U.S. patent application number 15/585963 was filed with the patent office on 2018-11-08 for systems and methods for engine control.
The applicant listed for this patent is Ford Global Technologies, LLC. Invention is credited to Chris Paul Glugla.
Application Number | 20180320611 15/585963 |
Document ID | / |
Family ID | 63895820 |
Filed Date | 2018-11-08 |
United States Patent
Application |
20180320611 |
Kind Code |
A1 |
Glugla; Chris Paul |
November 8, 2018 |
SYSTEMS AND METHODS FOR ENGINE CONTROL
Abstract
Methods and systems are provided for adjusting spark timing and
fueling in an engine in response to an indication of exhaust gas
recirculation (EGR) system degradation due to a disconnected
upstream hose of an EGR differential pressure sensor. In one
example, a method may include, responsive to an integrated knock
intensity being greater than a threshold intensity and a fuel
control correction being greater than a threshold enrichment,
setting an EGR rate to zero and triggering an EGR differential
pressure sensor upstream hose diagnostic routine to be performed.
Further, spark timing and fueling may be set for zero EGR.
Inventors: |
Glugla; Chris Paul; (Macomb,
MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ford Global Technologies, LLC |
Dearborn |
MI |
US |
|
|
Family ID: |
63895820 |
Appl. No.: |
15/585963 |
Filed: |
May 3, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F02D 43/04 20130101;
F02D 37/02 20130101; F02P 5/1516 20130101; F02M 26/49 20160201;
Y02T 10/40 20130101; F02P 5/045 20130101; F02D 41/0052 20130101;
F02D 41/1454 20130101; F02M 35/1038 20130101; F02D 35/027 20130101;
F02D 41/0072 20130101; F02P 5/1504 20130101; F02P 5/152
20130101 |
International
Class: |
F02D 41/00 20060101
F02D041/00; F02D 35/02 20060101 F02D035/02; F02D 41/14 20060101
F02D041/14; F02D 43/04 20060101 F02D043/04; F02P 5/152 20060101
F02P005/152; F02M 35/10 20060101 F02M035/10 |
Claims
1. A method, comprising: during engine operation with a commanded
amount of exhaust gas recirculation EGR, responsive to at least one
of an integrated knock intensity of an engine being greater than a
threshold intensity and a fuel control correction of fuel supplied
to the engine being greater than a threshold enrichment, setting an
EGR rate to zero.
2. The method of claim 1, wherein the integrated knock intensity is
determined based on an output of a knock sensor coupled to the
engine over a number of engine cycles.
3. The method of claim 1, wherein the fuel control correction is
determined based on a difference between a commanded air-fuel ratio
(AFR) of the engine and a measured AFR sensed via an exhaust gas
oxygen sensor.
4. The method of claim 1, wherein setting the EGR rate to zero
includes commanding closed an EGR valve coupled to an EGR passage
from an at least partially open position to block exhaust flow from
an exhaust system to an intake manifold and continuing to carry out
combustion after closing the EGR valve with fueling and spark
timing based on operation without EGR.
5. The method of claim 4, further comprising indicating potential
EGR system degradation due to detachment of an upstream hose of an
EGR differential pressure sensor coupled to the EGR passage.
6. The method of claim 4, further comprising: adjusting a spark
timing from a current spark timing based on the commanded amount of
EGR to an updated spark timing for the zero EGR rate; adjusting a
fuel command from a current pulse-width based on the commanded
amount of EGR to an updated pulse-width for the zero EGR rate; and
initiating a monitor for diagnosing an upstream hose of an EGR
differential pressure sensor.
7. The method of claim 6, wherein the upstream hose of the EGR
differential pressure sensor is fluidically coupled to the EGR
passage upstream of a metered orifice.
8. The method of claim 6, wherein the updated spark timing is
retarded relative to the current spark timing.
9. The method of claim 6, wherein the updated pulse-width is
increased relative to the current pulse-width as a function of a
cylinder air amount.
10. A method, comprising: while operating an engine with EGR,
adjusting spark responsive to an indication of knock; responsive to
the adjusted spark being retarded to a spark retard threshold,
integrating knock sensor output over a number of engine cycles and
determining a fuel control correction over the number of engine
cycles; and indicating degradation of an EGR system responsive to
one or more of the integrated output of the knock sensor being
greater than a first threshold and the fuel control correction
being greater than a second threshold.
11. The method of claim 10, wherein the fuel control correction
includes a fuel enrichment required to maintain an exhaust air-fuel
ratio (AFR) at a target AFR while operating the engine with the
EGR.
12. The method of claim 10, wherein the first threshold is a
threshold integrated knock intensity of the engine operating at
borderline, the first threshold based on a flow rate of the EGR and
a knock history of the engine, and the second threshold is a
threshold fuel enrichment based on the flow rate of the EGR and a
determined air charge.
13. The method of claim 10, further comprising, in response to the
indication of degradation of the EGR system, operating the engine
with no EGR while retarding spark timing and increasing a fuel
injection amount, the retarded spark timing and increased fuel
injection amount corresponding to a zero EGR flow rate.
14. The method of claim 13, wherein operating the engine with no
EGR includes fully closing an EGR valve coupling an exhaust passage
of the engine to an intake manifold of the engine.
15. The method of claim 14, further comprising, responsive to the
indication of degradation of the EGR system, diagnosing an upstream
hose of an EGR differential pressure sensor coupled to the EGR
valve.
16. The method of claim 15, wherein diagnosing the upstream hose of
the EGR differential pressure sensor includes, while maintaining
the EGR valve closed, measuring EGR flow through the EGR system
using the EGR differential pressure sensor and indicating a
disconnection of the upstream hose of the EGR differential pressure
sensor in response to an output of the sensor being greater than a
threshold.
17. A system, comprising: an engine having a cylinder; an intake
manifold and an exhaust system; an EGR system, comprising an EGR
passage fluidically coupling the intake manifold to the exhaust
system, the EGR passage including a restrictive orifice, an EGR
valve coupled to the EGR passage, and a differential pressure
sensor for sensing EGR flow, the sensor including an upstream hose
coupled to the EGR passage, upstream of the restrictive orifice,
and a downstream hose coupled to the EGR passage, downstream of the
restrictive orifice; a spark plug for providing spark to the
cylinder; a knock sensor; a manifold absolute pressure (MAP) sensor
coupled to the intake manifold for estimating an engine airflow; an
exhaust gas oxygen sensor coupled to the exhaust system; and a
controller configured with computer readable instructions stored on
non-transitory memory for: operating the engine with an EGR flow;
estimating a cylinder air amount based on each of the engine
airflow and the EGR flow; calculating each of a fuel command based
on the cylinder air amount and a correction to the fuel command
based on exhaust gas oxygen sensor output; calculating a spark
timing based in part on the EGR flow; detecting knock based on
output of the knock sensor; retarding spark from the determined
spark timing in response to knock detection; and indicating
potential disconnection of the upstream hose from at least one of
the EGR passage and the differential pressure sensor responsive to
each of the correction to the fuel command being greater than a
threshold enrichment, an integrated output of the knock sensor
being greater than a threshold intensity, and spark retard reaching
a spark retard threshold.
18. The system of claim 17, wherein the controller includes further
instructions for: responsive to the indication of potential
disconnection of the upstream hose, disabling the EGR system and
confirming the disconnection of the upstream hose of the
differential pressure sensor based on a presence of EGR flow
through the EGR passage.
19. The system of claim 18, wherein disabling the EGR system
further includes commanding the EGR valve fully closed and setting
the EGR flow to zero.
20. The system of claim 18, wherein confirming the disconnection of
the upstream hose based on the presence of EGR flow includes
measuring a delta pressure across the restrictive orifice with the
differential pressure sensor while the EGR valve is maintained
closed and indicating disconnection of the upstream hose in
response to the delta pressure being lower than a threshold.
Description
FIELD
[0001] The present description relates generally to methods and
systems for controlling an engine responsive to degradation of
exhaust gas recirculation control.
BACKGROUND
SUMMARY
[0002] An engine may include an external exhaust gas recirculation
(EGR) system to reduce NOx emissions and increase engine
efficiency. The external EGR system may couple an engine exhaust
manifold to an engine intake manifold via an EGR passage. Further,
the EGR system may include temperature and/or pressure sensors to
estimate the amount of EGR flowing to engine cylinders. During the
course of operation, an EGR actuator, sensor, conduit, or hose may
become disconnected. The EGR system component may become dislodged
due to engine boost pressure, vibrations caused by irregular road
surfaces, or other conditions. Degradation of the EGR system may
degrade engine performance, for example, by increasing emissions or
reducing fuel economy.
[0003] As one example, an EGR flow rate may be determined based on
output of a differential pressure sensor, such as a delta pressure
feedback of EGR (DPFE) sensor. Typically, the differential pressure
sensor includes an upstream hose and a downstream hose, which are
both coupled to the EGR passage on either side of a metered
orifice. When EGR flows through the EGR passage, a pressure drop
occurs across the metered orifice, which is measured by the
differential pressure sensor and used to determine the EGR flow
rate. If the upstream hose becomes disconnected, the differential
pressure sensor may measure a large pressure differential (e.g.,
delta pressure), indicating a high EGR flow rate, even if no EGR is
flowing. This may degrade air-fuel control, increase emissions, and
lead to engine knock, for example.
[0004] Various approaches are provided for periodically or
opportunistically monitoring EGR system components. One example
approach for diagnosing an EGR differential pressure sensor is
shown by Cullen et al. in U.S. Pat. No. 5,190,017. Therein, a
measured EGR flow is compared to an expected EGR flow based on
measurements from redundant sensors to determine whether one of the
EGR system components has become inoperable. If the two estimates
deviate by a calibrated amount for a sustained period of time, then
a fault condition in the EGR system is indicated. Specifically,
disconnection of the upstream hose may be indicated based on a
delta pressure measured by the EGR differential pressure sensor
being greater than an expected deviation from an exhaust
backpressure.
