Toyota eCVT vs. Ford HF35 transmission

Just so we are clear.... In that diagram, blue is the ring gear which is connected to G2 which connects to G4 which connects to G3 which connects to traction motor (MG2).

G2, G3 and G4 functions as reduction gears to slow down MG2. This design uses two shafts. Toyota implementation used another PSD to slow down MG2, allowing them to "sandwich" all on the same shaft -- perhaps easier cooling and allowing lighter parts to achieve the same.

G5 and G6 is the final drive to the differential.

What's the point of slowing down MG2? It kills four birds with one stone. You get more power from the smaller, (higher revving) lighter motor that is cheaper to produce.

 

What is your PSD acronym ? It's actually connected though the reduction gears by the sun gears.
The ring gears are running the planetary gears. MG1 isn't necessarily running if the ring gear is.

The gear change is final drive only, from my understanding. It was done to promote better MPG.

 

PSD - Power Split Device. This is what Toyota calls the planetary gearset.

MG1 is connected to the Sun gear. ICE connects to Planet gears. MG2 and wheels to the Ring gear. There is no clutch to connect/disconnect.

HF35 diagram shows the same thing.

Green=MG1=Sun
Red=ICE=Planet
Blue=MG2=Ring

Is there another source you looking at? Please share because there seem to be a disconnect in how Power-Split hybrid works.

 

Aisin-AW, which is now essentially controlled by Toyota, has had a role in Toyota, Ford and other hybrid transaxle systems development. Aisin-AW is perhaps the largest supplier of transmissions worldwide --- but other major
drivetrain suppliers like Jatco and ZF also show hybrid systems among their products.

 

Like McPherson strut, developed by Ford in Dearborn, but initially only installed on English Fords. Or the Bendix patent on pintle valve fuel injectors, which are now used virtually worldwide.

 

This is fascinating information. One difference I've observed in vehicle operation is that the Prius often shows the ICE sending power to the generator which then sends power to the wheels. Honda describes their new HAH as doing the same thing. The FFH never seems to do this. The Fusion though is almost always charging the battery when the ICE is on and rarely shows power to the wheels coming from a combination of ICE & electric motor. Perhaps someone with more engineering knowledge than I have can explain why this is based on the different setups as shown in the diagram.
Ford's HF35 explained:




Toyota's eCVT:

 

That is accurate for the Gen 1 and Gen 2 Prius.
The Gen 3, PiP, c and v have an additional planetary gearset and an all gear driven final drive.

 

The dotted line of the ISC in the diagram shows a direct connection between the generator and traction motor. If it is never actually observed in operation, that may have more to do with specific trip or driving style. It would be inefficient with the conversion loss of always going generator > battery > motor, but the system might do so if the battery SOC is always near max from excess energy from the ICE charging battery, or good use of the regen braking.

The display also might not be showing what the system is accurately doing. I believe the traction motor in these systems can also act to provide the virtual gear ratios of the eCVT. If so, the Ford display may only show energy going to the traction motor over a certain limit. In other words, when the motor is providing enough power to help propel the vehicle.

 

What I have been able to observe in the FFH is that almost all of the time when the ICE is on there is current flowing into the HVB according to my ScanGauge. Only when the HVB SOC is very high or you are climbing a mountain do you have the ICE running and current flowing out of the HVB. The FFH doesn't have a display like the Prius does on the center screen showing the arrows of energy flow. The FFH shows on the dash the power from the ICE and from the electric motor (traction motor) and almost never are both motors shown as active at the same time.

 

Check the owners' manual(couldn't do so online at this time). It is possible that the display doesn't show the motor on with the ICE, because the power for the motor is coming directly from the ICE. The display could just be showing is gasoline of battery charge is propelling the car the moment.

 

Unfortunately the OM doesn't really explain this. Sadly, too, Ford is not willing to allow owners to monitor very many functions with a ScanGauge. With the first gen FFH there was a lot more opportunity to get data about the operation of the electric motors. For the new gen Ford changed all the programming and removed the data that was published in some maintenance manuals that allowed SGII experts to figure out the XGauge coding.

 

You mean the MG1.

Ford may have changed the gear ratio so that MG1 revs lower at vehicle higher speed. Doing this will increase the torque split to the generator.

The trade-off is ICE torque split to the wheel (direct mechanical) will be lower, taking gas efficiency hit because more power will go through series path (conversion loss).

 

I recently got an Android tablet and the Torque app. With the app I can monitor the speed of MG1. I have only driven the FFH once since I got the app so I don't know much yet. I do know that MG1 spins with negative RPMs proportional to speed when the ICE is off. When the ICE is on it can spin the generator with positive RPMs to generate electricity to charge the battery/power MG2 to drive the car.

 

Most FFH owners seem to have seen an increase. We saw no improvement from the increased EV speed, only from the changes to the computer mapping for when to turn off the ICE with the heat on. The FFH now will turn off the ICE as low as 40C coolant temp with no HVAC on and 50C coolant temp with HVAC on.

 

What we need to know is this:

Accelerate to 85 mph and glide (with ICE off). See the MG1 rpm as soon as ICE turned off. It would be a negative rpm for sure but we want the value.

 

It might be a few weeks before I'm driving on a road where I can do this, but I will report back. I think I have enough wheel MPH and gen RPM that I can plot a regression equation which would allow us to predict the gen RPM speed at 85 MPH wheel speed without having to exceed the speed limit to get the data.

 

Here is the equation based on the 500 or so data points that I have already:
Gen RPM = -119.25*MPH - 33.925

What's the comparable equation for the Prius MG1 RPM?

This means that the previous FFH max Gen RPM was: ~7427 @ 62 MPH
Now the max Gen RPM is: ~10170 @ 85 MPH