High revs uphill
#11
08-02-2005, 10:52 PM
Re: High revs uphill
The challenge is getting over a couple of common misconceptions which are fueled by the simplification inflicted on us by the marketeers at both Toyota and Ford.
1. There are two electric motor/generators in the system (three in the AWD RX/Highlander), and they can be independently switched from being generators to being motors. So there are operating modes where both are motors, or either one is a motor and the other is a generator. This allows the torque from the engine to be "redirected" in the most efficient way possible, since gas engines are efficient at a relatively narrow band of RPM speeds, while electric motors have a more linear torque curve (most torque at 0 RPM). The motor generator can give the engine something to "push against" at a higher RPM without wasting the energy, as it can be routed to the other motor. By controlling the amount of draw off the generator you can control the torque ratio between this electrical path versus the mechanical path.
So while it behaves in some respects like a "CVT" transmission it really is something quite different, and ironically simpler (the mechanical simplicity being replaced by electronic/software complexity).
2. Another oversimplification is that the system switches "back and forth" between gas and electric operation as if it's an either/or choice. In fact, the electrical operation is constant, as the entire drivetrain doesn't work unless the motor generators are active in some way or another.
1. There are two electric motor/generators in the system (three in the AWD RX/Highlander), and they can be independently switched from being generators to being motors. So there are operating modes where both are motors, or either one is a motor and the other is a generator. This allows the torque from the engine to be "redirected" in the most efficient way possible, since gas engines are efficient at a relatively narrow band of RPM speeds, while electric motors have a more linear torque curve (most torque at 0 RPM). The motor generator can give the engine something to "push against" at a higher RPM without wasting the energy, as it can be routed to the other motor. By controlling the amount of draw off the generator you can control the torque ratio between this electrical path versus the mechanical path.
So while it behaves in some respects like a "CVT" transmission it really is something quite different, and ironically simpler (the mechanical simplicity being replaced by electronic/software complexity).
2. Another oversimplification is that the system switches "back and forth" between gas and electric operation as if it's an either/or choice. In fact, the electrical operation is constant, as the entire drivetrain doesn't work unless the motor generators are active in some way or another.
Last edited by stevewa; 08-02-2005 at 11:19 PM.
#12
08-03-2005, 12:40 AM
Re: High revs uphill
Steve thank you for trying to help.
What is funny about all this is that both Schwa and I are getting our ideas from Graham's site. I did not get any useful information from Toyota or Ford on this.
What is at issue is if the PSD gets all the low end torque from motors or if it "gears down" the ICE and multiplys the torque in the mechanical drive line.
I think the source of confusion is Graham's wording where he over stresses the high gear business. Check out his sidebar to better understand where I am coming from.
http://home.earthlink.net/~graham1/M.../Overdrive.htm
What is funny about all this is that both Schwa and I are getting our ideas from Graham's site. I did not get any useful information from Toyota or Ford on this.
What is at issue is if the PSD gets all the low end torque from motors or if it "gears down" the ICE and multiplys the torque in the mechanical drive line.
I think the source of confusion is Graham's wording where he over stresses the high gear business. Check out his sidebar to better understand where I am coming from.
http://home.earthlink.net/~graham1/M.../Overdrive.htm
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