[0005] However, the inventors herein have recognized potential
issues with such systems. As one example, redundant sensors and
methods for determining EGR flow may add to vehicle complexity and
costs. Additionally, if the upstream hose of the EGR differential
pressure sensor becomes disconnected after the upstream hose test
is performed, the disconnection may not be identified in a timely
fashion, which may degrade engine operation, increase emissions,
and reduce the life of engine components.
[0006] The inventors herein have recognized that EGR system
degradation due to a disconnected EGR differential pressure sensor
upstream hose may result in a specific combination of changes to
measurable engine parameters, which may be used to identify the EGR
system degradation.
[0007] In particular, if the upstream hose is disconnected, there
is actually no EGR, which causes engine knocking to increase. As a
result of the increased knock, adaptive spark may be retarded, such
as toward a maximum retard clip, even though the EGR sensor
continues to indicate that there is a high EGR flow rate (a
condition when knock is not expected). Additionally, since there is
no EGR actually displacing air in the induction system, a lower air
flow is measured, and the engine controller may fuel the engine in
accordance with the lower air flow. As a result, a measured exhaust
air-fuel ratio may run leaner than expected. By monitoring for the
above-mentioned change in engine parameters (or a combination
thereof), degradation of an EGR differential pressure sensor due to
a disconnected upstream hose can be opportunistically diagnosed
using existing engine components.
[0008] In one example, EGR system degradation may be diagnosed by a
method comprising: during engine operation with a commanded amount
of EGR, responsive to at least one of an integrated knock intensity
of an engine being greater than a threshold intensity and a fuel
control correction of fuel supplied to the engine being greater
than a threshold enrichment, setting an exhaust gas recirculation
(EGR) rate to zero. Further, EGR system degradation may be
indicated, and an active EGR differential pressure sensor upstream
hose diagnostic test may be performed to confirm the diagnosis.
[0009] As one example, during engine operation with EGR commanded,
an engine controller may non-intrusively monitor one or more engine
parameters to diagnose for EGR differential pressure sensor
upstream hose disconnection. For example, the controller may
monitor engine knock intensity and frequency over a number of
engine cycles. If the integrated intensity exceeds a threshold, a
criterion for potential disconnection of the hose may be considered
satisfied. As another example, adaptive spark may be monitored and
if spark hits a retard clip within a defined number of engine
cycles, another criterion for potential disconnection of the hose
may be considered satisfied. As a further example, feedback fuel
control may be monitored, and if fuel has to be enrichened by more
than a threshold to maintain a target air-fuel ratio (e.g., to
maintain a stoichiometric air-fuel ratio based on feedback from an
air-fuel ratio sensor), then a further criterion may be considered
met. If one or more or all of the criteria are met, the controller
may infer that the upstream hose coupled to the EGR system
differential pressure sensor is disconnected. Responsive to the
indication of degradation, further EGR flow may be disabled by
setting the EGR rate to zero, while spark and fuel are adjusted
based on a zero EGR flow rate, independent of the output of the EGR
sensor. For example, the spark timing may be retarded relative to
when a non-zero amount of EGR is supplied, and the fueling amount
may be increased in order to account for a greater cylinder air
amount compared to when EGR is supplied. In addition, an intrusive
EGR differential pressure sensor monitor may be run at the earliest
to confirm the indication of degradation.
[0010] In this way, EGR system degradation may be diagnosed using
existing engine sensors, without compromising the accuracy of
diagnosis. The technical effect of monitoring for a specific
combination of changes in engine knock intensity, spark control,
and fuel control during engine operation with commanded EGR is that
EGR hose disconnection can be reliably identified anytime it occurs
during engine operation, including after a dedicated upstream hose
monitor has run. By commanding the hose monitor to be run in
response to degradation being detected during engine operation,
disconnection may be confirmed and addressed in a timely fashion.
By disabling EGR and setting spark timing and fueling for zero EGR
responsive to the degradation, a further occurrence of knock may be
reduced, thereby improving fuel economy and extending the life of
engine components. In addition, exhaust emissions quality may be
improved.
[0011] 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
[0012] FIG. 1 shows a schematic depiction of an engine system of a
vehicle, including an exhaust gas recirculation (EGR) system.
[0013] FIG. 2 is a high-level flow chart of an example method for
detecting EGR system degradation and adjusting engine operation in
response to the degradation.
[0014] FIG. 3 depicts an example method for EGR control in an
engine.
[0015] FIG. 4 is an example method for air-fuel control in an
engine.
[0016] FIG. 5 shows an example method for determining degradation
of an EGR differential pressure sensor due to a disconnected
upstream hose.
[0017] FIG. 6 is a prophetic example of adjusting engine operation
responsive to an indication of
[0018] EGR system degradation due to a disconnected upstream hose
of an EGR differential pressure sensor.
DETAILED DESCRIPTION
[0019] The following description relates to systems and methods for
diagnosing degradation of an EGR system due to a disconnected
upstream hose of an EGR differential pressure sensor. An example
engine system, including an EGR system, is shown in FIG. 1. EGR may
be provided to achieve a desired engine dilution, for example,
according to the example method of FIG. 3. As shown in the method
of FIG. 4, the amount of EGR entering the engine may be used in
generating a fuel command. If the upstream hose of the EGR
differential pressure sensor becomes disconnected, it may appear
like more EGR is entering the engine than actually is, which may be
non-intrusively detected by an engine controller according to the
method of FIG. 2. Then, the EGR differential pressure sensor
upstream hose may be diagnosed, for example, by running a dedicated
monitor according to the method of FIG. 5. FIG. 6 shows an example
timeline for identifying EGR system degradation due to a
disconnected EGR differential pressure sensor upstream hose and
adjusting engine operation accordingly.
[0020] FIG. 1 illustrates a schematic diagram showing one cylinder
30 of a multi-cylinder engine 10, which may be included in an
engine system 1. Engine system 1 may be a propulsion system
included in a motor vehicle 5. Engine 10 may be controlled at least
partially by a control system, including a controller 12, and by
input from a vehicle operator 132 via an input device 130. In this
example, input device 130 includes an accelerator pedal and a pedal
position sensor 134 for generating a proportional pedal position
signal PP. Combustion chamber (e.g., cylinder) 30 of engine 10 may
include combustion chamber walls 32 with a piston 36 positioned
therein. Piston 36 may be coupled to a crankshaft 40 so that
reciprocating motion of the piston is translated into rotational
motion of the crankshaft. Crankshaft 40 may be coupled to at least
one drive wheel of the vehicle via an intermediate transmission
system. Further, a starter motor may be coupled to crankshaft 40
via a flywheel to enable a starting operation of engine 10.
[0021] Combustion chamber 30 may receive intake air from an intake
manifold 44 via an intake passage 42 and may exhaust combustion
gases via an exhaust passage 48. Intake manifold 44 and exhaust
passage 48 can selectively communicate with combustion chamber 30
via respective intake valve 52 and exhaust valve 54. In some
embodiments, combustion chamber 30 may include two or more intake
valves and/or two more exhaust valves. In this example, intake
valve 52 and exhaust valve 54 may be controlled by cam actuation
via one or more cams and may utilize one or more of cam profile
switching (CPS), variable cam timing (VCT), variable valve timing
(VVT), and/or variable valve lift (VVL) systems that may be
operated by controller 12 to vary valve operation. The position of
intake valve 52 and exhaust valve 54 may be determined by position
sensors 55 and 57, respectively. In alternative embodiments, intake
valve 52 and/or exhaust valve 54 may be controlled by electric
valve actuation. For example, cylinder 30 may alternatively include
an intake valve controlled via electric valve actuation and an
exhaust valve controlled via cam actuation including CPS and/or VCT
systems.
[0022] In some embodiments, each cylinder of engine 10 may be
configured with one or more fuel injectors for providing fuel
thereto. As a non-limiting example, cylinder 30 is shown including
one fuel injector 66, which is supplied fuel from a fuel system
172. Fuel injector 66 is shown coupled directly to cylinder 30 for
injecting fuel directly therein in proportion to the pulse width of
signal FPW received from controller 12 via an electronic driver 68.
In this manner, fuel injector 66 provides what is known as direct
injection (hereafter also referred to as "DI") of fuel into
combustion cylinder 30.
[0023] It will be appreciated that in an alternate embodiment, fuel
injector 66 may be a port injector providing fuel into an intake
port upstream of cylinder 30. It will also be appreciated that
cylinder 30 may receive fuel from a plurality of injectors, such as
a plurality of port injectors, a plurality of direct injectors, or
a combination thereof.
[0024] Continuing with FIG. 1, intake passage 42 may include a
throttle 62 having a throttle plate 64. In this particular example,
the position of throttle plate 64 may be varied by controller 12
via a signal provided to an electric motor or actuator included
with throttle 62, a configuration that is commonly referred to as
electronic throttle control (ETC). In this manner, throttle 62 may
be operated to vary the intake air provided to combustion chamber
30, among other engine cylinders, through intake passage 42 and
intake manifold 44. The position of throttle plate 64 may be
provided to controller 12 by throttle position signal TP. Intake
passage 42 may include a mass air flow (MAF) sensor 120 and a
manifold air pressure (MAP) sensor 122 for providing respective
signals MAF and MAP to controller 12.
[0025] An ignition system 88 can provide an ignition spark to
combustion chamber 30 via a spark plug 92 in response to spark
advance signal SA from controller 12, under select operating modes.
Although spark ignition components are shown, in some embodiments,
combustion chamber 30 or one or more other combustion chambers of
engine 10 may be operated in a compression ignition mode, with or
without an ignition spark.
