1010 Hydropneumatic automatic height correction suspension Citroen Figs 10701071 and 1072

The front suspension may be either a MacPherson strut (Fig. 10.70) or a transverse double wishbone arm arrangement (Fig. 10.71(a)), whereas the rear suspension is of the trailing arm type. Front and rear anti-roll bars are incorporated to increase the body roll stiffness and to actuate both front and rear height correction valves.

Spring unit (Fig. 10.71(a)) The suspension spring units (Fig. 10.71(a)) comprise two main parts;

1 a steel spherical canister containing a rubber diaphragm which separates the nitrogen spring media from the displacement fluid;

2 a steel cylinder and piston which relays the suspension's vertical deflection movement to the rubber diaphragm by displacing the fluid.

When the wheel meets a hump in the road, the piston is pushed inwards so that it displaces fluid from the cylinder into the sphere. Consequently the flexible rubber diaphragm squeezes the nitrogen gas into a small space (Fig. 10.71(b)). If the wheel hits a pot hole, the pressurized gas expands and forces fluid from the sphere into the cylinder, thereby making the piston move outward. By this method of changing the volume of fluid entering the sphere, the gas either is compressed or expanded relative to the initial charge pressure so that the resilience of the gas prevents the force of the road shocks from transferring to the body structure.

Pump accumulator and pressure regulator (Fig. 10.70) The initial fluid pressure source comes from a seven piston swashplate engine-driven hydraulic pump which is able to provide a continuous flow of fluid at a predetermined pressure. The pump feeds the spherically shaped accumulator which uses nitrogen as the spring media and a rubber diaphragm to accommodate the volume of stored fluid. The accumulator stores the highly pressurized fluid and can immediately deliver fluid to the system in the event of a sudden demand. It also permits the pump to idle and therefore eliminates repeated cutting in and out.

When the pump is idling the pressure generated is only enough to return the fluid to the reservoir through the pressure regulator. The pressure regulator and accumulator unit control the minimum pressure necessary for the operation of the system and the maximum pressure needed to charge the accumulator and to limit the maximum pressure delivered by the pump (the pump cut-in pressure of 140-150 bar and the cut-out pressure of 165-175 bar).

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