Abstract: Improving the injection fuel mass accuracy of fuel injector, it is necessary to make the fuel injector perform seat valve opening and closing operation quickly. When the shapes of a fixed core and an anchor are optimized to improve the responsiveness of a magnetic flux, it is necessary to ensure a sufficient fuel path area while preventing adhesion by making the adherence phenomenon rarely occur between an end face of the anchor and an end face of the fixed core. A through hole passes through an anchor forming an armature of an electromagnetic fuel injector from a face of the anchor where the anchor faces a fixed core to a back face where the through hole has a large-diameter portion and a small-diameter portion, and the large-diameter portion is located in an upstream part and is offset to the outer periphery with respect to the small-diameter portion.

Abstract: A method of controlling a fuel injection device that can control a small amount of injection is provided. A fuel injection device for use in an internal combustion engine, includes: a valve body that can open and close a fuel passage, a needle that transfers a force with the valve body, and executes valve opening/closing operation, and an electromagnet that includes a coil and a magnetic core provided as a driver for driving the needle, and a cylindrical nozzle holder disposed on an outer periphery of the magnetic core and the needle, in which a current is supplied to the coil to exert a magnetic attractive force between the magnetic core and the needle to open the valve body.

Abstract: In a fuel injection device, a driving unit structure has a magnetic aperture, in which an inner diameter is gradually enlarged toward the mover side, provided in an inner peripheral surface of the magnetic core. It is possible to reduce magnetic delay time upon valve opening from the supply of the electric current to the coil to the rise of magnetic flux and magnetic delay time upon valve closing from the stoppage of the electric current to the coil to reduction of magnetic flux, by providing a magnetic aperture in the inner peripheral surface of the magnetic core. Thus it is possible to improve the dynamic responsiveness upon valve opening and valve closing.

Abstract: The drive device is configured to, during a time interval between an earlier fuel injection (first fuel injection) and a later fuel injection (second fuel injection), supply an electromagnetic coil with an intermediate current at a voltage with a level of not opening the valve. Further, the drive device sets a voltage application for supplying the intermediate current to initiate before a valve closing in the earlier fuel injection and terminate before half a period of time between a first instant when the valve is closed in the earlier fuel injection and a second instant when a supply of a drive current for opening the valve is initiated in the later fuel injection.