Apparatus for determining the ignition characteristic of an internal combustion engine

An apparatus for determining the state of combustion in an internal combustion engine, said apparatus comprising:

• an ignition coil having a primary winding and a secondary winding;
• a power supply providing a primary current flow through said primary winding, and an ignition timing control means for interrupting said primary current flow upon receipt of a firing signal from a firing signal input port, connected to said primary winding;
• at least one spark plug gap in an engine combustion chamber connected to said secondary winding;
• an ionic current sensing, and computing circuit connected to said secondary winding, through a current limiting element, for measuring the flow of ionic current in said combustion chamber when a voltage potential has been applied to said at least one spark plug gap;
• a reference voltage input port connected to a reference voltage and an output port, said output port adapted to provide an indication of the state of the combustion and connected to said ionic current computing circuit;
• and
• circuit means for producing a voltage potential indicating a spark at said at least one spark plug gap, said circuit means being connected to said ionic current computing circuit;
• wherein
• said ionic current computing circuit computes a measured value of said ionic current after each spark over time and provides an output signal indicative of said measured value of said ionic current, said output signal being delivered to said output port,
• and further comprising a primary flyback voltage comparator circuit for measuring a flyback voltage developed in said primary winding at the instant said primary current is interrupted.

An apparatus for determining the state of combustion in an internal combustion engine, said apparatus comprising:

• an ignition coil having a primary winding and a secondary winding;
• a power supply providing a primary current flow through said primary winding, and an ignition timing control means for interrupting said primary current flow upon receipt of a firing signal from a firing signal input port, connected to said primary winding;
• at least one spark plug gap in an engine combustion chamber connected to said secondary winding;
• an ionic current sensing, and computing circuit connected to said secondary winding, through a current limiting element, for measuring the flow of ionic current in said combustion chamber when a voltage potential has been applied to said at least one spark plug gap;
• a reference voltage input port connected to a reference voltage and an output port, said output port adapted to provide an indication of the state of the combustion and connected to said ionic current computing circuit;
• circuit means for producing a voltage potential indicating a spark at said at least one spark plug gap, said circuit means being connected to said ionic current computing circuit;
• wherein
• said ionic current computing circuit computes a measured value of said ionic current after each spark over time and provides an output signal indicative of said measured value of said ionic current, said output signal being delivered to said output port,
• and wherein said ionic current computing circuit is electrically connected at a junction between said ignition timing control means and said primary winding.