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Does the Prius have a transmission?

Discussion in 'Gen 3 Prius Main Forum' started by Jeff N, Apr 2, 2014.

  1. 70AARCUDA

    70AARCUDA Active Member

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    Volt CVT compared/contrasted with Prius eCVT (from MOTOR TREND article):

    [​IMG]
     
  2. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    (I am taking Ford/Toyota at their word, those more cynical may not)

    You seem to be thinking that their is a technical reason for the different designs of the transaxle. Ford did independent R&D and invented a transaxle so close to Toyota's that they licensed Toyota's patent rather than get in a legal battle. To this date, detractors claim Ford copied Toyota, even though the lead times to design a car make this improbable. GM seems to have altered Toyota's design enough to avoid claims of copying. It is quite a bit more complex, and has claimed efficiencies over 70 MPH. However, my theory is that GM was motivated not to build a me-too hybrid, so they altered design features and minimized (to the point of duplicity) it's similarities to other hybrids.


    Unbolting the Chevy Volt to See How it Ticks - Motor Trend
     
  3. 70AARCUDA

    70AARCUDA Active Member

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    This picture illustrates the evolution of the old common limited-slip rear-axle differential into the new planetary-CVT concept similar to what's used in the eCVT:

    [​IMG]

    • source: Understanding Planetary Gears
     
  4. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    Correct, Toyota's innovation was NOT mechanical, but adding and consuming power at all of points 1, 2, and 4 in the rightmost diagram. Previous Planetary gearset usage had one or more of the points 1,2,3,4 fixed, and only flowed power though a singe input and out a single output. In the old LSD, all engine power enters in 4 and exits via 1 and 2.
     
  5. 70AARCUDA

    70AARCUDA Active Member

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    As was once said, "...it's like holding onto an Octopus: it depends upon which legs you ARE holding and which ones your AREN'T holding." (wink,wink)
     
  6. Jeff N

    Jeff N The answer is 0042

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    Patent legal claims or public perception of copying? In my original post when I created this thread I linked to GM's early 1995 "one-mode" patent which describes the basic mechanical design and operating theory of a Prius transaxle. GM then extended this pattern in the subsequent Two Mode patent that described the full hybrid design they commercialized for large trucks, buses, and a scaled down version for SUVs and pickups.

    The "one-mode" patent likely protects them from any lawsuits from Toyota if they chose to build a Prius style input-split transaxle (in fact, they could presumably could have threatened to counter-sue Toyota for violating that GM patent).

    That MotorTrend article is old and contains some misleading descriptions around the alleged "70 mph" behavior of the Volt transaxle. See the comments on that page for clarifications from their readers. Basically, there is no magic 70 mph behavior -- the clutching of the smaller motor and engine to the ring gear happens at speeds as low as 30 mph and is dependent on both vehicle speed and torque demand from the driver.

    "Toyota's innovation" is described in GM's 1995 patent which precedes Toyota's Prius hybrid patents and the production of the original Prius that came out in 1997.

    Specifically, see column 11 on the PDF document page 19 with the sub-header "Description of a third alternative embodiment" for a description of the essential design of the Prius transmission:

    http://www.google.com/patents/US5558595.pdf

    Toyota's main innovation was the managerial and marketing insight to build a long-term mass market line of passenger cars based on this hybrid technology and do it with their usual engineering refinement and reliability. That's not to minimize all the hard work that went into designing the exact gearing, motors, power electronics. They also had to innovate in the design of the computer modules and firmware to control the transaxle's power flows. GM presumably had some of this working in the labs in prototype form in the mid-90's but did not actually have their ultimate two-mode commercial truck and bus products ready until 2003.

    Not true. The old 1969 TRW patent is functionally equivalent in its basic design with the GM one-mode design and the Toyota Prius transmission although the components were hooked up differently to the planetary gears and the driver was expected to manually control the power split behavior rather than having a hybrid engine controller do it automatically.
     
  7. Bill Norton

    Bill Norton Senior Member

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    Gents,
    I'm glad this technical discussion has progressed, even though some have called it "crap" and "please stop".
    Those who don't like threads like this should find the "cheerleading/brand loyalty" threads.

