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Advanced Course in Hybrid Engineering

Kirstie_HKirstie_H Posts: 10,851
edited April 1 in Toyota
Want to talk about the merits of various engine designs? Need to debate IMA vs. HSD? Have a penchant for performance statistics?

You've hit the right topic. Roll on!

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  • toyolla2toyolla2 Posts: 158
    John 1701A observing that the two car companies active in the hybrid field have slightly different thrusts stated that :

     Toyota is for reduced emissions
     Honda is for increased efficiency

     But I would suggest a third thrust might be taken given that there is room for improvement in the efficacy of coupling the ICE to the road wheels.
     Consider the methods currently available:
      I am not saying that I don't enjoy driving stick in an Echo, it has great Torque/Mass ratio, equivalent to an Acura TSX , however efficient as it is; the Stick method is too tricky to lend itself to computer automation.
      So occasionally I drive the "relentless search for perfection" vehicle which comes with a transmission that is supposed to be computer friendly. And now I'll get the occasional tap in the rear while waiting at stoplights, the unexpected surge at low speed and finally when I egress the rolling backwards an inch or two. Sound familiar? So they can't get it right am I supposed to accept this as normal.
      Now for the hybrids, I invite you to observe the images provided by usbSEAWOLF2000 #193 on the Hybrid Honda Accord 2005 board. The first image is that of a Honda Civic Hybrid engine and the CVT as you can see is situated on the right hand side. That is one large and complicated piece of mechanical engineering I have to say.
       I find it incongruous with my experience in electronic drives that someone would come along and fit a mechanical variable speed device on shaft of this engine. This is probably the obvious
    solution for a company heavily biased in mechanical engineering. But in the new millennium I would have suggested alternative ideas. Such as increasing the stack length of that generator to up the capability
    to 80kw at 7000 rpm. Discard the CVT entirely. Select instead a 25hp (1800 rpm base speed )3-phase induction motor with rotor balanced for 12,000 rpm and a 30 second rating @ 75hp to be coupled into the trans axle with a 10:1 ratio.
    Additionally two inverters on the HV bus would be needed. The first would be the starter for the ICE and would subsequently degrade to become a 3-phase rectifier. The second would be the traction inverter. I would also place a couple of transistors in series across the HVbus as an UP/DOWN converter for the main battery pack. That's for those who want some "Stealth" capability and braking regen.
     I need to say something about the Prius. That planetary device with servo is way too complex IMHO for mechanics. Even on these boards there have been struggles to get a handle on the concept. Yeah a VCR/dvd player is complex but at least for $50 you can junk'em. But I gotta say I love that 200/500v bus idea. Constant v/f ratio would run out of headroom at 52mph otherwise.
    And because current costs but voltage is free it complements the fact that although we crave horsepower we drive torque (hybrid v Diesel Idletask #6) This means the system is able to maintain constant current (read torque) and optimal slip for the induction motor as the vehicle accelerates. As frequency increases it gets harder to force current into an induction motor so the torque would start dropping, not desirable obviously.Having extra voltage via an up converter (Prius) or increasing excitation to the alternator (series hybrid).
     I would carry over the technique to a series hybrid but go even further to as high as 800Vdc. Heck, European inverters hit 1000Vdc I'm told. If this doesn't sound too clear. Just trying to broach the idea of Power Envelopes. Hope this didn't appear preachy.

    Why series hybrid........
    The use of the traction inverter will insulate the driver from instantaneous power fluctuations from the ICE that the other systems are susceptible to. This was the original point I was trying to get over. But I got caught up in explaining how this would be done. After all you can talk the talk but how close is practicality is what I also wanted to demonstrate.

    I'm done.

