A specific eCVT transaxle question

[Rkbrumbelow]

Well after a couple hours it benefitted me also. I kept writing more and more because I realized I had to write it out to see that I didn't really understand some things. I finally understand now that there is not a clutch that engages the ICE with the power split, it's always connected. I'm still sitting here flailing around in the dark, both metaphorically and literally in this chair, trying to see in my minds eye how the sun gear, planetary gears, and ring gear can all be rotating at different (or the same!) speed, and somehow these three rotation speeds make so many different things happen. I just can't visualize it!

Off, underdrive, constant drive, overdrive... rotation... rotation... rota... eh, one day it'll make sense.

Feynman said if you can’t explain it to a 3yr Old you don’t really understand it.

he eitherknew some really smart 3yr olds or I am screwed out of understanding anything.

best way to really learn things is watch, do, teach. That’s what you have been doing. And when you screw up (which we all do) you have gone back and tried to understand better then share your new perspective.

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[fbov]

I'm questioning everything I wrote lol, just watch this.

I was watching this as the link was posted.

It's an ABSOLUTELY EXCELLENT explanation of how the planetary gearset works in a power-split device. The "10 modes of operation" hits all the combinations and permutations. I see every one of them. Pay special attention to the under-/direct-/over-drive demo (~17:00) showing how the charging motor speed changes allow the equivalent of gear changes.

Feynman said if you can’t explain it to a 3yr Old you don’t really understand it.

Feynman admitted that "I think I can safely say that nobody understands quantum mechanics" so I think he'll forgive us.

 

[Delbert]

This is a great thread. I'm going through the same learning curve. When the light first came on (the little bulb over my head in a bubble) I thought it was brilliant, and the future of all automobiles. Then I tried to explain it to someone and confused myself terribly. Then I went back to John Kelly's videos. No transmission, what a brilliant concept.

I think the future is a 500hp hybrid not a Lightning or a Cybertruck.

 

[grumpyunk]

Most planetary gearsets work by holding one of the triad stationary. The novel thing here is converting the planetary into a differential, where the triad can have all three pieces in motion and still deliver power. If I have the process and transfer correctly understood, a differential from a rear drive vehicle could do what the planetary gearset does.
The Professor does an excellent job of explaining the eCVT. I had some experience with the belt type CVT and gave the hybrid a pass for that reason. Not gonna change my order, but would definitely consider a hybrid in the future.
tom

 

[Delbert]

30 years ago I dismantled an electric screw driver. The secret inside was a planetary gear set. I was impressed by it. A little electric motor translated all it's speed to torque. Makita took that idea and started producing battery operated drill drivers that revolutionized the market.

 

[FriscoTXJoe]

Damn my head hurts just reading all that you have typed. I so wanna understand how this ECVT is different because I wouldn't buy a CVT if you paid me and I have ordered a Maverick Hybrid...... (And to make things worse, I am in sales, not any kind of engineering or mechanical field.)

Can someone r/explainitlikeImaSalesguy please?

 

[FirstFord]

Damn my head hurts just reading all that you have typed. I so wanna understand how this ECVT is different because I wouldn't buy a CVT if you paid me and I have ordered a Maverick Hybrid...... (And to make things worse, I am in sales, not any kind of engineering or mechanical feed.

Can someone r/explainitlikeImaSalesguy please?

I'm with you. I have hated every cat vehicle I've driven, until I recently drove a Prius...which has an EXIT.

It's a game changer.
As for how it works, hell I'm an electrical engineer. I get why it's super efficient and fundamentally robust. But I still don't see the gears in my head. But this is a guy that has always looked at open manual transmissions and limited slip diffs with awe and reverance.

 

[mamboman777]

Damn my head hurts just reading all that you have typed. I so wanna understand how this ECVT is different because I wouldn't buy a CVT if you paid me and I have ordered a Maverick Hybrid...... (And to make things worse, I am in sales, not any kind of engineering or mechanical feed.

Can someone r/explainitlikeImaSalesguy please?

Connect an internal combustion engine (ICE) to a gear that can either turn the wheels or turn the motor generator. Connect a motor generator to a gear that can either turn the wheels or the ICE.

When the ICE is running, it either turns the generator or the generator is stopped to make the wheels turn or any combination in-between. How much the motor generator is stopped will determine how fast the wheels turn in relation to the ICE. If the motor generator only slows a little, the ICE will only deliver a little speed to the wheels. If the motor generator stops completely, the wheels would go the same speed as the motor generator. If the motor generator turns in reverse, the wheels would get the power of the ICE+the motor generator.

When the ICE is off, the motor generator can turn the wheels.

*I know this is a simplification of the system and I completely ignore gearing, etc. But I thought a simplified explanation is what we are after.*

 

[clavicus]

Connect an internal combustion engine (ICE) to a gear that can either turn the wheels or turn the motor generator. Connect a motor generator to a gear that can either turn the wheels or the ICE.

