U.S. patent application number 16/396510 was filed with the patent office on 2020-10-29 for limiting engine on condition while coasting.
The applicant listed for this patent is TOYOTA MOTOR ENGINEERING & MANUFACTURING NORTH AMERICA, INC. Invention is credited to GEOFFREY D. GAITHER.
Application Number | 20200339100 16/396510 |
Document ID | / |
Family ID | 1000005147410 |
Filed Date | 2020-10-29 |
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United States Patent
Application |
20200339100 |
Kind Code |
A1 |
GAITHER; GEOFFREY D. |
October 29, 2020 |
LIMITING ENGINE ON CONDITION WHILE COASTING
Abstract
Systems and methods are provided that prevent or override a
hybrid electric vehicle (HEV) from operating in an engine-on mode
or condition when the HEV is coasting, such as when the HEV is
traveling on a downhill grade. Regenerative torque is generated by
one or more electric motors of the HEV so that the pinion gear of a
planetary gear set of a power distribution mechanism operates below
an overspeed limit at which hardware failure may occur.
Inventors: |
GAITHER; GEOFFREY D.;
(Brighton, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOYOTA MOTOR ENGINEERING & MANUFACTURING NORTH AMERICA,
INC |
PLANO |
TX |
US |
|
|
Family ID: |
1000005147410 |
Appl. No.: |
16/396510 |
Filed: |
April 26, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60W 20/40 20130101;
B60K 2028/006 20130101; B60W 20/11 20160101; B60K 28/10
20130101 |
International
Class: |
B60W 20/11 20060101
B60W020/11; B60K 28/10 20060101 B60K028/10; B60W 20/40 20060101
B60W020/40 |
Claims
1. A method comprising: determining a hybrid electric vehicle (HEV)
is experiencing a coast condition; setting an initial amount of
regenerative torque to be generated by a motor of the HEV;
determining whether a pinion gear of the HEV is approaching a
pinion gear overspeed limit; in response to a determination that
the pinion gear of the HEV is not approaching the pinion gear
overspeed limit, generating the initial amount of regenerative
torque and applying the initial regenerative torque amount to drive
the HEV while maintaining the HEV in an engine-off condition.
2. The method of claim 1, wherein the HEV is experiencing a
coasting condition while traversing a downhill grade.
3. The method of claim 2, further comprising calculating a state of
charge of a battery powering the HEV required to complete traversal
of the downhill grade.
4. The method of claim 3, further comprising determining if charge
power of the battery can be increased while maintaining the HEV in
an engine-off condition, and if so, increasing a charge power limit
of the battery to accommodate regenerated energy produced by
application of the initial amount of regenerative torque.
5. The method of claim 4, further comprising determining if a state
of charge limit of the battery can be increased while maintaining
the HEV in an engine-off condition, and if so, increasing the state
of charge limit to accommodate the regenerated energy produced by
application of the initial amount of regenerative torque.
6. The method of claim 1, further comprising, in response to a
determination that the pinion gear of the HEV is approaching the
pinion gear overspeed limit, determining whether the initial amount
of regenerative torque is approaching a regenerative torque
threshold.
7. The method of claim 6, further comprising, in response to a
determination that the initial amount of regenerative torque is not
approaching the regenerative torque threshold, generating an
additional amount of regenerative torque and applying the
additional amount of regenerative torque to drive the HEV while
maintaining the HEV in an engine-off condition.
8. The method of claim 6, further comprising, in response to a
determination that the initial amount of regenerative torque is
approaching the regenerative torque threshold, determining whether
the battery charge limit has reached a maximum level.
9. The method of claim 8, further comprising, in response to
determining that the battery has not reached the maximum level,
temporarily increasing the charge limit above the maximum level but
below an absolute maximum level.
10. The method of claim 8, further comprising, in response to
determining that the battery has reached the maximum level,
operating an engine of the HEV in a fuel cut off condition.
11. The method of claim 10, further comprising, engaging friction
bakes of the HEV.
12. The method of claim 10, further comprising, continuing
application of the initial amount of regenerative torque until
operating conditions of the HEV necessitate an engine-on condition,
and instructing the engine of the HEV to turn on.
13. A hybrid electric vehicle (HEV), comprising: a power
transmission path comprising: an internal combustion engine; at
least one electric motor operatively to the internal combustion
engine; and a power distribution mechanism generating drive power
from the internal combustion engine, the at least one electric
motor, or a combination thereof via operation of a planetary gear
set including a pinion gear; and an electronic control unit (ECU)
adapted to adjust regenerative torque generated by the at least one
electric motor to prevent the internal combustion engine from
generating drive power while the HEV is coasting on a downhill
grade.
14. The HEV of claim 13, wherein the ECU sets an initial amount of
regenerative torque based on current HEV operation conditions and
road conditions including a state of charge (SOC) of a battery
powering the at least one electric motor, a vehicle speed of the
HEV, temperature of the battery, temperature of the at least one
electric motor, and road grade.
15. The HEV of claim 13, wherein the ECU increases a charge power
limit of a battery powering the at least one electric motor as long
as the HEV can continue being operated without the internal
combustion engine generating drive power, the increased charge
power allowing the battery to recoup energy generated by the
initial amount of the regenerative torque.
16. The HEV of claim 15, wherein the ECU increases an SOC of the
battery as long as the HEV can continue being operated without the
internal combustion engine generating drive power, the increased
SOC allowing the battery to recoup the energy generated by the
initial amount of the regenerative torque.
17. The HEV of claim 13, wherein the ECU determines a current speed
at which the pinion gear is rotating.
18. The HEV of claim 17, wherein the ECU instructs the at least one
electric motor to generate additional regenerative torque, wherein
energy resulting from the additional regenerative torque is
recouped by the battery whose charge limit is temporarily
increased.
19. The HEV of claim 18, wherein the energy resulting from the
additional regenerative torque is recouped by the battery whose SOC
limit is temporarily increased.
20. The HEV of claim 13, wherein the ECU turns the internal
combustion engine on when operating conditions of the HEV and road
conditions do not allow for the generation of regenerative torque
in an amount sufficient to prevent the internal combustion engine
from generating drive power while the HEV is coasting on a downhill
grade.
Description
TECHNICAL FIELD
[0001] The present disclosure relates generally to controlling
drive power in a hybrid electric vehicle (HEV). In some
embodiments, actions can be performed in order to counteract
excessive pinion gear speed (or pinion overspeed) in the planetary
gear set of the HEV, which can be reflected by way of or indicated
as a maximum engine-on vehicle (EOV) speed.
DESCRIPTION OF RELATED ART
[0002] HEVs have become increasingly popular among consumers
concerned with their environmental impact and with increasing fuel
economy. HEVs generally utilize an engine, e.g., an internal
combustion engine (ICE), along with one or more electric motors,
which can also operate as a generator(s) to provide energy to a
battery that powers the electric motor(s). The drivetrain of an HEV
can include the engine, the one or more electric motors, and an
automatic transmission coupled to the engine and the one or more
electric motors for transmitting power from the engine, electric
motor(s), or a combination thereof.
[0003] Each HEV or model/make of HEV may have a determined pinion
gear speed or maximum EOV speed. This pinion gear speed or maximum
EOV speed can refer to the speed at which the pinion gear rotates
or the corresponding vehicle speed which when met or exceeded,
causes the HEV to turn on its engine (engine-on condition). The
HEV's engine is enabled, generally, in order to prevent bearing
failure and/or gear teeth penetration. Thus, in certain situations,
such as when the HEV is coasting while traveling on a downgrade,
the HEV's engine may start even if the HEV operator does not input
or make a request to start the engine. This can negatively impact
fuel economy as well as recouping regenerative energy.
BRIEF SUMMARY OF THE DISCLOSURE
[0004] In accordance with one embodiment, a method comprises
determining a hybrid electric vehicle (HEV) is experiencing a coast
condition, and setting an initial amount of regenerative torque to
be generated by a motor of the HEV. The method may further comprise
determining whether a pinion gear of the HEV is approaching a
pinion gear overspeed limit. In response to a determination that
the pinion gear of the HEV is not approaching the pinion gear
overspeed limit, the initial amount of regenerative torque is
generated and the initial regenerative torque amount is applied to
drive the HEV while maintaining the HEV in an engine-off
condition.
[0005] In some embodiments, the HEV is experiencing a coasting
condition while traversing a downhill grade.
[0006] In some embodiments, the method further comprises
calculating a state of charge of a battery powering the HEV
required to complete traversal of the downhill grade.
[0007] In some embodiments, the method further comprises
determining if charge power of the battery can be increased while
maintaining the HEV in an engine-off condition, and if so,
increasing a charge power limit of the battery to accommodate
regenerated energy produced by application of the initial amount of
regenerative torque.
[0008] In some embodiments, the method further comprises
determining if a state of charge limit of the battery can be
increased while maintaining the HEV in an engine-off condition, and
if so, increasing the state of charge limit to accommodate the
regenerated energy produced by application of the initial amount of
regenerative torque.
[0009] In response to a determination that the pinion gear of the
HEV is approaching the pinion gear overspeed limit, the method may
further comprise determining whether the initial amount of
regenerative torque is approaching a regenerative torque
threshold.
[0010] In response to a determination that the initial amount of
regenerative torque is not approaching the regenerative torque
threshold, the method may further comprise generating an additional
amount of regenerative torque and applying the additional amount of
regenerative torque to drive the HEV while maintaining the HEV in
an engine-off condition.
