U.S. patent application number 15/056745 was filed with the patent office on 2016-06-23 for methods and systems for an oxygen sensor.
The applicant listed for this patent is Ford Global Technologies, LLC. Invention is credited to Timothy Joseph Clark, Christopher House, Richard E. Soltis, Gopichandra Surnilla, Jacobus Hendrik Visser.
Application Number | 20160177858 15/056745 |
Document ID | / |
Family ID | 52738230 |
Filed Date | 2016-06-23 |
United States Patent
Application |
20160177858 |
Kind Code |
A1 |
Surnilla; Gopichandra ; et
al. |
June 23, 2016 |
METHODS AND SYSTEMS FOR AN OXYGEN SENSOR
Abstract
Methods and systems are provided for accurately learning the
zero point of an intake gas oxygen sensor in varying ambient
humidity conditions. The learned zero point is corrected based on
an estimated ambient humidity to calibrate the reading for dry air
conditions or standard humidity conditions. EGR control is
performed by comparing the output of an intake oxygen sensor during
EGR conditions relative to the humidity-corrected zero point.
Inventors: |
Surnilla; Gopichandra; (West
Bloomfield, MI) ; Clark; Timothy Joseph; (Livonia,
MI) ; Soltis; Richard E.; (Saline, MI) ;
Visser; Jacobus Hendrik; (Farmington Hills, MI) ;
House; Christopher; (Belleville, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ford Global Technologies, LLC |
Dearborn |
MI |
US |
|
|
Family ID: |
52738230 |
Appl. No.: |
15/056745 |
Filed: |
February 29, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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14052641 |
Oct 11, 2013 |
9273621 |
|
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15056745 |
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Current U.S.
Class: |
123/294 |
Current CPC
Class: |
F02D 41/005 20130101;
F02B 37/001 20130101; Y02T 10/47 20130101; F02D 41/123 20130101;
F02B 29/0406 20130101; F02D 41/0235 20130101; F02D 41/08 20130101;
F02D 41/2474 20130101; F02M 26/49 20160201; F02M 35/10222 20130101;
F02D 41/144 20130101; F02B 37/007 20130101; Y02T 10/40 20130101;
F02M 26/42 20160201; F02M 25/089 20130101; F02D 2200/0418 20130101;
F02M 35/10393 20130101; F02D 41/0072 20130101; F02M 26/08 20160201;
F02B 37/18 20130101; F02M 26/23 20160201 |
International
Class: |
F02D 41/24 20060101
F02D041/24; F02M 26/06 20060101 F02M026/06; F02B 37/12 20060101
F02B037/12; F02D 13/02 20060101 F02D013/02; F02D 41/00 20060101
F02D041/00; F02B 29/04 20060101 F02B029/04 |
Claims
1. A method for an engine with a turbocharger, comprising: cooling
boosted intake charge with a charge air cooler; estimating an
ambient humidity via an intake humidity sensor while learning a
reference point for an intake oxygen sensor at a reference intake
pressure, the reference point corresponding to an oxygen sensor
reading when no EGR is present; combusting cooled intake charge,
including EGR, with directly injected fuel in the engine; adjusting
valve timing of one of an intake and exhaust valve of the engine;
passing turbocharger compressor bypass flow through a ventuir to
generate a draw on an accessory passage; correcting the learned
reference point based on the estimated ambient humidity; and
adjusting an opening of an EGR valve based on the correcting.
2. The method of claim 1, wherein the accessory passage is a purge
passage, and wherein each of the humidity sensor and the oxygen
sensor are positioned upstream of an intake throttle and downstream
of the charge air cooler in an engine intake manifold.
3. The method of claim 1, wherein learning the reference point
includes learning a nominal amount of oxygen based on an output of
the intake oxygen sensor at the reference intake pressure during
selected engine idling conditions or selected engine non-fueling
conditions.
4. The method of claim 3, wherein correcting the learned reference
point based on the estimated ambient humidity includes calculating
an amount of oxygen displaced by the estimated ambient humidity,
and adding the calculated amount of oxygen to the learned nominal
amount of oxygen to correct the reference point to dry air.
5. The method of claim 4, wherein the correcting further includes,
after correcting the reference point to dry air, calibrating the
reference point to a standard humidity level.
6. The method of claim 5, further comprising, adjusting EGR flow to
the engine based on an intake oxygen concentration estimated by the
intake oxygen sensor relative to the corrected reference point, and
further based on a change in intake pressure from the reference
intake pressure.
7. The method of claim 5, wherein the reference intake pressure is
one of a throttle inlet pressure and an intake manifold
pressure.
8. The method of claim 3, wherein the selected engine idling
conditions include a first engine idle since an engine start.
9. The method of claim 3, wherein the selected engine idling
conditions include a first engine idle since installation of the
intake oxygen sensor or installation of an intake pressure sensor
configured to estimate the reference intake pressure.
10. The method of claim 3, wherein the selected engine non-fueling
conditions include a deceleration fuel shut-off condition.
11. The method of claim 6, wherein adjusting EGR flow to the engine
includes adjusting low-pressure EGR flow along an EGR passage from
an exhaust manifold, downstream of an exhaust turbine, to an intake
manifold, upstream of an intake compressor, via the EGR valve.
12. The method of claim 11, wherein each of the intake oxygen
sensor and humidity sensor are positioned downstream of an output
of the EGR passage.
13. A method for an engine, comprising: correcting a first, nominal
output of an intake oxygen sensor, learned during selected engine
idling conditions at a reference intake pressure, based on an
ambient humidity estimated by an intake humidity sensor; and
adjusting EGR flow to the engine via adjustments to an EGR valve
opening based on a second output of the oxygen sensor, estimated at
a second intake pressure, relative to the corrected first output;
and bypassing compressed air around a turbocharger compressor to
drawn purge flow into an engine intake system to the engine.
14. The method of claim 13, wherein the EGR flow is further
adjusted based on the second intake pressure relative to the
reference intake pressure, and wherein the selected engine idling
conditions include one of a first engine idle from engine start, a
first engine idle following installation of the intake oxygen
sensor, and a first engine idle following installation of an intake
pressure sensor.
15. The method of claim 13, wherein the correcting includes,
calculating an amount of oxygen displaced by the estimated ambient
humidity; and increasing the first output to include the amount of
displaced oxygen, wherein the increased first output is indicative
of a dry air oxygen content.
16. The method of claim 15, wherein the correcting further
includes, adjusting the increased first output based on an amount
of oxygen displaceable by a calibrated humidity level, the adjusted
output indicative of a calibrated humidity air oxygen content.
17. The method of claim 16, wherein adjusting the EGR flow includes
estimating a delivered EGR flow based on a difference between the
second output and the corrected first output, and adjusting a
position of an EGR valve based on a difference between the
delivered EGR flow and a target EGR flow, the target EGR flow based
on engine speed-load conditions.
18. An engine system, comprising: an engine including an intake
manifold; a turbocharger including an exhaust turbine and an intake
compressor; a charge air cooler coupled downstream of the
compressor; a direct fuel injector coupled to an engine cylinder; a
variable cam timing system coupled to engine intake and/or exhaust
valves; an intake oxygen sensor coupled to the intake manifold
downstream of the charge air cooler and upstream of an intake
throttle; a pressure sensor coupled to the intake manifold
downstream of the charge air cooler and upstream of the intake
throttle; a humidity sensor coupled to the intake manifold
downstream of the charge air cooler and upstream of the intake
throttle; an EGR system including an EGR passage and EGR valve for
recirculating exhaust residuals from downstream of the turbine to
upstream of the compressor; and a controller with computer readable
instructions for: during a first engine idle since an engine start,
learning an oxygen sensor output and a humidity sensor output at a
reference intake pressure; and adjusting the oxygen sensor output
based on the humidity sensor output; and during subsequent engine
non-idle conditions, adjusting an opening of the EGR valve based on
an intake oxygen concentration estimated by the intake oxygen
sensor relative to the increased oxygen sensor output, and further
based on an intake pressure relative to the reference intake
pressure.
19. The system of claim 18, wherein increasing the oxygen sensor
output based on the humidity sensor output includes, during a first
condition, estimating a first amount of oxygen displaced by total
humidity based on the humidity sensor output and increasing the
oxygen sensor output with the first amount of oxygen; and during a
second condition, estimating a second amount of oxygen displaced by
a calibrated humidity based on the humidity sensor output, and
decreasing the oxygen sensor output with the second amount of
oxygen.
20. The system of claim 19, wherein the first condition includes
ambient humidity higher than a threshold humidity level, and
wherein the second condition includes ambient humidity lower than
the threshold humidity level.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of U.S. patent
application Ser. No. 14/052,641, entitled "METHODS AND SYSTEMS FOR
AN OXYGEN SENSOR," filed on Oct. 11, 2013, the entire contents of
which are hereby incorporated by reference for all purposes.
TECHNICAL FIELD
[0002] The present application relates generally to a gas
constituent sensor included in an intake system of an internal
combustion engine.
BACKGROUND AND SUMMARY
[0003] Engine systems may utilize recirculation of exhaust gas from
an engine exhaust system to an engine intake system (intake
passage), a process referred to as exhaust gas recirculation (EGR),
to reduce regulated emissions. An EGR system may include various
sensors to measure and/or control the EGR. As one example, the EGR
system may include an intake gas constituent sensor, such as an
oxygen sensor, which may be employed to measure oxygen to determine
the proportion of combusted gases in an intake passage of the
engine. The sensor may also be used during non-EGR conditions to
determine the oxygen content of fresh intake air. The EGR system
may additionally or optionally include an exhaust gas oxygen sensor
coupled to the exhaust manifold for estimating a combustion
air-fuel ratio.
