Title of Invention

A SYSTEM FOR AND A METHOD TO CONTROL AN EXHAUST GAS RECIRCULATION SYSTEM OF AN ENGINE

Abstract A control system and method for an exhaust gas recirculation (EGR) system of an engine includes a first sensor that senses fresh mass air flow, a second sensor that senses charge air flow, where the charge air flow is based on the fresh mass air flow and EGR exhaust flow, and a calculation module that determines a difference between the fresh mass airflow and the charge air flow and generates an EGR valve control signal based on the difference.
Full Text GP-307889-PTE-CD
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EXHAUST GAS RECIRCULATION ESTIMATION SYSTEM
FIELD OF THE INVENTION
[0001] The present invention relates to diesel engines, and more
particularly to maintaining stable emissions of diesel engines.
BACKGROUND OF THE INVENTION
[0002] Diesel engine operation involves combustion that generates
exhaust gas. During combustion, air is delivered through an intake valve to
cylinders and fuel is injected into the cylinders forming an air/fuel mixture.
The air/fuel mixture is combusted therein. Air flow delivered to the cylinders
can be measured using a mass air flow (MAF) sensor. The MAF sensor
measures the total intake of fresh air flow through an air induction system.
After combustion, a piston forces exhaust gas in the cylinders into an exhaust
system. The exhaust gas may contain various emission components
including diesel particulates or soot.
[0003] Engine systems often include an exhaust gas recirculation
(EGR) system to reduce engine emissions and combustion noise as well as to
improve fuel economy. EGR involves re-circulating exhaust gases back into
the cylinders, which reduces the amount of oxygen available for combustion
and lowers cylinder temperatures. For exhaust gas to flow into the intake
manifold, exhaust pressure must be greater than the intake manifold pressure
(i.e. a boost condition). An EGR system enables ignition timing to remain at
an optimum point, which improves fuel economy and/or performance.
[0004] Advanced combustion approaches, such as premixed charge
compression ignition (PCCI), used to reduce emissions require large levels of
EGR. Currently EGR rates are estimated from the change in air flow that
occurs when an EGR valve is actuated. This method of EGR rate estimation
is accurate during steady state operation. The accuracy of estimation tends to
deteriorate during transient operation.

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[0005] Transitioning between various load-speed conditions and the
various levels of EGR during transient maneuvers can result in high
emissions, noise levels, and fuel consumption. Additionally, current
approaches of estimating the EGR level are dependent on calibrations
conducted when the air and EGR passages are clean. These estimations
are inaccurate when the EGR system becomes blocked (e.g. EGR cooler
fouling).
SUMMARY OF THE INVENTION
[0006] 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.
[0007] A control system and method for an exhaust gas
recirculation (EGR) system of an engine includes a first sensor that senses
fresh mass air flow, a second sensor that senses charge air flow, where the
charge air flow is based on the fresh mass air flow and EGR exhaust flow,
and a calculation module that determines a difference between the fresh
mass airflow and the charge air flow and generates an EGR valve control
signal based on the difference.
[0008] In other features, the system further comprises a controller
that controls an EGR valve based on at least one of the EGR valve control
signal and an engine operating point. The engine operating point is based on
at least one of engine speed and a fueling rate of the engine.
[0009] In other features, the system further comprises a bypass
module that controls a bypass valve based on an at least one of an engine
coolant temperature (Tcool) signal that indicates a temperature of an engine
coolant and an EGR exhaust temperature (Texhaust) signal that indicates a
temperature of the EGR exhaust, where the bypass valve selectively directs a

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portion of the EGR exhaust through a bypass conduit. The system further
comprises a Tcool sensor that generates the Tcool signal and a Texhaust
sensor that generates the Texhaust signal. The Texhaust sensor generates
the Texhaust signal before the EGR exhaust flows through exhaust treatment
devices.
[0010] In other features, the bypass module determines a degree of
actuation of the bypass valve based on actuation map stored by the bypass
module. The degree of actuation of the bypass valve is based on at least one
of the Tcool and the Texhaust.
[0011] A control system for an exhaust gas recirculation (EGR)
system of an engine includes an engine coolant temperature sensor that
senses a temperature of an engine coolant (Tcool), an EGR temperature
sensor that senses a temperature of EGR exhaust (Texhaust), and a bypass
module that controls a bypass valve that selectively directs a portion of the
EGR exhaust through a bypass conduit based on an at least one of the Tcool
and the Texhaust.
[0012] In other features, the control system further comprises a
calculation module that determines a difference between a mass air flow and
a charge air flow and generates an EGR valve control signal based on the
difference. The control system further comprises a controller that controls an
EGR valve based on at least one of the EGR valve control signal and an
engine operating point. The control system further comprises a first sensor
that generates a mass air flow signal that indicates the mass air flow and a
second sensor that generates a charge air flow signal that indicates charge air
flow.

