Method for operating an internal combustion engine, and control unit set up for carrying out the method

Abstract

The invention relates to a method for operating an internal combustion engine. According to the method, an exhaust gas produced by the internal combustion engine is conducted across a 3-way catalytic converter arranged in the exhaust duct. A lambda probe detects a value characteristic of an exhaust-gas lambda number upstream of the 3-way catalytic converter, and transmits said value to an engine control unit with an integrated PI or PID regulator. By means of the PI or PID regulator of the engine control unit, through the specification of a setpoint value, a substantially stoichiometric exhaust-gas lambda number is set, and the exhaust-gas lambda number is, with predefined periodic setpoint value variation, deflected alternately in the direction of a lean lambda number and a rich lambda number (lambda modulation). At the start of each setpoint value variation, a pilot-controlled P component with subsequent I component is predefined up to a time t, wherein the time tis defined by means of stored parameters, which characterize a section time behavior, such that the probe signal or a value derived therefrom would have had to have reached the setpoint value specification at said time t. From the time tonwards, for a predefinable time period until the end of the respective setpoint value variation, a switch is made to a regulating algorithm which is based on a difference between an actual value and the setpoint value of the lambda probe or a value derived therefrom.