Detailed introduction of eight common car suspension systems

The suspension system is a general term for all the force transmission devices between the frame of the car and the axle or the wheel. Its function is to transmit the force and force between the wheel and the frame, and the buffer is transmitted to the frame by the uneven road surface. Or the impact of the body, and attenuate the resulting vibration to ensure that the car can run smoothly.

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The typical suspension system structure is composed of elastic elements, guiding mechanisms, shock absorbers, etc., and individual structures include buffer blocks, lateral stabilizer bars, and the like. The elastic elements are in the form of leaf springs, air springs, coil springs and torsion bar springs. Modern car suspension systems use coil springs and torsion bar springs, and individual high-class cars use air springs.

The suspension system is an important assembly in the car. It elastically links the frame to the wheels and is related to the various performances of the car. From the outside, the car suspension system consists only of some rods, cylinders and springs, but don't assume that it is very simple. On the contrary, the car suspension is a car assembly that is difficult to achieve perfect requirements, because the suspension system is To meet the comfort requirements of the car, it must meet the requirements of its handling stability, and these two aspects are opposite each other. For example, in order to achieve good comfort, it is necessary to greatly buffer the vibration of the car, so that the spring is designed to be softer, but the spring is soft, but it is easy for the car to brake "nod", accelerate "head up" and serious left and right roll. The tendency is not conducive to the steering of the car, and it is easy to cause unstable operation of the car.

(1) Non-independent suspension system

The structural feature of the non-independent suspension system is that the wheels on both sides are connected by an integral frame, and the wheels together with the axle are suspended by the elastic suspension system under the frame or the body. The non-independent suspension system has the advantages of simple structure, low cost, high strength, easy maintenance, and small change of front wheel positioning in the vehicle. However, due to its poor comfort and steering stability, it is basically no longer used in modern cars. , used in trucks and buses.

(2) Independent suspension system

The independent suspension system is such that the wheels on each side are individually suspended under the frame or body by an elastic suspension system. The advantages are: light weight, reduced impact on the body, and improved ground adhesion of the wheel; softer springs with less stiffness can be used to improve the comfort of the car; the engine position can be lowered, and the center of gravity of the car is also reduced, thereby Improve the driving stability of the car; the left and right wheels are individually beating and irrelevant, which can reduce the tilt and vibration of the car body. However, the independent suspension system has the disadvantages of complicated structure, high cost and inconvenient maintenance. Modern cars mostly use independent suspension systems. According to their different structural forms, independent suspension systems can be divided into cross-arm type, trailing arm type, multi-link type, candle type and McPherson suspension system.

(3) Cross arm suspension system

The cross arm suspension system refers to an independent suspension system in which the wheels oscillate in the lateral plane of the vehicle, and is divided into a double wishbone type and a single cross arm type suspension system according to the number of the cross arms.

The single cross arm type has the advantages of simple structure, high roll center and strong anti-rolling ability. However, with the increase of the speed of modern cars, the high center of the roll will cause the wheel to change greatly when the wheel jumps, the tire wear will be intensified, and the vertical force transfer of the left and right wheels will be too large during the sharp turn, resulting in an increase in the rear wheel camber. The rear wheel has a side-to-side stiffness, resulting in a severe operating condition of high-speed tail. The single wishbone independent suspension system is mostly applied to the rear suspension system, but due to the inability to adapt to the requirements of high-speed driving, there are not many applications at present.

The double wishbone independent suspension system is divided into equal length double wishbone type and unequal length double cross arm type suspension system according to whether the upper and lower cross arms are of equal length. The isometric double wishbone suspension system keeps the kingpin inclination angle when the wheels are bouncing up and down, but the track variation is large (similar to the single cross arm type), causing serious tire wear and is rarely used. For the unequal length double wishbone suspension system, as long as the length of the upper and lower cross arms is properly selected and optimized, and the reasonable arrangement, the track and front wheel positioning parameters can be changed within an acceptable limit to ensure the car. Has good driving stability. At present, the unequal length double wishbone suspension system has been widely used in the front and rear suspension systems of cars, and the suspension system is also used in the rear wheels of some sports cars and racing cars.