[0026] Engine 10 may further include a knock sensor 90 coupled to
each cylinder 30 for identifying abnormal cylinder combustion
events. In alternate embodiments, one or more knock sensors 90 may
be coupled to selected locations of the engine block. The knock
sensor may be an accelerometer on the cylinder block or an
ionization sensor configured in the spark plug of each cylinder.
The output of the knock sensor may be combined with the output of a
crankshaft acceleration sensor to indicate an abnormal combustion
event in the cylinder. In one example, based on the output of knock
sensor 90 in one or more defined windows (e.g., crank angle timing
windows), abnormal combustion due to one or more of knock and
pre-ignition may be identified and differentiated. For example,
knock may be identified responsive to knock sensor output obtained
in a knock window being higher than a knock threshold, while
pre-ignition may be identified responsive to knock sensor output
obtained in a pre-ignition window being higher than a pre-ignition
threshold. The pre-ignition threshold may be higher than the knock
threshold, and the pre-ignition window may be earlier than the
knock window, for example. Further, once identified and
differentiated, the abnormal combustion event may be accordingly
addressed, as described further with respect to FIG. 2.
[0027] An exhaust gas sensor 126 is shown coupled to exhaust
passage 48 upstream of an emission control device 70. Exhaust gas
sensor 126 may be any suitable sensor for providing an indication
of exhaust gas air-fuel ratio (AFR), such as a linear wideband
oxygen sensor (UEGO); a two-state narrowband oxygen sensor (EGO); a
heated EGO (HEGO); or a NO.sub.x, HC, or CO sensor. In the
non-limiting embodiments described herein, exhaust gas sensor 126
is a UEGO sensor configured to provide output, such as a voltage
signal, that is proportional to the amount of oxygen present in the
exhaust gas. Controller 12 uses the output to determine the exhaust
gas AFR, which may be used as feedback for generating a fuel
command, as described further with respect to FIG. 4.
[0028] Emission control device 70 is shown arranged along exhaust
passage 48 downstream of exhaust gas sensor 126. In the
non-limiting embodiments described herein, emission control device
70 is a three-way catalyst (TWC) configured to reduce NO.sub.x and
oxidize CO and unburnt hydrocarbons. In other embodiments, however,
emission control device 70 may be a NO.sub.x trap, various other
emission control devices, or combinations thereof.
[0029] Engine system 1 may include an external exhaust gas
recirculation (EGR) system to route a desired portion of exhaust
gas from exhaust passage 48 to intake manifold 44 via an EGR
passage 140. The amount of EGR provided to intake manifold 44 may
be varied by controller 12 via an EGR valve 142. For example, EGR
valve 142 may be opened in variable amounts from fully open to
fully closed, thus supplying a desired amount of EGR. EGR valve 142
may be a vacuum actuated valve, an electronically activated
solenoid valve, or other type of flow control valve.
[0030] An EGR sensor may be arranged within EGR passage 140 to
provide an indication of one or more of pressure, temperature, and
oxygen concentration of the recirculated exhaust gas. In the
example of FIG. 1, the EGR sensor is a differential pressure sensor
144, such as a delta pressure feedback of EGR (DPFE) sensor.
Differential pressure sensor 144 may provide feedback for
controlling an EGR flow rate by monitoring a pressure differential
(e.g., delta pressure) across a metered (e.g., restrictive) orifice
150. Differential pressure sensor 144 includes an upstream hose 146
fluidically coupling an upstream pressure port of the sensor to EGR
passage 140 upstream of orifice 150 and a downstream hose 148
fluidically coupling a downstream pressure port of the sensor to
EGR passage 140 downstream of orifice 150. The upstream pressure
port and upstream hose 146 may have a larger internal diameter than
the downstream pressure port and downstream hose 148, for
example.
[0031] A pressure-sensitive disc, such as a piezo ceramic disc, may
be included within differential pressure sensor 144 between the
upstream and downstream pressure ports and may be used to generate
a voltage proportional to the delta pressure across orifice 150.
When EGR valve 142 is closed, no exhaust gas flows through orifice
150, and the pressure at the upstream pressure port is the same as
the pressure at the downstream pressure port of differential
pressure sensor 144. Without a pressure difference, differential
pressure sensor 144 may output a small voltage (e.g., 0.45-1.0 V)
equivalent to a 0 inH.sub.2O pressure differential. As EGR valve
142 is opened, exhaust gas flows through orifice 150 to replace the
exhaust gas that flows to intake manifold 44 via EGR valve 142. A
pressure drop occurs across orifice 150 due to the restriction of
orifice 150. For example, a first pressure at upstream hose 146 and
the upstream pressure port of differential pressure sensor 144,
which is equal to an exhaust gas pressure, is greater than a second
pressure at downstream hose 148 and the downstream pressure port,
creating a negative delta pressure (defined as the first pressure
subtracted from the second pressure). As the opening of EGR valve
142 increases, the pressure drop across orifice 150 increases
(e.g., becomes more negative), resulting in a greater voltage
output of differential pressure sensor 144.
[0032] Differential pressure sensor 144 may be used to determine an
EGR flow rate. For example, a controller (e.g., controller 12) may
reference a look-up table, with the voltage output of differential
pressure sensor 144 as the input and the EGR flow rate as the
output. The controller may then use the determined EGR flow rate as
feedback to adjust a position of EGR valve 142 until a desired
(e.g., commanded) EGR flow rate is reached, as described further
with respect to FIG. 3. For example, if the determined EGR flow
rate is higher than the desired EGR flow rate, the controller may
actuate EGR valve 142 to a more closed position, and if the
determined EGR flow rate is lower than the desired EGR flow rate,
the controller may actuate EGR valve 142 to a more open
position.
[0033] While differential pressure sensor 144 is shown upstream of
EGR valve 142, in other examples, differential pressure sensor 144
may be located downstream of EGR valve 142 and upstream of intake
manifold 44. In still other examples, differential pressure sensor
144 may be a combination sensor comprising both a differential
pressure sensing element and a manifold absolute pressure sensing
element.
[0034] Differential pressure sensor 144 may be intermittently
diagnosed by running one or more dedicated, intrusive monitors. For
example, upstream hose 146 may be diagnosed for disconnection once
per drive cycle, after a threshold duration has elapsed, or after a
threshold distance of vehicle travel, as described with respect to
FIG. 5. However, upstream hose 146 may become disconnected after
the monitor has been run. If upstream hose 146 becomes
disconnected, exhaust gas may escape to the atmosphere. For
example, if upstream hose 146 becomes disconnected while EGR is
requested, an amount of EGR being supplied to intake manifold 44
may be much lower than commanded, which may cause engine knock to
occur. Adaptive spark retard may be used to help mitigate the
occurrence of knock. Further, with a much smaller amount of EGR
displacing air in the intake manifold, a lower air flow is
measured, degrading air-fuel control, as described further with
respect to FIG. 4. As a result, a measured exhaust AFR may be
leaner than expected. The lean exhaust AFR may be used as feedback
for correcting the amount of fuel delivered to the engine to
achieve a desired AFR (e.g., stoichiometry), resulting in a large
fuel control correction enrichment. Controller 12 may monitor for
knock, adaptive spark retard, and fuel control correction while the
engine is running with EGR commanded and infer degradation of the
EGR system, such as due to a disconnection of upstream hose 146,
responsive to an integrated knock intensity surpassing a threshold
intensity, spark retard hitting a clip, and the fuel control
correction surpassing a threshold enrichment, as elaborated with
respect to FIG. 2.
[0035] Under some conditions, the EGR system may be used to
regulate the temperature of the air and fuel mixture within the
combustion chamber. Further, during some conditions, a portion of
combustion gases may be retained or trapped in the combustion
chamber by controlling exhaust valve timing, such as by controlling
a variable valve timing mechanism, in what is known as internal
EGR.
[0036] Controller 12 is shown in FIG. 1 as a microcomputer,
including microprocessor unit 102, input/output ports 104, an
electronic storage medium for executable programs and calibration
values shown as read-only memory chip 106 in this particular
example, random access memory 108, keep alive memory 110, and a
data bus. Controller 12 may receive various signals from sensors
coupled to engine 10 in addition to those signals previously
discussed, including measurement of inducted mass air flow (MAF)
from MAF sensor 120, engine coolant temperature (ECT) from a
temperature sensor 112 coupled to a cooling sleeve 114, a profile
ignition pickup signal (PIP) from a Hall effect sensor 118 (or
other type) coupled to crankshaft 40, throttle position (TP) from a
throttle position sensor, absolute manifold pressure (MAP) signal
from MAP sensor 122, and UEGO sensor output (UEGO) from UEGO sensor
126. An engine speed signal, RPM, may be generated by controller 12
from signal PIP. Controller 12 may receive input data from the
various sensors, process the input data, and trigger various
actuators, such as EGR valve 142 and fuel injector 66, in response
to the processed input data based on instructions or code
programmed therein corresponding to one or more routines. For
example, based on engine operating conditions, controller 12 may
actuate EGR valve 142 open to direct exhaust to intake manifold 44,
with the degree of opening corresponding to a desired amount of
EGR, and adjust the position of EGR valve 142 based on feedback
from differential pressure sensor 144 in order to achieve the
desired amount of EGR, as described further with respect to FIG. 3.
In another example, controller 12 may use the output of knock
sensor 90 to infer knock and the potential disconnection of
upstream hose 146 when EGR is requested, as elaborated with respect
to FIG. 2.
[0037] Storage medium read-only memory 106 can be programmed with
computer readable data representing non-transitory instructions
executable by processor 102 for performing the methods described
below as well as other variants that are anticipated but not
specifically listed.
[0038] As described above, FIG. 1 shows only one cylinder of a
multi-cylinder engine, and each cylinder may similarly include its
own set of intake/exhaust valves, fuel injector(s), spark plug(s),
etc.
