How does the Prius' CVT work? Is it at maximum efficiency at all times? Does it use any fuel starting on and off, considering it has the ability to shut down?

 

uh....jason....have you read the technical rundown i sent you?

anyway. it runs on a planetary gearset, the sun gear attached to a motor/generator called the MG1, the carrier gear is attached to the ICE, and the ring gear is attached to the driveline (and MG2, or the main electric motor). the torque from the engine is split at a constant 28/62 percent (i think) between the sun and ring gear respectivly (keep in mind, this is a torque split only, like an open differential one could get all the spin, but the same amount of torque). the MG1 rotates at differing speeds and drags controlled by the ECU to keep the ICE at optimal speed. this also means that when in "stealth" mode and regenerative braking, the MG1 rotates backwards to keep the ICE still. to start the ICE, the MG1 stops, and some power is put to the MG2 to keep the start smooth. (stoping the sun gear while the ring gear is turning causes the carrier to spin, starting the engine) this is also interesting in the fact that the MG1 must use electricity during regenerative braking, of course, it is more than made up for by the generation from the MG2. another interesting tidbit from this settup is that w/o a transmition and the ICE only able to spin in one direction, only the MG2 is used to reverse the car. hope that clears stuff up.

 

From what I understand a CVT is not the most effecient type of transmission, a manual in the right hands still is, but I assume they used the CVT for other reasons, character of the car, and ease of use, etc.

 

well, per say the HSD is not a true CVT, as it is geared, there is soem long argument against its designation as such, but i dont think ill go there.....the HSD has no loss from belt slip, the normal downfall of CVTs.

 

Does a grooved belt slip?
Thanks
Steve

 

Hi Hot_Georgia_2004:

___It has to slip as the belt rides up and down each of the two pulleys on the Honda’s. This is the Honda’s CVT, not the gear toothed based Prius’ CVT. Given the mileage you are receiving, I won’t say the Prius’ tranny solution is any better but the toothed gear - planetary/sun gear arrangement is needed for the HSD to work as it does …

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___Waynegerdes@earthlink.net

 

Stevo,

I have read it (though haven't had time to publish it yet). I'm not nearly as educated as you are as far as mechanical insight. I, for all practical purposes, don't know a radiator from a transmission if they're both staring me right in the face.

 

oh...right, i forgot

yah, xcel is right. a geared belt isnt really possible on a CVT as there is no way to change the size of the individual teeth on the belt, so it would only lock at certain points along its journy up and down the...err, whatever those conical things are called.

 

Here you go:

http://auto.howstuffworks.com/hybrid-car16.htm

http://auto.howstuffworks.com/hybrid-car.htm

http://auto.howstuffworks.com/transmission2.htm

 

oh rats...there goes the niceties of being one of the few that understood the inside and out of the HSD.....

how stuff works is great man.