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Oil pump driven *how*?!

Discussion in 'Gen 2 Prius Technical Discussion' started by ChapmanF, Apr 17, 2008.

  1. ChapmanF

    ChapmanF Senior Member

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    I was flipping through the NHW11 shop manuals for some light bedtime reading,
    but suddenly I'm not sleepy.

    The ICE oil pump lives in the timing chain cover and is driven by the
    crankshaft, so only when the ICE is running. Standard stuff, didn't really
    expect anything different, ok fine.

    The transaxle oil pump lives on the outside end of MG2. I think I must have
    been assuming that MG2 drove it. Or maybe MG1 somehow. But the drawings on
    pages HT-12 and HT-13 pretty clearly show an Oil Pump Drive Shaft that goes
    clear through MG2 and engages in - it looks like - the input shaft / planet
    carrier, which is the part that's splined to the ICE.

    So the transaxle oil pump also turns only when the ICE turns.

    In a hybrid?!

    Ok, so that sure explains why they warn against towing with the front wheels
    down.

    But what about stealth? What were they thinking? Do they just figure that
    because the stealth range is short, the ICE's going to start every mile or
    two and pump some oil around, and that's good enough? Has anybody seen the
    inside of one of these transaxles closely enough to see what parts rely on
    oil from the pump, as opposed to plain splash or something? Have I misread
    something, or is there some fact I've overlooked that would make this make
    sense?

    Rather curiously,
    -Chap
     
    #1 ChapmanF, Apr 17, 2008
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Hi Chap,

    Yes, this is one reason why engineering a PHEV Prius with extended battery-only range is not a trivial exercise. That oil pump problem is one of many to be solved.
     
    #2 Patrick Wong, Apr 18, 2008
  3. qbee42

    qbee42 My other car is a boat

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    Splash oiling can work pretty well. Our marine diesel only uses splash oiling - no oil pump. The valves are manually oiled through a drip oiler. That engine will still be running after our Prius is a pile of rust and plastic.

    The Prius doesn't run very long or fast without the ICE, and at speed the ICE spins even when it isn't running.

    Tom
     
    #3 qbee42, Apr 18, 2008
  4. hobbit

    hobbit Senior Member

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    The transaxle parts don't depend on a continuous *feed* of oil
    the same way as an engine does. Think of it like the oil you'd
    put into a regular manual transmission -- enough to bathe the
    gears and get thrown around when it's turning, but in most
    cases those don't need an actual pump to push it around. All
    the pump does is push oil down the center shaft where it then
    bleeds out side holes into the various bearings, most of which
    are ball or roller in the NHW20 and can run quite a while on
    their own without additional feed and without "going dry".
    .
    So far the PHEV folks have racked up many EV-only miles and not
    reported any problems, but if PHEV Priuses get more widespread
    and start going through many ICE-free drive cycles across the
    usual thermal/humidity/stress changes, then we'll see.
    .
    _H*
     
    #4 hobbit, Apr 18, 2008
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