Understanding the Toyota RAV4 Hybrid

Hello, I'm professor John Kelly and this is the  WeberAuto YouTube channel today we are coming   to you from our brand new building on the Weber  State University Davis campus in Layton Utah. Now   today we are going to talk about the transaxle the  hybrid transaxle that comes in the 2019 and above   Toyota Rav4 hybrid so this transaxle is called  the P710 transaxle and it is just a little bit   larger version of the P610 transaxle that comes  in the 2016 and above Toyota Prius this is not   the same transaxle that comes in the Toyota Rav4  prime uses a P810 transaxle and we'll talk a   little bit more about that later in this video,  I should also mention that this P710 transaxle   comes in a 2018 and above Toyota Camry hybrid  Toyota Avalon hybrid and a Lexus ES 300h this   transaxle is coupled with a very fuel-efficient  2.5-liter Atkinson cycle engine this is a very   special engine that has a very high brake thermal  efficiency rating which means that it can convert   almost 40 percent of the heat energy that it  produces into mechanical energy now that may   not sound very good but for an internal combustion  engine that's really good but in order to do that   it needs to operate within certain rpm and load  ranges and this transaxle can help it do that   so let's take a look at the parts inside this  transaxle that helps that engine maintain   its optimum efficiency so this transaxle has two  electric motors the electric motor that helps   move the vehicle down the road is called motor  generator number two this big motor right here   and so it connects to a gear shaft right here  called the motor speed reduction gear shaft   and it has 16 teeth on it and I will set  that down in the transaxle case right here and then the electric motor  MG2 sits right on top of that   there we go now that 16 tooth  gear that this motor turns meshes with a counter drive gear right  here this counter drive gear has 49 teeth   on it and it drives the pinion gear of the final  drive and so we'll put this down in here like that   the gear ratio between motor generator number  two and this counter gear right here is 3.0625   and we get that by dividing the 49 teeth  of the counter gear by the 16 teeth of the   motor reduction gear now this counter gear with  the pinion gear on the top drives the differential   assembly and like any other transmission  front-wheel-drive transmission we have a   differential to allow the front wheels to  turn at different speeds, while you turn a   corner so I'm going to set the differential case  with the ring gear on it down inside here now there we go this ring gear on the differential  case on the rav4 hybrid has 78 teeth and the   pinion portion of it has 20 teeth that give us a  gear ratio of 3.9 to 1 between the counter gear   and the ring gear on the rav4 if it's the Camry  or the Avalon or the Lexus ES300h then there are   22 teeth on this pinion and only 76 teeth on the  ring gear and that gives us a gear ratio of 3.4545   so what we are looking at right now is a motor  an electric motor this is the rotor of the motor   it sits inside of a stator back here in this  transmission case and the rotor rotates in   this direction to make the vehicle move forward  so this is the front of the vehicle back here   this differential has the cv half shafts  connect to it and through your hub and   bearing assemblies your tires and wheels and  so when you see this gear right here rotate   just think of that as your front tires because  it rotates the same speed as your front tires now   the overall gear ratio between this motor  generator number two and your tires to make them   rotate one time uh on the rav4 is 11.944 to 1.  in other words, it takes 11.944 rotations of this   motor MG2 to get one rotation of your tires now  if you've got the Camry or the Avalon or the Lexus   ES 300h then it's only 10.58 revolutions  of MG2 to get one revolution of the tire   the rav4 has more because it gives you a little  bit more torque a feeling of more power well it   is more power its torque multiplication uh in the  rav4 than you would have uh on the passenger cars   this motor is rated at 88 kilowatts  which is roughly 120 horsepower   it's also rated at 202-newton meters of torque  which is approximately 149 foot-pound-force   of torque and it has a maximum rpm of 17 000.  these really spin fast and they spin fast because   they use fewer permanent magnets in here  less of the rare earth permanent magnets   and so to make up for lower power motors  lower power rotors they spin them faster   at lower gear reductions or higher numerical  gear reductions to get approximately the same   power as the older hybrid transaxles that  had the stronger magnets in them the rav4   hybrid does have a rear electric  motor I don't have that here with me   if I can get my hands on one we'll take a look at  one in a future video all right so the final drive   differential right here its ring gear can  receive power from MG2 as you're driving down   the road under any operating condition, it's  either receiving power from the motor spinning   as receiving power from the stator and  the inverter assembly under the hood or   when you decelerate the wheels and tires through  the cv half shafts turn the differential case here   which force forces the MG2 rotor to spin and  in this case, it becomes a generator so that's   where you can pick up some regenerative braking  so MG2 is either a motor as you're accelerating   or trying to hold a steady speed or it can become  a generator when you decelerate all right now   that's one