U.S. patent application number 11/514664 was filed with the patent office on 2007-03-08 for fuel injector activity verification.
Invention is credited to Tobias Pallett.
Application Number | 20070051344 11/514664 |
Document ID | / |
Family ID | 37828911 |
Filed Date | 2007-03-08 |
United States Patent
Application |
20070051344 |
Kind Code |
A1 |
Pallett; Tobias |
March 8, 2007 |
FUEL INJECTOR ACTIVITY VERIFICATION
Abstract
An engine system comprising of at least one fuel injector sensor
coupled to at least one fuel injector of a first group of
cylinders; at least one fuel injector sensor coupled to at least
one fuel injector of a second group of cylinders; and a controller
configured to operate the engine system in at least a first mode
and a second mode, where in the first mode the first and second
cylinder groups combust air and injected fuel, where in the second
mode at least one of the first and second cylinder groups combusts
air and injected fuel and the other one of the first and second
cylinder groups pumps air without injecting fuel; where in the
first mode the controller sets a degradation condition responsive
to detection of inactivity of the at least one fuel injector by the
at least one fuel injection sensors; and where in the second mode
the controller sets a degradation condition responsive to at least
one of detection of fuel injection activity in both the first and
second groups of cylinders by the fuel injection sensors, and
detection of fuel injection inactivity in both the first and second
groups of cylinder by the fuel injection sensors.
Inventors: |
Pallett; Tobias; (Farmington
Hills, MI) |
Correspondence
Address: |
ALLEMAN HALL MCCOY RUSSELL & TUTTLE, LLP
806 S.W. BROADWAY, SUITE 600
PORTLAND
OR
97205
US
|
Family ID: |
37828911 |
Appl. No.: |
11/514664 |
Filed: |
September 1, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60713895 |
Sep 2, 2005 |
|
|
|
Current U.S.
Class: |
123/443 ;
123/198F; 123/479 |
Current CPC
Class: |
F02D 2200/1004 20130101;
F02D 2200/1006 20130101; F02D 13/06 20130101; F02D 41/1443
20130101; Y02T 10/12 20130101; F02D 17/02 20130101; F02D 41/221
20130101; F02D 41/0285 20130101; Y02T 10/18 20130101; F02D 41/0082
20130101 |
Class at
Publication: |
123/443 ;
123/198.00F; 123/479 |
International
Class: |
F02D 17/02 20060101
F02D017/02; F02D 41/14 20060101 F02D041/14; F02D 13/06 20060101
F02D013/06 |
Claims
1. An engine system comprising: at least one fuel injector sensor
coupled to at least one fuel injector of a first group of
cylinders; at least one fuel injector sensor coupled to at least
one fuel injector of a second group of cylinders; and a controller
configured to operate the engine system in at least a first mode
and a second mode, where in the first mode the first and second
cylinder groups combust air and injected fuel, where in the second
mode at least one of the first and second cylinder groups combusts
air and injected fuel and the other one of the first and second
cylinder groups pumps air without injecting fuel; where in the
first mode the controller sets a degradation condition responsive
to detection of inactivity of the at least one fuel injector by the
at least one fuel injection sensors; and where in the second mode
the controller sets a degradation condition responsive to at least
one of detection of fuel injection activity in both the first and
second groups of cylinders by the fuel injection sensors, and
detection of fuel injection inactivity in both the first and second
groups of cylinder by the fuel injection sensors.
2. The system of claim 1 wherein the controller is further
configured to exit a mode of operation when the degradation
condition is set a number of times that exceeds a predetermined
threshold.
3. The system of claim 1 wherein setting of the degradation
condition includes triggering of a diagnostic trouble code.
4. The system of claim 1 wherein the controller is further
configured to prevent entry to at least one mode of operation
responsive to setting of the degradation condition.
5. The system of claim 1 wherein the controller is further
configured to operate in a decontamination mode where at least one
of the first and second cylinder groups operates with an air-fuel
ratio lean of stoichiometry and the other one of the at least one
of the first and second cylinder groups operates with an air-fuel
ratio rich of stoichiometry.
6. The system of claim 1 wherein the first and second fuel injector
sensors are coupled to a first and second fuel injector activity
logic circuit for indicating that the engine is operating in the
second mode.
7. The system of claim 6 wherein the controller is configured to
set the degradation condition based on output of at least one of
the fuel injector activity detection logic circuits.
8. The system of claim 1 wherein the controller is further
configured to operate in a third mode, where at least one of the
first and second cylinder groups combusts air and injected fuel and
in the other one of the first and second cylinder groups the
controller deactivates the inlet and exhaust valves and disables
the fuel injectors;
9. The system of claim 1 wherein fuel injector inactivity includes
no injection of fuel for a predetermined amount of time
10. A fuel injector sensor system comprising: at least one fuel
injector to inject fuel to each cylinder in a first cylinder group;
at least one fuel injector to inject fuel to each cylinder in a
second cylinder group; a first fuel injector sensor device for
detecting fuel injector activity of each injector of the first
cylinder group; a second fuel injector sensor device for detecting
fuel injector activity of each injector of the second cylinder
group; a first fuel injector activity logic circuit configured to
receive input signals from each of the first fuel injector sensors;
a second fuel injector activity logic circuit configured to receive
input signals from each of the second fuel injector sensors; and a
fuel injector activity controller configured to detect the activity
and inactivity of a fuel injector cut-out mode based on the output
signals of the first and second fuel injector activity logic
circuit.
11. The system of claim 10 wherein the first and second fuel
injector sensor devices include a fuel injector sensor to detect
fuel injection activity for each fuel injector in the first and
second cylinder groups, and where said first and second fuel
injector activity logic circuits are AND gates.
12. The system of claim 10 wherein the fuel activity controller is
further configured to set a degradation condition based on the
output signal of at least one of the fuel injector activity logic
circuits.
13. The system of claim 12 wherein setting of a degradation
condition includes triggering a diagnostic trouble code.
14. The system of claim 12 wherein setting of a degradation
condition includes exiting a mode of engine operation.
15. The system of claim 12 wherein setting of a degradation
condition includes preventing entry to certain modes of
operation.
16. The system of claim 12 wherein the fuel injector activity logic
circuit includes a programmable microcontroller.
17. A method of detecting fuel injector degradation, the method
comprising: receiving a detected cylinder group sub-set fuel
injector activity signal from the output of a fuel injector
activity logic circuit; and setting a degradation condition based
on a discrepancy between the detected fuel injector activity signal
and a commanded cylinder group sub-set fuel injector activity
signal.
18. The method of claim 17 wherein the fuel injector activity logic
circuit is included in a fuel injector controller.
19. The method of claim 17 wherein setting the degradation
condition includes preventing fuel injector cut-out mode
operation.
20. The method of claim 17 wherein the detected fuel injector
activity signal indicates cylinder group specific fuel injector
activity.
Description
[0001] This application claims priority to U.S. Provisional
Application No. 60/713,895, filed Sep. 2, 2005, the entire contents
of which are incorporated herein by reference.
BACKGROUND
[0002] In some powertrain control systems it may be desirable to
disable fuel injection in some cylinders under various operating
conditions. For example, a variable displacement engine control
strategy may disable fuel injection and valve actuation in some
cylinders at various operating ranges in order to improve fuel
economy. As another example, an engine control strategy may disable
fuel injection in some cylinders and operating other cylinders that
are combusting a mixture of fuel and air with an increased air load
(e.g. a lean burn fuel injector cut-out mode) at various operating
ranges in order to improve engine efficiency and fuel economy. See,
for example, U.S. Pat. No. 6,758,185.
[0003] However, the inventers herein have recognized that when air
load is increased during a fuel injector cut-out mode, and fuel
injectors do not stop injecting fuel as commanded, errors in torque
and emissions control may be produced. Furthermore, in a variable
displacement engine control strategy if cylinder valves are
deactivated and fuel injectors do not stop injecting fuel as
commanded, the likelihood of hydro-locking the engine may be
increased.
