U.S. patent application number 11/319548 was filed with the patent office on 2007-07-05 for system for controlling exhaust emissions.
This patent application is currently assigned to CATERPILLAR INC.. Invention is credited to Michael S. Bond, Christopher R. Gehrke, Evan E. Jacobson, Matthew R. Roth, Clayton D. Walenta, Michael P. Withrow.
Application Number | 20070151230 11/319548 |
Document ID | / |
Family ID | 38222915 |
Filed Date | 2007-07-05 |
United States Patent
Application |
20070151230 |
Kind Code |
A1 |
Withrow; Michael P. ; et
al. |
July 5, 2007 |
System for controlling exhaust emissions
Abstract
A method for controlling exhaust emissions is disclosed. The
method includes producing exhaust having hydrocarbons and directing
the exhaust through a converter. The method also includes directing
the exhaust from the converter to an environment and determining a
first rate indicative of a rate of hydrocarbons directed to the
environment. The method further includes comparing the first rate
with a predetermined rate and adjusting the production of exhaust,
if the first rate is greater than the predetermined rate.
Inventors: |
Withrow; Michael P.;
(Peoria, IL) ; Bond; Michael S.; (Chillicothe,
IL) ; Gehrke; Christopher R.; (Chillicothe, IL)
; Roth; Matthew R.; (Metamora, IL) ; Walenta;
Clayton D.; (Peoria, IL) ; Jacobson; Evan E.;
(Peoria, IL) |
Correspondence
Address: |
CATERPILLAR/FINNEGAN, HENDERSON, L.L.P.
901 New York Avenue, NW
WASHINGTON
DC
20001-4413
US
|
Assignee: |
CATERPILLAR INC.
|
Family ID: |
38222915 |
Appl. No.: |
11/319548 |
Filed: |
December 29, 2005 |
Current U.S.
Class: |
60/285 ; 60/276;
60/297; 60/299 |
Current CPC
Class: |
F01N 9/00 20130101; Y02T
10/47 20130101; F01N 2550/02 20130101; Y02T 10/40 20130101; F01N
2560/06 20130101; F01N 3/10 20130101 |
Class at
Publication: |
060/285 ;
060/276; 060/299; 060/297 |
International
Class: |
F01N 3/00 20060101
F01N003/00; F01N 3/10 20060101 F01N003/10 |
Claims
1. A method for controlling exhaust emissions comprising: producing
exhaust, the exhaust including hydrocarbons; directing the exhaust
through a converter; directing the exhaust from the converter to an
environment; determining a first rate indicative of a rate of
hydrocarbons directed to the environment; comparing the first rate
with a predetermined rate; and adjusting the production of exhaust,
if the first rate is greater than the predetermined rate.
2. The method of claim 1, wherein producing exhaust includes
operating an engine and adjusting production of exhaust includes
changing parameters of the engine operation.
3. The method of claim 1, further including determining the first
rate as a function of a first amount indicative of an amount of
hydrocarbons absorbed by the converter
4. The method of claim 3, further including: determining a second
rate indicative of a rate of hydrocarbons converted by the
converter; and determining the first amount as a function of the
first rate and the second rate.
5. The method of claim 3, further including: estimating a
temperature of the converter; and determining the second rate as a
function of the temperature and the first amount.
6. The method of claim 5, wherein the temperature is an average
temperature of the exhaust upstream and downstream of the
converter.
7. A system for monitoring emissions comprising: an engine
configured to produce hydrocarbons at a first rate; a converter
configured to convert hydrocarbons at a second rate and release
hydrocarbons to an environment at a third rate; and a controller
configured to adjust parameters of the engine to produce
hydrocarbons at a fourth rate less than the first rate when the
third rate is greater than a predetermined rate.
8. The system of claim 7, further including at least one sensor
configured to establish at least one signal indicative of at least
one operating parameter of the engine, wherein the controller is
further configured to determine the first rate as a function of the
at least one signal.
9. The system of claim 7, further including at least one sensor
configured to establish a first temperature indicative of a
temperature of hydrocarbons within the converter.
