P610 transaxle

Discussion in 'Gen 4 Prius Technical Discussion' started by bwilson4web, Feb 4, 2016.

  1. bwilson4web

    bwilson4web i3 and Prime

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    Most of these notes come from the New Car Features:
    • Liquid cooling of ATF oil - the earlier transaxle used air cooling and an inverter coolant channel. Now there is a radiator loop, heat exchanger. Given the new stacking, it is likely MG1 and MG2 will have nearly identical temperature profiles. Best of all, the former coolant is no longer able to induce corrosion in the cooling channels.
    • Power Split Device - ring 78 teeth; sun 30. This gives 30/(78+30) give 27.8% of the engine torque goes via the sun gear. Some do not realize the torque ratios define how much engine power takes the MG1 path and the rest takes the ring gear path,
    • Weight - 179.2 lbs
    • ATF pump is still engine shaft driven. This is one feature that is weak for EV mode when the engine is off. A proper plug-in transaxle would use either wheel-side pump OR an electric oil pump (my preference.) An electric drive, oil pump might be used in a future engine to further reduce overhead at high power settings.
    • Charging when stopped - MG1 runs as a generator but MG2 provides counter torque, require current. This doesn't make sense unless the 'creep' has been turned off. Still, it suggests using "P" when stopped may save the current used by MG2. This is something to test with our Gen-3
    Bob Wilson
     
  2. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    Regarding the first bullet point, does it mean there's a radiator for the transaxle fluid?
     
  3. Jeff N

    Jeff N The answer is 0042

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    Some things never change.... The same ratios have been used since the very first Prius, I think. Are the pinion gears still 23 teeth? This has always been counterintuitive since simplistically the ring teeth are supposed to be (2 x pinion teeth) + Sun teeth which is 76 when the pinion gears have 23 teeth.

    As a highly technical matter, my understanding is that this is only true statically and once things start turning and motors and generators start doing their thing the mathematical dynamic flow of torque can differ from this fixed ratio. But, as a first approximation, the static view is useful.

    I'm guessing the future plugin Prius will have a plugin-specific transaxle.

    Huh? If creep is turned off while the brake pedal is held then I see no reason for MG2 to receive any current. The brakes will hold MG2 at zero rpm as the engine spins MG1 to generate recharge power to the battery.
     
    #3 Jeff N, Feb 4, 2016
    Last edited: Feb 4, 2016
  4. bwilson4web

    bwilson4web i3 and Prime

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    The diagram show the bottom of the radiator.

    Bob Wilson

    At the acceleration and strain rates of these parts, the torque is the gear teeth ratio. The other thing that blows minds is the torque is relative to the engine shaft. The power split is the engine power and nothing else. Others (at one time me) have tried to trace power as if it were a conservation of energy problem via the electrical and mechanical paths but that ultimately is a dead end. Just use the ratio of:
    • 27.8% - takes the electrical path
    • 72.2% - takes the mechanical path
    Then everything works. Any other approach leads to 'a bad place.'

    Yes, on the 23 teeth of the pinion gears but they really don't matter. The engine torque comes passes through their carrier.
    Think it through a few more steps:
    • brake energy needed to hold car static
    • parking paw energy needed to hold car static
    • use "N" when stopped even if engine is running effect on engine fuel consumption
    Bob Wilson
     
  5. energyandair

    energyandair Active Member

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    This isn't clear to me.
    Why would there be any brake energy if the brakes are holding the car static? Energy = Force x Distance (or Torque x Rotation) There is force but there is no motion so why would there be any energy transmitted, used or needed at this point?
    Same for parking pawl.
     
  6. bwilson4web

    bwilson4web i3 and Prime

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    brake energy needed to hold car static - requires the accumulator pump to run, small but real load and the brake lights
    parking paw energy needed to hold car static - no energy, brake to shift to "D"
    use "N" when stopped - quick shift to "D" lowest energy but requires level or rough road to stay still

    All three are subject to engine run overhead in some cases such as low battery or during warm-up. However, "N" minimizes the engine fuel burn.

    Bob Wilson
     
  7. bisco

    bisco cookie crumbler

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    human energy holding down the pedal?
     
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  8. EZW1

    EZW1 Active Member

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    This has always been a contention of mine since day 1. If the engine is not running, ATF is not getting pumped through the system. While this may work for limited travel in elec only modes, it is not a good idea for long term. I always wondered how the guys a few years back who were putting extra batteries in their 2nd gen prius' in order run for miles in elec only mode, were able to maintain proper lubrication. They never said...
     
  9. laevus

    laevus Junior Member

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    I think the incidence of MG1 path in ICE Power splitting can be expressed as:
    MG1 power = ( 1 – 72.2% (Ring rpm / ICE rpm ) ) ICE power

    What could be wrong in following calculation ?

    Ring 78 teeth
    Sun 30 teeth
    Carrier planet 23 teeth

    Torque relations
    Ts = 27.8% Tc
    Tr = 72.2% Tc

    Gear speeds relation
    ωs = 3.6 ωc – 2.6 ωr

    Carrier Power
    Pc =ωc Tc

    Sun Power
    Ps = ωs Ts = 27.8% ωs Tc
    Ps = 27.8% ( 3.6 ωc Tc – 2.6 ωr Tc)
    Ps = 27.8% ( 3.6 Pc – 2.6 ωr Tc)

    Sun / Carrier Power Ratio
    Ps/Pc= 27.8% ( 3.6 – 2.6 ωr/ ωc)

    Ps/Pc= 1 – 72.2% ωr / ωc

    Special cases:

    • Ps/Pc=27.8%
      ωr= ωc =ωs
    • Ps/Pc → 0
      ωs = 0
    • Ps/Pc →100%
      ωr = 0
    MG1% power ratio vs ( Ring / ICE) RPM
    upload_2016-2-6_20-19-54.png
     
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  10. bisco

    bisco cookie crumbler

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    now i'm curious about my pip, with 25,000 ev only miles.

    phev can go up to 62 mph, but only for 7 or 8 miles or so, unless going downhill.
     