[0011] In response to a determination that the initial amount of
regenerative torque is approaching the regenerative torque
threshold, the method may further comprise determining whether the
battery charge limit has reached a maximum level.
[0012] In response to determining that the battery has not reached
the maximum level, the method may further comprise temporarily
increasing the charge limit above the maximum level but below an
absolute maximum level.
[0013] In response to determining that the battery has reached the
maximum level, the method may further comprise operating an engine
of the HEV in a fuel cut off condition.
[0014] In some embodiments, the method may further comprise
engaging friction bakes of the HEV.
[0015] In some embodiments, the method may further comprise
continuing application of the initial amount of regenerative torque
until operating conditions of the HEV necessitate an engine-on
condition, and instructing the engine of the HEV to turn on.
[0016] In accordance with another embodiment, a hybrid electric
vehicle (HEV), may comprise a power transmission path. The power
transmission path may include an internal combustion engine, and at
least one electric motor operatively to the internal combustion
engine. The power transmission path may further include: a power
distribution mechanism generating drive power from the internal
combustion engine, the at least one electric motor, or a
combination thereof via operation of a planetary gear set including
a pinion gear; and an electronic control unit (ECU) adapted to
adjust regenerative torque generated by the at least one electric
motor to prevent the internal combustion engine from generating
drive power while the HEV is coasting on a downhill grade.
[0017] In some embodiments, the ECU sets an initial amount of
regenerative torque based on current HEV operation conditions and
road conditions including a state of charge (SOC) of a battery
powering the at least one electric motor, a vehicle speed of the
HEV, temperature of the battery, temperature of the at least one
electric motor, and road grade.
[0018] In some embodiments, the ECU increases a charge power limit
of a battery powering the at least one electric motor as long as
the HEV can continue being operated without the internal combustion
engine generating drive power, the increased charge power allowing
the battery to recoup energy generated by the initial amount of the
regenerative torque.
[0019] In some embodiments, the ECU increases an SOC of the battery
as long as the HEV can continue being operated without the internal
combustion engine generating drive power, the increased SOC
allowing the battery to recoup the energy generated by the initial
amount of the regenerative torque.
[0020] In some embodiments, the ECU determines a current speed at
which the pinion gear is rotating.
[0021] In some embodiments, the ECU instructs the at least one
electric motor to generate additional regenerative torque, wherein
energy resulting from the additional regenerative torque is
recouped by the battery whose charge limit is temporarily
increased.
[0022] In some embodiments, the energy resulting from the
additional regenerative torque is recouped by the battery whose SOC
limit is temporarily increased.
[0023] In some embodiments, the ECU turns the internal combustion
engine on when operating conditions of the HEV and road conditions
do not allow for the generation of regenerative torque in an amount
sufficient to prevent the internal combustion engine from
generating drive power while the HEV is coasting on a downhill
grade.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The present disclosure, in accordance with one or more
various embodiments, is described in detail with reference to the
following figures. The figures are provided for purposes of
illustration only and merely depict typical or example
embodiments.
[0025] FIG. 1 is a schematic representation of a hybrid electric
vehicle in which drive power can be controlled through the
application of negative or regenerative torque in accordance with
various embodiments of the present disclosure.
[0026] FIG. 2 is a functional block diagram illustrates component
parts of a control function included in an electronic control unit
of the hybrid vehicle illustrated in FIG. 1.
[0027] FIG. 3 is a graphical representation of road and vehicle
conditions during which an HEV may enter an engine-on condition in
accordance with various embodiments of the present disclosure.
[0028] FIG. 4 is a graphical representation of the application of
regenerative torque in response to the road and vehicle conditions
of FIG. 3 in accordance with various embodiments of the present
disclosure.
[0029] FIG. 5 is a flow chart illustrating example operations that
may be performed to apply regenerative torque in response to the
road and vehicle conditions of FIG. 2 in accordance with various
embodiments of the present disclosure.
[0030] FIG. 6 is a graphical representation of example mechanisms
controlling the application of regenerative torque in response to
the road and vehicle conditions of FIG. 2 in accordance with
various embodiments of the present disclosure.
[0031] FIG. 7A is a flow chart illustrating example operations that
may be performed to apply regenerative torque to prevent an
engine-on condition in accordance with various embodiments of the
present disclosure.
[0032] FIG. 7B is a continuation of the flow chart of FIG. 7A
illustrating example operations that may be performed to apply
regenerative torque to prevent an engine-on condition in accordance
with various embodiments of the present disclosure.
[0033] FIG. 8 is an example computing component that may be used to
implement various features of embodiments described in the present
disclosure.
[0034] The figures are not exhaustive and do not limit the present
disclosure to the precise form disclosed.
DETAILED DESCRIPTION
[0035] Various embodiments of the present disclosure are directed
to counteracting the engine-on condition in an HEV when the HEV is
coasting (e.g., while traveling along a downhill slope). A pinion
gear, also referred to as a sun gear, is one component of a
planetary gear set. A pinion gear overspeed condition may harm the
motor or motor-related hardware. Control systems for HEVs may
calculate a pinion gear speed limit in the transaxle above which
those failures may occur. Accordingly, such control systems
implement a mechanism whereby when the pinion gear speed surpasses
a threshold reflecting the pinion gear speed limit, the engine of
the HEV is automatically turned on. Use of the engine will cause a
reduction in pinion gear speed and/or the relative speed between
the pinion gear and other associated components, e.g., the planet
gears, the ring gear, the carrier, etc., avoiding hardware
failure.
[0036] As alluded to above, control systems for HEVs do not prevent
an HEV that is coasting from exceeding the pinion gear speed limit
or maximum EOV speed, thus necessitating entering the engine-on
condition to avoid hardware failure. Accordingly, in certain
scenarios, an HEV may be traveling along a down slope, and without
user input or a user request, the engine of the HEV will turn on.
This can result in less-than-ideal fuel economy because the engine
will consume fuel when on, even when use of the engine is not
necessarily needed (since the HEV is coasting, e.g., downhill).
Additionally, regenerative energy recuperation opportunities may be
missed. Moreover, a user (e.g., the driver of the HEV) may have an
undesirable driving experience due to an unwanted or unintended
engine-on condition.
[0037] In order to prevent the engine on-condition while an HEV is
coasting, negative motor torque can be used to generate a braking
force thereby decelerating the HEV. Decelerating the HEV will serve
to reduce the speed at which the pinion gears of the planetary gear
set are rotating (below the pinion gear speed limit), and
accordingly, reduce the speed of the vehicle below the maximum EOV
speed. This negative motor torque can be used to charge the HEV's
battery, referred to as, e.g., regenerative braking torque,
regenerative torque, or simply regen torque. A processing loop(s)
may be used to measure one or more operating conditions of the HEV.
Based on those operating conditions relative to certain thresholds,
when regenerative torque is applied and the amount of regenerative
torque generated and applied can be controlled.
[0038] It should be noted that the terms "optimize," "optimal" and
the like as used herein can be used to mean making or achieving
performance as effective or perfect as possible. However, as one of
ordinary skill in the art reading this document will recognize,
perfection cannot always be achieved. Accordingly, these terms can
also encompass making or achieving performance as good or effective
as possible or practical under the given circumstances, or making
or achieving performance better than that which can be achieved
with other settings or parameters.
[0039] FIG. 1 is a schematic representation of an example HEV 10 in
which, according to various embodiments, drive power may be
adjusted to counteract excessive pinion gear speed. It should be
noted that for clarity of the illustration, not all elements of HEV
10 are labeled with a reference numeral. For example, in some
cases, only one of two or more elements or components of HEV 10 are
labeled with a reference numeral. However, it can be assumed that
the functionality and/or operation of similarly-illustrated
elements or components are the same or substantially similar,
unless described otherwise. Moreover, aspects of HEV 10 may be
described from the perspective of one/one set of elements or
components. It can be assumed that secondary instances of those
elements or components may operate the same or in a similar manner.
It should also be noted that for ease of description and clarity of
figures, not all components of an HEV have been illustrated, and
that the figures and corresponding descriptions are not meant to be
limiting. It should be further noted that an HEV may embody certain
variations with respect to its elements or components, which are
contemplated herein. For example, HEV 10 may be configured with a
single motor or with two motors.
[0040] The drive system of HEV 10 may include an internal
combustion engine 14 and one or more electric motors 22 (which may
also serve as generators) as sources of motive power. Driving force
generated by the internal combustion engine 14 and motors 22 can be
transmitted to one or more wheels 34 via a torque converter 16, a
transmission 18 (which may be an automatic transmission, and can
include a power delivery mechanism 21), a differential gear device
28, and a pair of axles 30.
[0041] As an HEV, vehicle 10 may be driven/powered with either or
both of engine 14 and the motor(s) 22 as the drive source for
travel. For example, a first travel mode may be an engine-only
travel mode that only uses internal combustion engine 14 as the
source of motive power. A second travel mode may be an EV travel
mode that only uses the motor(s) 22 as the source of motive power.
A third travel mode may be an HEV travel mode that uses engine 14
and the motor(s) 22 as the sources of motive power. In the
engine-only and HEV travel modes, vehicle 10 relies on the motive
force generated at least by internal combustion engine 14. In the
EV travel mode, vehicle 10 is powered by the motive force generated
by motor 22 while engine 14 may be stopped.
