Controller for a common-rail injection system

A common-rail injection system comprising:

• a plurality of fuel injectors,
• a common fuel supply line for the fuel injectors,
• a high-pressure pump for supplying the common fuel supply line with fuel,
• a pressure sensor for determining a pressure in the common fuel supply line, and
• a controller having a determination unit configured to evaluate data of the pressure sensor during an evaluation interval chosen, depending on an actuation start time or an actuation end time of at least one test injection in the common fuel supply line made in addition to normal injections in the common fuel supply line for engine operation, to start after an attenuated half oscillation of a pressure signal caused by the at least one test injection and to end during a normal injection in the common fuel supply line for engine operation, and, from a pressure drop occurring during the evaluation interval caused by the at least one test injection in the common fuel supply line in addition to the normal injections, determines a fuel quantity actually injected during this injection or a value derived therefrom, and an adaption unit configured to use the results of the determination unit in order to adapt the actuation of the fuel injectors, wherein the determination unit is further configured to carry out at least one test injection by way of which the actually injected fuel quantity or the value derived therefrom is determined.

A method for actuating a common-rail injection system which includes a plurality of fuel injectors, a common fuel supply line for the fuel injectors, a high-pressure pump for supplying the common fuel supply line with fuel, a pressure sensor for determining a pressure in the common fuel supply line using a controller having a determination unit, and an adaption unit, the method comprising:

• evaluating data of the pressure sensor with the determination unit during an evaluation interval chosen, depending on an actuation start time or an actuation end time of at least one test injection in the common fuel supply line made in addition to normal injections in the common fuel supply line for engine operation, to start after an attenuated half oscillation of a pressure signal caused by the at least one test injection and to end during a normal injection in the common fuel supply line for engine operation,
• determining, with the determination unit, a fuel quantity actually injected during an injection or a value derived therefrom from a pressure drop occurring during the evaluation interval caused by way of the at least one test injection carried out by the determination unit in the common fuel supply line in addition to the normal injections in the common fuel supply line for engine operation, and
• adapting, with the adaption unit, actuation of the fuel injectors using results of the data evaluation.