Posted by Mr. G on January 31, 2009, 2:37 am
T. Johnson (djohnson@isomedia.com) says...
> Mr. G wrote:
>
> >
> > The ICE and electric motors are not just multiple inputs to the drive
> > system; the way it is designed, the speed of one directly affects the
> > speed of another.
> >
> > The planetary gear system is basically the same thing as the
> > differential on a rear-wheel drive car. In that scenario, the input to
> > the differential is the drive shaft, the the two outputs are the right
> > and left drive wheels. Turning the driveshaft causes both wheels to
> > move forward, but if one wheel is slowed down, the other will speed up,
> > so that their combined RPM is equal for any given input RPM.
>
> No. Please look at the diagram at this link:
>
> http://www.cleangreencar.co.nz/page/prius-technical-info
>
> The planetary gear system is not a 'differential' system. The only
> thing directly connected to the front wheels is the MG2 rotor. If you
> play with the sliders of the flash simulation that I posted a link to
> you can see the mechanical relationship of the MG1 (generator), ICE (gas
> engine) and MG2 (electric motor). The ICE speed can be be zero and the
> MG2 and MG1 will continue to turn. The MG2 speed can be zero (which
> means that the vehicle speed would be zero) and the ICE and MG1 can
> continue to turn. The MG1 speed can be zero if the MG2 and the ICE are
> turning. Or the ICE, MG1, and MG2 can all be zero. The MG2 speed will
> ALWAYS be zero if the car is not moving since there is no 'clutch' or
> 'torque converter' mechanism on the Prius.
All the components are connected to the wheels via the planetary gearbox
(what is essentially a differential) The speed of any 1 component is
directly in proportion to the other components.
I think much of the disagreement is due to which is being called MG1 vs
MG2. I may have had it reversed from what some descriptions use, but
the relationship between the components is still the same.
Here is a flash gadget that demonstrates this. The references to
MG1/MG2 are reversed from my earlier description, but the concept
illustrated is the same:
http://eahart.com/flash/PSDAnim.swf
This makes it very clear why you cannot exceed 42 MPH without spinning
the ICE, or else spinning the main EM above redline.
Posted by Was Istoben on January 31, 2009, 3:37 am
> This makes it very clear why you cannot exceed 42 MPH without spinning
> the ICE, or else spinning the main EM above redline.
Back to something close to the original question, then, are the modified
plug-in 2G Prius limited to 41 mph in the all-electric mode? Apparently so.
If that is the case, then achieving 100 mpg with a 40-mile round trip
commute would be difficult if the commute is largely rural with speed limits
of 55 mph & up. Certainly there would be an improvement under such
conditions.
I wonder if one of the improvements to the 3G eliminates or at least raises
this number closer to 60 mph. We'll know soon enough. In reading through
the sparse 3G material at the Toyota site I got the impression it was
configured for some future enhancement.
Posted by Tomes on January 31, 2009, 2:44 pm
"Mr. G" ...
> David
> T. Johnson...
>> Mr. G wrote:
>> > The ICE and electric motors are not just multiple inputs to the drive
>> > system; the way it is designed, the speed of one directly affects the
>> > speed of another.
>> >
>> > The planetary gear system is basically the same thing as the
>> > differential on a rear-wheel drive car. In that scenario, the input to
>> > the differential is the drive shaft, the the two outputs are the right
>> > and left drive wheels. Turning the driveshaft causes both wheels to
>> > move forward, but if one wheel is slowed down, the other will speed up,
>> > so that their combined RPM is equal for any given input RPM.
>>
>> No. Please look at the diagram at this link:
>>
>> http://www.cleangreencar.co.nz/page/prius-technical-info
>>
>> The planetary gear system is not a 'differential' system. The only
>> thing directly connected to the front wheels is the MG2 rotor. If you
>> play with the sliders of the flash simulation that I posted a link to
>> you can see the mechanical relationship of the MG1 (generator), ICE (gas
>> engine) and MG2 (electric motor). The ICE speed can be be zero and the
>> MG2 and MG1 will continue to turn. The MG2 speed can be zero (which
>> means that the vehicle speed would be zero) and the ICE and MG1 can
>> continue to turn. The MG1 speed can be zero if the MG2 and the ICE are
>> turning. Or the ICE, MG1, and MG2 can all be zero. The MG2 speed will
>> ALWAYS be zero if the car is not moving since there is no 'clutch' or
>> 'torque converter' mechanism on the Prius.
> All the components are connected to the wheels via the planetary gearbox
> (what is essentially a differential) The speed of any 1 component is
> directly in proportion to the other components.
> I think much of the disagreement is due to which is being called MG1 vs
> MG2. I may have had it reversed from what some descriptions use, but
> the relationship between the components is still the same.
> Here is a flash gadget that demonstrates this. The references to
> MG1/MG2 are reversed from my earlier description, but the concept
> illustrated is the same:
> http://eahart.com/flash/PSDAnim.swf
> This makes it very clear why you cannot exceed 42 MPH without spinning
> the ICE, or else spinning the main EM above redline.
Thanks for this link, it is enlightening. One thing that I can see clearly
from this is that I can set it so that at 110 MPH the MG2 is at 6500 RPM and
the ICE is at 0 RPM [zero]. This tells me that at over 42 MPH the ICE _can_
indeed be not spinning. Might there be some manner of connect/disconnect
between the ICE and the planets? Or how else is this explained?
Tomes
Posted by Mr. G on January 31, 2009, 3:34 pm
says...
> "Mr. G" ...
