Abnormality diagnosis system of downstream side air-fuel ratio sensor

Patent metadata

Field	Value
Publication number	US-10156200-B2
Application number	US-201615222372-A
Country	US
Kind code	B2
Filing date	Jul 28, 2016
Priority date	Jul 29, 2015
Publication date	Dec 18, 2018
Grant date	Dec 18, 2018

Abstract

The abnormality diagnosis system comprises an air-fuel ratio control means which sets the target air-fuel ratio of exhaust gas to a first set air-fuel ratio set to a first side of a rich side or a lean side, then, when a downstream side output air-fuel ratio is at the first side, switches the target air-fuel ratio to a second set air-fuel ratio set to a second side at the opposite side from the first side. The abnormality diagnosis system calculates the time from when the target air-fuel ratio is switched to when the downstream side output air-fuel ratio starts to change toward the stoichiometric air-fuel ratio based on a differential value of the downstream side output air-fuel ratio and, when the calculated time is a predetermined time or more, judges that a dead time at the downstream side air-fuel ratio sensor is abnormal.

First claim

The invention claimed is:

1. An abnormality diagnosis system of a downstream side air-fuel ratio sensor provided in an exhaust passage of an internal combustion engine at a downstream side of an exhaust purification catalyst in a direction of exhaust flow, comprising
an air flowmeter detecting an amount of intake air fed to a combustion chamber; and
an electronic control unit configured to:
set a target air-fuel ratio of exhaust gas flowing into the exhaust purification catalyst and control an amount of fuel fed to the combustion chamber so that an air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst matches the target air-fuel ratio, the electronic control unit sets the target air-fuel ratio to a first set air-fuel ratio set to a first side of either side of a rich side and lean side from a stoichiometric air-fuel ratio, then, when a downstream side output air-fuel ratio detected by the downstream side air-fuel ratio sensor is at the first side from the stoichiometric air-fuel ratio, switches the target air-fuel ratio from the first set air-fuel ratio to a second set air-fuel ratio set to a second side at the opposite side from the first side from the stoichiometric air-fuel ratio;
calculate a time from when the target air-fuel ratio is switched from the first set air-fuel ratio to the second set air-fuel ratio to when the downstream side output air-fuel ratio starts to change toward the stoichiometric air-fuel ratio based on a differential value of the downstream side output air-fuel ratio;
correct the calculated time based on an intake air amount detected by the air flowmeter from when the target air-fuel ratio is switched from the first set air-fuel ratio to the second set air-fuel ratio to when the downstream side output air-fuel ratio starts to change toward the stoichiometric air-fuel ratio; and
judge that a dead time at the downstream side air-fuel ratio sensor is abnormal when the corrected time is a predetermined time or more, and judge that the dead time at the downstream side air-fuel ratio sensor is not abnormal when the corrected time is less than the predetermined time.

2. The abnormality diagnosis system of a downstream side air-fuel ratio sensor according to claim 1 , wherein the first side is a side richer than the stoichiometric air-fuel ratio, the second side is a side leaner than the stoichiometric air-fuel ratio, and the electronic control unit is configured to judge that the downstream side output air-fuel ratio has started to change toward the stoichiometric air-fuel ratio when the differential value of the downstream side output air-fuel ratio becomes larger than a predetermined value after the target air-fuel ratio is switched from the first set air-fuel ratio to the second set air-fuel ratio.

3. The abnormality diagnosis system of a downstream side air-fuel ratio sensor according to claim 1 , wherein the first side is a side leaner than the stoichiometric air-fuel ratio, the second side is a side richer than the stoichiometric air-fuel ratio, and the electronic control unit is configured to judge that the downstream side output air-fuel ratio has started to change toward the stoichiometric air-fuel ratio when the differential value of the downstream side output air-fuel ratio becomes smaller than a predetermined value after the target air-fuel ratio is switched from the first set air-fuel ratio to the second set air-fuel ratio.

