Title of Invention	AN ENGINE CONTROL SYSTEM AND A METHOD FOR MONITORING FLOW RESTRICTION THROUGH AN EXHAUST GAS RECIRCULATION SYSTEM OF AN INTERNAL COMBUSTION ENGINE
Abstract	An engine control system that monitors flow restriction through an exhaust gas recirculation (EGR) system of an engine includes a first module that calculates a test EGR mass flow rate based on a first average EGR mass flow rate when the EGR system is in an EGR OFF mode and a second average EGR mass flow rate when the EGR system is in an EGR ON mode. A second module selectively generates a fault signal based on the test EGR mass flow rate.

Title of Invention

AN ENGINE CONTROL SYSTEM AND A METHOD FOR MONITORING FLOW RESTRICTION THROUGH AN EXHAUST GAS RECIRCULATION SYSTEM OF AN INTERNAL COMBUSTION ENGINE

Abstract

An engine control system that monitors flow restriction through an exhaust gas recirculation (EGR) system of an engine includes a first module that calculates a test EGR mass flow rate based on a first average EGR mass flow rate when the EGR system is in an EGR OFF mode and a second average EGR mass flow rate when the EGR system is in an EGR ON mode. A second module selectively generates a fault signal based on the test EGR mass flow rate.

Full Text	1 GP-306223 QUICK EGR FLOW RESTRICTION TEST BASED ON COMPENSATED MASS FLOW DIFFERENTIAL FIELD OF THE INVENTION [0001] The present invention relates to exhaust gas recirculation (EGR) systems for internal combustion engines, and more particularly to a flow restriction test for an EGR system. BACKGROUND OF THE INVENTION [0002J Internal combustion engines combust an air and fuel mixture within cylinders to reciprocally drive pistons within the cylinders. The pistons rotatably drive a crankshaft to provide drive torque to a powertrain. Exhaust generated by the combustion process is exhausted from the engine through an exhaust manifold, is treated in an exhaust system and is released to atmosphere. [0003] Engine systems often include an exhaust gas recirculation (EGR) system to reduce engine emissions. EGR involves re-circulating exhaust gases back into the cylinders, which limits the amount of oxygen available for combustion and lowers cylinder temperatures. EGR enables ignition timing to remain at an optimum point, which improves fuel economy and/or performance. However, debris build-up within the EGR system restricts exhaust flow therethrough and minimizes the effectiveness of the EGR system. [0004] A traditional method of monitoring the flow restriction through the EGR system is to determine a peak manifold absolute pressure (MAP) difference between MAP levels when the EGR is ON and when the EGR is OFF. This method provides distinct disadvantages in that the MAP difference can have high variation under different engine operating conditions and it is difficult to calibrate 2 compensation factors for the various engine operating conditions. Further, the MAP difference can be contributed to other factors that are independent of the EGR system. SUMMARY OF THE INVENTION [0005] Accordingly, the present invention provides an engine control system that monitors flow restriction through an exhaust gas recirculation (EGR) system of an engine. The engine control system includes a first module that calculates a test EGR mass flow rate based on a first average EGR mass flow rate when the EGR system is in an EGR OFF mode and a second average EGR mass flow rate when the EGR system is in an EGR ON mode. A second module selectively generates a fault signal based on the test EGR mass flow rate. [0006] In another feature, the second module generates the fault signal when the test EGR mass flow rate is below a threshold EGR mass flow rate. [0007] In other features, the first module monitors a manifold absolute pressure, an engine speed, a manifold temperature, a mass air flow into an intake manifold and a mass air flow into cylinders during operation of the engine in the EGR OFF mode and calculates the first average EGR mass flow rate based thereon. The first module calculates the first average EGR mass flow rate based on averages of the manifold absolute pressure, the engine speed, the manifold temperature, the mass air flow into the intake manifold and the mass air flow into the cylinders over operation of the engine in the EGR OFF mode. [0008] In still other features, the first module monitors a manifold absolute pressure, an engine speed, a manifold temperature, a mass air flow into the intake manifold and a mass air flow into the cylinders during operation of the engine in the EGR ON mode and calculates the second average EGR mass flow rate based thereon. 