    Hmm.. 5.00am it's really quiet on this board. Time for a Bark Off don't you think?
  • You really have delved deep and techno into this subject while I on the other hand have come to the Hybrid realm thru the world of railroading. Years ago in a galaxy far, far away there once was steam-powered locomotives but technology, as always, moved on and along came the diesel-powered engine that eventually became one of the first duel-powered vehicles of the 19th century when it was combined with traction-motors for the final power to the rails(kinda like the first hybrid).
    One thing for sure these hybrid cars sure can scare us with all the gadgetry and techno stuff. I've noticed quite abit of hesitation on the general public to grasp the transition to it all and take the plunge or as we say on the railroad,"Get On Board!". Toyota sure has made it more comfortable with the eight yr/100K coverage on the hybrid drivetrain. I must say that Motor Trend bestowing "CAR of the YEAR" award said volumes about the in the know thinking of an establishment long known for their love and bias to conventional combustion cars. One last tidbit, as to all your technical info shared with us novices,one question popped up several times...Where were you when American car manufactures piddled with turbine and the other like power sources? (they cudda used you)
                  Culliganman (retired hogger)
  • "...that Motor Trend bestowing "CAR of the YEAR" award ..."

    But you have to remember that Trend Micro has a very limited selection criteria, only brand new or substantially changed models

    and they have made some big fopahs in the past --Like when they named "Renault Alliance" car of the year.

    Me thinks the techno-gadgets and the current Hybrid-fad may have clouded their selection vision.

    YMMV,

    MidCow
  • Well, you touched on a tender spot when you pointed out the Renault. I once had the "Encore". It was quite inovative with its extended wheelbase and frontwheel drive. Price was very friendly not to mention decent MPG's. I think its downfall was a lack of quality control back then. Since I knew this car I can speak with some knowledge. Your point is fair to say that M/T could have made a better choice (IN HIND SIGHT). As to comparing the PRIUS to the Renault well, the jury's still out but do remember that Toyota has been into this hybrid game for the better part of 10 yrs not to mention R&D with over 300 of their own patents per Hybrid Techno. If you really think that Hybrid Technology is a fad you might might want to re-think that since half a dozen models are out now and more than another half dozen are on the way.
    P.S. Maybe you think the HUMMER should have been "CAR OF THE YEAR" perhaps?
    Culliganman (toot toot)
  • toyolla2toyolla2 Posts: 158
    Hi Culliganman,
                          it is encouraging to get a positive response now and then. Your view that the public is slow to 'Get on board' with hybrids may be in part due to cost concerns regarding the repair of the hybrid powertrain. These costs can be the automotive equivalent of 'dropping it on the floor' if railroad parlance serves me right. Then there's the fact that there are some good non-hybrids available out there which have nearly the mileage but without the price premiums of the hybrid.
      This is my thinking:-
                  What we have in the market is the result of but two design teams and their solutions, IMA and THS. I would judge the Honda solution to be 95% mechanical, the Toyota about 50/50 mechanical/electrical. But there is no 95% electrical solution which I take to be the series hybrid.
       Reverse logic would imply that if the two methods presented so far were in fact la creme de la creme how is it that neither company dabbles in the other company's technology? Shouldn't competing technologies be about equal? Someone posted that Honda had limited resources to go further into the development of full hybrids. This I believed until the launch, recently, of their version of the Learjet. Or perhaps this was a different Honda :-)
       The Honda method is about reclaiming energy from braking and hill descents, I believe it does very little for performance. Considering the Honda IMA with Manual transmission if it were fitted with a tall gear in fifth (0.7). This would give it the superior mileage in longer hiway trips.
        The Toyota method has to emulate the tall gear which is comparitively lossy to do, so it cannot compete against the Honda on long hiway trips. However when fluctuations in speed are required the THS, which is always in the 'right' gear, delivers superior acceleration performance because the ICE rpm will not be sawtoothing up and down as in the Honda M/T as the driver rows through the gears. Maintaining a constant high speed from the ICE means that the THS is able to provide a higher average continuous power to the road. 30-50 MPH times bear this out.

          I ought to mention the Honda CVT (w/IMA)variant. Like the THS, not so good on long hiway trips compared to the Honda M/T(w/IMA). OTOH acceleration with the CVT should be very good as long as the system stays in top shape. The question is how long will they stand up to aggressive driving.
         As I understand it the CVT in the Honda is some form of hydraulic computer gear-changing gizmo, very mechanical and prone to go wrong with wear. CVTs had been used industrially quite a lot until DC thyristor drives became popular - about 35 years ago. They were followed later with a transistor invertor /induction motor combination.

        As Seinfeld would say, we know they've seen the fork, we've shown them the fork, so why are chopsticks still around. Do they think we haven't noticed?

        My opinion is that less mechanics means increased reliability.

