Quote:
Originally Posted by mx73
anyone know the limits of the prius transmission?
|
Hi mx73,
I was hoping someone with more knowledge would respond, but nobody has made a peep. I found a nice old description of the original Toyota synergy drive and the Honda IMA
here by The Eindhoven Technical University. Figure 4 shows that the Prius Internal Combustion Engine (circa 2004) could produce about 100 nm. Figure 6 shows the electrical machine characteristics. MG1 can produce up to about 80 nm. (oddly, the motor & generator curves for MG1 are symmetrical)
Formula 2.6, shows the relationship between the ring gear rpm and ICE rpm and rpm of MG1. Essentially MG1 sets the equivalent gear ratio. For example if MG1 is held at 0 rpm then the ring gear will spin at 1.46 times the ICE speed. If MG1 is made to run at twice the ICE speed then the ring gear will spin at 0.57 times the ICE. And if MG1 runs backwards at twice the ICE speed the equivalent ratio is about 2.37 (btw I used the ratio given in the Eindhoven paper 78:36. But everybody else says 78:30)
This variable ratio scheme works as long at MG1 can produce (or absorb if running as a generator) enough torque to "over power" the ICE torque. The ratio between the engine driving the sun gear and MG1 driving the planet carrier is 30:23. So MG1 only needs to produce about 76% as much torque as the ICE at any rpm.
Getting back to your question, if you wanted to attach a synergy drive to a more powerful engine, you'd need to replace MG1 too. There are very similar eCVTs on other cars too, the Highlander Hybrid has a 3.5 L V-6 that produces 336 nm The Lexus GS 450h says 360 nm. So they must have appropriately powered MG1.
-mort