Can Anyone Explain How the Hybrid CVT Works

[rivermaverick]

When I saw that the 2.5L had a 'CVT' I was expecting the 'conventual' chain belt, variable pully system. Turns out the HF45 is nothing like that! It looks very simple mechanically, 2 Motor/Generator Units (MGUs) one planetary gear set and some constant mesh gears, no sliding parts or clutches. the only mechanical bit looks to be the parking pawl. It must have some very clever electronics controlling it all.
Variable transmission seems a bit of a misnomer, the gear ratios are fixed, I've seen it described as a 'power split device' which may be a bit more accurate.
My understanding is that the anulus of the planetary gear set is connected directly to the wheels via the main traction MGU which only works as a generator when braking.
The planet carrier is connected directly the the engine and the sun gear is connected to the smaller MGU which is mainly a generator to charge the battery's, it only works a a motor to start the engine.
It is easy to see how the MGU starts the engine when the vehicle and the gear set anulus are stationary but how does it do it when the vehicle is moving, the anulus, planet gears and sun gear are all spinning, I'm guessing the small MGU applies an electrical 'brake' to the sun gear causing the planet carrier to turn and start the engine. Are there situations when the engine has to start when reversing?
BTW will the Maverick go as fast in reverse as forward (useful for avoiding terrorist road blocks, the 'reverse spin' maneuver doesn't work with ABS equipped vehicles, I've tried it!).
Sorry if my train-of-thought piece is cluttering the forum.

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[Milqueman]

This thread should pretty much answer all your questions.

https://www.mavericktruckclub.com/f...-how-ecvt-works-in-a-toyota-ford-vehicle.463/

 

[mktmgrjrm]

 

[PanchoBarrancas]

When I saw that the 2.5L had a 'CVT' I was expecting the 'conventual' chain belt, variable pully system. Turns out the HF45 is nothing like that! It looks very simple mechanically, 2 Motor/Generator Units (MGUs) one planetary gear set and some constant mesh gears, no sliding parts or clutches. the only mechanical bit looks to be the parking pawl. It must have some very clever electronics controlling it all.
Variable transmission seems a bit of a misnomer, the gear ratios are fixed, I've seen it described as a 'power split device' which may be a bit more accurate.
My understanding is that the anulus of the planetary gear set is connected directly to the wheels via the main traction MGU which only works as a generator when braking.
The planet carrier is connected directly the the engine and the sun gear is connected to the smaller MGU which is mainly a generator to charge the battery's, it only works a a motor to start the engine.
It is easy to see how the MGU starts the engine when the vehicle and the gear set anulus are stationary but how does it do it when the vehicle is moving, the anulus, planet gears and sun gear are all spinning, I'm guessing the small MGU applies an electrical 'brake' to the sun gear causing the planet carrier to turn and start the engine. Are there situations when the engine has to start when reversing?
BTW will the Maverick go as fast in reverse as forward (useful for avoiding terrorist road blocks, the 'reverse spin' maneuver doesn't work with ABS equipped vehicles, I've tried it!).
Sorry if my train-of-thought piece is cluttering the forum.

You've pretty much nailed it. The small MGU varies its rotation/braking force which in turn causes the drive ratio experienced by the ICE to change despite no actual mechanical gear meshes changing. It's rather beautiful in its physical simplicity and mind-bending mode of operation.

For educational purposes you can think of the planetary eCVT as a differential. In equivalent terms the ICE would be connected to one wheel, small MGU to the other wheel, and the driveshaft is the output. The large MGU is coupled directly at the output as well.

As you brake one wheel connected to a differential, the other spins faster.

 

[rivermaverick]

This thread should pretty much answer all your questions.

https://www.mavericktruckclub.com/f...-how-ecvt-works-in-a-toyota-ford-vehicle.463/

Thank you, hopefully in a couple of months I'll be able to try it myself .

 

[NevergettinMaverick]

Its not a CVT, it's an ECVT

 

[billbillw]

This guy has many detailed videos about the ECVT systems that were originally designed by Toyota and have been adopted by others. They are all based on the same principles and are surprisingly simple.

 

[rivermaverick]

Here is another 'tear down' video:



This is actually a Toyota transmission with the MGU1, planetary gears and MGU2 in line but the principles are the same. It's actually pretty entertaining to watch, a 'shade tree' job for sure, including special tools - concrete blocks, a 2lb 'swing press' and an angle grinder!
The guy obviously knows his stuff and gives a very good explanation of how it all works - I don't think he is planning on putting it back together!!

