A method for monitoring a common-rail injector for large diesel and dual-fuel engines and injector configured to implement this method

An injector for common-rail injection systems, comprising:

• a delivery chamber connected to a pressurized fuel supply line and provided with a valve seat,
• an injector needle extending through said delivery chamber and having a sealing surface that cooperates with said valve seat, wherein the injector needle is movable along a longitudinal axis between a closed position in which said sealing surface abuts against said valve seat, and an open position in which said sealing surface is spaced apart from said valve seat,
• a control chamber connected to said fuel supply line through a calibrated inlet orifice and connected to a discharge line by means of a calibrated outlet orifice, wherein the control chamber is delimited partly by a head surface of the injector needle and partly by a reaction surface of a head plate, and wherein the head surface of the injector needle in the open position of the injector needle abuts against said reaction surface, and
• an electrically-operated control valve arranged to selectively open and close hydraulic communication between the control chamber and the discharge line,
• wherein said head plate has an integral diaphragm on which said reaction surface is formed, and wherein the injector comprises a sensor which supplies an electrical signal indicative of deformations of said diaphragm.