20000KM old car owners talk about their personal views on QX50CVT and finidi.

18, an elderly car owner, was invited by a friend to play in the home forum and saw many people complaining about the gearbox of QX50. But to be realistic, I think CVT itself is a good transmission technology, and my own experience is also very good, so I also want to talk about CVT by sharing some of my own car experience.

Presenting beautiful photos of my car, the weather is excellent these days and the effect is refreshing. There are two main considerations when deciding to buy this QX50. First, it's great to have no quality awareness. The second is not to follow the big slip.

I know a little about cars. Over the years, I have driven many models from time to time, starting from MT Fukang, in Liu Ma (5AT), in the second generation of Forester (4AT), and now the QX50 of CVT, so the experience of using the gearbox can still be roughly compared. After reading everyone's point of view, a common cognition is that CVT has poor performance and low grade. I want to say here that there are indeed many misunderstandings. In fact, each box has its own characteristics, and the performance positioning of each model also determines which box it uses. Every combination is made by engineers day and night, so it can be summarized in one or two sentences. Otherwise, the engineer's head will be bald? To talk about CVT, we have to start with the gearbox. Why is there such a device in the car? It's exactly the same as this thing on the bike.

We need a speed change device to transfer the power generated by the power source to the key parts that can be used for driving, that is, the wheels. Theoretically, as long as the driving force generated by the power source is greater than the resistance that needs to be overcome during driving, driving can be realized. However, the reality is that driving resistance is not constant. Air resistance, uphill resistance, resistance caused by vehicle load, etc. It all means that power and resistance will be accompanied by stumbling. It is not easy for a car to change its power source, and it is impossible for us to change a rider because we can't ride uphill. So, transmission appeared. Just like our common mountain bike sprocket, this is a very typical transmission device.

Without such a transmission structure, it is basically to rush downhill to accumulate strength, climb up and stand up and continue to exert strength. ...

But bicycles with this transmission are much easier.

When going uphill, it can be hung on a big sprocket, and the torque is instantly amplified. You can go up without thick thighs.

When pursuing high speed, you can hang a small sprocket, step on it once, the wheel can turn at least two or three times, and the two wheels step on it fiercely, which is very fast. This is the transmission. The shifting process of the transmission is actually to adjust the "transmission ratio" of the power input wheel and the power output wheel.

Archimedes said that if you give him a lever, he can pry up the earth, which is actually the prototype of the concept of transmission ratio. The input-output ratio is actually the transmission ratio.

Taking gear transmission as an example, when two gears are engaged, the radius R and power F of the gears make the engaged gears become a very typical lever system. When the two gears are the same size, input the power of F r 1 and output F r 1.

On the premise that the input wheel is unchanged, if the radius of the output wheel is reduced, then if F r 1 is also input, the resistance will increase due to the reduction of r2, but the input wheel can rotate several times once. This is actually a high gear in the car. This is actually the reason why the gear is too high and it is easy to turn off when driving MT models.

When we keep the output wheel unchanged and reduce the input wheel, the input power is still F r 1. Because the radius r of the output wheel is greater than R 1, it is equivalent to amplifying the torque of F r 1 to the level of F r2, which is actually the low-gear principle in the car. Therefore, the basic function of the transmission is to combine countless transmission ratios through a large number of such gears, large and small, and choose the appropriate transmission ratio matching according to our resistance during driving. Each gear ratio corresponds to a gear on the car. When we say fifth gear, we mean there are five groups, and sixth gear means there are six groups. When the vehicle is running, we need to choose the appropriate gear to match it according to the output power of the engine.

Because the transmission ratio of each gear is fixed, there is a very embarrassing situation here, that is, the low gear is not good and the high gear is not good. I feel that 3.5 gear is more suitable. The common driving feelings are "blocking" and "frustration". Even if the current transmission adjustment technology is awesome, it will still appear in situations such as queuing out of the basement or climbing in the wild. Therefore, the advantages of CVT are obvious, because it has no fixed transmission ratio, so it will not jump step by step, nor will it adapt to the engine speed like a fixed transmission ratio. This is also the reason why the CVT gearbox is smooth, because of the structure, it is very smooth.

Why CVT can realize stepless speed ratio? Actually, it's just like the picture above. It uses a steel chain to connect the input wheel and the output wheel, and the total circumference of the steel chain remains unchanged. The radii of the input wheel and the output wheel are variable. Therefore, under the premise that the total circumference of the chain remains unchanged, its input and output wheels are not fixed like gears and can be changed at will.

On this premise, CVT transmission can actually stabilize the engine speed while changing the transmission ratio, which is impossible for other types of transmission. This characteristic actually corresponds to the fuel consumption level of the vehicle.

