The suspension of our cars (III): hydropneumatic Suspension

The hydropneumatic suspension is based on a different concept that the suspensions simple or conventional. It has, among other things, the advantage of keeping the vehicle height constant regardless of the weight or inertia of the latter. It was invented by Citroen and they were the first to incorporate this type of suspension your car series in 1954, first in the rear suspension of the Traction Avant, and then, and so total, in the mythical Citroen DS 1955.

The objective of this suspension is all about comfort, maintaining the softness of a firm in a poor state and of course in the curves. Although it is true that this suspension has certain advantages over the steel suspension, it is also true that it has many disadvantages due to its degree of complexity.

During its release, the own Citroen suffered a negative impact, since many of their cars could not be repaired by any mechanic who has not had training in the system, depriving the brand of the beneficial “network effect” and forcing customers to go to dealers of the brand that had both training and tools necessary.


The Citroen DS of 1955 was the first car to incorporate a hydropneumatic suspension total

The hydropneumatic suspension consists of a circuit with the following elements:

  1. A deposit
  2. A set-circuit breaker
  3. Correction height
  4. pump pressure
  5. A safety valve
  6. 4-cylinder suspension (one for each wheel)

As we can see by the number of elements involved in this type of suspensions, the level of complexity with respect to the suspension of classical spring-damper is far superior.


Different elements of the hydropneumatic suspension

general Operation of the circuit

When a wheel deals with an irregularity in the terrain, it is moved in ascending or descending order. When the movement is upward, the piston rises pushing the fluid into the interior of the sphere by compressing the gas. When the movement is downward, the gas is expansiona pushing the liquid towards the cylinder of the suspension. Once past the obstacle, the pressure recovers its equilibrium value and the piston returns to its initial position.

The damping effect gets by limiting the passage of liquid towards the inside or outside of the sphere, since the sphere is where they are staying steps calibrated to perform the buffer effect. The elastic element of the suspension is the gas that allows the ascent and descent of the wheel.

The hydropneumatic suspension is currently in disuse, in favor of other systems that are cheaper and much more efficient as the suspensions smart of which we shall speak soon.