Air suspension

from Wikipedia, the free encyclopedia

The air suspension system is a suspension system that the compressibility of gases , in particular air exploited. A simple example is the air mattress ; the systems used for vehicle suspension are a more complex example .

Types

Air spring, cut
with hose roll bellows

Air springs in road vehicles are built in two forms.

Air spring with constant volume in the normal position
Here, the air is typically enclosed in a rolling bellows, which is connected to other fitting parts such as the cover and rolling piston in an airtight manner. The bellows is slipped over the piston and rolls on it under pressure. The air spring is supplied with compressed air by a compressor. Depending on the load, air is pumped in or out in order to keep the filling volume and thus the level of the vehicle constant. There are different designs such as belt bellows or half-roll bellows in rail vehicles. The bellows is placed on a rubber spring, the so-called emergency spring, which still ensures a certain spring effect if the air suspension fails. The air spring achieves the greatest gain in comfort in conjunction with an adaptive damping system. The pressure level in the normal position is approx. 5 to 12 bar, with dynamic compression approx. 10 to 20 bar, depending on the load.
Gas springs with constant gas mass
Here a certain gas mass is enclosed in a spring element. As the load increases, the volume decreases and the suspension becomes stiffer. Level compensation is achieved by an additional hydraulic system ( hydropneumatic from Citroën ).

advantages

The following advantages come into play in vehicles compared to metallic springs:

  • Sensitive response as there is almost no self-damping.
  • Preselectable and / or electronic air suspension / automatically adjustable preload: This allows the height of the vehicle body to be adjusted or held independently of the load ( level control ). It should be noted, however, that the suspension becomes harder under heavy loads. In buses, it is common to lower the vehicle body at times to make it easier to get in and out by deflating the bellows on the side of the doors ( kneeling ). The vehicle body is then based on mechanical emergency running springs, which are necessary in the event that the air pressure fails.

Passenger cars

The Cowles-MacDowell Pneumobile Company from the USA manufactured passenger cars with air suspension between 1914 and 1915.

General

In car -construction air suspension (in 2008) a clear upper classes mark and was in some vehicle types, for example, since the mid-1950s Cadillac Eldorado Brougham the Borgward P 100 , the Mercedes-Benz 300 SEL and the Mercedes-Benz 600 used . Air suspension, on the other hand, has not been used on a broad front due to its construction effort.

In car construction, in addition to simple and inexpensive steel suspension (for well over 95% of vehicles), hydropneumatics are also a competing system for air suspension. This is a Citroën development and was a typical feature of the manufacturer's medium and large sedans ( DS , SM , GS , CX , BX , Xantia , XM , C5 , C6 ), but was also licensed for the Mercedes-Benz 450 SEL 6.9 and installed in the Rolls-Royce Silver Shadow .

The first electronically controlled semi- active wheel suspension was in 1986 in combination with air suspension in the Toyota Soarer and from 1989 in Toyota Celsior (Lexus LS): Toyota Electronic Modulated Suspension (TEMS, current name: Adaptive Variable Suspension).

In the S-Class from Mercedes-Benz , the electronically controlled air suspension called Airmatic has been used as standard since 1998, with the exception of the top model S 600, which is equipped with the so-called Active Body Control suspension. This is an active chassis based on a conventional steel suspension with special hydraulic elements. The ABC chassis is technically superior to air suspension due to its fast response times in all driving situations. Air suspensions rely on stabilizers to support the body when cornering (increase the roll spring rate), which can be omitted with the ABC chassis.

For some time now, there has been an increase in the proportion of upper-middle-class and luxury-class cars with standard or optional air suspension.

Earlier cars with air suspension

(Selection)

Current cars with air suspension

(As of 2013, selection)

Air suspension for retrofitting

For several years there have been companies that have specialized in "air suspension" for retrofitting in series vehicles. There is full air suspension, which takes over the complete suspension, for show purposes these are also referred to as airride , or systems that support the standard suspension. This improves driving comfort and safety. These systems mostly use polyurethane bellows . The air pressure can be changed here either with a standard tire inflation device or with a retrofitted compressor.

Commercial vehicles, buses

Truck air suspension (black rubber bellows)
Remote control of a truck air suspension

General

Air suspension is also used in commercial vehicles, for example in buses . There, in many modern bus models, she can tilt the vehicle towards the curb to make it easier to get in and out (kneeling). Another area of ​​application for air suspension is trucks; almost half of all commercial vehicles in Europe are now equipped with it. With the help of the level control, a semi-trailer, for example, can be easily and uncomplicatedly detached and attached .

Current commercial vehicles with air suspension

(Status 2007, selection)

Almost every commercial vehicle manufacturer now offers air suspension.

railroad

Air suspension on a Stadler KISS multiple unit
Air suspension on a bogie

Modern passenger cars and railcars (e.g. ICE 2 ) have air suspension between the bogie and the car body. It mainly serves to improve driving comfort as well as for automatic level control, this ensures a constant height of the car floor above the upper edge of the rail . The constant height ensures, especially on local passenger trains, that the floor of the car is often level with the edge of the platform in order to enable barrier-free access for wheelchair users.

In addition, the air pressure in all bellows is determined and reported to the vehicle control system. This determines the current load status, the change of which can be up to 6 tons per car per stop in local traffic, and automatic load braking is controlled via the brake control in order to avoid overbraking and to achieve the best possible deceleration.

Aircraft

The airship LZ 129 Hindenburg (built in 1936) had air-sprung landing gear legs.

See also

Individual evidence

  1. ↑ kfz-tech.de: air suspension
  2. ^ A 75-Year History through Data> Automotive Business> Products, Technology> Technical Development> Chassis . Toyota. 2012. Retrieved January 19, 2015.
  3. ↑ Archived copy ( memento of the original from January 10, 2015 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.lexus.de
  4. ↑ basf: Cellasto - spring decoupling - lasting driving comfort
  5. ^ Karl Gerhard Baur: Bogies - Bogies. EK-Verlag , 2nd edition, Freiburg 2009, ISBN 978-3-88255-147-1
  6. ↑ https://www.hochsitzszuege.com/deutschland/ice-2.php
  7. ↑ https://books.google.com/books?id=m_nZDAAAQBAJ&pg=PA197&lpg=PA197&dq=luftfederung+ice&source=bl&ots=O6T5zTyeDK&sig=ACfU3U1H2E_SA5tBXqljikB6VYmmCSLgOg&hl=en&sa=X&ved=2ahUKEwiMwJaFxIbjAhWEpYsKHXh2AxI4ChDoATAAegQIAxAB#v=onepage&q=luftfederung%20ice&f=false

literature

  • Rolf Isermann (Ed.): Vehicle dynamics control; Modeling, driver assistance systems, mechatronics . Friedr. Vieweg & Sohn Verlag, GWV Fachverlage GmbH, Wiesbaden 2006, ISBN 978-3-8348-0109-8 , Chapter "12 Electronically Controlled Air Spring Systems".
  • Stefan Breuer, Andrea Rohrbach-Kerl: vehicle dynamics; Mechanics of the moving vehicle . Springer Fachmedien, Wiesbaden 2015, ISBN 978-3-658-09474-4 , section "6.3.1.4 Air suspension", doi : 10.1007 / 978-3-658-09475-1 .