Lift solenoid valve

4 Lowering solenoid valve

5 Motor

6 Hydraulic pump relay

7 Pressure limiting switch

8 Nummek axle control module

9 Trailing axle display field

K20 Lowering relay

K21 Lifting end shutoff relay

K52 Lowering relay

K53 30 km/h lowering relay

K54 30 km/h self-holding relay

S95 Lower axle ON switch

S96 Overload switch

A39 Nummek axle

K14 Starting-off aid time relay

K16 Lower time relay

K17 Drop-off delay time relay

K19 Lowering end shutoff relay

The raised trailing axle can be lowered in three ways.

1. By actuating the lower axle ON switch (S95).

2. Automatically when the vehicle exceeds a speed of 30 km/h and a drive axle load of 9 t is reached.

3. Automatically when the key in the steering lock is turned back from the driving position (longer than 15 seconds).

Function sequence for 1:

Function prerequisites:

 Ignition ON

 Trailing axle raised

 Speed < 30 km/h

If the lower axle ON switch (S95) is pressed down, the switch opens. The lowering relay (K52) drops out immediately and switches to its idle state.

-----------------------------------------------------------------------------------------

The power supply to input S is interrupted at the lower time relay (K16).

 The lower time relay, however, remains active for another 15 seconds.

The lowering solenoid valve (4) is supplied with power via the lowering relay (K52) and lowering end shutoff relay (K19) in its idle state. The lowering relay (K20) simultaneously picks up and supplies power to the hydraulic pump relay (6).

The hydraulic pump relay (6) picks up and switches B+ to the motor (5). The motor drives the pump component of the hydraulic pump in the hydraulics box. The trailing axle (2) is lowered.

The relay (K2) is also supplied with power and picks up. As a result the indicator lamp inversion relay (K1) and indicator lamp self-holding relay (K3) drop out and the display in the trailing axle display field (9) extinguishes.

-----------------------------------------------------------------------------------------

The pressure limiting switch (7) closes once the pressure reaches 128 bar. The lowering end shutoff relay (K19) is supplied with power via diode box V1 and switches via the diode box V10 to self-hold.

As a result the power supply is interrupted to the lowering solenoid valve (4) and the hydraulic pump relay (6) and they drop out. The motor (5) of the hydraulic pump is switched off.

Function sequence for 2:

Function prerequisites:

 Ignition: ON

 Drive axle load 9 t.

 Trailing axle raised

 Speed > 30 km/h

When the vehicle reaches a speed of > 30 km/h, power is supplied to the output B4 of the limit value sensor A56. The sensor picks up and supplies power to the 30 km/h lowering relay (K53).

When the drive axle load exceeds 9 t, the overload switch (S96) increases its resistance and the self-holding function of the starting-off aid time relay (K14) is no longer active.

The lowering solenoid valve (4) is supplied with power via the NC contact of the starting-off aid time relay (K14), the 30 km/h lowering relay (K53), the 30 km/h self-holding relay (K54) and the NC contact of the lowering end shutoff relay (K19).

The trailing axle is lowered in other cases as described for function sequence 1.

 It is no longer possible to raise the axle because the limit value sensor A56 picked up and interrupted the power supply at the lift axle switch (S94).

Function sequence for 3:

Function prerequisites:

 Ignition: ON

 Trailing axle raised

 Vehicle stationary

When the ignition is turned off, the power supply to input S of the drop-off delay time relay (K17) is interrupted. After 15 seconds, terminal 30 is switched thus interrupting the power supply to input S at the lower time relay (K16).

 The lower time relay, however, remains active for another 15 seconds.

The trailing axle is lowered in other cases as described for function sequence 1.