10. The system of claim 7, wherein the engine is configured to
produce exhaust, the exhaust being directed through the converter,
the produced hydrocarbons being a portion of the exhaust, the
system further including: a first sensor configured to sense a
temperature of the exhaust upstream of the converter; and a second
sensor configured to sense a temperature of the exhaust downstream
of the converter; wherein the controller is configured to determine
a first temperature as an average of the temperature of the exhaust
upstream of the converter and the temperature of the exhaust
downstream of the converter.
11. The system of claim 10, wherein the controller is further
configured to determine the third rate as a function of the first
temperature and an amount of hydrocarbons absorbed by the
converter.
12. The system of claim 11, wherein the controller is further
configured to determine the amount of hydrocarbons absorbed by the
converter as a function of the first, second, and third rates.
13. The system of claim 9, wherein: the converter is configured to
convert hydrocarbons into substances more innocuous to an
environment than hydrocarbons; and the controller is further
configured to determine the second rate as a function of the first
temperature.
14. The system of claim 13, wherein the controller is further
configured to: determine a first amount of hydrocarbons indicative
of an amount of hydrocarbons absorbed by the converter; and
determine the third rate as a function of the first temperature and
the first amount.
15. The system of claim 7, wherein the converter includes a
catalyst configured to absorb hydrocarbons into the catalyst or
transform hydrocarbons into innocuous substances.
16. A method of operating an engine comprising: monitoring at least
one engine parameter indicative of an operational condition of an
engine configured to produce exhaust including hydrocarbons;
monitoring a temperature and a pressure each indicative of an
operational condition of a converter, the converter including a
catalyst configured to convert the hydrocarbons at a first rate and
release the hydrocarbons to an environment at a second rate; and
changing a status of the engine when the second rate is greater
than a predetermined rate.
17. The method of claim 16, wherein the converter is further
configured to absorb the hydrocarbons at a fourth rate, the method
further including: determining a third rate indicative of a rate of
production of the hydrocarbons as a function of the at least one
engine parameter; determining the first rate as a function of the
temperature; determining the second rate as a function of the
temperature and an amount of the at least one hydrocarbon absorbed
by the catalyst.
18. The method of claim 17, wherein the third rate is substantially
equal to the sum of the first rate, the second rate, and the fourth
rate.
19. The method of claim 17, further including: determining a
standardizing factor as a function of the temperature and the
pressure; and adjusting the second rate as a function of the
standardizing factor.
20. The method of claim 19, further including determining the
amount of the hydrocarbons absorbed by the catalyst as a function
of the first rate, the third rate, and the adjusted second
rate.
21. The method of claim 20, wherein the converter is configured to
absorb the hydrocarbons by trapping the hydrocarbons within the
converter.
22. The method of claim 16, wherein changing a status of the engine
includes varying at least one of a valve timing, ignition timing,
or an air-fuel ratio.
Description
TECHNICAL FIELD
[0001] This disclosure relates to a system for controlling
emissions, and more particularly to a method and apparatus for
controlling exhaust emissions.
BACKGROUND
[0002] Combustion engines, such as, for example, compression or
spark ignition engines, can produce a variety of byproducts that
may be environmentally harmful, such as, for example, nitric
oxides, sulfur-containing acidic species, and/or hydrocarbons.
Various systems and methods have been used to minimize the release
of such byproducts to the environment. For example, new fuels are
being developed which lower the levels of sulfur-acids produced
during fuel combustion. Additionally, exhaust systems are available
which absorb, e.g., by trapping, and/or convert, e.g., by
transforming into innocuous substances, harmful chemicals before
release to the environment.
[0003] Usually, engine exhaust systems include one or more
catalysts that are configured to absorb and/or convert hydrocarbons
and thus reduce potentially harmful exhaust emissions to the
environment. Often, such catalysts have an optimum temperature
range for absorption of hydrocarbons. Specifically, such catalysts,
may be incapable or less capable of absorbing and/or converting
hydrocarbons when cold, e.g., after a cold engine start or after
extended periods of engine idling, as when warm. Until cold
catalysts are heated above a threshold temperature, significant
amounts of hydrocarbons may be released to the environment.
