A fuel injector includes fixed metal components, in particular an injector body, a solenoid actuator equipped with a retaining spring that holds a control valve stem, a control valve body including a seat for the control valve stem, a spacer between the body of the control valve and an injection nozzle, a control chamber, and an injection needle seat. The fuel injector also includes movable metal components, in particular the control valve stem and an armature thereof and an injection needle. Surfaces of the metal components that are in contact with one another are contact surfaces. Resistive surface coatings are arranged on a number of the contact surfaces. The overall electrical resistivity of the injector between the body of the solenoid actuator and the body of the injector varies by at least three distinct ohm values intermittently according to the kinetics of the injection needle of the injector.
1. A fuel injector comprising:
fixed metal components, including an injector body, a solenoid actuator equipped with a retaining spring that holds a control valve stem, a control valve body comprising a seat for the control valve stem, an injection nozzle having an injection needle seat, a spacer between the control valve body and the injection nozzle, and a control chamber; and
movable metal components, including the control valve stem and an armature thereof and an injection needle,
said solenoid actuator comprising control wires communicating with the outside of the fuel injector,
wherein surfaces of the metal components that are in contact with one another are contact surfaces, and
wherein resistive surface coatings are arranged on a number of the contact surfaces, the overall electrical resistivity of the fuel injector between a body of the solenoid actuator and the injector body varies by three distinct ohm values intermittently according to the kinetics of the injection needle of the fuel injector, and the resistive surface coatings are located:
on at least one contact surface between the injector needle seat and the injection needle,
on at least one contact surface between a body of the injection nozzle and the injection needle,
on at least one contact surface between the injection needle and the spacer,
on at least one contact surface between the body of the injection nozzle and the spacer,
on at least one contact surface between the injector body and the control valve body, and
on at least one contact surface between the injector body and the body of the solenoid actuator.
2. The fuel injector as claimed in claim 1 , further comprising an additional electrical resistor connected between the body of the solenoid actuator and one of the control wires, said one of the control wires being for measuring the overall electrical resistivity.
3. The fuel injector as claimed in claim 1 , further comprising an electric circuit with parallel topology connected between the body of the solenoid actuator and one of the control wires of the solenoid actuator, said one of the control wires being for measuring the overall electrical resistivity, said parallel electric circuit comprising a first electrical resistor in series with a first diode and a second electrical resistor in series with a second diode mounted in a direction opposite to the first diode.
4. The fuel injector as claimed in claim 1 , further comprising a wire connected to the body of the solenoid actuator, said wire being for measuring the overall electrical resistivity.
5. The fuel injector as claimed in claim 1 , wherein each resistive surface coating arranged on the contact surfaces is an amorphous carbon or a ceramic.