Hydropneumatic Suspension Systems: Mechanics and Operation

Hydropneumatic Suspension: Benefits and Drawbacks

Item 8-1. Hydropneumatic suspension: Provides excellent flexibility and allows for ride height adjustment independent of vehicle load.

Advantages

• Ensures suspension comfort and elasticity.
• Maintains constant ride height.
• Controls the center of gravity and improves operation.
• Cushions are suspended within the block to save space.
• Increased security in the event of a puncture.
• Reduced maintenance requirements.

Disadvantages

• If a leak occurs, the suspension collapses, softens the axles, and the vehicle becomes immobilized.

Principles of Hydraulic Suspension

The liquid ensures the movement and binding of moving parts due to its incompressibility. Gas provides elasticity, replacing the mechanical spring suspension. Damping is achieved by passing fluid through holes in the dampers, which also perform height adjustment functions.

System Components

• Main Components: Tank, pump, and accumulator.
• Damping Components: Side-involved suspension blocks and height correctors.

Hydraulic Main Circuit

This system generates and distributes flow to the vehicle's hydraulic circuits, including brakes, steering, and suspension.

Key Elements

• Fluid Reservoir: A container that stores liquid to ensure pump supply and allow for return and recovery after use.
• Pressure Source: A high-pressure mechanical pump with constant flow (Q). As the shaft rotates, the piston completes its full stroke; each turn produces admission and expulsion. Flow depends on the number of pistons, their capacity, and the RPM.
• Pressure Regulator: The conjuntor-disjunctor ensures regulated working pressure. It features two spring-loaded valves tared to a working pressure of 145 bar (minimum) and 170 bar (maximum) to saturate the accumulator volume.
  • Disjunction (170 bar): Pressure closes the springs, feeding the flow.
  • Conjunction (145 bar): Pressure reaches the level required for the regulator to supply the system, closing the tank outlet until pressure returns to 170 bar.
• Hydraulic Accumulator: Stores hydraulic fluid to supply the system during high demand and improves circuit elasticity. It contains a membrane dividing the area into two parts: one with high-pressure nitrogen and the other receiving pressurized liquid.
• Safety Valve: Prioritizes fluid supply to safety-critical systems like brakes and steering over the suspension. It may include a valve activated by a contactor at rest or a pressure-activated manocontact to inform the dashboard.