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March 2, 2010
New Technologies
Automatic Transmissions—Not What They Used to Be
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Toroidal transmissions may very well be the
way of the future.
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Unless you are in the business of restoring old cars, you can say goodbye to Powerglides, C-4s, FMXs, Turbo 350 and 400s, and the likes. There is barely any car or light truck left in the industry that is available with a three-speed automatic transmission and before long, even the four-speed trannies will be history. Right now, we are looking at five, six, seven, and even eight speed automatic gearboxes and more and more automakers are adopting the CVT system for better fuel economy. And that’s not it!
As these words are being written, one of the most advanced “regular” automatic transmissions has to be ZF’s 8-speed hybrid transmission. Thanks to advanced electronics and software controls, this gearbox outperforms most drivers with manual transmissions not only in performance, but also in fuel economy—when equipped with the optional start-stop function (which shuts the engine off when the vehicle is stopped at a red traffic light), this transmission, according to ZF, is 11% more economical than its predecessor. According to Dr. Michael Paul, executive president, Technology at ZF, around half of the potential was achieved by reducing the activation energy of the transmission and by moving the operating point of the engine… all thanks to electronic controls! The 8-speed hybrid transmission by ZF communicates with other subsystems in the vehicle via a multitude of interfaces. “The transmission in a hybrid vehicle has up to 400 signal interfaces to other components,” says Dr. Paul.
Say hello to the toroidal transmission
Recently, many manufacturers opted for the new Dual-Clutch transmission, a really new way of making gears shift. But now, there is something even newer coming up. You probably heard about toroidal transmissions in light machinery or in Formula One. Expect them sooner or later in regular passenger cars. For now, they seem headed towards medium-duty trucks as it was announced recently. As a matter of fact, British-based Torotrak has partnered with Allison Transmissions to develop a medium-duty truck transmission that will feature Torotrak’s full-toroidal transmission technology. The system works with a full-toroidal variator that consists of a set of discs and rollers instead of a system of gears. Consequently, it makes the infinitely variable transmission torque-controlled instead of ratio-controlled. According to Torotrak, this technology offers improved fuel-saving, emissions, and refinement benefits. Add to that an improved riding experience. Commercial vehicles will surely be taking advantage of the Torotrak system but already, there are plans to include it to passenger cars and light trucks.
For instance, BMW has included the Torotrak technology in its ActiveHybrid concept car and Mercedes-Benz has also unveiled it in its BlueHybrid concept vehicle too. Who’s next?
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Éric Descarries