Nissan Motor Company Limited

Kouji Ishihara

Yasuyuki Itou

Hirofumi Tsuchida

Hiroshi Miyakubo

Keiji Okada

Hisashi Mitsumoto

Tsuyoshi Taniyama

Hidetoshi Itou

Tarou Yokoi

An exhaust gas purification device including three-way catalysts connected to engine cylinder groups and arranged in parallel, and a NOx trapping catalyst connected with the three-way catalysts downstream thereof. A controller controls fuel injection for making an A/F ratio of exhaust gas flowing into one of the three-way catalysts rich relative to a stoichiometric A/F ratio when it is required to reduce the NOx trapped by the NOx trapping catalyst.

Exhaust gas purification device for an engine and A/F ratio control for early activating a NOx trapping catalyst

In a device for purifying an exhaust gas mixture from an engine, a catalyst traps and reduces NOx in dependence of the air fuel ratio of the exhaust gas mixture from the engine. A controller detects a predetermined condition to initiate a catalyst regenerating control to reduce NOx in the catalyst, and controls the engine in a catalyst regeneration control mode when the predetermined condition is detected. In the catalyst regeneration control mode, the controller sets the fuel injection timing on the compression stroke and the fuel injection quantity at a level to make the average air fuel ratio in a combustion chamber equal to or leaner than the stoichiometric ratio and to produce a rich air fuel mixture region richer than the stoichiometric ratio in the vicinity of a spark plug.

Exhaust gas purification device for 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.

Method and system for diagnosing deterioration of NOx catalyst

A deterioration diagnosing system for a NOx-occluded catalyst comprises an inlet NOx concentration estimating unit which estimates NOx concentration at an inlet part of the catalyst; an outlet NOx concentration detecting unit which detects NOx concentration at an outlet part of the catalyst; and a deterioration degree judging unit which judges a deterioration degree of the catalyst in accordance with a rate of the minimum value of NOx concentration detected by the detecting unit for a predetermined period to a value of NOx concentration estimated by the estimating unit at the time when the minimum value of NOx concentration is detected. The predetermined period is a period between a time when the engine exhaust gas shows the stoichiometric and/or richer air/fuel ratio and a subsequent time when the engine exhaust gas shows the stoichiometric and/or richer air/fuel ratio.

System and method for diagnosing deterioration of NOx-occluded catalyst

A cylinder direct injection spark-ignition engine in which fuel is directly injected from a fuel injector into each cylinder. The engine has an intake system having two intake ports for each cylinder. A swirl control valve is movably disposed in a passage connected to one of the intake ports. The swirl control valve functions to regulate the intensity (a swirl ratio) of swirl to be generated in the cylinder. Sensors are provided to detect an engine operating condition representative of a stratified charge combustion region. Additionally, a controller is provided to control the swirl control valve so as to change the swirl ratio in accordance an engine speed of the engine, when the current engine operating condition is detected to correspond to the stratified charge combustion region.

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Yokohama, Japan

Kouji Ishihara