The Oak Ridge Lab, as part of the Freedomcar project, performed a very thorough evaluation and teardown of a Camry Hybrid transaxle. The 102 page report is here: http://www.osti.gov/bridge/servlets/...fCi/922327.PDF

 

Looks very interesting. Quite a bit to read here! Thanks!

Stan

 

For the benefit of those with short attention spans...is it good or is it bad?

 

haroldo — I think it's very good!

Stan

 

All Good. The first thing I did after reading it was save it to my own hard drive. Basically, without taking any inovation away from the Prius, the report reveals the fact that the Camry HSD is newer, and that Toyota took advantage of what they learned in the Prius to improve the HSD in the Camry.

Here is a summary (for those with short attention spans):

Table 4.1. 2007 Camry/2004 Prius design comparison highlights

Parameter /Camry /Prius/ Comments

Transaxle

PCU

Nominal battery voltage./ 244.8 V/ 201.6 V /Up to 20% higher during
operation.

Maximum dc-link voltage./ 650 Vdc/ 500Vdc
Boost converter power rating./ 30 kW/ 20 kW
Filter capacitor (battery level)./ 500 Vdc,378

Boost converter power density./ 8.6 kW per L/ 3.9 kW per L/ Improved by a factor of 2.21.

 

Thanks! That's the kind of answer I like!

 

I don't want to sound inflamatory -- I LOVE my TCH and I have incredible technical respect for Toyota for the (obviously) years of R&D to pull off the HSD system... but, I find it both sad and infuriating that a US nationally-funded facility, in conjunction with the three Detroit automakers (as "co-sponsors" whatever that means to net tax dollars), can use nuke-grade labs to reverse-engineer somebodies innovation.

Sure Toyota has some core patents on HSD (they've been posted on this board elsewhere), but the overall know-how and how-to are spread all over these pages.

It just doesn't seem "fair" -- in the "ethical" sense.

(A tad like the GM ads with kids dancing around a GM hybrid in a grassy meadow with the fine print that says "not available").

Reverse engineering goes on all the time (I've seen a dozen "teardowns" on iPhones), but this is the first one that I've seen so blatant and government-funded.

I wonder what all those Kentucky TCH workers are thinking?

 

I think your concerns are little misguided:
First of all as you have mentioned it already patents are to protect one's intellectual property. I'm sure you are aware that Toyota didn't invent car, Atkinson cycle engine, NIMH batteries, electric driven cars (those were actually in use at the beginning of 20th century) etc. etc. etc. I'm also sure you are aware of the fact that Ford and Nissan use Toyota hybrid systems in some of their cars, so Toyota had to provide them with detailed technical specs to match rest of the car, even if the hybrid parts are shipped fully assembled from Toyota. That's how our whole education system works, in mathematics, physics, engineering, you take best work and their ideas, analyze it and then improve on it, otherwise we would be still living in caves , reinventing wheel over and over again. The fact Toyota is a leader in hybrid technology, makes it a natural target for this type of deep engineering analysis. This is how it's done, everywhere , from AMD analyzing Intel CPU and coming out with competitive design, at some point being better than original, to Japanese car makers looking at our SUV, mini van or pickups and improving on them. Does it bother you it's published on website so everybody can read it? Because people who actually can use all that info, will have it no matter what, I'm sure GM, Ford and other large companies did their own strip down analysis, probably much more detailed, you just can't access it. The whole report does not have any info, that anybody with proper tools and schooling couldn't get on their own.
I think it is very flattering they actually spend all that money and time to analyze and study this design , it shows how far ahead of everybody else Toyota is at the moment. I heard somewhere it used to be Japanese that would come here to look, study and admire US factories years ago to learn newest technologies, now we dissect their cars to learn.

 

I agree largely with the comments of TCHconn.

