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The superstructure is the real focus. The so-called “multi-link” is exactly the same as the former McPherson suspension: a single spring damping strut alone supports the overall situation, and there are no other links and other components. The use of integrated spring damping struts to take into account the degree of freedom of the wheel other than the vertical direction is the core element and identification basis of the MacPherson suspension.
So we said, regardless of whether your lower A-shaped arm is changed to “chopsticks”, “spoon” or “fork”, as long as it is still a single spring damping pillar, it must belong to McPhee The slender structure has nothing to do with the true multi-link suspension. To classify the “chopsticks”/double-link/rear Macpherson/spring sliding column suspension as “multi-link suspension” is purely a use of ordinary consumers to “multi-link suspension” I don’t understand the scam of forcibly affixing gold to my products.
Why can’t MacPherson?
Compared with the serious multi-link suspension, the MacPherson suspension has low cost, small space, simple structure, and the performance is obviously compromised. But useEspecially with rear suspension.
Because the front axle of the car has more steering functions, the design of the front suspension is more restricted. One has to take care of the steering angle of the front wheels, and second, there is a large engine taking up space in the middle. As a result, there are not many suspension structures that can be selected for the front axle. Many times it is impossible to use the MacPherson suspension, and it will pass with one eye closed.
In fact, the MacPherson suspension was originally invented to help them further reduce costs and save space in household grocery shopping carts with front-wheel drive with a transverse engine. However, the rear axle of the car does not need to consider the steering, and the space is relatively abundant, so the use of the MacPherson structure in the rear suspension can only be said to be cost-constrained.
The change in the gain characteristics of the negative camber angle is confusing, and the result is not conducive to improving vehicle cornering performance;
The roll arm formed by the roll center and the center of gravity is difficult to shorten. As a result, anti-roll ability is difficult to improve;
The trim lever formed by the trim center and the center of gravity is difficult to shorten. As a result, brake nodding is difficult to suppress.
1. Negative camber gain of Chikui
The MacPherson suspension rarely appears on vehicles that focus on driving performance. A big reason is the negative camber gain it can provide( camber gain) is too little.
The so-called negative camber (negtive camber) refers to the angle at which the upper end of the wheel tilts toward the inside of the vehicle. When the vehicle is cornering, we hope that as the degree of compression of the outer suspension increases, the negative camber of the outer wheels will increase accordingly. This allows the outer tires to have the maximum contact area at all times, thereby ensuring the tire’s grip in the corners. As the vehicle’s center of gravity shifts when turning, the grip of the outer tires is more important.
(We hope, pay attention to the ground of the left wheel)
However, the negative camber angle gain characteristic is the natural shortcoming of the MacPherson suspension:
First, when the wheel jumps up and the damping spring is compressed, the angle of the wheel relative to the ground changes non-linearly. Secondly, the greater the upward travel of the wheel, the slower the negative camber angle will increase (the gain of the negative camber angle decreases); as the wheel moves upward, When the angle between the spring strut and the lower arm exceeds 90°, the negative camber gain will even become a negative value. (The body continues to lean and compress the suspension, and the negative camber will be reversed. Decrease). The reason is actually a very simple geometric problem, not much explanation.
(Macpherson’s reality, the spring is compressed upwards, and the wheel inclination is almost unchanged)
The negative camber gain characteristics are much better for multi-link suspensions and double wishbone suspensions with the same principle. Because there are connecting rods both up and down, this type of suspension only needs to adjust the length of the upper and lower arms to easily achieve larger or smaller negative camber gain effects. I want to exercise, I want to be comfortable and comfortable. I don’t know where it is better than McPherson.
(Change of negative camber angle of double wishbone suspension)
So in the world of high-end cars with a value of several hundred thousand yuan, the front double wishbone rear multi-link (the real one) is The basic skills of survival. As for the MacPherson suspension, let alone the rear axle, as the price and class increase, the front axle can no longer accommodate it (only BMW and Porsche are a few exceptions) ).
2. Embarrassing roll center
Whether it’s for comfort or performance, we don’t want the car to roll too much when cornering. The vehicle will roll to the outside when cornering, because the center of gravity of the vehicle (CoG) is at the center of the suspension roll(Roll center/RC), the greater the height difference between the two “centers”, the longer the arm of the roll during roll, the more likely it is to roll. Therefore, for the suspension system, in order to reduce the tendency of roll, the roll center should be appropriately raised and the roll lever should be shortened.
