Toyota Jidosha Kabushiki Kaisha

Koji Hagiwara

Yasushi Iwazaki

Toru Kidokoro

Hirotaka Saitoh

Takahiko Fujiwara

Yuji Miyoshi

Hiroshi Miyamoto

Masahiko Masubuchi

Hirotaka Saito

Taisuke Yoshida

An exhaust gas sensor is diagnosed with high accuracy as much as possible while maintaining the function of an exhaust system of an internal combustion engine. In a diagnostic apparatus for an exhaust gas sensor which is applied to an internal combustion engine including an exhaust gas sensor, a fuel supplier, a controller configured to carry out predetermined fuel supply processing and predetermined oxygen concentration processing, and which diagnoses the exhaust gas sensor based on an output value thereof, provision is made for the controller that sets as a diagnostic output value a first output value, which is an output value at the side of the highest oxygen concentration in the output value of the exhaust gas sensor in a measurement period, and performs the diagnosis of the exhaust gas sensor based on the diagnostic output value, when predetermined fuel supply processing is carried out in the measurement period.

Diagnostic apparatus for exhaust gas sensor

An object is to prevent a wrong diagnosis from being made in diagnosis of an NOx sensor provided downstream of an SCR catalyst. A diagnosis apparatus is applied to an NOx sensor provided in an exhaust system including an SCR catalyst, a reducing agent supply device, an NOx sensor, an exhaust gas purification device provided upstream of the SCR catalyst, and a controller configured to raise the temperature of the exhaust gas purification device and control supply of reducing agent so as to adjust the ammonia adsorption amount to a specific amount. The controller is further configured to perform diagnosis of the NOx sensor on the basis of the concentration of ammonia slipping out of the SCR catalyst and disallow diagnosis of the NOx sensor since the ammonia adsorption amount is adjusted to the specific amount until a specific time elapses.

Diagnosis apparatus and diagnosis method for NOx sensor

The present invention provides a deterioration diagnosis apparatus for an exhaust gas purification apparatus, including a first sensor that measures the oxygen concentration of the exhaust gas flowing into the exhaust gas purification apparatus, a second sensor that measures the oxygen concentration of the exhaust gas flowing out of the exhaust gas purification apparatus, and diagnosing means for diagnosing deterioration of the exhaust gas purification apparatus on the basis of a difference that appears between a measurement value of the first sensor and a measurement value of the second sensor when the air-fuel ratio of the exhaust gas flowing into the exhaust pas purification apparatus is switched from a lean air-fuel ratio to a rich air-fuel ratio, wherein, when the air-fuel ratio of the exhaust gas is switched from a lean air-fuel ratio to a rich air-fuel ratio, a water-gas shift reaction is generated upstream of the first sensor.

Deterioration diagnosis apparatus for exhaust gas purification apparatus

An apparatus according to the present invention is adapted to calculate an NOstorage rate defined as the rate of the quantity of NOstored into the NSR catalyst to the quantity of NOflowing into the NSR catalyst, based on quantity of NOflowing into the NSR catalyst and the quantity of NOflowing out of the NSR catalyst in a state in which the amount of NOstored in the NSR catalyst is equal to or larger than the breakthrough start amount of a criterion catalyst and the flow rate of exhaust gas flowing through the NSR catalyst is equal to or higher than a predetermined lower limit flow rate. The apparatus diagnoses the NSR catalyst as normal if the NOstorage rate thus calculated is equal to or higher than a predetermined threshold and as abnormal if the NOstorage rate is lower than the predetermined threshold.

[object Object]

A deterioration diagnosis apparatus for an exhaust gas purification apparatus according to the invention performs an induction process when an internal combustion engine is operating at a lean air-fuel ratio, measures the air-fuel ratio of the exhaust gas flowing into the SCR catalyst and the air-fuel ratio of the exhaust gas flowing out of the SCR catalyst by the air-fuel ratio sensor during the period through which the induction process is performed, and diagnoses deterioration of the SCR catalyst based on the difference between the air-fuel ratios thus measured. The diagnosis apparatus adjusts the quantity of reducing agent supplied to a hydrogen production catalyst during the period through which the induction process is performed, taking account of the degree of deterioration of the hydrogen production catalyst.

