1. Advantages of rubber air spring air suspension
(1) Unique design ensures superior performance
The drive shaft air suspension uses unique high strength Stiffness design. No leaf springs and U-shaped bolts are needed, eliminating the vibration and breakage problems of metal springs. This rigid guide arm, together with the other components of the air suspension, provides the best combination of performance: ride comfort, easy installation and low maintenance.
The air suspension is based on a unique parallelogram design principle. The torque rod is always parallel to the line connecting the guide arm to minimize the change in pinion angle (P), thereby reducing the wear of splines and universal joints, reducing the swing of the drive shaft, and making the vehicle drive smoothly and quietly. In addition, the suspension system can maintain load balance when the vehicle accelerates and brakes.
(2) Axle installation features
The rigid guide arm of the air spring is connected to the frame bracket with a rubber bushing, allowing the axle to be controlled during acceleration and braking. Movement to reduce axle housing stress and prevent damage. This is an important consideration for high torque/low rpm generator vehicles. When braking, the axle moves slightly forward and downward to keep the tires close to the ground, shorten the braking distance and prevent the brakes from deflecting, making it safer. Increased tire and brake pad life.
(3) System simplicity
The greater the up and down movement of the axle, the better the ride comfort, and the greater the suspension system's ability to absorb road vibrations. The maximum travel of air suspension exceeds that of any other form of suspension. Because the unique design allows the axle to travel larger in the vertical direction, the air spring can absorb greater vibration loads before the axle reaches its travel limit. Other air suspensions have shorter vertical travel and often reach their travel limits, resulting in hard impacts.
(4) There is no large impact load
The axle of any suspension system may move when making sharp turns and crossing potholes in loading and unloading areas. Its upper limit travel. Air suspension airbags have rubber cushions in them to withstand the impact loads in this situation. Another function of the buffer is that in the event of damage to the air bag, this buffer pad can act as a rubber suspension so that the vehicle can continue to drive at a lower speed.
2. Types of air springs
The air springs used in bus air spring suspensions mainly include bladder type and membrane type.
1. Bladder-type air springs
The bladder-type air springs are used in buses such as Siping brand SP641C and SP650 and the SL-11-1307 produced in the Czech Republic. This kind of spring The earliest application was in the suspension of buses. Its characteristics are:
a. The stiffness of the air spring is related to the change rate of the effective area of ??the spring dF/dx. Therefore, for the bladder air spring with a large change rate of the effective area, the spring stiffness is relatively small. Large, the vibration frequency is higher.
b. It can be seen from the air spring frequency calculation formula that when the volume of the air spring is larger, its stiffness is lower. Therefore, using an auxiliary air chamber can reduce the stiffness of the air spring. At higher pressures, increasing the volume of the auxiliary air chamber has a more obvious effect on stiffness. But this effect will decrease as the volume increases. Therefore, for bladder air springs, a lower vibration frequency can be obtained by appropriately selecting the effective area change rate of the spring and the volume of the auxiliary air chamber.
c. When the number of curves of the airbag is increased, since the deformation of the airbag can be equally shared by each curved part, the greater the number of curves, the smaller the change rate of the effective diameter. It can be seen that increasing the number of air bag curves will reduce the stiffness of the bag air spring and reduce the vibration frequency of the spring. Three-curve bladder air springs are used in Siping brand SP641C and SP650 buses. In addition, according to some information, the service life of bladder air springs is relatively long.
2. Diaphragm air spring
With the development of automobile industry and rubber industry technology, the use of high-strength nylon, Capron and other cords has been used in buses at home and abroad in recent years. Diaphragm air springs are widely used in suspensions. For example, this type of spring is used in buses such as Leyland, Wuhan brand WH644 and WH643. Its characteristics are:
a. It can be regarded as the lower cover of the bladder air spring turning into a piston. Since this change greatly improves the elastic characteristics of the air spring, a more ideal inverse "S"-shaped spring characteristic curve is obtained than the bladder air spring.
It can be seen that within the normal working range of the diaphragm air spring, the spring stiffness change is smaller than that of the bladder air spring. Therefore, in terms of vibration performance, the diaphragm air spring is much superior to the bladder air spring. It is particularly worth mentioning that the diaphragm air spring can control the change rate of its effective area by changing the shape and size of the piston to obtain ideal elastic characteristics. This is not easy to do for bladder air springs.
b. The change rate of the effective area of ??the diaphragm air spring is smaller than that of the bladder air spring. Therefore, the diaphragm air spring can obtain a lower natural vibration frequency when the auxiliary air chamber is small. . It is not easy to design a bladder air spring with a very low spring frequency.
c. At present, the sealing form of diaphragm air springs generally adopts the pressure self-sealing type, while the sealing of bladder air springs is usually clamped with screws, so the sealing of diaphragm air springs is simple and Easy to disassemble and assemble.
d. Diaphragm air springs are simple to manufacture and convenient for mass production.