        The series hybrid in my 95% electrical solution works on the acceptance that controlling mechanical power is difficult and gives lots of problems involving clutch /gearbox/CVTs/ICE stability over extended speed ranges.

         The solution as I see it is not to control mechanically but to control electrically. In this regard it is necessary to convert mechanical power as early as possible into electrical power. The ICE being directly coupled to the generator. Then finally an invertor feeding an induction motor which drives a differential with a 10:1 ratio would complete the system.
       The 100kw invertor/induction motor package would be similar to that used by GM's EV1. No risk there.
       The ICE would be a 'CLEAN' engine meaning there would be no power takeoffs, at 15,000 RPM they would not be too reliable. Two pistons on the same crank would allow the use of just two main bearings. Balanced firing 360 degrees apart to each cylinder. The generator rotor containing Neodymium magnets could be fitted to one end of the crankshaft or divided in two and placed at each end if overhang is a problem. Valves would be magnetically actuated.
         Comments please
    T2
  • RELIABILITY:
    - As an engineer, one of the first things I consider is "What happens if a part fails?" I look at the Prius & I notice that if the electric motor #1 or motor #2 fails, the car will not move. The transmission will spin, but the car will go nowhere.

    - In contrast, the Honda Hybrids don't rely on the motor. Even if the motor is dead, the car can still move forward on engine power alone. And you can drive it as a conventional car until end-of-life.

    .

    MPGS:
    - Both the Prius & Civic Hybrid are approximately equal here (~50 mpg highway), but the Civic comes with a lean-burn engine. A careful Civic driver can watch the gauges, keep the engine in lean-burn, and routinely score 60 mpg highway.

    Troy
  • gagricegagrice San DiegoPosts: 28,903
    The 100kw invertor/induction motor package would be similar to that used by GM's EV1. No risk there.

    I appreciate what you said that I was able to understand. I lean toward the series hybrid with the more efficient diesel engine. I felt the EV-1 was buried before it had a chance to mature. Batteries being the big Achilles heel. I like the idea of plugging the car in at night with the option of a genset when out and about when no AC is available.
  • Sorry for the delay getting back to the details and you. I had some extenuating things come up. I too have had some miss-givings about the highly technical systems involved with the Prius and it's intricate electrical sys. but then I got to thinking...My wall switches and outlets at home (all 24 of them) are 52 yrs old and not one of them have gone bad. I have a ceiling fan thats 29 yrs old and again she's running like the first day up. Well, what I'm getting at is obvious. Toyota has put high quality electrics into the Prius starting with the main battery and continuing thru to the CVT transmittion. Let me add that we all put trust in our vehicles every day. When we turn the steering wheel, step on the brake, turn on the lights, wipers and even the electric starter. We've come to expect our cars to deliver unfailingly. Some do it better than others. Toyota (I think) is one of a select few. I now have nearly 12K on my PRIUS. I've had my hybrid over 110MPH and felt the car sure footed. I've driven her hard and I've babied her to extract as much as 56 MPG's. The Prius has delivered on all of my demands.
     People really fail to understand that to get a great car that delivers high mpg's (say over 45) and have roominess AND reasonable performance is almost unheard of until now. I'm convinced the PRIUS has filled the bill while others have only titillated the concept. Being an avid motorcyclist I have seen many a bike 2-4&;6 cylinders get a meager 34MPG's and even a few (Harley for one) get less while usually ridden hard. Bikes weigh in usually around 390 lbs while hybrids come in at around 2800 lbs There in lies the delimma. Alot of good milage is determined by one's own driving habits too. I simply find it satisfying that the hybrids have excelled at fuel efficiency and reduced pollutents to a very respectable and practacle low level.
    Culliganman (Green like Kermit)
  • explorerx4explorerx4 Central CTPosts: 9,622
    drove my sister's '05 prius today. it seems like a good real world vehicle. it drives normally and seems practicle for a family(4), plus attractively designed and well put together(interior). no faults with the exterior either. imo.
    to me the biggest problem is with peoples attitudes. when i told them my focus was rated pzev, they didn't know what that meant.
  • stevedebistevedebi LAPosts: 3,785
    "My wall switches and outlets at home (all 24 of them) are 52 yrs old and not one of them have gone bad. I have a ceiling fan thats 29 yrs old and again she's running like the first day up. Well, what I'm getting at is obvious."

