U.S. patent application number 16/403289 was filed with the patent office on 2020-11-05 for systems and methods for preventing engine stall.
The applicant listed for this patent is Ford Global Technologies, LLC. Invention is credited to Aed Dudar.
Application Number | 20200347804 16/403289 |
Document ID | / |
Family ID | 1000005162518 |
Filed Date | 2020-11-05 |
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United States Patent
Application |
20200347804 |
Kind Code |
A1 |
Dudar; Aed |
November 5, 2020 |
SYSTEMS AND METHODS FOR PREVENTING ENGINE STALL
Abstract
Methods and systems are provided for reducing or avoiding engine
hesitation and/or stall during engine idle conditions. In one
example, a method may include inferring an engine idle condition,
and in response, controlling a speed of an engine to a compensated
engine idle speed that is a function of an extent to which a
canister purge valve that regulates an amount of fluid flow to the
engine from a fuel system and/or an evaporative emissions system,
is degraded. In this way, an amount of fuel utilized to compensate
for the degraded canister purge valve may be proportionate to the
extent to which the canister purge valve is degraded.
Inventors: |
Dudar; Aed; (Canton,
MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ford Global Technologies, LLC |
Dearborn |
MI |
US |
|
|
Family ID: |
1000005162518 |
Appl. No.: |
16/403289 |
Filed: |
May 3, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60W 30/1884 20130101;
F02D 41/0035 20130101; F02M 25/0827 20130101; F04D 27/001
20130101 |
International
Class: |
F02M 25/08 20060101
F02M025/08; F02D 41/00 20060101 F02D041/00; F04D 27/00 20060101
F04D027/00; B60W 30/188 20060101 B60W030/188 |
Claims
1. A method comprising: inferring an engine idle condition, and in
response, controlling a speed of an engine to a compensated engine
idle speed that is a function of an extent to which a canister
purge valve that regulates an amount of fluid flow to the engine
from a fuel system and/or an evaporative emissions system, is
degraded.
2. The method of claim 1, wherein the compensated engine idle speed
is greater than a base engine idle speed, where the base engine
idle speed is used for the engine idle condition under conditions
of an absence of degradation of the canister purge valve.
3. The method of claim 1, wherein the extent to which the canister
purge valve is degraded is determined based on a rate at which an
engine vacuum reduces a pressure in the fuel system and the
evaporative emissions system under conditions where the fuel system
and the evaporative emissions system are sealed from atmosphere and
where the canister purge valve is commanded closed.
4. The method of claim 3, wherein the extent to which the canister
purge valve is degraded is further a function of a level of a fuel
in the fuel system and a rate at which the fuel is vaporizing while
the engine vacuum reduces the pressure in the fuel system and the
evaporative emissions system.
5. The method of claim 1, further comprising controlling the speed
of the engine to the compensated engine idle speed via
electronically controlling a position of a throttle that regulates
an amount of intake air flow to the engine.
6. The method of claim 1, wherein the compensated engine idle speed
is stored at a lookup table as a function of the extent of canister
purge valve degradation and further a function of a level of a
vacuum in intake manifold of the engine; and wherein the
compensated engine idle speed is periodically adjusted.
7. The method of claim 6, further comprising periodically learning
an engine stall point and wherein periodically adjusting the
compensated engine idle speed is based on the engine stall point
that is periodically learned.
8. The method of claim 1, wherein controlling the speed of the
engine to the compensated engine idle speed further comprises
preventing the engine from being shut down at the engine idle
condition under conditions where it is inferred that shutting down
the engine can result in a degraded engine startup at the next
engine start request.
9. The method of claim 1, wherein inferring the engine idle
condition is based on one of a deceleration fuel shut off event
ending, an indication provided via an onboard navigation system,
and a vehicle deceleration event.
10. A method for a hybrid electric vehicle comprising: inferring an
idle stop event and under conditions where a canister purge valve
that regulates a fluid flow from a fuel system and an evaporative
emissions system to an engine is degraded, determining a fuel
vaporization rate of a fuel stored in the fuel system in relation
to a threshold fuel vaporization rate; and controlling the engine
based on the fuel vaporization rate and an extent to which the
canister purge valve is degraded.
11. The method of claim 10, wherein controlling the engine further
comprises commanding the engine to be shut down and maintained
stationary at the idle stop event responsive to the fuel
vaporization rate being less than the threshold fuel vaporization
rate regardless of the extent to which the canister purge valve is
degraded.
12. The method of claim 10, further comprising determining whether
a state of charge of an onboard energy storage device is greater
than a threshold state of charge and whether a temperature of an
exhaust catalyst is greater than a threshold exhaust catalyst
temperature in response to an indication that the fuel vaporization
rate is greater than the threshold fuel vaporization rate; and
wherein controlling the engine is further a function of whether the
state of charge of the onboard energy storage device is greater
than the threshold state of charge and whether the temperature of
the exhaust catalyst is greater than the threshold exhaust catalyst
temperature.
13. The method of claim 12, wherein controlling the engine further
comprises stopping the engine from combusting air and fuel and
rotating the engine unfueled via a motor during the idle stop event
to route fuel vapors to the exhaust catalyst under conditions where
the fuel vaporization rate is greater than the threshold fuel
vaporization rate, where the state of charge of the onboard energy
storage device is greater than the threshold state of charge and
where the temperature of the exhaust catalyst is greater than the
threshold exhaust catalyst temperature.
14. The method of claim 13, wherein a speed at which the engine is
rotated unfueled is variable based on the fuel vaporization rate
and the extent to which the canister purge valve is degraded.
15. The method of claim 12, further comprising preventing the
engine from being shut down at the idle stop event under conditions
where the state of charge of the onboard energy storage device is
lower than the threshold state of charge or under conditions where
the temperature of the exhaust catalyst is lower than the threshold
exhaust catalyst temperature, and where the fuel vaporization rate
is greater than the threshold fuel vaporization rate.
16. The method of claim 15, further comprising controlling the
engine to a compensated engine idle speed at the idle stop event,
the compensated engine idle speed a function of the extent to which
the canister purge valve is degraded, and further a function of a
vacuum level in an intake manifold of the engine.
17. A system for a vehicle, comprising: a canister purge valve that
controls an amount of air and fuel vapor routed to an engine from a
fuel system and an evaporative emissions system; and a controller
with computer readable instructions stored on non-transitory memory
that when executed cause the controller to: responsive to an
indication that the canister purge valve is degraded and further in
response to an engine idle condition being inferred, controlling an
engine speed to a compensated engine idle speed as a function of an
extent to which the canister purge valve is degraded and a vacuum
level in an intake manifold of the engine.
18. The system of claim 17, further comprising a throttle that
regulates intake air flow to the engine, where the throttle is
electronically actuatable; and wherein the controller stores
further instructions to control the throttle in order to control
the engine speed to the compensated engine idle speed.
19. The system of claim 17, further comprising a canister vent
valve positioned in a vent line stemming from a fuel vapor storage
canister included in the evaporative emissions system, a vapor
bypass valve positioned in a conduit that couples the fuel system
to the evaporative emissions system, and a fuel tank pressure
transducer; and wherein the controller stores further instructions
to, with the engine combusting air and fuel, command closed the
canister purge valve and the canister vent valve and command open
the vapor bypass valve; monitor a rate at which a negative pressure
threshold is reached, the monitoring via the fuel tank pressure
transducer, and indicate the extent to which the canister purge
valve is degraded based on the rate at which the negative pressure
threshold is reached.
20. The system of claim 17, further comprising a lookup table
stored at the controller that returns the compensated engine idle
speed based on the extent to which the canister purge valve is
degraded and the vacuum level in the intake manifold of the engine;
and wherein the controller stores further instructions to update
the compensated engine idle speed based on a learned engine stall
point, the learned engine stall point determined after the vehicle
has been driven a predetermined number of miles since a prior
learned engine stall point was determined.
Description
FIELD
[0001] The present description relates generally to methods and
systems for adjusting an engine idle speed as a function of an
extent of degradation of a valve that regulates a fluid flow to the
engine.
BACKGROUND/SUMMARY
[0002] Vehicle evaporative emission control systems may be
configured to store fuel vapors from fuel tank refueling and
diurnal engine operations in a fuel vapor canister, and then purge
the stored vapors during a subsequent engine operation. The stored
vapors may be routed to engine intake for combustion, further
improving fuel economy.
[0003] In a typical fuel vapor canister purge operation, a canister
purge valve (CPV) coupled between the engine intake and the fuel
canister is duty cycled, allowing for intake manifold vacuum to be
applied to the fuel canister. Simultaneously, a canister vent valve
(CVV) coupled between the fuel canister and atmosphere is opened,
allowing for fresh air to enter the canister. This configuration
facilitates desorption of stored fuel vapors from the adsorbent
material in the fuel vapor canister, regenerating the adsorbent
material for further fuel vapor adsorption.
[0004] However, over time the act of duty cycling the CPV can
result in contaminants being introduced to the CPV or other forms
of degradation, which may result in the CPV not effectively
sealing. U.S. Pat. No. 9,255,553 discloses methodology for
detecting canister purge valve degradation that includes indicating
degradation in response to a canister temperature change (and in
some examples additionally based on a fuel system pressure
change)while an engine is in operation and under conditions where
the canister purge valve is closed. In response to such an
indication of canister purge valve degradation, U.S. Pat. No.
9,255,553 discloses taking mitigating action in the form of setting
a diagnostic code in an onboard diagnostics system and/or sending a
message to a message center in the vehicle to alert a vehicle
operator of the degraded canister purge valve condition. However,
the inventors have recognized potential issues with such an
approach. Specifically, the disclosure of setting a diagnostic
code/alerting the operator does not take into account undesired
issues related to engine operation which may occur while the
canister purge valve is degraded but before the degradation issue
has been remedied. For example, a degraded canister purge valve may
lead to unmetered fuel vapors being inducted into the engine, which
may result in engine hesitation and/or stall. Such a situation may
be exacerbated as a function of the extent of canister purge valve
degradation.
[0005] Accordingly, the inventors herein have recognized such
issues and have herein developed systems and methods to at least
partially address them. in one example, a method comprises
inferring an engine idle condition, and in response, controlling a
speed of an engine to a compensated engine idle speed that is a
function of an extent to which a canister purge valve that
regulates an amount of fluid flow to the engine from a fuel system
and/or an evaporative emissions system, is degraded. In this way,
the compensated engine idle speed may be proportionate to the
degree or extent to which the canister purge valve is degraded,
which may improve fuel economy as compared to simply raising engine
idle speed to a predetermined amount without accounting for the
degree to which the canister purge valve is degraded. By
compensating for the degraded canister purge valve in such fashion,
issues related to engine hesitation and/or stall may be reduced or
avoided.
[0006] In one example, the extent to which the canister purge valve
is degraded may be determined based on a rate at which an engine
vacuum reduces a pressure in the fuel system and the evaporative
emissions system under conditions where the fuel system and the
evaporative emissions system are sealed from atmosphere and where
the canister purge valve is commanded closed. Thus, by periodically
conducting such a diagnostic, the extent to which the canister
purge valve is degraded may be regularly determined, and engine
idle speed compensated accordingly.
[0007] The above advantages and other advantages, and features of
the present description will be readily apparent from the following
Detailed Description when taken alone or in connection with the
accompanying drawings.
[0008] It should be understood that the summary above is provided
to introduce in simplified form a selection of concepts that are
further described in the detailed description. It is not meant to
identify key or essential features of the claimed subject matter,
the scope of which is defined uniquely by the claims that follow
the detailed description. Furthermore, the claimed subject matter
is not limited to implementations that solve any disadvantages
noted above or in any part of this disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 shows a schematic description of an engine coupled to
a fuel system, and an evaporative emissions system.
[0010] FIG. 2 depicts a flowchart for an example method for
controlling engine idle speed based on an extent of canister purge
valve degradation.
[0011] FIG. 3 depicts a flowchart for an example method for
controlling an engine at an idle stop event depending on type of
engine and/or vehicle.
[0012] FIG. 4 depicts a flowchart for an example method for
conducting a canister purge valve diagnostic to determine an extent
of canister purge valve degradation.
[0013] FIG. 5 depicts an example lookup table for controlling an
engine idle speed.
[0014] FIG. 6 depicts a flowchart for an example method for
learning an engine stall point.
[0015] FIG. 7 depicts an example timeline for controlling engine
idle speed under conditions where the canister purge valve is
degraded.
[0016] FIG. 8 depicts an example timeline for conducting a canister
purge valve diagnostic according to the method of FIG. 4.
DETAILED DESCRIPTION
[0017] The following description relates to systems and methods for
controlling an engine idle speed based on an extent to which a
canister purge valve (CPV) that regulates a fluid flow from a fuel
system and an evaporative emissions system to an engine, is
degraded. Accordingly, depicted at FIG. 1 is a hybrid vehicle
system including an engine, a fuel system and an evaporative
emissions system. FIG. 2 depicts an example methodology for
controlling engine idle speed to a compensated engine idle speed
depending on the extent of CPV degradation and a current level of
intake manifold vacuum. Depending on whether the vehicle is a light
hybrid electric vehicle, a mild or full hybrid electric vehicle, or
a non-hybrid regular gasoline engine, there may be different
strategies pertaining to whether or not to shut the engine down at
an idle stop event. For example, under conditions where the CPV is
degraded and fuel vaporization is greater than a threshold fuel
vaporization level, it may be preferable to maintain engine
operation and control engine idle speed to the compensated engine
idle speed, rather than shutting down the engine which may lead to
degraded engine startup at the next engine startup request.
Accordingly, methodology pertaining to such strategies is depicted
at FIG. 3. As the methodologies discussed with regard to FIGS. 2-3
involve an indication of the extent to which the CPV is degraded,
an example method for determining the extent of CPV degradation is
depicted at FIG. 4. FIG. 5 depicts a lookup table that includes a
plurality of compensated engine idle speeds as a function of the
extent of CPV degradation determined via the methodology of FIG. 4,
and intake manifold vacuum level. FIG. 6 depicts an example method
for periodically determining an engine stall point as the engine
ages over time, and the engine stall point may be used to update
the compensated engine idle speed values stored at the lookup table
of FIG. 5. An example timeline for controlling engine idle speed to
the compensated engine idle speed according to the methods of FIGS.
