What is an eCVT? How does it work? Here is the answer

[majorleeslow]

Thanks for the video. This is why I wish someone would show us the inside of the new FFH design, to end the uncertainty.

I agree totally this car is gorgeous looking and gives great mpg if you treat her nice. But so many unknowns Ford has been very quiet on the inside specs. would love to open it up. scared to void the warranties.

[No1hedberg]

That is a great video. I saw earlier in parts diagrams that Ford has a clutch plate in their eCVT between the ICE and the planet carrier. This video confirms that Toyota has the same thing. It still appears that this clutch is passive (never released or locked) and just serves as a shock eliminator when the ICE starts and stops. At least the instructor never mentions the clutch playing a part in the power train. Anyone have another theory of the function of the clutch? The noise I have in my transmission "could" have a relationship to the clutch as it only happens when the ICE starts pulling or slacks off the load. I am learning to ignore the sound as it does not seem to be getting any louder. Yes, it would be great if we had a video of the Ford setup.

I'm certain that the infamous Prius "thunk" is related to this clutch locking and slipping as the ice starts and stops. Thankfully Ford found a way to smooth that transition. What an informative video. Thanks for posting it.

[hybridbear]

Additional info from the response to my PM to Ashley with technical questions:

 

1)The eCVT uses an electric motor, final drive, planetary gear set, a transfer shaft, and the starter/generator electric motor. The planetary gear set is used so that the ICE can drive either just the starter/generator or, if needed, provide extra power to the final drive in addition to what the electric motor is providing. The shop manual (which you can purchase access to here) will outline in more detail how these parts function. The Ford engineering team selected this design for many reasons, but that info is proprietary.

 

2) The ICE is not directly connected to the wheels. It can either just provide power by turning the generator of if needed can provide torque to the final drive through the planetary gear set.

Edited December 23, 2013 by hybridbear

[hybridbear]

Additional technical info from Ashley:

The primary purpose for the ICE is to the charge the battery. However, it is also possible under heavy load conditions to have the planetary set direct torque to the final drive of the transmission assembly from the ICE. So the ICE can provide extra power for acceleration by turning the generator or directly providing torque through the planetary set. Most of the time it will only turn the generator.

 

This sounds very similar to how Honda has described the operation of the new HAH...

[bsondhi]

Here is an article on Honda's new Hybrid. It uses the two motor system. Not very technical but iMMD seems like Ford and Toyota's Hybrid eCVT.

 

 

Honda's i-MMD is, in fact, a hybrid of a hybrid system. So long as there is sufficient juice in the battery (and typically at around-town speeds and moderate throttle demand) the Hybrid operates as a series hybrid, with the engine driving the generator that powers the e-motor and recharges the battery. As speeds increase—and, again, depending on a host of efficiency-minded powertrain algorithms—the car switches to more conventional parallel-hybrid power flow, with gas engine and e-motor contributing torque. The advantages are many, starting with packaging. Honda's system dispenses with a conventional continuously variable transmission (CVT), relying instead on fixed ratios between engine, e-motor and wheels. This power flow also avoids the slippage and incremental inefficiency of a CVT.

 

 

http://online.wsj.com/news/articles/SB10001424052702303870704579296424164040790?mod=WeekendHeader_Right

[lolder]

There is no slippage in Ford/Toyota eCVT's. There is no "incremental inefficiency" in them; in fact they are incremental EFFICIENT. The planetary gear heart of the eCVT is not very big. The Ford M/Gs are big. They have no electric clutch which can wear and has to engage very precisely to be smooth. The new ones seem to be doing so. Time will tell.

[jmellen]

After reading all the information I could find in this forum and some elsewhere as well regarding the eCVT I am thinking that the planetary gear is a key element. The three main components of the planetary gear set are the sun gear, planet gears and ring gear. I understand that in most applications of a planetary gear set one of these three is stationary but not so for the FFH. In this case all three can be moving at once. I am not sure of other valid combinations. Perhaps others can shed light on this. Then I found a web site with a great demo tool showing the application of the planetary gear set in an environment like the Prius or FFH. It show RPMs for MG1, MG2 and ICE and the resulting MPH. Here is the link: http://eahart.com/prius/psd/ Enjoy it and let me know what you think.

