U.S. patent application number 14/088886 was filed with the patent office on 2015-05-28 for methods and systems for a stop/start engine.
This patent application is currently assigned to Ford Global Technologies, LLC. The applicant listed for this patent is Ford Global Technologies, LLC. Invention is credited to Andrew Clement Dame, Alan Robert Dona, Peter Douglas Kuechler, Peter Mitchell Lyon.
Application Number | 20150148192 14/088886 |
Document ID | / |
Family ID | 53045690 |
Filed Date | 2015-05-28 |
United States Patent
Application |
20150148192 |
Kind Code |
A1 |
Lyon; Peter Mitchell ; et
al. |
May 28, 2015 |
METHODS AND SYSTEMS FOR A STOP/START ENGINE
Abstract
Systems and methods for improving operation of a vehicle are
presented. In one example, automatic engine stopping is inhibited
in response to a driver communicating a desire to not automatically
stop an engine. The driver communicates intentions to allow or
inhibit automatic engine stopping via a brake pedal.
Inventors: |
Lyon; Peter Mitchell;
(Birmingham, MI) ; Dame; Andrew Clement; (Saline,
MI) ; Kuechler; Peter Douglas; (Canton, MI) ;
Dona; Alan Robert; (Huntington Woods, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ford Global Technologies, LLC |
Dearborn |
MI |
US |
|
|
Assignee: |
Ford Global Technologies,
LLC
Dearborn
MI
|
Family ID: |
53045690 |
Appl. No.: |
14/088886 |
Filed: |
November 25, 2013 |
Current U.S.
Class: |
477/203 |
Current CPC
Class: |
Y02T 10/48 20130101;
F02N 11/0822 20130101; Y10T 477/87 20150115; B60W 30/18018
20130101; B60W 10/06 20130101; B60W 2540/12 20130101; Y02T 10/40
20130101; F02N 2200/102 20130101; B60W 10/184 20130101 |
Class at
Publication: |
477/203 |
International
Class: |
B60W 10/184 20060101
B60W010/184; B60W 10/06 20060101 B60W010/06 |
Claims
1. A method for operating an engine, comprising: inhibiting
automatic engine stopping in response to a secondary application of
vehicle brakes following an initial application of vehicle brakes,
the secondary application of vehicle brakes occurring after the
initial application of vehicle brakes and without vehicle brakes
being fully released.
2. The method of claim 1, where inhibiting automatic engine
stopping causes the engine to continue combusting air and fuel
mixtures during conditions where automatic engine stopping is
otherwise allowed.
3. The method of claim 1, where the secondary application of
vehicle brakes following the initial application of vehicle brakes
includes changing a brake pedal position by more than a threshold
amount.
4. The method of claim 3, further comprising not inhibiting
automatic engine stopping when changing the brake pedal position by
less than the threshold amount.
5. The method of claim 1, further comprising inhibiting automatic
engine stopping in response to a plurality of brake applications of
vehicle brakes while the vehicle brakes are activated.
6. The method of claim 5, where the plurality of brake applications
comprises depressing a brake pedal a plurality of times.
7. The method of claim 1, where vehicle brakes are fully released
when the brake pedal is fully released.
8. A method for operating an engine, comprising: inhibiting
automatic engine stopping in response to a secondary application of
vehicle brakes following an initial application of vehicle brakes,
the secondary application of vehicle brakes occurring after the
initial application of vehicle brakes and without vehicle brakes
being fully released; and automatically restarting the engine in
response to the secondary application of vehicle brakes.
9. The method of claim 8, where the engine is restarted without
engaging a starter while the engine is rotating.
10. The method of claim 8, where the engine is automatically
restarted from an engine stop.
11. The method of claim 8, further comprising inhibiting automatic
engine stopping until automatic engine stopping conditions are not
present.
12. The method of claim 8, further comprising inhibiting automatic
engine stopping until a vehicle in which the engine operates moves
and stops after inhibiting automatic engine stopping.
13. The method of claim 8, where the secondary application of
vehicle brakes includes moving a brake pedal is greater than a
threshold distance.
14. The method of claim 8, where the secondary application of
vehicle brakes includes increasing brake fluid pressure greater
than a threshold brake pressure amount.
15. A vehicle system, comprising: an engine; a brake pedal; and a
controller including non-transitory instructions executable to
inhibit automatic stopping of the engine in response to a driver
applying the brake pedal a plurality of times without fully
releasing the brake pedal once the brake pedal is applied during a
vehicle stop.
16. The vehicle system of claim 15, including additional
instructions to automatically restart the engine when the engine is
stopped in response to the driver applying the brake pedal a
plurality of times.
17. The vehicle system of claim 15, further comprising additional
instructions to reactivate an engine that is rotating without being
supplied fuel in response to the driver applying the brake pedal a
plurality of times.
18. The vehicle system of claim 17, where applying the brake pedal
a plurality of times includes increasing brake fluid pressure by
more than a predetermined pressure.
19. The vehicle system of claim 15, where applying the brake pedal
a plurality of times includes moving the brake pedal more than a
predetermined distance.
20. The vehicle system of claim 19, where the predetermined
distance varies with a distance the brake pedal is applied a first
time since the brake pedal is fully released.
Description
FIELD
[0001] The present description relates to a system and methods for
improving vehicle drivability and driver controls. The systems and
methods may be particularly useful for engines that may be
frequently stopped and restarted to conserve fuel.
BACKGROUND AND SUMMARY
[0002] An engine of a vehicle may be automatically stopped without
a driver providing input to a device that has a sole purpose or
function of stopping engine rotation so that fuel may be conserved
(e.g., engine stop/start devices). Fuel may be conserved when the
engine is automatically stopped since the engine does not consume
fuel when it is not operating. However, if the engine is restarted
immediately after it is stopped, the fuel reduction may be less
than desired. Further, the driver may be annoyed that the engine
has stopped and is being restarted so quickly after being stopped.