[0039] In this way, the components of FIG. 1 enable an engine
system comprising: an engine having a cylinder; an intake manifold
and an exhaust system; an EGR system, comprising an EGR passage
fluidically coupling the intake manifold to the exhaust system, the
EGR passage including a restrictive orifice; an EGR valve coupled
to the EGR passage, and a differential pressure sensor for sensing
EGR flow, the sensor including an upstream hose coupled to the EGR
passage, upstream of the restrictive orifice, and a downstream hose
coupled to the EGR passage, downstream of the restrictive orifice;
a spark plug for providing spark to the cylinder; a knock sensor; a
manifold absolute pressure (MAP) sensor coupled to the intake
manifold for estimating an engine airflow; an exhaust gas oxygen
sensor coupled to the exhaust system; and a controller configured
with computer readable instructions stored on non-transitory memory
for: operating the engine with an EGR flow; estimating a cylinder
air amount based on each of the engine airflow and the EGR flow;
calculating each of a fuel command based on the cylinder air amount
and a correction to the fuel command based on exhaust gas oxygen
sensor output; calculating a spark timing based in part on the EGR
flow; detecting knock based on output of the knock sensor;
retarding spark from the determined spark timing in response to
knock detection; and indicating potential disconnection of the
upstream hose from at least one of the EGR passage and the
differential pressure sensor responsive to each of the correction
to the fuel command being greater than a threshold enrichment, an
integrated output of the knock sensor being greater than a
threshold intensity, and spark retard reaching a spark retard
threshold. Additionally or alternatively, the controller may
include further instructions for, responsive to the indication of
potential disconnection of the upstream hose, disabling the EGR
system and confirming the disconnection of the upstream hose of the
differential pressure sensor based on a presence of EGR flow
through the EGR passage. In some examples, disabling the EGR system
may further include commanding the EGR valve fully closed and
setting the EGR flow to zero. As a further example, confirming the
disconnection of the upstream hose based on the presence of EGR
flow may include measuring a delta pressure across the restrictive
orifice with the differential pressure sensor while the EGR valve
is maintained closed and indicating disconnection of the upstream
hose in response to the delta pressure being lower than a
threshold.
[0040] Turning now to FIG. 2, an example method 200 for detecting
EGR system degradation in an engine system and prompting an EGR
differential pressure sensor upstream hose diagnostic to be
performed is shown. For example, if an upstream hose (e.g.,
upstream hose 146 of FIG. 1) of the EGR differential pressure
sensor becomes disconnected, the EGR differential pressure sensor
may measure a large differential pressure, equating to an
erroneously high EGR flow rate. Specifically, FIG. 2 shows a method
for determining EGR system degradation based on multiple criteria:
a propensity for engine knock, knock adaptive spark correction, and
a fuel control correction, which may all result from operating the
engine with a lower actual amount of EGR than commanded. Further,
method 200 includes adjustments to engine operation, including
spark timing and fueling, responsive to the degradation.
Instructions for carrying out method 200 and the rest of the
methods included herein may be executed by a controller, such as
controller 12 of FIG. 1, based on instructions stored on a memory
of the controller and in conjunction with signals received from
sensors of the engine system, such as the sensors described above
with reference to FIG. 1. The controller may employ engine
actuators of the engine system to adjust engine operation according
to the methods described below.
[0041] Method 200 begins at 202 and includes estimating and/or
measuring engine operating conditions. Conditions assessed may
include, for example, engine temperature; engine load; driver
torque demand; manifold air flow; manifold air pressure; engine
speed; throttle position; exhaust pressure; exhaust AFR; ambient
conditions, including ambient temperature, pressure, and humidity;
etc.
[0042] At 204, it is determined if EGR is desired. EGR may be
desired to attain a desired engine dilution, thereby improving fuel
efficiency and emissions quality. For example, EGR may be requested
at low to mid engine loads. Additionally, EGR may be desired after
an exhaust catalyst (e.g., emission control device 70 of FIG. 1)
has attained its light-off temperature. An amount of EGR requested
may be based on engine operating conditions, including engine load
(as estimated via a pedal position sensor), engine speed (as
estimated via a crankshaft acceleration sensor), engine temperature
(as estimated via an engine coolant temperature sensor), etc. For
example, the controller may refer a look-up table having the engine
speed and load as the input and output a desired amount of EGR
corresponding to the input engine speed-load, as elaborated with
respect to FIG. 3.
[0043] If EGR is not desired, method 200 proceeds to 206 and
includes maintaining current engine operating conditions without
supplying EGR. For example, an EGR valve (e.g., EGR valve 142) will
be maintained in a closed position, thereby blocking a flow of EGR
from an EGR passage to an intake manifold of the engine. Following
206, method 200 ends.
[0044] If it is determined that EGR is desired at 204, method 200
proceeds to 208 and includes supplying a commanded amount of EGR,
as described further with respect to FIG. 3. Briefly, the commanded
amount of EGR (or EGR flow rate) may be determined based on engine
speed and load, and the EGR valve may be opened to a position
corresponding to the commanded amount of EGR. Further, the EGR
differential pressure sensor may be used to measure an actual flow
rate of the EGR, thereby providing an indication of the actual EGR
amount and/or providing feedback for controlling the position of
the EGR valve.
[0045] At 210, method 200 includes adjusting fueling based on the
amount of EGR, as described further with respect to FIG. 4.
Briefly, the amount of EGR and a cylinder charge mass may be used
to determine an amount of fresh air within the cylinder, which is
then used to generate a fuel command that will give a desired
AFR.
[0046] At 212, it is determined if knock is detected. As described
with respect to FIG. 1, knock may be detected based on output of a
knock sensor (e.g., knock sensor 90 of FIG. 1) combined with output
of a crankshaft acceleration sensor obtained during a defined knock
window. For example, knock may be detected in a cylinder if the
output of the knock sensor, sensed in a crank angle window after a
spark event in the cylinder, is greater than a knock threshold.
[0047] If knock is not detected, method 200 proceeds to 222 and
includes continuing to supply EGR responsive to engine demand. For
example, a requested amount of EGR may continue to be determined
based on engine operating conditions and provided by adjusting the
EGR valve to a corresponding position. Following 222, method 200
ends.
[0048] If knock is detected at 212, method 200 proceeds to 214 and
includes retarding spark timing to provide knock adaptive spark
retard. For example, spark timing may be retarded from an original
timing selected based on engine operating conditions, including
engine speed, engine load, AFR, and EGR amount. By retarding spark
timing responsive to an indication of knock, in-cylinder pressures
may be decreased, thereby decreasing the propensity for further
knock. An amount of spark retard applied may be determined based on
the original spark timing and further based on the indication of
knock. For example, as the indication of knock increases (e.g., as
the output of the knock sensor further exceeds the knock
threshold), the amount of spark retard applied may be increased. As
another example, when the original spark timing is closer to
maximum brake torque (MBT), the amount of spark retard applied may
be increased. In one example, spark timing may be retarded by 1-2
crank angle degrees responsive to the indication of knock. As knock
is not expected when EGR is being used, the occurrence of knock in
the presence of EGR is indicative of errors (e.g., a drop) in EGR
flow, such as due to a disconnection of the upstream hose of the
EGR differential pressure sensor.
[0049] At 216, it is determined if spark retard usage is at a
limit. That is, it may be determined if spark retard usage is
hitting a clip (e.g., a spark retard threshold). The limit may
define a spark retard amount beyond which engine power losses,
overheating tendencies, and high emissions may occur. Spark may not
be further retarded from the limit. In addition, adaptive spark
retard approaching or being at a limit may be indicative of a high
knock incidence. If spark retard reaches the clip, a first
criterion indicative of potential EGR system degradation due to
disconnection of an upstream hose of the EGR differential pressure
sensor may be considered met.
[0050] If the spark retard usage is not at the limit, method 200
returns to 212 and includes determining if knock is detected, as
described above. Thus, spark may be incrementally retarded to a
greater degree responsive to knock being detected until the spark
retard usage is at the limit.
[0051] If the spark retard usage is at the limit at 216, method 200
proceeds to 218 and includes integrating knock intensity over a
duration. For example, the duration may correspond to a
pre-determined number of engine cycles following the spark retard
usage hitting the clip. In another example, the duration may
correspond to a pre-determined number of engine cycles following
the initial detection of knock.
[0052] At 220, it is determined if the integrated knock intensity
is greater than a threshold intensity. For example, the threshold
intensity may correspond to an amount above which, it may be
determined that knock is still prevalent despite the mitigating
action of retarding spark as much as can be afforded. Further, the
threshold intensity may correspond to an intensity above which it
may be determined that knock is occurring more than expected for
the given engine operating conditions, and that the higher than
expected knock may be triggered by the actual engine dilution being
lower than the commanded engine dilution due to degradation of a
component of the EGR system. As an example, based on engine knock
history, and further based on engine speed-load conditions, there
may be an expected propensity for knock, such as an expected
percentage of engine cycles with knock occurring while operating at
borderline spark timing. Based on the expected knock propensity and
the duration over which the knock intensity is integrated, a
corresponding threshold intensity may be determined. If the
integrated knock intensity reaches or exceeds the threshold
intensity, a second, additional criterion indicative of potential
EGR degradation due to disconnection of an upstream hose of the EGR
sensor may be considered met. If the integrated knock intensity is
not greater than the threshold intensity, method 200 proceeds to
222, as described above. Thus, it may be assumed that retarding
spark has successfully mitigated knock.
