U.S. patent application number 17/668702 was filed with the patent office on 2022-08-18 for vehicle control system.
The applicant listed for this patent is Mazda Motor Corporation. Invention is credited to Daisaku Ogawa, Daisuke Umetsu.
Application Number | 20220260029 17/668702 |
Document ID | / |
Family ID | |
Filed Date | 2022-08-18 |
United States Patent
Application |
20220260029 |
Kind Code |
A1 |
Ogawa; Daisaku ; et
al. |
August 18, 2022 |
VEHICLE CONTROL SYSTEM
Abstract
A control system for a vehicle is provided, which includes a
driving force source configured to generate torque for driving
drive wheels, a steering angle related value sensor configured to
detect a steering angle related value of a steering device of the
vehicle, a grille shutter configured to adjust an
opening-and-closing degree of an opening formed in a front surface
of a vehicle body, and a controller configured to control the
torque to control a vehicle attitude based on the steering angle
related value. Based on the steering angle related value, when the
controller determines that a turning operation of the steering
device is performed, it performs a torque decreasing control for
reducing the torque to add deceleration to the vehicle, and when
the grille shutter opening is large, the controller increases the
torque reduction amount in the torque decreasing control more than
when the opening is small.
Inventors: |
Ogawa; Daisaku; (Aki-gun,
JP) ; Umetsu; Daisuke; (Aki-gun, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Mazda Motor Corporation |
Hiroshima |
|
JP |
|
|
Appl. No.: |
17/668702 |
Filed: |
February 10, 2022 |
International
Class: |
F02D 41/12 20060101
F02D041/12; F02D 41/02 20060101 F02D041/02; F02P 5/145 20060101
F02P005/145 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 17, 2021 |
JP |
2021-023205 |
Claims
1. A control system for a vehicle, the control system comprising: a
driving force source configured to generate torque for driving
drive wheels of the vehicle; a steering angle related value sensor
configured to detect a steering angle related value of a steering
device of the vehicle; a grille shutter configured to adjust an
opening-and-closing degree of an opening formed in a front surface
of a body of the vehicle; and a controller configured to control
the torque generated by the driving force source to control a
vehicle attitude based on the steering angle related value,
wherein, when the controller determines that a turning operation of
the steering device is performed based on the steering angle
related value, the controller performs a torque decreasing control
that reduces the torque generated by the driving force source to
add deceleration to the vehicle, and when the opening of the grille
shutter is large, the controller increases the reduction amount of
the torque in the torque decreasing control more than when the
opening is small.
2. The control system of claim 1, wherein the grille shutter is
configured to adjust the opening-and-closing degree of the opening
up to a fully closed state.
3. The control system of claim 2, wherein the steering angle
related value is a steering angle
4. The control system of claim 3, wherein the driving force source
includes an internal combustion engine, and the controller controls
the torque generated by the internal combustion engine.
5. The control system of claim 1, wherein the steering angle
related value is a steering angle.
6. The control system of claim 1, wherein the driving force source
includes an internal combustion engine, and the controller controls
the torque generated by the internal combustion engine.
7. The control system of claim 1, wherein the steering angle
related value is one of a steering angle, a yaw rate, and a lateral
acceleration.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a control system for a
vehicle, which controls attitude of the vehicle according to
steering.
BACKGROUND OF THE DISCLOSURE
[0002] Conventionally, a technique is known for controlling the
vehicle attitude by causing deceleration or acceleration in the
vehicle according to a driver's operation of a steering wheel to
improve the response and the stability of the vehicle behavior with
respect to the steering operation. For example, when the steering
wheel is turned in one direction, the driving force of the vehicle
is reduced to add the deceleration. This control increases the load
of front wheels corresponding to the turning of the steering wheel,
and therefore, the cornering force of the front wheels increases.
Thus, the turnability of the vehicle in the early stage of the
curve entry improves, and the response and the steering stability
for the turning operation of the steering improve.
[0003] Meanwhile, for the purpose of improving fuel efficiency,
etc., a grille shutter is used to adjust the opening in the front
surface of the vehicle to adjust an amount of external air flowing
into the engine bay to perform a temperature control for the engine
coolant and the lubricant. Here, since the traveling air resistance
of the vehicle changes when the grille shutter is opened or closed
during the control for the vehicle attitude described above,
variation arises in the deceleration of the vehicle, and therefore,
the planned vehicle attitude control may not be achieved.