[0004] The above issues may be addressed by, in one example, an
engine comprising: at least one fuel injector sensor coupled to at
least one fuel injector of a first group of cylinders; at least one
fuel injector sensor coupled to at least one fuel injector of a
second group of cylinders; a controller configured to operate the
engine in at least a first mode and a second mode, where in the
first mode the first and second cylinder groups combust air and
injected fuel, where in the second mode at least one of the first
and second cylinder groups combusts air and injected fuel and the
other one of the first and second cylinder groups pumps air without
injecting fuel; where in the first mode the controller sets a
degradation condition responsive to detection of inactivity of the
at least one fuel injector by the at least one fuel injection
sensors; and where in the second mode the controller sets a
degradation condition responsive to detection of fuel injection
activity in both the first and second groups of cylinders by the
fuel injection sensors, and detection of fuel injection inactivity
in both the first and second groups of cylinder by the fuel
injection sensors. Furthermore, in some embodiments a controller
may be configured to operate the engine in a third mode, where both
the first and second cylinder groups pump air without injecting
fuel; and where the controller sets a degradation condition
responsive to detection of fuel injection activity on either of the
first and second groups of cylinders by the fuel injection
sensors.
[0005] In this way cylinder group specific fuel injection activity
may be verified during different modes of operation. Furthermore,
fuel injector degradation may be detected and engine control may be
reconfigured in order to reduce control errors and increased
emissions. Additionally, in the case of a variable displacement
engine detection of fuel injector degradation and changes of the
engine control strategy may be used to reduce the likelihood of
hydro-locking the engine.
BRIEF DESCRIPTION OF THE FIGURES
[0006] The above features and advantages will be readily apparent
from the following detailed description of example embodiment(s).
Further, these features and advantages will also be apparent from
the following figures.
[0007] FIG. 1 is a schematic depiction of an exemplary embodiment
of an engine according to the present disclosure.
[0008] FIGS. 2A-2C are schematic depictions of different exemplary
engine and exhaust system configurations.
[0009] FIGS. 3A-3B are flow diagrams of an exemplary embodiment of
a method of estimating maximum torque in an engine.
[0010] FIGS. 4A-4B are flow diagrams of an exemplary embodiment of
a method of validating air-fuel ratio measurements of UEGO sensors
in the exhaust system of an engine.
[0011] FIG. 5 is a flow diagram of an exemplary embodiment of a
method of verifying fuel injector activity in cylinder groups
during various modes of engine operation.
[0012] FIG. 6 is a flow diagram of an exemplary embodiment of
determining performance degradation in various modes of operation
of an engine.
[0013] FIG. 7 is a schematic diagram of an exemplary embodiment of
a fuel injector activity detection logic circuit.
[0014] FIG. 8 is a flow diagram of an alternative exemplary
embodiment of a method of verifying fuel injector cut-out mode and
fuel injector activity during various modes of engine
operation.
[0015] FIG. 9 is a schematic diagram of an alternative exemplary
embodiment of a fuel injector cut-out mode activity detection logic
circuit.
[0016] FIG. 10 is a truth table and graphical representation of the
inputs and output of the logic circuit of FIG. 9.
DETAILED DESCRIPTION
[0017] FIG. 1 shows a schematic diagram of one cylinder of
multi-cylinder internal combustion engine 10. Combustion chamber or
cylinder 30 of engine 10 is shown including combustion chamber
walls 32 and piston 36 positioned therein and connected to
crankshaft 40. A starter motor (not shown) may be coupled to
crankshaft 40 via a flywheel (not shown). Cylinder 30 may
communicate with intake port 44 and exhaust port 48 via respective
intake valve 52 and exhaust valve 54. Intake valve 52 and exhaust
valve 54 may be actuated via intake camshaft 51 and exhaust
camshaft 53. Further, the position of intake camshaft 51 and
exhaust camshaft 53 may be monitored by intake camshaft sensor 55
and exhaust camshaft sensor 57 respectively. In an exemplary
embodiment, intake and exhaust valve control may be provided by
signals supplied by controller 12 via electric valve actuation
(EVA). Additionally intake and exhaust valve may be controlled by
various other mechanical control systems including cam profile
switching (CPS), variable displacement engine (VDE), variable cam
timing (VCT), variable valve lift (VVL), and/or variable valve
timing (VVT). In some embodiments, valve control strategy may
include a combination of two or more of the above mentioned control
techniques. While cylinder 30 is shown having only one intake valve
and one exhaust valve, it should be appreciated that in some
embodiments cylinder 30 may have two or more intake and/or exhaust
valves.
[0018] Fuel injector 66 is shown coupled to intake port 44 for
delivering injected fuel in proportion to the pulse width of signal
FPW received from controller 12 via electronic driver 68. Fuel may
be delivered to fuel injector 66 by a fuel system (not shown)
including a fuel tank, fuel pumps, and a fuel rail. Engine 10 is
described herein with reference to a gasoline burning engine,
however it should be appreciated that in some embodiments, engine
10 may be configured to utilize a variety of fuels including
gasoline, diesel, alcohol, hydrogen, and combinations thereof.
[0019] Intake port 44 is shown communicating with intake manifold
42 via throttle plate 64. Further, throttle plate 64 may be coupled
to electric motor 62 such that the position of throttle plate 64
may be controlled by controller 12 via electric motor 62. Such a
configuration may be referred to as electronic throttle control
(ETC), which may be utilized during idle speed control. In an
alternative embodiment (not shown), a bypass air passageway may be
arranged substantially parallel with throttle plate 64 to control
inducted airflow during idle speed control via a throttle control
valve positioned within the air passageway.
[0020] Distributorless ignition system 88 may provide ignition
spark to combustion chamber 30 via spark plug 92 in response to
spark advance signal SA from controller 12. Though spark ignition
components are shown, engine 10 (or a portion of cylinders thereof)
may not include spark ignition components in some embodiments
and/or may be operated without requiring a spark.
[0021] Engine 10 may provide torque to a transmission system (not
shown) via crankshaft 40. Crankshaft 40 may be coupled to a torque
converter which is also coupled to a transmission via a turbine
shaft. Torque converter may include a bypass, or lock-up clutch.
The lock-up clutch may be actuated electrically, hydraulically, or
electro-hydraulically, for example. The transmission may comprise
an electronically controlled transmission with a plurality of
selectable discrete gear ratios. Alternatively, in some
embodiments, the transmission system may be configured as a
continuously variable transmission (CVT), or a manual
transmission.
[0022] Exhaust gas sensor 126 is shown coupled to exhaust port 48
upstream of catalytic converter 70. It should be noted that sensor
126 may correspond to a plurality of various different sensors and
catalytic converter 70 may correspond to a plurality of various
emissions devices positioned in the exhaust, depending on the
exhaust configuration (described in detail below with regard to
FIGS. 2A-2C). Sensor 126 may be any of many know sensors for
providing an indication of exhaust gas air/fuel ratio such as an
exhaust gas oxygen (EGO) sensor, linear oxygen sensor, an UEGO, a
two-state oxygen sensor, a HEGO, or an HC or CO sensor. For
example, a higher voltage state of signal EGO indicates that
exhaust gases may be rich of stoichiometry and a lower voltage
state of signal EGO indicates that exhaust gases may be lean of
stoichiometry. Further, signal EGO may be used during air/fuel
control in order to estimate and validate various aspects of a
desired engine control mode as will be described in greater detain
below.
[0023] Controller 12 is schematically shown in FIG. 1 as a
microcomputer, including microprocessor unit (CPU) 102,
input/output ports 104, an electronic storage medium, (ROM) 106,
random access memory (RAM) 108, keep alive memory (KAM) 110, and a
data bus. Controller 12 is shown receiving various signals from
sensors coupled to engine 10, in addition to those signals
previously discussed, including measurement of inducted mass air
flow (MAF) from mass air flow sensor 120 coupled to intake manifold
42; engine coolant temperature (ECT) from temperature sensor 112
coupled to cooling sleeve 114; a profile ignition pickup signal
(PIP) from Hall effect sensor 118 coupled to crankshaft 40; and
throttle position TP from throttle position sensor in electronic
motor 64; and absolute Manifold Pressure Signal MAP from sensor
122. A pedal position indication (PP) may be determined by a pedal
position sensor 134 that senses the angle of pedal 130 according to
driver input 132. Engine speed signal RPM may be generated by
controller 12 from signal PIP and manifold pressure signal MAP from
a manifold pressure sensor provides an indication of vacuum, or
pressure, in the intake manifold. Controller 12 may be configured
to cause combustion chamber 30 to operate in various modes of
operation including homogeneous or stratified spark ignition or
compression ignition modes, for example. Controller 12 may control
the amount of fuel delivered by fuel injector 66 so that the
air/fuel mixture in cylinder 30 may be selected to be at
stoichiometry, a value rich of stoichiometry or a value lean of
stoichiometry. In some embodiments, controller 12 may control the
amount of fuel vapors purged into the intake port via a fuel vapor
purge valve (not shown) communicatively coupled thereto. Further,
in some embodiments, engine 10 may include an exhaust gas
recirculation (EGR) system that routes a desired portion of exhaust
gas from exhaust port 48 to intake port 44 via an EGR valve (not
shown). Alternatively, a portion of combustion gases may be
retained in the combustion chambers by controlling exhaust valve
timing.
