U.S. patent application number 15/373154 was filed with the patent office on 2018-06-14 for system and method for diagnosing a postive crankcase ventilation valve.
The applicant listed for this patent is Ford Global Technologies, LLC. Invention is credited to Aed M. Dudar.
Application Number | 20180163659 15/373154 |
Document ID | / |
Family ID | 62489628 |
Filed Date | 2018-06-14 |
United States Patent
Application |
20180163659 |
Kind Code |
A1 |
Dudar; Aed M. |
June 14, 2018 |
SYSTEM AND METHOD FOR DIAGNOSING A POSTIVE CRANKCASE VENTILATION
VALVE
Abstract
Methods and systems are provided for diagnosing a positive
crankcase valve during a vehicle key-off event. In one example, a
method may include controlling a fluid flow from a crankcase of an
engine to an intake manifold of the engine via a positive crankcase
ventilation valve, and indicating whether the positive crankcase
valve is stuck open responsive to spinning the engine unfueled in a
reverse direction, and indicating whether the positive crankcase
valve is stuck closed responsive to spinning the engine fueled but
without spark in a forward direction. In this way, functionality of
a positive crankcase ventilation valve may be diagnosed effectively
during key-off conditions, which may prevent or reduce engine
complications arising from a stuck open or stuck closed positive
crankcase valve.
Inventors: |
Dudar; Aed M.; (Canton,
MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ford Global Technologies, LLC |
Dearborn |
MI |
US |
|
|
Family ID: |
62489628 |
Appl. No.: |
15/373154 |
Filed: |
December 8, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60W 50/0205 20130101;
B60W 20/50 20130101; F01M 11/10 20130101; F02D 2250/06 20130101;
F01M 2013/0083 20130101; F02D 41/042 20130101; B60W 2510/0619
20130101; Y10S 903/93 20130101; F02D 41/0025 20130101; F02D 41/221
20130101; B60W 2710/0605 20130101; F01M 13/0011 20130101; F02D
2200/04 20130101; F02D 2250/08 20130101 |
International
Class: |
F02D 41/22 20060101
F02D041/22; B60W 20/50 20060101 B60W020/50; B60N 2/00 20060101
B60N002/00; F01M 13/00 20060101 F01M013/00; F02D 41/00 20060101
F02D041/00 |
Claims
1. A method comprising: controlling a fluid flow from a crankcase
of an engine to an intake manifold of the engine via a positive
crankcase ventilation valve; and in a first condition, indicating
whether the positive crankcase valve is stuck open responsive to
spinning the engine unfueled in a reverse direction; and in a
second condition, indicating whether the positive crankcase valve
is stuck closed responsive to spinning the engine fueled in a
forward direction.
2. The method of claim 1, further comprising: indicating pressure
in a crankcase ventilation tube via a pressure sensor, the
crankcase ventilation tube fluidically coupling the crankcase to an
air intake system configured to draw intake air into the engine;
and in the first condition, indicating the positive crankcase valve
is stuck open responsive to an increase in pressure in the
crankcase ventilation tube above a predetermined pressure change
threshold as indicated via the pressure sensor.
3. The method of claim 1, further comprising: indicating an
air/fuel ratio in the intake manifold of the engine via an intake
air oxygen sensor; and in the second condition, indicating the
positive crankcase valve is stuck closed responsive to the
indicated air/fuel ratio less than a predetermined air/fuel ratio
threshold.
4. The method of claim 3, wherein the first condition further
comprises indicating air/fuel ratio in the intake manifold via the
intake air oxygen sensor during spinning the engine unfueled in
reverse; and wherein the second condition is commenced responsive
to an indication of a lean air/fuel ratio in the intake manifold as
indicated by the intake air oxygen sensor.
5. The method of claim 1, further comprising: sleeping a vehicle
controller responsive to a key-off event; and wherein both the
first condition and the second condition are carried out responsive
to the controller being woken up after a predetermined time period
after the key-off event.
6. The method of claim 1, further comprising: controlling an intake
air flow to the engine via a throttle positioned in the intake
manifold; and in the first condition, controlling the throttle to a
position more open than a closed position, and in the second
condition, controlling the throttle to a fully open position.
7. The method of claim 1, further comprising: controlling fuel
injection to one or more cylinders of the engine via one or more
fuel injectors; providing spark to one or more of the engine
cylinders via one or more spark plugs; wherein the first condition
includes spinning the engine unfueled in reverse without fuel
injection and without spark to any of the engine cylinders; and
wherein the second condition includes spinning the engine fueled in
the forward direction by providing fuel injection to one or more
cylinders, but not providing spark to the one or more cylinders
receiving fuel injection so that fuel injected to the one or more
engine cylinders is not combusted.
8. The method of claim 7, wherein fuel injected into the one or
more engine cylinders that is not combusted is drawn into the
crankcase.
9. The method of claim 1, further comprising: indicating a vehicle
occupancy state via seat load cells; and wherein both the first
condition and the second condition are conducted responsive to an
indication of an absence of vehicle occupancy.
10. A system for a hybrid vehicle, comprising: an engine including
an engine intake manifold, an engine exhaust manifold, a crankcase,
and a compressor supplying compressed air to the intake manifold;
an electric motor coupled to the engine; a crankcase ventilation
tube connecting the crankcase to a fresh air intake passage
upstream of the compressor; a pressure sensor configured to
indicate pressure in the crankcase ventilation tube; a positive
crankcase ventilation line connecting the crankcase to the intake
manifold; a positive crankcase valve positioned in the positive
crankcase ventilation line; an intake air oxygen sensor positioned
in the intake manifold; and a controller storing instructions in
non-transitory memory that, when executed, cause the controller to:
responsive to a predetermined time duration elapsing since a
key-off event, spin the engine in a reverse direction via the
electric motor and indicate whether the positive crankcase valve is
stuck open based on a pressure level indicated via the pressure
sensor configured to indicate pressure in the crankcase ventilation
tube; and responsive to an indication that the positive crankcase
valve is not stuck open: spin the engine in the forward direction
via the electric motor and indicate whether the positive crankcase
valve is stuck closed based on an air/fuel ratio in the intake
manifold as indicated via the intake air oxygen sensor positioned
in the intake manifold.
11. The system of claim 10, wherein the controller further stores
instructions in non-transitory memory, that when executed, cause
the controller to: indicate an air/fuel ratio in the intake
manifold via the intake air oxygen sensor positioned in the intake
manifold while the engine is being spun in the reverse direction;
and wherein the engine is spun in the forward direction further
responsive to an indication of a lean air/fuel ratio in the intake
manifold while the engine is being spun in the reverse
direction.
12. The system of claim 10, wherein the controller further stores
instructions in non-transitory memory, that when executed, cause
the controller to: indicate that the positive crankcase valve is
stuck open while the engine is being spun in the reverse direction
responsive to pressure in the crankcase ventilation tube rising
above a predetermined pressure change threshold as indicated via
the pressure sensor.
13. The system of claim 10, wherein the controller further stores
instructions in non-transitory memory, that when executed, cause
the controller to: indicate that the positive crankcase valve is
stuck closed while the engine is being spun in the forward
direction responsive to an air/fuel ratio in the intake manifold as
indicated via the intake air oxygen sensor being below a
predetermined air/fuel ratio threshold.
14. The system of claim 10, further comprising: a plurality of fuel
injectors configured to deliver fuel to a plurality of engine
cylinders; a plurality of spark plugs configured to provide spark
to the plurality of engine cylinders; and wherein the controller
further stores instructions in non-transitory memory, that when
executed, cause the controller to: spin the engine in the reverse
direction via the electric motor without delivering fuel to any of
the plurality of engine cylinders, and without providing spark to
any of the plurality of engine cylinders; and spin the engine in
the forward direction via the electric motor while delivering fuel
to one or more of the plurality of engine cylinders, but without
providing spark to any of the plurality of engine cylinders, such
that a portion of fuel injected into the one or more engine
cylinders that is not combusted is drawn into the crankcase.
15. The system of claim 10, further comprising: a throttle coupled
to the intake manifold; and wherein the controller further stores
instructions in non-transitory memory, that when executed, cause
the controller to: control the throttle to a position more open
than a fully closed position while the engine is being spun in the
reverse direction, and control the throttle to a fully open
position while the engine is being spun in the forward
direction.
16. The system of claim 10, further comprising: a plurality of seat
load cells; and wherein the controller further stores instructions
in non-transitory memory, that when executed, cause the controller
to: prevent the engine from being spun in the reverse direction or
the forward direction to determine with the positive crankcase
valve is stuck open or stuck closed, responsive to an indication
that the vehicle is occupied, as indicated via the plurality of
seat load cells.
17. A method comprising: controlling a fluid flow from a crankcase
of an engine to an intake manifold of the engine via a positive
crankcase ventilation valve positioned in a positive crankcase
line; monitoring a pressure in a crankcase ventilation tube
connecting the crankcase to an air intake system via a pressure
sensor positioned in the crankcase ventilation tube; indicating an
air/fuel ratio in the intake manifold via an intake air oxygen
sensor; providing fuel and spark to a plurality of engine cylinders
via a plurality of fuel injectors and a plurality of spark plugs;
and responsive to conditions being met for conducting a positive
crankcase valve diagnostic procedure: spinning the engine unfueled
and without spark in a reverse direction and indicating the
positive crankcase valve is stuck open responsive to pressure in
the crankcase ventilation tube coupling the crankcase to the air
intake system being greater than a predetermined pressure
threshold; and responsive to an indication that the positive
crankcase valve is not stuck closed and further responsive to an
indication of a lean air/fuel ratio in the intake manifold:
spinning the engine fueled but without providing spark in a forward
direction and indicating the positive crankcase valve is stuck
closed responsive to an air/fuel ratio in the intake manifold below
a predetermined air/fuel ratio threshold while spinning the engine
unfueled in the forward direction.
