Title of Invention

SYSTEM FOR CONTROLLING REGENERATION OF LEAN NOx TRAPS

Abstract A control system and method for controlling torque output of an engine include an air control module that receives an actual airflow and a desired airflow and outputs an adjusted actual airflow based on the actual airflow and the desired airflow. A fuel control module receives the adjusted actual airflow and controls fuel output based on the adjusted actual airflow, a ratio (λ) of an operating air-fuel mixture to an ideal air-fuel mixture, and an operating curve (λtraj).
Full Text 1 General Motors No GP-307810
Attorney Docket No. 8540P-000393
SYSTEM FOR CONTROLLING REGENERATION OF LEAN NOx TRAPS
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/842,511, filed on September 5, 2006. The disclosure of
the above application is incorporated herein by reference.
FIELD
[0002] The present disclosure relates to internal combustion
engines, and more particularly to a system for controlling the regeneration of a
lean NOx trap.
BACKGROUND
[0003] The statements in this section merely provide background
information related to the present disclosure and may not constitute prior art.
[0004] The engine controls the air-fuel mixture to achieve an ideal
air-fuel mixture ratio (stoichiometric ratio). At the optimum stoichiometric ratio,
all of the fuel is burned using all of the oxygen in the air. For internal
combustion engines, the stoichiometric ratio is about 14.7:1. In other words,
for each pound of gasoline, 14.7 pounds of air is burned. The air-fuel mixture
varies from the optimum stoichiometric ratio during driving. Sometimes the
air-fuel mixture is lean (an air-to-fuel mixture higher than 14.7) and other times
the air-fuel mixture is rich (an air-to-fuel mixture lower than 14.7).
[0005] Vehicle engines produce oxides of nitrogen (NOx) as a
component of vehicle emissions. In particular, lean-burn gasoline and diesel
engines tend to produce higher levels of NOx than conventional stoichiometric
gasoline engines.
[0006] In an effort to reduce NOx levels in vehicle emissions,
manufacturers employ emissions control systems with engine sensors and
NOx storage catalysts, sometimes referred to as Lean NOx traps (LNTs). The
NOx storage catalysts absorb and decompose the NOx with combustible
gases such as carbon monoxide (CO) or hydrocarbon (HC). While reducing

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NOx levels, these systems tend to increase the level of hydrocarbons in
vehicle emissions.
[0007] LNTs require periodic intervals of rich exhaust gas to
regenerate the stored NOx and convert it into harmless byproducts. This
control of the air-fuel ratio in a diesel engine can cause torque disturbance
during rich operation.
SUMMARY
[0008] A control system and method for controlling torque output of
an engine include an air control module that receives an actual airflow and a
desired airflow and outputs an adjusted actual airflow based on the actual
airflow and the desired airflow. A fuel' control module receives the adjusted
actual airflow and controls fuel output based on the adjusted actual airflow, a
ratio () of an operating air-fuel mixture to an ideal air-fuel mixture, and an
operating curve (traj).
[0009] In other features, a reference module generates the traj
based on the  and a desired  (des). The reference module generates the
traj by one of decaying the to the des and incrementing the  to the des.
The desired airflow and the des are based on one of lean operation of the
engine and rich operation of the engine. The lean operation corresponds to
the ideal air to fuel ratio exceeding 14.7 and the rich operation corresponds to
the ideal air to fuel ratio below 14.7.
[0010] In other features, the air control module includes an air feed
forward module. The air feed forward module controls boost based on the
desired mass airflow. The air control module includes an air feedback
module. The air feedback module adjusts exhaust gas recirculation (EGR)
and throttle based on the desired airflow and the actual airflow. The fuel
control module includes a fuel feed forward module that controls a feed
forward fuel quantity supplied to the engine based on the adjusted actual
airflow, the traj, and an air to fuel ratio model. The fuel control module
includes a delay module and a fuel feedback module. The delay module
retains the traj for an initial period of time. The fuel feedback module
determines a delta fuel quantity based on the  and said traj The initial

