U.S. patent application number 16/162952 was filed with the patent office on 2020-04-23 for emission control system.
The applicant listed for this patent is DENSO International America, Inc.. Invention is credited to Han-Yuan CHANG, Hiroki NOGAMI, Nicholas POLCYN.
Application Number | 20200122086 16/162952 |
Document ID | / |
Family ID | 69951632 |
Filed Date | 2020-04-23 |
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United States Patent
Application |
20200122086 |
Kind Code |
A1 |
CHANG; Han-Yuan ; et
al. |
April 23, 2020 |
EMISSION CONTROL SYSTEM
Abstract
A vehicle includes an engine, a fueling system, an exhaust
assembly, and a controller. The fueling system controls fuel to the
engine. The exhaust assembly releases combustion gas from the
engine and includes at least one sensor and a catalytic converter.
The controller is configured to control the engine, the fueling
system and the exhaust assembly. The controller evaluates engine
state and an output from the at least one sensor and commands a
fueling strategy to control an oxygen storage capacity of the
catalytic converter based on the engine state and output from the
at least one sensor.
Inventors: |
CHANG; Han-Yuan; (Ann Arbor,
MI) ; POLCYN; Nicholas; (Commerce, MI) ;
NOGAMI; Hiroki; (Novi, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DENSO International America, Inc. |
Southfield |
MI |
US |
|
|
Family ID: |
69951632 |
Appl. No.: |
16/162952 |
Filed: |
October 17, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01N 2250/12 20130101;
B01D 53/9495 20130101; B01D 2255/908 20130101; F01N 2900/1624
20130101; B01D 53/9454 20130101; F02D 41/02 20130101; F01N 3/101
20130101; F01N 2240/16 20130101; F01N 9/00 20130101; F01N 2560/025
20130101; B01D 53/9445 20130101; F01N 3/2093 20130101; F01N 3/0205
20130101; B01D 53/9481 20130101; F01N 2430/06 20130101 |
International
Class: |
B01D 53/94 20060101
B01D053/94; F01N 3/20 20060101 F01N003/20 |
Claims
1. A vehicle comprising: an engine; a fueling system controlling
fuel to the engine; an exhaust assembly releasing combustion gas
from the engine, the exhaust assembly including: a catalytic
converter, and a universal heated exhaust gas oxygen (UHEGO) sensor
disposed downstream at an exit of the catalytic converter; and a
controller configured to control the engine, the fueling system and
the exhaust assembly, wherein the controller is configured to
determine a current engine state, perform a first comparison
between an output from the UHEGO sensor with a first threshold, and
command a fueling strategy to control an oxygen storage capacity of
the catalytic converter based on the current engine state and the
first comparison.
2. The vehicle of claim 1, wherein the output from the UHEGO sensor
indicates a state of the oxygen storage capacity of the catalytic
converter.
3. The vehicle of claim 2, wherein the state of the oxygen storage
capacity is one of full, empty, or recharging.
4. (canceled)
5. (canceled)
6. The vehicle of claim 1, wherein the controller evaluates a slope
of the output of the UHEGO sensor and commands the fueling strategy
based on the engine state, the output from the UHEGO sensor, and
the slope of the output of the UHEGO sensor.
7. The vehicle of claim 1, wherein if the output of the UHEGO
sensor is not less than the first threshold, the controller
compares the output from the UHEGO sensor with a second
threshold.
8. A controller for a vehicle comprising: a comparison module
configured to determine a current engine state and perform a first
comparison between an output from a universal heated exhaust gas
oxygen (UHEGO) sensor with a first threshold in an exhaust system,
the UHEGO sensor being disposed at a downstream exit of a catalytic
converter; a catalyst control module configured to command a
fueling strategy to control an oxygen storage capacity of the
catalytic converter based on the current engine state and the first
comparison; and a fuel control module configured to command at
least one fuel system component based on the fueling strategy from
the catalyst control module.
9. The controller of claim 8, wherein the comparison module
determines a state of the oxygen storage capacity of the catalytic
converter based on the output of the UHEGO sensor.
10. The controller of claim 9, wherein the state of the oxygen
storage capacity is one of full, empty, or recharging.
11. (canceled)
12. (canceled)
13. The controller of claim 8, wherein the comparison module
determines and evaluates a slope of the output of the UHEGO sensor
and the catalyst control module commands the fueling strategy based
on the current engine state, the output from the UHEGO sensor, and
the slope of the output of the UHEGO sensor.
14. The controller of claim 8, wherein if the output of the UHEGO
sensor is not less than the first threshold, the comparison module
compares the output from the UHEGO sensor with a second
threshold.
15. A method of controlling an engine, a fuel system, and an
exhaust system of a vehicle, the method comprising: determining, by
a controller, a current engine state and an output of a universal
heated exhaust gas oxygen (UHEGO) sensor in an exhaust assembly,
the UHEGO sensor being disposed at a downstream exit of a catalytic
converter; comparing, by the controller, the output of the UHEGO
sensor with a first threshold; determining, by the controller, a
fueling strategy to control an oxygen storage capacity of the
catalytic converter based on the current engine state and the
comparison of the output with the first threshold; and commanding,
by the controller, at least one fuel system component based on the
fueling strategy.
