Patent ID: 8571821

Claim:
A method for determining the closing time (t 3 ) of an electromagnetic fuel injector ( 4 ), having a pin ( 23 ) movable between a closed position and an open position of an injection valve ( 15 ), and an electromagnetic actuator ( 14 ) equipped with a coil ( 16 ) and adapted to determine the displacement of the pin ( 23 ) between the closed position and the open position; the method including the steps of: applying at a starting time (t 1 ) of the injection a positive voltage (v) to the coil ( 16 ) of the electromagnetic actuator ( 14 ) in order to circulate through the coil ( 16 ) an electric current (i) which causes the opening of the injection valve ( 15 ); applying at an ending time (t 2 ) of the injection a negative voltage (v) to the coil ( 16 ) of the electromagnetic actuator ( 14 ) in order to annul the electric current (i) flowing through the coil ( 16 ); detecting the trend over time of the voltage (v) across the coil ( 16 ) of the electromagnetic actuator ( 14 ) when the voltage (v) is negative, after the annulment of the electric current (i) flowing through the coil ( 16 ) and until the annulment of the voltage (v); identifying a perturbation (P) of the voltage (v) across the coil ( 16 ) after the annulment of the electric current (i) flowing through the coil ( 16 ) by calculating the first derivative in time of the voltage (v) across the coil ( 16 ) after the annulment of the electric current (i) flowing through the coil ( 16 ); and recognizing the closing time (t 3 ) of the injector ( 4 ) that coincides with the time (t 3 ) of the perturbation (P) of the voltage (v) across the coil ( 16 ) after the annulment of the electric current (i) flowing through the coil ( 16 ); where the steps of identifying the perturbation (P) of the voltage (v) across the coil 16 ) further includes the steps of: calculating an absolute value of the first derivative in time of the voltage (v) across the coil ( 16 ); calculating an integral over time of the absolute value of the first derivative in time of the voltage (v) across the coil ( 16 ); and identifying the perturbation (P) when the absolute value of the integral over time of the first derivative in time of the voltage (v) across the coil ( 16 ) exceeds a second threshold value (S 2 ).