U.S. patent application number 15/596667 was filed with the patent office on 2018-11-22 for engine speed stabilization.
The applicant listed for this patent is Ford Global Technologies, LLC. Invention is credited to Bryan Whitney D. Belt, Jacob Doan, Kent Hancock, Carol Louise Okubo.
Application Number | 20180334169 15/596667 |
Document ID | / |
Family ID | 64176614 |
Filed Date | 2018-11-22 |
United States Patent
Application |
20180334169 |
Kind Code |
A1 |
Okubo; Carol Louise ; et
al. |
November 22, 2018 |
Engine Speed Stabilization
Abstract
A vehicle includes an engine. The vehicle includes a controller
configured to start a timer having a duration defined by a charge
limit of a traction battery and during which the engine braking is
maintained and reduce a predetermined rate of change speed limit of
the engine is reduced. The starting of the timer is responsive to
application of an accelerator pedal during engine braking. The
controller is further configured to increase the predetermined rate
of change speed limit such that engine braking is predicted based
on the limit of the battery, responsive to application of an
accelerator pedal during engine braking.
Inventors: |
Okubo; Carol Louise;
(Dearborn, MI) ; Hancock; Kent; (Ann Arbor,
MI) ; Doan; Jacob; (Royal Oak, MI) ; Belt;
Bryan Whitney D.; (Sterling Heights, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ford Global Technologies, LLC |
Dearborn |
MI |
US |
|
|
Family ID: |
64176614 |
Appl. No.: |
15/596667 |
Filed: |
May 16, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60Y 2200/92 20130101;
F02D 11/02 20130101; B60W 2710/0661 20130101; B60W 2710/0666
20130101; B60W 10/08 20130101; B60W 20/00 20130101; B60W 2540/10
20130101; F02D 2200/503 20130101; F02D 41/045 20130101; B60W
2710/083 20130101; B60W 10/06 20130101; F02D 41/107 20130101; F02D
41/12 20130101; Y10S 903/93 20130101; B60W 10/18 20130101; B60W
30/18136 20130101; B60W 2050/0042 20130101; F02D 2041/1431
20130101; B60W 30/18072 20130101; B60W 2510/244 20130101; B60W
20/13 20160101 |
International
Class: |
B60W 30/18 20060101
B60W030/18; B60W 10/06 20060101 B60W010/06; B60W 10/08 20060101
B60W010/08; B60W 20/13 20060101 B60W020/13; F02D 11/02 20060101
F02D011/02 |
Claims
1. A vehicle comprising: an engine; and a controller configured to,
responsive to application of an accelerator pedal during engine
braking, start a timer having a duration defined by a charge limit
of a traction battery and during which the engine braking is
maintained and a predetermined rate of change speed limit of the
engine is reduced; and responsive to expiration of the timer,
increase the predetermined rate of change speed limit.
2. The vehicle of claim 1, wherein the charge limit is based on a
state of charge of the traction battery.
3. The vehicle of claim 2, wherein a magnitude of the charge limit
is inversely proportional to the duration.
4. The vehicle of claim 3, wherein the duration is zero when the
charge limit is greater than a charge limit threshold associated
with the traction battery.
5. The vehicle of claim 1, wherein an output torque of the engine
increases during the duration.
6. The vehicle of claim 5, wherein the output torque of the engine
is offset by an electric motor associated with a powertrain of the
vehicle during the duration.
7. The vehicle of claim 6, wherein the electric motor accelerates
the vehicle during the duration.
8. The vehicle of claim 1, wherein the predetermined rate of change
speed limit is reduced such that a speed of the engine is
maintained during the duration.
9. The vehicle of claim 8, wherein the speed is maintained with
wheel torque of the vehicle and a reactionary force of a
generator.
10. The vehicle of claim 1, wherein the predetermined rate of
change speed limit is negative.
11. A vehicle comprising: an engine; and a controller configured
to, responsive to an accelerator pedal release during an
acceleration of the engine, start a timer having a duration defined
by a charge limit of a traction battery and reduce a predetermined
rate of change threshold of a speed of the engine; and responsive
to expiration of the timer, increase the predetermined rate of
change threshold.
12. The vehicle of claim 11, wherein the charge limit is based on a
state of charge of the traction battery.
13. The vehicle of claim 11, wherein a magnitude of the charge
limit is inversely proportional to the duration.
14. The vehicle of claim 13, wherein the duration is zero when the
charge limit is a maximum charge limit associated with the traction
battery.