[0004] As such, when the intake oxygen sensor is used for EGR
control, the EGR is measured as a function of the change in oxygen
due to EGR as a diluent. To determine the change in the amount of
oxygen, a reference point corresponding to an oxygen reading when
no EGR is present is required. Such a reference point is called the
"zero point" of the oxygen sensor. Due to the sensitivity of the
oxygen sensor to various conditions, such as pressure, aging, and
piece-to-piece variability, there may be large deviations in the
"zero point" at different engine operating conditions. Therefore
the oxygen sensor may need to be regularly calibrated and a
correction factor may need to be learned.
[0005] One example method for calibrating an exhaust gas oxygen
sensor is depicted by Ishiguro et al. in U.S. Pat. No. 8,417,413.
Therein, a correction factor is learned based on an oxygen sensor
output during engine fuel-cut off conditions. However, the
inventors have recognized that approaches used for zero point
estimation in exhaust oxygen sensors may not be applied for zero
point estimation of intake oxygen sensors. This is because in
addition to being sensitive to pressure and part-to-part
variability, due to equilibration of the sensed gas by a catalyzing
sensing element of the sensor, the intake oxygen sensor is also
sensitive to ambient humidity. Specifically, the water content of
the intake aircharge may displace oxygen. If the reading is used to
estimate EGR, more diluent may be estimated as the humidity
increases. As a result, the measurement and/or control of EGR may
be reduced.
[0006] In one example, some of the above issues may be addressed by
a method for an engine comprising: estimating an ambient humidity
while learning a reference point for an intake oxygen sensor at a
reference intake pressure; and correcting the learned reference
point based on the estimated ambient humidity. In this way, a zero
point reading for an intake oxygen sensor may be corrected for the
effect of varying ambient humidity, improving the accuracy of EGR
control.
[0007] For example, at the first engine idle following every engine
start, an idle adaptation of the intake oxygen sensor may be
performed. Therein, an output of the intake oxygen sensor may be
monitored, while also estimating a reference intake pressure (based
on an intake manifold pressure sensor output) and an ambient
humidity (based on an intake manifold humidity sensor output). The
output of the intake oxygen sensor is corrected based on the
estimated ambient humidity to learn a dry air nominal oxygen sensor
reading. Alternatively, the output of the intake oxygen sensor is
corrected based on the estimated ambient humidity to learn an
oxygen sensor reading for a calibrated amount of humidity (e.g.,
for a pre-defined standard humidity level). A relationship between
the corrected output of the intake oxygen sensor at the reference
intake pressure may then be learned as the reference "zero point".
During subsequent engine non-idling conditions, a difference
between an output of the intake oxygen sensor and the learned zero
point may be used to estimate an EGR concentration, and thereby
adjust an EGR flow.
[0008] In this way, the effect of humidity on the output an intake
oxygen sensor can be compensated for. By measuring the ambient
humidity at the time of learning the reference point of the intake
oxygen sensor, the amount of oxygen displaced by the ambient
humidity can be learned and used to correct the sensor output. By
calibrating the sensor output to a dry air condition, where the
effect of all humidity is removed, or to a standard air condition,
where the effect of a standard humidity level is learned, the
sensor output can be regulated to pre-defined conditions. By using
the humidity-corrected zero point to estimate EGR flow, EGR
calculation errors from variations in ambient humidity conditions
can be reduced. Overall, the accuracy of EGR estimation is
increased, allowing for improved EGR control.
[0009] It should be understood that the summary above is provided
to introduce in simplified form a selection of concepts that are
further described in the detailed description. It is not meant to
identify key or essential features of the claimed subject matter,
the scope of which is defined uniquely by the claims that follow
the detailed description. Furthermore, the claimed subject matter
is not limited to implementations that solve any disadvantages
noted above or in any part of this disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIGS. 1 and 2 are schematic diagrams of an engine
system.
[0011] FIG. 3 is a map depicting the relationship between intake
pressure and the pumping current of an intake oxygen sensor.
[0012] FIG. 4 depicts a flowchart for performing a zero point
estimation for an intake oxygen sensor during engine idling
conditions.
[0013] FIG. 5 depicts a flowchart for performing a zero point
estimation for an intake oxygen sensor during engine non-fueling
conditions.
[0014] FIG. 6 depicts a flowchart for identifying degradation of an
EGR valve based on the zero point estimated using idle adaptation
and the zero point estimated using DFSO adaptation.
[0015] FIG. 7 shows an example idle adaptation.
[0016] FIG. 8 depicts a flowchart for correcting a learned zero
point based on ambient humidity.
[0017] FIG. 9 depicts a flowchart for EGR control using the learned
intake oxygen zero point.
DETAILED DESCRIPTION
[0018] The present description is related to methods and system for
learning a reference point, or zero point, for an intake oxygen
sensor, such as the sensor coupled to the engine systems of FIGS.
1-2. The reference point may be determined based on a learned
relationship between the output of the intake oxygen sensor and an
output of an intake pressure sensor at selected conditions (FIG.
3). A controller may be configured to perform a control routine,
such as the routine of FIGS. 4-5 to learn the zero point for the
intake oxygen sensor during an idle adaptation or during a DFSO
adaptation. The learned reference point may be corrected based on
ambient humidity (FIG. 8). The controller may also be configured to
perform a routine (FIG. 6) to identify EGR valve leakage based on
discrepancies between the zero point estimated at idle conditions
and the zero point estimated at DFSO conditions. In response to EGR
valve leakage, EGR control may be adjusted (FIG. 9) so as to vary
the feedback component of EGR control from the oxygen sensor. An
example idle adaptation is shown at FIG. 7. In this way, an intake
oxygen sensor reading may be corrected for aging, part-to-part
variations, and effects from fuel and reductants.
[0019] FIG. 1 shows a schematic depiction of an example
turbocharged engine system 100 including a multi-cylinder internal
combustion engine 10 and twin turbochargers 120 and 130. As one
non-limiting example, engine system 100 can be included as part of
a propulsion system for a passenger vehicle. Engine system 100 can
receive intake air via intake passage 140. Intake passage 140 can
include an air filter 156 and an EGR throttle valve 230. Engine
system 100 may be a split-engine system wherein intake passage 140
is branched downstream of EGR throttle valve 230 into first and
second parallel intake passages, each including a turbocharger
compressor. Specifically, at least a portion of intake air is
directed to compressor 122 of turbocharger 120 via a first parallel
intake passage 142 and at least another portion of the intake air
is directed to compressor 132 of turbocharger 130 via a second
parallel intake passage 144 of the intake passage 140.
[0020] The first portion of the total intake air that is compressed
by compressor 122 may be supplied to intake manifold 160 via first
parallel branched intake passage 146. In this way, intake passages
142 and 146 form a first parallel branch of the engine's air intake
system. Similarly, a second portion of the total intake air can be
compressed via compressor 132 where it may be supplied to intake
manifold 160 via second parallel branched intake passage 148. Thus,
intake passages 144 and 148 form a second parallel branch of the
engine's air intake system. As shown in FIG. 1, intake air from
intake passages 146 and 148 can be recombined via a common intake
passage 149 before reaching intake manifold 160, where the intake
air may be provided to the engine.
[0021] A first EGR throttle valve 230 may be positioned in the
engine intake upstream of the first and second parallel intake
passages 142 and 144, while a second air intake throttle valve 158
may be positioned in the engine intake downstream of the first and
second parallel intake passages 142 and 144, and downstream of the
first and second parallel branched intake passages 146 and 148, for
example, in common intake passage 149.
[0022] In some examples, intake manifold 160 may include an intake
manifold pressure sensor 182 for estimating a manifold pressure
(MAP) and/or an intake manifold temperature sensor 183 for
estimating a manifold air temperature (MCT), each communicating
with controller 12. Intake passage 149 can include a charge air
cooler (CAC) 154 and/or a throttle (such as second throttle valve
158). The position of throttle valve 158 can be adjusted by the
control system via a throttle actuator (not shown) communicatively
coupled to controller 12. An anti-surge valve 152 may be provided
to selectively bypass the compressor stages of turbochargers 120
and 130 via bypass passage 150. As one example, anti-surge valve
152 can open to enable flow through bypass passage 150 when the
intake air pressure downstream of the compressors attains a
threshold value.
[0023] Intake manifold 160 may further include an intake gas oxygen
sensor 172. In one example, the oxygen sensor is a UEGO sensor. As
elaborated herein, the intake gas oxygen sensor may be configured
to provide an estimate regarding the oxygen content of fresh air
received in the intake manifold. In addition, when EGR is flowing,
a change in oxygen concentration at the sensor may be used to infer
an EGR amount and used for accurate EGR flow control. In the
depicted example, oxygen sensor 162 is positioned upstream of
throttle 158 and downstream of charge air cooler 154. However, in
alternate embodiments, the oxygen sensor may be positioned upstream
of the CAC.
[0024] A pressure sensor 174 may be positioned alongside the oxygen
sensor for estimating an intake pressure at which an output of the
oxygen sensor is received. Since the output of the oxygen sensor is
influenced by the intake pressure, a reference oxygen sensor output
may be learned at a reference intake pressure. In one example, the
reference intake pressure is a throttle inlet pressure (TIP) where
pressure sensor 174 is a TIP sensor. In alternate examples, the
reference intake pressure is a manifold pressure (MAP) as sensed by
MAP sensor 182.
