The Piezo Unit Injector System for Volkswagen Diesel Engines

Authors

Dipl.-Ing. D. Jovovic, Dr. M. Kronberger, Dipl.-Ing. R. Pirkl, Dr.-Ing. P. Voigt, Siemens VDO Automotive AG, Regensburg

Year

2005

Print Info

Fortschritt-Berichte VDI, Reihe 12, Nr. 595

Summary

In meeting the progressively lowering emission limits for passenger car diesel engines there is a real danger. The effort to develop and build these engines may not be balanced by the increase of their overall performance with respect to the gasoline engines. The diesel injection system is still one of the most important sources of progress in this matter. On the other hand it is a major cost factor of the engine. With the newly developed Piezo-actuated Unit Injector Siemens VDO and Volkswagen enrich the competition between the OEM’s diesel engines and, in consequence, between the system concepts Unit Injector and Common Rail. The paper describes three major evolution steps of this injection system starting with the initial concept until the specification and cost targets were met. Decisive for meeting the targets were detailed analyses of the real needs of the engine with respect to injection pressure level, metering accuracy and rate shaping. The aim was to meet the EU4 requirements for vehicles including the upper end of the Volkswagen Passat class without the mandatory need of a particulate trap. The utilisation of the Piezo elements as actuators and sensors for closed loop control circuits lead to the required metering precision under all engine operating conditions and over lifetime. The Piezo Unit Injector is produced in a factory in Germany which was recently built by Volkswagen and Siemens VDO. The electronic control unit comes from Siemens VDO. During the evolution of this injection system a considerable improvement potential was discovered. Among others there is the further increase of efficiency and peak pressure level as well as an improved Piezo part lift ability which the two partner companies want to look after soon. New driving forces for the Piezo technology will be originated by the de-mands of the homogenous diesel combustion.

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