This type of shock absorber is widely used in automotive suspension systems and provides damping during both compression and rebound strokes, hence it is also known as a double-acting shock absorber.
Its components include: piston rod, working cylinder, piston, rebound valve, reservoir tube, compression valve, compensation valve, flow valve, rod guide, dust cover, and oil seal.
When the vehicle wheel moves closer to the body, the shock absorber is compressed, the piston moves downward, the volume of the lower chamber decreases, and the oil pressure rises. The oil flows through the flow valve to the chamber above the piston (upper chamber). Because the piston rod occupies a portion of the space, the increased volume in the upper chamber is less than the decreased volume in the lower chamber, causing some oil to push open the compression valve and flow back into the reservoir tube. The throttling action of these valves creates the damping force for the suspension's compression movement. When the wheel moves away from the body, the shock absorber is extended, the piston moves upward, the oil pressure in the upper chamber rises, the flow valve closes, and the oil in the upper chamber pushes open the rebound valve and flows into the lower chamber.
Due to the presence of the piston rod, the oil flowing from the upper chamber is insufficient to fill the increased volume of the lower chamber, creating a vacuum in the lower chamber. At this point, the oil in the reservoir tube pushes open the compensation valve and flows into the lower chamber to replenish it. The throttling action of these valves causes the damping force generated by the shock absorber during rebound to be greater than the damping force during compression, thereby achieving rapid damping.