[0042] Engine 14 can be an internal combustion engine such as a
gasoline, diesel or similarly powered engine in which fuel is
injected into and combusted in a combustion chamber. A cooling
system 12 can be provided to cool the engine 14 such as, for
example, by removing excess heat from engine 14. For example,
cooling system 12 can be implemented to include a radiator, a water
pump and a series of cooling channels. In operation, the water pump
circulates coolant through the engine 14 to absorb excess heat from
the engine. The heated coolant is circulated through the radiator
to remove heat from the coolant, and the cold coolant can then be
recirculated through the engine. A fan may also be included to
increase the cooling capacity of the radiator. The water pump, and
in some instances the fan, may operate via a direct or indirect
coupling to the driveshaft of engine 14. In other applications,
either or both the water pump and the fan may be operated by
electric current such as from battery 44.
[0043] An output control circuit 14A may be provided to control
drive (output torque) of engine 14. Output control circuit 14A may
include a throttle actuator to control an electronic throttle valve
that controls fuel injection, an ignition device that controls
ignition timing, and the like. Output control circuit 14A may
execute output control of engine 14 according to a command control
signal(s) supplied from an electronic control unit 50, described
below. Such output control can include, for example, throttle
control, fuel injection control, and ignition timing control.
[0044] Motors 22 can also be used to provide motive power in HEV 10
and is powered electrically via a battery 44. Battery 44 may be
implemented as one or more batteries or other power storage devices
including, for example, lead-acid batteries, lithium ion batteries,
capacitive storage devices, and so on. Battery 44 may be charged by
a battery charger 45 that receives energy from internal combustion
engine 14. For example, an alternator or generator may be coupled
directly or indirectly to a drive shaft of internal combustion
engine 14 to generate an electrical current as a result of the
operation of internal combustion engine 14. A clutch can be
included to engage/disengage the battery charger 45. Battery 44 may
also be charged by motor 22 such as, for example, by regenerative
braking or by coasting during which time motors 22 operate as
generator.
[0045] Motors 22 can be powered by battery 44 to generate a motive
force to move the vehicle and adjust vehicle speed. Motors 22 can
also function as a generator to generate electrical power such as,
for example, when coasting or braking. Battery 44 may also be used
to power other electrical or electronic systems in the vehicle.
Motors 22 may be connected to battery 44 via an inverter 42.
Battery 44 can include, for example, one or more batteries,
capacitive storage units, or other storage reservoirs suitable for
storing electrical energy that can be used to power motor 22. When
battery 44 is implemented using one or more batteries, the
batteries can include, for example, nickel metal hydride batteries,
lithium ion batteries, lead acid batteries, nickel cadmium
batteries, lithium ion polymer batteries, and other types of
batteries. With the inverter 42 controlled by electronic control
unit 50 that will be described below, motor 22A torque T.sub.ma and
motor 22B torque T.sub.mb as output torque (or regenerative torque)
of each of motor 22A and motor 22B are controlled.
[0046] Power distribution mechanism 21 may be a single-pinion-type
planetary gear set having three rotating elements, i.e., a sun gear
S0, a ring gear R0 disposed concentrically with the sun gear S0,
and a carrier CA0 that supports pinion gears P0 that mesh with the
sun gear S0 and the ring gear R0 such that the pinion gears P0 can
rotate about themselves and rotate about the axis of the gear set.
Power distribution mechanism 21 functions as a differential
mechanism that performs differential operation. In transmission 18,
engine 14 is coupled to the carrier CA0 via a damper 23 such that
power can be transmitted between the engine 14 and the carrier CA0,
and motor 22 is coupled to the sun gear S0 such that power can be
transmitted between motor 22A and the sun gear S0, while second
motor 22B is coupled to the ring gear R0 such that power can be
transmitted between the second motor 22B and the ring gear R0. In
the power distribution mechanism 21, the carrier CA0 functions as
an input element, and the sun gear S0 functions as a reaction-force
element, while the ring gear R0 functions as an output element.
[0047] Power distribution mechanism 21 may have three rotating
elements, e.g., the carrier CA0 to which the engine 14 is
operatively coupled, the sun gear S0 to which motor 22A as an
electric motor for differential operation is operatively coupled,
and the ring gear R0 to which motor 22B as an electric motor for
running the vehicle is operatively coupled. Namely, transmission 18
has power distribution mechanism 21 operatively coupled to the
engine 14, and motor 22A operatively coupled to power distribution
mechanism 21. In transmission 18, an electric continuously variable
transmission 30 as an electric speed change mechanism (electric
differential mechanism) is constructed in which an operating state
of motor 22A is controlled so that a differential status of power
distribution mechanism 21 is controlled. The electric continuously
variable transmission 30 is operable to change the speed ratio
.gamma.0 (=engine speed N.sub.E/motor 22B rotational speed
N.sub.M).
[0048] Transmission 18 (which can be an automatic transmission
(AT)) may be a mechanical speed change mechanism that provides a
part of a power transmission path between a transmission member 32
as an output rotating member of the electric continuously variable
transmission 30, and the drive wheels 34. The transmission member
32 is coupled integrally with the ring gear R0 and is also coupled
integrally with a transmission input shaft (AT input shaft) 36 as
an input rotating member of automatic transmission 18. Motor 22B is
coupled to the transmission member 32 such that power can be
transmitted between motor 22B and the transmission member 32.
Accordingly, automatic transmission 18 is a mechanical speed change
mechanism that provides a part of a power transmission path between
motor 22B and the drive wheels 34. Transmission 18 performs
so-called clutch-to-clutch shifting by engaging and releasing
selected ones of the two or more engagement devices (namely, by
switching engaged and released states of the engagement devices).
Transmission 18 may change the speed ratio through engagement and
release of the engagement devices, so as to form a selected one of
two or more gear positions having difference speed ratios (gear
ratios) .gamma.at (=AT input rotational speed Ni/AT output
rotational speed No).
[0049] The above-mentioned engagement devices may be hydraulic
friction devices that transmit rotation and torque between the
transmission input shaft 34 that receives power from the engine 14
and motor 22B, and the transmission output shaft (AT output shaft)
36 as an output rotating member of transmission 18 that transmits
power to the drive wheels 34. The torque capacity (clutch torque)
of each of the engagement devices is changed by regulating the
engaging hydraulic pressure (clutch pressure) by means of a
solenoid valve, or the like, in a hydraulic control circuit 40
included in transmission 18, so that engagement and release of the
engagement device are controlled. In this embodiment, the two or
more engagement devices will be called "clutches C", for the sake
of convenience, but the clutches C include known brakes, etc., as
well as clutches.
[0050] An electronic control unit (ECU) 50 (described below) may be
included and may control the electric drive components of the
vehicle as well as other vehicle components. For example, ECU 50
may control inverter 42, adjust driving current supplied to motor
22, and adjust the current received from motor 22 during
regenerative coasting and breaking. As a more particular example,
output torque of the motor 22 can be increased or decreased by ECU
50 through the inverter 42.
[0051] A torque converter 16 can be included to control the
application of power from engine 14 and motor 22 to transmission
18. Torque converter 16 can include a viscous fluid coupling that
transfers rotational power from the motive power source to the
driveshaft via the transmission. Torque converter 16 can include a
conventional torque converter or a lockup torque converter. In
other embodiments, a mechanical clutch can be used in place of
torque converter 16.
[0052] As alluded to above, vehicle 102 may include an ECU 50. ECU
50 may include circuitry to control various aspects of the vehicle
operation. ECU 50 may include, for example, a microcomputer that
includes a one or more processing units (e.g., microprocessors),
memory storage (e.g., RAM, ROM, etc.), and I/O devices. The
processing units of ECU 50, execute instructions stored in memory
to control one or more electrical systems or subsystems in the
vehicle. ECU 50 can include a plurality of ECUs such as, for
example, an electronic engine control module, a powertrain control
module, a transmission control module, a suspension control module,
a body control module, and so on. As a further example, ECUs can be
included to control systems and functions such as doors and door
locking, lighting, human-machine interfaces, cruise control,
telematics, braking systems (e.g., ABS or ESC), battery management
systems, and so on. These various control units can be implemented
using two or more separate ECUs, or using a single ECU.
[0053] In the example illustrated in FIG. 1, ECU 50 receives
information from a plurality of sensors included in vehicle 10. For
example, ECU 50 may receive signals that indicate vehicle operating
conditions or characteristics, or signals that can be used to
derive vehicle operating conditions or characteristics. These may
include, but are not limited to accelerator operation amount,
A.sub.CC, a revolution speed, N.sub.E, of internal combustion
engine 14 (engine RPM), a rotational speed, N.sub.MG, of the motor
22 (motor rotational speed), and vehicle speed, N.sub.V. These may
also include torque converter 16 output, N.sub.T (e.g., output amps
indicative of motor output), regenerative torque (e.g., T.sub.MA
and T.sub.MB alluded to above), brake operation amount/pressure, B,
battery SOC (i.e., the charged amount for battery 44 detected by an
SOC sensor), battery temperature, T.sub.B, motor temperature
T.sub.M. Accordingly, HEV 10 can include a plurality of sensors 52
that can be used to detect various conditions internal or external
to the vehicle and provide sensed conditions to engine control unit
50 (which, again, may be implemented as one or a plurality of
individual control circuits). In one embodiment, sensors 52 may be
included to detect one or more conditions directly or indirectly
such as, for example, fuel efficiency, E.sub.F, motor efficiency,
E.sub.MG, hybrid (internal combustion engine 14+motor 22)
efficiency, acceleration, A.sub.CC, accelerator position, A.sub.P,
gear shift position, G.sub.P, sensed road grade, G.sub.R, road
load, RL, pinion gear speed, V.sub.P, heating ventilation and air
conditioning (HVAC) settings, etc.