[0053] If the integrated knock intensity is greater than the
threshold intensity, method 200 proceeds to 224 and includes
determining a fuel control correction. The fuel control correction
corresponds to an amount of fuel that is added to or subtracted
from a base fuel command, for example, due to feedback from an
exhaust gas oxygen sensor (e.g., UEGO sensor 126 of FIG. 1)
concerning the AFR of combusted gas in order to achieve a desired
(e.g., commanded) AFR. In one example, the commanded AFR is
stoichiometry. A fuel control module of the engine controller may
feed-forward determine a fuel mass to command to a fuel injector
based on a charge mass calculation for the cylinder so as to
operate the cylinder at stoichiometry (or another target AFR). The
charge mass calculation may account for an amount of fresh air
being received in the cylinder as well as an amount of exhaust gas
being recirculated into the cylinder from the exhaust manifold. In
particular, the fuel mass commanded may be commensurate with the
fresh air component of the charge mass. Based on feedback from an
exhaust AFR sensor, the commanded fuel mass may then be further
adjusted. For example, if the output of the AFR sensor is
indicative of a leaner than commanded AFR, a subsequent fuel
command may have a larger fuel pulse-width. Herein, the enrichening
is adjusted based on the difference between the commanded
stoichiometric AFR and the measured leaner than stoichiometric AFR.
As another example, if the output of the AFR sensor is indicative
of a richer than commanded AFR, a subsequent fuel command may have
a smaller fuel pulse-width. Herein, the enleaning is adjusted based
on the difference between the commanded stoichiometric AFR and the
measured richer than stoichiometric AFR.
[0054] At 226, it is determined if the fuel control correction is
greater than a threshold enrichment. For example, the threshold
enrichment may correspond to an enrichment amount above which, it
may be determined that the engine is running significantly leaner
(e.g., above a threshold AFR) than indicated by the determined air
charge. In some examples, the threshold enrichment may refer to a
fuel adjustment that would account for EGR not being provided to
the engine. In an illustrative example, if the EGR flow is
displacing 5% of the airflow, then the threshold enrichment is
equal to an amount of fuel that would be delivered for 5% more
airflow. As mentioned above and described in greater detail with
respect to FIG. 4, the air charge may be determined, in part, based
on the EGR flow rate. Thus, if the EGR flow rate is incorrectly
high, for example, due to a disconnected upstream hose of the EGR
differential pressure sensor, the fuel controller may calculate the
fuel command based on an incorrectly low determined air charge,
leading to a large fuel control correction enrichment in order to
achieve the desired AFR. If the fuel correction enrichment exceeds
the threshold enrichment, a third, additional criterion indicative
of potential EGR degradation due to disconnection of an upstream
hose of the EGR sensor may be considered met. As one example, the
controller may integrate the knock intensity of cylinder knocking
cycles over a number of combustion events. If the number of
knocking cycles is larger than an expected threshold percentage of
knocking cycles, the enrichment applied may be greater than or
equal to the adjustment needed to account for knocking if the EGR
mass were not present. Thus, if EGR mass was displacing 5% of the
airflow when working properly, then the enrichment applied may be
equal to or greater than 5% (assuming all fuel adaptation is
mature). If the fuel control correction is not greater than the
threshold enrichment, method 200 proceeds to 228 and includes
increasing the amount of EGR and/or performing one or more knock
mitigation actions, such as enriching fuel to reduce knock. For
example, by increasing the amount of EGR, combustion temperatures
may be decreased, which may reduce the occurrence of knock. In
another example, rich fuel conditions may reduce the occurrence of
knock due to the evaporative cooling effects of the additional
fuel. In still further examples, engine load may be temporarily
limited by reducing intake airflow to reduce knock incidence.
Following 228, method 200 ends.
[0055] If the fuel control correction is greater than the threshold
enrichment, method 200 proceeds to 230 and includes indicating EGR
system degradation responsive to each of the first, second, and
third criteria for EGR degradation being met. Responsive to the
indication of degradation, the method includes closing the EGR
valve. By closing the EGR valve, EGR flow may be reduced to a zero
flow rate. For example, it may be inferred that the EGR system may
be degraded due to a disconnected upstream hose of the EGR
differential pressure sensor. Since the EGR flow rate cannot be
reliably determined, commanding the EGR valve closed responsive to
the indication of degradation ensures that no EGR flows through the
EGR passage to the intake manifold. Indicating EGR system
degradation may include setting a diagnostic trouble code (DTC) and
may further include illuminating a malfunction indicator lamp (MIL)
to alert a vehicle operator of the degradation condition. Further,
an amount of internal EGR may be increased by increasing an amount
of intake valve and exhaust valve overlap (such as by actuating a
variable valve timing mechanism) in order to retain exhaust gas in
the cylinder for dilution effects and reduced emissions.
[0056] In some examples, the integrated knock intensity may be
compared to a first threshold at 220, wherein the first threshold
is a threshold integrated knock intensity of the engine operating
at borderline. For example, if the integrated knock intensity
indicates that 102% of the combustion cycles are knocking while the
cylinders are operated at borderline, it may be determined that the
first threshold has been exceeded. In some examples, the first
threshold may be adjusted based on a flow rate of the EGR that was
commanded during engine operation (at 208) and a knock history of
the engine (reflective of the engine's propensity for knock). The
fuel correction may be compared to a second threshold at 226,
wherein the second threshold is a threshold fuel enrichment based
on the flow rate of the EGR and a determined air charge. For
example, if there is no EGR system degradation, the enrichment
amount correction is expected to be approximately equal to the air
flow correction needed (by opening up the throttle) to account for
the commanded EGR flow rate. If the enrichment correction exceeds
the air flow correction for the commanded EGR flow rate, EGR system
degradation may be possible.
[0057] At 232, method 200 includes, after disabling EGR, setting
the spark timing and fueling for zero EGR. For example, spark
timing may be advanced when EGR is requested to compensate for a
reduced in-cylinder temperature and pressure due to EGR. Thus, when
zero EGR is delivered responsive to the indication of degradation,
the base spark timing may be retarded relative to the base spark
timing when EGR is delivered. For example, the controller may refer
a look-up table with engine operating conditions (e.g., engine
speed and load, ECT, MAP, and air temperature) as the input and
output the base spark timing. Further, with zero EGR, the air
charge is not diluted. Therefore, the amount of fuel delivered is
increased compared to when EGR is provided in order to achieve a
desired AFR, which may be calculated according to the method of
FIG. 4, for example. Note that as used herein, disabling EGR and
providing no EGR (or zero EGR) refers to external EGR and not to
internal EGR.
[0058] At 234, method 200 includes triggering a dedicated EGR
differential pressure sensor monitor responsive to the indication
of degradation. For example, the controller may perform an EGR
differential pressure sensor upstream hose diagnostic, as described
with respect to FIG. 5. For example, method 200 non-intrusively
indicates that there is possible degradation of the upstream hose,
which may be confirmed with a more active, intrusive monitor. While
the EGR differential pressure sensor upstream hose diagnostic is
typically performed once per drive cycle, the adaptive spark retard
reaching the spark retard limit (as determined at 216), the
integrated knock intensity being greater than the threshold
intensity (as determined at 220), and the fuel control correction
being greater than the threshold enrichment (as determined at 226)
trigger the upstream hose diagnostic to be performed even if it has
already been performed during the drive cycle or is not scheduled.
Thus, the intrusive monitor allows the controller to determine if
the upstream hose became disconnected after the last time the
monitor was performed. Following 234, method 200 ends.
[0059] It will be appreciated that while the method of FIG. 2
discloses EGR degradation being determined responsive to each of
multiple criteria being met, viz., a propensity for engine knock,
adaptive spark retard reaching a limit, and a fuel control
correction surpassing a threshold, in alternate examples,
degradation may be determined based on at least one of the criteria
being met. For example, degradation may be inferred responsive to
adaptive spark retard reaching the limit, even while engine knock
and the fuel control correction remain below their thresholds.
[0060] Continuing to FIG. 3, an example method 300 for controlling
an amount of EGR delivered to an engine, such as engine 10 of FIG.
1, is shown. For example, method 300 may be performed by a
controller (e.g., controller 12 of FIG. 1) as part of method 200 of
FIG. 2 (e.g., at 208) once it is determined that EGR is requested,
such as when the engine is operating at low to mid loads and after
the engine is warmed up.
[0061] Method 300 begins at 302 and includes determining an amount
of EGR requested. For example, the controller may refer to a
look-up table having the engine speed and load as the input and
output a dilution amount corresponding to the input engine
speed-load. In another example, the controller may determine the
EGR amount (e.g., EGR flow rate) through logic rules that directly
take into account parameters such as engine load, engine speed,
engine temperature, etc. In still other examples, the controller
may rely on a model that correlates a change in engine load with a
change in a dilution requirement, and further correlates the change
in the dilution requirement with a change in the amount of EGR
requested. For example, as the engine load increases from a low
load to a mid load, the amount of EGR requested may increase, and
then as the engine load increases from a mid load to a high load,
the amount of EGR requested may decrease. The controller may
further determine the amount of EGR requested by taking into
account a best fuel economy mapping for a desired dilution
rate.
[0062] At 304, method 300 includes opening an EGR valve to supply
the commanded (e.g., requested) amount of EGR. For example, the
controller may refer to a look-up table having the requested amount
of EGR as the input and having a signal corresponding to a degree
of opening to apply to the EGR valve as the output. As an example,
as the requested amount of EGR increases, the opening of the EGR
valve may be increased. Thus, the EGR valve (e.g., EGR valve 142 of
FIG. 1) may be actuated open to a position corresponding to the
requested EGR flow rate.
[0063] At 306, method 300 includes measuring the EGR flow rate. As
described with respect to FIG. 1, the EGR flow rate may be measured
using a differential pressure sensor (e.g., differential pressure
sensor 144 of FIG. 1). Alternatively, the EGR flow rate may be
inferred by one or more temperature, pressure, humidity, and
air-fuel ratio sensors.