[0024] As described above, FIG. 1 merely shows one exemplary
cylinder of a multi-cylinder engine, and that each cylinder has its
own set of intake/exhaust valves, fuel injectors, spark plugs, etc.
Furthermore, although the above described engine is shown with a
port injection configuration, it should be appreciated that an
engine may be configured to inject fuel directly into the cylinders
without parting from the scope of this disclosure.
[0025] FIGS. 2A-2C show exemplary multi-group engine configurations
(such as 2-bank engines, etc.) with Y-pipe exhaust, and/or an
asymmetric sensor configuration. Note that these Figures are purely
exemplary and other multi-group engine configurations also may be
used. It should be appreciated that a cylinder group may include
one or more cylinders. Further, note that while numerous sensors
are shown throughout the exhaust system, in some embodiments a
subset of these sensors may be used.
[0026] Referring now to FIG. 2A, an exemplary asymmetric exhaust
sensor configuration is described using a V-8 engine. The
asymmetric configuration may be beneficial for detection of
different operating condition throughout operation of different
engine modes. Cylinders of a first combustion chamber group (which
are shown as a bank, although the group may include cylinders from
multiple banks, or may include a subset of cylinder in a bank) 210
may be coupled to first catalytic converter 220, while cylinders of
a second combustion group 210 (which is also shown as a bank, but
as noted above is not necessarily limited to a bank) may be coupled
to second catalytic converter 222. Linear exhaust gas sensor 230
may be disposed between engine group 210 and first catalyst 220. In
some embodiments sensor 230 may be a universal exhaust gas oxygen
(UEGO) sensor. Further, switching type exhaust gas sensor 232 may
be disposed downstream of first catalyst 220. In some embodiments
sensor 232 may be a heated exhaust gas oxygen (HEGO) sensor.
Switching type exhaust gas sensor 234 may be disposed between
engine group 212 and second catalyst 222. Further, switching type
exhaust gas sensor 236 may be disposed downstream of second
catalyst 222. In some embodiments sensors 234 and 236 may be HEGO
sensors. Exhaust gas exiting from first catalyst 220 and second
catalyst 222 merge in a Y-pipe configuration before entering
downstream under body catalyst 224. In some embodiments downstream
catalyst 224 may be a lean NOx trap. Temperature sensor 238 may be
disposed in underbody catalyst 224, while a combined NOx-UEGO
sensor 240 may be disposed downstream of underbody catalyst
224.
[0027] Note that a linear exhaust gas sensor (more specifically a
UEGO sensor) may provide a substantially linear indication of
exhaust air-fuel ratio across a range of air-fuel ratios from at
least 12:1 to 18:1, or 11:1 to 20:1, or various other ranges and
subranges. The substantially linear relationship between the sensor
output voltage and exhaust gas oxygen concentration allows the
sensor to operate across a wide range of air-fuel ratios, and
therefore can provide advantageous information when operating away
from stoichiometry.
[0028] Further note that a switching type or non linear exhaust gas
sensor (more specifically a HEGO sensor) may provide a high gain
between measured oxygen concentration and voltage output. That is,
a nonlinear sensor may produce an output that is close to being a
step change in voltage at stoichiometry. Hence, the switching type
exhaust gas sensor may provide an accurate indication of the
stoichiometric point based on the voltage step output.
[0029] In some embodiments, various sensors may be integrated into
the catalysts while other sensors may be placed upstream or
downstream of the catalyst. For example, sensor 240 may be
integrated into underbody catalyst 224 or sensor 238 may be placed
upstream of underbody catalyst 224. Further, in some embodiments
sensors may be disposed between bricks in a multi-brick catalyst,
such as sensor 240.
[0030] Also, sensors 230-240 may be sensors of various types. For
example, the sensors may be any of many example sensors for
providing an indication of exhaust gas air/fuel ratio such as a
linear oxygen sensor for providing indication of air-fuel ratio
across a broad range, a switching type exhaust gas oxygen sensors
that provide a switch in sensor output at the stoichiometric point,
a UEGO, a two-state oxygen sensor, an EGO, a HEGO, or an HC or CO
sensor. Furthermore, in some embodiments, mixed sensor types may be
used, for example, a UEGO sensor may also have NOx detection
capabilities.
[0031] In some embodiments first catalyst 220 and second catalyst
222 may be three way catalysts that retain oxidants when operating
lean and release and reduce the retained oxidants when operating
rich. Additionally, underbody catalyst 224 may be configured to
operate as a lean NOx trap which may reduce residual oxidants that
flow downstream. Further, the illustrated catalysts may represent
multiple bricks, and/or may represent several separate emission
control devices. Note that in some embodiment various other
emission control devices may be used.
[0032] The above described configuration may be considered
asymmetric due to the fact that two or more engine banks or groups
may be monitored by at least one different type of sensor. In this
particular embodiment, feed gas from first bank or cylinder group
210 may be monitored by linear exhaust gas sensor 230, while feed
gas from second engine bank or cylinder group 212 may be monitored
by a switching type exhaust gas sensor 234. Furthermore, note that
in some embodiments the linear exhaust gas sensor and the switching
type exhaust gas sensor may be configured such that the sensors may
be disposed in exhaust flows of the engine banks or groups opposite
of what is shown in FIGS. 2A-2C. In some embodiments, the
asymmetric configuration may be applied to various other cylinder
groupings and/or exhaust system configurations. For example, in an
asymmetric configuration sensors may be located in positions
downstream of catalysts, or one sensor may be upstream and another
downstream.
[0033] Also, while FIG. 2A shows a V-8 engine, various other
numbers of cylinders may be used. For example, an I-4 engine may be
used, where there are two groups of two cylinders leading to a
common exhaust path with upstream and downstream emission control
devices.
[0034] Referring now to FIG. 2B, a system similar to that in FIG.
2A is shown, however a V-6 type engine is shown, rather than a V-8
engine.
[0035] Referring now to FIG. 2C, a system similar to that in FIG.
2A is shown, however an inline type engine (I-6) is shown, rather
than a V-8 engine.
[0036] As described below, such asymmetric configurations may be
used to advantage during various modes of operation, such as, for
example, stoichiometric operation, lean burn operation, operation
of decontamination cycles, in particular, desulfation (DeSOx) mode,
partial cylinder fuel cut-out mode, as well as various other modes
of operation.
[0037] For example, the engine may operate at stoichiometry, namely
one or more (e.g. both) engine banks or cylinder groups may operate
with an air-fuel ratio about stoichiometry. Furthermore, the engine
may operate lean wherein both engine banks or cylinder groups may
operate with an air-fuel ratio lean of stoichiometry in order to
increase fuel economy.
[0038] Additionally, during decontamination cycles, such as
desulfation (DeSOx) mode, for example, first engine group 210 may
operate with an air-fuel ratio that is rich and second engine group
212 may operate with an air-fuel ratio that is lean. In this way,
the mixed exhaust from the two engine banks may be substantially
stoichiometric downstream and generate exothermic heat. During
DeSOx mode the engine groups further may alternate between rich and
lean operation within each cycle in order to reduce particulate
buildup in the catalysts.
[0039] Furthermore, during lean burn partial cylinder fuel injector
cut-out mode a first group of cylinders may operate lean, and a
second group of cylinders may induct gasses without injected fuel.
This mode of engine operation may increase fuel economy while also
increasing engine output efficiency. Alternatively, in a
stoichiometric partial cylinder fuel injector cut-out mode, a first
group of cylinders may operate about stoichiometry, and a second
group of cylinders may induct gases without injected fuel. In still
another example, partial cylinder fuel injector and cylinder valve
deactivation may be used, where the cylinder valves and fuel
injectors may be deactivated. This mode of operation may provide
engine output characteristic similar to that of a variable
displacement engine due to the fact that the cylinders with fuel
cut-out also have valve deactivation in order to maintain
stoichiometric output by the active cylinders so that the exhaust
may be treated in the three way catalysts.
[0040] Furthermore, in some embodiments a controller may be
configured to operate the engine in a mode, where both the first
and second cylinder groups pump air without injecting fuel. This
mode of operation may be used for example, during vehicle
deceleration to further improve fuel economy.
