Picture of 2010 Prius Transaxle (Compared with others)

Nice. It really is an ingenious little device.

 

Well, mechanically HSD is relatively simple - but electronically it is amazingly complex.

 

Hi Patrick,

Electronically, its not complex at all. The only special electronics is the embeded heat sensor in each transitor die. 4 quandrant drives are as old as the hills. I have 4 in my kitchen that I bought off Ebay, but I am probably a true geek. The controllers are just computers that are tied together with networks. Allot of homes have networked computers.

The thermal engineering is somewhat complex, but the resulting product is simple.

The true complexity in the Prius is system multifunctionalism and the control software that makes it all work.

 

I totally agree and thank you for these comparisons ... they really do illustrate the relative mechanical complexity of the systems.

The compactness of the Prius Motor/Generator setup also illustrates the tremendous savings that automotive technology can potentially achieve if only we can develop more efficient sources of electrical power storage. Creating pure rotational motion in any driving device using a rotating magnetic field is far more efficient than that cranking monster sucking, squeezing, banging and blowing called the Internal Combustion Engine. While it is true it has undergone over 100 years of continuous refinement to a pretty high level, it is still an air breathing monster .... breathing OUR air! It would never have achieved the supremacy it has without that cheap, portable, highly abundant energy source we call gasoline. But we're starting to run out of the latter.

So it is time to move ahead, ultimately to that holy grail of motive power, all electric propulsion. Here's hoping for some future breakthoughs toward that goal.

 

I am sorry but the GM dual mode and the Audi look frighteningly complex. I cannot imagine them ever being 'rebuilt' and therefore are going to be amazingly expensive to replace.

 

Perhaps I should have said that Prius is incredibly complex when you consider the number of systems that must communicate and remain closely linked for the car to function properly. This means highly dense electronics hardware as well as complex firmware embedded within.

See the following post for a current example of the mess that can happen when this communication is disrupted due to accident damage.
http://priuschat.com/forums/prius-technical-discussion/59036-flashing-blinking-gas-gauge.html

 

But how does Hybrid Sinergy Drive compare to a simple 3 speed automatic?

Pretty well actually.
The thumbnail isn't working well, click here.
http://www.procarcare.com/includes/content/resourcecenter/encyclopedia/ch21/21Fig2.html

 

Why does that thumbnail open in white on a black background? It is almost impossible to decipher, other than it appears complicated. Which makes your point.

 

Well it doesn't cost 10K to replace a normal tranny, so either Toyota is hosing everyone whose fails or it is more complex than you think...

 

Who charges $10,000 to replace the transmission in a Prius?
It's just 2 electric motors and half the number of planetary gear sets a 3 speed transmission has in it.

I have no idea why the thumbnail opens in negative, odd.

 

MSRP of the transaxle is $3,460.
Champion ToyotaWorld

Considering dealer labor to remove and replace the engine/transaxle, you're probably talking around $6K for the complete job.

One big difference between Toyota hybrids and a run-of-the-mill vehicle is that you can find any number of independents who profess to be able to service the latter, thus increasing service competition and lowering prices. This is not generally true for Toyota (or any other make for that matter) hybrid vehicles.

 

Hopefully Bill Gates won't be putting any software into the Prius..

"Toyota Prius has encountered an error and will be shut down...."

 

Seawolf, in looking at the great pics you provided of the Prius transaxle a second time I have a question: where does the output of the ICE input into the transaxle? Is it through the center of one of the motor/generators?

Thanks for the pictures!

 

The engine torque passes through the hollow shaft of MG1 and the sun gear (the one in the center) and engages splines on the spider gear carrier (holds the shafts for the gears in the middle.) Spider gears are also called planetary gears because they rotate around the center sun gear and inside of the outer ring gear.

Now when MG1 does not apply any torque, a running engine can cause the planetary gears to race around the inside of the ring gear and spin the sun gear without any torque going out the ring gear. It is a type of "neutral" with the engine running.

One way to cause torque from the planetary gears to the ring gear is to make MG1 work as a generator. MG1 is connected to the sun gear so when it generates power, its torque is on the inner side of the planetary gears. This lets the engine torque at the planetary gear shafts force the outer side of the planetary gears to spin the ring gear and on to the wheels. But there is this left over power from the MG1 generator.

The MG1 electrical power races around to MG2 and turns it as a motor to recombine with the ICE power and move the car forward. That is why the planetary gear is called the Power Split Device.

Now many hybrid skeptics claim the power generation of MG1 and subsequent use by MG2, this power conversion is inefficient. But they typically use imprecise "very inefficient" instead of calculating the MG1-MG2 energy transfer efficiency:

92% generator efficiency
92% motor efficiency
~= .92 * .92 = 85% efficiency transfer
100% - 85% ~= 15% energy loss
​

This would be terrible inefficiency except it only applies to the power that is split out, ~28%, of the power. So this means the actual loss is closer to:

15% * 28% ~= 4% energy loss
2% is typical gear energy loss
​

There are more subtle aspects such as energy recirculate mode and that the engine shaft continues to turn the transaxle oil pump. But understanding the primary mode is enough.

Bob Wilson