    The devices you mention are simple mechanical designs. Wall switches and outlets have no moving parts, and the fan is a very simple set of coils through which the electric current passes.

    The Prius is far more complex. It is not just the quality of the parts that makes for longevity, it is how many parts have to work together. The Prius is even more complex than other (already complex) modern cars. Complexity means more problems down the line.
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 44,615
    Do you guys see dealerships actually *repairing* these cars, or rather just swapping out large modules after a standardized diagnostic? If the latter, this could get very expensive for Toyota should they find say an 5-8% failure rate on some major componentry. I only have one anecdote about this so far--my friend's Prius died and they replaced (my friend says) a "controller and some other parts" and (my friend says) the warranty charge (which he peeked at) was something like $5,000.

    I dunno, just a yarn over a beer but it got me thinking.

    MODERATOR

  • larsblarsb Posts: 8,204
    whole battery system. The batteries are modular and can be replaced without replacing the whole system. I don't know the diags they would do to determine WHICH modules are problematic, but I'd bet they have a diag for that....
  • A direct mechanical connection (stick-shift) provides the best efficiency.

    - You pointed out manual shifting is a pain, and automatic wastes energy, but VW has a solution called Direct Shift Gearing (DSG). It operates similar to an automatic, but has no torque converter, and provides 6 gears for optimum engine usage.

    - The Prius planetary gear is no more complex than an automatic planetary gear. In fact...it's simpler. No clutches. If a mechanic can fix an automatic, he can fix a prius transmission.

    .

    "Select instead a 25hp (1800 rpm base speed )3-phase induction motor with rotor balanced for 12,000 rpm and a 30 second rating @ 75hp to be coupled into the trans axle with a 10:1 ratio."

    This concept sounds like a supreme waste of electricity/energy. I see no benefit to using such a contraption.
  • robertsmxrobertsmx Posts: 5,525
    Actually, Honda has been testing its own 6-speed "torque-converterless" automatic transmission. Let us hope the next HCH is the car that gets it. The transmission is configurable to have up to 8 speed. BTW, this would be an AAD transmission (Antonov).
  • alcanalcan Posts: 2,550
    Ford and GM are also currently developing a torque converterless 6 speed automatic trans as a joint venture.
  • toyolla2toyolla2 Posts: 158
    Electrictroy takes issue with a statement from my previous postings :

    "Select instead a 25hp (1800 rpm base speed )3-phase induction motor with rotor balanced for 12,000 rpm and a 30 second rating @ 75hp to be coupled into the trans axle with a 10:1 ratio."

    The statement of 1800 rpm base speed was included only to give readers a handle on the motor frame size I am referring to. I mentioned 1800rpm as it is a popular size in industrial machines. This gives a 256T frame weighing 200lbs. We can double the speed of this motor by rewinding the stator from 2 polepairs/phase to one polepair/phase. Since we now use all the copper and iron circuits twice as often it's allowable to say that we have also doubled the power of this motor to 50hp.
    But this is at nominal 60Hz. If we shift the frequency up to 100Hz the motor now has the capability of 83Hp at 6000 rpm corresponding to a road speed of something exceeding 40 mph. Increasing the frequency again to 200Hz will yield the 12,000rpm I wrote of earlier. This is a 2:1 constant power ratio which may be relevant or not depending on whose math you look at.

     Perhaps some people have misgivings about a 200lb motor, well the use of aluminum frames and end bells could knock this down by 60lbs. Remember these speculations have been applied to a motor which was expected to perform 24/7 working. No road vehicle has to meet that severe duty cycle. The motor being protected within the vehicle, cast iron durability is not required nor the weight penalty that comes with it.

    The industrial motor is also expected to provide continuous maximum power in an ambient temperature of 40 degrees C. Liquid cooling should handle the thermal management requirements but generally at 60mph the motor will be called upon to deliver less than 10Hp most of the time.
    This fact suggests that overcurrent during acceleration of 300 % may be admissible. If most acceleration ramps are less than 30 seconds the thermal time constant of the motor may be able to absorb the heating losses of these relatively occasional events. Why would we want this ? Well as it stands now we don't get 83Hp until 40 mph. Even a Toyota Echo will get 108Hp at this speed with its torque of 105lbs-ft. Our induction motor will only push out nominally 80lbs-ft at full load current, a lot less. But the application of 300% overcurrent could yield 200lbs-ft from zero to 12 mph and then gradually tail off to 80lbs-ft at 40mph since the 83Hp from the ICE would be the limiting factor. However the initial 200lbs-ft would fire the vehicle off the mark wouldn't you say ?

