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In the diesel field, innovative technology development has been desired for fuel injection system from the points of severe emission reduction to meet increasingly stringent emission regulation year by year respecting environmental protection and product improvement for various customer requirements including fuel consumption improvement. We have been pursuing the ideal fuel injection system which is called “ECD-U2” to meet above expectations. “ECD-U2” is the injection system of highly pressurized fuel with optimum injection timing by using of the injector controlled by high speed response magnetic valve. This system also has the fuel injection pattern controllability in one injection ( injection rate ) as one of the greatest asset. This report focuses on the new injector structure development to achieve desirable injection rate shaping for diesel engine combustion.

This paper describes the Nippondenso in-line pump system designed for U.S. 1991 emissions regulation for medium duty diesel engines. With the combined use of the further improved in-line pump, NB-S and the multi-hole nozzle with a smaller orifice diameter, the required injection pressure of 100 MPa to 120 MPa at the nozzle can be achieved. However, some problems to be resolved exist in the subject fuel injection system: (1) secondary injection, (2) cavitation erosion of injection pipe, (3) higher pressure sealing of fuel, (4) undesirable fuel delivery curve vs. pump speed (called “Trumpet Shape” fuel delivery curve) Thus technical measures to cope with those problems are explained in details.

The dynamic characteristics of a diesel fuel injection system have a remarkable affect on the cyclic fluctuation of engine speed which is called “hunting”. The simulation analysis on these characteristics are discussed in this paper. First, we conducted experiments on frequency response of mechanical governors on the test stand. However, we could not establish good correlation between the experimental results and the calculations using the “linear governor equation” method. We investigated the results in detail, and by using a non-linear governor equation - “Itoh's equation”, we could simulate the dynamic characteristics of the governor quite well. However, after Itoh's equation was used in the “hunting” simulation, we still could not get good correlation between the experimental results and the calculation of “hunting”. Next, we have investigated the inditial response of fuel delivery characteristic.