Understanding the Honda Hybrid E-Drive

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, so I'm very   happy to be here in this building today we are  going to look at the incredible honda e-drive   hybrid transaxle now this transaxle is used in  the new CRV hybrid it's also used in the insight   it's also used in the accord hybrid and the  clarity plug-in hybrid so four different vehicles   use this design of hybrid transaxle this transaxle  has three different primary modes of operation   I'm going to show you all three of those  one of those modes is a series hybrid mode   yes a series hybrid mode so that is different  than what honda has used for many many years   the old integrated motor assist or the  ima system that came out in the late 1990s   and was used all the way up through 2016 in  the last version of the insight and many other   honda vehicles so this is the new e-drive system  in the sales literature, they call it an eCVT   an electronic continuously variable transmission  but that's only one of the three modes   three primary modes of operation so let's  take a look at the first mode of operation   and that is EV mode electric vehicle mode  where it can run on electric power only   so here in the front housing the bell housing  area of the transaxle we have a valve body an oil   filter and two oil pumps one oil pump is driven  when the engine is running the other oil pump   is driven when the vehicle is moving so for  EV mode we have to have a final drive the the   differential that allows your front wheels to turn  at different speeds as you turn corners so this   is the differential out of this particular  vehicle this transaxle I have is out of a 2019   Honda Accord hybrid but they're all very similar  so we have the differential gear set along   with the final driven gear right here some  lubrication dams there we're going to set that in and there is a countershaft and  both of these have to go in together there we go okay I've installed the  differential and the countershaft now   the differential driven gear and the  counter shaft drive gear for the final drive   have 65 teeth on the ring gear 19 teeth on the  counter gear which gives us a gear ratio of 3.421   to 1 and that's true on all of the hondas  that use this e drive system or eCVT   system except for the new 2020 and above CRV  hybrid and it has a 3.882 to 1 gear ratio   and they did that by increasing the  gear teeth from 65 to 66 on the   final driven gear and decreasing the gear teeth  from 19 down to 17 on the final drive gear   so a little bit a higher numerical gear  ratio which gives it a little bit more torque   now in all three modes of operation the the  final drive is driven by this gear right here   the countershaft gear and so whether we're  in electric vehicle mode or engine only mode   or hybrid mode they all drive this counter  gear which drives the final drive gear which   turns the final driven gear your axle half shafts  come in let's see this would be the driver's side   and then your passenger side would be going  the other way if we had this tilted up as it's   installed in the vehicle so no matter what this  gear ratio the 3.421 remains steady in all three   modes of operation unless you have  the new CRV hybrid which has a 3.882   gear ratio okay now let's look at in electric  vehicle mode what rotates this counter drive gear   right here so to do that we have another gear  shaft that I need I need to bring in and we'll   talk about what this gear does a little bit later  but right now it is going to act as a support   for what's called the motor gear and the  motor gear is going to mesh with this   counter gear right here and there's a great  big electric motor that slides on right here so now let me bring in the motor here's the rotor of the electric motor   I have the stator in the housing  behind me let me put this up on here there we go okay this motor as you can see  here on my labels is rated at 135 kilowatts   which is 183.6 horsepower this is called the motor  in all the honda literature and there's another   smaller one called the generator that we'll talk  about later but don't be fooled into thinking that   this is like any other two electric motor  hybrid out there this is not this is different so this has 315 newton meters of  torque or 232 pound-force of torque   as its maximum and if we rotate it in this  direction the teeth on the motor drive gear right   here are 22 and then there are 54 teeth on the  counter gear right there and that gives us a gear   ratio of 2.455 gear reduction so it takes 2.455  rotations of the electric motor rotor to rotate   the counter shaft one rotation and then it takes  another 3.421 to rotate the final drive gear   over here and if you multiply those two  together you get an overall gear ratio of 8.395   to 1 which means as you're driving down  the road and the rotor would spin in   this direction to make the vehicle move  forward we would have to rotate this rotor   times to get one revolution of your final driven  gear differential case and your axle half shafts   that connect out to your hub and bearing  assemblies and tires and wheels and make   you move down the road so this is electric  vehicle mode notice there's no engine connection   we just take power from the battery run it  through the inverter and