18. The method of claim 17, wherein conditions being met for the
positive crankcase valve diagnostic procedure include a time since
a key-off event greater than a predetermined time duration, and a
threshold duration of time elapsing since a previously conducted
positive crankcase valve diagnostic procedure; wherein a vehicle
controller is put into a sleep mode responsive to the key-off
event; and wherein the vehicle controller is woken up from the
sleep mode responsive to the predetermined time duration elapsing
after the key-off event.
19. The method of claim 17, wherein positive pressure with respect
to atmospheric pressure is routed from the intake manifold, through
the positive crankcase line, through the crankcase, and through the
crankcase ventilation tube while spinning the engine unfueled in
the reverse direction under conditions wherein the positive
crankcase valve is stuck open; and wherein fluid flow is routed
from the crankcase, through the positive crankcase line, and to the
intake manifold while spinning the engine fueled in the forward
direction responsive to the positive crankcase valve not being
stuck closed.
20. The method of claim 17, further comprising: controlling an
intake air flow to the engine via a throttle upstream of the intake
manifold; and controlling the throttle to a position greater than a
fully closed position while spinning the engine in reverse; and
controlling the throttle to a fully open position while spinning
the engine in the forward direction.
Description
FIELD
[0001] The present description relates generally to methods and
systems for controlling a vehicle engine to diagnose whether a
positive crankcase ventilation valve is functioning as desired.
BACKGROUND/SUMMARY
[0002] Engines may include crankcase ventilation systems to vent
gases out of the crankcase and into an engine intake manifold to
provide continual evacuation of gases from inside the crankcase in
order to reduce degradation of various engine components in the
crankcase. The crankcase ventilation system may include a positive
crankcase ventilation valve (PCV valve) for enabling one-way flow
of crankcase gases from inside the crankcase to the intake
manifold.
[0003] Crankcase ventilation systems may be intermittently
diagnosed for PCV valve degradation. One example approach for PCV
valve diagnostics is shown by Satou in US 2009/0211545. Therein,
PCV valve degradation is determined based on air changes (e.g.,
changes to a throttle position) and fuel changes (e.g., fuel
injection adjustments) required to maintain an idle speed as an
opening of the PCV valve is adjusted. The opening of the PCV valve
is, in turn, selected based on an air/fuel ratio of blow-by
gas.
[0004] However, the inventors herein have recognized potential
issues with such approaches. As one example, the blow-by based
diagnostics approach may have significant noise issue due to
various engine loads. These include, for example, engine friction,
barometric pressure, AC compressor load, alternator load, etc.
Consequently, computation intensive noise reduction algorithms may
be required.
[0005] In one approach, to at least partially address these issues,
a method for an engine crankcase ventilation system is provided.
The method comprises controlling a fluid flow from a crankcase of
an engine to an intake manifold of the engine via a positive
crankcase ventilation valve, and in a first condition, indicating
whether the positive crankcase valve is stuck open responsive to
spinning the engine unfueled in a reverse direction, and in a
second condition, indicating whether the positive crankcase valve
is stuck closed responsive to spinning the engine fueled in a
forward direction.
[0006] As one example, the method may further comprise indicating
pressure in a crankcase ventilation tube via a pressure sensor, the
crankcase ventilation tube fluidically coupling the crankcase to an
air intake system configured to draw intake air into the engine. In
the first condition, the method may include indicating the positive
crankcase valve is stuck open responsive to an increase in pressure
in the crankcase ventilation tube above a predetermined pressure
change threshold as indicated via the pressure sensor.
[0007] In one example, the method may further comprise indicating
an air/fuel ratio in the intake manifold of the engine via an
intake air oxygen sensor, and in the second condition, indicating
the positive crankcase valve is stuck closed responsive to the
indicated air/fuel ratio less than a predetermined air/fuel ratio
threshold. In this way, a positive crankcase valve may be diagnosed
as to whether the positive crankcase valve is either stuck open or
stuck closed. By periodically diagnosing the positive crankcase
valve, engine complications due to a stuck open or closed positive
crankcase valve may be reduced, or avoided.
[0008] 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.
[0009] It should be understood that the summary above is provided
to introduce in simplified form a selection of concepts that are
further described in the detailed description. It is not meant to
identify key or essential features of the claimed subject matter,
the scope of which is defined uniquely by the claims that follow
the detailed description. Furthermore, the claimed subject matter
is not limited to implementations that solve any disadvantages
noted above or in any part of this disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 shows a schematic description of an engine including
an engine positive crankcase ventilation system (PCV).
[0011] FIG. 2 schematically shows an example vehicle propulsion
system.
[0012] FIG. 3A illustrates a position of a PCV valve during idle
speed, high intake manifold vacuum conditions.
[0013] FIG. 3B illustrates a position of a PCV valve during high
speed, low intake manifold vacuum conditions.
[0014] FIG. 3C illustrates a position of a PCV valve during
conditions of positive intake manifold pressure conditions.
[0015] FIG. 4 shows a schematic description of an engine including
an engine PCV system, including indications of fluid flow
responsive to running the engine in a forward, or a reverse
direction.
[0016] FIG. 5A-5B show a schematic depiction of an electronic
circuit configured to reverse the spin orientation of an electric
motor.
[0017] FIG. 6 shows a high level flowchart for an example method
for diagnosing functionality of a PCV valve.
[0018] FIG. 7 shows a timeline for an example PCV diagnostic test
procedure.
DETAILED DESCRIPTION
[0019] The following description relates to systems and methods for
diagnosing whether a positive crankcase valve (PCV) is functioning
as desired, or if the positive crankcase valve is stuck in a closed
configuration, or an open configuration. Such a diagnostic may be
performed on a vehicle system configured with a positive crankcase
ventilation system, such as the vehicle system depicted in FIG. 1.
Conducting the diagnostic procedure on the PCV valve may include
first spinning an engine in a reverse direction, via an electric
motor configured to spin the engine in a reverse mode of operation,
and then spinning the engine in a forward direction via the
electric motor configured to spin the engine in a forward mode of
operation. Accordingly, the vehicle system may include an electric
motor, such as the vehicle system depicted at FIG. 2.
[0020] The PCV valve may occupy several different conformations,
depending on a pressure level in an intake manifold of the engine,
as illustrated in FIG. 3. To diagnose whether the PCV valve is
stuck open, the engine may be spun in the reverse direction,
without fueling and spark. In such a condition, if the PCV valve is
stuck open, then positive pressure may be routed along a first
flowpath, indicated at FIG. 4, and may be monitored via a crankcase
pressure sensor. To diagnose whether the PCV valve is stuck closed,
the engine may be spun with fuel to one or more engine cylinders
provided, but without spark provided to the one or more engine
cylinders. In such a condition, if the PCV valve is not stuck
closed, the fuel vapor may be routed to the intake manifold, along
a second flowpath, indicated at FIG. 4. Spinning the engine in the
forward and reverse direction via an electric motor may be
accomplished via an electronic circuit configured to reverse
direction of an electric motor, illustrated at FIGS. 5A-5B. An
example method for conducting the PCV valve diagnostic test
procedure is illustrated at FIG. 6. An example timeline for
conducting the PCV valve diagnostic, according to the method of
FIG. 6, is illustrated at FIG. 7.
[0021] 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 (not shown). An energy conversion device, such as
a generator (not shown), 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.
[0022] 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. 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.
[0023] 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.
[0024] 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.
[0025] A 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. 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. The
intake and exhaust valve systems are discussed in further detail
herein and with reference to FIG. 2. 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.
[0026] In some examples, an intake air oxygen sensor 43 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. As will be discussed in greater detail below, during conducting
a PCV valve 78 test diagnostic procedure, residual fuel vapors may
be captured and stored by AIS HC trap, such that fuel vapors are
not routed to atmosphere. Furthermore, the intake air oxygen sensor
may be used as a readout of the PCV valve test diagnostic to
determine whether the PCV valve 78 is functioning as desired, as
will be discussed in greater detail below.
[0027] 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 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.
[0028] 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.
[0029] 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). Any of the
above-mentioned pressure sensors may be absolute pressure sensor or
gauge sensors.
[0030] 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. Additionally or alternatively, PCV line 76 may
include a one-way valve (that is, a passive valve that tends to
seal when flow is in the opposite direction) to prevent airflow
from the intake manifold into the crankcase via PCV line 76 during
boost conditions. In one embodiment, the PCV valve may actively or
passively vary its flow restriction in response to the pressure
drop across it (or flow rate through it). It will be appreciated
that, as used herein, PCV flow refers to the flow of gases through
PCV line 76 from the crankcase to the intake manifold. Similarly,
as used herein, PCV backflow refers to the flow of gases through
PCV line 76 from the intake manifold to the crankcase. PCV backflow
may occur when intake manifold pressure is higher than crankcase
pressure (e.g., during boosted engine operation). In some examples,
PCV system 16 may be equipped with a check valve for preventing PCV
backflow. It will be appreciated that while the depicted example
shows PCV valve 78 as a passive valve, this is not meant to be
limiting, and in alternate embodiments, PCV valve 78 may be an
electronically controlled valve (e.g., a powertrain control module
(PCM) controlled valve) wherein a controller may command a signal
to change a position of the valve from an open position (or a
position of high flow) to a closed position (or a position of low
flow), or vice versa, or any position there-between.
[0031] The gases in crankcase 28 may consist of un-burned fuel,
un-combusted air, and fully or partially combusted gases. Further,
lubricant mist 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.
[0032] Engine system 8 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.
[0033] 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 canister 90,
via conduit 93, before being purged to engine intake manifold
44.
[0034] Fuel vapor canister 90 may be comprised 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, as well as diurnal vapors. 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 92. A loading state of vapor canister
90 may be indicated by a hydrocarbon sensor 120. While a single
canister 90 is shown, it will be appreciated that fuel system 18
may include any number of canisters. In one example, canister purge
valve 92 may be a solenoid valve wherein opening or closing of the
valve is performed via actuation of a canister purge solenoid.