16. The method of claim 15, further comprising: determining, by the
controller, an oxygen storage capacity state based on the output of
the UHEGO sensor, wherein the state of the oxygen storage capacity
is one of full, empty, or recharging.
17. The method of claim 15, further comprising: determining, by the
controller, a slope of the output of the UHEGO sensor; evaluating,
by the controller, whether the slope is positive or negative; and
determining, by the controller, the fueling strategy based on the
current engine state, the output from the UHEGO sensor, and the
slope of the output of the UHEGO sensor.
18. The method of claim 15, further comprising: determining, by the
controller, the first threshold based on at least one engine
condition.
19. The method of claim 15, further comprising: comparing, by the
controller, the output of the UHEGO sensor with a second threshold
if the output of the UHEGO sensor is not less than the first
threshold.
20. The method of claim 15, further comprising: commanding one of a
normal engine state and a lean engine state as the fueling
strategy, wherein the normal engine state is a stoichiometric
engine state, the normal engine state is commanded when the state
of the oxygen storage capacity is full, and the lean engine state
is commanded when the state of the oxygen storage capacity is
empty.
21. The vehicle of claim 7, wherein when the output of the UHEGO
sensor is less than the first threshold, the controller determines
that the oxygen storage capacity is empty, and when the output of
the UHEGO sensor is greater than the second threshold, the
controller determines that the oxygen storage capacity is recharged
to a preset threshold.
22. The vehicle of claim 1, wherein when the output of the UHEGO
sensor is less than the first threshold and the fueling strategy is
a stoichiometric state, the output of the UHEGO sensor indicates
that the oxygen storage capacity is empty.
23. The vehicle of claim 1, wherein when the output of the UHEGO
sensor is less than the first threshold and the fueling strategy is
a stoichiometric state, the controller is configured to command a
control state change to lean fueling to recharge the oxygen storage
capacity.
24. The vehicle of claim 1, wherein the output of the UHEGO sensor
indicates a carbon monoxide emission.
Description
FIELD
[0001] The present disclosure relates to an emission control
system, and, more particularly, to an emission control system that
utilizes a downstream Universal Heated Exhaust Gas Oxygen
sensor.
BACKGROUND
[0002] This section provides background information related to the
present disclosure which is not necessarily prior art.
[0003] Internal combustion engines ("ICEs") typically draw ambient
air into a combustion chamber where the air and a fuel are
compressed by a compression device, such as a piston-cylinder for
example, and ignited to cause combustion of the air-fuel mixture.
The combustion gases generally expand to do work on the compression
device, such as moving the piston to drive a crankshaft for
example. The combustion gases are typically then expelled from the
combustion chamber through an exhaust of the ICE. Combustion of the
fuel in the ICE, such as diesel, gasoline, ethanol, or natural gas
for example, typically results in emissions being released from the
exhaust, such as NOx and particulate matter (e.g. soot).
[0004] An exhaust gas after-treatment system, for example including
a catalytic converter such as a three-way catalyst (TWC), may be
used to convert the primary pollutants in exhaust gas from
automobiles into carbon dioxide, water and nitrogen. Catalytic
converters contain material which store and release oxygen (O2) to
aid the conversion. The O2 storage capacity (OSC) of a catalytic
converter is a measure of its ability to reduce the negative
effects of rich/lean oscillations in the exhaust gas composition
through catalyzing a redox (oxidation or reduction) reaction.
SUMMARY
[0005] This section provides a general summary of the disclosure,
and is not a comprehensive disclosure of its full scope or all of
its features.
[0006] An example vehicle according to the present disclosure
includes an engine, a fueling system, an exhaust assembly, and a
controller. The fueling system controls fuel to the engine. The
exhaust assembly releases combustion gas from the engine and
includes at least one sensor and a catalytic converter. The
controller is configured to control the engine, the fueling system
and the exhaust assembly. The controller evaluates engine state and
an output from the at least one sensor and commands a fueling
strategy to control an oxygen storage capacity of the catalytic
converter based on the engine state and output from the at least
one sensor.
[0007] The output from the at least one sensor may indicate a state
of the oxygen storage capacity of the catalytic converter.
[0008] The state of the oxygen storage capacity may be one of full,
empty, or recharging.
[0009] The at least one sensor may be a universal heated exhaust
gas oxygen (UHEGO) sensor.
[0010] The at least one sensor may be disposed downstream of the
catalytic converter.
[0011] The controller may evaluate a slope of the output of the at
least one sensor and may command the fueling strategy based on the
engine state, the output from the at least one sensor, and the
slope of the output of the at least one sensor.
[0012] The controller may compare the output from the at least one
sensor with at least one threshold.
[0013] An example controller for a vehicle according to the present
disclosure includes a comparison module, a catalyst control module,
and a fuel control module. The comparison module is configured to
determine an engine state and evaluate an output from at least one
sensor in an exhaust system. The catalyst control module is
configured to command a fueling strategy to control an oxygen
storage capacity of a catalytic converter based on the engine state
and the output from the at least one sensor. The fuel control
module is configured to command at least one fuel system component
based on the fueling strategy from the catalyst control module.
[0014] The comparison module may determine a state of the oxygen
storage capacity of the catalytic converter from the output of the
at least one sensor.
[0015] The state of the oxygen storage capacity may be one of full,
empty, or recharging.