    It was when I realized how elegant and simple the Prius eCVT was that I decided to sell my TDI and I bought a Gen3 Prius. I was always wary of automatic transmissions but the eCVT is not that. It is an amazing hybrid car!
    I had a Gen1 Honda Insight before the TDI. I'm into fuel efficient cars.

    When I realized I could afford a new '13 Volt ($23.6k), I sold the Gen3 ($15k).

    The Volt is a full blown EV. I can go a long time without gas. And when I'm on a road trip I live with 38-40 mpg, a more than fair trade off, IMO. But that's at +5 mph the posted.
    Depending on what the recipe of your local electricity is the Volt can be very 'Green'.
    The EV miles are like getting a 70% gas coupon, even better for me because I charge at work.
    Lutz wanted "A Leap in Technology" over the Prius. I think that it is. I no longer have monthly gas bills.

    The transaxles are the heart of both of these cars and who knows where the actual finished designs came from, the supplier or the car manufacturer.

    The PiP is a hybrid that can act like an EV if: you don't accelerate too hard, go too fast or want heat in the winter and only need ~11 miles of <62 MPH EV miles.
    One of the MG's is consuming power not to propel the car, but to keep the engine stopped.
    The first PiP's were homebuilts, then Toyota got on the bandwagon.

    That last paragraph is 'IMO'. Sorry if it offends.
     
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  8. john1701a

    john1701a Prius Guru

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    Ironically, that EV purity statement was cheerleading.

    It was the "redline" claim which stirred the pot. After having provided information showing that was incorrect, the claim continued to be spread anyway. Even the video itself was referred to as support of the false. What purpose could misrepresentation like that serve? You'll get burned by it eventually.

    Of course, the arguing of semantics isn't exactly a win either. Mainstream consumers certainly don't care what a technology is called. Heck, they don't care about operational detail either.

    If they cannot afford it, not much else matters. Cost engineering is the big challenge, a fact commonly disregarded in technical discussions, often distracted by cheerleading & misrepresentation.
     
  9. usbseawolf2000

    usbseawolf2000 HSD PhD

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    Since this is a technical discussion, you are wrong technically. MG1 is rotating freely and not consuming any electricity. Sure, there will be friction loss from the bearing but it is neglectable.

    Especially compared to the energy loss from Volt ICE dead weight. Volt has oversized MGs that has additional loss as well. This compact 4 seated weights more than a SUV!

    As pointed out in the other thread, PiP is more efficient than Volt in EV mode in the same EPA highway cycle (not US01).
     
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  10. john1701a

    john1701a Prius Guru

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    Addressing the "right size" aspect of Volt design certainly brings about passionate reaction. Point out the MG size/power for Leaf and Fusion-Energi. Compare to Volt. See the issue? Enthusiasts were not at all happy when I pointed out the electric potential for Camry-hybrid either.

    In other words, it goes beyond just technical. Need must be included too. More isn't necessarily better.
     
  11. Bill Norton

    Bill Norton Senior Member

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    john17,

    Where is there that 62mph limit coming from on the PiP? Is there current flow to MG1 when in EV, or does it "rotate freely"? Only your Torque app can tell. (I read the limit was MG1 reaching redline)

    Yes, that chunk of cast iron in the front of the Volt is a drag,,, but when needed, you can go anywhere at anytime compared to a BEV. (Oversize MG's? How does that affect efficiency? I wish they were bigger ! Think Spark EV)
    What about the battery's Thermal Management System the Volt has compared to the fan that blows cabin air in the PiP? Is that a drag on the weight of the car?
    What about the lack of maintenance required when 73% of your miles are EV?
    (I did an early oil change at 2500 GAS miles. I'm done with that work for a long, long time now !!)

    If you are OK with a slow EV for ~11 miles, fine. Most commuters need more. I can see where the PiP would suit some people that don't need heat in the winter and TMS for the battery in the summer. (The lack of TMS makes the 'Wall to Wheels' EV efficiency look better on the PiP. What about 'Battery to Wheels'?)

    If you want a fast, quiet, low C/G, sporty EV that let's you drive like you had a 70% off gas coupon (for the first ~40 miles), you should at least consider an American Made EREV. (The highest tech car on the road, IMO.)