15. The vehicle of claim 11, wherein an output torque of the engine
decreases during the duration.
16. The vehicle of claim 15, wherein the output torque of the
engine is offset by an electric motor associated with a powertrain
of the vehicle during the duration.
17. The vehicle of claim 11, wherein the predetermined rate of
change threshold is negative.
18. A vehicle comprising: an engine; and a controller configured
to, responsive to application of an accelerator pedal during engine
braking, start a timer and maintain a speed of the engine via a
wheel torque of the vehicle and a reactionary force of a generator
associated with the vehicle; and responsive to expiration of the
timer, reduce the speed of the engine.
19. The vehicle of claim 18, wherein a duration of the timer is
based on a charge limit of a traction battery.
20. The vehicle of claim 18, wherein an output torque of the engine
is offset by an electric motor associated with a powertrain of the
vehicle during the timer.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to engine speed
stabilization.
BACKGROUND
[0002] Vehicles may employ engine braking to supplement friction or
regenerative braking. The negative torque provided by engine
braking may be related, proportional or otherwise, to the speed of
the engine. An accelerator pedal actuation may cause a vehicle
system controller to reduce engine braking torque by reducing
engine speed, which may change aural engine noises perceived by
occupants of the vehicle. The changes in perceived noise may be
distracting to vehicle occupants, especially when engine braking
and engine propulsion sound similar.
SUMMARY
[0003] A vehicle an engine. The vehicle includes a controller
configured to start a timer having a duration defined by a charge
limit of a traction battery and during which the engine braking is
maintained and reduce a predetermined rate of change speed limit of
the engine is reduced. The starting of the timer is responsive to
application of an accelerator pedal during engine braking. The
controller is further configured to increase the predetermined rate
of change speed limit such that engine braking is predicted based
on the limit of the battery, responsive to application of an
accelerator pedal during engine braking.
[0004] A vehicle includes an engine. The vehicle includes a
controller configured to start a timer having a duration defined by
a charge limit of a traction battery. The controller is configured
to reduce a predetermined rate of change speed limit of the engine.
The controller may start the timer and reduce the rate responsive
to an accelerator pedal release during an acceleration of the
engine. The controller is further configured to increase the
predetermined rate of change of the threshold. The increase is
responsive to expiration of the timer.
[0005] A vehicle includes an engine. The vehicle includes a
controller configured to start a timer having a duration defined by
a charge limit of a traction battery. The controller is configured
to maintain a speed of the engine via a wheel torque of the vehicle
and a reactionary force of a generator associated with the vehicle.
The controller is further configured to increase the predetermined
rate of change of the speed. The increase is responsive to
expiration of the timer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a schematic diagram of a hybrid vehicle;
[0007] FIG. 2 is a graph including an accelerator pedal tip-in,
engine speed reduction, and timer;
[0008] FIG. 3 is a graph including an accelerator pedal tip-out,
engine speed reduction, and timer;
[0009] FIG. 4 is a graph including timer duration and charge limits
of a traction battery; and
[0010] FIG. 5 is a flow diagram of a timer used to reduce a rate of
change of the engine speed for a predetermined duration.
DETAILED DESCRIPTION
[0011] Embodiments of the present disclosure are described herein.
It is to be understood, however, that the disclosed embodiments are
merely examples and other embodiments may take various and
alternative forms. The figures are not necessarily to scale; some
features could be exaggerated or minimized to show details of
particular components. Therefore, specific structural and
functional details disclosed herein are not to be interpreted as
limiting, but merely as a representative basis for teaching one
skilled in the art to variously employ the present invention. As
those of ordinary skill in the art will understand, various
features illustrated and described with reference to any one of the
figures may be combined with features illustrated in one or more
other figures to produce embodiments that are not explicitly
illustrated or described. The combinations of features illustrated
provide representative embodiments for typical applications.
Various combinations and modifications of the features consistent
with the teachings of this disclosure, however, could be desired
for particular applications or implementations.
[0012] Combustion engines of hybrid electric vehicles may be used
to slow the vehicle through engine braking. Various types of engine
braking and hybrid electric vehicles are available and may be used.
Engine braking may use inherent compression caused by stroking of
the pistons and intrinsic frictional forces to resist engine
rotation, thereby imparting negative torque to the powertrain.
