1. Material angle division
From the perspective of generating damping materials, shock absorbers are mainly hydraulic and pneumatic, and there is also a variable damping shock absorber.
(1) Hydraulic type
When the frame and axle reciprocate and the piston reciprocates in the cylinder, the oil in the shock absorber housing will repeatedly flow from one cavity to the other through some narrow holes. At this time, the friction between the liquid and the inner wall and the internal friction of the liquid molecules form a damping force against vibration.
Pneumatic shock absorber is a new type of shock absorber developed since the 1960s. The feature is that a floating piston is installed in the lower part of the cylinder, and a closed air chamber filled with high-pressure nitrogen is formed by the floating piston and one end of the cylinder. A large cross-section O-ring seal is installed on the floating piston to completely separate the oil and gas. The working piston is equipped with a compression valve and an expansion valve, and the cross-sectional area of the passage can be changed according to its moving speed. When the wheel bounces up and down, the working piston of the shock absorber reciprocates in the oil, thereby generating an oil pressure difference between the upper and lower chambers of the working piston, pushing the compression valve and the expansion valve to flow back and forth. The valve produces a relatively large damping force on the pressure oil to attenuate the vibration.
2. Structural perspective division
The structure of the shock absorber is to insert the piston rod with the piston into the cylinder, and the cylinder is filled with oil. The orifice on the piston allows the oil in the two spaces separated by the piston to supplement each other. Damping occurs when viscous oil passes through the orifice. The smaller the orifice, the greater the damping force and the greater the viscosity of the oil. When the size of the orifice remains unchanged and the working speed of the shock absorber becomes faster, too much damping will affect the shock absorption. Therefore, a disc-shaped leaf spring valve is installed at the outlet of the orifice. When the pressure increases, the valve is pushed open, the opening of the orifice becomes larger, and the damping becomes smaller. Due to the bidirectional movement of the piston, leaf spring valves are installed on both sides of the piston, which are called compression valves and expansion valves. According to its structure, shock absorbers are divided into two types: single tube and double tube.