MG1 rating?

Hi,

I'm looking through my materials and I can't find any specs for MG1. Anyone have them handy?

Thanks,
Bob Wilson

That is for MG2. The 2010 spec sheet is silent regarding MG1.

I believe that is MG2 maximum torque. We already have the MG2 specifications as well as the ICE ratings both power and torque.

What I can't find is MG1 power or any specs. Knowing the MG1 power gives us the rough ratio of the PSD between the ICE and MG1. Today, that is 28%.

Bob Wilson

It doesn't say the ratio of MG2 speed reduction unit.

Source: Green Car Congress: Toyota Previews Generation III 2010 Prius Hybrid

I believe the 28% is fixed torque ratio, not power ratio.

Ken@Japan

Seeing that is really a pain.

The Classic model was always thought to have a larger MG1 than 10 kW, but no one cared since that was the tolerance.

What's the situation for the 2010?
.

Not much point rating MG2 at 60kW if the combination of battery and generator can't produce 60kW. The 2010 max battery discharge power is supposed to be 27kW, up from 25kW in NHW20.

NHW20's MG2 was rated at 50kW, so working backwards I would assume MG1 would have been around 30kW, to allow for conversion losses.

Conservation of energy pretty well requires the sum of ICE, MG1 and PSD output to be zero. In mechanical engineering, we often do a power analysis to gain insights about how a system works. Near as I can tell, we should be able to use the torque, gear ratio and rpms to measure the exact power flow and back into the gear ratios.

I'll see if I can work up the equations over the next day or so and then gather some Graham scanner data to confirm it. This is a little tricky.

What suggests a higher gear ratio between MG1 and the ICE is:

• max ICE rpm - max MG1 rpm - model
• 4,500 - 6,500 - NHW11, ~270 VAC
• 5,000 - 10,000 - NHW20, ~400 VAC
• 4,000 - 13,000 - 2010, ~600 VAC

Of course the definitive answer would be a Toyota posting, maintenance manual, or SAE paper. The earlier Lexus transaxle posting might also have some clues.

Bob Wilson

If the 2010 Prius battery is rated at a max. rating of 27kW, together with MG1 rated at 42kW output, together the two sum to 67kW ... 7kW higher than the quoted max rating for MG2 on the 2010 model. So that makes sense to me, since under max. power conditions both the Traction battery and MG1 are feeding electrical power to MG2, and finally to the road-wheels through the step down gearing and differential.
Also the max. torque rating for the 1.8L ICE 0n the 2010 model is quoted as 105 ft-lb at 4000 rpm. That compares with the rating on the 1.5L G2 Prius of 84.6 ft-lb at 4200 rpm.
Quote:
"The multifunction gearset incorporates two sets of planetary gears: a power-split planetary gearset and a speed reduction planetary gearset. Both gearsets share the same ring gear, which drives the transaxle’s counter gear. The sun gear of the power-split gearset is connected to the 42 kW motor generator 1 (MG1); the planet carrier is connected to the engine. In the speed reduction planetary gear set, the sun gear is connected to MG2, the carrier is fixed, and the ring gear connects to the counter gear. A parking pawl is also part of the assembly, which is connected to a differential with a final drive ration of 3.267:1".

Still trying to visualize this little jewel-of-a-gearset, and just how they interact!

Yes, the Iconic MG1 has been confirmed to be 30kW by a study done by the US Department of Energy. See the last paragraph of the page 3-2.

Energy Citations Database (ECD) - Sponsored by OSTI

Let's first review the Iconic Prius transaxle. One set of planetary gear-set is used as a Power Split Device.

Iconic Power Split Device
Sun = MG1
Carrier = ICE
Ring = MG2 = Final Drive -> Wheels





2010 Prius transaxle will be like the Camry hybrid / Highlander hybrid / RX400h / RX450h. Two sets of planetary gear-set is used. One for PSD and one for Speed Reduction Unit (SRU).

2010 Power Split Device
Sun = MG1
Carrier = ICE
Ring = Carrier of SRU = Final Drive -> Wheels

2010 Speed Reduction Unit
Sun = MG2
Carrier = Grounded (does not move)
Ring = Ring of PSD = Final Drive -> Wheels

Logical Connection View:


Physical Connection Illustration:


The real thing:


MG2 torque is being multiplied by the SRU the same way the MG1's torque is being multiplied by the PSD to turn the ICE (when the car is stationary).

In another word, when the MG1 starts the ICE, PSD is actually being utilized as SRU. MG1 high speed is converted to higher torque to spin the ICE.

Below is the good old Graham's animation of PSD being utilized as SRU. MG1 torque is multiplied as it turned the ICE but in the process it slowed down. i.e, the sun gear turns faster than the carrier.



Edit: I just realized that the "Logical Connection View" indicated the SRU ring gear being grounded while the "Physical Connection Illustration" showed the SRU Carrier being grounded. If the SRU carrier is grounded then the MG2's torque gets multiplied and turn the ring gear. It should look like this:

So in the color diagram you show MG1 is in blue and MG2 is in red?

THANKS!

Now I have a good mental picture of the new power-split device. The first stage has the ring gear with what appears to be bearings between it and the the second stage ring gear. The rest now makes perfect sense including the stiffening ribs from the power take-off gear along the cylinder of the outer ring gear, the second stage.

What I don't yet have is a good understanding of is the actual gear ratios in the primary planetary gear set. I'm pretty sure the ratio has changed to allow MG1 to spin faster. To make a smaller motor produce more power, the answer is to spin it faster and of course use a higher voltage to overcome the resulting back-EMF.

BTW, my complements on the photos of the transaxle MG1, MG2 and enhanced PSD. Just curious, where did they come from?

Any idea of what the MG1 cover is made of or why it exists? All I have are these speculations:

• some way to force or guide cooling oil around MG1
• some type of EMI shielding to reduce emission losses

MG1 tends to run hotter than MG2 because it has an engine block on one side and the rest of the transaxle on the other. In contrast, MG2 is effectively in a 'cap' with cooling air available on the radius as well as the end cap. So I see MG1 as having a somewhat more challenging cooling problem and needing something special. Also, I've never been a fan of 'sling oil' cooling against even potted stator coils.

The only thing we haven't seen is the 'differential' gear that drives the two axles. I'm very curious about how they handled lubrication. Also, I'd like to know where the fill and drain plugs are ... at least once I someday get to take delivery of mine. <GRINS>

Bob Wilson

You got it! I just noticed that SRU carrier is grounded (not the ring gear). So I updated the animation to reflect the MG1 torque being multiplied.

Yes, I was going to comment on that discrepancy, as the ring gear always carries torque to the final drive gear set!

Thanks much for the depictions. I think labels on the one showing every element diagrammatically would help a lot.

Sure is neat how they have packaged those gear-sets together into such a small space.

From Toyota Press Room Prius Image Library. See page 19 and on. They have more like this Gen2 to Gen3 comparison:

The correct logical connection should look like this. Does anyone knows how to get the updated? [ame]http://en.wikipedia.org/wiki/Hybrid_Synergy_Drive[/ame]