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BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The present invention will become more fully understood
from the detailed description and the accompanying drawings, wherein:
[0014] FIG. 1 is a functional block diagram of an exemplary diesel
engine system according to the present invention;
[0015] FIG. 2 is a functional block diagram depicting a calculation
module in accordance with the present invention;
[0016] FIG. 3 is a functional block diagram depicting a bypass
module in accordance with the present invention;
[0017] FIG. 4 is a flowchart illustrating exemplary steps executed by
an EGR estimation system according to the present invention; and
[0018] FIG. 5 is a flowchart illustrating exemplary steps executed by
the bypass module in accordance with the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] 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.
[0020] Referring now to Figure 1, an exemplary diesel engine
system 10 is schematically illustrated in accordance with the present
invention. It is appreciated that the diesel engine system 10 is merely
exemplary in nature and that the exhaust gas recirculation (EGR) estimation
system described herein can be implemented in various diesel engine
systems.

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[0021] The diesel engine system 10 includes a diesel engine 12, an
intake manifold 14, and an EGR system 16. The engine 12 combusts an
air/fuel mixture within cylinders to drive pistons that rotatably drive a
crankshaft. Exhaust from the combustion process is exhausted from the
cylinders and into the exhaust manifold 18.
[0022] Air is drawn through a throttle 20 into the intake manifold 14,
which distributes air to the cylinders. Fuel is injected into cylinders (e.g. by
the common rail injection system) and the heat of the compressed air ignites
the air/fuel mixture. The exhaust gas exits from the cylinders into the EGR
system 16.
[0023] The EGR system 16 includes an exhaust gas recirculation
(EGR) valve 34, an EGR conduit 35, an EGR cooler 36, a charge mass air
flow (CMAF) sensor 38, an EGR bypass valve 40, and an EGR bypass
conduit 42. The exhaust manifold 20 directs the exhaust segments from the
cylinders into the EGR system 16. The EGR valve 34 re-circulates a portion
of the exhaust (EGR exhaust) through the EGR conduit 35, as explained in
further detail below. The EGR bypass valve 40 selectively directs a portion of
the EGR exhaust (bypass exhaust) away from the EGR cooler 36 through the
bypass conduit 42. The bypass exhaust is not cooled by the EGR cooler 36
prior to being re-circulated to intake manifold 14. The remainder of the
exhaust is directed into an exhaust conduit (not shown). Conversely, the
exhaust directed through the EGR conduit 35 is cooled.
[0024] A controller 44 regulates operation of the diesel engine
system 10 according to the EGR estimation system of the present invention.
More particularly, the controller 44 communicates with an intake manifold
absolute pressure (MAP) sensor 46, an engine speed sensor 48, a mass air
flow (MAF) sensor 50, an engine coolant temperature (Tcool) sensor 52, an
exhaust temperature (Texhaust) sensor 54, and the CMAF sensor 38. The
MAP sensor 46 generates a signal indicating the boost, and the engine speed
sensor 48 generates a signal indicating engine speed (RPM). The Tcool
sensor 52 generates a signal indicating the engine coolant temperature, and

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the exhaust temperature sensor 54 generates a signal indicating the EGR
exhaust temperature. Preferably, the Texhaust sensor 54 determines the
Texhaust prior to the EGR exhaust flowing through the EGR cooler 36 and/or
other treatment devices (not shown).
[0025] The MAF sensor 50 generates a MAF signal indicating the
fresh mass airflow into the intake manifold 14. The CMAF sensor 38
generates a CMAF signal indicating the CMAF into the intake manifold 14.
The CMAF includes a mixture of fresh mass airflow and EGR flow. In various
embodiments, the MAF sensor 48 and the CMAF sensor 38 can include a
MAF temperature sensor (not shown) and a CMAF temperature sensor (not
shown), respectively. The MAF temperature sensor and CMAF temperature
sensor generate signals indicating a temperature of the fresh MAF and a
temperature of the CMAF into the intake manifold 14, respectively. The
controller 44 determines an engine load or engine operating point based in
part on the RPM and fueling rates of the engine 12. The fueling rate is
generally measured in fuel volume per combustion event. Engine output is
controlled via the fueling rate.
[0026] The controller 44 determines an EGR rate based on engine
load. For example, during periods of heavy engine load, the EGR rate is
reduced to enable increased oxygen for combustion within the cylinders.
During periods of low engine load, the EGR rate is increased to reduce
oxygen intake into the cylinders, which reduces cylinder temperature and
emissions. The EGR rate may vary from 0% to over 50% in the intake
manifold 14. More specifically, the EGR rate reflects the amount of re-
circulated exhaust. For example, an EGR rate of 20% recirculates 20% of the
total amount of exhaust generated. The controller 44 controls the EGR valve
34 to achieve the desired EGR rate.

