空气弹簧的结构及要点分析Structure and key points analysis of air spring

现如今，空气弹簧的使用范围变得越来越广，尤其是在许多震动设备上，空气弹簧成为了必不可少的设备之一。因而，探讨空气弹簧在震动设备上的应用十分有必要，这也是提升应用效果的重要工作之一。

空气弹簧的结构形式及特点

空气弹簧是利用橡胶气囊里面的压缩空气的反作用力当做弹性恢复力的一种弹性元件。空气弹簧凭借其良好的减振和隔振性能而被大量应用于汽车、铁道车辆、舰船、航空、工业等领域的动力机械、电子设备、仪器仪表、化工机械等设备。

1、空气弹簧结构形式

空气弹簧是在柔性的橡胶囊中充入有一定压力的空气，利用空气的可压缩性实现弹性功效的非金属弹簧。空气弹簧主要分为囊式空气弹簧和膜式空气弹簧两类。

在现如今机械设计过程中，空气弹簧早已像齿轮一样，能够当做标准件对待，按照载荷的重量和几何安装尺寸就能够选择相对应的空气弹簧。

2、空气弹簧的特点

(1)空气弹簧的弹性系数是可变的，随着所加载荷的增加，弹性系数也随之增大。空气弹簧能够设计各种以满足各种性能要求的效果曲线，是因为空气弹簧具有非线性的效果。

(2)空气弹簧橡胶本体较为轻，空气的质量也十分小，空气弹簧的重量大部分来自上盖和下盖，不像钢弹簧，金属质量较为重。

(3)空气弹簧的承载力可按照橡胶气囊内充气压力的大小进行调节，则针对同一空气弹簧，可以通过调节充气压力的大小来满足不同的承载力需要。

(4)由于空气弹簧以空气为弹性介质，当压缩时，内摩擦小，因而隔振效果较为好。此外，空气弹簧有很好的消除噪音能力，是因为空气和橡胶传播声音的能力都较为弱。

(5)空气弹簧抗疲劳能力较为强，实验表明:针对通常情况下的钢板弹簧可承受的应力循环数为50万至60万次，而一般空气弹簧能够可达到300万次左右，高质量空气弹簧可承受的应力循环数能够可达到500万次以上。因而空气弹簧在抵抗应变这方面功效突出。

(6)但制造空气弹簧工艺要求高且繁杂，因而成本较高。

空气弹簧的控制系统

空气弹簧的控制系统伴随着其他相关的高新科技的发展发生了两次变革，经历了三个发展阶段:机械控制，电子控制和智能控制。但不论哪种控制系统都大体上包含三个子模块:空气供给系统(气源)，控制元器件(包括软件)，安全装置(保证空气弹簧的正常运行)。三种控制系统的气源和安全装置伴随着控制元器件的不同会有相应的差异，但是它们最根本的差异在于控制元器件，对于机械控制系统来讲，它的控制元器件主要是高度控制阀，使用其自动地对空气弹簧实现充气和排气，实现空气弹簧高度的控制；电控系统较机械控制系统前进了一大步，是一个质的飞跃，这也是运用电子控制器(ECU)采集各种类型传感器传来的信号，对信号实现分析后将控制信号发送给执行器(主要是各种电磁阀)，从而实现对空气弹簧的控制；智能控制系统是在电控系统的基础之上依靠现如今自动控制理论发展起来的，它主要是对ECU的软件部份实现了改进，不但可以控制空气弹簧的高度和刚度，而且可以使用模糊神经网络等控制技术可以实现空气弹簧非线性特性的控制。

几个影响空气弹簧因素分析

气室与附加气室容积的比例，空气弹簧形状、材料、尺寸，以及气室与附加气室之间的节流孔的大小，对系统刚度和固有频率都会有相应的影响。

1、簧囊橡胶材料本身刚度对系统一阶谐振频率的影响。实验证明，橡胶气囊材料本身刚度对空气弹簧刚度影响极大，这也是导致空气弹簧刚度理论值与实验值差异比较大的原因。橡胶气囊材料刚度越大，空气弹簧的刚度就越大，其一阶谐振频率越高，其结果提高了系统工作时最小工作频率。因而，橡胶气囊隔震系统应当减小材料刚度，减小自振频率，使得空气弹簧隔振器的承载能力留出足够的余量情况下，系统最小工作频率尽可能低。

