Control apparatus for operating a fuel injector

A control apparatus for operating a fuel injector in fluid communication with a fuel rail to inject fuel into an internal combustion engine, wherein the control apparatus comprises an electronic control unit configured to:

• identify when the engine is running under a fuel cut-off condition;
• and
• perform a learning procedure to determine an actual value of energizing time that causes the fuel injector to inject a target fuel quantity in response to the fuel cut-off condition;
• wherein the learning procedure provides for the electronic control unit to:
• regulate the fuel rail pressure at a predetermined pressure value;
• energize the fuel injector to perform several test injections with different energizing time values;
• measure, for each one of the test injections, an engine torque value caused by the test injection;
• use the measured engine torque values and their correspondent energizing time values to extrapolate the actual value of the energizing time as the value that corresponds to a reference value of engine torque that is consistent with the target fuel quantity;
• and
• wherein the energizing time value of each one of the test injections is predetermined for the fuel injector to inject a fuel quantity that is greater than the target fuel quantity.

A method of operating a fuel injector in fluid communication with a fuel rail to inject fuel into an internal combustion engine, wherein the method comprising:

• identifying when the engine is running under a fuel cut-off condition;
• and
• in response to the fuel cut-off condition, performing a learning procedure to determine an actual value of energizing time that causes the fuel injector to inject a small target fuel quantity;
• wherein the learning procedure includes:
• regulating the fuel rail pressure at a predetermined value;
• energizing the fuel injector to perform several test injections with different values of the energizing time;
• measuring, for each one of the test injections, a value of engine torque caused by the test injection;
• and
• using the measured values of engine torque and their correspondent energizing time values to extrapolate the actual value of the energizing time as the energizing time value that corresponds to a reference value of engine torque that is consistent with the target fuel quantity;
• wherein the energizing time value of each one of the test injections is predetermined to cause the fuel injector to inject a fuel quantity whose value is bigger than the target value thereof.