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:
Mar. 28, 1995
Filed:
Feb. 10, 1994
Takashi Mukaihira, Katsuta, JP;
Toshio Ishii, Mito, JP;
Yutaka Takaku, Katsuta, JP;
Akihito Numata, Urizura, JP;
Hitachi, Ltd., , JP;
Abstract
A catalytic diagnostic apparatus for determining whether a catalyst of an internal combustion engine has deteriorated as disclosed. Air-fuel ratio sensors are placed at the upstream and downstream sides of the catalytic converter, and the output signal from the upstream air-fuel sensor is used to control the air-fuel mixture provided to the engine via the fuel injectors, in a conventional closed loop operation. Diagnosis of the condition of the catalytic converter is performed only when selected engine operating parameters fall within a predetermined diagnostic range. When the engine is operated in the diagnostic range, the condition of the catalytic converter is analyzed by calculating a deterioration index based on a comparison of the variation of the output signals from the upstream and downstream air-fuel ratio sensors. In a preferred embodiment, a look-up table is provided to correct the deterioration index, based on the intake air flow rate to the engine, and on the cyclic frequency of the variation of the downstream air-fuel ratio sensor.