Load regulation of air suspension, function

S32.22-0520-11

1 Inlet filter

2 Compressor

3 Drier with check valve and throttle

4 Drain valve

5 Electric motor

6 Transverse shutoff valve block

Task

The main task of air suspension is the adjustment of the vehicle level depending on load. This task is taken over by a closed loop, consisting of two height sensors (one each for the left and right side of the air suspension), the air suspension control module, the compressor unit, the air bellows and one transverse shutoff valve for each closed loop.

The vehicle level is constantly reported by the height sensors (right, left) to the control module.

Function

A Vehicle level too low (deviation > 20 mm)

If the vehicle level drops by more than 20 mm below the normal level when the vehicle is stationary, the compressor is switched on by the control module.

The check valve and the transverse shutoff valve of the closed loop which at this moment is at a low level are opened, the pressure in the bellows is increased until the vehicle level is adjusted again at the left and right of the rear axle.

If the vehicle level is still always outside the tolerance range of normal level, the pressure in the air bellows is increased alternately by cyclical actuation of the transverse shutoff valves until the vehicle specified level has again adjusted itself.

B Vehicle level too high (deviation from 7 to 20 mm)

If the vehicle level is more than 7 mm above the normal level for more than 3 seconds, the control module opens the discharge valve in cycles and actuates and opens the transverse shutoff valves alternately in cycles The pressure in the air bellows is slowly reduced via the throttle. This achieves a slow approximation of the vehicle level to the normal level. If the normal level is reached, the discharge valve is closed.

The check valve remains closed, the transverse shutoff valves are open. The pressure in the air bellows is slowly reduced via the throttle.

If the normal level is reached, the discharge valve is closed.

C Vehicle level much too high (deviation > 20 mm)

If the vehicle level rises by more than 20 mm above the normal level, the discharge valve is fully opened until the deviation is less than 20 mm. As of this level point the lowering process is continued as described under section B.