Therefore, for example, JP6481745B proposes a control device for
the vehicle, which reduces the reduction of the driving force by
the vehicle attitude control when the state of the grille shutter
changes to increase the traveling air resistance (i.e., when the
opening of the grille shutter increases).
[0004] In the meantime, when the opening of the grille shutter is
changed and the amount of the external air flowing into the engine
bay is changed, the pressure inside the engine bay is changed with
the change in the traveling air resistance, and therefore, the
aerodynamic lift which biases a front part of the vehicle upward
changes. As a result, this changes the load of the front wheels and
the cornering force changes. However, since the conventional
technique such as one disclosed in JP6481745B does not take the
change in the lift of the vehicle front part accompanying the
change in the opening of the grille shutter into consideration, the
response to the turning operation of the steering wheel may not be
improved, or the response may be adversely increased excessively.
For example, when the opening of the grille shutter is increased,
the pressure inside the engine bay increases. Therefore, the lift
which acts on the vehicle front part increases, and the load of the
front wheels decreases. In this case, according to the technique
disclosed in JP6481745B, since the reduction of the driving force
by the vehicle attitude control is reduced when the opening of the
grille shutter increases, it further decreases the load of the
front wheels. As the result, the cornering force of the front
wheels decreases, and the improvements in the response or the
steering stability for the turning operation of the steering may
not be obtained. Thus, according to the conventional technique, by
changing the opening of the grille shutter, the response and the
steering stability for the turning operation of the steering may
change. Therefore, it may cause the driver discomfort.
SUMMARY OF THE DISCLOSURE
[0005] The present disclosure is made in view of solving the
problems described above, and one purpose thereof is to provide a
control system for a vehicle which controls attitude of the vehicle
according to steering, capable of achieving response and steering
stability which are consistent with operation of a steering wheel,
without being influenced by an opening of a grille shutter.
[0006] According to one aspect of the present disclosure, a control
system for a vehicle is provided, which includes a driving force
source configured to generate torque for driving drive wheels of
the vehicle, a steering angle related value sensor configured to
detect a steering angle related value of a steering device of the
vehicle, a grille shutter configured to adjust an
opening-and-closing degree of an opening formed in a front surface
of a body of the vehicle, and a controller configured to control
the torque generated by the driving force source to control a
vehicle attitude based on the steering angle related value. When
the controller determines that a turning operation of the steering
device is performed based on the steering angle related value, the
controller performs a torque decreasing control for reducing the
torque generated by the driving force source to add deceleration to
the vehicle. When the opening of the grille shutter is large, the
controller increases the reduction amount of the torque in the
torque decreasing control more than when the opening is small.
[0007] According to this configuration, although when the opening
of the grille shutter increases during the execution of the torque
decreasing control, the aerodynamic lift which acts on the front
part of the vehicle increases, since the load added to the drive
wheel (front wheels) increases by increasing the reduction amount
of the torque in the torque decreasing control, it can suppress the
change in the cornering power of the front wheels resulting from
the change in the opening of the grille shutter. Therefore, the
response and the steering stability which are consistent with the
operation of the steering device (steering wheel) can be obtained,
without being influenced by the opening of the grille shutter.
[0008] The grille shutter may be configured to adjust the
opening-and-closing degree of the opening up to a fully closed
state.
[0009] According to this configuration, while preventing an
occurrence of discomfort for a driver, a forward deceleration can
be promptly applied to the vehicle during the turning operation
after a returning operation of the steering wheel is performed and
then the steering wheel passes through the neutral position.
Therefore, the maneuverability and the stability during the turning
operation of the steering wheel after passing the neutral position
can be improved to smoothen the behavior of the vehicle.
[0010] The steering angle related value may be a steering angle.
According to this configuration, the vehicle attitude can be
controlled promptly to improve the response and the stability of
the vehicle behavior with respect to the driver's steering
operation.
[0011] The driving force source may include an internal combustion
engine, and the controller controls the torque generated by the
internal combustion engine.
[0012] According to this configuration, in the vehicle which highly
requires the adjustment of the opening of the grille shutter in
order to improve the fuel efficiency, etc. of the engine, the
response and the steering stability which are consistent with the
operation of the steering wheel can be obtained without being
influenced by the opening of the grille shutter.
[0013] The steering angle related value may be one of a steering
angle, a yaw rate, and a lateral acceleration.
BRIEF DESCRIPTION OF DRAWINGS
[0014] FIG. 1 is a block diagram schematically illustrating the
overall configuration of a vehicle according to one embodiment of
the present disclosure.