2-3, is depicted at FIG. 7. An example timeline for determining the
extent of CPV degradation according to the method of FIG. 4 is
depicted at FIG. 8.
[0018] Turning now to FIG. 1, a schematic depiction of a hybrid
vehicle system 6 is presented that can derive propulsion power from
engine system 10 and/or an on-board energy storage device, such as
a battery system (see below). An energy conversion device, such as
a generator (see below), may be operated to absorb energy from
vehicle motion and/or engine operation, and then convert the
absorbed energy to an energy form suitable for storage by the
energy storage device. Engine system 10 may comprise a
multi-cylinder internal combustion engine, which may be included in
a propulsion system of an automotive vehicle. Engine 10 may be
controlled at least partially by a control system including
controller 12 and by input from a vehicle operator 130 via an input
device 132. In this example, input device 132 includes an
accelerator pedal and a pedal position sensor 134 for generating a
proportional pedal position signal PP.
[0019] Engine 10 may include a lower portion of the engine block,
indicated generally at 26, which may include a crankcase 28
encasing a crankshaft 30 with oil well 32 positioned below the
crankshaft. An oil fill port 29 may be disposed in crankcase 28 so
that oil may be supplied to oil well 32. Oil fill port 29 may
include an oil cap 33 to seal oil fill port 29 when the engine is
in operation. A dip stick tube 37 may also be disposed in crankcase
28 and may include a dipstick 35 for measuring a level of oil in
oil well 32. An oil temperature sensor 51 may be included in
crankcase 28, and may monitor temperature of oil in oil well 32. In
addition, crankcase 28 may include a plurality of other orifices
for servicing components in crankcase 28. These orifices in
crankcase 28 may be maintained closed during engine operation so
that a crankcase ventilation system (described below) may operate
during engine operation.
[0020] The upper portion of engine block 26 may include a
combustion chamber (i.e., cylinder) 34. The combustion chamber 34
may include combustion chamber walls 36 with piston 38 positioned
therein. Piston 38 may be coupled to crankshaft 30 so that
reciprocating motion of the piston is translated into rotational
motion of the crankshaft. Combustion chamber 34 may receive fuel
from fuel injector 45 (configured herein as a direct fuel injector)
and intake air from intake manifold 44 which is positioned
downstream of throttle 42. The engine block 26 may also include an
engine coolant temperature (ECT) sensor 46 input into an engine
controller 12.
[0021] In some embodiments, each cylinder of engine 10 may include
a spark plug 53 for initiating combustion. An ignition system (not
shown) may provide an ignition spark to cylinder 34 via spark plug
53 in response to a spark advance signal from a controller, under
select operating modes.
[0022] Throttle 42 may be disposed in the engine intake to control
the airflow entering intake manifold 44 and may be preceded
upstream by compressor 50 followed by charge air cooler 52, for
example. Throttle 42 may comprise an electrically actuated
throttle, in some examples. An air filter 54 may be positioned
upstream of compressor 50 and may filter fresh air entering intake
passage 13. The intake air may enter combustion chamber 34 via
electrically-actuated intake valve system 40. Likewise, combusted
exhaust gas may exit combustion chamber 34 via
electrically-actuated exhaust valve system 41. In an alternate
embodiment, one or more of the intake valve system and the exhaust
valve system may be cam-actuated. Intake air may bypass compressor
50 via compressor bypass conduit 56, during conditions wherein
compressor bypass valve (CBV) 55 is opened. In this way, pressure
buildup at the compressor inlet may be relieved.
[0023] Each cylinder of engine 10 may include one or more intake
valves and one or more exhaust valves. For example, cylinder 34 is
shown including at least one intake valve 94 and at least one
exhaust valve 95 located at an upper region of cylinder 34. The
valves of cylinder 34 may in some examples be deactivated via
hydraulically actuated lifters coupled to valve pushrods, or via a
cam profile switching mechanism in which a cam lobe with no lift is
used for deactivated valves. Still other valve deactivation
mechanisms may also be used, such as electrically actuated valves.
In one example, engine 10 may comprise a variable displacement
engine (VDE) where each cylinder of engine 10 may be selectively
deactivatable, where deactivatable refers to the ability of the
controller to command both intake and exhaust valves closed for
particular cylinder(s), thus sealing the particular cylinders. If
fuel injection is also stopped, then such action may result in the
particular cylinder(s) being essentially an air-spring.
Accordingly, as depicted herein, in one embodiment, deactivation of
intake valve 94 may be controlled by first VDE actuator 83 while
deactivation of exhaust valve 95 may be controlled by second VDE
actuator 84. In alternate embodiments, a single VDE actuator may
control deactivation of both intake and exhaust valves of the
deactivatable cylinder. In still other embodiments, a single
cylinder valve actuator deactivates a plurality of cylinders (both
intake and exhaust valves), for example all the cylinders in the
deactivated bank, or a distinct actuator may control deactivation
for all the intake valves while another distinct actuator controls
deactivation for all the exhaust valves of the deactivated
cylinders on a bank. It will be appreciated that if the cylinder is
a non-deactivatable cylinder of the VDE engine, then the cylinder
may not have any valve deactivating actuators. Cylinder 34 may have
a compression ratio, which is the ratio of volumes when piston 38
is at bottom center to top center. Conventionally, the compression
ratio is in the range of 9:1 to 10:1. However, in some examples
where different fuels are used, the compression ratio may be
increased. This may happen, for example, when higher octane fuels
or fuels with higher latent enthalpy of vaporization are used. The
compression ratio may also be increased if direct injection is used
due to its effect on engine knock.
[0024] In some examples, a first intake air oxygen sensor 43a
(first IAO2 sensor) may be positioned downstream of throttle 42.
Furthermore, in some examples, an air intake system hydrocarbon
(AIS HC) trap 47 may be positioned downstream of air filter 54, but
upstream of compressor 50. Still further, in some examples, a
second intake air oxygen sensor 43b (second IAO2 sensor) may be
positioned upstream of the throttle 42. Second intake air oxygen
sensor 43b may constitute an intake air oxygen sensor utilize for
exhaust gas recirculation (EGR) purposes, for example, and may be
used in vehicles in which fuel is injected directly, for example
gasoline turbo direct injection (GTDI) engines.
[0025] Exhaust combustion gases exit the combustion chamber 34 via
exhaust passage 60 located upstream of turbine 62. An exhaust gas
sensor 64 may be disposed along exhaust passage 60 upstream of
turbine 62. Turbine 62 may be equipped with a wastegate (not shown)
bypassing it. Exhaust gas sensor 64 may be a suitable sensor for
providing an indication of exhaust gas air/fuel ratio such as a
linear oxygen sensor or UEGO (universal or wide-range exhaust gas
oxygen), a two-state oxygen sensor or EGO, a HEGO (heated EGO), a
NOx, HC, or CO sensor. Exhaust gas sensor 64 may be connected with
controller 12. Engine exhaust 60 may further include one or more
emission control devices 63, also referred to herein as exhaust
catalyst(s), mounted in a close-coupled position. The one or more
emission control devices may include a three-way catalyst, lean NOx
trap, diesel particulate filter, oxidation catalyst, etc. In some
examples, multiple exhaust gas sensors may be positioned both
upstream and downstream of emission control device 63. In some
examples, an electric heater 119 may be coupled to the emission
control device(s), and may be under control of the controller. Such
an electric heater may be utilized in some examples to raise
temperature of the emission control device to a light-off
temperature, or otherwise referred to as operating temperature.
[0026] In the example of FIG. 1, a positive crankcase ventilation
(PCV) system 16 is coupled to the engine intake so that gases in
the crankcase may be vented in a controlled manner from the
crankcase. During non-boosted conditions (when manifold pressure
(MAP) is less than barometric pressure (BP)), the crankcase
ventilation system 16 draws air into crankcase 28 via a breather or
crankcase ventilation tube 74. A first side 101 of crankcase
ventilation tube 74 may be mechanically coupled, or connected, to
fresh air intake passage 13 upstream of compressor 50. In some
examples, the first side 101 of crankcase ventilation tube 74 may
be coupled to intake passage 13 downstream of air filter 54 (as
shown). In other examples, the crankcase ventilation tube may be
coupled to intake passage 13 upstream of air filter 54. A second,
opposite side 102 of crankcase ventilation tube 74 may be
mechanically coupled, or connected, to crankcase 28 via an oil
separator 81.
[0027] Crankcase ventilation tube 74 further includes a sensor 77
coupled therein for providing an estimate about air flowing through
crankcase ventilation tube 74 (e.g., flow rate, pressure, etc.). In
some embodiments, crankcase vent tube sensor 77 may be a pressure
sensor, referred to herein as a crankcase pressure sensor (CKCP
sensor) 77. When configured as a pressure sensor, CKCP sensor 77
may be an absolute pressure sensor or a gauge sensor. In an
alternate embodiment, sensor 77 may be a flow sensor or flow meter.
In still another embodiment, sensor 77 may be configured as a
venturi. In some embodiments, in addition to a pressure or flow
sensor 77, the crankcase vent tube may optionally include a venturi
75 for sensing flow there-through. In still other embodiments,
pressure sensor 77 may be coupled to a neck of venturi 75 to
estimate a pressure drop across the venturi. One or more additional
pressure and/or flow sensors may be coupled to the crankcase
ventilation system at alternate locations. For example, a
barometric pressure sensor (BP sensor) 57 may be coupled to intake
passage 13, upstream of air filter 54, for providing an estimate of
barometric pressure. In one example, where crankcase vent tube
sensor 77 is configured as a gauge sensor, BP sensor 57 may be used
in conjunction with gauge pressure sensor 77. In some embodiments,
pressure sensor 61 may be coupled in intake passage 13 downstream
of air filter 54 and upstream of compressor 50 to provide an
estimate of the compressor inlet pressure (CIP). However, since
crankcase vent tube pressure sensor 77 may provide an accurate
estimate of a compressor inlet pressure during elevated engine air
flow conditions (such as during engine run-up), the need for a
dedicated CIP sensor may be reduced. Further still, a pressure
sensor 59 may be coupled downstream of compressor 50 for providing
an estimate of a throttle inlet pressure (TIP). In some examples,
an intake manifold pressure sensor 198 may be positioned in the
intake manifold and may be relied upon as discussed in further
detail below for inferring a current level of intake manifold
vacuum. Any of the above-mentioned pressure sensors may be absolute
pressure sensor or gauge sensors.
[0028] PCV system 16 also vents gases out of the crankcase and into
intake manifold 44 via a conduit 76 (herein also referred to as PCV
line 76). In some examples, PCV line 76 may include a PCV valve 78,
which may be an electronically controlled valve that is controlled
by controller 12. In another example, the PCV valve 78 may comprise
a passively-actuatable mechanical valve. For example, the PCV valve
may actively or passively vary its flow restriction in response to
the pressure drop across it (or flow rate through it). Thus, in one
example PCV valve 78 may be an electronically controlled valve
wherein controller 12 may command a signal to change a position of
the valve from a fully open position (or a position of high flow)
to a fully closed position (or a position of no flow), or vice
versa, or any position there-between. In another example, the PCV
valve 78 may be passively actuated, as is commonly understood in
the art.
[0029] The gases (referred to herein as blow-by gasses) in
crankcase 28 may consist of un-burned fuel or un-combusted fuel,
un-combusted fuel vapor, un-combusted air, and fully or partially
combusted gases. Further, oil mist or vapor may also be present. As
such, various oil separators may be incorporated in crankcase
ventilation system 16 to reduce exiting of the oil mist from the
crankcase through the PCV system. For example, PCV line 76 may
include a uni-directional oil separator 80 which filters oil from
vapors exiting crankcase 28 before they re-enter the intake
manifold 44. Another oil separator 81 may be disposed in crankcase
ventilation tube 74 to remove oil from the stream of gases exiting
the crankcases during boosted operation. Additionally, PCV line 76
may also include a vacuum sensor 82 coupled to the PCV system. In
other embodiments, a MAP or manifold vacuum (ManVac) sensor may be
located in intake manifold 44.
[0030] Engine system 10 is coupled to a fuel system 18. Fuel system
18 includes a fuel tank 20 coupled to a fuel pump 21 and a fuel
vapor canister 90. During a fuel tank refueling event, fuel may be
pumped into the vehicle from an external source through refueling
port 25. Fuel tank 20 may hold a plurality of fuel blends,
including fuel with a range of alcohol concentrations, such as
various gasoline-ethanol blends, including E10, E85, gasoline,
etc., and combinations thereof. A fuel level sensor 22 located in
fuel tank 20 may provide an indication of the fuel level ("Fuel
Level Input") to controller 12. As depicted, fuel level sensor 22
may comprise a float connected to a variable resistor.
Alternatively, other types of fuel level sensors may be used.
[0031] Fuel pump 21 is configured to pressurize fuel delivered to
the injectors of engine 10, such as example injector 45. It will be
appreciated that fuel system 18 may be a return-less fuel system, a
return fuel system, or various other types of fuel system. Vapors
generated in fuel tank 20 may be routed to fuel vapor storage
canister 90 (also referred to herein as fuel vapor canister, or
just canister), via conduit 93, before being purged to engine
intake manifold 44.
[0032] Fuel vapor canister 90 (also referred to herein as fuel
vapor storage canister, fuel canister, fuel vapor canister, or
simply, canister) may be positioned in evaporative emissions system
19. Fuel vapor canister 90 is filled with an appropriate adsorbent
for temporarily trapping fuel vapors (including vaporized
hydrocarbons) generated during fuel tank refueling operations. In
one example, the adsorbent used is activated charcoal. When purging
conditions are met, such as when the canister is saturated, vapors
stored in fuel vapor canister 90 may be purged to engine intake
passage 13 by opening canister purge valve (CPV) 92. While a single
canister 90 is shown, it will be appreciated that evaporative
emissions system 19 may include any number of canisters. In one
example, CPV 92 may be a solenoid valve wherein opening or closing
of the valve is performed via actuation of a canister purge valve
solenoid.
