Matt wrote:
"Doctor Drivel" wrote:
"Dave Plowman (News)" wrote in message
...
In article
ws.net,
Doctor Drivel wrote:
The only thing that is Continually Variable is the ratio of the
two power inputs, The management system decides what level of
electric to petrol motor power to combine to output to the wheels.
Explain how it varies the relative powers of engine and motor to the
wheels while maintaining a constant ratio between each and all of
them.
By a management system, anything further It is a waste of time
explaining it to you as you are not very bright at all. You have
been told to look at the graphic.
Mr Clarkson had a seriously painful slipped disc and so decided to get
rid of his GT40 and replace it with a Prius. At 8am this morning the
Prius was traveling at 30 mph and then later when the traffic eased Mr
Clarkson's chauffeur put his foot down and they traveled at 60 mph.
Provide typical details of petrol engine rotational speeds, electric
"engine" rotational speeds, and road wheel rotational speeds for the
two situations detailed above.
30 mph 60 mph
Petrol Engine Speed
Electric "Engine" Speed
Road Wheel Speed
answers such as "x" "2x" "3x" etc are permitted
It isn't free to split speed/power any which way, it's all interlinked.
Reading from the simulation at
http://homepage.mac.com/inachan/prius/planet_e.html:
At 30mph (~50kmh):
electric 1800rpm
petrol 0-3105rpm
generator varies (with petrol engine speed) between -4680 and +6498 rpm
(+/-6500 allowed)
At 60mph (~100kph):
electric 3600rpm
petrol 1000-4405rpm
generator between -5760 and +6498rpm
As you can see, the electric motor speed is directly related to wheel speed,
the petrol engine runs variably depending how much power is required for
charging or topping up from the generator, and the generator runs at
whatever speed is needed to make the other speeds go right.
Other interesting points (from the simulation, the real car may be
different...):
At a standstill, the petrol engine can run from 0-1805rpm to get just the
generator running from 0-6500.
Max speed on just the electric motor ('stealth mode') is 69kmh, 43mph.
Not trivial to control, but well within current technology.
Hmm. Is it altering ratios? Not sure now I've looked at it more. It is
altering the split but all of the gears are fixed and constantly meshed.
What is controlled appears to be the petrol engine speed, chosen to suit the
amount of charge needed for battery and direct electric motor use, and to
keep the generator revs within limits. Also controlled is the electric motor
speed, directly affecting the road speed.
So the Power Split Device (PSD) is not really altering anything, the control
changes take place external to it.
Whether that makes it a CVT depends where you consider the 'transmission'
boundaries to be. Is it the entire system, or the system from the motor
output shafts to the driveshafts, or what?
Certainly the PSD does not do the same job as a gearbox or a 'normal' CVT as
attached to a single petrol engine.
Also, and this may be the most important point of all, does it matter? It
works, it's a step forward, it's interesting.