| Continental has developed a direct-acting piezo injector with closed-loop needle control. It hopes OEMs will use the technology in diesel cars to meet 2014’s Euro 6 emissions standards, but its first series application will be in a light commercial vehicle next year.
It is not the only supplier with direct actuation of the needle, which improves accuracy compared to injectors with hydraulic transmission. Delphi, Bosch and Denso also have this technology.
But Continental uses the piezo actuator as a sensor as well, reporting the precise position of the nozzle needle to the ECU. The firm said it is the first self-contained fuel mass control system.
“The smallest variations or drift can be detected and automatically corrected within the system. It is also possible to increase the injection pressure to over 2,000bar,” said Continental.
The injectors will be more expensive, but Continental’s senior vice-president for powertrain, Wendelin Klügl, said: “If you consider the overall cost of the engine, the injector could save money by simplifying other emissions-related components such as sensors and control algorithms. Even heavier vehicles will be able to meet Euro 6 emissions without NOx aftertreatment.”
Diesel systems design chief Dr Andreas Pfeifer said: “Trials with an engine optimised for Euro 6 are achieving almost a 3 per cent reduction in consumption. And we have reduced particulate and NOx emissions by 35 per cent.”
Piezo injectors use a stack of 300 or so wafer-thin ceramic platelets to control the nozzle needle, instead of an electromagnet. A switching voltage makes the piezo actuator expand, opening the nozzle more quickly.
This lets engineers dose the fuel more precisely and more frequently in each combustion cycle. The fuel-air mix burns better, so emissions and fuel use are lower and regeneration of the particulate filter is better controlled.
© Automotive Engineer, 2008 |
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