Key to understanding how the drive works is the fact that MG1 and MG2 are AC motor-generators and their speed can be controlled exactly by the computer. This is how the ratio between crankshaft, electric motors, and drive shaft speed is controlled, i.e., how the drive acts as a CVT.
Hi, Thanks for the comment and concern. You should have seen me try to do this demonstration on a steel bench, everything was sticking to the bench and to each other; it was a disaster. I could not even pick up the MG2 rotor when it was on its side. I had to roll it to the edge and slide it off. It is amazing how strong those magnets are. Cool technology!
This was a tremendously helpful video and I want to thank the presenter for all the work in doing it. It helped me to understand a lot about planetary gears and sun gears and ring gears and their arrangements. You have to remember what this system is actually doing (and doing very well) in your car. I own a 2016 Prius C, which I love. I suppose the gear ratios in it are even better. As a former operating engineer, I appreciate the genius of Toyota in building these amazing machines. They are only going to get even better. Again, thanks for the great presentation, WeberAuto!
Thanks for the comparison. I did not know there were any major changes to the transaxle for the 3rd generation prius. This does explain a lot, especially how the plug-in version can go faster in EV mode. I'd like to see an explanation of the Chevy Volt transaxle!
Thanks for taking the time to make a Long video...everything today is Rushed and just sucks because you end up missing details! I prefer videos like this, where it feels like you're in a REAL classroom and have time to absorb it! Good stuff!
My first model Prius 2001; Second Prius 2011. Now I think I understand how the 2011 cruise control is able to slow the car preventing overspeeding on downhill runs, a feature I didn't discover immediately. Very useful function.
Mechanically, these are very, VERY simple compared to a typical car transmission. All of the complexity is in the electronics and they're proving to be pretty bulletproof.
Thanks for helping me to understand how these ecvt transmissions work. The design is so elegant and robust. So much going on with the torque controlling from the ICE and motors. Mind blowing to think about gearing to change maximum e-only vehicle speed. Very cool!
Not really. The Prius is pretty hard to beat. There are thriftier cars to drive but they're almost exclusively tiny, not available in the US, or no longer made - or all of the above.
Are those actually the motors or just the rotors from the motors ? Either way when you look at the size of a washing machine motor which is only a couple of HP they are incredibly small.
Wow! This is extremely well prepared, well presented, demonstration. I just bought a Prius and, being an engineer, I need to know how it works. This and the simulation that’s available here are definitely clarifying this fascinating system for me. Thanks for all the hard work that obviously went into this. 👍👍👍
Almost no belts or chains. The 1st and 2nd gen had an internal chain link from the output of the planet gears to the differential area of the transaxle. 3rd/4th gen drives the diff directly.
@@alanowa123 thx....now 240000 on it with first battery and i did oil change in the 2 small gear boxes front and rear.. still runs strong ;-) ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-3bSB_TdBA8A.html
Great video. I watched an animated video years ago when we bought our 2010 prius. It illustrated the basic concept of how the system worked but left a lot to the imagination as to the actual mechanical setup. For me this video filled in the gap. Good stuff....
@WeberAuto. Thanks for the video. I was on the fence between getting the 2nd gen & the 3rd gen & now I'm going to pass on the 2nd gen. I also was hesitant on getting a Prius because I thought that it had a belt driven CVT. I feel a lot more comfortable about the decision now. I've also seen high mileage reviews & not one mentioned anything about the transmission or batteries failing.
@@VoiceAlertTexas Oh wow! I've heard that they make very good rebuilt battery kits for around $1,000. I think that beats all the other fails that a regular car could have.
A reason for the taller gearing on the Prius C is that it runs a lower voltage hybrid battery. Motor RPM is proportional to voltage and so it can't run the motors as fast meaning it needs taller gearing to get the same roadspeed. Given its a smaller, lighter car it needs less torque which is good because that's also what you get with taller ratios :) Great video, thanks.
Your explanations filled in a lot of the gaps in understanding I had after watching Niels Blaauw's excellent video. These two together cover the topic well.
Hi, the motors are three pase AC synchronous (with permanent magnets on the rotor) . They are not induction motors, they are not DC, and they do not use brushes. The ICE is not held stationary, but it stays stationary when off by the engine's own compression, friction, and lack of momentum. It takes much less energy to turn the MG1 motor while in electric mode. The charge rate is turned down to a low level allowing MG1 to rotate with less effort.
Very good ! but I have to say, perhaps it is because of this rainy Sunday afternoon, but he threw me in the quickest and deepest sleep I ever experienced in my life...