    It should be noted -
    Most vehicles at 40mph will have moved to 2nd gear
    including the Echo so its comparitive torque will be halved to 52.5lbs compared to 80lbs-ft of the induction motor which stays in its same fixed gear. You can see it's no contest.

    Hi Electrictroy,
     You wrote :

     "I see no benefit to using such a contraption."

    Have I changed your mind ?
     T2
  • No. I still see that you're wasting electrical energy with your engine---motor---wheel coupling. IMHO it is more efficient to just use the standard engine---gear---wheel coupling.
  • toyolla2toyolla2 Posts: 158
    electrictroy - I originally thought you were critiquing just the induction motor/gearbox part of the SHEV but it now appears you have expanded the argument to include the the ICE/generator portion.
     So I am taking the statement "your engine---motor---wheel coupling"
    more accurately to mean "your engine---generator---motor---wheel coupling"

     Since it was you that made that block statement in the previous post, I think it is concomitant that you provide us with an approx breakdown of the losses you expect in the two systems ? All I'm asking is for your guesstimation of what %age losses in what components exist within the system paths of both systems. Show me where the extra losses are.
     T2
  • First off, the burden of proof lies on the *inventor*. That would be you. Prove that your system is more efficient.

    .

    Second, you want to create a system like this:
    engine---generator---motor---wheels

    to replace the standard automatic or manual transmission. You are losing ~10% in the generator to electricity to motor conversion due to resistance losses.

    .

    The way cars are now:
    engine---auto/stick-shift transmission--wheels

    with the direct mechanical connection results in little energy loss.

    Troy
  • toyolla2toyolla2 Posts: 158
    Electrictroy,
             I agree with you that the two electrical conversions that define a SHEV will sustain total losses of around 10%. Even with the best design I doubt if any motor or generator will exceed 95% efficiency in its electrodynamic performance at the power levels being considered.

     Leaving that aside, you then make a qualitive statement to the effect that the direct mechanical connection (of a conventional M/T ) results in little energy loss.
     Hmm... I wonder what that little energy loss might be.
      I would be very interested to know what numerical value you would place on the %age loss through a M/T.

     In the meantime here is something to consider:-

    Spur gear to spur gear efficiency were both gears to have the same number of teeth is 95%. When the tooth ratio goes to 2:1 the transfer efficiency drops to 93%.

     This was an actual finding by the Eaton Corporation which built an EV with a two speed gearbox back in the early eighties as part of a DOE contract.

    Lets say that in a FWD M/T there are two of these gear interfaces including the final to the differential. A 5-speed M/T will also have losses of the other four meshed gears churning in the oil. Oil serving its secondary purpose of carrying away the heat generated by the sliding action of the gear teeth. Two gear interfaces means a total loss of 10%. But that's heaps better than a RWD.

    In a RWD M/T the second gear interface is a hypoid gear on the rear differential. Turning power through 90 degrees is very lossy. Hypoids are probably no more than 80% efficient. But the fact that manufacturers specify a special hypoid oil that won't overheat should give you a clue that it isn't business as usual back there.
    This efficiency issue is a good reason to avoid RWD platforms altogether.

    Leaving the RWD issue behind then the two systems are neck-a-neck at this point.

    However the SHEV does have one gear interface in the 10:1 step down. Which is another 5% loss the M/T doesn't have. Question is, does the SHEV have any mitigating conditions to counter this deficit, and I believe it does.

     It is the ability to use a two cylinder engine
    against a four or six cylinder.

    This should reduce friction budget quite a lot compared to a four or six cylinder engine, and now I am the one using a qualitive statement. I have no sources for stating this it just seems intuitive to me. There are just less moving parts to cause friction.

       Thus a two cylinder engine, that would be impractical to use with a M/T in a passenger vehicle otherwise, is able to become a viable candidate with electrodynamic conversion.

    That's my response ET.

