EXHAUST GAS SENSOR DIAGNOSTIC DEVICE

• US 20100300179A1
• Filed: 05/28/2010
• Published: 12/02/2010
• Est. Priority Date: 05/29/2009
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: UMEHARA, Akira
• Granted Patent: US 8,489,361 B2
• Time in Patent Office: Days
• US Class Current: 73/23.31
• CPC Class Codes: F02D 2041/1431 the system including an input-output delay
• CPC Class Codes: F02D 41/123 the fuel injection being cut-off
• CPC Class Codes: F02D 41/1454 the characteristics being an oxygen content or concentration or the air-fuel ratio
• CPC Class Codes: F02D 41/1495 Detection of abnormalities in the air/fuel ratio feedback system

Abstract

In a transient state caused by fuel cut, a normal output of an A/F sensor having normal response and a lowered output having response lowered by a predetermined value as compared to the normal output are estimated, and an actual output of the A/F sensor is sensed. S1 as an integration value of a deviation between the normal output and the lowered output and S2 as an integration value of a deviation between the normal output and the actual output are calculated respectively until the normal output and the lowered output converge to an oxygen concentration equivalent to an atmosphere. S2 changes in accordance with a lowering degree of the response of the actual output. Therefore, the lowering degree of the response of the A/F sensor can be diagnosed based on S2/S1.

Claims

1. An exhaust gas sensor diagnostic device that diagnoses response of an exhaust gas sensor, which is provided to an exhaust gas flow passage of an internal combustion engine and which senses a gas state in the exhaust gas flow passage, the exhaust gas sensor diagnostic device comprising:

a normal output estimating means for estimating a normal output of the exhaust gas sensor having normal response based on an operation state of the internal combustion engine;

a lowered output estimating means for estimating a lowered output of the exhaust gas sensor having the response lowered by a predetermined value as compared to the normal exhaust gas sensor;

an actual output sensing means for sensing an actual output of the exhaust gas sensor provided to the exhaust gas flow passage; and

a diagnosing means for diagnosing the response of the exhaust gas sensor based on the normal output estimated by the normal output estimating means, the lowered output estimated by the lowered output estimating means and the actual output sensed by the actual output sensing means.

2. The exhaust gas sensor diagnostic device as in claim 1, wherein

the normal output estimating means estimates the normal output based on a gas state in a cylinder estimated from the operation state of the internal combustion engine, time necessary for the exhaust gas to reach from the cylinder to the exhaust gas sensor and a response characteristic of the normal exhaust gas sensor.

3. The exhaust gas sensor diagnostic device as in claim 1, wherein

the normal output estimating means estimates the normal output based on parameters including at least a response characteristic of the normal exhaust gas sensor, and

the lowered output estimating means estimates the lowered output based on the parameters including at least a response characteristic of the exhaust gas sensor having the response lowered by the predetermined value as compared to the response characteristic of the normal exhaust gas sensor in place of the response characteristic of the normal exhaust gas sensor.

4. The exhaust gas sensor diagnostic device as in claim 1, wherein

the lowered output estimating means estimates the lowered output by applying first-order lag processing to the normal output estimated by the normal output estimating means.

5. The exhaust gas sensor diagnostic device as in claim 1, further comprising:

an integrating means for calculating S1, which represents an integration value of a deviation between the normal output and the lowered output, and S2, which represents an integration value of a deviation between the actual output and the normal output or the lowered output, wherein

the diagnosing means diagnoses the response of the exhaust gas sensor based on S1 and S2.

6. The exhaust gas sensor diagnostic device as in claim 5, wherein

the integrating means ends the calculation of S1 and S2 when the normal output, the lowered output and the actual output change after the calculation of S1 and S2 is started and at least one of the lowered output and the normal output converges thereafter.

7. The exhaust gas sensor diagnostic device as in claim 5, wherein

the integrating means starts the calculation of S1 and S2 when the normal output, the lowered output and the actual output are equal to each other.

8. The exhaust gas sensor diagnostic device as in claim 5, wherein

the integrating means starts the calculation of S1 and S2 when the operation state of the internal combustion engine shifts from a steady state to a transient state.

9. The exhaust gas sensor diagnostic device as in claim 5, wherein

the integrating means calculates S1 and S2 since the operation state of the internal combustion engine shifts from a steady state to a transient state until at least one of the lowered output and the normal output converges, and

the diagnosing means stops the diagnosis of the response of the exhaust gas sensor if the time since the operation state of the internal combustion engine shifts from the steady state to the transient state until at least one of the lowered output and the normal output converges exceeds a predetermined time.

10. The exhaust gas sensor diagnostic device as in claim 5, wherein

the integrating means calculates S1 and S2 since the operation state of the internal combustion engine shifts from the steady state to the transient state until at least one of the lowered output and the normal output converges, and

the diagnosing means stops the diagnosis of the response of the exhaust gas sensor when a change amount of the converged one of the lowered output and the normal output, the change amount occurring in the period since the operation state of the internal combustion engine shifts from the steady state to the transient state until at least one of the lowered output and the normal output converges, is smaller than a predetermined amount.

11. The exhaust gas sensor diagnostic device as in claim 1, further comprising:

a change rate calculating means for calculating change rates of the normal output, the lowered output and the actual output at the same timing, wherein

the diagnosing means diagnoses the response of the exhaust gas sensor based on the change rates at the same timing calculated by the change rate calculating means.

12. The exhaust gas sensor diagnostic device as in claim 1, further comprising:

a timing calculating means for calculating timings at which change rates of the normal output, the lowered output and the actual output are maximized respectively, wherein

the diagnosing means diagnoses the response of the exhaust gas sensor based on the timings calculated by the timing calculating means.

13. The exhaust gas sensor diagnostic device as in claim 1, wherein

the diagnosing means diagnoses the response of the exhaust gas sensor when the operation state of the internal combustion engine shifts to a fuel cut state.

14. The exhaust gas sensor diagnostic device as in claim 1, wherein

the actual output sensing means corrects the actual output based on a gas state in a cylinder during fuel cut.

15. The exhaust gas sensor diagnostic device as in claim 1, wherein

the normal output estimating means and the lowered output estimating means correct deviations of the normal output and the lowered output from the actual output when a gas state in a cylinder is a steady state.

16. The exhaust gas sensor diagnostic device as in claim 1, wherein

the diagnosing means suspends the diagnosis of the response of the exhaust gas sensor since the exhaust gas sensor is warmed up until a predetermined time elapses thereafter.