Method and device for repolarizing a piezoelectric actuator of an injector of an internal combustion engine of a used vehicle

Method for repolarizing a piezoelectric actuator of an injector of an internal combustion engine of a used vehicle, said piezoelectric actuator having undergone initial polarization before the vehicle was put into use, characterized in that the method comprises the following steps, the piezoelectric actuator being associated with the injector, and the latter being mounted on the engine, the engine being stopped:

• ensuring that the residual injector fuel supply pressure is less than a specified threshold below which no injection of fuel into the combustion chamber can take place,
• applying a first polarization voltage (V1) to the terminals of the piezoelectric actuator during a first specified time interval (T1) of not less than ten minutes,
• stopping the application of the first polarization voltage (V1) during a second time interval (T2), following the first time interval (T1) and at least equal to the latter, thus defining a pause time in which no voltage is applied to the actuator terminals,
• applying a second polarization voltage (V2) to the terminals of the piezoelectric actuator during a third specified time interval (T3), following the second time interval,
• stopping the application of the second polarization voltage (V2) to the terminals of the piezoelectric actuator after the third time interval (T3),
• said first (T1), second (T2) and third (T3) successive time intervals, in combination, defining a repolarization sequence of the piezoelectric actuator.