Thus, automatically stopping an engine may conserve fuel, but it
may also be less than desirable during some driving conditions.
Present implementation schemes for engine stop/start devices
provide a switch for a driver override that inhibits the automatic
engine stop feature. However, there may be conditions when the
driver wishes to override the engine stop functionality only once,
or desires to override the engine stop feature without looking away
from the vehicle's route to locate and active the switch.
[0003] The inventors herein have recognized the above-mentioned
disadvantages of automatic engine stopping and have developed a
method for operating an engine, comprising: inhibiting automatic
engine stopping in response to a secondary application or increased
application of vehicle brakes following an initial application of
vehicle brakes, the secondary application or increased application
of vehicle brakes occurring after the initial application of
vehicle brakes and without vehicle brakes being fully released.
[0004] By allowing a driver to communicate to an engine stop/start
controller via application of vehicle brakes, it may be possible to
reduce the possibility of aggravating the driver during conditions
where the driver may have more information than the vehicle engine
controller regarding whether or not conditions are desirable for
automatically stopping the engine. For example, a driver of a
vehicle may notice that traffic lights for opposing traffic are
about to change and give right of way to the driver. The driver may
apply vehicle brakes in a prescribed manner that allows the driver
to communicate with the automatic engine stop controller so that
automatic engine stopping is inhibited in response to the driver
applying vehicle brakes. As a result, the vehicle may accelerate in
a more timely manner when automatic engine stopping is inhibited,
thereby improving driver satisfaction.
[0005] The present description may provide several advantages. In
particular, the approach may improve driver satisfaction.
Additionally, the approach may save fuel when fuel consumption may
be increased by stopping and engine and restarting the engine
shortly thereafter. Further, the approach may provide the driver
improved vehicle control as compared to other systems where the
driver cannot communicate with the engine stop controller.
[0006] 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.
[0007] 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
[0008] The advantages described herein will be more fully
understood by reading an example of an embodiment, referred to
herein as the Detailed Description, when taken alone or with
reference to the drawings, where:
[0009] FIG. 1 is a schematic diagram of an engine;
[0010] FIG. 2 shows an example vehicle driveline;
[0011] FIG. 3 shows an example prophetic vehicle operating
sequence;
[0012] FIGS. 4 and 5 show an example brake pressure and brake
position threshold levels; and
[0013] FIG. 6 shows an example method for operating a stop/start
engine.
DETAILED DESCRIPTION
[0014] The present description is related to controlling operation
of an engine that may be automatically stopped and started in a
vehicle. The engine may be a sole source of torque for propelling
the vehicle. Alternatively, the vehicle may include an engine and a
motor that both supply torque to propel the vehicle. FIG. 1 shows
an example engine system. The engine may be part of a vehicle
driveline as is shown in FIG. 2. The engine may restart,
automatically stop, or be prevented from being automatically
stopped as shown in the engine operating sequence shown in FIG. 3.
Vehicle brake system conditions illustrated in FIGS. 4 and 5 may be
the basis for judging whether or not to automatically stop and/or
start an engine. The method of FIG. 6 may operate an engine and
driveline according to FIGS. 1 and 2 to provide the operating
sequence shown in FIG. 3.
[0015] Referring to FIG. 1, internal combustion engine 10,
comprising a plurality of cylinders, one cylinder of which is shown
in FIG. 1, is controlled by electronic engine controller 12. Engine
10 includes combustion chamber 30 and cylinder walls 32 with piston
36 positioned therein and connected to crankshaft 40. Flywheel 97
and ring gear 99 are coupled to crankshaft 40. Starter 96 includes
pinion shaft 98 and pinion gear 95. Pinion shaft 98 may selectively
advance pinion gear 95 to engage ring gear 99. Starter 96 may be
directly mounted to the front of the engine or the rear of the
engine. In some examples, starter 96 may selectively supply torque
to crankshaft 40 via a belt or chain. In one example, starter 96 is
in a base state when not engaged to the engine crankshaft.
Combustion chamber 30 is shown communicating with intake manifold
44 and exhaust manifold 48 via respective intake valve 52 and
exhaust valve 54. Each intake and exhaust valve may be operated by
an intake cam 51 and an exhaust cam 53. The position of intake cam
51 may be determined by intake cam sensor 55. The position of
exhaust cam 53 may be determined by exhaust cam sensor 57. Intake
cam 51 and exhaust cam 53 may be moved relative to crankshaft
40.
[0016] Fuel injector 66 is shown positioned to inject fuel directly
into cylinder 30, which is known to those skilled in the art as
direct injection. Alternatively, fuel may be injected to an intake
port, which is known to those skilled in the art as port injection.
Fuel injector 66 delivers liquid fuel in proportion to the pulse
width of signal from controller 12. Fuel is delivered to fuel
injector 66 by a fuel system (not shown) including a fuel tank,
fuel pump, and fuel rail (not shown). In addition, intake manifold
44 is shown communicating with optional electronic throttle 62
which adjusts a position of throttle plate 64 to control air flow
from air intake 42 to intake manifold 44. In one example, a low
pressure direct injection system may be used, where fuel pressure
can be raised to approximately 20-30 bar. Alternatively, a high
pressure, dual stage, fuel system may be used to generate higher
fuel pressures. In some examples, throttle 62 and throttle plate 64
may be positioned between intake valve 52 and intake manifold 44
such that throttle 62 is a port throttle.