[0054] In some embodiments, one or more of the sensors 52 may
include their own processing capability to compute the results for
additional information that can be provided to ECU 50. In other
embodiments, one or more sensors may be data-gathering-only sensors
that provide only raw data to ECU 50. In further embodiments,
hybrid sensors may be included that provide a combination of raw
data and processed data to ECU 50. Sensors 52 may provide an analog
output or a digital output.
[0055] Sensors 52 may be included to detect not only vehicle
conditions but also to detect external conditions as well. Sensors
that might be used to detect external conditions can include, for
example, sonar, radar, lidar or other vehicle proximity sensors,
and cameras or other image sensors. Image sensors can be used to
detect, for example, traffic signs indicating a current speed
limit, road curvature, obstacles, and so on. Still other sensors
may include those that can detect road grade. While some sensors
can be used to actively detect passive environmental objects, other
sensors can be included and used to detect active objects such as
those objects used to implement smart roadways that may actively
transmit and/or receive data or other information.
[0056] FIG. 2 illustrates an example architecture for controlling
the application of and the amount of regenerative torque applied in
an HEV during a coasting condition in accordance with at least one
embodiment of the systems and methods described herein. FIG. 2
illustrates a plurality of sensors 52 (some of which may have been
introduced in FIG. 1).
[0057] Sensors 52 may include a vehicle speed sensor 214 for
determining vehicle speed, N.sub.V. Vehicle speed sensor 214 may
be, for example, a transmission speed/transaxle or wheel speed
sensor. Sensors 52 may also include an engine speed (N.sub.E)
sensor 216 that may be attached to a crankshaft of engine 14 for
determining crankshaft spin speed which is indicative of the speed
of engine 14. Sensors 52 may include an engine mode sensor 218 to
determine whether the engine 14 is operating (in an engine-on mode
or condition) or non-operational (in an engine-off mode or
condition). It should be understood that engine mode sensor 218 may
be its own sensor or may be a monitoring component or function of
engine control component 270 (described below) or ECU 50 that is
aware of the operational mode of HEV 10. Further still, sensors 52
may include a battery temperature (B.sub.T) sensor 220, a motor
temperature (T.sub.M) sensor 222, an accelerator pedal position
sensor 224, gearshift position sensor 226, and pinion speed sensor
228. Moreover, sensors 52 may include a location sensor 230.
Location sensor 230 may comprise a global positioning systems (GPS)
sensor/receiver/transceiver or other location component configured
to determine a location of HEV 10. In some embodiments location
sensor 230 may incorporate other location-determining capabilities,
such as WiFi triangulation (as an alternative to or in addition to
GPS sensing). Sensors 52 may also include a road grade sensor 232
for determining the grade of a road/path being traversed by HEV 10.
Road grade sensor 232 may be, e.g., an inclinometer, tilt sensor,
gradient meter, or some component capable of computing or
estimating the slope of a road/path alone or in conjunction with
other sensor data. Still other sensors 234 may make up sensors 52
of HEV 10.
[0058] It should be noted that the sensor data provided by any one
or more of sensors 52 may be received from a sensor or entity
remotely located from HEV 10. For example, vehicle speed, location,
and/or grade data or information may be obtained from other
vehicles (either nearby vehicles or vehicles that have traveled or
are aware of such information). Such third-party information or
data may be received by HEV 10 via V2X communications or other
communications method(s).
[0059] The aforementioned sensor data or information may be
communicated to engine-on limiting circuit 210, to allow engine-on
limiting circuit 210 to determine when the engine-on condition
should be limited by applying regenerative torque, and the amount
of regenerative torque to be applied. Engine-on limitation circuit
210 may include communications circuit 201, which can include, but
is not limited to a wireless transceiver circuit 202 and a wired
input/output interface 204 (with an associated hardwired data port
(not illustrated)).
[0060] As this example illustrates, communications with engine-on
limiting circuit 210 can include either or both wired and wireless
communications circuits 201. Wireless transceiver circuit 202 can
include a transmitter and a receiver (not shown) to allow wireless
communications via any of a number of communication protocols such
as, for example, WiFi, Bluetooth, near field communications (NFC),
Zigbee, and any of a number of other wireless communication
protocols whether standardized, proprietary, open, point-to-point,
networked or otherwise. Antenna 214 is coupled to wireless
transceiver circuit 202 and is used by wireless transceiver circuit
202 to transmit radio signals wirelessly to wireless equipment with
which it is connected and to receive radio signals as well. These
RF signals can include information of almost any sort that is sent
or received by engine-on limiting circuit 210 to/from other
entities such as sensors 52 and vehicle systems 158 ECU 50.
[0061] Wired I/O interface 204 can include a transmitter and a
receiver (not shown) for hardwired communications with other
devices. For example, wired I/O interface 204 can provide a
hardwired interface to other components, including sensors 52 and
vehicle systems 158/ECU 50. Wired I/O interface 204 can communicate
with other devices using Ethernet or any of a number of other wired
communication protocols whether standardized, proprietary, open,
point-to-point, networked or otherwise.
[0062] Processor 206 can include a GPU, CPU, microprocessor, or any
other suitable processing system. The memory 208 may include one or
more various forms of memory or data storage (e.g., flash, RAM,
etc.) that may be used to store the calibration parameters, images
(analysis or historic), point parameters, instructions and
variables for processor 206 as well as any other suitable
information. Memory 208 can be made up of one or more modules of
one or more different types of memory, and may be configured to
store data and other information as well as operational
instructions that may be used by the processor 206 to assist-mode
detection/activation circuit 210.
[0063] Accordingly, communications circuit 201 may receive sensor
data regarding pinion speed (from pinion speed sensor 228), for
example, and engine-on limiting circuit 210 may determine that
regenerative torque should be added to the drivetrain in order to
reduce current pinion speed. For example, pinion speed sensor 228
may sense a particular pinion speed which can be transmitted, via
communications circuit 201, to decision circuit 203 where processor
206 is executing engine-on limiting logic 208A. Decision circuit
203 may, by way of engine-on limiting logic 208A, compare the
currently sensed pinion speed to a threshold pinion speed
reflecting, e.g., a maximum pinion speed above which, bearing/gear
damage or failure may occur. In response, such a determination,
engine-on limiting logic 208A by way of communications circuit 201
may transmit an appropriate control or instruction signal to, e.g.,
motor control 272 (described below) in order to effectuate the
application of regenerative torque vis-a-vis power delivery
mechanism 21 and/or any related components, e.g., torque converter
16, motor 22A, etc.
[0064] It should be understood that engine control component 270
controls the drive (output torque) of engine 14 via the output
control device 14A. Specifically, engine control component 270
controls output control device 14A by way of an electronic throttle
valve controlling the amount of fuel supplied by the fuel injection
device, the ignition timing of the ignition device, etc.
Accordingly, ECU 50 controls the manner in which engine 14 provides
drive power so that engine output required by engine 14 can be
achieved.
[0065] Engine control component 270 drives engine 14 in the
engine-only and HEV travel modes. For example, engine control
component 270 may control when engine 14 is started, e.g., when
switching from EV travel mode to the engine-only travel mode or the
HEV travel mode. For example, engine control component 270 can
instruct engine 14 to revolve resulting in an engine revolution
speed N.sub.E, and the supply of fuel to engine 14 is started via
the output control device 14A. Likewise, engine control component
270 may control when engine 14 is shut off, e.g., when switching
from engine-only or HEV travel mode to EV travel mode. This can
occur when HEV 10 is coasting. However, as noted above, engine 14
may turn on (via an engine-on control signal from engine control
component 270) upon a determination that the pinion speed of the
planetary gear set's pinion gear exceeds a pinion gear speed
threshold. To prevent this from occurring, in certain scenarios,
based on a temporary increase in, e.g., battery SOC limits, or
battery charging rate limits, this engine-on/engine-only travel
mode may be overridden. When hybrid vehicle 10 is to be operated in
EV mode, engine control component 50A outputs a control signal(s)
to output control device 14A for stopping engine 14.
[0066] Motor control component 272 controls actuation of the motor
22A, for example, via the inverter 42. Specifically, electric
energy is supplied from battery 44 to motor 22A via inverter 42.
Motor control component 272 outputs a control signal(s) for driving
motor 22A to rotate and generate positive or negative motor torque
to obtain the output required of the motor 22A. For example, upon
determining that HEV 10 is coasting in an EV travel mode, and that
the pinion gear speed has reached/exceeded (or is approaching its
threshold), motor control component 272 outputs a control signal(s)
instructing inverter 42 to switch phase and change the direction of
the magnetic field applied to motor 22A. This generates negative
motor torque that reduces the speed of the pinion gear, and resists
the forward momentum of HEV 10 so that HEV 10 decelerates.
