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Hybrid Power Swap

GM and partners vow to beat Toyota with mechanical engineering.

By Peter Fairley

Friday, September 01, 2006
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GM, DaimlerChrysler and BMW are counting on their dual-mode hybrid transmissions (shown here) to catch up with Toyota. (Credit: GM)
When it comes to hybrid vehicles, electronics and batteries tend to get the most attention. But it is elegant mechanical engineering that established Toyota as the market leader in hybrids. Now General Motors, DaimlerChrysler, and BMW are applying mechanical engineering to catch up. The three manufacturers have joined forces to develop transmission technology that could beat Toyota's system--at least on the highway.

Toyota's patents for their hybrid vehicle focus on the control systems and sophisticated transmission used to shift and share power among the engine, electric motors, and wheels. "There's a lot of mechanics in the system," says David Hermance, executive engineer for environmental engineering at Toyota's Gardena, CA, Technical Center. "Even if you make significant improvements on the electrical side, if you don't do a good job on the mechanical side you don't get as much efficiency, and you're looking to improve efficiency every place you can."

The first hybrids from GM and DaimlerChrysler were so-called "light hybrids" providing a relatively small efficiency boost. (BMW has yet to release a hybrid.)

Toyota's hybrid system is notably different because of its power-splitting transmission. To date, competitors such as Honda have integrated electric power by adding motors to more-conventional transmissions. As a result, a hybrid's engine must be operating for the vehicle to move. In contrast, Toyota's transmission enables hybrids such as the Prius sedan and the Highlander SUV to start in all-electric mode, leaving the engine off during the low-speed, high-torque regime where mechanical power from the engine is least efficient. The engine comes on only when the driver requests more power than the electric motors can provide or to recharge the vehicle's battery.

Toyota's transmission also employs its electric-vehicle (EV) mode to drive its hybrids in reverse, so there's no need to build in dedicated reverse gears found in conventional transmissions.

Some 500 engineers at GM, DaimlerChrysler, and BMW are developing a new transmission system that delivers EV-mode operation just like Toyota. The transmission will add one more trick: the system can also take the electric side of the drivetrain out of the loop and run in engine-only mode. Their two-mode hybrid transmission, patented in 1999 by GM and currently used in its hybrid buses, swaps out the motors with a set of fixed gears, locking the engine to the driveshaft. The electric motors help make the switch seamless by synchronizing the speed of the two sets of gears, but once the shift is done the motors are out of the picture. "The motors do all the fine-tuning and the clutches just cog over. That's the big revolution with the two-mode," says Tim Grewe, GM's chief engineer for the two-mode hybrid power train.

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Comments
  • Run in dual mode
    I would hope this tranny can run in dual op mode so as to use the electric motor (AC induction?) to act as a generator to recharge the batteries. Or they'll need to add additional infrastructure in order to use the ICE engine to charge the (probably very limited KW loaded) batteries. Add a plug-in option to these vehicles? Why ever would we do that?
    Rate this comment: 12345

    anonymole
    09/01/2006
    Posts:1
    Avg Rating:
    4/5
    • Re: Run in dual mode
      This GM patent, as described on www.hybridcenter.org appears not as good a concept as the Toyota mechanical transmission, and you point out that locking out the motor/generator locks out just that: the big generator.  How could this be an advantage?
         This looks like GM wants to patent at least something in the hybrid area, for better or worse.  Their now destroyed EV1 cars had far superior engineering, even back in 1995.
         Their latest effort to "show us their superiority", the new fuel cell car, has this major problem:  just where do you fuel up?  This looks an awful like, "See, we can develop new technology, but we're sorry you can't fuel it up.  So would you please go back to buying SUVs and Hummers?"
      Rate this comment: 12345