[0035] Canister 90 may include a buffer (or buffer region), each of
the canister and the buffer comprising the adsorbent. The volume of
the buffer may be smaller than (e.g., a fraction of) the volume of
canister 90. The 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 86 for routing gases out of the
canister 90 to the atmosphere when storing, or trapping, fuel
vapors from fuel tank 20. Vent 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 purge valve 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 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 and while the engine is not running) so that
air, stripped of fuel vapor after having passed through the
canister, can be pushed out to the atmosphere. Likewise, during
purging operations (for example, during canister regeneration and
while the engine is running), the vent valve may be opened to allow
a flow of fresh air to strip the fuel vapors stored in the
canister. 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 may be coupled in vent 86 between canister vent valve 87 and
atmosphere.
[0037] 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 fuel tank isolation valve 85 may
be optionally included in conduit 93 such that fuel tank 20 is
coupled to canister 90 via the valve. During regular engine
operation, isolation valve 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, isolation valve 85 may be temporarily opened,
e.g., for a duration, to direct fuel vapors from the fuel tank 20
to canister 90. By opening the valve during purging conditions when
the fuel tank pressure is higher than a threshold (e.g., above a
mechanical pressure limit of the fuel tank above which the fuel
tank and other fuel system components may incur mechanical damage),
the refueling vapors may be released into the canister and the fuel
tank pressure may be maintained below pressure limits. While the
depicted example shows isolation valve 85 positioned along conduit
93, in alternate embodiments, the isolation valve may be mounted on
fuel tank 20. The fuel system may be considered to be sealed when
isolation valve 85 is closed. In embodiments where the fuel system
does not include isolation valve 85, the fuel system may be
considered sealed when purge valve 92 and canister vent valve 87
are both closed.
[0038] 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 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 isolation valve 85. In some
embodiments, a pressure sensor may additionally be coupled between
the canister 90 and the canister vent valve 87, such as pressure
sensor 98, for example. In still further embodiments, a first
pressure sensor may be positioned upstream of the isolation valve
(between the isolation valve and the canister) while a second
pressure sensor is positioned downstream of the isolation valve
(between the isolation valve and the fuel tank), to provide an
estimate of a pressure difference across the valve. In some
examples, a vehicle control system may infer and indicate a fuel
system having undesired evaporative emissions based on changes in a
fuel tank pressure during a diagnostic routine. When a pressure
sensor is included upstream of isolation valve 85, such as canister
pressure sensor 98, an evaporative emissions system having
undesired evaporative emissions may be indicated based on changes
in canister pressure during a diagnostic routine while isolation
valve 85 is maintained closed.
[0039] 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 canister 90. 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/or the quantity of fuel
vapor desorbed during a purging operation. The canister temperature
may thus be used to infer the canister load, while changes in
canister temperature may be used to determine the capacity and/or
integrity of the fuel vapor canister.
[0040] 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 canister purge valve 92, coupled between the fuel
vapor canister and the engine intake. The quantity and rate of
vapors released by the canister purge valve may be determined by
the duty cycle of an associated canister purge valve solenoid (not
shown). As such, the duty cycle of the canister purge valve
solenoid may be determined by the vehicle's powertrain control
module (PCM), such as controller 12, responsive to engine operating
conditions, including, for example, engine speed-load conditions,
an air-fuel ratio, a canister load, etc. By commanding the canister
purge valve to be closed, the controller may seal the fuel vapor
recovery system from the engine intake. An optional canister check
valve (not shown) may be included in purge line 91 to prevent
intake manifold pressure from flowing gases in the opposite
direction of the purge flow. As such, the check valve may be
necessary if the canister purge valve control is not accurately
timed or the canister purge valve itself can be forced open by a
high intake manifold pressure.
[0041] 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 isolation valve 85 and canister vent valve 87 while
closing canister purge valve (CPV) 92 to direct refueling vapors
into canister 90 while preventing fuel vapors from being directed
into the intake manifold. 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 isolation valve 85 and canister vent valve 87, while
maintaining canister purge valve 92 closed, to depressurize the
fuel tank before allowing enabling fuel to be added therein. As
such, isolation valve 85 may be kept open during the refueling
operation to allow refueling vapors to be stored in the canister.
After refueling is completed, the isolation valve may be
closed.
[0042] As yet another example, 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 isolation valve 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, the 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.
[0043] 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, 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, and PCV valve 78, CPV 92, FTIV 85, 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.
[0044] 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 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. 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. Following the applying of vacuum
to the fuel 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, a fuel
system may be diagnosed for 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). Tests performed while the engine is not running
may include sealing the fuel system following engine shut-off and
monitoring a change in fuel tank pressure. This type of test is
referred to herein as an engine-off natural vacuum test (EONV). In
sealing the fuel system following engine shut-off, a vacuum will
develop in the fuel tank 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. Following a
vehicle-off event, as heat continues to be rejected from the engine
into the fuel tank, the fuel tank pressure will initially rise.
During conditions of relatively high ambient temperature, a
pressure build above a threshold may be considered a passing
test.
[0045] Further, controller 12 may be configured to intermittently
perform detection routines on the crankcase ventilation system.
This may include monitoring an output of crankcase vent line
pressure sensor 77 when pre-determined conditions are met. For
example, during engine cranking, intake manifold vacuum may be low.
As such, the PCV valve may be open, causing a threshold flow of air
through the crankcase and back into the intake manifold. As the
engine speed increases following cranking, the manifold airflow
increases. This may decrease the airflow through the crankcase vent
line. In a V-type engine, this sequence of events causes a
characteristic dip in the crankcase vent line pressure. However, if
the crankcase vent line is disconnected at the crankcase side
(e.g., second side 102), the characteristic dip may not be
observed, and degradation of the crankcase vent line may be
indicated.
[0046] FIG. 2 illustrates an example vehicle propulsion system 200.
It may be understood that vehicle propulsion system 200 may
comprise the same vehicle propulsion system as hybrid vehicle
system 6 depicted at FIG. 1. Vehicle propulsion system 200 includes
a fuel burning engine 210 and a motor 220. It may be understood
that engine 210 may be the same as engine 10 depicted above at FIG.
1. As a non-limiting example, engine 210 comprises an internal
combustion engine and motor 220 comprises an electric motor. Motor
220 may be configured to utilize or consume a different energy
source than engine 210. For example, engine 210 may consume a
liquid fuel (e.g., gasoline) to produce an engine output while
motor 220 may consume electrical energy to produce a motor output.
As such, a vehicle with propulsion system 200 may be referred to as
a hybrid electric vehicle (HEV).
[0047] Vehicle propulsion system 200 may utilize a variety of
different operational modes depending on operating conditions
encountered by the vehicle propulsion system. Some of these modes
may enable engine 210 to be maintained in an off state (i.e., set
to a deactivated state) where combustion of fuel at the engine is
discontinued. For example, under select operating conditions, motor
220 may propel the vehicle via drive wheel 230 as indicated by
arrow 222 while engine 210 is deactivated.
[0048] During other operating conditions, engine 210 may be set to
a deactivated state (as described above) while motor 220 may be
operated to charge energy storage device 250. For example, motor
220 may receive wheel torque from drive wheel 230 as indicated by
arrow 222 where the motor may convert the kinetic energy of the
vehicle to electrical energy for storage at energy storage device
250 as indicated by arrow 224. This operation may be referred to as
regenerative braking of the vehicle. Thus, motor 220 can provide a
generator function in some examples. However, in other examples,
generator 260 may instead receive wheel torque from drive wheel
230, where the generator may convert the kinetic energy of the
vehicle to electrical energy for storage at energy storage device
250 as indicated by arrow 262.
[0049] During still other operating conditions, engine 210 may be
operated by combusting fuel received from fuel system 240 as
indicated by arrow 242. It may be understood that fuel system 240
may comprise the same fuel system as fuel system 18 depicted above
at FIG. 1. For example, engine 210 may be operated to propel the
vehicle via drive wheel 230 as indicated by arrow 212 while motor
220 is deactivated. During other operating conditions, both engine
210 and motor 220 may each be operated to propel the vehicle via
drive wheel 230 as indicated by arrows 212 and 222, respectively. A
configuration where both the engine and the motor may selectively
propel the vehicle may be referred to as a parallel type vehicle
propulsion system. Note that in some examples, motor 220 may propel
the vehicle via a first set of drive wheels and engine 210 may
propel the vehicle via a second set of drive wheels.
[0050] In other examples, vehicle propulsion system 200 may be
configured as a series type vehicle propulsion system, whereby the
engine does not directly propel the drive wheels. Rather, engine
210 may be operated to power motor 220, which may in turn propel
the vehicle via drive wheel 230 as indicated by arrow 222. For
example, during select operating conditions, engine 210 may drive
generator 260 as indicated by arrow 216, which may in turn supply
electrical energy to one or more of motor 220 as indicated by arrow
214 or energy storage device 250 as indicated by arrow 262. As
another example, engine 210 may be operated to drive motor 220
which may in turn provide a generator function to convert the
engine output to electrical energy, where the electrical energy may
be stored at energy storage device 250 for later use by the
motor.
[0051] Fuel system 240 may include one or more fuel storage tanks
244 for storing fuel on-board the vehicle. It may be understood
that fuel storage tanks 244 may comprise the same fuel storage tank
as fuel tank 20 depicted at FIG. 1. For example, fuel tank 244 may
store one or more liquid fuels, including but not limited to:
gasoline, diesel, and alcohol fuels. In some examples, the fuel may
be stored on-board the vehicle as a blend of two or more different
fuels. For example, fuel tank 244 may be configured to store a
blend of gasoline and ethanol (e.g., E10, E85, etc.) or a blend of
gasoline and methanol (e.g., M10, M85, etc.), whereby these fuels
or fuel blends may be delivered to engine 210 as indicated by arrow
242. Still other suitable fuels or fuel blends may be supplied to
engine 210, where they may be combusted at the engine to produce an
engine output. The engine output may be utilized to propel the
vehicle as indicated by arrow 212 or to recharge energy storage
device 250 via motor 220 or generator 260.
