RESPONSE SENSING DEVICE OF EXHAUST GAS COMPONENT CONCENTRATION SENSOR

• US 20110011153A1
• Filed: 07/15/2010
• Published: 01/20/2011
• Est. Priority Date: 07/16/2009
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Umehara, Akira
• Granted Patent: US 8,240,188 B2
• Time in Patent Office: Days
• US Class Current: 73/23.31
• CPC Class Codes: F01N 13/009 having two or more separate purifying devices arranged in series
• CPC Class Codes: F01N 2560/025 for measuring or detecting O2, e.g. lambda sensors
• CPC Class Codes: F01N 3/0222 the structure being monolithic, e.g. honeycombs
• CPC Class Codes: F01N 3/103 Oxidation catalysts for HC and CO only
• CPC Class Codes: F02D 41/0055 Special engine operating conditions, e.g. for regeneration of exhaust gas treatment apparatus
• 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 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

An actual intake air quantity at the time when the intake air quantity is changed compulsorily with an EGR valve is measured with an airflow meter. An oxygen concentration of exhaust gas after combustion in a diesel engine is estimated based on the measured actual intake air quantity and a fuel injection quantity of the diesel engine. The estimated oxygen concentration is compared with an actual oxygen concentration sensed with an A/F sensor, thereby sensing response of the A/F sensor. Even if a response time for causing a change in the intake air quantity with the EGR valve changes, the change of the response time does not affect the estimate of the oxygen concentration since the oxygen concentration is estimated based on the actual intake air quantity. Therefore, the response of the A/F sensor can be sensed with high accuracy.

Claims

1. A response sensing device for an exhaust gas component concentration sensor, the response sensing device comprising:

an intake air quantity measuring means provided to an intake pipe of a diesel engine for measuring an intake air quantity introduced into the diesel engine;

an intake air quantity changing means for changing the intake air quantity of the diesel engine;

an exhaust gas component concentration estimating means for estimating a component concentration of exhaust gas after combustion in the diesel engine at least based on the measured intake air quantity and a fuel injection quantity injected and supplied to the diesel engine;

an exhaust gas component concentration sensor provided to an exhaust pipe of the diesel engine for sensing an actual component concentration of the exhaust gas of the diesel engine; and

a response sensing means for sensing response of the exhaust gas component concentration sensor by comparing the exhaust gas component concentration estimated by the exhaust gas component concentration estimating means and the actual exhaust gas component concentration sensed by the exhaust gas component concentration sensor when compulsorily changing the intake air quantity with the intake air quantity changing means.

2. The response sensing device as in claim 1, wherein

the response sensing means senses the response of the exhaust gas component concentration sensor while the diesel engine is idling.

3. The response sensing device as in claim 1, wherein

the exhaust gas component concentration estimating means calculates at least one of a normal estimate, which follows a characteristic of the exhaust gas component concentration sensor having normal response, and a degradation estimate, which follows a characteristic of the exhaust gas component concentration sensor having degraded response, as the estimate of the exhaust gas component concentration.

4. The response sensing device as in claim 3, wherein

a response time of the degradation estimate, which follows the characteristic of the exhaust gas component concentration sensor having the degraded response, lengthens as flow velocity of the exhaust gas decreases as compared to the normal estimate, which follows the characteristic of the exhaust gas component concentration sensor having the normal response.

5. The response sensing device as in claim 1, wherein

the exhaust gas component concentration estimating means calculates the exhaust gas component concentration at a position of a cylinder of the diesel engine first and then calculates the estimate of the exhaust gas component concentration, which is to be compared with the actual exhaust gas component concentration sensed with the exhaust gas component concentration sensor, in consideration of a delay until the exhaust gas component concentration calculated as the concentration at the position of the cylinder is sensed with the exhaust gas component concentration sensor.

6. The response sensing device as in claim 1, wherein

the exhaust gas component concentration estimating means has a map beforehand storing a relationship between the exhaust gas component concentration and at least the intake air quantity and the fuel injection quantity, and

the exhaust gas component concentration estimating means estimates the exhaust gas component concentration using the map.