of two paths for power to get into the  differential ear to move the vehicle down the road   the other path comes from the engine through the  second electric motor that this transaxle has   so this transaxle has another electric motor  right here called motor-generator number one   and motor-generator number one is not  used to propel the vehicle down the road   but instead, it is used with a planetary gear  set that Toyota calls the power split device   to control the gear ratio between the internal  combustion engine crankshaft and the counter   gear in the final drive gear right here so  let's take a look at this planetary gear set   every planetary gear set has a ring gear like this  one right here sometimes it's called an internal   gear or an annulus gear but you can see it inside  of there this ring gear has 78 teeth all Toyota   hybrid power split device ring gears have 78 teeth  every single one of them then we have a what's   called a planet carrier so we have these little  planet gears right here there's three of them   this piece that holds them or carries them  is called the planet carrier and it splines   directly to a special torque limiting clutch  pack that connects to the engine crankshaft so   what that means is this planet carrier spins with  the engine crankshaft at exactly the same speed as   the engine crankshaft so that sits inside of this  ring gear and then we have a sun gear right here   this sun gear has 30 teeth on  it just like all Toyota hybrid   transaxles have 30 teeth on the sun gear uh 78  teeth on the ring gear and 23 teeth I believe   on the planet carrier or on the planet gears  all right so this sun gear connects directly to   the MG1 electric motor back here so we  have three pieces of the planetary gear set   the ring gear on the inside is actually connected  to this housing that has a counter drive gear   on the outside and that counter drive gear has 53  teeth on it and so the counter drive gear spins   with the planetary gear set ring  gear and it drives the counter gear   right here that turns our pinion and ring  and makes the vehicle move down the road   so if this gear rotates the vehicle will move  so let's set this down in the transmission now so next we take our planet carrier and put it  down in the ring gear the input shaft that hooks   to the engine is going to go through into the  bell housing underneath here and so we will put   this down in get the gear teeth lined up and down  it goes and then we'll take our sun gear with its   30 teeth and put it in the middle of that planet  carrier and get its teeth lined up and we've got   a few bearings right here that go with it and then  finally motor-generator number one oh before I put   on motor generator number one this transmission  like almost all Toyota hybrid transmissions has   a mechanically engine mechanically driven oil  pump so there's a drive shaft that connects to the   planet carrier and spins with the engine that  drives an oil pump in the in the side cover of   the transmission so I just wanted to show you that  on the planet carrier before we put the motor on   but now let's put motor-generator number  one up here and we will spline it right to   that sun gear so now if the sun or  if the electric motor MG1 rotates   the sun gear rotates because they're splined  together with the sun gear with the electric motor   here the planet carrier is turning and it takes  3.6 revolutions of this motor generator number   one to get one rotation of the planet carrier  or the one rotation of the engine crankshaft   so one of the jobs of the MG1 motor is to start  the engine and it just simply does that by turning   faster than the planet carrier  and it takes 3.6 rotations of   motor generator one to get one rotation of the  crankshaft and that's with the vehicle stopped   so these little bumps right here on this on this  gear those are the part that is the parking gear   and we have a parking pawl right here  here's the parking pawl and a little pin   holds it in place and when you  put the transmission in park this moves forward and latches into the  parking gear and that prevents the ring gear   from rotating that also prevents the counter  drive and counter driven gear and final drive gear   differential from rotating which means the vehicle  won't move so we'll take it out of park further   our demonstration here but MG1 has several jobs  as I just showed you it can start the engine now   I showed you right there how it would start the  engine with the vehicle stopped but you. It can   start and stop the engine at any vehicle speed  it just needs to spin at the appropriate speed   to start the engine based on the vehicle speed  and the rpm of all these other parts all right   the second thing that motor generator number one  does is it generates power to recharge your high   voltage battery uh it also generates power to  feed power to motor generator number two under   certain conditions and that would be considered  a series hybrid operation at that point if we   have an engine-driven generator providing power to  the motor that propels the vehicle down the road   so it once again it generates power to charge the  high voltage battery this does not generate power   to charge the 12-volt battery the high voltage  battery provides power to a part called the dc   to dc converter which charges your 12-volt  battery this vehicle does not have an alternator   so there's a, that's a common point of confusion  with the mg 1 here is which battery does it charge   and it's just the high voltage one and then one  of the biggest jobs that it has is to