Hydropneumatic suspension: the principle of

Hydro-pneumatic suspension is a car unit which consists of elastic elements, interacting among themselves by means of hydraulic and pneumatic power. Modern system of this design is known under the name Hydractive. In the third generation provides automatic adjustment of the characteristics that makes the node active, depending on road and other transport conditions. Consider the features and characteristics of this unit.

History

For the First time hydropneumatic suspension "Citroen" appeared in 1954. It is on this stamp machine was tried more modern, in comparison with analogues, the system. In the intervening period, the designers actively worked on this site, I made drastic changes.

In modern times has been used for the third generation of this type of active suspension. The design allows to minimize the influence of human factor. Such a system license is also used by the companies, the ‘rolls Royce" and «Mercedes».

Advantages

The Main advantage of hydropneumatic suspension is smooth operation and minimum transmission of the shock to the car body. In addition, there is a possibility of adjustment of the clearance. The latest generation of the system is able to adapt to the driving style. High efficiency suppresses vibration even at fast driving on rough roads or sharp turns.

Manufacturers that have the official right to release the system often combine it with similar type "MacPherson". The complexity of the design and the high price cause that this node is primarily used in expensive cars.

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For Example, a hydropneumatic suspension “Citroen C5" aggregates with a multi-link unit in the rear, and the front is combined with ‘McPherson”. This combination makes it cheaper and easier to maintain. The main development site is in two directions: to increase functionality and improve reliability.

Device

Hydropneumatic suspension, the latest generation consists of the following elements:

• Front suspension rack.
• Hydro-pneumatic cylinders on the rear axle;
• Hydraulic and electronic unit;
• Reservoir for hydraulic fluid.

Each item performs its function, but, in some cases, may still be present in the circuit of hydraulic steering amplifier.

Combined hydroelectronic block (BBB) ensures stable system pressure and fluid level. Additional devices include:

• Motor;
• Pump;
• Piston;
• Electronic controls;
• Shut-off and safety valve.

The container of fluid is placed on the GEB. Front combines the hydropneumatics and the cylinder, and between them is the valve of depreciation, which is responsible for reduction of oscillations of the body of the car.

Work item, and a cylinder

Hydropneumatic suspension equipped item, which is a metal sphere inside of which is a multilayer membrane. Above it, the space is filled with liquefied nitrogen, and in the lower part there is a special liquid. Consequently, the fluid provides the pressure, and the gas serves as the primary elastic element.

The Latest modification of the considered node is equipped with one elastic detail at each wheel and a pair of spheres on the axis of the vehicle. Incremental elastic elements significantly increase the range of adjustment of rigidity, and the scope of grey used in the system have a working life of not less than 200 thousand kilometers.

A Hydraulic cylinder is used for the storage of liquids intended for elastic elements. In addition, it performs the function of a regulator of height of the body relative to the track. Item consists of a rod, the piston connected to the suspension arm. The front and rear cylinders are identical in construction, but back copies are placed at an angle.

Control stiffness

This item is designed to change suspension stiffness. The regulator consists of depreciation and the solenoid valve spool and additional areas. To achieve ultimate softness node allows you to pump the maximum internal volume of gas. When this solenoid valve is disconnected from the power supply.

When activated the solenoid valve hydropneumatic suspension goes into hard mode. In this case, the rear cylinders, the extension of the sphere and stand are in isolation from each other.

Additional input devices are sensors, switches modes. On the node type Hydractive 3 provides the sensors for measuring the height and angle of the steering wheel. Another indicator monitors the speed and rotation of the steering wheel. The switch forces a break in the height of the machine and the stiffness of the suspension.

Electronic control unit

The ECU is used for making and processing signals of the input devices. It then gives the signal to fit the suspension. The electronic unitcontrol usually operates in tandem with the engine control system and antilock brakes.

Actuator hydropneumatic suspension Citroen include an electric pump motor, headlight range control, valves. The motor controllably changes the rotational speed, the pressure in the system and the performance of the pump. In the latest generation of the considered node uses four solenoid valves, two of which regulate the rear axle, and the remaining pair – front analogue. Mostly these elements are placed in the liquid level regulators.

The Principle of operation of the hydropneumatic suspension

The Reporting node is used to automatically control ride height, adjust the stiffness and forced changes in these indicators. Adjustment of the clearance takes into account movement speed, manner of driving and road surfacing. For example, at a speed more than 110 km/h ground clearance is reduced automatically by 15 millimeters. On a bad road, and low speed (60 km/h or less), this parameter is increased by 20 mm. it Should be noted that the height is maintained regardless of the load.

This possibility exists due to the special fluid circulating in the loop system. This gives you the ability to maintain a given level of the car body when driving on rough roads.

The Work of the hydropneumatic suspension category “+” differs in that it provides for automatic adjustment of stiffness depending on acceleration on turns, at sharp braking and driving straight. The control unit takes into account the vehicle speed, the steering parameters, and other aspects, evolving in the course of the drive.

The System automatically controls the solenoid valve stiffness, increasing or decreasing this figure. Stiffness can vary for a particular wheel or on all elements. The designers have also provided for manual control of changes in clearance.

Repair and maintenance

A hydropneumatic suspension device which is described above, is quite expensive. Therefore, its repair will cost “money”. Below are approximate prices for repair of certain elements of the system:

• Fix a hydraulic shock absorber – from two thousand rubles.
• Replacement of the regulator stiffness – from 4.5 thousand.
• The Same procedure on the front of the field – 700 rubles and above.
• The Cost of the liquid used in the third generation – not less than 600 rubles.

The Final cost depends on the configuration of the host, and year of the car. It should be noted that the failure of one of the items often entails failure of other elements. As can be seen, the service will have to spend, but it's worth it.

Hydropneumatic suspension "Citroen C5": reviews

As confirmed by the owners, the main advantage machine “Citroen C5” is precisely the presence of the described suspension. And, as if to criticise it competitors, it allows to keep car confidently and smoothly on virtually any road surface. The reporting node allows you to adjust ground clearance of 15 to 20 millimeters in the direction of decrease or increase. It happens in automatic mode.

Among other advantages, users indicate smoothness, ease of removal of the wheels and the durability of the unit. Negative features consumers include high cost of repairs. In addition, when you move almost not to notice pits and potholes, which leads to more intense wear and tear of the suspension

Conclusion

The hydropneumatic suspension is undoubtedly a breakthrough in the automotive industry. It automatically allows you to adjust a range of parameters. Apparently, not in vain the license to use it has gained such giants of industry as the ‘rolls Royce" of the "Maserati" and «Mercedes». However, the first variation of the invented Paul Mages (French designer).

Starting test innovative site occurred on the Citroen Traction Avant in 1954. The company is still successfully uses this system, constantly modifying and renewing it. With the development of progress and dramatic improvement, but still one of the best in its class is considered to be the third generation of the Hydractive hydropneumatic suspension.