[0067] It should be understood that engine control 270 and motor
control 272, together may make up a travel mode component 274,
which can, for example, make determinations regarding a travel mode
established in HEV 10 or on the basis of a target driving force. A
determination can be made regarding which travel mode (electric
vehicle (EV), engine-only, HEV) HEV 10 is in on the basis of, e.g.,
vehicle speed N.sub.V, accelerator operation/pedal actuation
amount, A.sub.CC, battery SOC of battery 44, brake operation amount
B, etc. For example, if the battery SOC of battery 44 indicates a
low SOC, travel mode component 274 may determine a need to switch
from an EV/HEV travel mode to an engine-only travel mode.
[0068] As will be described below in greater detail, other
determinations impacting this decision and other actions taken in
response to this decision can be made and/or taken, e.g.,
considering and acting on battery state of charge (SOC) and charge
power limits, respectively, friction braking, etc. Accordingly,
engine-on-limiting circuit 210 may communicate appropriate control
signals to battery control component 278 (which can control one or
more operating aspects/conditions regarding battery 44 and/or
inverter 42), and brake control component 276 to control actuation
of friction brakes. Engine-on-limiting circuit 210 may further
communicate appropriate control signals to motor control 272 for,
e.g., putting motor 22A into a generator mode of operation, and
engine control 270 for, e.g., overriding a default engine-on
control signal.
[0069] It should be understood that vehicle systems 158/ECU 50 may
have other components or aspects with which engine-on-limiting
circuit 210 may communicate with/control/receive information from.
It should be further noted that vehicle systems 158 and ECU 50 are
sometimes described in conjunction with one another as the
above-noted components (and/or other components) may be controlled
or may be functionally implemented as part of ECU 50. However, one
or more of these components may alternatively be implemented as a
"standalone" component, system, or aspect of HEV 10 that operates
outside of, but e.g., in conjunction with ECU 50. For example,
another component 278 may be a navigation component that may
receive location sensor 230 information which can be leveraged by
engine-on-limiting circuit 210 to determine whether HEV 10 is on a
downhill slope while coasting. Further still, it should be
understood that engine-on limiting circuit 210 (or one or more
aspects thereof), may be implemented in or as part of ECU
50/vehicle systems 158.
[0070] FIG. 3 illustrates an example scenario in which HEV 10 is
coasting on a downhill slope from a vehicle operational
perspective. FIG. 3 illustrates two "stages" 300 and 310. A first
stage 300 can refer to a time at which a driver of HEV 10 releases
the accelerator pedal of HEV 10, and begins coasting, e.g., along a
downhill section of road. That is, as illustrated in FIG. 3, the
road profile at the first stage 300 begins to drop from a peak
height (indicating a down grade). Accelerator position at the first
stage 300 goes from some value or percentage down to zero due to
the driver releasing the accelerator pedal, while vehicle speed,
N.sub.V, may begin to increase as HEV 10 begins to pick up speed
from coasting downhill. Engine speed, similar to acceleration will
eventually drop to 0 revolutions per minute (RPM) as a result of
the accelerator pedal being released. It should be understood that
engine speed can be reduced gradually or very sharply. In some
cases, engine speed can be reduced to zero within one second.
[0071] Also at first stage 300, without implementing engine-on
logic 208A (see, FIG. 2), some regenerative torque may be applied.
The amount of regenerative torque capacity can vary by vehicle
(e.g., based on motor specification). With a typical HEV, for
example, approximately 200 Nm of maximum regenerative torque would
be available at the motor. The amount of regenerative torque can be
proportional to the amount of applied brake pedal actuation, until
very low vehicle speed. In this case however, with no brake pedal
being applied, a regenerative torque according to a speed and grade
look-up table can be induced. The table can be defined/configured
to set a "comfortable" level of deceleration feeling for the
driver, which may not change appreciably in value unless the driver
makes a change (vis-a-vis the accelerator pedal, brake pedal, or
changes gearshift position) because it is typically designed to
keep vehicle speed for a typical driving duration. This issue
arises when the driver continues coasting, allowing vehicle speed
to increase, without applying the brakes. It should be understood
that such driving behavior is something "eco-drivers" will perform
to improve fuel economy. For example, a table that can be used may
reflect deceleration/regenerative torque as a function of simulated
simulated gear and propeller shaft speed.
[0072] As HEV 10 continues to coast downhill, the second stage 310
is reached. Under conventional operating logic/control, when the
vehicle speed of HEV 10 exceeds a maximum speed threshold (EOV
speed 312), engine 14 is turned on to protect the motor 22A
hardware, such as the bearings, magnets, etc.
[0073] Under conventional operating logic, engine speed increases
from zero RPMs, and the speed of HEV 10 increases, while the amount
of regenerative torque (from motor 22A) remains constant regardless
of this condition. However, as already noted, this conventional
logic can result in decreased fuel economy due to engine 14 being
turned on and can be detrimental to the driving experience since
the driver has not requested that engine 14 be turned on.
[0074] Accordingly, in one embodiment, as illustrated in FIG. 4,
upon reaching the maximum vehicle speed threshold (EOV speed),
regenerative torque 314 may be added (or the amount of regenerative
torque may be increased from the conventional amount) to the drive
power. This causes HEV 10 to decelerate and reduces the vehicle
speed of HEV 10. This can cause engine 14 to remain in an
engine-off condition (maintaining HEV 10 in an EV travel mode),
i.e., engine RPMs remain at zero at the second stage 310 and after.
Vehicle speed at the second stage 310 and afterwards, does not
increase. Again, in conventional HEVs, vehicle speed, as a result
of coasting downhill, would increase past the EOV speed,
necessitating the engine-on condition. Here, that is not needed as
the vehicle speed is maintained below the EOV speed.
[0075] FIG. 5 is a flowchart illustrating example operations that
can be performed in accordance with one embodiment for adding
regenerative torque to the drive power to avoid an engine-on
condition. At operation 500 (which corresponds to first stage 300
of FIG. 4), the accelerator pedal may be released. This condition
may be sensed by accelerator pedal position sensor 224 (FIG. 2).
This may suggest that HEV 10 is coasting. Based on HEV 10 operating
conditions prior to releasing the accelerator pedal, an initial
regenerative torque amount may be set at operation 502, e.g., by
engine-on limiting circuit 208A. In some embodiments, current HEV
10 operating conditions may be confirmed. Current vehicle operating
conditions including, but not necessarily limited to the following
may be considered when setting the initial regenerative torque
amount: battery 44 SOC, vehicle speed of HEV 10, engine 14 speed,
current travel mode/engine mode, the respective temperatures of
battery 44 and motor 22A, the accelerator pedal position, and
gearshift position. Again, initial regenerative torque amount may
be determined by vehicle speed, in some instances primarily by
vehicle speed. Initial regenerative torque amount can be reflected
as a calibrated curve as part of zero percent accelerator pedal
driving force that simulates what a traditional transmission
provides by engine braking. Other conditions such as battery SOC
can limit the available regenerative torque (e.g., as a battery
approaches a completely full SOC), i.e., the amount of current that
can be generated and put into the battery is limited. This current
value can be impacted by many limitations including motor
temperature and battery temperature. It should be noted that if the
engine is already running, the motor doesn't need to command as
much torque, and the engine can run in fuel cut mode to increase
the pumping losses internal to the engine. This is what occurs, for
example, when the driver shifts to B-range in an HEV, and is
variable in S-range equipped HEVs.
[0076] As HEV 10 progresses past first stage 300 (and HEV 10
continues to coast in EV mode), HEV 10 vehicle speed may be checked
at operation 504. A determination may be made at operation 506
regarding whether HEV 10 is approaching the EOV speed. If the
vehicle speed of HEV 10 is not nearing the EOV speed 312, the
initial amount of regenerative torque (determined at operation 502)
may continue to be applied at operation 508. Checking the vehicle
speed of HEV 10 at operation 504 may be repeated periodically (or
aperiodically, e.g., the closer the vehicle speed of HEV 10
approaches the EOV speed 312, the more frequently vehicle speed is
checked).
[0077] On the other hand, if the vehicle speed of HEV 10 is
approaching the EOV speed 312, a determination is made as to
whether or not the amount of regenerative torque being added is
approaching a regenerative torque limit at operation 510. This
regenerative torque limit may be determined (or dynamically set)
based on, e.g., battery SOC, battery temperature, and/or other
operating conditions. For example, a battery, such as battery 44
may have an optimum SOC level (e.g., 80-85% full), a maximum
operating temperature (above which, battery 44 may begin to degrade
or experience performance degradation) and the like. In some
embodiments, the optimum SOC level may be impacted by forecasted
driving conditions, such as upcoming or current traffic conditions,
upcoming or current road grade, etc. For example, certain logic
used in HEV 10 may optimize battery SOC in terms of the length of a
downhill slope such that battery 44 may be depleted a certain
amount to maximize recouping of energy while traveling the downhill
slope.
[0078] If the amount of regenerative torque being applied is not
nearing the limit, additional regenerative torque may continue to
be added according to a determined EOV speed-to-regenerative torque
amount mapping in order to maintain HEV's speed below the EOV speed
at operation 512. Table 1 below is an example mapping.
TABLE-US-00001 TABLE 1 Maximum Torque Limit (~200 Nm) Small Small
Small Small Small Small EOV Speed Small Small Small Small Medium
Medium Limit Medium Medium Medium Medium Large Large (45 mph)
Medium Medium Medium Medium Large Large Medium Medium Medium Medium
Large Large
[0079] In Table 1, the "values" can represent how much additional
torque would be added based on a current value in the mapping. For
example, as the HEV approaches the EOV speed limit, torque can be
increased as much as possible to prevent over-running the limit,
until the torque gets closer to the torque limit. The actual values
could be approximately 5 Nm in the "small" case to 20 to about 50
Nm in the "large" case, for example.
