Air Spring: Description and Operation

DESCRIPTION
Four system-specific shock absorbers are used in the Automatic Ride Control (ARC) system, which consists of two similar shocks in the front and two similar shocks in the rear. Enclosed in each shock absorber is an air spring and a mechanism that enables switching between soft and firm damping. To repair a faulty shock absorber, replace the shock absorber as a unit.

OPERATION
The air spring integrated into each shock is capable of independently raising and lowering each corner of the vehicle based upon the pressure and volume of air supplied. The ARC system regulates the pressure in each air spring by compressing and venting system air. Increasing air pressure (compressing) raises the vehicle and increases the total spring rate (spring effect of the air shock plus the front torsion bar of rear leaf spring) of the wheel being modified. Conversely, decreasing air pressure (venting) lowers the vehicle and effective spring rate to a minimum in which the front torsion bars or rear leaf springs support the vehicle. Vehicle height is then maintained by the addition and removal of air in each air shock.

Inside each shock assembly is a hollow piston rod that contains a small rotary DC motor. The motor is connected through gear reduction to a bypass valve that opens or closes a fluid path through the piston rod. When the bypass valve is open, hydraulic fluid is allowed to flow through the piston rod as well as through fixed piston (base) valving, resulting in a soft damping rate. When the bypass valve is closed (by rotating the motor), hydraulic fluid is forced only through the piston (base) valving, resulting in a firm damping rate.