Control apparatus for a diesel exhaust fluid injector

A control apparatus for an exhaust fluid injector located in an exhaust pipe of an internal combustion engine and operable for exhaust fluid injection, wherein the control apparatus comprises an electronic control unit (ECU) configured to:

• energize a solenoid of the exhaust fluid injector to perform an exhaust fluid injection using a pulse width modulation (PWM) strategy or a peak to hold strategy communicated from the ECU to the exhaust fluid injector, wherein the ECU is configured to operate the exhaust fluid injector;
• determine, by the ECU, an electric voltage value (Vcoil) indicative of electric voltage applied to the solenoid during the exhaust fluid injection;
• determine an electric current value (Icoil) indicative of electric current flowing through the injector solenoid during the exhaust fluid injection;
• calculate an electric resistance (Rcoil) value of the injector solenoid as a function of the determined electric voltage value (Vcoil) and the electric current value (Icoil);
• and
• estimate an exhaust fluid injector temperature value (Tcoil) as a function of the calculated electric resistance value (Rcoil);
• determine an air temperature value (Tair) indicative of temperature of the ambient air flowing around an external casing of the exhaust fluid injector during the exhaust fluid injection;
• determine an air speed value (Sair) indicative of speed of the ambient air flowing around the external casing of the exhaust fluid injector during the exhaust fluid injection;
• estimate an air contribution (ΔTair) to an exhaust fluid injector temperature as a function of the determined air temperature value (Tair) and air speed value (Sair);
• correct the exhaust fluid injector temperature value (Tcoil) with the air contribution (ΔTair);
• and
• activate a cooling phase of the exhaust fluid injector when an estimated value of the exhaust fluid injector temperature (Ttip) exceeds a predetermined threshold value (Tth), by:
• determining a quantity of diesel exhaust fluid (DEF) required to cool the exhaust fluid injector;
• and
• injecting the quantity of DEF, by exhaust fluid injector, by energizing the exhaust fluid injector using the PWM strategy or the peak to hold strategy communicated from the ECU to the exhaust fluid injector.

A method of controlling an exhaust fluid injector located in an exhaust pipe of an internal combustion engine, wherein the method comprises:

• energizing a solenoid of the exhaust fluid injector to perform an exhaust fluid injection using a pulse width modulation (PWM) strategy or a peak to hold strategy communicated from an electronic control unit (ECU) to the exhaust fluid injector, wherein the ECU is configured to operate the exhaust fluid injector;
• determining, by the ECU, an electric voltage value (Vcoil) indicative of an electric voltage applied to an injector solenoid during the exhaust fluid injection, wherein the exhaust fluid injector comprises the injector solenoid;
• determining an electric current value (Icoil) indicative of an electric current flowing through the solenoid during the exhaust fluid injection;
• calculating an electric resistance (Rcoil) value of the solenoid as a function of the determined electric voltage value (Vcoil) and the electric current value (Icoil);
• and
• estimating an exhaust fluid injector temperature value (Tcoil) as a function of the calculated electric resistance value (Rcoil);
• determining an exhaust temperature value (Texh) indicative of temperature of the exhaust gas flowing along the exhaust pipe during the exhaust fluid injection;
• determining an exhaust mass flow rate value (Qexh) indicative of a mass flow rate of the exhaust gas flowing along the exhaust pipe during the exhaust fluid injection;
• estimating an exhaust gas contribution (ΔTexh) to an exhaust fluid injector temperature as a function of the determined exhaust temperature value (Texh) and exhaust mass flow rate value (Qexh);
• correcting the exhaust fluid injector temperature value (Tcoil) with the exhaust gas contribution (ΔTexh);
• and
• activating a cooling phase of the exhaust fluid injector when an estimated value of the exhaust fluid injector temperature (Ttip) exceeds a predetermined threshold value (Tth), by:
• determining a quantity of diesel exhaust fluid (DEF) required to cool the exhaust fluid injector;
• and
• injecting the quantity of DEF, by the exhaust fluid injector, by energizing the exhaust fluid injector using the PWM strategy or the peak to hold strategy communicated from the ECU to the exhaust fluid injector.