Prius (2nd Gen) P112 Hybrid Transaxle (eCVT) Operation

Prius (2nd Gen) P112 Hybrid Transaxle (eCVT) Operation


this is a demonstration of the hybrid transaxle of a second generation Toyota Prius the second generation Prius was the model years 2004 through 2009 the transaxle has several parts in it and what makes it most unique is that it uses two electric motors we have motor generator number two which drives the wheels and motor generator number one which is both the starter motor for the engine and the generator to replace the alternator on the vehicle these electric motors are made of very powerful magnets if we were to take this thing apart like I’ve taken this one apart if we pull the cap off of it you can see that there’s the slots in the laminated iron there where there are some very powerful magnets with north and south poles that fit down in to each of these slots and the magnetic field produced by those permanent magnets is repelled are attracted to the electric electro magnetic field created by this stator assembly this is very much like an alternator of any other vehicle this would be the rotor spinning inside of the stator and it generate power three-phase power the AC power that goes to the rectifier is changed to DC and charges the high voltage battery well this acts just like that when this is spinning when powered by the engine but it can also be reversed to where we apply three-phase power to the stator windings and it forces the electric motor mg1 to rotate mg2 that is connected ultimately to the front tires has a giant stator this except of course much much larger now the Toyota hybrid system that uses these two electric motors in the Prius is connected to a standard planetary gearset and a standard planetary gearset has a ring gear this is the ring gear right here sometimes it’s called an internal gear sometimes it’s called an annulus gear toyota calls it a ring gear it will also have a Sun gear the Sun gear like the Sun in our solar system will be in the center of our planetary gear set and then we have a planet carrier also that has four planet pinion gears as part of the drive for this vehicle now regular automatic transmission has at least one set of planetary gears these three components for each two forward gears that the transmission has so if it’s a two-speed the old two speed transmissions then it had one set of planetary gears if it’s a four-speed it has two sets of these if it’s a six speed as three eight speed has four well the the Toyota hybrid transaxle that’s in the Prius and very similar in the camera and the Highlander is an electronic variable racial transmission CVT continuously variable transmission as a matter of fact they call it an e CVT for electronic continuously variable transmission and what makes it continuously variable even though we’re using a planetary gearset is that unlike a standard automatic transmission with the ring gear planet carrier and a Sun gear in those transmissions we would hold one part drive another part and the third piece would be the responding component and then for a different gear we would hold another piece turn another piece and get a different gear ratio well that the Toyota Prius transaxle doesn’t hold anything solid of these three planetary gear cities so what we have is motor generator one that starts the engine and acts as the generator actually connects to the Sun gear of this planetary gearset motor generator to which drives the front tires actually connects to the ring so if the ring gear moves at all more to generate our two moves and it drives to the wheels if motor generator one moves at all then it drives the Sun gear of the planetary gear set and then the planet carrier that has the the pinion gears in it is connected to the internal combustion engine I’ve got you scoot this over the equivalent of a torque damper this replaces a torque converter this automatic continuously variable transmission has no torque converter but we’ve got flywheel it’s very similar to a manual transmission that bolts to the crankshaft we have a pressure plate there’s a bevel pressure plate that is going to keep constant pressure on the clutch disk and this clutch disc is always applied its engine driven and it drives the planet gears as a matter of fact this planet carrier splines right in and if the engine rotates at all so does the planet carrier so once again we’ve got the the planet carrier that’s connected to the engine we’ve got the Sun gear that’s connected to motor generator 1 and we’ve got the ring gear that’s connected to motor generator number 2 so now I’m going to get this [Music] flywheel out of the way and let’s put this assembly together and see if we can figure out how we get forward and reverse gear ratios so what we’re going to take motor-generator number two right here and we’re going to connect the planet carrier to it just like that we’re going to take the Sun gear with motor-generator number one connected to it and slide it into place and then there’s an oil pump there’s a little miniature oil pump in this transaxle that’s driven off the planet carrier and I’m going to slide that into this other side so that we’ve got