Text/Qin Ming
If the engine and gearbox are the heart and neurovascular of the car, then the suspension is the muscle of the limbs, although it does not affect the size of the vehicle power, but directly determines the quality of the vehicle running, providing different driving experience, so this is also what many users value when choosing a car, the suspension on the market is dazzling, the former McPherson, multi-link, torque beam, and even air suspension, do not know who is better and who is worse, which is more comfortable, which control is good? So today we're going to talk about what suspension is all about.
Independent suspension and non-independent suspension
The suspension is in the connecting part between the body and the tire, and the suspension system not only supports the weight of the body, but also has a major responsibility to reduce the vibration of the vehicle and improve the driving experience and the handling performance of the vehicle. As an important component on the car, the suspension is generally composed of three parts: elastic elements, shock absorbers and guide mechanisms.
In general, the suspension system of the car is divided into two kinds of non-independent suspension and independent suspension, the two wheels of the non-independent suspension are mounted on the same girder, when one side of the wheel runs, the other side of the wheel will also be affected by the corresponding runout, so the entire body vibration or tilt, so the vibration of the non-independent suspension is also the strongest. But it is more holistic, the structure is simple, and the support for the vehicle is strong enough. However, due to the increasing demand for car comfort and handling stability, non-independent suspension systems have gradually been eliminated.
Independent suspension as the name suggests is two independent suspension, can be divided into two sections, both sides of the wheel by the coil spring independently installed under the frame, when one side of the wheel jumps, the other side of the wheel will not be affected, the two sides of the wheel can move independently, thereby improving the smoothness and comfort of the car.
The two sides of the independent suspension are not completely disconnected, so the stability of the vehicle will plummet, which is very unstable when turning, so it will be connected with anti-roll bars between the left and right suspensions.
Torsion beam suspension
Since the comfort of non-independent suspension is so poor, why are many car companies willing to spend effort to tune a good pair of torque beams? First of all, because the torque beam structure is simple, the occupancy is small, there is no subframe, so it can be separated into more space into the car and the trunk, in the same size model, the torque beam model often has a larger rear space, such as the Volkswagen Golf low version using the front McPherson rear torsion beam suspension, and the high-end with the front McPherson rear multi-link type, in the same body size, the low and medium version of the wheelbase is a few millimeters more, and the overall quality is lighter. So you'll find that some family cars with small body sizes, rear suspensions with torsion beams, rear and trunk space are more regular than mid-sized cars that pursue greater comfort.
Then the cost of the torque beam is lower, less than a pair of frames, the cost is naturally saved. Therefore, the torsion beam suspension is generally mounted on some entry cars, but it cannot be completely said that the torque beam is at the bottom. Take Citroen's Versailles C5 X, the Versailles C5 X uses Citroën's second-generation torsion beam suspension, and in order to improve comfort, it is also equipped with a PHC adaptive hydraulic system, which can automatically adjust the damping of the shock absorber by scanning the road surface conditions and change the shock absorption effect of the vehicle. Compared with the traditional torque beam, Citroën's connection system composed of high-strength steel beams and rubber shock blocks at the torsion beam suspension and body connection can better absorb the vibration caused by the tire, and its operating quality is completely comparable to most multi-link independent suspensions.
And now the urban road surface construction is more flat, the advantages and disadvantages of the torsion beam suspension are also well covered up, the comfort in the urban area is not bad, the cost is low and cost-effective, the support will be better to bring better cornering stability, which also makes many entry-level models on the market including Mercedes-Benz A-class choose the torque beam as the rear suspension structure of the vehicle, so the future entry model equipped with torsion beam is also very likely to become a popular trend.
Independent suspension
However, even if the torsion beam suspension is adjusted no matter how it is adjusted, there is no way to compensate for the physical defects, which is that its fixed overall structure limits the degree of freedom, and the inclination beam angle of the wheel cannot be changed according to the up and down jump of the wheel, and the angle compensation of the wheel cannot be made when the suspension is compressed or stretched. Therefore, the independent suspension with better vibration damping effect is more favored by people.
McPherson independent suspension
The types of independent suspensions are more complex and diverse, the most common of which is the McPherson-style independent suspension, and the front suspension of almost all models on the market is the MacPherson suspension structure. McPherson uses a control arm to connect the wheel frame, which is supported by springs and acts as a support. Similarly, its design is relatively simple, the parts are smaller, and it can make more room for the powertrain, especially the horizontal engine, which is often coordinated with McPherson.
However, McPherson also because of the simple structure brought the most fatal shortcomings, stability is not enough, only the spring and shock absorber resistance structure, need to resist the front and rear and lateral forces, causing the vehicle to roll and brake when prostrating is very obvious, although there are also McPherson suspension will add a lateral stability bar, but can not completely solve this problem. So McPherson is also mainly mounted on small and medium-sized vehicles, so why do sports cars like the Porsche 718 and 911 choose the former McPherson suspension structure? Personally, sports cars are more demanding of performance and performance, and the powertrain with more horsepower occupies more space, McPherson can provide good space, and lighter weight can also bring power improvement.