[0004] U.S. Pat. No. 6,666,021 ("the '021 patent") issued to Lewis
et al. discloses a method for adaptive engine control for vehicle
starting. The system of the '021 patent compares an exhaust
temperature, subsequent to engine cranking, to a predetermined
temperature. If the exhaust temperature is below the predetermined
temperature, the engine is operated in a cold mode to minimize
emissions of hydrocarbons to a cold catalyst. A cold mode operation
provides a lean air-fuel ratio and retards the ignition timing to
minimize hydrocarbon emissions. The system of the '021 patent,
monitors the exhaust temperature and subsequently operates the
engine in a run mode when the exhaust temperature is above the
predetermined temperature.
[0005] Although the system of the '021 patent may minimize
hydrocarbon emissions during a cold mode, the system of the '021
patent estimates the operability of the catalyst based on exhaust
temperatures. Additionally, the system of the '021 patent may
inadequately estimate when the catalyst is within a suitable
temperature range and may unnecessarily sacrifice engine
performance for lower emissions when the catalyst may be capable of
absorbing and/or converting a sufficient amount of hydrocarbons
from the exhaust.
[0006] The present disclosure is directed at overcoming one or more
of the shortcomings set forth above.
SUMMARY OF THE INVENTION
[0007] In a first aspect, the present disclosure is directed to a
method for controlling exhaust emissions. The method includes
producing exhaust having hydrocarbons and directing the exhaust
through a converter. The method also includes directing the exhaust
from the converter to an environment and determining a first rate
indicative of a rate of hydrocarbons directed to the environment.
The method further includes comparing the first rate with a
predetermined rate and adjusting the production of exhaust, if the
first rate is greater than the predetermined rate.
[0008] In another aspect, the present disclosure is directed to a
system for monitoring emissions. The system includes an engine
configured to produce hydrocarbons at a first rate. The system also
includes a converter configured to convert hydrocarbons at a second
rate and release hydrocarbons to an environment at a third rate.
The system further includes a controller configured to adjust
parameters of the engine to produce hydrocarbons at a fourth rate
less than the first rate when the third rate is greater than a
predetermined rate.
[0009] In yet another aspect, the present disclosure is directed to
a method of operating an engine. The method includes monitoring at
least one engine parameter indicative of an operational condition
of an engine configured to produce exhaust including hydrocarbons.
The method also includes monitoring a temperature and a pressure,
each indicative of an operational condition of a converter, the
converter including a catalyst configured to convert the
hydrocarbons at a first rate and release the hydrocarbons to an
environment at a second rate. The method further includes changing
a status of the engine when the second rate is greater than a
predetermined rate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a schematic illustration of an engine exhaust
system in accordance with the present disclosure; and
[0011] FIG. 2 is a schematic illustration of an exemplary control
logic executable by the controller of FIG. 1.
DETAILED DESCRIPTION
[0012] FIG. 1 illustrates an exemplary exhaust system 10. Exhaust
system 10 may include an engine 12, a converter 14, and a
controller 18 configured to control engine 12. Exhaust system 10
may be configured to direct an exhaust produced by engine 12
through converter 14 to an environment 16. Specifically, engine 12
may produce an exhaust as a byproduct of a combustion process and
exhaust system 10 may be configured to direct the exhaust through
converter 14 and toward environment 16. It is contemplated that
exhaust system 10 may include additional components such as, for
example, a manifold, a recirculation device, a muffler, and/or
other components known in the art. It is also contemplated that
environment 16 may include any type of environment known in the
art, such as, for example, an atmosphere.
[0013] Engine 12 may include, for example, a diesel engine, a
gasoline engine, a gaseous fuel driven engine, or any other engine
known in the art. Engine 12 may be configured to supply power to
operatively connected loads, such as, for example, traction
devices, hydraulic pumps, and/or other loads known in the art.
