Ignition coil with ionization and digital feedback for an internal combustion engine

Abstract

Systems and methods for controlling an internal combustion engine include an ignition coil that generates a pre-discharge ionization signal during charging of the ignition coil after reaching a first threshold charge level and prior to spark discharge and a controller that determines an engine operating condition, such as pre-ignition or plug fouling, in response to the pre-discharge ionization signal. The ignition coil may also generate digital feedback and ionization signals used to by the controller to control ignition coil dwell and repetitive sparking, as well as providing various combustion diagnostics.

What is claimed is: 
     
         1 . A method for controlling an engine, comprising:
 generating digital feedback signals from an ignition coil each combustion cycle, at least a first digital feedback signal generated in response to an ignition control signal prior to spark discharge;   generating a third signal being either a digital feedback signal or a pre-discharge ionization signal after the first digital feedback signal; and   controlling the engine in response to the digital feedback signals and the third signal.   
     
     
         2 . The method of  claim 1  wherein signals from at least two ignition coils are combined and communicated to a controller on a single wire, the method further comprising:
 determining a plug fouling condition in response to the third signal exceeding a corresponding plug fouling threshold. 
 
     
     
         3 . The method of  claim 1  wherein the first digital feedback signal terminates when the ignition coil charges to a first threshold, the first threshold being less than a spark discharge threshold. 
     
     
         4 . The method of  claim 3  wherein the second digital feedback signal is generated in response to a transition in the ignition control signal while the ignition coil charge exceeds the first threshold. 
     
     
         5 . The method of  claim 3  wherein the third signal is generated in response to an asserted ignition control signal while the ignition coil charge exceeds a first threshold. 
     
     
         6 . The method of  claim 3  further comprising:
 repetitively charging the ignition coil to generate repetitive spark discharges during a single combustion cycle in a single cylinder until the third signal exceeds a corresponding threshold associated with a flame front reaching the spark plug. 
 
     
     
         7 . The method of  claim 1  wherein the third signal is a pre-discharge ionization current signal, the method further comprising:
 detecting pre-ignition based on at least one characteristic of the pre-discharge ionization signal. 
 
     
     
         8 . The method of  claim 1  further comprising:
 detecting pre-ignition based on a slope and peak position of an ionization signal after the second digital feedback signal. 
 
     
     
         9 . A system for controlling an engine, comprising:
 a controller; and   an ignition coil in communication with the controller and at least one spark plug, the ignition coil generating at least first and second digital feedback signals during each combustion cycle with at least a first digital feedback signal generated in response to an ignition control signal from the controller prior to spark discharge.   
     
     
         10 . The system of  claim 9  wherein the ignition coil asserts the first digital feedback signal in response to a first ignition control signal transition and unasserts the first digital signal when ignition coil charging reaches a first threshold, the first threshold being below a spark discharge threshold. 
     
     
         11 . The system of  claim 9  wherein the ignition coil asserts the second digital feedback signal in response to a second ignition control signal transition and unasserts the second digital feedback signal at completion of spark discharge. 
     
     
         12 . The system of  claim 9  wherein the ignition coil generates a third signal after the first digital feedback signal. 
     
     
         13 . The system of  claim 12  wherein the third signal is a digital feedback signal. 
     
     
         14 . The system of  claim 12  wherein the third signal is a pre-discharge ionization signal and wherein the controller determines a spark plug condition based on the pre-discharge ionization signal. 
     
     
         15 . The system of  claim 12  wherein the ignition coil generates a fourth signal after the second digital feedback signal. 
     
     
         16 . The system of  claim 15  wherein the fourth signal is an ionization signal.