Method and apparatus for closed-loop ignition time control

An apparatus for controlling the instant of ignition in closed-loop fashion in an internal combustion engine, comprising:

• at least one ionic current sensor located at a predetermined distance from the point of ignition in a combustion chamber of the engine, where the flame front reaching said distance has ignited a mixture volume less than 5% of the total volume, and in the path of the ionic current released during combustion of the operational mixture in the combustion chamber, said at lease one ionic current sensor generating a signal representative of the ionic current detected;
• a pulse shaper connected to each ionic current sensor for receiving the output signal from each ionic current sensor and generating an actual value signal therefrom representing the end of the ignition phase of the operational mixture;
• ignition angle set-point transducer means for generating a set-point value signal before top dead center representing a desired end of the ignition phase of the operational mixture;
• a comparator circuit connected to the output of said pulse shaper and said ignition angle set-point transducer means for comparing the phase relationship between the actual value signal and the set-point value signal, and generating a difference signal as an output;
• an integrator circuit connected to the comparator circuit for integrating the difference signal;
• and
• an ignition time adjusting device connected to the integrator circuit and being actuated as a function of the difference signal.

In combination with an internal combustion engine, including at least one main combustion chamber, an associated precombustion chamber and connecting channel connecting the main combustion chamber with the precombustion chamber, an apparatus for controlling the instant of ignition in closed-loop fashion in said associated precombustion chamber, said apparatus comprising:

• an ionic current sensor located in the connecting channel in the path of the ionic current released during combustion of the operational mixture in the precombustion chamber, and where the flame front has ignited a mixture volume less than 5% of the total volume, said ionic current sensor generating a signal representative of the ionic current detected;
• a pulse shaper connected to the ionic current sensor for receiving the output signal therefrom and generating an actual value signal representing the end of the ignition phase of the operational mixture;
• ignition angle set-point transducer means for generating a set-point value signal before top dead center representing a desired end of the ignition phase of the operational mixture;
• a comparator circuit connected to the output of said pulse shaper and said ignition angle set-point transducer means for comparing the phase relationship between the actual value signal and the set-point value signal, and generating a difference signal as an output;
• an integrator circuit connected to the comparator circuit for integrating the difference signal;
• and
• an ignition time adjusting device connected to the integrator circuit and being actuated as a function of the difference signal.