3 The first module calculates the second average EGR mass flow rate based on averages of the manifold absolute pressure, the engine speed, the manifold temperature, the mass air flow into the intake manifold and the mass air flow into the cylinders over operation of the engine in the EGR ON mode. [0009] In still another feature, the engine control system further includes an enable module that selectively generates an enable signal. The first module calculates the first and second average EGR mass flow rates based on the enable signal. [0010] Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS [0011] The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: [0012] Figure 1 is a schematic illustration of an exemplary engine system including an EGR system; [0013] Figure 2 is a graph illustrating exemplary manifold absolute pressure (MAP) values for EGR ON and EGR OFF conditions; [0014] Figure 3 is a flowchart illustrating exemplary steps executed by the EGR flow restriction control according to the present invention; [0015] Figure 4 is a signal flow diagram illustrating exemplary modules that execute the EGR flow restriction control of the present invention. 4 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0016] The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the term module refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. [0017] Referring now to Figure 1, an exemplary engine system 10 is illustrated. The engine system 10 includes an engine 12, an intake manifold 14 and an exhaust manifold 16. The engine 12 combusts an air and fuel mixture within cylinders (not shown) to drive pistons (not shown) that rotatably drive a crankshaft 18. Air is drawn through a throttle 20 and into the intake manifold 14, which distributes air to the cylinders. Exhaust from the combustion process is exhausted from the cylinders and into the exhaust manifold 16. The exhaust is treated in an exhaust system (not shown) and is released to atmosphere. [0018] The engine system 10 further includes an exhaust gas recirculation (EGR) system 22 having an EGR valve 24. The EGR valve 24 is selectively actuated to re-direct a portion of the exhaust gas back into the intake manifold 14. The EGR system 22 operates in one of an EGR ON mode and an EGR OFF mode. In the EGR OFF mode, the EGR valve 24 is. closed and no exhaust gas is circulated back into the intake manifold 14. In the EGR ON mode, the EGR valve 24 is open and a portion of the exhaust gas is circulated back into the intake manifold 14. 5 [0019] A control module 30 regulates engine operation and executes the EGR flow restriction control of the present invention. An engine speed sensor 32 is responsive to engine speed (RPM) and generates an RPM signal based thereon. A manifold absolute pressure (Pm) sensor 34 is responsive to the pressure within the intake manifold and generates a Pm signal based thereon. Similarly, an intake manifold temperature sensor 36 is responsive to the temperature within the intake manifold (Tm) and generates a Tm signal based thereon. A mass air flow (il#^,.-) sensor 38 is responsive to the mass air flow into the intake manifold 14 and generates a ^^F signal based thereon. As discussed in further detail below, the control module 30 receives the RPM signal, the Pm signal, the Tm signal and the A&MJF signal, and executes the EGR flow restriction control based thereon. [0020] The EGR flow restriction control of the present invention determines an average or test EGR mass flow rate {$-EGR) based on the difference between an average EGR ON mass flow rate (1$-EGRON) and an average EGR OFF mass flow rate {1$-EGROFF). More specifically, an intake manifold mass air flow (l&m) is determined from the following gas equation of state: (1) where: is the intake manifold volumetric flow rate; AMs a constant; and R is the gas constant. Based on the Mass Balance Principle, a continuous equation for the intake manifold while the EGR is ON is provided as: or where:is a reference flow at steady-state; and r is the total mass air flow into all of the cylinders. Similarly, when the EGR is OFF, a continuous equation for the intake manifold is provided as: (4) or (5) is equal toduring steady-state engine operation. It is also anticipated that $-CylAir can be calculated based on a throttle position and the number of cylinders, as disclosed in commonly assigned U.S. Pat. No. 5,270,935 entitled Engine with Prediction/Estimation Air Flow Determination and issued on December 14, 1993, the disclosure of which is expressly incorporated herein by reference. 7 [0021] Assuming that is the same for a specified monitoring condition, for the monitoring periods (i.e., EGR ON and EGR OFF) is provided as: where: is the average tfeEGR over the monitoring period; is the average Pm over the monitoring period; is the average RPM over the monitoring period; is the average Tm over the monitoring period; is the averageover the monitoring period; and is the average over the monitoring period. Figure 2 is a graph that illustrates exemplary Pm values for EGR ON and EGR OFF monitoring periods. The phantom lines illustrate Pm for the EGR OFF and EGR ON monitoring periods, respectively. [0022] The EGR flow restriction control of the present invention is a diagnostic test that runs when enable conditions have been met. Exemplary enable conditions include, but are not limited to, deceleration, throttle closed and engine RPM within a predetermined range. If the enable conditions are met, the EGR flow restriction control turns the EGR ON (i.e., EGR valve is open) for a first time period (e.g., 500ms). The EGR flow restriction control monitors