Method for monitoring the performance of a catalytic converter

A method for monitoring the performance of a catalytic converter comprising the steps of:

• providing a first gas sensor in an exhaust gas stream at a location upstream from the catalytic converter and a second gas sensor in the exhaust gas stream at a location downstream from the catalytic converter;
• monitoring the dynamic voltage output of the second gas sensor to detect a lean breakthrough to define a first integration limit;
• monitoring the dynamic voltage output of the second gas sensor to detect a rich breakthrough to define a second integration limit,
• wherein the dynamic voltage output can change from rich to lean and from lean to rich over a short time interval without defining a first or second integration limit;
• providing normalized air-fuel ratio for the exhaust gas stream;
• determining an amount of oxygen stored in the catalytic converter by integrating a mathematical expression selected from the group consisting of Cm(.lambda.-1)/.lambda. and Cm'(.lambda.-1), from the first integration limit to the second integration limit, where C is a constant representing an approximate mass fraction of oxygen in air, m is an air mass flow rate in the exhaust gas stream, m' is a fuel mass flow rate in the exhaust gas stream, and .lambda. is the normalized air-fuel ratio;
• and
• providing pass/fail criteria and comparing the amount of oxygen stored in the catalytic converter with the pass/fail criteria to determine the performance of the catalytic converter.

A method for monitoring the performance of a catalytic converter comprising the steps of:

• receiving information from a plurality of sensors,
• wherein the information includes a mass flow rate of air flowing into an engine and an excess air ratio in an exhaust gas stream flowing into and out of the catalytic converter;
• calculating the mass flow rate of oxygen into the catalytic converter;
• integrating the mass flow rate of oxygen from a first integration limit to a second integration limit by integrating a mathematical expression including the term (.lambda.-1)/.lambda. to determine the amount of oxygen stored by a catalyst within the catalytic converter and the amount of oxygen released by the catalyst, where .lambda. is an excess air/fuel ratio, and
• wherein the information includes dynamic sensor data and the integration limits are determined from the dynamic sensor data;
• and
• comparing the amount of oxygen stored and released with threshold values to determine a pass/fail condition;
• and
• alerting an operator for a fail condition.

A method for monitoring the performance of a catalytic converter comprising the steps of:

• analyzing the voltage signals from a first gas sensor positioned in an exhaust system at a location upstream from the catalytic converter to determine a rich or a lean state;
• analyzing the voltage signals from a second gas sensor positioned in the exhaust system at a location downstream from the catalytic converter to determine a rich or a lean state;
• continuously calculating the mass flow rate of oxygen flowing into the catalytic converter, using a numerical integration algorithm in which first and second integration limits are determined by dynamic voltage signal analysis, and using a mathematical expression including the term (.lambda.-1)/.lambda., where .lambda. is an excess air/fuel ratio;
• enabling an integrator to sum iteration values of the mass flow rate of oxygen over a predetermined time interval;
• receiving state information from the first and second gas sensors and storing sums calculated by the integrator into discrete storage locations;
• summing average values from each storage location and calculating a mean amount of stored oxygen;
• and
• comparing the mean amount of stored oxygen with a threshold level and activating an alarm circuit when the total amount of stored oxygen is less than the threshold level.