Specifically, engine 12 may be configured to operate in one or more
operational modes in which engine 12 may have different operating
conditions. For example, engine 12 may be configured to operate in
a first mode in which an exhaust is produced including an amount of
hydrocarbons less than an amount of hydrocarbons produced in a
second mode. Engine 12 may be controlled to operate in different
modes by controller 18 as a function of a determined desired status
of engine 12. It is contemplated that engine 12 may include one or
more piston-cylinder arrangements disposed in an "in-line" or "V"
configuration defining combustion chambers and connected to a
crankshaft, one or more valves operatively associated with the
combustion chambers to affect the flow of fluids into and out of
the combustion chambers, and a fuel delivery system configured to
deliver fuel to the combustion chamber as is conventional in the
art. It is also contemplated that engine 12 may capable of
operating in any number of different modes in which operational
parameters, such as, for example, fuel delivery timing, valve
timing, ignition timing, clean exhaust recirculation amounts, fuel
amounts, and/or any other parameter known in the art may be varied
either in conjunction or independently. It is further contemplated
that engine 12 may, alternatively, include a rotary engine.
[0014] Converter 14 may include any conventional catalyst device
such as, for example, a catalyst trap, a catalytic converter,
and/or a particulate filter, and may be configured to absorb and/or
convert hydrocarbons. Specifically, converter 14 may include a
catalyst such as, for example, platinum or ammonia, in any mass
phase, such as, for example, gaseous, aqueous, or solid, configured
to absorb and/or convert hydrocarbons present within an exhaust.
Converter 14, via the catalyst, may convert hydrocarbons into
innocuous elements or molecules such as, for example, inert gases
and/or water. Converter 14, via the catalyst, may absorb
hydrocarbons by physically trapping molecules within the catalyst
and/or any other suitable filter. It is contemplated that converter
14, and in particular, the catalyst, may be less active, e.g., may
be less capable of absorbing and/or converting hydrocarbons, within
certain temperature ranges. For example, the catalyst may, above a
first threshold temperature, be capable of absorbing and/or
converting substantially all hydrocarbons from an exhaust, may
below the first threshold temperature and above a second threshold
temperature be capable of absorbing and/or converting significantly
less hydrocarbons from an exhaust, and may below the second
threshold temperature be capable of absorbing and/or converting
substantially no hydrocarbons from an exhaust. It is also
contemplated that first and second threshold temperatures may be
any temperature and may be dependent upon the type of catalyst. It
is further contemplated that an innocuous substance may be any
substance less harmful to environment 16 than the hydrocarbons
produced by engine 12.
[0015] Controller 18 may be configured to affect the operation of
engine 12 between the different modes. Controller 18 may include
one or more microprocessors, a memory, a data storage device, a
communications hub, and/or other components known in the art. It is
contemplated that controller 18 may be integrated within a general
control system capable of controlling additional various functions
of a exhaust system 10 and/or system other than exhaust system 10.
Controller 18 may be configured to receive input signals from
sensors 20, 22, 24, 26 via respective communication lines.
Controller 18 may perform one or more algorithms to determine
appropriate output signals to affect the operation of engine 12 and
may deliver the output signals via one or more suitable
communication lines. It is contemplated that controller 18 may be
further configured to receive additional inputs indicative of
various operating parameters of exhaust system 10, such as, for
example, exhaust flow rate.
[0016] Sensors 20, 22 may include any conventional sensor
configured to deliver a signal indicative of a temperature. Sensor
20 may be disposed between engine 12 and converter 14 and may be
configured to communicate a signal indicative of a temperature of
an exhaust upstream of converter 14. Sensor 22 may be disposed
between converter 14 and environment 16 and may be configured to
communicate a signal indicative of a temperature of an exhaust
downstream of converter 14. Sensor 24 may include any conventional
sensor configured to deliver a signal indicative of a pressure.
Sensor 24 may be disposed relative to converter 14 and may be
configured to communicate a signal indicative of a pressure within
converter 14, e.g., indicative of the pressure of an exhaust within
converter 14. It is contemplated that sensors 20, 22, 24 may be
disposed at any location suitable for sensing and communicating
temperature or pressure, as desired. It is also contemplated that
sensors 20, 22, 24 may be configured to communicate any type of
signal such as, for example, a voltage or a current.
