The driving road can not be absolutely flat, which will produce vibration, the continuous vibration make drivers and passengers feel uncomfortable and fatigue. the shock absorber is designed for rapid attenuation of vibration. The shock absorber is an important component of automobile suspension system, which is used to control the rebound of the spring motor and suspension. In addition to ensuring that the car can pass stably in the rugged road at the same time, the key point is to ensure that the shock absorber of vehicle tire has been able to contact with the ground, which can ensure the safety of the vehicle braking performance. The following is the impact on the vehicle comprehensive characteristics:

☆Rapid attenuation of vibration by the road to the body vibration, improve  ride  comfort.

☆ It is not easy to make drivers fatigue and goods is not easy to damage, improve the ride comfort.

☆ Reduce the relevant parts of the impact to reduce wear and tear ,improve the use of economy.

☆ To improve the tire grounding to suppress high-speed running beating, improve driving safety.

☆ Some vehicles in the rapid acceleration, brakes, sharp turns, improve the operational stability.

☆ Shock absorbers can be divided into: cylinder shock absorber and strut shock absorber. Both are very similar in function, but different in design. Under normal circumstances the shock absorber with double cylinder design.

Double tube shock absorber: This is the most common shock absorber, generally have the restoring force and compression force, also known as  the two-way role shock absorber, because of its relatively simple manufacturing, compact structure, stable performance, can meet the  wide range of damping requirements, so it has been the most widely used. At present, most of the vehicles are equipped with this form of shock absorber.

The double tube, refers to the working cylinder and storage cylinder, the piston in the cylinder movement, the outer tube is used for storing shock absorber oil, in most cases with recovery valve and a compression valve.

A double cylinder hydraulic shock absorber cycle includes restoration and compression stroke, as shown in the figure. The recovery stroke: the piston rod relative to the shock absorber upward movement, the piston chamber oil pressure increases, the lower chamber pressure decreases, the piston pressure difference between the upper and the lower makes the recovery valve open, the oil flow from the upper chamber to the lower chamber. at the same time, the upper piston rod occupies part of volume, resulting in the upper chamber discharge oil volume is not enough to compensate the lower chamber, so part of the oil will flow from the outer tube into the lower chamber. The compression stroke: the piston moves down, the volume of the chamber decreases, the oil pressure increases, a part of the oil circulation through the valve flow to the upper chamber, the increased volume of the upper chamber is less than the decreased volume of the lower chamber. There is a part of the oil pushing compression valve to the outer tube. In the process of recovery and compression, the valve on the oil throttle will cause the suspension of the damping, so as to attenuate the vibration.