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:
Dec. 21, 1999
Filed:
Dec. 04, 1997
Rogelio B Agustin, Hitachinaka, JP;
Akihito Numata, Urizura-machi, JP;
Eisaku Fukuchi, Hitachi, JP;
Yutaka Takaku, Mito, JP;
Toshio Ishii, Mito, JP;
Hitachi, Ltd., , JP;
Abstract
A diagnostic apparatus for exhaust gas clarification apparatus for internal combustion engine diagnoses the individual catalyst independently by an air/fuel ratio sensor mounted before and after the individual catalyst. The individual catalyst is diagnosed by estimating the correlation of the output signals from the air/fuel ratio sensors mounted before and after the individual catalyst. The individual diagnosis operation is performed at distinctive operation regions adequate for their corresponding diagnostic mode. A by-pass route is provided for by-passing the exhaust gas from the upstream catalyst, and a by-pass valve switches the exhaust gas flow into the upstream catalyst or into the by-pass routes. A cross-correlation function calculation valve based upon outputs from air/fuel ratio sensors permits diagnosis of degradation of the overall catalyst.