Basic principle
Basic principle behind all type of air springs are the same, there are some subtle differences between them. Most notably, the reversible sleeve air spring has a piston which is an additional component that the convoluted air spring does
not have. The piston is the component that is fastened to the moving trailing arm or axle mount and as a result plunges in and out of the air cavity within the rubber
bellows. In general, a piston gives the reversible sleeve air spring an advantage over the convoluted air spring in that spring rates can be further tuned using a variety of piston profiles. For straight-sided pistons, the reversible sleeve air spring has an advantage over the convoluted air spring in that a constant load for a given internal pressure may be maintained over a range of heights.
The other two major components of an air spring are the bead plate(s) and the fabric-reinforced rubber bellows or sleeve. The bead plate allows for a rigid attachment to the mounting surface(s) and the bellow is the dynamically
functioning suspension component that contains the air.
Advantages
The main advantages of an air spring over its steel leaf and coil counterparts are:
• Variable load-carrying capability
• Adjustable spring rate
• User-friendly height control
• Low friction action
Variable Load-carrying Capability
As already mentioned, the load an air spring can carry can be adjusted over a wide range, without changing the air spring height, simply by changing the air pressure. Traditional steel springs need to be replaced if the height must be maintained.
Adjustable Spring Rate
In addition to changing the load-carrying capability, a change in air pressure will also afford the benefit of changing the spring rate without changing the height and without a significant change in the natural frequency. Steel springs exhibit one spring rate for a given height and, once again,will need to be replaced if the height must be maintained.
User-friendly Height Control
Using air pressure from the compressor, the air spring height can be maintained by a closed loop control system or adjusted to other desired heights. This allows for “load leveling” and “squatting” capabilities that steel springs cannot offer.
Low Friction Action
Because there is a flexible rubber member separating the rigid attachment points to the frame and suspension, there is freedom to move about all six degrees of freedom without the resistance and squeaks experienced by the rigid interactions characteristic of steel leaf and coil springs.