I have observed and visualised one thing. From 26:38 MG1 is idling in reverse. To run the engine the MG1 field reduces its speed transferring the resisted ring gear motive force to turning the planetary,hence starting the engine which turns in a clockwise direction (in the video the engine is turning in the wrong direction). This confirms the namograph presentations upon running on MG2 and upon MG2 + engine. MG1 changes direction upon the engine running.
Kudzanai MG1 only changes direction with the engine running when the vehicle is stopped, otherwise, it will always rotate the same direction as the engine. Good catch on the entire presentation being shown with the components rotating the opposite direction as they should have been, It makes no difference in the theory of operation though (other than it is backwards). Thanks for watching.
WeberAuto Alright. I had taken it from your P111/P112 presentation, though i now notice MG2 forward has changed owing to the motor speed reduction gearset. You have a wonderful initiative (video lessons).
The IC motor (driving the planetary gear set) must rotate in the opposite direction from the electric motors (both driving sun gears). As the IC motor starts, MG2 must slow down, not speed up. You should re-edit the video to show this, including the IC motor driving the wheels with MG2 stopped.
These late versions are much superior to the cone and pulley CVTs which most other cars have. There are no torque converters, gears meshing and un-meshing. None of those wear prone devices. Everything is “tight” at all times. That’s why these transmissions are so reliable.
Excellent video! Question: Does an eCVT require any maintenance like fluid changes? If the car is high mileage (e.g. over 300,000km) and the fluid had never been changed, do you recommend to change it or at this point leave it as is? Thanks in advance.
Weber Inst. Thanks a lot for the videos.. they are very usefull for us, people in the third world where innovations arrive a little late but unfortunely the tecnology for repair it is only for a little groups that prefer to hidden it and be only with the truth. Thanks to you and your org. we can have a better understanding for accomlish the repair labor. In case of electrical vehicles it will be necessary to develop an a very simple way to detect failures with help of a multimeter because other devces are or impossible to get them or innoperable due to lack of escolar education in the electrical area and in the mechanical. thanks once again...
Great video! Watching this because i recently did a hard acceleration onto the freeway with my rav4 hybrid and was worried thinking it had a belt drive cvt.
Clutch I think on the 400H might cost thousands, if I don't do it my self. Easy but time consuming. Patience along with all the good info to try swap transfer should be easier specially if I'm not sure what part is wrong like a pin bearing or final drive gear in power split or burnt coils or clutch. Soon as engine comes on its like a broken piston ring bit goes n comes back. Might just be bad gas clogged injector or coil n plugs are toast it looks like. I was driving Ving fast yesterday so I think clutch because it had new oil change. Thanks for the videos top notch
Thanks for this great video. This makes many things clear! I think you made a mistake in the description of the transition of MG2 drive to ICE drive (27:00): You turn the ICE clutch damper in the wrong direction so that MG1 will turn faster (obviously too fast if it´s already a bit quicker than MG2). Actually MG1 will turn slower (breaking as a generator) to start moving the ICE in the SAME direction as the wheelgear already rotates. At eahart.com/prius/psd/ this is well demonstrated with the shown nomograph. Moreover at higher speeds there is a point where MG1 stops spinning and reverses direction. Remarkable difference to 2nd generation PSD: In normal forward drive the ICE and MG2 rotate in reverse directions! This is caused by the additional planetary gear set in gen. 3.
Yes, when the vehicle is in good forward motion and the Internal Combustion Engine (ICE) is to be started, the rotational speed of MG1 is decreased by applying a breaking force by means of electric current to MG1 from an electric converter. At low forward (or reverse) motion of the vehicle, or high rotational speed (RPM) of the ICE, MG1 reverses rotational direction. In 4th. generation Prius, MG2 is no longer coaxial with MG1 and the ICE. I'm unsure as to whether MG2 employs a planetary gear set or not in 4th. generation Prius.
good work Weber, this is hard information to find. I watched your whole video at regular speed and found it informative but i wish you'd work on your presentation a bit better as i didn't think to use 2x speed.
Wow, great illustration of hybrid synergy drive. I have the Prius Plugin. Now I understand how this works,it gives me a piece of mind that it will last for a long long time! With this explanation, I can see why the Prius Prime evolved the same pathway to even higher electric only speed with the same concept. No wonder it is so reliable. By evolution road proven approach, you have real life test runs already done instead of revolutionary method that needs to be take a good time proven initially to get it right.
Thanks for the feedback. Here is a new series on all four generations of Toyota hybrid transaxles. ru-vid.com/group/PLIn3FrDiB1lyzmzZNBM24V_FsyuDx8ow_ Have a good day!