The arrangement of air springs should consider the lateral angular stiffness of the car. When the layout allows, the air spring should be arranged outside the frame as much as possible to increase the center distance of the spring and improve the lateral angular stiffness of the car. On the rear suspension of buses such as Hino and Benz 0303 (see Figure 6), a curved beam structure is adopted, and two airbags with the same size as the front suspension airbag are installed at the end of each curved beam. Another example is the rear suspension of buses such as MAN and Leyland (see Figure 4), which adopts an A-frame structure and arranges the air springs near the rear wheels, increasing the spring center distance and improving the car's anti-roll resistance. ability, so some people call the air spring arranged in this way an anti-roll suspension. However, there are also some buses, such as Japan's Mitsubishi (MITSUBISHI), Isuzu (Isuzu), Nissan-Diesel (NISSAN-DIESEL) and other buses, which basically install air springs in the position of the leaf springs of the car chassis. In this way, whether it is a leaf spring or an air spring car, the position where the spring is placed remains unchanged. Some people call this air spring suspension standard air suspension. This kind of suspension uses a unified car chassis and different spring elements as much as possible to meet the needs of different users. Doing so can simplify the production process and reduce the manufacturing cost of the car. However, due to the small center distance of this arrangement, it cannot ensure that the car has sufficient lateral angular stiffness. Therefore, when the car is acted upon by lateral forces, the body inclination angle is large, giving people an uncomfortable feeling.
3. Height control valve
Height control valves are installed in the air suspension of buses. Its main functions are:
1) Ensure that the height of the car does not change with the load of the car. The height of the car can be adjusted to maintain a certain height to facilitate passengers getting on and off the car.
2) Keep the air volume in the air spring at a certain value to ensure that approximately the same vibration frequency is obtained under different loads.
3) When there is a slight leakage in the air spring, the height control valve can be continuously inflated to ensure the normal operation of the air spring.
In addition, in order to ensure that the car body is stably placed flat on the suspension, three-height control valves are usually used, one on the front axle and two on the rear axle. When a height valve is installed, some cars are also equipped with an isolation valve to prevent high-pressure air from flowing from one side of the airbag to the other when the body tilts, aggravating the tilt of the body. However, the test results of Siping brand SP641C, SP650 and other automobiles showed that the isolation valve was not effective, so the isolation valve was canceled in future designs.
4. Rebound limit
Some elastic elements (such as leaf springs) have a large reverse stiffness, so in a suspension using such elastic elements, it is almost impossible to Consider the rebound limit issue. However, the reverse stiffness of the air spring is very small. If reverse limiting measures are not taken, the following problems will inevitably occur:
1) Because the air bag has limited freedom, it will rebound endlessly. The air bag will inevitably come off (if there is no clamping measure) or the air bag will be broken (if there is clamping measure).
2) Because the free length and connection strength of the shock absorber are limited, endless rebound will inevitably cause damage to the shock absorber.
3) The bag-type airbag has the smallest effective pressure-bearing area and the largest pressure relief area during rebound. Therefore, excessive rebound stroke can easily cause the airbag to explode.
Considering the above situation, the air suspension system of buses is generally equipped with a wire rope reverse limit device.
5. Shock absorber
Because air springs, like coil springs and torsion bar springs, have no ability to attenuate vibrations. Therefore, higher requirements are placed on the performance of the shock absorber, and the performance of the shock absorber is expected to be stable and reliable. In addition, in order to meet the requirements for shock absorbers when the car is no-load and fully loaded, it is best for the performance of the shock absorber to change as the load increases, and to keep the non-periodic coefficient within a roughly constant range
Rubber air springs, also known as air springs, pneumatic tires, air bags, rubber springs, etc., were born in the mid-19th century and were used for vibration reduction in mechanical equipment in the early days.
Due to its many advantages, it has been widely used in modern highway and rail transportation vehicles and industrial machinery.
Rubber air spring uses compressed air (water) as the medium, and is an elastic element that uses the reaction force of its internal compressed air as its elastic restoring force.
It is a non-metallic spring with spring function.
3. Rubber air springs have many superior characteristics of metal springs:
◆The stiffness of rubber air springs, rubber air bags, and rubber pneumatic tires changes with the load, making the spring device unique Ideal characteristics;
◆Rubber air springs, rubber air bags, and rubber pneumatic tires have nonlinear characteristics. Their characteristic curves can be designed into ideal shapes and can withstand axial and radial loads at the same time. They can also Transmit torque;
◆Rubber air springs, rubber air bags, and rubber pneumatic tires can obtain different load-bearing capacities by adjusting the internal pressure, thus adapting to the needs of various loads;
◆ Rubber air springs, rubber air bags, and rubber pneumatic tires have light weight and long service life;
◆Rubber air springs, rubber air bags, and rubber pneumatic tires have good high-frequency vibration isolation and sound insulation properties. Rubber air springs require small installation space and are easy to replace.