Nivomat level control, function - GF32.30-P-2300P

MODEL 203.2 (except 203.242 /243 /246) as of 13.1.03 with CODE (480) Level control system at rear 

MODEL 203.242 /243 /246 with CODE (480) Level control system at rear 

Fig 1: Nivomat Level Control, Function Diagram

Rebound 

The pump (29) of the Nivomat system is driven by the piston rod (31). As the piston rod (31) extends (rebound movement) the size of the pump chamber increases. Oil is drawn out of the low pressure reservoir (27) into the pump chamber through the suction pipe, the hollow pump rod and the open inlet valve.

Jounce 

As the piston rod moves in (31) (jounce movement) the size of the pump chamber decreases, the inlet valve closes and the outlet valve opens. Oil is pressed between the outer side of the control sleeve and the inner side of the piston rod (31) into the working chamber. Oil is simultaneously forced out of the working chamber through the open side of the cylindrical tube into the high pressure reservoir (26). The pressure on the gas cushion of the high pressure reservoir (26) is increased during pumping.

Hold level 

As the vehicle approaches the specified level, a groove becomes accessible. This groove is located on the pump rod and is concealed by the control sleeve until the specified vehicle level has been reached. The opened groove forms a bypass (28) between the pump chamber and the high pressure reservoir (26). As a result, oil is no longer drawn from the low pressure reservoir (27), rather oil is only pressed between the pump chamber and working chamber.

Lower level 

When the vehicle is unloaded when stationary, the piston rod (31) first extends since the balance between the Nivomat extension force and the Nivomat load is disturbed. As the piston rod (31) extends, a drain hole (30) at the pump rod is exposed which is otherwise covered by the control sleeve. The drain hole (30) allows oil to flow from the high pressure reservoir (26) into the low pressure reservoir (27). This results in a reduction in pressure.