[0080] If the amount of regenerative torque is nearing the limit,
the amount of regenerative torque is maintained at its current
level at operation 514 until conventional engine-on logic initiates
and engine 14 turns on (to offset the EOV speed) at operation
516.
[0081] It should be understood that the above-described operations
of FIG. 5 may be performed by engine-on limiting logic 208A of
engine-on limiting circuit 210. For example, the initial amount of
regenerative torque to be applied to the drive power can be set by
calculations performed vis-a-vis engine-on limiting logic 208A
and/or vehicle/pinion gear speed to regenerative torque mappings
maintained in memory 208. One or more of the aforementioned sensors
52 can transmit sensed data, such as accelerator pedal position,
road profile/grade, vehicle speed, etc. which can be received by
communications circuit 201 and processed by processor 206 in
accordance with engine-on limiting logic 208A embodied by the
operations of FIG. 5.
[0082] FIG. 6 illustrates another example scenario in which HEV 10
is coasting on a downhill slope from a vehicle operational
perspective, along with one or more related actions for preventing
an engine-on condition from occurring. Similar to FIGS. 3 and 4,
FIG. 6 illustrates the occurrence of stages 300 and 310. A first
stage 300 can refer to a time at which a driver of HEV 10 releases
the accelerator pedal of HEV 10, and begins coasting, e.g., along a
downhill section of road. This is evidenced by the road profile at
the first stage 300, which begins to drop from a peak height
(indicating a downhill grade). Accelerator position at the first
stage 300 goes from some value or percentage down to zero due to
the driver releasing the accelerator pedal, while vehicle speed,
N.sub.V, may begin to increase as HEV 10 begins to pick up speed
from coasting downhill. Engine speed, similar to acceleration will
eventually drop to zero revolutions per minute (RPM) as a result of
the accelerator pedal being released. Also, at first stage 300,
without implementing engine-on logic 208A, some regenerative torque
may be applied. As HEV 10 continues to coast downhill, the second
stage 310 is reached.
[0083] However, FIG. 6 illustrates an intermediate stage 304, which
coincides with the engine speed dropping to zero RPM. That is, in
accordance with one embodiment of the systems and technologies
disclosed herein, a method for preventing the engine-on condition
during coasting can involving operating engine 14 of HEV 10 in a
fuel cut mode. For example, engine-on limiting logic 208A may
instruct or send a control signal to engine control component 270
to stop injecting fuel into engine 14, e.g., by shutting off the
fuel injector(s) and/or reducing injector pulse. In doing so, as
engine speed rises (upon nearing or reaching the EOV speed at stage
310).
[0084] Again, and similar to FIGS. 3 and 4, FIG. 6 illustrates that
as HEV 10 continues to coast downhill, stage 310 is reached which
reflects when the vehicle speed of HEV 10 (reaches or exceeds a
maximum speed threshold (EOV speed). Conventionally, it is at or
near this stage when engine 14 would be turned on, and engine speed
would increase (316A) to protect the motor 22A hardware, the
planetary gear set, and battery 44. Under conventional operating
logic, engine speed increases from zero RPMs, and the vehicle speed
of HEV 10 increases, while the amount of regenerative torque (318A)
from motor 22A remains constant regardless of this condition.
Accordingly, battery SOC (322A) also increases as battery 44 will
absorb the addition energy or power (will be charged) vis-a-vis the
regenerative torque.
[0085] As also previously illustrated in FIG. 4, upon reaching the
maximum vehicle speed threshold (EOV speed), regenerative torque
318B may be added (or the amount of regenerative torque may be
increased from the conventional amount) to the drive power. This
causes HEV 10 to decelerate and reduces the vehicle speed of HEV
10. This can cause engine 14 to remain in an engine-off condition
(maintaining HEV 10 in an EV travel mode), i.e., engine RPMs remain
at zero at the second stage 310 and after (316B). Vehicle speed at
the second stage 310 and afterwards, does not increase.
Alternatively, however, by operating engine 14 in a fuel cut mode
as alluded to above, engine speed may increase at stage 310, but
still remain below the "unchecked" engine speed if no compensatory
action(s) were taken (316C). Accordingly, the engine-on condition
can still be avoided in accordance with this embodiment.
[0086] Moreover, referring to the relative pinion gear speed
illustrated in FIG. 6, it can be appreciated that pinion relative
speed may rise at stage 304 (due to the downhill coasting
condition). As noted above, the planetary gear set and associated
componentry of HEV 10 should also be protected from damage or
failure. Thus, this increase in pinion relative speed (320A), if
left unchecked, can be deleterious to the operation of HEV 10. FIG.
6 illustrates yet another intermediate stage 308, where the pinion
relative speed increases even more due to the increased downhill
grade (evidenced by the road profile). However, by operating engine
14 of HEV 10 in a fuel cut mode as described above, at stage 310,
pinion relative speed can be reduced (320C) as well so that the
engine-on condition or threshold is not reached.
[0087] Regarding the addition of increased regenerative torque to
the drive system of HEV 14 during coasting conditions, it should be
understood that in some embodiments, the amount of regenerative
torque added can be governed by road grade. For example, the amount
of regenerative torque that is to be added can be mapped according
to how steep the downhill grade of a road may be. Between stages
300 and 308, for example, it can be appreciated that the road
profile is a relatively constant downhill grade that begins to
level off. In some examples, a relatively constant downhill grade
may be, e.g., approximately two to eight percent grade
(temporarily) depending on start speed. If start speed is
relatively low, a steeper grade may be handled. Accordingly, the
amount of regenerative torque that is added (318D) is
commensurately reduced as that leveling off occurs. Between stages
308 and 310, the road profile indicates that the downhill grade
levels off even more. Accordingly, the amount of regenerative
torque needed to offset the EOV speed and/or pinion relative speed
can decrease. After stage 310, where the road profile levels out
further, again, the amount of regenerative torque is commensurately
reduced. It should be appreciated that the impact to pinion
relative speed (320D) is to reduce it and remain below the
engine-on pinion relative speed threshold. Due to the increased
regenerative torque being generated, the battery SOC may increase
commensurately (322D). It should be understood that in this
context, pinion relative speed can be the speed differential
between S0 and engine 14 (FIG. 1) which is zero. As the engine
speed is zero, the pinions are spinning close to, e.g., 10,000 rpm
as they rotate around the sun gear. Moreover, as battery 42
recharges, the ability to apply torque and control based on that
speed differential is reduced. As alluded to above, the state of
battery 44 may also be taken into account when attempting to reduce
pinion relative speed and/or vehicle speed to avoid an engine-on
condition when HEV 10 is coasting. For example, in some
embodiments, a temporary increase in charging rate may be enabled,
allowing battery 44 to be charged regeneratively above its normal
or default maximum charging rate. For example, a standard charging
rate of 35 kW at approximately 200 amps, (although this can differ
depending on motor capacity and inverter characteristics) whereas
in accordance with one embodiment, the charging rate can be
increased to, e.g., 40 kW at approximately 200 amps. Accordingly,
the amount of regenerative torque (318E), which recharges battery
44 thereby increasing the battery SOC (322E), can be increased and
applied to the drive power, again reducing the pinion relative
speed (320E). It should be noted that this (and other increases in
other vehicle operating conditions) is temporary, and not intended
to be a prolonged increase. As noted above, batteries may
experience quicker degradation due to increased charging rates,
increased battery SOC, etc.
[0088] Various embodiments as will be described in greater detail
below, may also use feedback logic to ensure that such increases
are temporary and/or the state or condition of certain HEV 10
hardware is not damaged. As alluded to above, power limitation can
be a function of battery SOC and can also factor into this
scenario. In some embodiments the engine-on limiting logic 208A can
begin reducing charging power limits as battery SOC begins to
approach (but remains) less than approximately 80%, for example.
The logic will reduce power from, e.g., 35 kW down to 0 kW
gradually. Regenerative torque is limited by this power (again
speed is set by vehicle speed and gear ratio) so torque can be
cut/reduced in the same or similar fashion. Motor temperature as
mentioned previously, can also be a consideration.
[0089] As noted above, vehicles utilizing two motors (such as HEV
10), one motor, e.g., motor 22A, can be used as an electric motor
for differential operation, while another motor, e.g., motor 22B
can be used for running the vehicle. Accordingly, it should be
understood that in some embodiments, temperature of motor 22B (for
generating regenerative torque) can be considered alone, while in
some embodiments, temperature of both motors 22A and 22B can be
considered as will be described below.
[0090] Still referring to the state of battery 44, yet another
method of avoiding the engine-on condition can involve temporarily
increasing the battery SOC upper limit. This allows for temporary
over-charging of battery 44 (322F) vis-a-vis increased regeneration
torque being generated and charging battery 44. This can be done in
conjunction with, e.g., the application of additional regenerative
torque (322B), boosted charging rate (322E). Further still, in
accordance with another embodiment, a temporary charging
temperature increase (322G) for battery 44 may be enabled in order
to accommodate the added regenerative torque (and corresponding
increase in heat). Enabling a temporary operating temperature
increase would avoid the need for increasing the battery SOC limit
(described above), providing yet another alternative mechanism for
absorbing the additional energy associated with increased
regenerative torque application to the drive power/drive train of
HEV 10.