[0017] Sensor 26 may include any conventional sensor configured to
deliver a signal indicative of an operating parameter of engine 12.
For example, sensor 26 may include one or more sensors disposed
relative to components of engine 12 and may be configured to
communicate signals indicative of one or more parameters, such as,
for example, rotational speed of a crankshaft, valve position,
air-fuel ratio, temperature, pressure, and/or any other parameter
known in the art.
[0018] FIG. 2 illustrates an exemplary status logic 30 which
controller 18 may perform to determine a desired status of engine
12. Status logic 30 may receive inputs from sensors 20, 22, 24, 26
and determine a status output 60 with which controller 18 may
affect the operation of engine 12, e.g., controller 18 may control
engine 12 to operate in a desired mode as a function of engine
status 60. Specifically, status logic 30 may receive a first
temperature input 32 from sensor 22 indicative of a temperature of
exhaust upstream of converter 14 and may receive a second
temperature input 34 from sensor 24 indicative of a temperature of
exhaust downstream of converter 14. Status logic 30 may receive a
pressure input 36 from sensor 26 indicative of a pressure within
converter 14 and may receive an engine input 40 indicative of an
operational parameter of engine 12. It is contemplated that engine
input 40 may include one or more inputs indicative of one or more
operating parameters of engine 12, such as, for example, rotational
speed of a crankshaft, fuel consumption, and/or torque output. It
is also contemplated that status logic 30 may receive inputs from
additional sensors indicative of additional operational parameters
of exhaust system 10, such as, for example, exhaust flow rate.
[0019] Status logic 30 may include one or more algorithms
configured to be performed and/or executed by controller 18 to
determine a desired operating status of engine 12. Specifically,
status logic 30 may include one or more databases, two- or
three-dimensional maps, look-up tables, equations, functions,
and/or any other mathematical relationship known in the art. Status
logic 30 may manipulate inputs received from sensors 20, 22, 24, 26
as a function of one or more variable or non-variable parameters,
and/or predetermined constants, to determine status output 60. For
example, status logic 30 may be configured to determine if a rate
of hydrocarbons released to environment 16 by converter 14, e.g.,
that converter 14 has not absorbed and/or converted from the
exhaust, is above a predetermined value. Controller 18 may be
configured to vary one or more parameters of engine 12 as a
function of status output 60, to reduce the amount of hydrocarbons
produced by engine 12. It is noted that the references within the
description of status logic 30 set forth below regarding algorithms
including a particular mathematical relationship, e.g., an equation
or a two-dimensional map, are for exemplary purposes only and it is
contemplated that controller 18 may perform algorithms via any
suitable mathematical relationship known in the art, e.g., an
equation, any-dimensional map, a physics based model, an empirical
model, and/or a look-up table, to determine a desired variable. It
is contemplated that each and/or any of the variables determined
via one or more algorithms within status logic 30 may include
predetermined minimum and/or maximum values which status logic 30
may utilize within subsequent algorithms regardless of the
determined variable as is conventional in the art. For example, one
or more of the mathematical relationships within status logic 30
may determine a first variable by a division of a second variable
that could be zero. As such, status logic 30 may determine the
first variable to be a predetermined maximum value instead of
determining the first variable to be a mathematical unknown, e.g.,
a positive number divided by zero.
[0020] Step 42 may be configured to determine a rate of
hydrocarbons produced (d_Produced/d_Time) by engine 12.
Specifically, step 42 may include one or more two- or
three-dimensional maps and may be configured to determine an amount
of hydrocarbons produced by engine 12 per a unit time. For example,
step 42 may include one or more maps configured to relate engine
input 40 and predetermined rates of hydrocarbon produced.
[0021] Step 44 may be configured to determine a temperature
indicative of an average temperature (Avg-Temp) of converter 14.
Specifically step 44 may include one or more equations configured
to functionally relate temperature inputs 32, 34 to determine an
average thereof as is conventional in the art. Hereinafter the
temperature as determined in step 44 will be referenced as an
average converter temperature, however, it is noted that the
temperature determined in step 44 may be indicative of the average
temperature of converter 14 and may or may not be equal to an
actual average temperature of converter 14.
