Abnormality diagnosis system of air-fuel ratio sensor

• US 9,903,292 B2
• Filed: 10/23/2015
• Issued: 02/27/2018
• Est. Priority Date: 10/23/2014
• Status: Active Grant

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Miyamoto, Hiroshi, Kidokoro, Toru, Iwazaki, Yasushi, Suzuki, Kenji, Ide, Koji
• Primary Examiner(s): Nguyen, Hung Q
• Assistant Examiner(s): Mo, Xiao
• Application Number:
  US14/921,198
• Publication Number:
  US 20160115893A1
• Time in Patent Office: 858 Days
• CPC Class Codes: F02D 41/1441 Plural sensors
• CPC Class Codes: F02D 41/1454 the characteristics being an oxygen content or concentration or the air-fuel ratio
• CPC Class Codes: F02D 41/1494 Control of sensor heater
• CPC Class Codes: F02D 41/1495 Detection of abnormalities in the air/fuel ratio feedback system
• CPC Class Codes: F02D 41/222 relating to the failure of sensors or parameter detection devices
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

An abnormality diagnosis system of limit current type air-fuel ratio sensors comprises a current detecting part and a sensor temperature control device. The abnormality diagnosis system uses the current detecting part to detect the output current of the air-fuel ratio sensor when the air-fuel ratio is made the rich air-fuel ratio in the state where temperature of the air-fuel ratio is made the first temperature and when the air-fuel ratio is made the rich air-fuel ratio in the state where the temperature of the air-fuel ratio is made a second temperature higher than the first temperature. It is judged that the air-fuel ratio sensor is abnormal if the output current when the temperature of the air-fuel ratio sensor is the first temperature is larger than the output current when it is the second temperature by a predetermined value or more.

Claims

1. An abnormality diagnosis system of an air-fuel ratio sensor provided in an exhaust passage of an internal combustion engine and generating a limit current corresponding to an air-fuel ratio, comprising:

a current detecting part detecting an output current of said air-fuel ratio sensor; and

a sensor temperature control device controlling a temperature of said air-fuel ratio sensor,

said system is programmed to control the temperature of said air-fuel ratio sensor to a first temperature by said sensor temperature control device, and to detect the output current of said air-fuel ratio sensor by said current detecting part, when said internal combustion engine controls the air-fuel ratio so that the air-fuel ratio of the exhaust gas flowing around said air-fuel ratio sensor becomes a rich air-fuel ratio in the state where the temperature of said air-fuel ratio sensor is made the first temperature,

said system is programmed to control the temperature of said air-fuel ratio sensor to a second temperature higher than said first temperature by said sensor temperature control device, and to detect the output current of said air-fuel ratio sensor by said current detecting part, when said internal combustion engine controls the air-fuel ratio so that the air-fuel ratio of the exhaust gas flowing around said air-fuel ratio sensor becomes a rich air-fuel ratio in the state where the temperature of said air-fuel ratio sensor is made said second temperature, and

said system is programmed to judge that said air-fuel ratio sensor has become abnormal when the output current when controlling the temperature of said air-fuel ratio sensor to said first temperature is larger than the output current when controlling the temperature of said air-fuel ratio sensor to said second temperature by a predetermined value or more.

2. The abnormality diagnosis system of an air-fuel ratio sensor according to claim 1, wherein

said system is configured to provisionally judge said air-fuel ratio sensor is abnormal when said internal combustion engine controls the air-fuel ratio so that the air-fuel ratio of the exhaust gas flowing around said air-fuel ratio sensor becomes a rich air-fuel ratio in the state where the temperature of said air-fuel ratio sensor is made said first temperature, if the output current of said air-fuel ratio sensor has become a current value indicating an air-fuel ratio equal to or greater than a predetermined lean air-fuel ratio leaner than the stoichiometric air-fuel ratio,

said system is configured, when it is provisionally judged that said air-fuel ratio sensor is abnormal, to control the temperature of said air-fuel ratio sensor to said second temperature, and to detect the output current of said air-fuel ratio sensor by said current detecting part when said internal combustion engine controls the air-fuel ratio so that the air-fuel ratio of the exhaust gas flowing around said air-fuel ratio sensor becomes a rich air-fuel ratio in the state where the temperature of said air-fuel ratio sensor is made said second temperature, and

said system is configured to finally judge that said air-fuel ratio sensor has become abnormal when the output current when controlling the temperature of said air-fuel ratio sensor to said first temperature is larger than the output current when controlling the temperature of said air-fuel ratio sensor to said second temperature by a predetermined value or more.

5. The abnormality diagnosis system of an air-fuel ratio sensor according to claim 1, wherein

said internal combustion engine is provided with an exhaust purification catalyst in its exhaust passage and can control the air-fuel ratio so that the air-fuel ratio of the exhaust gas flowing into said exhaust purification catalyst becomes a target air-fuel ratio, and

said system is configured to lower a lower limit value of said target air-fuel ratio which can be set, when it is provisionally judged or finally judged that said air-fuel ratio sensor is abnormal.

