U.S. patent application number 10/248760 was filed with the patent office on 2004-08-19 for computer controller for vehicle and engine system with carbon canister vapor storage.
This patent application is currently assigned to FORD GLOBAL TECHNOLOGIES, INC.. Invention is credited to Bidner, David Karl, Li, Yonghua, Surnilla, Gopichandra.
Application Number | 20040162666 10/248760 |
Document ID | / |
Family ID | 32849396 |
Filed Date | 2004-08-19 |
United States Patent
Application |
20040162666 |
Kind Code |
A1 |
Bidner, David Karl ; et
al. |
August 19, 2004 |
COMPUTER CONTROLLER FOR VEHICLE AND ENGINE SYSTEM WITH CARBON
CANISTER VAPOR STORAGE
Abstract
A method is described for controlling fuel vapor purging and
adaptive learning in a lean burn engine system. Fuel vapor purging
is carried out during lean operating conditions to minimize impact
on vehicle emissions, while adaptive learning is carried out during
near stoichiometric conditions (oscillations around stoichiometry).
This allows faster fuel vapor purging and additional adaptive
learning opportunity.
Inventors: |
Bidner, David Karl;
(Livonia, MI) ; Surnilla, Gopichandra; (West
Bloomfield, MI) ; Li, Yonghua; (Windor, CA) |
Correspondence
Address: |
KOLISCH HARTWELL, P.C.
200 PACIFIC BUILDING
520 SW YAMHILL STREET
PORTLAND
OR
97204
US
|
Assignee: |
FORD GLOBAL TECHNOLOGIES,
INC.
One Parklane Boulevard Suite 600 - Parklane Towers East
Dearborn
MI
|
Family ID: |
32849396 |
Appl. No.: |
10/248760 |
Filed: |
February 14, 2003 |
Current U.S.
Class: |
701/109 ;
123/674 |
Current CPC
Class: |
F02D 41/2441 20130101;
F02B 17/005 20130101; F02D 41/0042 20130101; F02D 41/0045 20130101;
Y02T 10/123 20130101; Y02T 10/12 20130101; F02D 41/2451 20130101;
F02D 41/2467 20130101; F02B 2075/125 20130101; F02B 23/104
20130101; F02D 41/2474 20130101 |
Class at
Publication: |
701/109 ;
123/674 |
International
Class: |
G05D 001/00 |
Claims
We claim:
1. An electronic control device for a vehicle, comprising: a
computer storage medium having a computer program encoded therein
for controlling an internal combustion engine coupled to an
emission control device and a sensor, the engine also coupled to a
fuel vapor storage device, said computer storage medium comprising:
code for operating the engine lean with periodic rich operating
durations; code for during at least said lean operation with
periodic rich operation, learning a fuel vapor amount from said
fuel vapor storage device based on the sensor, wherein fuel vapor
is combusted in the engine at least during a part of the lean and
rich operation; code for operating the engine at near
stoichiometric operating conditions; and code for during at least
said stoichiometric conditions, learning adaptive data.
2. The method recited in claim 1 wherein said sensor is a HEGO
sensor coupled upstream of the emission control device.
3. The method recited in claim 1 wherein said sensor is a UEGO
sensor coupled downstream of the emission control device.
4. The method recited in claim 1 further comprising code for
learning said adaptive data based on said sensor.
5. A method for controlling an engine coupled to a fuel system
having a fuel tank, the method comprising: operating the engine
with a first group of cylinders inducting air with substantially no
injected fuel, and a second group of cylinders inducting air and
receiving injected fuel; determining whether pressure in the tank
is greater than a threshold value; in response to said
determination, disabling said operation, and operating all of the
cylinders to combust air and fuel, said cylinders also combusting
inducted fuel vapors from the tank; and learning a fuel vapor
amount based on a sensor.
6. The method recited in claim 5 wherein said first group of
cylinders is equal to said second group of cylinders.
7. The method recited in claim 5 wherein said sensor is a UEGO
sensor.
8. The method recited in claim 5 wherein said sensor is a HEGO
sensor.
9. The method recited in claim 5 wherein said air with
substantially no injected fuel and said air with injected fuel mix
in an exhaust component.
10. The method recited in claim 5 wherein during the combusting of
all of the engine cylinders, the overall mixture of air to fuel in
the cylinders is lean of stoichiometry.
11. The method recited in claim 5 wherein said second group of
cylinders with air and injected fuel operates lean of
stoichiometry.
12. A system comprising: an emission control device capable of
storing NOx during at least some operating conditions; and a
controller programmed to operate an engine lean at least during a
light load operation; during at least a portion of said lean
operation, operate the engine to induct fuel vapors; and while
inducting said fuel vapors, switching the engine to stoichiometric
or rich operation to react NOx stored in said emission control
device.
Description
BACKGROUND OF INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a method and system for
controlling fuel vapor purging of a lean burn engine in addition to
performing adaptive learning at near stoichiometric operation.
[0003] 2. Background of the Invention
[0004] Engine fuel systems typically contain a canister for
collecting fuel vapors produced in the fueling system.
Periodically, these fuel vapors are passed through to the engine
and burned during engine combustion. In this way, the generated
fuel vapors are utilized by the engine and emissions are
decreased.
[0005] Engines also contain adaptive learning methods to learn air
flow sensor and fuel injector variations. These sensors and
actuators can vary from engine to engine, and can also vary over
time. These adaptive methods are used to learn this variation and
take corrective action.
[0006] One approach to incorporating fuel vapor purging and
adaptive learning into a lean burn engine discontinues lean
operation when fuel vapor purging is requested since this allows
learning of the fuel vapor concentration.
[0007] In another example, fuel vapors are periodically purged from
a fuel system into an engine's air/fuel intake. A measurement of
the massive inductive fuel vapors is provided by a purge
compensation signal is derived from an exhaust gas oxygen sensor
output. Lean air/fuel operation is enabled when the purge
compensation signal is below a predetermined value. Such a system
is described in U.S. Pat. No. 5,735,255.
[0008] However, the present inventors have recognized a
disadvantage with such approaches. In particular, since adaptive
learning is also performed during stoichiometric operation, there
is limited ability to learn both the fuel vapor concentration and
the air and fuel adaptive errors. In particular, air and fuel
adaptive errors, as well as changes in fuel vapor concentration,
affect the engine exhaust sensors in similar ways. As such, during
stoichiometric operation, it is generally possible to only perform
one at a time, thereby providing only limited operating time for
each. This can lead to degraded fuel vapor control, as well as
degraded adaptive learning. Furthermore, fuel vapor purging
performed during lean and high load operation can give degraded
performance since all of the fuel vapors may not be burned during
such high load lean operation.
