Siemens Aktiengesellschaft

Ludwig Kettl

Stefan Krebs

Bernhard Bauer

Wojciech Cianciara

A method for distinguishing sources of error in a mixture formation or mixture regulating system of an internal combustion engine having an exhaust system with a lambda regulator and a heated lambda sensor is disclosed. A value of a sensor voltage is continuously measured. The value of the sensor voltage is compared with a lower diagnostic limit value and an upper diagnostic limit value. A lambda regulator value of the lambda regulator is varied in an enriching direction to a maximum lambda regulation limit if the lower diagnostic limit value fails to be attained, and the lambda regulator value is varied in a leaning down direction to a minimum lambda regulation limit if the upper diagnostic limit value is exceeded. The heating output of the sensor heater is raised after a time period has elapsed during which there is no departure from the maximum lambda regulation limit, and the heating output of the sensor heater is lowered after a time period has elapsed during which there is no departure from the minimum lambda regulation limit. A conclusion is drawn that there is a permanently lean mixture formation error if the lower diagnostic limit value for permanently lean mixtures is exceeded again, and a conclusion is drawn that there is a permanently rich mixture formation error if the upper diagnostic limit value fails to be attained again. Otherwise a sensor error is detected.

Method for distinguishing causes of error in the mixture forming or

An internal combustion engine includes a lambda control device having a lambda sensor and a lambda control for regulating a fuel-air mixture to be supplied to an internal combustion engine to a set-point value, outside of full load operation, as a function of an output signal of the lambda sensor, and a mixture control device for setting the fuel-air mixture to a value being less than the set-point value, during full load operation of the internal combustion engine and with the lambda control switched off. A method for operating the internal combustion engine under full load includes continuously detecting and comparing the output signal of the lambda sensor with a rich and a lean threshold value, with the lambda control switched off, releasing the lambda control for a selectable number of mixture state changes, if the output signal of the lambda sensor falls below the lean threshold value during a period of time being greater than a preset value, and keeping the lambda control released until a mean value of the lambda control value indicates a rich main mixture.

Growing community of inventors

Aiterhofen, Germany

Ludwig Kettl