Bosch's new steel belt has been very powerful in transmitting torque, which has just exceeded 500 N m. For some 3.0T models with high power adjustment on the market, there is no "hmm ~" sliding in place, and "hmm ~" becomes like this, so it can't be used.
Manual gearbox has higher transmission efficiency and fuel economy than automatic gearbox, more mature technology in all aspects, and lower manufacturing and maintenance costs. However, the operation is complicated, and it is necessary to operate the clutch pedal, accelerator pedal and gear handle at the same time, and it also requires a lot of experience to grasp the timing of gear shifting.
For our novice driver friends, it is not very friendly, and the market share is shrinking year by year. The future think tank released an in-depth report on the automatic transmission industry. The sales volume of manual gears has been declining year after year, 20 16, 20 17, 20 18. Sales in the first seven months accounted for 38.68%, 32.77% and 24.44% of the total sales of passenger cars respectively. You see, 38 has dropped to 24. Generally speaking, manual gearbox has many advantages, but it is more difficult to operate, the threshold is higher, novices don't like it very much, and fewer and fewer people buy cars with lower cost.
Sequential manual gearbox
What's the second one called? Sequential gearbox. It's actually an enhanced version of the manual gearbox. The difference is that the sequential gearbox only needs to step on the clutch in the starting and reversing gears, and it does not need to be stepped on in normal gear shifting. There are papers in Mechatronics magazine, and lectures on the analysis, modeling and simulation of gearbox shifting mechanism in racing series. The sequential gearbox cancels the synchronizer.
In order to avoid tooth impact, engineers directly designed some teeth with large size and large gap on the gear, which are called "dog teeth" in the local dialect. When shifting gears, just give it a fierce "help" and don't worry about damage.
Just like: chopsticks are easy to break, so the engineer directly made two iron bars, or glued three chopsticks together for you to use, constantly. Therefore, the sequential gearbox does not need synchronous gears when shifting gears, so there is no need to step on the clutch.
It sounds convenient and good, but in fact, the sequential gearbox was developed for racing, with the purpose of reducing the shift steps and shortening the shift time. Shift impact, frustration, noise and life span are irrelevant. As long as you are quick and can win, you can only shift gears up and down in sequence. There are not many models of series gearboxes available in the market. In the past, only BMW M-Power and Lamborghini used this model.
Three kinds: AMT
AMT is no different from manual gear in structure. Hunan University has a paper "Research on the Electronic Control System of AMT Automatic Transmission". AMT is to add a set of automatic starting shift mechanism on the basis of traditional manual shift. To put it bluntly, it is a "cheat" and a "plug-in" for manual transmission. So AMT basically has the advantages of manual transmission, high transmission efficiency, simple structure and low cost.
However, the engagement and disengagement of the clutch are easily affected by various factors such as road conditions, vehicle load and engine speed. Therefore, it is very difficult to adjust the clutch if you want to replace the human brain with a computer.
Type 4: Double clutch
In fact, the dual clutch was invented very early, around 1940, but no one made it for a long time. It was not until 1980s that Porsche picked it up as a treasure, and it was also improved on the basis of traditional manual transmission.
Chongqing University has a paper "Design and Analysis of Dry Double Clutch of Double Clutch Automatic Transmission", which says that the double clutch gearbox separates the teeth of odd and even gears, and the two clutches control the odd and even gears respectively.
This has the advantage that the pre-selected gear can be realized, and 1 gear is in use. At work, the second gear has been prepared for you in advance and put into gear, and the shift speed is very fast. At the same time, the two clutches cooperate with each other to avoid the interruption of power output, and the comfort, fuel consumption and emissions are improved to a certain extent compared with manual transmission.
It's like: When you walk normally, you always have one foot on the ground, right? Left foot on the ground, right foot in the air; Right foot on the ground, left foot flying. This is a double clutch. What's a normal gear shift like? Jumping with your feet over there is uncomfortable and more tiring, isn't it? However, it is similar to AMT: the dual clutch still has a lot of room for improvement in clutch control and shift logic.
AT, let's talk about the fifth kind: AT, is this common? The structure of AT gearbox is different from that mentioned above. Although all gears are used for transmission, not every gear corresponds to a gear. Instead, several gears are stuffed into a hollow gear to form a planetary gear set to take charge of several gears.
It's a bit like a Russian doll: how did it get smaller when you took one off? If you take it off again, it's smaller, it's all the same. In this way, only a few sets of gears are needed to realize multi-stage speed change. For example, Ford and GM 10AT have only four sets of planetary gears, which are not bigger in size and weight than some 8-speed gearboxes, and the loads in each gear are evenly distributed.
Therefore, the reliability and carrying capacity of AT are still good. This is like saying: in the past, everyone was responsible for a project, but now everyone is sharing it equally, so there will be no personal fatigue. Nanjing University of Aeronautics and Astronautics has a paper "Study on Stability and Bifurcation Characteristics of Planetary Gear Transmission System". Planetary gear transmission system has the advantages of compact structure, high bearing capacity, light weight and small volume, which is mainly determined by its power split transmission characteristics. How can there be no shortcomings?
The disadvantage is that to ensure the average load distribution of each planetary gear, the manufacturing and assembly errors of parts are very high, which is actually the so-called "high cost". At the same time, there is no rigid connection between the torque converter and the engine, and the power loss is relatively large under some working conditions. The old AT gearbox, when we were driving, didn't we feel "Hey, it's much more fuel efficient than manual transmission, two or three dollars." That's why.
Type 6: CVT. CVT is completely out of gear, so it is not needed. The main structure is a bit like an old tape recorder. There is a plastic box outside, wrapped in two wheels, with a brown belt moving on it.
CVT relies on bevel wheels and steel belts, similar to magnetic tape. It is rotated and gathered together. As long as the diameter of bevel gear is changed, CVT can realize any transmission ratio change within the transmission ratio range, including 1.5 and 2.843. If other gearboxes take the stairs, CVT is a disabled passage, that is, a slope, and the wheels can be directly pushed up. Because of this, CVT can find an optimal transmission ratio to match the current working condition at any time. Hunan University has a paper "Vehicle Modeling and Performance Evaluation of Metal Belt CVT".