provide a   variable gear ratio between the engine crankshaft  and our counter shaft and final drive here   so right now if I were to reach under this  transaxle and get up and grab that input shaft   right that I showed you on the planet carrier  and try to try to rotate it i can rotate it   and notice with the vehicle stopped with us in  park all that does is spin motor-generator number   one three-point six times faster than the than  the engine and under those conditions it can be   a generator or could just be neutralized and free  spin but notice it's not making the vehicle move   this ring gear is not rotating the vehicle is  not moving so in order to make the vehicle move   uh with power supplied from the engine motor  generator number one we play some tricks   with motor-generator number one's rotational  speed and direction of rotation so in any other   automatic transmission that you drive uh it has  low gears and high gears a low gear it would be   considered an underdrive gear ratio and what that  means is that the engine is spinning faster than   the output shaft of the transmission to drive the  wheels the engine crankshaft is spinning faster   then there's another situation called direct drive  where the engine crankshaft is spinning the same   speed as the output shaft of the transmission and  then there's another condition called overdrive   where the engine crankshaft is spinning slower  than the output shaft of the transmission this   power split device planetary gear set that  we have right here can do all three of those   and have variable infinitely variable gear ratios  in between and so I want to walk you through   the different modes of operation that this ecvt  electronic continuously variable transmission has   there are nine different modes of operation this  is a CVT but it is not one of those belt driven   either the push build or the pull chain style CVTs  that you read about in other vehicle manufacturers   or even in other Toyotas this is a much more  reliable but more expensive way of accomplishing   the same thing so let's walk through the  nine different modes of operation of the   eCVT transmission okay mode number one we are  in park vehicle, at a stop, the vehicle is off   and you reach in step on the brake pedal and  hit your power button and your ready light comes   on on the dash at that point the engine might  start it might not start it just depends on the   state of charge of the battery the high voltage  battery so if it does start I just showed you how   MG1 right here will rotate 3.6 times for  each revolution of the engine crankshaft   and it'll rotate at a high speed to get the engine  started very quickly so once the engine starts   then we enter mode 2 which is charging  while stopped so with the vehicle stopped   engine running the engine is spinning  the engine crankshaft is spinning   the planet carrier MG1 spins 3.6 times faster than  the engine crankshaft and acts as a generator as   needed you may have noticed that the engine  will shut off after a while then it'll start   again it'll shut off start again it's doing  that to recharge the high voltage battery   the battery state of charge will come down to a  certain point engine starts uses MG1 to recharge   the high voltage battery once it reaches a certain  state of charge then it shuts the engine back off   and it'll sit there cycling for days if you let  it do that I've left vehicles on over the weekend left on a Friday come back on a Monday and all of  a sudden a Prius engine fires up and it's like oh   I forgot to shut that off but anyway that's   start that is charging while stopped  mode three now is we take it out of park   put it in drive and we're ready to take off to  start driving at low speeds under those conditions   the engine could be off let's say that the  battery's state of charge is high so when   it's high it the battery will through the inverter  will provide power to MG2 and propel the vehicle   and so it will turn MG2 just like this notice that  causes MG1 to also rotate what you cannot see is   that the planet carrier or the engine crankshaft  is not rotating and this is just the electric   vehicle mode and depending on the battery state of  charge you can drive up to a certain vehicle speed   uh as long as you accelerate slowly before  the engine comes on to assist with that   so so in mode number four the bat the high  voltage battery state of charge is getting low   and that battery provides power to MG2  to keep to propel the vehicle but if the   battery state of charge is low then  we need to start the engine and so   MG1 starts the engine when the engine is  running I'll spin the crank the equivalent   of the crankshaft here the transmission input  shaft that planet carrier notice now the speed   of MG1 has picked up it's faster and that's  because it's acting as a generator to supply   power to the battery and to supply power to the  MG2 rotor to help move the vehicle down the road   okay mode number five is called constant speed  cruising and under those conditions under low load   so you're not going up a hill you're not going  downhill you're just going on a nice flat surface   under those conditions the eCVT portion of our  planetary gear set here tries to let the engine   rpm go to the point where it is the most fuel  efficient for the existing load and vehicle speed   that the vehicle is experiencing if  you look at this table right here   this is from a report published in 2019 from  the EPA the u.s environmental protection agency   they did a study of the thermal efficiencies  the brake thermal