[0016] The at least one sensor may be a universal heated exhaust
gas oxygen (UHEGO) sensor.
[0017] The at least one sensor may be disposed downstream of the
catalytic converter.
[0018] The comparison module may determine and evaluate a slope of
the output of the at least one sensor, and the catalyst control
module may command the fueling strategy based on the engine state,
the output from the at least one sensor, and the slope of the
output of the at least one sensor.
[0019] The comparison module may compare the output from the at
least one sensor with at least one threshold.
[0020] An example method of controlling an engine, a fuel system,
and an exhaust system of a vehicle according to the present
disclosure includes: determining, by a controller, an engine state
and an output of at least one sensor in an exhaust assembly;
comparing, by the controller, the output of the at least one sensor
with at least one threshold; determining, by the controller, a
fueling strategy to control an oxygen storage capacity of a
catalytic converter based on the engine state and the comparison of
the output with the at least one threshold; and commanding, by the
controller, at least one fuel system component based on the fueling
strategy.
[0021] The method may further include determining, by the
controller, an oxygen storage capacity state based on the output of
the at least one sensor, wherein the state of the oxygen storage
capacity is one of full, empty, or recharging.
[0022] The method may further include determining, by the
controller, a slope of the output of the at least one sensor;
evaluating, by the controller, whether the slope is positive or
negative; and determining, by the controller, the fueling strategy
based on the engine state, the output from the at least one sensor,
and the slope of the output of the at least one sensor.
[0023] The method may further include determining, by the
controller, the at least one threshold based on at least one engine
condition.
[0024] The method may further include comparing, by the controller,
the output of the at least one sensor with a first threshold and a
second threshold, wherein the at least one sensor is a universal
heated exhaust gas oxygen (UHEGO) sensor.
[0025] The method may further include commanding one of a normal
engine state and a lean engine state as the fueling strategy,
wherein the normal engine state is commanded when the state of the
oxygen storage capacity is full, and the lean engine state is
commanded when the state of the oxygen storage capacity is
empty.
[0026] Further areas of applicability will become apparent from the
description provided herein. The description and specific examples
in this summary are intended for purposes of illustration only and
are not intended to limit the scope of the present disclosure.
DRAWINGS
[0027] The drawings described herein are for illustrative purposes
only of selected embodiments and not all possible implementations,
and are not intended to limit the scope of the present
disclosure.
[0028] FIG. 1 is a schematic illustration of an example exhaust
assembly according to the present disclosure.
[0029] FIG. 2 is a schematic illustration of an example control
module of the exhaust assembly of FIG. 1.
[0030] FIG. 3 is a graphical representation of the output signals
of various sensors of the exhaust assembly of FIG. 1.
[0031] FIG. 4 is another graphical representation of the output
signals of various sensors of the exhaust assembly of FIG. 1.
[0032] FIG. 5 is a flow diagram for operation of an example method
for catalyst control according to the present disclosure.
[0033] FIGS. 6A and 6B are flow diagrams for operation of another
example method for catalyst control according to the present
disclosure.
[0034] Corresponding reference numerals indicate corresponding
parts throughout the several views of the drawings.
DETAILED DESCRIPTION
[0035] Example embodiments will now be described more fully with
reference to the accompanying drawings.
[0036] Example embodiments are provided so that this disclosure
will be thorough, and will fully convey the scope to those who are
skilled in the art. Numerous specific details are set forth such as
examples of specific components, devices, and methods, to provide a
thorough understanding of embodiments of the present disclosure. It
will be apparent to those skilled in the art that specific details
need not be employed, that example embodiments may be embodied in
many different forms and that neither should be construed to limit
the scope of the disclosure. In some example embodiments,
well-known processes, well-known device structures, and well-known
technologies are not described in detail.
[0037] The terminology used herein is for the purpose of describing
particular example embodiments only and is not intended to be
limiting. As used herein, the singular forms "a," "an," and "the"
may be intended to include the plural forms as well, unless the
context clearly indicates otherwise. The terms "comprises,"
"comprising," "including," and "having," are inclusive and
therefore specify the presence of stated features, integers, steps,
operations, elements, and/or components, but do not preclude the
presence or addition of one or more other features, integers,
steps, operations, elements, components, and/or groups thereof. The
method steps, processes, and operations described herein are not to
be construed as necessarily requiring their performance in the
particular order discussed or illustrated, unless specifically
identified as an order of performance. It is also to be understood
that additional or alternative steps may be employed.
[0038] When an element or layer is referred to as being "on,"
"engaged to," "connected to," or "coupled to" another element or
layer, it may be directly on, engaged, connected or coupled to the
other element or layer, or intervening elements or layers may be
present. In contrast, when an element is referred to as being
"directly on," "directly engaged to," "directly connected to," or
"directly coupled to" another element or layer, there may be no
intervening elements or layers present. Other words used to
describe the relationship between elements should be interpreted in
a like fashion (e.g., "between" versus "directly between,"
"adjacent" versus "directly adjacent," etc.). As used herein, the
term "and/or" includes any and all combinations of one or more of
the associated listed items.