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period of time compensates for a lapse in time between supplying the fuel
feed forward to the engine and communicating with a  sensor.
[0011] In other features, the control system and method receive a
mode input that corresponds to one of lean operation of the engine and rich
operation of the engine. The lean operation corresponds to the ideal air to
fuel ratio exceeding 14.7 and the rich operation corresponds to the ideal air to
fuel ratio below 14.7.
[0012] Further areas of applicability will become apparent from the
description provided herein. It should be understood that the description and
specific examples are intended for purposes of illustration only and are not
intended to limit the scope of the present disclosure.
DRAWINGS
[0013] The drawings described herein are for illustration purposes
only and are not intended to limit the scope of the present disclosure in any
way.
[0014] Figure 1 is a block diagram of an engine control system
including a lambda sensor according to the present invention;
[0015] Figure 2 is a functional block diagram of a controller
according to the present invention; and
[0016] Figure 3 is a flowchart illustrating a method of controlling
regeneration of a NOx trap according to the present invention.
DETAILED DESCRIPTION
[0017] 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.

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[0018] Referring now to Figure 1, an engine control system 10 of an
engine 14 is shown. A controller 30 communicates with various components
of the engine control system 10 including, but not limited to, a throttle position
sensor 32 (TPS), a fuel system 34, an injection system 36, and the engine
speed sensor 34. The engine speed sensor 34 determines an engine speed
in rotations per minute (RPM). The controller 30 receives a mass air flow
(MAF) from the MAF sensor 40 and uses the information to determine air flow
into the engine 14. The air flow data is then used to calculate fuel delivery
from the fuel system 34 to the engine 14. The controller 30 further
communicates with an ignition (not shown) or the injection system 36 to
determine ignition spark or injection timing. The controller 30 may receive
additional inputs from other components in the engine control system 10,
including an accelerator pedal 42.
[0019] In an exhaust gas recirculation (EGR) system, a conduit 44
connects the exhaust manifold 46 to the intake manifold 48. An EGR valve 12
that is positioned along the conduit 44 and meters EGR according to input
from the controller 30. In the preferred embodiment, a lambda () sensor 50
or exhaust gas oxygen sensor determines a ratio of the operating air-fuel
mixture to the stoichiometric operating condition (). The  sensor 50
communicates values to the controller 30. The controller 30 may
communicate with the EGR valve 12 or a boost mechanism (not shown) in
response to the data from the  sensor 50. The controller 30 adjusts the EGR
valve 12 and/or the boost mechanism to correct performance thereof.
[0020] Referring now to Figure 2, the controller 10 includes an air
set point (ASP) module 106 that receives a MAF signal from the MAF sensor
40 and a mode signal. The mode signal indicates whether the engine 14
requires a switch from the current air-fuel (A/F) operation. For example, the
mode signal may include a required change from a lean A/F operation to a
rich A/F operation. Conversely, the required change may be from a rich A/F
operation to a lean A/F operation. The ASP module 106 determines a current
mass airflow (mcurr) and a desired mass airflow (mdes). The mcurr represents
the airflow at the current A/F operation of the engine 14 prior to a mode

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switch, and mdes represents the airflow corresponding to desired A/F. The
mdes is based on the MAF.
[0021] A regeneration control system 100 includes an air control
module 102 that controls airflow delivered to the engine 14 and a fuel control
module 104 that controls fuel delivered to the engine 14. The air control
module 102 includes an air feed forward (air FF) module 110 that outputs a
boost signal based on the mdes. The boost signal, an EGR valve signal, and a
throttle signal command the air control plant (Pair) device 114 which produces
the plant airflow (mfinal)- The Pair device 114 is a combination of air actuators
including, but not limited to, an EGR valve 12, a throttle valve 19, and a boost
mechanism (not shown). In various embodiments, the boost mechanism may
include, but is not limited to, a variable geometry turbo and/or a fixed
geometry turbo.
[0022] The air control module 104 includes an air feedback loop that
provides air closed loop control to the regeneration control system 100. An air
feedback (air FB) module 112 receives an error signal 113 and outputs the
EGR signal and throttle signal to adjust the EGR valve 12 and throttle valve
19, respectively, to compensate for the disparity between the mfinal and mdes.
During the operation of the engine 14, a first comparator 108 compares the
mfinal to the mdes and outputs the difference, the error signal 113, to the air FB
module 112. In an exemplary embodiment, the air FB module 112 can be, but
is not limited to, a proportional-integral-derivative controller (PID) controller.
[0023] A lambda module116 calculates and outputs a current
lambda (curr) value and a desired lambda (des) value to a reference module
118.  values represent a ratio of an operating A/F mixture to the
stoichiometric operating condition described above. The curr value is based
on mcurr and a current fuel quantity (Qcurr) being utilized by the engine 14. The
des can be a predetermined value based on operating at rich or lean A/F
conditions or can be determined based on the curr.
[0024] The reference module generates a lambda trajectory curve
(traj) based on the curr and the des The reference module 118 shapes the
des by either decaying the curr to the des when transitioning from a lean to
rich operation or by incrementing the curr to the des when transitioning from