[0052] In some examples, energy storage device 250 may be
configured to store electrical energy that may be supplied to other
electrical loads residing on-board the vehicle (other than the
motor), including cabin heating and air conditioning, engine
starting, headlights, cabin audio and video systems, etc. As a
non-limiting example, energy storage device 150 may include one or
more batteries and/or capacitors.
[0053] Control system 290 may communicate with one or more of
engine 210, motor 220, fuel system 240, energy storage device 250,
and generator 260. It may be understood that control system 290 may
comprise the same control system as controller 12, depicted above
at FIG. 1. Control system 290 may receive sensory feedback
information from one or more of engine 210, motor 220, fuel system
240, energy storage device 250, and generator 260. Further, control
system 290 may send control signals to one or more of engine 210,
motor 220, fuel system 240, energy storage device 250, and
generator 260 responsive to this sensory feedback. Control system
290 may receive an indication of an operator requested output of
the vehicle propulsion system from a vehicle operator 202. For
example, control system 290 may receive sensory feedback from pedal
position sensor 294 which communicates with pedal 292. Pedal 292
may refer schematically to a brake pedal and/or an accelerator
pedal. It may be understood that pedal 292 may be comprise the same
pedal as pedal 132 depicted above at FIG. 1. It may be further
understood that pedal position sensor 294 may comprise the same
pedal position sensor as pedal position sensor 134 depicted above
at FIG. 1.
[0054] Energy storage device 250 may periodically receive
electrical energy from a power source 280 residing external to the
vehicle (e.g., not part of the vehicle) as indicated by arrow 284.
As a non-limiting example, vehicle propulsion system 200 may be
configured as a plug-in hybrid electric vehicle (HEV), whereby
electrical energy may be supplied to energy storage device 250 from
power source 280 via an electrical energy transmission cable 282.
During a recharging operation of energy storage device 250 from
power source 280, electrical transmission cable 282 may
electrically couple energy storage device 250 and power source 280.
While the vehicle propulsion system is operated to propel the
vehicle, electrical transmission cable 282 may disconnected between
power source 280 and energy storage device 250. Control system 290
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).
[0055] In other examples, electrical transmission cable 282 may be
omitted, where electrical energy may be received wirelessly at
energy storage device 250 from power source 280. For example,
energy storage device 250 may receive electrical energy from power
source 280 via one or more of electromagnetic induction, radio
waves, and electromagnetic resonance. As such, it should be
appreciated that any suitable approach may be used for recharging
energy storage device 250 from a power source that does not
comprise part of the vehicle. In this way, motor 220 may propel the
vehicle by utilizing an energy source other than the fuel utilized
by engine 210.
[0056] Fuel system 240 may periodically receive fuel from a fuel
source residing external to the vehicle. As a non-limiting example,
vehicle propulsion system 200 may be refueled by receiving fuel via
a fuel dispensing device 270 as indicated by arrow 272. In some
examples, fuel tank 244 may be configured to store the fuel
received from fuel dispensing device 270 until it is supplied to
engine 210 for combustion. In some examples, control system 290 may
receive an indication of the level of fuel stored at fuel tank 244
via a fuel level sensor. The level of fuel stored at fuel tank 244
(e.g., as identified by the fuel level sensor) may be communicated
to the vehicle operator, for example, via a fuel gauge or
indication in a vehicle instrument panel 296.
[0057] The vehicle propulsion system 200 may also include an
ambient temperature/humidity sensor 298, and sensors dedicated to
indicating the occupancy-state of the vehicle, for example seat
load cells 207, door sensing technology 208, and onboard cameras
209. Vehicle propulsion system 200 may further include a roll
stability control sensor, such as a lateral and/or longitudinal
and/or yaw rate sensor(s) 299. The vehicle instrument panel 296 may
include indicator light(s) and/or a text-based display in which
messages are displayed to an operator. The vehicle instrument panel
296 may also include various input portions for receiving an
operator input, such as buttons, touch screens, voice
input/recognition, etc. For example, the vehicle instrument panel
296 may include a refueling button 297 which may be manually
actuated or pressed by a vehicle operator to initiate refueling.
For example, as described in more detail below, in response to the
vehicle operator actuating refueling button 297, a fuel tank in the
vehicle may be depressurized so that refueling may be
performed.
[0058] Control system 290 may be communicatively coupled to other
vehicles or infrastructures using appropriate communications
technology, as is known in the art. For example, control system 290
may be coupled to other vehicles or infrastructures via a wireless
network 231, which may comprise Wi-Fi, Bluetooth, a type of
cellular service, a wireless data transfer protocol, and so on.
Control system 290 may broadcast (and receive) information
regarding vehicle data, vehicle diagnostics, traffic conditions,
vehicle location information, vehicle operating procedures, etc.,
via vehicle-to-vehicle (V2V), vehicle-to-infrastructure-to-vehicle
(V2I2V), and/or vehicle-to-infrastructure (V2I) technology. The
communication and the information exchanged between vehicles can be
either direct between vehicles, or can be multi-hop. In some
examples, longer range communications (e.g. WiMax) may be used in
place of, or in conjunction with, V2V, or V2I2V, to extend the
coverage area by a few miles. In still other examples, vehicle
control system 290 may be communicatively coupled to other vehicles
or infrastructures via a wireless network 231 and the internet
(e.g. cloud), as is commonly known in the art. Vehicle system 200
may also include an on-board navigation system 232 (for example,
a
[0059] Global Positioning System) that an operator of the vehicle
may interact with. The navigation system 232 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. As discussed above, control system 290 may
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,
etc.
[0060] Turning to FIGS. 3A-3C, example illustrations of various
conformations of a PCV valve during various engine operating
conditions, is shown. More specifically, FIG. 3A illustrates a PCV
valve 300 conformation during idle speed, high intake manifold
vacuum conditions. FIG. 3B illustrates a conformation of PCV valve
300 during high speed, low intake manifold conditions. FIG. 3C
illustrates a conformation of PCV valve 300 during conditions of
positive pressure with respect to atmospheric pressure in the
intake manifold. It may be understood that PCV valve 300 depicted
at FIGS. 3A-3C may comprise the same PCV valve as PCV valve 78
depicted above at FIG. 1.
[0061] Turning to FIG. 3A, PCV valve 300 may include a PCV valve
housing 305, a plunger 310, and a spring 311. Furthermore, PCV
valve 300 may include a first pintle 312, and a second pintle 313.
Responsive to conditions of idle speed and high intake manifold
vacuum, the high intake manifold vacuum may draw the plunger 310
toward the intake manifold, resulting in the first pintle 312
seating against a first valve seat 314. As such, under high intake
manifold vacuum conditions, PCV valve 300 adopts a low flow
conformation. In other words, fluid flow from the crankcase may be
prevented as a result of the first pintle 312 seating against the
first valve seat 314.
[0062] Turning to FIG. 3B, PCV valve 300 is illustrated under
conditions of high engine speed, and low intake manifold vacuum.
Responsive to conditions of high engine speed, and low intake
manifold vacuum, spring 311 may push first pintle 312 away from
first valve seat 314, thus allowing more fluid flow. Furthermore,
second pintle 313 may not contact second valve seat 315, and as
such, a high engine speed, low intake manifold vacuum condition may
represent a condition where fluid flow through PCV valve 300 is the
least restricted.
[0063] Turning to FIG. 3C, PCV valve 300 is illustrated under
conditions of positive intake manifold pressure. Under such
conditions, PCV valve 300 may close. More specifically, positive
pressure in the intake manifold may result in second pintle 313
seating against second valve seat 315, thus preventing fluid flow
from the intake manifold to the crankcase.
[0064] As discussed above, the PCV valve may occupy different
configurations as a function of intake manifold pressure. As such,
by actively manipulating pressure in the intake manifold, the PCV
may be diagnosed as to whether the PCV valve is stuck open, or
stuck closed, as will be discussed in greater detail below.
Specifically, a stuck open or closed PCV valve may result in
driveability issues, which may include hesitation, surges, etc. For
example, a stuck open PCV valve may result in surges at engine
idle, the result of vapors being drawn from the crankcase to the
intake manifold, as the air/fuel ratio is very sensitive to vapor
concentrations at engine idle conditions. However, there are other
engine malfunctions that may result in engine surges, hesitations,
etc., and as such, indications of engine surge, hesitation, etc.,
may not effectively be utilized to diagnose PCV valve
functionality. Thus, a diagnostic to accurately indicate PCV valve
functionality, is desired.
[0065] Turning to FIG. 4, such a diagnostic may be conducted by
actively manipulating pressure in a vehicle intake manifold, such
that it may be inferred as to whether the PCV valve is functioning
as desired. FIG. 4 depicts the same illustration of hybrid vehicle
6 depicted at FIG. 1, but with indications of fluid flow during
conditions where a PCV valve diagnostic procedure is being
conducted.
[0066] Specifically, after a predetermined time duration after a
key off event, the vehicle controller may be awakened to conduct a
PCV valve diagnostic. First, the engine may be spun unfueled and
without spark in reverse, which may result in a positive pressure
build in the intake manifold. Positive pressure may develop in the
intake manifold as a result of the engine running in reverse, due
to the combination of the engine running in reverse and the
restrictive nature of the air filter (e.g. 54). As such, positive
pressure may build in the PCV line (e.g. 76). If the PCV is stuck
in an open conformation, positive pressure may travel along first
flowpath, represented by solid arrows 401. More specifically,
positive pressure may travel from the intake manifold (e.g. 44),
through the PCV line, through the crankcase (e.g. 28), and through
the crankcase ventilation tube (e.g. 74), and may thus reach the
crankcase pressure sensor (CKCP) (e.g. 77). Accordingly, if, during
spinning the engine in reverse, positive pressure is indicated via
the CKCP sensor, then it may be indicated that the PCV is stuck in
an open conformation. However, if the PCV valve is functioning as
desired, then no pressure change may be expected as indicated via
the CKCP sensor, the result of the PCV valve closing responsive to
positive intake manifold pressure, as discussed above with regard
to FIG. 3C.
