It looks like a set up for hybrid technology as well as a transmission improvement.

Is this the same CVT layout the Prius uses?

Mike -

there are more than 3 shafts in the newly designed transmission: if only one planetary gear is present, and that is anchored in the housing, the number is 4. If multiple planetary gears are used and the planet carrier can rotate, the number is at least 6. Truth in advertising please.

Bill W. -

you are right, Daihatsu does not elaborate how the planetary reducer is used to reverse direction. The special magic can be achieved with a planet carrier and some additional gears and clutches. Alternatively, the required torque could be provided by an electric motor driving the planet carrier when a tangential clutch is disengaged.

However, I consider it unlikely that such a microcar would be hybridized for volume production, even though the 660cc ICE class enjoys tax advantages in Japan. The cost, weight and cargo space penalties would be severe. Fuel consumption is already low, so the fuel savings would be small in absolute terms.

The Toyota Prius does not use a mechanical CVT at all. Instead, its two electric permanent-magnet machines plus the power electronics are the serial path of a power split transmission. The two power streams recombine in a planetary gear.

Adding an electric motor to a 660cc powered vehicle seems like a "convenient" way to get more power to the people without paying the heavier taxes for vehicles over 660cc (as assessed in Japan). That is until the tax laws catch up with the technology.

This post and the original release are correct that this is a 3 shaft transmission by the conventional definition used in transmission design. Nobody counts the small little stubs of metal in the planetary gear sets -- this would make a conventional automatic a ~20 shaft design, which wouldn't be a useful distinction. Additionally, although it is not shown the conventional CVT would most likely have a planetary gear and clutches in this position in order to achieve reverse gear.

That said, the benefits of this design seem to be overblown. It's relatively unique, but the change doesn't really provide any theoretical advantage over a conventional CVT (practical advantages are implementation-dependant).

Why does GCC always quote power in both kW and hp, but torque only in Nm? We want our lb-ft!

How is this "input speed reduction" an improvement over the previous practice of "output speed production"? Let's be reminded that belted-type of CVT has problem handling high torque in comparison to a conventional geared-type of transmission, due to the inherent weakness of the belt itself. Thus, to avoid the high torque handling by the CVT belt, "output speed reduction" magnifies the torque after the belted unit, making the gears handle all the high torque at the end. Here Daihatsu claims that by "input speed reduction", the belt speed will be lower, and hence preventing "belt dislocation by high centrifugal force", well, now, that can easily be handled by sufficient tension on the belt and by a pair of belt tensioners closely pushing the belt against the pulleys, and by making belt lighter. Again, by making belt lighter, "transmission unit inertia can also be reduced", or so, I would think. The belt is probably made of steel, which is strong, but very heavy. And, by making the belt handles more torque, the belt will have to be even heavier. Ah, the catch here is F=1/2M(Vsquared), so by reducing the speed by for example, 1/2, the centrifugal force will by reduced to 1/4, but the mass only has to be doubled to handle the doubling of torque. But why worry about "transmission unit inertia", when the whole belted unit can be used as the engine's flywheel? Just put the clutch or torque converter after the belted unit but before the output reduction gear unit, and let the whole belted unit turns with the engine all the time, acting as flywheel?

May be someone out there can clarify me on this?

Roger, you read my mind. This solution does indeed increase torque on the CVT. But how much torque does this engine produce? Next to nothing.

I think you answered your own question by stating:
"..that can easily be handled by sufficient tension on the belt..."

This would increase friction, and thus transmission losses.

"...and by a pair of belt tensioners closely pushing the belt against the pulleys..."

How do you plan to do that in a CVT where the belt continuously changes position?

What puzzles me is why this new CVT design seems to need a torque convertor as opposed to the old design, where it is absent. Won't this torque converter introduce new losses?

Ahhhhahaha....
This could really use a boost through Hybrid. What are the cons to an IVT (torotrak) transmission?

Thanks, anne, for your answer. To counteract the loss due to increase belt tension, the belt tensioners will be designed so as to increase the tension only at high engine speed, whereby the increase in centrifugal force produced by the belt will reduce contact force of the belt on the pulley. Belt tensioners will be place in location between the two pulleys, where the belt will not significantly change position.

Without torque converter, clutch will be needed, which may cause wear and more maintenance issue. A torque converter lock-up means is all needed to prevent loss via the torque converter at minimum vehicle speed.

Just an idiosyncrasy. :-)

This may get great MPG. But since it's a turbo engine, more than likely you will need mid or premium fuel. So you may not save too much at the pump. And I agree, it is so you can park in tokyo.