[0041] It should be appreciated that during fuel injector cut-out
modes cylinders designated for fuel cut-out may be grouped by
engine group or bank. Alternatively, in some embodiments a
particular cylinder grouping may include cylinders in both engine
banks. Further, fuel cut-out may be limited to individual cylinders
or groups of cylinders. Cylinder groupings may be designated
according to an engine control strategy. Such a strategy may
designate an engine bank or cylinder group for fuel injector
cut-out based on detection of various operating conditions. For
example, fuel injector cut-out mode may switch between engine banks
or cylinder groups to maintain even wear on cylinders in each
engine bank or cylinder group.
[0042] Note that the above engine modes are exemplary. Further, the
above described engine operations may be employed in combination
with other operating modes or may include variations based on
different operating parameters. For example, each of the above
modes may include further variations based on, for example, cam
timing, valve lift, throttle position, etc.
[0043] Additional details of control routines are included below
which may be used with various engine configurations, such as those
described in FIGS. 1 and 2A-2C. As will be appreciated by one of
ordinary skill in the art, the specific routines described below in
the flowcharts 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 acts
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 of the invention
described herein, but is provided for ease of illustration and
description. Although not explicitly illustrated, one of ordinary
skill in the art will recognize that one or more of the illustrated
acts or functions may be repeatedly performed depending on the
particular strategy being used. Further, these figures may
graphically represent code to be programmed into the computer
readable storage medium in controller 12.
[0044] FIGS. 3A-3B show flow diagrams depicting a method of
estimating maximum torque produced by an engine during various
modes of operation, wherein the engine exhaust may be configured
with an asymmetric exhaust sensor configuration. Specifically, the
example approaches described herein may be used to estimate torque
in a robust manner such that issues associated with inaccurate
torque estimations may be addressed. For example, in the case of a
continuously variable transmission, if the actual torque is higher
than the estimated torque, excessive wear and/or damage to the
transmission may occur over time due to insufficient clutch/band
pressure. However, if the estimated torque is less than the actual
torque the clutch/band pressure may be set higher than optimal
resulting in reduced drivability and fuel economy. The torque
estimation process described in FIGS. 3A-3B may be used to overcome
some of these issues resulting in a more robust control
strategy.
[0045] Now referring to FIG. 3A, one example routine of torque
estimation begins at 310, where the engine bank or cylinder group
specific air-fuel ratios are determined. While this routine
describes a bank specific approach, various types of cylinder
groupings may be used, as noted herein with regard to FIG. 2. As
shown in FIG. 3B, the determination of 310 varies according to the
detected mode of operation. If it is determined that the engine is
operating in a lean burn mode, the routine moves to 312, where the
air-fuel ratio measured by the feedgas UEGO sensor may be validated
via an air-fuel ratio validation routine (described in more detail
below with regard to FIGS. 4A-4B). If the air-fuel ratio
measurement from the feedgas UEGO sensor is validated, it may be
assumed that each engine bank or cylinder group is operating under
the same or similar lean conditions. Thus, the air-fuel ratio
determination can be assumed to be the same for each engine bank or
cylinder group. Accordingly, the air-fuel ratio of each engine bank
or cylinder group may be determined by comparing the commanded
(desired) air-fuel ratio for each engine bank or cylinder group
from the engine controller to the actual air-fuel ratio measured by
the feedgas UEGO sensor. The smaller (richer) of the two air-fuel
ratios may be determined to be the air-fuel ratio used for the
maximum torque estimation. If the determined air-fuel ratio is rich
beyond a desired torque output value, the air-fuel ratio may be
clipped to the desired torque output value.
[0046] In the case where the feedgas UEGO sensor validation is
unsuccessful, the commanded air-fuel ratio may be used for the
maximum torque estimation. Furthermore, if the commanded air-fuel
ratio is rich beyond a desired torque output value, the air-fuel
ratio may be clipped to the desired torque output value.
[0047] If it is determined that the engine is operating in a DeSOx
mode, the routine moves to 314. As discussed above, during DeSOx
mode a first engine bank or cylinder group may operate lean and a
second engine bank or cylinder group may operate rich. The air-fuel
ratio of the engine bank or cylinder group operating lean may be
determined by comparing the commanded air-fuel ratio from the
engine controller to the actual air-fuel ratio measured by the
feedgas UEGO sensor. The smaller (richer) of the two air-fuel
ratios may be determined to be the air-fuel ratio used for the
maximum torque estimation. If the determined air-fuel ratio is rich
beyond a desired torque output value, the air-fuel ratio may be
clipped to the desired torque output value.
[0048] Furthermore, the air-fuel ratio of the engine bank or
cylinder group operating rich may be assumed to be operating at
stoichiometry or slightly rich for a desired maximum output
value.
[0049] If it is determined that the engine is operating in a lean
burn injector cut-out mode, the routine moves to 316. In this
engine operation mode, the air-fuel ratio determination may be made
for the active engine bank or cylinder group. When the engine bank
or cylinder group upstream of the feedgas UEGO sensor is active,
the air-fuel ratio may be determined by comparing the commanded
air-fuel ratio from the engine controller to the actual air-fuel
ratio measured by the feedgas UEGO sensor. The smaller (richer) of
the two air-fuel ratios may be determined to be the air-fuel ratio
used for the maximum torque estimation. If the determined air-fuel
ratio is rich beyond a desired torque output value, the air-fuel
ratio may be clipped to the desired torque output value. In some
instances the desired output value may be a maximum torque
value.
[0050] Otherwise, if the active engine bank or cylinder group is on
the other branch of the Y-pipe exhaust (non UEGO sensor branch) the
air-fuel ratio may be determined to be the commanded air-fuel
ratio.
[0051] It should be appreciated that in some embodiments the
air-fuel ratio for each engine bank or cylinder group may be
determined only using the commanded air-fuel ratio. For example, in
some V-8 engine configurations cylinders may be grouped such that a
cylinder group may produce exhaust down both pipes of a Y-pipe
exhaust configuration. In such a configuration not all exhaust from
the active cylinder group may travel past the feedgas UEGO sensor
making the measurements from the feedgas UEGO sensor erroneous with
regard to accurately determining the cylinder group's air-fuel
ratio. In this example, when the engine is in lean burn fuel
injector cut-out mode, the air-fuel ratio for each engine bank or
cylinder group is assumed to be the commanded air-fuel ratio.
[0052] If it is determined that the engine is operating in a
stoichiometric injector cut-out mode, the routine moves to 318. In
this engine operating mode, the air-fuel ratio determination is
made for the active engine bank or cylinder group, and the air-fuel
ratio of the active engine bank or cylinder group may be assumed to
be stoichiometry or slightly rich of stoichiometry for the estimate
of maximum torque output value.
[0053] If it is determined that the both engine banks or cylinder
groups are operating at stoichiometry, the routine moves to 320. At
320, the air-fuel ratio of both engine banks or cylinder groups can
be assumed to be stoichiometry or slightly rich of stoichiometry
for the estimate of maximum torque output value.
[0054] It should be appreciated that in some embodiments the
commanded air-fuel ratio term used in the above described engine
bank or cylinder group specific air-fuel ratio determination may
further include a long term correction term which may take into
account engine component degradation and other suitable correction
factors.
[0055] After the engine bank or cylinder group specific air-fuel
ratios are determined, the routine moves to 330 where the spark
delta of each engine bank or cylinder group may be calculated. This
calculation may be performed in different ways. In one example, a
spark delta figure may be retrieved from a lookup table mapped to
the minimum spark timing for best torque (MBT) output across the
operating range of the engine, based on such conditions as coolant
temperature, humidity, air temperature, and/or various others.
[0056] Next, the routine calculates the torque ratio of each engine
bank or cylinder group at 340 using the previously determined
engine bank or cylinder group specific air-fuel ratios and spark
delta. Further at 350, the routine calculates the torque ratio of
the active engine bank if the engine is operating in a fuel
injector cut-out mode. This calculation may also be supported by
verification of the fuel injector activity by a fuel injector
activity verification routine (discussed in more detail below with
regard to FIGS. 5A-5B).
[0057] Continuing on, the routine calculates the total torque ratio
of each engine bank at 360 using the determined air-fuel ratios,
spark delta, and fuel injector activity verification information.
In some embodiments a percent methanol figure may also be taken
into consideration to account for the combustibility and/or energy
density of the fuel.