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[0027] Referring now to FIG. 2, the controller 44 includes a
calculation module 100 that receives a MAF signal and a CMAF signal sensed
by the MAF sensor 50 and the CMAF sensor 38, respectively. The MAF
signal indicates the total intake of fresh air flow through the air induction
system. The CMAF signal indicates the mixture of fresh airflow and EGR
exhaust gas. The calculation module 100 estimates the EGR flow rate of the
diesel engine system 10. The calculation module 100 determines a value of
the mass air flow based on the MAF signal and determines the value of the
total charge air flow based on the CMAF signal. The calculation module 100
calculates a difference between the mass air flow and the charged air flow.
The difference between the mass air flow and the charged mass air flow
provides an accurate estimation of the EGR flow rate during steady state and
transient engine operating conditions of the diesel engine system 10.
[0028] Referring to FIG. 3, the controller 44 includes a bypass
module 150 that receives a Tcool signal and a Texhaust signal sensed by the
Tcool sensor 52 and the Texhaust sensor 54, respectively. The bypass
module 150 controls the bypass valve 40 based on the Tcool and the
Texhaust. In various implementations, the bypass module 150 may
determine a degree of actuation of the bypass valve 40 based on an actuation
map (not shown) stored in a memory (not shown) of the bypass module 150.
The actuation map may be indexed by the Tcool and Texhaust for an engine
operating point of the engine 12.
[0029] Referring now to FIG. 4, a method 400 of controlling EGR
flow rate will be discussed in more detail. The controller 44 begins the
method 400 in step 402. In step 404, the controller 44 determines whether
the engine 12 is turned on. If the engine 12 is turned off, the method 400
returns to step 404. If the engine 12 is turned on, the controller 44 proceeds
to step 406.

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[0030] In step 406, the calculation module 100 determines the fresh
mass air flow to the engine 12. In step 208, the calculation module 100
determines the charge mass flow to the engine 12. In step 410, the
calculation module 100 estimates the EGR flow rate by determining the
difference between the mass air flow and the charge air flow. In step 412, the
controller 44 generates a control signal for the EGR valve 34 (EGR valve
control signal). In step 414, the calculation module 100 adjusts the
positioning of the EGR valve 34 based on the EGR valve control signal. The
method 400 ends in step 416.
[0031] Referring now to FIG. 5, a method 500 of actuating the
bypass module 150 will be discussed in more detail. The controller 44 begins
the method 500 in step 502. In step 504, the controller 44 determines if the
engine 12 is turned on. If the engine 12 is turned off, the method 500 returns
to step 504. If the engine 12 is turned on, the controller 44 proceeds to step
506.
[0032] In step 506, the bypass module 150 determines the Tcool of
the engine 12 at an operating point. In step 508, the bypass module 150
determines the Texhaust of the engine 12 at the operating point. In step 510,
the bypass module 150 generates a control signal for the bypass valve 40
(bypass valve control signal) based on the Tcool and Texhaust. In step 512,
the controller 44 adjusts the bypass valve 40 based on the bypass valve
control signal. In step 514, the method 500 ends.

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CLAIMS
What is claimed is:
1. A control system for an exhaust gas recirculation (EGR) system
of an engine, comprising:
a first sensor that senses fresh mass air flow;
a second sensor that senses charge air flow, wherein said
charge air flow is based on said fresh mass air flow and EGR exhaust flow;
and
a calculation module that determines a difference between said
fresh mass airflow and said charge air flow and generates an EGR valve
control signal based on said difference.
2. The system of claim 1 further comprising a controller that
controls an EGR valve based on at least one of said EGR valve control signal
and an engine operating point.
3. The system of claim 1 further comprising a bypass module that
controls a bypass valve based on an at least one of an engine coolant
temperature (Tcool) signal that indicates a temperature of an engine coolant
and an EGR exhaust temperature (Texhaust) signal that indicates a
temperature of said EGR exhaust, wherein the bypass valve selectively
directs a portion of said EGR exhaust through a bypass conduit.
4. The system of claim 3 further comprising a Tcool sensor that
generates said Tcool signal and a Texhaust sensor that generates said
Texhaust signal.
5. The system of claim 4 wherein said Texhaust sensor generates
said Texhaust signal before said EGR exhaust flows through exhaust
treatment devices.

