Structure and key points analysis of air spring
1. Structure of air spring
Air spring is a kind of non-metallic spring which is filled with a certain pressure air in the flexible rubber capsule and uses the compressibility of air to achieve the elastic effect. The air spring is mainly divided into two types: bag type air spring and membrane type air spring. In today's mechanical design process, the air spring has long been like a gear, can be treated as a standard part, according to the weight of the load and geometric installation size can choose the corresponding air spring.
2. Characteristics of air spring
(1) The elastic coefficient of the air spring is variable. With the increase of the load, the elastic coefficient also increases. Air spring can design various effect curves to meet various performance requirements because of its nonlinear effect.
(2) The rubber body of the air spring is lighter, and the mass of the air is also very small. Most of the weight of the air spring comes from the upper cover and the lower cover. Unlike the steel spring, the metal mass is heavier.
(3) The bearing capacity of the air spring can be adjusted according to the inflation pressure in the rubber airbag. For the same air spring, different bearing capacity needs can be met by adjusting the inflation pressure.
(4) Because the air spring takes air as the elastic medium, when compressed, the internal friction is small, so the vibration isolation effect is better. In addition, the air spring has a good ability to eliminate noise, because the ability of air and rubber to transmit sound is relatively weak.
(5) The air spring has strong anti fatigue ability. The experiment shows that the number of stress cycles that the leaf spring can bear under normal conditions is 500000 to 600000 times, while the general air spring can bear about 3 million times, and the number of stress cycles that the high-quality air spring can bear can reach more than 5 million times. Therefore, the air spring has outstanding effect in resisting strain.
(6) However, the manufacturing process of air spring is demanding and complicated, so the cost is high.
Control system of air spring
The control system of air spring has undergone two changes with the development of other related high and new technologies, and has experienced three development stages: mechanical control, electronic control and intelligent control. But no matter which kind of control system generally includes three sub modules: air supply system (air source), control components (including software), safety device (to ensure the normal operation of air spring). The air source and safety devices of the three control systems will have corresponding differences with the different control components, but the most fundamental difference lies in the control components. For the mechanical control system, its control components are mainly the height control valve, which can automatically inflate and exhaust the air spring to control the height of the air spring; the electric control system is more mechanical The control system has made a big step forward, which is a qualitative leap. This is also the use of electronic controller (ECU) to collect the signals from various types of sensors, analyze the signals and send the control signals to the actuators (mainly various solenoid valves), so as to realize the control of the air spring. The intelligent control system is based on the electronic control system and relies on the current automatic control theory It can not only control the height and stiffness of the air spring, but also control the nonlinear characteristics of the air spring by using fuzzy neural network and other control techniques.
Analysis of several factors affecting air spring
The ratio of the volume of the air chamber and the additional air chamber, the shape, material and size of the air spring, and the size of the orifice between the air chamber and the additional air chamber will have corresponding effects on the stiffness and natural frequency of the system.
1. The influence of the stiffness of the spring rubber material on the first resonance frequency of the system is analyzed. The experimental results show that the stiffness of the rubber airbag material itself has a great influence on the stiffness of the air spring, which is also the reason why the theoretical value of the stiffness of the air spring is quite different from the experimental value. The greater the stiffness of the rubber airbag material, the greater the stiffness of the air spring, and the higher the first-order resonance frequency. As a result, the minimum working frequency of the system is increased. Therefore, the rubber air bag isolation system should reduce the material stiffness and natural frequency, so that the minimum working frequency of the system can be as low as possible with enough allowance for the bearing capacity of the air spring isolator.
2. When the shaking table vibrates laterally, the stiffness of the spring capsule rubber material is much higher. The main structure of rubber air spring is soft, so it has the comprehensive isolation function of axial, transverse and rotational direction. When the mechanical vibration table vibrates laterally, the stiffness of the spring bag rubber material is much higher.
3. An orifice is set between the air spring and the additional air chamber. When the air flows through the orifice, a small part of the vibration energy is absorbed because of the resistance, which plays a role of damping. In addition to the stiffness and natural frequency of the system, the size of the orifice mainly affects the damping of the system.
The results show that the stiffness of the system decreases with the increase of the orifice opening, and the damping first increases and then decreases with the increase of the orifice opening. The increase of the additional chamber volume can reduce the stiffness and increase the damping ratio of the system. The increase of the excitation frequency can increase the stiffness and decrease the damping ratio of the system. The change of static load has little effect on the vibration characteristics of the system.