Nissan Motor Company Limited

Other

Osamu Matsuno

Masatomo Kakuyama

Shigeaki Kakizaki

Katsuhiko Kawamura

Hiroshi Abe

Toshio Hori

Takeshi Tsuyuki

Satoru Osaki

Hirofumi Tsuchida

Hideaki Kobayashi

Akira Tayama

Masato Kobayashi

Hideaki Takahashi

Ritsuo Sato

Toshio Takahata

Takashi Aramaki

Youichi Kishimoto

Jun Nakanowatari

Saburo Tomikawa

Yoichi Kishimoto

A failure diagnosis apparatus for an exhaust gas recirculation system eliminates the influence of various disturbance factors that vary the suction air pressure, diagnoses a failure of the exhaust gas recirculation system on the basis of the suction air pressure, and prevents incorrect diagnosis. The system includes a fresh air pressure unit for determining an estimated fresh air pressure inside a suction pipe from the operating condition of an internal combustion engine and an actual exhaust gas recirculation pressure estimating unit for determining an EGR gas pressure on the basis of a measured suction pipe pressure detected by a suction pipe pressure detecting unit and estimated fresh air pressure. A failure is judged on the basis of the estimated EGR gas pressure and the detected operating condition.

Failure diagnosis apparatus for exhaust gas recirculation system

To provide a failure diagnosis apparatus for an exhaust gas recirculation system which is capable of eliminating the influence of various disturbance factors that vary the suction air pressure, diagnosing a failure of the exhaust gas recirculation system on the basis of the suction air pressure, and preventing wrong diagnosis. A failure diagnosis apparatus for an exhaust gas recirculation system consists of a fresh air pressure estimating means for calculating an estimated fresh air pressure inside a suction pipe from the operating condition of an internal combustion engine, an actual EGR (exhaust gas recirculation) gas pressure estimating means for estimating an EGR gas pressure on the basis of a measured suction pipe pressure detected by a suction pipe pressure detecting means and an estimated fresh air pressure calculated above, and a failure judging means for judging the failure on the basis of the estimated EGR gas pressure and the detected operating condition.

An engine exhaust emission control arrangement has a catalytic converter including a three-way catalyst. A first oxygen sensor detects an oxygen concentration of exhaust gas upstream of the catalyst and a second oxygen sensor detects an oxygen concentration of exhaust gas downstream of the catalyst. A microprocessor calculates a specific period oxygen storage amount of a catalyst while the upstream oxygen concentration is higher than the stoichiometric concentration and the downstream oxygen concentration is in a predetermined concentration range which has a value approximately equal to the stoichiometric oxygen concentration. The microprocessor also calculates a specific period oxygen release amount of a catalyst while the upstream oxygen concentration is lower than the stoichiometric concentration and the downstream oxygen concentration produces an indication of a predetermined concentration range. A specific period oxygen storage amount is sampled at a time at which the downstream oxygen concentration becomes greater than the predetermined concentration range as a maximum oxygen storage amount and a specific period oxygen release amount is sampled at a time at which the downstream oxygen concentration becomes smaller than the predetermined concentration range as a maximum oxygen release amount. The engine air-fuel ratio is controlled to cause the oxygen storage amount of the catalyst to coincide with a target value which is set at approximately half of an average value of the maximum oxygen storage amount and the maximum oxygen release amount.

Exhaust emission control for engine

A controller ( ) computes the oxygen storage amount of the catalyst ( ) separately as a high-speed component and a low speed component in accordance with actual characteristic. A target air-fuel ratio of an engine ( ) is computed so that the oxygen storage amount is a predetermined target amount, and air-fuel ratio control of the engine ( ) is performed. The oxygen storage amount is computed using an storage/release rate set according to the exhaust air-fuel ratio and catalyst temperature, etc. In this way, the oxygen storage amount of the catalyst can be precisely computed regardless of the variation in the storage/release rate which accompanies a catalyst temperature variation, and the real oxygen storage amount can therefore be controlled with a higher level of precision.

Engine exhaust purification device

A microprocessor ( ) computes an oxygen storage amount of a catalyst ( ) separately for a high speed component and a low speed component in accordance with real characteristic. A target air-fuel ratio of an engine ( ) is computed and air-fuel ratio control of the engine ( ) it is performed so that the high speed component is constant. The deterioration of the catalyst ( ) is determined by integrating the high speed component of the oxygen storage amount computed during the air-fuel ratio control process for a predetermined number of times, and comparing its average value with a determining value. The oxygen storage amount of the high speed component which is sensitive to catalyst deterioration is integrated so as to obtain a highly precise determining result to determine the deterioration.

A controller ( ) computes an oxygen storage amount of a catalyst ( ) separately as a high speed component/amount and a low speed component/amount according to predetermined release/adsorption characteristics. A target air-fuel ratio of an engine is computed and the air-fuel ratio of the engine is controlled so that the high speed component is maintained constant. The target air-fuel ratio of the engine ( ) is limited by an upper limiter and lower limiter so that the high speed component converges to the target value, an excessively large variation of the air-fuel ratio is prevented, and impairment of drivability and fuel cost-performance is also prevented. Further, after lean running due to fuel cut, etc., the lower limiter is lowered to the rich side, and the oxygen storage amount is rapidly induced to converge on the target value.

