US5508926A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Exhaust gas recirculation diagnostic
Assignee: GM Global Technology Operations LLC
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Filing: 1994-06-24
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Granted: 1996-04-16
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Expires: 2014-06-24
Abstract
Abstract Restrictions in a path of flow of recirculated internal combustion engine exhaust gas from an engine exhaust system to an engine intake manifold are diagnosed when the engine is determined to be in a steady state operating condition through a monitoring of the air pressure in the engine intake manifold while the flow of exhaust gas thereto is varied according to a predetermined flow schedule. Changes in the monitored air pressure are determined over a test period, are filtered through a lag filter process having a dynamic filter coefficient, and are compared to a dynamic threshold to determine a presence of a restriction. The filter coefficient and the threshold may be adjusted in accord with the outcome of the diagnostic.
Inventors
- 👤 David R. Wade
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 08:36
CPC Classifications
F; F02; F02D; F02D41/00; F02D41/22; F02D41/221; F02M; F02M26/00; F02M26/49; F02M26/45; F02M26/48; F02M26/52; F02M26/53
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
216 words
A method for detecting restriction in an internal combustion engine exhaust gas flow path through which exhaust gas is recirculated to an engine intake manifold in accord with a degree of opening of a controlled valve in the flow path, comprising the steps of: providing a predetermined schedule of valve opening positions including a plurality of intermediate valve positions between a valve closed position and a valve fully open position; determining when the engine is operating within a predetermined one of a predetermined cruise state characterized by a substantially stable engine intake air valve and a predetermined deceleration state characterized by a substantially closed engine intake air valve; establishing a test period while the engine is determined to be operating within the predetermined one; analyzing a relationship between valve position and engine intake manifold pressure during the established test period, comprising the steps of (a) moving the valve through the predetermined schedule of valve opening positions, (b) periodically sampling intake manifold pressure while the valve is moving through the predetermined schedule, (c) determining a maximum change in sampled intake manifold pressure between samples, (d) comparing a predetermined function of the determined maximum to a predetermined pressure change threshold, and (e) diagnosing a restriction in the flow path when the predetermined function exceeds the pressure change threshold.
Claim 2
Independent Claim
216 words
A method for detecting restriction in an internal combustion engine exhaust gas flow path through which exhaust gas is recirculated to an engine intake manifold in accord with a degree of opening of a controlled valve in the flow path, comprising the steps of: providing a predetermined schedule of valve opening positions including a plurality of intermediate valve positions between a valve closed position and a valve fully open position; determining when the engine is operating within a predetermined one of a predetermined cruise state characterized by a substantially stable engine intake air valve and a predetermined deceleration state characterized by a substantially closed engine intake air valve; establishing a test period while the engine is determined to be operating within the predetermined one; analyzing a relationship between valve position and engine intake manifold pressure during the established test period, comprising the steps of (a) moving the valve through the predetermined schedule of valve opening positions, (b) periodically sampling intake manifold pressure while the valve is moving through the predetermined schedule, (c) determining a maximum change in sampled intake manifold pressure between samples, (d) comparing a predetermined function of the determined maximum to a predetermined pressure change threshold, and (e) diagnosing a restriction in the flow path when the predetermined function exceeds the pressure change threshold.
Claim 3
Dependent Claim
33 words
The method of claim 1, further comprising the step of: adjusting the magnitude of the predetermined pressure change threshold by setting the threshold to a predetermined adjustment value when the restriction is diagnosed.
Claim 4
Dependent Claim
20 words
The method of claim 1, wherein the predetermined function is a lag filter function having a predetermined lag filter coefficient.
Claim 5
Dependent Claim
20 words
The method of claim 3, wherein the predetermined lag filter coefficient is determined through the exponentially weighted moving average process.
Claim 6
Dependent Claim
30 words
The method of claim 3, further comprising the steps of: adjusting the predetermined lag filter coefficient by setting the coefficient to a predetermined adjustment coefficient when the restriction is diagnosed.
Claim 7
Independent Claim
178 words
A method for diagnosing restriction in an internal combustion engine exhaust gas recirculation EGR system having a controlled EGR valve for metering exhaust gas flow to an engine intake manifold, comprising the steps of: sensing present values of a predetermined set of operating parameters; characterizing a stable operating condition while the sensed present values are determined to be within corresponding predetermined parameter ranges; providing an EGR valve motion trajectory including a plurality of EGR valve positions between a fully closed EGR valve position and a fully open EGR valve position; moving the EGR valve through the motion trajectory while the operating conditions are characterized as stable; periodically sampling air pressure in the engine intake manifold while the EGR valve is moving through the motion trajectory; determining change in air pressure between samples; establishing a maximum change in air pressure over a predetermined test period; comparing a predetermined function of the maximum change to a predetermined pressure change threshold value; and diagnosing a restriction in the EGR system when the predetermined function exceeds the predetermined pressure change threshold value.
Claim 8
Independent Claim
178 words
A method for diagnosing restriction in an internal combustion engine exhaust gas recirculation EGR system having a controlled EGR valve for metering exhaust gas flow to an engine intake manifold, comprising the steps of: sensing present values of a predetermined set of operating parameters; characterizing a stable operating condition while the sensed present values are determined to be within corresponding predetermined parameter ranges; providing an EGR valve motion trajectory including a plurality of EGR valve positions between a fully closed EGR valve position and a fully open EGR valve position; moving the EGR valve through the motion trajectory while the operating conditions are characterized as stable; periodically sampling air pressure in the engine intake manifold while the EGR valve is moving through the motion trajectory; determining change in air pressure between samples; establishing a maximum change in air pressure over a predetermined test period; comparing a predetermined function of the maximum change to a predetermined pressure change threshold value; and diagnosing a restriction in the EGR system when the predetermined function exceeds the predetermined pressure change threshold value.
Claim 9
Dependent Claim
27 words
The method of claim 6, further comprising the step of decreasing the predetermined pressure change threshold value by a predetermined decrease amount when a restriction is diagnosed.
Claim 10
Dependent Claim
41 words
The method of claim 6, wherein the predetermined function is a lag filter function including a predetermined lag filter coefficient, further comprising the step of: decreasing the filter coefficient by a predetermined amount upon diagnosing a restriction in the EGR system.
Claim 11
Dependent Claim
104 words
The method of claim 6, wherein the internal combustion engine receives fresh air across an intake air valve, the method further comprising the steps of: sensing operation within a predetermined cruise state characterized by the intake air valve being within a predetermined position range over a predetermined time interval; and sensing operation within a predetermined deceleration state characterized by the intake air valve being substantially closed to fresh air flow; and wherein the characterizing step characterizes a stable operating condition while operation with the predetermined cruise state is sensed and characterizes a stable operating condition while operation within the predetermined deceleration state is sensed.
References Cited (Backward Citations)
US3977373A
Cited
US4114575A
Cited
US4125100A
Cited
US4114576A
Cited
US4173205A
Cited
US4165650A
Cited
US4269156A
Cited
US4473056A
Cited
US4383441A
Cited
US4373497A
Cited
US4513713A
Cited
US4671107A
Cited
US4719893A
Cited
US5014203A
Cited
US5257610A
Cited
US5341300A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1999-04-16 | 1999-10-16 | 2000-04-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-04-16 | 2003-10-16 | 2004-04-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-04-16 | 2007-10-16 | 2008-04-16 | $7700.00 | Window Closed / Lapsed |