7. The abnormality diagnosis system of an air-fuel ratio sensor according to claim 1, wherein

said internal combustion engine comprises an exhaust purification catalyst arranged in the exhaust passage, an upstream side air-fuel ratio sensor arranged upstream of said exhaust purification catalyst in said exhaust passage, and a downstream side air-fuel ratio sensor arranged at a downstream side, in the direction of exhaust flow, of said exhaust purification catalyst, and

said downstream side air-fuel ratio sensor is said limit current type air-fuel ratio sensor.

9. The abnormality diagnosis system of an air-fuel ratio sensor according to claim 1, wherein

said internal combustion engine comprises an exhaust purification catalyst arranged in the exhaust passage, an upstream side air-fuel ratio sensor arranged upstream of said exhaust purification catalyst in said exhaust passage, and a downstream side air-fuel ratio sensor arranged at a downstream side, in the direction of exhaust flow, of said exhaust purification catalyst, and

said upstream side air-fuel ratio sensor is said limit current type air-fuel ratio sensor.

11. The abnormality diagnosis system of an air-fuel ratio sensor according to claim 1, wherein

said internal combustion engine comprises an exhaust purification catalyst in the exhaust passage, controls the air-fuel ratio so that the air-fuel ratio of the exhaust gas flowing to said exhaust purification catalyst becomes the target air-fuel ratio, and can perform normal control alternately changing said target air-fuel ratio between the rich air-fuel ratio and a lean air-fuel ratio leaner than the stoichiometric air-fuel ratio;

and active control making said target air-fuel ratio richer than the rich air-fuel ratio at the time of said normal control, and

when the air-fuel ratio is controlled so that the air-fuel ratio of the exhaust gas flowing around said air-fuel ratio sensor becomes the rich air-fuel ratio, said active control is being executed.

13. The abnormality diagnosis system of an air-fuel ratio sensor according to claim 1, wherein

said internal combustion engine comprises an exhaust purification catalyst in the exhaust passage, controls the air-fuel ratio so that the air-fuel ratio of the exhaust gas flowing to said exhaust purification catalyst becomes the target air-fuel ratio, and can perform normal control alternately changing said target air-fuel ratio between the rich air-fuel ratio and a lean air-fuel ratio leaner than the stoichiometric air-fuel ratio, and

the time when the air-fuel ratio is controlled so that the air-fuel ratio of the exhaust gas flowing around said air-fuel ratio sensor becomes a rich air-fuel ratio is the time when said target air-fuel ratio is made a rich air-fuel ratio during said normal control.

15. The abnormality diagnosis system of an air-fuel ratio sensor according to claim 1, wherein

the output current when controlling the temperature of said air-fuel ratio sensor used for judgment of abnormality of said air-fuel ratio sensor is an average value of the output current of said air-fuel ratio sensor when controlling the temperature of said air-fuel ratio sensor to said first temperature or said second temperature.

3. An abnormality diagnosis system of an air-fuel ratio sensor provided in an exhaust passage of an internal combustion engine and generating a limit current corresponding to an air-fuel ratio, comprising:

a current detecting part detecting an output current of said air-fuel ratio sensor; and

a sensor temperature control device controlling a temperature of said air-fuel ratio sensor,

said system is programmed to control a temperature of said air-fuel ratio sensor to a first temperature by said sensor temperature control device, and to provisionally judge that said air-fuel ratio sensor is abnormal when said internal combustion engine controls the air-fuel ratio so that the air-fuel ratio of the exhaust gas flowing around said air-fuel ratio sensor becomes a rich air-fuel ratio richer than the stoichiometric air-fuel ratio in the state where the temperature of said air-fuel ratio sensor is made the first temperature, if the output current of said air-fuel ratio sensor detected by said current detecting part becomes a current value indicating an air-fuel ratio equal to or greater than a predetermined first lean air-fuel ratio leaner than the stoichiometric air-fuel ratio,

said system is programmed to control the temperature of said air-fuel ratio sensor to a second temperature higher than said first temperature by said sensor temperature control device when it is provisionally judged that said air-fuel ratio sensor is abnormal, and to detect the output current of said air-fuel ratio sensor by said current detecting part when said internal combustion engine controls the air-fuel ratio so that the air-fuel ratio of the exhaust gas flowing around said air-fuel ratio sensor becomes a rich air-fuel ratio in the state where the temperature of said air-fuel ratio sensor is made said second temperature, and

said system is programmed to finally judge that said air-fuel ratio sensor has become abnormal when the output current when controlling the temperature of said air-fuel ratio sensor to said second temperature becomes a current value indicating an air-fuel ratio equal to or greater than a second lean air-fuel ratio leaner than said first lean air-fuel ratio.

