Method for monitoring the performance of a catalytic converter
First Claim
1. A method for monitoring the performance of a catalytic converter comprising the steps of:
- providing a value for a mass flow rate selected from one of a mass flow rate of air and a mass flow rate of fuel in an exhaust gas stream entering the catalytic converter;
providing a value for a first normalized air-fuel ratio;
calculating an amount of oxygen stored in the catalytic converter using one of the mass flow rate of air and the mass flow rate of fuel together with the first normalized air-fuel ratio,wherein a numerical integration is performed using integration limits determined from dynamic voltage signals, andwherein a pumping delay from an engine and a transport delay within an exhaust system coupling the engine to the catalytic converter is used in determining the amount of oxygen stored in the catalytic converter; and
comparing the amount of oxygen stored in the catalytic converter with pass-fail criteria to determine the performance of the catalytic converter.
3 Assignments
0 Petitions
Accused Products
Abstract
A method for monitoring the performance of a catalytic converter (34) computes the oxygen storage capacity and desorption capacity of a catalyst within the catalytic converter (34). An engine control unit (10) receives mass flow rate information of air from a mass air flow rate sensor (12) and an injector driver (24), and receives electrical signals from an upstream exhaust gas sensor (28) and a downstream exhaust gas sensor (30). The engine control unit (10) calculates normalized air fuel ratios for the exhaust gas entering and leaving the catalytic converter (34) and performs numerical integration to determine the oxygen storage capacity and oxygen desorption capacity of the catalyst in the catalytic converter (34). The calculated oxygen storage and desorption capacities of the catalyst are compared with threshold values to determine the performance of the catalytic converter (34).
-
Citations
15 Claims
-
1. A method for monitoring the performance of a catalytic converter comprising the steps of:
-
providing a value for a mass flow rate selected from one of a mass flow rate of air and a mass flow rate of fuel in an exhaust gas stream entering the catalytic converter; providing a value for a first normalized air-fuel ratio; calculating an amount of oxygen stored in the catalytic converter using one of the mass flow rate of air and the mass flow rate of fuel together with the first normalized air-fuel ratio, wherein a numerical integration is performed using integration limits determined from dynamic voltage signals, and wherein a pumping delay from an engine and a transport delay within an exhaust system coupling the engine to the catalytic converter is used in determining the amount of oxygen stored in the catalytic converter; and comparing the amount of oxygen stored in the catalytic converter with pass-fail criteria to determine the performance of the catalytic converter. - View Dependent Claims (2, 3, 4, 5, 6)
-
-
7. 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(λ
-1)/λ and
Cm'"'"'(λ
-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 λ
is the normalized air-fuel ratio; andproviding 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. - View Dependent Claims (8, 9, 10)
-
-
11. 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 (λ
-1)/λ
to determine the amount of oxygen stored by a catalyst within the catalytic converter and the amount of oxygen released by the catalyst, where λ
is an excess air/fuel ratio, andwherein 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. - View Dependent Claims (12, 13, 14)
-
-
15. 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 (λ
-1)/λ
, where λ
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.
-
Specification