[0022] Step 46 may be configured to determine a rate of
hydrocarbons converted (d_Converted/d_Time), e.g., converted into
an innocuous substance, by converter 14 and may include one or more
equations and/or one or more two- or three-dimensional maps.
Specifically, step 46 may compare a current average converter
temperature, e.g., the average converter temperature determined in
step 44, a previous average converter temperature, e.g., an average
converter temperature determined when controller 18 performed a
prior sequence of status logic 30, and an elapsed time since
determining the previous average temperature to determine a rate of
change in average temperature of converter 14 (d_Avg-Temp/d_Time).
It is contemplated that a previous average converter temperature,
e.g., zero, may be assumed when controller 18 performs the first
sequence of status logic 30.
[0023] Additionally, step 46 may determine a current available
hydrocarbon conversion capacity of converter 14 via one or more
two- or three-dimensional maps relating average converter
temperatures and predetermined hydrocarbon conversion capacities of
converter 14. For example, step 46 may determine a capacity as a
function of the current average converter temperature via one or
more two- or three-dimensional maps relating capacity and
temperatures. Step 46 may further compare the current capacity of
converter 14, a previously determined capacity of converter 14,
e.g., a determined capacity determined when controller 18 performed
a prior sequence of status logic 30, and a change between the
current and previous average temperatures to determine a change in
hydrocarbon conversion capacity relative to a change in temperature
(d_Converted/d_Avg-Temp). It is contemplated that the conversion
capacity of converter 14 may be indicative of the rate of
hydrocarbons converted by converter 14. For example, converter 14
may be configured to convert hydrocarbons at substantially full
capacity less an efficiency factor. As such, step 46 may relate the
determined rate of change of average temperatures
(d_Avg-Temp/d_Time) and the determined change in hydrocarbon
conversion capacity relative to the change in temperature
(d_Converted/d_Avg-Temp) to determine a hydrocarbon conversion rate
(d_Converted/d_Time). It is also contemplated that a previously
determined capacity of converter 14, e.g., 100%, may be assumed
when controller 18 performs the first sequence of status logic
30.
[0024] Step 48 may be configured to determine a rate of
hydrocarbons released (d_Released/d_Time), e.g., a rate of
hydrocarbons that are neither absorbed nor converted by converter
14. Specifically, step 48 may include one or more two- or
three-dimensional maps configured to relate the current average
converter temperature, a cumulative amount of hydrocarbons absorbed
by converter 14, and predetermined amounts of hydrocarbons released
by converter 14. It is contemplated that the cumulative amount of
hydrocarbons absorbed by converter 14 may be determined in step 56,
however, an initial amount of hydrocarbons absorbed by converter
14, e.g., zero, may be assumed when controller 18 performs the
first sequence of status logic 30.
[0025] Step 50 may be configured to determine a standardizing
factor and may include one or more equations and/or one or more
two- or three-dimensional maps. Specifically, step 50 may be
configured to determine a standardizing factor as a function of a
space velocity of converter 14. For example, the average converter
temperature may be functionally related with an appropriate
universal gas constant and pressure input 36 to establish a density
of the exhaust. Step 50 may additionally include receiving
additional parameters to determine a mass flow rate of exhaust
which may be functionally related with the density to determine a
gas flow rate which may be functionally related with a volume of
converter 14 to establish a space velocity (Gas_flowrate/Volume).
Step 50 may further include one or more two- or three-dimensional
maps relating space velocities and predetermined standardized
factors. As such, a determined standardized factor may be
configured to adjust a determined rate of hydrocarbons released, as
determined in step 48, as a function of operational conditions of
exhaust system 10. It is contemplated that step 50 may resolve
received inputs according to any system of units known in the art.
It is also contemplated that an exhaust rate may be established in
any suitable manner known in the art, such as, for example, as a
function of one or more operating parameters of engine 12 or flow
meters disposed within exhaust system 10.
[0026] Step 52 may be configured to determine a standardized rate
of hydrocarbons released by converter 14 (d_Released'/d_Time).