[0017] Distributorless ignition system 88 provides an ignition
spark to combustion chamber 30 via spark plug 92 in response to
controller 12. Universal Exhaust Gas Oxygen (UEGO) sensor 126 is
shown coupled to exhaust manifold 48 upstream of catalytic
converter 70. Alternatively, a two-state exhaust gas oxygen sensor
may be substituted for UEGO sensor 126.
[0018] Converter 70 can include multiple catalyst bricks, in one
example. In another example, multiple emission control devices,
each with multiple bricks, can be used. Converter 70 can be a
three-way type catalyst in one example.
[0019] Controller 12 is shown in FIG. 1 as a conventional
microcomputer including: microprocessor unit 102, input/output
ports 104, read-only memory 106 (e.g., non-transitory memory),
random access memory 108, keep alive memory 110, and a conventional
data bus. Controller 12 is shown receiving various signals from
sensors coupled to engine 10, in addition to those signals
previously discussed, including: engine coolant temperature (ECT)
from temperature sensor 112 coupled to cooling sleeve 114; a
position sensor 134 coupled to an accelerator pedal 130 for sensing
force applied by driver 132; a measurement of engine manifold
pressure (MAP) from pressure sensor 122 coupled to intake manifold
44; an engine position sensor from a Hall effect sensor 118 sensing
crankshaft 40 position; a measurement of air mass entering the
engine from sensor 120; brake pedal position from brake pedal
position sensor 154 when driver 132 applies brake pedal 150; and a
measurement of throttle position from sensor 58. Barometric
pressure may also be sensed (sensor not shown) for processing by
controller 12. In a preferred aspect of the present description,
engine position sensor 118 produces a predetermined number of
equally spaced pulses every revolution of the crankshaft from which
engine speed (RPM) can be determined.
[0020] In some examples, the engine may be coupled to an electric
motor/battery system in a hybrid vehicle. Further, in some
examples, other engine configurations may be employed, for example
a diesel engine.
[0021] During operation, each cylinder within engine 10 typically
undergoes a four stroke cycle: the cycle includes the intake
stroke, compression stroke, expansion stroke, and exhaust stroke.
During the intake stroke, generally, the exhaust valve 54 closes
and intake valve 52 opens. Air is introduced into combustion
chamber 30 via intake manifold 44, and piston 36 moves to the
bottom of the cylinder so as to increase the volume within
combustion chamber 30. The position at which piston 36 is near the
bottom of the cylinder and at the end of its stroke (e.g. when
combustion chamber 30 is at its largest volume) is typically
referred to by those of skill in the art as bottom dead center
(BDC). During the compression stroke, intake valve 52 and exhaust
valve 54 are closed. Piston 36 moves toward the cylinder head so as
to compress the air within combustion chamber 30. The point at
which piston 36 is at the end of its stroke and closest to the
cylinder head (e.g. when combustion chamber 30 is at its smallest
volume) is typically referred to by those of skill in the art as
top dead center (TDC). In a process hereinafter referred to as
injection, fuel is introduced into the combustion chamber. In a
process hereinafter referred to as ignition, the injected fuel is
ignited by known ignition means such as spark plug 92, resulting in
combustion. During the expansion stroke, the expanding gases push
piston 36 back to BDC. Crankshaft 40 converts piston movement into
a rotational torque of the rotary shaft. Finally, during the
exhaust stroke, the exhaust valve 54 opens to release the combusted
air-fuel mixture to exhaust manifold 48 and the piston returns to
TDC. Note that the above is shown merely as an example, and that
intake and exhaust valve opening and/or closing timings may vary,
such as to provide positive or negative valve overlap, late intake
valve closing, or various other examples.
[0022] Referring now to FIG. 2, an example vehicle driveline 200 is
shown. Vehicle driveline 200 includes engine 10 as shown in greater
detail in FIG. 1. Engine 10 may include one or more torque
actuators 204. Torque actuator 204 may be an engine throttle,
variable camshaft, fuel injector, ignition system, or other device
that may affect engine torque. Engine torque may be increased or
decreased via operating the torque actuator.
[0023] Engine 10 provides torque to torque converter 206 via
crankshaft 40. Torque converter 306 hydraulically couples engine 10
to transmission input shaft 251. Automatic transmission 208
includes a forward clutch 212 and gear clutches 210. Mechanical
pump 214 supplies pressurized transmission fluid to torque
converter 206, gear clutches 210, and forward clutch 212.
[0024] Driveshaft 253 directs torque from transmission 208 to
vehicle wheels 291. Force may be supplied to vehicle wheels via
hydraulic or air brakes 290. Hydraulic brake pressure or air
pressure applies force to activate brakes 290 and may be observed
or measured via brake pressure sensor 234. Brakes 290 may be
applied while vehicle 290 is moving, is desired to be held in a
stopped state, and as holding or parking brakes. Additionally,
hydraulic brakes 290 may be applied when inclinometer 271 indicates
a road grade greater than a threshold road grade when vehicle 290
is stopped. Brake system pressure and vehicle incline information
may be input to controller 12.
[0025] Thus, the system of FIGS. 1 and 2 provides for a vehicle
system, comprising: an engine; a brake pedal; and a controller
including non-transitory instructions executable to inhibit
automatic stopping of the engine in response to a driver applying
the brake pedal a plurality of times without fully releasing the
brake pedal once the brake pedal is applied during a vehicle stop.
The vehicle system includes additional instructions to
automatically restart the engine when the engine is stopped in
response to the driver applying the brake pedal a plurality of
times. The vehicle system further comprises additional instructions
to reactivate an engine that is rotating without being supplied
fuel in response to the driver applying the brake pedal a plurality
of times. The vehicle system includes where applying the brake
pedal a plurality of times includes increasing brake fluid pressure
by more than a predetermined pressure. The vehicle system includes
where applying the brake pedal a plurality of times includes moving
the brake pedal more than a predetermined distance. The vehicle
system includes where the predetermined distance varies with a
distance the brake pedal is applied a first time since the brake
pedal is fully released.