[lolder]

The Toyota/Prius, etal, system works the same as Ford's, the architecture is different. Block diagrams would look the same. The computer controls the torque, both positive and negative in either rotation direction on M/G 1 which is connected to the sun gear. That controls the eCVT and ICE RPM. All the complicated stuff is done by software and the brushless, 3 phase, synchronous M/G 1. There's almost nothing to wear out. There are no valves, bands, torque converters, clutches, transmission fluid ( only gear oil ), alternators, starters or belts ( after 2012 ). They should run forever. They won't but the most likely failures will be ICE wear out and eventual HVB open circuit failure. There seem to be few of either yet and many are now over 100 K miles and first generation Ford's and Toyota hybrids are holding up well in Taxi fleets. There are a lot of other gadjets to fail as in all cars but the Ford's have extremely comprehensive failure detection systems. Let's hope those are reliable.

[jmellen]

I have several questions.

1. Does MG1 operates as a motor other than to start the ICE? I figure it must or it must freewheel as it has to rotate if the ICE is off for one thing. It doesn't make sense to me that it would act as a generator if the ICE is off (that is, powered by MG2). There is no useful purpose for that, that I can see.

2. Does someone know the gear counts for the ring, planet and sun gears and/ or the formula for their interaction. I have run into one for the Prius. I have viewed the very helpful demo/simulator at eahart.com/prius/psd . I would like to know the 'rules' for the 2013/2014 FFH (RPM ranges, amp ranges, etc.)

3. Does anyone have more insight into the computer logic that controls the power split via the planetary gear. I woud like to understand the parameters better for ICE only, MG@ ony, ICE and MG2. At least I would like to know what the variables are like torque at the wheels, accelerator position, SOC, SoC, outside temp, engine temp, HVAC on/off state ( with engine cold and what is 'cold'), etc.

[hybridbear]

In my ScanGauge observation thread I've made some observations about when the car uses the ICE to charge the battery versus not based on observing SOC on the SGII. I don't believe MG1 is ever used to power the wheels. It's used as a generator and to start the ICE. I'm not sure which motor is used in reverse, but like the Prius I believe the FFH ICE will never connect to wheels in reverse.

[acdii]

It may also be used during braking.

[hybridbear]

It may also be used during braking.

Which does the regen braking? MG1 (generator motor)? Or MG2 (traction motor)?

[acdii]

Which does the regen braking? MG1 (generator motor)? Or MG2 (traction motor)?

Maybe both? That I dont know. Would be neat to open one up and to see how it all works. Knowing the basics of generators, you spin an armature inside a coil, you generate electricity, so either one can be made to generate. An electric motor is really no different in design, instead of turning the armature with a motor or some other source, you turn it using the coils surrounding it with electricity, creating magnetic fields that alternate. So by that theory either motor can generate, all depends on how they are wired up and the logic.

 

 

 

Been wanting to say this

 

Where's Waldo? maybe he can answer it.

Edited January 15, 2014 by acdii

[corncobs]

You are right on acdii but even if both could be turned into generators I think only one is used.

 

Based on this principal you can generate energy back into the grid on large machine with servo motors when they are slowing down.

[airbusguy]

All questioned answered on pages 5 to 8

http://www.motorcraftservice.com/vdirs/diagnostics/pdf/OBDSM1303_HEV.pdf

[acdii]

All questioned answered on pages 5 to 8

http://www.motorcraftservice.com/vdirs/diagnostics/pdf/OBDSM1303_HEV.pdf

AHA they do! Sweet.

[lolder]

MG2 does all the regen braking.

[hybridbear]

MG2 does all the regen braking.

That's what I thought. MG2 does regen braking, MG1 is spun by the ICE to provide electricity to MG2 for driving and to charge the HVB. Thus, MG1 can be slightly smaller but still keep up by being spun faster by the ICE. MG2 seems to peak at about 15-20 kW in regen braking due to the battery limits. But, considering what Ashley said about how the ICE is rarely connected to the wheels and that usually the car uses the ICE just to make electricity which is then used by MG2 to drive the wheels, this means that MG2 is able to put out much more power for accelerating.

