Edmunds.com | Inside Line | Auto Observer Your Account | Help | Directory
You are here:
![[F]](http://a332.g.akamai.net/f/332/936/12h/www.edmunds.com/media/townhall/webxicons/site.gif){kind=small}
Forums
Hybrid Vehicles Hybrid Vehicles - Archived Discussions How do Hybrids work? Newbie questions encouraged! 
139 messages, Last post on Aug 02, 2007 at 5:38 PM
You are in the Hybrid Vehicles - Archived Discussions Forum. Your Host is pf_flyer
This discussion is ARCHIVED. To reactivate the discussion, post a request in the Lost? Ask the Hybrids Host for directions! discussion.
|
|
|---|---|
|
Replying to: toyolla2 (Oct 23, 2005 12:12 pm) It seems to me that the wider the CVT range the better. With the palnetray CVT concept is is practical to be able to get a very low equivalaent first gear and a very high evivalent high gear. Typically a apread of 5-6 is considered very wide. This afford the best acceleration and the best no load mileage. However, with the torque of the electric motor the lwo end is already sufficient. Actually you are really trying to simplify it too much to call the torque cure triangular and the power outpiut profile retangular.While it might approxiamte to that on an occiliscope it is actually closer to a standard bell curve and inverted "U" . Actually an ideal engine would always run at the most efficient output maxiumm torque , WOT. The with CVT you just adjust the effective gear ratio to the desires speed. But once you have charege the battery and are at the desired speed what do you do with the excess power. You could back off the engine speed but then you reduce the eficiency of the engine, which an ICE has low effciency to start with or you could pulse the engine, but there is a startup lag time. I am sure you realize the torque curve of an electric brushless motor , It is almost maximu torque from 0 to approximately 1000 rpm after that is significantly falls off. The HSD system effectively extends this by mutiplying the efective rpm through gearing. If you need more explanation please let me know, but you have pretty well written most of the information written in the Prius technical manual. Let me guess, you are an engineering student just getting ready to graduate. Good luck with your futre job search. Again thanks for your efforts to explain the Prius CVT system. YMMV, MidCow
|
|
|
Replying to: midnightcowboy (Oct 24, 2005 7:47 am) too bad you couldn't follow my explanation. I tried hard to put up the best post I could. I even used spell check, something that you could use also if you don't mind my saying. Perhaps this is the bit that you, or the person reading for you, may have missed. MG1 is always extracting power from the sun gear in order for the HSD output (the ring gear) to be able send power to the wheels. So MG1 never spins needlessly. BTW where does the generated power go?, it goes to the electronic inverter which powers MG2. MG2 is made to devour all the electrical energy brought in by MG1 unless the battery happens to need charging in which case it cuts back to allow the battery to absorb the excess. MG2 happens to be conveniently connected to the ring gear where it drives the wheels (through the 3.95 : 1 reduction) Of course when the cruise speed is reached, accelerating torque will no longer be needed and power will drop considerably. MG1 must still act as a generator albeit at a much lower level in order to maintain control of the sun gear speed. Remember the car still needs torque transfer from the engine's planetary to the ring gear and it can only do that with an (dare I use this word with you midcow) "obstinate" sun gear. If a sun gear were to offer no resistance you may as well not have it there at that time. Now in that circumstance can you tell me where the torque would be coming from to continue to propel the vehicle. ? BTW If you going to reply spare me the remarks that appeared in the last paragraph of your previous post please and thankyou. T2
|
|
|
Replying to: midnightcowboy (Oct 24, 2005 7:47 am) By the way, this is NOT an electric brushless (DC) motor. It's a permanent-magnet, 3-phase AC motor. Same for MG2. IMA uses a brushless DC motor. Easier to wire but more complicated mechanically and electrically. The rate of rotation of MG1 is controlled by the computer to deliver the ideal "effective gear ratio" for the ICE. Depending on conditions that could mean that MG1 is acting as a generator, acting as a motor, or being forced back-EMF to provide a braking effect against it's input shaft. When acting as a generator, the power from MG1 can go to either MG2, the battery, or both. Oh, and internal combustion engines have their maximum POWER at or near redline, not their maximum TORQUE. I would not dismiss John out of hand, he's probably more knowledgable about THS and HSD than most Toyota dealership staffs. |
