U.S. patent application number 15/427142 was filed with the patent office on 2017-08-17 for warning device for vehicle.
This patent application is currently assigned to JTEKT CORPORATION. The applicant listed for this patent is JTEKT CORPORATION. Invention is credited to Yuji KARIATSUMARI, Yuichi MIURA, Kohei MORIKI.
Application Number | 20170232889 15/427142 |
Document ID | / |
Family ID | 58009751 |
Filed Date | 2017-08-17 |
United States Patent
Application |
20170232889 |
Kind Code |
A1 |
MIURA; Yuichi ; et
al. |
August 17, 2017 |
Warning Device For Vehicle
Abstract
A warning device for a vehicle includes a warning vibration wave
generator and a vibration applying device. For each of a plurality
of vehicle conditions, the warning vibration wave generator
generates a warning vibration wave having a frequency that varies
with the vehicle speed detected by a vehicle speed sensor, and that
differs for each vehicle condition at the same vehicle speed. Based
on the warning vibration wave generated by the warning vibration
wave generator, the vibration applying device applies a warning
vibration corresponding to the warning vibration wave to a steering
member.
Inventors: |
MIURA; Yuichi; (Kariya-shi,
JP) ; KARIATSUMARI; Yuji; (Kitakatsuragi-gun, JP)
; MORIKI; Kohei; (Okazaki-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
JTEKT CORPORATION |
Osaka |
|
JP |
|
|
Assignee: |
JTEKT CORPORATION
Osaka
JP
|
Family ID: |
58009751 |
Appl. No.: |
15/427142 |
Filed: |
February 8, 2017 |
Current U.S.
Class: |
340/441 |
Current CPC
Class: |
B62D 15/029 20130101;
B60W 2520/10 20130101; B60Q 9/00 20130101; B60W 30/12 20130101;
B60W 50/16 20130101; B60W 10/20 20130101 |
International
Class: |
B60Q 9/00 20060101
B60Q009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 15, 2016 |
JP |
2016-026110 |
Claims
1. A warning device for a vehicle comprising: a vehicle speed
detector that detects a vehicle speed; a vibration wave generator
that generates, for each of a plurality of vehicle conditions
determined in advance, a warning vibration wave having a frequency
that varies with the vehicle speed detected by the vehicle speed
detector, the frequency at an identical vehicle speed being
different for each vehicle condition; and a vibration applying
device that applies a warning vibration corresponding to the
warning vibration wave to a steering member, based on the warning
vibration wave generated by the vibration wave generator.
2. The warning device for a vehicle according to claim 1, wherein
the vibration wave generator includes a time-division output unit
that, when two or more vehicle conditions among the plurality of
vehicle conditions have simultaneously arisen, outputs two or more
warning vibration waves corresponding to each of the vehicle
conditions individually in a time-division manner such that the
output warning vibration waves do not overlap temporally.
3. The warning device for a vehicle according to claim 1, wherein
the frequency of the warning vibration wave generated for each
vehicle condition is set so as to become lower as the vehicle speed
detected by the vehicle speed detector increases, and a difference
in frequency between the warning vibration waves generated for the
corresponding vehicle conditions is set so as to increase as the
vehicle speed detected by the vehicle speed detector decreases.
4. The warning device for a vehicle according to claim 1, wherein
the frequency of the warning vibration wave generated for each
vehicle condition is set so as to become higher as the vehicle
speed detected by the vehicle speed detector increases, and a
difference in frequency between the warning vibration waves
generated for the corresponding vehicle conditions is set so as to
increase as the vehicle speed detected by the vehicle speed
detector increases.
5. The warning device for a vehicle according to claim 1, wherein
the vibration applying device includes an EPS electric motor that
generates steering assisting force.
6. A warning device for a vehicle comprising: an electric motor
that applies steering assisting force to a steering operation
mechanism of a vehicle; a vehicle speed detector that detects a
vehicle speed; a torque detector that detects a steering torque; a
basic assist current value setting unit that sets a basic assist
current value based on the steering torque detected by the torque
detector; a vibration wave generator that generates, for each of a
plurality of vehicle conditions, a warning vibration wave having a
frequency that varies with the vehicle speed detected by the
vehicle speed detector, the frequency at an identical vehicle speed
being different for each vehicle condition; a target current value
computing unit that computes a target current value for the
electric motor by adding the warning vibration wave generated by
the vibration wave generator to the basic assist current value set
by the basic assist current value setting unit; and a motor
controller that controls the electric motor based on the target
current value computed by the target current value computing
unit.