[0067] Furthermore, while monitoring the CKCP during spinning the
engine in reverse, the intake air oxygen sensor (e.g. 43) may
additionally be utilized to indicate when residual vapors present
in the intake manifold, cylinders, and exhaust, are purged, the
result of spinning the engine in reverse. For example, it may be
indicated that the residual vapors have been purged from the intake
manifold responsive to a lean condition (e.g. lean air/fuel ratio)
indicated by the intake air oxygen sensor. If, while spinning the
engine in reverse, no pressure change is indicated in the crankcase
ventilation tube (e.g. 74), it may be indicated that the PCV valve
is closed. However, there is the possibility that the PCV valve is
not functioning as desired, but rather is stuck closed.
[0068] Thus, responsive to the indication that residual vapors have
been purged from the intake manifold, and further responsive to an
indication that the PCV valve is not stuck open, the engine may be
spun in a forward direction. Furthermore the engine may be fueled,
but without spark. More specifically, one or more fuel injector(s)
(e.g. 45) may be activated during spinning the engine in the
forward direction. Still further, a throttle (e.g. 42) may be
commanded to an open position, to prevent intake manifold vacuum
from developing while spinning the engine in the forward direction.
As such, the PCV valve may be expected to occupy an open, high
flow, configuration, such as depicted above with regard to FIG. 3B.
By fueling the engine during spinning the engine in the forward
direction, injected fuel may be drawn into the crankcase (e.g. 28)
via piston wall crevices. For example, a sealing ability between
piston rings (not shown), and the cylinder walls may be compromised
when the engine is cold as compared to when the engine is hot. With
fuel vapors drawn into the crankcase, and with the engine being
spun in the forward direction, fuel vapors may travel along a
second flowpath, indicated by dashed arrows 402. Accordingly, if
the PCV valve is stuck closed, then the vapors may not reach the
intake air oxygen sensor (e.g. 43). However, if the PCV valve is
functioning as desired (e.g. not stuck closed), then the crankcase
vapors may travel along the second flowpath, indicated by dashed
arrows 402, and may result in a rich air/fuel ratio as indicated
via the intake air oxygen sensor (e.g. 43). Such a method for
diagnosing either a stuck open or stuck close PCV valve will be
discussed in further detail below with regard to the method
depicted at FIG. 6.
[0069] As discussed above, the method for conducting the PCV valve
diagnostic relies on the ability to spin the engine in reverse
after predetermined duration after a key off event. FIGS. 5A and 5B
show an example circuit 500 that may be used for reversing a spin
orientation of an electric motor (e.g. 220), where the electric
motor may be utilized to spin the engine. Circuit 500 schematically
depicts an H-Bridge circuit that may be used to run a motor 510 in
a first (forward) direction and alternately in a second (reverse)
direction. Circuit 500 comprises a first (LO) side 520 and a second
(HI) side 530. Side 520 includes transistors 521 and 522, while
side 530 includes transistors 531 and 532. Circuit 500 further
includes a power source 540.
[0070] In FIG. 5A, transistors 521 and 532 are activated, while
transistors 522 and 531 are off. In this confirmation, the left
lead 551 of motor 510 is connected to power source 540, and the
right lead 552 of motor 510 is connected to ground. In this way,
motor 500 may run in a forward direction. When operating the engine
in a forward direction via the motor, the engine may be in a
cranking mode for initial combustion commencement.
[0071] In FIG. 5B, transistors 522 and 531 are activated, while
transistors 521 and 532 are off. In this confirmation, the right
lead 552 of motor 510 is connected to power source 540, and the
left lead 551 of motor 510 is connected to ground. In this way,
motor 500 may run in a reverse direction to drive the engine in a
reverse orientation.
[0072] Thus, a system for a hybrid vehicle may comprise an engine
including an engine intake manifold, and engine exhaust manifold, a
crankcase, and a compressor supplying compressed air to the intake
manifold. The system may further include an electric motor coupled
to the engine, a crankcase ventilation tube connecting the
crankcase to a fresh air intake passage upstream of the compressor,
and a pressure sensor configured to indicate pressure in the
crankcase ventilation tube. The system may further include a
positive crankcase ventilation line connecting the crankcase to the
intake manifold, a positive crankcase valve positioned in the
positive crankcase ventilation line, and an intake air oxygen
sensor positioned in the intake manifold. The system may further
include a controller storing instructions in non-transitory memory
that, when executed, cause the controller to, responsive to a
predetermined time duration elapsing since a key-off event, spin
the engine in a reverse direction via the electric motor and
indicate whether the positive crankcase valve is stuck open based
on a pressure level indicated via the pressure sensor configured to
indicate pressure in the crankcase ventilation tube. Responsive to
an indication that the positive crankcase valve is not stuck open,
the controller may spin the engine in the forward direction via the
electric motor and indicate whether the positive crankcase valve is
stuck closed based on an air/fuel ratio in the intake manifold as
indicated via the intake air oxygen sensor positioned in the intake
manifold.
[0073] In a first example of the system, the system may further
include wherein the controller further stores instructions in
non-transitory memory, that when executed, cause the controller to
indicate an air/fuel ratio in the intake manifold via the intake
air oxygen sensor positioned in the intake manifold while the
engine is being spun in the reverse direction, and wherein the
engine is spun in the forward direction further responsive to an
indication of a lean air/fuel ratio in the intake manifold while
the engine is being spun in the reverse direction.
[0074] A second example of the system optionally includes the first
example and further includes wherein the controller further stores
instructions in non-transitory memory, that when executed, cause
the controller to indicate that the positive crankcase valve is
stuck open while the engine is being spun in the reverse direction
responsive to pressure in the crankcase ventilation tube rising
above a predetermined pressure change threshold as indicated via
the pressure sensor.
[0075] A third example of the system optionally includes any one or
more or each of the first and second examples, and further includes
wherein the controller further stores instructions in
non-transitory memory, that when executed, cause the controller to
indicate that the positive crankcase valve is stuck closed while
the engine is being spun in the forward direction responsive to an
air/fuel ratio in the intake manifold as indicated via the intake
air oxygen sensor being below a predetermined air/fuel ratio
threshold.
[0076] A fourth example of the system optionally includes any one
or more or each of the first through third examples, and further
comprises a plurality of fuel injectors configured to deliver fuel
to a plurality of engine cylinders, a plurality of spark plugs
configured to provide spark to the plurality of engine cylinders.
The controller may further store instructions in non-transitory
memory, that when executed, case the controller to spin the engine
in the reverse direction via the electric motor without delivering
fuel to any of the plurality of engine cylinders, and without
providing spark to any of the plurality of engine cylinders; and
spin the engine in the forward direction via the electric motor
while delivering fuel to one or more of the plurality of engine
cylinders, but without providing spark to any of the plurality of
engine cylinders, such that a portion of fuel injected into the one
or more engine cylinders that is not combusted is drawn into the
crankcase.
[0077] A fifth example of the system optionally includes any one or
more or each of the first through fourth examples, and further
comprises a throttle coupled to the intake manifold, and wherein
the controller further stores instructions in non-transitory
memory, that when executed, cause the controller to control the
throttle to a position more open than a fully closed position while
the engine is being spun in the reverse direction, and control the
throttle to a fully open position while the engine is being spun in
the forward direction.
[0078] A sixth example of the system optionally includes any one or
more or each of the first through fifth examples, and further
comprises a plurality of seat load cells; and wherein the
controller further stores instructions in non-transitory memory,
that when executed, cause the controller to prevent the engine from
being spun in the reverse direction or the forward direction to
determine with the positive crankcase valve is stuck open or stuck
closed, responsive to an indication that the vehicle is occupied,
as indicated via the plurality of seat load cells.
[0079] Turning now to FIG. 6, an example method for conducting a
PCV valve diagnostic procedure is shown. More specifically, method
600 may be used to diagnose whether the PCV valve is stuck open, or
stuck closed, by conducting the diagnostic after a predetermined
time duration after a key-off event.
[0080] Method 600 will be described with reference to the systems
described herein and shown in FIGS. 1-5B, though it should be
understood that similar methods may be applied to other systems
without departing from the scope of this disclosure. Method 600 may
be carried out by a controller, such as controller 12 in FIG. 1,
and may be stored at the controller as executable instructions in
non-transitory memory. Instructions for carrying out method 600 and
the rest of the methods included herein may be executed by the
controller based on instructions stored on a memory of the
controller and in conjunction with signals received from sensors of
the engine system, such as the sensors described above with
reference to FIG. 1, FIG. 2, and FIG. 4. The controller may
transform operating states of the engine system via actuators, such
as electric motor (e.g. 220), throttle (e.g. 42), etc., according
to the method below.
[0081] Method 600 begins at 605 and may include evaluating current
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, 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. Continuing at 610, method 600 may include indicating
whether conditions are met for conducting a positive crankcase
ventilation (PCV) valve diagnostic. Conditions being met for a PCV
valve diagnostic may include a time duration since a key-off event
greater than a predetermined time duration. For example, the
predetermined time duration may comprise an amount of time where it
may be expected that engine oil in the crankcase (e.g. 28) has
cooled to a predetermined temperature. The predetermined time
duration may in some examples comprise less than one hour, greater
than one hour but less than three hours, or greater than three
hours. However, such examples are meant to be illustrative, and are
not meant to be limiting. In some examples, conditions being met
for a PCV valve diagnostic may further include an indication that
the vehicle is not occupied. For example, such an indication may be
provided via seat load cells (e.g. 207) configured to indicate the
presence or absence of a vehicle operator and/or passengers in the
vehicle. Conditions being met for the PCV valve diagnostic
procedure may further include an indication that a predetermined
time period has elapsed since a previous PCV valve diagnostic
procedure.