Specifically, step 52 may include one or more equations configured
to functionally relate the determined rate of hydrocarbons released
by converter 14, as determined in step 48, and the determined
standardized factor, as determined in step 50, to approximate the
determined rate of hydrocarbons released as a function of the
current operating conditions of exhaust system 10, e.g., average
temperature, pressure, or flow rate, of exhaust system 10. As such,
step 52 may adjust the rate of hydrocarbons released as a function
of current operating conditions to, for example, improve the
accuracy of the determined rate of hydrocarbons.
[0027] Step 54 may be configured to determine a rate of
hydrocarbons absorbed by converter 14. Specifically, step 54 may
resolve the rate of hydrocarbons produced by engine 12
(d_Produced/d_Time), the rate of hydrocarbons converted by
converter 14 (d_Converted/d_Time) and the standardized rate of
hydrocarbons released by converter 14 (d_Released'/d_Time). For
example, step 54 may functionally combine the rate of hydrocarbons
produced by engine 12, the rate of hydrocarbons converted by
converter 14, and the rate of hydrocarbons released by converter 14
to determine the rate of hydrocarbons absorbed by converter 14
(d_Absorbed/d_Time). It is contemplated that step 54 may
functionally subtract the rate of hydrocarbons converted and the
rate of hydrocarbons released from the rate of hydrocarbons
produced to determine the rate of hydrocarbons absorbed by
converter 14.
[0028] Step 56 may be configured to determine a cumulative amount
of hydrocarbons absorbed by converter 14. Specifically, step 56 may
functionally relate the rate of hydrocarbons absorbed
(d_Absorbed/d_Time), determined in step 54, and an elapsed time
(d_Time) to determine an amount of hydrocarbons absorbed by
converter 54, e.g., an amount of hydrocarbons currently absorbed by
converter 14. Step 56 may combine the currently absorbed amount of
hydrocarbons with a previously determined amount of hydrocarbons
absorbed, e.g., an amount of hydrocarbons absorbed by converter 14
as determined by controller 18 performing a prior sequence of
status logic 30, to determine the cumulative amount of hydrocarbons
absorbed by converter 14. The determined cumulative amount of
hydrocarbons absorbed may be related within step 48 to determine a
rate of hydrocarbons released by converter 14. It is contemplated
that an initial amount of hydrocarbons absorbed by converter 14,
e.g., zero, may be assumed when controller 18 performs the first
sequence of status logic 30.
[0029] Step 58 may be configured to compare the rate of
hydrocarbons released by converter 14, as determined in step 48,
with a predetermined value. Step 58 may further be configured to
establish status output 60 to indicate a first mode if the rate of
hydrocarbons released by converter 14 is greater than a
predetermined value. Step 58 may also be configured to establish
status output 60 to indicate a second mode if the rate of
hydrocarbons released by converter 14 is less than a predetermined
value. Specifically, step 58 may include one or more equations
configured to functionally relate the determined rate of
hydrocarbons released and a predetermined value to determine if the
rate of hydrocarbons released to environment 18 is greater than the
predetermined value. As such, controller 18 and, in particular
status logic 30, may affect control of engine 12 to operate in at
least two modes, a first and a second mode.
[0030] Controller 18 may be configured to control one or more
parameters of engine 12 in response to status output 60. For
example, in response to a status output 60 indicative of a first
mode, controller 18 may, for example, advance ignition timing,
increase the amount of clean exhaust recirculated into engine 12,
operate engine 12 with a lean air-fuel ratio, and/or may vary other
operational parameters of engine 12. Additionally, in response to
status output 60 indicative of a second mode, controller 18 may not
adjust the operational parameters of engine 12. As such, engine 12
may, in the first mode, produce less hydrocarbons than that
produced by engine 12 in the second mode. Accordingly, status logic
30 may be configured to control engine 12 as a function of a rate
of hydrocarbons released to environment 16. Specifically, control
logic 30 may be configured to control engine 12 to produce less
hydrocarbons when converter 14 is less capable of absorbing and/or
converting hydrocarbons and control engine 12 to produce more
hydrocarbons when converter 14 is more capable of absorbing and/or
converting hydrocarbons.
