P610 transaxle

OK, looking through things, the torque flow is:

MG2 driving gear and PSD ring gear drive reduction device driven gear (53T)
Compound geared into differential

Somewhere in there is a 21/73 ratio, too, I'm assuming. But, there's definitely a gearing change between the differential and the counter gear.

Edit: Got it mathematically. Outer edge of the ring gear is 65T, counter gear is 53T, shaft to a 21T gear into a 73T gear, I think. (53/65) * (73/21) = 2.834. So, 2.834 is the PSD ring to wheels, and it'll be 10.838 for MG2 to wheels.

 

Hi everyone, any new opinions about which ratio (3.476 or 2.834) would be the one ?

What @bhtooefr posted makes sense for me too, as a two stage reduction gear. Anyways I could not find the New Car Features article to have a look aswell, only the Previews from the SAE Papers. I guess that comparing the values of Differential Ratios in this case does not count as what we need for the final ratio, as said before here.

Cheers

 

The short answer is that both 3.476 and 2.834 are right, depending on where you're measuring - and 10.838 is also right. 3.476 is an intermediate ratio that no component that you care about actually sees, but it's a necessary ratio for calculating the rest. 2.834 is the ratio from PSD ring to differential. 10.838 is the ratio from MG2 to differential.

For comparison, the Gen 3 specs (from here) are a PSD ring to differential ratio of 3.268 (not 3.267, rounding error in that post), and a MG2 to differential ratio of 8.615. The gear layout is different, but those two numbers are directly comparable to the Gen 4 numbers.

The long answer is that the "true" last stage of final drive (and also the ratio that must be calculated to understand everything else) is 73/21, or 3.476. But, nothing is directly geared to the final drive, there's intermediate gears that everything goes through. In past FWD Toyota hybrid gearboxes, MG2's gear reduction device (if present) was geared to the PSD ring, so everything went through the same reduction gearing to the true final drive, so the "final drive" was reported as all gears between the PSD ring and the differential, not just the last stage.

The power split device ring to final drive ratio is 53/65. So, by the old definition (PSD ring to differential), this means that the final drive ratio would be (53/65)*(73/21), or 2.834. However, because MG2's reduction gear is directly connected to the final drive, rather than going through the PSD ring, this doesn't tell the whole story. It is sufficient, however, for comparing engine and MG1 speeds to wheel speeds, compared to previous generations' final drive ratios which include all reduction gearing between PSD ring and differential. Not sufficient for comparing MG2 to wheel speeds, though (which were, for Gen 1/2, simply the PSD ring to differential reduction gearing ratio, and for Gen 3, that ratio times the MG2 reduction ratio).

In this case, the MG2 to final drive ratio is 53/17. This is where 10.838 is coming in - it's (53/17)*(73/21).

Do note that the 53 tooth gear that MG2's gear reduction and the PSD ring gear's gear multiplication are using, is actually the same gear, which is the main difference between the P610 and the Ford designs (Aisin HD-10/HD-20, Ford HF-35) conceptually, as far as I can tell. The Ford designs have separate gears on the same shaft for MG2 gear reduction and for PSD ring gear multiplication.

 

So, therefore the MG1 contribution during dual motor use would be (-)2.6 X 2.834 = 7.368?

 

I believe that is correct.

At 84 mph, 836 revolutions per mile, ICE off, MG1 will be spinning at -8625 RPM. MG2 will be spinning at 12684 RPM.

 

I've Read this thread and looked for some pics in the web, in the end I think you got the point.
Here I put a link of cutaway picture where you can see the 53 teeth common path gear to the differential.
http://st.motortrend.com/uploads/sites/5/2015/10/2016-Toyota-Prius-transaxle-cutaway.jpg

 

I came across this presentation:

 

i just hope they fixed the gen 3 ipm module problems.

 

OK, so some more info to toss in this thread. All math will be using the original equipment Toyo NanoEnergy A29 P195/65R15 89S - that's the slowest-spinning tire, at 832 revolutions per mile per Tire Rack.

From the EPA certification data, the Liftback (both NiMH and Li-ion) has an "axle ratio" of 2.83 - this matches up perfectly with the entire geartrain from the Power Split Device's ring gear, all the way to the half shafts, of (53/65) * (73/21) = 2.834.

Conversely, the Prime's certification data claims an axle ratio of 3.22. There's plenty of ways to get that ratio, but the simplest would be to just change the final drive. (53/65) * (75/19) = 3.219, and I'm 99% sure that that's what they did. Yes, they made the ratio shorter. I'm almost certain that this means that vehicle top speed on the Prime is somewhere around 99-100 mph depending on tire, and it'll probably be displayed as about 102-104 mph on the cluster. (Compare to the Liftback, at a calculated 113 mph actual top speed, and probably about 115-116 on the cluster.)

Now, there's been speculation that MG1's been re-rated to 13,500 RPM in the P610. It's basically what you get if you do this: (84 mph * 832 revs per mile / 60) * ((53/65) * (75/19)) * 3.6.

However, there's a math error (and I made it too while composing this post) - the formula for MG1 RPM in the Power Split device is this: MG1 = (3.6 * ICE RPM) - (2.6 * PSD ring RPM). So, if ICE RPM is 0, and PSD ring RPM is 3750 RPM... MG1 = (3.6 * 0) - (2.6 * 3750), or -9750 RPM. I believe that that is the true rev limit of the P610's MG1.

Fun fact: this also means that the Liftback could hypothetically kill its engine while going as fast as 95.4 mph. It just chooses not to.

Edit: Decided to toss a couple graphs in. Top line is maximum RPM (assuming a rev limit of 5200 - there's certainly no reason to go above the power peak in this transmission, it's not engine RPM-limited at the top speed), bottom line is minimum RPM (note that even at top speed, you're well below the actual minimum engine running RPM - upshot is, MG1's not going to be running at max negative RPM once it has to start the engine).

 

I'm at the SAE World Congress and Toyota gave a couple of new Prius P610 papers that trickle out a few more details.

First, they confirmed that the max rpm of MG1 is 10,000.

Second, they reported a consistent increase in the Prime's final drive ratio versus the regular gen 4 Prius. In the SAE papers they report the final drive ratio as 3.476 and for the Prime it is 3.947. This is the same relative ratio difference as the 2.834 versus the Prime's 3.22 mentioned in the previous post as being reported to the EPA but obviously calculated differently. I asked the presenter and he said the reason for the increased ratio was to compensate for the Prime's heavier weight due to the bigger battery pack.

Another difference in the Prime is the electric ATF fluid pump versus the mechanical pump on the regular gen 4. The electric pump is more expensive but is needed when driving in EV mode for long periods with the engine off since the mechanical pump is driven by the engine input axle.

Finally, they clarified the details of the Prime's one-way clutch. It is located on the flywheel on the engine-facing side. On the other side of the flywheel is the damper and then the transaxle.

The paper has a 5-page preview (which is the entire paper length) at:

Development of New Plug-In Hybrid Transaxle for Compact-Class Vehicles

A related paper is:
Development of New Hybrid Transaxle for Compact-Class Vehicles

 

I'll need to re-do my graphs assuming a 10,000 RPM rev limit, then:

 

Hi
Somebody knows the answer to the question above?

 

Where RPM's under 1000 RPM will not occur, so the engine will jump to 1000 RPM (or a bit less) when it has to spin.