- Main parts of air suspension system comprises of compressor , supplying air to air tank
- Pressure to be maintained in air suspension system is around 5.6 to 7 kg/sq.m
- Air bags would be present on each wheel
- As load applied , air bags compressed actuating the leveling valve .
- Air from the tank fills the compressed air bag & hence raise the level of the frame.
- Air from air bag gets released as load on chassis decreases .
LAYOUT OF AIR SUSPENSION SYSTEM:
air suspension layout
Air suspension is a type of vehicle suspension powered by an engine driven or electric air pump or compressor. This pump pressurizes the air, using compressed air as a spring. Air suspension replaces conventional steel springs. If the engine is left off for an extended period, the car will settle to the ground. The purpose of air suspension is to provide a smooth ride quality and in some cases self-leveling
While not using high pressure mineral oil, the system aims to achieve a result similar to the hydro pneumatic suspension arrangement introduced in 1954 by Citroen
WORKING:
A suspension system that is a combination of hydraulic fluid and air has been developed in which the elastic medium is a sealed-in, fixed mass of air, and no air compressor is required.
The hydraulic portion of each spring is a cylinder mounted on the body sill and fitted with a plunger that is pivot-ally attached to the wheel linkage to form a hydraulic strut. Each spring cylinder has a spherical air chamber attached to its outer end. The sphere is divided into two chambers by a flexible diaphragm, the upper occupied by air and the lower by hydraulic fluid that is in communication with the hydraulic cylinder through a two-way restrictor valve. This valve limits the rate of movement of the plunger in the cylinder, since fluid must be pushed into the sphere when the body descends and returned when it rises. This damping action thus controls the motion of the wheel with respect to the sprung portion of the vehicle supported by the spring. They are also called as pneumatic suspensions.
FUNCTIONS OF AIR SUSPENSION SYSTEM:
The suspension system has two basic functions, to keep the car’s wheels in firm contact with the road and to provide a comfortable ride for the passengers. A lot of the system’s work is done by the springs. Under normal conditions, the springs support the body of the car evenly by compressing and rebounding with every up-and-down movement. This up-and-down movement, however, causes bouncing and swaying after each bump and is very uncomfortable to the passenger. These undesirable effects are reduced by the shock absorbers.
ADVANTAGES:
- These maintain a constant frequency of vibration whether the vehicle is laden or unladen.
- Constant frame height is maintained.
- It helps to reduce the load while the vehicle in motion i.e. the dynamic loading as the spring rate variation between laden and unladen weight is much less.
- It gives smooth and comfort ride of the vehicle.
- The stiffness of the system increases with the increase of the deflection.
AIR SUSPENSION PROBLEMS:
- Air bag or air strut failure is usually caused by wet rot, due to old age, or moisture within the air system that damages it from the inside. Air ride suspension parts may fail because rubber dries out. Punctures to the air bag may be caused from debris on the road. With custom applications, improper installation may cause the air bags to rub against the vehicle’s frame or other surrounding parts, damaging it. The over extension of an air spring which is not sufficiently constrained by other suspension components such as a shock absorber may also lead to the premature failure of an air spring through the tearing of the flexible layers.
- Air line failure is a failure of the tubing which connects the air bags or struts to the rest of the air system, and is typically DOT-approved nylon air brake line. This usually occurs when the air lines, which must be routed to the air bags through the chassis of the vehicle, rub against a sharp edge of a chassis member or a moving suspension component, causing a hole to be formed. This mode of failure will typically take some time to occur after the initial installation of the system as the integrity of a section of air line is compromised to the point of failure due to the rubbing and resultant abrasion of the material. An air line failure may also occur if a piece of road debris hits an air line and punctures or tears it.
- Compressor failure is primarily due to leaking air springs or air struts. The compressor will burn out trying to maintain the correct air pressure in a leaking air system. Compressor burnout may also be caused by moisture from within the air system coming into contact with its electronic parts.
- In Dryer failure the dryer, which functions to remove moisture from the air system, eventually becomes saturated and unable to perform that function. This causes moisture to build up in the system and can result in damaged air springs and/or a burned out compressor