[0033] A hydrocarbon sensor 67 may be positioned in purge line 91.
By incorporating hydrocarbon sensor 67, purging of the canister 90
may be optimized while maintaining a stoichiometric air/fuel ratio
for engine combustion. More specifically, hydrocarbon sensor 67 may
enable feed-forward air/fuel ratio control of engine combustion
during purging of a fuel vapor storage canister. For example, based
on an indication of hydrocarbon concentration being purged from the
canister, an engine fueling strategy may compensate fuel injection
pulses in order to maintain a stoichiometric air/fuel ratio, which
may prevent a risk of engine stall, hesitation, etc., from a rich
mixture of air and fuel.
[0034] Hydrocarbon sensor 67 may comprise an adsorption sensitive
resistor which may operate on a principle of adsorption according
to Vander Walls "a" constant, where an electrical resistance of the
hydrocarbon sensor 67 varies with respect to fuel vapor
concentration present. Discussed herein, output of the hydrocarbon
sensor may be a function of the electrical resistance of the
hydrocarbon sensor. For example, an output for a particular
resistance may comprise a particular concentration of fuel vapor
sensed via the hydrocarbon sensor.
[0035] Canister 90 may include a buffer (or buffer region) (not
shown), each of the canister and the buffer comprising adsorbent.
The volume of the buffer may be smaller than (e.g., a fraction of)
the volume of canister 90. Adsorbent in the buffer may be same as,
or different from, the adsorbent in the canister (e.g., both may
include charcoal). The buffer may be positioned within canister 90
such that during canister loading, fuel tank vapors are first
adsorbed within the buffer, and then when the buffer is saturated,
further fuel tank vapors are adsorbed in the canister. In
comparison, during canister purging, fuel vapors are first desorbed
from the canister (e.g., to a threshold amount) before being
desorbed from the buffer. In other words, loading and unloading of
the buffer is not linear with the loading and unloading of the
canister. As such, the effect of the canister buffer is to dampen
any fuel vapor spikes flowing from the fuel tank to the canister,
thereby reducing the possibility of any fuel vapor spikes going to
the engine.
[0036] Canister 90 includes a vent line 86 for routing gases out of
the canister 90 to the atmosphere when storing, or trapping, fuel
vapors from fuel tank 20. Vent line 86 may also allow fresh air to
be drawn into fuel vapor canister 90 when purging stored fuel
vapors to engine intake passage 13 via purge line 91 and CPV 92.
While this example shows vent 86 communicating with fresh, unheated
air, various modifications may also be used. Vent 86 may include a
canister vent valve (CVV) 87 to adjust a flow of air and vapors
between canister 90 and the atmosphere. The canister vent valve may
also be used for diagnostic routines. When included, the vent valve
may be opened during fuel vapor storing operations (for example,
during fuel tank refueling) so that air, stripped of fuel vapor
after having passed through the canister, can be pushed out to the
atmosphere.
[0037] Likewise, during purging operations (for example, during
canister regeneration and while the engine is running), the vent
valve may be opened to allow a flow of fresh air to strip the fuel
vapors stored in the canister. In one example, canister vent valve
87 may be a solenoid valve wherein opening or closing of the valve
is performed via actuation of a canister vent solenoid. In
particular, the canister vent valve may be a default-open valve
that is closed upon actuation of the canister vent solenoid. In
some examples, an air filter (not shown) may be coupled in vent 86
between canister vent valve 87 and atmosphere.
[0038] Hybrid vehicle system 6 may have reduced engine operation
times due to the vehicle being powered by engine system 10 during
some conditions, and by the energy storage device under other
conditions. While the reduced engine operation times reduce overall
carbon emissions from the vehicle, they may also lead to
insufficient purging of fuel vapors from the vehicle's emission
control system. To address this, a vapor bypass valve (VBV) 85 may
be included in conduit 93 such that fuel tank 20 is coupled to
canister 90 via the valve. VBV 85 may include a notch opening or
orifice, such that even when closed, the fuel tank may be allowed
to vent pressure through said notch opening or orifice. A size of
the notch opening or orifice may be calibratable. In one example,
the notch opening or orifice may comprise a diameter of 0.09'', for
example. During regular engine operation, VBV 85 may be kept closed
to limit the amount of diurnal or "running loss" vapors directed to
canister 90 from fuel tank 20. During refueling operations, and
selected purging conditions, VBV 85 may be temporarily opened,
e.g., for a duration, to direct fuel vapors from the fuel tank 20
to canister 90. While the depicted example shows VBV 85 positioned
along conduit 93, in alternate embodiments, the VBV may be mounted
on fuel tank 20.
[0039] One or more pressure sensors 23 may be coupled to fuel
system 18 for providing an estimate of a fuel system pressure. In
one example, the fuel system pressure is a fuel tank pressure,
wherein pressure sensor 23 is a fuel tank pressure sensor (also
referred to herein as a fuel tank pressure transducer) coupled to
fuel tank 20 for estimating a fuel tank pressure or vacuum level.
While the depicted example shows pressure sensor 23 directly
coupled to fuel tank 20, in alternate embodiments, the pressure
sensor may be coupled between the fuel tank and canister 90,
specifically between the fuel tank and VBV 85.
[0040] One or more temperature sensors 24 may also be coupled to
fuel system 18 for providing an estimate of a fuel system
temperature. In one example, the fuel system temperature is a fuel
tank temperature, wherein temperature sensor 24 is a fuel tank
temperature sensor coupled to fuel tank 20 for estimating a fuel
tank temperature. While the depicted example shows temperature
sensor 24 directly coupled to fuel tank 20, in alternate
embodiments, the temperature sensor may be coupled between the fuel
tank and VBV 85. A canister temperature sensor 97 may be coupled to
canister 90 and configured to indicate temperature changes of the
adsorbent material within the canister. As fuel vapor adsorption is
an exothermic reaction and fuel vapor desorption is an endothermic
reaction, the canister temperature may be used to indicate a
quantity of fuel vapor adsorbed during a venting event (e.g.,
during refueling and, which will be discussed further below, during
a diagnostic to rationalize hydrocarbon sensor 67), and/or the
quantity of fuel vapor desorbed during a purging operation.
[0041] Fuel vapors released from canister 90, for example during a
purging operation, may be directed into engine intake manifold 44
via purge line 91. The flow of vapors along purge line 91 may be
regulated by CPV 92, coupled between the fuel vapor canister and
the engine intake. The quantity and rate of vapors released by the
CPV may be determined by the duty cycle of an associated canister
purge valve solenoid (not shown). As such, the duty cycle of the
canister purge valve solenoid may be determined by the vehicle's
powertrain control module (PCM), such as controller 12, responsive
to engine operating conditions, including, for example, engine
speed-load conditions, an air-fuel ratio, a canister load, etc. As
discussed above, in some examples feed-forward air/fuel ratio
control during purging of a fuel vapor storage canister may be
utilized via the controller, based on a concentration of fuel
vapors being directed to engine intake manifold 44, where the
concentration of fuel vapors is measured via the hydrocarbon sensor
67.
[0042] By commanding the canister purge valve to be closed, the
controller may seal the canister and evaporative emissions system
from the engine intake.
[0043] Fuel system 18 may be operated by controller 12 in a
plurality of modes by selective adjustment of the various valves
and solenoids. For example, the fuel system may be operated in a
fuel vapor storage mode (e.g., during a fuel tank refueling
operation and with the engine not running), wherein the controller
12 may open VBV valve 85 and CVV 87 while closing CPV 92 to direct
refueling vapors into canister 90 while preventing fuel vapors from
being directed into the intake manifold.
[0044] As another example, the fuel system may be operated in a
refueling mode (e.g., when fuel tank refueling is requested by a
vehicle operator), wherein the controller 12 may open VBV 85 and
CVV 87, while maintaining CPV 92 closed, to depressurize the fuel
tank before allowing fuel to be added therein. As such, VBV 85 may
be kept open during the refueling operation to allow refueling
vapors to be stored in the canister. After refueling is completed,
the VBV may be closed.
[0045] As discussed, the fuel system may be operated in a canister
purging mode (e.g., after an emission control device light-off
temperature has been attained and with the engine running), wherein
the controller 12 may open canister purge valve 92 and canister
vent valve while closing VBV 85. Herein, the vacuum generated by
the intake manifold of the operating engine may be used to draw
fresh air through vent 86 and through fuel vapor canister 90 to
purge the stored fuel vapors into intake manifold 44. In this mode,
the purged fuel vapors from the canister are combusted in the
engine. The purging may be continued until the stored fuel vapor
amount in the canister is below a threshold. During purging, a
learned vapor amount/concentration can be used to determine the
amount of fuel vapors stored in the canister, and then during a
later portion of the purging operation (when the canister is
sufficiently purged or empty), the learned vapor
amount/concentration can be used to estimate a loading state of the
fuel vapor canister. Such a vapor amount/concentration may be
learned via the output of hydrocarbon sensor 67, in one example.
Still further, in some examples the IAO2 sensor 43a may be utilized
to learn the vapor amount/concentration. Additionally or
alternatively, exhaust gas sensor 64 may be used to learn the vapor
amount/concentration.
[0046] Controller 12 is shown in FIG. 1 as a microcomputer,
including microprocessor unit 108, input/output ports 110, an
electronic storage medium for executable programs and calibration
values shown as read only memory chip 112 in this particular
example, random access memory 114, keep alive memory 116, and a
data bus. Controller 12 may receive various signals from sensors
117 coupled to engine 10, including measurement of inducted mass
air flow (MAF) from mass air flow sensor 58; engine coolant
temperature (ECT) from temperature sensor 46; PCV pressure from
vacuum sensor 82; exhaust gas air/fuel ratio from exhaust gas
sensor 64; exhaust temperature sensor 65; crankcase vent tube
pressure sensor 77, BP sensor 57, CIP sensor 61, TIP sensor 59,
canister temperature sensor 97, hydrocarbon sensor 67, etc.
Furthermore, controller 12 may monitor and adjust the position of
various actuators 118 based on input received from the various
sensors. These actuators may include, for example, throttle 42,
intake and exhaust valve systems 40, 41, PCV valve 78, CPV 92, VBV
85, CVV 87, etc. Storage medium read-only memory 112 can be
programmed with computer readable data representing instructions
executable by processor 108 for performing the methods described
below, as well as other variants that are anticipated but not
specifically listed.
[0047] Controller 12 may also be configured to intermittently
perform undesired evaporative emission detection routines on fuel
system 18 and/or evaporative emissions system 19. Tests may be
performed by an evaporative level check module (ELCM) 99
communicatively coupled to controller 12. ELCM 99 may be coupled in
vent 86, between canister 90 and the atmosphere. ELCM 99 may
include a vacuum pump for applying negative pressure to the fuel
system and/or evaporative emission system when administering a
test. In some embodiments, the vacuum pump may be configured to be
reversible. In other words, the vacuum pump may be configured to
apply either a negative pressure or a positive pressure on the fuel
system and/or evaporative emissions system. ELCM 99 may further
include a reference orifice and a pressure sensor 98. The reference
orifice may enable a threshold pressure to be determined based on
current ambient and operating conditions.
[0048] Furthermore, while not explicitly illustrated, ELCM 99 may
include a changeover valve that, when actuated via the controller
to a first position, couples the ELCM to atmosphere, and when
actuated to a second position, seals the ELCM from atmosphere.
Thus, in some examples where the ELCM is included, the CVV may or
may not be additionally included. However, in a situation where the
ELCM is not included, the CVV may be included. Following the
applying of vacuum to the fuel system and/or evaporative emissions
system, a change in pressure at pressure sensor 98 (e.g., an
absolute change or a rate of change) may be monitored and compared
to the threshold pressure. Based on the comparison, the fuel system
and/or evaporative emissions system may be diagnosed for a presence
or absence of undesired evaporative emissions. As such, various
diagnostic detection tests may be performed while the engine is off
(engine-off test) or while the engine is running (engine-on test).
Tests performed while the engine is running may include applying a
negative pressure on the fuel system for a duration (e.g., until a
target fuel tank vacuum is reached) and then sealing the fuel
system while monitoring a change in fuel tank pressure (e.g., a
rate of change in the vacuum level, or a final pressure value). It
may be understood that such a test may be performed via the ELCM
(where included), and/or may additionally or alternatively be
performed via relying on vacuum generated from the engine. Tests
performed while the engine is not running may include sealing the
fuel system and/or evaporative emissions system following engine
shut-off and monitoring a change in fuel system and/or evaporative
emissions system pressure. This type of test is referred to herein
as an engine-off natural vacuum test (EONV). In sealing the fuel
system and/or evaporative emissions system following engine
shut-off, a vacuum may develop in the fuel system and/or
evaporative emissions system as the tank cools and fuel vapors are
condensed to liquid fuel. The amount of vacuum and/or the rate of
vacuum development may be compared to expected values. In another
example, at a vehicle-off event, as heat continues to be rejected
from the engine into the fuel tank, the fuel system pressure and/or
evaporative emissions system pressure may initially rise. During
conditions of relatively high ambient temperature, a pressure build
above a threshold may be considered a passing test.
[0049] As discussed, hybrid vehicle system 6 may include multiple
sources of torque available to one or more vehicle wheels 171,
however, in other examples, the vehicle may include an engine
without other sources of torque available. In the example shown,
hybrid vehicle system 6 includes an electric machine 152. Electric
machine 152 may be a motor or a motor/generator. Crankshaft 30 of
engine 10 and electric machine 152 are connected via a transmission
154 to vehicle wheels 171 when one or more clutches 172 are
engaged. In the depicted example, a first clutch is provided
between crankshaft 30 and electric machine 152, and a second clutch
is provided between electric machine 152 and transmission 154.
