Question about the Prius transmission

I guess it really comes down to how you define a Prius. What components, features, and attributes are necessary to call it a Prius?

 

Hi All,

I think a manual HSD transmission might be doable. Here is how:

1) Lever with haptic (force feedback when one pushes so that MG1 does not go overspeed) and variable range limits (hard limit to avoid MG1 going overspeed) - controls engine to wheels rotational ratio. Full forward is max ratio, full back is min ratio.


2) Left Foot Pedal push pull - controls electric power on push, and electric regeneration on pull. Neutral position - no electric input or output, unless battery needs charging/depleting. Dash panel light to indicate when pedal is partially over-ridden. Pushing on center (brake) pedal locks left pedal at neutral position.

3) MG1 is controlled based on computer programing during Left Pedal push.

4) Brake pedal can be switchable to be as is now, or only friction brakes.

5) Taking foot off right pedal (accellerator pedal now) results in engine stoping, unless speed exceeds 40 mph. Otherwise the left pedal is a direct match to engine RPM.


So, lets do some accelleration/decelleration thought-experiments, to see if its practical.

1) Accelleration - Both left and right pedals pushed, and one lifts off right pedal as one gets to speed. Lever is initially full forward (at stop) and pulled back to match engine Revs to wheel revs - engine revs set by right pedal. Car recharges battery as one cruises along.

1a) Transition from accelleration to cruise - left pedal is lifted, and lever pulled even further back until haptic force is felt. Based on degree of force, driver pushes pedal to keep engine RPM's practical. Car cruises along at min RPM, max ratio.

2) Braking - Left pedal is lifted, until 7 mph, then center pedal is pushed. Will probably need some kinda beeper that goes to a solid tone at 7 mph to do this right. Lifting foot off right pedal to go to brake, turns off engine. As car slows - haptic forces lever forward, or driver can preceed the hard limit moving the lever by moving it. If driver wants engine to cut, and the car is below 40 mph, pulling against the haptic force tells the car to go into a glide.

3) EV maneuver - one uses left pedal as go/slow pedal. No application of right pedal at all - engine off.


This is getting pretty complicated - not quite helicopter level , but close.

 

I didn't really mean to start a fight or anything, I just hate the use of the word "impossible" when it's not. FWIW when I originally posted what I envisaged was some sort of (2-speed) transmission following the PSD in the powertrain. As we know the Prius is not able to exert it's maximum power until it reaches 45 MPH or so (I can't remember the exact number) and a higher numerically final drive ratio might be welcome at low speeds and in hilly areas in reverse.

 

See the graphs of Prius power and torque at
Honda Accord Hybrid vs. Toyota Camry Hybrid - CarSpace Automotive Forums
There's little point in having even more torque at low speed, it would only burn up the tires :_>
I will never again buy a car with any sort of variable gearing system or clutch. The HSD is simply too reliable and efficient.

 

Wow, the old discussion of HSD vs. IMA topic. HSD superiority became more clear to a lot of people after four years. It was not clear back then....

You can also read Wayne Geredes' (xcel) negative view of Prius on page 13 and on...

John1701a joined in the discussion on page 15. This discussion did not get ugly like the 'Are hybrids up to the chore?' thread which got removed.

 

Lexus LS600h has dual stage HSD that you just described.

 

When will Prius come in a 2 range all wheel drive configuration? Just move half of MG2 to the back axle.

 

The 4WD-i version of Highlander Hybrid has an MGR which powers the rear axle. The Highlander model is named Kluger outside North America - have you noticed this sold in Australia?

 

We have Kluger here but not in the hybrid form. I know of the highlander butI was thinking an AWD Prius for stability and safety.

 

I didn't say much on that particular thread 4.5 years ago. But what was posted certainly was profound: Prius will become the icon for change... the one that inspired this new age in automotive history.

Sweet!

.

 

Looks like the 3G Prius has too. http://priuschat.com/forums/prius-hybrid-news/57277-2010-prius-news-detroit-published-jan-13th.html

 

Having SRU does not mean it will have dual stage. SRU adds a second planetary gear-set and Dual Stage (with SRU) adds a third planetary gear-set.





Below is the RX 400h Transaxle:

 

What are those chassis connections: clutches? If so, eww!

 

Hi Richard,

In the GS/LS schematic those are clutches.

In the RX transmission the chasis connections are just fixed locatings. No Clutches. Just locating the bearings and motor stators, and keeping the planet carrier from turning.

 

So, to be clear: there are no clutches in the 2010 Prius?

 

I don't think so. Dual stage HSD is only for muscle hybrids. I don't think 2010 Prius will have it.

 

Hi Rich and USB,

The dual stage HSD is to give a cruising speed up around 100 mph, and a max speed somewhat north of 125 mh.

SO, no, there probably wont be clutches in the 2010 Prius.

In the HSD's with clutches, is the clutch engaged for slow speed operation? If not, then a failed clutch transmission would still work just fine up to about 80 mph.

I think there are two reasons Toyota is doing this. With $50 in gears, they can get rid of the $75 chain and cogs, and reduce motor cost to about 2/3's of what it was. Those prices are guestimate volume vendor price to Toyota. To buy replacements from Toyota through a dealer would probably be 3 times the cost. This also allows the transmission casing to be smaller, which saves aluminum and aluminum refining energy.

The disadvantage is high rotational speed of MG2, which means one really really wants to keep that AT fluid changed on schedule, if not earlier.