Method and apparatus for monitoring the ignition device of an internal combustion engine

In an ignition device of an externally ignited internal combustion engine including at least two primary current circuits each having one ignition end stage transistor with base and emitter terminals;

• and secondary current circuits,
• an apparatus for monitoring the secondary current circuits, comprising an engine or ignition control unit for making said ignition end stage transistors conducting or nonconducting, said control unit having:
• a measurement input connected to the base terminals of said ignition end stage transistors;
• a measurement circuit connected to said measurement input for measuring values of successive base-to-emitter voltages of said ignition end stage transistors;
• a memory connected to said measurement circuit for storing at least two successive measured values;
• a comparison circuit connected to said memory for forming a difference value of the stored measured values;
• and
• at least one comparator connected to said comparison circuit for comparing the difference value with a predetermined limit value and for outputting a failure signal at an output if the difference value exceeds the limit value.

In an ignition device of an externally ignited internal combustion engine including at least two primary current circuits each having one ignition end stage transistor with base and emitter terminals;

• and secondary current circuits,
• an apparatus for monitoring the secondary current circuits, comprising an engine or ignition control unit for making said ignition end stage transistors conducting or nonconducting, said control unit having:
• a measurement input connected to the base terminals of said ignition end stage transistors;
• a measurement circuit connected to said measurement input for measuring values of successive base-to-emitter voltages of said ignition end stage transistors;
• a memory connected to said measurement circuit for storing at least two successive measured values;
• a comparison circuit connected to said memory for forming a quotient of the stored measured values;
• and
• at least one comparator connected to said comparison circuit for comparing the quotient with an upper limit value and a lower limit value and for outputting a failure signal at an output if the quotient exceeds the upper limit value or fails to attain the lower limit value.