Its working principle is that when the frame and the axle reciprocate relative to each other, and the piston reciprocates in the cylinder, the oil in the shock absorber reciprocates between the two isolated cavities through the narrow pores on the valve. , Due to the friction between the hole wall and the oil and the internal friction of the liquid molecules, a damping force is formed, so that the mechanical energy of the body vibration is converted into heat energy, which is absorbed by the oil and the shell, and then dissipated into the atmosphere. The damping force is related to the cross-sectional area of the passage through the oil, the spring stiffness of the valve and the viscosity of the oil.