Abstract: A method is provided for determining the point in time of a predetermined open state (e.g., start or stop time of an opening or closing process) of a fuel injector having a coil drive for an internal combustion engine of a motor vehicle. The method includes applying a first voltage pulse to the magnetic coil drive of the fuel injector, detecting a first temporal progression of the current intensity of a current flowing through the coil drive, applying a second voltage pulse to the magnetic coil drive of the fuel injector, detecting a second temporal progression of the current intensity of the current flowing through the coil drive, determining a differential progression based on the first and second temporal progressions of the current intensity, and determining a point in time at which the differential progression exhibits an extremum, which corresponds with the point in time of the predetermined open state.

Abstract: A method for determining a reference current curve for a fuel injector having a magnetic coil drive in an internal combustion engine of a motor vehicle includes: (a) applying a first voltage pulse to the magnetic coil drive to open the fuel injector, (b) applying a holding voltage to the magnetic coil drive to hold the fuel injector open, (c) switching off the holding voltage, (d) waiting for substantially no current to flow through the magnetic coil drive for a predetermined time period that is sufficiently short that the fuel injector remains open, (e) applying a second voltage pulse to the magnetic coil drive, and (f) recording a time-based curve of the current that flows through the magnetic coil drive during the second voltage pulse, which forms the reference current curve. This reference current curve is used for determining a time of a predetermined opening state of the fuel injector.

Abstract: A method for adapting a current profile for a multi-injection process by a fuel injector includes applying to a coil a first excitation profile causing a first multi-injection in which two sub-injection processes are separated such that the fuel injector completely closes in the meantime, determining the closing point of the fuel injector, calculating a minimally possible separation time between the end of the excitation for a first sub-injection process and the beginning of the excitation for a second sub-injection process for a second multi-injection, the fuel injector completely closing between the two sub-injection processes, applying to the coil a second excitation profile leading to the second multi-injection, determining a current intensity rise time during a boost phase of the second sub-injection process, and applying to the coil a third electric excitation profile having a pre-charge phase that pre-magnetizes the coil drive, for each sub-injection process.

Abstract: A method for determining the movement behavior of a fuel injector having a coil drive includes: (a) applying an electrical excitation to a coil of the coil drive, which prompts an opening movement of a valve needle; (b) recording the temporal progression of a first electrical measurement variable of the coil; (c) determining the time when the opening movement ends based on the recorded temporal progression of the first electrical measurement variable; (d) modifying the electrical excitation of the coil such that the valve needle performs a closing movement; (e) recording the temporal progression of a second electrical measurement variable of the coil; and (f) determining the time when the closing movement ends based on the recorded temporal progression of the second electrical measurement variable. One of the two measurement variables is the voltage present at the coil and the other is the intensity of current flowing through the coil.