[0039] Although the terms first, second, third, etc. may be used
herein to describe various elements, components, regions, layers
and/or sections, these elements, components, regions, layers and/or
sections should not be limited by these terms. These terms may be
only used to distinguish one element, component, region, layer or
section from another region, layer or section. Terms such as
"first," "second," and other numerical terms when used herein do
not imply a sequence or order unless clearly indicated by the
context. Thus, a first element, component, region, layer or section
discussed below could be termed a second element, component,
region, layer or section without departing from the teachings of
the example embodiments.
[0040] Spatially relative terms, such as "inner," "outer,"
"beneath," "below," "lower," "above," "upper," and the like, may be
used herein for ease of description to describe one element or
feature's relationship to another element(s) or feature(s) as
illustrated in the figures. Spatially relative terms may be
intended to encompass different orientations of the device in use
or operation in addition to the orientation depicted in the
figures. For example, if the device in the figures is turned over,
elements described as "below" or "beneath" other elements or
features would then be oriented "above" the other elements or
features. Thus, the example term "below" can encompass both an
orientation of above and below. The device may be otherwise
oriented (rotated 90 degrees or at other orientations) and the
spatially relative descriptors used herein interpreted
accordingly.
[0041] In the figures, the direction of an arrow, as indicated by
the arrowhead, generally demonstrates the flow of information (such
as data or instructions) that is of interest to the illustration.
For example, when element A and element B exchange a variety of
information but information transmitted from element A to element B
is relevant to the illustration, the arrow may point from element A
to element B. This unidirectional arrow does not imply that no
other information is transmitted from element B to element A.
Further, for information sent from element A to element B, element
B may send requests for, or receipt acknowledgements of, the
information to element A.
[0042] In this application, including the definitions below, the
term "module," the term "unit," or the term "controller" may be
replaced with the term "circuit." The term "module" or the term
"unit" may refer to, be part of, or include: an Application
Specific Integrated Circuit (ASIC); a digital, analog, or mixed
analog/digital discrete circuit; a digital, analog, or mixed
analog/digital integrated circuit; a combinational logic circuit; a
field programmable gate array (FPGA); a processor circuit (shared,
dedicated, or group) that executes code; a memory circuit (shared,
dedicated, or group) that stores code executed by the processor
circuit; other suitable hardware components that provide the
described functionality; or a combination of some or all of the
above, such as in a system-on-chip.
[0043] The module or unit may include one or more interface
circuits. In some examples, the interface circuits may include
wired or wireless interfaces that are connected to a local area
network (LAN), the Internet, a wide area network (WAN), or
combinations thereof. The functionality of any given module or unit
of the present disclosure may be distributed among multiple modules
or units that are connected via interface circuits. For example,
multiple modules or units may allow load balancing. In a further
example, a server (also known as remote, or cloud) module or unit
may accomplish some functionality on behalf of a client module or
unit.
[0044] The term code, as used above, may include software,
firmware, and/or microcode, and may refer to programs, routines,
functions, classes, data structures, and/or objects. The term
shared processor circuit encompasses a single processor circuit
that executes some or all code from multiple modules or units. The
term group processor circuit encompasses a processor circuit that,
in combination with additional processor circuits, executes some or
all code from one or more modules or units. References to multiple
processor circuits encompass multiple processor circuits on
discrete dies, multiple processor circuits on a single die,
multiple cores of a single processor circuit, multiple threads of a
single processor circuit, or a combination of the above. The term
shared memory circuit encompasses a single memory circuit that
stores some or all code from multiple modules or units. The term
group memory circuit encompasses a memory circuit that, in
combination with additional memories, stores some or all code from
one or more modules or units.
[0045] The term memory circuit is a subset of the term
computer-readable medium. The term computer-readable medium, as
used herein, does not encompass transitory electrical or
electromagnetic signals propagating through a medium (such as on a
carrier wave); the term computer-readable medium may therefore be
considered tangible and non-transitory. Non-limiting examples of a
non-transitory, tangible computer-readable medium are nonvolatile
memory circuits (such as a flash memory circuit, an erasable
programmable read-only memory circuit, or a mask read-only memory
circuit), volatile memory circuits (such as a static random access
memory circuit or a dynamic random access memory circuit), magnetic
storage media (such as an analog or digital magnetic tape or a hard
disk drive), and optical storage media (such as a CD, a DVD, or a
Blu-ray Disc).
[0046] The apparatuses and methods described in this application
may be partially or fully implemented by a special purpose computer
created by configuring a general purpose computer to execute one or
more particular functions embodied in computer programs. The
functional blocks and flowchart elements described above serve as
software specifications, which can be translated into the computer
programs by the routine work of a skilled technician or
programmer.
[0047] The computer programs include processor-executable
instructions that are stored on at least one non-transitory,
tangible computer-readable medium. The computer programs may also
include or rely on stored data. The computer programs may encompass
a basic input/output system (BIOS) that interacts with hardware of
the special purpose computer, device drivers that interact with
particular devices of the special purpose computer, one or more
operating systems, user applications, background services,
background applications, etc.