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rich to lean operation of the engine 14. In an exemplary embodiment, the
transition can be accomplished exponentially to limit the amount of torque
disturbance. The traj serves as input to a fuel feed forward (fuel FF) module
120 and a delay module 130. The fuel FF module 120 outputs a feed forward
fuel quantity (Qff) command based on the traj, the mfinal signal, and an A/F
ratio (AFR) model.
[0025] The Qff and a fuel quantity differential (∆Q) are summed at a
first summing junction 124. In various embodiments, the Qff may either be
incremented or decremented by the ∆Q. A fuel plant (Pfuel) device 126
simultaneously receives the mode input. The Pfuel device 126 schematically
represents mechanisms for the addition of fuel including, but not limited to,
fuel injectors (not shown) of the engine 14. In various embodiments, a
compensated fuel quantity (Qcomp) can be added directly to the main injection
pulse of the injector and/or by additional pulse injections such as post
injections.
[0026] The mode input signals the need for the Pfuel device 126 to
change operating modes from Qcurr operation to a desired fuel quantity (Qdes)
operation. In various embodiments, the Pfuel device 126 is not enabled during
lean operation. As a result, during lean operation, a predetermined lean fuel
quantity is provided by controller 30.
[0027] The Pfuel device 126 injects a final fuel quantity (Qfinal) based
on the Qcomp outputted by the first summing junction 124. A combustion plant
(Pcomb) device 128 outputs a measured lambda (meas) that is detected by the
 sensor 50. The meas is electrically communicated to a second comparator
132.
[0028] The control process also utilizes a fuel feedback loop that
provides fuel closed loop control to the regeneration control system 100 by
adjusting the Qff command to correct for any error. A delay module 130 holds
the traj value for an initial period of time prior to outputting the traj to the
second comparator 132. The time delay associated with the delay module 130
compensates for the lapse in time between injecting the Qff into the cylinders
(not shown) of the Pcomb device 128 and receiving a signal from the  sensor
50 indicating that the exhaust gas 16 has been expelled to the  sensor 50.

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[0029] The second comparator 132 compares the meas and the traj.
A fuel error signal 133 indicating the difference between the traj and the meas
is input into a fuel feedback (fuel FB) module 134. Prior to receiving the fuel
error signal 133, the fuel FB module 134 is commanded by the mode input to
change modes of operation. In an exemplary embodiment, the fuel FB module
134 can be, but is not limited to, a PID controller. The fuel FB module 134
determines the ∆Q based on the fuel error signal 133.
[0030] Referring now to Figure 3, a method 300 of controlling the
regeneration of a NOx trap will be discussed in more detail. The ASP module
106 begins the method 300 at 302. At 304, the ASP module 106 determines
whether the engine 14 requires changing the A/F operation. If the engine 14
does not require a change of A/F operation, the ASP module 106 returns to
304. If engine 14 does require a change of the A/F operation, the ASP module
106 proceeds to 308. The ASP module 106 determines the mdes needed by
the engine 14 that corresponds to the change of A/F operation.
[0031] In 310, the air FF module 110 determines the boost pressure
signal that commands the boost mechanism of the engine 14. The air control
module 102 commands the Pair device 114 based on the boost pressure
signal, the EGR signal, and the throttle signal in 312. In 314, the first
comparator 108 determines the air error signal based on mfinal and mdes In
316, the air FB module 112 determines the EGR signal and the throttle signal
based on the air correction signal.
[0032] In 318, the  module 116 determines the traj based on the
curr and des In 320, the fuel FF module 120 determines the Qff based on the
traj The first summing junction 124 determines the Qcomp based on the sum of
the Qff and the AQ in 322. In 324, the Pfuel device 126 delivers Qfinal based on
the Qcomp. The second comparator 132 determines the fuel error signal in 326
based on the traj and the meas outputted by the  sensor 50. In 328, fuel FB
module 134 determines ∆Q based on the fuel error signal.
[0033] 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

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Attorney Docket No. 8540P-000393
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.