[0058] Next at 370, routine 300 calculates the combined engine bank
torque ratio while taking into consideration the weighted torque
contribution of the active cylinders in each engine bank.
Specifically, the combined torque ratio of the engine (tr_act_cond)
may be calculated by adding the actual torque (tr_act_cond_a[0])
produced by cylinders in a fist engine bank (bank [0]) multiplied
by the number of active cylinder in that bank (numcyl_A[0]) to the
actual torque (tr_act_cond_a[1]) produced by cylinders in a second
engine bank (bank [1]) multiplied by the number of active cylinders
in that engine bank (numcyl_A[1]).
[0059] Further at 380, the routine calculates the
combustion/indicated torque. Specifically, the combustion/indicated
torque (tqe_ind_act) may be calculated by multiplying the
previously calculated combined torque ratio of the engine
(tr_act_cond) with the indicated torque (tqe_ind), where the
indicated torque is the MBT torque output at stoichiometry.
[0060] Finally at 390, the routine calculates the brake (net)
torque. Specifically, the brake torque (tqe_brk) equals the
combustion/indicated torque (tqe_ind_act) minus the total torque
loss (tqe_loss). The total torque loss may be the sum of the losses
due to friction, pumping losses, parasitic losses associated with a
front engine accessory drive (FEAD), and any other suitable loss
determinant. Accordingly, torque estimation routine 300 may be
repeated numerous times throughout engine operation in order to
provide a robust engine control strategy.
[0061] In this way, a robust maximum engine torque estimation may
be made for an engine control system that includes different modes
of engine operation. Furthermore, the robust torque estimation may
facilitate engine output according to driver demand without causing
adverse affects such as for example, reduced fuel economy and
lowered drivability. The above estimated torque may be used for
various operations, such as controlling/adjusting a ratio of a
stepped or continuously variable transmission,
controlling/adjusting transmission clutch pressures, monitoring
engine torque production versus driver demand, adjusting engine
actuators such as a throttle position or spark timing, and various
others.
[0062] Furthermore, in some embodiments an additional feedgas
linear exhaust gas sensor may be disposed in the exhaust passage
coupled to the second cylinder group, so that a linear exhaust gas
sensor may be used to detect the air-fuel ratio of each of the
first and second cylinder groups. In such a configuration the
smaller (richer) air-fuel ratio of the two feedgas linear exhaust
gas sensors may be used for the maximum torque estimation. Note
that in some embodiments additional linear exhaust gas sensors may
be disposed in the exhaust system downstream of the feedgas linear
exhaust gas sensors for added redundancy and confirmation of
measured air-fuel ratios.
[0063] In an exemplary embodiment, electronic engine controller 12
may further include an on-board diagnostic (OBD) system (not
shown). The OBD system may detect operating component degradation
through various diagnostic routines. In some instances, if a
routine detects performance degradation, the routine may set a
fault (or condition) flag and may trigger a diagnostic trouble code
(alternatively referred to as a service code) in the electronic
engine controller. As another example, if a routine detects
performance degradation, one or more modes of operation may become
restricted or disabled. Many routines within the on-board
diagnostics system may detect emission related degradation in a
range of operating conditions of the engine.
[0064] One embodiment advantageously implements a routine to
monitor air-fuel measurements from a feedgas UEGO sensor in order
to prevent air-fuel control operation based on errors in the
feedgas UEGO sensor. Exemplary air-fuel validation routine 400 may
be used to validate a feedgas UEGO sensor measurement in an
asymmetric exhaust sensor configuration based on a downstream UEGO
sensor measurement. Specifically, the routine validates the feedgas
UEGO senor measurement by comparing it to the tailpipe UEGO sensor
measurement, while also taking into consideration mode of engine
operation, transportation delay times, catalyst impact and other
noise factors.
[0065] Now Referring to FIG. 4A, routine 400 begins by buffering
feedgas UEGO measurements taken over a period of three seconds into
memory in the engine controller at 410. Although the routine
buffers feedgas UEGO sensor measurements over a period of three
seconds, it should be appreciated that any suitable period of time
or number of events, such as crank angles, may be buffered so long
as it is sufficient to cover the maximum exhaust transportation
time from the feedgas to tailpipe UEGO locations.
[0066] Next at 412, routine 400 checks the entry conditions for the
air-fuel validation routine. Specifically, the routine confirms
that both engine banks are operating in a lean burn mode, that all
fuel injectors are active, and that no misfires are taking place.
These checks are performed because certain modes of operation and
engine conditions may cause the UEGO sensors' readings to not
accurately represent the air-fuel ratio of the engine.
[0067] For example, in DeSOx mode a lean air-fuel ratio exhausted
from one engine bank may be read by the feedgas UEGO sensor, and a
rich air-fuel ratio may be exhausted from the other engine bank.
Further, the air-fuel ratios may combine downstream to become
approximately stoichiometric before being read by the tailpipe UEGO
sensor. In this case, the feedgas UEGO sensor on one engine bank
measures lean, however the rich exhaust from the other engine bank
causes the measurement of the air-fuel ratio read by the tailpipe
UEGO sensor to be skewed. As another example, when fuel injectors
are deactivated in an engine bank but the valves are left active,
the air flowing through these cylinders into the exhaust may also
skew the tailpipe UEGO reading. Furthermore, cylinder misfires may
skew UEGO sensor measurements by producing inconsistent air-fuel
ratios. Thus, air-fuel measurements may be validated when both
engine banks operate in a lean burn mode, all fuel injectors are
active, and no cylinder misfires are taking place.
[0068] If conditions in 412 are not met, the routine the routine
ends. Otherwise, if the conditions in 412 are met, the routine
transitions to step 414.
[0069] Next at 414, routine 400 increments a timer to measure the
amount of time for the exhaust gas to travel from the feedgas UEGO
sensor downstream and saturate the catalysts causing an oxygen
breakthrough to occur. While this example uses time, various other
durations may be used, such as a number of engine cycles, or other
such non-time based duration.
[0070] At 416, routine 400 determines if the measured time is
greater than an expected breakthrough time or if the exhaust sensor
system detects an oxygen breakthrough. The expected breakthrough
time may be calculated using a function based on the measured air
mass (fn(AM)) of the exhaust. If not enough time has elapsed since
the entry conditions were determined to be suitable for air-fuel
validation and the oxygen breakthrough in the catalysts has not
been detected, routine 400 ends. However, if enough time has
elapsed or an oxygen breakthrough has occurred routine 400 moves to
418.
[0071] At 418, routine 400 calculates the expected transportation
delay time for the exhaust to travel from the feedgas UEGO sensor
to the tailpipe UEGO sensor. The expected transportation delay time
may be calculated using a function based on the measured air mass
and air speed (FN(AM,N)). It should be noted that a variety of
other parameters could also be used to determine the transportation
delay time.
[0072] Next at 420, routine 400 looks up the buffered feedgas UEGO
measurements (see 410) based on the expected transportation delay.
Specifically, the expected delay time is subtracted from the
present time and the feedgas UEGO reading taken at that time may be
used. Additionally, routine 400 looks up buffered feedgas UEGO
measurements taken at a time before and at a time after the
measurement taken at the expected time delay. The measurement times
may be shifted a distance from the expected time delay measurement
according to a calibratible time shift based on various operational
conditions, for example, component degradation, and other suitable
control strategies.
[0073] At 422, routine 400 determines a maximum value (MAX) and a
minimum value (MIN) of the three feedgas UEGO measurements.
[0074] Next at 424, routine 400 shifts the minimum and maximum
values to account for a known signal measurement shift between the
feedgas UEGO sensor reading and the tailpipe UEGO sensor reading.
Specifically, a tailpipe UEGO sensor measurement in many cases
reads lower than a feedgas UEGO sensor measurement. This shift may
be based on the dynamics of the exhaust system and the interaction
of the exhaust flow with the catalysts.
[0075] Continuing on at 426, routine 400 compares the maximum and
the minimum values to the tailpipe UEGO sensor measurement of the
air-fuel ratio. These comparisons determine if the tailpipe UEGO
sensor is operating within the expected window (or range). In some
embodiments, the maximum and minimum values further may be shifted
by calibratible limits that may be used to account for the
tolerances of the exhaust sensor system. If it is determined that
the tailpipe UEGO sensor measurement is between the maximum and
minimum value +/- a calibratible limit, it may be assumed that the
tailpipe UEGO sensor is operating as expected, and routine 400
decrements a fault counter at 428 and the routine ends.
