What types of shock absorbers are there for cars?

I. Classification by Material: Shock absorbers are mainly divided into two types: hydraulic and pneumatic.

1. Hydraulic Shock Absorbers: Hydraulic shock absorbers are widely used in automotive suspension systems. The principle is that when the frame and axle reciprocate, and the piston reciprocates within the shock absorber cylinder, the oil inside the shock absorber housing flows repeatedly from one inner cavity to another through narrow orifices. The friction between the liquid and the inner wall, as well as the friction between liquid molecules, creates a damping force on the vibration.

2. Pneumatic Shock Absorbers: These are a new type of shock absorber developed since the 1960s. Their structural feature is a floating piston installed at the bottom of the cylinder. A sealed chamber formed by the floating piston and one end of the cylinder is filled with high-pressure nitrogen. A large-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 extension valve whose cross-sectional area changes according to its speed. When the wheel bounces up and down, the working piston of the shock absorber reciprocates in the oil, creating a pressure difference between the upper and lower chambers of the piston. This pressure causes the oil to push open the compression and extension valves, allowing it to flow back and forth. The valves exert a significant damping force on the pressure oil, thus attenuating the vibration.

II. Classification from a structural perspective: Shock absorbers are classified into single-tube and twin-tube types based on their structure.

1. Twin-tube type: This type of shock absorber has two cylinders, an inner and an outer cylinder. The piston moves in the inner cylinder. Due to the piston rod's entry and exit, the volume of oil in the inner cylinder increases and decreases accordingly. Therefore, oil exchange with the outer cylinder is necessary to maintain the balance of the oil in the inner cylinder. Thus, a twin-tube shock absorber requires four valves: in addition to the two throttle valves on the piston mentioned above, there is a flow valve and a compensation valve installed between the inner and outer cylinders to perform the exchange function.

2. Single-tube type: The single-tube shock absorber has a simpler structure, eliminating one valve system. A floating piston is installed at the bottom of the cylinder (floating means that its movement is not controlled by a piston rod). A sealed gas chamber filled with high-pressure nitrogen is formed below the floating piston. The changes in oil level caused by the piston rod entering and exiting the oil, as mentioned above, are automatically adapted to by the floating piston.