Fast iterative Toyota CVT gearbox
= Toyota Direct? Shift? Sectional view of CVT gearbox
The full name of CVT gearbox is continuous? Variable? Transmission stepless automatic gearbox. The transmission mode of CVT is different from the gear transmission used in most automatic gearboxes, but adopts steel belt friction transmission. The speed ratio is controlled by a set of two pulley grooves with variable width. Low speed mode "low? Gear. The input pulley groove is wide and the output pulley groove is narrow. The transmission radius of the guided input is small, and the transmission radius of the output is large. Therefore, the speed of the input shaft of the engine is higher than that of the output shaft. The corresponding overspeed mode "overspeed? Gear. The input pulley groove is narrow and the output pulley groove is wide. The input transmission radius is large and the output transmission radius is small. Therefore, the rotational speed of the engine input shaft is lower than that of the output shaft. This is similar to the speed regulation principle of variable speed mountain bike. Because the width of the pulley groove is continuously variable, the corresponding output speed ratio is also continuously variable.
Fast iteration of Toyota CVT gearbox
Due to the high market share of CVT gearbox in Japan, Toyota Group has been continuously investing in the research and development of CVT gearbox. Since 2000, Toyota CVT gearbox has been iterated to the fourth generation. Among them, fuel economy is an important indicator of evolution, and the latest Toyota direct? Shift? Compared with the previous generation CVT gearbox, CVT saves more than 6% fuel. So what is the secret to help Toyota keep the fuel economy optimized in the process of constantly updating CVT gearbox? Let's look at the secret.
= Toyota Direct? Shift? Working schematic diagram of CVT gearbox
The latest Toyota direct? Shift? Code name of CVT gearbox is K 120. It innovatively adds a set of first gear direct drive gear system. Switch to gear transmission gear through clutch at low speed? In the driving mode, the power is directly transmitted by the gear, as shown by the green path. When the speed is higher, switch to the pulley drive belt through the clutch? In the driving mode, the power is transmitted by the steel belt and pulley groove at a continuously variable speed ratio, as shown by the red path.
= Toyota Direct? Shift? Working mode of CVT gearbox
Due to the above working principle, CVT gearbox has several remarkable characteristics.
Advantages:
1. Better fuel economy
2. It is more fun to drive.
3. Lighter and more compact gearbox design.
= Toyota Direct? Shift? Direct drive gear system of CVT gearbox
Toyota direct sales? Shift? Direct drive gear system is introduced into CVT gearbox to overcome the shortcomings of traditional CVT. Because CVT gearbox adopts steel belt friction transmission, power output is bound to be limited. Otherwise, the relative friction may exceed the static friction, thus wearing the steel strip. Direct and direct drive gears? Shift? CVT gearbox no longer needs to limit the output power and torque of the engine at low speed.
Comparison between Nissan XTronic gearbox and traditional CVT gearbox
In fact, the first Nissan Group introduced the gear system, but it was not divided into two independent driving modes. Because Nissan's SUV model is very heavy, it should be matched with a high-powered engine. Therefore, Nissan developed XTronic gearbox scheme. Based on the hydraulic torque converter and two sets of transmission pulleys in the traditional CVT gearbox scheme, the clutch module was removed and replaced with planetary gear sets that can transmit more power. Toyota, on the other hand, makes the gear system fully responsible for the low-speed gear drive mode and widely adapts to the TNGA platform.
Toyota direct sales? Shift? Detailed description of CVT gearbox advantages
A. Better fuel economy
= Toyota Direct? Shift? Comparison of transmission range of CVT gearbox
Now the development direction of gearbox is a wider speed range. Both low-grade acceleration performance and high-grade fuel consumption are taken into account. This has always been a difficult point in the development of CVT gearbox. The volume speed ratio of traditional CVT subject to pulley groove is generally around 6.5. Toyota direct sales? Shift? Because the CVT gearbox is directly driven by gears at low speed, the partial continuous transmission with pulleys takes better care of the middle and high speed range than the design. Therefore, the overall speed ratio has reached a good 7.5. The engine can be easily kept in the economic speed range, thus achieving better fuel economy.
B.driving is more interesting
= Toyota Direct? Shift? Comparison of acceleration characteristics of continuously variable transmission
Because the low gear is directly driven by gears, Toyota direct? Shift? The black curve of CVT gearbox acceleration characteristics has better acceleration response and higher acceleration than the gray curve of traditional CVT. On the one hand, the potential of the engine can be directly exploded in the gear transmission mode. On the other hand, the design of pulley drive is optimized, and the included angle of pulley groove is reduced from 1 1 to 9 degrees, and the response speed is improved by 20%. It makes the TNGA platform model equipped with this CVT more fun to drive.
C. Lighter and more compact gearbox design
= Toyota Direct? Shift? Comparison of pulley volume of CVT gearbox
Although Toyota is directly operated? Shift? CVT gearbox has more complex structure and better performance, but the pulley groove as the main body of gearbox is simplified. The design of pulley groove tends to take care of medium and high speed, which reduces the load requirement. So the inertia of pulley groove is optimized by 40%. The gearbox design is lighter and more compact.
In summary, Toyota direct sales? Shift? CVT gearbox innovatively introduces gear transmission mode and pulley transmission mode. Therefore, on the basis of traditional CVT, better fuel economy, better driving pleasure and lighter and more compact gearbox design are obtained. I hope the above introduction will give you a better understanding of Toyota CVT gearbox.
Introduction video:
Reference materials and extended reading
American Society of Automotive Engineers Paper 2018-01-1062? Development? Yes? New? Continuous? Variable? Transmission? For what? 2.0 liters? Class? vehicle
SAE paper 2015-01-11? Development? Yes? New? Continuous? Variable? Transmission? For what?
2.0 liters? Class? vehicle
American Society of Automotive Engineers Paper 2014-01-1730? Development? Yes? Driving? Force? Control? Technology? Yes? CVT？ For what? North? American? Market?
American Society of Automotive Engineers Paper 2014-01-1728? Development? Yes? New? A generation? Continuous? Variable? Transmission device [machine] transmission
American Society of Automotive Engineers Paper 20 13-0 1-0367? Development? Yes? Proportion? Control? System? For what? Toyota? New? Continuous? Variable? Transmission device [machine] transmission
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