SUMMARY OF INVENTION
[0009] The above disadvantages are overcome by a method for an
internal combustion engine coupled to an emission control device
and a sensor, the method comprises: operating the engine lean with
periodic rich operating durations; during said lean operation with
periodic rich operation, learning a fuel vapor amount based on the
sensor, wherein fuel vapor is combusted in the engine at least
during a part of the lean and rich operation; operating the engine
at near stoichiometric operating conditions; and during said
stoichiometric conditions, learning adaptive data.
[0010] By performing the fuel vapor purging during the lean/rich
operating conditions, while performing adaptive learning during
stoichiometric conditions, it is possible to provide sufficient
time to achieve accurate adaptive learning and accurate fuel vapor
learning. Further, an added advantage is that any errors in the
fuel vapor concentration during the lean operation, thereby causing
an error in the engine air-fuel ratio, provides only a minimal
impact since high accuracy air-fuel ratio control is not required
during lean operation (i.e., the primary emission is NOx, which is
being stored in the emission control device). Still further, an
added advantage is that when there is no need to perform fuel vapor
purging and adaptive learning, it is possible to run the engine
with a reduced number of cylinders, thus further reducing pumping
losses and improving fuel economy.
[0011] In another aspect of the invention, the above disadvantages
are overcome by a system. The system comprises an emission control
device capable of storing NOx during at least some operating
conditions; and a controller programmed to operate an engine lean
at least during a light load operation; during at least a portion
of said lean operation, operate the engine to induct fuel vapors;
and while inducting said fuel vapors, switching the engine to
stoichiometric or rich operation to react NOx stored in said
emission control device.
[0012] By using an emission control device that can store NOx
during certain operating conditions, one can operate lean while
combusting fuel vapors without having to stop the fuel vapor
purging when transitioning to stoichiometric or rich operation.
Also, any changes in the fuel vapor concentration provide only a
minimal impact since the engine is operating lean of
stoichiometry.
[0013] In other words, the present inventors have recognized that
if fuel vapors are inducted during certain lean operating
conditions, emissions are less susceptible to sudden changes in the
fuel vapor concentration due to fuel tank sloshing. Also, because
of this reduced sensitivity, it is possible to rapidly open or
close the fuel vapor purging valve, thereby allowing quicker fuel
vapor purging. Further still, feedback can be used to adjust and
check fuel to maintain the desired air-fuel ratio, as well as the
desired engine output torque.
BRIEF DESCRIPTION OF DRAWINGS
[0014] FIG. 1 is a block diagram of an engine for use with various
embodiments of the present invention;
[0015] FIG. 2 is a simplified block diagram of an example
embodiment of an engine and exhaust system;
[0016] FIGS. 2 and 2A are schematic representations of the
methodology of various aspects of the present invention;
[0017] FIGS. 3, 5-6, and 8-10 are high level flowcharts
illustrating various embodiments of the present invention; and
[0018] FIGS. 4-4D are high level flowcharts, while FIGS. 4E and F4
are graphs showing operating according to an embodiment of the
invention,
[0019] FIG. 7 shows a sequence of different operating modes
according to one embodiment of the present invention.
DETAILED DESCRIPTION
[0020] FIG. 1 shows one cylinder of a multi-cylinder engine, as
well as the intake and exhaust path connected to that cylinder.
[0021] Continuing with FIG. 1, direct injection spark ignited
internal combustion engine 10, comprising a plurality of combustion
chambers, is controlled by electronic engine controller 12.
Combustion chamber 30 of engine 10 is shown including combustion
chamber walls 32 with piston 36 positioned therein and connected to
crankshaft 40. A starter motor (not shown) is coupled to crankshaft
40 via a flywheel (not shown). In this particular example, piston
36 includes a recess or bowl (not shown) to help in forming
stratified charges of air and fuel. Combustion chamber, or
cylinder, 30 is shown communicating with intake manifold 44 and
exhaust manifold 48 via respective intake valves 52a and 52b (not
shown), and exhaust valves 54a and 54b (not shown). Fuel injector
66A is shown directly coupled to combustion chamber 30 for
delivering injected fuel directly therein in proportion to the
pulse width of signal fpw received from controller 12 via
conventional electronic driver 68. Fuel is delivered to fuel
injector 66A by a high pressure fuel system (not shown) including a
fuel tank, fuel pumps, and a fuel rail.
[0022] Intake manifold 44 is shown communicating with throttle body
58 via throttle plate 62. In this particular example, throttle
plate 62 is coupled to electric motor 94 so that the position of
throttle plate 62 is controlled by controller 12 via electric motor
94. This configuration is commonly referred to as electronic
throttle control (ETC), which is also utilized advantageously
during idle speed control. In an alternative embodiment (not
shown), which is well known to those skilled in the art, a bypass
air passageway is arranged in parallel with throttle plate 62 to
control inducted airflow during idle speed control via a throttle
control valve positioned within the air passageway.
[0023] Exhaust gas sensor 76 is shown coupled to exhaust manifold
48 upstream of catalytic converter 70. Sensor 76 may be any of many
known sensors for providing an indication of exhaust gas air/fuel
ratio such as a linear oxygen sensor (UEGO), a two-state oxygen
sensor (HEGO or EGO), or an HC or CO sensor. In this particular
example, sensor 76 is a two-state oxygen sensor that provides
signal EGO to controller 12 which converts signal EGO into
two-state signal EGOS. A high voltage state of signal EGOS
indicates exhaust gases are rich of stoichiometry and a low voltage
state of signal EGOS indicates exhaust gases are lean of
stoichiometry. Signal EGOS is used to advantage during feedback
air/fuel control in a conventional manner to maintain average
air/fuel at stoichiometry during the stoichiometric homogeneous
mode of operation.
[0024] Conventional distributorless ignition system 88 provides
ignition spark to combustion chamber 30 via spark plug 92 in
response to spark advance signal SA from controller 12.
[0025] Controller 12 causes combustion chamber 30 to operate in
either a homogeneous air/fuel mode or a stratified air/fuel mode by
controlling injection timing. In the stratified mode, controller 12
activates fuel injector 66A during the engine compression stroke so
that fuel is sprayed directly into the bowl of piston 36.
