Hydropneumatic suspension#Hydractive

The Hydractive is an anabolic on the hydro- pneumatic suspension system for passenger car of the French car manufacturer Citroen. She realized for the first time a variable suspension with electronically controlled, variable spring and damping settings.

Since the spring hardness of the hydropneumatic is determined by pressure and volume of the spring balls, the attenuation by the size of the bypass hole in the valve members ( 7) can be achieved by adding one (or more ) spring balls in the hydraulic part of an axis of a variation of the suspension and achieve damping settings.

For this purpose, the ball spring couples a shaft was inserted in each case one electrically controlled hydraulic valve ( 6) in the connecting lines, that includes an additional spring in the ball per axle suspension circuit upon command of an electronic control unit (8) towards each.

The responsible for their activation control unit switches the basis of stored maps based on the evaluation of five sensors (9 )

• Steering sensor
• Speed sensor
• Accelerator sensor
• Brake pressure sensor
• Travel sensor

Between each of the two possible votes to.

The aim is to combine a comfortable, soft suspension with a sporty yet - taut road-holding.

The control unit switches by activating the Hydractive valves add the additional spring ball on each axis, which results by the so enlarged total gas volume, a softer suspension response. A reduction of the damping is achieved due to the larger bore of the bypass valve in the damping of this additional third sphere ( similar to the parallel connection of electrical resistances through which the overall resistance is lowered in accordance with the Ohm's law ).

This condition is by the control unit as much as possible with a uniform procedure, when the sensor information is at a limit, and generally at speeds below 30 km / h induced.

If the control unit on the basis of sensor information to exceed the stored in the characteristic field values ​​registered ( abrupt steering movement, heavy braking, the see-saw body, fast tight curve, etc.), it separates the additional spring balls from the hydraulic system. The relatively lower gas filling pressure in the remaining balls spring is compressed more from now on, the total volume is smaller and the suspension thus harder. Reduced the overall cross-section for the hydraulic fluid through the smaller holes of the remaining bypass shock elements results in firmer damping.

History

Hydractive was introduced in 1989 with the Citroën XM. In the first series to 1994, built the XM initially very unreliable so-called Hydractive I learned two updates in the form of a new computer ( host H1, H2, H3). In 1993 came the Citroën Xantia, the new generation Hydractive II (computer H4) with triple computing power on the market, which has been used since 1994 in the second series of XM.

• Citroën
• Chassis Technology