In the suspension system, the elastic element is impacted and vibrates. In order to improve the ride comfort of the car, a shock absorber is installed in parallel with the elastic element in the suspension, and dao is used to attenuate the vibration. Most of the shock absorbers used in automobile suspension system are hydraulic shock absorbers. Its working principle is that when the frame (or car body) vibrates relative to the axle, the piston in the shock absorber moves up and down, and the oil in the shock absorber cavity repeatedly flows from one cavity to another through different small holes. At this time, the friction between the hole wall and the engine oil and the internal friction between the engine oil molecules form a damping force on the vibration, so that the vibration energy of the automobile is converted into engine oil heat energy, which is absorbed by the shock absorber and radiated to the atmosphere. When the oil channel section and other factors are constant, the damping force increases or decreases with the relative movement speed of the frame and axle (or wheel), and it is related to the viscosity of oil.
Shock absorbers and elastic elements undertake the tasks of shock absorption and shock absorption. Excessive damping force will worsen the elasticity of suspension and even damage the connecting piece of shock absorber. Therefore, it is necessary to adjust the contradiction between elastic elements and shock absorbers.
(1) During the compression stroke (the axle is close to the frame), the damping force of the shock absorber is small, so as to give full play to the elastic function of the elastic element and reduce the impact. At this time, the elastic element plays a major role.
(2) In the extension stroke of the suspension (the axle is far away from the frame), the damping force of the shock absorber should be large and the shock absorption should be rapid.
(3) When the relative speed between the axle (or wheel) and the axle is too large, the shock absorber is required to automatically increase the liquid flow, so that the damping force is always kept within a certain limit to avoid bearing too large impact load.
Cylindrical shock absorber is widely used in automobile suspension system, which can damp both compression stroke and tension stroke. There are also new shock absorbers, including inflatable shock absorbers and resistance adjustable shock absorbers.
The working principle of double-acting cylindrical shock absorber shows that in the compression stroke, it means that the automobile wheels are close to the body and the shock absorber is compressed. At this time, 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 to the chamber (upper chamber) above the piston through the circulation valve. Part of the space of the upper chamber is occupied by the piston rod, so the increased volume of the upper chamber is smaller than the decreased volume of the lower chamber, and then part of the oil pushes open the compression valve and flows back to the oil storage cylinder. The oil saved by these valves forms the damping force of the suspension under compression. In the stretching stroke of the shock absorber, the wheel is equivalent to being far away from the vehicle 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 rises, the circulation valve closes, and the oil in the upper chamber pushes the extension valve open and flows into the lower chamber. Because of the existence of the piston rod, the oil flowing out of the upper cavity is not enough to fill the increased volume of the lower cavity, which makes the lower cavity produce vacuum. At this time, the oil in the oil storage cylinder pushes open the compensation valve 7 and flows into the lower cavity for replenishment. Due to the throttling effect of these valves, the suspension plays a damping role in the extension movement.
Because the stiffness and preload of the tension valve spring are designed to be greater than those of the compression valve, the sum of the channel load areas of the tension valve and the corresponding normally slotted channel is less than the sum of the cross-sectional areas of the compression valve and the corresponding normally slotted channel under the same pressure. This makes the damping force generated by the extension stroke of the shock absorber greater than that generated by the compression stroke, thus meeting the requirements of rapid shock absorption.