[0025] A humidity sensor 173 may be positioned alongside the intake
oxygen sensor and the intake pressure sensor. Specifically, as
depicted, each of the humidity sensor 173, intake oxygen sensor
172, and intake pressure sensor 174 are positioned upstream of
intake throttle 158 and downstream of charge air cooler 154 in the
engine intake manifold. The humidity sensor may be configured to
provide an estimate of the ambient humidity. As elaborated with
reference to FIG. 8, a controller may estimate an ambient humidity
while learning a reference point for the intake oxygen sensor at a
reference intake pressure and correct the learned reference point
based on the estimated ambient humidity. This allows variations in
oxygen sensor output due to variations in ambient humidity to be
learned and used for accurately estimating EGR.
[0026] Engine 10 may include a plurality of cylinders 14. In the
depicted example, engine 10 includes six cylinders arrange in a
V-configuration. Specifically, the six cylinders are arranged on
two banks 13 and 15, with each bank including three cylinders. In
alternate examples, engine 10 can include two or more cylinders
such as 3, 4, 5, 8, 10 or more cylinders. These various cylinders
can be equally divided and arranged in alternate configurations,
such as V, in-line, boxed, etc. Each cylinder 14 may be configured
with a fuel injector 166. In the depicted example, fuel injector
166 is a direct in-cylinder injector. However, in other examples,
fuel injector 166 can be configured as a port based fuel
injector.
[0027] Intake air supplied to each cylinder 14 (herein, also
referred to as combustion chamber 14) via common intake passage 149
may be used for fuel combustion and products of combustion may then
be exhausted from via bank-specific parallel exhaust passages. In
the depicted example, a first bank 13 of cylinders of engine 10 can
exhaust products of combustion via a first parallel exhaust passage
17 and a second bank 15 of cylinders can exhaust products of
combustion via a second parallel exhaust passage 19. Each of the
first and second parallel exhaust passages 17 and 19 may further
include a turbocharger turbine. Specifically, products of
combustion that are exhausted via exhaust passage 17 can be
directed through exhaust turbine 124 of turbocharger 120, which in
turn can provide mechanical work to compressor 122 via shaft 126 in
order to provide compression to the intake air. Alternatively, some
or all of the exhaust gases flowing through exhaust passage 17 can
bypass turbine 124 via turbine bypass passage 123 as controlled by
wastegate 128. Similarly, products of combustion that are exhausted
via exhaust passage 19 can be directed through exhaust turbine 134
of turbocharger 130, which in turn can provide mechanical work to
compressor 132 via shaft 136 in order to provide compression to
intake air flowing through the second branch of the engine's intake
system. Alternatively, some or all of the exhaust gas flowing
through exhaust passage 19 can bypass turbine 134 via turbine
bypass passage 133 as controlled by wastegate 138.
[0028] In some examples, exhaust turbines 124 and 134 may be
configured as variable geometry turbines, wherein controller 12 may
adjust the position of the turbine impeller blades (or vanes) to
vary the level of energy that is obtained from the exhaust gas flow
and imparted to their respective compressor. Alternatively, exhaust
turbines 124 and 134 may be configured as variable nozzle turbines,
wherein controller 12 may adjust the position of the turbine nozzle
to vary the level of energy that is obtained from the exhaust gas
flow and imparted to their respective compressor. For example, the
control system can be configured to independently vary the vane or
nozzle position of the exhaust gas turbines 124 and 134 via
respective actuators.
[0029] Exhaust gases in first parallel exhaust passage 17 may be
directed to the atmosphere via branched parallel exhaust passage
170 while exhaust gases in second parallel exhaust passage 19 may
be directed to the atmosphere via branched parallel exhaust passage
180. Exhaust passages 170 and 180 may include one or more exhaust
after-treatment devices, such as a catalyst, and one or more
exhaust gas sensors.
[0030] Engine 10 may further include one or more exhaust gas
recirculation (EGR) passages, or loops, for recirculating at least
a portion of exhaust gas from the exhaust manifold to the intake
manifold. These may include high-pressure EGR loops for proving
high-pressure EGR (HP-EGR) and low-pressure EGR-loops for providing
low-pressure EGR (LP-EGR). In one example, HP-EGR may be provided
in the absence of boost provided by turbochargers 120, 130, while
LP-EGR may be provided in the presence of turbocharger boost and/or
when exhaust gas temperature is above a threshold. In still other
examples, both HP-EGR and LP-EGR may be provided
simultaneously.
[0031] In the depicted example, engine 10 may include a
low-pressure EGR loop 202 for recirculating at least some exhaust
gas from the first branched parallel exhaust passage 170,
downstream of the turbine 124, to the first parallel intake passage
142, upstream of the compressor 122. In some embodiments, a second
low-pressure EGR loop (not shown) may be likewise provided for
recirculating at least some exhaust gas from the second branched
parallel exhaust passage 180, downstream of the turbine 134, to the
second parallel intake passage 144, upstream of the compressor 132.
LP-EGR loop 202 may include LP-EGR valve 204 for controlling an EGR
flow (i.e., an amount of exhaust gas recirculated) through the
loops, as well as an EGR cooler 206 for lowering a temperature of
exhaust gas flowing through the EGR loop before recirculation into
the engine intake. The LP-EGR valve 204 can be positioned upstream
or downstream of the LP EGR cooler 206. Under certain conditions,
the EGR cooler 206 may also be used to heat the exhaust gas flowing
through LP-EGR loop 202 before the exhaust gas enters the
compressor to avoid water droplets impinging on the
compressors.
[0032] Engine 10 may further include a first high-pressure EGR loop
208 for recirculating at least some exhaust gas from the first
parallel exhaust passage 17, upstream of the turbine 124, to the
intake manifold 160 downstream of the engine throttle 158.
Likewise, the engine may include a second high-pressure EGR loop
(not shown) for recirculating at least some exhaust gas from the
second parallel exhaust passage 19, upstream of the turbine 134, to
the intake manifold 160 downstream of the engine throttle 158. EGR
flow through HP-EGR loops 208 may be controlled via HP-EGR valve
210. If two HP-EGR loops are present coupled to each branch of the
air induction system, they may each utilize their own HP-EGR valves
210 or join together prior to and share the same HP-EGR valve
before introduction into the intake manifold. It will be
appreciated that as an alternate to the above described single and
dual HP-EGR loop configurations, HP-EGR may be introduced into
intake passages 146 and/or 148 instead of into intake manifold
160.
[0033] A PCV port 102 may be configured to deliver crankcase
ventilation gases (blow-by gases) to the engine intake manifold
along second parallel intake passage 144. In some embodiments, flow
of PCV air through PCV port 102 may be controlled by a dedicated
PCV port valve. Likewise, a purge port 104 may be configured to
deliver purge gases from a fuel system canister to the engine
intake manifold along passage 144. In some embodiments, flow of
purge air through purge port 104 may be controlled by a dedicated
purge port valve. As elaborated with reference to FIG. 2, the PCV
and purge ports in the pre-compressor air induction tube only flow
into the induction tube during boosted conditions. In non-boosted
conditions, purge and PCV air are supplied directly to the intake
manifold. In other words, during boosted conditions, the purge and
PCV gases are received upstream of intake oxygen sensor 172, and
therefore affect the output of the sensor during boosted
conditions. In comparison, during non-boosted conditions, the purge
and PCV gases are received downstream of intake oxygen sensor 172,
and therefore do not affect the output of the sensor during
non-boosted conditions.
[0034] Humidity sensor 232 and pressure sensor 234 may be included
in only one of the parallel intake passages (herein, depicted in
the first parallel intake air passage 142 but not in the second
parallel intake passage 144), downstream of EGR throttle valve 230.
Specifically, the humidity sensor and the pressure sensor may be
included in the intake passage not receiving the PCV or purge air.
Humidity sensor 232 may be configured to estimate a relative
humidity of the intake air. In one embodiment, humidity sensor 232
is a UEGO sensor configured to estimate the relative humidity of
the intake air based on the output of the sensor at one or more
voltages. Since purge air and PCV air can confound the results of
the humidity sensor, the purge port and PCV port are positioned in
a distinct intake passage from the humidity sensor. Pressure sensor
234 may be configured to estimate a pressure of the intake air. In
some embodiments, a temperature sensor may also be included in the
same parallel intake passage, downstream of the EGR throttle valve
230.
[0035] As such, intake oxygen sensor 172 may be used for estimating
an intake oxygen concentration and inferring an amount of EGR flow
through the engine based on a change in the intake oxygen
concentration upon opening of the EGR valve 204. Specifically, a
change in the output of the sensor upon opening the EGR valve is
compared to a reference point where the sensor is operating with no
EGR (the zero point). Based on the change (e.g., decrease) in
oxygen amount from the time of operating with no EGR, an EGR flow
currently provided to the engine can be calculated. Then, based on
a deviation of the estimated EGR flow from the expected (or target)
EGR flow, further EGR control may be performed. As elaborated with
reference to FIG. 9, a controller may feed-forward adjust the
opening of the EGR valve based on engine speed-load conditions
while feedback adjusting the EGR valve based on an EGR flow
estimated by the oxygen sensor. However, EGR estimation and EGR
control requires accurate estimation of the zero point. Since the
output of the oxygen sensor is impacted by changes in intake
pressure, changes in exhaust air-fuel ratio, part-to-part
variations, and reductants (such as those from PCV and purge
gases), accurate zero point estimation can be complicated. Without
accurate zero point estimation, however, EGR flow control may be
not be reliably performed.