7. The warning device for a vehicle according to claim 6, wherein
the vibration wave generator includes a time-division output unit
that, when two or more vehicle conditions among the plurality of
vehicle conditions have simultaneously arisen, outputs two or more
warning vibration waves corresponding to each of the vehicle
conditions individually in a time-division manner such that the
output warning vibration waves do not overlap temporally.
Description
INCORPORATION BY REFERENCE
[0001] The disclosure of Japanese Patent Application No.
2016-026110 filed on Feb. 15, 2016 including the specification,
drawings and abstract, is incorporated herein by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a warning device for a
vehicle that issues a warning based on vehicle conditions.
[0004] 2. Description of Related Art
[0005] Vehicles are known that have steering assist control
functions such as a lane keeping assist function of assisting a
driver in performing a steering operation and a lane changing
assist function of assisting a driver in changing lanes in order to
facilitate traveling of a vehicle along a traveling path. For the
purpose of informing a driver of an undesired vehicle condition
during the execution of steering assist control, a warning device
for a vehicle, which vibrates a steering wheel as a steering member
to warn the driver, has been developed. For example, see Japanese
Patent No. 4292562 (JP 4292562 B) and Japanese Patent Application
Publication No. 11-34774 (JP 11-34774 A).
[0006] Under a plurality of vehicle conditions about which a driver
needs to be warned, it is considered that a warning vibration is
generated to be applied to a steering wheel when these vehicle
conditions have arisen. In this case, for example, when a plurality
of undesired vehicle conditions have simultaneously arisen, it is
preferable to notify the driver that these vehicle conditions have
simultaneously arisen.
SUMMARY OF THE INVENTION
[0007] It is an object of the present invention to provide a
warning device for a vehicle that, when a plurality of vehicle
conditions about which a driver needs to be warned have
simultaneously arisen, allows the driver to know that a plurality
of vehicle conditions have simultaneously arisen with warning
vibrations applied to a steering member.
[0008] A warning device for a vehicle according to one aspect of
the present invention include: a vehicle speed detector that
detects a vehicle speed; a vibration wave generator that generates,
for each of a plurality of vehicle conditions determined in
advance, a warning vibration wave having a frequency that varies
with the vehicle speed detected by the vehicle speed detector, the
frequency at an identical vehicle speed being different for each
vehicle condition; and a vibration applying device that applies a
warning vibration corresponding to the warning vibration wave to a
steering member, based on the warning vibration wave generated by
the vibration wave generator.
[0009] In the warning device for a vehicle according to the above
aspect, when a plurality of vehicle conditions have simultaneously
arisen, a plurality of warning vibration waves corresponding to
each of the vehicle conditions having simultaneously arisen are
generated. The warning vibration waves corresponding to each of the
vehicle conditions each have a frequency that varies with the
vehicle speed, and the frequency for the identical vehicle speed is
different for each vehicle condition. Based on these warning
vibration waves, warning vibrations corresponding to the warning
vibration waves are applied to the steering member. Thus, when a
plurality of vehicle conditions have simultaneously arisen, the
driver can be notified that a plurality of vehicle conditions have
simultaneously arisen with the warning vibrations.
[0010] A warning device for a vehicle according to another aspect
of the present invention includes: an electric motor that applies
steering assisting force to a steering operation mechanism of a
vehicle; a vehicle speed detector that detects a vehicle speed; a
torque detector that detects a steering torque; a basic assist
current value setting unit that sets a basic assist current value
based on the steering torque detected by the torque detector; a
vibration wave generator that generates, for each of a plurality of
vehicle conditions, a warning vibration wave having a frequency
that varies with the vehicle speed detected by the vehicle speed
detector, the frequency at an identical vehicle speed being
different for each vehicle condition; a target current value
computing unit that computes a target current value for the
electric motor by adding the warning vibration wave generated by
the vibration wave generator to the basic assist current value set
by the basic assist current value setting unit; and a motor
controller that controls the electric motor based on the target
current value computed by the target current value computing
unit.
