U.S. patent application number 11/987523 was filed with the patent office on 2009-06-04 for gas concentration sensor drift and failure detection system.
Invention is credited to Rodrigo Lain Sanchez.
Application Number | 20090139210 11/987523 |
Document ID | / |
Family ID | 40674354 |
Filed Date | 2009-06-04 |
United States Patent
Application |
20090139210 |
Kind Code |
A1 |
Sanchez; Rodrigo Lain |
June 4, 2009 |
Gas concentration sensor drift and failure detection system
Abstract
A system for detecting when a gas concentration sensor has
drifted or failed is disclosed. The system has a first gas
concentration sensor configured to detect a first gas concentration
and generate a corresponding first signal. The system also has a
second gas concentration sensor configured to detect a second gas
concentration and generate a corresponding second signal. In
addition, the system has a controller in communication with the
first and second gas concentration sensors. Based on the first and
second signals, the controller is configured to provide an
out-of-tolerance gas concentration sensor warning.
Inventors: |
Sanchez; Rodrigo Lain;
(Dunlap, IL) |
Correspondence
Address: |
CATERPILLAR/FINNEGAN, HENDERSON, L.L.P.
901 New York Avenue, NW
WASHINGTON
DC
20001-4413
US
|
Family ID: |
40674354 |
Appl. No.: |
11/987523 |
Filed: |
November 30, 2007 |
Current U.S.
Class: |
60/276 ; 60/277;
701/102 |
Current CPC
Class: |
G01N 27/4175
20130101 |
Class at
Publication: |
60/276 ; 60/277;
701/102 |
International
Class: |
F01N 11/00 20060101
F01N011/00; F01N 9/00 20060101 F01N009/00 |
Claims
1. A drift and failure detection system for a gas concentration
sensor, comprising: a first gas concentration sensor configured to
detect a first gas concentration and generate a corresponding first
signal; a second gas concentration sensor configured to detect a
second gas concentration and generate a corresponding second
signal; and a controller in communication with the first and second
gas concentration sensors, and configured to provide an
out-of-tolerance gas concentration sensor warning based on the
first and second signals.
2. The drift and failure detection system of claim 1, further
including an exhaust system, wherein the first and second gas
concentration sensors are located within the exhaust system.
3. The drift and failure detection system of claim 2, wherein the
exhaust system includes a first bypass, and the second gas
concentration sensor is located within the first bypass.
4. The drift and failure detection system of claim 3, wherein: the
controller includes a clock configured to measure time and generate
a corresponding time signal; the first bypass includes at least one
valve to adjust a flow; and the controller is in further
communication with the at least one valve and configured to control
the at least one valve based upon at least one of the first,
second, and clock signals.
5. The drift and failure detection system of claim 4, wherein the
flow is an exhaust flow.
6. The drift and failure detection system of claim 3, wherein the
exhaust system includes a second bypass, and the first gas
concentration sensor is located within the second bypass.
7. The drift and failure detection system of claim 1, further
including an air/fuel supply system, wherein the controller is in
further communication with the air/fuel supply system and
configured to adjust an air/fuel ratio based on at least one of the
first and second signals.
8. The drift and failure detection system of claim 1, further
including a warning device, wherein the controller is in further
communication with the warning device and configured to activate
the warning device based on the first and second signals.
9. A method of detecting when a gas concentration sensor has
drifted or failed, comprising: detecting a first gas concentration
with a first gas concentration sensor; detecting a second gas
concentration with a second gas concentration sensor; calculating a
difference between the detected first and second gas
concentrations; and providing an out-of-tolerance gas concentration
sensor warning based on the calculated difference between the
detected first and second gas concentrations.
10. The method of claim 9, further including measuring a time.
11. The method of claim 10, further including adjusting a flow
based on the measured time.
12. The method of claim 11, wherein the flow is an exhaust
flow.
13. The method of claim 9, wherein calculating the difference
between the detected first and second gas concentrations includes:
calculating an average detected first gas concentration;
calculating an average detected second gas concentration; and
comparing the average detected first gas concentration and the
average detected second gas concentration.