Engine exhaust purification arrangement

To provide a failure diagnosis apparatus for an exhaust gas recirculation system which is capable of eliminating the influence of various disturbance factors that vary the suction air pressure, diagnosing a failure of the exhaust gas recirculation system on the basis of the suction air pressure, and preventing wrong diagnosis. A failure diagnosis apparatus for an exhaust gas recirculation system consists of a fresh air pressure estimating device for calculating an estimated fresh air pressure inside a suction pipe from the operating condition of an internal combustion engine, an actual EGR (exhaust gas recirculation) gas pressure estimating device for estimating an EGR gas pressure on the basis of a measured suction pipe pressure detected by a suction pipe pressure detecting device and an estimated fresh air pressure calculated above, and a failure judging device for judging the failure on the basis of the estimated EGR gas pressure and the detected operating condition.

A controller ( ) controls an air-fuel ratio of an engine ( ) so that an oxygen storage amount of a catalyst ( ) provided in an exhaust passage ( ) is maintained constant. At this time, the controller ( ) computes or estimates the oxygen storage amount separately for a first amount and a second amount, where the first amount is estimated based on a relationship between the first and second amount. The controller ( ) controls the air/fuel ratio based on the estimated first amount.

A catalyst which has oxygen storage performance is installed in an engine exhaust passage an oxygen storage amount is estimated based on the output of an upstream air-fuel ratio sensor installed in the upstream of the catalyst and an air-fuel ratio is controlled so that this oxygen storage amount coincides with a target value. When the output of a downstream air-fuel ratio sensor has become lean or rich for longer than a fixed time, the output of the upstream air-fuel ratio sensor is corrected based on the output of the downstream air-fuel ratio sensor placed in the downstream of the catalyst In this way, the output fluctuation due to deterioration of the air-fuel ratio sensor upstream of the catalyst is corrected, and the catalyst oxygen storage amount is always precisely controlled to the target value.

Engine air-fuel ratio controller

An oxygen storage amount of the catalyst ( ) is estimated using a detection result from a front A/F sensor ( ). An HC storage amount is calculated as a time integral of the product of the storage rate by the catalyst ( ), the air-fuel ratio and the intake air amount, and a target air-fuel ratio is corrected so that a deficiency relative to a target amount of the oxygen storage amount is compensated based on this computation result.

An EGR system comprises a vacuum-operated EGR valve and an auxiliary valve of a diaphragm type for assisting the operation of the EGR valve. A diagnostic control unit monitors an engine rotational fluctuation parameter such as a misfire parameter under the condition of EGR and judges that there is a possibility of abnormality in the auxiliary valve when the fluctuation parameter is greater than a first judgment value. In response to this judgment, the diagnostic control unit forcibly cuts off the EGR and calculates the fluctuation parameter under the condition of EGR cutoff. The diagnostic control unit concludes that the auxiliary valve is abnormal when the fluctuation parameter in the EGR cutoff state is smaller than or equal to a second judgment value which is smaller than the first judgment value.

Diagnosis for EGR system

A catalytic converter ( ) having a three-way catalyst which stores oxygen is disposed in the exhaust passage ( ) of an engine ( ). An oxygen storage amount of the catalyst is estimated based on the output of a universal exhaust gas oxygen sensor ( ) provided upstream of the catalytic converter ( ). A control unit ( ) controls an air-fuel ratio of the fuel mixture supplied to the engine ( ) through a fuel injector ( ) so that the oxygen storage amount coincides with a target value. An excess/deficiency oxygen amount in the exhaust gas is accumulated when the output of an oxygen sensor ( ) which detects the oxygen concentration downstream of the catalytic converter ( ) is in an excess oxygen region which is higher than a stoichiometric oxygen concentration region. An average oxygen excess ratio is calculated by dividing the accumulated value by an accumulated intake air amount. The output of the universal exhaust gas oxygen sensor ( ) is corrected based on the average oxygen excess ratio. In the same manner, the output of the universal exhaust gas oxygen sensor ( ) is corrected based on the average oxygen excess ratio when the output of the oxygen sensor ( ) is in an deficiency oxygen region which is lower than the stoichiometric oxygen concentration region. These corrections compensate for fluctuations in the output resulting from deterioration of the universal exhaust gas oxygen sensor ( ) or due to manufacturing errors and the calculation accuracy of the oxygen storage amount of the catalyst is thereby increased.

Air-fuel ratio control of engine

In an automotive vehicle with at least one catalyst located in an exhaust passage for adsorbing oxygen contained within exhaust gases entering the catalyst, and an air/fuel ratio sensor located in the exhaust passage upstream of the catalyst for detecting an air/fuel ratio based on a percentage of oxygen contained within the exhaust gases flowing through the exhaust passage and entering the catalyst, an air/fuel ratio control system controls an air/fuel mixture ratio of the engine at as close to stoichiometric as possible, an air/fuel ratio control system calculates a quantity of oxygen stored in the catalyst on the basis of a deviation of the air/fuel ratio detected by the air/fuel ratio sensor from a stoichiometric air/fuel ratio to produce informational data indicative of a calculated value of the quantity of oxygen stored. The control system controls the air/fuel mixture ratio of the engine so that the calculated value of the quantity of oxygen stored is adjusted to a desired value. The control system has a limiter capable of preventing the calculated value of the quantity of oxygen stored from exceeding a specified level.

Air/fuel ratio control system of internal combustion engine

Air/fuel ration control system of internal combustion engine

Faults in a variable valve timing mechanism can be accurately diagnosed without influence of a detection error by a crank angle sensor and the like. A phase difference of a crank angle between a standard angular signal REF output from the crank angle sensor and a phase detection signal detected at a predetermined angular position of a cam shaft is counted every control state of the variable valve timing mechanism. Next, a variation between a phase difference counted at a time of OFF control state and a phase difference counted at a time of ON control state is calculated as a diagnosis parameter. Then, in the case that the diagnosis parameter is smaller than a standard value for determination, a fault in the variable valve timing mechanism is determined.

Growing community of inventors

Ayase, Japan

Osamu Matsuno