efficiencies of several   different engines and one of them was  this 2.5-liter engine used by Toyota and   if you notice there on the chart it has a  maximum brake thermal efficiency of 39.8 percent   now in that at that 39.8 mark, you'll notice  that the engine rpm at the bottom of the screen   is approximately 2500 and the amount of torque in  newton meters off to the left of the screen is 180   which is about 133-foot pound-force of  torque and then notice at the same time   that red arc coming down to the 50 kilowatts  text there on the right-hand side of the graph   indicates that the 39.8 percent of brake thermal  efficiency is occurring while delivering 50   kilowatts of power 50 000 watts of power well we  don't need 50 000 watts of power when we're just   at a steady-state cruise speed, we need less than  that it might be as low as 30 kilowatts of power   so if you look at this next chart i have marked  the lowest engine rpm and the highest engine rpm   that we could use and still be at 39 brake thermal  efficiency I've also marked the highest torque and   the lowest torque so between 190-newton meters  and 140-newton meters of torque we will still be   in that 39 thermal efficiency range and that also  if you look on the right-hand side of the graph   gives us anywhere between 25 kilowatts of power  which would be like for steady-state cruising   clear up to 265 kilowatts of power okay let's  see how the planetary gear set or the power   split device as Toyota calls it helps the  engine stay in that operating range that   maximum efficiency operating range that we  just looked at on the chart so if we look at   the relationship between the rotational speed of  the MG1 rotor which is the sun gear the engine   crankshaft which is the planet carrier and the  ring gear here which is our counter drive gear   we can achieve and see how underdrive  direct-drive and overdrive occur   so in underdrive which is what we want when we're  accelerating we want a low gear ratio we just spin   MG1 faster than we spin the planet carrier and  the larger the difference between the speeds   of those two parts the higher numerically  the gear ratio is and you get really good   acceleration but as vehicle speed starts to  increase we bring the rotational speeds of   these two closer and closer together until  eventually, they become the same speed   now at that point which in our example at  104 kilometers per hour or 65 miles per hour   that occurs at 1650 engine rpm on the rav4 hybrid  and so at 1650 the sun gear the planet carrier   which is the engine crankshaft and the counter  drive gear all spin together as one assembly now   once we want to go a little faster and get into  overdrive gear then we slow down MG1 to where   it's spinning slower than the planet carrier here  so we spin slower than than the ring gear here and   that forces it to go into an overdrive situation  and eventually, we will get to a point where   MG1 actually stops rotating while you're driving  down the road and at 65 miles an hour that   actually occurs at 2109 engine rpm so if you're  driving 65 miles an hour your engine rpm hits 2109   this motor physically stops moving and  that puts if i turn the engine crankshaft   here that causes an overdrive situation to occur  between the planet carrier and the ring gear here   then if we want even more overdrive since the  motor stopped and it was spinning in one direction   now we will spin it in the opposite  direction so all of this time the underdrive   gear ratios we were spinning the  motor in the same direction as the planet carrier down below but when we stop and  want to go into more overdrive we turn it in the   opposite direction so now they're spinning  opposite directions and that gives us an   overdrive situation so if we want to underdrive  we just spin MG1 faster than the planet carrier  if we want direct drive we spin at the same  speed if we want overdrive we spin it slower   than the planet carrier and slowed down to a point  where it physically stops and then we can turn it   backward to force an even higher overdrive gear  ratio for maximum fuel efficiency by and what   that does is it allows the engine rpm to be  controlled by the rotational speed difference   here transferring torque to our final drive all  right this also has a maximum rpm of 17 000.   it can produce approximately 31 kilowatts of power  in generation mode which is about 42 horsepower   it has about 54-newton meters of torque or 40 foot  pound-force of torque okay so that was mode 5 of 9   which is steady-state cruising in mode 6 we have  steady-state or constant speed cruising but with   a low state of charge in the high voltage battery  and in that case, we just speed up the engine to   force MG1 to spin even faster to provide power to  the high voltage battery that then supplies power   to MG2 at the same time and at that time there's a  combination of power being delivered to the final   drive through MG2 through the counter gear to the  final drive and not only are we generating power   by spinning the engine faster here for MG1 but  some of that torque is also delivered from the   engine to our counter gear to the final drive  so we have two separate paths for power to be   delivered to the final drive here okay mode  number seven is full-throttle acceleration   and under those conditions the high voltage  battery supplies extra power to the inverter   to help MG2 have all the power that it can  electrically and then the engine goes to   an under drive gear ratio through the planetary  gear set here to also help provide power and we   get maximum