[0013] Rotation of the engine may provide aural indication of
vehicle operation to vehicle occupants. Meaning, occupants can
glean vehicle acceleration characteristics from the noises made by
the engine. Hybrid vehicles that employ engine braking, as
discussed above, may confuse occupants because sounds caused by
engine speed do not coincide with torques imparted on the power
train or vehicle acceleration and deceleration. A timer may be
implemented to reduce unsteady engine speeds and reduce confusion
for vehicle occupants. The timer may be based on an engine braking
prediction. The engine braking prediction may be based on roadway
grade, battery charge limits, and other factors. Battery charge
limits specify the amount of regenerative braking available. As
charge limits decrease, based on a state of charge of the battery,
regenerative braking capabilities are diminished. With diminished
regenerative braking capacity, unstable engine speeds can be
predicted because engine braking will be used, along with
diminished regenerative braking capacity, to maintain vehicle speed
while traveling down a slope having a grade requiring vehicle speed
management.
[0014] A powertrain for a hybrid electric vehicle is illustrated
schematically in FIG. 1. The powertrain includes an internal
combustion engine 20 driveably connected to a planet carrier 22, a
generator 24 driveably connected to a sun gear 26, and an output
shaft 28 driveably connected to a ring gear 30. Elements are
driveably connected when there is a mechanical power flow path
between them such that the speeds of the elements are constrained
to be substantially proportional. Planet carrier 22 supports a set
of planet gears 32 such that each planet gear is in continuous
meshing engagement with sun gear 26 and ring gear 30. Output shaft
28 drives the vehicle wheels directly or indirectly, such as via a
differential assembly, for example.
[0015] Traction motor 34 is driveably connected to the output shaft
28. Both the generator 24 and the traction motor 34 are reversible
electrical machines that are capable of converting electrical power
into rotational mechanical power or converting rotational
mechanical power into electrical power. The terms generator and
motor should be regarded merely as labels for ease of description
and does not limit the function or operation of either electrical
machine. Generator 24 and traction motor 34 are both electrically
connected to battery 36.
[0016] The rotational speed of sun gear 26, carrier 22, and ring
gear 30 are linearly related such that speed of carrier 22 is a
weighted average of the speed of sun gear 26 and ring gear 30.
Consequently, the speed of the engine 20 is not constrained to be
proportional to the speed of the output shaft 28 in this
arrangement. Instead, the engine speed can be selected or
controlled independently of the vehicle speed by setting the
generator speed accordingly. Power flows from the engine to the
output shaft through a combination of mechanical power transfer and
electrical power transfer. During some operating conditions, the
engine 20 can generate more power than what is delivered to the
output shaft 28 with the difference, neglecting efficiency losses,
delivered to battery 36. Under other operating conditions, the
battery 36 in combination with generator 24 and/or traction motor
34 can supplement the power delivered by the engine 20 such that
more power is delivered to the output shaft 28.
[0017] The engine 20, generator 24, and traction motor 34, all
respond to control signals from controller 38. These control
signals determine the amount of torque generated. The controller
also receives speed signals from the engine 20, generator 24, and
traction motor 34 and a state of charge signal from battery 36. The
controller accepts input signals indicating driver intention from
an accelerator pedal 40 and road grade detection 46.
[0018] FIG. 2 illustrates vehicle accelerator pedal position 102,
engine speed 110, and timer 120 status. The accelerator pedal
position 102 curve indicates a tip-in event 104 while the vehicle
10 is on a downward grade and speed assist is engaged. The
accelerator pedal indicates that the driver may require
acceleration. The tip-in event 104 may be determined based on a
percent change or a rate of change of the accelerator pedal
position 102, indicating a change in demand by the driver. In
response to the change in pedal position 102, the controller 38 may
be configured to reduce engine speed 110 under normal operation at
point 116 as shown. Under normal operation, the engine speed 110
may have a rate of change 112. In response to the tip-in event 104,
a timer 120 may be initiated at point 124 having a duration 122.
The timer 120 may reduce the rate of change 112 such that the
engine speed 110 is maintained, as shown in curve 114. The engine
speed 110 may have a reduced rate of change 112 such that the curve
114 is not horizontal. The curve 114 may be positively or
negatively linear. The curve 114 may be concave, convex, or a
different function altogether. The reduced rate of change 112 may
be a function of the timer duration 122 or a function of the tip-in
event duration 106, which would accumulate over time.