create three phase ac   power this is an internal permanent magnet  rotor right here and we just rotate this   and this mode is on by default every time you get  in the vehicle and power it on and drive away and   the only limit on the speed is the top speed of  the vehicle you can stay in this electric mode   as as fast as you want to drive it or as fast  as it'll let you drive it within the legal   speed limit or higher I believe it was  rated at 87 miles an hour or 140 kilometers   per hour was the maximum speed in EV mode so  that's EV mode only so once again we use power   to drive the motor to make the vehicle move  down the road yes we have regenerative braking   so now instead of turning the rotor  to make the final drive gear rotate   the tires through the half shafts into the side  gears of our open differential here are going   to turn the final drive gear and that will cause  the rotor to spin 8.39 times faster than the tires   which can give us regenerative braking depending  on the state of charge of the battery and and   several other things but that would help put power  back into the battery all right so this is just   EV mode for regular driving all right  next, let's go into engine only mode so if you have a hybrid vehicle reaching 87  miles an hour in EV mode it's probably not   going to happen and if it does it won't last very  long because you will run out of battery power but if you have the honda clarity plug-in  hybrid then that will give you some additional   battery power that will allow you to drive a  certain number of miles on that battery range   and you yes you could continue driving clear  up to as high as 87 miles an hour but you   will reach a point where driving the electric  motor won't be as efficient as just running the   internal combustion engine now this typically  starts around 62 miles per hour or 100 kilometers   per hour and in the engine-only mode we directly  connect the engine's crankshaft that rotates   to our final drive countershaft and drive and  driven gear here so let's see how we do that so this is the flywheel that connects to the back of the engine  crankshaft. it has a permanently applied clutch   in here this permanently applied clutch  disc is there as a safety breakaway   if for some reason something in the transmission  or something in the engine seized up   it would allow this to slip and allow for  a difference in the speed of those two   pieces but all hybrids have some sort of  a clutch like this but the main point i   wanted to point out here is there's  a set of splines here in the middle   so this crank or this flywheel is rotated by the  crankshaft there are some splines right there and there's a gear right here called the input  shaft so it literally has the input shaft   that connects to the flywheel right there and  if the flywheel rotates so does this input shaft   now the input shaft has a multiple plate clutch  disc set up inside of it there's a couple of   seals down there and a hydraulic passage  that comes down and you can see down inside   here there are little notches of the clutch  disc itself but if we slide that on here and add an additional gear this is called the overdrive gear now remember  we're talking about driving down the road in   engine-only mode and it's called the overdrive  gear because the gear ratio we end up getting   is an overdrive gear ratio if you were to compare  that to any other automatic transmission out   there so let me set this down in I want you  to notice that the input shaft gear and the   overdrive gear is not connected together  but there's an overdrive clutch right there that if we take some compressed air we can  apply it simulating the pressurized fluid   that would come from the oil pump and the valve  body if I hit air to this passage here to apply   this clutch the whole thing should rotate  so right now it's free but if I apply it so we have a gear that we can connect to the  engine or disconnect from the engine that will   turn the countershaft gear over here   to drive us down the road well let's put all  this in the housing over here and see how it works okay there's our input shaft and gear  installed here comes our overdrive clutch pack installed bearing and then our overdrive gear so now you can see this overdrive  gear that we can connect   to the engine's input shaft or disconnect now  can turn the counter shaft gear which turns   our counter or our final drive gear and driven  gear and the tires so if we rotate the flywheel   underneath the housing here I'm  rotating the flywheel we will take   the 67 teeth of our overdrive gear and drive the  54 teeth of the counter gear that will be over   driving it because the overdrive gear is  bigger and that overdrives it with an overdrive   gear ratio of 0.8059, so it's a 20 percent overdrive  and then that drives are 3.421 gear reduction   so for the final drive so if you multiply those  two together now we have an overall engine two   tires gear ratio of 2.757 and that's  on everything except for the CRV hybrid   okay so that's engine only mode we come in to apply  the clutch and drive with the engine crankshaft   but that can only work at higher vehicle speeds  because with an overdrive gear ratio of 0.8   you can't slow down very slow without loading  the engine too much and so this mode