Deterioration diagnosis apparatus for exhaust gas purification apparatus

Patent metadata

Field	Value
Publication number	US-10302002-B2
Application number	US-201515319450-A
Country	US
Kind code	B2
Filing date	Jun 15, 2015
Priority date	Jun 20, 2014
Publication date	May 28, 2019
Grant date	May 28, 2019

Abstract

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.

First claim

The invention claimed is:

1. A deterioration diagnosis apparatus for use in an exhaust gas purification apparatus which comprises:
a first exhaust gas purification apparatus that is provided in an exhaust passage of an internal combustion engine capable of performing a lean burn operation, and that is configured to include a catalyst that promotes a water-gas shift reaction when an air-fuel ratio of exhaust gas is a rich air-fuel ratio that is lower than a stoichiometric air-fuel ratio; and
a second exhaust gas purification apparatus that is disposed in the exhaust passage downstream of the first exhaust gas purification apparatus, and that is configured to include a selective catalytic reduction catalyst that occludes oxygen contained in the exhaust gas when the air-fuel ratio of the exhaust gas is a lean air-fuel ratio that is higher than the stoichiometric air-fuel ratio, and releases the occluded oxygen when the air-fuel ratio of the exhaust gas is equal to or lower than the stoichiometric air-fuel ratio,
the deterioration diagnosis apparatus comprising:
a first sensor configured to measure a physical quantity that correlates with an oxygen concentration of exhaust gas flowing into the second exhaust gas purification apparatus;
a second sensor configured to measure a physical quantity that correlates with an oxygen concentration of exhaust gas flowing out of the second exhaust gas purification apparatus; and
a controller configured to diagnose deterioration of the second exhaust gas purification apparatus,
wherein the controller is configured to:
execute induction processing, which is processing for inducing the water-gas shift reaction in the first exhaust gas purification apparatus, by modifying an air-fuel ratio of exhaust gas flowing into the first exhaust gas purification apparatus to a rich air-fuel ratio that is lower than the stoichiometric air-fuel ratio when an air-fuel ratio of exhaust gas discharged from the internal combustion engine is a lean air-fuel ratio; and
diagnose deterioration of the second exhaust gas purification apparatus using, as a parameter, a difference that appears between a measurement value of the first sensor and a measurement value of the second sensor when the induction processing is executed.

2. The deterioration diagnosis apparatus for use an exhaust gas purification apparatus according to claim 1 , wherein
the controller executes the induction processing when a temperature of the second exhaust gas purification apparatus falls within a temperature range in which hydrogen contained in the exhaust gas can be oxidized by the selective catalytic reduction catalyst in the second exhaust gas purification apparatus, an amount by which a hydrogen oxidation amount varies within the temperature range being equal to or smaller than a predetermined amount.

3. The deterioration diagnosis apparatus for use an exhaust gas purification apparatus according to claim 2 , wherein
the catalyst included in the first exhaust gas purification apparatus is a NO x storage reduction catalyst that is configured to occlude nitrogen oxide contained in the exhaust gas when the air-fuel ratio of the exhaust gas is a lean air-fuel ratio, and to reduce the nitrogen oxide while releasing the nitrogen oxide when the air-fuel ratio of the exhaust gas is a rich air-fuel ratio, and
the controller makes the air-fuel ratio of the exhaust gas flowing into the first exhaust gas purification apparatus during execution of the induction processing lower than the air-fuel ratio of the exhaust gas flowing into the first exhaust gas purification apparatus during execution of rich spike processing, which is processing for regenerating a NO x storage ability of the NO x storage reduction catalyst.

4. The deterioration diagnosis apparatus for use an exhaust gas purification apparatus according to claim 3 , wherein
the controller is configured to correct the difference appearing between the measurement value of the first sensor and the measurement value of the second sensor upon execution of the induction processing when the catalyst in the first exhaust gas purification apparatus has deteriorated, and correct the difference so as to increase steadily as a degree of deterioration of the catalyst in the first exhaust gas purification apparatus increases, and
the controller diagnoses deterioration of the second exhaust gas purification apparatus using a corrected value as a parameter.

5. The deterioration diagnosis apparatus for use an exhaust gas purification apparatus according to claim 3 , wherein
the controller diagnoses deterioration of the second exhaust gas purification apparatus using, as a parameter, a sum of a difference between the measurement value of the first sensor and the measurement value of the second sensor obtained when the air-fuel ratio of the exhaust gas flowing into the first exhaust gas purification apparatus is modified from a lean air-fuel ratio to a rich air-fuel ratio in response to execution of the induction processing, and a difference between the measurement value of the first sensor and the measurement value of the second sensor obtained when the air-fuel ratio of the exhaust gas flowing into the first exhaust gas purification apparatus is modified from a rich air-fuel ratio to a lean air-fuel ratio upon termination of the induction processing.

6. The deterioration diagnosis apparatus for use an exhaust gas purification apparatus according to claim 2 , wherein
the controller is configured to correct the difference appearing between the measurement value of the first sensor and the measurement value of the second sensor upon execution of the induction processing when the catalyst in the first exhaust gas purification apparatus has deteriorated, and correct the difference so as to increase steadily as a degree of deterioration of the catalyst in the first exhaust gas purification apparatus increases, and
the controller diagnoses deterioration of the second exhaust gas purification apparatus using a corrected value as a parameter.

7. The deterioration diagnosis apparatus for use an exhaust gas purification apparatus according to claim 1 , wherein
the catalyst included in the first exhaust gas purification apparatus is a NO x storage reduction catalyst that is configured to occlude nitrogen oxide contained in the exhaust gas when the air-fuel ratio of the exhaust gas is a lean air-fuel ratio, and to reduce the nitrogen oxide while releasing the nitrogen oxide when the air-fuel ratio of the exhaust gas is a rich air-fuel ratio, and
the controller makes the air-fuel ratio of the exhaust gas flowing into the first exhaust gas purification apparatus during execution of the induction processing lower than the air-fuel ratio of the exhaust gas flowing into the first exhaust gas purification apparatus during execution of rich spike processing, which is processing for regenerating a NO x storage ability of the NO x storage reduction catalyst.

8. The deterioration diagnosis apparatus for use an exhaust gas purification apparatus according to claim 7 , wherein
the controller diagnoses deterioration of the second exhaust gas purification apparatus using, as a parameter, a sum of a difference between the measurement value of the first sensor and the measurement value of the second sensor obtained when the air-fuel ratio of the exhaust gas flowing into the first exhaust gas purification apparatus is modified from a lean air-fuel ratio to a rich air-fuel ratio in response to execution of the induction processing, and a difference between the measurement value of the first sensor and the measurement value of the second sensor obtained when the air-fuel ratio of the exhaust gas flowing into the first exhaust gas purification apparatus is m

Assignees

• Toyota Motor Co Ltd

Inventors

• Hagiwara Koji
• Kidokoro Toru
• Iwazaki Yasushi
• Yoshida Taisuke

Classifications

• F01N11/002

  the diagnostic devices measuring or estimating temperature or pressure in, or downstream of the exhaust apparatus · CPC title

• F01N2560/025

  for measuring or detecting O2, e.g. lambda sensors · CPC title

• F01N3/0814

  combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts · CPC title

• B01D53/9418

  for removing nitrogen oxides by selective catalytic reduction [SCR] using a reducing agent in a lean exhaust gas · CPC title

• F02D41/027

  to purge or regenerate the exhaust gas treating apparatus · CPC title