[0082] If conditions are not indicated to be met for conducting the
PCV valve diagnostic procedure, method 600 may proceed to 615, and
may include maintaining current vehicle operating conditions. For
example, if the vehicle is operating via the engine, then engine
operation may be maintained. If the vehicle is in a key-off
condition, yet the predetermined time duration has not yet elapsed
in order to conduct the PCV valve diagnostic, then the vehicle
controller may be maintained in a sleep mode, for example.
[0083] Returning to 615, responsive to conditions being met for
conducting the PCV valve diagnostic procedure, method 600 may
proceed to 620, and may include waking the controller. Upon waking
the controller, method 600 may proceed to 625, and may include
spinning the engine in reverse. As discussed above, an electric
motor (e.g. 220), may be operated to spin the engine in reverse.
Accordingly, the controller may send a signal to the electric
motor, commanding the electric motor to spin the engine in the
reverse direction. More specifically, spinning the engine in
reverse may include the controller actuating the electric motor to
spin the engine in reverse. The controller may be further
configured to disable spark and fuel injection. The engine may be
spun unfueled at a predetermined speed, for example the engine may
be spun in reverse at a relatively low speed, but may be spun at a
higher speed if a larger pressure gradient is desired. When the
engine is spun in the reverse direction, a vacuum is generated in
the exhaust system, while a positive pressure with respect to
atmospheric pressure is generated in the intake manifold.
Furthermore, at 625, the controller may send a signal actuating the
throttle (e.g. 42) to an open configuration. In some examples the
degree to which the throttle is commanded open by the controller
may be a percentage of a maximum amount of throttle opening
possible (e.g. a position greater than, or more open, than a fully
closed position). In still other examples, the throttle may be
commanded open to a maximum, or fully open, amount (e.g. wide-open
throttle).
[0084] Accordingly, at 625, with the engine being spun in reverse,
and with the throttle at least partially opened, residual fuel
vapors in the engine, intake manifold, cylinders, etc., may be
routed past the compressor (e.g. 50), toward the air filter (e.g.
54). The air filter may act as a resistor to fluid flow, thus
resulting in a buildup of positive pressure with respect to
atmospheric pressure in the intake manifold. Furthermore, to
prevent the routing of fuel vapors to atmosphere during spinning
the engine in reverse, fuel vapors may be adsorbed via an AIS HC
trap (e.g. 47) positioned downstream of the air filter, but
upstream of the compressor (e.g. 50), and at a location where the
crankcase ventilation tube (e.g. 74) couples to the intake passage
(e.g. 13).
[0085] As positive pressure builds in the intake manifold while the
engine is spun in reverse, such positive pressure may be
communicated to the PCV valve (e.g. 78). As discussed above with
regard to FIG. 3C, responsive to positive pressure communicated to
the PCV valve, if the PCV valve is functioning as desired, then the
PCV valve may be expected to close. Accordingly, if the PCV valve
is functioning as desired, then pressure may be prevented from
traveling along the first flowpath, where the first flowpath is
indicated by solid arrows (e.g. 401) described above with respect
to FIG. 4. Thus, responsive to the PCV valve functioning as
desired, the CKCP sensor (e.g. 77) may not be expected to respond,
as positive pressure may be prevented from being communicated along
the first flowpath due to the closed PCV valve. However, in a
condition where the PCV valve is stuck in an open configuration,
similar to that depicted in FIG. 3B, then positive pressure may be
communicated along the first flowpath, from the intake manifold,
through the open PCV valve, through the crankcase (e.g. 28) and
crankcase ventilation tube (e.g. 74), wherein the CKCP sensor may
respond to the increased pressure.
[0086] Accordingly, proceeding to 630, it may be indicated as to
whether the CKCP sensor response is greater than a predetermined
CKCP pressure change threshold. Responsive to the CKCP sensor
sensing an increase in positive pressure with respect to
atmospheric pressure greater than the predetermined CKCP pressure
change threshold during spinning the engine in reverse, method 600
may proceed to 635. At 635, method 600 may include indicating the
PCV valve is stuck in an open configuration. Such an indication may
be stored at the controller, for example. For example, a flag may
be set at the controller, and a corresponding diagnostic trouble
code may be set. Furthermore, indicating the PCV valve is stuck in
an open configuration may include illuminating a malfunction
indicator light (MIL) on a vehicle dashboard, for example,
providing an indication to the vehicle operator of the need to
service the vehicle.
[0087] Proceeding to 640, method 600 may include taking mitigating
action responsive to the indication of the stuck open PCV valve. In
one example, boosted engine operation may be limited, or
discontinued during future drive cycles, until it is indicated that
actions have been taken to ensure the PCV valve is functioning as
desired. For example, if boosted engine operation were not limited,
or discontinued, then the stuck open PCV valve may result in
crankcase gasses and oil mist being blown into the inlet of the
compressor, which may lead to a rapid oil consumption risk.
Accordingly, such an adverse conditions may be reduced by limiting
or discontinuing boosted engine operation.
[0088] Proceeding to 645, method 600 may include returning the
engine system to default, key-off conditions. For example, the
motor may be commanded by the controller to stop spinning the
engine in reverse orientation. Furthermore the controller may send
a signal actuating the throttle to a default key-off configuration.
Method 600 may then end.
[0089] Returning to 630, if the CKCP sensor response during
spinning the engine in reverse is less than the predetermined CKCP
pressure change threshold, method 600 may proceed to 650. For
example, although the CKCP response at 630 was indicated to be less
than the predetermined CKCP pressure change threshold, thus
indicating that the PCV valve is not stuck in an open
configuration, it may be that the PCV valve is stuck in a closed
configuration. Accordingly, at 650, method 600 may include
indicating whether a lean condition (e.g. lean air/fuel ratio) is
indicated in the intake manifold. For example, while spinning the
engine in reverse, an air/fuel ratio in the intake manifold may be
monitored via an intake air oxygen sensor (e.g. 43) positioned in
the intake manifold. Initially, responsive to spinning the engine
in reverse, the intake air oxygen sensor may indicate a rich
air/fuel ratio, as residual fuel vapors in the intake, as well as
the engine cylinders and exhaust are routed in the direction of the
intake air oxygen sensor. However, over the course of spinning the
engine in reverse, as residual fuel vapors are routed towards the
air filter (e.g. 54) whereby the residual fuel vapors may be
adsorbed via the AIS HC trap (e.g. 47), the intake air oxygen
sensor may switch to indicating a lean condition.
[0090] Responsive to an indication of a lean air/fuel ratio in the
intake manifold, and under conditions wherein the CKCP response is
indicated to be less than the predetermined CKCP pressure change
threshold, method 600 may proceed to 655. At 655, method 600 may
include spinning the engine in the forward direction, and may
further include commanding the throttle to a fully open
configuration. For example, the controller may send a signal to the
electric motor (e.g. 220), actuating the electric motor to spin the
engine in the forward direction, instead of the reverse direction.
Furthermore, the controller may send a signal to the throttle
actuating the throttle to a fully open configuration. Commanding
the throttle to the fully open position may prevent substantial
intake manifold vacuum from developing responsive to spinning the
engine in the forward direction. By preventing the development of
significant intake manifold vacuum, the PCV valve may be prevented
from closing. For example, as discussed above with regard to FIG.
3A, responsive to intake manifold vacuum, the PCV valve may close.
However, because the PCV valve diagnostic is concerned with whether
the PCV valve is stuck closed, it is desired that the PCV valve
adopt a configuration wherein the PCV valve is in an open
configuration, such as that depicted above with regard to FIG. 3B.
As such, while spinning the engine in the forward direction with
the throttle commanded open, significant intake manifold vacuum may
be prevented, thus rendering the PCV valve in the open
configuration depicted in FIG. 3B, provided the PCV valve is
functioning as desired.
[0091] Proceeding to 660, method 600 may include activating fuel
injection to one or more engine cylinders, without providing spark
to the one or more engine cylinders. More specifically the
controller may send a signal to one or more fuel injector(s) (e.g.
45), actuating the one or more fuel injectors to supply fuel to the
one or more engine cylinders, while preventing the fuel from being
combusted by not providing spark to the one or more engine
cylinders.
[0092] By spinning the engine in the forward direction, while
providing fueling to one or more engine cylinders, the fuel
provided to the one or more engine cylinders may be drawn into the
crankcase via piston wall crevices as the pistons (e.g. 38) move up
and down within the cylinders. For example, because the PCV valve
diagnostic depicted herein is conducted after a predetermined time
duration since a key-off event, it may be understood that the
engine may be cold as compared to a condition where the engine has
been recently operating, and as such, a sealing ability between
piston rings and engine cylinders may be less when cold as compared
to hot. Thus, fuel may be drawn into the crankcase during spinning
the engine in the forward direction while injecting fuel into one
or more engine cylinders.
[0093] The injected fuel and vapors may thus travel from the
crankcase, through the PCV line (e.g. 76), past the PCV valve (e.g.
78), and to the intake manifold (e.g. 44) responsive to the PCV
valve functioning as desired. In other words, if the PCV valve is
functioning as desired, the PCV valve may be expected to adopt a
primarily open configuration, which may enable fuel vapors in the
crankcase to flow through the open PCV valve to the intake
manifold. However, if the PCV valve is not functioning as desired
(e.g. stuck closed), then the flow of fuel vapors from the
crankcase may be prevented.
