I would like to understand some of the mechanical details of how the continuously variable transmission works. I know the basics of how a planetary gear set works, but I don't understand how they turned this into a CVT.<br><br>TIA -- Keith.

This article includes some explaination of<br>the transmission:<br><br><a href=http://www.spectrum.ieee.org/select/1198/hyb.html target=new>http://www.spectrum.ieee.org/select/1198/hyb.html</a>

If you still have questions after reading the ieee article, post 'em and I'll try to answer. The problem is it gets messy without diagrams. The are some SAE presentations, but they don't fit into this format and I'm not aware of any being on-line.

ee_of_ee<br><br>Posting the engine, generator, PSD, motor cut-away might help somewhat. Also, the IEEE diagram isn't quite "right". Would T have a problem with a post of the cut-away from the TU material? What about an animation of the PDS in "action"?<br>Just asking first. Don't want to "honk off" somebody at T and wind up at the back of the line.<br><br>Bill Powell<br>Is it fair to call the Prius "shiftless"? :-)

See the links in 546

Thanks ee_of_ee!<br><br>Now - where's the "transmission"? :-)<br>Guess we can't call "it" a gearshift anymore...<br>The use of the planetary gearset with the generator "modulating" the engine output is CUTE!<br>Imagine trying to do that without a computer - er... ECU to do the hard work.<br>Just a curious question: to "lock up" the gearset and allow the engine to couple power thru the PSD to the output shaft, the generator is going to have to dump power somewhere. Where? The motor?<br><br>Thanks!<br>Now - what about my ham radio? :-)<br>Bill Powell<br>waiting and waiting and.....

Yes the power is dumped to the motor.<br>After reading article, Here's the way I see it:<br>The Motor is a direct drive(the outer ring) to the wheels. It can get it's power from the battery or the generator but will never turn the generator. The gas engine can either turn just the generator (during idle)if the motor(outer ring)is locked or turn just the outer ring (motor) during hi speed driving if the generator is locked. Anything in the middle is a split power. The more the generator "Holds Back" the planetary gears the more power from the gas engine is directed to the motor(outer ring). This energy from the generator due to this "Holding Back" can then help the motor or charge the battery or both. During a fully charged battery, the generator will "Hold Back" the planetary gears enough so the engine is running at most efficient RPM and in return, will put that power to the motor which in turn helps the Gas Engine drive the outer ring. A heck of a lot better than an Automatic transmission with a torgue converter that generates so much heat from slippage that the fluid has to be cooled in the radiator.

Thanks for the explanations. I think I'm starting to get it - scary!<br><br>This is looking simpler than a regular automatic transmission. Then again, I'm probably underestimating the computing power that seems would be required to run the ECVT. Maybe that's why we haven't seen these in in widespread use - the processing power hadn't been readily available until now, and to implement it any other way (e.g. with fluid pressures and valves) was too complicated to do.<br><br>I also understand computers much more than anything mechanically complicated. But perhaps I'm not getting this as much as I think I am!<br><br>Perhaps this is also part of why Toyota's offering the maintainance incentive. I assumed the reason was two-fold - to make sure that the cars are running well and that we have a good experience with the car, and to collect data that would help Toyota development. A third reason would be great - it would allow Toyota to upgrade the software and improve the performance of our cars - then again, I've seen the comments about the ECUs not being upgradable (at least those associated with the cruise control).<br><br>Paul.<br><br>FYI - Re the cruise control. I didn't realize that the Prius didn't have one until after I had put my money down... Disappointing, but hardly enough to make me change my mind. I even avoided the use of the Cruise Control on a recent road trip in my girlfriend's Acura just so I could see what it was like not having one, in preparation for delivery of my Prius! I also find myself wondering, as I'm driving about town, "how would the Prius handle this situation!"

Thanks!<br>Looks like we both read it the same way.<br>Just for grins - try to imagine the possible failure modes?<br>Wonder if redundant computers are an option?<br>Sure hope they're NOT running a MS O/S! :-)<br>Bill Powell

In general the generator does not lock-up the gear set, but just alters engine speed to get to peak efficiency. Your other assumption is correct but incomplete, power generated can go to either the battery or, if not needed there, to the motor to drive the wheels.<br><br>I see someone else got you a radio answer.

Good explanation, I should have read it before responding. Congrats

Although it takes computer power to run the system, the main reason you don't see ECVT in other applications is that they require high voltage power electronics and would be mostly added weight without the battery pack for regen and power storage. Tis a system.

Thanks again!<br>Guess I shouldn't have said lock-up in the absolute sense. Are there any available figures as to the percent split from generator at full output thru generator unloaded (or does the engine shut down then?)<br>I agree - The Prius is a technological marvel and deserves the spotlight. Yes - hide the "rocket science" from mom and pop but PLEASE make it available to us "geeks" and "technoweenies".<br>I'm buying my Prius for a bunch of reasons besides the technology - all the reasons add together to make me wish that the manufacturing was not limited to a single line. There should be MORE people driving Prius-like cars - a LOT more!

The torque split is a constant and a function of the planetary gear set. However the power split varies depending on rotational speed. Torque split is 72% to final drive and 28% to generator.