Pm, RPM, Tm and . over the first time period and determines their respective averages The EGR flow 8 restriction control then turns the EGR OFF (i.e., EGR valve is closed) for a second time period (e.g., 500ms). The EGR flow restriction test control monitors Pm, RPM, Tm and over the second time period and determines their respective averages [0023] The EGR flow restriction test control determines based on the average values and the equations described above. is filtered (e.g., using an exponentially weighted moving average (EWMA) or a first order lag filter) to reduce the impact of noise to provide is less than a threshold value i , a fault is signaled. In this manner, a single incident of being greater than may not trigger a fault. If is not less than a pass is signaled. [0024] Referring now to Figure 3, exemplary steps executed by the EGR flow restriction test control will be described in detail. In step 300, control determines whether the enable conditions are met. If the enable conditions are not met, control loops back. If the enable conditions are met, control sets a timer (t) equal to zero in step 302. In step 304, control sets the EGR mode to OFF. In step 306, control monitors Control increments t in step 308. In step 310, control determines whether t is equal to or greater than a calibratable threshold time (tTHR) (e.g., 500ms). If t is not equal tc or greater than tTHR, control loops back to step 306. If t is equal to or greater than tTHR, control continues in step 312. [0025] Control resets t equal to zero in step 312. In step 314, control sets the EGR mode to ON. In step 316, control monitors Pm, RPM , Control increments t in step 318. In step 320, control determines whether t is equal to or greater than tTHR (e.g., 9 500ms). If t is not equal to or greater than tTHR, control loops back to step 316. If t is equal to or greater than tTHR, control continues in step 322. In step 322, control determines for the EGR OFF monitoring period. In step 324, control determines for the EGR ON monitoring period. [0026] Control calculates for the EGR ON and EGR OFF monitoring periods, respectively, in step 326. In step 328, control determines based on and Control updates the in step 330. In step 332, control determines whether the is less than If the is less than control signals a fault in step 334 and control ends. If the is not less than control signals a pass in step 336 and control ends. [0027] Referring now to Figure 4, exemplary modules that execute the EGR flow restriction control of the present invention are illustrated. The modules include an enable module 400, an EGR module 402, an averaging module 404, a calculating module 406 and a comparator module 408. The enable module 400 receives a throttle position (TP) signal, a vehicle acceleration (aVEhi) signal and the RPM signal and generates an enable signal based thereon to selectively enable the EGR flow restriction test control. The EGR module 402 switches the EGR system between the ON and OFF modes while the EGR flow restriction control is enabled. [0028] The averaging module 404 receives the Pm, RPM, signals and determines their respective averages for both the EGR OFF and EGR ON monitoring periods. The calculating module 406 calculates 10 based on the signal averages for both the EGR ON and EGR OFF monitoring periods and then calculates The comparator module 408 generates a fault or pass status based on and [0029] Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims. 11 CLAIMS What is claimed is: 1. An engine control system that monitors flow restriction through an exhaust gas recirculation (EGR) system of an engine, comprising: a first module that calculates a test EGR mass flow rate based on a first average EGR mass flow rate when said EGR system is in an EGR OFF mode and a second average EGR mass flow rate when said EGR system is in an EGR ON mode; and a second module that selectively generates a fault signal based on said test EGR mass flow rate. 2. The engine control system of claim 1 wherein said second module generates said fault signal when said test EGR mass flow rate is less than a threshold EGR mass flow rate. 3. The engine control system of claim 1 wherein said first module monitors a manifold absolute pressure, an engine speed, a manifold temperature a mass air flow into an intake manifold and a mass air flow into cylinders during operation of said engine in said EGR OFF mode and calculates said first average EGR mass flow rate based thereon. 4. The engine control system of claim 3 wherein said first module calculates said first average EGR mass flow rate based on averages of said manifold absolute pressure, said engine speed, said manifold temperature, said mass air flow into said intake manifold and said mass air flow into said cylinders over operation of said engine in said EGR OFF mode. 12 5. The engine control system of claim 1 wherein said first module monitors a manifold absolute pressure, an engine speed, a manifold temperature, a mass air flow into an intake manifold and a mass air flow into cylinders during operation of said engine in said EGR ON mode and calculates said second average EGR mass flow rate based thereon. 