Stratified air/fuel layers are thereby formed. The strata closest
to the spark plug contains a stoichiometric mixture or a mixture
slightly rich of stoichiometry, and subsequent strata contain
progressively leaner mixtures. During the homogeneous mode,
controller 12 activates fuel injector 66A during the intake stroke
so that a substantially homogeneous air/fuel mixture is formed when
ignition power is supplied to spark plug 92 by ignition system 88.
Controller 12 controls the amount of fuel delivered by fuel
injector 66A so that the homogeneous air/fuel mixture in chamber 30
can be selected to be at stoichiometry, a value rich of
stoichiometry, or a value lean of stoichiometry. The stratified
air/fuel mixture will always be at a value lean of stoichiometry,
the exact air/fuel being a function of the amount of fuel delivered
to combustion chamber 30. An additional split mode of operation
wherein additional fuel is injected during the exhaust stroke while
operating in the stratified mode is also possible.
[0026] Emission control device 72 can be various types of devices,
such as a three-way catalyst known as a nitrogen oxide (NOx)
adsorbent or trap. Device 72 is shown positioned downstream of
device 70. Device 72 is a three-way catalyst that absorbs NOx when
engine 10 is operating lean of stoichiometry. The absorbed NOx is
subsequently reacted with HC and CO and catalyzed when controller
12 causes engine 10 to operate in either a rich homogeneous mode or
a near stoichiometric homogeneous mode such operation occurs during
a NOx purge cycle when it is desired to purge stored NOx from
device 72, or during a vapor purge cycle to recover fuel vapors
from fuel tank 160 and fuel vapor storage canister 164 via purge
control valve 168 (as described below), or during operating modes
requiring more engine power, or during operation modes regulating
temperature of the omission control devices such as device 70 or
72. (Again, note that emission control devices 70 and 72 can
correspond to various devices such as three way catalysts, or other
types of catalytic converters.) Further, canister 164, in one
embodiment, is a charcoal carbon canister.
[0027] Controller 12 is shown in FIG. 1 as a conventional
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 conventional 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 100 coupled
to throttle body 58; 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 120; and absolute Manifold Pressure Signal MAP from sensor
122. Engine speed signal RPM is generated by controller 12 from
signal PIP in a conventional manner and manifold pressure signal
MAP from a manifold pressure sensor provides an indication of
vacuum, or pressure, in the intake manifold. During stoichiometric
operation, this sensor can give and indication of engine load.
Further, this sensor, along with engine speed, can provide an
estimate of charge (including air) inducted into the cylinder. In a
preferred aspect of the present invention, sensor 118, which is
also used as an engine speed sensor, produces a predetermined
number of equally spaced pulses every revolution of the
crankshaft.
[0028] In this particular example, temperature Tcat1 of catalytic
converter 70 and temperature Tcat2 of device 72 are inferred from
engine operation as disclosed in U.S. Pat. No. 5,414,994, the
specification of which is incorporated herein by reference. In an
alternate embodiment, temperature Tcat1 is provided by temperature
sensor 124 and temperature Tcat2 is provided by temperature sensor
126.
[0029] Continuing with FIG. 1, camshaft 130 of engine 10 is shown
communicating with rocker arms 132 and 134 for actuating intake
valves 52a, 52b and exhaust valve 54a, 54b . Camshaft 130 is
directly coupled to housing 136. Housing 136 forms a toothed wheel
having a plurality of teeth 138. Housing 136 is hydraulically
coupled to an inner shaft (not shown), which is in turn directly
linked to camshaft 130 via a timing chain (not shown). Therefore,
housing 136 and camshaft 130 rotate at a speed substantially
equivalent to the inner camshaft. The inner camshaft rotates at a
constant speed ratio to crankshaft 40. However, by manipulation of
the hydraulic coupling as will be described later herein, the
relative position of camshaft 130 to crankshaft 40 can be varied by
hydraulic pressures in advance chamber 142 and retard chamber 144.
By allowing high pressure hydraulic fluid to enter advance chamber
142, the relative relationship between camshaft 130 and crankshaft
40 is advanced. Thus, intake valves 52a, 52b and exhaust valves
54a, 54b open and close at a time earlier than normal relative to
crankshaft 40. Similarly, by allowing high pressure hydraulic fluid
to enter retard chamber 144, the relative relationship between
camshaft 130 and crankshaft 40 is retarded. Thus, intake valves
52a, 52b, and exhaust valves 54a, 54b open and close at a time
later than normal relative to crankshaft 40.
[0030] Teeth 138, being coupled to housing 136 and camshaft 130,
allow for measurement of relative cam position via cam timing
sensor 150 providing signal VCT to controller 12. Teeth 1, 2, 3,
and 4 are preferably used for measurement of cam timing and are
equally spaced (for example, in a V-8 dual bank engine, spaced 90
degrees apart from one another) while tooth 5 is preferably used
for cylinder identification, as described later herein. In
addition, controller 12 sends control signals (LACT, RACT) to
conventional solenoid valves (not shown) to control the flow of
hydraulic fluid either into advance chamber 142, retard chamber
144, or neither.
[0031] Relative cam timing is measured using the method described
in U.S. Pat. No. 5,548,995, which is incorporated herein by
reference. In general terms, the time, or rotation angle between
the rising edge of the PIP signal and receiving a signal from one
of the plurality of teeth 138 on housing 136 gives a measure of the
relative cam timing. For the particular example of a V-8 engine,
with two cylinder banks and a five-toothed wheel, a measure of cam
timing for a particular bank is received four times per revolution,
with the extra signal used for cylinder identification.
[0032] Sensor 160 provides an indication of oxygen concentration in
the exhaust gas. In one example, sensor 160 is a UEGO sensor that
provides signal UEGO to controller 12.
[0033] As described above, FIG. 1 merely shows one cylinder of a
multi-cylinder engine, and that each cylinder has its own set of
intake/exhaust valves, fuel injectors, spark plugs, etc.
[0034] Also, in each embodiment of the present invention, the
engine is coupled to a starter motor (not shown) for starting the
engine. The starter motor is powered when the driver turns a key in
the ignition switch on the steering column, for example. The
starter is disengaged after engine start as evidence, for example,
by engine 10 reaching a predetermined speed after a predetermined
time. Further, in each embodiment, an exhaust gas recirculation
(EGR) System routes a desired portion of exhaust gas from exhaust
manifold 48 to intake manifold 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.