[0091] FIGS. 7A and 7B illustrate a flow chart of example
operations that can be performed by engine-on limiting logic 208A
executed by processor 206 (FIG. 2) to limit an engine-on condition
in accordance with one embodiment. Similar to the method of FIG. 5,
the method of FIG. 7A may begin at operation 700 with the
accelerator pedal being released by the driver. This may correspond
with the stage 300 of FIG. 6. Again, sensor 224 may sense and
report this condition to engine-on limiting circuit 208A to suggest
that HEV 10 is coasting. At the same/approximately the same time,
the following operating conditions and/or road conditions may be
determined or obtained: battery 44 SOC; vehicle speed; engine
speed; engine mode; battery 44 temperature; motor 22 temperature;
gearshift position; HVAC operating conditions/settings; location;
and/or road grade. Any one or more of the aforementioned sensors 52
may be used to ascertain these conditions. It should be understood
that in this context, engine mode can refer to whether the engine
is on with no load, on with a load, on under fuel cut mode
(motoring), or shutting down. This can aid in identifying what is
the current engine control strategy, and what to anticipate for,
e.g., immediate future engine behavior.
[0092] At operation 702, a required battery SOC may be calculated,
the required battery SOC being an SOC that allows HEV 10 to
complete traversing a current downhill slope without engaging
engine 14. This required battery SOC can be considered when setting
an initial regenerative torque amount to be applied at operation
712. The initial amount of regenerative torque to be applied can be
based on a mapping (e.g., table stored on memory 208) between road
grade, duration to travel the road grade, and regenerative torque.
For example, location of HEV 10 may be determined using location
sensor/GPS receiver 230 along with a length of a current downhill
grade being traversed by HEV 10. In some embodiments, road grade
can be determined from known location/GPS information, or gravity
sensor 232 along with calculated road load and vehicle speed based
on sensor 214 can be used to determine, e.g., more accurate road
grade. Based on the determined road grade and duration, a
regenerative torque can be selected. Based on the selected
regenerative torque, it can be determined whether or not
regenerative torque can be added (without overcharging battery 44)
or regenerative torque can be used to charge battery 44 as it
coasts (e.g., if the battery SOC is insufficient to complete
traversing the downhill grade without additional power).
[0093] At operation 704, a check may be performed to determine if
charging power of battery 44 can be increased, and if so, whether
engine 14 can be kept in an engine-off condition (e.g., EV travel
mode). Whether or not charging power of battery 44 can be based on
current operating characteristics of battery 44. For example,
battery 44 may currently be in a state where additional charging
power cannot be added without harming or damaging battery 44. For
example, due to previous traffic, road grade, or other
operating/road conditions, battery 44 may not be able to support
increased charging power. However, increased charge power may be
possible, while keeping engine 14 off, in which case, at operation
706, the charging power limit of battery 44 may be increased. As
discussed above in conjunction with FIG. 6, increased charging
power may allow for additional regenerative torque to be added to
the drive power of HEV 10 to protect the pinion gears and
associated hardware/componentry of HEV 10. Accordingly, the
increased charging power may be considered when setting the amount
of initial regenerative torque at operation 712.
[0094] If charging power cannot be increased, at operation 708, a
check is performed to determine whether or not the battery SOC
limit can be increased while keeping engine 14 off. Again, as
described above with respect to FIG. 6, battery SOC can be
increased in order to support increased regenerative torque being
added to the drive power of HEV 10 so that the pinion relative
speed can be reduced, thereby avoiding the need to turn engine 14
on. If the battery SOC cannot be increased (again, as noted above,
due to current battery state or condition), the initial amount of
regenerative torque can be set without considering the temporary
battery SOC increase.
[0095] At operation 714, after the initial regenerative torque
amount is set, the pinion speed may be checked. Again, various
embodiments are directed to ensuring that the pinion gear does not
reach or exceed the pinion gear speed limit. Engine-on limiting
logic 208A may cause processor 206 to communicate with pinion speed
sensor 228 via communications circuit 201 to retrieve current
pinion speed data. It should also be understood that pinion speed
may refer to pinion relative speed, described above. Accordingly,
other sensors 234 capable of or configured to measure speeds of
associated components, e.g., the speed of ring gear R0, the speed
of rotation of carrier CA0, etc. may be queried to determine the
relative speed of the pinion gear.
[0096] At operation 716, another check can be performed to
determine whether the pinion speed is approaching the pinion speed
limit (overspeed). Again, pinion speed sensor 228 and/or other
sensors 234 may be queried to obtain now-current pinion/relative
speed(s). It should be understood that engine-on limiting circuit
210 need not explicitly request a current speed. Rather, these
sensors may periodically or a periodically transmit their
respective sensor data to engine-on limiting circuit 210 to be
evaluated. For example, this sensor data may be transmitted via
communications circuit 201 and stored or buffered/cached in memory
208, which can be accessed by processor 206 executing engine-on
limiting logic 208A and compared to a set overspeed value. If the
pinion speed is not approaching the pinion speed limit, motor
control component 272 may continue to generate/apply the current
amount of regenerative torque. This process of checking pinion
speed and continuing to generate regenerative torque may continue
until the pinion speed begins to approach the pinion speed limit or
the downhill grade is complete at 720.
[0097] Referring now to FIG. 7B if the pinion speed does begin to
approach the pinion speed limit, a check is performed to determine
if the regenerative torque being generated is approaching its limit
at operation 722. Again, regenerative torque can be thought of or
reflected as a calibrated curve based on recreating a desired level
of deceleration (gravitational force equivalent) feeling for the
driver while coasting. The limit can be set by the maximum amount
of motor torque as set by the motor's
specification/characteristics. In a regular use case scenario,
engine pumping loss torque can be added to generate more overall
deceleration torque to meet driver demand. Battery SOC and
motor/battery temperatures can affect the total available motor
torque to use in this control logic. If the amount of regenerative
torque being generated is not approaching the regenerative torque
limit, additional regenerative torque may continue to be generated
and added to the drive power of HEV 10 at operation 724. The
aforementioned road grade to duration to regenerative torque
mapping may be used to determine how much regenerative torque can
be generated. As noted above, increased regenerative torque or
negative torque can positively contribute to fuel efficiency by
keeping motor 22 operative in EV mode.
[0098] It should be noted that generally, regenerative torque can
be limited by the temperature of motor 22B, as motor 22B generally
provides the regenerative torque/drive power in EV mode. That is,
vehicle 10 may operate in EV mode, in part, by preventing engine 14
from turning and providing a torque balance for motor 22A to push
against through the use of a one-way clutch. However, in some
instances, a vehicle may operate in a dual motor EV mode, where
both motors provide drive power through the use of a clutch device
that enables motor 22A to also provide regenerative torque. Such a
clutch can provide counter-torque in both positive and negative
directions. Accordingly, in some embodiments, additional
regenerative torque can be provided by motor 22A under certain
conditions, including but not necessarily limited to the following:
when motor 22B temperature increases to the point that the amount
of regenerative torque that can be provided is limited; when motor
22B is at maximum capacity, and more regenerative torque is being
requested as described in accordance with various embodiments
herein; and/or vehicle speed and the amount of regenerative torque
requests results in decreased efficiency in the operation of motor
22B if motor 22B were to solely provide regenerative torque (versus
motor 22B and 22A providing the regenerative torque).
[0099] Thus, in some embodiments, the logic/methods described
herein can be adapted such that as the temperature of one motor,
e.g., motor 22B (the one providing regenerative torque by default),
increases, a certain percentage of the regenerative torque to be
generated is requested of motor 22A. That is, regenerative torque
generation responsibility can, in some instances, be relegated to a
second motor. In some embodiments the higher the temperature of
motor 22B (or the closer the temperature of motor 22B gets to a
motor over-temperature limit or threshold), the more regenerative
torque motor 22A will be configured/requested to generate. In some
embodiments, extra regenerative torque may be deferred to motor 22A
(or a portion thereof, e.g., extra regenerative torque request plus
some given amount to aid in reducing the load on motor 22B). In
some embodiments, the efficiency of each motor may be considered,
along with the gearing ratio between the motors in the planetary
gear set. In some embodiments, it may be a combination of the
aforementioned scenarios. It should be noted that in some
embodiments, maps can be generated for each of the aforementioned
scenarios or possible regenerative torque responsibility handoffs
to another motor, such that appropriate amounts or percentages of
regenerative torque to be generated by the second motor can be
determined. In still other embodiments, such mappings can be
overlaid with one another to determine an ideal motor-motor
combination for overall efficiency.
[0100] If, however, the regenerative torque limit is being
approached, a check is performed to determine if the battery SOC is
approaching the maximum charge limit of battery 44 at operation
726. The maximum charge limit may be that charge, which exceed,
negatively impacts battery performance, such as a reduction in
charge capacity. If battery 44 is not approaching this maximum
charge limit, the charge limit may be temporarily increased as
described above with respect to FIG. 6. Temporarily increasing the
charge limit allows additional regenerative to be generated which
can then be used to charge battery 44, optimizing the recuperation
of energy and keeping engine 14 off. It should be understood that
this temporary increase in charge limit takes into account an
"absolute" charge limit that, e.g., cannot be surpassed, even
temporarily, as doing so would permanently harm battery 44 or cause
battery 44 to fail.