[0015] FIG. 2 is a cross-sectional view illustrating a front part
of the vehicle mounted with a control device for the vehicle
according to this embodiment, when seen from the left side.
[0016] FIG. 3 is a diagram illustrating a relationship between an
opening of a grille shutter and a cornering power of front
wheels.
[0017] FIG. 4 is a block diagram illustrating an electric
configuration of the vehicle according to this embodiment.
[0018] FIG. 5 is a flowchart of a torque decreasing control
processing according to this embodiment.
[0019] FIG. 6 is a flowchart of a reducing torque setting
processing according to this embodiment.
[0020] FIG. 7 is a map illustrating a relationship between a
steering speed and an additional deceleration according to this
embodiment.
[0021] FIG. 8 is a map illustrating a relationship between the
opening of the grille shutter and a correction gain to the reducing
torque according to this embodiment.
[0022] FIG. 9 is a time chart when performing the torque decreasing
control according to this embodiment.
DETAILED DESCRIPTION OF THE DISCLOSURE
[0023] Hereinafter, a control system for a vehicle according to one
embodiment of the present disclosure is described with reference to
the accompanying drawings.
<Configuration of Vehicle>
[0024] First, referring to FIGS. 1 and 2, the vehicle to which the
control system for the vehicle according to this embodiment is
applied is described. FIG. 1 is a block diagram schematically
illustrating the overall configuration of the vehicle according to
this embodiment, and FIG. 2 is a cross-sectional view illustrating
a front part of the vehicle mounted with the control device for the
vehicle according to this embodiment, when seen from the left
side.
[0025] As illustrated in FIG. 1, an engine 4 is mounted on a front
part of a vehicle 1, as a motor (driving force source) which drives
left and right front wheels 2 which are drive wheels. The engine 4
is an internal combustion engine, such as a gasoline engine or a
diesel engine, and in this embodiment, it is a gasoline engine
having a throttle valve 26, a spark plug 28, a variable valve
mechanism 30, and a fuel injection device 32. This vehicle 1 is
configured as a so-called "front-engine, front-wheel drive (FF)
vehicle."
[0026] The vehicle 1 includes a steering device (a steering wheel
6, etc.) for steering the vehicle 1, a steering angle sensor 8
which detects a turning angle of a steering column (not
illustrated) coupled to the steering wheel 6 in this steering
device, a gyroscope 34 which detects a yaw rate of the vehicle 1
(see FIG. 4), an accelerometer 36 which detects a lateral
acceleration of the vehicle (see FIG. 4), an accelerator opening
sensor 10 which detects an accelerator opening equivalent to a
stepping amount of an accelerator pedal, and a vehicle speed sensor
12 which detects a traveling speed of the vehicle 1. Note that the
steering angle sensor 8 may detect various properties in the
steering system (a rotation angle of a motor which applies
assisting torque, a displacement of a rack in a rack-and-pinion
mechanism), and a steered angle (tire angle) of the front wheels 2,
as the steering angle, instead of the turning angle of the steering
wheel 6. Each sensor outputs the detection values to a controller
14. This controller 14 is comprised of a PCM (Power-train Control
Module), for example.
[0027] The vehicle 1 is provided with a grille shutter 16 (an air
inflow adjustment mechanism, an opening-and-closing device) which
opens and closes an opening formed in a front surface of the
vehicle body. As illustrated in FIG. 2, the grille shutter 16 is
provided to an opening formed in front of the engine 4, in the
front surface of the vehicle 1. The grille shutter 16 is provided
with a plurality of elongated plate-like fins 18 extending in the
vehicle width direction. Each fin 18 is rotatable between an
orientation in which its plate surface is parallel to the
front-and-rear direction of the vehicle 1 and an orientation in
which its plate surface is perpendicular to the front-and-rear
direction of the vehicle 1. In detail, when the orientation of the
fins 18 is parallel to the front-and-rear direction of the vehicle
1 (illustrated by solid lines in FIG. 2), the opening of the grille
shutter 16 becomes a maximum opening, and a flow rate of air which
passes through the grille shutter 16 from the front of the vehicle
1 and enters into an engine bay 20 becomes a maximum air flow
(illustrated by solid-line arrows in FIG. 2). In this case, the
pressure inside the engine bay 20 rises and the aerodynamic lift
which biases the front part of the vehicle 1 upward increases.
