P610 transaxle

In my head, it's doing this: all loads, torques, and power flows are small. The engine has stopped, and the only power being put into the system is electrically applied to MG2 under the HV ECU's control.

That torque is spinning MG2, final drive train and wheels at the creep rate. I don't know whether the HV ECU has an actual target creep speed, or just a target amount of power or torque, with the final component speeds settling in at whatever point that just balances the mechanical losses. Those are three different answers (target speed, target torque, target power) and an experiment like this could be extended to distinguish between them, which would be an interesting thing to learn about how the HV ECU is programmed.

There is no spot on the nomograph where MG2 is spinning but both MG1 and ICE are stopped, so one of those guys is also spinning. Most likely MG1, and the engine with its substantially higher friction is stopped. MG1 is spinning at just the speed the nomograph says it has to, given the speed of MG2.

Newton is watching, so there is a torque being applied to the engine ... 1 / .72 of ... (the electromagnetic torque acting on MG2, minus the torque between MG2 and the final drive), conveying no power because the engine isn't moving. There is a torque (.28 / .72 of that same MG2 torque-minus-final-drive) acting on MG1, which is conveying some power, just enough to spin it around against bearing and seal resistance and slosh some oil.

I predict a steady-state speed is reached, where that amount of power (whatever it takes to spin MG1 at that speed against miscellaneous losses), plus whatever it takes to spin MG2, final drive and wheels at their speed against their miscellaneous losses) ... plus a bit of heat in MG2 ... add up to the total electrical power being fed in.

Will the HV ECU have any interesting plans for the volts being developed as MG1 spins, or just leave those IGBTs gated off? I don't know.

-Chap

 

I believe that the #ZR series have a variable capacity engine oil pump of some description.
Variable discharge oil pump
I know that there is an SAE paper on it, but I can't find it at the moment.

 

Interesting. I wonder if MG1 could be used to add more torque at the wheels.

 

If ICE is parked, wouldn't MG1 be able to?

 

No, because MG1 would just start pushing the ICE. You need to have a clutch of some kind to lock the ICE to the transmission case so that MG1 can push against that and impart all of its output force to the ring gear and the wheels along with MG2.

This is why the new gen Volt has a one-way clutch and also is why Toyota's new PHEV patent, http://patentimages.storage.googleapis.com/pdfs/US20150005125.pdf, which I revealed in my "Revenge of the Two-mode Hybrid" article includes a clutch that can lock the ICE in place to enable dual-motor driving with the ICE off. Similar one-way clutches or ICE clutch brakes are included in the new GM RWD CT6 PHEV and the new Chrysler Pacifica PHEV minivan.

It's not worth doing until the battery pack can output more power than MG2 is capable of handing by itself. That wasn't a problem in the original Prius PHEV but it could possibly be an issue in the new PHEV depending upon the size and capability of the new battery pack and the size of MG2.

 

Where can I find this pdf?

Does anyone know what the max rpm of mg1 is for the P610 transaxle? I'm assuming it is the same for the Prius Prime variant of the P610...

We know that mg1 spins about 15% slower than in gen 3 at the same vehicle speed with the engine off due to the change in the final gear ratio. I'm wondering if there is an improved mg1 max rpm that also contributes to allowing Prius Prime to hit up to 84 mph in EV.

 

The SAE 2016 World Congress Technical Session Schedule is online (as of 03/24/2016).
Here are some papers from Toyota & Aisin realated to the Prius Gen IV (the list may be incomplete):
The New Toyota Inline 4 Cylinder 1.8L ESTEC 2ZR-FXE Gasoline Engine for Hybrid Car
Development of the Li-ion Battery Cell for Hybrid Vehicle
The New Generation Front Wheel Drive Hybrid System
Development of New Hybrid Transaxle for Compact-Class Vehicles
Development of Power Control Unit for Compact-Class Vehicle
Efficiency Improvement in Exhaust Heat Recirculation System
Development of Compact Electric Rear-Drive Unit
The full texts are not online yet, but most of them have 5-pages free preview already.
The new MG2 is 53kW/163Nm/17000rpm MAX (Gen III: 60kW/207Nm/13500rpm MAX).
But I haven't seen the numbers for MG1.

 

I still cannot get my head around the fact that the MG2 is less powerful than in the Gen3 (ICE being in the end with the same HP and better delivery of torque at lower rpms), the Hybrid system has 14HP less, the car weighs the same but the performance seems to be the same. I am wondering if it is really the same, or has it lost some "mpfh" especially at higher highway speeds. The Gen3 always had something left even at 150km/h, will the Gen4 be the same? What really gets at the wheels considering that the PSD is now has some different gears?

 

Apart number 3, I could not do the other 2 as it would void the warranty...
And I do number 3 in any case already
I have to check the old Gen3 tests from Quattroruote and the new one of Gen4 to see what is the difference. They make very accurate measurements about performance of the cars they test, always in the same way.
Once I have the data I will make a post about that. I need to find my own post here in PC about the Gen3 test they did back in 2009.
BTW I am realising I am talking about Gen4 here and there, I don't even know when they are delivering mine.....

 

[QUOTE="Huh? If creep is turned off while the brake pedal is held then I see no reason for MG2 to receive any current. The brakes will hold MG2 at zero rpm as the engine spins MG1 to generate recharge power to the battery.[/QUOTE]

In my Gen 4, I have noticed that if I forcefully apply the brake at a stop the "Energy" display shows no current to the wheel drive. However, half-hearted brake pressure shows constant flow of current from the battery to the electric wheel drive and to the wheels. There is a definite "feel" for when the brake is pushed sufficiently, and this is confirmed by the Energy display. So, at a stop there is both an energy-saving mode where the brakes are used for wheel lock, and an energy-consuming state for creep.

 

I've observed much the same behavior in my 3rd-generation, except that moderate force on the brake pedal suffices to shut off the creep current, and except that I'm watching battery current with a ScanGauge. I see no point in requiring "forceful" braking. If the car is stopped and your foot is on the brake hard enough to keep it stopped, creep current is waste.

 

One of the new SAE papers from Toyota says the final gear ratio in gen 4 in the P610 is 3.476, not the 2.834 assumed here. Using the new number the gen 4 torque at the wheels would be 1,301 or about the same as gen 3.

The paper is linked below and the gear ratio can be seen on page 1 of the free preview:

Development of New Hybrid Transaxle for Compact-Class Vehicles

H/T @bhtooefr

 

How do you interpret that? If the "differential gear ratio" is 3.476 according to the SAE paper then what the heck is 2.834? The 3.476 is being compared in the SAE paper's table to the gen 3's 3.267.

I'm confused.

 

Must be more stages of gearing (which I could believe, given the positioning of components), and the New Car Features must only be reporting the last stage.

I'm getting a 17/6 ratio on the 2.834, but the intermediate ratio of 1.227 that would be needed isn't cleanly working with any factors of 6.

Edit: So the 3.476 is 73/21 I think, in a single stage. There are other ways to skin that cat, though, so it could still be multiple stages. It could also be different applications being described, or even different markets or last-second gearing changes.