Shock absorber, also known as absorber, is a key component in the automobile suspension system. Its core function is to suppress the rebound oscillation generated by the spring after vibration absorption, and to effectively buffer the impact from the road surface. Shock absorbers are widely used to accelerate the vibration attenuation of the frame and body, thereby improving the driving smoothness of the car. When facing uneven roads, although the vibration absorbing spring can filter some vibrations, its main function is still buffering, by converting kinetic energy into potential energy, and then from potential energy back to kinetic energy, to achieve self-generated reciprocating motion. The shock absorber is specifically responsible for suppressing the jumping phenomenon of this spring.

In the automobile suspension system, shock absorbers are mostly hydraulically designed. Its working principle is that when the vibration between the frame and the axle causes relative movement, the piston in the shock absorber will move up and down. In this process, the oil in the shock absorber cavity will pass through different pores and flow repeatedly between the chambers. In this flow process, the friction between the pore wall and the oil and the internal friction between the oil molecules jointly generate the damping force. This damping force allows the vibration energy of the car to be converted into heat energy of the oil, which is then absorbed by the shock absorber and dissipated into the atmosphere. It is worth noting that when factors such as the cross-section of the oil channel and the pore size remain unchanged, the damping force will change with the increase or decrease of the relative movement speed between the frame and the axle (or wheel), and will also be affected by the viscosity of the oil.

(1) In the compression stroke, that is, when the axle and the frame are close to each other, the damping force of the shock absorber should be kept small to make full use of the elasticity of the elastic element to mitigate the impact. At this time, the elastic element plays a major role.

(2) When the suspension enters the extension stroke, that is, when the axle and the frame begin to move away from each other, the damping force of the shock absorber should increase to quickly attenuate the vibration.

(3) If the relative speed between the axle (or wheel) and the frame is too large, the shock absorber needs to be able to automatically increase the fluid flow to ensure that the damping force is maintained within a certain range to avoid excessive impact loads.

In automobile suspension systems, cylinder shock absorbers are widely used. Among them, the double-acting shock absorber can play a damping role in both compression and extension strokes. In addition, there are new shock absorber technologies, such as pneumatic and resistance-adjustable shock absorbers.

Taking the double-acting cylinder shock absorber as an example, its working principle is as follows: During the compression stroke, as the car wheel moves toward the body, the shock absorber is compressed, causing the piston to move downward. At this time, the volume of the lower chamber of the piston decreases, and the oil pressure increases, causing the oil to flow through the flow valve to the chamber above the piston (upper chamber).