i just had a semi-technical question about the continuously variable transmission in the prius - if it is continuously moving back and forth to find the optimal gear for your speed, does this mean there are infinite gears or are there really just like 20 different ones that it switches from?

 

No gears!

The different ratios between the input and output shafts are achieved by the use of adjustable pulleys and a v-belt.

Here's a pretty cool video and the wiki on CVT's.

http://www.youtube.com/watch?v=ABaJidk9SJA
http://en.wikipedia.org/wiki/Continu...e_transmission

Happy reading!

 

WRONG!!! If you don't know, don't answer.

The Prius eCVT (aka HSD or PSD) has no belts or pulleys. It is a set of planetary gears with two torque inputs (the ICE and a MG) and an output (with the drive MG). It's operation can be visualized as being a standard differencial running backwards with the ICE and MG connected where the wheels would be. The MG at one input can then adjust the apparant "Gear Ratio" that is seen by the ICE. There are explanations and simulations of how this works on the web:

http://www.eahart.com/prius/psd/

JeffD

 

Actually there are 4 Inputs and outputs to be "summed". The ICE, MG1 & MG2 can all be providing output torque, DRIVE, simultaneously. In turn the final drive output shaft can become an input "driving" MG1 & MG2 for regen and even the ICE for engine compression braking.

 

that simulation is pretty cool, thanks!

 

Dr. Denenberg's ratings are pretty good, as those things go

http://www.ratemyprofessors.com/Show...jsp?tid=373157

Halle *did* say it was a Prius question. Cohen answered well enough about the Insight, so I'd give partial credit on a test before midterm. By that time your reading skills should have sharpened up.

DAS (another easy grader