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Piezo Injector With Direct Drive

Published Wed, 2008-04-30 14:06

Piezo technology makes diesel engines efficient, clean and quiet. At the 29th Vienna International Engine Symposium, the Powertrain Division of Continental will be presenting a new piezo injector with direct drive and closed-loop needle control, opening the way for engine developers to further reduce consumption and emissions.

Piezo injectors have been installed as standard components in vehicles since the beginning of the millennium. Instead of an electromagnet, a piezo actuator, consisting of a stack of over 300 wafer-thin ceramic platelets, controls the nozzle needle in the injector. When a switching voltage is applied, the piezo actuator expands, opening the injection nozzle within milliseconds. These extremely rapid response times allow the fuel to be apportioned precisely and reproducibly between up to seven injections per combustion cycle. This permits optimized combustion of the fuel-air mixture, so that consumption is lowered, pollutant emissions are reduced and more ef-fective regeneration of the particulate filter is achieved through selective temperature control.

While continuing to develop the current generation of injectors, Continental is relying on a new design which, from the engine manufacturer's perspective, offers numerous advantages for par-ticularly demanding diesel applications. The direct drive allows the nozzle needle to be actuated even more rapidly and accurately without hydraulic transmission. In addition, for the first time, this can give flexibility to the injection rate pattern for individual injections, thus ideally comple-menting the already well-established multiple injection systems in today's common-rail diesel engines. With this design, the piezo actuator simultaneously acts as a sensor by reporting the precise position of the nozzle needle to the electronic control unit, producing the first self-contained fuel mass control system. The smallest instances of variations or drift in the course of a vehicle's life can be detected and automatically corrected within the system. It is also possible, with the new injector, to increase the injection pressure to over 2000 bar.


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