[0036] To overcome these issues, a zero point estimation of the
intake oxygen sensor is performed during idle conditions, herein
also referred to as an idle adaptation, and discussed at FIG. 4. By
performing the adaptation during idling conditions, where intake
pressure fluctuations are minimal and when no PCV or purge air is
ingested into the low pressure air induction system upstream of the
compressor, sensor reading variations due to those noise factors is
reduced. As such, purge and PCV air may flow into the engine during
idle via the intake manifold. However, they will not affect the
intake oxygen sensor output since they are ingested downstream of
the sensor, directly into the intake manifold. By also performing
the idle adaptation periodically, such as at every first idle
following an engine start, the effect of sensor aging and
part-to-part variability on the sensor output is also corrected
for. Overall a more accurate zero point can be learned.
[0037] A zero point estimation of the intake oxygen sensor is also
performed during engine non-fueling conditions, such as during a
deceleration fuel shut off (DFSO), herein also referred to as a
DFSO adaptation, and discussed at FIG. 5. By performing the
adaptation during DFSO conditions, in addition to reduced noise
factors such as those achieved during idle adaptation, sensor
reading variations due to EGR valve leakage is also reduced.
[0038] Returning to FIG. 1, the position of intake and exhaust
valves of each cylinder 14 may be regulated via hydraulically
actuated lifters coupled to valve pushrods, or via direct acting
mechanical buckets in which cam lobes are used. In this example, at
least the intake valves of each cylinder 14 may be controlled by
cam actuation using a cam actuation system. Specifically, the valve
cam actuation system 25 may include one or more cams and may
utilize variable cam timing or lift for intake and/or exhaust
valves. In alternative embodiments, the intake valves may be
controlled by electric valve actuation. Similarly, the exhaust
valves may be controlled by cam actuation systems or electric valve
actuation.
[0039] Engine system 100 may be controlled at least partially by a
control system 15 including controller 12 and by input from a
vehicle operator via an input device (not shown). Control system 15
is shown receiving information from a plurality of sensors 16
(various examples of which are described herein) and sending
control signals to a plurality of actuators 81. As one example,
sensors 16 may include humidity sensor 232, intake air pressure
sensor 234, MAP sensor 182, MCT sensor 183, TIP sensor 174, and
intake air oxygen sensor 172. In some examples, common intake
passage 149 may further include a throttle inlet temperature sensor
for estimating a throttle air temperature (TCT). In other examples,
one or more of the EGR passages may include pressure, temperature,
and air-to-fuel ratio sensors, for determining EGR flow
characteristics. As another example, actuators 81 may include fuel
injector 166, HP-EGR valve 210, LP-EGR valve 204, throttle valves
158 and 230, and wastegates 128, 138. Other actuators, such as a
variety of additional valves and throttles, may be coupled to
various locations in engine system 100. Controller 12 may receive
input data from the various sensors, process the input data, and
trigger the actuators in response to the processed input data based
on instruction or code programmed therein corresponding to one or
more routines. Example control routines are described herein with
regard to FIGS. 4-6 and 8.
[0040] Now turning to FIG. 2, another example embodiment 200 of the
engine of FIG. 1 is shown. As such, components previously
introduced in FIG. 1 are numbered similarly and not re-introduced
here for reasons of brevity.
[0041] Embodiment 200 shows a fuel tank 218 configured to deliver
fuel to engine fuel injectors. A fuel pump (not shown) immersed in
fuel tank 218 may be configured to pressurize fuel delivered to the
injectors of engine 10, such as to injector 166. Fuel may be pumped
into the fuel tank from an external source through a refueling door
(not shown). Fuel tank 218 may hold a plurality of fuel blends,
including fuel with a range of alcohol concentrations, such as
various gasoline-ethanol blends, including E10, E85, gasoline,
etc., and combinations thereof. A fuel level sensor 219 located in
fuel tank 218 may provide an indication of the fuel level to
controller 12. As depicted, fuel level sensor 219 may comprise a
float connected to a variable resistor. Alternatively, other types
of fuel level sensors may be used. One or more other sensors may be
coupled to fuel tank 218 such as a fuel tank pressure transducer
220 for estimating a fuel tank pressure.
[0042] Vapors generated in fuel tank 218 may be routed to fuel
vapor canister 22, via conduit 31, before being purged to engine
intake 23. These may include, for example, diurnal and refueling
fuel tank vapors. The canister may be filled with an appropriate
adsorbent, such as activated charcoal, for temporarily trapping
fuel vapors (including vaporized hydrocarbons) generated in the
fuel tank. Then, during a later engine operation, when purge
conditions are met, such as when the canister is saturated, the
fuel vapors may be purged from the canister into the engine intake
by opening canister purge valve 112 and canister vent valve
114.
[0043] Canister 22 includes a vent 27 for routing gases out of the
canister 22 to the atmosphere when storing, or trapping, fuel
vapors from fuel tank 218. Vent 27 may also allow fresh air to be
drawn into fuel vapor canister 22 when purging stored fuel vapors
to engine intake 23 via purge lines 90 or 92 (depending on boost
level) and purge valve 112. While this example shows vent 27
communicating with fresh, unheated air, various modifications may
also be used. Vent 27 may include a canister vent valve 114 to
adjust a flow of air and vapors between canister 22 and the
atmosphere. The vent valve may be opened during fuel vapor storing
operations (for example, during fuel tank refueling and while the
engine is not running) so that air, stripped of fuel vapor after
having passed through the canister, can be pushed out to the
atmosphere. Likewise, during purging operations (for example,
during canister regeneration and while the engine is running), the
vent valve may be opened to allow a flow of fresh air to strip the
fuel vapors stored in the canister.
[0044] Fuel vapors released from canister 22, for example during a
purging operation, may be directed into engine intake manifold 160
via purge line 28. The flow of vapors along purge line 28 may be
regulated by canister purge valve 112, coupled between the fuel
vapor canister and the engine intake. The quantity and rate of
vapors released by the canister purge valve may be determined by
the duty cycle of an associated canister purge valve solenoid (not
shown). As such, the duty cycle of the canister purge valve
solenoid may be determined by the vehicle's powertrain control
module (PCM), such as controller 12, responsive to engine operating
conditions, including, for example, engine speed-load conditions,
an air-fuel ratio, a canister load, etc.
[0045] An optional canister check valve (not shown) may be included
in purge line 28 to prevent intake manifold pressure from flowing
gases in the opposite direction of the purge flow. As such, the
check valve may be necessary if the canister purge valve control is
not accurately timed or the canister purge valve itself can be
forced open by a high intake manifold pressure. An estimate of the
manifold absolute pressure (MAP) may be obtained from MAP sensor
182 coupled to intake manifold 160, and communicated with
controller 12. Alternatively, MAP may be inferred from alternate
engine operating conditions, such as mass air flow (MAF), as
measured by a MAF sensor coupled to the intake manifold.
[0046] Purge hydrocarbons may be directed to intake manifold 160
via either a boost path 92 or a vacuum path 90 based on engine
operating conditions. Specifically, during conditions when
turbocharger 120 is operated to provide a boosted aircharge to the
intake manifold, the elevated pressure in the intake manifold
causes one-way valve 94 in the vacuum path 90 to close while
opening one-way valve 96 in the boost path 92. As a result, purge
air is directed into the air intake passage 140, downstream of air
filter 156 and upstream of charge air cooler 154 via the boost path
92. Herein, the purge air is introduced upstream of intake oxygen
sensor 172. In some embodiments, as depicted, a venturi 98 may be
positioned in the boost path such that the purge air is directed to
the intake upon passing through the venturi and passage 99. This
allows the flow of compressor bypass air to be advantageously
harnessed for enhanced purge flow.
[0047] During conditions when engine 10 is operated without boost,
elevated vacuum in the intake manifold causes one-way valve 94 in
the vacuum path to open while closing one-way valve 96 in the boost
path. As a result, purge air is directed into the intake manifold
160, downstream of throttle 158 via the vacuum path 90. Herein, the
purge air is introduced downstream of intake oxygen sensor 172,
directly into intake manifold 160, and therefore does not affect
the output of oxygen sensor 172. In comparison, during conditions
when engine 10 is operated with boost, the purge air is introduced
upstream of intake oxygen sensor 172, and therefore does affect the
output of oxygen sensor 172.
[0048] PCV hydrocarbons may also be directed to intake manifold 160
via either a boost side PCV hose 252 or a vacuum side PCV hose 254
based on engine operating conditions. Specifically, blow-by gases
from engine cylinders 14 flow past the piston rings and enter
crankcase 255. During conditions when turbocharger 120 is operated
to provide a boosted aircharge to the intake manifold, the elevated
pressure in the intake manifold causes one-way valve 256 in vacuum
side PCV hose 254 to close. As a result, PCV air is directed into
the air intake passage 140, downstream of air filter 156 and
upstream of charge air cooler 154 via boost side PCV hose 252. The
PCV flow may be directed to the intake passage upon passage through
a boost side oil separator 260. The boost side oil separator may be
integrated into the cam cover or may be an external component.
Thus, during boosted conditions, the PCV gases are introduced
upstream of intake oxygen sensor 172 therefore do affect the output
of oxygen sensor 172.
[0049] In comparison, during conditions when engine 10 is operated
without boost, elevated vacuum in the intake manifold causes
one-way valve 256 in the vacuum side PCV hose 254 to open. As a
result, PCV air is directed into the intake manifold 160, directly,
downstream of throttle 158 via the vacuum side PCV hose 254.
Herein, the PCV air is introduced downstream of intake oxygen
sensor 172, and therefore does not affect the output of oxygen
sensor 172.
