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Thursday, 1 May 2014


Continuos variable transmission is the next development thing for car maker these days. The development of CVT could be the key attractions for maker to attract new generations customers. The development of CVT also will benefit for their hybrid or green car as CVT were highly praise to be fuel saving and less parts compared to conventional automatic transmission. Here are some update on CVT development from Japan CVT maker Jatco.

ATSUGI, Japan -- Jatco Ltd., a leading maker of fuel-efficient continuously variable transmissions, is seeking ways to make the pulley-style gearboxes more appealing to U.S. customers.
The transmissions are a big hit in Japan. And they are more efficient than four- and five-speed automatics.
But they still repel some drivers in other markets with their "rubber band" feel. And engineers still struggle to match the mechanical efficiency of some rival automatic drivetrains.
Jatco is pursuing answers to both issues.
Its gambit aims to boost the efficiency of the gearless transmissions while winning acceptance for their feel. The advances are needed to fend off the latest wave of automatic and dual-clutch transmissions from automakers rushing to cut emissions.
The Japanese supplier, in which Nissan Motor Co. has a 75 percent stake, also is targeting new segments. Engineers are working on a CVT for electric vehicles that will extend battery life and a low-cost automatic transmission for rapidly expanding emerging markets.
Yo Usuba, executive vice president for r&d, outlined the strategy, saying its next generation of CVTs will reduce mechanical friction loss to the same level of dual- clutch transmissions. He also predicts consumers gradually will warm to CVTs because they are more easily programmable to the array of driving modes, from sporty to eco, offered in today's cars.
"Japanese customers already don't care about the rubber band feel," Usuba said of the CVT's driving dynamic in a July 9 interview. "U.S. customers are still in the learning process. So far it's still kind of a strange feeling [for them]. How to provide a more natural driving experience is our challenge."
When a driver steps on the accelerator in a CVT-equipped car, the engine revs but vehicle speed follows after a delay -- eliciting the rubber band feel. With a traditional automatic, vehicle speed is more in sync with the engine's rpms.
Jatco gets around that by programming the transmission to mimic gearshifts by pausing at points along the acceleration curve.
The problem: Doing so lowers fuel economy.
Jatco and Nissan aren't alone in pushing CVTs. Honda Motor Co. will deploy the pulley-style gearboxes across its lineup, and Toyota Motor Corp. will use one on its next Corolla.
Honda and Toyota will be taking their CVTs to the United States but are programming more pronounced "steps" into their shifting pattern to mitigate the rubber band feel.
Globally and in North America, CVTs are expected to eat into the share of automatic transmissions over the next six years, IHS Automotive powertrain analyst Toru Hatano says.
But Japanese and South Korean makes will be the biggest advocates, while U.S. and European brands remain skeptics.
But CVTs have made slow inroads outside Japan. In the United States, traditional step-geared automatics prevail, while dual-clutch transmissions are Europe's automatic answer.
Jatco aims to dig further into those markets by making its CVTs more efficient. The reasoning: Fuel efficiency gains will be so impressive that they will outweigh qualms about driving dynamics.
CVTs typically are more efficient because they slide steplessly between their maximum and minimum gear ratios.
Tooth-geared automatics or dual-clutch transmissions require the extra expense and weight of another gear to improve efficiency.
CVTs are up to 10 percent more efficient than traditional four-speed automatic transmissions. But automatic transmissions have moved on. Today's carmakers are chasing nine-speed and even 10-speed automatics and dual-clutch transmissions for more efficiency.
CVTs have plenty of room for improvement. The transmissions, for example, lose about 15 percent of their efficiency because of mechanical loss, compared with a mechanical loss of only 10 percent with dual-clutch transmissions, Usuba said.
Usuba's goal is to erase that gap in Jatco's next generation of CVTs.
Engineers will get there by reducing friction in the oil pump and bearings and by reducing the amount of oil splash caused by the gear bands as they slosh through the lubricant reservoir.
The CVT8, used in mid-sized and large cars, was introduced just last year in the Nissan Altima sedan. It achieved a 10 percent improvement in fuel efficiency over its predecessor CVT.
CVT8 chief engineer Jun Shiomi says he is already working on the next generation. To trim costs, Shiomi is considering developing a CVT that can be used in standard gasoline vehicles and in hybrid vehicles. Right now, Jatco has two CVT8s to cover both kinds of drivetrains.
Jatco also is developing a CVT for EVs that will be more efficient than the simple reduction gears used in today's EVs, such as the Nissan Leaf.
Carmakers tend to choose reduction gears because they are a cheaper option for otherwise expensive battery-powered vehicles, Usuba said.
But CVTs would help preserve battery life because they are more efficient in recharging the battery through brake regeneration, Usuba said. A CVT allows the electric motor to operate in a wider zone of maximum efficiency, further saving power.
Jatco also is working on a low-cost automatic transmission for emerging markets, where stick shifts still reign.
Jatco is weighing whether that transmission will be a CVT or a traditional step-geared automatic. But the key is cutting cost to compete with manual transmissions.
Jatco President Takashi Hata told Automotive News in January that he aims to unveil both technologies -- the CVT for EVs and the low-cost emerging market transmission -- by year end.
P/S Time to change my cvt oil.


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