[0064] At 308, it is determined if the measured EGR flow rate is
greater than commanded (or if the measured EGR flow rate exceeds
the commanded flow rate by more than a threshold amount). In one
example, the measured EGR flow rate may be accumulated for a
pre-determined duration and compared to the commanded EGR flow rate
accumulated over the same duration. Alternatively, the measured EGR
flow rate may be compared to a first threshold flow rate, the first
threshold flow rate set based on the commanded EGR flow rate such
that if the measured EGR flow rate is greater than the first
threshold flow rate, the amount of EGR being delivered to the
engine is greater than desired.
[0065] If the measured EGR flow rate is greater than commanded,
method 300 proceeds to 310 and includes decreasing the opening of
the EGR valve. By further closing the EGR valve, the amount of EGR
delivered is reduced. For example, the controller may refer a
look-up table having a difference between the commanded EGR flow
rate and the measured EGR flow rate as the input and a signal
corresponding to a new, decreased degree of opening to apply to the
EGR valve as the output. In still other examples, the controller
may rely on a model that correlates the difference between the
commanded EGR flow rate and the measured EGR flow rate with a
change in the EGR valve position and further correlates the change
in the EGR valve position with a signal to apply to the EGR valve.
Following 310, method 300 may return to 306 to measure the EGR flow
rate.
[0066] Returning to 308, if the measured EGR flow rate is not
greater than commanded, method 300 proceeds to 312 and includes
determining if the measured EGR flow rate is less than commanded.
As at 308, in one example, the measured EGR flow rate may be
accumulated for the pre-determined duration and compared to the
commanded EGR flow rate accumulated over the same duration.
Alternatively, the measured EGR flow rate may be compared to a
second threshold flow rate, the second threshold flow rate set
based on the commanded EGR flow rate such that if the measured EGR
flow rate is less than the second threshold flow rate, the amount
of EGR being delivered to the engine is less than desired. Thus,
the first threshold flow rate (as described at 308) and the second
threshold flow rate may define a range between which the measured
EGR flow rate is considered to be equal to the commanded EGR flow
rate.
[0067] If the measured EGR flow rate is less than commanded (or if
the measured EGR flow rate falls below the commanded flow rate by
more than the threshold amount), method 300 proceeds to 314 and
includes increasing the opening of the EGR valve. By further
opening the EGR valve, the amount of EGR delivered is increased.
For example, the controller may refer a look-up table having a
difference between the commanded EGR flow rate and the measured EGR
flow rate as the input and a signal corresponding to a new,
increased degree of opening to apply to the EGR valve as the
output. In still other examples, the controller may rely on a model
that correlates the difference between the commanded EGR flow rate
and the measured EGR flow rate with a change in the EGR valve
position and further correlates the change in the EGR valve
position with a signal to apply to the EGR valve. Following 314,
method 300 may return to 306 to measure the EGR flow rate, as
described above. Thus, the position of the EGR valve may be
iteratively adjusted until the measured EGR flow rate is equal to
the commanded EGR flow rate.
[0068] If, at 312, the measured EGR flow rate is not less than
commanded, if may be assumed that the EGR flow rate is considered
to be substantially equal to the commanded EGR flow rate (or within
a threshold of the commanded EGR flow rate). Therefore, method 300
proceeds to 316 and includes continuing to supply EGR responsive to
engine demand. For example, the current position of the EGR valve
may be maintained until engine operating conditions change, such as
the engine load changing responsive to a change in driver demand,
at which time the position of the EGR valve may be updated to
provide a new commanded amount of EGR. Following 316, method 300
ends.
[0069] Thus, FIG. 3 provides a method for determining an EGR amount
to provide to an engine, measuring an EGR flow rate as an
indication of the amount of EGR actually being delivered to the
engine, and iteratively adjusting the EGR valve if the amount of
EGR being delivered to the engine is not equal to the desired
amount. In this way, the amount of EGR being delivered to the
engine may be precisely controlled for increased emissions control.
However, inaccuracies in determining the EGR flow may directly
affect estimated cylinder air charge, leading to inaccuracies in
calculated fuel injection and degraded AFR control, as described
below.
[0070] FIG. 4 shows an example method 400 for determining an amount
of fuel to inject into cylinders of an engine (e.g., generating a
fuel command). Additionally, an exhaust gas oxygen sensor, such as
UEGO sensor 126 of FIG. 1, may be used to measure the AFR of
exhaust gas, thereby providing feedback for the fuel command, as
described further below. Method 400 may be performed as part of
method 200 of FIG. 2, such as at 210. Further, method 400 may be
executed synchronously with engine firing (e.g., once per engine
firing event). Method 400 may be performed by an engine controller,
such as controller 12 of FIG. 1. For example, method 400 may be
performed by a fuel control module of the engine controller. In
another example, all or some of method 400 may be performed by a
dedicated fuel controller that is communicatively coupled to the
engine controller. While FIG. 4 depicts a speed-density method for
estimating air flow into the engine, such as based on output of a
MAP sensor (e.g., MAP sensor 122 of FIG. 1) coupled to an intake
manifold of the engine, in other examples, output of a MAF sensor
(e.g., MAF sensor 120 of FIG. 1) may be used in generating the fuel
command.
[0071] Method 400 begins at 402 and includes estimating airflow
into the engine. The airflow into the engine refers to a sum of an
amount of EGR and an amount of fresh air entering the engine and
may be determined based on a plurality of engine operating
parameters, such as engine speed, MAP (as measured using the MAP
sensor), manifold temperature, engine displacement, and engine
volumetric efficiency. For example, a controller (e.g., controller
12 of FIG. 1) may input the plurality of engine operating
parameters into an equation and output the airflow into the engine.
Further, the airflow may be divided by the number of engine
cylinders to determine a total cylinder charge mass.
[0072] At 404, method 400 includes determining the amount of EGR
entering the intake manifold. The amount of EGR (e.g., an EGR
charge) entering the intake manifold may be determined based on an
EGR flow rate, such as measured with an EGR differential pressure
sensor (e.g., differential pressure sensor 144 of FIG. 1), as
described with respect to FIG. 3.
[0073] At 406, method 400 includes calculating a cylinder EGR
amount. For example, the cylinder EGR amount may be determined by
dividing the EGR charge entering the intake manifold by the number
of engine cylinders and engine speed.
[0074] At 408, method 400 includes calculating a cylinder air
amount based on the total cylinder charge mass and the cylinder EGR
amount. For example, the controller may calculate the cylinder air
amount by subtracting the cylinder EGR amount (as determined at
406) from the total cylinder charge mass (as determined at
402).
[0075] At 410, method 400 includes calculating a fuel injection
amount based on the cylinder air amount. The fuel injection amount
refers to an amount of fuel that will achieve a desired AFR given
the cylinder air amount. For example, the controller may calculate
the fuel injection amount by dividing the cylinder air amount by
the desired AFR. The controller may then generate a signal with a
pulse width corresponding to the fuel injection amount to send to
fuel injectors. In one example, the desired AFR is
stoichiometry.
[0076] At 412, method 400 includes determining a fuel control
correction based on exhaust gas oxygen sensor feedback and
adjusting the fuel injection amount accordingly. The exhaust gas
oxygen sensor may measure a concentration of oxygen in the exhaust
gas, which may then be used to determine the AFR of the exhaust
gas. If the AFR of the exhaust gas is leaner than the desired AFR,
the fuel control correction may include increasing the fuel
injection amount, such as by increasing a fuel pulse-width on the
next fuel injection event. If the AFR of the exhaust gas is richer
than the desired AFR, the fuel control correction may include
decreasing the fuel injection amount, such as by decreasing the
fuel pulse-width on the next fuel injection event. The degree to
which the fuel injection amount is increased (enriched) or
decreased (enleaned) may be proportional to the amount of deviation
of the determined AFR of the exhaust gas from the desired AFR.
Thus, the fuel injection amount may be controlled in a closed-loop
manner. Following 412, method 400 ends.
[0077] As can be seen from the above methods, in particular method
400 of FIG. 4, if a determined cylinder EGR amount is larger than
the actual cylinder EGR amount, the engine will be fueled as if
there is little air charge, making the system lean. Thus, based on
AFR feedback from an exhaust gas oxygen sensor, the fuel control
will be corrected, increasing a fuel injection amount (e.g., fuel
pulse-width). The fuel control correction being above a threshold
enrichment may indicate that the determined cylinder EGR amount is
larger than the actual cylinder EGR amount, particularly when
combined with a high knock intensity and adaptive spark retard
hitting a limit, as described with respect to FIG. 2. Thus, the EGR
system may be determined to be degraded and therefore disabled. The
determined cylinder EGR amount may be larger than the actual
cylinder EGR amount due to a disconnected upstream hose of an EGR
differential pressure sensor causing a large delta pressure
measurement, for example. Thus, disconnection of the upstream hose
may be confirmed using an intrusive monitor.
[0078] FIG. 5 shows an example method 500 for diagnosing an
upstream hose of an EGR differential pressure sensor (e.g.,
differential pressure sensor 144 of FIG. 1) in a vehicle. Method
500 may be performed by a controller (e.g., controller 12 of FIG.
1) as part of method 200 of FIG. 2 (e.g., at 234), for example. In
other examples, method 500 may be performed once per drive cycle in
accordance with general on-board diagnostics. It will be
appreciated that the method of FIG. 5 may also be referred to
herein as an EGR upstream hose monitor.
[0079] Method 500 begins at 502 and includes determining if
conditions for diagnosing the upstream hose are met. In one
example, the conditions may be considered met if a threshold
duration or distance of vehicle travel has elapsed since a last
diagnosis of the upstream hose. In another example, conditions for
diagnosing the upstream hose may be considered met if the vehicle
is undergoing conditions that can trigger the dislocation of the
hose, such as an acceleration event, rough road conditions, vehicle
travel on a slope (uphill or downhill), windy conditions, and
extended duration of vehicle operation at higher than threshold
vehicle speeds.