14. The method of claim 9, further including adjusting an air/fuel
ratio based on at least one of the detected first and second gas
concentrations.
15. The method of claim 9, further including activating a warning
device based on the calculated difference between the detected
first and second gas concentrations.
16. A combustion engine, comprising: an air/fuel supply system; a
combustion chamber located downstream of the air/fuel supply
system; an exhaust system located downstream of the combustion
chamber, the exhaust system including: a first gas concentration
sensor configured to detect a first gas concentration and generate
a corresponding first signal; and a second gas concentration sensor
configured to detect a second gas concentration and generate a
corresponding second signal; and an engine control module in
communication with the first and second gas concentration sensors,
and the air/fuel supply system, and configured to: provide an
out-of-tolerance gas concentration sensor warning based on the
first and second signals; and adjust an air/fuel ratio based on at
least one of the first and second signals.
17. The combustion engine of claim 16, wherein the exhaust system
further includes a first bypass, and the second gas concentration
sensor is located within the first bypass.
18. The combustion engine of claim 17, wherein: the engine control
module includes a clock configured to measure time and generate a
corresponding time signal; the first bypass includes at least one
valve to adjust a flow; and the engine control module is in further
communication with the at least one valve and configured to control
the at least one valve based on at least one of the first, second,
and clock signals.
19. The combustion engine of claim 17, wherein the exhaust system
further includes a second bypass, and the first gas concentration
sensor is located within the second bypass.
20. The combustion engine of claim 16, wherein: the first gas
concentration sensor is a NO.sub.x concentration sensor; and the
second gas concentration sensor is a NO.sub.x concentration sensor.
Description
TECHNICAL FIELD
[0001] The present disclosure relates generally to a detection
system and, more particularly, to a system for detecting when a gas
concentration sensor has drifted or failed.
BACKGROUND
[0002] Combustion engines, including diesel engines, gasoline
engines, natural gas engines, and other engines known in the art,
may exhaust a complex mixture of air pollutants. The air pollutants
may be composed of gaseous and solid compounds, including
particulate matter, nitrogen oxides (NO.sub.x), and sulfur
compounds. Due to heightened environmental concerns, exhaust
emission standards have become increasingly stringent. To comply
with these emission standards, engine manufacturers employ gas
concentration sensors. But, gas concentration sensors are wear-out
devices that eventually fail and require replacement (i.e. gas
concentration sensors eventually become faulty). Furthermore, gas
concentration sensors drift over time (i.e. measurements become
miscalibrated). Miscalibrated measurements may result in
noncompliance with the emission standards. Therefore, gas
concentration sensors must be recalibrated periodically. Replacing
and recalibrating gas concentration sensors is costly in both labor
and parts, and this problem can be exacerbated when the engine is
remotely located. Specifically, because reliable testing and
calibration equipment may be unavailable, gas concentration sensors
may be needlessly replaced.
[0003] One way to minimize the affect of a faulty gas concentration
sensor is described in U.S. Patent Application Publication No.
2004/0221641 (the '641 publication) by Moritsugu et al., published
on Nov. 11, 2004. The '641 publication describes a fault detecting
apparatus for a gas concentration sensor. The fault detecting
apparatus includes a storage device and a fault detecting circuit.
The storage device stores conditions in which certain fault types
may be detected. When one of these conditions is detected, the
fault detecting circuit initiates detection of the corresponding
fault type. Specifically, the fault detecting circuit determines
whether there is a fault based on an output of the gas
concentration sensor. If there is a fault, the fault detecting
apparatus turns on a malfunction indicator lamp. Additionally, if
the fault is minor, the fault detecting apparatus adjusts the
functioning of the gas concentration sensor. But, if the fault is
major, the fault detecting apparatus discontinues use of the gas
concentration sensor.