[0035] The engine 10 operates in various modes, including lean
operation, rich operation, and "near stoichiometric" operation.
"Near stoichiometric" operation refers to oscillatory operation
around the stoichiometric air fuel ratio. Typically, this
oscillatory operation is governed by feedback from exhaust gas
oxygen sensors. In this near stoichiometric operating mode, the
engine is operated within one air-fuel ratio of the stoichiometric
air-fuel ratio. Engine 10 can also be operated in an injector
cut-out mode as described below herein. In particular, in this
mode, fuel is provided to some of the cylinders, but not others,
even though all of the cylinders are pumping air from intake
manifold 44 to exhaust manifold 48.
[0036] As described below, feedback air-fuel ratio is used for
providing the near stoichiometric operation. Further, feedback from
exhaust gas oxygen sensors can be used for controlling air-fuel
ratio during lean and during rich operation. In particular, a
switching type, heated exhaust gas oxygen sensor (HEGO) can be used
for stoichiometric air-fuel ratio control by controlling fuel
injected (or additional air via throttle or VCT) based on feedback
from the HEGO sensor and the desired air-fuel ratio. Further, a
UEGO sensor (which provides a substantially linear output versus
exhaust air-fuel ratio) can be used for controlling air-fuel ratio
during lean, rich, and stoichiometric operation. In this case, fuel
injection (or additional air via throttle or VCT) is adjusted based
on a desired air-fuel ratio and the air-fuel ratio from the sensor.
Further still, individual cylinder air-fuel ratio control could be
used if desired.
[0037] Also note that various methods can be used according to the
present invention to maintain the desired torque such as, for
example, adjusting ignition timing, throttle position, variable cam
timing position, and exhaust gas recirculation amount. Further,
these variables can be individually adjusted for each cylinder to
maintain cylinder balance among all the cylinder groups.
[0038] Note that in an alternative embodiment, engine 10 can be a
port injected engine where injector 66A is positioned in manifold
44, rather than in the combustion chamber 30. Such a port injected
engine can operated rich, near stoichiometric, or lean in a
homogenous mode. For this embodiment, the fuel system is not
required to be a high pressure system, but can utilize a fuel pump,
fuel rail, and pressure regulator to provide pressurized fuel to
injector 66.
[0039] The routines described in the following Figures manage
engine operation, taking into account lean burn conditions, lean
burn with injector cut-out (i.e., some cylinders operating lean
with other cylinders inducting air with substantially no injected
fuel), and closed loop adaptive algorithms to compensate for fuel
injector and/or air metering errors. The routines attempt to
provide increased fuel economy while balancing activities related
to fuel system learning and canister purging.
[0040] The following definitions are used:
[0041] PCOMP--Canister Purge Compensation feature (see FIG. 6)
[0042] FADPT--Stoichiometric closed loop sensor (HEGO or UEGO) long
term adaptive feature (see FIG. 5)
[0043] LADPT--lean burn adaptive feature (see FIG. 5)
[0044] LB--is overall total exhaust lean, including:
[0045] LBIC--lean burn injector cut-out, and
[0046] LBV8--all cylinders lean, (in this case for the example of a
V-8 type engine).
[0047] LB/LBIC and Canister Purge (PCOMP) modes:
[0048] 1) PCOMP (stoichiometric or LBV8) and FADPT (stoichiometric
closed loop HEGO adaptive) are generally conducted at different
times;
[0049] 2) FADPT (stoichiometric closed loop HEGO adaptive) and
LADPT (LB closed loop UEGO adaptive) are generally conducted at
different times;
[0050] 3) LBIC and PCOMP are generally conducted at different times
to minimize lost fuel economy;
[0051] 4) LB and FADPT (stoichiometric closed loop HEGO adaptive)
are generally conducted at different times;
[0052] 5) PCOMP (LB) and LADPT (LB closed loop UEGO adaptive) are
generally conducted at different times;
[0053] 6) PCOMP can run during lean or stoichiometric conditions
because feed back can come from either the UEGO or HEGO sensor;
[0054] 7) LADPT (LB closed loop UEGO adaptive) has a low priority
because it has a small effect on emissions compared with PCOMP and
FADPT;
[0055] 8) With increased NOx storage capacity, the FADPT routine
can be run early in order to allow completion while NOx storage
catalytic elements are warming up in temperature and
efficiency;
[0056] 9) With decreased NOx storage capacity (where lean operation
is limited to a certain temperature window and engine airflow space
velocity) FADPT can be completed later;
[0057] 10) During normal operating conditions, FADPT can be engaged
based on a timer if lean conditions should prevail too long;
[0058] 11) During normal operating conditions, stoichiometric FADPT
is interrupted by PCOMP if tank pressure is greater than a
preselected threshold, or time since last fuel vapor purging is too
long;
[0059] 12) During normal operating conditions, LBIC is interrupted
by PCOMP if tank pressure is greater than a preselected threshold,
or time since last fuel vapor purging is too long;
[0060] 13) LB mode is allowed if FADPT is not ready to run;
[0061] 14) LBIC stoichiometric operation and FADPT are generally
not run at the same time, unless the cylinder arrangement allows
stoichiometric isolation for the HEGO; and
[0062] 15) The UEGO signal is used with a threshold to control the
PCOMP ramp rate.
[0063] These modes will be better understood when read together
with the specific algorithms described in the following flow
charts.
