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Smooth Transmission

Discussion in 'Prius v Technical Discussion' started by almhath, Nov 25, 2012.

  1. almhath

    almhath Junior Member

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    Hi. I have a new Prius, and I'm finding I enjoy driving it a lot. I think one of the reasons is the transmission is so smooth.

    Why is it so smooth?

    I know most cars with small engines seem to have this rev-up-and-then-shift-gears thing going on, but this Prius doesn't do that. It's smooth. I've heard of Continuously Variable Transmissions. Is that what it is? IT seems to me that the engine speed dosn't rev much on normal driving or acceleration, though it will sometimes getting onto the freeway.

    Otherwise, it seems to be quiet and at a normal speed, for itself. I find myself accelerating to 65 or so without the engine speeding up.

    I was wondering if someone could explain to me how it works?

    Thank you

    Jen
     
    #1 almhath, Nov 25, 2012
  2. jdenenberg

    jdenenberg EE Professor

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    Your Prius has a unique transmission that behaves like a CVT. Toyota calls it an "eCVT" (Ford uses the same system in their hybrids). There are two electric Motor-Generators (MGs). One is used to drive the front wheels in parallel with the Internal Combustion Engine (ICE). The other is used to adjust the torque seen by the ICE through a planetary gear set they together are called the Hybrid Synergy Drive (HSD).

    You ICE actually is speeding up as you accelerate (or go uphill), but as it is a very smooth process, the only indication is in the sound of the Engine.

    Note that this system has no reverse gear as the MG can run backwards as required (you have an EV when running in reverse).

    JeffD
     
    #2 jdenenberg, Nov 25, 2012
    GerryL likes this.
  3. jonb505

    jonb505 Member

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    I share your enthusiasm Jen. Going back to a conventional automobile would be hard to do after experiencing the smoothness of the HSD.

    Not to take away from JeffD's explanation, but if your up for a longer read, heres a bunch more information on the HSD, how it works:
    Hybrid Synergy Drive (HSD) - Prius Wiki

    I hope its alright to post the above link. I'm fairly new to Prius ownership as well so still have lots to learn, but loving every minute of it. :D
     
    #3 jonb505, Nov 29, 2012
  4. qbee42

    qbee42 My other car is a boat

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    Translated into non-technical language: Your Prius never shifts gears, which is why you never feel it shifting. Part of the power goes through the electrical path, part through the mechanical path, and varying the ratio of those two changes the effective gearing without actually shifting.

    Tom
     
    #4 qbee42, Nov 29, 2012
  5. almhath

    almhath Junior Member

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    Yes, I like this. I think the engineering is innovative. My husband was an aeronautical engineer and loved engines, and I think he'd love learning about it, too. EV in reverse; not shifting gears; smooth transmission, 51 mpg. And I'm actually getting that, too, if I can rely n the meter, which varies between maybe 53 and 47 or so, depending.

    What I want next for it is a little antigrav, so I can go over obstructions on the freeway, sometimes (when the freeway stops). :)

    Jen
     
    #5 almhath, Dec 6, 2012
  6. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    #6 JimboPalmer, Dec 6, 2012
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