  11. Trollbait

    Trollbait It's a D&D thing

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    The transaxle isn't an automatic transmission in which the fluid also has to act as an hydraulic fluid. The dual purpose nature of those fluids is why they are sensitive to high heat, and require cooling through the radiator. Cooling the fluid in the Prius know is likely for tiny efficiency gains, and to prevent owner concerns of cooked smelling fluid, which may not have been a true concern for this transaxle.

    EV operation, even in the PHEV, is mostly during low speeds. Fluid splashing is likely enough to lube the gear set; it is in most manual transmissions. At higher speeds, the engine may be off, but is still spinning, and still driving the pump.
     
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  12. bwilson4web

    bwilson4web i3 and Prime

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    Have you had the transaxle oil changed?

    I would love to have a sample to analyze. Use a dry, small water bottle and we'll coordinate getting it tested. Perhaps @john1701a might join in the study too?

    I have a credit to use up with my testing service.

    Bob Wilson
     
  13. bisco

    bisco cookie crumbler

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    no, you want me to crawl under the car and unscrew the drain plug? i can barely get up off the floor to reach my beer.:p

    what i can say is, my '08 with 100k has no tranny issues, and my '04 with 140k has none either. never had the fluid changed. i'm sure long term ownership may benefit, but we're not in that group. i'll be purchasing the new pip when it comes out, and passing mine down the line.

    nevertheless, if you think i can be of help to others by trying to get a sample, i will do it. but let's at least wait until may.:barefoot:
     
    #13 bisco, Feb 6, 2016
    Last edited: Feb 6, 2016
  14. bwilson4web

    bwilson4web i3 and Prime

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    This is something the Toyota service center can handle. Just you need to bring the sample bottle and make sure the service writer writes 'fill at least a half-way.' I had one sample come back with just a couple of tablespoons but it was enough.

    Bob Wilson
     
    #14 bwilson4web, Feb 7, 2016
    Last edited: Feb 7, 2016
  15. MünchnerFax

    MünchnerFax New Member

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    I'm sorry if my very first post on this board may sound a bit too assertive. Hi everybody, by the way. :)
    If I understand correctly (not sure about this, I admit), you are stating those figures apply to both torque and power - that is, 27.8% of the power would take the electrical path and the rest would go through the mechanical path. I'm afraid this is incorrect though - statically or dinamically. This is only true for the torque due to the PSD geometry, as you said. However, the power being the torque multiplied by the rotational speed of the element the torque is applied on, there is only one special situation in which the above figures also hold true for the power, that is when all the PSD parts - sun/MG1, carrier/ICE, and ring - spin at the very same speed. In the general case though, the power split shares depend on the relative speeds of the components and are therefore vastly different from those figures most of the time. "laevus" above has written the related formula.
     
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  16. bwilson4web

    bwilson4web i3 and Prime

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    Then we'll have to agree to disagree:
    • One engine shaft - feeds the planetary gear carrier
    • One engine torque - feeds the planetary gear carrier
      • 27.8% of counter torque comes from the MG1 torque
      • 72.2% of the counter torque comes from MG2 and vehicle load
    Newton's second law applies to torque, in this case, the counter torque. Occam's razor, the simplest explanation.

    Bob Wilson
     
  17. ChapmanF

    ChapmanF Senior Member

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    I think you've just actually agreed to agree. :)

    Torque follows a fixed, 27.8/72.2 split at all times, determined by nothing but gear geometry.

    Power, being torque ✕ rpm, follows a variable split, as the relative speeds of the three players vary with driving conditions.

    I agree too. :)

    -Chap
     
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  18. EZW1

    EZW1 Active Member

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    Sure. Low operating speeds should be fine for a limited period of time. I was referring to those folks who put extra Traction batteries in their 2nd Gens so that they could drive for dozens of miles in EV mode. In the 2nd Gen the coolant pump constantly circulates cooling fluid from the reservor to the pump to the Inverter to the Transaxle to the radiator and back to the reservoir. So the Transaxle is always cooled. I'm not concerned about this but rather the fact that if the Engine is not running there is no fluid forced through the HSD, Differential, and bearings to assure proper lubrication - kiinda like driving your manual transmission or rear-end differential after its been drained of its supply of lubricant. Sure it will run for awhile but not forever. And therefore those guys running their cars for dozens of miles in EV mode must be stressing their parts. 'nuff said.
     
  19. Trollbait

    Trollbait It's a D&D thing

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    They probably are stressing the parts, but even with extra batteries, a gen2's EV only speed is very low with very low acceleration rates. Those conversions would have a zero mile EV range under current testing. During an EV glide at higher speeds, the MG1 spins the ICE, which will spin the fluid pump.

    Does the gen1 Prius PHEV have a transaxle fluid circulation system different from the gen3 Prius? If not, does its drive train warranty have less coverage? If the answer is no to both those questions, then Toyota's engineers, lawyers, and accountants all feel having the fluid not circulating for such extended EV operation isn't a concern.
     
  20. EZW1

    EZW1 Active Member

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    Perhaps youre right. MG1 does indeed keep ICE spinning at speeds above approx. 40mph. This would also run thelube pump. Perhaps damage/stess below these speeds is small enough to not be a concern. Thx
     
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