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Discussion Starter #1
Greetings all.
If you haven't read
http://www.toyota.co.jp/IRweb/special_r ... rts_12.pdf
please take the time to do so.......very interesting and well laid-out. A question I have concerns the power split device. The attachment included shows the ICE, generator, motor and power split device. Toyota explains that there is a linear relationship between the rpm's of the three gears in the planetary gear arrangement (see drawings labeled "Colinear graphing of planetary gear relationships" in the aforementioned pdf). Looking at these drawings, it appears (and makes good sense) that at any one moment, any one of the three component gears (the sun gear connected to the generator, planetary gear carrier connected to the ICE and the ring gear connected to the motor/power shaft) could be motionless while the others are spinning. The power shaft could keep the ring gear motionless via the parking brake mechanism as is the case when the ICE is running to charge the battery when parked. The ICE compression could keep the planetary carrier motionless during stealth mode but I'm not sure that compression alone is used. I have no idea what would keep the sun gear motionless during normal driving when no electricity is being generated. Could it be that the sun gear is never motionless or is there some kind of clutch/braking element that would hold it motionless thereby putting all available power generated by the ICE and motor to the power shaft? Either way, what a great and simple system!
Also, I'd like to see the shaft arrangement that connects the ICE to the planetary gear carrier. I can't quite visualize how it works as it passes through the generator.
These Toyota engineers are to be commended!
 

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The computers actively control the speed of the smaller motor/generator (MG1) attached to the sun gear in order to control the speed of the engine.

Interestingly, based on RPM measurements I did while coasting downhill with my foot off the gas/brake pedals, the engine is allowed to spin slowly forward while the car is moving. Probably because it's too hard to measure zero rpm and they want to avoid the engine turning backward even slowly.
 

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Discussion Starter #4
mho and RSnyder,
Thanks both for the reponses.
mho,
Graham's site did the trick--extremely good explanation and visuals. Makes me appreciate the engineering even more. Also, the shaft for the ICE running through the shaft for the generator with the planetary gear carrier on the backside of the PSD is a very cool approach.
RSnyder,
What do you think re: cruise control v. feathering? Also, does the cruise control's memory really reset after speed drops below 24 mph making resume unusable until a new set is achieved? This seems counter to any cruise control I've ever used.
Once again, thanks to both!
 

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cruise control vs. feathering: I think that a human driver, aware of the upcoming terrain, can do a better job than cruise control. In most cases, however, I think the CC will do better than the human because humans tend to lose focus. So for a one time challenge where you can keep your focus, you're better off doing it yourself. For your daily commute, use the CC, it will beat you most days.

The CC really does forget the set speed if your actual speed drops below 25 mph. (On the 2001-3 model anyway). It's not normally a big deal, but can give you one more reason to hate tolls. :)
 
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