[0050] Thus, due to the specific engine configuration, during
engine idle conditions, when no boosted aircharge is provided, a
reference point (herein also referred to as the zero point) of the
intake air sensor may be learned without incurring interference
from PCV and purge air hydrocarbons.
[0051] As such, the intake air oxygen sensor can be used to measure
the amount of EGR in the intake aircharge as a function of the
amount of change in oxygen content due to the addition of EGR as a
diluent. Thus, as more EGR is introduced, a sensor output
corresponding to a lower oxygen concentration may be output.
However, to accurately determine this change in the amount of
oxygen, it is important to know the oxygen reading of the sensor
when no EGR is present. This reference point, also known as a zero
point, needs to be calibrated and learned. However, the zero point
reading has a large range of values that vary based on intake
pressure, sensor age, and part-to-part variation, rendering
accurate EGR measurement difficult.
[0052] FIG. 3 depicts this variation in the reading of the intake
sensor. Specifically, map 300 depicts intake pressure along the
x-axis and a pumping current output by the sensor, upon application
of a reference voltage, along the y-axis. Plots 301a-d show a first
set of intake oxygen sensor outputs at a first condition with no
EGR. Plots 302a-d, 303a-d, and 304a-d show the sensor outputs at
gradually increasing EGR levels, with 304a-d representing a nominal
EGR percentage.
[0053] As can be seen by comparing the output at any given intake
pressure (compare 301a to 301b, c, and d, and likewise for each
set), a large amount of piece to piece variation occurs in the base
oxygen measurement output by the sensor. As such, this
piece-to-piece variation accounts for the largest amount of
variation in the output of a given sensor. In addition, aging of
the sensor adds to the variation. The variation makes learning of
the zero point difficult, confounding the results of an EGR
estimation.
[0054] As elaborated with reference to FIG. 4, the variation can be
reduced by performing an idle adaptation for the sensor at each
engine start. Specifically, at the first engine idle since every
engine start, a zero point of the sensor may be learned and
updated. This allows part-to-part variation and sensor aging to be
learned and compensated for. By then using the most recently
learned zero point as a reference for EGR estimation, EGR amounts
can be determined more accurately and reliably.
[0055] Now turning to FIG. 4, an example routine 400 for learning a
zero point of an intake oxygen sensor during selected engine idling
conditions is shown. The method allows for a reference point of the
sensor to be accurately learned without being confounded by PCV or
purge hydrocarbons. In addition by learning the relationship
between the intake pressure and the oxygen sensor output, oxygen
concentrations and EGR flow can be measured accurately even if
there is any inaccuracy in either sensor.
[0056] At 402, the routine includes estimating and/or measuring
engine operating conditions. These may include, for example, engine
speed, torque demand, barometric pressure, engine temperature, etc.
Next it may be determined if selected engine idling conditions are
present. As elaborated below at 404 and 406, the selected engine
idling conditions may include a first engine idle since
installation of one of a new intake oxygen sensor or new intake
pressure sensor, or a first engine idle since an engine start.
[0057] Specifically, at 404, it may be determined if a new intake
air oxygen (IAO2) sensor or a new intake pressure sensor was
installed in the vehicle. For example, it may be determined if a
new sensor was installed since the last engine shut-down and the
current engine start. In one example, following installation of a
new sensor, an indication that calibration of the new sensor is
required may be received at the controller.
[0058] If a new oxygen sensor or pressure sensor was installed,
then at 405, the routine includes resetting the previously learned
adaptive values of the intake air oxygen sensor. That is, the
previously learned zero point and pressure correction factors saved
in a look-up table of the controller's memory (e.g., in the KAM)
may be reset. Then, the table may be repopulated with data from the
current zero point learning, and subsequent iterations of the
routine.
[0059] If a new oxygen or pressure sensor was not installed, or
after resetting the table if a new sensor was installed, the
routine proceeds to 406 to confirm a first engine idle condition
since the current engine start. If a first engine idle condition is
not confirmed, at 407, the look-up table in the controller's memory
may not be further updated and the current zero point readings may
be used. As such, by re-learning the reference point each time a
new sensor is installed, differences in oxygen sensor readings due
to part-to-part variations can be better accounted for. By updating
and re-learning the reference point on each engine start,
differences in oxygen sensor readings due to sensor aging can be
better accounted for.
[0060] Upon confirmation of a first engine idle condition since the
current engine start, at 408, the routine includes learning a
reference point for the intake oxygen sensor at a reference intake
pressure during the selected engine idling condition. Specifically,
the controller may learn the oxygen sensor output at the first
engine idle condition and may also note the reference intake
pressure at which the oxygen sensor output was learned. The
controller may update the look-up table saved in the controller's
KAM with the oxygen sensor output learned at the given pressure. In
one example, the reference intake pressure is a throttle inlet
pressure estimated by a TIP sensor coupled to the intake manifold
at a location similar to the oxygen sensor (e.g., downstream of the
charge air cooler and upstream of the intake throttle). In another
example, the reference intake pressure is a manifold pressure
estimated by a MAP sensor coupled to the intake manifold at a
location similar to the oxygen sensor.
[0061] As such, learning the reference point includes learning a
relationship between a first output of the intake oxygen sensor at
a first intake pressure during the first engine idle since start,
and then using the learned relationship, the idle reference oxygen
(iao2_ref) at the reference pressure (iao2_ref_press) is
calculated. It is calculated by determining a correction factor
(iao2_press_corr) as:
iao2_press_corr=a0+a1*(iao2_ref_press-iao2_press)+a2*(iao2_ref_press-iao-
2.sup.+press).sup.2
[0062] The idle reference oxygen is then calculated as:
iao2_ref=iao2_o2*iao2_press_corr
[0063] By performing this learning during idle conditions, various
advantages are achieved. First, any error caused due to noise
factors from purge or PCV hydrocarbons is reduced. Second, since
pressure changes at the intake oxygen sensor location are minimal
during idle conditions, changes in the oxygen sensor output due to
the pressure effect (as described at FIG. 3) are also minimized.
Overall, a more accurate zero point learning can be achieved.
[0064] At 410, the intake oxygen sensor output is corrected for
humidity. As elaborated with reference to FIG. 8, the output of the
intake oxygen sensor estimated at the reference pressure is
corrected with a correction factor based on ambient humidity. This
may include correcting for no humidity (that is, zero % humidity or
dry conditions) wherein the output of the oxygen sensor is
corrected by removing all the contribution of humidity.
Alternatively, this may include correcting to a known standard or
reference humidity level. For example, the oxygen sensor output may
be corrected to a reference 1.2% of humidity.
[0065] At 412, it may be determined if the idle adaptation is
complete. As such, the intake oxygen sensor readings at the given
reference intake pressure may be monitored for a duration of the
first engine idle since the engine start and the look-up table may
be continue to be populated over the duration with readings from
the intake oxygen sensor. In one example, when the idle adaptation
is initiated at 408, a timer may be started and at 412, it may be
determined if a threshold duration has elapsed on the timer. In one
example, the idle adaptation may be complete if 15 seconds has
elapsed.
[0066] Upon confirming that the idle adaptation has been completed,
at 414, the routine includes calculating a pressure correction
factor. The pressure correction factor is a factor that compensates
for the effect of intake pressure on the output of the intake
oxygen sensor. The pressure correction factor is determined by
taking the ratio of the measured oxygen and the reference oxygen
reading (iao2_ref), the reference oxygen reading being the
reference oxygen reading of the intake oxygen sensor at the
reference pressure. Nominally, the reference pressure may be 100
kPa. The pressure correction adaptation may be performed by
calculating a pressure correction factor based on the output of the
intake oxygen sensor (iao2_o2) relative to the zero point
(iao2_ref) of the sensor (that is, iao2_o2/iao2_ref). In addition,
a delta pressure may also be determined based on the reference
pressure, wherein the delta pressure is calculated as
TIP-iao2_ref_press. Herein, TIP may be the same as boost pressure.
The delta pressure is calculated as the difference between the
measured boost pressure TIP and the reference pressure. The delta
pressure from the reference pressure provides information about the
change in oxygen reading from iao2_ref versus the change in the
pressure from the reference pressure. The reference pressure
corresponds with the pressure at which iao2_ref was determined.
[0067] At 418, the routine includes calculating and learning the
zero point of the intake oxygen sensor. This may include, for
example, performing a recursive least squares adaptation for
pressure correction. The correction may be denoted as:
Iao2_press_corr_new=a2*dp_corr.sup.2+a1*dp_corr+a0,
wherein a0, a1, and a2 are pressure correction coefficients, and
dp_corr is the delta pressure correction (that is, delta pressure
from reference pressure).
[0068] Once the zero point is learned, an EGR flow to the engine
can be adjusted based on an output of the intake oxygen sensor
during EGR conditions, as elaborated at FIG. 9. Therein, an EGR
flow to the engine is adjusted based on an intake oxygen
concentration estimated by the intake oxygen sensor relative to the
learned reference point, and further based on a change in intake
pressure relative to the reference intake pressure (where the
reference point was learned).
[0069] At 420, the routine includes diagnosing an EGR valve based
on the zero point estimated during the idle adaptation relative to
a zero point estimated during selected engine non-fueling
conditions, such as during a deceleration fuel shut off (DFSO)
adaptation. An example DFSO adaptation is described in FIG. 5. As
such, the zero point learned during the idle adaptation may be a
first learned reference point, while the zero point learned during
the DFSO adaptation may be a second learned reference point (both
learned at a given reference intake pressure). As elaborated at
FIG. 6, the controller may indicate EGR valve degradation based on
a difference between the first learned reference point and the
second learned reference point being larger than a threshold
amount.
