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Development of High-efficiency CVT for 2020 Model Year CITY

Article of Honda R&D Technical Review Vol.32 No.2

Summary

A CVT has been developed for use in the 2020 model year CITY with the aim of realizing a good balance between fuel efficiency and power performance.
As new mechanisms, the developed CVT employs a belt with a modified rocking position, pulleys with multiple V-surface shapes, and mechanical and electric oil pump systems in series connection. The application of these technologies has made it possible to reduce the main sources of loss in a metal pushing V-belt CVT and to increase power transmission efficiency. When these new mechanisms were combined, CVT control was optimized in order to help ensure a reduction of loss in the CVT itself.
In addition, the driver’s intention in accelerating the vehicle is realized by switching CVT control in order to help ensure that there is no decline in power performance, due to the application of control that optimizes fuel efficiency. By setting drive power as the target parameter for CVT shift control, it has been possible to help avoid decline in drive power. Furthermore, the application of stepped shift has meant that vehicle speed follows engine speed linearly, and vehicle occupants experience an increase in drive power.
As a result, the CVT has realized a reduction of 5.7 g/km in CO2 emissions against the previous unit in the New European Driving Cycle mode. In addition, the 2020 model year CITY meets the 100 g/km or below CO2 emissions standard for the second phase of Thailand’s eco-car project.

Reference

(1) Sakagami, K.: Method of Estimating Instantaneous Safety Factor for Self-optimizing Control of Clamping Force in CVT, Honda R&D Technical Review, Vol. 31, No. 2, p. 89-97
(2) Tomomatsu, D., Shimizu, M., Yamaguchi, K., Kuwabara, S., Fukao, M., Tanabe, M., Ootsuki, T.: Development of New Continuously Variable Transmission for 2.0-Liter Class Vehicles, 2018 JSAE Annual Congress (Spring) Proceedings, No. 70-18, JSAE Paper No. 20185322, (2018) (in Japanese)
(3) Ohgata, Y., Ninomiya, K., Kurisawa, S., Tamura, N.: Development of CVT Which Improved Fuel Economy, Belt Noise and Drivability, Transactions of Society of Automotive Engineers of Japan, Vol. 44, No. 5, p. 1211-1214, (2013) (in Japanese)
(4) Sumida, S., Yagasaki, T., Aoki, R., Asai, H.: Enhancement of Power Transmission Efficiency in Metal Pushing V-belt CVT with Multi-V-surface Pulley and Modified-pitch Belt, Honda R&D Technical Review, Vol. 31, No. 2, p. 82-88
(5) Harada, M., Sakagami, K., Nakasone, M.: Technology to Boost CVT Fuel Efficiency through Series Connection of Mechanical and Electric Oil Pumps, Honda R&D Technical Review, Vol. 31, No. 2, p. 34-40

Author (organization or company)

Soichiro SUMIDA(Honda Motor Co., Ltd.)、Yoshifumi MURAKAMI(Honda Motor Co., Ltd.)、Makito NAKASONE(Honda Motor Co., Ltd.)

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