[0028] On the other hand, when the orientation of the fins 18 is
perpendicular to the front-and-rear direction of the vehicle 1
(illustrated by broken lines in FIG. 2), the opening of the grille
shutter 16 becomes a minimum opening, and the flow of air which
passes through the grille shutter 16 from the front of the vehicle
1 and enters into the engine bay 20 is intercepted. Therefore, the
lift accompanying the pressure increase inside the engine bay 20 is
suppressed. Further, by reducing the opening of the grille shutter
16, the flow rate of air which flows underneath the vehicle 1
(illustrated by broken-line arrows in FIG. 2) increases, and a flow
velocity of the air which flows underneath a floor 22 increases. In
this case, the pressure underneath the floor 22 decreases and a
downforce F which downwardly biases the front part of the vehicle 1
increases.
[0029] As described above, by changing the opening of the grille
shutter 16, the lift or downforce F which acts on the front part of
the vehicle 1 changes. As a result, since the grounding load of the
front wheels 2 changes, the cornering power changes. Referring to
FIG. 3, a relationship between the opening of the grille shutter 16
and the cornering power of the front wheels 2 is described. FIG. 3
is a diagram illustrating a relationship between the opening of the
grille shutter 16 and the cornering power of the front wheel 2,
when changing the opening of the grille shutter 16 from fully
closed to fully open under a condition of constant traveling
speed.
[0030] In FIG. 3, the horizontal axis indicates the opening (deg)
of the grille shutter 16. Here, the opening when the fins 18 of the
grille shutter 16 are oriented perpendicular to the front-and-rear
direction of the vehicle 1 (i.e., fully close) is 0.degree., and
the opening when the fins 18 are oriented horizontal to the
front-and-rear direction of the vehicle 1 (i.e., fully open) is
90.degree.. Further, in FIG. 3, the vertical axis indicates the
cornering power (CP) (N/deg) of the front wheels 2.
[0031] As illustrated in FIG. 3, since the downforce F which
downwardly biases the front part of the vehicle 1 becomes a maximum
force when the opening of the grille shutter 16 is 0.degree. (i.e.,
fully closed), the cornering power of the front wheels 2 becomes a
maximum power. Then, as the opening of the grille shutter 16
increases, the downforce F which acts on the front part of the
vehicle 1 decreases, and the lift accompanying the pressure
increase inside the engine bay 20 increases. Therefore, the
cornering power of the front wheels 2 decreases, and when the
opening of the grille shutter 16 is 90.degree. (i.e., fully open),
the cornering power becomes a minimum power. That is, the response
of the behavior of the vehicle 1 to the operation of the steering
wheel 6 tends to fall as the opening of the grille shutter 16
increases.
[0032] Next, referring to FIG. 4, an electric configuration of a
control device for the vehicle according to this embodiment of the
present disclosure is described. FIG. 4 is a block diagram
illustrating the electric configuration of the control device for
the vehicle according to this embodiment.
[0033] As illustrated in FIG. 4, based on detection signals
outputted from various sensors which detect the operating state of
the vehicle 1, in addition to detection signals from the sensors 8,
10, 12, 34, and 36 described above, the controller 14 outputs a
control signal to perform a control of each part of the engine 4
(for example, the throttle valve 26, the spark plug 28, the
variable valve mechanism 30, the fuel injection valve 32, etc.) and
the grille shutter 16.
[0034] The controller 14 is comprised of a circuitry and is a
controller based on a well-known microcomputer. The controller 14
includes one or more microprocessors as a CPU (Central Processing
Unit) which executes a program, memory which is comprised of, for
example, RAM (Random Access Memory) and/or ROM (Read Only Memory),
and stores the program and data, an input/output bus which performs
input/output of an electric signal. Note that the system including
the steering wheel 6, the steering angle sensor 8, and the
controller 14 is an example of a "control system for a vehicle" in
the present disclosure.
<Vehicle Attitude Control>
[0035] Below, a vehicle attitude control according to this
embodiment of the present disclosure is described. Fundamentally,
in this embodiment, the controller 14 controls vehicle attitude
(vehicle behavior) based on the steering angle detected by the
steering angle sensor 8. In detail, when the steering wheel 6 is
turned in one direction so that it separates from the neutral
position (i.e., when the steering angle increases), the controller
14 performs a torque decreasing control to reduce torque generated
by the engine 4 so that a deceleration is added to the vehicle 1
(i.e., deceleration to decelerate the vehicle 1 which moves
forward). By performing such a torque decreasing control, it can
improve the turnability and the steering stability of the vehicle 1
when entering into a corner.