7. The response sensing device as in claim 1, wherein

the response sensing means changes the intake air quantity stepwise with the intake air quantity changing means such that change in the intake air quantity becomes equal to or larger than a predetermined amount.

8. The response sensing device as in claim 7, further comprising:

an injection quantity controlling means for controlling the fuel injection quantity such that rotation speed of the diesel engine remains constant before and after the change of the intake air quantity when the intake air quantity is changed stepwise with the intake air quantity changing means.

9. The response sensing device as in claim 7, wherein

the response sensing means gradually controls the intake air quantity changing means until the intake air quantity changing means reaches a predetermined set state such that the intake air quantity decreases gradually and confirms whether an abnormality occurs in the diesel engine at that time before changing the intake air quantity stepwise with the intake air quantity changing means, and

when it is confirmed that the abnormality does not occur, the response sensing means uses the set state as an initial state or an end state of the intake air quantity changing means at the time when the intake air quantity is changed stepwise.

10. The response sensing device as in claim 9, further comprising:

an injection quantity controlling means for controlling the fuel injection quantity such that rotation speed of the diesel engine remains constant regardless of decrease of the intake air quantity when the intake air quantity changing means is controlled gradually until the intake air quantity changing means reaches the predetermined set state such that the intake air quantity decreases gradually.

11. The response sensing device as in claim 10, wherein

the response sensing means determines that the abnormality has occurred in the diesel engine if the fuel injection quantity increases to a predetermined injection quantity or over or if the actual intake air quantity decreases to a predetermined air quantity or under when the intake air quantity changing means is gradually controlled until the intake air quantity changing means reaches the predetermined set state.

12. The response sensing device as in claim 7, wherein

the response sensing means gradually controls the intake air quantity changing means until the intake air quantity changing means reaches a predetermined set state such that the intake air quantity decreases gradually before changing the intake air quantity stepwise with the intake air quantity changing means, and

when the actual intake air quantity decreases to a predetermined air quantity or under or when the fuel injection quantity increases to a predetermined injection quantity or over during the gradual control, the response sensing means changes the set state based on a state of the intake air quantity changing means at that time, and

the response sensing means uses the set state as an initial state or an end state of the intake air quantity changing means at the time when the intake air quantity is changed stepwise.

13. The response sensing device as in claim 12, wherein

the response sensing means further controls the intake air quantity changing means to decrease the intake air quantity if the actual intake air quantity does not decrease to the predetermined air quantity or under or if the fuel injection quantity does not increase to the predetermined injection quantity or over even when the intake air quantity changing means reaches the set state, and

the response sensing means changes the set state based on a state of the intake air quantity changing means at the time when the actual intake air quantity becomes equal to or smaller than the predetermined air quantity or when the fuel injection quantity becomes equal to or larger than the predetermined injection quantity.

14. The response sensing device as in claim 1, wherein

the exhaust gas component concentration estimating means calculates a calibration value for calibrating the estimate of the exhaust gas component concentration when an operation state of the diesel engine is constant and there occurs a difference between the estimate of the exhaust gas component concentration and the actual exhaust gas component concentration sensed with the exhaust gas component concentration sensor.

15. The response sensing device as in claim 14, wherein

the exhaust gas component concentration estimating means performs the calculation of the calibration value of the estimate of the exhaust gas component concentration before the response of the exhaust gas component concentration sensor is sensed.

16. The response sensing device as in claim 1, further comprising:

an abnormality detecting means for detecting an abnormality in the intake air quantity measuring means, wherein

the sensing of the response of the exhaust gas component concentration sensor is prohibited when the abnormality in the intake air quantity measuring means is detected by the abnormality detecting means.

17. The response sensing device as in claim 16, wherein

the abnormality detecting means detects that the intake air quantity measuring means is abnormal when the response sensing means detects that the exhaust gas component concentration sensor has response quicker than a predetermined standard response.