    Have you noticed how .... ?
      ...people that favor a particular platform are always looking for the V6 availability (Cavalier and Corolla owners) Yeah, you know who you are.

      ...people who are V8 advocates out there describe a V6 engine as having a shortage of extra cylinders !

      ... Dennis Miller can bank on a cheap laugh when he states " The (PRIUS) would have to have a V8 to get me in one ".

     Remnants of 20th century thinking in a 21st century world.
     
      With the pure mechanical route we cling to now, of course cars become easier to drive the more cylinders the engine has. Now tell us something we don't know.

    As I have stated before an anachronism in automobiles is that while people have a penchant for horsepower in fact they drive torque. No one drives downtown @4000 rpm and only few drive more than 4000rpm on the hiway for that matter. Unless they are looking to find a police officer they didn't need.

     But most engines today need to hit 6300rpm or more, sometimes much more, to reach max horsepower. Most people change gear around 4000rpm so the horsepower envelope of the vehicles engine map is rarely tested. But the torque envelope is tested nearly every time we drive. Who hasn't put the pedal to the metal one or two times a week ?

    And that highlights one of the differences between the two systems. Maximum accelerator pedal depression in a M/T is a demand for instant max torque. In a SHEV (above base speed) maximum accelerator pedal depression is a demand for instant max power. For this reason an 80Hp ICE would rival a 160 Hp ICE in a M/T.
    T2
  • Interesting post you wrote about efficiency of different gear setups.
    Do you happen to know how efficient chain connection to gears is (as in bicycles)? I remember an offhand remark by someone once that the old chain drives on cars was the most efficient method for transferring power...I was always curious whether that was true or not. TIA
  • "Spur gear to spur gear efficiency were both gears to have the same number of teeth is 95%. When the tooth ratio goes to 2:1 the transfer efficiency drops to 93%."

    Interesting. That's almost as low as the 90% generator--->electric---> motor conversion.

    Perhaps your idea is "better" in terms of improving engine-to-wheel efficient? Do you know of any company that has tried the pure electric transmission?

    Troy
  • 37453745 Posts: 152
    I'm also interested in the efficiency of chain drive because many transverse engines are coupled to the transmission by means of a chain. GM in particular uses it on all of its front drive vehicles.
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 44,615
    I can tell you from motorcycle experience that chain drive is more efficient that drive shafts for power transfer to the rear wheel, and more efficient than direct gearing for camshaft/crankshaft synchronization. But I don't know how this translates to automotive uses.

    MODERATOR

  • Similar to a chain is the "belt drive" used in CVT cars. Any efficiency numbers on those?
  • 37453745 Posts: 152
    Thanks for that. Very interesting. Seems as if chain drive is pretty efficient compared to other methods.
  • toyolla2toyolla2 Posts: 158
    The constructive responses are appreciated, no one person can ever monopolize all the pieces necessary to put this jigsaw together.

     

      Following up on those links it became apparent that there were two major differences :

     

         Firstly the more favorable 1 : 1 ratios were under consideration.

      The induction motor on a SHEV needs a 10 : 1 ratio. This brings the implication that since the drive sprocket would need to have a 4" dia. to be efficient that would force the driven sprocket to be around 40" dia. !! (assuming a single stage step down) Clearly a spur gear system will scale down in size better since it doesn't have to accomodate the comparatively large chain rollers.

     

         Secondly the sprocket speeds of 200 revs/min under consideration are also quite removed from the 200 revs/sec encountered with the induction motor in the SHEV. In this environment the chain speed with a 12" circumference drive sprocket would be around 200'/sec.

    Of course as we know a motorcycle chain doesn't go anywhere near this velocity because primary gear reduction has already been accomplished inside its transmission.

      

    But applying this to the SHEV which is trying for the more efficient single stage reduction : -

     

    The ramification being that centrifugal forces proportional to the square of the chain velocity will end up at least 60 times 60 larger than those experienced in the bicycle application. This may promote a wear anomaly which may have not been significant before in that research carried out earlier at a mere 200 revs/min. Inertial losses in flexing the chain around the sprockets will go up 3600 times. That prediction could knock the 96.8% efficiency figure out of the ball park. Anyway the 40" driven sprocket is also a showstopper. Reducing the drive and driven sprockets is a research project in itself but who knows how far this could be done. GM decided in their wisdom to use a single reduction from the induction motor shaft to the differential shaft and I am pleased to leave it at that for now.