|
|
|
|
Replying to: toyolla2 (Oct 24, 2005 8:14 pm) You didn't like my spelling; sorry I didn't go back an spell check or reread! I am bad about that sometimes and yes I am a crummy typist and I don't always spell the words correctly. It is just that the spell check on Edmunds doesn't suggest the correct spelling and sometimes I am too lazy to look it up. Let's see you didn't like my last paragraph but yet you said "...or the person reading for you." Actually, you don't know anything about my intelligence, experience or abilities or if I read it myself or had someone read it too me. My implication was that you gave a rather long drawn-out engineering oriented answer that really didn't answer the question. Maybe, it would have been appropriate in the "advanced engineering" thread. But assuming that I was a Newbie, it was out of place, too complicated of an answer, but interesting to me! That was the intent of my point, sorry if it offened you. The MG1 spins all of the time. Sometimes it supplies the MG2 and sometime it supplies the battery when acting as a generator. And sometimes receives power form the battery and acts as a motor. It is debatable whether or not it spins needlessly. But let me explain further .... When one form of energy is converted to another, there is always a loss of efficiency. No conversion is 100% efficient. I think it is a poor design to always spin the MG1. Why in the world would someone design something where the ICE power is converted into electrical power of the MG1 which is immediately converted into supply power for the MG2. Then the MG2 acts as a motor further converting power with additional energy loss. Why not use the power directly from the ICE? Double and triple conversion of energy is just not an efficient design. Lets look at two designs the Honda Insight 5-speed and the Prius The Insight doesn't needlessly spin a MG1 and double/triple convert nenrgy and it has an EPA rating of 60 City and 66 highway. The Prius always spins the MG1 ( it is up in the air whether it is needless or not) and it has an EPA rating of 60 City and 51 highway. In my higher math, before calculus of several variables, I thought that 66 was greater than 51. Why is the highway mileage of the Prius less than the City mileage while the Insight is higher ? Okay, some would save the HSD full hybrid uses electric power to gain City efficincy and higher City EPA. Perhaps a ICE only Prius would have mileage in the range 35/48 with a gain of 25 mpg City and 3 mpg Highway because of HSD. Man that sounds like a whole lot of regenerative braking to get that +25 City. I just don't by it. True is could be the CD. However the Prius has a low CD of 0.29 which isn't htat much higher than the Insight's 0.25. There there is the weight difference, but then we digress ... Back to my hypothesis: The Prius has lower highway mileage than city becuase the MG1 spins needlessly and wastes energy by double/triple converting enegy and/or charging fully charged batteries. Cheers, MidCow P.S. Oh by the way you notice I did not mention anything derrogatory about you driving an Echo  P.S.S. - I was a member of Eta Kappa Nu and Sigma Tau. Then later with my MBA, Beta Gamma Sigma. But, hey who's counting. |
|
|
Replying to: midnightcowboy (Oct 27, 2005 7:47 am)
|
|
| Let's drop the personal comments and stick to the topics please. | |
|
Replying to: falconone (Oct 27, 2005 10:05 am) Actually, Einstein wasn't that good at basic math either, which I find even more interesting. His forte was theoretical physics. But math and spelling are not necessary for proper logic...
|
|
|
|
|
Replying to: stevedebi (Oct 27, 2005 11:10 am) I wonder, what kind of hybrid enhancements Albert would make today if he were still alive. That man had vision I would low to see what kind of transmission he could design. 6-speed manual Prius, (the best of all worlds) MidCow P.S.- With Mod to allow MG1 to idle when not need on highway cruising have gotten MPG specs up to 60/55 thats a 4 mpg improvement
|
|
|
|
|
Replying to: midnightcowboy (Oct 27, 2005 1:08 pm) He probably would see it for what it's worth and not bother with it...LOL |
|
|
quote zodiac2004-"He probably would see it for what it's worth and not bother with it...LOL"-end quote Albert, being frugal, would have loved to only spend $32.86 for 31 days of driving like I did in my last fillup. 
|
|
You are here:
Forums
Hybrid Vehicles Hybrid Vehicles - Archived Discussions How do Hybrids work? Newbie questions encouraged!