6. The engine control system of claim 5 wherein said first module calculates said second average EGR mass flow rate based on averages of said manifold absolute pressure, said engine speed, said manifold temperature, said mass air flow into said intake manifold and said mass air flow into said cylinders over operation of said engine in said EGR ON mode. 7. The engine control system of claim 1 further comprising an enable module that selectively generates an enable signal, wherein said first module calculates said first and second average EGR mass flow rates based on said enable signal. 8. A method of monitoring flow restriction through an exhaust gas recirculation (EGR) system of an internal combustion engine, comprising: calculating a test EGR mass flow rate based on a first average EGR mass flow rate when said EGR system is in an EGR OFF mode and a second average EGR mass flow rate when said EGR system is in an EGR ON mode; and generating a fault signal based on said test EGR mass flow rate. 9. The method of claim 8 wherein said fault signal is generated when said test EGR mass flow rate is less than a threshold EGR mass flow rate. 13 10. The method of claim 8 wherein further comprising: monitoring a manifold absolute pressure, an engine speed, a manifold temperature, a mass air flow into an intake manifold and a mass air flow into cylinders during operation of said engine in said EGR OFF mode; and calculating said first average EGR mass flow rate based thereon. 11. The method of claim 10 wherein said first average EGR mass flow rate is calculated based on averages of said manifold absolute pressure, said engine speed, said manifold temperature, said mass air flow into said intake manifold and said mass air flow into said cylinders over operation of said engine in said EGR OFF mode. 12. The method of claim 8 further comprising: monitoring a manifold absolute pressure, an engine speed, a manifold temperature, a mass air flow into an intake manifold and a mass air flow into cylinders during operation of said engine in said EGR ON mode; and calculating said second average EGR mass flow rate based thereon. 13. The method of claim 12 wherein said second average EGR mass flow rate is calculated based on averages of said manifold absolute pressure, said engine speed, said manifold temperature, said mass air flow into said intake manifold and said mass air flow into said cylinders over operation of said engine in said EGR ON mode. 14. The method of claim 8 further comprising generating an enable signal, wherein said first and second average EGR mass flow rates are calculated based on said enable signal. 14 15. A method of monitoring performance of an exhaust gas recirculation (EGR) system that re-circulates exhaust into an intake manifold of an internal combustion engine, comprising: generating an enable signal; calculating a test EGR mass flow rate based on a first average EGR mass flow rate when said EGR system is in an EGR OFF mode and a second average EGR mass flow rate when said EGR system is in an EGR ON mode based on said enable signal; and generating a fault signal based when said test EGR mass flow rate is less than a threshold EGR mass flow rate. 16. The method of claim 15 wherein further comprising: monitoring a manifold absolute pressure, an engine speed, a manifold temperature, a mass air flow into an intake manifold and a mass air flow into cylinders during operation of said engine in said EGR OFF mode; and calculating said first average EGR mass flow rate based thereon. 17. The method of claim 16 wherein said first average EGR mass flow rate is calculated based on averages of said manifold absolute pressure, said engine speed, said manifold temperature, said mass air flow into said intake manifold and said mass air flow into said cylinders over operation of said engine in said EGR OFF mode. 15 18. The method of claim 15 further comprising: monitoring a manifold absolute pressure, an engine speed, a manifold temperature, a mass air flow into an intake manifold and a mass air flow into cylinders during operation of said engine in said EGR ON mode; and calculating said second average EGR mass flow rate based thereon. 19. The method of claim 18 wherein said second average EGR mass flow rate is calculated based on averages of said manifold absolute pressure, said engine speed, said manifold temperature, said mass air flow into said intake manifold and said mass air flow into said cylinders over operation of said engine in said EGR ON mode. 20. The method of claim 15 wherein said enable signal is based on at least one of an engine speed, a throttle position and a vehicle acceleration. An engine control system that monitors flow restriction through an exhaust gas recirculation (EGR) system of an engine includes a first module that calculates a test EGR mass flow rate based on a first average EGR mass flow rate when the EGR system is in an EGR OFF mode and a second average EGR mass flow rate when the EGR system is in an EGR ON mode. A second module selectively generates a fault signal based on the test EGR mass flow rate.

