Nissan Motor Company Limited

Yasuji Ishizuka

Kimiyoshi Nishizawa

Masaki Koga

Yoshiyuki Ootake

Kenichi Sato

Hideaki Takahashi

Takashi Yamada

Hiroyuki Nagai

Yoshiaki Yoshioka

Kengo Kubo

Satoshi Nishii

An air-fuel ratio control device is provided for controlling the air-fuel ratio of an engine. The device includes an exhaust passage having a main catalytic converter and a bypass passage having a bypass catalytic converter, the bypass passage diverging from the exhaust passage at an upstream junction and rejoining the exhaust passage at a downstream junction. A valve mechanism disposed in the exhaust passage between the upstream junction and the downstream junction moves between a closed state and an open state. During a predetermined period of time after the valve mechanism opens to permit flow in the exhaust passage, the air-fuel ratio of the engine is controlled based on a signal from a first air-fuel ratio sensor in the bypass passage using a low response correction value that is less than a normal response correction value that would be used when the valve mechanism is closed.

Air-fuel ratio control device

An air-fuel ratio control apparatus is basically provided with an exhaust system, a pair of sensors and a controller. The exhaust system includes an exhaust channel having a main catalytic converter, a bypass channel having a bypass catalytic converter, and a valve mechanism disposed in the exhaust channel to switch a pathway for exhaust gas from the exhaust channel to the bypass channel. The sensors output signals indicative of air-fuel ratios of exhaust flowing in their respective channels. The controller has first and second air-fuel ratio control sections that control an engine air-fuel ratio based on outputs of the sensors, respectively. The controller has a control mode switching section that switches control from the first air-fuel ratio control section to the second air-fuel ratio control section after a prescribed interval of time has elapsed from when the valve mechanism is switched from a closed state to an open state.

Air-fuel ratio control apparatus

An air-fuel ratio control apparatus is basically provided with an exhaust system, a first sensor and a controller. The exhaust system includes an exhaust channel with a main catalytic converter disposed therein, a bypass channel with a bypass catalytic converter disposed therein, and a valve mechanism disposed in the exhaust channel between the connection points of the exhaust channel to switch a pathway for exhaust gas from the exhaust channel to the bypass channel. The first sensor detects a property indicative of an air-fuel ratio of exhaust flowing in the exhaust channel at a point downstream of the valve mechanism. The controller adjusts an element temperature of the first sensor to a prescribed temperature or less during a prescribed interval of time from when the valve mechanism is switched from a closed state to an open state.

Sulphur oxides in the exhaust gas of a vehicle engine () are trapped by a nitrogen oxide trapping catalyst (A). A controller () calculates the sulphur oxide poisoning amount of the trapping catalyst (A) from the running condition of the vehicle (S), and desulphating the sulphur oxides by a removing mechanism (). The release amount of sulphur oxides per unit time due to desulphating is set as a parameter based on the sulphur oxide poisoning amount (S), and by integrating the calculated release amount using the parameter, the current poisoning amount is calculated, and the release completion timing is precisely found.

Desulphating of nitrogen oxide trapping catalyst

A first catalyst which stores or releases oxygen according to an air-fuel ratio, and a second catalyst which traps or releases NOx according to the air-fuel ratio, are provided in an exhaust passage of an engine . A controller temporarily shifts the air-fuel ratio of the engine to rich when it is determined that the NOx trap catalyst second catalyst is released. At this time, the controller increases a reducing agent supply amount due to the rich shift to be larger, the larger the oxygen amount stored by the two catalysts . In this way, the air-fuel ratio in the second catalyst is maintained at a target stoichiometric or rich air-fuel ratio.

Engine exhaust purification device

An exhaust emission control device of an engine,comprises an NOx storage catalyst,which traps and stores NOx in exhaust gas and reduces the stored NOx according to an air fuel ratio of inflowing exhaust gas. A controller,determines conditions for discharging the SOx stored in the catalyst,. When SOx discharge conditions are satisfied and the engine running conditions are in a predetermined SOx discharge running region, the controller,performs SOx discharge control of the catalyst,. As lean air fuel ratio control is prohibited from when SOx discharge conditions are satisfied to when SOx discharge is complete, lean air fuel ratio control is prevented from taking place when the NOx trapping capacity of the catalyst,is insufficient, and increase of exhaust emission is thereby prevented.

Exhaust emission control device for internal combustion engine

An exhaust emission control system for an internal combustion engine amounted on an automotive vehicle. The exhaust emission control system comprises a first catalyst disposed in an exhaust gas passage of the engine. The first catalyst functions to store NOx in an atmosphere having an air-fuel ratio leaner than a stoichiometric level and to release NOx in an atmosphere having an air-fuel ratio ocher than the stoichiometric level and reduce released NOx in presence of HC and CO. A second catalyst is disposed in the exhaust gas passage upstream of the first catalyst and having an oxygen absorbing ability. A control unit is provided including a first section for accomplishing an enrichment treatment by enriching stepwise an air-fuel ratio of an air-fuel mixture to be supplied to the engine to an enrichment degree at a timing at which a lean operation is changed to a stoichiometric operation in the engine, and recovering the enriched air-fuel ratio to the stoichiometric level at a recovery rate immediately after the enriching the air-fuel ratio. A second section of the control unit is for estimating the oxygen absorbing ability of the second catalyst. A third section of the control unit is for correcting the enrichment degree to decrease in the stepwise enriching as the estimated oxygen absorbing ability decreases.

Exhaust emission control system for internal combustion engine

For proper treatment of NOx released from NOx absorbent catalyst as well as HC and CO in exhaust gas, a measure of A/F of exhaust gas downstream of the NOx absorbent is used as the input to a feedback control loop. The feedback control loop alters a feedback correction factor (or coefficient) of a fuel control command applied to each fuel injector in such a direction to decrease a deviation of the actual A/F input from a target A/F (stoichiometry or rich) When the measure of A/F has switched the side to rich, a measure of A/F of exhaust gas upstream of the NOx absorbent catalyst is used as the input to perform usual feedback control loop to maintain lean combustion mode.

Internal combustion engine with NOx absorbent catalyst

To optimally operate a NOx-occluded type catalytic converter installed in an exhaust passage of an internal combustion engine, there are employed an air/fuel ratio sensor for detecting an exhaust air/fuel ratio of the exhaust gas downstream of the converter; and a control device for controlling an air/fuel ratio of a combustible mixture fed to the engine. The control device comprises a first section for causing the converter to effect NOx-reduction treatment by making the air/fuel ratio of the combustible mixture richer and/or stoichiometric; and a second section for learning and correcting the condition of the NOx-reduction treatment, based on the exhaust air/fuel ratio detected by the sensor under the NOx-reduction treatment.

Exhaust gas purifying system of internal combustion engine

An exhaust emission control apparatus for an internal combustion engine includes an electrically-heated catalytic converter and a secondary air supply device. The converter is electrically heated with a predetermined delay after the secondary air supply device starts supplying fresh air to exhaust gases of the engine. This prevents the increase of an intake air flow due to the no-delay electric heating of the converter, and therefore the thermal reactor effect of the secondary air supply device is ensured.

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Chigasaki, Japan

Yasuji Ishizuka