[0004] Although the fault detecting apparatus of the '641
publication may improve detection of a faulty gas concentration
sensor, it may do little to improve detection of a miscalibrated
gas concentration sensor. Furthermore, though the fault detecting
apparatus of the '641 publication may turn on a malfunction
indicator lamp, it may do little to reduce the economic impact of
the gas concentration sensor's failure. In particular, the operator
may need to discontinue use of an affected engine until the gas
concentration sensor can be replaced. In addition, the fault
detecting apparatus of the '641 publication may increase the
complexity and cost of the gas concentration sensor, but it may do
little to prolong the life of the gas concentration sensor.
[0005] The disclosed system and method are directed to overcoming
one or more of the problems set forth above.
SUMMARY
[0006] In one aspect, the present disclosure is directed to a drift
and failure detection system for a gas concentration sensor. The
system includes a first gas concentration sensor configured to
detect a first gas concentration and generate a corresponding first
signal. The system also includes a second gas concentration sensor
configured to detect a second gas concentration and generate a
corresponding second signal. In addition, the system includes a
controller in communication with the first and second gas
concentration sensors. Based on the first and second signals, the
controller is configured to provide an out-of-tolerance gas
concentration sensor warning.
[0007] In another aspect, the present disclosure is directed to a
method of detecting when a gas concentration sensor has drifted or
failed. The method includes detecting a first gas concentration
with a first gas concentration sensor. Additionally, the method
includes detecting a second gas concentration with a second gas
concentration sensor. The method also includes calculating a
difference between the detected first and second gas
concentrations. In addition, the method includes providing an
out-of-tolerance gas concentration sensor warning based on the
calculated difference between the detected first and second gas
concentrations.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a diagrammatic illustration of an exemplary
disclosed combustion engine;
[0009] FIG. 2 is a diagrammatic illustration of another exemplary
disclosed combustion engine;
[0010] FIG. 3 is a diagrammatic illustration of yet another
exemplary disclosed combustion engine; and
[0011] FIG. 4 is a flow chart describing an exemplary method of
operating the exemplary combustion engines of FIGS. 1-3.
DETAILED DESCRIPTION
[0012] FIG. 1 illustrates a combustion engine 10, which may be
utilized by various types of machines such as, for example, fixed
or mobile machines that perform some type of operation associated
with an industry such as mining, construction, farming,
transportation, power generation, tree harvesting, forestry, or
another industry known in the art. Combustion engine 10 may be an
internal combustion engine, such as, for example, a diesel engine,
a gasoline engine, or a natural gas engine. Combustion engine 10
may alternatively be another power source such as a furnace.
[0013] Operation of combustion engine 10 may produce power and a
flow of exhaust. In particular, a controller 12 of combustion
engine 10 may operate an air/fuel supply system 14 to supply an
air/fuel mixture to a combustion chamber 16 of combustion engine
10. The air/fuel mixture may be combusted within combustion chamber
16, thereby producing power and the flow of exhaust. The flow of
exhaust may include several chemicals such as, for example, carbon
monoxide, carbon dioxide, NO.sub.x, ammonia, aldehyde(s), soot,
oxygen, nitrogen, sulfur, water vapor, and/or hydrocarbons such as
hydrogen and methane.
