Does Gas Engine ever directly drive wheels

Go to a different dealer or never speak to that salesman again because they do not know what they are talking about at all.

The Prius has no transmission. It has a planetary power split device (PSD). It is a series of ring gears and inner gears with everything permanently connected. No clutches, no torque converter, nothing of the sort. There are 2 electric motors and 1 petrol powered engine. The gas engine when on is always directly driving the same part of the gear ring. When the gas engine is off, it is still spinning because it is permanently attached, just no gas is being injected. The 2 electric motors work at different speeds and rotations to emulate different gearing and changing the amount of power needed by the gas engine for a certain amount of power and this changes constantly automatically.



The 2nd gen has an SKS button that disabled the smart key system. The GenIII does not have it and does it automatically after some time period (I am not sure what it is off the top of my head). The 12v battery will last many weeks as long as you keep the lights off and radio off and so on. It is a very small battery so dont expect to sit in your car with it not in READY and listen to the radio for hours and hours.

The car will protect itself no matter what the idiot at the wheel tells it. So if you drain the battery down to 2 bars (50%-ish) it will disable EV mode and kick on the gas engine to recharge it to a minimum of 60%. If you go down a mountain and you fill the battery bar completely full, you are at 80% charged. The car will automatically spin the gas engine as an air brake to waste energy in combination with spinning the electric motors against themselves. This will make sure the charge drops below 80% where it is happy.

The car takes care of itself, just drive it and be happy. Also know that EV mode does NOT improve your gas mileage, it makes it worse, much much worse. It is only for using to move your car in and out of the garage like if you wanted to roll it out and wash it, or move things around. Moving spaces in parking lots, and that sort of thing.

 

Play with the PSD here: Toyota Prius - Power Split Device

There is a good animation that sort of helps explain what is going on.

 

72% of engine torque goes to the wheels, the remaining 28% goes to one of the motor/generators (it has two.)
The primary method for moving down the road in a prius is gas, with some electrical assistance. The car decides what is best at this instant (Electric, Electric-Gas, Gas) and uses it, and is capable of switching modes in under a second. that is all automatic.

Yes, two weeks away could drain the 12V. you can deactivate the smartkey system for some extra time(should be detailed in the handbook)

If the traction battery gets too low then yes, the engine starts to recharge it to a set level.

 

Well said, until that ending there. Generalizations like that are not the case for all. Driving into my neighborhood, EV is great. It provides the extra electric power needed to climb the hill without the engine starting, allowing the rest of the drive home to remain electric only... definitely not worse for me.
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The only exception is if you go down a hill that will fill your battery right after EVing. If your hill does not fill your battery, then yes it is a waste.

If I'm at the mountain house, then I use EV mode to fully drain the battery getting from the garage through the neighbourhood and to the road that begins the decent into town. This "hill" however fully charges the battery less than 1/3rd of the way down so it is very slightly beneficial.

 

:thumb:

WOW! That is the best visual for a planetary gear system I have ever seen! Now I understand!
Thank you!:thumb:

 

... i have this opinion.. as i usually do... that the ICE doesn't actually ever really directly spin the wheels. it's torque is always used in combination with the electric motors.

from how i see it, the outer ringer gear (mg2 i think) is the real speed controller. without the electric motors, the car wouldn't turn at all. if you seized up the ICE, the car would move till the battery dies... (in a physical sense.. programming would never allow it)

so... all in all, it's a ballet where the ICE ramps up as it can while the inner gear limits spin and regens to keep the ICE from ripping itself apart while the outer ring torques out to keep the ICE rpms down...

sloppy explanation of how i see it.. but.. i just needed respond before i do errands for the day.

 

Hmm, if I understand what you are saying, no, under 46 mph (Gen III) the engine can shut down (zero RPMs).

 

If you seized up MG1 the car would move from the ICE. This in fact happens when driving at exactly the right sweet spot. Obviously you need MG1 to start the ICE. Other than that, MG1 and MG2 provide the virtual gearing. Without the electrical path the Prius would be a single speed gas car.

Tom

 

Without an operable clutch

 

It depends on the definition of "directly". MG1 (sun gear) has to create resistence for the ICE to turn the wheels.

Volt has a similar setup and per GM's take, ICE does not directly turn the wheels.

 

Correct. In my haste to reply, I did not preface that sentence with "at high speed...".

 

Think of it this way. Remove Mg2, its actually geared through another planetary gear, and mg1 provides gearing to the ICE to the trans-axle. Now that power from mg1 often goes to mg2 to provide more power, but its a easier conceptual idea for the psd. If mg1 or mg2 were not working the prius can't run though.