[0019] FIG. 3 illustrates vehicle accelerator pedal position 202,
engine speed 210, and timer 220 status. The accelerator pedal
position 202 curve indicates a tip-out event 204 while the vehicle
10 is on a downward grade and speed assist is engaged. The driver
may have accelerated down the grade and is now backing off the
accelerator pedal. The tip-out event 204 may be determined based on
a percent change or a rate of change of the accelerator pedal
position 202, indicating a change in demand by the driver. In
response to the change in pedal position 202, the controller 38 may
be configured to reduce engine speed 210 under normal operation at
point 216 as shown. Under normal operation, the engine speed 210
may have a rate of change 212. In response to the tip-out event
204, a timer 220 may be initiated at point 124 having a duration
222. The timer 220 may reduce the rate of change 212 such that the
engine speed 210 is maintained, as shown in curve 214. The engine
speed 210 may have a reduced rate of change 212 such that the curve
214 is not horizontal. The curve 214 may be positively or
negatively linear. The curve 214 may be concave, convex, or a
different function altogether. The reduced rate of change 212 may
be a function of the timer duration 222.
[0020] FIG. 4 illustrates a graph 300 of timer 304 and charge
limits 306. The timer-limit curve 302 discloses timer durations 304
against charge limits 306. The charge limits 306 may be based on
the state of charge of the traction battery 36. The charge limits
306 may be based on thermal limits. As shown, a magnitude of the
charge limit 306 may be inversely proportional to the duration of
the timer 304. The duration of the timer 304 is zero when the
charge limit 306 is a maximum charge limit or a charge limit
threshold associated with the traction battery 36, which may vary
depending on battery manufacturer and model.
[0021] FIG. 5 illustrates a flow diagram 400. The flow chart begins
at start 402. The controller 38 determines whether the engine 20 is
rotating in step 404. In step 406 the controller 38 determines
whether an accelerator pedal 40 has been applied or released.
Determination of whether the accelerator pedal 40 has been applied
or released may be dependent on a percent change of the accelerator
pedal position, an absolute position of the pedal crossing a
threshold, or a combination thereof. If the accelerator pedal 40
has been applied or released in step 406 a timer 304 may be started
in step 408. The start of the timer may be adjusted or delayed to
compensate for other environmental factors.
[0022] During the timed period 302, the controller 38 may reduce a
rate of change of the engine speed limit 110, 210 in step 410.
Meaning, the rate of change 112, 212 of the engine speed 20 is
limited. In other words, it may be maintained in particular
embodiments. For example, the engine may have a particular speed
driven by a torque setting of the controller 38. The torque setting
may be determined by an accelerator position or environmental
factors. In a speed controlled circumstance, the engine speed 110,
210 may change with the position of the accelerator pedal 40. For
example, an engine brake torque may be based on the speed 110, 210
of the engine. As engine speed 110, 210 increases, engine braking
torque increases. The application of the accelerator pedal in this
situation may cause the engine speed 110, 210 to decrease, which
would lower the negative torque by the engine 20. Under low charge
limit 306 conditions (e.g., a high battery state of charge), engine
braking may be anticipated during a downhill decent with vehicle
speed control engaged. Therefore, engine speed 110, 210 may be
maintained, while engine torque is decreased, to anticipate engine
braking in the future. Maintaining the speed 110, 210 of the engine
can reduce driver confusion created when the vehicle speed is
maintained and the engine speed varies because drivers generally
associate engine noise with vehicle speed. The speed 110, 210 of
the engine may be maintained for a duration 122, 222 of the timer
304. The rate of change of the speed 110, 210 of the engine may be
reduced for a duration 122, 222 of the timer 304. When the timer
expires in step 412, the rate of change of the speed of the engine
may be changed in step 414. The process may end in step 416 or run
continuously.
[0023] The words used in the specification are words of description
rather than limitation, and it is understood that various changes
may be made without departing from the spirit and scope of the
disclosure. As previously described, the features of various
embodiments may be combined to form further embodiments of the
invention that may not be explicitly described or illustrated.
While various embodiments could have been described as providing
advantages or being preferred over other embodiments or prior art
implementations with respect to one or more desired
characteristics, those of ordinary skill in the art recognize that
one or more features or characteristics may be compromised to
achieve desired overall system attributes, which depend on the
specific application and implementation. These attributes may
include, but are not limited to cost, strength, durability, life
cycle cost, marketability, appearance, packaging, size,
serviceability, weight, manufacturability, ease of assembly, etc.
As such, embodiments described as less desirable than other
embodiments or prior art implementations with respect to one or
more characteristics are not outside the scope of the disclosure
and may be desirable for particular applications.
* * * * *