[0014] Some of the chemicals may be subject to emission standards
(i.e. subject to minimum and/or maximum allowable emission
concentrations). Therefore, the flow of exhaust may be directed to
an exhaust system 18, which may directly and/or indirectly modify
concentrations of the chemicals. For example, exhaust system 18 may
include a catalytic converter 20 (referring to FIG. 2), a filter
(not shown), an SCR system (not shown) and/or another exhaust
treatment device to directly modify concentrations of the
chemicals. And, exhaust system 18 may include a gas concentration
sensor 22, and/or another sensing device known in the art to
indirectly modify concentrations of the chemicals. This indirect
modification may be by way of controller 12, which may adjust the
air/fuel ratio of the air/fuel mixture (hereafter "the air/fuel
ratio") based on a first gas concentration detected by gas
concentration sensor 22. It is contemplated, however, that gas
concentration sensor 22 may become faulty or miscalibrated
(hereafter "broken"). Therefore, exhaust system 18 may include
another gas concentration sensor 24, which controller 12 may use to
verify the gas concentrations detected by gas concentration sensor
22. If gas concentration sensor 22 is out-of-tolerance (i.e.
broken, and therefore providing inaccurate gas concentrations to
controller 12), controller 12 may alternatively adjust the air/fuel
ratio based on a second gas concentration detected by gas
concentration sensor 24. Controller 12 may also activate a warning
device 25 if gas concentration sensor 22 is out-of-tolerance. For
example, warning device 25 may embody a warning lamp; alarm; horn;
head-up display; odorant or tissue-irritating substance dispenser;
transmission means; or other device operable to provide an
out-of-tolerance gas concentration sensor 22 warning to an
individual located nearby or remote to combustion engine 10.
Alternatively, it is contemplated that controller 12 may use gas
concentration sensor 22 to verify the second gas concentration
detected by gas concentration sensor 24.
[0015] Controller 12 may embody, for example, an engine control
module, and may include means for monitoring, recording, storing,
indexing, processing, and/or communicating information. These means
may include, for example, a memory, one or more data storage
devices, a central processing unit, and/or another component that
may be used to run the disclosed applications. In particular,
controller 12 may include a clock 26 to measure time and generate a
corresponding time signal. Furthermore, although aspects of the
present disclosure may be described generally as being stored in
memory, one skilled in the art will appreciate that these aspects
can be stored on or read from different types of computer program
products or computer-readable media such as computer chips and
secondary storage devices, including hard disks, floppy disks,
optical media, CD-ROM, or other forms of RAM or ROM.
[0016] As previously discussed, controller 12 may operate air/fuel
supply system 14 to adjust the air/fuel ratio supplied to
combustion chamber 16. Air/fuel supply system 14 may be in fluid
communication with and located upstream of combustion chamber 16.
Air/fuel supply system 14 may include an air intake system 28 and a
fuel system 30, both operable by controller 12. Air intake system
28 may include various components and/or systems for adjusting the
amount of air supplied to combustion chamber 16, including, but not
limited to, throttles, variable-output superchargers, and
variable-valve-timing systems. Fuel system 30 may include various
components for adjusting the amount of fuel supplied to combustion
chamber 16, including, but not limited to, fuel injectors,
variable-output pumps, valves, and carburetors.
[0017] Combustion chamber 16 may be formed out of a cylinder, a
piston, and a cylinder head. It is contemplated that combustion
engine 10 may include one or more combustion chambers 16, and that
combustion chambers 16 may be disposed in an "in-line"
configuration, a "V" configuration, or another suitable
configuration. Alternatively, combustion chamber 16 may be formed
out of a rotor, which is roughly triangular, and a housing
(applicable to rotary engines). In yet another alternative,
combustion chamber 16 may be formed out of other components known
in the art and may embody, for example, a firebox (applicable to a
furnace or boiler) or a flame holder (applicable to a jet engine).
As previously discussed, combustion within combustion chamber 16
may produce a flow of exhaust, which may be directed to exhaust
system 18, located downstream of combustion chamber 16.
[0018] Exhaust system 18 may include a flow line 32, which may
further direct the flow of exhaust along a path 34. Path 34 may
lead to one or more exhaust system 18 components. For example, flow
line 32 may embody a pipe, a tube, a conduit, or another
exhaust-carrying structure known in the art. It is contemplated
that flow line 32 may branch into two or more subsidiary flow lines
36, thereby creating alternative paths 38. For example, flow line
32 may branch into subsidiary flow lines 36a and 36b, thereby
creating alternative paths 38a and 38b, respectively. Furthermore,
it is contemplated that two or more subsidiary flow lines 36 may
rejoin into flow line 32, thereby rejoining alternative paths 38
into path 34. For example, subsidiary flow lines 36a and 36b may
rejoin into flow line 32, thereby rejoining alternative paths 38a
and 38b into path 34. If alternative paths 38 rejoin into path 34,
it is contemplated that one alternative path 38 may be designated a
normal path 40, and another alternative path 38 may be designated a
bypass path 42 (hereafter "bypass 42"). These designations may
correspond to an average level of exhaust flow (hereafter "exhaust
flow") along each alternative path 38. For example, the exhaust
flow along normal path 40 may be greater than the exhaust flow
along bypass 42.
