Damper Working Principle

Due to the impact on the elastic elements in the suspension system, causing vibrations, shock absorbers are installed in parallel with the elastic elements in the suspension to improve the smoothness of the vehicle's ride. Most shock absorbers used in the vehicle's suspension system are hydraulic shock absorbers. Their working principle is that when the frame (or body) and the axle vibrate and relative motion occurs, the piston inside the shock absorber moves up and down. The oil inside the shock absorber cavity is repeatedly pumped from one chamber through different orifices to another. At this point, the friction between the orifice walls and the oil, as well as the internal friction between the oil molecules, generates a damping force that converts the vehicle's vibration energy into oil heat energy, which is then absorbed and dissipated into the atmosphere by the shock absorber. When the cross-sectional area of the oil passage and other factors remain constant, the damping force varies with the relative motion speed between the frame and the axle (or wheel) and is related to the oil viscosity.

Dampers and elastic elements are responsible for absorbing shock and reducing vibration. Excessive damping force can degrade the suspension's elasticity, even damaging the damper connections. Therefore, it is necessary to adjust the矛盾 between the elastic elements and dampers.

In the process of compacting the journey (where the vehicle bridge and frame are brought closer together), the shock absorber's damping force is reduced to fully utilize the elasticity of the elastic elements and mitigate impacts. At this point, the elastic elements play a primary role.

(2) During the suspension extension stroke (when the axle and chassis move apart), the damper's damping force should be strong and the shock absorption should be rapid.

(3) When the relative speed between the axle (or wheel) and the axle housing is excessively high, the shock absorber is required to automatically increase the fluid flow, ensuring that the damping force remains within a certain limit to avoid excessive impact loads.

Tubular shock absorbers are widely used in automotive suspension systems, offering dampening effects in both compression and extension strokes, known as bidirectional shock absorbers. Additionally, new types of shock absorbers are being adopted, including inflatable shock absorbers and adjustable resistance shock absorbers.

The working principle of the bi-directional action cylindrical shock absorber is as follows: During the compression stroke, when the car's wheels move closer to the body, the shock absorber is compressed, causing the piston within to move downward. This decreases the volume of the lower cylinder chamber, resulting in increased oil pressure. The oil then flows through the flow valve to the upper chamber (top chamber). Since the piston rod occupies part of the space, the increase in volume of the upper chamber is less than the decrease in the lower chamber's volume, pushing some oil to open the compression valve and return to the reservoir. These valves save oil and create the damping force against the suspension's compression movement. In the extension stroke, when the wheels are akin to moving away from the body, the shock absorber is stretched. The piston then moves upward. The oil pressure in the upper chamber rises, closing the flow valve, and the oil pushes open the extension valve to flow into the lower chamber. Due to the piston rod, the oil flowing from the upper chamber is insufficient to fill the expanded volume of the lower chamber, creating a vacuum. At this point, oil from the reservoir is pushed through the compensation valve 7 to supplement the lower chamber. These valves, through their throttling effect, act as damping for the suspension during extension movement.

Due to the greater stiffness and pre-tension design of the expansion valve spring compared to the compression valve, under the same pressure, the total cross-sectional area of the channels in the expansion valve and the corresponding normally open gap is less than that of the compression valve and the corresponding normally open gap channel. This results in the damping force generated by the expansion stroke of the damper being greater than that of the compression stroke, meeting the requirement for rapid damping.