> > Here is a flash gadget that demonstrates this. The references to
> > MG1/MG2 are reversed from my earlier description, but the concept
> > illustrated is the same:
> >
> > http://eahart.com/flash/PSDAnim.swf
> >
> > This makes it very clear why you cannot exceed 42 MPH without spinning
> > the ICE, or else spinning the main EM above redline.
>
> Thanks for this link, it is enlightening. One thing that I can see clearly
> from this is that I can set it so that at 110 MPH the MG2 is at 6500 RPM and
> the ICE is at 0 RPM [zero]. This tells me that at over 42 MPH the ICE _can_
> indeed be not spinning. Might there be some manner of connect/disconnect
> between the ICE and the planets? Or how else is this explained?
> Tomes
>
The simulator will let you set it for 110 MPH with the ICE not running,
but that doesn't mean it can happen in reality (though the simulator
DOES try to indicate you're exceeding the limits). At 110 MPG and the
ICE at 0, MG1 would need to spin backwards at 16,900 RPM, which is more
that 2.5x the 6500 redline.
Try this: Set the ICE RPM to zero, and slide MG2 up until you hit 42
MPH. Everything is fine. BUT, if you try to make MG2 go any faster to
increase the vehicle speed, 3 things happen to indicate you're exceeding
the limits:
- The MG1 tach turns red, to show you're exceeding the +/-6500 RPM
redline
- The line showing the connection among the ICE/MG1/MG2 turns red
because you've gone beyond the parameters of what the flash can properly
display (it can't show any motor past its redline)
- The line actually starts to bend, which becomes more obvious the
further you push MG2. This line must be straight, which illustrates the
direct mechanical connection via the planetary gears, just as in a RWD
differential.
So to your last question, there is NO disconnect anywhere in this
system; no clutch, torque converter, etc. When one turns, either one or
both of the other components must also turn, and at an RPM in direct
proportion to the sum of the other two.
Posted by Tomes on February 2, 2009, 3:58 am
"Mr. G" ...
> Tomes says...
>> "Mr. G" ...
>> > Here is a flash gadget that demonstrates this. The references to
>> > MG1/MG2 are reversed from my earlier description, but the concept
>> > illustrated is the same:
>> >
>> > http://eahart.com/flash/PSDAnim.swf
>> >
>> > This makes it very clear why you cannot exceed 42 MPH without spinning
>> > the ICE, or else spinning the main EM above redline.
>>
>> Thanks for this link, it is enlightening. One thing that I can see
>> clearly
>> from this is that I can set it so that at 110 MPH the MG2 is at 6500 RPM
>> and
>> the ICE is at 0 RPM [zero]. This tells me that at over 42 MPH the ICE
>> _can_
>> indeed be not spinning. Might there be some manner of connect/disconnect
>> between the ICE and the planets? Or how else is this explained?
>> Tomes
>>
> The simulator will let you set it for 110 MPH with the ICE not running,
> but that doesn't mean it can happen in reality (though the simulator
> DOES try to indicate you're exceeding the limits). At 110 MPG and the
> ICE at 0, MG1 would need to spin backwards at 16,900 RPM, which is more
> that 2.5x the 6500 redline.
> Try this: Set the ICE RPM to zero, and slide MG2 up until you hit 42
> MPH. Everything is fine. BUT, if you try to make MG2 go any faster to
> increase the vehicle speed, 3 things happen to indicate you're exceeding
> the limits:
> - The MG1 tach turns red, to show you're exceeding the +/-6500 RPM
> redline
> - The line showing the connection among the ICE/MG1/MG2 turns red
> because you've gone beyond the parameters of what the flash can properly
> display (it can't show any motor past its redline)
> - The line actually starts to bend, which becomes more obvious the
> further you push MG2. This line must be straight, which illustrates the
> direct mechanical connection via the planetary gears, just as in a RWD
> differential.
> So to your last question, there is NO disconnect anywhere in this
> system; no clutch, torque converter, etc. When one turns, either one or
> both of the other components must also turn, and at an RPM in direct
> proportion to the sum of the other two.
Thanks for the explanation. I will consider all this and play with it a bit
more...
Tomes
>
> >
> > The ICE and electric motors are not just multiple inputs to the drive
> > system; the way it is designed, the speed of one directly affects the
> > speed of another.
> >
> > The planetary gear system is basically the same thing as the
> > differential on a rear-wheel drive car. In that scenario, the input to
> > the differential is the drive shaft, the the two outputs are the right
> > and left drive wheels. Turning the driveshaft causes both wheels to
> > move forward, but if one wheel is slowed down, the other will speed up,
> > so that their combined RPM is equal for any given input RPM.
>
> No. Please look at the diagram at this link:
>
> http://www.cleangreencar.co.nz/page/prius-technical-info
>
> The planetary gear system is not a 'differential' system. The only
> thing directly connected to the front wheels is the MG2 rotor. If you
> play with the sliders of the flash simulation that I posted a link to
> you can see the mechanical relationship of the MG1 (generator), ICE (gas
> engine) and MG2 (electric motor). The ICE speed can be be zero and the
> MG2 and MG1 will continue to turn. The MG2 speed can be zero (which
> means that the vehicle speed would be zero) and the ICE and MG1 can
> continue to turn. The MG1 speed can be zero if the MG2 and the ICE are
> turning. Or the ICE, MG1, and MG2 can all be zero. The MG2 speed will
> ALWAYS be zero if the car is not moving since there is no 'clutch' or
> 'torque converter' mechanism on the Prius.