Rear Axle Height & Integral Pneumatic Suspension Systems
Rear Axle Height Adjustment
The body always remains at the factory design height. The system adjusts air pressure in the air springs according to the load, modifying the stiffness coefficient. This achieves a constant frequency and comfort regardless of the load.
Constitution
- Level Transmitter: Located on the rear axle, this sensor measures variations in the distance between the axle and the bodywork.
- Air Springs: Air bags with a sealed internal piston that allows them to fold on their outer perimeter. Raising and lowering the level is achieved by increasing or decreasing the air pressure through an electrically powered air suspension system.
- Level Adjustment Warning Light: A light on the instrument panel that indicates if there are issues with the system or if it is disabled. Blinking indicates high or low level issues, requiring diagnosis of actuators and leveling components.
- Air Feeder Group: A metal box containing the following components:
- Compressor: Provides pressurized air.
- Dehydrator Filter: Prevents water from entering the air circuit.
- Discharge Valve: (3/2 N/C) Decreases the normal level for maintenance and limits air pressure.
- Suspension Valve: (2/2 N/C) Releases air from the air springs.
- UC (Control Unit): Monitors and diagnoses the suspension system.
- Compressor Relay: Powers the compressor’s electric motor, commanded by the UC.
Function
The engine-driven compressor provides pressurized air. The piston’s movement draws air through a filter into the crankcase. The air then passes through the upper valve, the dehydrator, and finally to the valves and air springs. This process is controlled by the UC, which activates the system when needed. If the load decreases and the suspension needs to lower, the discharge valve opens and releases air. The system compensates for changes in rear axle load, which can be verified with diagnostic equipment.
Integral Pneumatic Suspension
This system controls all four wheels, maintaining a constant vehicle height at its theoretical value. It utilizes four level sensors (transmitters) that communicate with the compressor and solenoid valves to adjust the air volume in the air springs. The system offers four manually selectable positions and automatically adapts to various driving conditions.
Constitution
- Air Supply Group
- Compressor Temperature Sensor: An NTC sensor controlled by the UC to determine compressor operating time.
- Solenoid Valve Block: Contains the pressure sensor and solenoid valves that control air flow to the air springs.
- Pressure Sensor: Measures pressure in the telescopic suspension arms using two electrodes that form a capacitor. The distance between the electrodes varies with pressure, changing the capacitance.
- Air Reservoir
- Level Transmitter
- Control Panel: Allows for manual adjustment of the suspension height.
Function
The system maintains a constant vehicle level based on the driver’s selected height or automatically adjusts based on input from the level sensors, which transmit data to the UC. Each suspension unit is controlled by a solenoid valve.
Pressurization:
If the vehicle is parked on an uneven surface, the system individually adjusts the air pressure in each air spring to compensate for the unevenness.
Depressurization:
Air is released from the system through a valve, a pneumatic silencer, and a filter. The desiccant in the dehydrator is regenerated by passing air through it.
Lock:
If the UC detects a loss of air pressure in all four wheels, the valves close to maintain the current vehicle level.