The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 24, 1997
Filed:
Oct. 18, 1995
Yuki Nakajima, Yokosuka, JP;
Hideki Uema, Zushi, JP;
Nissan Motor Co., Ltd., Yokohama, JP;
Abstract
A catalyst deterioration diagnosis system for an internal combustion engine having an exhaust gas passageway in which a catalytic converter having a catalyst is disposed. The diagnosis system comprises a first air-fuel ratio sensor disposed in the exhaust gas passageway upstream of the catalytic converter, and a second air-fuel ratio sensor disposed in the exhaust gas passageway downstream of the catalytic converter. The diagnosis system further comprises a control unit connected to the air-fuel ratio sensors and arranged to make an air-fuel ratio feedback control mainly in response to an output signal of the first air-fuel ratio sensor. The control unit includes means for calculating an inversion ratio value relating to an inversion ratio of output signals from the first and second air-fuel ratio sensors when the engine operating condition is within a diagnosis region requiring a diagnosis of deterioration of the catalyst, means for detecting an inversion state value relating to a state of inversion of the output signal of the first air-fuel ratio sensor, means for setting a decision standard value in accordance with the inversion state value from the inversion state value detecting means, and means for judging the deterioration of the catalyst by comparing the inversion ratio value from the inversion ratio value calculating means with the decision standard value from the decision standard value setting means.