output potential from MG2 and maximum  output potential with a variable gear ratio out of   MG1 through the planet or through the power split  device to our counter gear to the final drive mode number eight is deceleration when you let off  on the throttle when you are driving down the road   MG2 which has been a motor up to this point now  becomes a generator and it will induce current   into the MG2 stator back here and send power back  to the battery if the battery state of charge is   low enough and needs it uh under those conditions  there's some physical resistance to rotating   the MG2 rotor caused by like magnetic fields  opposing each other as it rotates uh and that   gives you not only regeneration of power but  regenerative braking it helps slow the vehicle the   same thing can occur when you move your shifter  to the b or braking position on this vehicle   all right mode 9 is just simply reverse and  we've talked about that already we just turn   the electric motor in the opposite direction  so that's reverse right there here's forward   no reverse gear we just turn the motor backward  all right let's take a look at the rotors here   just for a moment there are three different  transaxles in this series that look very much   alike there's the P610 that's in the Prius the  P710 that we're looking at right now and then the   P810 that comes in the Rav4 prime it's in the new  sienna uh van and it's in the highlander hybrid   um by comparison the P610 in the Prius has a rotor  MG1 rotor same diameter but it's 24.3 millimeters   thinner the rotor the MG2 rotor in the Prius  is 10 millimeters thinner than this one   but if we talk about the P810  transaxle in the rav4 prime we've got jets flying overhead right next to  an air force base it's there's always something if we talk about the P810 MG2 rotor in the rav4  prime it's actually 36.5 millimeters thicker than   this one but with the same diameter and its  MG1 rotor is the same thickness as this one   so that will give the mg or the P810 in the Rav4  prime and the highlander and the sienna more power   which it needs because those are bigger heavier  vehicles and if you're driving in ev mode only   on the rav4 prime, you don't have the additional  power coming from the internal combustion engine   to propel the vehicle so you need a more powerful  electric motor to give you the same feel to give   you the same acceleration if not more than  you had with the internal combustion engine   let's get the motors out of the way just for a  moment we're just about done let's take a look at   the stators the rest of the transaxle case right  here all right this right here is a stator for   MG2 and this is a stator for MG1 and each of  these have three wires you can see down inside   here there's six there's five right here  a sixth one over there there's six bolts   there are three wires there are three  phase cables for each of these stators and   the stators are what have current going through  them that produces a magnetic field that attracts   and repels the permanent magnet rotors that  are in the transaxle and and makes them rotate   these stators get very hot and so they are liquid  cooled by the transmission fluid the Toyota world   standard transmission fluid it has spray cooling  there's a tube right here and a tube right here   and this is the top of the transaxle I've got  it upside down but it sprays transmission fluid   on to the windings in the housing and the stator  frame to help cool it with the transmission fluid   it has temperature sensors there's one right here  and one right here one for each of the two stators   this has an oil pump as I mentioned before it  has an oil pump pickup tube right here in the   bottom of the transmission and then the oil pump  itself is in the front cover or the side cover   of the transaxle so here's the side  cover and if you look right there   is the identification the P710  transaxle and the oil pump that's driven off of the engine crankshaft through the planet  carrier has its drive shaft sticking through   right here and rotates with the engine crankshaft  at engine speed these two pieces right here are   called resolvers and they are the parts that  measure the rotational speed direction of   rotation and position of the MG1 and the MG2  rotors over there these are serviceable you   have to replace them as a set and then there's a  scan tool function to go in and have it auto-learn   the position of the the rotors actual magnetic  pulls to the uh reluctors here in the side case   there's one more thing I want to show  you about this transaxle and that is uh   these six wires right here there's three wires  right here for the MG1 stator and three wires   right here for the MG2 stator and these are where  the current and the voltage are supplied from the   inverter assembly that's on top of this transaxle  under the hood now these wires are fairly thick   and they're a lot thicker if you look at  this photo here in comparison with the P610   the Prius transaxle uh transfer wires and I assume  that the P810 wires are even thicker it's just an   indication of how much more power electrical power  each transaxle uses the P610 not using near as   much as the P710 the P810 going to use even more  all right as I mentioned before the rav4 hybrid   has a rear axle it's actually called the Q610 I'll  try to get my hands on one of those and I'm still   looking for and always looking for the P810 but  it's so new it's they're hard to come by and as   soon as I get one I'll tear it apart and show you  what's inside of it as well thank you for watching