[0070] As such, while the idle adaptation performed during idle
conditions removes the effect of purge and PCV hydrocarbons on the
intake oxygen sensor output, as well as the effect of pressure
variations, the idle adaptation is susceptible to EGR leakage.
Thus, if the EGR valve is leaking, assuming there is no EGR
backflow, EGR may flow over the intake oxygen sensor even during
the idle conditions. As a result, the output from the oxygen sensor
output may be lower than the actual value. In comparison, an
adaptation performed during DFSO is insensitive to the effect of a
leaking EGR valve. This is because even if the valve were leaking,
the leaking "EGR" would be air since no fuel is being injected
during these conditions. As a result, the exhaust leak does not
affect the output of the oxygen sensor. Thus, by comparing the zero
point learned during the idle adaptation with the zero point
learned during the DFSO adaptation, EGR valve leakage can be
identified.
[0071] An example idle adaptation is shown with reference to FIG.
7. Map 700 depicts an idle adaptation timer at plot 702, and a
change in oxygen concentration sensed by the intake oxygen sensor
at plot 704.
[0072] Prior to t1, idle adaptation conditions may not be present.
At t1, a first engine idle since an engine start may be confirmed
and an idle adaptation timer may be started. Plot 704 (solid line)
shows a zero point of the intake oxygen sensor relative to an
expected value 708. Plot 706 (dashed line) shows the intake sensor
output. As such, prior to the idle adaptation, the deviation of the
estimated zero point from the expected zero point is larger. Then,
during the adaptation, based on the sensor reading (plot 706), the
zero point is corrected and the learned zero point gradually merges
with the expected value. At t2, the idle adaptation is completed
and the learned zero point is used for accurate EGR control.
[0073] In one example, a method for an engine comprises: learning a
relationship between a first intake oxygen sensor output estimated
at a first intake pressure during a first engine idle since engine
start, and adjusting EGR flow to the engine at a second intake
pressure based on a second intake oxygen sensor output estimated at
the second intake pressure and the learned relationship. The
adjusting includes calculating a pressure correction factor based
on a difference between the first intake pressure and the second
intake pressure, calculating a humidity correction factor based on
a difference between ambient humidity at the second intake pressure
and a reference humidity, modifying the second intake oxygen sensor
output based on each of the calculated pressure correction factor,
humidity correction factor, and the learned relationship, and
adjusting a position of an EGR valve based on the modified second
intake oxygen sensor output. The EGR valve may be coupled in a low
pressure EGR passage and wherein the learning is performed at a
first engine idle following each engine restart. Herein, each of
the first and second intake oxygen sensor output is generated by an
intake oxygen sensor coupled upstream of an intake throttle and
downstream of a charge air cooler, and each of the first and second
intake pressure is estimated by an intake pressure sensor coupled
upstream of the intake throttle and downstream of the charge air
cooler. The learning is performed at a first engine idle following
installation of one or more of the intake oxygen sensor and the
intake pressure sensor in the engine, so as to correct for
part-to-part variations as well as sensor aging. In addition,
degradation of the EGR valve can be indicated based on the first
intake oxygen sensor output estimated at the first intake pressure
during the first engine idle since engine start relative to a
second intake oxygen sensor output estimated at the first intake
pressure during an engine deceleration fuel shut-off condition.
[0074] Now turning to FIG. 5, an example routine 500 for learning a
zero point of an intake oxygen sensor during selected engine
non-fueling conditions is shown. The method allows for a reference
point of the sensor to be accurately learned without being
confounded by EGR valve leakage.
[0075] At 502, as at 402, the routine includes estimating and/or
measuring engine operating conditions. These may include, for
example, engine speed, torque demand, barometric pressure, engine
temperature, etc. Next it may be determined if selected engine
non-fueling conditions are present. As elaborated below, the
selected engine non-fueling conditions may include a deceleration
fuel shut-off condition. The routine may be repeated at the first
DFSO event after every engine start and/or the first DFSO event
after a new oxygen or pressure sensor is installed.
[0076] At 504, it may be determined if a new intake air oxygen
(IAO2) sensor or a new intake pressure sensor was installed in the
vehicle. For example, it may be determined if a new sensor was
installed since the last engine shut-down and the current engine
start. In one example, following installation of a new sensor, an
indication that calibration of the new sensor is required may be
received at the controller.
[0077] If a new oxygen sensor or pressure sensor was installed,
then at 505, the routine includes resetting the previously learned
adaptive values of the intake air oxygen sensor. That is, the
previously learned zero point and pressure correction factors saved
in a look-up table of the controller's memory (e.g., in the KAM)
may be reset. Then, the table may be repopulated with data from the
current zero point learning, and subsequent iterations of the DFSO
adaptation routine.
[0078] If a new oxygen or pressure sensor was not installed, or
after resetting the table if a new sensor was installed, the
routine proceeds to 506 to confirm if engine non-fueling conditions
are present. Specifically, a deceleration fuel shut off (DFSO)
condition may be confirmed. If a DFSO condition is not confirmed,
at 507, the look-up table in the controller's memory may not be
further updated and the current zero point readings may be used. As
such, by re-learning the reference point each time a new sensor is
installed, differences in oxygen sensor readings due to
part-to-part variations can be better accounted for. By updating
and re-learning the reference point on each engine start,
differences in oxygen sensor readings due to sensor aging can be
better accounted for.
[0079] Upon confirmation of the DFSO condition, at 508, the routine
includes learning a reference point for the intake oxygen sensor at
a reference intake pressure during the non-fueling condition.
Specifically, the controller may learn the oxygen sensor output at
the first engine idle condition and may also note the reference
intake pressure at which the oxygen sensor output was learned. The
controller may update the look-up table saved in the controller's
KAM with the oxygen sensor output learned at the given pressure. In
one example, the reference intake pressure is a throttle inlet
pressure estimated by a TIP sensor coupled to the intake manifold
at a location similar to the oxygen sensor (e.g., downstream of the
charge air cooler and upstream of the intake throttle). In another
example, the reference intake pressure is a manifold pressure
estimated by a MAP sensor coupled to the intake manifold at a
location similar to the oxygen sensor.
[0080] As such, learning the reference point includes learning a
relationship between a first output of the intake oxygen sensor at
a first intake pressure during the first DFSO event since engine
start, and then using the learned relationship to determine the
zero point. The learned relationship is used to determine the zero
point by calculating the oxygen reading at the reference pressure,
by substituting the delta pressure from the reference pressure. By
performing this learning during DFSO conditions, various advantages
are achieved. First, any error caused due to noise factors from
purge or PCV hydrocarbons is reduced. Second, errors due to EGR
valve leakage are reduced. This is because during the non-fueling
conditions, any leaked "EGR" is the same as the intake air.
Overall, a more accurate zero point learning can be achieved.
[0081] At 510, the intake oxygen sensor output is corrected for
humidity. As elaborated with reference to FIG. 8, the output of the
intake oxygen sensor estimated at the reference pressure is
corrected with a correction factor based on ambient humidity. As
such, this may include correcting for no humidity (that is, zero %
humidity or dry conditions) wherein the output of the oxygen sensor
is corrected by removing all the contribution of humidity.
Alternatively, this may include correcting to a known standard or
reference humidity level. For example, the oxygen sensor output may
be corrected to a reference 1.2% of humidity.
[0082] At 512, it may be determined if the DFSO adaptation is
complete. As such, the intake oxygen sensor readings at the given
reference intake pressure may be monitored for a duration of the
DFSO and the look-up table may be continue to be populated over the
duration with readings from the intake oxygen sensor. In one
example, when the DFSO is initiated at 508, a timer may be started
and at 512, it may be determined if a threshold duration has
elapsed on the timer. In one example, the DFSO adaptation may be
complete if 4 seconds has elapsed.
[0083] Upon confirming that the DFSO adaptation has been completed,
at 514, the routine includes calculating a pressure correction
factor. The pressure correction factor is a factor that compensates
for the effect of intake pressure on the output of the intake
oxygen sensor. The pressure correction adaptation may be performed
by calculating a pressure correction factor based on the output of
the intake oxygen sensor (iao2_o2) relative to the zero point
(iao2_ref) of the sensor (that is, iao2_o2/iao2_ref). In addition,
a delta pressure may also be determined based on the reference
pressure, wherein the delta pressure is calculated as
TIP-iao2_ref_press. Herein, TIP may be the same as boost pressure.
At idle condition, the reference intake oxygen and preference
intake pressure are determined. The pressure correction factor at a
given pressure condition is calculated as the ratio of intake
oxygen sensor reading and the reference oxygen concentration (that
is, iao2_o2/iao2_ref). This corrected factor is learned as a
relation between the delta pressure and the reference pressure. By
doing this, the pressure input into the relationship is normalized
to the reference pressure.
[0084] At 518, the routine includes calculating and learning the
zero point of the intake oxygen sensor. This may include, for
example, performing a recursive least squares adaptation for
pressure correction. The correction may be denoted as:
Iao2_press_corr_new=a2*dp_corr.sup.2+a1*dp_corr+a0,
wherein a0, a1, and a2 are pressure correction coefficients, and
dp_corr is the delta pressure correction.
