How does a car's shock absorber work?

The working principle of the automotive shock absorber suspension system due to the impact of the impact of vibration components, in order to improve the car ride, suspension and the elastic element in parallel to install the shock absorber, in order to dampen the vibration, the use of shock absorber in the vehicle suspension system The device is mostly a hydraulic shock absorber. Its working principle is that when the vehicle frame (or body) and the axle vibrate and the relative movement occurs, the piston in the shock absorber moves up and down, and the fluid in the shock absorber cavity repeats From one cavity passes through different pores into another cavity. At this time, the friction between the wall of the hole and the oil and the internal friction between the oil molecules form a damping force on the vibration, so that the vibration energy of the car is converted into the heat energy of the oil and then is absorbed by the shock absorber to be emitted to the atmosphere. When the cross section of the oil passage and other factors are constant, the damping force increases or decreases with the relative movement speed between the frame and the axle (or wheel), and is related to the viscosity of the oil.

The shock absorber and the elastic element bear the task of shock and shock absorption. If the damping force is too large, the elasticity of the suspension will be deteriorated, and even the shock absorber connector will be damaged. Because of the need to adjust the contradiction between elastic elements and shock absorbers.
(1) In the compression stroke (the axle and frame are close to each other), the damping force of the shock absorber is small, so that the elastic effect of the elastic element can be fully exerted and the impact can be mitigated. At this time, the elastic member plays a major role.

(2) During the extension of the suspension (the axle and the frame are far away from each other), the damping force of the shock absorber should be large and it should be quickly damped.

(3) When the relative speed between the axle (or wheel) and the axle is too large, it is required that the shock absorber can automatically increase the liquid flow so that the damping force is always kept within a certain limit so as to avoid bearing excessive shocks. Load. Widely used in the automotive suspension system is a drum type shock absorber, and can both play a damping role in the compression and extension stroke called two-way action type shock absorbers, as well as the use of new shock absorbers, which include inflatable minus Shock absorbers and adjustable resistance shock absorbers.

Two-way drum shock absorber working principle description. During the compression stroke, the vehicle wheel is moved closer to the body and the shock absorber is compressed. At this time, the piston 3 in the shock absorber moves downwards. The volume of the lower chamber of the piston is reduced and the oil pressure rises, and the oil flows through the flow-through valve 8 to the chamber above the piston (upper chamber). The upper chamber is occupied by a portion of the space by the piston rod 1, and thus the volume of the upper chamber is smaller than the reduced volume of the lower chamber. A part of the oil then pushes the compression valve 6 back to the storage tank 5. The oil saving of these valves forms the damping force of the suspension compressive motion. When the shock absorber stretches the stroke, the wheel is equivalent to being away from the body and the shock absorber is stretched. The shock absorber piston moves upwards. The oil pressure in the upper chamber of the piston increases, the flow-through valve 8 closes, and the oil in the upper chamber pushes the extension valve 4 into the lower chamber. Due to the existence of the piston rod, the oil flowing from the upper chamber is insufficient to fill the increased volume of the lower chamber, and the main chamber causes the lower chamber to generate a vacuum. At this time, the oil in the reservoir pushes the compensation valve 7 to flow into the lower chamber. supplement. Because of the throttling effect of these valves, the suspension plays a damping role in the extension movement.

Since the stiffness of the extension valve spring and the pre-tightening force are greater than those of the compression valve, under the same pressure, the sum of the channel loading areas of the extension valve and the corresponding constant-passage gap is smaller than the sum of the sectional areas of the compression valve and the corresponding constant-passage slot passage. This causes the damping force generated by the extension stroke of the shock absorber to be greater than the damping force of the compression stroke to achieve the requirement of rapid shock absorption.