[0048] The computer programs may include: (i) descriptive text to
be parsed, such as HTML (hypertext markup language) or XML
(extensible markup language), (ii) assembly code, (iii) object code
generated from source code by a compiler, (iv) source code for
execution by an interpreter, (v) source code for compilation and
execution by a just-in-time compiler, etc. As examples only, source
code may be written using syntax from languages including C, C++,
C#, Objective-C, Swift, Haskell, Go, SQL, R, Lisp, Java.RTM.,
Fortran, Perl, Pascal, Curl, OCaml, Javascript.RTM., HTML5
(Hypertext Markup Language 5th revision), Ada, ASP (Active Server
Pages), PHP (PHP: Hypertext Preprocessor), Scala, Eiffel,
Smalltalk, Erlang, Ruby, Flash.RTM., Visual Basic.RTM., Lua,
MATLAB, SIMULINK, and Python.RTM..
[0049] None of the elements recited in the claims are intended to
be a means-plus-function element within the meaning of 35 U.S.C.
.sctn. 112(f) unless an element is expressly recited using the
phrase "means for," or in the case of a method claim using the
phrases "operation for" or "step for."
[0050] The emission control system described herein improves oxygen
storage capacity (OSC) control of a catalyst by utilizing a
downstream universal heated exhaust gas oxygen (UHEGO) sensor's
capability of gaseous emission detection. The emission control
system controls catalyst OSC more accurately to prevent over
charging OSC, prevent nitrogen oxide (NOx) breakthrough, and
prevent a spike in an air/fuel (A/F) ratio by monitoring the signal
from the downstream UHEGO sensor. The characteristics of the
downstream UHEGO sensor provide an indication for carbon monoxide
(CO) emission which can be correlated to the status of OSC. By
monitoring the signal from the downstream UHEGO sensor, overfilled
OSC, which leads to NOx breakthrough, can be avoided.
[0051] In the present disclosure, the status of OSC (empty,
recharging level, full) can be identified through the correlation
of the downstream UHEGO sensor signal to CO emission. Therefore, an
OSC value calculation/modeling/estimation is unnecessary,
increasing reliability and decreasing cost of the exhaust
assembly.
[0052] Now referring to FIG. 1, an engine 10 and exhaust assembly
14 according to the present disclosure is illustrated. The engine
10 may be, for example, an internal combustion engine ("ICE"). The
engine 10 may draw ambient air into a combustion chamber (not
illustrated) where the air and a fuel are compressed by a
compression device (not illustrated), such as a piston-cylinder for
example. The air-fuel mixture may be ignited to cause combustion.
The combustion gases expand to move the piston to drive a
crankshaft, for example. The combustion gases may then be expelled
from the combustion chamber through an exhaust port 18 of the ICE.
The combustion gasses include emissions, for example nitrogen oxide
(NOx), hydrocarbons (HC), carbon monoxide (CO), and particulate
matter (e.g. soot).
[0053] The exhaust assembly 14 may include a catalytic converter
22, such as a three-way catalyst (TWC), to convert the primary
pollutants (i.e., NOx, CO, HC, etc.) into carbon dioxide, water and
nitrogen. Catalytic converters 22 decrease the emissions or
pollutants by catalyzing a reaction (oxidation or reduction) to
break down the emissions. For example, the TWC simultaneously
reduces the NOx while oxidizing the HC and CO. Catalytic converters
22 contain material which stores and releases oxygen (O2) to aid
the conversion. For example, the material may be (INVENTOR PLEASE
ADD). An Oxygen Storage Capacity (OSC) of the catalytic converter
22 indicates an amount of oxygen stored in the material of the
catalytic converter 22.
[0054] The exhaust assembly 14 may further include an upstream
sensor 26 and a downstream sensor 30 positioned on an upstream side
of the catalytic converter 22 and a downstream side of the
catalytic converter 22, respectively, to measure an air/fuel ratio
before and after the catalytic converter 22. For example, the
upstream sensor 26 and the downstream sensor 30 may each be lambda
sensors, or universal heated exhaust gas oxygen (UHEGO)
sensors.
[0055] Additional sensors 34 may also be placed upstream and
downstream from the catalytic converter 22. For example, the
additional sensors 34 may measure CO emissions, NOx emissions, HC
emissions, particulate matter, etc.
[0056] A control module 38 may communicate with the various sensors
26, 30, 34 to control the components of the engine 10 and exhaust
assembly 14. In this application, the term "module" or "unit" may
be replaced with the term "circuit." The term "module" may refer
to, be part of, or include processor hardware (shared, dedicated,
or group) that executes code and memory hardware (shared,
dedicated, or group) that stores code executed by the processor
hardware. The code is configured to provide the features of the
modules described herein. The term memory hardware is a subset of
the term computer-readable medium. The term computer-readable
medium, as used herein, does not encompass transitory electrical or
electromagnetic signals propagating through a medium (such as on a
carrier wave). The term computer-readable medium is therefore
considered tangible and non-transitory. Non-limiting examples of a
non-transitory computer-readable medium are nonvolatile memory
devices (such as a flash memory device, an erasable programmable
read-only memory device, or a mask read-only memory device),
volatile memory devices (such as a static random access memory
device or a dynamic random access memory device), magnetic storage
media (such as an analog or digital magnetic tape or a hard disk
drive), and optical storage media (such as a CD, a DVD, or a
Blu-ray Disc).