Multi-link independent suspension
Multi-link is a suspension structure with 3 to 5 members combined together, the front suspension generally uses 3 or 4 connecting rod independent suspension, and the rear suspension is a 4-link or 5-link suspension structure. In fact, the more connecting rods, the more connection points, the more wheels can control the direction of the wheel changes in all directions when they run, so that the tires can provide the best adhesion at any time, and even help improve the performance of the car.
Therefore, the most five connecting rods can be said to be the current top suspension structure, not only can guarantee a certain degree of comfort, but also because of the more connecting rods, you can achieve accurate guidance of the wheels, the body tilt is smaller, and there is no longitudinal drag arm, when subjected to road bumps, the wheels can beat perpendicular to the center of the wheel, the optimization of the longitudinal impact is also better, and the comfort is better. High-end cars mostly use multi-link suspension due to their ample space, comfort and handling stability.
In terms of comfort and control, there are no major drawbacks to multi-link, so the only disadvantage of multi-link is that it is expensive, the structural design is complex, and it is necessary to adjust the position between each connecting rod to achieve a balance of performance, adjust more complex, and design cost is higher. Sure enough, the only drawback of something that is expensive is that it is expensive. As for the large space occupied, it is not a very obvious disadvantage, the first model is equipped with multi-link suspension, and the space occupancy rate will naturally not be a problem.
Dual wishbone independent suspension
Double wishbone suspension, also known as double A-arm independent suspension, consists of an upper wishbone, a lower wishbone, a swing bearing, and a shock absorbing pillar. The lateral force is absorbed by both wishbones at the same time, and the vibration reduction struts only carry the weight of the body, so there is a large lateral support force. Compared with the MacPherson suspension structure, more stable and reliable, the upper and lower two wishbones of the double wishbone suspension can be reasonably cooperated when the wheels are shaken up and down, the wheel tilt amplitude is very small, in fact, the double wishbones can be seen as a reinforced version of McPherson, plus a wisharm to improve the stability of the suspension structure, and the strong lateral support is a big boost for the control, so it is generally mounted on the models that pursue athletic performance and even some supercars.
Then one will ask, who is better with multiple connecting rods and double wishbones? This question is really an accurate answer, multi-link is not equipped with a luxury car on the stable pressure double wishbones, you know, multi-link is actually a kind of deformation and reorganization of double wishbones, the two sides of the upper and lower two "A" type wishbones are disassembled and connected to the girder, it becomes a 4-link suspension, and the linkage of the five connecting rods is an extra balance bar, so the multi-link is actually a double wishbond suspension structure, but a form of transformation. So these two suspension structures, the advantages and disadvantages are the same, but the more complex structure of the multi-link can also bring a higher upper limit, the upper limit of the comfort and handling of the multi-link suspension, better than any form of double wishbone transformation, the multi-link can also arrange the rear wheel steering function, and the rear wheel active steering function of some luxury models requires a five-link suspension to be carried. But if these electronic equipment is canceled, the double wishbones will not be weaker than the multi-link under the bare hands.
Air suspension
In addition to the above suspension structures, many people will ask the more advanced "air suspension" and "electromagnetic suspension"? In fact, the air suspension can not be regarded as a new suspension structure, the air suspension is replaced by the original steel coil spring replaced by a rubber air spring, and the other structures have not changed. Of course, there are other components of the air spring system, such as air pumps, air valves, gas tanks, height sensors, controllers and gas circuits, circuit accessories, which are not available in ordinary steel coil springs.
The air spring can be used to use the sensors installed on the chassis of the vehicle to automatically control the air compressor and exhaust valve according to the change of body height, by changing the air pressure, raising the chassis or lowering the chassis, and can also manually adjust the ground clearance of the vehicle, adjust the softness of the suspension and the height of the body. Because it is actively adjusted at any time, although it has better adaptability, the natural loss is very high, and if it needs to be repaired and replaced, it will be a big expense, so the gas springs are optional or equipped on the first model.
Electromagnetic suspension
Similarly, electromagnetic suspension is not a new suspension structure, electromagnetic suspension is a suspension system composed of on-board control system, wheel displacement sensor, electromagnetic hydraulic rod and straight drum shock absorber, composed of vehicle control system, wheel displacement sensor, electromagnetic hydraulic rod and straight drum shock absorber. At each wheel and body connection, there is a wheel displacement sensor, which is connected to the on-board control system, which is connected to the electromagnetic hydraulic rod and the straight-barrel shock absorber, and the ordinary hydraulic oil in the original shock absorber is turned into a magneto-rheological fluid.
Through the sensor trigger, the electromagnetic shock absorber is energized, an electromagnetic field is generated, and the particles in the magneto-rheological liquid will be arranged with each other, so that the liquid becomes viscous, so that the damping in the shock absorber increases, and the reaction time is very short, it can react quickly, and the magnitude of the current can also be controlled, and the damping can be precisely controlled. In fact, the air spring and electromagnetic vibration damping are not in conflict, if the control and comfort are more pursued and the balance is sufficient for the user, both are the best choice.
Write at the end:
The suspension design of the car must take into account various factors, more biased performance control or stable and comfortable, is the suspension spring hardness, shock absorber damping force and the use of a variety of soft pads of the comprehensive effect of the comprehensive action, absolutely not only by the suspension structure can be determined alone, the factory's adjustment of the components is the real determine the intuitive factor of the vehicle running quality.