Method to control a burner for an exhaust system of an internal combustion engine

A method to control an internal combustion engine (1) provided with an exhaust system (2) for the exhaust gases of a motor vehicle having an exhaust duct (10) and an exhaust gas after-treatment system (14) comprising at least one catalytic converter (15, 17) arranged along the exhaust duct (10);

• and an oxygen sensor (18, 18*), preferably a linear one, which is housed along the exhaust duct (10) and is arranged upstream of said at least one catalytic converter (15, 17) in order to detect the air/fuel ratio of the exhaust gases providing an output that indicates the content of oxygen in the exhaust gases;
• and a burner (21), which is suited to introduce exhaust gases into the exhaust duct (10) upstream of the oxygen sensor (18, 18*) so as to speed up the heating of said at least one catalytic converter (15, 17), wherein inside the burner (21) there is defined a combustion chamber (22), which receives fresh air through an air feeding device (23), which is provided with a pumping device (24) feeding air, and fuel from an injector (27), which is designed to inject fuel into the combustion chamber (22), and a spark plug (28) coupled to the burner (21) so as to ignite the mixture present inside the combustion chamber (22);
• the method comprises the following steps:
• a) identifying operation phases in which the internal combustion engine (1) is turned off and the burner (21) is turned on, so that the oxygen sensor (18, 18*) is exclusively hit by the exhaust gases produced by the burner (21);
• b) acquiring the signal generated by the oxygen sensor (18, 18*);
• and
• c) using the signal generated by the oxygen sensor (18, 18*) in order to control the objective air flow rate ({dot over (m)}A_OBJ) and determine the objective fuel flow rate ({dot over (m)}F_OBJ) to be fed to the burner (21).