Toyota direct shift CVT continuously variable transmission

Recently a lot of friends to buy a new car to consider Toyota's models, from the Corolla, Lei Ling, RAV4 to Camry, Asian Dragon. Asked Starlet in the end how Toyota's CVT transmission, what are the advantages. Even some professional friends compared to try different brands of CVT models found that Toyota's CVT no matter how to toss the fuel consumption is very low. Today along with the Starlet to understand the technical details of Toyota's patented direct?shift?CVT it.

Rapid iteration of the Toyota CVT transmission

↑Toyota direct?shift?CVT transmission sectional view

CVT transmission is the full name of Continuously?Variable?Transmission continuous variable automatic transmission. The CVT's transmission differs from the gearing used in most automatic transmissions by using a steel belt friction drive. The speed ratio is controlled by a set of two variable-width pulley slots. Low speed mode "Low?Gear". The input pulley groove is wide and the output pulley groove is narrow. The input transmission radius is small and the output transmission radius is large. As a result, the engine input shaft speed is higher than the output shaft. Corresponding overdrive mode "Overdrive?Gear". Narrow input pulley groove, wide output pulley groove. The input transmission radius is large and the output transmission radius is small. As a result, the engine input shaft rotates at a lower speed than the output shaft. This is similar to the principle of speed regulation in a variable speed mountain bike. Since the width of the pulley groove is continuously electrically variable, the corresponding output speed ratio is also continuously variable.

↑Rapid iteration of Toyota's CVT transmission

The Toyota Group has continued to invest in the development of the CVT transmission due to its high market share in Japan. From 2000 to now Toyota's CVT transmission has been iterated to the fourth generation. Fuel economy has been a key indicator of this evolution, with the latest Toyota direct?shift?CVT being more than 6% more fuel efficient than the previous generation of CVTs. So what's the secret sauce that helps Toyota keep fuel economy optimized as it continues to update its CVT transmission? Let's take a look at the secrets.

↑Toyota direct?shift?CVT transmission working schematic

The latest Toyota direct?shift?CVT transmission is codenamed K120. it innovates by incorporating a first-speed direct-drive gear system. At low speeds it is switched via the clutch to the gear-drive Gear?Drive mode, where power is transmitted directly from the gears as shown by the green path. At higher speeds, the clutch switches to Belt Drive mode, where power is transmitted by a continuously variable ratio of steel belts and pulley grooves as shown in the red path.

↑Toyota direct?shift?CVT transmission working mode

Because of the above working principle, the CVT transmission has several distinctive features.

Benefits:

1. Better fuel economy

2. More fun to drive.

3. Lighter and more compact transmission design.

↑Toyota direct?shift?CVT transmission's direct-drive gear system

Toyota's direct?shift?CVT transmission introduces a direct-drive gear system to overcome the shortcomings of conventional CVTs. Since the CVT transmission uses a steel belt friction drive, power output must be limited. Otherwise the static friction may be exceeded and relative friction may occur, thus wearing out the steel belt. With direct drive gears for direct?shift?CVT transmissions no longer need to limit engine output and torque at low speeds.

↑Nissan XTronic transmission vs. conventional CVT

The gearing system was actually first introduced by the Nissan Group, though it did not differentiate into two separate driving modes. Since Nissan's SUVs are very heavy and have to work with high-horsepower engines. Therefore, Nissan developed the XTronic transmission program, in the traditional CVT transmission program of torque converter and two sets of transmission pulleys based on the removal of the clutch module and replaced with a planetary gear set can transmit more power. Toyota, on the other hand, has gone even further by making the gearing system entirely responsible for the low-speed gear-drive mode, which is widely adapted to models on the TNGA platform.

Toyota direct?shift?CVT transmission advantages in detail

A. Better fuel economy

↑Toyota direct?shift?CVT transmission gear range comparison

Today's direction of transmission development is a wider gear range. It takes into account both the acceleration performance of low-speed gears and the fuel consumption of high-speed gears. This has been the difficulty in the development of CVT transmission. Conventional CVTs are limited by the size of the pulley grooves and the speed ratio is generally around 6.5. Toyota direct?shift?CVT transmission due to the low-speed by gear direct drive, pulley part of the continuous variable ratio design to take better care of the middle and high-speed range. As a result, the overall speed ratio reaches a better 7.5. The engine can be easily kept in the economical rev range, resulting in better fuel economy.

B. More fun to drive

↑Comparison of Toyota's direct?shift?CVT acceleration characteristics

With the low-speed gears being driven directly by the gears, the black curve of the acceleration characteristics of Toyota's direct?shift?CVT has a much better acceleration response and higher acceleration than the gray curve of a conventional CVT. On the one hand, the potential of the engine can be exploded directly in the gear drive mode. On the other hand, the design of the pulley drive has been optimized for performance, and the angle of the pulley groove has been reduced from 11 degrees to 9 degrees, gaining a 20% increase in response speed. This makes the TNGA platform models equipped with this CVT more fun to drive.

C. Lighter and more compact transmission design

↑Comparison of pulley volume of Toyota's direct?shift?CVT transmission

While Toyota's direct?shift?CVT transmission boasts a more complex structure and better performance, the pulley grooves, which are the main body of the transmission, have been simplified. The design of the pulley groove is biased to take care of medium and high rpm, reducing load requirements. As a result, the pulley groove inertia has been optimized by 40%. The gearbox design is lighter and more compact.

In summary, Toyota's direct?shift?CVT transmission innovatively introduces a gear drive mode and a pulley drive mode. This results in better fuel economy, more driving pleasure and a lighter, more compact transmission design than traditional CVTs. I hope the above introduction can help you understand Toyota CVT transmission further.

Introduction Video:

References and Extended Reading

SAE Paper 2018-01-1062?Development?of?New?Continuously?Variable?Transmission?for?2.0-Liter?Class? Vehicles

SAE Paper 2015-01-1101?Development?of?New?Continuously?Variable?Transmission?for?

2.0-Liter?Class?Vehicles

SAE Paper 2014-01-1730?Development?of?Driving?Force?Control?Technology?of?CVT?for?North?American?Market?

SAE Paper 2014-01-1728? Development?of?New?Generation?Continuously?Variable?Transmission

SAE Paper 2013-01-0367?Development?of?Ratio?Control?System?for? Toyota's?New?Continuously?Variable?Transmission

This article comes from the author of Automobile Home Car Family, and does not represent the viewpoint position of Automobile Home.