General Motors No. GP-307810
9 Attorney Docket No. 8540P-000393
CLAIMS
What is claimed is:
1. A control system for controlling torque output of an engine,
comprising:
an air control module that receives an actual airflow and a
desired airflow and outputs an adjusted actual airflow based on said actual
airflow and said desired airflow; and
a fuel control module that receives said adjusted actual airflow
and controls fuel output based on said adjusted actual airflow, a ratio () of an
operating air-fuel mixture to an ideal air-fuel mixture, and an operating curve
(tral).
2. The control system of claim 1 further comprising:
a reference module that generates said tral based on said  and
a desired  (tral).
3. The control system of claim 2 wherein said reference module
generates said tral by one of decaying said to said des and incrementing
said  to said tdes.
4. The control system of claim 1 wherein said air control module
includes an air feed forward module; and
wherein said air feed forward module controls boost based on
said desired mass airflow.
5. The control system of claim 4 wherein said air control module
includes an air feedback module; and
wherein said air feedback module adjusts exhaust gas
recirculation (EGR) and throttle based on said desired airflow and said actual
airflow.

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Attorney Docket No. 8540P-000393
6. The control system of claim 5 wherein said fuel control module
includes a fuel feed forward module that controls a feed forward fuel quantity
supplied to said engine based on said adjusted actual airflow, said traj and
an air to fuel ratio model.
7. The control system of claim 6 wherein said fuel control module
includes a delay module and a fuel feedback module;
wherein said delay module retains said traj for an initial period of
time;
wherein said fuel feedback module determines a delta fuel
quantity based on said  and said traj.
8. The control system of claim 7 wherein said initial period of time
compensates for a lapse in time between supplying said fuel feed forward to
said engine and communicating with a  sensor.
9. The control system of claim 2 wherein said desired airflow and
said des are based on one of lean operation of said engine and rich operation
of said engine;
wherein said lean operation corresponds to said ideal air to fuel
ratio exceeding 14.7 and said rich operation corresponds to said ideal air to
fuel ratio below 14.7.
10. The control system of claim 1 wherein said control system
receives a mode input that corresponds to one of lean operation of said
engine and rich operation of said engine;
wherein said lean operation corresponds to said ideal air to fuel
ratio exceeding 14.7 and said rich operation corresponds to said ideal air to
fuel ratio below 14.7.

11 General Motors No. GP-307810
Attorney Docket No. 8540P-000393
11. A method for controlling torque output of an engine, comprising:
controlling an adjusted airflow to said engine based on a desired
airflow and an actual airflow; and
controlling a second final fuel quantity to said engine based on
said adjusted airflow, a ratio () of an operating air-fuel mixture to an ideal air-
fuel mixture, and an operating curve (traj).
12. The method of claim 11 further comprising:
generating said traj based on said  and a desired  (des).
13. The method of claim 12 wherein said traj is generated by one of
decaying said  to said des and incrementing said  to said des.
14. The method of claim 11 further comprising:
controlling boost based on said desired mass airflow.
15. The method of claim 14 further comprising:
controlling exhaust gas recirculation (EGR) and throttle based
on said desired airflow and said actual airflow.
16. The method of claim 15 further comprising:
controlling a feed forward fuel quantity supplied to said engine
based on said adjusted airflow, said traj and an air to fuel ratio model.
17. The method of claim 16 further comprising:
retaining said traj for an initial period of time; and
determining a delta fuel quantity based on said  and said traj.
18. The method of claim 17 wherein said initial period of time
compensates for a lapse in time between supplying said fuel feed forward to
said engine and communicating with a  sensor.