[0026] Referring now to FIG. 3, an example prophetic engine
operating sequence according to the method of FIG. 6 is shown.
Vertical markers T0-T11 represent times of interest during the
sequence. Further, the sequence of FIG. 3 may be provided by the
system of FIGS. 1 and 2.
[0027] The first plot from the top of FIG. 3 is a plot of vehicle
speed versus time. The X axis represents time and time increases
from the left side of FIG. 3 to the right side of FIG. 3. The Y
axis represents vehicle speed and vehicle speed increases in the
direction of the Y axis.
[0028] The second plot from the top of FIG. 3 is a plot of brake
pedal position versus time. The X axis represents time and time
increases from the left side of FIG. 3 to the right side of FIG. 3.
The Y axis represents brake pedal position and the brake pedal is
applied further (e.g., commanding more braking force) in the
direction of the Y axis arrow.
[0029] The third plot from the top of FIG. 3 is a plot of brake
fluid pressure (e.g., hydraulic or air) versus time. The X axis
represents time and time increases from the left side of FIG. 3 to
the right side of FIG. 3. The Y axis represents brake fluid
pressure and brake fluid pressure increases in the direction of the
Y axis arrow.
[0030] The fourth plot from the top of FIG. 3 is a plot of engine
operating state versus time. The X axis represents time and time
increases from the left side of FIG. 3 to the right side of FIG. 3.
The Y axis represents engine operating state. An engine operating
state value of zero represents an engine that is commanded to stop
rotation. An engine operating state value of one represents an
engine that is commanded to rotate and combust an air-fuel
mixture.
[0031] The fifth plot from the top of FIG. 3 is a plot of an
automatic engine stop enable flag or indicator versus time. The X
axis represents time and time increases from the left side of FIG.
3 to the right side of FIG. 3. The Y axis represents a state of an
automatic engine stop enable flag or indicator and a value of one
indicates that the engine start/stop system is at operating
conditions where automatic engine stopping is desired. A value of
zero indicates that the engine stop/start system is operating at
conditions where automatic engine stopping is not desired. The
automatic engine stop enable flag may be set to a value of one when
the vehicle is stopped, the vehicle brake pedal is applied, and
when the engine is warm to conserve fuel. The automatic engine stop
enable flag may be set to a value of one when the vehicle is
traveling downhill or decelerating when the driver demand torque is
at a low level or during other selected operating conditions. In
one example, automatic engine stopping is allowed when the engine
is stopped rotating based on vehicle operating conditions without a
driver operating a switch or device that has a sole purpose of
starting/stopping the engine (e.g., an ignition switch).
[0032] The sixth plot from the top of FIG. 3 is a plot of
accelerator pedal position versus time. The X axis represents time
and time increases from the left side of FIG. 3 to the right side
of FIG. 3. The Y axis represents vehicle accelerator pedal position
and the accelerator pedal position increases and indicates an
increase in driver demand torque in the direction of the Y axis
arrow.
[0033] At time T0, the vehicle speed is at a middle level and the
brake pedal position indicates that the brake is not applied. The
brake pressure is at a lower level indicating that no pressure is
applied to the vehicle brakes. The engine is operating and rotating
and the vehicle is not presently at conditions for automatic engine
stopping as indicated by the automatic engine stop enable flag
being at a level of zero. The accelerator pedal is at a lower level
indicating a lower level driver demand torque.
[0034] At time T1, the brake pedal is applied and the brake pedal
position increases to indicate that the brake pedal is being
applied. The vehicle speed decreases and the brake pressure
increases in response to the brake pedal being applied. The engine
continues to operate and the automatic engine stop enable flag is
not asserted. Additionally, the accelerator pedal is released near
time T1 and the accelerator pedal position goes to zero in response
to the driver decelerating the vehicle.
[0035] At time T2, the driver applies the vehicle brake pedal to a
further extent for a second time without fully releasing the brake
pedal as indicated by the brake pedal position increasing. The
brake pressure also increases as the brake pedal position increases
and the vehicle decelerates at a higher rate. The engine continues
to operate and the automatic engine stop enable flag is not
activated. By increasing the brake pedal position after the brake
pedal has been initially applied, the automatic engine stopping may
be inhibited or stopped. Alternatively, or in addition, the
automatic engine stopping mode may be inhibited or stopped in
response to applying the brake pedal a plurality of times without
fully releasing the brake pedal. When automatic engine stopping is
deactivated, the engine may not be stopped during conditions where
the engine would otherwise be automatically stopped.
[0036] Additionally, in some examples, method 400 may deactivate
automatic engine stopping in response to brake fluid pressure or
brake line pressure instead of brake position. For example, if
brake pressure increases in response to an applied brake pedal, and
if brake pressure increases by a predetermined amount of pressure
over the brake pressure when the brake pedal is first applied,
automatic engine stopping may be inhibited.
[0037] At time T3, vehicle speed is zero, the brake pedal continues
to be applied, the brake pressure is at a higher level, and the
automatic engine stop enable flag is asserted to indicate that
conditions are present to automatically stop the engine. However,
the engine is not stopped as indicated by the engine operating
state remaining at a higher level to show that the engine is
operating. The engine is not stopped even though the automatic
engine stop enable flag is activated since the brake pedal or brake
pressure has increased by more than a threshold amount after an
initial brake application. In other words, application of the
vehicle brake and applying more than a threshold amount of pressure
to the brakes acts as a signal or condition to bypass or ignore the
automatic engine stop enable flag so that the engine is not
automatically stopped.
