28 December 2004
Volkswagen Mechatronic—a Volkswagen-Siemens joint venture—has launched the industry’s first unit injector with piezo actuators. The new piezo-electric unit injection system is characterized by a more precise and flexible multi-point fuel injection control, enabled by replacing the conventional solenoid valves by a piezo actuator, said Volkswagen Mechatronic.
Piezo-electric crystals provide motion when given a pulse of electrical energy. Piezo-electric crystals are arranged in wafer form, and when several wafers are stacked and energized, they are capable of producing displacements of a few hundredths of a millimeter that are sufficient for precise valve needle opening and closing in high-pressure injection systems. Piezo actuators have response times on the order of just a few tenths of a millisecond.
The piezo-electric technology was commercialized in common rail injection systems by Siemens in September 2000. But unit injectors—a technology featured in several Volkswagen engines since 1998—still relied on solenoid-actuated valves. Unit injectors, due to the absence of long, high pressure fuel lines, allow for higher pressures (up to 2,000 bar) than other types of injection systems, including the common rail.
Source: Siemens VDO | all4engineers