CVT being used in EV mode?

Discussion in 'Prime Technical Discussion' started by Marine Ray, Dec 12, 2019.

  1. Marine Ray

    Marine Ray Senior Member

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    Question for the Group - It's well known that the Prius Prime's internal combustion engine runs less due to electric motor usage. Does the same apply for the transmission? i.e. does the transmission run regardless of ICE or EV mode?
     
  2. fuzzy1

    fuzzy1 Senior Member

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    If the car is moving, in any mode, something in the 'transmission' or transaxle is being used.

    Unlike an ICE, electric motors have a continuous RPM operating range all the way down to zero, so the raw need for a 'transmission' is reduced or eliminated. But with the gasoline engine still sitting there and connected, it gets used anyway.
     
    #2 fuzzy1, Dec 12, 2019
    Last edited: Dec 12, 2019
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  3. ChapmanF

    ChapmanF Senior Member

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    Easy way to remember it: the transmission is where the electric motors are.
     
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  4. Tideland Prius

    Tideland Prius Moderator of the North
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    The Power Split Device is a planetary gear set. Even if the sun gear planetary carrier isn't moving (the one connected to the engine), the planet carrier other gears are still moving and transferring torque to the ring gear.

    So, yes the eCVT is still in use in EV Drive Mode.
     
    #4 Tideland Prius, Dec 13, 2019
    Last edited: Dec 13, 2019
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  5. JirkaV

    JirkaV JirkaV

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    I believe that the sun gear is connected to the MG1, while the planet carrier is connected to the engine. Might be wrong though. Either way, the e-CVT (not CVT) is always moving when the vehicle is moving. The Prime can be hauled forward by MG2 only (the Power Split Device "outer ring") or combination of MG2 and MG1 ("outer ring" and "sun").
     
  6. Prodigyplace

    Prodigyplace Senior Member

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    Actually, on the Prime there is a one-way clutch that lets MG1 add power at low speeds, IIRC.
     
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  7. ChapmanF

    ChapmanF Senior Member

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    The Prius transmission (or rather 'transaxle', because the final drive and differential are also inside it), when viewed as a whole, which functionally includes the electronics inside the box above it, is absolutely a "continuously variable transmission", or CVT. You can call it an e-CVT if for some reason you want to emphasize the way it works, but there is no point to saying "not CVT", because there is no functional attribute of a CVT that the Prius transmission doesn't provide.

    "Not CVT"-style comments boil down to it not being the kind of CVT that is built with cones and pushbelts and so on. Which, sure, it isn't, but that's like saying a gas kitchen range isn't a kitchen range because it isn't electric.
     
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  8. JirkaV

    JirkaV JirkaV

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    I believe the clutch is in place to allow MG1 to help MG2 when extra power is needed. But I'm no technical expert on the matter...

    EDIT: This might help a bit:
     
    #8 JirkaV, Dec 13, 2019
    Last edited: Dec 13, 2019
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  9. Marine Ray

    Marine Ray Senior Member

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    If you got some time, this gentleman is the authoritive word on the matter of this post. :)

     
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  10. mr88cet

    mr88cet Senior Member

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    Uhmmm... the ICE is connected to the planet-gear carrier, not the sun gear.
     
  11. Tideland Prius

    Tideland Prius Moderator of the North
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    Oops. I'll edit it.
     
  12. Chazman62

    Chazman62 Junior Member

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    Please pardon my ignorance here... I just bought a new 2020 Prime last wee and am trying to learn.
    Have some questions if you would be kind enough to answer.
    > Prime has e-CVT, not the conventional CVTwith a steel belt and a pair of converters or cones. Correct?
    > Is there transmission or transaxle oil to be replaced? If so, is there a drain plug and fill hole?
    > Are there clutch/friction plates that would wear out?
    Thanks in advance.
     
  13. ChapmanF

    ChapmanF Senior Member

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    You could say it that way, if it's important to you. The CVT in a Prius is not the kind of CVT that is made with cones and a pushbelt, or the kind of CVT made with perpendicular disks. There are many kinds of CVT that it is not. It is the kind of CVT that is made with two electric motors, an inverter, and a planetary gear set. You can call it "e-CVT" if you want and you're in the kind of conversation where anybody cares how the CVT works inside. (Although, in that kind of conversation, maybe it's more interesting to just describe how it works inside; what does "e-CVT" really tell you?).

    There are plugs for draining and filling. It is factory filled with an oil that only serves to lubricate things and not degrade the electrical insulation of the motors. It is not pumped through torque converters or clutch packs or anything like that. It lives the life of a manual tranny oil, more or less. People might change it after several tens of thousands of miles, or a small number of times in the car's life, more or less.

    There is one dry-plate torque limiter (like a clutch that is never disengaged), really just there to protect the engine and gear train from very rough bounces. It isn't expected to be a wear item in the normal life of the car. It can be, if, for example, the car is driven around with a severe misfire, that kind of thing.
     
  14. CharlesH

    CharlesH CA HOV Decal #5 on former PiP

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    I am still reminded of the AAMCO commercial where they have an exploded view of an automatic transmission, and they brag that they can maintain all 800 of its parts. Versus the Prius transaxle, with about a dozen parts that are permanently connected to each other, and really nothing to maintain.

    Concerning clutches in the Prime, there is also a one-way clutch that allows MG-1 to move the car without the gasoline engine being turned backwards. But there are no pressure plates or anything like that to wear out in this sort of device. This is specific to the Prime, and is not in the non-plugin Prius models.
     
    #14 CharlesH, Dec 13, 2019
    Last edited: Dec 13, 2019
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  15. Marine Ray

    Marine Ray Senior Member

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    Welcome to this great forum and your new Prius Prime. For all you need to know about the Prius Prime P610 transaxle, check out the video in my post no. 9 above. The guy is incredible.
     
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