[0101] If battery 44 is approaching the maximum charge limit, a
check is performed to determine if the battery SOC is greater than
a determined threshold amount at operation 730. If the battery SOC
of battery 44 is not greater than the determined threshold, the
battery SOC may be temporarily increased at operation 732 (as
described above in conjunction with FIG. 6). However, as with the
charge limit, this temporary increase may be calculated relative to
an absolute maximum battery SOC that cannot be or should not be
surpassed, even temporarily.
[0102] If the battery SOC is greater than the threshold, at
operation 734, engine motoring may be enabled, i.e., engine 14 may
be operated in a fuel cut mode to absorb any additional regenerated
energy to prevent the engine-on condition from occurring. In some
embodiments, friction brakes can be engaged at operation 736
vis-a-vis brake control component 276. Operating (in this case,
dragging) the friction brakes of HEV 10 can slow down pinion speed.
This may be useful when HEV 10 cannot temporarily increase battery
operating conditions, and/or when other operating conditions are
"full" or at maximum in electrified drive power mode.
[0103] At operation 738, regenerative torque addition may be held
at its current level until the default or conventional engine-on
logic initiates, and engine 14 is turned on at 740. This engine-on
logic may reside in ECU 50 or engine control component 270. In some
embodiments, the engine-on condition may be initiated by the driver
of HEV 10, and/or the battery SOC is at its absolute maximum. In
some embodiments, the amount of regenerative torque
requested/calculated by engine-on limiting circuit 210 exceeds the
regenerative capabilities of HEV 10, and/or some other request,
such as the driver or passenger enabling some HVAC component, or
other vehicle component requires engine 14 to be turned on in order
to support the request.
[0104] As used herein, the term component might describe a given
unit of functionality that can be performed in accordance with one
or more embodiments of the present application. As used herein, a
component might be implemented utilizing any form of hardware,
software, or a combination thereof. For example, one or more
processors, controllers, ASICs, PLAs, PALs, CPLDs, FPGAs, logical
components, software routines or other mechanisms might be
implemented to make up a component. Various components described
herein may be implemented as discrete components or described
functions and features can be shared in part or in total among one
or more components. In other words, as would be apparent to one of
ordinary skill in the art after reading this description, the
various features and functionality described herein may be
implemented in any given application. They can be implemented in
one or more separate or shared components in various combinations
and permutations. Although various features or functional elements
may be individually described or claimed as separate components, it
should be understood that these features/functionality can be
shared among one or more common software and hardware elements.
Such a description shall not require or imply that separate
hardware or software components are used to implement such features
or functionality.
[0105] Where components are implemented in whole or in part using
software, these software elements can be implemented to operate
with a computing or processing component capable of carrying out
the functionality described with respect thereto. One such example
computing component is shown in FIG. 8. Various embodiments are
described in terms of this example-computing component 800. After
reading this description, it will become apparent to a person
skilled in the relevant art how to implement the application using
other computing components or architectures.
[0106] Referring now to FIG. 8, computing component 800 may
represent, for example, computing or processing capabilities found
within computer processing units or any other type of
special-purpose or general-purpose computing devices as may be
desirable or appropriate for a given application or environment.
Computing component 800 might also represent computing capabilities
embedded within or otherwise available to a given device. For
example, a computing component might be found in other electronic
devices such as, for example, electronic devices that might include
some form of processing capability.
[0107] Computing component 800 might include, for example, one or
more processors, controllers, control components, or other
processing devices. This can include a processor, and/or any one or
more of the components making up electronic control device 100
and/or its component parts, hydraulic control circuit 80, or other
components or elements of vehicle, e.g., signal sensors, etc.
Processor 804 might be implemented using a general-purpose or
special-purpose processing engine such as, for example, a
microprocessor, controller, or other control logic. Processor 804
may be connected to a bus 802. However, any communication medium
can be used to facilitate interaction with other components of
computing component 800 or to communicate externally.
[0108] Computing component 800 might also include one or more
memory components, simply referred to herein as main memory 808.
For example, random access memory (RAM) or other dynamic memory,
might be used for storing information and instructions to be
executed by processor 804. Main memory 808 might also be used for
storing temporary variables or other intermediate information
during execution of instructions to be executed by processor 804.
Computing component 800 might likewise include a read only memory
("ROM") or other static storage device coupled to bus 802 for
storing static information and instructions for processor 804.
[0109] The computing component 800 might also include one or more
various forms of information storage mechanism 810, which might
include, for example, a media drive 812 and a storage unit
interface 820. The media drive 812 might include a drive or other
mechanism to support fixed or removable storage media 814. For
example, a hard disk drive, a solid state drive, a magnetic tape
drive, an optical drive, a compact disc (CD) or digital video disc
(DVD) drive (R or RW), or other removable or fixed media drive
might be provided. Storage media 814 might include, for example, a
hard disk, an integrated circuit assembly, magnetic tape,
cartridge, optical disk, a CD or DVD. Storage media 814 may be any
other fixed or removable medium that is read by, written to or
accessed by media drive 812. As these examples illustrate, the
storage media 814 can include a computer usable storage medium
having stored therein computer software or data.
[0110] In alternative embodiments, information storage mechanism
810 might include other similar instrumentalities for allowing
computer programs or other instructions or data to be loaded into
computing component 800. Such instrumentalities might include, for
example, a fixed or removable storage unit 822 and an interface
820. Examples of such storage units 822 and interfaces 820 can
include a program cartridge and cartridge interface, a removable
memory (for example, a flash memory or other removable memory
component) and memory slot. Other examples may include a PCMCIA
slot and card, and other fixed or removable storage units 822 and
interfaces 820 that allow software and data to be transferred from
storage unit 822 to computing component 800.
[0111] Computing component 800 might also include a communications
interface 824. Communications interface 824 might be used to allow
software and data to be transferred between computing component 800
and external devices. Examples of communications interface 824
might include a modem or softmodem, a network interface (such as an
Ethernet, network interface card, WiMedia, IEEE 802.XX or other
interface). Other examples include a communications port (such as
for example, a USB port, IR port, RS232 port Bluetooth.RTM.
interface, or other port), or other communications interface.
Software/data transferred via communications interface 824 may be
carried on signals, which can be electronic, electromagnetic (which
includes optical) or other signals capable of being exchanged by a
given communications interface 824. These signals might be provided
to communications interface 824 via a channel 828. Channel 828
might carry signals and might be implemented using a wired or
wireless communication medium. Some examples of a channel might
include a phone line, a cellular link, an RF link, an optical link,
a network interface, a local or wide area network, and other wired
or wireless communications channels.
[0112] In this document, the terms "computer program medium" and
"computer usable medium" are used to generally refer to transitory
or non-transitory media. Such media may be, e.g., memory 808,
storage unit 820, media 814, and channel 828. These and other
various forms of computer program media or computer usable media
may be involved in carrying one or more sequences of one or more
instructions to a processing device for execution. Such
instructions embodied on the medium, are generally referred to as
"computer program code" or a "computer program product" (which may
be grouped in the form of computer programs or other groupings).
When executed, such instructions might enable the computing
component 800 to perform features or functions of the present
application as discussed herein.
[0113] It should be understood that the various features, aspects
and functionality described in one or more of the individual
embodiments are not limited in their applicability to the
particular embodiment with which they are described. Instead, they
can be applied, alone or in various combinations, to one or more
other embodiments, whether or not such embodiments are described
and whether or not such features are presented as being a part of a
described embodiment. Thus, the breadth and scope of the present
application should not be limited by any of the above-described
exemplary embodiments.
[0114] Terms and phrases used in this document, and variations
thereof, unless otherwise expressly stated, should be construed as
open ended as opposed to limiting. As examples of the foregoing,
the term "including" should be read as meaning "including, without
limitation" or the like. The term "example" is used to provide
exemplary instances of the item in discussion, not an exhaustive or
limiting list thereof. The terms "a" or "an" should be read as
meaning "at least one," "one or more" or the like; and adjectives
such as "conventional," "traditional," "normal," "standard,"
"known." Terms of similar meaning should not be construed as
limiting the item described to a given time period or to an item
available as of a given time. Instead, they should be read to
encompass conventional, traditional, normal, or standard
technologies that may be available or known now or at any time in
the future. Where this document refers to technologies that would
be apparent or known to one of ordinary skill in the art, such
technologies encompass those apparent or known to the skilled
artisan now or at any time in the future.
[0115] The presence of broadening words and phrases such as "one or
more," "at least," "but not limited to" or other like phrases in
some instances shall not be read to mean that the narrower case is
intended or required in instances where such broadening phrases may
be absent. The use of the term "component" does not imply that the
aspects or functionality described or claimed as part of the
component are all configured in a common package. Indeed, any or
all of the various aspects of a component, whether control logic or
other components, can be combined in a single package or separately
maintained and can further be distributed in multiple groupings or
packages or across multiple locations.
[0116] Additionally, the various embodiments set forth herein are
described in terms of exemplary block diagrams, flow charts and
other illustrations. As will become apparent to one of ordinary
skill in the art after reading this document, the illustrated
embodiments and their various alternatives can be implemented
without confinement to the illustrated examples. For example, block
diagrams and their accompanying description should not be construed
as mandating a particular architecture or configuration.
* * * * *