When the ICE is running, it either turns the generator or the generator is stopped to make the wheels turn or any combination in-between. How much the motor generator is stopped will determine how fast the wheels turn in relation to the ICE. If the motor generator only slows a little, the ICE will only deliver a little speed to the wheels. If the motor generator stops completely, the wheels world go the same speed as the motor generator. If the motor generator turns in reverse, the wheels would get the power of the ICE+the motor generator.

When the ICE is off, the motor generator can turn the wheels.

*I know this is a simplification of the system and I completely ignore gearing, etc. But I thought a simplified explanation is what we are after.*

My only clarification (that I don't know the answer to for sure) is if the generator motor (MG1) actually can apply any driving force at all itself, or if it simply "allows" more of the ICE power to flow to the wheels. Maybe that's just semantics.

That said, the entirely separate traction motor (MG2) is physically tied to the drive gear/wheels turning and can resist (regenerative braking) or propel the final drive gear/wheels separately.

 

[mamboman777]

My only clarification (that I don't know the answer to for sure) is if the generator motor (MG1) actually can apply any driving force at all itself, or if it simply "allows" more of the ICE power to flow to the wheels. Maybe that's just semantics.

That said, the entirely separate traction motor (MG2) is physically tied to the drive gear/wheels turning and can resist (regenerative braking) or propel the final drive gear/wheels separately.

I thought that one of the motor generators (I forget which one) was directly connected to the ICE serving as a starter for the ICE and when the ICE is running as a generator. Whether it has an impact on power to the drive...

 

[fbov]

If I have the process and transfer correctly understood, a differential from a rear drive vehicle could do what the planetary gearset does.

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.

 

[clavicus]

I thought that one of the motor generators (I forget which one) was directly connected to the ICE serving as a starter for the ICE and when the ICE is running as a generator. Whether it has an impact on power to the drive...

Yes you got it, MG1 (generator motor, the smaller electric motor) is always physically connected to the sun gear, and the ICE crankshaft is always physically connected to the planetary gears that can rotate around the sun gear. The ring gear that sits on the outside of the planetary gears is physically connected to the final drive gear (wheels) through a couple other transfer gears.

My clarification is that I am leaning towards the idea that the sun gear (MG1) cannot actually exert force on the ring gear (and hence cannot push power to the wheels). The sun gear can only exert force on the planetary gears, if the sun gear is given some battery power to spin relatively faster than the ring gear is spinning (this will turn the crankshaft of the ICE to start it), and thereafter the ICE (planetary gears) is spinning itself, and now exerting force on the sun gear to spin (generator mode). And then the planetary gears can put force on the ring gear if the sun gear resists rotation via resistance in the MG1 stator's magnetic field, and MG1 can even be forced to rotate in the reverse direction for an even greater ratio of ICE power to the ring gear (wheels). But, again, MG1 (sun gear) is not exerting force on the ring gear at any point no matter how it is rotating. I hope that's right, this stuff hurts my feeble mind.

 

[fbov]

I am leaning towards the idea that the sun gear (MG1) cannot actually exert force on the ring gear...

I disagree. We know the ICE turns the planet carrier, and we know MG1 applies torque to the planet carrier to start the ICE. I see no reason MG1 can't use the same torque path as the ICE, looking like a boost in ICE power through the ring gear to the road.

 

[clavicus]

I disagree. We know the ICE turns the planet carrier, and we know MG1 applies torque to the planet carrier to start the ICE. I see no reason MG1 can't use the same torque path as the ICE, looking like a boost in ICE power through the ring gear to the road.

Doesn't that invalidate the whole magic of the power split, where the relative opposing rotation speed of the sun gear is what allows the planetary gears to apply force to the ring gear?

For example, let's say we're stopped. The ring gear is not turning at all. The sun gear is given juice to spin, and it turns the planet carrier/crankshaft since the sun gear is moving faster than the ring gear, and the ICE starts. We're still stopped, ICE is spinning the planet carrier (itself) and the sun gear (MG1) to generate electricity, but the ring gear isn't spinning. If MG1 (the sun gear) uses battery power to spin faster than the planetary gears, what happens?

I'm looking again at this video for review.

And this part of a simplified hybrid model video here. With the wheels stopped, ICE at some fixed RPM, if MG1 is spun fast, the wheels don't move. Only when MG1 is slowed down, relative to ICE crankshaft, does the ICE begin applying force to the wheels. So I'm not sure if this is still in the woods of semantics or not, but this all appears to me like MG1 itself is not ever going to apply force to the wheels.

 

[RickAns]

I say it all works by magic you Muggles!


Seriously though, great discussion. Really interesting in learning how this electric motor and gas engine combo works.

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