Method and system for monitoring the operation of a catalytic converter

Abstract

The present disclosure concerns a method for monitoring the operation of a catalytic converter that is disposed in an exhaust system of an internal combustion engine, in particular of a motor vehicle, wherein an exhaust gas temperature upstream of the catalytic converter and an exhaust gas temperature downstream of the catalytic converter are determined. In order to improve the monitoring of such a catalytic converter regardless of the respective type of catalytic converter used, it is proposed with the present disclosure that an exhaust gas mass flow through the catalytic converter is determined, wherein it is determined whether a thermal inertia of the catalytic converter is present or absent according to the presence of a triggering event taking into account the exhaust gas temperatures and the exhaust gas mass flow.

1 . A method for monitoring an operation of a catalytic converter disposed in an exhaust system of an internal combustion engine of a motor vehicle, wherein an exhaust gas temperature upstream of the catalytic converter and an exhaust gas temperature downstream of the catalytic converter are determined, wherein an exhaust gas mass flow through the catalytic converter is determined, wherein it is determined whether a thermal inertia of the catalytic converter is present or absent according to a presence of a triggering event taking into account the exhaust gas temperatures and the exhaust gas mass flow. 
     
     
         2 . The method of  claim 1 , wherein a temperature signal corresponding to the exhaust gas temperature upstream of the catalytic converter is determined and is then low-pass filtered, wherein a degree of change of the low-pass filtered temperature signal is detected, wherein a magnitude of the degree of change of the low-pass filtered temperature signal is detected, low-pass filtered and then compared with a predetermined limit value, and wherein the presence of the triggering event is concluded if the low-pass filtered magnitude exceeds the predetermined limit value. 
     
     
         3 . The method of  claim 1 , wherein a mass flow signal corresponding to the exhaust gas mass flow is produced and low-pass filtered, wherein the low-pass filtered mass flow signal is compared with a predetermined mass flow limit value, and wherein the presence of the triggering event is concluded if the low-pass filtered mass flow signal is less than the predetermined mass flow limit value. 
     
     
         4 . The method of  claim 1 , wherein a first temperature signal corresponding to the exhaust gas temperature upstream of the catalytic converter is produced and low-pass filtered, wherein a magnitude of a degree of change of the low-pass filtered first temperature signal is detected, wherein a second temperature signal corresponding to the exhaust gas temperature downstream of the catalytic converter is produced and low-pass filtered, wherein a change of the low-pass filtered second temperature signal is detected, wherein a mass flow signal corresponding to the exhaust gas mass flow is produced and low-pass filtered, wherein the change of the low-pass filtered second temperature signal is subtracted from the change of the low-pass filtered first temperature signal and a corresponding temperature difference signal is produced, wherein a magnitude of the temperature difference signal is detected, wherein the magnitude of the temperature difference signal is multiplied by the low-pass filtered mass flow signal and a corresponding product signal is produced, wherein the product signal is low-pass filtered, wherein a magnitude of the change of the low-pass filtered first temperature signal is detected and is low-pass filtered, wherein the low-pass filtered product signal is divided either by the low-pass filtered magnitude of the change of the low-pass filtered first temperature signal or, if the same is less than a predefined minimum value, by the minimum value and a corresponding assessment signal is produced, based on which it is determined whether the thermal inertia of the catalytic converter is present or absent. 
     
     
         5 . A system for monitoring an operation of a catalytic converter disposed in an exhaust system of an internal combustion engine of a motor vehicle, comprising at least one temperature sensor that is disposed upstream of the catalytic converter for detecting a first exhaust gas temperature and at least one temperature sensor that is disposed downstream of the catalytic converter for detecting a second exhaust gas temperature, characterized by at least one device for detecting an exhaust gas mass flow through the catalytic converter and at least one electronic unit that has a signaling connection to the temperature sensors and the device and that is designed to detect whether a triggering event exists or not, and to determine whether a thermal inertia of the catalytic converter is present or absent following the detection of the existence of the triggering event while taking into account the exhaust gas temperatures and the exhaust gas mass flow. 
     
     
         6 . The system of  claim 5 , wherein the electronic unit is designed to produce a temperature signal corresponding to the first exhaust gas temperature and then to subject the signal to low-pass filtering, to detect a degree of change of the low-pass filtered temperature signal, to detect a magnitude of the degree of change of the low-pass filtered temperature signal, to subject the magnitude to low-pass filtering and then to compare the low-pass filtered magnitude with a predetermined limit value, and to conclude the triggering event being present if the low-pass filtered magnitude exceeds the predetermined limit value. 
     
     
         7 . The system of  claim 5 , wherein the electronic unit produces a mass flow signal corresponding to the exhaust gas mass flow and subjects the signal to low-pass filtering, to compare the low-pass filtered mass flow signal with a predetermined mass flow limit value, and to determine the triggering event being present if the low-pass filtered mass flow signal is less than the predetermined mass flow limit value. 
     
     
         8 . The system of  claim 5 , wherein the electronic unit produces a first temperature signal corresponding to the first exhaust gas temperature and then to subject the signal to low-pass filtering, to detect a change of the low-pass filtered first temperature signal, to produce a second temperature signal corresponding to the second exhaust gas temperature and then to subject the signal to low-pass filtering, to detect a change of the low-pass filtered second temperature signal, to produce a mass flow signal corresponding to the exhaust gas mass flow and then to subject the signal to low-pass filtering, to subtract the change of the low-pass filtered second temperature signal from the change of the low-pass filtered first temperature signal and to produce a corresponding temperature difference signal, to detect a magnitude of the temperature difference signal, to multiply the magnitude of the temperature difference signal by the low-pass filtered mass flow signal and to produce a corresponding product signal, to subject the product signal to low-pass filtering, to detect a magnitude of the detected change of the low-pass filtered first temperature signal and to subject the signal to low-pass filtering, to divide the low-pass filtered product signal either by the low-pass filtered magnitude of the change of the low-pass filtered first temperature signal or, if the low-pass filtered magnitude is less than a predefined minimum value, by the minimum value and to produce a corresponding assessment signal, and to determine whether the thermal inertia of the catalytic converter is present or absent based on said assessment signal. 
     
     
         9 . A method comprising:
 determining upstream and downstream emissions control device temperature changes by differentiating low-pass filtered upstream and downstream temperature measurements against time;   calculating a product by multiplying a difference between the upstream and downstream temperature change signals by a low-pass filtered exhaust mass flow; and   estimating an assessment of the device by low-pass filtering the product and dividing the low-pass filtered product by each of a threshold value or a low-pass filter of a magnitude of a difference between the upstream temperature change signal and an upstream temperature measurement depending on the magnitude.   
     
     
         10 . The method of  claim 9 , further comprising indicating the device as catalytically active when the assessment signal is greater than a threshold assessment signal. 
     
     
         11 . The method of  claim 10 , further comprising indicating the device as catalytically inactive when the assessment signal is less than a threshold assessment signal and adjusting engine operating parameters in response to the catalyst being inactive. 
     
     
         12 . The method of  claim 9 , wherein the upstream and downstream temperature measurements are measured via temperature sensors upstream and downstream of the device, respectively. 
     
     
         13 . The method of  claim 9 , wherein the low-pass filtered exhaust mass flow is calculated from a measured exhaust mass flow.