[0057] Now referring to FIG. 2, the control module 38 may include a
comparison module 42, a catalyst control module 46, and a fuel
control module 50. The comparison module 42 may communicate with
sensors 26, 30, 34 and various other sensors or inputs 54 (for
example, vehicle speed, steering wheel position, engine speed,
engine load, etc) to determine a current engine condition. Although
it is not necessary, in some embodiments sensors/inputs 54 may be
communicated to the control module 38 through a control area
network (CAN) or other vehicle communication network. For example,
sensors/inputs 54, a comparison of outputs of the downstream UHEGO
sensor 30 and/or sensors 34, or a combination of these may provide
a current engine control state (such as normal or lean, for
example).
[0058] The comparison module 42 may compare an output signal from
the downstream UHEGO sensor 30 to a plurality thresholds, A and B.
The thresholds A and B may indicate a change from normal operation
to lean operation or a change from lean operation to normal
operation. The thresholds A and B may be determined based on engine
testing data.
[0059] For example, referring to FIG. 3, during a lean-to-rich
switching test, the following observations are possible: (1) a
shape of a CO emission curve is inversely similar to a shape of a
curve representing the output signal of the downstream UHEGO sensor
30, and (2) the increasing CO emission indicates that oxygen stored
in catalyst is depleted and OSC is empty while the decreasing CO
emission indicates that oxygen stored in the catalyst is increased
and OSC is being recharged. As such, an output of the downstream
UHEGO sensor 30 may be used as an indicator for the status of OSC.
Alternatively, an inflection point may be used as an indicator for
the status of OSC. The inflection point may be the value where the
slope of the signal of the downstream UHEGO sensor 30 changes from
negative to positive.
[0060] Accordingly, referring to FIG. 4, the threshold A may
indicate when the OSC is empty and needs to be recharged, while the
threshold B may indicate when the OSC is recharged to a particular
level (which includes a safety margin to full-charge). When the
signal of the downstream UHEGO sensor 30 drops below threshold A
while the fuel is controlled in the normal state (i.e., while in
stoichiometric Air-Fuel-Ratio, AFR, control), the signal may
indicate an empty OSC. Additionally, when the signal of the
downstream UHEGO sensor 30 increases above threshold B while the
fuel is controlled in a lean state (i.e. lean AFR control), the
signal may indicate a recharged OSC.
[0061] The values of A and B may be different for each engine
condition (i.e., may be specific for each engine operating point).
For example, the values of A and B may differ depending on speed,
load, etc. To account for the different engine conditions, a set of
coefficients Ki may be compiled as a function of engine condition
(speed, load, etc.). The values A and B may then be determined from
the following equations:
A=Ka*A.sub.Original
B=Ka*B.sub.Original
[0062] Returning to FIG. 2, the catalyst control module 46 may
communicate with the comparison module 42 and command a control
state based on the output from the comparison module 42. For
example, if the comparison module 42 determines that OSC is empty,
for example, when the signal of the downstream UHEGO sensor 30
drops below threshold A while the fuel is controlled in the normal
state (i.e., while in stoichiometric Air-Fuel-Ratio, AFR, control),
the catalyst control module 46 may command a control state change
to lean AFR control to recharge the OSC. Further, if the comparison
module 42 determines that OSC is recharged, for example, when the
signal of the downstream UHEGO sensor 30 increases above threshold
B while the fuel is controlled in a lean state (i.e. lean AFR
control), the catalyst control module 46 may command a control
state change to normal control (i.e., stoichiometric AFR control)
to prevent OSC from further charging, prevent NOx breakthrough, and
prevent a spike in AFR.
[0063] For example, in FIG. 4, if the catalyst control module 46
commands a control state change to normal control when the output
from the downstream UHEGO sensor 30 crosses the threshold B, the
spike following the threshold B is reduced or eliminated, as shown
by the X-ed portion. Instead, the output from the downstream UHEGO
sensor 30 would gradually ramp back to approximately 14.5 A/F. The
spike, or X-ed portion indicates over-charge of the OSC which can
lead to NOx breakthrough. Therefore, with the spiked portion
eliminated (as shown with the X), over-charge of the OSC and NOx
breakthrough is also eliminated.
[0064] Returning to FIG. 2, the fuel control module 50 may
communicate with the catalyst control module 46 and command various
fueling components 58 (such as fuel pumps, fuel injectors, etc.) to
operate in the commanded state provided by the catalyst control
module 46. For example, if the catalyst control module 46 commands
a lean engine state, the fuel control module 50 may operate under
lean control and command the various components 58 to a leaner
air-fuel mixture (i.e. a higher air fuel ratio, AFR). Further, if
the catalyst control module 46 commands a normal engine state, the
fuel control module 50 may operate under normal control and command
the various components 58 to a more stoichiometric air-fuel mixture
(i.e. a stoichiometric air fuel ratio, AFR, of around 14.7:1).
INVENTOR PLEASE CONFIRM
[0065] Now referring to FIG. 5, an example method 100 for catalyst
control is illustrated. Method 100 starts at 104. At 108, the
engine conditions (for example, speed, load, etc.) are determined.
For example only the engine conditions may be determined by the
control module 38 and based on outputs from sensors 26, 30, 34 and
various other sensors or inputs 54 (for example, vehicle speed,
steering wheel position, engine speed, engine load, etc). In some
embodiments, sensors/inputs 54, a comparison of outputs of the
downstream UHEGO sensor 30 and/or sensors 34, or a combination of
these may provide a current engine control state (such as normal or
lean, for example).