     

    But there is another solution which I did some work on in 1985 and which was similarly later proposed by Aeronvironment, the contractor used by GM, to produce the original "Show Car" the Impact. GM renamed it EV1. The solution in the original vehicle was to have individual induction motors for each of the front wheels, as some of you may recall. Well I do, still having a copy of the 1990 video they made about it. They were able to do this despite the limited distance between the front wheels by building the single stage planetary gear box of 10.75 ratio into the end bell of each motor.

     

     The internal tooth ring gear being rigidly fixed to the end bell as you would expect.

     One advantage of the planetary is that there is no side force on the bearings (load overhang) that you would get using a simple take off gear or a belt or chain drive. In fact you may be able to get away with just one bearing on the rotor. The other end of the rotor shaft would just have the sun gear on it. This gear would sit surrounded by three planet gears and be supported in place by them. It seems reasonable that once rotation begins that symmetrical gear tooth forces will ensure this gear will be forced to ride exactly in the centre. I don't know if they actually did this. At 12,000 rpm you want as few components involved as possible that can affect reliability.

     

    The third part of this system is the planetary carrier on which the bearings for the planet gears are mounted. A flange on the output shaft connects to the carrier and transfers the power outside the motor to the CV joints which is now plain vanilla engineering. Maybe GM was concerned for the longevity of these components plus they needed two motor/invertor sets which was why this idea was dropped.

     As a twin motor design of course it would have given automatic traction control and perhaps steering assist by shifting the torque ratio away from 1 : 1.

     

     And something the SHEV and HSD can do, but not the IMA, is electronic reverse. For mechanics who may not be familiar with the properties of the 3-phase ac motor, the following may be of interest. The ac induction motor can run with equal efficiency in either direction. The industrial motor is generally found to be reversed by using two switching contactors. One contactor connects for forward motion. The other contactor is hardwired such that two of the phases running to the motor are crossed over. When this contactor is pulled in we say that the phase rotation is now reversed, thus causing the motor to run backwards. But this is doing it the hard way.

     

     When you have the ac being generated by solid state equipment usually known as the 3-phase invertor, you have the three phases being each electronically synthesised to be equally spaced apart in a fixed order. But it requires only a change in the software to cause those signals to be issued in the reverse order. There are no contactors to be switched, the motor will just start running backwards.

     

      There has been some activity in the HAH board lately, surrounding the Dec 3rd release of this model. It bugs me that there are steep price premiums on these vehicles even before MSRP add-ons. Someone computed that use of an aluminum hood and run flat tires (no spare) (being some of the ameliorating measures taken to offset hybrid equipment) indicated actual weight of hybridism to be 300lbs. Don't these cretins learn anything ? Of course a 16Hp machine @ 840rpm is heavy. As a comparison, on the EV1 the whole 137Hp transaxle complete with induction motor weighed in at 68kg (150lb?) How come ? Well, its base speed was 6600rpm NOT 840rpm. I understand that they wish to retain the top road speed of 131 mph which would be compromised if the IMA was put anywhere else but on the crankshaft side of the gearbox.

     T2
  • xcelxcel Posts: 1,025
    Hi Toyolla2:

     

    ___Great post. Inside info on the EV-1 from almost 15 years ago! Did you have anything to do with any of the work on the “GM Precept” CI-DI-ICE/Hybrid as well? I would love to know the details of that one …

     

    ___Thanks

     

    ___Wayne R. Gerdes
  • Thanks for the response, that was a lot of typing and its appreciated.

     

    "The second factor that affected efficiency was tension in the chain. The higher the chain tension, Spicer says, the higher the efficiency score. "This is actually not in the direction you'd expect, based simply on friction," he says. "It's not clear to us at this time why this occurs."

      This is a quote from one of the links..do you have any theories on it? Also they downplay the importance of lubricants on the chain. They say its only important as a displacement of dirt. How can something with so many little parts not have its performance improved by being lubricated? It also seems a chain would wear out very quickly without lubricant, gears certainly do.

    Sorry for being off your topic, I know this isn't the intention of your discussion but you peaked my curiosity on this stuff. TIA
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