Exhaust gas cleaning system with trimming of upstream lambda sensor output

摘要

In an internal combustion engine 20 with a three-way catalytic converter 22, a certain signal level of the upstream lambda probe 23 is assigned a lambda value g 0 which is close to 1. In place of a lambda probe downstream of the three- way catalytic converter 22, use is made of an NOx-sensitive sensor 24, in which a connection between NOx concentration in the exhaust gas and lambda value, and an internal signal Ip0 of the sensor 24 has a change of sign at lambda = 1, since the signal of the sensor 24 due to an NH3 cross sensitivity at lambda = 1 has only a local minimum. The outputs of the NOx sensor are used to correct (trim) the values assigned to g 0. The NOx sensor has an oxygen sensing cell 4, a NOx sensing cell 8, with the current Ip2 measured at A indicating the NOx concentration.