Nissan Motor Company Limited

Hidetoshi Itou

Kimiyoshi Nishizawa

Hideaki Takahashi

Ken Oouchi

Katsuhiro Shibata

Yasuyuki Itou

Kouji Ishihara

For resiliently and safely supporting a monolith in a housing, a supporting structure is proposed. An annular seat structure is defined in the housing. An annular resilient washer is made of wire mesh and is put on the annular seat structure for supporting thereon a circular peripheral edge of the monolith. A biasing structure biases the monolith toward the annular resilient washer to compress the washer. The washer has a generally rectangular cross section and has a chamfered surface around a circular outer surface thereof. The chamfered surface is positioned radially outside the circular peripheral edge of the monolith. With this, even when compressed by the monolith, the washer is prevented from producing a biasing force for pulling the circular peripheral edge of the monolith radially outward, and thus, damage of the edge is suppressed.

Monolith supporting structure for use in catalytic converter

A primary deterioration diagnosis of a front catalyst (,) is performed based on the air-fuel ratio of the exhaust gas downstream of the front catalyst (,) detected in a first period each time the first period elapses when the engine (,) is running in a diagnosis region. A secondary deterioration diagnosis of the front catalyst (,) is performed based on the air-fuel ratio of the exhaust gas downstream of the front catalyst (,) detected in a second period longer than the first period each time the second period elapses when the engine (,) is running in the diagnosis region. When SOx discharge control is performed, primary diagnosis and secondary diagnosis are prohibited, and if it is determined in the primary diagnosis that the front catalyst (,) has deteriorated, SOx discharge control is prohibited to provide an opportunity for secondary diagnosis. In this way, the deterioration diagnosis of the front catalyst (,) can be precisely performed even if there are few opportunities for diagnosis due to lean air-fuel ratio running or SOx discharge control.

Exhaust emission control device of internal combustion engine

A system and method for diagnosing deterioration of a nitrogen oxide (NOx) catalyst for an internal combustion engine. An output signal indicative of concentration of nitrogen oxides (NOx) in exhaust gas passing through the NOx catalyst is generated from a NOx sensor. Rates of change in the detected NOx concentration are calculated a plurality of times over a predetermined period of time after an air/fuel ratio becomes less than a stoichiometric air/fuel ratio. A representative value derived from the calculated rates of change in the detected NOx concentration is compared with a predetermined reference value for determining that the NOx catalyst is deteriorated.

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Yokohama, Japan

Hidetoshi Itou