[0064] In general terms, the PCOMP routine adjusts engine fuel
injection to account for fuel vapors inducted from the fuel tank
and canister system. The following equations illustrate how the
purge compensation (PCOMP) adjusts the required injected fuel
calculation:
fuel.sub.--bk_temp=(CYL_AIR.sub.--CHG).times.(KAMREF)/(14.64.times.LAM_FIN-
AL)-PCOMP.sub.--LBM+TFC.sub.--HR
[0065] Where:
[0066] CYL_AIR_CHG=Current cylinder air charge (sum of MAF and
purge air flow)
[0067] LAM_FINAL=Equivalence ratio
[0068] PCOMP_LBM=Fuel compensation from PCOMP logic
[0069] TFC_HR=Fuel compensation from Transient Fuel logic
[0070] fuel_bk_temp=Fuel mass required per bank
[0071] The following represent adaptation and learning
parameters:
[0072] KAMREF=long term adaptive, stoich HEGO
[0073] LBKAMREF=long term adaptive, lean burn UEGO
[0074] PCOMP_LBM=learned fuel content in purge flow
[0075] For stoichiometric FADPT:
fuel.sub.--bk_temp=(CYL_AIR.sub.--CHG).times.(KAMREF)/(14.64.times.LAM_FIN-
AL)-PCOMP.sub.--LBM+TFC.sub.--HR
[0076] For stoichiometric PCOMP:
fuel.sub.--bk_temp=(CYL_AIR.sub.--CHG).times.(KAMREF)/(14.64.times.LAM_FIN-
AL)-PCOMP.sub.--LBM+TFC.sub.--HR
[0077] For LB LADPT:
fuel.sub.--bk_temp=(CYL_AIR.sub.--CHG).times.(LBKAMREF)/(14.64.times.LAM_F-
INAL)-PCOMP.sub.--LBM+TFC.sub.--HR
[0078] For LB PCOMP:
fuel.sub.--bk_temp=(CYL_AIR.sub.--CHG).times.(LBKAMREF)/(14.64.times.LAM_F-
INAL)-PCOMP.sub.--LBM+TFC.sub.--HR
[0079] Thus, the above equations illustrate for each of the various
modes how the adaptive learning values and vapor purge compensation
affect the requested fuel to be injected into the engine.
[0080] Next, the interaction between PCOMP and FADPT is generally
described. At engine start up, if ECT (engine coolant temperature)
is suitable for PCOMP (i.e., temperature greater than a threshold
value), the controller will start PCOMP. Otherwise, PCOMP is not
enabled for the first PIP. FADPT will not start directly after an
engine start because it operates more effectively with ECT
stabilized for a calibrated period of time. PCOMP is an adaptive
routine. Fuel injection is controlled based on the estimated purge
fuel, while purge air is calculated in air charge estimation.
Generally, injected fuel is obtained by subtracting purge fuel from
desired fuel based on air charge estimation, as described in the
equations above.
[0081] Referring now to FIG. 2, a general block diagram is now
described. This block diagram shows a particular embodiment of
engine 10 as a six cylinder V-type engine with catalysts 70 and 72
arranged in parallel. Further, in this example, three oxygen type
sensors are utilized (HEGO1, HEGO2, and UEGO). Note that in an
alternative embodiment, three HEGO sensors can be used, or three
UEGO sensors, or any other combination of the two types of sensors.
Further, less than 3 sensors can be utilized.
[0082] Referring now to FIG. 3, a routine is described for enabling
adaptive learning and fuel vapor purging. First, in step 310, the
routine reads the pedal position (pp). Then, in step 312, the
routine determines a desired engine torque based on the pedal
position. In an alternative embodiment, the desired engine torque
can be based on pedal position and engine speed. And still an
alternative embodiment, the routine can utilize desired wheel
torque, desired engine power, or desired engine airflow.
[0083] From step 312, the routine continues to step 314. In step
314, the routine determines whether lean operation or
stoicihometric operation is desired based on the desired engine
output torque and exhaust temperature. In particular, as described
in FIG. 4, the engine air-fuel operating mode is selected based on
a torque speed basis. For low torque low speed, lean operation is
desired. For mid torque mid speed regions, stoichiometric operation
is desired. For high torque operation, a rich engine air-fuel ratio
is scheduled.
[0084] Next, in step 316, the routine determines a desired air
amount (desired air flow, air mask or air charge) based on the
desired engine torque and the air-fuel region. Further, the
specific desired air-fuel ratio is also utilized to determine the
desired air amount. Next, in step 318, the routine controls the air
actuated to provide the desired air amount. For example, in the
case of an electronic throttle system, the routine determines a
desired throttle position to provide the desired air amount.
Further, feedback from a mass air flow sensor can be used to adjust
the throttle position.
[0085] Next, the routine continues to step 320 and determines
whether the lean operating mode is requested. When the answer to
step 320 is no, the routine continues to step 350, where fuel vapor
safety condition is checked by comparing tank pressure with a
calibrated value, and time since last fuel vapor purging to another
calibrated value. If the answer to step 350 is yes, the routine
continues to step 322 and allows, or enables, adaptive learning of
the fuel injector offsets and air meter biases. In particular, in
step 324, the routine adaptively learns the injector offsets and
mass air flow data as described later herein with particular
reference to FIG. 5. Next, in step 326, the routine adjusts the
fuel injection amount to maintain the desired air-fuel ratio. In
particular, the routine adjusts the fuel injection amount based on
measurements from exhaust gas oxygen sensors located upstream
and/or downstream of an emission control device. These exhaust gas
oxygen sensors can be either a switching type EGO, or linear type
UEGO. When the answer to step 350 is no, the routine continues to
step 352 and allows fuel vapor purging. Next, in step 354, the
routine adaptively learns fuel vapor content (HEGO based, see FIG.
6), and in step 356, adjusts fuel injection amount based on HEGO
sensor to maintain desired air fuel ratio.
[0086] When the answer to step 320 is yes, the routine continues to
step 328 to allow fuel vapor purging. Next, in step 330 the routine
adaptively learns the fuel vapor concentration coming from the
carbon canister as described below herein with particular reference
to FIG. 6A. Next, in step 332, the routine adjusts the fuel
injection amount based on exhaust gas oxygen sensors to maintain
the desired air fuel ratio. Note that if the fuel injector pulse
widths required to maintain the desired air-fuel ratio during the
fuel vapor for purging becomes too small, the routine either
discontinues lean operation, or discontinues fuel vapor
purging.
[0087] From step 332, the routine continues to step 334 where a
determination is made as to whether the amount of stored NOx is
greater than a threshold. Alternatively, the routine can determine
whether a tailpipe amount of NOx is greater than a second
threshold. Further still, the routine can determine whether an
amount of tailpipe NOx per distance traveled is greater than a
third threshold. When the answer to step 334 is yes, the routine
continues to step 336 and changes operation from lean to
stoichiometric, from rich to purge the NOx stored in the emission
control device as described below herein with respect to FIG.
7.
[0088] Note that the high level management described in FIG. 4 is
an alternative embodiment to the overall engine management
described in FIG. 3.
[0089] Referring now to FIG. 4, a high level flow chart for
managing lean burn operation, injector cutout operation,
stoichiometric long term HEGO adaptive fuel, and lean burn long
term adaptive UEGO, and stoichiometric or lean burn canister
purging. This routine manages whether to allow lean, or injector
cutout, operation, as well as whether to enable canister purging or
adaptive fuel learning.
[0090] In steps 410, 412, and 416, the routine allows increased
lean operation in between FADPT operation under certain conditions.