[0038] The driver may purposefully apply the vehicle brakes one or
more times without fully releasing the vehicle brakes to
communicate with the engine controller that the engine is not to be
automatically stopped at the present time. The driver may apply the
brakes twice or several more times when the driver knows that rapid
vehicle acceleration will soon be desired, or during other
conditions when the driver wishes to inhibit automatic engine
stopping. Consequently, the engine is not stopped at time T3 even
though the driver demand torque as indicated by the accelerator
pedal position is at a lower level and the vehicle is stopped.
[0039] At time T4, the driver releases the brake pedal in response
to driving conditions and brake pressure is reduced in response to
the released brake pedal. The engine continues to operate and the
automatic engine stop enable flag transitions to a low level to
indicate that the engine is not to be automatically stopped. The
accelerator pedal is applied shortly after the brake pedal is
released and the vehicle begins to accelerate. The engine may be
automatically stopped after the vehicle begins to accelerate.
Alternatively, the engine may be automatically stopped in response
to application of the accelerator pedal or other conditions that
may be the basis for clearing inhibiting of automatic engine
stopping.
[0040] Between time T4 and time T5, the vehicle accelerates in
response to the released brake pedal and accelerator pedal
application. Further, the automatic engine stop enable flag is not
asserted and the accelerator pedal is released by the driver near
time T5.
[0041] At time T5, the driver applies the brake pedal as indicated
by the brake pedal position increasing in response to the driver's
desired to stop the vehicle. The brake pressure increases in
response to the brake pedal being applied and the vehicle slows in
response to the vehicle brakes being applied via the brake pedal.
The automatic engine stop enable flag remains in a not asserted
state and the engine continues to operate as the vehicle
decelerates.
[0042] At time T6, the vehicle brake is applied to a further extent
for a second time. However, the vehicle brake is not applied to an
extent where the brake pedal position exceeds a threshold level
beyond the position the brake pedal assumed after initial brake
pedal application or to an extent that the brake pressure exceeds a
threshold level beyond the brake pressure assumed after initial
brake pedal application. Consequently, automatic engine stopping is
not inhibited. The automatic engine stop flag is not asserted and
the engine continues to operate as indicated by the engine
operating state.
[0043] At time T7, vehicle speed reaches zero speed in response to
the accelerator pedal being released and the vehicle brake being
applied. Shortly thereafter, the automatic engine stop enable flag
is asserted and the engine is stopped as indicated by the engine
operating state transitioning to a low level. The accelerator
remains not applied and the brake pressure holds the vehicle in a
stopped position.
[0044] At time T8, the driver releases the vehicle brake pedal in
response to vehicle operating conditions as is indicated by the
brake pedal position being reduced. The automatic engine stop
enable flag transitions to a lower level to indicated the engine is
no longer to be automatically stopped. The engine operating state
changes to a higher level in response to the automatic engine stop
flag transitioning to a lower level and the engine is started by
cranking the engine and supplying spark and fuel to the engine.
Shortly thereafter, the driver applies the accelerator pedal to
accelerate the vehicle. In this way, the automatically stopped
engine is restarted.
[0045] At time T9, the driver releases the accelerator and shortly
thereafter applies the vehicle brake pedal in response to vehicle
operating conditions. The brake pressure increases in response to
the increase in brake pedal position and the vehicle begins to
decelerate as indicated by the vehicle speed decreasing. The
automatic engine stop enable flag is not asserted and the engine
operating state is at a higher level indicating that the engine is
continuing to operate. The brake pedal position and brake pressure
remain at steady values shortly after the brake is applied.
[0046] Between time T9 and time T10, the vehicle stops in response
to the brake pedal being applied and the accelerator pedal not
being applied. The engine remains operating and rotating and the
automatic engine stop enable flag remains not asserted.
[0047] At time T10, the automatic engine stop enable flag
transitions to a higher level in response to automatic engine
stopping conditions being present. The engine operating state
transitions to a higher level to indicate that the engine is
commanded to stop rotating in response to the automatic engine stop
enable flag being asserted. Thus, the engine is automatically
stopped in response to operating conditions. Operating conditions
may include but are not limited to vehicle speed equal to zero,
time since vehicle stop greater than a threshold time, and vehicle
brake being applied.
[0048] At time T11, the driver applies the vehicle brake to a
greater extent to signal the engine controller that the driver
wishes the engine to start. The driver may depress the brake pedal
to a further extent to restart the engine based on conditions the
driver observes (e.g., traffic lights changing state), or the
driver's intent to start the engine for other purposes (e.g., start
the engine to keep the cabin heater operating at a higher level).
The engine is inhibited or prevented from stopping after the engine
is restarted until the vehicle accelerates or another condition
occurs.
[0049] In these ways, the engine may be automatically restarted and
stopped from being automatically stopped in response to a driver
applying a brake pedal. In this example, the driver applies the
brake pedal to move the brake pedal more than a threshold distance
or angle to inhibit automatic engine stopping or to restart the
engine. In other examples, the driver may apply the brake pedal a
predetermined number of times to inhibit the engine from
automatically stopping or to restart a stopped engine.
[0050] Referring now to FIG. 4, a plot of a first example of a way
to inhibit automatic engine stopping or to activate automatic
engine starting in response to brake pressure or force during a
braking event is shown. The plot of FIG. 4 includes an X axis that
represents time and time increases from the left to right side of
FIG. 4. The Y axis represents brake pressure or brake force. Brake
pressure may be measured via a pressure sensor or estimated. Line
401 represents brake pressure versus time for initial brake
application. Line 403 represents brake pressure versus time for a
first example second brake application that provides greater than a
threshold brake pressure and that is sufficient to inhibit
automatic engine stopping or to initiate starting of an
automatically stopped engine. Line 405 represents brake pressure
versus time for a second example second brake application that
provides less than a threshold brake pressure and that is not
sufficient to inhibit automatic engine stopping or to initiate
starting of an automatically stopped engine. Lines 405 and 403 may
be in a same braking event as line 401, but only one of line 405
and 403 may be present in the same braking event. Lines 405 and 403
are shown together to distinguish between different braking
conditions. Vertical lines at T20-T22 represent times of interest
during the sequence of FIG. 4.