[0011] In the warning device for a vehicle according to the above
aspect, when a plurality of vehicle conditions have simultaneously
arisen, a plurality of warning vibration waves corresponding to
each of the vehicle conditions having simultaneously arisen are
generated. The warning vibration waves corresponding to each of the
vehicle conditions each have a frequency that varies with the
vehicle speed, and the frequency at the identical vehicle speed is
different for each vehicle condition. By adding these warning
vibration waves to the basic assist current value, target current
values for the electric motor are computed. The electric motor is
controlled based on the target current values. Thus, when a
plurality of vehicle conditions have simultaneously arisen, the
driver can be notified that the plurality of vehicle conditions
have simultaneously arisen with the warning vibrations.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The foregoing and further features and advantages of the
invention will become apparent from the following description of
example embodiments with reference to the accompanying drawings,
wherein like numerals are used to represent like elements and
wherein:
[0013] FIG. 1 is a schematic diagram illustrating a schematic
configuration of an electric power steering system in which a
warning device for a vehicle according to an embodiment of the
present invention is used;
[0014] FIG. 2 is a block diagram illustrating an electrical
configuration of an ECU;
[0015] FIG. 3 is a graph illustrating an example of the manner of
setting a basic target current value Io* with respect to a detected
steering torque T;
[0016] FIG. 4A is a graph illustrating an example of the manner of
setting a frequency f1(V) of a first warning vibration wave Ie1
with respect to a vehicle speed and a frequency f2(V) of a second
warning vibration wave Ie2 with respect to the vehicle speed;
[0017] FIG. 4B is a graph illustrating another example of the
manner of setting the frequency f1(V) of the first warning
vibration wave Ie1 with respect to the vehicle speed and the
frequency f2(V) of the second warning vibration wave Ie2 with
respect to the vehicle speed;
[0018] FIG. 5 is a waveform diagram illustrating an example of the
first warning vibration wave Ie1 and the second warning vibration
wave Ie2; and
[0019] FIG. 6 is a block diagram illustrating another example of
the electrical configuration of the ECU.
DETAILED DESCRIPTION OF EMBODIMENTS
[0020] Embodiments of the present invention will now be described
in detail with reference to the attached drawings.
[0021] FIG. 1 is a schematic diagram illustrating a schematic
configuration of an electric power steering system in which a
warning device for a vehicle according to an embodiment of the
present invention is used.
[0022] An electric power steering (EPS) system 1 includes a
steering wheel 2 as a steering member used to steer a vehicle, a
steering operation mechanism 4 that steers steered wheels 3 in
response to the rotation of the steering wheel 2, and a steering
assist mechanism 5 that assists a driver in performing a steering
operation. The steering wheel 2 and the steering operation
mechanism 4 are mechanically connected to each other via a steering
shaft 6 and an intermediate shaft 7. Herein, the present invention
can be applied to a steer-by-wire electric power steering system in
which the steering wheel 2 is not mechanically connected to the
steering operation mechanism 4.
[0023] The steering shaft 6 includes an input shaft 8 coupled to
the steering wheel 2 and an output shaft 9 coupled to the
intermediate shaft 7. The input shaft 8 and the output shaft 9 are
connected to each other via a torsion bar 10 so as to be rotatable
relative to each other.
[0024] Near the torsion bar 10, a torque sensor 11 is disposed. The
torque sensor 11 detects a steering torque T applied to the
steering wheel 2, based on the relative rotation displacement
between the input shaft 8 and the output shaft 9. In the present
embodiment, the steering torque T is detected by the torque sensor
11 such that, for example, a torque for steering the vehicle to the
right is detected as a positive value and a torque for steering the
vehicle to the left is detected as a negative value. Thus, the
magnitude of the steering torque increases as the absolute value of
the detected steering torque increases.
[0025] The steering operation mechanism 4 is a rack-and-pinion
mechanism including a pinion shaft 13 and a rack shaft 14 serving
as a steered shaft. Each end of the rack shaft 14 is connected to
the corresponding steered wheel 3 via a tie rod 15 and a knuckle
arm (not depicted). The pinion shaft 13 is connected to the
intermediate shaft 7. The pinion shaft 13 is configured to rotate
in response to a steering operation of the steering wheel 2. A
distal end (lower end in FIG. 1) of the pinion shaft 13 is
connected to a pinion 16.
[0026] The rack shaft 14 linearly extends along the lateral
direction of the vehicle. In an intermediate portion of the rack
shaft 14 in the axial direction, a rack 17 that meshes with the
pinion 16 is formed. The pinion 16 and the rack 17 convert the
rotation of the pinion shaft 13 into an axial motion of the rack
shaft 14. The axial motion of the rack shaft 14 allows the steered
wheels 3 to be steered.
[0027] When the steering wheel 2 is steered (rotated), this
rotation is transmitted to the pinion shaft 13 through the steering
shaft 6 and the intermediate shaft 7. The rotation of the pinion
shaft 13 is converted into the axial motion of the rack shaft 14 by
the pinion 16 and the rack 17. Consequently, the steered wheels 3
are steered.
