Do You Truly Understand Air Suspension for Semi Trailers?

Air suspension structure

The air suspension used in semi-trailers in China is basically European-style air suspension, mainly composed of front support frame, rear support frame, spring beam, spring beam axis, air spring, shock absorber, and U-bolt.

The air spring is the core component of the semi-trailer air suspension, and its performance directly determines the performance of the suspension. The upper end of the air spring is connected to the semi-trailer frame, and the lower end is connected to the spring beam. The two ends of the spring beam are respectively connected to the air spring and the front support frame hinge points, and the middle is fixed to the axle through the U-shaped bolts. The shock absorber is connected to the spring beam and the front support frame through the hinge point.

Air suspension working principle

When working, the semi-trailer air suspension is connected to the semi-trailer air supply system. The air supply system includes a height adjustment valve. When the load of the vehicle increases and the suspension height decreases, the height adjustment valve controls the air supply system to supply air to the air spring, and the pressure in the airbag increases. When the vehicle load decreases, the height adjustment valve controls the airbag to deflate so that the suspension height can be maintained at the design position.

Air suspension important parameters

Stiffness

The stiffness of the suspension is a measure of the ability of the suspension to resist deformation, which refers to the vertical load that must be added to the suspension per unit distance of upward movement of the wheel center relative to the chassis and body (that is, even if the suspension produces a unit vertical compression deformation). In the actual working process of semi-trailers, the main constraint to stiffness comes from the lateral inclination angle limitation.

Durability

The durability of the air suspension refers to the service life of the air suspension under a certain load while maintaining quality and function, generally expressed by the number of vibrations. From a structural point of view, the transmission of force and torque between the vehicle axle (vehicle bridge) and the frame of the semi-trailer air suspension is highly consistent with the working load of the air suspension and the axle.

Smoothness

Smoothness is the ability of a vehicle to maintain the influence of vibration and shock on passenger comfort and cargo integrity within a certain range during driving. The smoothness of semi-trailers is closely related to the performance of air suspension.

The suspension system is coupled with multiple systems of the vehicle, which is related to the smoothness, stability, and acceleration and braking performance of the vehicle. Simply changing the suspension structure to increase lateral stiffness will bring about changes in other performance. The lateral stabilizer bar is closely related to the lateral stiffness of the suspension. The stabilizer bar mainly relies on its own twisting and bending to produce anti-roll torque during operation. Without changing the vehicle suspension design, improving the vehicle's lateral stability through the lateral stabilizer bar is a more effective way.