AIR SUSPENSION SYSTEM

AIR SUSPENSION SYSTEM

ABSTRACT:

In air suspension systems, conventional metal spring is replaced by a rubber bellows or an air-bag at each wheel.
In this system an air compressor, driven by the engine of the car or by an electric motor, to provide a source of compressed air which inflates the suspension units. The latter usually take the form of rubber bags, partly folded inwards on themselves and termed rolling lobes. A piston on the suspension arm to which the wheel is attached forces the base of the bag inwards, or compresses the rubber bellows, when this is used instead of a rolling lobe. Levelling valves, also operated by the movements of the suspension arms, maintain the correct riding height for the vehicle, admitting additional air when the vehicle is loaded and the suspension units are compressed, and releasing air when the load is reduced.

Some form of delay mechanism is normally incorporated in the levelling valve to prevent it responding immediately to every movement of the suspension arm or the body of the car.


INTRODUCTION:

The automobile chassis is mounted on the axles, not direct but through some form of springs. This is done to isolate the vehicle body from the road shocks which may be in the form of bounce, pitch, roll or sway. These tendencies give rise to an uncomfortable ride and also cause additional stress in the automobile frame and body. All the parts which perform the function of isolating the automobile from the road shocks are collectively called a suspension system. It includes the springing device used and various mountings for the same.

1. Objective of Suspension System

The following are the objectives of suspension system,

• To safeguard the occupants against road shocks and provides riding comfort.
• To isolate the structure of vehicle from shock loading and vibration due to irregularities of road surface without affecting its stability.
• To minimise the rolling and pitching tendency.
• To keep vehicle body in perfect level while travelling over rough roads.
• To support the weight of the vehicle.

2. Basic Suspension movements

• Bouncing – The complete body movement in the vertical direction on rising up and down of vehicle body known as ‘Bouncing’.
• Pitching – The rotating action produced in a vehicle about a transverse axis through it parallel to ground known as ‘Pitching’. It is due to out of phase movement of front suspension with respect to rear suspension causing rotating effect in the vehicle.
• Rolling – The centre of gravity of the vehicles is considerably above the ground. Due to this reason, while taking the turns, the centrifugal force acts outwards, on the C.G. of vehicle, while the road resistance acts inward, at the wheels. This gives rise to a couple turning the vehicle about a longitudinal axis. This is called rolling. (Ref. Fig. 1.2))


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