The W220 Airmatic system is a fully supporting air suspension system which provides both static and dynamic support by means of four air bellows or struts located at the wheels. Each strut has an air bag and a dampener built-in the one unit. The struts get air from an air compressor located behind the front bumper close to the front wheel well. On the opposite side is the central reservoir which supplies pressure via pressure lines and a valve unit. The valve unit is connected to a computer which monitors the air pressure, the vehicle weight, the vehicle height requirement and vehicle stance (angle) and then sets the ride height accordingly.
Higher level of driving safety and ride comfort due to:
Individual adaptation due to:
Driver information due to:
The functions of the AIRmatic with ADS control module are divided as follows:
The following input signals are processed by the function logic component and used for calculations or to provide information:
Function logic component
The conditioned input signals are processed in the logic component and converted into output signals.
A parked vehicle is "woken up" before the engine is started. That is to say, the AIRmatic with ADS control module receives signals from the door contact switches, the trunk switch and infrared remote control indicating that the driver may soon start the engine and drive the vehicle. The current vehicle level is checked immediately and corrected if required. The vehicle level at the front axle is considered to be critical, for instance, if the full wheel angle can no longer be guaranteed. In this case a message appears on the multifunction display in the instrument cluster to warn the driver: "Stop car too low". If the control module is woken (for example by opening one of the doors), there follows a period of spare time before the driver actually starts the engine during which the vehicle level is corrected. This reduces the waiting time required to correct the vehicle level and the vehicle is ready for driving more promptly. Pressure in the main reservoir is used to raise the stationary vehicle. The compressor is only used if the pressure reservoir is empty. It must be ensured that the battery voltage is sufficient to then start the engine.
If the control module detects that all wheels are unloaded when the vehicle is stationary, the valves of the sprint struts are closed. The vehicle therefore remains at the current level. This is essential, for example, when changing a wheel or during repair work (lifting platform).
The AIRmatic with ADS control module monitors all the important components of the system after they are switched on and during operation. The safety circuit detects faulty signals from sensors, faults in the control module and in the electric line system. If a fault is detected, the system is switched off and a message is displayed on the multifunction display in the instrument cluster to warn the driver. The damper valves for ADS are no longer controlled and remain set to the "hard" damping level (driving safety level). In addition, a fault code is stored in the control module. The level control is partially switched off depending on the fault that occurred. The system always strives to maintain the selected vehicle level. Moreover, the safety circuit continuously monitors the battery voltage. If the voltage falls below 10.5 V or exceeds 17.5 V, the system is switched off until the voltage returns to the specified range.
In normal driving mode, AIRmatic works with a pressure of between 6 and 10 bar depending on the load. An electrical compressor is used to supply pressure. This is installed in the AIRmatic compressor unit (A9/1).
In addition the system has an AIRmatic central reservoir (42) which stores the compressed-air. The reservoir pressure is between 13 and 16 bar (at sea level). The system is either supplied with pressure via the AIRmatic central reservoir or via the air compressor.
The AIRmatic at the front and rear axle is a fully supporting suspension system. It keeps the vehicle level constant when the engine is running irrespective of the load. At the same time air from the air compressor is delivered to the spring struts via the valve unit until the vehicle level has been adjusted. The vehicle level at the front axle is recorded by two level sensors at the rear axle and conveyed to the AIRmatic with ADS control module. The level at the individual spring struts is controlled by four level valves in the valve unit and a pressure relief valve on the AIRmatic compressor unit.
An AIRmatic central reservoir for compressed air also enables the vehicle level to be controlled when the engine is not running. In addition the adjustment of the vehicle level is decoupled from the air compressor.
Shut-off position function
If the unloading of all the wheels when the vehicle is stationary is recognized by the control module, the spring strut valves are closed. The vehicle therefore remains at the current level. This is required when changing a wheel or for repair work (hoist) for example.
Normal function (engine running)
When the vehicle is stationary the level is readjusted if there is a difference of more than +/- 10 mm after a door or the trunk lid is opened.
While driving the level is readjusted if there is a difference of more than +/- 20 mm. The level is adjusted to +/- 10 mm every 15 minutes.
Depending on the situation, pressure can be generated by the compressor or the pressure supply of the AIRmatic central reservoir can be used to raise the vehicle. When the vehicle is stationary the pressure from the reservoir is used for noise reasons. Pressure can also be supplied from the compressor and AIRmatic central reservoir at the same time when there is a particularly high pressure demand.
The lowering of the vehicle level is recognized by the control module from the level sensors when loading the vehicle. By actuating solenoid valves air is delivered to the spring struts of the particular front wheel or rear axle until the vehicle has reached its specified value. In addition the pressure relief valve is opened to actuate the respective wheel valve when unloading the vehicle.
Wake-up function (operating period approx. 1 minute)
The AIRmatic with ADS control module is "woken up" using the remote control, door contact switches or trunk illumination switch in order to check the current vehicle level for critical conditions (level too low) and if necessary to raise the vehicle or lower it when unloading. If the vehicle level is lowered by more than 30 mm, it is raised to the normal level by the reservoir (only with a reservoir pressure > 11 bar). At a vehicle level of < -65 mm and even at a reservoir pressure of <11 bar it is raised out of the "critical range" by the compressor to -63 mm (condition: battery voltage > 12.4 V).
If the vehicle level is raised by more than 10 mm when unloading, it is lowered to the normal level by relieving the pressure.
The vehicle cannot be raised by the level control switch.
Function in vehicle condition "Ignition ON"
The same function as for the wake-up function, but without time limit.
Run-on function (operating period approx. 1 minute)
After "ignition OFF" the control module performs changes in the level in order to be able to readjust the vehicle level (raise or lower) during any loading or unloading operations. (The same function as for the wake-up function).
AIRmatic, location of electrical/electronic components:
AIRmatic, location of pneumatic/hydraulic components: