preface
In the past two years, everyone has been rolling up the suspension, first BYD's Yun Yuan, and then there is Weilai ET9 tribute champagne tower, and Yu Chengdong's dual-cavity air spring uselessness theory, as well as Xiaopeng X9 rear-wheel steering, all kinds of new terms, new technologies, it sounds very black technology, and the industry is constantly stepping on its own commercial value, trying to confuse the standard cognition, so in order to let everyone really systematically figure out the knowledge structure of suspension, Lao Wang specially produced a season of program, hoping to give you a new vision to look at the new suspension technology.
First of all, let's think about a question, that is, why is the suspension called suspension? In fact, the literal translation of the English suspension is indeed suspension, and this word also has the meaning of suspension in chemistry, and some provinces and cities in the south are also very vividly translated as suspension. When someone asks why the suspension isn't called Sustainer support, or Snubber cushioning, or dampering, it's about the history of the suspension and its basic components.
First, the origin history of suspension
Early carriages had no suspension, tires were nearly rigid, and ride was poor when it came to bumpy roads. In the early 19th century, some British carriages began to be equipped with wooden springs for vibration protection, while larger carriage springs were made of iron.
Note, however, that the springs in question are not coil springs, but leaf springs made of mild steel. However, the Americans later discovered that this system was not suitable for the rougher roads of the American continent at that time, and when turning too fast, it could even cause the carriage to disintegrate. In 1820, a company called Downing developed a system of propped up on a simple belt, nicknamed through braces, which allowed the movement of the carriage to move from bumps to swings. The body is suspended by a belt at the end of the pillar, which acts both as a spring, as well as a shock damping and part of the suspension. So if this system is taken as the starting point of the suspension, then in the process of evolution, a certain angle of the body does start with the action of hanging on the chassis, so the name of Suspension is appropriate and reasonable.
There are dozens of types of suspensions, but the basic functions remain the same, which is to provide vertical kneading to isolate vibrations, and to maximize the stability of the contact between the tire and the road surface. In fact, the suspension also has several functions, such as height retention and adjustment, wheel restraint, tire force transmission, and body roll suppression. But you must know that it is not easy for cars to evolve the above clear needs and positive research and development theories, and they are all exchanged for blood and fire.
It was not until about 1930 that automobile suspension and vehicle dynamics developed into an independent discipline, and it is conceivable how many people and equipment have been sacrificed in the first 40 years of automobile development. Especially after 1910, the rapid development of engines and gearboxes and better road conditions brought about an increase in vehicle speed, making the wheels unpredictable in extreme situations, and a large number of vicious accidents caused people to think about suspension, and the suspension began to develop from the earliest axle leaf springs to today's real suspension system composed of springs, shock absorbers, connecting rods and stabilizer bars and bushings.
Second, the suspension structure is an element
The above points happen to be the components of modern suspension, you must know that the tire grounding area is only the size of a palm, the most afraid is the longitudinal beating, once a moment because of the bump to let the tire off the road, responsible for stable lateral friction and responsible for the longitudinal force of the vehicle will disappear, you don't keep watching the movie in the car drift or vacant can continue to drive, ordinary cars out of control after landing in the next second the body hit where it is not easy to say, a few years ago there was a cc vacant landing to see how miserable the result was. So what are these components of the suspension responsible for?
1. Springs
First of all, the main role of the spring is to carry the weight, for example, the leaf spring is also a generalized spring, in the field of commercial vehicles, in recent years, the rise of air suspension has not affected the 80% shipment rate of the leaf spring, just because of the weight bearing reliability, the leaf spring is still ranked first.
Another function of the spring is cushioning, but it should be noted here that the existence of the spring is not to eliminate vibration, it can only be said to be a conversion of vibration, the short-wave impact into a long-wave wave, so that the car becomes more comfortable, and the spring parameters are very complex, take the coil spring as an example, the wire diameter, pitch and effective number of turns of each car spring are different. In principle, the design requirements of the spring need to be set according to the preload height of the body, that is, the suspension height, and the suspension height depends on the vertical height difference between the inner and outer points of the lower swing arm.