[0066] At 112, coefficients (Ki) are determined to alter an
original A and B threshold to thresholds A and B that accurately
represent the specific engine condition. For example, the set of
coefficients Ki may be compiled as a function of engine condition
(speed, load, etc.) and may be stored as a map, array, or otherwise
in the control module 38.
[0067] At 116, the thresholds A and B are determined based on the
original A and B thresholds and the coefficients Ki. For example,
the values A and B may be determined from the following
equations:
A=Ka*A.sub.Original
B=Ka*B.sub.Original
[0068] At 120, the current engine state is determined. For example,
the control module 38 may determine the current engine state based
on the current fueling control, such as lean control or normal,
stoichiometric, control. Stoichiometric control may be when an AFR
is approximately 14.7:1 (14.7 parts of air to one part of fuel). A
lower AFR number contains less air than the stoichiometric AFR, and
is therefore a richer mixture and linked with rich control. A
higher AFR number contains more air than the stoichiometric AFR,
and is therefore a leaner mixture and linked with lean control.
[0069] At 124, method 100 determines whether the output from the
downstream, or rear, UHEGO sensor 30 is less than threshold A. For
example, threshold A may be a number signifying that the AFR is
ramping down (having a negative slope) and the OSC is empty and
needs to be recharged. In some embodiments, an example number for
threshold A may be within a range of 14.0 to 14.5, and more
particularly within a range of 14.3 to 14.45 (INVENTOR PLEASE
CONFIRM).
[0070] If true, method 100 determines whether a current engine
state is lean at 128. In some embodiments, a normal engine state
may be stoichiometric control and a lean engine state may have a
leaner air-fuel mixture and a higher AFR number (contains more air
than the stoichiometric AFR). If false, the engine state is changed
to lean control at 132. For example, the catalyst control module 46
may command the fuel control module 50 to operate the fueling
system in lean control. The method ends at 136.
[0071] If true at 128, the engine state is maintained in lean
control at 140. The method then ends at 136.
[0072] If false at 124, method 100 determines whether the output
from the downstream, or rear, UHEGO sensor 30 is greater than
threshold B. For example, threshold B may be a number indicating
that the AFR is ramping up (having a positive slope) and the OSC is
recharged (less a margin of safety, for example, approximately
30%). As such, the threshold B value may be set within a range of
60%-80% of the total OSC, and more particularly at 70% of the total
OSC. In some embodiments, an example number for threshold B may be
within a range of 14.0 to 14.5, and more particularly within a
range of 14.4 to 14.5 (INVENTOR PLEASE CONFIRM).
[0073] If true, method 100 determines whether a current engine
state is normal at 148. As previously stated, in some embodiments,
a normal engine state may be stoichiometric control. If false, the
engine state is changed to normal control at 152. For example, the
catalyst control module 46 may command the fuel control module 50
to operate the fueling system in normal (i.e., stoichiometric)
control. The method then ends at 136.
[0074] If true at 148, the engine state is maintained in normal
control at 156. The method then ends at 136.
[0075] If false at 144, the method 100 determines whether a current
engine state is lean at 160. As previously stated, in some
embodiments, a lean engine state may have a leaner air-fuel mixture
and a higher AFR number (contains more air than the stoichiometric
AFR). If false, the method returns to 120. If true at 160, the
engine state is maintained in lean control at 164. The method then
ends at 136.
[0076] Now referring to FIGS. 6A and 6B, another example method 200
for catalyst control is illustrated. Method 200 starts at 204. At
208, the engine conditions (for example, speed, load, etc.) are
determined. For example only the engine conditions may be
determined by the control module 38 and based on outputs from
sensors 26, 30, 34 and various other sensors or inputs 54 (for
example, vehicle speed, steering wheel position, engine speed,
engine load, etc). In some embodiments, sensors/inputs 54, a
comparison of outputs of the downstream UHEGO sensor 30 and/or
sensors 34, or a combination of these may provide a current engine
control state (such as normal or lean, for example).
[0077] At 212, coefficients (Ki) are determined to alter an
original A and B threshold to thresholds A and B that accurately
represent the specific engine condition. For example, the set of
coefficients Ki may be compiled as a function of engine condition
(speed, load, etc.) and may be stored as a map, array, or otherwise
in the control module 38.
[0078] At 216, the thresholds A and B are determined based on the
original A and B thresholds and the coefficients Ki. For example,
the values A and B may be determined from the following
equations:
A=Ka*A.sub.Original
B=Ka*B.sub.Original
[0079] At 220, the current engine state is determined. For example,
the control module 38 may determine the current engine state based
on the current fueling control, such as lean control or normal,
stoichiometric, control. Stoichiometric control may be when an AFR
is approximately 14.7:1 (14.7 parts of air to one part of fuel). A
lower AFR number contains less air than the stoichiometric AFR, and
is therefore a richer mixture and linked with rich control. A
higher AFR number contains more air than the stoichiometric AFR,
and is therefore a leaner mixture and linked with lean control.
[0080] At 224, the slope of the output signal of the downstream, or
rear, UHEGO sensor 30 is determined. In some embodiments, the
comparison module 42 or the catalyst control module 46 may
determine the slope of the output of the downstream UHEGO sensor
30. For example only, the control module 38 may analyze a prior
period (such as within a range of 0.01-1 second, or, more
specifically, within a range of 0.1-0.3 seconds) to determine the
slope.