 

[Dionharris]

When I saw that the 2.5L had a 'CVT' I was expecting the 'conventual' chain belt, variable pully system. Turns out the HF45 is nothing like that! It looks very simple mechanically, 2 Motor/Generator Units (MGUs) one planetary gear set and some constant mesh gears, no sliding parts or clutches. the only mechanical bit looks to be the parking pawl. It must have some very clever electronics controlling it all.
Variable transmission seems a bit of a misnomer, the gear ratios are fixed, I've seen it described as a 'power split device' which may be a bit more accurate.
My understanding is that the anulus of the planetary gear set is connected directly to the wheels via the main traction MGU which only works as a generator when braking.
The planet carrier is connected directly the the engine and the sun gear is connected to the smaller MGU which is mainly a generator to charge the battery's, it only works a a motor to start the engine.
It is easy to see how the MGU starts the engine when the vehicle and the gear set anulus are stationary but how does it do it when the vehicle is moving, the anulus, planet gears and sun gear are all spinning, I'm guessing the small MGU applies an electrical 'brake' to the sun gear causing the planet carrier to turn and start the engine. Are there situations when the engine has to start when reversing?
BTW will the Maverick go as fast in reverse as forward (useful for avoiding terrorist road blocks, the 'reverse spin' maneuver doesn't work with ABS equipped vehicles, I've tried it!).
Sorry if my train-of-thought piece is cluttering the forum.

i believe the maverick only is electric in reverse.

 

[athertonbt]

Works fine until the battery dies or the brakes grab when you’re trying to park

 

[clavicus]

i believe the maverick only is electric in reverse.

Yes, and I think it’s a neat point that my engine can be on while actively reversing (although rare). I believe it just will not provide direct torque in reverse the way it is engineered.

 

[allienhere]

You've pretty much nailed it. The small MGU varies its rotation/braking force which in turn causes the drive ratio experienced by the ICE to change despite no actual mechanical gear meshes changing. It's rather beautiful in its physical simplicity and mind-bending mode of operation.

For educational purposes you can think of the planetary eCVT as a differential. In equivalent terms the ICE would be connected to one wheel, small MGU to the other wheel, and the driveshaft is the output. The large MGU is coupled directly at the output as well.

As you brake one wheel connected to a differential, the other spins faster.

Sorry, but I perceive it differently. It's like a mind-bending magic trick—no gears change, but the drive ratio experienced by the ICE does. Pretty cool. To simplify it, think of the planetary eCVT as a fancy differential. The ICE is connected to one wheel, the small MGU to the other, and the output is like the driveshaft. Uhm, and there's a big MGU connected to the output too. Now, when you brake one wheel connected to the differential, the other starts spinning faster. It's like a wheel speed swap game. I see you try saying it in for educational purpose, but I recommend https://paperell.net/buy-research-papers because this research paper online service will simplify the task of learning for anyone. I mean that here I done my project due to the help from expert writers and researchers. A lot of topics about physics I succeed to study via this source. So try it and you'll see that the theme about we speak is a beautiful and simple system that messes with your mind in the coolest way. Gotta love these engineering marvels. That's all I wanna say, thanks

 

[PanchoBarrancas]

Sorry, but I perceive it differently. It's like a mind-bending magic trick—no gears change, but the drive ratio experienced by the ICE does. Pretty cool.

To simplify it, think of the planetary eCVT as a fancy differential. The ICE is connected to one wheel, the small MGU to the other, and the output is like the driveshaft. Uhm, and there's a big MGU connected to the output too.

Now, when you brake one wheel connected to the differential, the other starts spinning faster. It's like a wheel speed swap game.

It's a beautiful and simple system that messes with your mind in the coolest way. Gotta love these engineering marvels.
That's all I wanna say, thanks

????? You took my comment and reworded it... And did it as a reply to mine... What were you trying to accomplish? Were you trying to win an argument elsewhere in the forum without coming up with an original idea and pressed the wrong button?

 

[GPSMan]

I'll just add while torque in reverse only comes from the traction motor, you can drive in reverse an unlimited number of miles. The gas engine will spin the generator making power in real-time to power the traction motor, for as long as you have gasoline.

 

[cyberdog]

For those wondering, the feel of the eCVT in the Maverick feels very much different than say the CVT in my wife's Crosstrek, with Subaru having one of the better CVT models. I say this from experience, having logged quite a bit of seat time in CVT equipped vehicles. There's no 'rubber' band effect, where the engine spins up, with no initial feeling of torque, as do a chain or belt CVT. If you hit the gas in a Maverick hybrid, you actually get a nice 'push' feeling, as you would in a traditional transmission, and actually feels eager and peppy in normal driving.

I actually like the way the powertrain in Maverick Hybrid feels, its very smooth feeling, and oddly quiet when in electric mode. Once the ICE has warmed up, you don't even realize the ICE has kicked in, aside from a slight engine growl when accelerating, more audible with the window down. - The ICE is actually quieter than even the 3.6 H6 in my Outback was, which was more refined & quieter sounding than the 2.0 H4 in my wife's Crosstrek, as a comparison perspective.

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