Of course, even if it has developed to the present, there are still a large number of cases of non-coil springs in the responsibility of springs in passenger car suspensions, such as leaf springs in many pickup trucks, air springs in luxury cars, and more characteristic ones such as the use of polymer materials as springs in Volvo SPA platforms. Suffice it to say, any form of spring, as long as it can give the wheel a restrained preload and preload height, can convert short waves to long waves and carry weight, it can assume the corresponding responsibility.
2. Shock absorbers
Another important part that works with the height of the spring is the shock absorber. In principle, both it and the spring can be cushioned, but ideally, if the spring is not damped, it will keep jumping. In the field of engineering, springs can indeed convert vibrations into heat to dissipate energy, but for the continuous large amount of vibration from the ground is insignificant, the suspension has to receive energy input from road excitation at all times, so the function of the shock absorber becomes extremely important, because it has one more ability than springs, which is to converge vibrations quickly and effectively.
In the field of suspension, we use the vibration next to the handle to describe the shock absorber, the handle represents the mechanical properties, not the vibration of the word rain, that represents a natural phenomenon, and there are many words on the official website of the brand that are written incorrectly. When receiving the road surface excitation to produce relative motion, the piston inside the vibration damper will move up and down, and the oil in the cavity will repeatedly flow into another cavity through different pores, and a lot of energy will be consumed in the process to attenuate the vibration. In principle, the smaller the oil flow rate and the greater the damping, the stiffer the suspension. There are actively adjustable shock absorbers on the market that can change the bore size by electronically controlled or hydraulic devices, thereby changing the flow rate, the higher the oil flow rate, the smaller the damping, the softer the suspension feel, and vice versa, the stiffer the suspension.
This is the case with the previously disassembled Citroen PHC, which is a progressive hydraulic cushion damper, which is very different from ordinary shock absorbers. After being dissected, you can see the upper and lower parts of the inner part, the upper part is the reset buffer spring, which prevents the iron from hitting the iron when stretching to the limit position, and some suspension similar positions will choose nylon rubber rings, and the essence of PHC lies in a row of large to small throttle holes on the black side below. The piston is in the middle position during normal driving and is filtered out if it is only a slight small bump. When the piston is close to the compression limit, the orifice is gradually closed, the oil flow rate is gradually slowed down, the damping increases, when the piston compresses to the lowest stroke, all the orifice are closed, the damping is maximum, and the suspension is the hardest.
In addition to this mechanical type, there is also electronically controlled vibration damping, such as ZF's CDC, which is designed with a solenoid valve that can change the oil level in a matter of milliseconds to adjust the vibration damping force. And it was mass-produced in '97, and the latest model can also calculate the optimal damping based on the signal of the body gyroscope to each axis. Recently, many domestic manufacturers have used similar CDC.
In addition, there is also magnetofluid vibration damping, which was first invented by Delphi in the United States in 02 and was first installed on the Cadillac Seville STS. The first generation of magnetorheological converter has a big drawback, it uses a single electromagnetic coil, will produce a large eddy current loss, the responsiveness is average, and later Beijing West Heavy Industries acquired Delphi, using dual coil technology to avoid the eddy current problem, the responsiveness is improved a lot, it is said that it can change 1000 times per second, the industry says that the shock absorber can be quickly adjusted is a watershed in the development of suspension.
Let the suspension evolve from passive to active, with adjustable solenoid valves, with air springs and inertial modules and even cameras, the character of the suspension is more changeable, and the feed forward and feedback coexist, predicting road information in advance, and even driving without bumps. Previously, Lao Wang said that Mercedes-Benz's magic body and BYD's Yun Yuan are all combined with ESP, steering multi-axle IMU and active suspension, and now some electric vehicles such as Weilai have achieved faster adjustment in longitudinal functions, and also integrated chassis domain control, and also support remote upgrades. So you can imagine how important the suspension and vehicle dynamics will be in the future products, the more advanced the car, the more quickly the shock absorber can be matched with the spring to optimize the body attitude, in 2024 this equipment is a sign of whether the vehicle is advanced.
