(l) Non-independent suspension: wheels on both sides are mounted on an integral axle, and the axle is connected with the frame through suspension. This suspension is simple in structure and reliable in force transmission, but the two wheels interact when they are impacted and vibrated. Moreover, due to the heavy weight of non-suspension, the cushioning performance of suspension is poor, and the car has great vibration and impact when driving. This kind of suspension is generally used in trucks, ordinary buses and other vehicles.
(2) Independent suspension: each wheel is respectively installed on the vehicle body or axle through a set of suspension, the axle is disconnected, and the middle section is fixed on the vehicle frame or vehicle body; The wheels on both sides of this suspension do not affect each other when they are hit, and because of the poor quality of non-suspension; Strong cushioning and shock absorption ability, comfortable ride. All indexes are better than dependent suspension, but the suspension structure is complicated, and the drive axle and steering system will become complicated. There are two main types of vehicles using this suspension.
① Cars, buses and manned vehicles. It can obviously improve the ride comfort and improve the stability of high-speed driving.
② Off-road vehicles, military vehicles and mining vehicles. In the case of bad road conditions and no road surface, it can ensure the contact between all wheels and the ground, improve the driving stability and adhesion of the car, and give full play to the driving speed of the car.
2. Types of elastic elements
(1) leaf spring: It is composed of several good steel plates with different lengths and curvatures, and is used for automobile suspension. After installation, both ends naturally bend upwards. Leaf springs not only have the function of cushioning, but also have the function of shock absorption. When they are arranged vertically, they also have the function of guiding and transmitting force. Most dependent suspensions use leaf springs as elastic elements, which can save guide devices and shock absorbers and have simple structure.
(2) Spiral spring: It only plays a buffering role and is mostly used for independent suspension devices of automobiles. Because there is no function of shock absorption and force transmission, special shock absorbers and guide devices must be provided.
(3) Oil-gas spring: gas is used as elastic medium, and liquid is used as force transmission medium. It not only has good cushioning ability, but also has shock absorption effect and can adjust the height of the frame, so it is suitable for heavy vehicles and buses.
(4) torsion bar spring; One end of the torsion bar made of spring rod is fixed on the frame, and the other end is connected with the wheel through the swing arm, so that the torsional deformation of the torsion bar plays a buffering role when the wheel jumps, and it is suitable for independent suspension.
3. Buffer
Cylinder shock absorber is often used to consume vibration energy by using the throttling effect of oil in small holes. The upper end of the shock absorber is connected with the vehicle body or frame, and the lower end is connected with the axle. Most of them are double-acting shock absorbers with both compression stroke and tension stroke.
4. Guide device
Most elastic elements on independent suspension can only transmit vertical load, but not longitudinal force and lateral force, so it is necessary to set up another guide device. As above, the lower rocker arm and longitudinal and lateral stabilizers, etc.
5. Dependent suspension and independent suspension
Generally speaking, automobile suspension systems are divided into two types: dependent suspension and independent suspension. The wheels of the dependent suspension are installed at both ends of the integral axle. When one wheel jumps, the other wheel also jumps accordingly, making the whole body vibrate or tilt; The independent suspension axle is divided into two sections, and each wheel is independently installed under the frame through a coil spring. When one wheel jumps, the other wheel is not affected, and the wheels on both sides can move independently, which improves the stability and comfort of the car.
Because modern people have higher and higher requirements for comfort and handling stability, dependent suspension systems have been gradually eliminated. Independent suspension system is widely used by automobile manufacturers because of its good wheel contact, greatly improved suspension type, free movement of left and right wheels, great freedom between tire and ground, and good vehicle handling. Common independent suspension systems include multi-link suspension system, McPherson suspension system and trailing arm suspension system. Each method has its own advantages and disadvantages and adaptability.
McPherson, double wishbone and multi-link are the most popular, and we often hear them. So what are the characteristics of these three mainstream suspensions? What are their performance characteristics?
Although according to the grade, complexity and materials of suspension, multi-link type is the best, followed by double wishbone and McPherson type. Although it can be classified in this way, everything in the world has advantages and disadvantages. The reason why these three kinds of suspension can exist in a large number of models certainly has its own performance advantages.
Among the three kinds of suspension, McPherson suspension has the simplest structure, the lowest manufacturing cost and the widest application. Mainly used in the front axle of most small and medium-sized cars. It dominates the world with simplicity. Because of his simplicity, he is light and quick. In addition, the camber angle of the wheel can be automatically adjusted under the geometric structure of the lower rocker arm and the strut, so that it can adapt to the road surface when turning, maximize the grounding area of the automobile suspension system of the tire, occupy less space, and be suitable for small cars and most medium-sized cars. However, due to the simple structure, weak suspension stiffness and poor stability, the steering roll is obvious.