[0080] If conditions for diagnosing the upstream hose are not met,
method 500 proceeds to 504 and includes maintaining current engine
operating conditions. For example, EGR conditions may be
maintained, and the upstream hose of the EGR differential pressure
sensor is not intrusively diagnosed. However, as elaborated with
reference to FIG. 2, engine operating conditions may continue to be
monitored, allowing for the EGR differential pressure sensor to be
opportunistically and non-intrusively diagnosed during engine
operation. If method 500 was performed responsive to an indication
of EGR system degradation (e.g., as at 234 of FIG. 2), the EGR
valve may remain closed at the onset of the monitor following the
indication of degradation. If method 500 was performed as a part of
general on-board diagnostics, the EGR system may remain enabled,
with EGR supplied responsive to engine demand (as elaborated with
respect to FIG. 3). Following 504, method 500 ends.
[0081] If conditions for diagnosing the upstream hose are met,
method 500 proceeds to 506 and includes commanding the EGR valve
closed. For example, if the EGR valve is open and exhaust gas is
being supplied to an intake manifold of the engine via an EGR
passage, the EGR valve will be closed, temporarily disrupting the
flow of exhaust gas to the intake manifold. If the EGR valve is
already closed, then the EGR valve is maintained closed throughout
the monitor. Herein, closing the EGR valve includes fully closing
the EGR valve.
[0082] At 508, it is determined if EGR flow is detected. If the EGR
system is functioning nominally, no flow is expected with the EGR
valve closed. The EGR differential pressure sensor may be used to
measure an amount of EGR flowing through the EGR valve and output a
voltage signal corresponding to the amount, as further described
with respect to FIG. 1. Therefore, if the voltage output of the EGR
differential pressure sensor indicates a positive EGR flow (e.g., a
delta pressure is less than a threshold), it may be determined that
EGR flow is detected, and method 500 proceeds to 510.
[0083] At 510, method 500 includes indicating degradation of the
EGR differential pressure sensor upstream hose. For example, it is
indicated that the upstream hose may be disconnected from the EGR
passage or the differential pressure sensor, making the pressure at
an upstream port of the differential pressure sensor equal to
atmospheric pressure. This creates a pressure differential between
the upstream port and a downstream port, which results in EGR flow
being measured even when the EGR valve is closed and EGR is not
flowing. Indicating degradation of the upstream hose may include
the controller setting a DTC and may further include illuminating a
MIL to alert a vehicle operator of the degradation condition.
[0084] At 512, method 500 includes disabling the EGR system.
Disabling the EGR system includes commanding the EGR valve fully
closed and not allowing EGR to be commanded even if engine dilution
is required. For example, with a disconnected upstream hose,
exhaust gases may escape to the atmosphere instead of being routed
to the intake manifold. Thus, EGR cannot be relied upon to supply a
desired engine dilution, and so the EGR system may be disabled
until the DTC is cleared. Without EGR, fuel enrichment may be used
to reduce peak cylinder temperatures, for example. In addition,
engine dilution may be provided via alternate approaches, such as
internal EGR (e.g., by increasing valve overlap using a variable
valve timing mechanism). In another example, if the engine system
includes a water injection system, water injection may be used,
such as by injecting water into the intake manifold or directly
in-cylinder, to dilute the air charge and/or provide evaporative
cooling effects.
[0085] If EGR flow is not detected at 508 (e.g., the voltage output
of the EGR differential pressure sensor is consistent with a no
flow condition), method 500 proceeds to 514 and includes indicating
an absence of degradation of the EGR differential pressure sensor
upstream hose. With the EGR valve closed and the upstream hose and
a downstream hose of the EGR pressure sensor both connected, the
pressure differential between the upstream and downstream ports of
the EGR pressure sensor is equal to 0. Therefore, EGR flow not
being detected shows that the upstream hose is connected to both
the EGR passage and the differential pressure sensor.
[0086] At 516, method 500 includes continuing to supply EGR
responsive to engine demand. For example, if the EGR valve was
closed to test the EGR differential pressure sensor upstream hose,
it may be actuated open to an appropriate position for an amount of
EGR requested, as described further with respect to FIG. 3.
Following 516, method 500 ends.
[0087] Thus, the upstream hose of an EGR differential pressure
sensor may be diagnosed in a timely fashion responsive to an
indication of EGR system degradation in which more EGR flow is
measured than is actually delivered. Quickly diagnosing a
disconnected upstream hose may streamline the diagnostic and repair
procedure.
[0088] FIG. 6 shows a graph 600 of an example timeline for
detecting EGR system degradation due to a disconnected upstream
hose of a differential pressure sensor and adjusting fueling and
spark timing accordingly. Specifically, in the example of FIG. 6,
two criteria are used to determine EGR system degradation, such as
according to method 200 of FIG. 2. An EGR valve opening is shown in
plot 602, a measured EGR flow is shown in plot 604, an exhaust gas
AFR is shown in plot 606, a fuel control correction is shown in
plot 610, a knock signal is shown in plot 616, spark timing is
shown in plot 622, an indication of EGR system degradation is shown
in plot 626, and an indication of a disconnected upstream hose of
an EGR differential pressure sensor is shown in plot 628.
Furthermore, dashed line 608 represents an exhaust gas AFR of
stoichiometry, above which the AFR is lean and below which the AFR
is rich; dashed line 612 represents a fuel control correction of
zero, above which fuel is added to a base fuel command and below
which fuel is subtracted from the base fuel command in order to
achieve a desired AFR; dashed line 614 represents a threshold fuel
control correction enrichment for determining EGR system
degradation; dashed line 618 represents a knock threshold; and
dashed line 624 represents MBT spark timing. For all of the above,
the X-axis represents time, with time increasing along the X-axis
from left to right. The Y-axis represents the labeled parameter,
with values increasing from bottom to top, except for plots 626 and
628, in which EGR system degradation (plot 626) and the
disconnected upstream hose (plot 628) are indicated as "yes" or
"no."
[0089] Prior to t1, the engine is operated without EGR requested.
For example, EGR may not be requested due to the engine operating
at a high load. As shown in plot 602, with no EGR requested, an EGR
valve (e.g., EGR valve 142 of FIG. 1) is closed. In the example of
FIG. 6, EGR flow is determined using an EGR differential pressure
sensor, such as differential pressure sensor 144 of FIG. 1. With
the EGR valve closed, the differential pressure sensor measures a
no flow condition (plot 604). The exhaust gas AFR (plot 606), as
measured by an exhaust gas oxygen sensor (e.g., UEGO sensor 126 of
FIG. 1), fluctuates about stoichiometry (dashed line 608), with the
fuel control correction (plot 610) increasing or decreasing fueling
in response to the AFR fluctuation. The knock signal (plot 616), as
output by a knock sensor (e.g., knock sensor 90 of FIG. 1) remains
below a knock threshold (dashed line 618), indicating that knock is
not occurring. Thus, spark timing (plot 622) is set to MBT (dashed
line 624). EGR system degradation (plot 626), including degradation
due to a disconnected upstream hose of the EGR differential
pressure sensor (plot 628), is not indicated.
[0090] Beginning at t1, EGR is requested responsive to the engine
load decreasing (not shown). Thus, the EGR valve is opened to a
first open position (plot 602). As the EGR valve is opened, the
measured EGR flow (plot 604) also increases. A base fuel command is
adjusted to take into account the amount of EGR entering the
engine, as described with respect to FIG. 4. Thus, the exhaust gas
AFR continues to fluctuate about stoichiometry, as shown in plot
606, with the fuel control correction (plot 610) responding
accordingly. Further, MBT (dashed line 624) is advanced relative to
when no EGR is provided, with spark timing (plot 624) advancing
accordingly to remain at MBT. The knock signal (plot 616) remains
below the knock threshold (dashed line 618).
[0091] At t2, the amount of EGR requested increases, for example,
responsive to the engine load further decreasing. The EGR valve is
further opened to a second open position (plot 602). The measured
EGR flow (plot 604) increases accordingly. MBT spark timing (dashed
line 624) is further advanced in response to the increased amount
of EGR, and the actual spark timing (plot 622) is further advanced
to remain at MBT. The exhaust gas AFR (plot 606) continues to
fluctuate nominally about stoichiometry (dashed line 608). The
knock signal (plot 616) remains below the knock threshold (plot
618). Further, EGR system degradation is not indicated (plot
628).
[0092] At t3, the measured EGR flow increases (plot 604) despite
the EGR valve position remaining constant (plot 602). In the
example of FIG. 6, at t3, the upstream hose of the EGR differential
pressure sensor disconnects, making it appear as if a large amount
of EGR is entering the engine. A controller may use the measured
EGR flow as feedback for adjusting the position of the EGR valve in
order to achieve a desired EGR flow, as described with respect to
FIG. 3. Therefore, responsive to the measured EGR flow increasing,
the EGR valve is further closed in an attempt to achieve the amount
of EGR requested. However, the measured EGR flow does not decrease
as the EGR valve opening decreases. Further, the exhaust gas AFR
(plot 606) becomes lean. Knock is detected, for example, due to the
lean fueling conditions, as shown by the knock signal (plot 616)
surpassing the knock threshold (dashed line 618). In order to
achieve the desired AFR (e.g., stoichiometry), the fuel control
correction (plot 610) increases, adding additional fuel to the base
fuel command, which is determined in part based on the measured EGR
flow. The fuel control correction surpasses the threshold fuel
control correction enrichment (dashed line 618) at t4. Therefore,
if only one criterion for determining EGR system degradation is
being used instead of both criteria, as described with respect to
FIG. 2, EGR system degradation may be indicated at t4 (dashed
segment 627).
