Method, program product and computer for estimating the static flow rate of a piezoelectric injector

A method for determining a static flow rate of a piezo-electric injector of a combustion engine injection system, the piezo-electric injector comprised of a needle and a piezo-electric actuator that controls a valve of the injector, the injection system also including an electric generator that sends electric current pulses to the piezo-electric actuator of the injector, and a voltage sensor that measures voltage values at terminals of the piezo-electric actuator, the method comprising the steps of:

• determining a duration between an instant of closure of the valve and an instant of closure of the needle;
• and
• determining a temperature of the engine;
• determining an engine speed;
• and
• if i) the determined duration between the instant of closure of the valve and the instant of closure of the needle is greater than a predetermined threshold, ii) the temperature of the engine is between a first predetermined temperature and a second predetermined temperature, and iii) the engine speed is between a first predetermined speed of rotation and a second predetermined speed of rotation, then:
• sending, via the electric generator, an electric current pulse to the piezo-electric actuator, such that the piezo-electric actuator contacts the valve without opening the valve, the electric generator sending the electric current pulse during a time of an injection cycle of the injector when the needle is returning from an open position to a closed position,
• measuring, via the voltage sensor, a plurality of voltage values of the piezo-electric actuator, and
• determining the static flow rate of the piezo-electric injector based on the plurality of voltage values measured of the piezo-electric actuator.

A combustion engine, comprising:

• an injection system, comprised of a piezo-electric injector that includes a needle and a piezo-electric actuator that controls a valve of the injector,
• the injection system also comprised of a fuel supply rail, an electric generator that sends electric current pulses to the piezo-electric actuator of the injector, and a voltage sensor that measures voltage values at the terminals of the piezo-electric actuator;
• and
• a computer that controls the injection system, the computer configured to
• send, via the electric generator, an electric current pulse to the piezo-electric actuator, such that the piezo-electric actuator contacts the valve without opening the valve, the electric generator sending the electric current pulse during a time of an injection cycle of the injector when the needle is returning from an open position to a closed position;
• measure, via the voltage sensor, a plurality of voltage values of the piezo-electric actuator;
• and
• determine the static flow rate of the piezo-electric injector based on the plurality of voltage values measured of the piezo-electric actuator.