    Go on, take a test drive so you know what GM has to offer.
    It truly is a "Leap in Technology". (IMO)
     
  12. 70AARCUDA

    70AARCUDA Active Member

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    For some *odd* reason this adulterated-revision of a Childrens Nursery Rhyme seems appropriate:

    "The Bird in the hand, is the Best in the land..." (...translation: MY XYZ is better than YOUR ZYX ).
     
  13. Jeff N

    Jeff N The answer is 0042

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    A small and lightweight non-hybrid SUV...

    The Volt weighs less than the CMAX or Fusion Energi even though it has a bit more than twice the battery size and bigger motors.

    The argument about dragging around the dead weight of the ICE doesn't fully hold up. Without the ICE you would want a bigger battery to give it good range. Quite a few people buy the Volt because the LEAF doesn't have enough range to eliminate their range anxiety. The LEAF battery is about 225 pounds heavier than the Volt battery. Doubling the LEAF's range to 150 miles would require doubling its battery weight so that would be a further 650 pounds for a total of around 3840 pounds or about the same weight as a Ford Energi and therefore heavier than a Volt.

    Presumably GM has worked to further reduce the curb weight of the 2016 Volt but the argument that the existing Volt is uniquely heavy or SUV-like for its purpose isn't really true.
     
  14. 70AARCUDA

    70AARCUDA Active Member

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    Weight is bad, regardless of whether it's ICE, EV, or hybrid. Weight kills both acceleration and milage, and necessitates higher HP motive source(s). About the ONLY thing it doesn't 'kill' is crash safety...ie: TANK vs. Yugo or tin-can.

    What we need is a Neutrino-like car...basically NO weight!
     
  15. john1701a

    john1701a Prius Guru

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    There it is again.

    My commute this morning was 16.7 miles. 9 of that was at 70 mph. The result was 121 MPG.
     
  16. Bill Norton

    Bill Norton Senior Member

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    My commute was 25 miles, 70-75 mph 85% of the way, NO GAS usage. Display shows +250 MPG, stupid display.
    Maybe $0.60 worth of home electricity. Top up at work for a free commute home.
    No using engine life, oil life, only consuming tires !!! (Will there be a payback from my old fashioned Prius?)
    Sporty handling! Very quiet ride! Did someone mention 'crash safety' ratings?
     
  17. john1701a

    john1701a Prius Guru

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    Take your own advice.
     
  18. Bill Norton

    Bill Norton Senior Member

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    But,, we're just comparing technical specs and observed performance for our cars with transaxles from the same supplier, right?

    Each one serves a niche, right?
     
  19. usbseawolf2000

    usbseawolf2000 HSD PhD

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    Yes, the same supplier from Japan.

    Fundamental difference in how it works is what you don't get it or unable to accept/appreciate.

    PiP single speed "transmission" use electricity for City cycle and gas for Highway cycle. You can think of it as low and high "gears" but in PiP case, it is switching fuels, not gears. Electric motor is low gear and Atkinson ICE is geared for high.

    It is not only the speed. Power demand will also trigger fuel switching and even blending. That mixing is what creates CVT effect. Electricity is used to achieve so it is eCVT. PiP has much stronger (than regular Prius) eCVT due to bigger battery enabling higher EV speed (62 vs 25mph) and power (38 vs 15kW).

    You have a problem with PiP gas engine starting. Don't worry, it is per design and you are seeing eCVT in action. Preventing ICE from starting is like driving only in 1st gear.

    Volt is a different animal as it has two mechanical gears in both EV mode and HV mode. Modes are switched with clutches where PiP has no clutch.
     
  20. usbseawolf2000

    usbseawolf2000 HSD PhD

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    That's the gas consumption. You consumed very little gas (you seem very proud of this) but a lot of electricity.

    Let me ask you this. Do you know your fuel economy?

    To answer that, you need to know the difference between gas consumption and fuel economy.

    They used to mean the same in single fuel gas cars but NOT ANYMORE with plugin hybrids with two fuels.

    To get the fuel economy of your plugin hybrid, you will need four basic numbers.

    - Gas gallon
    - Miles driven with gas
    - kWh electricity
    - Miles driven with electricity

    Without knowing them, you are clueless on your fuel economy. Just looking at big MPG displayed on the screen is as you said, stupid.

    Here is my first year average with PiP. 132 MPGe on electricity and 56 MPG on gas. Combined 75 MPGe.

    [​IMG]