[0081] At 228, method 200 determines whether the output from the
downstream, or rear, UHEGO sensor 30 is less than threshold A. For
example, threshold A may be a number signifying that the AFR is
ramping down (having a negative slope) and the OSC is empty and
needs to be recharged. In some embodiments, an example number for
threshold A may be within a range of 14.0 to 14.5, and more
particularly within a range of 14.3 to 14.45 (INVENTOR PLEASE
CONFIRM).
[0082] If true, method 200 determines whether the output from the
downstream, or rear, UHEGO sensor 30 is greater than threshold B at
232. For example, threshold B may be a number indicating that the
AFR is ramping up (having a positive slope) and the OSC is
recharged (less a margin of safety, for example, approximately
30%). As such, the threshold B value may be set within a range of
60%-80% of the total OSC, and more particularly at approximately
70% of the total OSC. In some embodiments, an example number for
threshold B may be within a range of 14.0 to 14.5, and more
particularly within a range of 14.4 to 14.5 (INVENTOR PLEASE
CONFIRM).
[0083] If true at 232, method 200 determines whether the slope is
positive at 236. For example, the control module 38 may evaluate
the slope from 224 and determine whether the value is positive. If
true, method 200 determines whether a current engine state is
normal at 240. As previously stated, in some embodiments, a normal
engine state may be stoichiometric control. If false, the engine
state is changed to normal control at 244. For example, the
catalyst control module 46 may command the fuel control module 50
to operate the fueling system in normal (i.e., stoichiometric)
control. The method then ends at 248.
[0084] If true at 240, the normal engine state is maintained at
252. The method 200 then ends at 248.
[0085] If false at 236, method 200 determines whether the current
engine state is lean at 256. As previously stated, in some
embodiments, a lean engine state may have a leaner air-fuel mixture
and a higher AFR number (contains more air than the stoichiometric
AFR). If true, the method 200 maintains the lean engine state at
260. The method then ends at 248.
[0086] If false at 256, the control module 38 switches the engine
state to lean control at 264. The method then ends at 248.
[0087] If false at 232, method 200 determines whether the current
engine state is lean at 268. As previously stated, in some
embodiments, a lean engine state may have a leaner air-fuel mixture
and a higher AFR number (contains more air than the stoichiometric
AFR). If true, the method 200 maintains the lean engine state at
272. The method then ends at 248.
[0088] If false at 268, the control module 38 switches the engine
state to lean control at 276. The method then ends at 248.
[0089] Returning to 228, if false (i.e., the rear UHEGO is not less
than threshold A), method 200 proceeds to FIG. 7B. At 280, method
200 determines whether the output from the downstream, or rear,
UHEGO sensor 30 is greater than threshold B. For example, threshold
B may be a number indicating that the AFR is ramping up (having a
positive slope) and the OSC is recharged (less a margin of safety,
for example, approximately 30%). As such, the threshold B value may
be set within a range of 60%-80% of the total OSC, and more
particularly at approximately 70% of the total OSC. In some
embodiments, an example number for threshold B may be within a
range of 14.0 to 14.5, and more particularly within a range of 14.4
to 14.5 (INVENTOR PLEASE CONFIRM).
[0090] If true at 280, method 200 determines whether the current
engine state is normal at 284. As previously stated, in some
embodiments, a normal engine state may be stoichiometric control.
If true, the method 200 maintains the normal engine state at 288.
The method then ends at 296.
[0091] If false at 284, the control module 38 switches the engine
state to normal control at 292. For example, the catalyst control
module 46 may command the fuel control module 50 to operate the
fueling system in normal (i.e., stoichiometric) control. The method
then ends at 296.
[0092] If false at 280, method 200 determines whether the slope is
positive at 300. For example, the control module 38 may evaluate
the slope from 224 and determine whether the value is positive. If
true, method 200 determines whether a current engine state is lean
at 304. As previously stated, in some embodiments, a lean engine
state may have a leaner air-fuel mixture and a higher AFR number
(contains more air than the stoichiometric AFR). If true, the
engine state is maintained in lean engine control at 308. The
method then ends at 296.
[0093] If false at 304, the control module 38 switches to lean
engine control at 312. For example, the catalyst control module 46
may command the fuel control module 50 to operate the fueling
system in lean (i.e., greater than stoichiometric) control. The
method 200 then ends at 296.
[0094] If false at 300, method 200 determines whether the current
engine state is lean at 316. As previously stated, in some
embodiments, a lean engine state may have a leaner air-fuel mixture
and a higher AFR number (contains more air than the stoichiometric
AFR). If true, the method 200 maintains the lean engine state at
320. The method then ends at 296.
[0095] If false at 316, the control module 38 switches the engine
state to lean control at 324. The method then ends at 296.
[0096] The foregoing description of the embodiments has been
provided for purposes of illustration and description. It is not
intended to be exhaustive or to limit the disclosure. Individual
elements or features of a particular embodiment are generally not
limited to that particular embodiment, but, where applicable, are
interchangeable and can be used in a selected embodiment, even if
not specifically shown or described. The same may also be varied in
many ways. Such variations are not to be regarded as a departure
from the disclosure, and all such modifications are intended to be
included within the scope of the disclosure.
* * * * *