Full Text

1
GP-306223
QUICK EGR FLOW RESTRICTION TEST BASED ON COMPENSATED MASS FLOW DIFFERENTIAL
FIELD OF THE INVENTION
[0001] The present invention relates to exhaust gas recirculation (EGR) systems for internal combustion engines, and more particularly to a flow restriction test for an EGR system.
BACKGROUND OF THE INVENTION
[0002J Internal combustion engines combust an air and fuel mixture within cylinders to reciprocally drive pistons within the cylinders. The pistons rotatably drive a crankshaft to provide drive torque to a powertrain. Exhaust generated by the combustion process is exhausted from the engine through an exhaust manifold, is treated in an exhaust system and is released to atmosphere.
[0003] Engine systems often include an exhaust gas recirculation (EGR) system to reduce engine emissions. EGR involves re-circulating exhaust gases back into the cylinders, which limits the amount of oxygen available for combustion and lowers cylinder temperatures. EGR enables ignition timing to remain at an optimum point, which improves fuel economy and/or performance. However, debris build-up within the EGR system restricts exhaust flow therethrough and minimizes the effectiveness of the EGR system.
[0004] A traditional method of monitoring the flow restriction through the EGR system is to determine a peak manifold absolute pressure (MAP) difference between MAP levels when the EGR is ON and when the EGR is OFF. This method provides distinct disadvantages in that the MAP difference can have high variation under different engine operating conditions and it is difficult to calibrate

2
compensation factors for the various engine operating conditions. Further, the MAP difference can be contributed to other factors that are independent of the EGR system.
SUMMARY OF THE INVENTION
[0005] Accordingly, the present invention provides an engine control system that monitors flow restriction through an exhaust gas recirculation (EGR) system of an engine. The engine control system includes a first module that calculates a test EGR mass flow rate based on a first average EGR mass flow rate when the EGR system is in an EGR OFF mode and a second average EGR mass flow rate when the EGR system is in an EGR ON mode. A second module selectively generates a fault signal based on the test EGR mass flow rate.
[0006] In another feature, the second module generates the fault signal when the test EGR mass flow rate is below a threshold EGR mass flow rate.
[0007] In other features, the first module monitors a manifold absolute pressure, an engine speed, a manifold temperature, a mass air flow into an intake manifold and a mass air flow into cylinders during operation of the engine in the EGR OFF mode and calculates the first average EGR mass flow rate based thereon. The first module calculates the first average EGR mass flow rate based on averages of the manifold absolute pressure, the engine speed, the manifold temperature, the mass air flow into the intake manifold and the mass air flow into the cylinders over operation of the engine in the EGR OFF mode.
[0008] In still other features, the first module monitors a manifold absolute pressure, an engine speed, a manifold temperature, a mass air flow into the intake manifold and a mass air flow into the cylinders during operation of the engine in the EGR ON mode and calculates the second average EGR mass flow rate based thereon.

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The first module calculates the second average EGR mass flow rate based on averages of the manifold absolute pressure, the engine speed, the manifold temperature, the mass air flow into the intake manifold and the mass air flow into the cylinders over operation of the engine in the EGR ON mode.
[0009] In still another feature, the engine control system further includes an enable module that selectively generates an enable signal. The first module calculates the first and second average EGR mass flow rates based on the enable signal.
[0010] Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
[0012] Figure 1 is a schematic illustration of an exemplary engine system including an EGR system;
[0013] Figure 2 is a graph illustrating exemplary manifold absolute pressure (MAP) values for EGR ON and EGR OFF conditions;
[0014] Figure 3 is a flowchart illustrating exemplary steps executed by the EGR flow restriction control according to the present invention;
[0015] Figure 4 is a signal flow diagram illustrating exemplary modules that execute the EGR flow restriction control of the present invention.

