[Jim Biggs]

Hello,
Well I've had my '05 Prius for a week now.
I have noted that I can "feel" what I think is the PSD reapportioning the load as I accelerate and settle out at cruse speed.

It feels a little like a sooth automatic transmission shifting.

Do others notice this also?
Thanks,
Jim :lol:

 

[flare]

There's no shifting involved. Its not a normal transmission that uses gears you need to switch to.

 

[finman]

PSD

I also "feel" this, but I am guessing it's my 'automatic tranny' brain that is expecting this. I have noticed that when you really floor it and go, there is absolutely NO 'feel' of 'shifting'. And yes this is true, no shifting. The "gears" are always engaged in the PSD and it's all RPM controlled. But...if I accelerate fairly normally and 'play' with the pedal, I notice when and where the gas engine kicks in and out as needed. What a totally cool concept! One does seem to feel more in tune with this car than any other out there. Drive fun, drive clean, drive Prius.

 

[Jim Biggs]

Shifting

I understand that it does not shift gears...

I think I am observing that as one approaches speed and reduces accelleration, that there seems to be various torque effects that one can feel as it shifts to electric etc. It's not a sound issue.

Jim
:shock:

 

[BIF]

Yeah, I noticed it on rare occasions when my car was new. Engine and electric motor trying to decide who's gonna do most of the work, and who's gonna be the "helper." And the computer finally saying, "waitaminnit, I'm the brains of this outfit!".

Wigged me out the first time. Only felt it one other time. And I haven't noticed it for at least....oh, about 10,000 miles now...

 

[flare]

i dont think it can shift to electric but it can shift to the gas engine
i think the electric motor is engaged all the time.

 

[Victor]

i dont think it can shift to electric but it can shift to the gas engine
i think the electric motor is engaged all the time.

Both are constantly engaged. There is no shifting of gears at all. Check here to find a good description of how the gears work

http://home.earthlink.net/~graham1/MyToyotaPrius/PriusFrames.htm

 

[BIF]

i dont think it can shift to electric but it can shift to the gas engine
i think the electric motor is engaged all the time.

Both are constantly engaged. There is no shifting of gears at all. Check here to find a good description of how the gears work

http://home.earthlink.net/~graham1/MyToyotaPrius/PriusFrames.htm

No, they aren't necessarily "constantly engaged."

At low speeds, the ICE sometimes stops rotating, even while the car is still in motion. The crank and cam(s) stop moving, and the planet-carrier stops turning, while the planet gears themselves still revolve. To me, that means it's quite disengaged.

MG1 doesn't always spin, and sometimes it reverses direction. When the ICE is stopped and you are in motion, MG1 sits and waits for the signal to restart the ICE.

Once MG1 has restarted the ICE, MG1 typically either "does nothing" or goes into generator-mode. If MG1 is doing nothing, it's not spinning, right? Or maybe it's freewheeling? This part I'm not clear on, but if at times, MG1 is neither producing nor using electricity, woudln't that be disengaged?

MG2 is always turning when the car is in motion, but sometimes, it is neither producing nor using electricity, therefore, it's not really "engaged". Yes, it's connected to the wheels, but it is in a non-functioning state sometimes, so to me that also means it's disengaged.

But that last one is a fine line, I suppose.

 

[RSnyder]

Once MG1 has restarted the ICE, MG1 typically either "does nothing" or goes into generator-mode. If MG1 is doing nothing, it's not spinning, right? Or maybe it's freewheeling? This part I'm not clear on, but if at times, MG1 is neither producing nor using electricity, wouldn't that be disengaged?

If the ICE is spinning, then "does nothing" better mean freewheeling unless you're travelling at least 25 MPH. My understanding is that MG1 almost never "does nothing" when the ICE is running, except in N mode. MG1 actively controls the speed of the ICE under normal conditions. Unfortunately, I don't have a good source for this information, so treat it as rumor at best.

 

[CaPriusLover]

I've looked at quite a few websites and get the basic understanding of how the speed is regulated without changing gears. Either MG1 or MG2 are rotating to regulate the speed of the ICE. My assumption was that it was MG2 that regulated the speed of the vehicle, simply becuase it is part of the planetary gearbox. Isn't MG1 outside of the loop, "connected" to the power to the wheels?

 

[RSnyder]

Just to be sure of terminology: MG2 is the larger motor generator directly connected to the drive train. It's rotational speed is a fixed ratio to the vehicle's speed (when travelling in a straight line). MG1 is the smaller motor generator connected to the sun gear. It makes up the difference between the ring gear (MG2) and the planet carrier (engine) rotations.

The only time the computers set a target speed for the vehicle is when cruise control is engaged. But this control loop is operating on the total power request much as the human pushing on the accelerator pedal does. The total power request is satisfied by a combination of power from the engine and the battery, with MG2 and MG1 acting as intermediaries. So I would not say that MG2 regulates the speed of the vehicle. Whereas, I believe the computers set a target speed for the engine and this is effected very rapidly with a control loop using MG1. So I would say that MG1 regulates the speed of the engine (though it's really the computers using MG1 to regulate engine speed).