[0094] Accordingly, proceeding to 665, method 600 may include
indicating whether a rich air/fuel ratio is indicated in the intake
manifold. As discussed above, a rich condition may be indicated via
the intake air oxygen sensor (e.g. 43) positioned in the intake
manifold. In some examples, indicating a rich condition may
comprise the intake air oxygen sensor indicating an air fuel ratio
less than a predetermined air/fuel ratio threshold. If a rich
air/fuel ratio in the intake manifold is not indicated, method 600
may proceed to 670, and may include indicating the PCV valve is
stuck in a closed configuration. Such a closed configuration may
comprise the PCV valve being stuck in a configuration such as that
depicted in FIG. 3A, or a configuration such as that depicted in
FIG. 3C.
[0095] Indicating the PCV valve is stuck closed at 670 may include
storing the result at the controller. For example, a flag may be
set at the controller, and a corresponding diagnostic trouble code
may be set. Furthermore, indicating the PCV valve is stuck in a
closed configuration may include illuminating a malfunction
indicator light (MIL) on a vehicle dashboard, for example,
providing an indication to the vehicle operator of the need to
service the vehicle.
[0096] Proceeding to 675, method 600 may include taking mitigating
action responsive to the indication of the stuck closed PCV valve.
In one example, engine speed may be limited responsive to the
indication of the stuck closed PCV valve. However, a stuck closed
PCV valve may result in engine sludge formation in the oiled
portions of the engine, and may further result in crankcase
pressures that may result in comprised engine operation due to
degraded gaskets and seals due to the elevated crankcase pressures.
Accordingly, appropriate mitigating action may include remedying
the stuck closed PCV valve by having the vehicle serviced, as
discussed above.
[0097] Proceeding to 645, method 600 may include returning the
engine system to default, key-off conditions. For example, the
motor may be commanded by the controller to stop spinning the
engine in forward orientation. Furthermore the controller may send
a signal actuating the throttle to a default key-off configuration.
Still further, the controller may send a signal actuating the one
or more fuel injectors to stop the injection of fuel to the one or
more engine cylinders. Method 600 may then end.
[0098] Returning to 665, responsive to a rich air/fuel ratio being
indicated during spinning the engine in the forward direction, with
the throttle commanded by the controller to a fully opened
position, and with fuel being provided to one or more engine
cylinders, method 600 may proceed to 680. At 680, method 600 may
include indicating the PCV valve is functioning as desired. More
specifically, because injected fuel that has been drawn into the
crankcase during spinning the engine in the forward direction is
indicated to have traveled through the PCV line, past the PCV
valve, and to the intake manifold, wherein the intake oxygen sensor
(e.g. 43) responded to the presence of fuel vapors, it may be
determined that the PCV valve is not stuck closed, but rather is
functioning as desired. If the PCV valve were not functioning as
desired, then the intake oxygen sensor would not have responded to
the presence of fuel vapors, as the stuck closed PCV valve would
have prevented the fuel vapors from traveling to the intake
manifold.
[0099] As the PCV valve is indicated to be functioning as desired,
such an indication may be stored at the controller. For example, it
may be indicated that the PCV valve diagnostic was conducted, and
that the PCV valve is functioning as desired. Furthermore, because
the PCV valve is indicated to be functioning as desired, no
mitigating action may be taken.
[0100] Accordingly, proceeding to 645, method 600 may include
returning the engine system to default, key-off conditions. For
example, the motor may be commanded by the controller to stop
spinning the engine in forward orientation. Furthermore the
controller may send a signal actuating the throttle to a default
key-off configuration. Still further, the controller may send a
signal actuating the one or more fuel injectors to stop the
injection of fuel to the one or more engine cylinders. Method 600
may then end.
[0101] Thus, in one example, a method comprises controlling a fluid
flow from a crankcase of an engine to an intake manifold of the
engine via a positive crankcase ventilation valve; and in a first
condition, indicating whether the positive crankcase valve is stuck
open responsive to spinning the engine unfueled in a reverse
direction; and in a second condition, indicating whether the
positive crankcase valve is stuck closed responsive to spinning the
engine fueled in a forward direction. In a first example of the
method, the method further comprises indicating pressure in a
crankcase ventilation tube via a pressure sensor, the crankcase
ventilation tube fluidically coupling the crankcase to an air
intake system configured to draw intake air into the engine; and in
the first condition, indicating the positive crankcase valve is
stuck open responsive to an increase in pressure in the crankcase
ventilation tube above a predetermined pressure change threshold as
indicated via the pressure sensor. A second example of the method
optionally includes the first example, and further comprises
indicating an air/fuel ratio in the intake manifold of the engine
via an intake air oxygen sensor; and in the second condition,
indicating the positive crankcase valve is stuck closed responsive
to the indicated air/fuel ratio less than a predetermined air/fuel
ratio threshold. A third example of the method optionally includes
any one or more or each of the first and second examples, and
further includes wherein the first condition further comprises
indicating air/fuel ratio in the intake manifold via the intake air
oxygen sensor during spinning the engine unfueled in reverse; and
wherein the second condition is commenced responsive to an
indication of a lean air/fuel ratio in the intake manifold as
indicated by the intake air oxygen sensor. A fourth example of the
method optionally includes any one or more or each of the first
through third examples, and wherein the first condition further
comprises sleeping a vehicle controller responsive to a key-off
event; and wherein both the first condition and the second
condition are carried out responsive to the controller being woken
up after a predetermined time period after the key-off event. A
fifth example of the method optionally includes any one or more or
each of the first through fourth examples and further comprises
controlling an intake air flow to the engine via a throttle
positioned in the intake manifold; and in the first condition,
controlling the throttle to a position more open than a closed
position, and in the second condition, controlling the throttle to
a fully open position. A sixth example of the method optionally
includes any one or more or each of the first through fifth
examples and further comprises controlling fuel injection to one or
more cylinders of the engine via one or more fuel injectors;
providing spark to one or more of the engine cylinders via one or
more spark plugs; wherein the first condition includes spinning the
engine unfueled in reverse without fuel injection and without spark
to any of the engine cylinders; and wherein the second condition
includes spinning the engine fueled in the forward direction by
providing fuel injection to one or more cylinders, but not
providing spark to the one or more cylinders receiving fuel
injection so that fuel injected to the one or more engine cylinders
is not combusted. A seventh example of the method optionally
includes any one or more or each of the first through sixth
examples, and further includes wherein fuel injected into the one
or more engine cylinders that is not combusted is drawn into the
crankcase. A ninth example of the method optionally includes any
one or more or each of the first through eighth examples and
further comprises indicating a vehicle occupancy state via seat
load cells; and wherein both the first condition and the second
condition are conducted responsive to an indication of an absence
of vehicle occupancy.
[0102] Another example of a method comprises controlling a fluid
flow from a crankcase of an engine to an intake manifold of the
engine via a positive crankcase ventilation valve positioned in a
positive crankcase line; monitoring a pressure in a crankcase
ventilation tube connecting the crankcase to an air intake system
via a pressure sensor positioned in the crankcase ventilation tube;
indicating an air/fuel ratio in the intake manifold via an intake
air oxygen sensor; and providing fuel and spark to a plurality of
engine cylinders via a plurality of fuel injectors and a plurality
of spark plugs. Responsive to conditions being met for conducting a
positive crankcase valve diagnostic procedure, the method may
include spinning the engine unfueled and without spark in a reverse
direction and indicating the positive crankcase valve is stuck open
responsive to pressure in the crankcase ventilation tube coupling
the crankcase to the air intake system being greater than a
predetermined pressure threshold. Responsive to an indication that
the positive crankcase valve is not stuck closed and further
responsive to an indication of a lean air/fuel ratio in the intake
manifold, the method may include spinning the engine fueled but
without providing spark in a forward direction and indicating the
positive crankcase valve is stuck closed responsive to an air/fuel
ratio in the intake manifold below a predetermined air/fuel ratio
threshold while spinning the engine unfueled in the forward
direction.
[0103] In a first example of the method, the method may further
include wherein conditions being met for the positive crankcase
valve diagnostic procedure include a time since a key-off event
greater than a predetermined time duration, and a threshold
duration of time elapsing since a previously conducted positive
crankcase valve diagnostic procedure; wherein a vehicle controller
is put into a sleep mode responsive to the key-off event; and
wherein the vehicle controller is woken up from the sleep mode
responsive to the predetermined time duration elapsing after the
key-off event. A second example of the method optionally includes
the first example and further includes wherein positive pressure
with respect to atmospheric pressure is routed from the intake
manifold, through the positive crankcase line, through the
crankcase, and through the crankcase ventilation tube while
spinning the engine unfueled in the reverse direction under
conditions wherein the positive crankcase valve is stuck open; and
wherein fluid flow is routed from the crankcase, through the
positive crankcase line, and to the intake manifold while spinning
the engine fueled in the forward direction responsive to the
positive crankcase valve not being stuck closed. A third example of
the method optionally includes any one or more or each of the first
and second examples, and further comprises controlling an intake
air flow to the engine via a throttle upstream of the intake
manifold; controlling the throttle to a position greater than a
fully closed position while spinning the engine in reverse; and
controlling the throttle to a fully open position while spinning
the engine in the forward direction.
[0104] Turning now to FIG. 7, an example timeline 700 is shown for
conducting a PCV valve diagnostic procedure according to the method
depicted herein and shown in FIG. 6, and as applied to the systems
described herein and with reference to FIGS. 1-5B. Timeline 700
includes plot 705, indicating whether conditions are met (yes), or
not (no), for conducting a PCV valve diagnostic procedure, over
time. Timeline 700 further includes plot 710, indicating an engine
status including whether an engine is spinning in the forward
(fwd), or reverse (rev) direction, over time. Timeline 700 further
includes plot 715, indicating a throttle position status, over
time. The throttle may be in a closed configuration, an open
configuration, or a position between open and closed. Timeline 700
further includes plot 720, indicating whether a controller is
asleep, or awake, over time. Timeline 700 further includes plot
725, indicating pressure in a crankcase ventilation tube via a
crankcase pressure (CKCP) sensor, over time. Pressure in the
crankcase ventilation tube as indicated via the CKCP sensor may be
at atmospheric pressure (atm), or positive (+) with respect to
atmospheric pressure. Line 726 represents a predetermined CKCP
pressure change threshold which, if reached may indicate a stuck
open PCV valve.