Controller 12 may send a signal to an actuator of each clutch 172
to engage or disengage the clutch, so as to connect or disconnect
crankshaft from electric machine 152 and the components connected
thereto, and/or connect or disconnect electric machine 152 from
transmission 154 and the components connected thereto. Transmission
154 may be a gearbox, a planetary gear system, or another type of
transmission. The powertrain may be configured in various manners
including as a parallel, a series, or a series-parallel hybrid
vehicle.
[0050] Electric machine 152 receives electrical power from a
traction battery 158 (also described herein as onboard energy
storage device, energy storage device, or battery) to provide
torque to vehicle wheels 171. Electric machine 152 may also be
operated as a generator to provide electrical power to charge
traction battery 158, for example during a braking operation.
[0051] Onboard energy storage device 158 may periodically receive
electrical energy from a power source 191 residing external to the
vehicle (e.g., not part of the vehicle) as indicated by arrow 192.
As a non-limiting example, hybrid vehicle system 6 may be
configured as a PHEV, whereby electrical energy may be supplied to
energy storage device 158 from power source 191 via an electrical
energy transmission cable 193. During a recharging operation of
energy storage device 158 from power source 191, electrical
transmission cable 193 may electrically couple energy storage
device 158 and power source 191. While the vehicle propulsion
system is operated to propel the vehicle, electrical transmission
cable 193 may disconnected between power source 191 and energy
storage device 158. Controller 12 may identify and/or control the
amount of electrical energy stored at the energy storage device,
which may be referred to as the state of charge (SOC).
[0052] In other examples, electrical transmission cable 193 may be
omitted, where electrical energy may be received wirelessly at
energy storage device 158 from power source 191. For example,
energy storage device 158 may receive electrical energy from power
source 191 via one or more of electromagnetic induction, radio
waves, and electromagnetic resonance. As such, it may be
appreciated that any suitable approach may be used for recharging
energy storage device 158 from a power source that does not
comprise part of the vehicle.
[0053] Hybrid vehicle system 6 may include an exhaust gas
recirculation (EGR) system. Specifically, the EGR system may
include one or more of high pressure EGR, or low pressure EGR. In
the example illustration depicted at FIG. 1, a low pressure EGR
system is illustrated. Specifically, an EGR passage is indicated,
the EGR passage comprising passage 162a and 162b. It may be
understood that passage 162a and 162b may comprise the same EGR
passage, but is indicated as a broken passage for clarity. The EGR
passage comprising passage 162a and 162b may further include EGR
valve 164. By controlling timing of opening and closing of EGR
valve 164, an amount of exhaust gas recirculation may be
appropriately regulated.
[0054] In some examples, hybrid vehicle system 6 may include an
onboard navigation system 199 (for example a Global Positioning
System) that an operator of the vehicle may interact with. The
navigation system 199 may include one or more location sensors for
assisting in estimating vehicle speed, vehicle altitude, vehicle
position/location, etc. This information may be used to infer
engine operating parameters, such as local barometric pressure, an
engine idle event, etc. Controller 12 may in some examples further
be configured to receive information via the internet or other
communication networks. Information received from the GPS may be
cross-referenced to information available via the internet to
determine local weather conditions, local vehicle regulations,
traffic information, etc. In one example, information received from
the GPS may be utilized in conjunction with route learning
methodology, such that routes commonly traveled by a vehicle, or
commonly traveled by a particular vehicle operator, or commonly
traveled by a passenger (in the case of an autonomous vehicle) may
be learned over time. In some examples, other sensors 133, such as
lasers, radar, sonar, acoustic sensors, etc., may be additionally
or alternatively utilized in conjunction with the onboard
navigation system to conduct route learning of commonly traveled
routes by the vehicle. The GPS may in some examples also provide
suggested routes for a vehicle to take, depending on current
vehicle operating conditions, current traffic conditions, etc.
[0055] In some examples, hybrid vehicle system 6 may include
occupancy sensors 185 dedicated to indicating the occupancy state
of the vehicle, for example one or more of seat load cells, door
sensing technology and/or onboard camera(s).
[0056] As discussed above, under situations where the CPV (e.g. 92)
is degraded, engine operation may result in a drawing of fuel
vapors through the degraded CPV and into the engine. Such a
situation may be exacerbated during an engine idle condition, where
engine manifold vacuum is increased and where engine speed (e.g.
engine RPM) is decreased in comparison to, for example, transient
or other driving conditions. At engine idle where engine speed is
low, the engine may be susceptible to hesitation and/or stall
events if unintended fuel vapor (and/or fresh air) enters the
engine by way of the degraded CPV.
[0057] Thus, discussed herein, a system for a vehicle may comprise
a canister purge valve that controls an amount of air and fuel
vapor routed to an engine from a fuel system and an evaporative
emissions system. The system may further comprise a controller with
computer readable instructions stored on non-transitory memory that
when executed cause the controller to, responsive to an indication
that the canister purge valve is degraded and further in response
to an engine idle condition being inferred, controlling an engine
speed to a compensated engine idle speed as a function of an extent
to which the canister purge valve is degraded and a vacuum level in
an intake manifold of the engine.
[0058] For such a system, the system may further comprise a
throttle that regulates intake air flow to the engine, where the
throttle is electronically actuatable. The controller may store
further instructions to control the throttle in order to control
the engine speed to the compensated engine idle speed.
[0059] For such a system, the system may further comprise a
canister vent valve positioned in a vent line stemming from a fuel
vapor storage canister included in the evaporative emissions
system, a vapor bypass valve positioned in a conduit that couples
the fuel system to the evaporative emissions system, and a fuel
tank pressure transducer. The controller may store further
instructions to, with the engine combusting air and fuel, command
closed the canister purge valve and the canister vent valve and
command open the vapor bypass valve. The controller may store
further instructions to monitor a rate at which a negative pressure
threshold is reached, the monitoring via the fuel tank pressure
transducer, and indicate the extent to which the canister purge
valve is degraded based on the rate at which the negative pressure
threshold is reached.
[0060] For such a system, the system may further comprise a lookup
table stored at the controller that returns the compensated engine
idle speed based on the extent to which the canister purge valve is
degraded and the vacuum level in the intake manifold of the engine.
The controller may store further instructions to update the
compensated engine idle speed based on a learned engine stall
point, the learned engine stall point determined after the vehicle
has been driven a predetermined number of miles since a prior
learned engine stall point was determined.
[0061] One approach to avoid engine hesitation and/or stall may be
to simply raise engine speed a fixed arbitrary or predetermined
amount under conditions of a degraded CPV. However, in relying on
such a strategy, in order to account for varying degrees of CPV
degradation the fixed amount may be excessive for a current extent
or level of CPV degradation. Raising engine speed to a fixed level
may thus in some examples undesirably decrease fuel economy and
contribute to higher than desired levels of noise, vibration and
harshness (NVH).
[0062] Accordingly, a smart method for raising engine idle speed
based on a measured extent of CPV degradation may reduce chances
for engine hesitation and/or stall under conditions of CPV
degradation, while also avoiding a reduction in fuel economy and
while further reducing issues related to NVH. Thus, turning to FIG.
2, a high level example method 200 is shown, depicting methodology
for compensating engine idle speed as a function of a degree or
extent to which the CPV is degraded. Method 200 will be described
with reference to the systems described herein and shown in FIG. 1,
though it will be appreciated that similar methods may be applied
to other systems without departing from the scope of this
disclosure. Instructions for carrying out method 200 and the rest
of the methods included herein may be executed by a controller,
such as controller 12 of FIG. 1, based on instructions stored in
non-transitory memory, and in conjunction with signals received
from sensors of the engine system, such as temperature sensors,
pressure sensors, and other sensors described in FIG. 1. The
controller may employ actuators such as throttle (e.g. 42), CPV
(e.g. 92), CVV (e.g. 87), VBV (e.g. 85), etc., to alter states of
devices in the physical world according to the methods depicted
below.
[0063] Method 200 begins at 205 and may include estimating and/or
measuring vehicle operating conditions. Operating conditions may be
estimated, measured, and/or inferred, and may include one or more
vehicle conditions, such as vehicle speed, vehicle location, etc.,
various engine conditions, such as engine status, engine load,
engine speed, A/F ratio, manifold air pressure, etc., various fuel
system conditions, such as fuel level, fuel type, fuel temperature,
etc., various evaporative emissions system conditions, such as fuel
vapor canister load, fuel tank pressure, etc., as well as various
ambient conditions, such as ambient temperature, humidity,
barometric pressure, etc.
[0064] Proceeding to 210, method 200 may include indicating whether
an engine idle condition is inferred. The engine idle event may be
inferred based on a vehicle deceleration event, where the
controller infers an upcoming engine idle event within a
predetermined threshold duration (e.g. within 1-2 seconds or less).
Additionally or alternatively, the engine idle event may be
inferred based on information retrieved via the onboard navigation
system. For example, based on information retrieved from the
onboard navigation system related to vehicle location, traffic
light(s) or stop signs, current traffic density, etc., the
controller may infer an upcoming engine idle event within the
predetermined threshold duration. In yet another additional or
alternative example, an engine idle event may be inferred as a
function of a deceleration fuel shut off (DFSO) event. For example,
in response to an indication that a DFSO event has ended, the
engine may be fueled at an engine idle speed.
[0065] Accordingly, if an engine idle condition is not inferred at
210, method 200 may proceed to 215. At 215, method 200 may include
maintaining current operating conditions. For example, if the
engine is in operation, current engine operating parameters may be
maintained. If the engine is not in operation, such operation may
be maintained. Furthermore, position of valves including but not
limited to the CPV, VBV, CVV, etc., may be maintained in their
current operational status. Method 200 may then end.
[0066] Returning to 210, in response to an engine idle condition
being inferred, method 200 may proceed to 220. At 220, method 200
may include indicating whether CPV degradation is indicated. If
there is no indication that the CPV is degraded to any extent,
method 200 may proceed to 215, where current operating conditions
may be maintained. Specifically, there may be a base engine idle
speed for a given current level of intake manifold vacuum that is
used under conditions where the CPV is not degraded. In such a
condition where the engine idle condition is inferred but where the
CPV is not degraded, maintaining current operating conditions at
215 may include controlling the engine speed to the base engine
idle speed for the current level of intake manifold vacuum (refer
to the lookup table of FIG. 5, which will be elaborated in further
detail below). Method 200 may then end.
[0067] Returning to 220, in response to an indication that the CPV
is degraded, method 200 may proceed to 225. At 225, method 200 may
retrieve the extent to which the CPV is degraded from the
controller. Specifically, the extent to which the CPV is degraded
may be determined via the methodology of FIG. 4. Accordingly, the
methodology of FIG. 4 will now be discussed. Method 400 will be
described with reference to the systems described herein and shown
in FIG. 1, though it will be appreciated that similar methods may
be applied to other systems without departing from the scope of
this disclosure. Instructions for carrying out method 400 may be
executed by a controller, such as controller 12 of FIG. 1, based on
instructions stored in non-transitory memory, and in conjunction
with signals received from sensors of the engine system, such as
temperature sensors, pressure sensors, and other sensors described
in FIG. 1. The controller may employ actuators such as throttle
(e.g. 42), CPV (e.g. 92), CVV (e.g. 87), VBV (e.g. 85), etc., to
alter states of devices in the physical world according to the
methods depicted below.
[0068] Method 400 begins at 405 and may include estimating and/or
measuring vehicle operating conditions. Operating conditions may be
estimated, measured, and/or inferred, and may include one or more
vehicle conditions, such as vehicle speed, vehicle location, etc.,
various engine conditions, such as engine status, engine load,
engine speed, A/F ratio, manifold air pressure, etc., various fuel
system conditions, such as fuel level, fuel type, fuel temperature,
etc., various evaporative emissions system conditions, such as fuel
vapor canister load, fuel tank pressure, etc., as well as various
ambient conditions, such as ambient temperature, humidity,
barometric pressure, etc.
[0069] Proceeding to 410, method 400 includes indicating whether
conditions are met for conducting the CPV degradation diagnostic.
In one example, conditions may be met at a cold start event where
fuel temperature is measured or inferred to be below a
predetermined fuel temperature. Additionally or alternatively,
conditions being met at 410 may include an estimated or inferred
fuel vaporization rate below a predetermined fuel vaporization rate
threshold. Additionally or alternatively, conditions being met at
410 may include a threshold duration of time elapsing since a prior
CPV diagnostic was conducted. Additionally or alternatively,
conditions being met at 410 may include the vehicle being
stationary. However, in other examples, conditions being met at 410
may include a steady-state cruise condition, without departing from
the scope of this disclosure. Conditions being met at 410 may
additionally or alternatively include an intake manifold vacuum
greater than a predetermined threshold vacuum. Conditions being met
at 410 may additionally or alternatively include an indication of
an absence of a source of undesired evaporative emissions stemming
from the fuel system and/or evaporative emissions system. In other
words, if there is an indication of fuel system or evaporative
emissions system degradation in the form of a source of undesired
evaporative emissions, then conditions may not be met for
conducting the CPV degradation diagnostic. In response to
conditions being met for conducting the CPV diagnostic at 410,
method 400 may proceed to 415. At 415, method 400 may include
commanding open the VBV (e.g. 85) and commanding closed the CPV
(e.g. 92). While not explicitly illustrated, it may be understood
that at 415, method 400 may further include commanding open the CVV
(e.g. 87), in a situation where the CVV is not already open.
Continuing to 410, method 400 may include indicating whether fuel
system pressure is less than a predetermined fuel system pressure
threshold. The predetermined fuel system pressure threshold may be
within a predetermined pressure from atmospheric pressure, for
example. In other words, prior to conducting the CPV diagnostic,
pressure in the fuel system and evaporative emissions may first be
relieved, to within the predetermined pressure from atmospheric
pressure as set by the predetermined fuel system pressure
threshold. In this way, existing pressure in the fuel system and/or
evaporative emissions system may be relieved so as to not impact
the CPV diagnostic, discussed in further detail below.