Because the internal combustion engine is not like an electric motor, its power (power &; Torque) is not released at once, but only at the optimal speed. The dynamic performance of the engine can only be fully released when it is close to a specific speed range, but for the transmission that needs to shift gears gradually, the engine speed can't be kept at a specific speed all the time with the shift process, because once the shift is started, the speed will drop. But CVT can. It doesn't have those complicated gear structures, which can keep the engine at an appropriate speed, so the engine can always be kept in the best working condition, with higher efficiency and lower fuel consumption. This is why the fuel consumption of a car as big as QX50 is not particularly high. With the variable compression ratio engine technology VC-Turbo, the working efficiency can be by going up one flight of stairs. PS: The essence of Infineon's engine black technology is actually to improve the working efficiency of the engine and improve the power waste at low speed by changing the compression ratio. From this perspective, VC-Turbo and CVT are a perfect match. In a word, from the mechanical design, I think CVT is definitely a new transmission structure with high efficiency (refer to the transmission manual, the belt transmission efficiency is higher), small volume and light weight, and it is a very good transmission structure. As for the popular point: 1, CVT skidded. Normal CVT will not slip. On the one hand, because the system has a protection mechanism, it is impossible to let it slip away; Second, as long as the sliding box is still there, it is useless and it is impossible to open it again. Slipping is called fault, which is not a daily feature of CVT. The working basis of CVT is actually friction. Through pressure adjustment, the friction between steel belt and helical gear can realize power transmission. Therefore, combined with the physical knowledge learned, the main harm of slipping is that relative friction generates a lot of heat, which directly burns the gearbox. Q=fs, where F =μF(Q- friction heat generation, f- friction force, s- relative sliding distance, F- pressure, μ-friction coefficient) In CVT gearbox, the most important force is friction force, that is, F. The so-called slippage means that the output of the engine exceeds this F. The friction force before slipping is called static friction force, and the friction force after slipping is called sliding friction force. The friction coefficient μ is determined by the contact surface between the steel strip and the cam. At the same time, another factor that affects F is F, and this force is the pressure on the vertical contact surface. Unlike the coefficient of friction, this force can be actively increased. When the driving computer senses that the steel belt is about to slip, the relevant machinery will adjust the cam and steel belt and increase the F value to prevent slipping. Therefore, regarding CVT slipping, it is actually scrapped if it does not slip. In fact, many friends feel that stepping on oil is not slipping, but CVT itself keeps the engine shifting at the best speed, and there is no strong acceleration. Actually, it's just not as layered as other gearboxes. It seems to be dry and screaming, but it has been accelerating and has not slipped. 2, CVT performance meat. Strictly speaking, the theory of CVT performance meat belongs to historical issues, and at is also meat. All the old rangers I have driven before, Liu, have this problem. Because the structure of hydraulic torque converter is adopted, it is not directly driven like clutch, so the car with this structure is really difficult to drive earlier. Because at the moment of stepping on the accelerator, the engine has to stir up the oil in the hydraulic torque converter to transfer the power to the gearbox, so the meat. But this is an old calendar, and the CVT now is not the CVT before. Lockup clutch is designed in the current hydraulic torque converter. As long as the system meets the conditions, it will be locked directly through the clutch, and it will not waste so much oil stirring resistance as before.

By the way, the transmission ratio setting. I specifically asked the technicians about this. The 1 gear transmission ratio of QX50 will be lower (about 2.6, and the 1 gear of AT gearbox is about 4), so the first gear of QX50 is close to the second gear of others, which is equivalent to starting the second gear. This is equivalent to saving the shift time of 1-2 and pulling it directly by the engine. The highest gear ratio of QX50 can reach 0.38 (generally at gearbox is around 0.7-0.8), which is equivalent to driving at high speed when the engine speed is very low, so it is more fuel efficient.

3, CVT torque is low, let go of the measurement and talk about toxicity = hooliganism. Any structure has its design strength standard, so no matter how much torque the engine outputs, it must be equipped with a gearbox that carries much torque, regardless of the structure. DQ200 is a dual clutch, but the maximum torque is only 250n·m, so it is wasted when it is directly used on QX50 (the maximum torque of 2.0T VC-Turbo engine is 380n·m). This is actually like the dosage of medicine, which has to match your physical condition. In fact, Williams once considered using CVT gearbox in F 1 racing car in the early days, because this gearbox structure can keep the engine at the best performance speed. However, considering that F 1 should return to the competitive spirit of drivers, the FIA announced that it was forbidden to use CVT and other driver-assisted driving devices. Of course, the performance cognition of CVT gearbox varies from person to person, and only after driving and feeling can you have a say. And the model positioning of QX50 is also here. It is impossible to develop a set of AT alone, and GTR's dual clutch and QX are not right. Anyway, personally, it is really comfortable to run leisurely on the mountain road with the sound simulated by QX50. Here are some odds and ends of me and my car.

My QX50 has just run more than 20,000 kilometers, not much. Usually, I still run in the city most of the time. Now that the epidemic has come, I will go even less.

Clean, neat and elegant. Unlike some brands that have various lighting effects, they are very comfortable to use.

Infineon's interior has always been so low-key, but it feels great in actual use.

VC-Turbo black technology is a bit dirty, please ignore it, but this technology is really second to none in the industry.

Finally, every technology has its reasons. It's easy for the keyboard party to say a few words casually, but do you really understand the technical principles? Keyboard parties are not terrible. What is terrible is that their casual speculation will make people who don't understand believe it. So I still hope that everyone has the ability to think independently and learn more about everything by themselves, which is better than anything else.