Fuel injection control device for internal combustion engine.

摘要

Piezoelectric element used in a fuel injection valve is to be improved in its response to expansion and contraction, while the supply of an excess energy to the piezoelectric element is to be controlled. In a fuel injection control device in which an output voltage of the dc-dc converter (1) is applied to a piezoelectric element (PZT) via a choke coil (Lc) and a thyristor (SCR1, a current detection unit (2) is provided between the dc-dc converter and the thyristor. A measured value of the electric charge, as found by integrating a charging current flowing through the current detection unit is compared by a comparator (5) to a command value of electrical charges as found by processing the dc-dc converter output voltage. The results of comparison are supplied to a latch unit (9) so as to be latched at the timing of a peak value of the charging current. A capacitor (Cv is charged and discharged depending on an output of the latch unit, and the terminal voltage across the capacitor and the output voltage of the dc-dc converter are compared to each other for controlling the output voltage of the dc-dc converter.