Thank you for.your explanation was considering purchasing a gen 2 from 2009......but will hold off and purchase a gen 3.....looks like a more efficient and durable design.......
In reference to ToyotaKTM, possibly Toyota Engineering wanted to use a starter motor on the original ICE. So, they ordered the ring gear on the flywheel. Then, at some later point, the starter was eliminated. The other theory could be that this flywheel is a multi-purpose flywheel that can be used in another vehicle, not propriety to Prius. I saw the ring gear on the flywheel and questioned the same thing.
How wrapped my mind around how my Prius works. 1) The Atkins cycle ICE engine has very low torque because compression is very low which increases gas mileage by 20%. 2) The ICE engine is always directly connected to the drive wheels. 3)The gear ratio of the Prius us the same at all times and at all speeds. 4) Because the ICE engine is low torque and the gear ratio is the same at all times and at all vehicle speeds the Prius uses the electric motor to start the car moving, once moving the ICE can start sending power to the wheels. The engine can be running at zero speed. 5) The Prius has no clutch or torque converter to disconnect the wheels from any of its motors, all are directly connected at all times at the same gear ratio. (the clutch shown in the video us not controlled, it's always engaged, it is there to absorb drive train shock. There is no reverse gear. The ICE engine CA start while the car is moving in reverse or forward. What makes all this possible are the sun gears. The engine room very very little to maximize efficiency. If sitting still in neutral and you step on the gas the ICE engine does not change speed. When the car excel erases the computer determines how much power us needed to be directed to the wheels by the ICE and electric motor, as it accelerates the ICE engine rpm's remains fairly constant. Speed of the car is changed by how much power is directed to the wheels, excess power from the ICE is sent to the generator to charge the batters and during breaking. 6) A good way to visualize how this all works is the computer determines how much power is directed to the cars wheels to get it to move, accelerate. The planetary gear system that directly connects the cars drive wheels to two electric motors and the gas engine at all times is what makes all this happen by directing none, more or less power to the cars drive wheels.
alan connelly Another view: 1) There is never direct connection from motor to wheels even with pure ICEs (or there wouldn't be a neutral position without stopping the engine). Thats why there are transmissions. 2) HSD and eCVT, are names to new transmission types coupled to electric motors that can merge torque from all sources controlled by its clutches and planetary gear sets similar to an automatic transmission. 3) The use of late admission valve closing and a kind of Atkinson cycle is motivated to get higher thermal efficiency from the ICE. In other words extract more useful work from the same amount of fuel energy supplied, translated into a smaller BSFC (Break Specific Fuel Consumption). 4) BSFC is not constant, but a function of many variables including load and speed of the engine. There are sweet regions of best BSFC which are target for economy driving, as well as bad regions to be avoided for economy, noise, vibration, wear,... 5) Electronic drive of electric motors enable precise merging of torque on the eCVT allowing the upspeeding ou downspeeding of the vehicle without acelerating or decelerating the ICE. Thats why PCM algorithms avoid "aceleration enrichment" and ICE moving mass acceleration or deceleration using electric motors to add or remove torque from the system with the equivalent amount of electrical energy transfer to and from batteries. 6) By design, most of the time the ICE is operated in its sweet regions achiving from 35 to 40% thermal efficiencies in a gasoline powered small ICE which is a record. 7) As batteries are not cheap, total energy stored in this small hybrids won't allow for many electric only miles to be driven anyway. All the electric components are used to allow the traditional ICE adapted to Atkinson to run in it's sweet spots at best efficiencies relieving the ICE from the multiple demands in all regions of the load-speed map needed for "drivability" now supplied by the electrical motors. ICE is run like a stationery engine changing load within the best BSFC region when needed. 8) A variety of clutches, brakes, planetaries coupled to the motors in the eCVT is designed to allow best operation of those components and there use within its limits of speed, torque, current, heat,... 9) The idea can be easily applied to most ICE driven vehicles, if needed/desired. Its a point in the design space between the traditional ICE-driven and ER-EV like Chevy Volt with full electric mode capabilities. Both are handicapped in relation to pure EVs by the extra complexity when cheap practical EVs become a reality. 10) Hybrids like Toyota Prius enable the best use of our traditional liquid fuels lowering it's consumption for unit miles driven. ER-EVs Plug-ins like Chevy Volt enable displacing a large amount of liquid (fossil?!) fuel by electrical energy (source?) with the least amount of expensive batteries. Pure Plug-in EVs are the most efficiency all electrical driven vehicles with no ICE related overhead or overweight. All of them have a place in the transition of energy sources for transportation depending on external circumstances. All of them are beautiful engineering accomplishments. :-)
@@celsostarec6735 That's really useful information, so seeing how the Prius works, is it bad push the accelerator all the way down? is there a chance of damaging something?
