Working Principle Of Vibration Damper

In a suspension system, vibrations occur due to impacts on the elastic elements. To improve ride comfort, shock absorbers are installed in parallel with the elastic elements. To dampen vibrations, hydraulic shock absorbers are commonly used in automotive suspension systems. Their working principle is that when relative motion occurs between the vehicle frame (or body) and the axle due to vibration, the piston inside the shock absorber moves up and down, causing the oil in the shock absorber chamber to repeatedly flow from one chamber to another through different orifices. The friction between the orifice walls and the oil, as well as the internal friction between oil molecules, creates a damping force, converting the vehicle's vibration energy into oil heat energy, which is then absorbed by the shock absorber and dissipated into the atmosphere. With constant factors such as the cross-section of the oil passage, the damping force increases or decreases with the relative speed between the vehicle frame and the axle (or wheels) and is related to the oil viscosity.

 

The shock absorber and the elastic elements are responsible for buffering impacts and damping vibrations. Excessive damping force will degrade the suspension's elasticity and may even damage the shock absorber's connecting components. Therefore, it is necessary to adjust the inherent contradiction between the elastic elements and the shock absorber.

 

(1) During the compression stroke (when the axle and frame are close together), the damper force is relatively small to fully utilize the elasticity of the elastic element and mitigate the impact. At this time, the elastic element plays a major role.

 

(2) During the suspension extension stroke (when the axle and frame are far apart), the damper force should be large to rapidly reduce vibration.

 

(3) When the relative speed between the axle (or wheel) and the axle is too high, the damper should automatically increase the fluid flow to keep the damping force within a certain limit to avoid excessive impact load.

 

Cylindrical shock absorbers are widely used in automotive suspension systems. Those that can dampen vibrations in both the compression and extension strokes are called two-way shock absorbers. Newer types of shock absorbers are also used, including pneumatic shock absorbers and adjustable-drag shock absorbers.