[acdii]

That's what I thought. MG2 does regen braking, MG1 is spun by the ICE to provide electricity to MG2 for driving and to charge the HVB. Thus, MG1 can be slightly smaller but still keep up by being spun faster by the ICE. MG2 seems to peak at about 15-20 kW in regen braking due to the battery limits. But, considering what Ashley said about how the ICE is rarely connected to the wheels and that usually the car uses the ICE just to make electricity which is then used by MG2 to drive the wheels, this means that MG2 is able to put out much more power for accelerating.

Considering that the Energi uses the same powertrain, I would sure hope so. The only thing limiting the FFH is the battery.

[lolder]

The ICE is always connected to the wheels through the eCVT but it's not always delivering torque to the wheels. That's determined by MG1. It is USUALLY delivering torque when it's running. I differ with Ashley there. The power "split" varies instant to instant with the intent to have the least EV action when the ICE is running in it's low specific fuel consumption sweet spot. EV action by MG! helps the ICE run in this spot. When the HVB is at it's nominal SOC and constant mid-range power is called for, the aim is for little EV activity.

[hybridbear]

The ICE is always connected to the wheels through the eCVT but it's not always delivering torque to the wheels. That's determined by MG1. It is USUALLY delivering torque when it's running. I differ with Ashley there. The power "split" varies instant to instant with the intent to have the least EV action when the ICE is running in it's low specific fuel consumption sweet spot. EV action by MG! helps the ICE run in this spot. When the HVB is at it's nominal SOC and constant mid-range power is called for, the aim is for little EV activity.

Here is what Ashley was told by the technical team:

Hi Joel,

 

My technical adviser sent me this info:

 

1)The eCVT uses an electric motor, final drive, planetary gear set, a transfer shaft, and the starter/generator. The planetary gear set is used so that the ICE can drive either just the starter/generator or, if needed, provide extra power to the final drive in addition to what the electric motor is providing. The shop manual (which you can purchase access to here) will outline in more detail how these parts function. The Ford engineering team selected this design for many reasons, but that info is proprietary.

 

2) The ICE is not directly connected to the wheels. It can either just provide extra power by turning the generator of if needed can provide torque to the final drive through the planetary gear set.

In response to a request for further clarification:

I think we've hit a wall when it comes to proprietary info. I did get this clarification, which I hope helps:

The primary purpose for the ICE is the charge the battery. However, it is also possible under heavy load conditions to have the planetary set direct torque to the final drive of the transmission assembly from the ICE. So the ICE can provide extra power for acceleration by turning the generator or directly providing torque through the planetary set. Most of the time it will only turn the generator.

I replied:

One follow-up question then in response to the ICE and charging...if the ICE is being used to spin the generator to make electricity used by the traction motor to power the wheels then why does the powerflow screen show a white line connecting the ICE to the wheels in addition to showing the ICE sending power to the electric motor and from the electric motor to the wheels as shown below?

Her reply:

The ICE can either turn the generator or, if the planetary set is held differently, then it can apply torque directly to the final drive that goes out to the wheels. Primarily it just provides power by turning the generator but under hard accelerations it can divert torque directly to the final drive gears and then out to the wheels.

My question in response:

I feel like the answer is dancing around the question. I clearly have in my head what my final question is, but I'm not sure I've conveyed it correctly, so I'll try again. When the ICE is only turning the generator and is not providing torque to the final drive to the wheels what will be displayed on the power flow screen? I ask this question because I have not seen the power flow screen without the line from the ICE to the wheels. However, if the ICE isn't sending torque to the wheels through the final drive but is just running the generator then it seems to me that the power flow should not show the ICE connected to the wheels.

Her reply:

If the ICE is on just to charge the battery then it will show similar on the power flow but would not say “Engine on due to acceleration” and would not have the white line from the “Engine” to the “Drive” showing power transfer.

The white line will always be there. It just it won’t show the little color changes along it to make it look like there is power flow (the white and gray dashes looking like they are moving from one to the other).

[acdii]

The ICE is always connected to the wheels through the eCVT but it's not always delivering torque to the wheels. That's determined by MG1. It is USUALLY delivering torque when it's running. I differ with Ashley there. The power "split" varies instant to instant with the intent to have the least EV action when the ICE is running in it's low specific fuel consumption sweet spot. EV action by MG! helps the ICE run in this spot. When the HVB is at it's nominal SOC and constant mid-range power is called for, the aim is for little EV activity.