In particular, in step 410, a determination is made as to whether
the engine operation mode is stoichiometric, and FADTP is ready and
this is the first operation of FADPT. If so, then the routine
determines in step 412 if lean burn operation is ready; and if the
timer (atmr) is less than a calibrated value (CAL_ATMR). If not,
lean operation is not allowed in step 414. The routine continues to
step 422, where a process, as represented in FIG. 4A, is performed.
FIG. 4A is basically fuel vapor purging and adaptive learning (HEGO
based) in stoichiometric operation mode, as it will be described
below.
[0091] If the answer to step 410 is NO, then the routine continues
to step 416. Further, if the answer to step 412 is YES, the routine
continues to step 416 as well. In step 416, a flag is set to allow
lean burn operation from the fuel adaptive learning
requirement.
[0092] In step 418, which follows step 416, the routine determines
the engine operation mode. If in step 418 the engine operation mode
is determined to be lean burn but without injector cutout (LBIC),
the routine continues to step 424, where a process, as represented
in FIG. 4B, is performed. FIG. 4B is basically fuel vapor purging
and lean fuel adaptive learning (UEGO based) in lean operation
mode, as it will be described below.
[0093] If the answer to step 418 is NO, the routine further checks
if the operation mode is stoichiometric in step 420, which
determines if the engine operation mode is stoichiometric. If the
answer to step 420 is YES, the routine continues to step 422, which
performs the process represented in FIG. 4A, as it will be
described below. If the answer to step 420 is NO, it means the
operation mode is LBIC (lean burn with injector cutout), the
routine continues to step 426, which performs the process
represented in FIG. 4C, as it will be described below. FIG. 4C is
basically for determining whether the engine needs to exit LBIC
mode based on fuel vapor and lean fuel adaptive learning
requirements.
[0094] Referring now to FIG. 4A, which is the process defined in
FIG. 4, step 422. In FIG. 4A, a routine for performing fuel vapor
purging (stoichiometric) and adaptive function (FADPT) is now
described. In particular, in step 430, the routine determines if it
is safe not to perform fuel vapor purging, based on fuel tank
pressure and time since last fuel vapor purging. When the answer to
step 430 is NO, the routine continues to step 438. In step 438, the
routine disables the adaptive fuel learning (FADPT), while enabling
fuel vapor purging and fuel vapor purging learning (PCOMP). Next,
the routine continues to step 440 where the routine operates the
engine to induct fuel vapors from the fuel vapor system. Further,
the routine learns the fuel vapor concentration as described below
herein with particular reference to FIG. 6. In step 440, the
routine allows for stoichiometric operation while performing the
fuel vapor purging. From step 440, the routine continues to step
442. In step 442, the routine determines whether the tank pressure
has fallen below a hysteresis calibration level which is lower than
the threshold (CAL_TANK_PRES_MAX) and that the fuel vapor content
is lower than a calibrated value (CAL_VAPOR_SAFE). When the answer
to step 442 is "no," the routine returns to step 440 to continue
fuel vapor purging and the fuel vapor concentration learning.
Otherwise, when the answer to step 442 is yes, the routine
continues to step 444, which allows fuel adaptive learning.
Following step 444, the routine continues to step 432. Notice that
routine continues to step 432 when the answer to step 430 is YES.
In step 432, the routine checks if fuel adaptive learning is ready.
When the answer to step 432 is NO, the routine continues to step
438, as described above. When the answer in step 432 is YES, the
routine continues to step 434, where fuel adaptive learning is
performed. The routine then continues to step 436 to check if fuel
adaptive learning (stoichiometric operation) is complete. This is
done by checking if adaptive learning timer (adap_tmr) is greater
than a calibrated value (ADP_TM). When the answer to step 436 is
NO, fuel adaptive learning in step 434 will continue. When the
answer to step 436 is YES, a flag fadpt_lb_ok is set at step 446,
which allows lean burn operation mode based on the statues of fuel
adaptive learning.
[0095] Referring now to FIG. 4B, which is the process defined in
FIG. 4, step 424. In FIG. 4B, a routine for performing lean burn
fuel vapor purge and lean fuel adaptive learning, is now described.
In particular, the routine starts at step 460, which determines
whether it is allowed not to do fuel vapor purging. When the answer
to step 460 is YES, the routine continues to step 466, where a flag
is set, which allows lean burn with injector cutout (LBIC)
operation with regard to fuel vapor purging requirement. When the
answer to step 460 is NO, the routine continues to step 462, where
fuel vapor purging is done aggressively based on UEGO sensor
information as described below herein with regard to FIG. 6A. From
step 462, the routine continues to step 464. In step 464, the
routine determines whether the fuel vapor purging has been
completed to a sufficiently low level. When the answer to step 464
is NO, the routine repeats fuel vapor purging at step 462. When the
answer to step 464 is YES, the routine continues to step 466.
Following step 466, the routine continues to step 468, where a
determination is made as to whether the lean fuel adaptive learning
is ready and it is necessary to perform lean fuel adaptive
learning. When the answer to step 468 is YES, the routine continues
to step 470, where lean fuel adaptive learning is performed.
Following step 470, the routine continues to step 472, which checks
if lean fuel adaptive learning is ready. When the answer to step
472 is NO, the routine repeats lean fuel adaptive learning at step
470. When the answer to step 472 is YES, the routine continues to
step 474. Notice that when the answer to step 468 is NO, the
routine continues to step 474 as well. In step 474, a flag is set,
which allows lean burn with injector cutout (LBIC) operation with
regard to lean fuel adaptive learning requirement.
[0096] Referring now to FIG. 4C, which is the process defined in
FIG. 4, step 426. In FIG. 4C, a routine for determining fuel vapor
purging and lean fuel adaptive learning associated with LBIC
operation, is now described. In particular, in step 480, a
determination is made as to whether it is necessary to exit LBIC
mode to perform fuel vapor purging based on the consideration of
fuel economy. When the answer to step 480 is YES, the routine
continues to step 484. In step 484, a flag is set to disallow LBIC
and the engine operation mode will be forced back to lean burn.
When the answer to step 480 is NO, the routine continues to step
482. In step 482, a determination is made as to whether it is
necessary to exit LBIC mode to perform lean fuel adaptive learning.
When the answer to step 482 is YES, the routine continues to step
486. In step 486, a flag is set to disallow LBIC and the engine
operation mode will be forced back to lean burn. When the answer to
step 482 is NO,. conditions allowing LBIC mode from fuel vapor
purging and lean fuel adaptive learning are met and the process
will repeat.