The geometry of the suspension system determines the position of the roll center. You guessed it right, this is another natural shortcoming of the MacPherson structure.
The roll center height of the MacPherson suspension is related to the lower swing arm angle and the spring strut angle. The greater the inclination angle of the spring strut, the closer the IC in the figure is, and the higher the intersection of the IC-wheel grounding point line and the central axis, the shorter the roll arm will be-it doesn’t matter if the previous sentence looks confused, simple But the cumbersome geometric problem is just that, knowing that the greater the inclination angle of the spring strut, the smaller the tendency of roll
However, this angle is not about adding more. The reason why the MacPherson suspension is more space-saving than other types of suspension is largely because the upper wishbone is omitted. If the spring sliding column is inclined inward at a large angle, it will inevitably erode the inner space of the car. If all the advantages in space are lost, using McPherson will not make much sense.
(activeFigure: The inclination angle of the spring strut cannot be increased indefinitely)
There are exceptions. For example, the front and rear of the Porsche 718 sports car are of Macpherson structure. At first glance, it seems to be the same model as BYD Han, Tang, Song plus and other models? I think too much, after all, a sports car is a sports car, and there is no need to take too much into consideration of space, so the 718’s MacPherson suspension has a considerable angle of inward tilting of the spring struts. The resulting negative camber gain, anti-rolling ability, etc., are far from the same as the front and rear Macpherson cars and SUVs.
So don’t smile when you see Porsche also use McPherson before and after, Porsche is Porsche, you are you.
(Porsche 718, the inclination angles of the four spring struts are not small)
3. The hard to suppress nodding effect
Not only horizontal movement, MacPherson is also subject to its own structure in vertical movement.
We know that due to the center of gravity and inertia, the vehicle will “nod” when braking and “raise” when accelerating. Everyone can also think that if you want to suppress nodding and raising your head, can you increase the stiffness of the spring shock absorber? But this can’t be added casually, the spring is too hard, and it hurts skr.The bottom is (the simple comparison structure does not represent specific application performance). In addition to McPherson, the latter four names are the suspension types that can truly be called “multi-link”. However, in most official documents, you can only see three uniform words, “multi-link” (or it may be a manufacturer’s Weird name).
There are four ways to write the word “fen”, and there are 365 ways to write the word “multi-link”.
1. Three horizontal and one vertical E-shaped multi-links
Speaking less professionally, the E-shaped multi-link can be regarded as the “beginner model” in the real multi-link world. The name is straightforward: it is named after the four connecting rods with a “three horizontal and one vertical” structure, which look like the letter E from top to bottom. The E-shaped multi-link is sometimes called a four-link, but the name is as meaningless as “multi-link”: who knows what kind of four-bar you are?
This kind of rear suspension structure is gradually becoming popular among mid-priced models, replacing many old models that used MacPherson rear suspensions. As mentioned earlier, Toyota’s old Camry uses a rear McPherson suspension (Toyota is called a double link, mentioned above), and today The new generation of Camry has changed to an E-shaped multi-link (however Toyota calls it a double wishbone, you are not crazy about it).
Similar to the rear McPherson, the E-shaped multi-link has two trailing arms, also called control blades; however, the difference is that the E-shaped multi-link has three otherWith this staggered horizontal connecting rod, the wheel position is completely bound by three horizontal and one vertical four connecting rods. The spring shock absorber only bears the force in the vertical direction and performs its own duties.
(When the vertical arm jumps up and down, there will be a forward and backward displacement)
As a type of multi-link suspension with simpler structure and lower cost, the E-shaped multi-link suspension also has obvious shortcomings. Because the control blade extends forward for a long time, the top end cannot be connected to the sub-frame, and can only be directly connected to the body. Without the buffer of the subframe, vibration and noise will be directly transmitted to the body. In addition, the geometric motion trajectory of the control blade is a fan from the side of the car. When the rear wheel bounces up and down, it will inevitably have a certain front and rear displacement, which is not precise enough for the restraint positioning of the rear wheel (Macpherson after this point is the same).
However, in the vehicle configuration table, only three words, “multi-link” appear.
2. Easy to use but expensive trapezoidal multi-link
In the true sense, the superiority of “multi-link” can be counted as trapezoidal multi-link and five-link.