[0051] At time T20, the brake pressure is at a value of zero
indicating that the brake pedal is not applied. The driver
increases brake pressure at time T21 via applying the vehicle brake
pedal. Brake pressure stabilizes at a constant level between time
T21 and time T22.
[0052] At time T22, the brake pressure in line 403 is shown
increasing a second time since time T20 during a second brake
application from the level of line 401. The second brake
application occurs without the brake being completely released
between the first brake application and the second brake
application. The brake pressure in line 405 is also shown
increasing a second time since time T20 during a second brake
application from the level of line 401. A pressure increase from
line 401 to line 403 is represented by the length of arrow 404. A
pressure increase from line 401 to line 405 is represented by the
length of arrow 402. The length of arrow 406 represents a minimum
pressure change from the brake pressure of line 401 that may be a
condition for inhibit automatic engine stopping or initiating
starting of an automatically stopped engine. Thus, arrow 406
represents a threshold pressure to be exceeded in order to inhibit
automatic engine stopping or to initiate starting of an
automatically stopped engine.
[0053] In this way, line 403 shows a brake pressure increase that
is greater than the brake pressure of line 405. Consequently, the
brake pressure of line 403 relative to the brake pressure of line
401 is sufficient to provide conditions to inhibit automatic engine
stopping or to initiate starting of an automatically stopped
engine. On the other hand, the brake pressure of line 405 relative
to the brake pressure of line 401 is insufficient to provide
conditions to inhibit automatic engine stopping or to initiate
starting of an automatically stopped engine. The threshold pressure
represented by arrow 406 may be adjusted for vehicle operating
conditions and based on initial applied brake pressure that is
present before a second brake application.
[0054] Referring now to FIG. 5, a plot of a first example of a way
to inhibit automatic engine stopping or to activate automatic
engine starting in response to brake pedal or actuator position is
shown. The plot of FIG. 5 includes an X axis that represents time
and time increases from the left to right side of FIG. 4. The Y
axis represents brake pedal position. Brake pedal position may be
measured via a pressure sensor or estimated. Line 501 represents
brake pedal position versus time for initial brake application.
Line 503 represents brake pedal position versus time for a first
example second brake application that provides greater than a
threshold brake position increase and that is sufficient to inhibit
automatic engine stopping or to initiate starting of an
automatically stopped engine. Line 505 represents brake pedal
position versus time for a second example second brake application
that provides less than a threshold brake position increase and
that is not sufficient to inhibit automatic engine stopping or to
initiate starting of an automatically stopped engine. Lines 505 and
503 may be in a same braking event as line 501, but only one of
line 505 and 503 may be present in the same braking event. Lines
505 and 503 are shown together to distinguish between different
conditions. Vertical lines at T30-T34 represent times of interest
during the sequence of FIG. 5.
[0055] At time T30, the brake position is at a value of zero
indicating that the brake pedal is not applied. The driver
increases brake position (e.g., applies the brake pedal) at time
T31 via applying the vehicle brake pedal. Brake pedal position
stabilizes at a constant level between time T31 and time T32.
[0056] At time T32, the brake pedal position shown in line 503
increases a second time since time T30 during a second brake
application from the level of line 501. The second brake
application occurs without the brake pedal being completely
released between the first brake application and the second brake
application. The brake position shown in line 505 is also shown
increasing a second time since time T30 during a second brake
application from the level of line 501. A brake pedal position
increase from line 501 to line 503 is represented by the length of
arrow 504. A brake pedal position increase from line 501 to line
505 is represented by the length of arrow 502. The length of arrow
506 represents a minimum brake pedal position change from the brake
position of line 501 that may be a condition for inhibit automatic
engine stopping or initiating starting of an automatically stopped
engine. Thus, arrow 506 represents a threshold brake pedal position
to be exceeded in order to inhibit automatic engine stopping or to
initiate starting of an automatically stopped engine.
[0057] In this way, line 503 shows a brake pedal position increase
that is greater than the brake pedal position increase of line 505.
Consequently, the brake pedal position increase of line 503
relative to the brake pedal position of line 501 is sufficient to
provide conditions to inhibit automatic engine stopping or to
initiate starting of an automatically stopped engine. On the other
hand, the brake pedal position increase of line 505 relative to the
brake pedal position increase of line 501 is insufficient to
provide conditions to inhibit automatic engine stopping or to
initiate starting of an automatically stopped engine. The threshold
brake pedal position increase represented by arrow 506 may be
adjusted for vehicle operating conditions and based on initial
applied brake pedal position that is present before a second brake
application.
[0058] FIG. 5 also shows a second application of the brake pedal
beginning at time T33 after the brake pedal is released. In
particular, at time T33, the brake pedal is applied and the brake
pedal position 509 begins to increase. The brake pedal position
stabilizes between time T33 and time T34.
[0059] At time T34, the brake pedal position shown in line 509
increases a second time since time T33 during a second brake
application from the level of line 509. The second brake
application after time T33 occurs without the brake pedal being
completely released between the first brake application and the
second brake application.
[0060] A brake pedal position increase from line 509 to line 513 is
represented by the length of arrow 514. A brake pedal position
increase from line 509 to line 511 is represented by the length of
arrow 512. Lines 511 and 513 represent different brake applications
after the brake application of line 509 in a same braking event.