[0019] Controller 12 may use a valve 44, situated along bypass 42,
to adjust the exhaust flow along bypass 42. Controller 12 may open
valve 44 to upwardly adjust the exhaust flow along bypass 42. And,
controller 12 may close valve 44 to downwardly adjust the exhaust
flow along bypass 42. It is contemplated that controller 12 may use
another valve 46, also situated along bypass 42, to further adjust
the exhaust flow along bypass 42. Controller 12 may open valve 46
to adjust upwardly the exhaust flow along bypass 42. And,
controller 12 may close valve 46 to adjust downwardly the exhaust
flow along bypass 42. It is further contemplated that controller 12
may use yet another valve 48, situated between bypass 42 and an
atmospheric vent 50, to further adjust the exhaust flow along
bypass 42. Atmospheric vent 50 may embody a fluid connection
between bypass 42 and an atmosphere (i.e. a fluid external to
exhaust system 18). When controller 12 opens valve 48, this fluid
connection may serve to adjust the exhaust flow along bypass 42
downward and an atmospheric air flow along bypass 42 upward. And,
when controller 12 closes valve 48, the fluid connection may serve
to adjust the exhaust flow along bypass 42 upward and the
atmospheric air flow along bypass 42 downward.
[0020] As previously discussed, exhaust system 18 may include gas
concentration sensors 22 and 24. Each of gas concentration sensors
22 and 24 may embody a device that detects a gas concentration and
generates a corresponding signal that may be communicated to
controller 12. For example, each of gas concentration sensors 22
and 24 may embody a NO.sub.x sensor. It is contemplated that the
arrangement of exhaust system 18 components, including gas
concentration sensors 22 and 24, may vary depending on
application.
[0021] As illustrated in FIG. 1, gas concentration sensor 22 may be
located along path 34. Bypass 42 may be located downstream of gas
concentration sensor 22. Valve 44 may be located along bypass 42
and upstream of gas concentration sensor 24. And, valve 46 may be
located along bypass 42 and downstream of gas concentration sensor
24. Valve 48 may be located downstream of valve 44 and upstream of
valve 46.
[0022] Alternatively, as illustrated in FIG. 2, gas concentration
sensor 22 may be located along path 34. Catalytic converter 20 may
be located along path 34 and downstream of gas concentration sensor
22. Bypass 42 may be located downstream of catalytic converter 20.
Valve 44 may be located along bypass 42 and upstream of gas
concentration sensor 24. And, valve 46 may be located along bypass
42 and downstream of gas concentration sensor 24. Valve 48 may be
located downstream of valve 44 and upstream of valve 46.
[0023] In yet another alternative, as illustrated in FIG. 3,
exhaust system 18 may include a bypass 42a and a bypass 42b. Valve
44a may be located along bypass 42a and upstream of gas
concentration sensor 22. And, valve 46a may be located along bypass
42a and downstream of gas concentration sensor 22. Valve 48a may be
located downstream of valve 44a and upstream of valve 46a. Bypass
42b may be located downstream of bypass 42a. Valve 44b may be
located along bypass 42b and upstream of gas concentration sensor
24. And, valve 46b may be located along bypass 42b and downstream
of gas concentration sensor 24. Valve 48b may be located downstream
of valve 44b and upstream of valve 46b.
[0024] FIG. 4 illustrates an exemplary method of operating the
disclosed system. FIG. 4 will be discussed in the following section
to further illustrate the disclosed system and its operation.
INDUSTRIAL APPLICABILITY
[0025] The disclosed system may be applicable to combustion
engines, which may be subject to emission standards. The system may
determine whether the combustion engine is operating properly. In
particular, the system may detect when a gas concentration sensor
has drifted or failed. Operation of the system will now be
described.