[0028] The steering assist mechanism 5 includes an electric motor
(EPS electric motor) 18 that assists steering and a speed reducer
19 that transmits the torque output by the electric motor 18 to the
steering operation mechanism 4. The speed reducer 19 is a worm gear
mechanism including a worm shaft 20 and a worm wheel 21 that meshes
with the worm shaft 20. The speed reducer 19 is housed in a gear
housing 22 serving as a transmitting mechanism housing.
[0029] The worm shaft 20 is driven to be rotated by the electric
motor 18. The worm wheel 21 is connected to the steering shaft 6 so
as to be rotatable in the same direction as the rotation direction
of the steering shaft 6. The worm wheel 21 is driven to be rotated
by the worm shaft 20.
[0030] When the worm shaft 20 is driven to be rotated by the
electric motor 18, the worm wheel 21 is driven to be rotated, and
thus the steering shaft 6 rotates. The rotation of the steering
shaft 6 is transmitted to the pinion shaft 13 through the
intermediate shaft 7. The rotation of the pinion shaft 13 is
converted into an axial motion of the rack shaft 14. Thus, the
steered wheels 3 are steered. That is, the worm shaft 20 is driven
to be rotated by the electric motor 18, whereby the steered wheels
3 are steered.
[0031] In the vehicle, a vehicle speed sensor 23 that detects a
vehicle speed V is provided, and a charge-coupled device (CCD)
camera 24 that captures an image of a road ahead of the vehicle in
the traveling direction is mounted. The CCD camera 24 is provided
to monitor the operating state of the vehicle. Wheels of the
vehicle are each provided with air-pressure sensors 25, 26, 27, and
28 that detect air pressures of the corresponding tires.
[0032] The steering torque T detected by the torque sensor 11, the
vehicle speed V detected by the vehicle speed sensor 23, air
pressures P1, P2, P3, and P4 detected by the respective
air-pressure sensors 25, 26, 27, and 28, and an image signal output
by the CCD camera 24 are input into an electronic control unit
(ECU) 12. The ECU 12 controls the electric motor 18 based on these
input signals.
[0033] FIG. 2 is a block diagram illustrating an electrical
configuration of the ECU 12.
[0034] The ECU 12 includes a microcomputer 31 that controls the
electric motor 18, a drive circuit (inverter circuit) 32 that is
controlled by the microcomputer 31 to supply electric power to the
electric motor 18, and a current detection circuit 33 that detects
a motor current (actual current value) I flowing through the
electric motor 18.
[0035] The microcomputer 31 includes a CPU and memories (e.g., a
ROM, a RAM, and a nonvolatile memory 34), and executes
predetermined programs to function as a plurality of function
processing units. These function processing units include a basic
target current value setting unit 41, a lane deviation determining
unit 42, an air-pressure drop determining unit 43, a warning
vibration wave generator 44, a vibration wave adding unit 45, a
current deviation computing unit 46, a PI controller 47, and a PWM
controller 48.
[0036] The basic target current value setting unit 41 sets a basic
target current value Io* based on the steering torque T detected by
the torque sensor 11 and the vehicle speed V detected by the
vehicle speed sensor 23. An example of the manner of setting the
basic target current value Io* with respect to the detected
steering torque T is illustrated in FIG. 3. In the detected
steering torque T, for example, the torque for steering the vehicle
to the right takes a positive value, and the torque for steering
the vehicle to the left takes a negative value. The basic target
current value Io* is set as a positive value when the steering
assisting force for steering the vehicle to the right needs to be
generated by the electric motor 18, and is set as a negative value
when the steering assisting force for steering the vehicle to the
left needs to be generated by the electric motor 18.
[0037] The basic target current value Io* takes a positive value
when the detected steering torque T is a positive value, and takes
a negative value when the detected steering torque T is a negative
value. When the detected steering torque T is a significantly low
value within a range from -T1 to T1 (e.g., T1=0.4 Nm) (torque dead
zone), the basic target current value Io* is set to zero. When the
detected steering torque T is a value outside the range from -T1 to
T1, the basic target current value Io* is set such that the
absolute value increases as the absolute value of the detected
steering torque T increases. Furthermore, the basic target current
value Io* is set such that the absolute value decreases as the
vehicle speed V detected by the vehicle speed sensor 23 increases.
By these settings, a larger steering assisting force can be
generated in low-speed traveling, and a smaller steering assisting
force can be generated in high-speed traveling.
[0038] Based on the image captured by the CCD camera 24, the lane
deviation determining unit 42 determines whether the vehicle is
highly likely to deviate from the lane, and provides the
determination result to the warning vibration wave generator 44.
The technique of capturing an image of a road ahead of the vehicle
in the traveling direction and determining whether the vehicle is
highly likely to deviate from the lane is known as described in,
for example, JP 4292562 B and JP 11-34774 A, and thus description
thereof is omitted.
