Method for determining the closing time of an electromagnetic fuel injector

A method for determining the closing time (t3) 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 (t1) 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 (t2) 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 (t3) of the injector (4) that coincides with the time (t3) 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 (S2).