INDUSTRIAL APPLICABILITY
[0031] The present disclosure provides a system for controlling
exhaust emissions and may be applicable to any exhaust system. The
disclosed system may absorb and/or convert hydrocarbons within
exhaust and may adjust the production of exhaust as a function of
the hydrocarbons directed to an environment. The operation of
exhaust system 10 will be explained below.
[0032] Exhaust system 10 may be operated at different conditions.
For example, engine 12 may be operated in a start-up, idle,
shut-down, or at various power, e.g., torque and rotational speed,
output conditions. As such, engine 12 may produce exhaust having
different properties, such as, for example, temperature or
emissions, at different conditions. Additionally, converter 14 may
be operated at various conditions as a function of the condition of
engine 12. For example, during a start-up or an idle engine
condition, converter 14 may be operating at a cold condition,
whereas during a prolonged power output condition, converter 14 may
be operating at a warm condition. A cold operational condition of
converter 14 may adversely impact the performance of a catalyst
therein, e.g., a catalyst may be capable of converting less
hydrocarbons at a cold condition than at a warm condition. As such,
during operation of converter 14 at cold conditions, an undesirable
amount and/or rate of hydrocarbons may released by converter 14 and
may be directed to environment 16. Because converter 14 may not be
capable of absorbing and/or converting hydrocarbons as desired,
engine 12 may be controlled by controller 18 to produce less
hydrocarbons.
[0033] Controller 18 may receive inputs from sensors 20, 22, 24, 26
to monitor the parameters of converter 14 and engine 12.
Specifically, controller 18 may perform status logic 30 to
determine a rate of hydrocarbons released by converter 14 and
establish an appropriate status output 60 as a function thereof.
For example, controller 18 may determine a rate of hydrocarbons
released by converter 14 to be greater than a desirable rate.
Accordingly, controller 18 may determine a status output 60
configured to adjust the performance of engine 12 to produce less
hydrocarbons, e.g., determine status output 60 to indicate a first
mode. It is contemplated that controller 18 may be configured to
adjust any suitable parameter of engine 12 so as to produce less
hydrocarbons, such as, for example, advance ignition timing, retard
valve timing, operate engine 12 with a leaner air-fuel ratio,
and/or adjust any other parameter.
[0034] Controller 18 may be configured to repeat status logic 30 at
any desired frequency, such as, for example, periodically,
substantially continuously, and/or at non-uniform cycle times. As
such, controller 18 may determine status output 60 as a function of
a rate of hydrocarbons released by converter 14, which may be
determined as a function of operational conditions of exhaust
system 10 and, in particular, engine 12 and converter 14.
Accordingly, controller 18 may adjust the operation of engine 12 as
a function of a rate of hydrocarbons released by converter 14.
[0035] Because controller 18 determines a rate of hydrocarbons
released by converter 14, engine 12 may be controlled to produce
less hydrocarbons when converter 14 is less capable of absorbing
and/or converting hydrocarbons. For example, controller 18 may
control engine 12 to produce less hydrocarbons when converter 14
and, in particular, a catalyst therein, may be incapable of
absorbing and/or converting hydrocarbons from an exhaust as
desired. Because controller 18 controls engine 12 as a function of
a rate of hydrocarbons released by converter 14, engine 12 may be
more accurately controlled than if controlled in response to a
temperature or time sensor configured to indicate when a catalyst
may be capable of absorbing and/or converting hydrocarbons as
desired. The above disclosure has been described with reference to
reducing hydrocarbons generically for clarification purposes and it
is contemplated that the present disclosure may be applicable to
control any type of hydrocarbons, such as, for example, unburned
fuel and/or soluble organic fractions.
[0036] It will be apparent to those skilled in the art that various
modifications and variations can be made to the disclosed system
for reducing exhaust emissions. Other embodiments will be apparent
to those skilled in the art from consideration of the specification
and practice of the disclosed system. It is intended that the
specification and examples be considered as exemplary only, with a
true scope being indicated by the following claims and their
equivalents.
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