There appear to be at least two errors in the report's Table 4.1 (page 80), and these also appear in the sections excerpted by FastMover in post #5. Near the bottom, the figure for "Motor inverter specific power" improvement factor should be 1.6 and not 2.8;and the figure for "Motor inverter power density" improvement factor should be 2.1 and not 1.3.

After perusing the document, I have the following additional comments, conclusions, and conjectures:

1. The speed limit of 14 000 rpm for MG2 (and presumably also for MG1, as its construction is similar) seems to rule out mechanical over-revving of MG1 as the most likely reason why Toyota places a limit of 64 km/h (~40 miles per hour) on the vehicle before spinning up the ICE electrically when coasting in "fuel-cut" mode [pages 3 & 80].
2. Furthermore, the over-voltage (back-emf) threat to the MGs and their control electronics from high MG rpm when the car is coasting or being towed wheels-down in 'N,' also may not be the reason for Toyota's concern, since the generated back-emf, shown in Fig. 3.8 on page 61, reaches only 400 Vrms = 566 Vpeak. This is well below the claimed 650-V limit of the MGs and electronics.
3. More likely in my view is the fact that the transaxle's primary lubrication comes from the oil pump driven from the ICE's output shaft [pages 39 & 40]. If the ICE was not spun (in order to operate the transaxle oil pump) while coasting at speed, there would probably be insufficient lubrication of the transaxle's gears and bearings. The oil pump drive cannot simply be moved to the MG2 output shaft instead, since then there would be no lubrication if the ICE were running with the car stationary — for example when the ICE is charging the battery, warming up, or providing heat for the cabin. So, the oil pump is driven by the appropriate shaft. [It now appears that I was mistaken when I said in another thread that the transaxle oil pump was driven by the MG2 output shaft. I shall correct that error.]
4. Pages 65 - 71, and especially Figs. 3.18, 3.20, & 3.22 show that the combined (motor+inverter) efficiency is >90% over much of the operating region in the rpm-torque plane, and even reaches as high as 92% in the central region. So, my initial assumption of 90% efficiency (post #1) in the thread "An Unpalatable Fact (with apologies to Al Gore!)" was reasonably close, and my post-experiment deduction (posts #58 & 83) that it could in fact be significantly >90% wasn't far out either.

Stan

 

I don't think the limitation in neutral is related to lubrication. An analysis of the lubrication system reveals that the oil slinging arrangment is quite a bit more sophisticated that might be initially evident. The gear systems contain machined areas to accomodate oil transport by slinging and the housing contains a number of reserviors that receive oil in this manner that are actually supplly containers for gravity fed lubrication points. Besides, at speeds above 42 miles per hour, the ICE is turning (in fuel cutoff) to protect MG1. Neutral does not prevent the ICE from turning, it just shuts down fuel injection and ignition.

So what is neutral for? The primary thing is probably to let the car be moved on the ground over short distances without the danger of an engine start. This can't be done in park, and in any other gear, an engine start is a possibility, even in reverse (in fact, probably). The electrics are probably kept up for the power steering motor to permit the car to be controlled while rolling, but dynamic braking is disabled to prevent the artificial "drag" used to simulate the coast of a conventionally powered car.

Is it useful as an easier way to "stealth" the TCH? That's a matter of pure opion and personal preference. My take is that, yes, it does essentially the same thing as an accelerator position in the drive gears that results in no battery charge or discharge, and that that accelerator position is harder to hold in the TCH than the Prius. BUT, the benefit is very slight because it requires a very precise grade wherein the coast requires neither power or braking to maintain (you don't have access to power, and braking costs you energy becasue only friction brakes are available), and the coast must be long enough that you cannot hold it with the accelerator, and you accept the extra complication and risk that comes with an extra action (shift lever) for a sudden power demand or hard braking. All of this is for a very small efficiency gain of about 10% at idle or speeds below 42MPH (above that the ICE is turning so you are not in "stealth" anyway) for a very limited time period. SO, I don't do it as I simply don't think there is enough gain for the effort and risk increase.