[0097] The procedure and processes described in FIG. 4, FIG. 4A,
FIG. 4B, and FIG. 4C can be summarized into a high level diagram,
as represented in FIG. 4D.
[0098] Referring to FIG. 4D, which gives a high level description
of the activities described in FIG. 4, FIG. 4A, FIG. 4B and FIG.
4C. In particular, in block 490, which represents stoichiometric
mode, a transition from stoichiometric mode to lean burn mode is
made possible when lean burn entry conditions are met and fuel
adaptive learning allows lean burn operation (reference to FIG. 4,
FIG. 4A and FIG. 4B). In block 492, which represents lean burn
without injector cutout mode, a transition from lean burn to lean
burn with injector cutout mode (LBIC) is made possible if LBIC
entry conditions are met, and that fuel vapor purging and lean fuel
adaptive learning requirements allow LBIC operation (reference to
FIG. 4, FIG. 4B and FIG. 4C). Again in block 492, a transition from
lean burn to stoichiometric is made possible if lean burn entry
conditions are not met, or fuel adaptive learning does not allow
lean burn operation (reference to FIG. 4 and FIG. 4A and FIG. 4B).
In block 494, which represents LBIC operation, a transition to lean
burn without injector cutout is made possible when LBIC entry
conditions are not met, or fuel vapor purging requirement does not
allow LBIC operation, or lean fuel adaptive learning does not allow
LBIC operation (reference to FIG. 4, FIG. 4B and FIG. 4C).
[0099] Representative running for a limited lean system is shown in
FIG. 4E. For this kind of system, lean operation opportunity is
very limited, and it is thus necessary to defer stoichiometric fuel
adaptive learning when it is possible (reference to FIG. 4, step
410, step 412 and step 416). A comparative representative running
for a high capacity lean system is shown in FIG. 4F. For this
system, lean operation opportunity abounds and there is no need to
defer stoichiometric fuel adaptive learning. Considerations of
these two different systems can be realized through calibration,
reference to FIG. 4, step 412.
[0100] Referring now to FIG. 5, a routine for performing adaptive
functions (LADPT and FADPT) is now described. In particular, in
step 510, the routine determines whether adaptive learning is
enabled, based on various conditions such as air charge
temperature, engine coolant temperature, throttle position, mass
air flow, engine load, feedback air-fuel control mode (open or
closed loop), and various other conditions. When the answer to step
510 is YES, the routine continues to step 514 where a determination
is made as to whether the engine is operating in stoichiometric
operation mode. When the answer to step 514 is YES, the routine
continues to step 516 and learns adaptive data (e.g., KAMREF) based
on the HEGO sensor for each speed/load range. The routine then
continues to step 520 where the routine looks up KAMREF for
stoichiometric operation. When the answer to step 514 is NO, the
routine continues to step 522, where a determination is made as to
whether the operation mode is LBIC. When the answer to step 522 is
YES, it is LBIC mode, thus no fuel adaptation is made and the
routine continues to step 520, where the routine looks up LKAMREF.
When the answer to step 522 is NO, it is lean burn without injector
cutout mode, the routine continues to step 518 and learns adaptive
data (e.g., LKAMREF) based on the UEGO sensor for each speed/load
range. Following step 518, the routine continues to step 520, where
the routine looks up LKAMREF. Finally, when the answer to step 510
is NO, the routine continues to step 520, where the routine looks
up KAMREF or LKAMREF based on engine operation mode, speed and
load.
[0101] The PCOMP enabling logic generally works as follows, with
particular reference to FIG. 6 (for stoichiometric operation mode),
and FIG. 6A (for lean burn mode).
[0102] Referring now to FIG. 6. First, in step 610, a determination
is made as to whether FADPT has run over timer limit ADP_TM_MAX, by
checking the timer (adap_tmr). If the answer to step 610 is YES,
then PCOMP is enabled (and FADPT is disabled) in step 612.
Otherwise, in step 614 a determination is made as to whether fuel
tank pressure is low (below a preselected pressure value), FADPT
has run over a certain timer ADP_TM (which is less than time
ADP_TM_MAX), and the lambse value (desired air-fuel ratio value) is
outside an acceptable window. If the answer to step 614 is YES,
then PCOMP is disabled in step 616. Otherwise, the routine
continues to step 618.
[0103] In step 618, the routine determines whether fuel tank
pressure is high or FADPT has run over a certain timer ADP_TM. If
the answer to step 618 is YES, then PCOMP is enabled in step 620.
Otherwise, in step 622, the routine determines whether fuel vapor
content is lower than a safe level, and that fuel adaptive learning
is ready; or FADPT has not been performed even once
(first_adpt=FALSE), and fuel adaptive learning is ready; or time
since last fuel adaptive learning is larger than a time limit
(CAL_FADPT_S) by checking a timer (tsladp_tmr_s), and fuel adaptive
learning is ready. When the answer to step 622 is YES, then PCOMP
is disabled in step 624.
[0104] The routine of FIG. 6 is generally executed in background
timing in controller 12, and as described above, enables and
disables PCOMP. The control of the fuel vapor purge is described in
more detail below with particular reference to FIG. 8.
[0105] Referring now to FIG. 6A. First, in step 650, a
determination is made as to whether time since last fuel vapor
purging has run over timer limit CAL_PCOMP_TM_LB by checking the
timer (tslapcomp_tmr_lb). If the answer to step 650 is YES, then
PCOMP is enabled (and Lean FADPT is disabled) in step 652.
Otherwise, in step 654 a determination is made as to whether fuel
tank pressure is low (below a pre-selected pressure value), time
since last fuel vapor purging has run over a certain timer
CAL_PCOMP_TM_LB-CAL_PCOMP_TM_LB_HYS (which is less than time
CAL_PCOMP_TM_LB), and the lambse value (desired air-fuel ratio
value) is outside an acceptable window. If the answer to step 654
is YES, then PCOMP is disabled in step 656. Otherwise, the routine
continues to step 618.
