A method for operating a fuel injector having at least one injection orifice that is controlled by an injector needle, in which pressure variations during the opening and/or closing of the injector needle are ascertained with the aid of a sensor. In order to determine the opening/closing instant of the injector needle, a variable that characterizes the velocity of sound of a pressure wave by the opening and/or closing is measured, and the wave propagation time, by which the needle or valve opening/closing instant is corrected, is inferred therefrom.

A fuel injection control device is adapted for a fuel injection system including an injector and a high-pressure pump that raises pressure of fuel and supplies the fuel to the injector. The fuel injection control device includes a selecting unit for selecting by which one of full lift injection and partial injection to inject fuel, and a pump control unit for controlling operation of the high-pressure pump such that a pressure of fuel supplied to the injector coincides with a target pressure. The selecting unit selects the partial injection when a required injection quantity of fuel is equal to or smaller than a partial maximum injection quantity. A fuel injection system includes the fuel injection control device, the injector, and the high-pressure pump.

A method for detecting an opening time of a valve, includes receiving a valve current profile of the valve and processing the valve current profile using at least a slope reflection detector to determine a status of the valve based on an output of the slope reflection detector.

A method is disclosed of controlling operation of a fuel injector in response to measuring a quantity of fuel injected by the fuel injector from a fuel accumulator to an engine cylinder during operation of a fuel pump that delivers fuel to the accumulator, comprising: determining an average pressure of the fuel accumulator during a first time period before a fuel injection event; predicting a mass of fuel delivered to the fuel accumulator during a pumping event (Q.sub.pump); determining an average pressure of the fuel accumulator during a second time period after the fuel injection event; estimating a leakage of fuel; computing the injected fuel quantity by adding the average pressure during the first time period to Q.sub.pump, and subtracting the average pressure during the second time period and the leakage; and using the computed injected fuel quantity to control operation of the fuel injector.

Methods and systems are provided for adjusting injection timing of closely spaced multiple injections via a same injector. In one example, during an inter-injection spacing between a first injection and a second injection in a set of multiple injections being lower than a threshold period, an opening time of the second injection in the set of multiple injections may be adjusted based on another opening time of another second injection in a previous set of multiple injections.

Methods and systems are provided for detection of a closing time for a solenoid valve. In one example, a method may include monitoring a current of the solenoid valve, filtering the current, and determining the closing time of the solenoid valve based on each of the current and the filtered current. In some examples, the solenoid valve may be an electrically-actuated fuel injection valve. In some examples, determining the closing time may include using the filtered current to determine an inflection point of the current.

An injection control device includes: an area correction unit that calculates an energization time correction amount when executing a current drive of the fuel injection valve to inject a fuel from the fuel injection valve; an estimation unit that independently calculates an estimated energization time correction amount; a comparison unit that compares the energization time correction amount c with the estimated energization time correction amount; and a first abnormality determination unit that determines that the energization time correction amount is abnormal.

A method for operating an internal combustion engine having at least one fuel injector that is activated for opening and closing via a solenoid valve of a respective fuel injector. Commencing with the activation of the fuel injector for opening, structure-borne sound waves emitted by the fuel injector over the time are detected by measurement. A structure-borne sound wave signal detected by measurement over the time is evaluated such that dependent on the amount of at least one maximum of the structure-borne sound wave signal and/or dependent on the number of the maximums of the structure-borne sound wave signal and/or in the presence of multiple maximums dependent on the time sequence and/or on the amount of the maximums, an operating state of the respective fuel injector is deduced.

In some embodiments, a method includes: setting an actuation time based on a predefined injection quantity; detecting a duration of a resulting closing process; calculating an injection quantity based on the time and the duration; determining the difference of the injection quantity and the predefined quantity; and determining a corrected value of the actuation time based on the difference; and using the corrected value to control further actuation of the fuel injector. The injection quantities and the actuation time are on a characteristic diagram of the relationship between the actuation time, the duration of the closing process, and the injection quantity.

An injector for injecting fuel including an injector housing, a movable nozzle needle with a nozzle needle tip arranged in the injector housing, and a nozzle needle seat for receiving the nozzle needle tip. A contact pairing of the nozzle needle and the nozzle needle seat here represents a mechanical switch that adopts a closed state upon contact of the nozzle needle tip with the nozzle needle seat and an open state upon interruption of the contact. Provision is additionally made that the injector has an input line and an output line for controlling movement of the nozzle needle, the switch has a first connector connected to the input line and a second connector connected to the injector housing, and a resistor connected between the first connector of the switch and the input line.