[0093] Between t4 and t5, the exhaust gas AFR returns to
fluctuating about stoichiometry (plot 606) due to the exhaust gas
AFR being used as feedback for the fuel control correction. In
order to maintain an AFR around stoichiometry, the fuel control
correction (plot 610) remains above the threshold enrichment
(dashed line 614), as the inaccurately large measured EGR flow
(plot 604) continues to influence the base fuel command. In
response to continued knock (plot 616), for example, due to a
desired engine dilution not being achieved, spark timing is
retarded from MBT, as shown in plot 622. At t5, spark retard usage
reaches a limit from which it cannot be further reduced. Therefore,
the controller integrates the knock intensity over a duration
spanning from t5 to t6. The integrated knock intensity, indicated
by shaded area 620, is greater than a threshold intensity (not
shown). Thus, the two criteria are met, and at t6, EGR system
degradation is indicated by setting a flag (plot 626) and the EGR
system is disabled.
[0094] In response to EGR system degradation being indicated at t6,
the EGR valve is commanded closed (plot 602) and spark timing and
fueling are set for zero EGR. For example, MBT (dashed line 624) is
set for zero EGR, which may be less advanced than when EGR is
requested. Spark timing (plot 622) is advanced from the spark
retard limit so that spark timing occurs at MBT. With fueling set
for zero EGR, all of the estimated airflow into the engine is
determined to be fresh air, and the base fuel command is generated
accordingly. Thus, the fuel control correction (plot 614) is
reduced below the threshold enrichment (dashed line 614) and
fluctuates about a correction of zero (dashed line 612) based on
exhaust gas AFR feedback (plot 606). Further, with the appropriate
fueling and spark timing supplied for the engine operating
conditions, knock no longer occurs, as shown by the knock signal
(plot 616) decreasing below the knock threshold (dashed line
618).
[0095] At t7, the controller initiates an EGR differential pressure
sensor monitor, such as the method of FIG. 5, responsive to the
indication of EGR system degradation and entry conditions for the
monitor being met (e.g., a vehicle acceleration condition). With
the EGR system disabled and the EGR valve closed (plot 602), an EGR
no flow condition is expected. However, the measured EGR flow
remains high (plot 604), indicating that the upstream hose of the
EGR differential pressure sensor is disconnected. Therefore, a
disconnected upstream hose is indicated by setting a flag (plot
628).
[0096] In this way, degradation of an EGR system due to
disconnection of an upstream hose of an EGR differential pressure
sensor may be determined non-intrusively based on a specific
combination of changes to engine operating parameters during engine
operation. The technical effect of monitoring changes in knock
intensity, adaptive spark, and feedback fuel correction for AFR
control during engine operation with commanded EGR is that
degradation of the EGR system may be accurately predicted using
existing sensors. Further, disconnection of the upstream hose of
the EGR differential pressure sensor may be diagnosed in a timely
fashion if the upstream hose becomes disconnected in between
iterations of a dedicated EGR differential pressure sensor monitor.
By identifying hose disconnection and addressing the degradation
promptly, heavy knock induced by EGR flow errors may be reduced,
extending engine component life. Furthermore, by disabling EGR
responsive to the indication of hose decoupling, unwanted release
of exhaust to the atmosphere through the disconnected hose is
reduced, improving exhaust emissions.
[0097] As one example, a method is provided, comprising: during
engine operation with a commanded amount of EGR, responsive to at
least one of an integrated knock intensity of an engine being
greater than a threshold intensity and a fuel control correction of
fuel supplied to the engine being greater than a threshold
enrichment, setting an exhaust gas recirculation (EGR) rate to
zero. In the preceding example, additionally or optionally, the
integrated knock intensity is determined based on an output of a
knock sensor coupled to the engine over a number of engine cycles.
In any or all of the preceding examples, additionally or
optionally, the fuel control correction is determined based on a
difference between a commanded air-fuel ratio (AFR) of the engine
and a measured AFR sensed via an exhaust gas oxygen sensor. In any
or all of the preceding examples, additionally or optionally,
setting the EGR rate to zero includes commanding closed an EGR
valve coupled to an EGR passage from an at least partially open
position to block exhaust flow from an exhaust system to an intake
manifold and continuing to carry out combustion after closing the
EGR valve with fueling and spark timing based on operation without
EGR. In any or all of the preceding examples, additionally or
optionally, the method may further comprise indicating potential
EGR system degradation due to detachment of an upstream hose of an
EGR differential pressure sensor coupled to the EGR passage. In any
or all of the preceding examples, additionally or optionally, the
method may further comprise adjusting a spark timing from a current
spark timing based on the commanded amount of EGR to an updated
spark timing for the zero EGR; adjusting a fuel command from a
current pulse-width based on the commanded amount of EGR to an
updated pulse-width for the zero EGR; and initiating a monitor for
diagnosing an upstream hose of an EGR differential pressure sensor.
In any or all of the preceding examples, additionally or
optionally, the upstream hose of the EGR differential pressure
sensor is fluidically coupled to the EGR passage upstream of a
metered orifice. In any or all of the preceding examples,
additionally or optionally, the updated spark timing is retarded
relative to the current spark timing. In any or all of the
preceding examples, additionally or optionally, the updated fuel
pulse-width is increased relative to the current fuel pulse-width
as a function of a cylinder air amount.
[0098] As another example, a method comprises: while operating an
engine with EGR, adjusting spark responsive to an indication of
knock; responsive to the adjusted spark being retarded to a spark
retard threshold, integrating knock sensor output over a number of
engine cycles and determining a fuel control correction over the
number of engine cycles; and indicating degradation of an EGR
system responsive to one or more of the integrated output of the
knock sensor being greater than a first threshold and the fuel
control correction being greater than a second threshold. In the
preceding example, additionally or optionally, the fuel control
correction includes a fuel enrichment required to maintain an
exhaust air-fuel ratio (AFR) at a target AFR while operating the
engine with the EGR. In any or all of the preceding examples,
additionally or optionally, the first threshold is a threshold
integrated knock intensity of the engine operating at borderline,
the first threshold based on a flow rate of the EGR and a knock
history of the engine, and the second threshold is a threshold fuel
enrichment based on the flow rate of the EGR and a determined air
charge. In any or all of the preceding examples, the method
additionally or optionally further comprises, in response to the
indication of degradation of the EGR system, operating the engine
with no EGR while retarding spark timing and increasing a fuel
injection amount, the retarded spark timing and increased fuel
injection amount corresponding to a zero EGR flow rate. In any or
all of the preceding examples, additionally or optionally,
operating the engine with no EGR includes fully closing an EGR
valve coupling an exhaust passage of the engine to an intake
manifold of the engine. In any or all of the preceding examples,
the method additionally or optionally further comprises, responsive
to the indication of degradation of the EGR system, diagnosing an
upstream hose of an EGR differential pressure sensor coupled to the
EGR valve. In any or all of the preceding examples, additionally or
optionally, diagnosing the upstream hose of the EGR differential
pressure sensor includes, while maintaining the EGR valve closed,
measuring EGR flow through the EGR system using the EGR
differential pressure sensor and indicating a disconnection of the
upstream hose of the EGR differential pressure sensor in response
to an output of the sensor being greater than a threshold.
[0099] As another example, a system is provided, comprising: an
engine having a cylinder; an intake manifold and an exhaust system;
an EGR system, comprising an EGR passage fluidically coupling the
intake manifold to the exhaust system, the EGR passage including a
restrictive orifice, an EGR valve coupled to the EGR passage, and a
differential pressure sensor for sensing EGR flow, the sensor
including an upstream hose coupled to the EGR passage, upstream of
the restrictive orifice, and a downstream hose coupled to the EGR
passage, downstream of the restrictive orifice; a spark plug for
providing spark to the cylinder; a knock sensor; a manifold
absolute pressure (MAP) sensor coupled to the intake manifold for
estimating an engine airflow; an exhaust gas oxygen sensor coupled
to the exhaust system; and a controller configured with computer
readable instructions stored on non-transitory memory for:
operating the engine with an EGR flow; estimating a cylinder air
amount based on each of the engine airflow and the EGR flow;
calculating each of a fuel command based on the cylinder air amount
and a correction to the fuel command based on exhaust gas oxygen
sensor output; calculating a spark timing based in part on the EGR
flow; detecting knock based on output of the knock sensor;
retarding spark from the determined spark timing in response to
knock detection; and indicating potential disconnection of the
upstream hose from at least one of the EGR passage and the
differential pressure sensor responsive to each of the correction
to the fuel command being greater than a threshold enrichment, an
integrated output of the knock sensor being greater than a
threshold intensity, and spark retard reaching a spark retard
threshold. In the preceding example, additionally or optionally,
the controller includes further instructions for: responsive to the
indication of potential disconnection of the upstream hose,
disabling the EGR system and confirming the disconnection of the
upstream hose of the differential pressure sensor based on a
presence of EGR flow through the EGR passage. In any or all of the
preceding examples, additionally or optionally, disabling the EGR
system further includes commanding the EGR valve fully closed and
setting the EGR flow to zero. In any or all of the preceding
examples, additionally or optionally, confirming the disconnection
of the upstream hose based on the presence of EGR flow includes
measuring a delta pressure across the restrictive orifice with the
differential pressure sensor while the EGR valve is maintained
closed and indicating disconnection of the upstream hose in
response to the delta pressure being lower than a threshold.
[0100] Note that the example control and estimation routines
included herein can be used with various engine and/or vehicle
system configurations. The control methods and routines disclosed
herein may be stored as executable instructions in non-transitory
memory and may be carried out by the control system including the
controller in combination with the various sensors, actuators, and
other engine hardware. 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, where the described actions are carried out by
executing the instructions in a system including the various engine
hardware components in combination with the electronic
controller.
[0101] 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, 1-4, 1-6, 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.
[0102] 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.
* * * * *