Method and apparatus for closed-loop control of the air number in a self-igniting internal combustion engine

An apparatus for the closed-loop control of the air number .lambda. of the operating mixture for combustion in a self-igniting internal combustion engine, comprising:

• an ion current sensor disposed in the immediate vicinity of an outlet value of one of the engine cylinders, said ion current sensor detecting, during a measurement interval, the ion current associated with a permissible soot number of the exhaust gas exhausted from the engine;
• means for generating a set-point value of the ion current which corresponds to the value of the ion current in the range of .lambda.=1.0-1.5, said ion current increasing sharply in this air number range;
• a comparator circuit connected to the ion current sensor and the means for generating a set-point value for comparing the detected ion current with the set-point value and establishing a deviation of the detected ion current from the set-point value;
• and
• an adjustment device connected to the comparator circuit for adjusting the composition of the operating mixture and consequently the air number .lambda. as a function of the deviation, whereby the set-point value of the ion current is maintained and the permissible soot number of the exhaust gas is not exceeded.

An apparatus for the closed-loop control of the air number of the operating mixture for combustion in a self-igniting internal combustion engine, comprising:

• a crankshaft angle transducer;
• an ion current sensor disposed in the immediate vicinity of an outlet value of one of the engine cylinders, said ion current sensor detecting, during a measurement interval, the ion current associated with the post-combustion reaction of the various gas components of the exhaust gas exhausted from the engine;
• means for generating a set-point value of the ion current which corresponds to the value of the ion current in the range of .lambda.=1.0-1.5, said ion current increasing sharply in this air number range;
• a comparator circuit connected to the ion current sensor and the means for generating a set-point value for comparing the detected ion current with the set-point value and establishing a deviation of the detected ion current from the set-point value;
• an integrating device connected to the ion current sensor and to the comparator circuit;
• and
• a control circuit connected to the crankshaft angle transducer and to the integrating device, said control circuit being rendered rpm-dependent by the crankshaft angle transducer, wherein the integrating device is switched between the comparator circuit and the ion current sensor as a result of which the integrating device is set at the beginning of each measurement interval and as a result of which the comparator circuit establishes the deviation of the detected ion current from the set-point value;
• and
• an adjustment device connected to the comparator circuit for adjusting the composition of the operating mixture and consequently the air number .lambda. as a function of the deviation.