(4) Multi-link suspension system

The multi-link suspension system is a suspension system in which (3-5) members are combined to control the positional change of the wheel. The multi-link type enables the wheel to oscillate about an axis at a fixed angle to the longitudinal axis of the vehicle. It is a compromise between the cross arm type and the trailing arm type, and the angle between the axis of the swing arm and the longitudinal axis of the vehicle is appropriately selected. The advantages of the cross arm type and the trailing arm type suspension system can be obtained to different extents, and can meet different performance requirements. The main advantage of the multi-link suspension system is that the wheel track and the toe change are small when the wheel is bouncing, and the car can be smoothly steered according to the driver's intention regardless of the driving or braking state. The disadvantage is that the car is in a car. There is a shaft swing phenomenon at high speed.

(5) Longitudinal arm suspension system

The trailing arm type independent suspension system refers to the suspension system structure in which the wheel oscillates in the longitudinal plane of the vehicle, and is divided into two types: a single trailing arm type and a double trailing arm type. The single trailing arm suspension system causes a large change in the caster angle when the wheels are bouncing up and down, so the single trailing arm suspension system is not used on the steering wheel. The two swing arms of the double trailing arm suspension system are generally of equal length to form a parallel four-bar structure such that the caster angle of the kingpin remains unchanged as the wheel jumps up and down. Double trailing arm suspension systems are often used on steering wheels.

(6) Candle suspension system

The structural feature of the candle suspension system is that the wheel moves up and down along the axis of the kingpin rigidly fixed to the frame. The advantage of the candle suspension system is that when the suspension system is deformed, the positioning angle of the kingpin does not change, and only the wheelbase and the wheelbase are slightly changed, which is particularly advantageous for the steering stability and stability of the vehicle. However, the candle suspension system has a major drawback: that the lateral force of the vehicle when traveling is entirely carried by the kingpin of the kingpin sleeve, so that the frictional resistance between the sleeve and the kingpin is increased, and the wear is also serious. The candle suspension system is currently not widely used.

(7) MacPherson suspension system

The wheel of the MacPherson suspension system is also a suspension system that slides along the kingpin, but it is not exactly the same as the candle suspension system. Its kingpin is swingable. The MacPherson suspension system is swing arm and candle. The combination of suspension systems. Compared with the double wishbone suspension system, the MacPherson suspension system has the advantages of compact structure, small change of front wheel positioning parameters when the wheel is bouncing, good steering stability, and cancellation of the upper cross arm. The arrangement of the engine and steering system is convenient; the lateral force of the spool is greatly improved compared to the candle suspension system. The MacPherson suspension system is mostly used in the front suspension system of small and medium-sized cars. The front suspension systems of Porsche 911, domestic Audi, Santana, Xiali and Beverly are all MacPherson independent suspension systems. Although the McPherson suspension system is not the most technically advanced suspension system structure, it is still a durable independent suspension system with strong road adaptability.

(8) Active suspension system

The active suspension system is a new type of suspension system developed by computer for more than ten years. It brings together the technical knowledge of mechanics and electronics and is a relatively complex high-tech device. For example, the French Citroen Santilla equipped with an active suspension system, the center of the suspension system is a microcomputer, and the five sensors on the suspension system respectively transmit the vehicle speed, the front wheel brake pressure, the speed of the accelerator pedal, and the speed of the accelerator pedal to the microcomputer. Data such as amplitude and frequency in the vertical direction of the vehicle body, steering wheel angle and steering speed. The computer continuously receives the data and compares it with a preset threshold to select the appropriate suspension system status. At the same time, the microcomputer independently controls the actuators on each wheel and generates twitch by controlling the change of oil pressure in the damper, so that the required suspension system motion can be generated at any time and on any wheel. Therefore, the Santilla car is available in a variety of driving mode options. The driver will automatically set the optimal suspension system status by simply pulling the “normal” or “sports” button on the sub-dashboard. Good comfort.

The active suspension system has the function of controlling the movement of the body. When the inertia of the car brakes or turns causes the spring to deform, the active suspension system generates a force that opposes the inertia and reduces the change in the position of the body. For example, the German Mercedes-Benz 2000 Cl-type sports car, when the vehicle turns, the suspension system sensor will immediately detect the tilt and lateral acceleration of the body. Based on the sensor information, the computer compares it with a preset threshold and immediately determines how much load is applied to the suspension system to minimize the tilt of the vehicle body.

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