In the past ten years, the speed of automatic transmission popularization is very fast, the mainstream AT transmission has reached 9 or even 10 gears, and the passenger car manual transmission has only 6 gears at most (the truck transmission is another matter), still stuck at the level of 20 years ago, why automatic transmission can continue to increase gear, and manual transmission is not, why can't you create a 10-speed manual transmission for passenger cars?
In fact, the manual transmission can have more gears, as shown in the above figure, the manual transmission used in the truck has 16 gears, and the 7-speed manual transmission in the following figure is a customized product for high-end drivers by some supercar brands, such as Porsche, Corvette, etc. There are requirements for the driver's operation skills. It can be said that the manual transmission of the passenger car stops at 7 gears, and it still cannot increase the gear as unscrupulously as the AT transmission.
What causes manual transmissions to be difficult to increase gear?
Passenger car manual transmission is mostly 5 gear, 6 gears the reason is the difficulty of operation, as shown above this 7-speed manual transmission has 7 forward gears, then in the condition of not considering the reverse gear selection mechanism reached 7, that is to say, the lateral selection from 3 to 4, the difficulty of operation will increase; of course, this is not much for some manual masters, then the current gear position increased to 8, 9 or even 10? The lateral selection of gear levers reaches 5, at this time the control of the transmission will no longer be handy, and it can also be understood that the learning cost is too high.
On the other hand, the reuse rate of the fixed shaft (parallel shaft) transmission gear mechanism is too low, each additional gear needs to add a pair of gears (the upper and lower two-axis gears are one-to-one correspondence), and at the same time, there is a synchronizer and a fork, the 5-speed manual transmission in the figure above has 3 synchronizers and 3 forks, what if the gear is increased to 10? There will be 6 synchronizers, 6 forks, the lateral arrangement of gear gears will reach 10 pairs, at this time the weight and cost of the transmission will be greatly improved, followed by every two gears between the synchronizer to leave space, then the longitudinal length of the 10-speed manual transmission will become more and more uncontrollable.
The game between fixed shaft gear mechanism and planetary gear mechanism
The biggest disadvantage of the fixed shaft (parallel shaft) gear mechanism is that the reuse rate of the gear group is too low, as mentioned above, a pair of gears can only achieve one gear, such as when the 6MT manual transmission is hung in 5 gears, the other 4 gear spindles, the 4 groups of gears hanging on the middle shaft are idling, and can not play any other role; and the advantage of the planetary gear mechanism is that it can use fewer planetary rows to achieve more transmission ratios, such as the common 6AT transmission, whether it is Aisin, or ZF have only 3 planetary rows, Aisin can also achieve 8 gear ratios (8AT) using 3 planetary rows.
The advantage of the planetary gear mechanism is that it can use a number of different combinations of clutches and brakes, the use of limited planetary rows to achieve more transmission ratios, can also be understood as the combination of clutch and brake, as shown in the above figure Mercedes-Benz 9AT transmission, although the number of gears reached 9, but only used 4 planetary rows, theoretically 4 planetary rows using clutches, different arrangements of the controller can achieve up to 12 gears; so talk about the good and bad of the transmission, It is not only necessary to look at the specific number of gears, but also to consider the degree of compactness and the reuse rate of components.
It is also because the fixed shaft (parallel shaft) gear mechanism reuse rate is too low, so the Honda parallel shaft transmission stops at 8 gears, which is not only the cost level of the restriction, the space constraint is the most important; other such as double clutch transmission to increase the gear will also face such a dilemma, because the dual clutch transmission, parallel shaft transmission, manual transmission are fixed shaft type, are a set of gears to achieve a gear, as shown above 6 speed double clutch 6 gears are arranged on two input shafts, The gears of the manual transmission are arranged in longitudinal order.
If the manual transmission reaches 10 gears, it is like doubling the length of the above picture, how can such a long transmission be arranged? For most passenger cars, it is impossible to provide such a large space for a 10-speed manual transmission; the truck is of course no problem, because it has enough space to equip a 16-speed transmission, but the family model is different, so there are many difficulties in increasing the gear of the manual transmission, one is the difficulty of operation, and the other is the significance of realization.
Building a product requires a physical environment that suits its survival
To create any mechanical products need to have a suitable for its survival of the actual environment, can be simply understood as the demand, installed capacity, the above has mentioned that the volume of the 10-speed manual transmission will be very large (long), followed by the addition of 5 pairs of gears, 3 forks, 3 groups of synchronizers on the basis of 5-speed manual will greatly increase the production and manufacturing costs, when the cost of a manual transmission is higher than the common CVT, 6AT, then what is the meaning of its existence? The reason why there are models equipped with manual transmissions is more about its low-cost advantage, thereby reducing the threshold price of the vehicle.
And once the manual transmission loses its cost advantage, then its existence is gone (surely some people will say that manual transmission is more fun?). It can only be said that the car is a very small number of people, the main engine factory to retain a small number of models of the manual version is not to bring fun to consumers, just to reduce the cost of the price), so the number of manual gears for most passenger cars stop at 6 gears, although the AT transmission can have 10 gears, that is to rely on the advantages of the planetary gear mechanism, but the fixed shaft gear mechanism does not have this compact advantage.
Each additional gear can only continuously lengthen the gearbox, so increasing the gear is unrealistic, because today's manual transmissions are entry-level cars, there is no compromise in space; and the AT transmission is not unlimited to pile gears, it is likely to stop at 10 gears (there are 12 gears, but not mass production), because more gears will lead to extremely dense transmission ratios, each gear transmission ratio corresponding to the speed range is too small, and our road conditions are increasingly congested, and the speed changes frequently in daily driving. This will lead to 12AT, 13AT tired of constantly jumping gears, but reduce the efficiency; in short, the fundamental reason for the manual transmission of passenger cars with up to 6 gears lies in the disadvantages of the fixed shaft gear mechanism, and secondly, the human brain control logic is far less fast than that of the computer, so more gears reduce the fault tolerance rate.