Lines 511 and 513 are shown together to distinguish between
different braking conditions.
[0061] The length of arrow 514 represents a minimum brake pedal
position change from the brake position of line 509 that may be a
condition for inhibit automatic engine stopping or initiating
starting of an automatically stopped engine. Thus, arrow 514
represents a threshold brake pedal position to be exceeded in order
to inhibit automatic engine stopping or to initiate starting of an
automatically stopped engine.
[0062] It may be observed that the change in brake pedal position
at time T34 that enables inhibiting automatic engine stopping or
initiating starting of an automatically stopped engine requires a
shorter or smaller change in brake pedal position than the brake
pedal position change at time T32 that inhibits automatic engine
stopping or initiating starting of an automatically stopped engine.
Thus, different threshold changes in brake pedal position may
enable inhibiting automatic engine stopping or initiating starting
of an automatically stopped engine at different operating
conditions. One reason for allowing a smaller change in brake pedal
position to enable automatic engine stopping after a brake pedal
has been applied a distance is that the brake pedal force increases
as the brake pedal displacement increases. Further, much higher
force must be applied to the brake pedal for the brake pedal to
move after the brake pedal has been applied to a greater extent as
compared to when the brake pedal is applied to a lesser extent.
Therefore, in this example, a shorter or smaller change in brake
pedal position enables inhibiting automatic engine stopping when
the brake pedal has been initially applied to a greater extent. A
larger or greater change in brake pedal position enables inhibiting
automatic engine stopping when the brake pedal has been initially
applied to a lesser extent.
[0063] Referring now to FIG. 6, a method for operating a stop/start
engine is shown. The method of FIG. 6 may be incorporated in to the
system of FIGS. 1 and 2 as executable instructions stored in
non-transitory memory. The method of FIG. 6 may provide the
operating sequence shown in FIG. 3.
[0064] At 602, method 600 judges whether or not the vehicle brake
is applied. In one example, the vehicle brake may be determined to
be applied based on brake pedal position. In other examples, the
vehicle brake may be determined to be applied based on brake line
or brake fluid pressure. If method 600 judges that the vehicle
brakes are applied, method 600 proceeds to 604. Otherwise, method
600 proceeds to 622.
[0065] At 604, method 600 judges whether or not conditions for an
automatic engine stop are present. In one example, conditions for
an automatic engine stop are present when vehicle speed is less
than a threshold speed, the vehicle brakes are applied, and the
engine temperature is greater than a threshold temperature. In
other examples, conditions for automatic engine stop may be present
when vehicle brakes are applied and driver demand torque (e.g.,
torque demanded by the driver via the accelerator pedal) is less
than a threshold amount of torque. If method 600 judges that
conditions are present for an automatic engine stop, the answer is
yes and method 600 proceeds to 610. Otherwise, the answer is no and
method 600 proceeds to 606.
[0066] At 606, method 600 restarts the engine if the engine is
already stopped rotating. The engine may be restarted via engaging
the engine starter, rotating the engine, and supplying spark and
fuel to the engine. Method 600 proceeds to 622 after the engine is
restarted.
[0067] At 610, method 600 judges whether or not a secondary brake
application greater than a threshold is present. In one example, a
secondary brake application after a first brake application during
a same or single braking event of a vehicle deceleration may be
determined via monitoring brake pedal position. In other examples,
secondary brake application after a first brake application during
a vehicle deceleration may be determined via monitoring brake line
or brake fluid pressure. Thus, the vehicle driver may communicate
with the automatic engine stop/start controller via application of
a brake pedal or actuator.
[0068] In examples where a secondary brake application is
determined via brake pedal position, different brake position
change amounts for different initial brake positions may be the
basis for determining whether or not a secondary brake application
(e.g., where brakes are applied or brake pedal position is
increased a second time after brakes are initially applied without
the brakes being released) brake position change amount is greater
than a threshold amount. For example, as shown in FIG. 5,
inhibiting automatic engine stopping or restarting an automatically
stopped engine may be performed in response to a change in brake
pedal position after a brake pedal is applied to a greater extent
(e.g., time after time T34 in FIG. 5) in response to a smaller
change in brake pedal position as compared to a change in brake
pedal position after the brake pedal is applied to a lesser extent
(e.g., time between time T31 and time T33 in FIG. 5).
[0069] Similarly, in examples where a secondary brake application
is determined via brake pressure or brake force, different brake
pressure change amounts for different initial brake application
pressures may be the basis for determining whether or not a
secondary brake application (e.g., where brakes are applied or
brake pedal position is increased a second time after brakes are
initially applied without the brakes being released) brake pressure
or force change amount is greater than a threshold amount.
[0070] If method 600 judges that a secondary brake pedal position
or brake force change is greater than a threshold amount, the
answer is yes and method 600 proceeds to 614. Otherwise, the answer
is no and method 600 proceeds to 612.
[0071] At 612, method 600 judges whether or not there have been a
plurality of brake applications after the initial brake application
in a same or single braking event without the vehicle brakes being
released. For example, method 600 may judge whether the brake pedal
has been applied and partially released twice to indicate the
driver's intent to inhibit automatic engine stopping or to
automatically restart an automatically stopped engine. Similarly,
method 600 may judge whether or not the brake line or brake fluid
pressure has increased and subsequently decreased to a value
greater than zero a predetermined number of times to indicate the
driver's intent to inhibit automatic engine stopping or to
automatically restart an automatically stopped engine. If method
600 judges that a plurality of brake applications (e.g., increasing
brake force) have occurred while the vehicle brakes are activated,
the answer is yes and method 600 proceeds to 614. Otherwise, the
answer is no and method 600 returns to 604.