2、振动台横向振动时，簧囊橡胶材料刚度要大上许多。橡胶空气弹簧的本体结构柔软，因而具有轴向、横向和旋转向的综合隔震作用。机械式振动台横向振动时，簧囊橡胶材料刚度要大上许多。

3、在空气弹簧和附加气室之间设一节流孔，当空气流过节流孔时，因为阻力而吸收一小部分振动能量，进而起到减振阻尼的作用。除去影响系统的刚度和固有频率之外，节流孔的大小主要影响了系统的阻尼。

系统刚度随节流孔开度增大而减小，阻尼随节流孔的增大先增大后减小，附加气室容积的增大能使系统刚度减小并使阻尼比增大，激励频率的增大会增大系统刚度并减小系统阻尼比，静载荷的变化对系统振动特性影响不大。

Nowadays, the use of air spring has become more and more widely, especially in many vibration equipment, air spring has become one of the essential equipment. Therefore, it is necessary to explore the application of air spring in vibration equipment, which is also one of the important work to improve the application effect.

Structure and characteristics of air spring

Air spring is an elastic element which uses the reaction force of compressed air in rubber airbag as elastic restoring force. Air spring is widely used in power machinery, electronic equipment, instrumentation, chemical machinery and other equipment in the fields of automobile, railway vehicle, ship, aviation, industry and so on.

1. Air spring structure

Air spring is a kind of non-metallic spring which is filled with air with certain pressure in flexible rubber capsule, which makes use of the compressibility of air to realize elastic effect. Air spring is mainly divided into two types: bag type air spring and membrane type air spring.

In today's mechanical design process, 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 dimensions can choose the corresponding air spring.

2. Characteristics of air spring

(1) The elastic coefficient of air spring is variable, and the elastic coefficient increases with the increase of load. 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 air mass 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, the different bearing capacity needs can be met by adjusting the inflation pressure.

(4) Because the air spring takes air as 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 experimental results show that the number of stress cycles that the leaf spring can bear is 500000 to 600000 times, while the general air spring can reach about 3 million times, and the high-quality air spring can bear more than 5 million cycles. Therefore, the effect of air spring in resisting strain is outstanding.

(6) However, the manufacturing process of air spring requires high and complicated technology, so the cost is high.

Control system of air spring

With the development of other related high-tech, the control system of air spring has undergone two changes and experienced three development stages: mechanical control, electronic control and intelligent control. However, no matter what kind of control system, it generally includes three sub modules: air supply system (air source), control components (including software), and safety device (to ensure the normal operation of air spring). The air source and safety device of the three control systems will have corresponding differences along with the difference of control components, but their most fundamental difference lies in the control components. For the mechanical control system, its control component is mainly the height control valve, which can automatically inflate and exhaust the air spring to realize the control of air spring height; the electronic control system is more mechanical The control system has made a big step forward, which is a qualitative leap. It is also the use of electronic controller (ECU) to collect the signals from various types of sensors, and send the control signals to the actuator (mainly various solenoid valves) after the signal is analyzed, 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 present 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 technologies.

Analysis of several factors affecting air spring

The ratio of the volume of the air chamber to the additional chamber, the shape, material and size of the air spring, as well as the size of the throttle hole between the air chamber and the additional air chamber, have corresponding effects on the system stiffness and natural frequency.

1. The influence of the stiffness of the rubber material on the first-order resonance frequency of the system. The experimental results show that the stiffness of the rubber airbag material has a great influence on the stiffness of the air spring, which is also the reason for the large difference between the theoretical value and the experimental value of the air spring stiffness. The greater the material stiffness of the rubber airbag, the greater the stiffness of the air spring, and the higher the first-order resonance frequency, which results in the increase of the minimum working frequency of the system. Therefore, the rubber air bag isolation system should reduce the material stiffness and natural vibration frequency, so that the minimum working frequency of the system can be as low as possible when the bearing capacity of the air spring isolator is sufficient.

2. When the shaking table vibrates laterally, the stiffness of the spring bag rubber material is much larger. Because of its soft structure, rubber air spring has comprehensive isolation effect in axial, transverse and rotational directions. When the mechanical shaking table vibrates laterally, the stiffness of the spring bag rubber material is much larger.

3. A throttle hole is set between the air spring and the additional air chamber. When the air flows through the orifice, it absorbs a small part of the vibration energy due to the resistance, thus playing the role of vibration damping. In addition to affecting the stiffness and natural frequency of the system, the size of the orifice mainly affects the damping of the system.

The system stiffness decreases with the increase of orifice opening,