4. The abnormality diagnosis system of an air-fuel ratio sensor according to claim 3, wherein

said system is configured to finally judge that said air-fuel ratio sensor is abnormal if the output current of said air-fuel ratio sensor becomes a current value indicating an air-fuel ratio equal to or greater than said second lean air-fuel ratio when the air-fuel ratio is controlled so that the air-fuel ratio of the exhaust gas flowing around said air-fuel ratio sensor becomes a rich air-fuel ratio in the state where the temperature of said air-fuel ratio sensor is made said first temperature.

6. The abnormality diagnosis system of an air-fuel ratio sensor according to claim 3, wherein

said internal combustion engine is provided with an exhaust purification catalyst in its exhaust passage and can control the air-fuel ratio so that the air-fuel ratio of the exhaust gas flowing into said exhaust purification catalyst becomes a target air-fuel ratio, and

said system is configured to lower a lower limit value of said target air-fuel ratio which can be set, when it is provisionally judged or finally judged that said air-fuel ratio sensor is abnormal.

8. The abnormality diagnosis system of an air-fuel ratio sensor according to claim 3, wherein

said internal combustion engine comprises an exhaust purification catalyst arranged in the exhaust passage, an upstream side air-fuel ratio sensor arranged upstream of said exhaust purification catalyst in said exhaust passage, and a downstream side air-fuel ratio sensor arranged at a downstream side, in the direction of exhaust flow, of said exhaust purification catalyst, and

said downstream side air-fuel ratio sensor is said limit current type air-fuel ratio sensor.

10. The abnormality diagnosis system of an air-fuel ratio sensor according to claim 3, wherein

said internal combustion engine comprises an exhaust purification catalyst arranged in the exhaust passage, an upstream side air-fuel ratio sensor arranged upstream of said exhaust purification catalyst in said exhaust passage, and a downstream side air-fuel ratio sensor arranged at a downstream side, in the direction of exhaust flow, of said exhaust purification catalyst, and

said upstream side air-fuel ratio sensor is said limit current type air-fuel ratio sensor.

12. The abnormality diagnosis system of an air-fuel ratio sensor according to claim 3, wherein

said internal combustion engine comprises an exhaust purification catalyst in the exhaust passage, controls the air-fuel ratio so that the air-fuel ratio of the exhaust gas flowing to said exhaust purification catalyst becomes the target air-fuel ratio, and can perform normal control alternately changing said target air-fuel ratio between the rich air-fuel ratio and a lean air-fuel ratio leaner than the stoichiometric air-fuel ratio;

and active control making said target air-fuel ratio richer than the rich air-fuel ratio at the time of said normal control, and

when the air-fuel ratio is controlled so that the air-fuel ratio of the exhaust gas flowing around said air-fuel ratio sensor becomes the rich air-fuel ratio, said active control is being executed.

14. The abnormality diagnosis system of an air-fuel ratio sensor according to claim 3, wherein

said internal combustion engine comprises an exhaust purification catalyst in the exhaust passage, controls the air-fuel ratio so that the air-fuel ratio of the exhaust gas flowing to said exhaust purification catalyst becomes the target air-fuel ratio, and can perform normal control alternately changing said target air-fuel ratio between the rich air-fuel ratio and a lean air-fuel ratio leaner than the stoichiometric air-fuel ratio, and

the time when the air-fuel ratio is controlled so that the air-fuel ratio of the exhaust gas flowing around said air-fuel ratio sensor becomes a rich air-fuel ratio is the time when said target air-fuel ratio is made a rich air-fuel ratio during said normal control.

16. The abnormality diagnosis system of an air-fuel ratio sensor according to claim 3, wherein

the output current when controlling the temperature of said air-fuel ratio sensor used for judgment of abnormality of said air-fuel ratio sensor is an average value of the output current of said air-fuel ratio sensor when controlling the temperature of said air-fuel ratio sensor to said first temperature or said second temperature.

17. The abnormality diagnosis system of an air-fuel ratio sensor according to claim 3, wherein

when the ratio of the time period where the output current of the air-fuel ratio sensor becomes a current value indicating an air-fuel ratio equal to or greater than said first lean air-fuel ratio with respect to the diagnosis period during which the air-fuel ratio is controlled so that the air-fuel ratio of the exhaust gas flowing around the air-fuel ratio sensor becomes the rich air-fuel ratio in the state where the temperature of the air-fuel ratio sensor is made said first temperature, becomes equal to or greater than a predetermined ratio, it is judged that an output current of said air-fuel ratio sensor has become a current value indicating an air-fuel ratio equal to or greater than said first lean air-fuel ratio, and

when the ratio of the time period where the output current of the air-fuel ratio sensor becomes a current value indicating an air-fuel ratio equal to or greater than said second lean air-fuel ratio with respect to the diagnosis period during which the air-fuel ratio is controlled so that the air-fuel ratio of the exhaust gas flowing around the air-fuel ratio sensor becomes the rich air-fuel ratio in the state where the temperature of the air-fuel ratio sensor is made said second temperature, becomes equal to or greater than a predetermined ratio, it is judged that an output current of said air-fuel ratio sensor has become a current value indicating an air-fuel ratio equal to or greater than said second lean air-fuel ratio.