Classification of shock absorbers

- Aug 29, 2019-

Material Angle Division

From the point of view of producing damping materials, there are two main types of shock absorbers: hydraulic and pneumatic. There is also a variable damping shock absorber.

(1) Hydraulic type

Hydraulic shock absorbers are widely used in vehicle suspension systems. The principle is that when the piston moves in the cylinder of the shock absorber in reciprocating relative motion between the frame and the bridge, the oil in the shock absorber shell will flow repeatedly from the inner cavity to another cavity through some narrow holes. At this time, the friction between the liquid and the inner wall and the internal friction of the liquid molecule will form the damping force to the vibration.

(2) Inflatable

Inflatable shock absorber is a new type of shock absorber developed since 1960s. The structure features that a floating piston is installed at the lower part of the cylinder, and a sealed air chamber formed at the end of the floating piston and the cylinder is filled with high pressure nitrogen. A large cross-section O-ring is installed on the floating piston, which completely separates oil from gas. The working piston is equipped with compression valves and expansion valves which vary the cross-section area of the passage with the motion speed. When the wheel bounces up and down, the working piston of the shock absorber moves back and forth between the upper chamber and the lower chamber of the working piston, causing the oil pressure difference between the upper chamber and the lower chamber of the working piston, and the pressure oil pushes the compression valve and the extension valve back and forth to flow. The vibration of the valve is attenuated due to the large damp force of the valve on the pressure oil.

Structural Angle Division

The structure of the shock absorber is that the piston rod with piston is inserted into the cylinder and filled with oil. There are throttle holes on the piston, so that the oil in the two parts of the space separated by the piston can complement each other. Damping is produced when viscous oil passes through the throttle hole. The smaller the throttle hole, the greater the damping force, the greater the oil viscosity and the greater the damping force. If the size of throttle hole is unchanged, when the shock absorber works fast, excessive damping will affect the absorption of shock. Therefore, a disc-shaped leaf spring valve is installed at the outlet of the throttle hole. When the pressure increases, the valve is opened, the opening of the throttle hole becomes larger, and the damping becomes smaller. Since the piston is bidirectional, there are leaf spring valves on both sides of the piston, called compression valves and extension valves, respectively.

According to its structure, shock absorbers can be divided into two types: single cylinder and double cylinder. It can be further divided into single barrel pneumatic shock absorber, double barrel oil shock absorber and double barrel oil and gas shock absorber.

(1) Double barrel type

It means that the shock absorber has two cylinders inside and outside, and the piston moves in the inner cylinder. As the piston rod enters and withdraws, the volume of oil in the inner cylinder increases and shrinks. Therefore, the balance of oil in the inner cylinder should be maintained by exchanging with the outer cylinder. So there are four valves in the double-barrel shock absorber, that is, besides the two throttle valves on the piston mentioned above, there are also flow valves and compensation valves installed between the inner and outer barrels to complete the exchange function.

(2) Single barrel type

Compared with the double-barrel shock absorber, the single-barrel shock absorber has simple structure and reduces a set of valve system. It is equipped with a floating piston at the lower part of the cylinder barrel (floating means that there is no piston rod to control its movement), forming a closed chamber under the floating piston, filled with high-pressure nitrogen. The above mentioned changes in the liquid level height caused by the piston rod entering and leaving the oil are automatically adapted by the floating piston. In addition to the two types of shock absorbers mentioned above, there are also resistance adjustable shock absorbers. It can change the size of throttle hole by external operation. Recently, electronic control shock absorber is used as standard equipment in automobiles. The driving state is detected by sensors, and the optimum damping force is calculated by computer, so that the damping force adjustment mechanism on the shock absorber can work automatically.