Patent ID: 11898511
Assignee: TOYOTA JIDOSHA KABUSHIKI KAISHA
Field: Engines, pumps, turbines (Mechanical engineering)
Classification: CPC F | IPC F

Claim 4:
5. A catalyst abnormality diagnosis method for diagnosing an abnormality in a catalyst located in an exhaust passage of an internal combustion engine and configured to absorb oxygen, the catalyst abnormality diagnosis method comprising:
detecting an air-fuel ratio of exhaust gas flowing out of the catalyst;
setting a target air-fuel ratio for incoming exhaust gas flowing into the catalyst to a lean set air-fuel ratio that is leaner than a stoichiometric air-fuel ratio when the detected air-fuel ratio is equal to or less than a predetermined oxygen depletion determination air-fuel ratio;
setting the target air-fuel ratio to a rich set air-fuel ratio that is richer than the stoichiometric air-fuel ratio when the detected air-fuel ratio is equal to or higher than a predetermined oxygen saturation determination air-fuel ratio;
calculating a maximum oxygen storage capacity of the catalyst based on an amount of oxygen stored in the catalyst when the target air-fuel ratio is maintained at the lean set air-fuel ratio; and
determining whether the catalyst is abnormal based on the maximum oxygen storage capacity, wherein
the oxygen depletion determination air-fuel ratio is an air-fuel ratio richer than the stoichiometric air-fuel ratio, and the oxygen saturation determination air-fuel ratio is leaner than the oxygen depletion determination air-fuel ratio and richer than the stoichiometric air-fuel ratio.