[0036] Note that, below, torque which is applied to the torque
decreasing control, i.e., a negative torque which is added to the
torque generated by the engine 4 in order to add the deceleration
to the vehicle 1 is referred to as the "reducing torque." In the
torque decreasing control, the reducing torque is subtracted from
the torque to be generated by the engine 4 (hereinafter, referred
to as the "basic torque") in order to achieve the acceleration
according to the operating state of the vehicle 1 (accelerator
opening, etc.). Below, the torque after the reducing torque is thus
subtracted (i.e., the torque to be finally generated by the engine
4) is referred to as the "final target torque" with respect to the
basic torque.
[0037] Next, referring to FIG. 5, the overall flow of the torque
decreasing control according to this embodiment of the present
disclosure is described. FIG. 5 is a flowchart of the torque
decreasing control processing according to this embodiment.
[0038] The torque decreasing control processing in FIG. 5 is
started when the ignition of the vehicle 1 is turned ON and the
power is supplied to the controller 14, and it is repeatedly
performed at a given period (for example, 50 ms). As the torque
decreasing control processing is started, at Step S1, the
controller 14 acquires various sensor information on the operating
state of the vehicle 1. In detail, the controller 14 acquires, as
the information on the operating state, the detection signals
outputted from the various sensors including the steering angle
detected by the steering angle sensor 8, the accelerator opening
detected by the accelerator opening sensor 10, the traveling speed
detected by the vehicle speed sensor 12, and the current opening of
the grille shutter 16.
[0039] Next, at Step S2, the controller 14 sets a target
acceleration based on the operating state of the vehicle 1 acquired
at Step S1. In detail, for example, the controller 14 selects an
acceleration characteristics map corresponding to the current
traveling speed and the current gear stage from acceleration
characteristics maps which are defined for various traveling speeds
and various gear stages (created beforehand and stored in the
memory, etc.), and sets the target acceleration corresponding to
the current accelerator opening with reference to the selected
acceleration characteristics map.
[0040] Next, at Step S3, the controller 14 sets the basic torque of
the engine 4 for achieving the target acceleration set at Step S2.
In this case, the controller 14 sets the basic torque within a
range of torque which the engine 4 is possible to the output, based
on the current traveling speed, the current gear stage, the road
surface gradient, the road surface .mu., etc.
[0041] Further, at Step S4, in parallel to the processing at Steps
S2 and S3, the controller 14 performs the reducing torque setting
processing which will be described later (see FIG. 6), and based on
the steering speed, etc. of the steering wheel 6, it sets the
reducing torque to be applied to the torque generated by the engine
4 in order to control the vehicle attitude.
[0042] Next, at Step S5 after Steps S2 to S4, the controller 14
sets the final target torque based on the basic torque set at Step
S3 and the reducing torque set at Step S4. Fundamentally, the
controller 14 calculates the final target torque by subtracting the
reducing torque from the basic torque.
[0043] Next, at Step S6, the controller 14 controls the engine 4 to
output the final target torque set at Step S5. In detail, the
controller 14 determines, based on the final target torque set at
Step S5 and the engine speed, various properties (for example, an
air filling amount, a fuel injection amount, an intake air
temperature, an oxygen concentration, etc.) which are required for
achieving the final target torque, and based on the properties,
controls actuators which drive the respective components of the
engine 4. In this case, the controller 14 sets a limit value and a
limit area according to the properties, and sets such a controlled
variable for each actuator that the properties complies the limit
value and the limit area and performs the control.
[0044] In more detail, the controller 14 reduces the torque
generated by the engine 4 by retarding the ignition timing of the
spark plug 28 from the ignition timing at which the basic torque is
set to the final target torque as it is at Step S5. Note that, when
the engine 4 is a diesel engine, the controller 14 can reduce the
torque generated by the engine 4 by reducing a fuel injection
amount from the fuel injection amount at which the basic torque is
set to the final target torque as it is at Step S5. After Step S6,
the controller 14 ends the torque decreasing control
processing.
[0045] Next, referring to FIG. 6, the reducing torque setting
processing according to this embodiment of the present disclosure
is described. FIG. 6 is a flowchart of the reducing torque setting
processing according to this embodiment. This reducing torque
setting processing is performed at Step S4 of the torque decreasing
control processing illustrated in FIG. 5.
[0046] When the reducing torque setting processing is started, at
Step S11, the controller 14 acquires the steering speed based on
the steering angle acquired from the steering angle sensor 8 at
Step S1 of the torque decreasing control processing illustrated in
FIG. 5. Next, at Step S12, the controller 14 determines whether the
steering speed acquired at Step S11 is above a given value. As a
result, if determined that the steering speed is above the given
value (Step S12: YES), the controller 14 shifts to Step S13.