McPherson suspension system, also known as strut suspension system, is the most widely used suspension system, which is common in front suspension. This is a suspension form that uses shock absorbers as the wheel positioning pillars. The upper part of the column is fixed on the vehicle body through rubber insulators, and the lower part of the column is connected and positioned through connecting rods. The shock absorber is cylindrical and installed in the pillar. The strut can slide up and down in the guide tube, and the biggest advantage is that the structure is simple, the occupied position is small, and the inclination angle behind the front wheel will not change because of the jumping of the wheel. In addition, for the suspension other than McPherson suspension, the upper arm is needed to locate the camber direction, which sacrifices space. McPherson suspension can increase the cabin space because the shock absorber has this function, and FF car with transverse engine is particularly important because there is no room for layout. The disadvantage is that when driving on uneven roads, the wheels are easy to turn automatically, and the driver must keep the steering wheel hard. When subjected to severe impact, the strut is easy to bend, which affects the steering performance.
McPherson is actually a suspension type evolved from double A-arms. He replaced the upper arm of the double A-arm with a shock absorber+spring, and the lower arm remained unchanged. In addition, because the shock absorber is McPherson's upper arm, such a shock absorber should be particularly strong. Basically McPherson is widely used in front suspension system. Because the upper arm is missing, the space occupied by the front wheel chassis is reduced, and the car with transverse engine can be easily placed, which can bring good control effect and take into account the design cost.
McPherson style (McPherson is also translated as McPherson or pillar style)
McPherson suspension system, also known as strut suspension system, is the most widely used suspension system, which is common in front suspension. This is a suspension form that uses shock absorbers as the wheel positioning pillars. The upper part of the column is fixed on the vehicle body through rubber insulators, and the lower part of the column is connected and positioned through connecting rods. The shock absorber is cylindrical and installed in the pillar. The strut can slide up and down in the guide tube, and the biggest advantage is that the structure is simple, the occupied position is small, and the inclination angle behind the front wheel will not change because of the jumping of the wheel. In addition, for suspension other than McPherson suspension, the plane positioning of automobile suspension in camber direction needs upper arm, which sacrifices space. McPherson suspension has this function because of the shock absorber, which can increase the cabin space, while FF car with transverse engine is particularly important because there is no room for layout. The disadvantage is that when driving on uneven roads, the wheels are easy to turn automatically, and the driver must keep the steering wheel hard. When subjected to severe impact, the strut is easy to bend, which affects the steering performance.
McPherson is actually a suspension type evolved from double A-arms. He replaced the upper arm of the double A-arm with a shock absorber+spring, and the lower arm remained unchanged. In addition, because the shock absorber is McPherson's upper arm, such a shock absorber should be particularly strong. Basically McPherson is widely used in front suspension system. Because the upper arm is missing, the space occupied by the front wheel chassis is reduced, and the car with transverse engine can be easily placed, which can bring good control effect and take into account the design cost.
Trailing arm (also called trailing arm)
Trailingarmtype is a suspension system specially designed for rear wheels. It combines the main axle of the car body with the axle in front of the axle with one arm, in which the rotation axis of the main axle of the car body is perpendicular to the center line of the car body, which is called trailing arm type or full trailing arm type. Vehicles using this system include Peugeot, Citroen and Opel. , and the semi-trailing-arm swing arm inclines to the center line of the car body, that is, obliquely backwards. The structure of trailing arm suspension is that the main shaft of the car body is directly combined with the car body, and then the main shaft is combined with the suspension system, and then this component is installed on the car body. Springs and shock absorbers are usually installed separately or integrally and vertically near the axle. In the movement of the suspension system itself, the boom moves around the axis perpendicular to the center line of the car body, that is, parallel to the axis of the axle, and the axle is not inclined to the car body. At any up-and-down movement position, the axle is parallel to the car body, and the inclination angle of the car body becomes zero. Its biggest advantage is that the distance between the left and right wheels is large, the camber angle of the car body is unchanged, and the shock absorber does not produce bending stress, so the friction force is small. When braking, the rear wheel of the trailing arm suspension will also sink to balance the car body, but its disadvantage is that it can not provide accurate geometric control of the automobile suspension spring.
The simple trailing arm design is actually an outdated product. Can not adjust the tilt angle, can not provide better ride comfort, are all serious injuries. But PSA Group can adjust the traction arm of its car better than the double A or multi-link of most Japanese cars! I have to admire the French adjustment technology and have a set of their own philosophy. Although there is no outstanding achievement in engine technology, the control is excellent, as evidenced by the success of wrc (this year's driver champion must be Citroen, and the team is produced by Citroen and logo ... not bad, anyway, it is all psa Group ...). However, even so, the trailing arm is gradually replaced by multi-link in its advanced RV. After all, the most sought-after comfort is the essence of high-end RV.