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6. The system of claim 3 wherein said bypass module determines
a degree of actuation of said bypass valve based on actuation map stored by
said bypass module.
7. The system of claim 6 wherein said degree of actuation of said
bypass valve is based on at least one of said Tcool and said Texhaust.
8. The system of claim 2 wherein said engine operating point is
based on at least one of engine speed and a fueling rate of the engine.
9. A control method for an exhaust gas recirculation (EGR) system
of an engine, comprising:
sensing fresh mass air flow to the engine;
sensing charge air flow to the engine; and
determining a difference between said fresh mass airflow and
said charge air flow and generating an EGR valve control signal based on
said difference, wherein said charge air flow is based on said fresh air flow
and EGR exhaust flow.
10. The method of claim 9 further comprising controlling an EGR
valve based on at least one of said EGR valve control signal and an engine
operating point.
11. The method of claim 9 further comprising controlling a bypass
valve based on an at least one of an engine coolant temperature (Tcool)
signal that indicates a temperature of an engine coolant and an EGR exhaust
temperature (Texhaust) signal that indicates a temperature of said EGR
exhaust.

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12. The method of claim 11 further comprising generating said Tcool
signal and said Texhaust signal.
13. The method of claim 12 further comprising generating said
Texhaust signal before said EGR exhaust flows through exhaust treatment
devices.
14. The method of claim 11 further comprising determining a degree
of actuation of said bypass valve based on actuation map stored by said
bypass module.
15. The method of claim 14 wherein said degree of actuation of said
bypass valve is based on at least one of said Tcool and said Texhaust.
16. The system of claim 10 wherein said engine operating point is
based on at least one of engine speed and a fueling rate of the engine.
17. A control system for an exhaust gas recirculation (EGR) system
of an engine, comprising:
an engine coolant temperature sensor that senses a
temperature of an engine coolant (Tcool);
an EGR temperature sensor that senses a temperature of EGR
exhaust (Texhaust); and
a bypass module that controls a bypass valve that selectively
directs a portion of said EGR exhaust through a bypass conduit based on an
at least one of said Tcool and said Texhaust.
18. The control system of claim 17 further comprising a calculation
module that determines a difference between a mass air flow and a charge air
flow and generates an EGR valve control signal based on said difference.

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19. The control system of claim 18 further comprising a controller
that controls an EGR valve based on at least one of said EGR valve control
signal and an engine operating point.
20. The control system of claim 18 further comprising a first sensor
that
generates a mass air flow signal that indicates said mass air flow and a
second sensor that generates a charge air flow signal that indicates charge air
flow.

A control system and method for an exhaust gas
recirculation (EGR) system of an engine includes a first sensor that senses
fresh mass air flow, a second sensor that senses charge air flow, where the
charge air flow is based on the fresh mass air flow and EGR exhaust flow,
and a calculation module that determines a difference between the fresh
mass airflow and the charge air flow and generates an EGR valve control
signal based on the difference.

Documents:

01568-kol-2007-abstract.pdf

01568-kol-2007-assignment.pdf

01568-kol-2007-claims.pdf

01568-kol-2007-correspondence others 1.1.pdf

01568-kol-2007-correspondence others.pdf

01568-kol-2007-description complete.pdf

01568-kol-2007-drawings.pdf

01568-kol-2007-form 1.pdf

01568-kol-2007-form 2.pdf

01568-kol-2007-form 3.pdf

01568-kol-2007-form 5.pdf

01568-kol-2007-priority document.pdf

1568-KOL-2007-ABSTRACT.pdf

1568-KOL-2007-AMANDED CLAIMS.pdf

1568-KOL-2007-AMANDED PAGES OF SPECIFICATION.pdf

1568-KOL-2007-CORRESPONDENCE 1.1.pdf

1568-kol-2007-CORRESPONDENCE OTHERS 1.2.pdf

1568-KOL-2007-DESCRIPTION (COMPLETE).pdf

1568-KOL-2007-DRAWINGS.pdf

1568-KOL-2007-FORM 1.pdf

1568-kol-2007-FORM 18.pdf

1568-KOL-2007-FORM 2.pdf

1568-KOL-2007-FORM 26.pdf

1568-KOL-2007-FORM 3.pdf

1568-KOL-2007-OTHERS.pdf

1568-KOL-2007-PETITION UNDER RULE 137.pdf

1568-KOL-2007-REPLY TO EXAMINATION REPORT.pdf

abstract-01568-kol-2007.jpg


Patent Number 248735
Indian Patent Application Number 1568/KOL/2007
PG Journal Number 33/2011
Publication Date 19-Aug-2011
Grant Date 16-Aug-2011
Date of Filing 21-Nov-2007
Name of Patentee GM GLOBAL TECHNOLOGY OPERATIONS, INC.
Applicant Address 300 GM RENAISSANCE CENTER, DETROIT, MICHIGAN
Inventors:
# Inventor's Name Inventor's Address
1 SHERIF H. EL TAHRY 1645 HEATHERWOOD, TROY, MICHIGAN 48098
2 OGNYAN N. YANAKIEV 41817 CONNERWOOD COURT, CANTON, MICHIGAN 48187
PCT International Classification Number F02M25/07; F02B33/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 11/646611 2006-12-27 U.S.A.