[0076] Otherwise, if it is determined that the tailpipe UEGO sensor
measurement is outside of the maximum and minimum values then the
fault counter is incremented at 430.
[0077] Next at 432, routine 400 compares the fault counter to a
calibratible threshold to determine if degradation has occurred in
the UEGO sensors. If the fault counter is greater than the
calibratible threshold then it may be assumed that degradation has
occurred and an air-fuel validation condition flag may be set at
434. Note that setting of an air-fuel validation flag may result in
engine control strategy reconfiguration which may include default
engine operations (discussed in more detail below with reference to
FIG. 6). Otherwise the fault counter is not greater than the
calibratible limit and the routine ends. Accordingly, air-fuel
validation routine 400 may be repeated numerous times throughout
engine operation in order to provide a robust engine control
strategy.
[0078] Note that according to the above routine, the feedgas linear
exhaust gas sensor readings may not be verified based on the
downstream linear exhaust gas sensor readings under various
operating conditions and in various modes of engine operation. In
particular, if the entry conditions for the verification routine
are not met, the engine operating conditions are likely to produce
confounded readings in the downstream linear exhaust gas sensor due
to a combination of different air-fuel ratios produced by each
cylinder group which mix as the exhaust gas travels through the
exhaust system. Additionally, engine misfires and/or no fuel
injection may skew the detected air-fuel ratio to be leaner than
during full cylinder group combustion.
[0079] Furthermore, the above routine advantageously checks for
suitable entry conditions including lean operation because linear
exhaust gas sensors may have more accurate air-fuel ratio readings
in a lean air-fuel ratio range. By performing linear exhaust gas
sensor verification and diagnosis of degradation in an asymmetric
exhaust configuration during lean operation errors related to
sensor type and respective range of measurement accuracy may be
reduced.
[0080] In this way, a feedgas UEGO sensor in an asymmetric exhaust
sensor system may be validated in order to prevent unexpected
engine output and maintain a functional engine control
strategy.
[0081] One exemplary embodiment advantageously implements a fuel
injector activity verification routine as part of a robust engine
control strategy. Referring to FIG. 5, exemplary fuel injector
activity verification routine 500 is shown. Specifically, routine
500 verifies that fuel injectors are, in fact, deactivated when the
associated cylinder are commanded to be cut-out and/or disabled as
part of the engine control strategy. For example, in some
powertrain control strategies it may be desirable from a fuel
economy standpoint to disable a portion of the cylinder fuel
injection and increase the air load of the remaining active
cylinders in order to maintain a desired engine torque. During such
a mode of operation if the cylinders are commanded to be
deactivated but the fuel injectors remain active and the air load
is increased, then an increased amount of torque may be produced.
The verification routine described in FIG. 5 may be used to
overcome some of these issues resulting in a more robust control
strategy.
[0082] Fuel injector activity verification routine 500 begins at
510 where the fuel injection activity signals may be read to
determine the actual fuel injector activity for each of the
cylinder groups. In some embodiments, fuel injection activity may
be communicated to the electronic engine controller via logic
circuitry.
[0083] Referring now to FIG. 7, an exemplary sense fuel injector
activity circuit 700 is shown. In this example cylinder group 210
and cylinder group 212 each include four cylinders (not shown) and
four fuel injectors, respectively. However, note that the number of
cylinders and/or fuel injectors may vary in each cylinder group.
Furthermore, each fuel injector may be connected to a sense
injector line that shows the fuel injection activity for each
cylinder. The sense injector lines associated with cylinder group
210 may be inputs into "AND" logic gate 702 and the sense injector
lines associated with cylinder group 212 may be inputs into "AND"
logic gate 704. The outputs of "AND" logic gates 702 and 704 may
provide signals showing whether or not there is fuel injector
activity in either of the cylinder groups. The outputs of "AND"
logic gates 702 and 704 further may be inputs into the electronic
engine controller 12, which may indicate whether or not there is
any fuel injector activity in a specific group of cylinders.
[0084] It should be appreciated that the above described Boolean
logic circuit is exemplary. Note that the exemplary circuit may be
included as part of a larger logic circuit. Alternatively, other
logic operations may be performed to indicate fuel injector
activity from the sense injector lines. In some embodiments, the
logic circuit may include feedback from a commanded fuel injection
signal. Although the Boolean logic circuit is schematically
illustrated with discrete logic gates, it should be appreciated
that in some embodiments, logical operations may be performed using
customizable integrated circuits, a programmable microcontroller
and/or the engine controller.
[0085] Continuing at 520, the routine determines if the controller
has commanded fuel injector activity for any of the specific
cylinder groups. For example, if at least one fuel injector in the
group has been commanded on, the group of cylinders may be
considered to be actively injecting fuel. If no fuel injectors are
commanded on, the group of cylinders may be considered to be
inactive.
[0086] Next at step 530, the routine checks if the actual fuel
injector activity for the first cylinder group from step 510 agrees
with the commanded injector activity for the first cylinder group
determined in step 520. If the commanded activity agrees with the
actual activity, the routine moves on to step 540. At 540, the
routine decrements a fault counter and transitions to step 560. If
at step 530 the commanded activity does not agree with the actual
activity, the routine moves to step 550. At 550, the routine
increments a fault (or condition) counter and then checks the fault
(or condition) counter to a calibratible threshold at step 552. If
the fault (or condition) counter exceeds this threshold, the
routine sets a condition flag and transitions to step 560. The
condition flag may be used by other routines to change the mode of
operation as will be discussed in further detail below (see steps
644 and 652 of FIG. 6). If the fault (or condition) counter does
exceed the calibratible threshold, the routine transitions to step
560.
[0087] Next at step 560, the routine checks if the actual fuel
injector activity for the second group from step 510 agrees with
the commanded injector activity for the second group determined in
step 520. If the commanded activity agrees with the actual
activity, the routine moves to step 570. At 570, the routine
decrements a fault counter and exits the routine. If at step 560
the commanded activity does not agree with the actual activity, the
routine moves to step 580. At 580, the routine increments a fault
(or condition) counter and then checks the fault (or condition)
counter to a calibratible threshold at step 582. If the fault
counter exceeds this threshold, the routine sets a condition flag
and exits the routine. The condition flag may be used by other
routines to change the mode of operation as will be discussed in
further detail below (see steps 644 and 652 of FIG. 6). If the
fault (or condition) counter does exceed the calibratible
threshold, the routine ends. The fuel injector activity
verification routine 500 may be repeated numerous times throughout
engine operation in order to provide a robust engine control
strategy.
[0088] In an alternative embodiment, fuel injection activity may be
communicated to the electronic engine controller through a single
line using logic circuitry. Specifically, logic circuitry may be
used to determine if a fuel-injector cut-out mode is active or
inactive.
[0089] Referring to FIG. 8, Fuel injector activity verification
routine 800 begins at 810 where the fuel injection signal may be
read off of the sense injector line to determine the fuel injector
activity for the engine groups. Next, at 820 it may be determined
if the engine is in fuel injector cut-out mode.
[0090] In some embodiments, the fuel injector cut-out mode
determination may be performed using a Boolean logic circuit.
Referring now to FIG. 9, an exemplary fuel injector cut-out
determination circuit 900 is shown. In this example cylinder group
210 and cylinder group 212 each include four cylinders (not shown)
and four fuel injectors, respectively. However, note that the
number of cylinders and/or fuel injectors may vary in each cylinder
group. Furthermore, each fuel injector may be connected to a sense
injector line that shows the fuel injection activity for each
cylinder. The sense injector lines associated with cylinder group
210 may be inputs into "AND" logic gate 902 and the sense injector
lines associated with cylinder group 212 may be inputs into "AND"
logic gate 904. The outputs of the "AND" logic gates 902 and 904
may provide signals showing whether or not there is fuel injector
activity in either of the cylinder groups. The outputs of "AND"
logic gates 902 and 904 further may be inputs into exclusive "OR"
logic gate 906, in order to provide a feedback signal to electronic
engine controller 12, which may indicate whether or not there is
injector activity only in a single group of cylinders (i.e. fuel
injector cut-out mode).
[0091] It should be appreciated that the above described Boolean
logic circuit is exemplary. Note that the exemplary circuit may be
included as part of a larger logic circuit. Alternatively, other
logic operations may be performed to indicate fuel injector
activity and detection of a fuel injector cut-out mode from the
sense injector lines. In some embodiments, the logic circuit may
include feedback from a commanded fuel injection signal. Although
the Boolean logic circuit is schematically illustrated with
discrete logic gates, it should be appreciated that in some
embodiments, logical operations may be performed using customizable
integrated circuits, a programmable microcontroller and/or the
engine controller.
