Patent ID: 8688402

Claim:
A method of estimating a fluid injector tip temperature by a controller having a processor and a memory, the method comprising: supplying a current to a coil of a fluid injector; measuring by the controller a resistance of the coil when the current is supplied to the coil; determining by the controller a coil temperature based on the measured resistance; estimating by the controller a tip temperature of a fluid injector tip based on the determined coil temperature; storing in the memory a three-dimensional map of exhaust gas temperatures and exhaust gas mass flows; sensing an exhaust gas temperature; sensing an exhaust gas mass flow; determining a temperature increase of the fluid injector tip based on the sensed exhaust gas temperature and the sensed exhaust gas mass flow using the three-dimensional map of exhaust gas temperatures and exhaust gas mass flows; determining a no-flow tip temperature by adding the determined coil temperature to the determined temperature increase, wherein the estimated tip temperature is based on the determined no-flow tip temperature and the determined coil temperature; sensing a fluid temperature; determining a full-flow tip temperature by subtracting the sensed fluid temperature from the determined no-flow tip temperature; storing in the memory a two-dimensional curve of duty cycles of the fluid injector; determining a duty cycle of the fluid injector; determining a duty cycle modification factor based on the determined duty cycle and the two-dimensional curve of duty cycles of the fluid injector; and determining an offset by multiplying the determined duty cycle modification factor by the determined full-flow tip temperature.