[0106] In step 658, the routine determines whether fuel tank
pressure is high or time since last fuel vapor purging has run over
a certain timer CAL_PCOMP_TM_LB-CAL_PCOMP_TM_LB_HYS. If the answer
to step 658 is YES, then PCOMP is enabled in step 660. Otherwise,
in step 662, the routine determines whether fuel vapor content is
lower than a sufficiently purged level, and that fuel adaptive
learning is ready, or LBIC entry condition is ready; or time since
last lean fuel adaptive learning is larger than a time limit
(CAL_FADPT_L) by checking a timer (tsladp_tmr_lb), and fuel
adaptive learning is ready. When the answer to step 662 is YES,
then PCOMP is disabled in step 664.
[0107] The routine of FIG. 6A is generally executed in background
timing in controller 12, and as described above, enables and
disables PCOMP. The control of the fuel vapor purge is described in
more detail below with particular reference to FIG. 8.
[0108] Referring now to FIG. 7, a graph shows the NO.sub.X purge
cycle where the engine switches between lean to stoichiometric or
rich operation to purge NO.sub.X stored in the emission control
devices. As shown in FIG. 7, the engine is first operated in the
closed loop lean burn mode where the engine air-fuel ratio is
controlled to a lean value based on the downstream UEGO sensor. As
shown in point 1, the routine transitions from closed loop lean
operation to a desired rich air-fuel ratio at point 2 and then
transitions to a second desired rich air fuel ratio at point 3 and
continues at that air fuel ratio until point 4. Then, at point 4,
the routine reduces the air-fuel ratio towards stoichiometry at
point 5 and continues to the desired lean air-fuel ratio at point 6
in an open loop fashion. At point 7, the routine continues to close
loop lean burn operation and thereby continues lean operation until
point 8 and beyond. Between points 1 and 7, the routine freezes the
learned fuel vapor concentration value (PCOMP_PPM) and disables
updating this value during this period. Alternatively, during the
points 1 to 7 in an alternate embodiment the routine completely
disables the fuel vapor concentration learning and disables fuel
vapor purging during this period. However, as described above, it
is possible to continue the fuel vapor purging during the rich
operation, or rich cycle of the NO.sub.X lean/rich cycle. This is
described more specifically below with regard to the routine of
FIG. 9.
[0109] Referring now to FIG. 8, a routine for controlling fuel
vapor purging is described. Specifically, the case of
stoichiometric PCOMP is described. However, changes and adjustments
are indicated to also describe lean burn fuel vapor purging control
using the UEGO sensor rather than, or in addition to, the HEGO
sensor.
[0110] Note that when purging fuel vapors, adaptive fuel is frozen,
so the kamref (Keep Alive Memory learned adaptive value) is not
updated (although it is still calculated based on engine speed and
load).
[0111] First, in step 810, the routine calculates a PCOMP vapor
amount (pcomp-ppm). Then, in step 812, the routine calculates a
tolerance level within which the purge vapor concentration should
be maintained. These are calibratable values based on engine and
vehicle testing.
[0112] Next, in step 814, the routine calculates a rate increment
inhibitor, which limits the rate at which the fuel vapor valve can
be adjusted. Next, in step 816, the routine determines whether
PCOMP is disable. If so, in step 818 the ramp rate (pg_ramp_rate)
is set to zero. Otherwise, the routine continues to step 820.
[0113] In step 820, the routine determines whether the PCOMP
percent fuel content is greater than the upper tolerance level. If
so, the ramp rate is decreased in step 822. Otherwise, in step 824,
the routine determines, for stoichiometric operation, HEGO sensor
switching. HEGO switching is used to control the purge rate
ramping. If switching is seen, it indicates that purge vapor fuel
is within limit and it is OK to increase the purge rate in step
826. On the other hand, if a percentage of PCOMP over fuel is seen
as greater than a limit, then purge rate is ramped down.
[0114] There are also special cases, for example no HEGO switching
for an extended period of time, when PCOMP is disabled (duty cycle
set to zero).
[0115] For lean operation, the common points for PCOMP are that
adaptive fuel is frozen, and that the philosophy for ramping purge
duty cycle remains the same. However, instead of using the HEGO
sensor switching signal for incrementing purge rate, a UEGO sensor
signal from downstream of the second catalyst can be used. In other
words, rather than using HEGO switching, the routine can determine
if the difference between the downstream UEGO value and the desired
lean air-fuel ratio is less than a threshold. If so, then the purge
is within tolerance.
[0116] Referring to FIG. 9, the routine is described for
controlling the canister purging and lean fuel vapor concentration
learning during a NO.sub.X purge cycle. First, in step 910, the
routine determines whether the lean burn fuel vapor concentration
learning routine is operating and whether the engine is operating
in the lean burn close loop air-fuel ratio control condition. When
the answer to step 910 is "yes", the routine continues to step 912.
In step 912, the routine freezes the canister purge adaptation but
allows for open loop fuel vapor concentration adjustment if the
fuel vapor purging is continued during the NO.sub.X purge. In other
words, the routine disables adaptive learning of the fuel vapor
concentration based on the UEGO sensor during the rich engine
air-fuel ratio. However, the routine continues to adjust the
injected fuel amount based on the last updated value of the fuel
vapor concentration. In this way, the routine can maintain the
desired rich air-fuel ratio even in the presence of the fuel vapor
purging. Since the rich operation to purge the NO.sub.X stored in
the emission control device is relatively short, there is only a
generally small change in the fuel vapor concentration during this
short period, therefore the open loop estimate based on the last
updated fuel vapor concentration allows for accurate engine
air-fuel ratio control.
[0117] Note that various calibration switches can be added to the
routine of FIG. 9 to allow such a feature to be enabled or
disabled.
[0118] Referring now to FIG. 10, a routine is described to
illustrate the interaction between adaptation and fuel vapor
learning. First, in step 1010, the routine determines whether the
adaptive routines are ready. If not, the routine disables
adaptation in step 1012. Otherwise, in step 1014, a determination
is made whether PCOMP is disabled. If not, adaptation is disabled
in step 1016. When the answer to step 1014 is YES, the routine
enables adaptive fuel in step 1018.
[0119] As will be appreciated by one of ordinary skill in the art,
the routines described above represent a pictorial of code that can
be programmed into a computer such as controller 12. The flowcharts
may represent one or more of any number of processing strategies
such as event-driven, interrupt-driven, multi-tasking, and the
like. As such, various steps or function 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 or advantages of the different
embodiments of the invention, but is provided for ease of
illustration, and description. Further, these Figures graphically
represent code to be programmed into the computer readable storage
medium in controller 12.
[0120] This concludes the detailed description. Various embodiments
and different aspects have been described. The scope of the
invention is therefore defined by the following claims:
* * * * *