Advantages and Common Classifications of Car Shock Absorbers

Classification of car shock absorbers

To accelerate the attenuation of vibrations between the chassis and body of a car, to improve its driving smoothness (comfort), shock absorbers are installed inside most car suspension systems. From the perspective of materials that produce damping, shock absorbers can be mainly divided into two types: hydraulic and pneumatic, as well as one type of shock absorber that can adjust damping.

Hydraulic shock absorbers

Hydraulic shock absorbers are widely used in car suspension systems. Their principle lies in the fact that when the chassis and the car axle move relatively back and forth, the piston inside the shock absorber's cylinder tube also moves back and forth. During this, oil inside the shock absorber's shell repeatedly flows from one chamber to another through some narrow pores. Then, friction between the liquid and the inner wall as well as the internal molecular friction form damping force on the vibration.

Pneumatic shock absorbers

Pneumatic shock absorbers are a new type of shock absorber developed since the 1960s. Its structural feature is that a floating piston is installed in the lower part of the cylinder tube, and a sealed air chamber filled with high-pressure nitrogen is formed at one end of the floating piston and the cylinder tube. A large cross-section O-ring seal is installed on the floating piston, which completely separates oil and gas. The working piston is equipped with compression valve and extension valve whose channel sectional area changes according to its movement speed.

When the car wheel jumps up and down, the working piston in the oil makes reciprocating motion, creating an oil pressure difference between the upper and lower chambers of the working piston. As a result, pressure oil pushes the compression valve and extension valve to flow back and forth. Because the valve exerts greater damping force on the pressure oil, the vibration is reduced.

Adjustable resistance shock absorbers

Usually, the suspension of a car equipped with adjustable resistance shock absorbers is made of air springs with variable stiffness as elastic elements. The principle lies in the fact that if the air pressure in the air spring increases, the pressure inside the shock absorber's air chamber will also increase, causing changes to the flow aperture of the oil by altering the pressure and thus achieving the purpose of changing the damping stiffness.

Shock absorbers are vulnerable parts of a car in daily use. The good or bad of shock absorber operation directly affects the vehicle's smoothness of driving and the lifespan of other components. Therefore, shock absorbers should always be in good working status.

How to check whether the shock absorbers are working properly?

• When the car travels on the poor road surface for about 10km, stop the car and touch the shock absorber's outer shell with your hand. If it is not hot enough, it means that there is no resistance inside the shock absorber and the shock absorber is not working. At this time, proper lubricating oil can be added for the test. If the outer shell heats up, it indicates that the shock absorber is lacking oil inside and needs to be fully oiled; otherwise, the shock absorber is invalidated.

• Press hard on the bumper and then release it. If the car jumps 2-3 times, it means that the shock absorber is working well.
  

• When the car is driving slowly and an emergency braking is applied, if the car vibrates violently, it indicates that there is a problem with the shock absorber.
  

• Remove the shock absorber, stand it upright, and clip the lower ring to the vise. Pull and push the shock absorber several times with force, and there should be stable resistance. When pulling upwards (restoring), the resistance should be greater than when pushing downwards. If the resistance is inconsistent or no resistance, it may be due to lack of oil inside the shock absorber or damage to valve parts, and repair or parts replacement should be performed.