[0070] Once fuel system and evaporative emissions system pressure
has been relieved, method 400 may proceed to 425. At 425, method
400 may include commanding closed the CVV. With the CPV closed as
well as the CVV, method 400 may proceed to 430. At 430, method 400
may include monitoring pressure in the fuel system and evaporative
emissions system over a predetermined duration. In one example, the
fuel tank pressure transducer (e.g. 23) may be relied upon for
monitoring pressure in the fuel system and evaporative emissions
system. In another example where an ELCM (e.g. 99) is included in
the vehicle, the ELCM pressure sensor (e.g. 98) may additionally or
alternatively be relied upon for monitoring pressure in the fuel
system and evaporative emissions system.
[0071] Continuing at 435, method 400 may include indicating whether
pressure in the fuel system and evaporative emissions system
reached a negative pressure threshold while pressure was being
monitored over the predetermined duration. In one example, the
negative pressure threshold may comprise -4 InH.sub.2O, however the
negative pressure threshold may in other examples comprise any
negative pressure in a range of -8 InH.sub.2O to -2 InH.sub.2O.
[0072] If, at 435, it is indicated that the negative pressure
threshold was not reached, method 400 may proceed to 440, where it
may be indicated that that the CPV is not degraded to any
appreciable extent. In other words, at 440, an absence of CPV
degradation may be indicated. Specifically, as mentioned above, an
entry condition for the CPV diagnostic may include an indication
that the fuel system and evaporative emissions system are free from
sources of undesired evaporative emissions. Thus, in a case where
the negative pressure threshold is not reached at 435, it may be
understood that the reason is not due to a source of gross
undesired evaporative emissions that is preventing the negative
pressure threshold from being reached, but rather is due to the CPV
effectively sealing and preventing engine manifold vacuum from
being communicated to the fuel system and evaporative emissions
system. Accordingly, with the absence of CPV degradation indicated
at 440, method 400 may proceed to 445. At 445, method 400 may
include commanding open the CVV, and may further include commanding
closed the VBV. In some examples, the VBV may be commanded closed
once pressure in the fuel system and evaporative emissions system
is relieved. Although, because the VBV includes a small orifice as
discussed above, in other examples the VBV may be commanded closed
at a substantially similar time (e.g. within one or two seconds) as
when the CVV is commanded open.
[0073] Proceeding to 450, method 400 may include updating vehicle
operating parameters. Specifically, in a case where the CPV was
found to not be degraded to any appreciable extent, updating
vehicle operating parameters at 450 may include storing the result
at the controller, and maintaining current engine idle speed
settings. In other words, because there is an indication of an
absence of CPV degradation, any stored settings pertaining to
engine idle speed may be maintained without being modified. Method
400 may then end.
[0074] Alternatively, returning to 435, in a case where pressure in
the fuel system and evaporative emissions system was reduced to the
negative pressure threshold, method 400 may proceed to 455. At 455,
method 400 may include determining the extent to which the CPV is
degraded as a function of a rate at which the negative pressure
threshold was reached. For example, it may be understood that as
CPV degradation increases, the rate at which the negative pressure
threshold is reached may be faster. Alternatively, lesser CPV
degradation may correspond to slower rates at which the negative
pressure threshold is reached. Said another way, the faster the
negative pressure threshold is reached for the CPV degradation
diagnostic, the greater the extent of CPV degradation. Conversely,
the slower the negative pressure threshold is reached for the CPV
degradation diagnostic, the lesser the extent of CPV
degradation.
[0075] The rate at which the negative pressure threshold is reached
may be dependent on a number of other variables, in addition to the
extent of CPV degradation. For example, the rate at which the
negative pressure threshold is reached may be slower, for a given
extent of CPV degradation, when there is a lesser intake manifold
vacuum magnitude, as compared to a faster rate for the same given
extent of CPV degradation, when there is a greater (e.g. more
negative) intake manifold vacuum magnitude. Accordingly,
determination of the extent of CPV degradation may further be a
function of a level of intake manifold vacuum magnitude during the
CPV degradation diagnostic.
[0076] In another additional or alternative example, the rate at
which the negative pressure threshold is reached may be a function
of fuel vaporization level of fuel in the fuel tank during the CPV
degradation diagnostic. More specifically, fuel vaporization may
counter the buildup of negative pressure in the fuel system and
evaporative emissions system, thus resulting in the rate at which
the negative pressure threshold is reached being slower under
conditions where fuel vaporization is an issue to contend with.
Accordingly, determination of the extent of CPV degradation may
further be a function of a level of fuel vaporization during the
CPV degradation diagnostic. The level of fuel vaporization may be a
function of ambient temperature and fuel RVP, and thus determining
the extent of CPV degradation may further include compensating for
current ambient temperature and fuel RVP.
[0077] In yet another additional or alternative example, the rate
at which the negative pressure threshold is reached may be a
function of fuel level in the fuel tank. For example, as fuel level
decreases, it may take more time for the negative pressure
threshold to be reached, as compared to situations where fuel level
is higher. Accordingly, determining the extent of CPV degradation
may further include compensating for current fuel level in the fuel
tank.
[0078] Based on the above, it may be understood that determining
the extent of CPV degradation may include determining the rate at
which the negative pressure threshold is reached, and compensating
the rate and thereby the extent of CPV degradation as a function of
one or more of the current rate of fuel vaporization, current
ambient temperature, current fuel level, fuel RVP, current level of
intake manifold vacuum, etc.
[0079] Determining the extent of CPV degradation as a function of
the above-mentioned variables may include the controller comparing
said variables to one or more lookup tables stored at the
controller, to infer the extent of CPV degradation. In other
examples, values pertaining to the above-mentioned variables along
with the rate at which the negative pressure threshold was reached
may be input into a formula or model stored at the controller,
which may output a result corresponding to the extent of CPV
degradation. As an example, consider a CPV with a 0.02'' diameter
source of degradation, such that when commanded closed, the engine
manifold vacuum draws air and/or fuel vapors through the 0.02''
diameter source. By comparing the rate at which the negative
pressure threshold was reached, and compensating for current level
of intake manifold vacuum, current level of fuel vaporization,
current ambient temperature, fuel RVP, fuel level, etc., it may be
indicated that the CPV includes a 0.02'' source of degradation.
Thus, discussed herein, CPV degradation refers to a degree to which
the CPV is not properly sealing. In one example, the CPV may be not
properly sealing such that there remains a 0.02'' diameter opening
that air and/or fuel vapor may be able to travel through. In other
examples where the CPV is degraded to a greater extent, the opening
associated with the non-sealing CPV may be greater than 0.02'' in
diameter. The values for CPV degradation discussed herein (e.g.
0.02'', 0.04'', etc.) may be approximate in some examples. For
example, it may be determined that the source of degradation of the
CPV is approximately 0.02'' in diameter.
[0080] With the extent of CPV degradation determined at 455, method
400 may proceed to 445. At 445, method 400 may include commanding
open the CVV, and may further include commanding closed the VBV, in
similar fashion as that discussed above. Proceeding to 450, method
400 may include updating vehicle operating parameters. Updating
vehicle operating parameters may include storing the results of the
CPV degradation diagnostic at the controller. Updating vehicle
operating parameters may in some examples additionally or
alternatively include setting diagnostic trouble code and
illuminating a malfunction indicator light (MIL) at the vehicle
dash, alerting the vehicle operator of a request to service the
vehicle. Updating vehicle operating parameters may additionally or
alternatively include using the obtained extent of degradation of
the CPV to update a lookup table that is used to by the controller
to regulate engine idle speed as a function of engine intake
manifold vacuum. Specifically, based on the determined extent of
CPV degradation, current values of engine idle speed may be
increased as a function of the extent of CPV degradation and intake
manifold vacuum. In this way, engine speed at idle may be increased
to compensate for the extra fuel vapor and/or air being drawn into
the engine while the engine is idling or fueled at engine idle
speed, which may prevent or reduce issues related to engine
hesitation and/or stall which may otherwise occur if the CPV
degradation were not accounted for by raising engine idle speed.
Method 400 may then end.
[0081] Turning to FIG. 5, an example illustration 500 is shown,
depicting a lookup table that determines engine idle speed as a
function of the extent of CPV degradation and intake manifold
vacuum. While not explicitly illustrated, it may be understood that
in some examples, the determined engine idle speed may further be
modified or compensated for as a function of a current level of
fuel vaporization.
[0082] Briefly, in a case where there is a 0.0'' source of
degradation, it may be understood that there is an absence of CPV
degradation. Accordingly, engine idle speed may be determined as a
function of intake manifold vacuum level. Discussed herein, when
there is an absence of CPV degradation, engine idle speeds at
different levels of intake manifold vacuum may be referred to as
base engine idle speeds. Intake manifold vacuum level may be
monitored, for example, via the intake manifold pressure sensor
(e.g. 198). In other examples, intake manifold vacuum level may be
determined as a pressure difference across the CPV (e.g. manifold
pressure-fuel system pressure).
[0083] In a case where the CPV is degraded, see for example 0.02''
source of degradation, the engine idle speed may be raised a
predetermined amount as a function of intake manifold vacuum level,
from the base engine idle speeds. As can be seen from the lookup
table depicted at FIG. 5, as the extent of CPV degradation
increases, compensated engine idle speed correspondingly increases
as a function of intake manifold vacuum level. Thus, as an example,
in a case where there is a 0.08'' source of CPV degradation and
intake manifold vacuum is -16 InHg, engine idle speed may be raised
from 110 RPM (in the case of an absence of CPV degradation) to 190
RPM in order to compensate for the fuel vapors and/or air expected
to be inducted to the engine via the degraded CPV.
[0084] Returning now to step 225 at FIG. 2, it may be understood
that the above-described methodology of FIG. 4 may be used to
determine the extent of CPV degradation, which may be stored at the
controller. Accordingly, at step 225 of FIG. 2, in response to an
engine idle condition where the CPV is indicated to be degraded,
method 200 may include retrieving the current extent of CPV
degradation from the controller, the current extent of CPV
degradation stored at the controller based on the outcome of the
control methodology depicted at FIG. 4.
[0085] Continuing to 230, method 200 may include determining engine
idle speed as a function of the current level of CPV degradation,
and as a function of the current level of intake manifold vacuum,
as discussed above with regard to FIG. 5. In other words, the
controller may use the lookup table of FIG. 5 in order to determine
engine idle speed.
[0086] Once engine idle speed is determined at 230, method 200 may
include controlling engine idle speed to the compensated engine
idle speed based on the value pulled from the lookup table of FIG.
5. Controlling engine idle speed to the compensated engine idle
speed may include commanding the throttle to a more open position,
such that an increased air charge may be delivered to the engine,
thereby increasing engine speed.
[0087] Proceeding to 240, method 200 may include indicating whether
conditions are met for discontinuing controlling engine speed to
the compensated engine idle speed. In other words, in response to a
request for vehicle acceleration or some other request (e.g. an
engine-off event) such that the engine is no longer requested to be
controlled at the compensated engine idle speed, method 200 may
proceed to 245, where current engine operating parameters may be
updated. Updating current engine operating parameters at 245 may
include controlling engine operation as a function of the request
that resulted in the exit from engine idle. As an example, in
response to a request for vehicle acceleration, the fueling, spark
and the throttle may be controlled so as to meet the acceleration
request via the engine. Method 200 may then end.
[0088] While a degraded CPV may allow for fuel vapors to be drawn
into the engine at engine idle with the engine combusting air and
fuel, it is herein recognized that there are certain types of
vehicles which may shut down the engine at idle-stop events. While
shutting down the engine may serve to avoid engine hesitation
and/or engine stall issues which may otherwise occur if the engine
were left combusting in the presence of a degraded CPV, a degraded
CPV may allow for fuel vapors to migrate to the intake manifold of
the deactivated engine, which may cause a degraded engine start
event (e.g. hesitation, misfire, long crank time, etc.) upon the
engine being commanded to again combust air and fuel.
[0089] Accordingly, turning now to FIG. 3, a high-level example
method 300 is depicted, illustrating how engine operation may be
controlled under circumstances where the CPV is indicated to be
degraded to some extent, and where the controller includes
instructions to shut down the engine at idle-stop events. Method
300 will be described with reference to the systems described
herein and shown in FIG. 1, though it will be appreciated that
similar methods may be applied to other systems without departing
from the scope of this disclosure. Instructions for carrying out
method 300 may be executed by a controller, such as controller 12
of FIG. 1, based on instructions stored in non-transitory memory,
and in conjunction with signals received from sensors of the engine
system, such as temperature sensors, pressure sensors, and other
sensors described in FIG. 1. The controller may employ actuators
such as throttle (e.g. 42), CPV (e.g. 92), CVV (e.g. 87), VBV (e.g.
85), etc., to alter states of devices in the physical world
according to the methods depicted below.
[0090] Method 300 begins at 305 and may include estimating and/or
measuring vehicle operating conditions. Operating conditions may be
estimated, measured, and/or inferred, and may include one or more
vehicle conditions, such as vehicle speed, vehicle location, etc.,
various engine conditions, such as engine status, engine load,
engine speed, A/F ratio, manifold air pressure, etc., various fuel
system conditions, such as fuel level, fuel type, fuel temperature,
etc., various evaporative emissions system conditions, such as fuel
vapor canister load, fuel tank pressure, etc., as well as various
ambient conditions, such as ambient temperature, humidity,
barometric pressure, etc.
[0091] Proceeding to 310, method 300 includes indicating whether
the CPV is degraded as discussed with regard to the methodology of
FIG. 4. If the CPV is not indicated to be degraded to any
appreciable extent, method 400 may end. Alternatively, if the CPV
is indicated to be degraded as per the methodology of FIG. 4,
method 300 may proceed to 315. At 315, method 300 may include
indicating whether an idle stop condition is inferred.