      marvkausch
      09/10/2006
      Posts:1
      Avg Rating:
      4/5
      • Re: Run in dual mode
        They lock out the "big generators" when cruising down the highway (we have many long highways in the US).  Hybrid cars run the "generators" during regenerative BREAKING.  For (hopefully) obvious reason using regenerative breaking while driving down the freeway is a bad idea.  Try driving your car down the freeway at 60mph with your foot pressed firmly on the breaks.  The motors engage while slowing down and recharge the battery when you want to decrease the kinetic energy of your vehicle not when you want to maintain it (they are converting kinetic energy into electrical energy).
        Rate this comment: 12345

        zifos
        04/10/2007
        Posts:11
        Avg Rating:
        4/5
        • Re: Run in dual mode
          My Prius runs the generator and charges the battery while driving down the highway, with no ill effects. Basically the generator runs under light loads over 37 mph when the electric motor is not being used, i.e. accelerating. Regenerative braking is only built into the hybrids to recover energy that would normally be dissipated through heat. (Very nice benefit of brake pad life being extended. A lot.) The regenerative braking alone will not keep the batteries charged.  If the car did not run the generator to keep the charge at 50-80% the life of the battery would be cut short.  Unless there is a big change in batteries, deep cycle capability and faster charge rates, or capacitors, the vehicles will have to continue to run their generators, while cruising, to charge the batteries. 
            Reading this article leads me to believe GM is looking more towards developing a transmission that they can use with their existing engine and vehicle inventory, and are not interested in actual change. 
            “By swapping out the motors under high-power operation, the alliance partners get by with smaller motors”
            This seems to be more for performance boosting than anything else.  Instead of using a big electric motor with a small gas motor, they will be using small electric motors with large gas motors. 
            Does anyone else find this a bit backwards?

          Rate this comment: 12345

          timcen
          05/11/2007
          Posts:1
          • Re: Run in dual mode
            I think you missed the point of the new system GM designed.  They don't use the electric motors while cruising, only the ICE, so therefore they don't need to continuously charge the batteries.  The toyota hybrid uses both the electric motors all the time so yes, it has to charge the batteries while cruising.  The idea is to use the motors when they are most efficient (low rpm, high torque) and use the ICE when it is most efficient (cruising). 
            Rate this comment: 12345

            zifos
            10/11/2007
            Posts:11
            Avg Rating:
            4/5
  • Micro-Projectors for your laptop Anyone?
    The number of possibly applications for a cheap (lower than $50) small size (wallet or cell phone size) projector technology are impressive, like projectors for cell phones, PDAs, in store advertising devices, laptops, not to mention creating a new type of portable TV.  Of course, the premise here is that nothing more than a three color laser pen and a small set of optics and driver electronics will be needed to create a (MLD) projector.
    However, the development time for high volume production will be length (3+ years).  Regardless, I see the development and commercializing of these Micro-Laser-Displays (MLDs) as another promising result of the research in the MEMs Field.
         Brian Glassman
    Innovation Management
    Commercialization of technology
    Rate this comment: 12345

    briang1621
    09/01/2006
    Posts:124
    Avg Rating:
    4/5
  • Rethink cars
    I am waiting to play with a SMART. I am a tall 6ft4 American and classic small cars don't work for me. My problem is headroom.

    The SMART as I understand it has the space and headroom of an S Class for the two seats that it does have.

    That is what I need, then I can lose the rest of the car.

    I would also like to see NEV's taken up to 45mph so they can become second cars and pickups running on eletric only. I would buy one today, but they can't touch the 45mph roads to go grocery shopping.
    Rate this comment: 12345

    Braxton
    09/07/2006
    Posts:4
  • [no subject]
    unfortunately, if toyota doesnt get with the program and plan on incorporating a variety of different fuel options, people know toyota as the hybrid company now and think only of priuses when the word hybrid comes up. so they'll probably be able to survive without having to adapt to market fuel options and their popularity on just brand name alone. hopefully and i think probably, the people at toyota are smart enough to get involved in other options like having toyota truck parts
    Rate this comment: 12345

    MickeyFouse
    04/22/2009
    Posts:47
    Avg Rating:
    1/5
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