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Why electromagnetic
engine valves? Why not a camshaft? … Because a camshaft represents
a fixed mechanical “program” for valve motion. Mechanical variable valve
timing (VVT) offers a range of improvements, depending on the complexity
(and cost) of the system. It is possible to vary the valve lift, duration
from opening time to closing time, and/or the separate phases for opening
and closing of the intake and/or exhaust valves. The most important function
of VVT is to provide for earlier valve opening, preferably with increased
open duration, as the engine runs faster, thus compensating for the effects
of gas flow resistance and flow inertia. Electromagnetic variable valve timing
(EVVT) can do the work of the most complex mechanical VVT system and more:
it can independently change valve opening and closing on individual valves
in a program that changes entirely from one stroke to the next, even "idling"
individual cylinders in a rotating sequence for reduced power with low engine
drag at high RPM. With this electronic flexibility, computer-controlled electromagnetic
valves can perform functions beyond the reach of mechanical VVT:
Hybrids are especially suited to city stop-and-go. With regenerative braking to recover the car’s kinetic energy at each stop, the hybrid approach will be hard to beat, but EVVT can make this approach better. An extreme version of the "hybrid concept" would be to operate the engine at just one optimum speed and power level, then shut the engine down completely while the car continues on stored energy from some combination of batteries and supercapacitors. Extended operation would then call for continuing on-off-on-off operation of the engine and a great deal of energy cycling through the electrical energy storage system (of batteries and/or supercapacitors.) This approach leads to costly electrical energy storage. To unburden that storage system and make it cheaper, one can cause engine power to vary with demand. Going to the extreme in this design direction, one arrives at no energy storage and a conventional non-hybrid vehicle. An optimum system for city driving is expected to lie somewhere between these extremes. Variable valve timing broadens the range of near-optimum engine operation, thus helping the designer rely less on electrical energy storage while still conserving fuel. A vehicle optimized for highway use might thus rely entirely on EVVT with no hybrid electrical system, while a vehicle for city postal delivery might rely heavily on a hybrid electrical system. A Magnesense goal is to help make EVVT systems that are cost-competitive with mechanical VVT and more effective then their mechanical counterparts at conserving fuel, improving performance, and reducing emissions. Another issue is frequent stopping and re-starting of a hybrid engine. Some engines include mechanical compression relief, where a cylinder valve is held open, allowing the cylinder to breathe freely. This unburdens the starter motor while the engine is revved up, or in a pull-start lawnmower, this unburdens the person pulling the starter rope. An engine with EVVT accomplishes compression relief trivially and without extra mechanical devices, since it has full electronic control of the valves. Even with compression relief, however, a conventional engine must reach a certain minimum speed for starting. If engine rotation is too slow, the first compression stroke will stop the engine. EVVT programming can get around this limitation by "programming" the cylinder to compress only a small amount of air and fuel on the first stroke, just enough to kick the engine over with more speed on the next stroke. Techniques like this promise to provide very efficient restarting of hybrid engines and very easy starting of pull-start lawnmowers. Diesel has been touted as ideal for long hauls, since diesels cost less than hybrids and since the regenerative braking of hybrids is unimportant on level highway. Even with greatly improved computer-timed high-pressure diesel fuel injection systems, diesel emissions, diesel smell, and low-sulfur diesel fuels remain stumbling blocks. Car and Driver magazine's Editor-in-Chief Csaba Csere points out technical reasons why diesel engines offer lower RPM and lower horsepower-per-weight than spark ignition, concluding that diesels are an unlikely “solution” for our automotive future. Even without breakthroughs in EVVT/HCCI technology, EVVT can bring spark ignition engines close to diesel mileage while sticking to the U.S. mainstay of low-sulfur regular gas. If HCCI technology gets out of the laboratory, it will require EVVT and the mileage will be unbeatable. Much of the supposed “hybrid advantage” of high mileage has nothing to do with electric/gas hybridization. Hybrids are built with attention to efficiency throughout the design. They are small, light, very well streamlined, and very carefully engineered. We project that efficient non-hybrid autos with excellent engineering, including EVVT, will compete in the marketplace with the much more expensive hybrids and with diesel. How does Magnesense technology make electromagnetic valves better? We improve on dynamic servo control, making valves quieter and longer-lasting. We make them cheaper and more reliable by eliminating motion sensors and wiring while sensing motion indirectly. We have patented methods for making stronger armatures with low magnetic loss and for making springs that are inexpensive, lighter, and more compact, leading to faster valves for higher-revving engines. We know how to make inexpensive fixed-point digital processors do the job of more expensive floating-point hardware. Between our patents and our know-how, we can help a manufacturer bring this technology to life in both small engines and automotive-scale engines. For details on these Magnesense improvements in two contexts, view our sections of Small Engines and Automotive Engines. |
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