Specifically, the idle stop condition of step 315 may comprise an
upcoming (e.g. within 1-2 seconds) vehicle stop event where the
vehicle is expected to come to a complete stop and where the engine
may be stopped. Similar to that discussed above at FIG. 2,
inferring the idle stop event may be based on information retrieved
from the onboard navigation system, and/or inferred based on
vehicle speed, learned driving routines, etc.
[0092] If, at 315, an idle stop condition is not inferred, method
300 may proceed to 320. At 320, method 300 may include maintaining
current operating conditions. For example, if the engine is
operating to propel the vehicle, such engine operation may be
maintained. If the vehicle is being propelled, at least in part,
via electrical energy, such operating conditions may be maintained.
A current status of valves including but not limited to the CPV,
VBV, and CVV may be maintained. Method 300 may then end.
[0093] Returning to 315, in response to the idle stop condition
being inferred, method 300 may proceed to 325. At 325, method 300
may include estimating the fuel vaporization rate. For example, the
fuel vaporization rate may be estimated as a function of one or
more of fuel RVP, ambient temperature, engine run-time, mass air
flow summed over the duration of the current drive cycle, fuel
level, fuel system pressure (and in some examples evaporative
emissions system pressure as well), current environmental
conditions (e.g. wind, rain, snow, etc.), etc. For vehicles with a
VBV, fuel vaporization rate may be inferred by commanding closed
the VBV, and monitoring a rate at which pressure in the fuel tank
builds. For example, any standing pressure in the fuel tank may be
relieved via coupling the fuel tank to atmosphere, and then the VBV
may be commanded closed. The rate at which pressure builds may be
monitored via the FTPT to infer fuel vaporization rate. In another
example case for vehicles that do not include a VBV, vaporization
rate may be inferred based on output from a hydrocarbon sensor
positioned in the canister load line (e.g. 93). In yet another
example, fuel vaporization rate may be inferred via the use of
temperature sensor(s) (e.g. 97) configured to monitor canister
temperature changes. For example, during a purging event where the
canister is being desorbed of fuel vapor, a heat gain instead of an
expected temperature drop may indicate a high rate of fuel
vaporization, or in other words, fuel vaporization greater than a
threshold fuel vaporization rate (see below). In yet another
example, a fuel vaporization rate greater than the threshold fuel
vaporization rate may be inferred during a canister purging event
where, after a threshold number of liters of air have been inferred
to have flowed through the canister (e.g. for a 2 L canister, 600 L
of air), the exhaust gas oxygen sensor (e.g. HEGO) is continuing to
register a rich response.
[0094] With the fuel vaporization rate determined at 325, method
300 may proceed to 330. At 330, method 300 may include indicating
whether the vehicle comprises a non-hybrid vehicle or "light
hybrid" equipped with stop/start capabilities. Such a vehicle may
be capable of shutting down the engine when the vehicle is coming
to a stop, and then restarting the engine when a request for
acceleration is received, but may not be capable of rotating the
engine unfueled via a motor that receives power from an onboard
energy storage device (e.g. battery). If, at 330, it is indicated
that the vehicle is a non-hybrid or light hybrid with stop/start
capabilities, method 300 may proceed to 335. At 335, method 300 may
include indicating whether the fuel vaporization rate is greater
than a threshold fuel vaporization rate. The threshold fuel
vaporization rate may comprise a rate where, even with the VBV
closed (but with the predetermined orifice size included therein)
and with the CPV degraded to some extent, it may be expected that
fuel vapors may migrate to the intake manifold under circumstances
where the engine is stopped, which may thus cause a degraded (e.g.
misfires, long crank, etc.) engine start event when requested.
[0095] If, at 335, it is indicated that the fuel vaporization rate
is not greater than the threshold fuel vaporization rate, method
300 may proceed to 340. At 340, method 300 may include shutting
down the engine for the idle stop event. In other words, because
the fuel vaporization rate is below the threshold fuel vaporization
rate, an amount of fuel vapors expected to migrate to the intake
manifold may be low enough so as to not result in a degraded engine
start event when the next engine start event is requested. Method
300 may then end.
[0096] Alternatively, if at 335 it is indicated that the fuel
vaporization rate is greater than the threshold fuel vaporization
rate, method 300 may proceed to 345. At 345, method 300 may include
preventing engine shut down for the idle stop event. Instead, the
engine may be maintained combusting air and fuel, and method 300
may proceed to step 225 of method 200. Then, the rest of method 200
may be carried out as discussed in detail above. Briefly, with the
engine still combusting air and fuel, the extent of CPV degradation
may be retrieved from the controller and, via the lookup table of
FIG. 5, the compensated engine idle speed may be determined. In
this way, by maintaining the engine combusting and controlling
engine idle speed as a function of intake manifold vacuum level and
extent of CPV degradation, engine hesitation and/or stall may be
avoided, while also avoiding degraded engine start issues which may
otherwise result if the engine were stopped at the idle stop
event.
[0097] Returning to 330, responsive to an indication that the
vehicle is not a non-hybrid or light hybrid with stop/start
capabilities, method 300 may proceed to 350. At 350, method 300 may
include indicating whether the vehicle is a mild hybrid electric
vehicle (HEV) or a full HEV. IN other words, at 350, method 300 may
include determining whether the vehicle includes a motor capable of
rotating the engine unfueled for an extended period of time via
power supplied from a traction battery (e.g. 158), for example. If
the vehicle is neither a non-hybrid or light hybrid equipped with
stop/start capabilities (refer to step 330), nor a mild or full HEV
(refer to step 350), method 300 may proceed directly to step 225 of
method 200, and from there the rest of method 200 may be carried
out as discussed above. Said another way, because the vehicle is
not equipped with stop/start capabilities and because there is an
indication of CPV degradation, engine idle speed may be increased
as per the methodology of FIG. 2 in order to compensate for fuel
vapors and/or air that may be drawn into the engine via the
degraded CPV while the vehicle is stopped.
[0098] Returning to 350, in response to an indication that the
vehicle is a mild or full HEV, method 300 may proceed to 355. At
355, method 300 may include indicating whether the fuel
vaporization rate is greater than the threshold fuel vaporization
rate, similar to that already discussed with regard to step 335. If
not, method 300 may proceed to 358, where the engine may be shut
down and maintained stationary while the vehicle is stopped. In
other words, in such a situation, although the CPV is degraded,
because the fuel vaporization rate is below the threshold fuel
vaporization rate an amount of fuel vapors that may enter the
intake manifold via the degraded CPV while the engine is shut down
may not be sufficient to result in a degraded engine start event at
the next engine start request. Accordingly, in such a situation
method 300 may include shutting down the engine at 358. While not
explicitly illustrated, it may be understood that the engine may be
restarted in response to a request for vehicle acceleration.
[0099] Returning to 355, responsive to an indication that the fuel
vaporization rate is greater than the threshold fuel vaporization
rate, method 300 may proceed to 360. At 360, method 300 may include
indicating whether a state of charge (SOC) is greater than an SOC
threshold and whether a temperature of the exhaust catalyst, also
referred to herein as an emissions control device (e.g. 63), is
above a threshold exhaust catalyst temperature. As an example, the
threshold exhaust catalyst temperature may comprise a light-off
temperature, or in other words, a temperature at which catalytic
reactions are effectively initiated via the exhaust catalyst. If
both conditions are not met at 360, method 300 may proceed to 365.
At 365, method 300 may prevent engine shutdown, and may then
proceed to step 225 where the rest of method 200 may be carried
out, as discussed above. However, while not explicitly illustrated,
it may be understood that in some examples, if the SOC is above the
SOC threshold, also referred to as a first SOC threshold, but the
exhaust catalyst temperature is not above the threshold exhaust
catalyst temperature, there may be an opportunity to use an
electric heater (e.g. 119) coupled to the exhaust catalyst if the
vehicle is equipped with such an electric heater, to raise the
temperature of the exhaust catalyst above the threshold exhaust
catalyst temperature. Because raising the temperature of the
exhaust catalyst above the threshold exhaust catalyst temperature
via the electric heater may utilize battery power, in examples
where the electric heater is relied upon, in some examples the
electric heater may only be used if the SOC is above a second SOC
threshold that is greater than the first SOC threshold.
[0100] In other words, the electric heater may be used provided
that the amount of battery power used to raise the temperature of
the exhaust catalyst to the threshold exhaust catalyst temperature
is such that, once the exhaust catalyst has reached the threshold
exhaust catalyst temperature, the SOC of the onboard energy storage
device remains above the first SOC threshold. In such a case,
rather than preventing engine shutdown at 365, method 300 may
instead proceed to 370.
[0101] Thus, if both conditions are met at step 360, either because
the SOC is above the first SOC threshold and the exhaust catalyst
temperature is above the threshold exhaust catalyst temperature, or
because the electric heater was utilized to raise the temperature
of the exhaust catalyst to the threshold exhaust catalyst
temperature, method 300 may proceed to 370. At 370, method 300 may
include stopping providing fueling and spark to the engine. In
other words, the engine may be deactivated at step 370.
[0102] Continuing to 375, method 300 may include rotating the
engine unfueled via the motor (e.g. 152) in the forward, or default
direction. It may be understood that the forward, or default
direction may comprise the same direction the engine spins when
combusting air and fuel. By rotating the engine unfueled, fuel
vapors may be drawn from the fuel system and evaporative emissions
system through the degraded CPV, and routed to the exhaust
catalyst. While not explicitly illustrated, it may be understood
that the controller may command a speed at which the engine is
rotated as a function of the extent of CPV degradation and fuel
vaporization rate. For example, the controller may rely on a lookup
table that enables determination of engine speed as the current
extent of CPV degradation and the current fuel vaporization rate.
In this way, unfueled engine rotation may reduce opportunity for a
degraded engine start at the next engine start request, which may
otherwise occur if the engine were simply shut down while the
vehicle is stopped.
[0103] Thus, continuing to 380, method 300 may include indicating
whether conditions are met for discontinuing unfueled engine
rotation. For example, conditions being met for discontinuing such
operation may include a request for vehicle acceleration that
involves starting the engine again. In some examples, while the
engine is rotating unfueled, a concentration of fuel vapors
entering into the engine and/or exiting the engine may be monitored
via a hydrocarbon sensor (e.g. 67) and/or an exhaust gas sensor
(e.g. 64), respectively. In response to the concentration of fuel
vapors dropping below a predetermined threshold fuel vapor
concentration, then conditions may be indicated to be met for
discontinuing unfueled engine rotation. In such an example, while
not explicitly illustrated, it may be understood that fuel
vaporization rate may continue to be monitored, and if deemed
appropriate (e.g. fuel vaporization rate rises above the
threshold), the engine may again be commanded to rotate unfueled to
route fuel vapors to the exhaust catalyst.
[0104] As an example, the hydrocarbon sensor may continue to
monitor fuel vapor concentration, and in a situation where the
engine was stopped from rotating unfueled, but then fuel vapor
concentration rises above another threshold fuel vapor
concentration, then the engine may once again be commanded to
rotate unfueled. In this way, engine rotation via the motor may be
minimized.
[0105] If conditions are not met for discontinuing unfueled engine
rotation at 380, method 300 may return to 375. Alternatively, in
response to conditions being met at 380, method 300 may proceed to
385. At 385, method 300 may include discontinuing unfueled engine
rotation. Specifically, the motor may be commanded via the
controller to stop rotating the engine unfueled. Proceeding to 390,
method 300 may include updating engine operating parameters. For
example, in a case where vehicle acceleration was requested,
updating engine operating parameters may include controlling
actuators (e.g. throttle, fuel injector(s), spark plug(s), etc.) to
meet the acceleration request. Method 300 may then end.
[0106] Returning to the lookup table of FIG. 5, it may be
understood that it may be desirable to periodically populate the
table with new values for engine idle speed, due to the fact that
over time, an engine stall point may change as a function of aging
engine components, degradation, etc. Populating the table with new
values may be possible provided that the engine stall point is
known, over time. In other words, referring to FIG. 5, while a
particular engine idle speed (e.g. 110 RPM) may be sufficient for
preventing engine hesitation and/or stall for the engine at a
particular intake manifold vacuum (e.g. -12 InHg) where the CPV is
degraded to a particular extent (e.g. 0.04''), the same engine idle
speed may not be sufficient under the same intake manifold vacuum
and extent of CPV degradation as the engine ages and the stall
point changes. In such an example, the engine idle speed may need
to be increased even further, to avoid engine hesitation and/or
stall issues.
[0107] Accordingly, turning to FIG. 6, a high-level example method
600 for learning an engine stall point, is depicted. Method 600
will be described with reference to the systems described herein
and shown in FIG. 1, though it will be appreciated that similar
methods may be applied to other systems without departing from the
scope of this disclosure. Instructions for carrying out method 600
may be executed by a controller, such as controller 12 of FIG. 1,
based on instructions stored in non-transitory memory, and in
conjunction with signals received from sensors of the engine
system, such as temperature sensors, pressure sensors, and other
sensors described in FIG. 1. The controller may employ actuators
such as throttle (e.g. 42), CPV (e.g. 92), CVV (e.g. 87), VBV (e.g.
85), etc., to alter states of devices in the physical world
according to the methods depicted below.
[0108] Method 600 begins at 605 and may include estimating and/or
measuring vehicle operating conditions. Operating conditions may be
estimated, measured, and/or inferred, and may include one or more
vehicle conditions, such as vehicle speed, vehicle location, etc.,
various engine conditions, such as engine status, engine load,
engine speed, A/F ratio, manifold air pressure, etc., various fuel
system conditions, such as fuel level, fuel type, fuel temperature,
etc., various evaporative emissions system conditions, such as fuel
vapor canister load, fuel tank pressure, etc., as well as various
ambient conditions, such as ambient temperature, humidity,
barometric pressure, etc.
[0109] Proceeding to 610, method 600 may include indicating whether
conditions are met for learning the engine stall point. In one
example, conditions being met may include an indication that the
vehicle has been driven a predetermined number of miles (e.g.
