Internal-combustion engines – Charge forming device – Including exhaust gas condition responsive means
Reexamination Certificate
1999-02-18
2002-04-16
Wolfe, Willis R. (Department: 3747)
Internal-combustion engines
Charge forming device
Including exhaust gas condition responsive means
C123S696000
Reexamination Certificate
active
06371096
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an abnormality diagnosing system of a wide-range A/F (air-fuel ratio) sensor.
A Japanese Patent Provisional Publication No. 10-169493 discloses a conventional abnormality diagnosing system of a wide-range A/F sensor. This abnormality diagnosing system is arranged to diagnose the degradation of the wide-range A/F sensor by monitoring the change of the output of the wide-range A/F sensor.
SUMMARY OF THE INVENTION
However, the conventional abnormality diagnosing system has been arranged to employ an air-fuel ratio control constant used in a normal air-fuel ratio (A/F) control even when the diagnosis of the wide-range A/F sensor is executed. The A/F control constant includes a proportional term (P-term), an integration term (I-term) and a derivative term (D-term). Therefore, the dispersion of the products of the wide-range A/F sensor and the dispersion of the air-fuel ratio at a start of the diagnosis cause a fluctuation of the time period until the output of the wide-range A/F sensor reaches a target air-fuel ratio. This fluctuation of the time period to the target value may cause a misdiagnosis as shown in
FIGS. 7A and 7B
and degrade the accuracy of the diagnosis. The conventional system has been arranged such that the air-fuel ratio control constant under a normal air-fuel ratio control range is set on the basis of an amplitude and a convergence of the air-fuel ratio control so as to satisfy the desired characteristics required in the normal control range as shown in FIG.
8
.
It is therefore an object of the present invention to provide an improved diagnosis system for a wide-range air-fuel ratio sensor. The improved diagnosis system further accurately diagnoses whether a wide-range air-fuel ratio sensor operates correctly or not without complicating its construction.
A diagnosis system according to the present invention comprises a wide-range air-fuel ratio sensor, an air-fuel ratio feedback control section, a target air-fuel ratio switching section, a detection value variation detecting section, an abnormality diagnosing section and a diagnosis control gain setting section which are arranged as shown in FIG.
6
. The wide-range air-fuel ratio sensor detects an air-fuel ratio of air-fuel mixture supplied to an engine. The air-fuel ratio feedback control section corrects an air-fuel ratio controlled object on the basis of a detection result of the wide-range air-fuel ratio sensor so as to adjust the air-fuel ratio to the engine at a target air-fuel ratio. The target air-fuel ratio switching section switches the target air-fuel ratio. The detection value variation detecting section detects variation of the detection value of the wide-range air-fuel ratio sensor. The abnormality diagnosing section diagnoses the wide-range air-fuel ratio sensor on the basis of a detection result of the detection value variation detecting section during a time period from the start of the switching of the target air-fuel ratio by the target air-fuel ratio switching section. The diagnosis control gain setting section sets a control gain of the air-fuel ratio feedback control section at a value greater than a normal control gain when the diagnosis of the wide-range air-fuel ratio sensor is executed.
REFERENCES:
patent: 5212947 (1993-05-01), Fujimoto et al.
patent: 5235957 (1993-08-01), Furuya
patent: 5614666 (1997-03-01), Hara et al.
patent: 5758632 (1998-06-01), Yamashita et al.
patent: 5970967 (1999-10-01), Uchikawa
patent: 10-169493 (1998-06-01), None
Ohsaki Masanobu
Ohtani Seiichi
Shiobara Katsuyoshi
Foley & Lardner
Gimie Mahmoud
Unisia Jecs Corporation
Wolfe Willis R.
LandOfFree
Diagnosis system for wide-range air-fuel ratio sensor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Diagnosis system for wide-range air-fuel ratio sensor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Diagnosis system for wide-range air-fuel ratio sensor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2900636