Appointment
It is logical that the hydropneumatic suspension shall be operated by hydropneumatic elastic elements. Their role is gas under pressure and a working liquid entered into the special tanks.
Such suspension is called adaptive-the car moves smoothly and is able to change the position of the body over the road. The pneumatic suspension can coexist with other types of suspension. For example, in Citroen C5, the hydropneumosuspension on the front axle is integrated with the McPherson suspension, and on the back, with the multi-side suspension.
But let' s go back to the beginning of the story. At the Paris car dealership in 1955, the new company Citroen DS produced a real buffet. For the automotive industry of the time, it was just a miracle machine. With any number of passengers, regardless of whether the trunk was full or empty, the car kept a steady driveway and provided an unparallesivity of the movement. The machine was not only able to move forward or backward-it was possible to outweigh any wheel without a jack. The ability to manually adjust the height of the bodywork was particularly pleased by motorists. For the French side roads it was important to make it easy to drive in difficult conditions.
For the next thirty years, the device of hydropneumatic signs improved. The result of Citroen is the active suspension of Hydractive, which is used by the French company to this day. The first generation Hydractive 1 appeared in 1989. With electronics, the suspension controls the situation on the road and adjusts to it. Four years later, Citroen cars were equipped with a new Hydractive 2 suspension, and in 2000, Hydractive 3 was introduced, which had a set of the best characteristics of hydropneumatic pendants of previous generations. Unlike the earlier versions, where the suspension was linked to the braking system, in Hydractive 3 the braking system is independent. Such suspension is installed on the current Citroen models-for example, C6. According to the license, Hydractive used Mercedes, Bentley, Rolls-Royce cars for their cars. The latter continue to apply this pattern.
Device
Hydropneumatic surfacers of the Hydractive suspension are bound into a complex system. Modern Hydractive 3 can automatically adjust and adjust the car's light by the desired amount (according to the speed of traffic). In addition, the enhanced version of Hydractive 3 + can regulate its rigidity-depending on the nature of the movement (acceleration, braking, rotation or direct).
The Hydractive 3 hydraulic suspension consists of the following main elements:
-Hydropneumatic stelastic elements;
-Hydroelectronic Unit;
-Rear hydropneumatic cylinders;
-the front pendant;
-stiffness regulators;
-management system.
Hydropneumatic elastic elements are metal spheres. Inside they are separated by flexible partitions. Over bulkhead is nitrogen under pressure. A partition is a liquid that transmits the pressure to the entire system. Earlier modifications used the LHM LHM liquid, and then replaced it with an orange LDS. The elasticity of the bulkheads allows to change the pressure of the gas and the liquid within the spheres. As a rule, one elastic element per wheel is set.
The function of the hydro-electronic unit (or hydrographic) is to ensure the necessary pressure of the fluid in the reservoir and to monitor its quantity. This is done by means of pump and valves.
The back hydropneumatic cylinders with pistons inside the liquid are injected into the elastic elements. Thus, they help to regulate the position of the car in relation to the road surface.
The racks of the front suspension shall be combined hydropneumatic with hydraulic cylinders.
The hardness regulators, which are attached to the front and rear suspension, change its stiffness and ensure that all elastic elements work together in a consistent fashion. The stiffness regulators have additional areas (one for each), so the overall situation on the road is transmitted to them.
The control system combines the electronic unit with the input and the executive devices. The input devices are sensors and the operating mode switch. The sensors shall transmit the mean height of the body and the direction and speed of the rudder. Use the operating mode switch manually (force) to adjust the stiffness of the suspension and height of the body.
How it works
The interaction between these elements is as follows:
The hydropneumatic cylinders are fuelling the liquid in the sphere (elastic elements). The hydroelectronics unit monitors its quantity and pressure. A valve position is located between the elastic elements and the cylinders. When the body fluctuates, the liquid passes through the valve-and the oscillations are overshadled.
In soft mode, all hydropneumatic elastic elements are combined, the volume of gas is maximum. The elastic elements maintain the necessary pressure and the heeling of the car is compensated.
When there is a need to enable the suspension of the suspension system, the control system automatically gives the voltage. Then the cylinders, the front suspension racks and the additional areas (stiffness controls) are isolated from each other. In turn, the stiffness may change for a single elastic element, and in a straightest direction, for the whole system.
Hydractive is slightly different from the Active Body Control design-the system of active body control developed by the engineers of Mercrdes. However, the principle of work is very similar: the hydraulic cylinders are squeezoned, the pressure changes, and the position of the body and the stiffness of the suspension is set.
Volkswagen developed its version of adaptive suspension. The DCC System (aDaptive Chassis Control) controls the adjustment of shock absorbers using sensors and changes the rigidity of the chassis.
The pros and cons. Operational issues
The advantages of hydropneumatic suspension clearly include the possibility of manually changing the height of the body. This helps to overcome obstacles, as well as provides convenience of parking at the curb, loading-unloading and cleaning of the car. In addition, automatic regulation of the position of the body is also provided for.
Another plus is comfort during the trip thanks to the easing of the move. Many car owners point out that they are floating on the water, not on a solid asphalt.
And, of course, we must not forget about the adaptability of hydraulic pneumatic suspension-it is adapted to the most different road surfaces and driving styles.
However, these signs have drawbacks. First, the hydraulic pneumatic suspension system is complex, and it is not expensive to manufacture. The weight of the suspension increases the price of the car. The repair of this machine will also cost the owner.
Secondly, the reliability of hydropneumatic sub-signs is somewhat lower than usual. Such suspension is quite delicate, and therefore it is not always good to withstand extreme loads.