10,000) since a previous engine stall point learning diagnostic was
conducted. Conditions being met at 610 may additionally or
alternatively include an indication that the engine is in
operation, and that the vehicle is stationary. Conditions being met
at 610 may additionally or alternatively include an indication that
the vehicle is unoccupied. For example, an engine start may be
initiated remotely, and one or more of seat load sensors, door
sensors, onboard cameras, etc., may be relied upon for inferring
that the vehicle is unoccupied. It is herein recognized that it may
be beneficial to conduct the engine stall point learning diagnostic
under situations where the vehicle is not occupied, so as to avoid
disturbing the vehicle operator and/or passengers. However, in
other examples, responsive to conditions being met for conducting
the engine stall point learning diagnostic, and under conditions
where the vehicle is occupied, an alert may be communicated to the
vehicle operator in the form of an audible message, a text-based
message displayed at the vehicle dash, a text message sent to the
vehicle operator's phone, etc., to notify the vehicle operator of
the request to conduct the engine stall point learning diagnostic.
In such an example, in order to proceed with the diagnostic, the
vehicle operator may have to confirm the request. For example, the
vehicle operator may confirm the request via a touch screen
associated with the vehicle dash, via a software application on the
vehicle operator's phone, audibly, or any other manner in which the
vehicle operator may communicate with the controller of the vehicle
to confirm the request. Conditions being met at 610 may
additionally or alternatively include an indication that other
diagnostics are not currently being conducted, which may interfere
with the engine stall point learning diagnostic.
[0110] If, at 610, it is indicated that conditions are not met for
learning the engine stall point, method 600 may proceed to 615,
where current operating conditions may be maintained. For example,
in a situation where the vehicle surpasses the predetermined number
of miles while the vehicle is being propelled via the engine and
thus rendering conditions not being met at the current time for
conducting the engine stall point learning diagnostic, current
engine operating conditions may be maintained at 615. Method 600
may then end.
[0111] Returning to 610, in response to conditions being met for
learning the engine stall point, method 600 may proceed to 620. At
620, method 600 may include controlling engine speed to a first
speed, and monitoring engine idle quality for a predetermined
duration (e.g. 5 seconds, 10 seconds, etc.). Monitoring engine idle
quality may include monitoring engine RPM for fluctuations
indicative of engine hesitation, for example. For example, RPM
fluctuations outside of a predetermined RPM range may be indicative
of engine hesitation. It may be understood that the first speed may
comprise a speed where engine hesitation and/or stall may be
expected to not occur.
[0112] Continuing to 625, method 600 may include reducing the
engine RPM by a predetermined amount (e.g. 10 RPM), and once again
monitoring engine idle quality. Reducing engine RPM may include
restricting engine air flow via controlling the throttle such that
engine RPM drops by the predetermined amount. Continuing to 630,
method 600 may include indicating whether an engine stall condition
is indicated. For example, as discussed above, if RPM fluctuations
are outside of a predetermined RPM range for a given engine speed,
then it may be determined that an engine stall condition is
indicated. In other words, if the RPM fluctuations are in excess of
an expected amount of RPM fluctuation, then the engine stall
condition may be indicated. Thus, if at 630 the engine stall
condition is not indicated, method 600 may return to 625, where
engine RPM may once again be reduced by the predetermined amount
and engine idle quality may again be monitored to determine whether
the engine stall condition is indicated.
[0113] Responsive to the engine stall condition being indicated at
630, method 600 may proceed to 635. At 635, method 600 may include
raising engine speed to the first engine speed, to avoid stalling
out the engine. In other words, the throttle may be commanded to
its original position it was commanded to for controlling engine
speed to the first speed. Continuing to 640, method 600 may include
storing the results of the engine stall point learning diagnostic
at the controller. Proceeding to 645, method 600 may include
indicating whether the engine stall point that has been just
determined is different than a previously determined engine stall
point. If not, method 600 may proceed to 650. At 650, because the
engine stall point has not changed, method 600 may include not
adjusting the values of FIG. 5 pertaining to engine idle speed.
Method 600 may then end.
[0114] Alternatively, returning to 645, in response to the current
engine stall point differing from the previously determined engine
stall point, method 600 may proceed to 655. At 655, method 600 may
include adjusting the values of the table of FIG. 5 based on the
recently determined engine stall point. For example, the controller
may store a model which may receive as input the engine stall
point, and which may thus output updated values for engine idle
speed as a function of the extent of CPV degradation and intake
manifold vacuum level. In this way, the lookup table of FIG. 5 may
be periodically updated to account for engine aging, such that the
engine idle speeds retrieved from the lookup table may effectively
prevent engine hesitation and/or stall issues under conditions of a
degraded CPV.
[0115] Thus, discussed herein, a method may comprise inferring an
engine idle condition, and in response, controlling a speed of an
engine to a compensated engine idle speed that is a function of an
extent to which a canister purge valve that regulates an amount of
fluid flow to the engine from a fuel system and/or an evaporative
emissions system, is degraded.
[0116] In such a method, the compensated engine idle speed may be
greater than a base engine idle speed, where the base engine idle
speed is used for the engine idle condition under conditions of an
absence of degradation of the canister purge valve.
[0117] In such a method, the extent to which the canister purge
valve is degraded may be determined based on a rate at which an
engine vacuum reduces a pressure in the fuel system and the
evaporative emissions system under conditions where the fuel system
and the evaporative emissions system are sealed from atmosphere and
where the canister purge valve is commanded closed. The extent to
which the canister purge valve is degraded may further be a
function of a level of a fuel in the fuel system and a rate at
which the fuel is vaporizing while the engine vacuum reduces the
pressure in the fuel system and the evaporative emissions
system.
[0118] In such a method, the method may further comprise
controlling the speed of the engine to the compensated engine idle
speed via electronically controlling a position of a throttle that
regulates an amount of intake air flow to the engine.
[0119] In such a method, the compensated engine idle speed may be
stored at a lookup table as a function of the extent of canister
purge valve degradation and further a function of a level of a
vacuum in intake manifold of the engine. The compensated engine
idle speed may periodically be adjusted. For example, the method
may include periodically learning an engine stall point and wherein
periodically adjusting the compensated engine idle speed is based
on the engine stall point that is periodically learned.
[0120] In such a method, controlling the speed of the engine to the
compensated engine idle speed may further comprise preventing the
engine from being shut down at the engine idle condition under
conditions where it is inferred that shutting down the engine can
result in a degraded engine startup at the next engine start
request.
[0121] In such a method, inferring the engine idle condition may be
based on one of a deceleration fuel shut off event ending, an
indication provided via an onboard navigation system, and a vehicle
deceleration event.
[0122] Another example of a method for a hybrid electric vehicle
may comprise inferring an idle stop event and under conditions
where a canister purge valve that regulates a fluid flow from a
fuel system and an evaporative emissions system to an engine is
degraded, determining a fuel vaporization rate of a fuel stored in
the fuel system in relation to a threshold fuel vaporization rate,
and controlling the engine based on the fuel vaporization rate and
an extent to which the canister purge valve is degraded.
[0123] In such a method, controlling the engine may further
comprise commanding the engine to be shut down and maintained
stationary at the idle stop event responsive to the fuel
vaporization rate being less than the threshold fuel vaporization
rate regardless of the extent to which the canister purge valve is
degraded.
[0124] In such a method, the method may further comprise
determining whether a state of charge of an onboard energy storage
device is greater than a threshold state of charge and whether a
temperature of an exhaust catalyst is greater than a threshold
exhaust catalyst temperature in response to an indication that the
fuel vaporization rate is greater than the threshold fuel
vaporization rate. Controlling the engine may further be a function
of whether the state of charge of the onboard energy storage device
is greater than the threshold state of charge and whether the
temperature of the exhaust catalyst is greater than the threshold
exhaust catalyst temperature. Controlling the engine may further
comprise stopping the engine from combusting air and fuel and
rotating the engine unfueled via a motor during the idle stop event
to route fuel vapors to the exhaust catalyst under conditions where
the fuel vaporization rate is greater than the threshold fuel
vaporization rate, where the state of charge of the onboard energy
storage device is greater than the threshold state of charge and
where the temperature of the exhaust catalyst is greater than the
threshold exhaust catalyst temperature. A speed at which the engine
is rotated unfueled may be variable based on the fuel vaporization
rate and the extent to which the canister purge valve is degraded.
The method may further comprise preventing the engine from being
shut down at the idle stop event under conditions where the state
of charge of the onboard energy storage device is lower than the
threshold state of charge or under conditions where the temperature
of the exhaust catalyst is lower than the threshold exhaust
catalyst temperature, and where the fuel vaporization rate is
greater than the threshold fuel vaporization rate. The method may
further comprise controlling the engine to a compensated engine
idle speed at the idle stop event, the compensated engine idle
speed a function of the extent to which the canister purge valve is
degraded, and further a function of a vacuum level in an intake
manifold of the engine.
[0125] Turning now to FIG. 7, an example timeline 700 is shown,
illustrating how an engine idle speed may be controlled as a
function of an extent to which the CPV is degraded. Timeline 700
includes plot 705, indicating whether an engine idle condition is
indicated, over time. Timeline 700 further includes plot 710,
indicating engine speed (e.g. RPM), over time. The engine may be
stopped (0), or may be at a speed greater than stopped (+).
Timeline 700 further includes plot 715, indicating whether CPV
degradation is indicated (yes or no), over time. Timeline 700
further includes plot 720, indicating a position of a throttle
(e.g. 42), over time. The throttle may be fully closed, fully open,
or somewhere between fully open and fully closed. Timeline 700
further includes plot 725, indicating a status of the CPV (e.g.
92), over time. The CPV may be fully open or fully closed. Timeline
700 further includes plot 730, indicating a status of the VBV (e.g.
85), over time. The VBV may be fully open or fully closed. It may
be understood that, due to the notch or orifice associated with the
VBV, the VBV may allow the fuel tank to breathe even while the VBV
is closed. Timeline 700 further includes plot 735, indicating a
status of the CVV (e.g. 87), over time. The CVV may be fully open
or fully closed. Timeline 700 further includes plot 740, indicating
a fuel vaporization rate, over time. Timeline 700 further includes
plot 745, indicating whether the vehicle is a light-hybrid (yes or
no), over time. It may be understood that a light hybrid may be
configured with stop/start capabilities, but may not include a
motor capable of rotating the engine unfueled for an extended
period of time. Timeline 700 further includes plot 750, indicating
a status of the engine, over time. For this example timeline, the
engine may be either off, or may be on and fueled, or in other
words, combusting air and fuel, over time.
[0126] At time t0, an engine idle conditions is not inferred (plot
705). Accordingly, engine speed (plot 710) is a function of driver
demand, and the throttle position (plot 720) corresponds to driver
demand. The CPV is degraded (plot 715), and while not explicitly
illustrated, it may be understood that the CPV is degraded to a
particular extent, as determined via the methodology of FIG. 4. At
time t0, the CPV is closed (plot 725), and the VBV is closed (plot
730). Alternatively, the CVV is open (plot 735). Fuel vaporization
rate (plot 740) is determined to be above the threshold fuel
vaporization rate, represented by line 741. The vehicle is a
light-hybrid (plot 745), and the engine is operating to combust air
and fuel at time t0 (plot 750).
[0127] Between time t0 and t1, an engine idle condition is not
inferred, and accordingly, engine speed and throttle position
fluctuate as a function of driver demand. At time t1, an engine
idle condition is inferred. Because the fuel vaporization rate is
greater than the threshold fuel vaporization rate (line 741) and
because the vehicle is a light-hybrid, the controller prevents the
engine from pulling down, or in other words, being deactivated, at
the engine idle condition. Instead the engine is maintained
combusting air and fuel at time t1. Responsive to the engine idle
conditions being inferred at time t1 and because the CPV is
indicated to be degraded, at time t1 the controller queries the
lookup table of FIG. 5, and retrieves a compensated engine idle
speed as a function of the current extent of CPV degradation and
current intake manifold vacuum level. While not explicitly
illustrated, as discussed above the controller may infer intake
manifold vacuum level based on a pressure difference between the
intake manifold pressure sensor (e.g. 198) and atmospheric
pressure, monitored for example via the barometric pressure sensor
(e.g. 57).
[0128] Accordingly, between time t1 and t2, the controller commands
the engine speed to the compensated engine idle speed retrieved
from the lookup table of FIG. 5 (refer to plot 710). Controlling
the engine speed to the compensated engine idle speed involves
commanding the throttle to a more open position (refer to plot
720). For reference, dashed line 711 depicts a situation where the
CPV is not degraded, and thus, engine speed is not compensated.
Correspondingly, dashed line 721 represents a throttle position
status under conditions where the CPV is not indicated to be
degraded. Thus, it is clear from comparing plot 710 with dashed
line 711 that engine idle speed has been controlled to an increased
engine idle speed to compensate for the CPV degradation during the
engine idle condition. It may be further understood that the
increasing of the engine idle speed is controlled via actuating the
throttle to a more open position.
[0129] At time t2, an engine idle condition is no longer indicated.
In this example timeline, it may be understood that the engine idle
condition is no longer indicated because the vehicle operator has
requested vehicle acceleration. For example, the vehicle operator
may request vehicle acceleration via depressing the accelerator
pedal of the vehicle. Accordingly, after time t2, engine speed once
again is a function of driver demand, controlled at least in part
via the throttle.
[0130] Turning now to FIG. 8, another example timeline 800 is
shown, depicting example methodology for determining an extent of
CPV degradation, as discussed above with regard to the method of
FIG. 4. Timeline 800 includes plot 805, indicating whether
conditions are met for conducting the CPV degradation diagnostic
(yes or no), over time. Timeline 800 further includes plot 810,
indicating a status of the engine, over time. In this example
timeline, the engine may be off (e.g. stationary and not
combusting), or may be on and fueled (e.g. combusting air and
fuel). Timeline 800 further includes plot 815, indicating a status
of the CPV (e.g. 92), plot 820, indicating a status of the VBV
(e.g. 85), and plot 825, indicating a status of the CVV (e.g. 87),
over time. For each of plots 815, 820 and 825, the respective
valves may be either fully open or fully closed, over time.