[0047] On the other hand, if not determined that the steering speed
is above the given value (Step S12: NO), the controller 14 ends the
reducing torque setting processing, and returns to the main
routine. In this case, the reducing torque becomes 0, and the basic
torque set at Step S3 of the torque decreasing control processing
illustrated in FIG. 5 becomes the final target torque.
[0048] Next, at Step S13, the controller 14 determines whether the
steering wheel 6 is under the turning operation. In detail, for
example, when an absolute value of the steering angle acquired from
the steering angle sensor 8 is increasing (i.e., when the steering
angle of the steering wheel 6 is separating from the neutral
position), the controller 14 determines that the steering wheel 6
is under the turning operation. On the other hand, for example,
when the absolute value of the steering angle acquired from the
steering angle sensor 8 is decreasing (i.e., when the steering
angle of the steering wheel 6 is approaching the neutral position),
the controller 14 determines that the steering wheel 6 is under a
returning operation (that is, it is not under the turning
operation). As a result, when the controller 14 determines that the
steering wheel 6 is under the turning operation (Step S13: YES), it
shifts to Step S14.
[0049] Next, at Step S14, the controller 14 acquires the reducing
torque based on the steering speed. In detail, before acquiring the
reducing torque, the controller 14 first sets the additional
deceleration corresponding to the current steering speed based on
the relationship between the steering speed and the additional
deceleration as illustrated in the map of FIG. 7. This additional
deceleration is a forward deceleration to be added to the vehicle 1
according to the steering operation in order to control the vehicle
attitude in accordance with the driver's intention of the turning
operation of the steering wheel 6. In FIG. 7, the horizontal axis
indicates the steering speed, and the vertical axis indicates the
additional deceleration. As illustrated in FIG. 7, when the
steering speed is below a threshold S1, the additional deceleration
is 0. When the steering speed exceeds the threshold S1, the
additional deceleration corresponding to this steering speed
gradually approaches a given upper limit AD.sub.max as the steering
speed increases. That is, as the steering speed increases, the
additional deceleration increases, and an increasing rate of the
amount of increase becomes smaller. This upper limit AD.sub.max is
set to such a deceleration that, even if the deceleration is added
to the vehicle 1 according to the steering operation, the driver
does not sense a control intervention (for example, 0.5
m/s.sup.2.apprxeq.0.05 G). Further, when the steering speed becomes
above the given value, the additional deceleration is maintained at
the upper limit AD.sub.max. Then, the controller 14 acquires the
reducing torque based on the additional deceleration set in this
way. In detail, the controller 14 determines the reducing torque
required for achieving the additional deceleration by the reduction
of the basic torque, based on the current traveling speed, gear
stage, road surface gradient, etc.
[0050] Next, at Step S15, the controller 14 acquires the opening of
the grille shutter 16. The opening of the grille shutter 16 can be
acquired, for example, from an instructed value outputted from
controller 14 to the actuator which operates the fins 18, a
rotational position of the actuator, etc.
[0051] Next, at Step S16, the controller 14 acquires a correction
gain for correcting the reducing torque according to the opening of
the grille shutter 16. In detail, the controller 14 acquires the
correction gain corresponding to the current opening of the grille
shutter 16 based on the relationship between the opening of the
grille shutter 16 and the correction gain illustrated in the map of
FIG. 8.
[0052] In FIG. 8, the horizontal axis indicates the opening of the
grille shutter 16, and the vertical axis indicates the correction
gain. As illustrated in FIG. 8, when the opening of the grille
shutter 16 is 0.degree. (i.e., fully closed), the correction gain
is the minimum (about 0.92 in the example of FIG. 8). The
correction gain corresponding to the opening of the grille shutter
16 increases as the opening of the grille shutter 16 approaches
90.degree. (that is, the opening of the grille shutter 16 becomes
larger). When the opening of the grille shutter 16 is 90.degree.
(i.e., fully open), the correction gain becomes 1. The rate of
change in the correction gain according to the change in the
opening of the grille shutter 16 (a slope of the graph illustrated
in FIG. 8) becomes smaller as the opening of the grille shutter 16
approaches 0.degree..
[0053] As described with reference to FIG. 3, as the opening of the
grille shutter 16 increases, the downforce F which acts on the
front part of the vehicle 1 decreases, and the lift accompanying
the pressure increase inside the engine bay 20 increases.
