When the wheel jumps up, the shock absorber is compressed, and the piston moves down relative to the cylinder, so the volume of the lower chamber of the working cylinder decreases, the oil pressure rises, and the oil flows into the upper chamber of the working cylinder through the flow valve. Because the upper cavity is occupied by the piston rod, the increased volume of the upper cavity is smaller than the reduced volume of the lower cavity, so there is still a part of the oil that pushes open the compression valve and flows back to the oil storage cylinder 5. The throttling of the oil by these valves forms Damping force on the compression motion of the suspension. When the wheel falls, the shock absorber is stretched, and the piston moves up relative to the cylinder, so the oil pressure in the upper chamber of the working cylinder rises, the flow valve is closed, and the oil pushes the expansion valve into the lower chamber. Similarly, due to the existence of the piston rod, the oil flowing from the upper cavity into the lower cavity is not enough to fill the increased volume of the lower cavity, and a certain degree of vacuum is generated in the lower cavity. At this time, the oil in the oil storage cylinder pushes open the compensation valve and flows into the lower cavity. Replenish. The throttling action of this process valve creates a damping force on the extension movement of the suspension.