[0092] Referring to FIG. 10, a truth table 1000 and graphical
representation 1010 show the possible inputs (i.e. cylinder group
specific fuel injector activity) and outputs (i.e. fuel injector
cut-out mode determination) of the exclusive "OR" logic circuit. In
a first exemplary condition, for example such as during a key-on
and engine-off situation, both inputs values may be zero.
Accordingly, the circuit may produce an output value of zero
indicating that a fuel injector cut-out mode is inactive.
[0093] In a second exemplary condition, for example such as when
the engine is running with all cylinders active, both input values
may be one. Accordingly, the circuit may produce an output value of
zero indicating that a fuel injector cut-out mode is inactive.
[0094] In a third exemplary condition, for example during a fuel
injector cut-out mode a first input value may be one and a second
input value may be zero. Accordingly, the circuit may produce an
output value of one indicating that a fuel injector cut-out mode is
active. Similarly, in a forth exemplary condition the engine may
operate in fuel injector cut-out mode with the other cylinder group
disabled. Accordingly, the input values of the circuit may be zero
and one and the output value may be one indicating that fuel
injector cut-out mode may be active.
[0095] Note that fuel injector activity further may be represented
according to a fuel injection pulse frequency. Additionally, in
some embodiments fuel injector activity/inactivity may be
determined according to a time threshold which may be longer than
the fuel injector pulse frequency. Such that when elapsed time
between fuel injection pulses remains below the threshold, the fuel
injectors may be determined to be active. Furthermore, if time
elapses longer than the threshold time, the fuel injectors may be
determined to be inactive.
[0096] Note that in some embodiment the routine may further detect
cylinder group sub-set fuel injector degradation. A group sub-set
may include one or more cylinders in a cylinder group. Furthermore,
fuel injector activity sensors may be configured to detect the fuel
injection activity of a particular cylinder group sub-set.
[0097] Continuing on with routine 800, if it is determined that the
fuel injector cut-out mode is active, the routine moves to 830. At
830, the actual fuel injector activity of each group or bank of
fuel injectors may be compared to the desired fuel injector
activity for each engine bank.
[0098] Next at 832, routine 800 determines if only the desired
group of fuel injectors is active. If only the desired group of
fuel injectors is active then a fault counter is decremented at
536. Otherwise, the fault counter is incremented at 834. Next at
838, the fault counter is compared to a calibratible threshold. The
threshold may be calibrated to vary the tolerance of the control
strategy to account for component degradation, desired engine
output, or another suitable calibration metrics. If it is
determined that the fault counter is greater than the calibratible
threshold then a sense injector activity condition flag is set, at
840. Otherwise, if it is determined that the fault counter is not
greater than the calibratible threshold then the routine ends.
Note, that the setting of a condition flag may result in various
operational changes that will be discussed in further detail
below.
[0099] Referring back to 820, if it is determined that the fuel
injector cut-out mode is inactive, the routine moves to 850 and
undergoes a similar sub-routine to verify the fuel injector
activity in both groups of cylinders. Namely, at 850, the actual
fuel injector activity in each group of cylinders is compared to
the commanded injector activity for each group of cylinders. At
852, routine 800 determines if both groups of cylinders show the
same fuel injector activity (i.e. both groups are active or
inactive). If it is determined that the fuel injector activity is,
in fact, the same between the groups of cylinders then the fault
counter is decremented at 856. If it is determined that the fuel
injector activity differs between the groups of cylinders the fault
counter is incremented at 854.
[0100] Next at 858, the fault counter is compared to a calibratible
threshold. As discussed above, the threshold may be calibrated
according to various operational conditions and control strategies.
If it is determined that the fault counter is greater than the
calibratible threshold then a sense injector activity fault (or
condition) flag is set, at 860. Otherwise, if it is determined that
the fault (or condition) counter is not greater than the
calibratible threshold then the routine ends. Accordingly, fuel
injector activity verification routine 800 may be repeated numerous
times throughout engine operation in order to provide a robust
engine control strategy.
[0101] In this way fuel injector activity may be verified during
different modes of engine operation to aid in reducing an undesired
engine response upon an error in fuel injector cutout control.
[0102] Note, that the setting of a condition flag may result in
various engine control strategy reconfigurations included in the
default mode strategy (discussed in further detail below with
regard to FIG. 6).
[0103] In some embodiments, the fuel injector activity verification
routine may be used in combination with the maximum torque
estimation routine as discussed above (see FIGS. 3A-3B). For
example, an engine control strategy may include modes to improve
fuel economy, such as fuel injector cut-out mode. In such a
strategy, air load may be increased by operating cylinder valves
without injecting fuel to maintain a desired torque. In such
situations, it may be desirable to verify fuel injector activity in
order to reduce torque produced when the air load is increased. In
this way, the fuel injector activity verification routine may be
used to make the maximum torque estimation more robust.
[0104] Note that the fuel injector activity verification routines
as described above also may be applied to variable displacement
engine control strategies where both fuel injection and cylinder
valve operation may be deactivated. In particular, fuel injection
activity may be monitored using the above described routine to aid
in reduce the likelihood of hydro-locking the engine due to fuel
injection activity in deactivated cylinders.
[0105] One embodiment advantageously implements a high-level
diagnostic routine as part of the default operation strategy.
Specifically, the diagnostic routine monitors performance
conditions during various modes of engine operation in order to
determine if the engine is able to perform as desired in the
particular mode of operation. Furthermore, the diagnostic routine
may make degradation determinations regarding different components
based on detection of various operating conditions. For example, a
determined degradation may result in setting a service code in the
electronic engine controller. Additionally, in some embodiments a
degradation determination may result in the change of an engine,
powertrain, and/or vehicle operating parameter. Moreover, the
degradation determination may result in prevention of entering or
exiting specific operational modes, or may trigger mode
transitions, in order to accommodate driver demand.
[0106] Referring to FIG. 6, diagnostic routine 600 detects the mode
of engine operation at 610. In the illustrated embodiment, the
determination may result in one of five monitored engine modes,
including lean burn, DeSOx, lean burn fuel injector cut-out,
stoichiometric fuel injector cut-out and stoichiometric operation.
However, it should be appreciated that in some embodiments various
modes of operation may be omitted or added to the list of monitored
engine modes in the diagnostic routine.
[0107] If it is determined that the engine is operating in lean
burn mode, the routine moves to 620 to begin the lean burn
diagnostic sub-routine.
[0108] At 622, diagnostic routine 600 determines if a condition has
occurred showing degradation of the feedgas UEGO sensor. Note that
degradation of the feedgas UEGO sensor may be detected when the
associated engine bank is command to run lean due to the linear
nature of the UEGO sensor output. If it determined that the feedgas
UEGO sensor has degraded, the routine move to 628.
[0109] Otherwise, diagnostic routine 600 determines if a condition
has occurred based on degraded validation of the air-fuel ratio
between the feedgas UEGO sensor and the tailpipe UEGO sensor at
624. This condition may be retrieved from air-fuel validation
routine 400 (discussed above). If it is determined that the
air-fuel validation has degraded, it may be assumed that the
tailpipe UEGO sensor has degraded and the routine moves to 628.
[0110] Otherwise, diagnostic routine 600 determines if a condition
has occurred based on degradation of components relating to the
electronic throttle control (ETC) and the torque monitor
independent plausibility check (IPC) of the vehicle at 626. If it
is determined that a component degradation condition has occurred
the routine moves to 628. Otherwise, no degradation condition has
been detected and the routine ends.
[0111] At 628, diagnostic routine 600 has detected degradation of a
component that affects the performance of the engine, and further
affects the effectiveness of the engine control strategy.
Specifically, lean burn diagnostic sub-routine 620 may concentrate
on detection of UEGO sensor degradation since the lean burn engine
control strategy uses accurate detection of the air-fuel ratio to
adjust the engine output such that both engine banks or groups run
lean. Accordingly, diagnostic routine 600 may reconfigure the
engine control strategy in order to avoid engine mode degradation
and to facilitate driver demand. Specifically, the routine may
initiate a coordinated exit from lean burn engine mode.
[0112] If it is determined that the engine is operating in DeSOx
mode, the routine moves to 630 to begin the DeSOx diagnostic
sub-routine.