Therefore, the cornering power of the front wheels 2 tends to
decrease and the response of the behavior of the vehicle 1 to the
operation of the steering wheel 6 tends to decrease. Thus, as
illustrated in FIG. 8, the correction gain is set so that, as the
opening of the grille shutter 16 becomes larger, the reducing
torque increases and the deceleration added to the vehicle 1 by the
torque decreasing control increases (that is, the load added to the
front wheels 2 increases and the cornering power increases).
[0054] Next, at Step S17, the controller 14 corrects the reducing
torque acquired at Step S14 by using the correction gain acquired
at Step S16. In detail, the controller 14 multiplies the reducing
torque acquired at Step S14 by the correction gain acquired at Step
S16. By correcting in this way, the reducing torque increases as
the opening of the grille shutter 16 becomes larger.
[0055] Next, at Step S18, the controller 14 sets the reducing
torque in this processing cycle so that a rate of change in the
reducing torque becomes below a threshold, based on the reducing
torque corrected at Step S17 and the threshold (defined beforehand
and stored in the memory, etc.) which defines an upper limit of the
rate of change in the reducing torque. After Step S18, the
controller 14 ends the reducing torque setting processing, and
returns to the main routine. In this case, at Step S5 of the torque
decreasing control processing in FIG. 5, the controller 14 sets the
final target torque based on the basic torque set at Step S3 and
the reducing torque set at Step S18.
[0056] Further, at Step S13, if the controller 14 determines that
the steering wheel 6 is not under the turning operating (Step S13:
NO), in detail, for example, if the absolute value of the steering
angle acquired from the steering angle sensor 8 is decreasing
(i.e., if the steering angle of the steering wheel 6 is approaching
the neutral position), the controller 14 ends the reducing torque
setting processing, and returns to the main routine. In this case,
the reducing torque becomes 0, and the basic torque set at Step S3
of the torque decreasing control processing illustrated in FIG. 5
becomes the final target torque.
<Operation and Effects>
[0057] Next, operation and effects of the control system for the
vehicle according to this embodiment of the present disclosure are
described with reference to the time chart in FIG. 9. FIG. 9 is a
time chart when performing the torque decreasing control according
to this embodiment. In FIG. 9, the horizontal axis indicates time.
Further, the vertical axis indicates (a) the steering angle, (b)
the steering speed, (c) the reducing torque, and (d) the final
target torque, sequentially from the top. In the graphs (c) and (d)
of FIG. 9, solid lines indicate changes in the reducing torque and
the final target torque when the opening of the grille shutter 16
is 90.degree. (fully open) (that is, when the correction gain is
1), and one-dot chain lines indicate changes in the reducing torque
and the final target torque when applying the correction gain at
which the opening of the grille shutter 16 is 0.degree. (fully
closed) to the reducing torque.
[0058] As illustrated in the graph (a) of FIG. 9, it illustrates a
case where the steering wheel 6 is first turned clockwise (CW) from
the neutral position, and the rotational position of the steering
wheel 6 is then held at a certain steering angle.
[0059] In connection with the turning operation of the steering
wheel 6 in the clockwise (CW) direction from the neutral position
being started, the steering speed (absolute value) in the CW
direction increases. When the steering speed becomes above the
threshold S1 at time t1, the controller 14 sets the reducing torque
based on the steering speed so as to add the deceleration to the
vehicle 1, and performs the torque decreasing control for reducing
the torque generated by the engine 4. Then, while the steering
speed increases, the controller 14 increases the reducing torque
(absolute value) according to the steering speed, and when the
steering speed becomes constant, it maintains the reducing torque.
Further, when the steering speed decreases, the controller 14
decreases the reducing torque (absolute value) in accordance
therewith.
[0060] Then, when the steering speed becomes below the threshold S1
at time t2 by the steering wheel 6 being held at the turned state,
the controller 14 ends the torque decreasing control and the
reducing torque becomes 0. That is, the deceleration added to the
vehicle 1 becomes 0.
[0061] The controller 14 applies the correction gain according to
the opening of the grille shutter 16 to the reducing torque, and
performs the torque decreasing control by the corrected reducing
torque. As described above, the correction gain corresponding to
the opening of the grille shutter 16 is set so that it becomes
larger as the opening of the grille shutter 16 increases.