Double differential arm suspension has upper and lower rocker arms, the lateral force is absorbed by both rocker arms at the same time, and the strut only bears the weight of the car body. Therefore, the lateral stiffness is large. Because the rocker arm with unequal length is adopted (the upper part is long and the lower part is short), the camber angle can be automatically changed when the wheel moves up and down, so as to reduce the change of track distance and tire wear. But also can adapt to the road surface, so that the tire has a larger ground contact area and good ground adhesion. However, due to the addition of the upper rocker arm, it is necessary to stand in more space, so the front axle of a small car is generally not equipped with such a suspension.
Before the strut suspension system appeared, the independent front suspension of passenger cars was a double differential arm suspension. However, after the emergence of strut suspension system, almost all passenger car front suspensions have been changed into strut suspension systems. Recently, however, vehicles with high requirements for ride comfort and handling stability began to adopt double A-arm suspension with high design freedom such as geometric change and soft coordination at the front and rear wheels, which is a suspension form with camber change control arm. The arrangement of the arms is that the lower arm is similar to a column, and the upper arm is an A-shaped arm with rubber bushings at both ends, which combines the car body and the axle. The car body often has a subframe, and the main shaft is mounted on the subframe. The subframe and the car body are usually bonded with insulators in four places. Install springs and shock absorbers between the upper arm and the car body to maximize the stroke. Through the arrangement design of these connecting rods, the camber angle can be changed. The advantage of double A-arm suspension is firstly to improve the design freedom. Because there is no bending moment acting on the shock absorber, the friction is very small. Because the connecting rod is arranged on the subframe, it is easy to give consideration to the rigidity and vibration isolation of the suspension system. The disadvantage is that there are many parts, positioning accuracy is also required, and the cost and weight are not good for commercial vehicles such as single-room vans. This is Honda's concept from F 1 racing car, and it is also the most popular suspension system of Honda.
Double A-arm, which has achieved a perfect balance between cost and control, has existed for quite a long time, such as multi-link and McPherson, all of which are derivative designs. Double A-arm suspension is the strongest suspension in structure, which can bring more geometric adjustment and provide effective comfort and handling. For example, the popularity of Civic k9 is basically based on the excellent handling brought by its front and rear double A-arm suspension design (unfortunately, the Civic of later generations pulled out the double A and replaced the front suspension with McPherson). However, because there are only four connecting rods, which can only provide the change of inclination angle, and can't greatly adjust toe angle, he is still not good enough. So, a clever designer designed a composite suspension with horizontal and vertical tie rods (providing more geometric angle control), and multi-link was born. It is also worth mentioning that double A-arm is the best choice for F 1.
Drag arm type (DoubleWishbone is also translated as double wishbone type or double wishbone type)
Multi-link suspension, through various connecting rod configurations (usually three-link, four-link and five-link), can first realize all the performance of double wishbone suspension, and then on the basis of double wishbone, the toe angle can be changed correspondingly when the tire moves up and down through the constraint of the connecting shaft of the connecting rod, that is to say, the curve adaptability is better. If it is used on the front suspension of the front drive, it can alleviate the understeer to a certain extent and give people the feeling of precise steering. If it is used on the rear suspension, the toe angle of the rear wheel can be changed under the steering roll, which means that the rear wheel can steer with the front wheel to a certain extent, thus achieving the purpose of comfortable handling. Like the double wishbone, multi-link suspension also needs to occupy more space, and the manufacturing cost and research and development cost of multi-link suspension are the highest, so it is often used on the rear axle of mid-to high-end cars.
In recent years, automobile factories have high requirements on the chassis performance of ride comfort and handling stability, so double A-arm suspension and multi-link suspension system are adopted to form the so-called multi-links, but the principles of the two are the same, and the naming methods of each automobile factory are different because of the different number and fixing points of the links. In order to locate the axle, the connecting rod is mostly installed with the subframe through bushings, and the subframe is fixed on the vehicle body through insulators. This principle is similar to that of the double A-arm suspension, except that the double A-arm suspension consists of an A-shaped connection consisting of two upper and lower A-arms or three connecting rods, and the other group is connected by a mechanism fixed on the car body. The so-called multi-link in Mercedes-Benz Factory only adopts trailing arm suspension and double A-arm suspension system (one more link). Formed the so-called multi-link. The reason for this design is that the unique connecting rod configuration of multi-link combines the comfort of trailing arm with the maneuverability and grip of double A-arm, which can provide a stable driving urgency, absorb most of the vibration from the road surface, automatically adjust the tire angle and eliminate the change of camber angle. When the car body shakes, the tire and the road surface will always be 90 degrees vertical, and the grip is naturally good. Therefore, in order to give consideration to handling safety and riding comfort, it is necessary to set the installation position, angle, bushing and other characteristics of the connecting rod. The reason why the multi-link crane of each vehicle can realize such complicated linkage configuration is that it is easy to analyze and simulate the advantages and disadvantages of multi-link suspension system with computer. The multi-link double A-arm suspension structure is also complicated, and the parts need high precision and high cost. The increase of weight (some aluminum alloy connecting rods are used to reduce weight) is its shortcoming, but other suspension methods can also be realized, but it cannot be realized.