The trapezoidal multi-link is also called H-arm multi-link. The core component is an H-arm with four connection points at the bottom or trapezoidal link(yellow in the picture below), in addition to this, there will be two separate horizontal links (one Blue, the other one is not marked in color), plus an integral link called an active guide (purple) span>.
The trapezoidal multi-link rear suspension is very common in high-end luxury cars. Squatting down at the rear of the car, you can see it in the bottom of various Mercedes-Benz and BMW cars. Electric car enthusiasts can also exaggerate. The rear suspensions of Tesla Model S and Model X are all standard trapezoidal multi-link structures, which are just two-character advanced. When I talk about Tesla in the future, don’t just know an “air suspension”. Air suspension just means replacing the coil spring with an air spring. What determines its performance is the basic structure of the suspension system. .
(Model S, pay attention to the integral link marked in blue)
In the trapezoidal multi-link suspension, only one H arm can constrain the freedom of the wheels in multiple directions. The longitudinal and lateral space is small, but it can achieve perfect wheel positioning control. However, the H-arm structure requires high rigidity, and it will be heavy if it is made of steel. High-end models sometimes use expensive aluminum. The large-size cast aluminum hollow H-arm has a good absorbing and filtering effect on shock and vibration, which is naturally suitable for high-end models.
However, in the model configuration table, the name is only three words, “multi-link”.
3. Five Links: The Big Trend of the New Era
Although the five-link is the most connected, it is also the best understood: any object has six degrees of freedom in space(x, y, z axis, translation and roll, 3×2=6), the wheel should be allowed to move up and down(damper and spring expansion) span>, so the remaining five degrees of freedom need to be restricted (there are four on the front wheel), each link can bind one degree of freedom , Here, five-link.
The connecting rod of the five-link suspension(5) and the bushing(5×2=10)More, it has high flexibility in adjustment. The weight of the five-link using aluminum can be very light, and the advantages of light weight can help car companies cope with increasingly stringent emission regulations. In recent years, almost without exception, Mercedes-Benz, BMW, Audi and other manufacturers have switched from trapezoidal multi-link rear suspension to five-link rear suspension. The five connecting points of the connecting rod on the wheel (called hard points) are larger in spacing, which is better for motors with instantaneous large torque characteristics. , Tesla switched to a five-link rear suspension on Model 3 and Model Y.
However, in the vehicle configuration table, there are still three simple words, “multi-link”.
(Red and yellow wishbone, disassembled into a five-link, integrated into a double wishbone, blue is the steering lever)< /p>
The four multi-link categories mentioned above, there is still a double wishbone suspension (double wishbone), it is compatible with the five-linkGreat interoperability. The five links of a five-link suspension, the upper two are combined into one to become an upper wishbone, and the lower two are combined into one to become a lower wishbone. The remaining one is used on the rear axle to restrain the rear wheel angle (toe angle). If it is used on the front axle, it is used as a steering rod. Double wishbone is usually used for the front axle, because the five hard points on the wheel end are combined into two to form a steering axis (king pin).
You can only rely on yourself if you want to be exempt from “tuition tax”
It needs to be clarified: The suspension is only a part of the chassis system, and the geometric structure is only a foundation of the suspension system. The materials, materials, and adjustments will affect the final chassis performance. Therefore, we must not rely solely on structure theory and judge reality based on structure alone. But in any case, first explain the suspension structure to consumers clearly, this requirement is not excessive.
Macpherson is called McPherson on the front axle, and when he moved to the rear axle, he changed his body and became a high-end expensive “multi-link”. The “multi-link rear suspension”, which is vague in itself and “skilled” by the manufacturer, is simply a flicker born out of industry-wide acquiescence. No one wants to tell you the truth, and tacitly admits that you are not interested in understanding, and guides you not to feel important. So the manufacturer and the media colluded, wiped the edge of false propaganda, and jointly fabricated a beautiful configuration parameter, why not do it?
The Chinese auto market is and will be in the primary stage of cognition for a long time. This is not alarmist or self-defeating.
Just a few days ago, a certain self-media made a big joke: an interviewed car owner questioned the manufacturer on the grounds of “stepping on the accelerator to accelerate the vehicle’s automatic downshift.” “It stands to reason that the acceleration gear of the vehicle increases and the deceleration gear of the vehicle decreases, but Mr. He’s car is completely the opposite.”-In this case, I don’t know the Canadian Alfred Horner Munro who invented the automatic transmission in 1921. Will smash the coffin board.