Working principle of double-acting cylinder shock absorber

During the compression stroke, the car wheel moves closer to the car body, the shock absorber is compressed, and the piston in the shock absorber moves downward. The volume of the lower chamber of the piston decreases, the oil pressure increases, and the oil flows through the circulation valve to the chamber above the piston (upper chamber). The upper chamber is partially occupied by the piston rod, so the increased volume of the upper chamber is less than the reduced volume of the lower chamber, so part of the oil pushes the compression valve open and flows back to the oil storage cylinder. The oil conservation of these valves forms the damping force of the compression movement of the suspension. When the shock absorber is in the extension stroke, the wheel is equivalent to moving away from the car body, and the shock absorber is stretched. At this time, the piston of the shock absorber moves upward. The oil pressure in the upper chamber of the piston increases, the circulation valve is closed, and the oil in the upper chamber pushes the extension valve open and flows into the lower chamber. Due to the existence of the piston rod, the oil flowing from the upper chamber is not enough to fill the increased volume of the lower chamber, causing a vacuum in the lower chamber. At this time, the oil in the oil storage cylinder pushes the compensation valve 7 open and flows into the lower chamber for replenishment. The throttling effect of these valves acts as a damping force on the suspension during extension.
Since the stiffness and preload of the extension valve spring are designed to be greater than those of the compression valve, under the same pressure, the sum of the channel load area of ​​the extension valve and the corresponding normally open gap is less than the sum of the channel cross-sectional area of ​​the compression valve and the corresponding normally open gap. This makes the damping force generated by the extension stroke of the shock absorber greater than the damping force of the compression stroke, achieving the requirement of rapid shock absorption.