[0105] Timeline 700 further includes plot 730, indicating whether
an intake air oxygen sensor (IAO2) positioned downstream of a
throttle (e.g. 42) indicates a rich, or lean air/fuel ratio, over
time. Line 731 represents a threshold concentration of air/fuel
ratio, below which may indicate a stuck closed PCV valve. Timeline
700 further includes plot 735, indicating a fuel injection status
(on or off) of one or more fuel injectors, over time. Timeline 700
further includes plot 740, indicating whether the PCV valve is
stuck open (yes) or not (no), and plot 745, indicating whether the
PCV valve is stuck closed (yes) or not (no), over time.
[0106] At time t0, it may be understood that the vehicle is in a
key-off condition. However, conditions for conducting the PCV valve
test diagnostic are not yet indicated to be met, illustrated by
plot 705. As the vehicle is in a key-off condition, the engine is
off, indicated by plot 710. The throttle is in a substantially
closed conformation, indicated by plot 715, and the controller is
in a sleep mode of operation, indicated by plot 720. As the vehicle
is in a key-off condition, pressure in the crankcase ventilation
tube (e.g. 74) is near atmospheric pressure, as determined via the
CKCP sensor (e.g. 77), illustrated by plot 725. Furthermore, an
air/fuel ratio in the intake manifold is slightly lean, indicated
by plot 730. However, while both the pressure in the crankcase
ventilation tube, and the concentration of fuel vapors in the
intake manifold are indicated between time t0 and t1, it may be
understood that in fact, with the controller in a sleep mode of
operation, such information may not be indicated by either the CKCP
sensor, or the IAO2 sensor. Rather, the representation of pressure
via plot 725, and the representation of fuel vapor concentration
via plot 730 are indicated between time t0 and t1 for reference.
Responsive to a transition to an awake mode, both pressure in the
crankcase ventilation tube and fuel vapor concentration in the
intake manifold may be measurable via the CKCP sensor and IAO2
sensor, respectively.
[0107] Furthermore, at time t0, fuel injection to one or more
engine cylinders, via one or more fuel injectors (e.g. 45), is
indicated to be off, illustrated by plot 735. As the current PCV
valve diagnostic has not yet been conducted, the PCV valve is not
indicated to be stuck in an open conformation, illustrated by plot
740. Similarly, the PCV valve is not indicated to be stuck in a
closed conformation, illustrated by plot 745.
[0108] At time t1, conditions are indicated to be met for
conducting the PCV valve diagnostic procedure. As discussed above,
conditions being met for a PCV valve diagnostic may include a time
duration since a key-off event greater than a predetermined time
duration, an indication that the vehicle is not occupied, that a
predetermined time period has elapsed since a previous PCV valve
diagnostic procedure, etc.
[0109] As conditions are indicated to be met for conducting the PCV
valve diagnostic procedure at time t1, the controller is triggered
to an awake mode, thus enabling the controller to command, or
actuate, the throttle (e.g. 42) to a position between fully open
and fully closed, and further to command, or actuate, the engine to
spin in a reverse mode of operation. More specifically, the
controller may actuate an electric motor (e.g. 220) to spin the
engine in a reverse mode. With the engine commanded via the
controller to spin in a reverse direction, pressure in the
crankcase ventilation tube (e.g. 74) may be monitored via the CKCP
sensor (e.g. 77). As discussed above, if the CKCP sensor responds
during the period of time that the engine is being spun in reverse,
it may be indicative of a stuck open PCV valve. However, between
time t1 and t2, pressure in the crankcase ventilation tube as
monitored by the CKCP sensor remains below the predetermined CKCP
pressure change threshold represented by line 726. As such, it may
be indicated that the PCV valve is not stuck in an open
configuration. Accordingly, a determination that the PCV valve is
stuck open is not indicated between time t1 and t2, as illustrated
by plot 740.
[0110] Furthermore, between time t1 and t2, fuel vapor
concentration in the intake manifold (e.g. 44) rises (e.g. becomes
more rich), and then falls (e.g. becomes more lean), as indicated
by an intake air oxygen sensor (e.g. 43), positioned in the intake
manifold. More specifically, residual fuel vapors in the intake
manifold, engine cylinders, exhaust, etc., may result in the intake
air oxygen sensor indicating an increase in fuel vapor
concentration (e.g. rich air/fuel ratio) while the engine is
spinning in reverse. However, as the fuel vapors are routed towards
an intake air filter (e.g. 54), the concentration is indicated to
drop (e.g. the air/fuel ratio becomes more lean). As discussed
above, to prevent fuel vapors from being routed through the intake
air filter, to atmosphere, an air intake system hydrocarbon (AIS
HC) trap may be positioned just downstream of the air intake
filter, such that fuel vapors routed toward the air filter during
spinning the engine in reverse may be adsorbed via the AIS HC
trap.
[0111] At time t2, responsive to an indication that the PCV valve
is not stuck in an open configuration, and further responsive to an
indication that the air/fuel ratio is lean, the engine may be
commanded to spin in a forward mode of operation. More
specifically, an electric motor (e.g. 220) may be commanded, or
actuated, via the controller to spin the engine in the forward mode
of operation. Furthermore, the controller may send a signal to the
throttle (e.g. 42), actuating the throttle to a fully-open
position.
[0112] At time t3, with the engine spinning in the forward
direction, and with the throttle commanded to the fully-open
position, fuel injection to the engine cylinders may be commanded
via the controller. For example, the controller may send a signal
to one or more fuel injectors (e.g. 45), actuating the one or more
fuel injectors to commence injection of fuel into one or more
engine cylinders. However, spark may not be provided to the engine
cylinders, such that fuel is injected but no fuel is combusted
during the spinning of the engine in the forward direction. As
discussed above, with the engine spinning in the forward direction,
and with the throttle positioned in the fully-open configuration,
the PCV valve may be expected to adopt an open configuration, such
as the configuration illustrated in FIG. 3B. However, it may be
possible that the PCV valve is stuck in a closed configuration.
[0113] Between time t3 and t4, with fuel being injected to one or
more engine cylinders, and with the engine being spun in the
forward direction, fuel vapors may be drawn into the crankcase,
into the PCV line (e.g. 76), through the PCV valve, and to the
intake manifold. However, if the PCV valve is stuck closed, then
fuel vapors may not be routed through the PCV line, to the intake
manifold. Accordingly, by monitoring air/fuel ratio in the intake
manifold between time t3 and t4, it may be indicated as to whether
the PCV valve is functioning as desired, or if the PCV valve is
indicated to be stuck closed.
[0114] Accordingly, between time t3 and t4, the air/fuel ratio in
the intake manifold may be monitored via the intake air oxygen
sensor. In example timeline 700, the air/fuel ratio as monitored
via the intake air oxygen sensor is indicated to remain below an
air/fuel ratio threshold, represented by line 731. Thus, because
fuel vapors are not indicated to be traveling from the crankcase,
through the PCV line, and to the intake manifold, it may be
determined that the PCV valve is in a stuck closed configuration.
Accordingly, at time t4, the PCV valve is indicated to be stuck
closed, illustrated by plot 745. As discussed above, such a result
may be stored at the controller, and a malfunction indicator light
(MIL) may be illuminated on the vehicle dash to alert the vehicle
operator of the need to service the vehicle. In some examples,
vehicle speed may be limited responsive to the indication of the
stuck closed PCV valve, as discussed above.
[0115] At time t5, responsive to the indication that the PCV valve
is stuck closed, conditions for conducting the PCV valve test may
no longer be indicated to be met, as the test is complete. As such,
the engine may be commanded via the controller to an off status,
indicated by plot 710. Furthermore, the throttle may be returned to
a default key-off position, indicated by plot 715. With the PCV
valve diagnostic test complete at time t6, and with the engine
commanded to an off configuration and the throttle commanded to a
default configuration, the controller may be triggered to a sleep
mode, indicated by plot 720.
[0116] In this way, a PCV valve may be diagnosed as to whether the
PCV valve is in a stuck open, or stuck closed conformation, after a
key-off event, and under conditions where a vehicle operator or
other passengers may not be present in the vehicle to notice the
test being conducted. By diagnosing whether the PCV valve is stuck
open or closed, potential issues resulting from a degraded PCV
valve may be reduced or avoided, such as engine degradation due to
compromised gaskets, seals, etc., resulting from elevated crankcase
pressures in the case of a stuck closed PCV valve, or surges at
idle due to a stuck open PCV valve.
[0117] The technical effect is to recognize that a stuck open PCV
valve may be diagnosed by spinning an engine unfueled and without
spark in reverse via an electric motor, and that a stuck closed PCV
valve may be diagnosed by spinning the engine fueled but without
spark in the forward direction. More specifically, the technical
effect is to recognize that positive pressure in the intake
manifold during spinning the engine in reverse may result in a
crankcase pressure sensor positioned in a crankcase ventilation
tube responding to the positive pressure in a condition where the
PCV valve is stuck open. Furthermore, the technical effect is to
recognize that by spinning the engine fueled but without spark in
the forward direction, fuel vapors may be drawn into the crankcase
and routed to the intake manifold under conditions where the PCV
valve is functioning as desired, but not under conditions where the
PCV valve is stuck closed. As such, the system and methods depicted
herein enables a diagnosis of whether the PCV valve is stuck open,
or closed, during a key off condition.
[0118] 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.
[0119] 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.
[0120] 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.
* * * * *