Mg1 can turn counter to mg2 to "seize it up" virtually, but only for a short distance

Think of it this way, the ECU decides how much power the ICE should provide, then MG1 turns to the proper gear ratio, mg2 draws power or provides power based on those settings. The battery acts as a buffer for mg2s power. If no electrical power is drawn from the battery, you can think of the power flowing from mg1 to mg2 (or mg2 to mg1 in heretical mode) as completion of that virtual gear.

 

Hmmm... well, in any car, does the engine ever directly drive the wheels? Seems to me it's always through a transmission and perhaps a torque converter. Even in ancient cars where high gear was "direct drive" the power had to go through the transmission. And then there's the differential.

So with that in mind, YES, the Prius engine DOES sometimes directly drive the wheels with no assist from the electric motors (they are "locked up" by the HSD or otherwise engaged). Yes, that takes -some- electric power, but it doesn't -drive- the vehicle.
You can also say that if the engine is running and you are moving -some- of the power to the wheels is always from the engine EXCEPT when in "stealth mode" or "warp stealth mode" and EXCEPT when in reverse. In reverse ALL motive power comes from the electric motors. In "stealth mode" you are on electric power or coasting and ditto in "warp stealth mode". Both are fleeting and difficult for beginners to attain.

But with the current Prius -ALL POWER- comes from burning gasoline. Once the plugin is available -some- power will come from plugging in, but not much.

Do be careful to distinguish between motive power and power that will become motive power eventually (momentum and battery power).

 

Coincidentally, that's exactly what happens. The light turns green, I hit the pedal accelerate and climb up the final bit of hill in EV... then roll down immediately following that. Of course, it's still not a waste even starting from near the bottom where my home is... since the engine needs to warm-up later on when leaving anyway.

Then there's the situation of the final 2 stoplights at work. Due to the commute traffic, it's pretty easy staying in EV and there's plenty of opportunity for the hybrid system to squeeze out charging without penalty overall... especially in the winter.

Prius takes advantage, the best of both worlds. It sends some thrust directly to the wheels and some to the generator for electricity with some getting used immediately and some topping off the pack. The flow of power changes several times per minute too. So quantifying "waste" is a bit of a challenge. Whatever the case, my 50 MPG average speaks for itself.
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I guess it depends on what you mean by "directly". In the Prius the engine is connected to the wheels by gears, same as a regular car.

The Prius has a transmission that uses epicyclic gears to change the ratio, just like most (but not all) regular transmissions. Look at the Allison 1000:
File:Allison 1000.JPG - Wikipedia, the free encyclopedia

See the 3 epicyclic gearsets?..and all those clutchpacks? By being clever about how it locks which gearset to which other gearset, it gets 6 forward ratios and 1 reverse.

After the ratio-adjusting gears, the Prius has a final drive stepdown before the driveshafts, just like a regular car. In any FWD car, the final drive is inside the transmission with the diff (Prius or otherwise). In a RWD car, the final drive gear stepdown is integrated within the differential housing at the real axle.

The fundamental difference is that a conventional transmission using epicyclic gears sets the in/out ratio by locking one of multiple planet carriers or ring gears to the case (0 rotation) or to an intermediate shaft at some other fixed ratio via clutches. By being clever how this is done, 3 epicyclic gearsets can provide 6 fixed ratios plus reverse...but they're fixed, discrete speed ratios.

The Prius uses an electrical path from the sun gear to the ring gear. Of course, power/torque can flow either way. Since this "bypass" path is electrical and computer controlled, the ratios are infinite (including reverse ratios). Some power flows through the epicyclic gears "directly" (most efficient) and some flows through the electrical path (MG1->inverter->MG2).

One of the tricks the Prius version can do is hold the ring gear (output) zero speed and zero torque, while the engine turns. So there's no need for any clutchpacks at all.

It's hard to say how much power flows through the gears and how much flows through the MG's/inverter. It depends on the speeds of the wheels and the engine. Sometimes power leaves the system to the battery. Sometimes it comes in from the battery. The engine speed and torque are chosen to keep the engine in it's happy place (efficient) as often as possible.

Since there's a battery in the loop, power across the transmission doesn't have to balance either. Another trick it can do is zero wheel torque, zero wheel rotation, zero and positive engine speed, and negative engine torque...in other words, it can start the engine...still with no clutchpacks.

The "heart" of the Prius transmission, that single epicyclic gearset between the engine and final drive gears (we call it a PSD), really isn't much different from a regular transmission. The addition of the MG's and their electrical path for power is really what enables all the magic tricks.

 

Dang hippies and your kaleidoscope mobiles.

 

Ok, I've read the article about the engine and planetary set.

But what I don't understand is why the engine is still running when my car is stopped sometimes. Are those gears (and electric motors) still turning? If the engine is permanently connected to the planet carrier, how can it run while the car is stopped?

It seems wasteful, although I'm sure Toyota has it figured out very well.