4. The abnormality diagnosis system of a downstream side air-fuel ratio sensor according to claim 1 , wherein
the abnormality diagnosis system further comprises an upstream side air-fuel ratio sensor provided in the exhaust passage at an upstream side of the exhaust purification catalyst in the direction of exhaust flow, and
the electronic control unit is configured to perform feedback control of the amount of fuel fed to the combustion chamber so that an upstream side output air-fuel ratio detected by the upstream side air-fuel ratio sensor matches the target air-fuel ratio.

5. The abnormality diagnosis system of a downstream side air-fuel ratio sensor according to claim 1 , wherein
the predetermined time is calculated based on an intake air amount detected by the air flowmeter from when the target air-fuel ratio is switched from the first set air-fuel ratio to the second set air-fuel ratio to when the downstream side output air-fuel ratio starts to change toward the stoichiometric air-fuel ratio.

6. An abnormality diagnosis system of a downstream side air-fuel ratio sensor provided in an exhaust passage of an internal combustion engine at a downstream side of an exhaust purification catalyst in a direction of exhaust flow, comprising
an air flowmeter detecting an amount of intake air fed to a combustion chamber; and
an electronic control unit configured to:
set a target air-fuel ratio of exhaust gas flowing into the exhaust purification catalyst and control an amount of fuel fed to the combustion chamber so that an air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst matches the target air-fuel ratio,
the electronic control unit sets the target air-fuel ratio to a first set air-fuel ratio set to a first side of either side of a rich side and lean side from a stoichiometric air-fuel ratio, then, when a downstream side output air-fuel ratio detected by the downstream side air-fuel ratio sensor is at the first side from the stoichiometric air-fuel ratio, switches the target air-fuel ratio from the first set air-fuel ratio to a second set air-fuel ratio set to a second side at the opposite side from the first side from the stoichiometric air-fuel ratio;
calculate a time from when the target air-fuel ratio is switched from the first set air-fuel ratio to the second set air-fuel ratio to when the downstream side output air-fuel ratio starts to change toward the stoichiometric air-fuel ratio based on a differential value of the downstream side output air-fuel ratio and, when the calculated time is a predetermined time or more, to judge that a dead time at the downstream side air-fuel ratio sensor is abnormal, and
the predetermined time is calculated based on an intake air amount detected by the air flowmeter from when the target air-fuel ratio is switched from the first set air-fuel ratio to the second set air-fuel ratio to when the downstream side output air-fuel ratio starts to change toward the stoichiometric air-fuel ratio.

7. The abnormality diagnosis system of a downstream side air-fuel ratio sensor according to claim 6 , wherein the electronic control unit is configured to judge that the dead time in the downstream side air-fuel ratio sensor is not abnormal when the calculated time is less than the predetermined time.

8. The abnormality diagnosis system of a downstream side air-fuel ratio sensor according to claim 7 , wherein the first side is a side richer than the stoichiometric air-fuel ratio, the second side is a side leaner than the stoichiometric air-fuel ratio, and the electronic control unit is configured to judge that the downstream side output air-fuel ratio has started to change toward the stoichiometric air-fuel ratio when the differential value of the downstream side output air-fuel ratio becomes larger than a predetermined value after the target air-fuel ratio is switched from the first set air-fuel ratio to the second set air-fuel ratio.

9. The abnormality diagnosis system of a downstream side air-fuel ratio sensor according to claim 7 , wherein the first side is a side leaner than the stoichiometric air-fuel ratio, the second side is a side richer than the stoichiometric air-fuel ratio, and the electronic control unit is configured to judge that the downstream side output air-fuel ratio has started to change toward

Assignees

• Toyota Motor Co Ltd

Inventors

• Miyamoto Hiroshi

Classifications

• F02D41/1495

  Detection of abnormalities in the air/fuel ratio feedback system · CPC title

• F02D41/1454

  the characteristics being an oxygen content or concentration or the air-fuel ratio · CPC title

• G01M15/104

  using oxygen or lambda-sensors (testing catalytic converters F01N3/18, F01N11/007) · CPC title

• F02D41/1474

  by detecting the commutation time of the sensor · CPC title

• F02D41/1441

  Plural sensors · CPC title