the engine   only mode starts at around 62 miles an hour or 100  kilometers per hour and goes up to the top speed   of the vehicle all right now that is the  our second mode our first mode was electric   vehicle mode only our second mode is engine only  notice there are no electric motors involved in   engine only before we look at our third mode  I want to show you the purpose of this shaft   right here so this shaft comes in and splines  right to the input shaft of the transmission   that turns at engine crankshaft speed  so if I put that in there just like that   this gear has 39 teeth and the engine input  shaft gear has 76 and if you do the math on that   it is overdriving this little shaft almost  two to one has a gear ratio of 0.513 to 1   which is 1.948 times faster than engine crankshaft  speed so this little shaft right here is turning   almost twice as fast as engine rpm so that  is where we come in with our power generator   rotor right here and it splines  right to the top so anytime   whether the overdrive clutch is applied or not  anytime that engine is running it is also rotating   this generator anytime now that  doesn't mean it's charging because   with the inverter, we have the ability to turn  on or off the charge or anywhere in between   but the capability is there so this gives it  a little bit more flywheel action as well but   this is rated at 106 kilowatts of power as its  maximum output so that's pretty impressive for its capability so now we have a generator  that's capable of producing 106 kilowatts of power   let's take that off for a  moment while we put together   the rest of the electric  motor side of the transmission here is our motor electric motor  drive gear it has some teeth   on the bottom here where the parking  gear can come and spline in place   just like that, it rotates with the gear and then  there's a parking pawl that will come in and   grab one of those teeth and keep it from rotating  when you put your transmission in park and since   that is splined directly to the countershaft it  prevents your cv half shafts from rotating but I'm   going to leave that off in this demonstration  I'm going to put on the motor drive gear now it only makes contact with the counter  shaft it does not contact the overdrive gear   from the engine and now we will put on our motor right there our kilowatt motor and we will  put on our 106-kilowatt generator right there   so now we have completely assembled the trans  axle as far as the gear train is concerned   okay in the third mode of operation we have the  engine running and we use the electric motor   to move the vehicle down the road the with  the engine running it is rotating the 106 kilowatt   generator and so it can turn it at any speed  so the engine rpm can go up and down and have   nothing to do with vehicle speed because we have  we have not applied the overdrive clutch and we're   not driving the overdrive gear so the only thing  the engine is doing at this point is turning this   little tiny gear and shaft to turn this generator  to create electrical power now that electrical   power then is fed to the inverter where some of it  could go to charge the battery some of it or but   the majority of it will come back to the electric  motor to drive the vehicle down the road so   there's no direct mechanical connection between  these two motors and that is by definition   a series hybrid now honda's old ima system  was a parallel hybrid this is a series hybrid   all the Toyota hybrids are series-parallel  the Chrysler Pacifica series-parallel   Chevrolet has one mode in their latest  model Chevrolet volt that is a series   parallel operation so there are different  types of hybrids not all hybrids are equal   so I think this is a really cool design i  really like it i think it's well thought out   this is the second generation one right  here the first generation came out in the   2014 honda accord this is a second  generation there's a third generation one   this is just a light overview of the honda  e drive system I will spend some more time   with additional components, I've got a battery  in the inverter and the dc to dc converter and   everything else coming here shortly but i  thought that this was interesting enough   to show you something different out  there and honda's known for that they   they come up with a lot of unique ideas  and a lot of really cool ideas as well so   that's it thanks for watching have a good day

Channel: WeberAuto

Views: 347,686

Keywords: WSU, Weber State Automotive, Weber State University, John D. Kelly, Guy in Wheelchair, Professor Kelly, EV Boot Camp, Ogden, Utah, Honda CR-V, E-Drive, E-CVT, Layton, Honda, Honda Hybrid, Hond Clarity, Honda Insight, Honda Accord, i-MMD

Id: QLUIExAnNcE

Length: 25min 15sec (1515 seconds)

Published: Sat Dec 12 2020

Reddit Comments

[u/cwnorman]

Great video breaking down the inner workings of the Honda hybrid drive unit that is used in the Clarity.

[u/SuprBased]

I watched this before I leaped on my Clarity. Anytime I see the word CVT I freak out, but this isn’t one of those crap belt driven CVT’s. This video helped cement my purchase and now I’ve been seeing with Clarity for a whole week 😌

[u/Korax234]

I have almost 50k miles and I am going to change out the transmission fluid. I wonder how dirty it will be.