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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the term module refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality.
[0017] Referring now to Figure 1, an exemplary engine system 10 is illustrated. The engine system 10 includes an engine 12, an intake manifold 14 and an exhaust manifold 16. The engine 12 combusts an air and fuel mixture within cylinders (not shown) to drive pistons (not shown) that rotatably drive a crankshaft 18. Air is drawn through a throttle 20 and into the intake manifold 14, which distributes air to the cylinders. Exhaust from the combustion process is exhausted from the cylinders and into the exhaust manifold 16. The exhaust is treated in an exhaust system (not shown) and is released to atmosphere.
[0018] The engine system 10 further includes an exhaust gas recirculation (EGR) system 22 having an EGR valve 24. The EGR valve 24 is selectively actuated to re-direct a portion of the exhaust gas back into the intake manifold 14. The EGR system 22 operates in one of an EGR ON mode and an EGR OFF mode. In the EGR OFF mode, the EGR valve 24 is. closed and no exhaust gas is circulated back into the intake manifold 14. In the EGR ON mode, the EGR valve 24 is open and a portion of the exhaust gas is circulated back into the intake manifold 14.

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[0019] A control module 30 regulates engine operation and executes the EGR flow restriction control of the present invention. An engine speed sensor 32 is responsive to engine speed (RPM) and generates an RPM signal based thereon. A manifold absolute pressure (Pm) sensor 34 is responsive to the pressure within the intake
manifold and generates a Pm signal based thereon. Similarly, an intake manifold temperature sensor 36 is responsive to the temperature within the intake manifold (Tm) and generates a Tm signal
based thereon. A mass air flow (il#^,.-) sensor 38 is responsive to the mass air flow into the intake manifold 14 and generates a ^^F signal based thereon. As discussed in further detail below, the control module 30 receives the RPM signal, the Pm signal, the Tm signal and
the A&MJF signal, and executes the EGR flow restriction control based thereon.
[0020] The EGR flow restriction control of the present
invention determines an average or test EGR mass flow rate {$-EGR) based on the difference between an average EGR ON mass flow rate (1$-EGRON) and an average EGR OFF mass flow rate {1$-EGROFF). More specifically, an intake manifold mass air flow (l&m) is determined from the following gas equation of state:
(1)
where: is the intake manifold volumetric flow rate;
AMs a constant; and R is the gas constant.

Based on the Mass Balance Principle, a continuous equation for the intake manifold while the EGR is ON is provided as:
or
where:is a reference flow at steady-state; and
r is the total mass air flow into all of the cylinders.
Similarly, when the EGR is OFF, a continuous equation for the intake manifold is provided as:
(4)
or
(5)
is equal toduring steady-state engine operation. It is
also anticipated that $-CylAir can be calculated based on
a throttle position and the number of cylinders, as disclosed in commonly assigned U.S. Pat. No. 5,270,935 entitled Engine with Prediction/Estimation Air Flow Determination and issued on December 14, 1993, the disclosure of which is expressly incorporated herein by reference.

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[0021] Assuming that is the same for a specified
monitoring condition, for the monitoring periods (i.e., EGR ON
and EGR OFF) is provided as:

where: is the average tfeEGR over the monitoring period;
is the average Pm over the monitoring period;
is the average RPM over the monitoring period; is the average Tm over the monitoring period;
is the averageover the monitoring period;
and
is the average over the monitoring period.
Figure 2 is a graph that illustrates exemplary Pm values for EGR ON and EGR OFF monitoring periods. The phantom lines illustrate Pm for
the EGR OFF and EGR ON monitoring periods, respectively.
[0022] The EGR flow restriction control of the present invention is a diagnostic test that runs when enable conditions have been met. Exemplary enable conditions include, but are not limited to, deceleration, throttle closed and engine RPM within a predetermined range. If the enable conditions are met, the EGR flow restriction control turns the EGR ON (i.e., EGR valve is open) for a first time period (e.g., 500ms). The EGR flow restriction control monitors Pm,
RPM, Tm and . over the first time period and determines their respective averages The EGR flow

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restriction control then turns the EGR OFF (i.e., EGR valve is closed) for a second time period (e.g., 500ms). The EGR flow restriction test control monitors Pm, RPM, Tm and over the second time period
and determines their respective averages
[0023] The EGR flow restriction test control determines based on the average values and the equations described above.
is filtered (e.g., using an exponentially weighted moving average (EWMA) or a first order lag filter) to reduce the impact of noise to provide is less than a threshold value i , a
fault is signaled. In this manner, a single incident of being
greater than may not trigger a fault. If is not less than
a pass is signaled.
[0024] Referring now to Figure 3, exemplary steps executed by the EGR flow restriction test control will be described in detail. In step 300, control determines whether the enable conditions are met. If the enable conditions are not met, control loops back. If the enable conditions are met, control sets a timer (t) equal to zero in step 302. In step 304, control sets the EGR mode to OFF. In step 306, control monitors Control increments t in step
308. In step 310, control determines whether t is equal to or greater than a calibratable threshold time (tTHR) (e.g., 500ms). If t is not equal tc or greater than tTHR, control loops back to step 306. If t is equal to or greater than tTHR, control continues in step 312.
[0025] Control resets t equal to zero in step 312. In step 314, control sets the EGR mode to ON. In step 316, control monitors Pm,
RPM , Control increments t in step 318. In step
320, control determines whether t is equal to or greater than tTHR (e.g.,

