Control Equipment
d) Control Equipment
Level Control Unit
The level control unit (3) is fixed to the bracket on the frame floor and is connected to the lever (81) on the torsion bar by means of a connecting rod (7).
The oil drain plug (3p) in the level control unit serves for reducing the pressure in the system for repairs and test work.
"Neutral" Position
The vehicle is in level position, and the lever (3a) in the middle position.
Oil entering via the supply duct (P) is returned unpressurized via the return flow duct and the return line (T) into the oil reservoir. The discharge valve (3d) remains closed.
"Filling" Position
The vehicle rear end has lowered after loading with the lever above middle position. The control disc (3c) has closed the return flow duct (T). When adequate pressure has built up, the oil is guided via a springless ball check valve to the pressure duct and the suspension elements. By lifting the vehicle rear end into the level position, "neutral" position is attained again. The system is protected against overload by the pressure relief valve (3g) which opens when the maximum permissible pressure is obtained.
"Emptying" Position
The vehicle rear end has risen after unloading and lever below middle position. The control disc (3c) has opened the discharge valve (3d). This will lower the pressure prevailing in the suspension elements. The oil flows through the opened discharge valve and the fully opened return flow duct (T) together with the oil delivered by the pump back to the oil reservoir. When the level position of the vehicle is regained, the control disc closes the discharge valve (3d). Attainment of the basic pressure required for the operation of the spring struts as shock absorbers is assured, independent of the position of the controller, by the fact that any lowering of the pressure in the spring elements below a given value will cause the outer pressure spring of the discharge valve (3d) to push this valve out of the range of the control disc, so that the pressure can no longer drop.