Why do electric vehicles now pay so much attention to suspension development, because there is no engine and gearbox, the premium rate reflects a sharp reduction in the field, some car companies are other people's, by telling the story of suspension tuning, car companies can quickly form a product force cognition for users. Therefore, various suspension technologies are being promoted more and more, and it has become a kind of obvious learning at the media level.
3. Connecting rods and stabilizers
Then it is not enough to solve the vertical problem, the suspension must also ensure the mechanical characteristics of other directions, at this time the design of the connecting rod becomes particularly important, many suspensions are distinguished by the number and design of the connecting rod, including the independence of the rear suspension, what is independent suspension, what is the non-independent suspension and what is worth sharing, the next few issues of Lao Wang will run through the explanation of this issue We will talk about a point.
It is why the independent suspension should be equipped with a lateral stabilizer, what is the difference between this and non-independent suspension, the role of the lateral stabilizer bar is to produce additional roll stiffness and reduce the roll of the body, but the lateral stabilizer bar does also make the left and right suspension related, reducing the independence of the suspension and detrimental to smoothness. The simple understanding is that the stabilizer provides roll stiffness so that the attitude is not too ugly in sharp corners, while the independent suspension, especially the rear independent suspension, is designed to be independent of the spring and shock absorber position for a given core parameter. To put it bluntly, the independent suspension wants to reduce the wheel jump, but it still needs to have a certain roll steering support. The reduction of tire runout does not conflict with the provision of roll stiffness, so the correlation between the left and right wheels is enhanced by the stabilizer bar and the wheel jump optimization brought about by the control arm independently. This is sometimes confusing even for people at OEMs.
4. Bushings
The next thing may not be so important in the eyes of many people, but it is indeed an important part of the suspension, it is the bushing, and it is a watershed in the gold content of the suspension. In the case of suspension, the vibrations are rooted in the road surface, and the undulations of the road surface act on the wheels and are transmitted to the body through the suspension. Then the transmission path becomes two: one is the spring and shock absorber, and the other is the direct transmission of the control arm.
In order to solve the noise and high-frequency vibration, passenger cars often need special rubber or hydraulic bushings, think about why the woodpecker must not be concussed, some people dissected and found that its tongue can wrap a circle, neck muscles can be used as a cushion, the car bushing is similar, the suspension rods are connected in a flexible way.
Moreover, the bushing not only absorbs and isolates vibrations, but also optimizes the suspension characteristics and changes the frequency response through deformation during braking acceleration pitching and roll during cornering.
There is a contradiction in the bushing, that is, from the comfort point of view, the bushing should be softer, and from the perspective of stability, the bushing needs to be hard. And the extreme hard is not to design the bushing, many racing suspensions are not set bushings, driving will require the driver to operate the steering frequently, a little careless is like being kicked from the side, but this is the so-called gap between the driver and ordinary people, ordinary people you can't accept this kind of frequent operation and comfort.
Before Lao Wang went to the Great Wall's Nobo rubber technology exchange, the experts there had a classic saying, saying that the bushing has both spring-like elasticity to store energy, and damping like a shock absorber to absorb energy. Rubber, on the other hand, is difficult to separate from its elasticity and energy-absorbing properties. Often, the softer the rubber, the better the vibration isolation, but it is more likely to cause jitter, and the harder the rubber, the better the energy attenuation, but not good at isolating vibration. So people invented the hydraulic bushing. The rubber is hollowed out internally and filled with oil, and as the oil flows through these channels, it acts like a hydraulic shock absorber, attenuating the vibration energy and providing additional damping, resulting in improved damping as a whole and a softer bushing.
In short, several major elements of the suspension, spring bearing strength, shock absorber and bushing depth absorption of vibration and attenuation, stabilizer bar and suspension connecting rod, ensure the system pattern.
end
We'll talk about it here in this issue, and you'll find that in the first episode, we've only been sharing the basics of suspension, which has been more than ten minutes, but it's a series, and we'll talk about the relationship between them and the classification of suspension in the next few episodes. Many people don't like to listen to theory, but unfortunately, only by combining theory with practice can we obtain true knowledge. Those who recognize Lao Wang will always be recognized, and if he is not interested, he will not be able to hear the last paragraph, are you right? I am Lao Wang, see you next time