Crystal Power

摘要

An old dog is learning some hip new tricks. Pierre and Jacque Curie first documented the piezoelectric effect in the 1880s, and the technology has made phonograph needles and guitar-amp pickups work for decades. It's also the secret behind push-button gas-grille igniters, but the technology is hitting a new groove in the noughties.The nutshell basics: Certain crystal, ceramic, and polymer materials produce an electric voltage when compressed-and, conversely, they expand when voltage is applied to them. It's that converse effect that has most influenced automobiledom, since Continental AG first employed it in ultra-precise fuel injectors capable of squirting multiple short bursts of fuel at pressures as high as 30,000 psi in diesels. Piezo injectors generally involve a stack of small, lead zirconate titanate crystal pucks. The expansion that occurs when voltage is applied to this stack pushes a pin out of the injector tip allowing fuel to flow around it in a cone-shaped spray pattern. By contrast, older solenoid-type injectors tended to pull a stopper up into the injector allowing the pressurized fuel to spray straight out of the hole.