[0113] At 632, diagnostic routine 600 determines if a condition has
occurred showing degradation of the feedgas UEGO sensor. Note that
due to the linear nature of the UEGO sensor output, degradation of
the feedgas UEGO sensor may be detected when the associated engine
bank is command to run lean. If it determined that the feedgas UEGO
sensor has degraded, the routine moves to 638.
[0114] Otherwise, diagnostic routine 600 determines if a condition
has occurred based on degraded validation of the air-fuel ratio
between the feedgas UEGO sensor and the tailpipe UEGO sensor at
634. This condition may be retrieved from air-fuel validation
routine 400 (discussed above). If it is determined that the
air-fuel validation has degraded, it may be assumed that the
tailpipe UEGO sensor has degraded and the routine moves to 638.
[0115] Otherwise, diagnostic routine 600 determines if a condition
has occurred based on degradation of components relating to the
electronic throttle control (ETC) and the torque monitor
independent plausibility check (IPC) of the vehicle at 636. If it
is determined that a component degradation condition has occurred
the routine moves to 638. Otherwise, no degradation condition has
been detected and the routine ends.
[0116] At 638, diagnostic routine 600 has detected degradation of a
component that affects the performance of the engine, and further
affects the effectiveness of the engine control strategy.
Specifically, DeSOx diagnostic sub-routine 630 may concentrate on
detection of UEGO sensor degradation since the DeSOx engine control
strategy uses accurate detection of the air-fuel ratio to adjust
the engine output such that one engine bank or group runs lean and
the other engine bank or group runs rich. Accordingly, diagnostic
routine 600 may reconfigure the engine control strategy in order to
avoid engine mode degradation and to facilitate driver demand.
Specifically, the routine may initiate a coordinated exit from
DeSOx engine mode.
[0117] If it is determined that the engine is operating in lean
burn fuel injector cut-out mode, the routine moves to 640 to begin
the lean burn fuel injector cut-out diagnostic sub-routine.
[0118] At 642, diagnostic routine 600 determines if a condition has
occurred showing degradation of the feedgas UEGO sensor. Note that
due to the linear nature of the UEGO sensor output, degradation of
the feedgas UEGO sensor may be detected when the associated engine
bank is command to run lean. Additionally, in some embodiments,
this act may be omitted since the feedgas UEGO sensor may provide
incomplete readings during lean burn injector cut-out mode due to
some engine configurations (i.e. cylinder groupings). If it
determined that the feedgas UEGO sensor has degraded, the routine
moves to 638.
[0119] Otherwise, diagnostic routine 600 determines if a condition
has occurred based on unexpected fuel injector activity read off
the sense injector line at 634. This condition may be retrieved
from fuel injector activity verification routine 500 (discussed
above). If it is determined that unexpected fuel injector activity
has occurred more times than a calibratible threshold, it may be
assumed that a fuel injection system related component has degraded
and the routine moves to 648.
[0120] Otherwise, diagnostic routine 600 determines if a condition
has occurred based on degradation of components relating to the
electronic throttle control (ETC) and the torque monitor
independent plausibility check (IPC) of the vehicle at 646. If it
is determined that a component degradation condition has occurred
the routine moves to 648. Otherwise, no degradation condition has
been detected and the routine ends.
[0121] At 648, diagnostic routine 600 has detected degradation of a
component that affects the performance of the engine, and further
affects the effectiveness of the engine control strategy.
Specifically, lean burn fuel injector cut-out diagnostic,
sub-routine 640 may concentrate on detecting fuel injector
degradation since the lean burn fuel injector cut-out engine
control strategy uses accurate detection of fuel injector activity
to reduce increased torque production. Accordingly, diagnostic
routine 600 may reconfigure the engine control strategy in order to
reduce engine mode degradation and to facilitate driver demand.
Specifically, the routine may initiate a coordinated exit from lean
burn fuel injector cut-out engine mode and transition to another
mode of engine operation.
[0122] If it is determined that the engine is operating in
stoichiometric fuel injector cut-out mode, the routine moves to 650
to begin the stoichiometric fuel injector cut-out diagnostic
sub-routine.
[0123] At 652, diagnostic routine 600 determines if a condition has
occurred based on unexpected fuel injector activity read off the
sense injector line at 652. This condition may be retrieved from
fuel injector activity verification routine 500 (discussed above).
If it is determined that unexpected fuel injector activity has
occurred more times than a calibratible threshold, it may be
assumed that a fuel injection system related component has degraded
and the routine moves to 656.
[0124] Otherwise, diagnostic routine 600 determines if a condition
has occurred based on degradation of components relating to the
electronic throttle control (ETC) and the torque monitor
independent plausibility check (IPC) of the vehicle at 654. If it
is determined that a component degradation condition has occurred
the routine moves to 656. Otherwise, no degradation condition has
been detected and the routine ends.
[0125] At 656, diagnostic routine 600 has detected degradation of a
component that affects the performance of the engine, and further
affects the effectiveness of the engine control strategy.
Specifically, stoichiometric fuel injector cut-out diagnostic
sub-routine 650 is concentrated on detecting fuel injector
degradation since the stoichiometric fuel injector cut-out engine
control strategy uses accurate detection of fuel injector activity
reduce torque production. Accordingly, diagnostic routine 600 may
reconfigure the engine control strategy in order to reduce engine
mode degradation and to facilitate driver demand. Specifically, the
routine may initiate a coordinated exit from stoichiometric fuel
injector cut-out engine mode and transition to another mode of
engine operation.
[0126] In the above described routine, note that upon detection of
component degradation, coordinated exit from an engine mode may be
implemented as part of the default operation strategy. In one
embodiment, the strategy may prioritize maintaining engine output
over component degradation upon detection of a degraded mode of
engine operation. Specifically, immediate exit from a potentially
degraded engine mode may be prevented in order to maintain engine
output in accordance with driver demand for a specified transition
duration. For example, the strategy may prevent exit from lean burn
engine mode when the air load has been raised in order to maintain
driver requested torque.
[0127] Coordinated exit from an engine mode may further include a
reconfiguration of the engine control strategy. In particular, the
controller may prevent entry into a mode based on detection of a
degradation condition. Furthermore, detection of a degradation
condition may cause the controller to prevent entry into multiple
modes of engine operation. For example, if a UEGO sensor detecting
air-fuel readings for a cylinder group is determined to be
degraded, the engine control strategy may prevent entry into any
modes where the cylinder group operates with a lean air-fuel ratio
in order to reduce engine control errors.
[0128] Furthermore, in some embodiments the engine may transition
out of different modes at different rates in order to accommodate
changes in operating conditions. For example, a transition out of
stoichiometric engine operation mode to a lean burn fuel injector
cut-out mode may occur faster than another mode transitions such as
transitioning out of a fuel injector cut-out mode. Specifically,
once fuel injection is disabled in a cylinder group, air load may
need to be increased quickly to increase engine torque output in
order meet driver demands.
[0129] As another example, during a fuel injector cut-out mode, air
load in the engine may be increased to produce a sufficient amount
of torque in the active cylinder group. If the engine transitions
out of the fuel injector cut-out mode to a mode where all cylinder
groups combust air and fuel without allowing for the air in the
engine to decrease and match the injected fuel, errors in torque
output and emissions may be increased. Therefore, the mode
transition may last over a longer duration than the above mentioned
transition out of stoichiometric engine operation.
[0130] Note that in some embodiments, an engine mode transition in
response to sensor degradation may be slower than a mode transition
in response to a driver request in order to provide a period to
match air and fuel amounts as discussed above, thus reducing the
likelihood of increased emissions due to un-matched air and fuel
amounts.
[0131] Furthermore, it should be appreciated that high level
diagnostic routine 600 may be repeated numerous times throughout
engine operation in order to provide a robust engine control
strategy. Alternatively, in some embodiments the diagnostic routine
may be omitted from the engine control strategy.
[0132] It will be appreciated that the configurations and routines
disclosed herein are exemplary in nature, and that these specific
embodiments are not to be considered in a limiting sense, because
numerous variations are possible. For example, the above technology
can be applied to V-6, I-4, I-6, V-12, opposed 4, and other engine
types. The subject matter of the present disclosure includes all
novel and nonobvious combinations and subcombinations of the
various systems and configurations, and other features, functions,
and/or properties disclosed herein.
[0133] The following claims particularly point out certain
combinations and subcombinations regarded as novel and nonobvious.
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
subcombinations 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.
* * * * *