[0026] As illustrated in FIG. 4, the disclosed system, and more
specifically, controller 12 (referring to FIGS. 1-3), may
continuously or intermittently adjust the/air fuel ratio supplied
to combustion chamber 16 (referring to FIGS. 1-3) based on the
detections of gas concentration sensor 22 (referring to FIGS. 1-3)
(step 100). At certain time intervals and without discontinuing
step 100 (i.e. while still continuously or intermittently adjusting
the air/fuel ratio), controller 12 may test gas concentration
sensor 22 (step 110). If gas concentration sensor 22 is not broken,
controller 12 may return to step 100 without further action. But,
if gas concentration sensor 22 is broken, controller 12 may
discontinue step 100 (step 120), and provide an out-of-tolerance
warning (step 140). Additionally, controller 12 may continuously or
intermittently adjust the air/fuel ratio supplied to combustion
chamber 16 based on the detections of gas concentration sensor 24
(referring to FIGS. 1-3) (step 150).
[0027] The adjustment of step 100 may include sub-steps. In
particular, step 100 may include the sub-step of adjusting the
air/fuel ratio based on the detections of gas concentration sensor
22 (sub-step 160). Step 100 may also include the sub-step of
determining whether to test gas concentration sensor 22 (sub-step
170). Additionally, step 100 may include the sub-step of pausing,
thereby causing the adjustment of sub-step 160 to be intermittent
(sub-step 180). Alternatively, step 100 may not include sub-step
180, and the adjustment of sub-step 160 may be continuous.
[0028] At sub-step 160, it is contemplated that controller 12 may
communicate with air/fuel supply system 14 to adjust the air/fuel
ratio supplied to combustion chamber 16 based on the detection of
gas concentration sensor 22. For example, controller 12 may adjust
the air/fuel ratio until gas concentration sensor 22 senses
NO.sub.x at a concentration within five parts-per-million of the
nominal.
[0029] After or while adjusting the air/fuel ratio, controller 12
may proceed to sub-step 170 and determine whether to test gas
concentration sensor 22. Controller 12 may base this determination
on the signal of clock 26. In particular, controller 12 may test
gas concentration sensor 22 (i.e. proceed to step 110) at
predetermined time intervals. Alternatively, controller 12 may test
gas concentration sensor 22 based on measured parameters such as,
for example, the detections of gas concentration sensor 22.
Specifically, if the detections of gas concentration sensor 22 vary
substantially and unexpectedly over time, controller 12 may test
gas concentration sensor 22.
[0030] Next, controller 12 may pause (sub-step 180). This pause may
temporarily prevent the adjustment of sub-step 160, thereby
allowing for the temporary disablement of gas concentration sensor
22. When gas concentration sensor 22 is disabled, it may be
shielded from the flow of exhaust. For example, controller 12 may
shield gas concentration sensor 22 from the flow of exhaust by
opening valve 48a, and closing valves 44a and 46a (referring to
FIG. 3). Based on the signal of clock 26, after a predetermined
amount of time, controller 12 may unshield and reenable gas
concentration sensor 22, and proceed back to sub-step 160.
Alternatively, step 100 may not include sub-step 180, and the
adjustment of sub-step 160 may be continuous. This continuous
adjustment may be necessitated by certain emission standards such
as, for example, those applicable to gasoline engines.
[0031] The testing of step 110 may include sub-steps. In
particular, step 110 may include the sub-step of adjusting the
exhaust and atmospheric air flows along bypass 42 to unshield gas
concentration sensor 24 from the flow of exhaust (sub-step 190).
Step 110 may also include the sub-step of pausing, thereby allowing
the adjusted flows to increase the temperature of gas concentration
sensor 24 (sub-step 200). Additionally, step 110 may include the
sub-step of detecting and calculating an average of a first gas
concentration, and detecting and calculating an average of a second
gas concentration (sub-step 210). Step 110 may also include the
sub-step of calculating the difference between the calculated
averages of sub-step 210 (sub-step 220). Step 110 may further
include the sub-step of adjusting the exhaust and atmospheric air
flows along bypass 42 to shield gas concentration sensor 24 from
the flow of exhaust (sub-step 230). In addition, step 110 may
include the sub-step of determining whether the difference of
sub-step 220 is greater than an allowable tolerance (sub-step 240).
