Exhaust gas recirculation diagnostic
First Claim
1. 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.
13 Assignments
0 Petitions
Accused Products
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.
72 Citations
9 Claims
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1. 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:
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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. - View Dependent Claims (2, 3, 4, 5)
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6. 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:
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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. - View Dependent Claims (7, 8, 9)
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Specification