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500ms). If t is not equal to or greater than tTHR, control loops back to step 316. If t is equal to or greater than tTHR, control continues in step
322. In step 322, control determines for the EGR OFF monitoring period. In step 324, control determines
for the EGR ON monitoring period.
[0026] Control calculates for the EGR
ON and EGR OFF monitoring periods, respectively, in step 326. In step 328, control determines based on and
Control updates the in step 330. In step 332, control
determines whether the is less than If the
is less than control signals a fault in step 334 and control
ends. If the is not less than control signals a pass in
step 336 and control ends.
[0027] Referring now to Figure 4, exemplary modules that execute the EGR flow restriction control of the present invention are illustrated. The modules include an enable module 400, an EGR module 402, an averaging module 404, a calculating module 406 and a comparator module 408. The enable module 400 receives a throttle position (TP) signal, a vehicle acceleration (aVEhi) signal and the RPM signal and generates an enable signal based thereon to selectively enable the EGR flow restriction test control. The EGR module 402 switches the EGR system between the ON and OFF modes while the EGR flow restriction control is enabled.
[0028] The averaging module 404 receives the Pm, RPM,
signals and determines their respective averages for both the EGR OFF and EGR ON monitoring periods. The calculating module 406 calculates

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based on the signal averages for both the EGR ON and EGR OFF monitoring periods and then calculates The comparator
module 408 generates a fault or pass status based on and
[0029] Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.

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CLAIMS
What is claimed is:
1. An engine control system that monitors flow restriction through
an exhaust gas recirculation (EGR) system of an engine, comprising:
a first module that calculates a test EGR mass flow rate based on a first average EGR mass flow rate when said EGR system is in an EGR OFF mode and a second average EGR mass flow rate when said EGR system is in an EGR ON mode; and
a second module that selectively generates a fault signal based on said test EGR mass flow rate.
2. The engine control system of claim 1 wherein said second
module generates said fault signal when said test EGR mass flow rate
is less than a threshold EGR mass flow rate.
3. The engine control system of claim 1 wherein said first module
monitors a manifold absolute pressure, an engine speed, a manifold
temperature a mass air flow into an intake manifold and a mass air flow
into cylinders during operation of said engine in said EGR OFF mode
and calculates said first average EGR mass flow rate based thereon.
4. The engine control system of claim 3 wherein said first module
calculates said first average EGR mass flow rate based on averages of
said manifold absolute pressure, said engine speed, said manifold
temperature, said mass air flow into said intake manifold and said
mass air flow into said cylinders over operation of said engine in said
EGR OFF mode.

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5. The engine control system of claim 1 wherein said first module
monitors a manifold absolute pressure, an engine speed, a manifold
temperature, a mass air flow into an intake manifold and a mass air
flow into cylinders during operation of said engine in said EGR ON
mode and calculates said second average EGR mass flow rate based
thereon.
6. The engine control system of claim 5 wherein said first module
calculates said second average EGR mass flow rate based on
averages of said manifold absolute pressure, said engine speed, said
manifold temperature, said mass air flow into said intake manifold and
said mass air flow into said cylinders over operation of said engine in
said EGR ON mode.
7. The engine control system of claim 1 further comprising an
enable module that selectively generates an enable signal, wherein
said first module calculates said first and second average EGR mass
flow rates based on said enable signal.
8. A method of monitoring flow restriction through an exhaust gas
recirculation (EGR) system of an internal combustion engine,
comprising:
calculating a test EGR mass flow rate based on a first average EGR mass flow rate when said EGR system is in an EGR OFF mode and a second average EGR mass flow rate when said EGR system is in an EGR ON mode; and
generating a fault signal based on said test EGR mass flow rate.
9. The method of claim 8 wherein said fault signal is generated
when said test EGR mass flow rate is less than a threshold EGR mass
flow rate.