[0072] It should be noted that the engine may be automatically
stopped while portions of the method of FIG. 6 are executing. The
engine may be automatically stopped based on conditions such as
vehicle speed, brake pedal application, and absence of driver
demand torque.
[0073] At 614, method 600 judges whether or not the engine is
stopped or being stopped. The engine may determined to be stopped
when engine rotational speed is zero. The engine may be determined
to be being stopped if spark and/or fuel supplied to the engine is
deactivated while the engine continues to rotate. If method 600
determines that the engine is stopped or being stopped, the answer
is yes and method 600 proceeds to 620. Otherwise, the answer is no
and method 600 proceeds to 616.
[0074] At 616, method 600 inhibits or stops automatic engine
stopping until automatic engine stop conditions are cleared or not
present and subsequently are indicated and present. For example,
automatic engine stopping may not be allowed after the brake pedal
is applied a second time after an initial brake application and
until the vehicle moves and later reaches zero speed. In another
example, automatic engine stopping may not be allowed after a brake
pedal is applied three times without releasing the vehicle brake
until the vehicle brake is fully released and subsequently applied
three times without the brake pedal being released.
[0075] Inhibiting automatic engine stopping causes the engine to
continue to combust air-fuel mixtures even though conditions are
present for automatic engine stopping. Consequently, the engine
does not have to be restarted to accelerate the vehicle or to
provide power to vehicle accessories. Method 600 proceeds to 622
after automatic engine stopping is inhibited.
[0076] At 620, method 600 restarts or reactivates a rotating engine
and inhibits automatic engine stopping until automatic engine
stopping conditions are cleared or not present and are subsequently
present. For example, if engine speed is zero, the engine is
cranked and restarted by supplying spark and fuel to the engine.
The engine may not be automatically stopped until automatic engine
stopping conditions are present after automatic engine starting
conditions have been cleared. In another example, the engine may
inhibited from automatically stopping until the vehicle speed has
increased to a value greater than zero and returned to a value of
zero. In yet another example, spark and/or fuel may be supplied to
an engine that is rotating to reactivate the engine and combust
air-fuel mixtures in the engine. The reactivated engine may not be
automatically stopped until automatic engine stopping conditions
are not present and are subsequently present. In this way, a
deactivated decelerating engine may be restarted in response to a
driver applying a brake pedal. Method 600 proceeds to 622 after the
engine is restarted or reactivated.
[0077] At 622, method 600 supplies a limited amount of engine
torque in response to a driver demand torque while the vehicle
brakes are applied. For example, if the driver is applying vehicle
brakes and requesting 75 N-m of torque, method 600 may supply 30
N-m of torque. If the driver is not applying the vehicle brakes,
the engine output torque follows the driver demand torque. Engine
torque is adjusted via adjusting engine spark, air amount, and fuel
amount based on the driver demand torque and engine torque limits.
Method 600 proceeds to exit after engine torque is adjusted.
[0078] Thus, the method of FIG. 6 provides for a method for
operating an engine, comprising: inhibiting automatic engine
stopping in response to a secondary application of vehicle brakes
following an initial application of vehicle brakes, the secondary
application of vehicle brakes occurring after the initial
application of vehicle brakes and without vehicle brakes being
fully released. The method includes where inhibiting automatic
engine stopping causes the engine to continue combusting air and
fuel mixtures during conditions where automatic engine stopping is
otherwise allowed. The method includes where the secondary
application of vehicle brakes following the initial application of
vehicle brakes includes changing a brake pedal position by more
than a threshold amount.
[0079] In another example, the method further comprises not
inhibiting automatic engine stopping when changing the brake pedal
position by less than the threshold amount. The method further
comprises inhibiting automatic engine stopping in response to a
plurality of brake applications of vehicle brakes while the vehicle
brakes are activated. The method includes where the plurality of
brake applications comprises depressing a brake pedal a plurality
of times. The method also includes where vehicle brakes are fully
released when the brake pedal is fully released.
[0080] The method of FIG. 6 also includes a method for operating an
engine, comprising: inhibiting automatic engine stopping in
response to a secondary application of vehicle brakes following an
initial application of vehicle brakes, the secondary application of
vehicle brakes occurring after the initial application of vehicle
brakes and without vehicle brakes being fully released; and
automatically restarting the engine in response to the secondary
application of vehicle brakes. The method includes where the engine
is restarted without engaging a starter while the engine is
rotating. The method includes where the engine is automatically
restarted from an engine stop.
[0081] In some examples, the method further comprises inhibiting
automatic engine stopping until automatic engine stopping
conditions are not present. The method further comprises inhibiting
automatic engine stopping until a vehicle in which the engine
operates moves and stops after inhibiting automatic engine
stopping. The method includes where the secondary application of
vehicle brakes includes moving a brake pedal is greater than a
threshold distance. The method includes where the secondary
application of vehicle brakes includes increasing brake fluid
pressure greater than a threshold brake pressure amount. The method
also includes where the brake pedal is required to move a
predetermined distance that varies with a distance the brake pedal
is applied a first time since the brake pedal is fully released to
inhibit automatic engine stopping.
[0082] As will be appreciated by one of ordinary skill in the art,
method described in FIG. 6 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
steps 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
objects, features, and advantages described herein, but is provided
for ease of illustration and description. Although not explicitly
illustrated, one of ordinary skill in the art will recognize that
one or more of the illustrated steps or functions may be repeatedly
performed depending on the particular strategy being used. Further,
the described actions, operations, methods, 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.
[0083] This concludes the description. The reading of it by those
skilled in the art would bring to mind many alterations and
modifications without departing from the spirit and the scope of
the description. For example, I3, I4, I5, V6, V8, V10, and V12
engines operating in natural gas, gasoline, diesel, or alternative
fuel configurations could use the present description to
advantage.
* * * * *