If this difference is greater than the allowable tolerance, gas
concentration sensor 22 may be broken, and controller 12 may
proceed to step 120. But, if the difference is not greater than the
allowable tolerance, gas concentration sensor 22 may not be broken,
and controller 12 may return to step 100.
[0032] The adjustment of sub-step 190 may also include sub-steps.
In particular, sub-step 190 may include the sub-step of closing
valve 48 (referring to FIGS. 1 and 3, and referring to valve 48a in
FIG. 2) (sub-step 250). Closing valve 48 may adjust downwardly the
atmospheric air flow along bypass 42 (referring to FIGS. 1 and 3,
and referring to bypass 42a in FIG. 2). Sub-step 190 may also
include the sub-steps of opening valve 44 (referring to FIGS. 1 and
3, and referring to valve 44a in FIG. 2) (sub-step 260) and opening
valve 46 (referring to FIGS. 1 and 3, and referring to valve 46a in
FIG. 2) (sub-step 270). Opening valve 44 may adjust upwardly the
exhaust flow along bypass 42. And, opening valve 46 may also adjust
upwardly the exhaust flow along bypass 42. It is contemplated that
controller 12 may execute sub-step 250 before proceeding to
sub-steps 260 and 270, thereby reducing communication of exhaust
gasses to the atmosphere. Alternatively, controller 12 may execute
sub-steps 250, 260, and 270 concurrently.
[0033] Next, controller 12 may pause (sub-step 200). This pause may
temporarily prevent controller 12 from receiving signals regarding
gas concentration sensor 24 detections. This pause may be necessary
to allow gas concentration sensor 24 to reach its operational
temperature. In particular, this pause may allow the exhaust flow
to increase the temperature of gas concentration sensor 24.
[0034] After sub-step 200, controller 12 may detect and calculate
an average of a first gas concentration, and detect and calculate
an average of a second gas concentration (sub-step 210). Sub-step
210 may include the sub-step of detecting concentrations of the
first and second gas (sub-step 280). It is contemplated that
controller 12 may concurrently receive signals from gas
concentration sensors 22 and 24 regarding detections of the
concentrations of the first and second gasses, respectively. These
signals may be received for a predetermined amount of time.
Therefore, controller 12 may receive a certain number of detections
from each of gas concentration sensors 22 and 24. Controller 12 may
calculate a moving average of these detections as they are
received. Alternatively, sub-step 210 may include the sub-step of
calculating the averages of the first and second detected gas
concentrations, respectively, after the predetermined amount of
time has expired (i.e. when controller 12 is no longer receiving
detections from gas concentration sensors 22 and 24) (sub-step
290). For example, these averages may be arithmetic means.
[0035] Next, controller 12 may calculate the difference between the
calculated averages of sub-step 210 (sub-step 220). It is
contemplated, however, that these averages may not be directly
comparable if gas concentration sensors 22 and 24 are separated by
another exhaust system 18 component that alters the gas. For
example, if catalytic converter 20 is located downstream of gas
concentration sensor 22 and upstream of gas concentration sensor 24
(referring to FIG. 2), the detections of gas concentration sensor
22 may not be directly comparable to those of gas concentration
sensor 24 (i.e. the average of the first gas concentration may not
be directly comparable to the average of the second gas
concentration). It is contemplated that the averages may be
compared after adjusting the average of the second gas
concentration. Controller 12 may adjust the average of the second
gas concentration based on a known affect of the intermediary
exhaust system 18 component. Controller 12 may then subtract the
adjusted average of the second gas concentration from the average
of the first gas concentration. Alternatively, controller 12 may
subtract the average of the first gas concentration from the
adjusted average of the second gas concentration. Controller 12 may
then determine the absolute value of the result of either of the
above subtractions. This absolute value may be the difference
between the calculated averages of sub-step 210.
