"Andy Dingley" wrote in message
...
On Sun, 14 Aug 2005 12:28:47 +0100, (Steve Firth)
wrote:

The Prius has an automatic gearbox
with planetary gears which acts as a
CVT.

That's a dubious statement though.
The epicyclic gearing is there as
torque splitter, not as a controllable change in ratio.

You are learning. ;-)

Effectively it's an electrically controlled
torque converter with additional
external power input (unlike a fluid torque
converter) - but that's really stretching
the point to call it a CVT,

Split a powertrain into three modules:

1 petrol motor,
2 gearbox (CVT or otherwise),
3 diff/wheels It is in sequence,

1, 2, 3. Simple.

The petrol motor need module 2 because of its poor torque delivery
characteristics.
An electric motor has modules 1 and 3, eliminating 2, as it can deliver 100%
torque to 3 on start up. Super simple. The best.

A Prius has modules 1 and 3, like an electric motor. In module 1 it has an
electric and petrol motor. In module 1 it has a mechanism to automatically
combine the power/torque of an electric and petrol motor to give the torque
delivery characteristics of an electric motor.

Some experimental petrol engines can have modules 1 and 3 only, eliminating
2. This is by automatically varying the valve timing by using solenoid
controlled valves. This will deliver the torque to module 3 similar to an
electric motor. As with a Prius an auto mechanism is there to present to
module 3 torques characteristics like an electric motor.

So, no in-line gearbox, gear cogs, or CVT or otherwise in a Prius.

The whole point about a Prius is
that it's a hybrid.

The point behind a Pirus is to:

- Have no to very low emissions in urban conditions
- reduce fuel consumption, and hence emissions

It uses the electric motor because
that just doesn't need a variable speed
transmission (as has been done with
electric cars since 1900).

Nearly there, not quite. Ferdinand Porche raced (and won) a sort of hybrid
in the early 1900s. They were petrol motors - generators - electric
motor - diff/wheels . In effect an electric CVT "gearbox", all in-line,
where the generator and electric motor replaced a mechanical gearbox/CVT.
The generator/electric motor does the same job as a mechanical gearbox/CVT.
A Prius does not use this setup at all, as what you have sort of implied.

The clever part of the Prius is the
use of this transmission to improve the
efficiency of the engine cut-in, compared
to previous hybrids.

One again.....it doesn't have an "in-line" transmission (gearbox/CVT). The
"clever part" is that is combines the outputs of the electric and petrol
motors to give the characteristics of one electric motor, presenting the
characteristics of an electric motor to the diff/wheels. Module 3 thinks
that its input is an electric motor.

Just because Drivel drives one
doesn't mean that they're a bad idea.

If Doctor Drivel drives one it is great finger clicking trendy idea.