In a deterioration diagnosis apparatus for a selective catalytic reduction (SCR) catalyst in which when an air fuel ratio of a mixture to be combusted in an internal combustion engine is a lean air fuel ratio, inducement processing is executed which is to induce a water gas shift reaction in a pre-stage catalyst, by changing the air fuel ratio of the mixture from the lean air fuel ratio to a predetermined rich air fuel ratio, and diagnosis processing is executed which is to diagnose deterioration of the SCR catalyst based on an output difference between two air fuel ratio sensors at the time of the execution of the inducement processing, when the SCR catalyst is in a state of being subjected to sulfur poisoning resulting from the execution of the S purge processing of the pre-stage catalyst, diagnosis processing is not executed.

Deterioration diagnosis apparatus for selective catalytic reduction catalyst

Deterioration of a selective catalytic reduction (SCR) catalyst can be diagnosed with sufficient accuracy, by making use of a sensor for measuring an air fuel ratio of exhaust gas flowing into an exhaust gas purification apparatus, which is equipped with the SCR catalyst, and a sensor for measuring an air fuel ratio of exhaust gas flowing out from the exhaust gas purification apparatus.

Deterioration diagnosis apparatus for the exhaust gas purification apparatus

An object of the present invention is to detect an abnormality in an exhaust gas purification apparatus having an NSR catalyst and an SCR catalyst disposed on a downstream side of the NSR catalyst more favorably. Air-fuel ratio reduction control is executed to reduce NOoccluded to the NSR catalyst when an integrated value of an amount of NOflowing into the NSR catalyst reaches an upper limit value of an amount of NOthat can be occluded to the NSR catalyst in a normal condition. It is determined whether or not the exhaust gas purification apparatus is in an abnormal state on the basis of a NOpurification ratio of the exhaust gas purification apparatus calculated at this time.

Abnormality detection apparatus for exhaust gas purification apparatus

A deterioration diagnosis device for an exhaust gas purification apparatus which performs inducement processing when the internal combustion engine is operated at a lean air fuel ratio, measures, by means of air fuel ratio sensors, the air fuel ratio of exhaust gas flowing into the SCR catalyst and the air fuel ratio of exhaust gas flowing out from the SCR catalyst during a period while the inducement processing is performed, and diagnoses deterioration of the SCR catalyst based on a difference between the measured values of these sensors, wherein an amount of hydrogen produced by each of a three-way catalyst and an NSR catalyst is estimated based on the deterioration degree thereof, and an air fuel ratio of exhaust gas discharged from the internal combustion engine is feedback-controlled so that the air fuel ratio of the exhaust gas flowing into one of the three-way catalyst and the NSR catalyst in which the hydrogen production amount thus estimated is larger than that in the other becomes a target value.

Deterioration diagnosis device for an exhaust gas purification apparatus

In an deterioration diagnosis device for the exhaust gas purification apparatus in which in a period of time in which inducement processing is carried out which is to induce a water-gas-shift-reaction in a catalyst disposed at the upstream side of the SCR catalyst, by changing an air fuel ratio of exhaust gas discharged from an internal combustion engine from a lean air fuel ratio into a predetermined rich air fuel ratio, an air fuel ratio of exhaust gas flowing into the SCR catalyst and an air fuel ratio of exhaust gas flowing out from the SCR catalyst are measured by the air fuel ratio sensors, respectively, so that deterioration of the SCR catalyst is diagnosed based on a difference between the measured values of these sensors, wherein an end time of the execution of the inducement processing is adjusted in such a manner that an amount of hydrogen oxidized in the SCR catalyst during the period of the execution of the inducement processing becomes constant.

Growing community of inventors

Susono, Japan

Koji Hagiwara