Automobile shock absorber is mainly used to suppress the shock when the spring rebounds after absorbing shock and the impact from the road surface. It is widely used in automobile suspension system to improve the smoothness of automobile driving.

The working principle of automobile shock absorber is as follows:

In automobile suspension system, most shock absorbers are hydraulic shock absorbers. When the frame (or body) and the axle produce relative movement due to vibration, the piston in the shock absorber will move up and down. At this time, the oil in the shock absorber cavity will repeatedly flow from one cavity to another through different pores. In this process, the friction between the pore wall and the oil and the internal friction between the oil molecules will form a damping force on the vibration. This damping force can convert the energy of automobile vibration into the heat energy of the oil, which is then absorbed by the shock absorber and dissipated into the atmosphere. When the cross-section of the oil channel and other factors remain unchanged, the damping force will increase or decrease with the relative movement speed between the frame and the axle (or wheel), and is related to the viscosity of the oil. For example, when a car drives over a bumpy road, the spring will first be compressed and stretched to cushion the impact of the road, but the reciprocating motion of the spring will cause the body to continue to shake, and this is where the shock absorber comes into play. It uses damping force to suppress excessive rebound or excessive compression of the spring, so that the body can quickly return to a stable state. Double-acting cylinder shock absorbers are widely used in automobiles. In the compression stroke (such as when the axle approaches the frame and the wheel approaches the body), the shock absorber is compressed, the piston moves downward, the volume of the piston's lower chamber decreases, the oil pressure increases, and the oil flows through the circulation valve to the chamber above the piston (upper chamber). Since the piston rod occupies part of the space in the upper chamber, the increased volume of the upper chamber is less than the reduced volume of the lower chamber, and part of the oil will push open the compression valve and flow back to the oil storage cylinder. At this time, the throttling effect of these valves forms the damping force when the suspension is compressed. In the extension stroke, the piston moves upward, the oil pressure in the piston's upper chamber increases, the circulation valve closes, and the oil in the upper chamber pushes open the extension valve and flows into the lower chamber. The presence of the piston rod makes the oil flowing from the upper chamber insufficient to fill the increased volume of the lower chamber, and a vacuum will be generated in the lower chamber. At this time, the oil in the oil storage cylinder pushes the compensation valve to flow into the lower chamber for replenishment. The throttling effect of these valves damps the suspension during its extension movement. And during the extension stroke of the suspension, the damping force of the shock absorber is usually large, which can attenuate the vibration more quickly. With the development of technology, in addition to the common hydraulic shock absorbers, new shock absorbers such as pneumatic shock absorbers and adjustable resistance shock absorbers have also appeared. Pneumatic shock absorbers use the compressibility of gas to achieve shock absorption function. For example, they are used in some high-end cars or models with high comfort requirements, which can provide a softer shock absorption effect; adjustable resistance shock absorbers can automatically or manually adjust the damping force according to different driving conditions and driving needs to adapt to various driving conditions.