Hydractive
The Hydractiv is on the hydropneumatic anabolic suspension system for cars of the French car manufacturer Citroën . For the first time, she implemented a suspension with electronically controlled, variable spring and damping coordination.
history
Hydractiv was introduced in 1988 in the Citroën Activa concept and launched in series production in 1989 with the Citroën XM . In 1993, the new generation Hydractiv II came onto the market in the Citroën Xantia, with triple computing power, which was also used in the second series of the XM from 1994.
function
The aim was to implement an electronically controlled suspension. In most versions, the electronics can switch the car between two spring rates so that it is softly sprung during normal driving and still does not lean too much in curves.
For this purpose, an additional spring ball is built into each axis. It is switched on by the control unit as often as possible, with a steady driving style and low lateral acceleration, which results in a softer response of the suspension due to the increased gas volume. A larger bypass hole in the damping valve of this additional third ball also reduces damping (comparable to switching electrical resistances in parallel, which reduces the total resistance according to Ohm's law).
This state is generally brought about by the control unit at speeds below 30 km / h.
If the control unit uses the sensor information to register that the limit values stored in the map are exceeded (abrupt steering movement, heavy braking, teetering of the body, fast tight bends, and so on), it separates the additional spring balls from the hydraulic system . The gas volume, which is now smaller in the remaining spring balls, is now compressed more and the suspension becomes harder. The smaller bypass bores of the remaining shock absorber elements result in a reduced flow cross-section for the hydraulic fluid and thus tighter damping.
Hydractiv I
A control unit decides whether the suspension is soft or hard. If the Hydractiv button in the interior is pressed, the suspension is hard.
Hydractiv II
A control unit decides whether the suspension is soft or hard. If the Hydractiv button in the interior is pressed, the characteristics are changed so that the car is switched to hard even at low cornering speed, acceleration, etc.
Hydractiv III
Introduced with the Citroën C5 . Hydractiv III is the simplest version, without the usual two spring rates. From 110 km / h the vehicle is lowered by a few millimeters at the front and raised by 10 mm at the front and rear on poor roads up to 40 km / h. In addition, the hydraulic pump is electric so that it also works when the vehicle is stationary and z. B. enables the lowering of the rear to load and unload the trunk more conveniently. Without the "Sport" button on the dashboard.
Hydractiv III +
Introduced with the Citroën C5 . Like Hydractiv II, with additional automatic adjustment of the vehicle height as with Hydractiv III. With "Sport" button on the dashboard.
construction
Since the spring stiffness of the hydropneumatics is determined by the pressure and volume of the spring balls , the damping by the size of the bypass hole in the valve pieces (7), this suspension and suspension can be changed by adding one (or more) spring balls to the hydraulic part of an axle Achieve attenuation tuning.
For this purpose, an electrically controlled hydraulic valve (6) was inserted into the connecting lines of the spring ball pairs of an axle , which includes an additional spring ball per axle in the suspension circuit at the command of an electronic control unit (8).
The control unit responsible for their activation switches on the basis of stored maps based on the evaluation of 5 sensors (9)
- Steering sensor
- Speed sensor
- Accelerator pedal sensor
- Brake pressure sensor
- Vehicle height
between the two possible votes.
vehicles
Citroën XM : Hydractiv I, from the beginning of 1994 Hydractiv II. There were also vehicles without Hydractiv.
Citroën Xantia : Hydractiv II. There were also vehicles without Hydractiv and with roll compensation (only in conjunction with Hydractiv).
Citroën C5 : Hydractiv III, Hydractiv III +
Citroën C6 : Hydractiv III + (with two spring balls per rear wheel)