Hydropneumatic Suspension
General
The hydroneumatic suspension is a gas pressure suspension system with hydraulic level control. The vehicle load
is supported by four suspension elements, which are simultaneously serving as shock absorbers. The suspension
elements comprise one gas pressure shock (13, 20, 30 and 31) each and one pressure reservoir (11, 12, 28 and 29),
which are connected to each other by means of a hose line (Fig. 1 and 2). The vehicle load is hydraulically transmit-
ted to the pressure reservoirs by way of the gas pressure shocks. Suspension is effected by the compression and
decompression of the gas cushion in the pressure reservoirs.
To regulate the vehicle level, the oil volume in the gas pressure shocks is increased or reduced by means of a
pressure oil system. The pressure oil system comprises the pressure oil pump (1), the pressure regulator (3a), the
central pressure reservoir (4) and the oil reservoir (2). The pressure regulator (3a) and the adjusting switch (3b) of the
control device are combined into one valve unit (Fig. 2)
The central pressure reservoir supplies the system when the engine is stopped.
The control device controls the oil volume by means of one level controller (6 and 24) each at front and rear axle
and by the adjusting screw (3b) of the valve unit. The following adjustments of the system can be made by means of
the adjusting switch:
N = Normal Level
(Switch pushed-in or control disc at front stop)
S =- Locking Position
(Switch engaged in center position or control disc pulled in first detent)
H = Higher level
(Switch completely pulled or control disc pulled in second detent)
M = Assembly Position
Suspension system up to level controllers pressureless (control disc pulled against rear stop with pull knob re-
leased)
Operation
The pressure oil pump driven by the engine delivers oil from oil reservoir to central reservoir via pressure regulator of
valve unit.
When the max. oil pressure in central reservoir is attained, the pressure regulator of the valve unit will reverse the oil
flow. The oil now delivered can flow back into the reservoir.
If the pressure in the central reservoir drops to minimum pressure as the result of consumption (lowering on level
controller) the pressure regulator will reverse and oil will be pumped into reservoir until the max. pressure is again
attained.
The pressure oil in central reservoir is connected to the adjusting switch of the valve unit and to the level controllers
by means of pertinent lines.
If the vehicle level drops under the influence of a load, the level controller will open the passage to the suspension
elements. The oil flowing into the suspension elements will lift the vehicle until the normal level is attained and the
level controller has again closed the connection. If the vehicle load is relaxed, the level controller will permit oil to
flow from suspension elements until the vehicle is back to its normal level. The oil flowing out of the suspension
elements is returned to the oil reservoir through a filter
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