[0085] Once the zero point is learned, an EGR flow to the engine
can be adjusted based on an output of the intake oxygen sensor
during EGR conditions, as elaborated at FIG. 9. Therein, an EGR
flow to the engine is adjusted based on an intake oxygen
concentration estimated by the intake oxygen sensor relative to the
learned reference point, and further based on a change in intake
pressure relative to the reference point
[0086] At 520, the routine includes diagnosing an EGR valve based
on the zero point estimated during the DFSO adaptation relative to
a zero point estimated during an idle adaptation. An example idle
adaptation is described in FIG. 4. As such, the zero point learned
during the idle adaptation may be a first learned reference point,
while the zero point learned during the DFSO adaptation may be a
second learned reference point (both learned at a given reference
intake pressure). As elaborated at FIG. 6, the controller may
indicate EGR valve degradation based on a difference between the
first learned reference point and the second learned reference
point being larger than a threshold amount.
[0087] Turning now to FIG. 8. An example routine 800 is shown for
correcting a nominal output of an intake oxygen sensor during zero
point learning based on an ambient humidity estimate. The routine
allows for oxygen displaced by the humidity to be accounted
for.
[0088] At 802, the routine includes confirming that zero point
learning is enabled. Specifically, it may be confirmed that either
idle adaptation or DFSO adaptation of the intake oxygen sensor is
being performed, as previously discussed with reference to FIGS.
4-5.
[0089] Upon confirmation, at 804, the routine includes learning a
reference point for the intake oxygen sensor at a reference intake
pressure. This includes learning a nominal amount of oxygen based
on an output of the intake oxygen sensor at the reference intake
pressure during selected engine idling conditions or selected
engine non-fueling conditions. As such, the reference intake
pressure is one of a throttle inlet pressure and an intake manifold
pressure. The selected engine idling conditions include a first
engine idle since an engine start, a first engine idle since
installation of the intake oxygen sensor or installation of an
intake pressure sensor configured to estimate the reference intake
pressure. The selected non-fueling conditions include a
deceleration fuel shut-off condition.
[0090] At 806, an intake oxygen concentration is estimated based on
the sensor output. At 808, ambient humidity is estimated, for
example, via an intake manifold humidity sensor (such as sensor 173
of FIG. 1). At 810, the routine includes calculating an amount of
oxygen displaced by the estimated ambient humidity. As such, the
change in oxygen concentration due to humidity may be defined as
per the equation:
O.sub.2MeasuredConcentration=21%/1+volume % g water,
wherein O.sub.2MeasuredConcentration is the measured oxygen
concentration with volume % water (fraction) amount of water in air
(that is, humidity).
[0091] At 812, it may be determined if the nominal oxygen
concentration is to be corrected based on the ambient humidity to
reflect dry conditions or standard humidity conditions. In one
example, during a first condition (at 814), the reference point may
be calibrated to dry conditions (zero humidity) where the effect of
all humidity is removed from the oxygen sensor output. In another
example, during a second condition (at 816), the reference point
may be calibrated to standard humidity conditions where the effect
of humidity on the oxygen sensor output is corrected to pre-defined
humidity conditions. An example of a standard humidity condition
may be a humidity of 8 g/kg or 1.28%.
[0092] If dry condition calibration is selected, then at 814, the
routine includes correcting the learned reference point by adding
the calculated amount of oxygen to the learned nominal amount of
oxygen. This corrects the reference point to dry air conditions
(that is, zero humidity) and the effect of all humidity on the
oxygen sensor output is removed. The routine then moves to 820 to
update the zero point value in the adaptive values table.
Specifically, the corrected zero point is learned with relation to
the reference intake pressure and stored in the controller's
memory.
[0093] If the standard humidity condition calibration is selected,
then at 816, the routine includes adding the calculated amount of
oxygen to the learned nominal amount of oxygen, as at 814. Then, at
818, after correcting the reference point to dry air, the routine
includes further calibrating the reference point to a standard
humidity level. In one example, the standard humidity level is 1.2%
humidity. The routine then proceeds to 520 to update the zero point
value in the adaptive values table.
[0094] As such, the humidity corrected zero point is then used to
estimate EGR and adjust EGR flow. For example, the controller may
subsequently (that is, after learning and during engine non-idling
conditions) adjust EGR flow to the engine based on an intake oxygen
concentration estimated by the sensor relative to the corrected
reference point, and further based on a change in intake pressure
from the reference intake pressure.
[0095] In one example, the intake oxygen sensor reading may
correspond to 19.5% oxygen and the estimated ambient humidity read
by the humidity sensor may be 30 grams/KG of air. The humidity
reading may be converted to molar percent of water as per the
calculation 100*(30/1000)*29/18=4.83%, where 29 is the molecular
weight of air and 18 is the molecular weight of water. The 4.83%
water displaces an amount of oxygen corresponding to
4.83*21/100=1.01% oxygen, where 21 is the atmospheric dry oxygen
reading. The corrected dry air reading of the intake oxygen sensor
is then calculated as 19.5% (intake air sensor reading)+1.01%
(humidity correction)=20.5%.
[0096] Alternatively, the dry air oxygen reading learned above is
further adjusted to a standard humidity level oxygen reading.
Therein, the humidity sensor information is used to calculate the
dry air oxygen reading which is then adjusted with the amount of
oxygen that would be displaceable by a calibratable amount of
humidity. With reference to the above example, if the calibratable
amount of humidity is 10 g/KG of air, the displaced oxygen
corresponding to this amount of humidity would be 0.34%. The
nominal intake oxygen sensor reading would then be adjusted to
20.5% (dry air reading)-0.34% (displaced oxygen for the calibrated
humidity level)=20.16%.
[0097] As another example, an engine system may comprise an engine
including an intake manifold, a turbocharger including an exhaust
turbine and an intake compressor, a charge air cooler coupled
downstream of the compressor, and an intake oxygen sensor coupled
to the intake manifold downstream of the charge air cooler and
upstream of an intake throttle. Alternatively, the intake oxygen
sensor can be located upstream of the CAC if the total LP-EGR
concentration going to the engine is well mixed. The engine system
may further include a pressure sensor coupled to the intake
manifold downstream of the charge air cooler and upstream of the
intake throttle, as well as a humidity sensor coupled to the intake
manifold downstream of the charge air cooler and upstream of an
intake throttle. An EGR system may be included in the engine
including an EGR passage and EGR valve for recirculating exhaust
residuals from downstream of the turbine to upstream of the
compressor. An engine controller may be configured with computer
readable instructions for: during a first engine idle since an
engine start, learning an oxygen sensor output and a humidity
sensor output at a reference intake pressure and adjusting the
oxygen sensor output based on the humidity sensor output. Then,
during subsequent engine non-idle conditions, the controller may be
configured to adjust an opening of the EGR valve based on an intake
oxygen concentration estimated by the intake oxygen sensor relative
to the reference oxygen sensor output, and further based on an
intake pressure relative to the reference intake pressure. Herein,
adjusting the oxygen sensor output based on the humidity sensor
output includes, during a first condition at idle, estimating a
first amount of oxygen displaced by total humidity based on the
humidity sensor output and adjusting (e.g., increasing) the
reference oxygen sensor output for either dry or standard humidity
conditions. In comparison, during a second condition, such as
non-idle conditions, the oxygen sensor can reliably predict the
oxygen concentration and adjust the EGR valve accordingly having
been previously corrected for part to part variations, change over
time and variable humidity levels.
[0098] In this way, a controller may correct a first, nominal
output of an intake oxygen sensor, learned during selected engine
idling conditions at a reference intake pressure, based on an
measured ambient humidity. The selected engine idling conditions
include one of a first engine idle from engine start, a first
engine idle following installation of the intake oxygen sensor, and
a first engine idle following installation of an intake pressure
sensor. The controller may then adjust EGR flow to the engine based
on a second output of the sensor, estimated at a second intake
pressure, relative to the corrected first output. The EGR flow may
be further adjusted based on the second intake pressure relative to
the reference intake pressure.
[0099] The correcting performed by the controller may include
calculating an amount of oxygen displaced by the estimated ambient
humidity, and increasing the first output to include the amount of
displaced oxygen, wherein the increased first output is indicative
of a dry air oxygen content. In this way, the effect of all
humidity is removed from the oxygen sensor output. The correcting
may alternatively further include adjusting the increased first
output based on an amount of oxygen displaceable by a calibrated
humidity level, the adjusted output indicative of a calibrated
humidity air oxygen content. In this way, the oxygen sensor output
is calibrated to a standard humidity level.
[0100] The controller may adjust the EGR flow by estimating a
delivered EGR flow based on a difference between the second output
and the corrected first output, and adjusting a position of an EGR
valve based on a difference between the delivered EGR flow and a
target EGR flow, wherein the target EGR flow based on engine
speed-load conditions.
[0101] Now turning to FIG. 6, an example routine 600 for diagnosing
an EGR valve coupled to a low pressure EGR system based on intake
oxygen sensor reference points learned during an idle adaptation
and a DFSO adaptation is shown. The method allows an EGR valve leak
to be identified and compensated for.
[0102] At 602, the routine includes retrieving a first reference
point learned during an idle adaptation (ref_idle) such as the idle
adaptation of FIG. 4. At 604, the routine includes retrieving a
second reference point learned during a DFSO adaptation (ref DFSO)
such as the DFSO adaptation of FIG. 5. At 606, the two reference
points may be compared and it may be determined if there are any
discrepancies between them. Specifically, it may be determined if
the first reference point is within a threshold range of the second
reference point, or if they differ by more than a threshold amount.
The controller may then indicate EGR valve leakage based on the
first reference point of the intake oxygen sensor learned during
engine idling conditions relative to the second reference point of
the oxygen sensor learned during engine non-fueling conditions.