Therefore, the controller 14 increases the reducing torque
(absolute value) when the opening of the grille shutter 16 is large
(for example, when the opening of the grille shutter 16 is
90.degree. (fully open), as illustrated by the solid line in the
graph (c) of FIG. 9) more than when the opening of the grille
shutter 16 is small (for example, when the opening of the grille
shutter 16 is 0.degree. (fully closed), as illustrated by the
one-dot chain line in the graph (c) of FIG. 9). Therefore, when the
opening of the grille shutter 16 is large, the deceleration added
to the vehicle 1 by the torque decreasing control increases more
than when the opening is small. That is, the load added to the
front wheels 2 by the torque decreasing control increases.
[0062] Thus, in this embodiment, the controller 14 performs the
torque decreasing control so as to add the deceleration to the
vehicle 1 when it determines that the turning operation of the
steering wheel 6 is performed based on the steering angle, and it
increases the reduction amount of the torque in the torque
decreasing control when the opening of the grille shutter 16 is
large more than when the opening is small. When the opening of the
grille shutter 16 increases during the execution of the torque
decreasing control, the lift which acts on the front part of the
vehicle 1 increases. However, since the load added to the front
wheels 2 increases by increasing the reduction amount of the torque
in the torque decreasing control, it can suppress the change in the
cornering power of the front wheels 2 resulting from the change in
the opening of the grille shutter 16. Therefore, the response and
the steering stability which are consistent with the operation of
the steering wheel 6 can be obtained, without being influenced by
the opening of the grille shutter 16.
[0063] Further, in this embodiment, the grille shutter 16 is
adjustable in the opening-and-closing degree of the opening up to
the fully closed state. When the opening of the grille shutter 16
is fully closed, the lift accompanying the pressure increase inside
the engine bay 20 is suppressed, and the downforce F for downwardly
biasing the front part of the vehicle 1 increases. However, by
reducing the reduction amount of the torque in the torque
decreasing control accordingly, the load added to the front wheels
2 becomes smaller. Thus, it can suppress the change in the
cornering power of the front wheels 2 resulting from the change in
the opening of the grille shutter 16.
[0064] Further, since in this embodiment the controller 14 sets the
reducing torque at least based on the steering angle detected by
the steering angle sensor 8, it can control the vehicle attitude
promptly to improve the response and the stability of the vehicle
behavior with respect to the driver's steering operation.
[0065] Moreover, in this embodiment, the driving force source of
the vehicle 1 is the engine 4 and the controller 14 controls the
torque generated by the engine 4. Therefore, in the vehicle which
highly requires the adjustment of the opening of the grille shutter
16 in order to improve the fuel efficiency, etc. of the engine 4,
the response and the steering stability which are consistent with
the operation of the steering wheel 6 can be obtained, without
being influenced by the opening of the grille shutter 16.
<Modifications>
[0066] Although in the above embodiment the present disclosure is
applied to the vehicle 1 having the internal combustion engine as
the driving force source, the present disclosure may also be
applied to a vehicle having an electric motor as the driving force
source. In this case, for example, current supplied to the electric
motor from an inverter may be controlled in order to achieve the
reducing torque in the torque decreasing control.
[0067] Further, in the above embodiment, the controller 14 performs
the torque decreasing control at least based on the steering angle
detected by the steering angle sensor 8. However, instead of or in
addition to the steering angle, the torque decreasing control may
be performed based on the operating state of the vehicle 1 other
than the operation of the accelerator pedal (a lateral
acceleration, a yaw rate, a slip ratio, etc.). For example, the
vehicle 1 may be provided with a yaw rate sensor (e.g., gyroscope
34) which detects the yaw rate of the vehicle 1 and an acceleration
sensor (e.g., accelerometer 36) which detects the acceleration of
the vehicle 1. The controller 14 may perform the torque decreasing
control based on a steering angle related value, such as the yaw
rate detected by the yaw rate sensor or the lateral acceleration
detected by the acceleration sensor, instead of the steering angle.
Each of the steering angle, the yaw rate, and the lateral
acceleration is one example of a "steering angle related value" in
the present disclosure.
[0068] It should be understood that the embodiments herein are
illustrative and not restrictive, since the scope of the invention
is defined by the appended claims rather than by the description
preceding them, and all changes that fall within metes and bounds
of the claims, or equivalence of such metes and bounds thereof, are
therefore intended to be embraced by the claims.
DESCRIPTION OF REFERENCE CHARACTERS
[0069] 1 Vehicle
[0070] 2 Wheel
[0071] 4 Engine
[0072] 6 Steering Wheel
[0073] 8 Steering Angle Sensor
[0074] 10 Accelerator Opening Sensor
[0075] 12 Vehicle Speed Sensor
[0076] 14 Controller
[0077] 16 Grille Shutter
* * * * *