Basically, multi-link can be regarded as a derivative design of double A-arm. But the reason why we want to separate him from the double A is that the multi-link design has become more and more diversified, and some multi-links can't even find the trace of the double A (even the crazy design of the upper and lower A-arm three-link makes the material cost of the whole car suspension 2-4 times higher than others, so it's not unreasonable that some cars are expensive ...). When many car manufacturers advertise their high-end RVs, they will publicize what new designs their multi-link has participated in, which is synonymous with high-end. But the cost is high and it takes up a lot of chassis space, so it can only be used for rear suspension.
Multilink
So in general, the front independent suspension with the highest cost performance is McPherson type, and the suspension with high performance adjustment and matching is multi-link type and double wishbone type. The link with that most complex structure and the most performance. However, because the latter two make it heavier in structure, aluminum alloy is often used to achieve better response speed, so the cost can be imagined.
Generally speaking, the front and rear suspension systems of automobiles include springs and shock absorbers. According to the structure, the common structural forms are as follows: McPherson type, double A-arm (double crossbar), trailing arm, torsion beam and multi-link.
McPherson suspension is mostly used for front wheels. It is an independent suspension with a very simple structure. Compact layout, space saving, little change in front wheel positioning and good driving stability. Therefore, most automobile front suspensions adopt this structure, and the difference is mainly in the selection of materials and the adjustment of shock absorbers and springs. However, McPherson suspension also has shortcomings in use, that is, when driving on uneven roads, the wheels are easy to turn automatically, so the driver must keep the direction of the steering wheel hard. When subjected to severe impact, the shock absorber is easy to bend, thus affecting the steering performance, so many luxury cars that do not care about space and cost do not adopt this form.
Double A-arm suspension has upper and lower rocker arms, the lateral force is absorbed by both rocker arms at the same time, and the strut only bears the weight of the car body. Therefore, the lateral stiffness is large. Because the rocker arm with unequal length is adopted (the upper part is long and the lower part is short), the camber angle can be automatically changed when the wheel moves up and down, so as to reduce the change of track distance and tire wear. But also can adapt to the road surface, so that the tire has a larger ground contact area and good ground adhesion. However, due to the addition of the upper rocker arm, it is necessary to stand in a larger space. Honda's car front suspension likes to adopt this structure. Civic's maneuverability is praised, and the double A-arms hanging in front have some credit. Unfortunately, the eighth generation Civic did not adopt this structure, but adopted McPherson, which is a pity for many other car fans.
The trailing arm suspension system is a suspension system specially designed for rear wheels. European cars such as Peugeot, Citroen and Opel prefer to use this suspension system. The biggest advantage of trailing arm suspension system is that the distance between left and right wheels is large, the camber angle of the car body is unchanged, and the shock absorber has no bending stress, so the friction is small and the ride comfort is good. When braking, the rear wheel suspended by the trailing arm will sink to balance the car body, but its disadvantage is that it can not provide accurate geometric control, but if it is properly adjusted, it can achieve the best effect with the least cost and space, so this form of rear car is often used now.
Torsion beam suspension is a semi-independent suspension system of automobile electronic control suspension. This suspension is simple in structure and reliable in force transmission, but the two wheels will affect each other when they are impacted and vibrated. Small vibrations can be filtered well, but the response to large potholes will be blunt. This kind of rear suspension is mostly used in Volkswagen Group models, but the latest PQ35 platform has been changed to multi-link.
Multi-link suspension system is divided into five-link suspension system and four-link suspension system. Multi-link rear suspension can achieve the best position of caster angle of kingpin, greatly reducing the front and rear force from the road surface, thus improving the ride comfort and comfort during acceleration and braking, and ensuring the stability of straight driving. When the vehicle turns or brakes, the 5-link rear suspension structure can make the rear wheel form a positive toe-in, which improves the handling performance of the vehicle and reduces the situation of understeer. Many luxury cars also use 4-link front suspension, which skillfully separates traction, braking force and steering force through kinematics principle, giving the vehicle precise steering control.
To sum up, although multi-link has many inherent advantages, it seems to be the best way, but with so many stress points at once, it will be more difficult to adjust, and there is no advantage in occupying space and cost, so don't care too much about whether multi-link is used when buying a car. If it is a model below A, the front McPherson and the rear trailing arm are a very good match. If it is above B, the preferences of each car factory are different. In principle, as long as it is coordinated with the style of the whole vehicle, we