13
10. The method of claim 8 wherein further comprising:
monitoring a manifold absolute pressure, an engine speed, a
manifold temperature, a mass air flow into an intake manifold and a mass air flow into cylinders during operation of said engine in said EGR OFF mode; and
calculating said first average EGR mass flow rate based thereon.
11. The method of claim 10 wherein said first average EGR mass
flow rate is calculated based on averages of said manifold absolute
pressure, said engine speed, said manifold temperature, said mass air
flow into said intake manifold and said mass air flow into said cylinders
over operation of said engine in said EGR OFF mode.
12. The method of claim 8 further comprising:
monitoring a manifold absolute pressure, an engine speed, a manifold temperature, a mass air flow into an intake manifold and a mass air flow into cylinders during operation of said engine in said EGR ON mode; and
calculating said second average EGR mass flow rate based thereon.
13. The method of claim 12 wherein said second average EGR
mass flow rate is calculated based on averages of said manifold
absolute pressure, said engine speed, said manifold temperature, said
mass air flow into said intake manifold and said mass air flow into said
cylinders over operation of said engine in said EGR ON mode.
14. The method of claim 8 further comprising generating an enable
signal, wherein said first and second average EGR mass flow rates are
calculated based on said enable signal.

14
15. A method of monitoring performance of an exhaust gas
recirculation (EGR) system that re-circulates exhaust into an intake
manifold of an internal combustion engine, comprising:
generating an enable signal;
calculating a test EGR mass flow rate based on a first average EGR mass flow rate when said EGR system is in an EGR OFF mode and a second average EGR mass flow rate when said EGR system is in an EGR ON mode based on said enable signal; and
generating a fault signal based when said test EGR mass flow rate is less than a threshold EGR mass flow rate.
16. The method of claim 15 wherein further comprising:
monitoring a manifold absolute pressure, an engine speed, a
manifold temperature, a mass air flow into an intake manifold and a mass air flow into cylinders during operation of said engine in said EGR OFF mode; and
calculating said first average EGR mass flow rate based thereon.
17. The method of claim 16 wherein said first average EGR mass
flow rate is calculated based on averages of said manifold absolute
pressure, said engine speed, said manifold temperature, said mass air
flow into said intake manifold and said mass air flow into said cylinders
over operation of said engine in said EGR OFF mode.

15
18. The method of claim 15 further comprising:
monitoring a manifold absolute pressure, an engine speed, a manifold temperature, a mass air flow into an intake manifold and a mass air flow into cylinders during operation of said engine in said EGR ON mode; and
calculating said second average EGR mass flow rate based thereon.
19. The method of claim 18 wherein said second average EGR
mass flow rate is calculated based on averages of said manifold
absolute pressure, said engine speed, said manifold temperature, said
mass air flow into said intake manifold and said mass air flow into said
cylinders over operation of said engine in said EGR ON mode.
20. The method of claim 15 wherein said enable signal is based on
at least one of an engine speed, a throttle position and a vehicle
acceleration.

An engine control system that monitors flow restriction through an exhaust gas recirculation (EGR) system of an engine includes a first module that calculates a test EGR mass flow rate based on a first average EGR mass flow rate when the EGR system is in an EGR OFF mode and a second average EGR mass flow rate when the EGR system is in an EGR ON mode. A second module selectively generates a fault signal based on the test EGR mass flow rate.

Documents:

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Patent Number

269125

Indian Patent Application Number

987/KOL/2006

PG Journal Number

41/2015

Publication Date

09-Oct-2015

Grant Date

30-Sep-2015

Date of Filing

27-Sep-2006

Name of Patentee

GM GLOBAL TECHNOLOGY OPERATIONS, INC.

Applicant Address

300 GM Renaissance CenterDetroit, Michigan 48265-3000

Inventors:

#	Inventor's Name	Inventor's Address
1	WENBO WANG	25831 TRESTLE STREET NOVI, MICHIGAN 48375
2	KURT D. MC LAIN	8020 TIYANOGA TRAIL CLARKSTON, MICHIGAN 48348

PCT International Classification Number

F02M25/07; F02B47/08; G01M19/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	11/289,946	2005-11-30	U.S.A.