@@hedgehogthesonic3181 Despite the Prius not beeing intended as a sports car, I suppose Toyota has thoroughly tested their project and put any needed safeguard in place.
@@celsostarec6735 I see, thanks for answering. And since the gears of the Prius are fixed in place and only rotate, is a lot more robust and durable than the standard automatic transmission. I don't push the accelerator of my Prius all the way down, i try to drive as efficient as possible, but since i bought it used i wanted to know, i don't know who the previous owner was and how he treated this Prius.
Hi, This video is great. Do you also have a video that describes how the eCVT works with the power splitter, MG1 and MG2. Is it that when the wheels are turning at a slow speed that is slower than the engine speed. The engine turns MG1 to cause it to generate electric power. That is then used to power MG2. And doing this then gives a gear ratio that allows the engine to run at the most efficient speed. And when the wheels are turning at a high speed, that is at a higher speed than the engine. MG2 generates electric power that is used to power MG1. Again giving a gear ratio that allows the engine to run at the most efficient speed. And keeping the gear ratio such to keep the engine at the sweet tune point, at whatever the wheel speed is at. And does placing a electrical load onto MG1 causes the engine power to be split between the wheels and MG1. There is a power splitter, how does this work? Placing a electrical load onto MG1 will cause MG1 to generate electrical power to either charge the battery or to power MG2. Please describe how this all works. Thanks for your great videos. But they should also describe how eCVT transmission works.
+Arlen Ung Hi, no, the plug-in transaxle is very similar, but has different gear ratios to allow the engine to stay off until 61.5 mph rather than 40 mph. Thanks for watching.
DUF was first to use, not to create.. CVT is older than Manual or automatic.. 1490: Leonardo da Vinci drew sketches of his ideas for a CVT. 1886:The first CVT was built by Daimler and Benz. 1930’s: GM developed a toroidal CVT. 1958: Daf (Netherlands) developed and produced a belt driven CVT for a 0.6L engine
Thanks for the very informative video! I have a couple questions if you don't mind... What kind of motors are MG1 and MG2? DC brushless? Also, what holds the ICE stationary when in pure electric mode? Is there some sort of brake band?
Thank you for the best informative videos about the different kinds of transmissions. Do you know what kind of CVT transmission is on the new Toyota C-HR? Is it a eCVT on their hybrid and a normal CVT on the petrol engine one, or is a normal CVT on both? Is impossible to find this information on web. Thank you again and keep up the incredible good work on this channel.
Hello John, Thank you for this video as I/we just purchased our second Prius (2010) which is a 3rd Gen. Our first one is a 2nd Gen. We have a friend who also had the 2nd Gen...but (supposedly, according to HER mechanic) the Transmission FAILED (she only had @145k miles on it). That didn't seem plausible being THAT it is a CVT, however MAYBE I need to learn something. In your experience....are the 2nd Gens prone to FAILURE, and if so, How So ? I ask this because on our newest one....I'm considering CHANGING THE TRANS-FLUID as it just now turned 100k miles. In looking up the Fluids for both Gens, I noticed that the fluid for our 2nd Gen (which is a 2004 model) may actually use a DIFFERENT FLUID than the 3rd Gen (both are RATED Toyota WS, howEVER, Valvoline Synthetic Trans Fluid (also with WS Rating) shows that theirs can only be used in the 3rd Gen CVT. Can you clarify for me ? (thanks for letting us know that the 2nd Gen CVT uses a Chain-Drive vs. the Gear Drive.....does this also mean that the 3rd Gen CVT is Superior, partly because of this ? ) Also, one last thing, some people think....yes EVEN SOME TECHNICIANS...that because the Toyota CVT is a "sealed unit" that it does NOT require the changing of the fluid. What say Ye, Ole Master Tech ??? Thanks again.
+ConnectTheDotsNOW Hi, No, the 2nd generation transaxles have been very reliable. I wonder what "Failed"? Unless there was a fluid leak leading to oil starvation at the bearings or physical damage from running over something, there is very little that can fail. As you know, all generations of Prius transaxles are not sealed units. There is a fluid fill and drain plug. All of the "sealed transmission" stuff is just a marketing ploy to trick people into purchasing their vehicles that don't require service under "Normal" circumstances. See your maintenance guide, there is a fluid change interval. The WS fluid is compatible with all 2004 and newer Toyota transaxles. I don't know why Valvoline would say that if their fluid meets the WS specification. Best wishes!
