Technology Development to Improve Jatco CVT8 Efficiency

Yohei Shimokawa

doi:10.4271/2013-01-0364

This paper explains the developed technologies for improving the efficiency of Jatco CVT8 and the procedures followed in developing and verifying them.

CVT8 has 40% less mechanical loss than the existing base CVT and contributes substantially to improving the fuel economy of the new 2013 Nissan Altima 2.5L.

First, a loss analysis of the existing base CVT revealed that the largest loss factors were the belt-pulley system, oil pump and fluid churning. They were reduced by downsizing the oil pump and lowering the line pressure, followed by optimization of the belt shape and then reduction of churning loss.

Reducing churning loss is not so simple because fluid dispersion also functions to lubricate some parts. Computational fluid dynamics (CFD) was used to design the baffle plate shape and the fluid level. An experiment was then conducted to visualize the fluid behavior, and the results were used to refine the baffle plate shape and adjust the fluid level so as to reduce churning loss while maintaining product quality.

A method was adopted for verifying the fuel economy improvement using motor benches with the HILS. Using this method, a relative evaluation was made of the energy efficiency of the existing base CVT and CVT8 for the same engine and vehicle model during operation under regulatory test driving modes. The results showed that CVT8 contributes to a fuel economy gain of more than 10% compared with the existing unit.

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Technology Development to Improve Jatco CVT8 Efficiency 2013-01-0364

SAE MOBILUS