A specific eCVT transaxle question

[MakinDoForNow]

I didn't say it doesn't generate when driving with the ICE. Maybe it's just the way the instrument cluster displays it but I've never seen low ICE power and EV motor power indicating that the ICE is generating but the traction motor is doing the driving. Usually only a mix when going up hills.

When the ice is generating some or all of the power is used to generate current which is then sent to the convertor which is furnishing current to the drive motor. If there is not enough current coming from the generator the additional is withdrawn from the HVB and if too much is coming it will flow into the battery at the proper voltage and current. So without looking at the charge discharge current of the HVB the current used by the drive motor is the NET combined generated and battery current.

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[clavicus]

Ok this is by memory without reviewing the video yet again. There is a shaft from the ice damper which passes through or is the same shaft as the armature of the starter/generator which winds up turning with the final output shaft to wheels. John Kelley mentions this shaft when he is stacking the gears near the s/g motor. I will look at video and see if I can get time it happens in video for you. ( N th time viewing ).

The basics of the planetary gearset are clear-ish to me at this point. I think my question was: how much energy does the stator use to slow down the motor (sun gear) relative to the planet carrier when ICE is on to achieve certain (underdrive?) gear ratios? Because without any resistance by the motor, the planet carrier (ICE) will spin the sun gear (motor) via the rotating planets. Unless the ring gear (wheels) is rotating relatively faster than the planet carrier and thus the planets aren’t able to push against the ring gear to rotate the sun gear in that ‘normal’ direction. I think. Damn my brain broke again trying to picture all of this happening at once.

 

[TexasHybrid]

Sorry if already posted. Here is an interactive model.

Planetary Gear Simulator

 

[clavicus]

Sorry if already posted. Here is an interactive model.

Planetary Gear Simulator

This is so freakin helpful!

 

[MaverickTopGun]

There is one central fact. Might help to boil gear operation down to a simple equation:

Equation (1) is about as simple as engineering can get. It's a law, it's always true here.

The "omegas", or "w-looking" Greek letters are simply the spin rate variables (RPM or radians/second, whatever units you want) of the various parts of the planetary gearset, subscripts "s" for Sun gear, "r" for Ring gear, and "c" for Carrier gear. (The big letters "S" and "R" are just constants, not variables.)

The ICE engine turns the Carrier gear, MG1 turns the Sun gear, and MG2 turns the Ring gear, and the Ring gear only moves when the Maverick is moving (turns the wheels directly).

Your right foot commands the Ring gear (MG2) directly, and the engine & MG1 simply spin to satisfy the equation.

Think of our Hybrid Mav as a pure EV, conceptually, ...... with an engine and MG1 kind of "helping" it out when necessary. ... So, MG2 on the ring gear is the master (your right foot controls it!), and the engine & MG1 are really just doing whatever they have to do in order to help with power or generate power.

Now zero out any omega you want, to illustrate some ways it works:

Example: Zero out the engine omega(carrier) to show that the sun gear must spin in the opposite direction as the ring gear when the engine (carrier gear) is zero, engine off.

Example: Zero out the ring gear, which means the Maverick is not moving, so MG1 must spin when the engine is running.

Example: Zero out the Sun gear (MG1 not turning). This means the engine is spinning with MG2

https://huei.engin.umich.edu/wp-content/uploads/sites/186/2015/02/DSCC-2012-Zhang.pdf

 

[clavicus]

There is one central fact. Might help to boil gear operation down to a simple equation:

Equation (1) is about as simple as engineering can get. It's a law, it's always true here.

The "omegas", or "w-looking" Greek letters are simply the spin rate variables (RPM or radians/second, whatever units you want) of the various parts of the planetary gearset, subscripts "s" for Sun gear, "r" for Ring gear, and "c" for Carrier gear. (The big letters "S" and "R" are just constants, not variables.)

The ICE engine turns the Carrier gear, MG1 turns the Sun gear, and MG2 turns the Ring gear, and the Ring gear only moves when the Maverick is moving (turns the wheels directly).