Great video. I'm a petrol head at heart, but I drove a camry hybrid recently and was amazed at how much I enjoyed it. Something about knowing just how clever it is really made the experience special, and definitely better than a belt cvt. Do you know if the transmission in the Lexus is300h is the same just mounted longitudinally? Thanks!
Thank you! I am not familiar with the Lexus 300h transmission yet. I hope to be soon. At first glance, it appears to be more that just a longitudinal version.
@@WeberAuto Dear Professor Kelly, I have 2 questions please: How is the lubrication implemented? Is it splash lubrication? I see several caged, open deep groove ball bearings and I assume the planet gears use needle bearings. 2) I know Toyota WS (World Standard) ATF is used. How well does the lubrication work at cold temperatures? With the car stationary and the ICE idling high (1300rpm because warm-up), MG1 spins at ~4750rpm. When moving at 50mph, MG2 already spins at ~6000rpm. What if the car sat outside in winter at 5-10°F? Does the lubrication still work reliably? Would it maybe be a good idea to drive a bit slower during the first few miles? I could not find a PID for ATF temperature to monitor how long it takes to warm up. Thank you! Regards Dan
Great explanation. Makes a great piece of engineering understandable One interesting thing is that the IS300h is supposed to have 3rd gen (Lexus info), but since it switches off EV at around 35mph, 40+ if going downhill (if doing just enough power to maintain speed), maybe that doesn't apply to all model years.
My es300h will use just electric even on the freeway if the load is low enough. It can do full electric, the electric motor is 116hp but the battery doesnt have the capacity.
@@CrazyForCooCooPuffs , that's great, it just needs the bigger battery from the Nx450+. If it had that power train and fully foldable seats, it'd be close to perfect. They don't fold to force people to buy SUVs. A real shame
Excellent presentation. It looks like planetary gears are becoming the norm on new designs of automatic transaxles (e.g. the 9-gear ZF 9HP, etc.) - perhaps the eCVT is the inspiration or are there other early examples of such planetary gear transmissions in automobile application?
Planetary gear set equipped automatic transmissions have been in mass produced vehicles since 1940. They are great to use because they are compact and can give many different gear ratios. Thanks for your feedback!
Exactly what you said, is what is so confusing. MG2 is mechanically coupled with the wheels, but the ICE is not. The only conceivable way for me to believe that the ICE can power the wheels is if MG2 where to provide a magnetic force to couple split which separates the ICE from the wheels. I hope I've simplified my question.
What happens when you hold MG1 still and turn the ICE? In your demo all 3 motors are spinning the same direction. ICE causes MG1 to spin faster in the same direction. MG2 causes MG1 to spin faster in the same direction. MG2+ICE spinning in the same direction show MG1 spinning crazy fast in the same direction. Shouldn't one of these spin the opposite direction? I wish I could find a video that shows not just gear ratios, but also power distribution. Like, how does increasing the engine RPM actually make the car go faster instead of just spinning the electric motors? When I look at my Torque app MG1 actually spins backwards until I rev the engine. At highway speeds MG1 is usually close to 0 RPM while ICE as at 2500 and MG2 is at 10,000 or so. The Torque app will show -20 ft-lbs of torque at MG1 (0 rpm still) Obviously you can't use the battery to apply constant resistance to the MG to redirect ICE power to the wheels because the battery would run out of power. Amperage to the HV battery system usually is around 0. (negative amps = charge) So I'm guessing the MG1 spinning in generator mode is used to power MG2, and the resistance created in MG1 is used to force the ICE power into the final drive. Then, breaking is still confusing. I think MG2 generates while MG1 is free-spinning. I guess that's the most difficult spot to visualize is which MG are free-spinning vs which ones are generating power and which are using power. Sorry for the streaming brain dump.
MG1 is attached to the sun gear, so it can control where the motor power goes. In another video, he says that for the car to operate at 65 MPH, the ICE can spin at 3300 RPMs with MG1 matching speed, or the ICE can spin at 2200 RPMs and MG1 can be stationary. Since MG1 controls the sun gear, it being stationary would push all engine power to the ring gears and then the wheels. MG1 can be free-spinning to generate electricity, or it can be given power to transfer engine power to MG2 and then the wheels.
Perhaps the concept that either of the motors can apply torque in either direction, so they may appear to be freely spinning, but the system can apply torque both in the direction of rotation (adding speed) or in the opposite direction (braking or generating) giving whatever control output is required.
As a neophyte to this design, I was looking for how the vehicle changes gears. Is it correct to say that gears don't need to be changed because the electric motors can operate at widely variable RPM, and the gas engine just helps out by charging the battery, and when needed for a power boost?
