Service Communautaire d'Information sur la Recherche et le Développement - CORDIS

Design and manufacturing of FIS capable of up to five injections

The CRIP-MI is a common rail based fuel injection system for passenger cars. In comparison with the state of the art injectors the MI (multi injection) injector is capable of up to five injections per cycle with a minimum dwell time of 150µs. Furthermore the injector features an almost linear characteristic injection map quantity versus energizing time. This feature not only permits to adopt the quantity of the pre injections more freely but also the characteristic map can be easier mathematical described and therefore enhanced controlling strategies used to larger extend.

Examples therefore would be the "Injector Quantity Adjustment" to compensate the sample-to-sample production tolerances or the "Zero Fuel Calibration" for a accurate control of the pilot injection and compensation of the drift over life time. Another result clearly showed the potential of such an enhanced temporal control strategy to reduce the emissions. The funding for this project offered just a small fraction of the total development costs of this MI technology. The focus of this project was more research orientated: development and the special needs of a small engine.

The hydraulic stability is essential for such a fuel injection system: The deviation of the quantity for small changes of the control parameters or the boundary conditions (e.g. small deviations of the dwell time, energising time or viscosity of the fluid) must not be high - otherwise, big deviations in terms of quantity in a series application with different injectors under real life conditions would occur. As a result of the poor control of the injected quantities no clean and efficient combustion could be achieved.

The hydraulic stability is the reason why the actual Common Rail systems of 1st generation are limited to a dwell time of about 1800µs and the 2nd generation of about 900µs. This goal of reproducible injected quantities and a linear injection map quantity vs. energising time was achieved by:

- First, introducing an overlift for the armature for a more defined movement of the armature and, hence, a better control of the pull-in force of the solenoid.
- Second, increased nozzle needle lift for a ballistic behaviour and for a linear injection map for medium and big quantities as well as a reduced needle throttling at full load.
- Third, the hydraulic as well as the solenoid behaviour were adjusted for a linear injection map for small and medium quantities.

The design phase of this injector is closed and prototypes are available.

Informations connexes

Reported by

Robert Bosch GmbH
Wernerstrasse 51
70469 Stuttgart
See on map