[0036] Before or after sub-step 220, controller 12 may again adjust
the exhaust and atmospheric air flows along bypass 42 (sub-step
230). This adjustment of the flows may include sub-steps. In
particular, sub-step 230 may include the sub-step of opening valve
48 (sub-step 300). Opening valve 48 may adjust upwardly the
atmospheric air flow along bypass 42. Sub-step 230 may also include
the sub-steps of closing valve 44 (sub-step 310) and closing valve
46 (sub-step 320). Closing valve 44 may adjust downwardly the
exhaust flow along bypass 42. And, closing valve 46 may also adjust
downwardly the exhaust flow along bypass 42. It is contemplated
that controller 12 may execute sub-steps 310 and 320 before
proceeding to sub-steps 300, thereby reducing communication of
exhaust gasses to the atmosphere. Alternatively, controller 12 may
execute sub-steps 300, 310, and 320 concurrently.
[0037] After sub-step 220, controller 12 may determine whether the
difference between the calculated averages of sub-step 210 (i.e.
the difference of sub-step 220) is greater than an allowable
tolerance. The allowable tolerance may be dictated by the emission
standards applicable to combustion engine 10. In particular,
controller 12 may subtract the difference of sub-step 220 from the
allowable tolerance. If the result of this subtraction is a
non-negative number (i.e. the difference between the calculated
averages of sub-step 210 is not greater than the allowable
tolerance), controller 12 may determine that gas concentration
sensor 22 is not broken. Controller 12 may then proceed to step
100. On the other hand, if the result of the subtraction is a
negative number, controller 12 may determine that gas concentration
sensor 22 is broken. Controller 12 may then proceed to step
120.
[0038] At step 120, controller 12 may discontinue step 100 (i.e.
discontinue adjustment of the air/fuel ratio based on gas
concentration sensor 22 detections). Controller 12 may then provide
an out-of-tolerance warning (step 140). In particular, controller
12 may activate warning device 25.
[0039] Next, controller 12 may continuously or intermittently
adjust the/air fuel ratio based on the detections of gas
concentration sensor 24 (step 150). Similar to step 100, the
adjustment may include sub-steps. In particular, step 150 may
include the sub-step of adjusting the air/fuel ratio based on the
detections of gas concentration sensor 24 (sub-step 330).
Additionally, step 150 may include the sub-step of pausing, thereby
causing the adjustment of sub-step 330 to be intermittent (sub-step
340). Alternatively, step 150 may not include sub-step 340, and the
adjustment of sub-step 330 may be continuous.
[0040] It is contemplated that adjusting the air/fuel ratio based
on the detections of gas concentration sensor 24 may reduce the
economic impact of a failure of gas concentration sensor 22.
Specifically, after gas concentration sensor 22 has failed,
combustion engine 10 may remain in compliance with emission
standards while continuing to produce power and an exhaust flow.
Therefore, gas concentration sensor 22 may be replaced when it is
convenient to do so, for example, at a standard maintenance
interval. Thus, combustion engine 10 maintenance costs may be
reduced by reducing the need for maintenance between standard
maintenance intervals. Furthermore, shielding gas concentration
sensors 22 and/or 24 from the exhaust flow may increase their
respective functional lives. Thus, combustion engine 10 maintenance
costs may be further reduced.
[0041] It is further contemplated that a detection of a
miscalibrated gas concentration sensor 22 may further decrease
combustion engine 10 maintenance costs. Specifically, where
reliable testing and calibration equipment is unavailable, it need
not be assumed that gas concentration sensor 22 has failed.
Instead, as discussed above, combustion engine 10 may continue to
produce power and a flow of exhaust while remaining in compliance
with emission standards. Therefore, gas concentration sensor 22
need not be immediately replaced, but may instead be recalibrated
when it is convenient to do so. Thus, combustion engine 10
maintenance costs may be further reduced by reducing the need for
replacement parts.
[0042] It will be apparent to those skilled in the art that various
modifications and variations can be made to the method and system
of the present disclosure. Other embodiments of the method and
system will be apparent to those skilled in the art from
consideration of the specification and practice of the method and
system disclosed herein. It is intended that the specification and
examples be considered as exemplary only, with a true scope of the
disclosure being indicated by the following claims and their
equivalents.
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