Timeline 800 further includes plot 830, indicating fuel system
pressure, over time. In this example timeline it may be understood
that fuel system pressure (and evaporative emissions system
pressure) may be monitored via the fuel tank pressure transducer
(FTPT) (e.g. 23). In this example timeline, pressure in the fuel
system is either near atmospheric pressure, or negative (-) with
respect to atmospheric pressure. Timeline 800 further includes plot
840, indicating to what extent the CPV is degraded, over time. For
simplicity, in this example timeline the CPV may either be not
degraded (no), include a 0.04'' source of degradation, or include a
0.08'' source of degradation. At time t0, conditions are not yet
indicated to be met for conducting the CPV degradation diagnostic
(plot 805). The engine is off (plot 810), and the CPV is closed
(plot 815) while the CVV is open (plot 825). Furthermore, the VBV
is open (plot 820). With the VBV and the CVV open, fuel system (and
evaporative emissions system) pressure is near atmospheric
pressure.
[0131] At time t2, the engine is commanded to combust air and fuel
(plot 810). While not explicit illustrated, it may be understood
that for this example timeline, the engine activation at time t2
comprises a cold start event. With the engine in operation, at time
t2 it is indicated that conditions are met for conducting the CPV
diagnostic (plot 805). Accordingly, the CVV is commanded closed
(plot 825), the CPV is maintained closed (plot 815), and the VBV is
maintained open (plot 820). With the CVV commanded closed, between
time t2 and t3 a negative pressure with respect to atmospheric
pressure builds as monitored via the FTPT (plot 830), and at time
t3, the negative pressure build reaches a negative pressure
threshold represented as dashed line 831. The rate at which the
negative pressure threshold is reached is then used to determine an
extent of CPV degradation, which may involve the controller
retrieving the extent of CPV degradation from a lookup table. The
lookup table may further include information pertaining to intake
manifold vacuum, current rate of fuel vaporization and current fuel
level, as discussed above. In other words, while not explicitly
illustrated, the rate at which the negative pressure threshold is
reached, along with current intake manifold vacuum level, current
fuel vaporization rate and fuel level in the fuel tank may all be
taken into account when determining the extent of CPV
degradation.
[0132] In this example timeline, it may be understood that the rate
at which the negative pressure threshold was reached (taking into
account current fuel vaporization rate, current fuel level, and
current intake manifold vacuum level) corresponds to a CPV with a
0.04'' source of degradation. For illustrative purposes, plot 832
represents an example where the rate at which the negative pressure
threshold was reached is faster than the rate depicted by plot 830.
In such an example, the faster rate as illustrated by plot 832 may
correspond to a 0.08'' source of degradation, depicted by plot 841.
As further illustration, plot 833 depicts a situation where fuel
system pressure did not decrease with the CVV closed. In such an
example, it may be understood that it may be determined that the
CPV is not degraded to any appreciable extent.
[0133] Accordingly, with CPV degradation determined to be 0.04'' at
time t3, conditions are no longer indicated to be met for
conducting the CPV degradation diagnostic (plot 805). Accordingly,
the CVV is commanded open (plot 825), and the VBV is maintained
open (plot 820). With the VBV and the CVV both open, pressure in
the fuel system and evaporative emissions system rapidly returns to
atmospheric pressure (plot 830). At time t4, the VBV is commanded
closed, and after time t4 the engine is maintained on combusting
air and fuel with the VBV closed, the CPV closed, and the CVV
open.
[0134] In this way, engine idle speed may be controlled
proportionate to a degree or extent to which the CPV is degraded.
By controlling engine idle speed in such fashion, fuel economy may
be improved as compared to other methodologies which may involve
raising engine idle speed to a fixed predetermined speed.
Compensating engine idle speed as a function of the extent to which
the CPV is degraded may reduce opportunity for engine hesitation
and/or stall, which may improve engine lifetime and increase
overall customer satisfaction.
[0135] The technical effect of raising engine idle speed
proportionate to an extent to which the CPV is indicated to be
degraded, is that fuel economy may be improved and opportunities
for engine hesitation and/or stall reduced or avoided. In another
example, the technical effect of learning an engine stall point is
to enable periodic updating of a lookup table that stores
compensated engine idle speeds as a function of intake manifold
vacuum and extent of CPV degradation.
[0136] The systems discussed herein and with regard to FIG. 1,
along with the method described herein and with regard to FIGS. 2-4
and FIG. 6, may enable one or more systems and one or more methods.
In one example, a method comprises inferring an engine idle
condition, and in response, controlling a speed of an engine to a
compensated engine idle speed that is a function of an extent to
which a canister purge valve that regulates an amount of fluid flow
to the engine from a fuel system and/or an evaporative emissions
system, is degraded. In a first example of the method, the method
includes wherein the compensated engine idle speed is greater than
a base engine idle speed, where the base engine idle speed is used
for the engine idle condition under conditions of an absence of
degradation of the canister purge valve. A second example of the
method optionally includes the first example, and further includes
wherein the extent to which the canister purge valve is degraded is
determined based on a rate at which an engine vacuum reduces a
pressure in the fuel system and the evaporative emissions system
under conditions where the fuel system and the evaporative
emissions system are sealed from atmosphere and where the canister
purge valve is commanded closed. A third example of the method
optionally includes any one or more or each of the first through
second examples, and further includes wherein the extent to which
the canister purge valve is degraded is further a function of a
level of a fuel in the fuel system and a rate at which the fuel is
vaporizing while the engine vacuum reduces the pressure in the fuel
system and the evaporative emissions system. A fourth example of
the method optionally includes any one or more or each of the first
through third examples, and further comprises controlling the speed
of the engine to the compensated engine idle speed via
electronically controlling a position of a throttle that regulates
an amount of intake air flow to the engine. A fifth example of the
method optionally includes any one or more or each of the first
through fourth examples, and further includes wherein the
compensated engine idle speed is stored at a lookup table as a
function of the extent of canister purge valve degradation and
further a function of a level of a vacuum in intake manifold of the
engine; and wherein the compensated engine idle speed is
periodically adjusted. A sixth example of the method optionally
includes any one or more or each of the first through fifth
examples, and further comprises periodically learning an engine
stall point and wherein periodically adjusting the compensated
engine idle speed is based on the engine stall point that is
periodically learned. A seventh example of the method optionally
includes any one or more or each of the first through sixth
examples, and further includes wherein controlling the speed of the
engine to the compensated engine idle speed further comprises
preventing the engine from being shut down at the engine idle
condition under conditions where it is inferred that shutting down
the engine can result in a degraded engine startup at the next
engine start request. An eighth example of the method optionally
includes any one or more or each of the firs through seventh
examples, and further includes wherein inferring the engine idle
condition is based on one of a deceleration fuel shut off event
ending, an indication provided via an onboard navigation system,
and a vehicle deceleration event.
[0137] Another example of a method for a hybrid electric vehicle
comprises inferring an idle stop event and under conditions where a
canister purge valve that regulates a fluid flow from a fuel system
and an evaporative emissions system to an engine is degraded,
determining a fuel vaporization rate of a fuel stored in the fuel
system in relation to a threshold fuel vaporization rate; and
controlling the engine based on the fuel vaporization rate and an
extent to which the canister purge valve is degraded. In a first
example of the method, the method further includes wherein
controlling the engine further comprises commanding the engine to
be shut down and maintained stationary at the idle stop event
responsive to the fuel vaporization rate being less than the
threshold fuel vaporization rate regardless of the extent to which
the canister purge valve is degraded. A second example of the
method optionally includes the first example, and further comprises
determining whether a state of charge of an onboard energy storage
device is greater than a threshold state of charge and whether a
temperature of an exhaust catalyst is greater than a threshold
exhaust catalyst temperature in response to an indication that the
fuel vaporization rate is greater than the threshold fuel
vaporization rate; and wherein controlling the engine is further a
function of whether the state of charge of the onboard energy
storage device is greater than the threshold state of charge and
whether the temperature of the exhaust catalyst is greater than the
threshold exhaust catalyst temperature. A third example of the
method optionally includes any one or more or each of the first
through second examples, and further includes wherein controlling
the engine further comprises stopping the engine from combusting
air and fuel and rotating the engine unfueled via a motor during
the idle stop event to route fuel vapors to the exhaust catalyst
under conditions where the fuel vaporization rate is greater than
the threshold fuel vaporization rate, where the state of charge of
the onboard energy storage device is greater than the threshold
state of charge and where the temperature of the exhaust catalyst
is greater than the threshold exhaust catalyst temperature. A
fourth example of the method optionally includes any one or more or
each of the first through third examples, and further includes
wherein a speed at which the engine is rotated unfueled is variable
based on the fuel vaporization rate and the extent to which the
canister purge valve is degraded. A fifth example of the method
optionally includes any one or more or each of the first through
fourth examples, and further comprises preventing the engine from
being shut down at the idle stop event under conditions where the
state of charge of the onboard energy storage device is lower than
the threshold state of charge or under conditions where the
temperature of the exhaust catalyst is lower than the threshold
exhaust catalyst temperature, and where the fuel vaporization rate
is greater than the threshold fuel vaporization rate. A sixth
example of the method optionally includes any one or more or each
of the first through fifth examples, and further comprises
controlling the engine to a compensated engine idle speed at the
idle stop event, the compensated engine idle speed a function of
the extent to which the canister purge valve is degraded, and
further a function of a vacuum level in an intake manifold of the
engine.
[0138] An example of a system for a vehicle comprises a canister
purge valve that controls an amount of air and fuel vapor routed to
an engine from a fuel system and an evaporative emissions system;
and a controller with computer readable instructions stored on
non-transitory memory that when executed cause the controller to:
responsive to an indication that the canister purge valve is
degraded and further in response to an engine idle condition being
inferred, controlling an engine speed to a compensated engine idle
speed as a function of an extent to which the canister purge valve
is degraded and a vacuum level in an intake manifold of the engine.
A first example of the system further comprises a throttle that
regulates intake air flow to the engine, where the throttle is
electronically actuatable; and wherein the controller stores
further instructions to control the throttle in order to control
the engine speed to the compensated engine idle speed. A second
example of the system optionally includes the first example, and
further comprises a canister vent valve positioned in a vent line
stemming from a fuel vapor storage canister included in the
evaporative emissions system, a vapor bypass valve positioned in a
conduit that couples the fuel system to the evaporative emissions
system, and a fuel tank pressure transducer; and wherein the
controller stores further instructions to, with the engine
combusting air and fuel, command closed the canister purge valve
and the canister vent valve and command open the vapor bypass
valve; monitor a rate at which a negative pressure threshold is
reached, the monitoring via the fuel tank pressure transducer, and
indicate the extent to which the canister purge valve is degraded
based on the rate at which the negative pressure threshold is
reached. A third example of the system optionally includes any one
or more or each of the first through second examples, and further
comprises a lookup table stored at the controller that returns the
compensated engine idle speed based on the extent to which the
canister purge valve is degraded and the vacuum level in the intake
manifold of the engine; and wherein the controller stores further
instructions to update the compensated engine idle speed based on a
learned engine stall point, the learned engine stall point
determined after the vehicle has been driven a predetermined number
of miles since a prior learned engine stall point was
determined.
[0139] In another representation, a method comprises determining an
extent to which a canister purge valve that regulates a fluid flow
from a fuel system and an evaporative emissions system to an engine
is degraded, updating a plurality of engine idle speeds stored at a
lookup table based on the extent to which the canister purge valve
is degraded, and further updating the plurality of engine idle
speeds based on a learned engine stall point.
[0140] In still another representation, a method comprises
controlling an engine idle speed to a compensated engine idle speed
that is proportionate to a degree or extent to which a canister
purge valve that regulates a fluid flow from a fuel system and/or
evaporative emissions system, is degraded.
[0141] In yet another representation, a method comprises
controlling a usage of fuel for regulating an engine idle speed to
be proportionate to a degree or extent to which a canister purge
valve is degraded.
[0142] Note that the example control and estimation routines
included herein can be used with various engine and/or vehicle
system configurations. The control methods and routines disclosed
herein may be stored as executable instructions in non-transitory
memory and may be carried out by the control system including the
controller in combination with the various sensors, actuators, and
other engine hardware. The specific routines described herein may
represent one or more of any number of processing strategies such
as event-driven, interrupt-driven, multi-tasking, multi-threading,
and the like. As such, various actions, operations, and/or
functions illustrated may be performed in the sequence illustrated,
in parallel, or in some cases omitted. Likewise, the order of
processing is not necessarily required to achieve the features and
advantages of the example embodiments described herein, but is
provided for ease of illustration and description. One or more of
the illustrated actions, operations, and/or functions may be
repeatedly performed depending on the particular strategy being
used. Further, the described actions, operations, and/or functions
may graphically represent code to be programmed into non-transitory
memory of the computer readable storage medium in the engine
control system, where the described actions are carried out by
executing the instructions in a system including the various engine
hardware components in combination with the electronic
controller.
[0143] 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 non-obvious combinations and sub-combinations of the
various systems and configurations, and other features, functions,
and/or properties disclosed herein.
[0144] As used herein, the term "approximately" is construed to
mean plus or minus five percent of the range unless otherwise
specified.
[0145] The following claims particularly point out certain
combinations and sub-combinations regarded as novel and
non-obvious. These claims may refer to "an" element or "a first"
element or the equivalent thereof. Such claims should be understood
to include incorporation of one or more such elements, neither
requiring nor excluding two or more such elements. Other
combinations and sub-combinations of the disclosed features,
functions, elements, and/or properties may be claimed through
amendment of the present claims or through presentation of new
claims in this or a related application. Such claims, whether
broader, narrower, equal, or different in scope to the original
claims, also are regarded as included within the subject matter of
the present disclosure.
* * * * *