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Attorney Docket No. 8540P-000393
19. The method of claim 12 wherein said desired airflow and said
des are based on one of lean operation of said engine and rich operation of
said engine;
wherein said lean operation corresponds to said ideal air to fuel
ratio exceeding 14.7 and said rich operation corresponds to said idea air to
fuel ratio below 14.7.
20. The method of claim 11 wherein said method receives a mode
input that corresponds to one of lean operation of said engine and rich
operation of said engine;
wherein said lean operation corresponds to said ideal air to fuel
ratio exceeding 14.7 and said rich operation corresponds to said ideal air to
fuel ratio below 14.7.
Dated this 30th day of AUGUST 2007


A control system and method for controlling torque output of an engine
include an air control module that receives an actual airflow and a desired
airflow and outputs an adjusted actual airflow based on the actual airflow and
the desired airflow. A fuel control module receives the adjusted actual airflow
and controls fuel output based on the adjusted actual airflow, a ratio (λ) of an
operating air-fuel mixture to an ideal air-fuel mixture, and an operating curve (λtraj).

Documents:

01193-kol-2007-abstract.pdf

01193-kol-2007-assignment.pdf

01193-kol-2007-claims.pdf

01193-kol-2007-correspondence others 1.1.pdf

01193-kol-2007-correspondence others 1.2.pdf

01193-kol-2007-correspondence others 1.3.pdf

01193-kol-2007-correspondence others.pdf

01193-kol-2007-description complete.pdf

01193-kol-2007-drawings.pdf

01193-kol-2007-form 1.pdf

01193-kol-2007-form 18.pdf

01193-kol-2007-form 2.pdf

01193-kol-2007-form 3.pdf

01193-kol-2007-form 5.pdf

01193-kol-2007-priority document.pdf

1193-KOL-2007-(22-03-2012)-AMANDED CLAIMS.pdf

1193-KOL-2007-(22-03-2012)-CORRESPONDENCE.pdf

1193-KOL-2007-ABSTRACT.pdf

1193-KOL-2007-AMANDED CLAIMS.pdf

1193-KOL-2007-AMANDED PAGES OF SPECIFICATION.pdf

1193-KOL-2007-ASSIGNMENT.pdf

1193-KOL-2007-CORRESPONDENCE 1.1.pdf

1193-KOL-2007-CORRESPONDENCE OTHERS 1.4.pdf

1193-KOL-2007-CORRESPONDENCE.pdf

1193-KOL-2007-DESCRIPTION (COMPLETE).pdf

1193-KOL-2007-DRAWINGS.pdf

1193-KOL-2007-EXAMINATION REPORT REPLY RECIEVED.pdf

1193-KOL-2007-EXAMINATION REPORT.pdf

1193-KOL-2007-FORM 1.pdf

1193-KOL-2007-FORM 18.pdf

1193-KOL-2007-FORM 2.pdf

1193-KOL-2007-FORM 26.pdf

1193-KOL-2007-FORM 3 1.1.pdf

1193-KOL-2007-FORM 3.pdf

1193-KOL-2007-FORM 5.pdf

1193-KOL-2007-GRANTED-ABSTRACT.pdf

1193-KOL-2007-GRANTED-CLAIMS.pdf

1193-KOL-2007-GRANTED-DESCRIPTION (COMPLETE).pdf

1193-KOL-2007-GRANTED-DRAWINGS.pdf

1193-KOL-2007-GRANTED-FORM 1.pdf

1193-KOL-2007-GRANTED-FORM 2.pdf

1193-KOL-2007-GRANTED-LETTER PATENT.pdf

1193-KOL-2007-GRANTED-SPECIFICATION.pdf

1193-KOL-2007-OTHERS 1.1.pdf

1193-KOL-2007-OTHERS.pdf

1193-KOL-2007-PETITION UNDER RULR 137.pdf

1193-KOL-2007-PRIORITY DOCUMENT.pdf

1193-KOL-2007-REPLY TO EXAMINATION REPORT.pdf

abstract-01193-kol-2007.jpg


Patent Number 253212
Indian Patent Application Number 1193/KOL/2007
PG Journal Number 27/2012
Publication Date 06-Jul-2012
Grant Date 04-Jul-2012
Date of Filing 30-Aug-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 DAVID J. STROH 38251 SARATOGA CIRCLE, FARMINGTON HILLS, MICHIGAN 48331
PCT International Classification Number F02D41/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 60/842511 2006-09-05 U.S.A.