Your right foot commands the Ring gear (MG2) directly, and the engine & MG1 simply spin to satisfy the equation.

Think of our Hybrid Mav as a pure EV, conceptually, ...... with an engine and MG1 kind of "helping" it out when necessary. ... So, MG2 on the ring gear is the master (your right foot controls it!), and the engine & MG1 are really just doing whatever they have to do in order to help with power or generate power.

Now zero out any omega you want, to illustrate some ways it works:

Example: Zero out the engine omega(carrier) to show that the sun gear must spin in the opposite direction as the ring gear when the engine (carrier gear) is zero, engine off.

Example: Zero out the ring gear, which means the Maverick is not moving, so MG1 must spin when the engine is running.

Example: Zero out the Sun gear (MG1 not turning). This means the engine is spinning with MG2

https://huei.engin.umich.edu/wp-content/uploads/sites/186/2015/02/DSCC-2012-Zhang.pdf

I think it is worth pointing out the the majority of the power of the drivetrain comes from the ICE, not MG2, but it's not clear at what situations the eCVT is performing series hybrid transfer of electricity from MG1 to MG2, vs pushing on the ring gear directly. So I would say that MG2 is more the component that fills the niche use cases, rather than the ICE being the support.

 

[PanchoBarrancas]

I don't see how. A differential allows one input shaft to drive two output shafts whose speeds vary. In a hybrid, they're usually connected downstream of the traction motor, with the motor as the input shaft.

You just need to invert the power flow through a differential to see how it is equivalent to the planetary gearset. You attach the ICE to one wheel, MG1 to the other wheel, and MG2 to the driveshaft which would become the power output.

In a car if you lift it off the ground with the transmission in park and you spin one of the drive wheels, the other will spin in the opposite direction. If you were to put it in drive and let the wheels spin, and you stopped the left wheel by hand, the right wheel would spin faster as full power is now going to that wheel. If you were to spin the left wheel backwards the right wheel would spin even faster forwards.

 

[Timothyd]

There is one central fact. Might help to boil gear operation down to a simple equation:

Equation (1) is about as simple as engineering can get. It's a law, it's always true here.

The "omegas", or "w-looking" Greek letters are simply the spin rate variables (RPM or radians/second, whatever units you want) of the various parts of the planetary gearset, subscripts "s" for Sun gear, "r" for Ring gear, and "c" for Carrier gear. (The big letters "S" and "R" are just constants, not variables.)

The ICE engine turns the Carrier gear, MG1 turns the Sun gear, and MG2 turns the Ring gear, and the Ring gear only moves when the Maverick is moving (turns the wheels directly).

Your right foot commands the Ring gear (MG2) directly, and the engine & MG1 simply spin to satisfy the equation.

Think of our Hybrid Mav as a pure EV, conceptually, ...... with an engine and MG1 kind of "helping" it out when necessary. ... So, MG2 on the ring gear is the master (your right foot controls it!), and the engine & MG1 are really just doing whatever they have to do in order to help with power or generate power.

Now zero out any omega you want, to illustrate some ways it works:

Example: Zero out the engine omega(carrier) to show that the sun gear must spin in the opposite direction as the ring gear when the engine (carrier gear) is zero, engine off.

Example: Zero out the ring gear, which means the Maverick is not moving, so MG1 must spin when the engine is running.

Example: Zero out the Sun gear (MG1 not turning). This means the engine is spinning with MG2

https://huei.engin.umich.edu/wp-content/uploads/sites/186/2015/02/DSCC-2012-Zhang.pdf

Planetaries are pretty cool, been around for a long time. I used to work on large Epicycles for my old company.

 

[GPSMan]

I didn't say it doesn't generate when driving with the ICE. Maybe it's just the way the instrument cluster displays it but I've never seen low ICE power and EV motor power indicating that the ICE is generating but the traction motor is doing the driving. Usually only a mix when going up hills.

This is exactly what happens when moving in reverse.

Moving in reverse can be pure EV.

or

Moving in reverse can be ICE spins MG1 to just generate power to power MG2 which is providing 100% of the torque to the wheels.

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