Specifically, at 610, EGR valve leakage is indicated based on a
difference between the first reference point and the second
reference point being larger than a threshold. The controller may
indicate the EGR valve degradation by setting a diagnostic code. In
comparison, at 608, no EGR valve leakage is indicated when the
difference is smaller than the threshold.
[0103] As discussed at FIG. 9, based on the indication of EGR valve
leakage, EGR control responsive to an output of the intake oxygen
sensor may be adjusted. Specifically, in response to the indication
of no EGR valve leakage, the EGR valve may be feed-forward adjusted
based on engine speed-load conditions and feedback adjusted based
on an output of the intake manifold sensor relative to one of the
first and second reference point. In comparison, in response to an
indication of EGR valve leakage, the controller may continue
feed-forward adjusting the EGR valve based on engine speed-load
conditions but may terminate feedback adjusting of the EGR valve
based on the output of the intake manifold sensor relative to one
of the first and second reference point.
[0104] As used herein, indication EGR valve degradation includes
indicating leakage of an EGR valve coupled to a low pressure EGR
passage configured to recirculate exhaust residuals from an exhaust
manifold, downstream of a turbine to an intake manifold, upstream
of a compressor. The intake oxygen sensor may be coupled to the
engine intake manifold, upstream of an intake throttle and either
upstream or downstream of a charge air cooler, the cooler coupled
downstream of the compressor. Herein, each of the first and second
reference points are learned at a reference intake pressure, the
reference intake pressure estimated by an intake pressure sensor
coupled to the engine intake manifold, upstream of the intake
throttle and downstream of the charge air cooler.
[0105] Now turning to FIG. 9, routine 900 depicts an example method
for performing EGR control using the output of an intake manifold
oxygen sensor relative to a zero point of the sensor learned during
an idle adaptation and/or a DFSO adaptation. The method further
adjusts the feed-forward feedback components of EGR control based
on any indication of EGR valve degradation.
[0106] At 902, the output of an intake manifold oxygen sensor is
received. An intake pressure at which the output was received is
also noted since the output is affected by intake pressure. At 904,
a pressure correction of the output is performed based on the
intake pressure at which the sensor output was taken relative to a
reference intake pressure. Also at 904, a difference between the
pressure-corrected oxygen sensor output and the zero point of the
oxygen sensor is learned. As such, as an amount of EGR flow
increases, exhaust dilution of intake air increases, reducing the
amount of oxygen available in the intake air, and thereby reducing
the output of the intake sensor. The EGR dilution may be reflected
as a drop in oxygen concentration sensed by the intake oxygen
sensor.
[0107] Thus at 906, a change in oxygen concentration may be
determined based on the determined difference between the oxygen
sensor output relative to the zero point. At 908, an amount of EGR
dilution of intake air is determined based on the change in oxygen
concentration. At 910, an EGR flow is controlled based on the EGR
dilution determined and the desired EGR. As used herein, the EGR
flow may be a low pressure EGR flow along an EGR passage from an
exhaust manifold, downstream of an exhaust turbine, to an intake
manifold, upstream of an intake compressor, via an EGR valve. In
addition, the EGR may be provided at a fixed rate or variable rate
relative to intake air flow based on engine operating conditions.
For example, at all engine speed-load conditions from a medium load
down to a minimum load, low pressure EGR may be delivered at a
fixed rate relative to the intake air flow (that is, at a fixed EGR
percentage). In comparison, at engine speed-load conditions above a
medium load, low pressure EGR may be delivered at a variable rate
relative to the intake air flow (that is, at a variable EGR
percentage).
[0108] Controlling the EGR flow includes, at 911, feed-forward
adjusting the EGR valve based on engine operating conditions, such
as speed-load conditions. For example, at higher engine speed-load
conditions, an opening of the EGR valve may be increased while at
lower engine speed-load conditions, the EGR valve opening may be
decreased. In addition, at 912, the controlling includes feedback
adjusting the EGR valve based on the calculated EGR flow relative
to a desired EGR flow. For example, if the actual flow estimated by
the intake oxygen sensor exceeds the desired or expected flow, the
EGR valve opening may be decreased. As another example, if the
actual flow estimated by the intake oxygen sensor is below the
desired or expected flow, the EGR valve opening may be
increased.
[0109] At 914, it may be determined if there is an indication of
EGR valve leakage. As elaborated at FIG. 6, EGR valve leakage may
be identified based on deviations between an oxygen sensor zero
point learned using the idle adaptation and a zero point learned
using the DFSO adaptation. If no EGR valve leakage is identified,
the routine may end. Else at 816, in response to the indication of
EGR valve leakage, the controller may terminate the feedback
adjustment of the EGR valve based on the output of the intake
oxygen sensor and temporarily shift to using only feed-forward
control of the EGR valve. In alternate embodiments, in response to
the indication of EGR valve leakage, EGR may be transiently
disabled or a diagnostic flag may be set.
[0110] In other words, in response to an indication of no EGR valve
leakage, the EGR valve is feed-forward adjusted based on engine
speed-load conditions and feedback adjusted based on an output of
the intake manifold sensor relative to at least one of the first
and second reference points learned during idle and DFSO
adaptations, respectively. In comparison, in response to an
indication of EGR valve leakage, the EGR valve is only feed-forward
adjusted based on engine speed-load conditions while feedback
adjusting of the EGR valve based on the output of the intake
manifold sensor relative to at least one of the first and second
reference points is terminated. This allows EGR control to be
improved when EGR valve leakage is known.
[0111] In one example, an engine system comprises an engine
including an intake manifold, a turbocharger including an exhaust
turbine and an intake compressor, a charge air cooler coupled
downstream of the compressor, and an intake oxygen sensor coupled
to the intake manifold downstream of the charge air cooler and
upstream of an intake throttle. A pressure sensor may be coupled to
the intake manifold downstream of the charge air cooler and
upstream of the intake throttle. The engine system may further
comprise an EGR system including an EGR passage and EGR valve for
recirculating exhaust residuals from downstream of the turbine to
upstream of the compressor. A controller of the engine system may
be configured with computer readable instructions for: during a
first engine idle since an engine start, learning a reference point
for the oxygen sensor at a reference intake pressure; and adjust an
opening of the EGR valve based on an intake oxygen concentration
estimated by the sensor relative to the learned reference point,
and further based on an intake pressure relative to the reference
intake pressure. The controller may additionally, or optionally,
during an engine deceleration fuel shut-off condition, learn a
reference point for the oxygen sensor at the reference intake
pressure; and adjust an opening of the EGR valve based on an intake
oxygen concentration estimated by the sensor relative to the
learned reference point, and further based on an intake pressure
relative to the reference intake pressure. The engine system may
further comprise a humidity sensor for estimating an ambient
humidity, the controller then further adjusting the opening of the
EGR valve based on an ambient humidity relative to a reference
humidity. The controller may further determine degradation of the
EGR valve based on differences between the reference points learned
during the idle condition relative to the DFSO condition.
[0112] In this way, a relationship between an intake oxygen sensor
and an intake pressure sensor can be learned at varying humidity
conditions, and an EGR flow can be learned based on a change in the
output of the oxygen sensor, independent of the accuracy of either
the oxygen sensor or the pressure sensor. By adjusting the output
of an intake oxygen sensor based on an ambient humidity estimated
by an intake humidity sensor, the displacement of intake oxygen by
humidity can be accurately estimated and accounted for, improving
the reliability of the oxygen sensor's zero point reading. By
performing the learning during idling conditions, noise factors due
to ingestion of PCV and purge HCs, intake pressure variations,
sensor aging, as well as part-to-part variations is reduced. By
also performing the learning during engine non-fueling conditions,
such as a DFSO, noise factors due to EGR valve leakage are reduced.
By increasing the accuracy of the intake oxygen sensor's zero point
reading, EGR can be estimated more reliably, improving EGR
control.
[0113] Note that the example control and estimation routines
included herein can be used with various engine and/or vehicle
system configurations. The specific routines described herein may
represent one or more of any number of processing strategies such
as event-driven, interrupt-driven, multi-tasking, multi-threading,
and the like. As such, various actions, operations, and/or
functions illustrated may be performed in the sequence illustrated,
in parallel, or in some cases omitted. Likewise, the order of
processing is not necessarily required to achieve the features and
advantages of the example embodiments described herein, but is
provided for ease of illustration and description. One or more of
the illustrated actions, operations and/or functions may be
repeatedly performed depending on the particular strategy being
used. Further, the described actions, operations and/or functions
may graphically represent code to be programmed into non-transitory
memory of the computer readable storage medium in the engine
control system.
[0114] It will be appreciated that the configurations and routines
disclosed herein are exemplary in nature, and that these specific
embodiments are not to be considered in a limiting sense, because
numerous variations are possible. For example, the above technology
can be applied to V-6, I-3, I-4, I-6, V-12, opposed 4, and other
engine types. The subject matter of the present disclosure includes
all novel and non-obvious combinations and sub-combinations of the
various systems and configurations, and other features, functions,
and/or properties disclosed herein.
[0115] The following claims particularly point out certain
combinations and sub-combinations regarded as novel and
non-obvious. These claims may refer to "an" element or "a first"
element or the equivalent thereof. Such claims should be understood
to include incorporation of one or more such elements, neither
requiring nor excluding two or more such elements. Other
combinations and sub-combinations of the disclosed features,
functions, elements, and/or properties may be claimed through
amendment of the present claims or through presentation of new
claims in this or a related application. Such claims, whether
broader, narrower, equal, or different in scope to the original
claims, also are regarded as included within the subject matter of
the present disclosure.
* * * * *