Here's another one dated May 19, 1997 -- Vehicle manufacturers have long sought an electronic method to control engine intake and exhaust valves and meet market demands for greater engine performance and improved fuel economy. Engineers at Southwest Research Institute (SwRI) are currently testing a novel electromagnetic valve actuator (EVA) system that provides these benefits.
"Preliminary test results show that the EVA variable valve timing system gives a ten percent increase in engine efficiency and a substantial improvement in power at low speeds," says Principal Investigator Daniel Podnar, a senior research engineer in SwRI's Engine and Vehicle Research Division.
In conventional combustion engines, a mechanically driven camshaft is used to operate the valves with fixed values for valve lift, timing, and duration. This system does not allow any operational variation to maintain peak engine efficiency as road or driving conditions change. Most cam-operated car valves are tuned to operate at a specific range of engine speeds. These speeds are typically when the vehicle is running between 40 and 55 mph, and there are severe penalties in combustion efficiency and fuel economy at other speeds or at partial load.
The EVA system under evaluation is one of a series of electromagnetic valves patented by Aura Systems of El Segundo, California. The valve system is being tested in a two-cylinder, 18-horsepower, Kohler Command utility engine converted by SwRI to operate on natural gas. The project is part of a multi-year program sponsored by the Defense Advanced Research Projects Agency (DARPA) to develop efficient hybrid vehicles using natural gas auxiliary power units for military and commercial applications.
"Using the EVA system provides an engineer with an infinite number of camshaft profiles at the touch of a control," says Edward Bass, manager of Advanced Vehicle Technology and project manager. "This capability allows us to tune and test the benefits of variable valve timing under a variety of operating conditions. For example, Miller cycle operation, where the intake valve is closed earlier or later than in conventional engines for more efficient throttleless operation, is one technique currently being evaluated."
The EVA system places one actuator at each valve site. Two opposing spring coils are also fitted at each site providing the primary force to open and close the valves, and to reduce power consumption and increase reliability. The spring forces are supplemented by electromagnetic force from the EVA coils. The intake and exhaust valves are independently computer-controlled and timed, making it possible to fine-tune air-fuel and exhaust flows to engine needs in a way no camshaft can.
"Use of the EVA system eliminates the need for a lot of parts that are subject to wear such as the camshaft, rocker assembly, pulley and timing belt," adds Bass. "Hybrid vehicles represent an ideal use for this kind of valve because of the high voltage available that increases the efficiency of the EVA system. There are, however, numerous applications for electronic valve actuation systems within the vehicle field, and we are looking forward to applying this technology to other combustion engines, such as heavy-duty engines."
SwRI has a long history of research in designing and developing advanced engine and vehicle electronic control systems and a wealth of experience in combustion analysis and engine design.
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So it looks like there is research being done. Sounds like it's just a matter of time before perhaps we see some of these technologies being used. It really wouldn't shock me.. since so many aspects of the engine running are computer controlled already. It could be made to be reliable. It all sounds quite interesting, actually.
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