Channel: WeberAuto

Views: 821,742

Keywords: WSU, Weber State Automotive, Weber State University, John D. Kelly, Guy in Wheelchair, Professor Kelly, EV Boot Camp, Utah, Toyota, RAV4 Hybrid, RAV4 Prime, P710, P810, 40% BTE, BTE, Brake Thermal Efficiency, Venza Hybrid, Sienna Hyrbid, Highlander Hybrid, ES300h, Lexus, Layton Utah, WSU Davis

Id: O61WihMRdjM

Length: 39min 8sec (2348 seconds)

Published: Sat Jan 23 2021

Reddit Comments

[u/ExplosiveMachine]

Wow this is awesome. what a great video. That's a super smart way of doing it! and it does seem much more reliable than any belt system purely because it has less moving parts and no belts to wear and slip. Though since you're directly counteracting the power produced by the engine with an electric motor, it seems to me that there's a limit on how much power the ICE can produce before the electric motor that drives the sun gear in the power split becomes too big. I guess that's what the extra electric motor is for, the ICE doesn't have to be huge, it's a hybrid after all.

Very cool tech.

[u/BuckTheFuckNaked]

I've always been curious about the way the RAV4 Hybrid drivetrain works. I don't know how I missed this one, but it's the best explanation I've seen.

[u/rmws11]

This is great!! Thank you for sharing!!

[u/SecretAntWorshiper]

TLDW?

[u/Soggy-Can8110]

It is said that RAV4 Hybrid offers the same specification and luggage space as the 2-litre GX petrol, the RAV4 GX 2.5-litre Hybrid offers a fuel efficient all-wheel-drive system for fleet and family users. Wouldn't it be wonderful if Toyota Commuter had the same configuration......