everything lined up just like it is in the transaxle motor generator two connected to the ring gear that drives the vehicle these little logs right here connect to a drive gear of a chain that goes to the final drive we’ve got the motor generator one the hooks to the Sun gear and then we’ve got the planet carrier that connects to the engine now I’m going to attempt to set this up in these B blocks here it’s very heavy and then I’m going to bring the clutch disc the damper disc from the engine over here and connect it to the planet carrier so what we’ve got is the clutch disc represents the engine we’ve got motor generator one that’s our starter and our alternator and we have motor generator two that drives the vehicle down the road so with the let’s go through the different modes of operation with the vehicle stopped motor generator two is always going to turn the same speed as the tire so if the vehicles stopped motor january two is stopped if our high voltage battery is low on charge we need to charge it up then we can turn motor generator 1 notice as I turn motor generator 1 it turns the engine we’ve got the disc for the engine it will start the engine and then as the engine starts and continues to run notice that the engine turns motor generator 1 and makes it be a generator alternator ok so that will charge the battery we’re going to take the AC voltage created by motor generator 1 convert it to DC and sent it back to our 201 volt battery now the engine can start and stop as is necessary to charge the battery without motor generator to doing anything now let’s say the engine is off and we want to start driving down the road if the engine is off then motor everyone is stopped motor-generator two is stopped and as we start to drive down the road I’m going to hold the engine from turning motor-generator 2 is going to start to rotate because we’re going to apply a magnetic field electromagnetic field to its field coil and make it start to turn so notice as we start to turn motor-generator 2 that forces motor-generator 1 to spin in the opposite direction at this time as you’re driving on electric motor power only motor-generator 1 even though it could act as an alternator at this point they turn the charge rate way down to where it doesn’t charge very much at all and we’re just running on electric power we’re taking the DC voltage from the battery we’re converting it to AC and turning motor-generator number 2 now we reach a point where we’ve reached a vehicle speed that to run any faster on motor generator to power if we rotate this any faster we’re really going to over rev motor generator number 1 because it’s actually a 2.6 to 1 gear ratio for every 1 turn of this we’re going to get 2.6 terms of the generator and it turns out that around 37 to 40 miles an hour motor generator 2 reaches a speed where motor generator 1 is spinning too fast to spin any faster it’s limited at 6500 rpm so at that point with modern generator 2 spinning in motor generator one another spinning what we do is we slow down with electromagnetic field motor generator 1 and what’s what that does to the engine as we start slow down motor generator one we still allow it to spin backwards but notice now the engine is turning creaks after the engine is turning and the engine will start so now the engine is turning clockwise just as the motor generator – driving the vehicle is and we’re driving down the road as we drive down the road if the engine speed and motor generator to speed were the same like they are now motor generator one also spins the same speed but typically the engine is going to spin a little faster than motor generator – and so motor generator – spins faster becomes a charging unit generator and as the engine is running it forces motor generator 1 to become a generator that feeds power back to the battery it can also feed it to jet motor generator – through our electronics to continue driving the vehicle at higher speeds so at the higher speeds we still have motor generator – rotating we have motor generator one rotating but only because the engine is spinning it at a faster speed and in being a generator now that’s as we’re driving down the road we still have motor generator – propelling the vehicle the engine is assisting in the propulsion but I want you to notice that the engine is not connected to motor generator – there is no direct mechanical connection so at no time does the engine all by itself propel the vehicle it can only assist motor generator – in propelling the vehicle and by doing that it causes motor generator 1 to become the generator or alternator is as we like to call it sometimes now if we come to a complete stop and we want to back up then what we do is with the we can do it two ways we can stop the engine which holds the planet carrier from rotating and we can turn motor-generator one use it as an electric motor and notice that causes motor generator to to spin in the reverse direction and that backs us up but if the engine needs to be running we can still have the engine run but we’d have to spend motor generator one much faster to still get reversed


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