HSD and Gen 1 Fusion/escape HD use this. The Ecvt in Gen 2 though acts differently, the traction motor does most of the work now. Like I said before, there is no difference between the Energi and the FFH other than the larger battery and the charging system. The Energi runs 100% off battery when in EV Only, and from what I understand if called upon for added power the ICE can come on depending on SOC.

 

The ICE is connected through the PGS, and its output is controlled to provide power on demand where needed, mainly through the generator, but can have its power redirected to the final drive when called for, but mostly its only driving the generator. Positive split mode splits the power output between the generator and wheels, Negative sends all the power to the generator and is used for cruising at highway speeds when only the traction motor is needed to maintain speed.

 

 

Unlike HSD and Gen1 HD, the traction motor can drive the car up to 85 MPH, where HSD and Gen1 can go a maximum of 45 MPH and then ICE is 100% powering the wheels.

Gotta love this new system. Understanding how it works helps to understand how to use it.

 

 

Plug-In hybrids have all of the functions and capabilities of a full hybrid, however, they use a larger battery which

gives them greater electric-only driving range. In addition, plug-in hybrids have a charge port which can be used to

charge the battery externally from electric mains to allow them to have full electric range without having to run the

combustion engine

Energi is a PHEV, so it matches the above description.

[lolder]

Well the Gen 2 may do that but I don't know why. Generating with MG1 to power MG2 will have more losses than providing torque from the ICE directly though the eCVT to the wheels. I would guess there's twice the loss in the EV path over the eCVT path. The Volt mostly does the generating-motor thing and it's mpg when the ICE is on is uncompetitive with the larger Toyota/Ford hybrids. A motor generator with only 5% loss is very good. Two of them would be 10% while the eCVT gear path I think would be less than 5%. If you go in and out of the HVB that's probably another 10%. The Gen 1 FFH's seem to have a total EV path loss of 30%. The Gen 2 mileage, weight and power would seem to argue they have about 20% loss because of a better HVB.

In any case, it's an elegant system. Don't buy those ones with clutches and manual/automatic transmissions.

[hybridbear]

Well the Gen 2 may do that but I don't know why. Generating with MG1 to power MG2 will have more losses than providing torque from the ICE directly though the eCVT to the wheels. I would guess there's twice the loss in the EV path over the eCVT path. The Volt mostly does the generating-motor thing and it's mpg when the ICE is on is uncompetitive with the larger Toyota/Ford hybrids. A motor generator with only 5% loss is very good. Two of them would be 10% while the eCVT gear path I think would be less than 5%. If you go in and out of the HVB that's probably another 10%. The Gen 1 FFH's seem to have a total EV path loss of 30%. The Gen 2 mileage, weight and power would seem to argue they have about 20% loss because of a better HVB.

In any case, it's an elegant system. Don't buy those ones with clutches and manual/automatic transmissions.

I agree! That's why I have found Ashley's comments to be confusing. That's why I included the whole conversation so that you & others could suggest additional questions to ask her to understand the system better.

[lolder]

The systems are essentially the same. Ford has always had MG2's powerfull enough for EV use to 86 mph. Even Gen 1's are over 100 hp. Electric motors are rated for temperature rise so if you cool them more you can get more power if you put more electricity in them. They sometimes have peak powers twice the rated power. The Gen 1 HVB's only put out about 30 hp. I think the Gen 2's are about 50% more, hence the ability to go faster. If you physically look at the transmissions for both, they're very similar. The main differences between Gen 1 & 2 seem to be the better HVB and software. I think upping the EV speed was a mistake and doesn't help many drivers. I see the car magazines don't see a change with the software update.

About the Gen 1 30% EV losses; somewhere a Ford guy threw out that number. I checked it. If I drive around my small town late at night at 30 mph on cruise control in summer temps with EV cycling about 50%, I get about 64 mpg. If I pulse and glide between 25 and 35 mph being very careful to avoid HVB charge and discharge arrows, I get 78 mpg ! The latter technique avoids EV use almost completely. If you go through the math, that's yields close to a 30% loss for the approximately 50% contributions of the EV cycle to the constant speed test.

Edited December 6, 2014 by lolder