Towing revisited: Weber State

This makes WAY more sense than any of the cut-away diagrams I've failed to wrap my head around. Thank you!

 

Great overview and thank you for posting. A must see for anyone interested in how this system works.

The machining and finish on those parts looks amazing. Must be something to see and touch first hand. At 9:46 into the video when the two MG2 motors started moving toward eachother was amazing to watch. Actually laughed out loud here.

You must have a theory regarding the gearing ratios and their relationships to efficiency. Makes me wonder what Toyota's engineers have built into this design in terms of weighing efficiency and power against safety and durability. Replacing components of that transaxle assembly would be time consuming for sure.

Have read that Toyota is redesigning MG1/2 less dependent on rare earth minerals.

What are your thoughts on these 3rd gen eMotors? Smaller than the second generations, which makes me think stronger magnets and additional winds? More precise manufacturing techniques? I can understand higher driving speeds via gear reduction, but more torque from a smaller motor is unresolved in my mind.

Thanks again, and in advance for any additional information.

 

Bob,

I am trying to understand the differences between the Toyota and the GM design. I think that one of the significant differences is where they clamp the plate to the bench, GM is using a clutch, allowing an additional mode where the gas engine is more directly driving the wheels, when appropriate.

It also looks like the GM design keeps the electric motors below 6500 rpm.

 

The way that cart was wobbling around, he's lucky none of that stuff landed on his foot, although the one set of vice grips may have.

 

It's amazing the small size of MG2 motor can take the Gen3 to 60 mph all by itself.
Does it make sense to recycle used MG1 and MG2 to get the rare earths back out?

 

The Volt uses a fundamentally different variation on how to hook things together on the planetary gears.

The Prius uses an "input split" design where the big motor (mg2) has a fixed ratio connection to the wheels and the gas engine and small motor are separately connected to the planetary gears.

The Volt uses an "output split" design where the gas engine has a fixed ratio connection to the smaller motor and the wheels and big motor are separately connected to the planetary gears.

The Volt also uses 2 clutches to enable the gas engine and smaller motor to be disconnect from each other and from the planetary gears and an additional clutch/brake that can selectively lock the ring gear to the transmission gas in order to allow a fixed ratio connection between the big motor and the wheels.

 

^^
The PSD has 3 connectors, allowing 6 variations.
Toyota picked first, Ford second, and GM third.

Feel free to spin that as a 'fundamentally different variation,' but in the end it is just a late draft pick.

 

Um no, it's a different design but both are E-CVT and allow for serial/parallel mode.

Toyota and Ford use the same basic "input split" design with only minor variations between the two companies and car models/generations. The Toyota/Ford "input split" design was covered in a GM patent filed in 1995 and their hybrid transmission patents reference the GM patent as prior art.

Here is Toyota's hybrid patent from 1997: Patent US5907191 - Power output apparatus and method of controlling the same - Google Patents

Here are their prior art citations:

Cited Patent Filing date Issue date Original Assignee Title
US5558588 Feb 16, 1995 Sep 24, 1996 General Motors Corporation Two-mode, input-split, parallel, hybrid transmission
US5558589 Jul 20, 1995 Sep 24, 1996 General Motors Corporation Two-mode, compound-split, electro-mechanical vehicular transmission
US5558595 Feb 17, 1995 Sep 24, 1996 General Motors Corporation One-mode, input-split, parallel, hybrid transmission

See column 11 on page 19 with the sub-header "Description of a third alternative embodiment" on that last GM patent (US5558595) for a description of the design used by Toyota/Ford.


GM uses an input split stage in its 2-mode transmission design. The Volt design follows different tradeoffs and enables the large motor to drive the wheels under full torque and speed with the smaller motor/generator and ICE completely disconnected from the planetary gears.

 

You are cherry picking Jeff. I can do the same, 30 years earlier:

 

Interesting but I'm not sure what the applicability is. The claims start with a plurality of "prime movers" in addition to the electric "generators" and "couplers". Is this an example of the lineage of the Toyota HSD?

 

Bob,
This is an excellent find. Long watching, but totally worth it. The best action (in motion) is at 25' or so for some people who don't have time to watch the whole thing.

This brings some questions. While the chain to gear change clearly improves the reliability of the system, one can be concerned about the increased complexity of the MG2 RPM reduction gearset and the very high MG2 RPM (did he say 12,000?).

I would like to know how the whole thing is lubricated and cooled. It could be a critical thing as we know that bearing failures and coil insulation failures are the main failure modes in transaxles in the gen 2 Prius in taxi service (circa 250,000 miles).

The video briefly mentions oil pump, but doesn't say more. Looks that oil pump only works when ICE is spinning. I'm curious how much of the assembly is immersed in the ATF and how it's lubricated with ICE not spinning.

Finally, I suspect heat cycles kills the insulation in motor windings. I would be skeptical in using grill blocking, at least in hot climates.

Anyone has any info on cooling and lubrication?

 

I think so -- I found it referenced in the HSD patent.

Two power sources, one mechanical one electric. Blended at an EM coupling with the specific intent of high ICE efficiency. Sound familiar ?

It is also instructive to read the GM two-mode patent, and compare it to the HSD and control mode patents from Toyota. GM (in summary) writes: thinking of two power sources connected by planetary gears(s) in some way(s). Toyota obviously has a working implementation. Their diagrams are instantly recognizable as what we drive today. The specific algorithm to manage instantaneous torque is spelled out.

At best, GM was playing patent defense, by putting out an idea variant. Toyota was building our hybrids.

So far as I know, two americans first patented the idea of an e-cvt in the 1960s. I do not know who first patented the idea of combining the power sources with a planetary gear with the output shaft to the wheels, although this implementation is completely analogous to a differential gear, so prior art arguments are likely to go nowhere.

 

...ouch

 

I did some googling and can't find much on the new design transaxle failures in hybrid Camry, Highlander, Lexus 400h, or third gen Prius. Sounds like a good, heavy duty design.

However, there are troubling accounts of coolant leaks requiring transaxle replacement near 100,000 miles in Camry, Highlander, and Lexus 400h. Time will tell if gen 3 Prius is affected.

 

No, I'm not. That 30 year old Japanese marine drivetrain patent sounds interesting -- I'll go check it out. But from your description, it had one electrical path (motor) and an ICE.

The first truly HSD-like patent is the TRW patent (US3566717) from around 1970 which had 2 motors and the ICE hooked up to a planetary gear. However, they assigned the components to the gears differently and assumed (unrealistically) that the driver would manually control the hybrid power flows in the transmission since computer technology wasn't realistically up to the task back then.

The GM one-mode input split patent that I referenced earlier (and is referenced in Toyota's first U.S. "HSD" patent) describes the Prius hybrid design -- ICE hooked up to the planetary carrier, small MG1 hooked to the sun gear, and the large MG2 motor hooked up to the ring gear together with the wheels and with a battery pack and a hybrid computer controlling everything automatically.

I agree that it would have been nice if GM had built their own one-mode input split hybrid transmission and commercialized it in a small sedan but for whatever reason they decided to build a hybrid transmission for large busses and trucks based on their two-mode enhanced design and then later downsize that into a transmission for SUVs.