[0039] Based on the air pressures P1 to P4 of the tires
respectively detected by the air-pressure sensors 25 to 28, the
air-pressure drop determining unit 43 determines whether the air
pressure of at least one tire is lower than a predetermined
threshold A, and provides the determination result to the warning
vibration wave generator 44.
[0040] The warning vibration wave generator 44 includes a first
warning vibration wave generator 51 and a second warning vibration
wave generator 52. The first warning vibration wave generator 51
receives the determination result from the lane deviation
determining unit 42. When the lane deviation determining unit 42
determines that the vehicle is highly likely to deviate from the
lane, the first warning vibration wave generator 51 generates a
first warning vibration wave (excitation signal) Ie1 to warn the
driver about this likelihood. The first warning vibration wave Ie1
is a wave having a frequency that varies with the vehicle speed V
detected by the vehicle speed sensor 23. In the present embodiment,
the first warning vibration wave Ie1 is a sinusoidal signal having
a frequency that varies with the vehicle speed V. Herein, the first
warning vibration wave Ie1 may be a wave other than the sinusoidal
signal having a frequency that varies with the vehicle speed V,
such as a triangular wave, a rectangular wave, or a wave obtained
by combining a triangular wave with a rectangular wave.
[0041] The second warning vibration wave generator 52 receives the
determination result from the air-pressure drop determining unit
43. When the air-pressure drop determining unit 43 determines that
the air pressure of at least one tire is lower than the threshold
A, the second warning vibration wave generator 52 generates a
second warning vibration wave (excitation signal) Ie2 having a
frequency that is different from that of the first warning
vibration wave Ie1 to warn the driver about this air pressure. The
second warning vibration wave Ie2 is a wave having a frequency that
varies with the vehicle speed V detected by the vehicle speed
sensor 23. In the present embodiment, like the first warning
vibration wave Ie1, the second warning vibration wave Ie2 is a
sinusoidal signal having a frequency that varies with the vehicle
speed V. However, the frequency f2(V) of the second warning
vibration wave Ie2 is set such that the frequency f2(V) of the
second warning vibration wave Ie2 for a certain vehicle speed V is
different from the frequency f1(V) of the first warning vibration
wave Ie1 for this vehicle speed V. Herein, the second warning
vibration wave Ie2 may be a wave other than the sinusoidal signal
having a frequency that varies with the vehicle speed V, such as a
triangular wave, a rectangular wave, or a wave obtained by
combining a triangular wave with a rectangular wave.
[0042] FIG. 4A illustrates an example of the manner of setting the
frequency f1(V) (hereinafter also called "first frequency f1(V)")
of the first warning vibration wave Ie1 with respect to the vehicle
speed V and the frequency f2(V) (hereinafter also called "second
frequency f2(V)") of the second warning vibration wave Ie2 with
respect to the vehicle speed V.
[0043] In the example in FIG. 4A, the first frequency f1(V) and the
second frequency f2(V) are set such that the frequencies become
lower as the vehicle speed V increases. In this example, this
setting is made such that the first frequency f1(V) is higher than
the second frequency f2(V) at the same vehicle speed V. The setting
is also made such that the difference between the first frequency
f1(V) and the second frequency f2(V) increases as the vehicle speed
V decreases. This is because it is more difficult to distinguish
between the first frequency f1(V) and the second frequency f2(V) at
higher frequencies. FIG. 5 illustrates an example of the first
warning vibration wave Ie1 and the second warning vibration wave
Ie2. The setting may be made such that the first frequency f1(V) is
lower than the second frequency f2(V) at the same vehicle speed
V.
[0044] FIG. 4B illustrates another example of the manner of setting
the frequency f1(V) of the first warning vibration wave Ie1 with
respect to the vehicle speed V and the frequency f2(V) of the
second warning vibration wave Ie2 with respect to the vehicle speed
V.
[0045] In the example in FIG. 4B, the first frequency f1(V) and the
second frequency f2(V) are set such that the frequencies become
higher as the vehicle speed V increases. In this example, this
setting is made such that the first frequency f1(V) is higher than
the second frequency f2(V) at the same vehicle speed V. The setting
is also made such that the difference between the first frequency
f1(V) and the second frequency f2(V) increases as the vehicle speed
increases. This is because it is more difficult to distinguish
between the first frequency f1(V) and the second frequency f2(V) at
higher frequencies. The setting may be made such that the first
frequency f1(V) is lower than the second frequency f2(V) at the
same vehicle speed V.
[0046] First warning vibration wave data for each vehicle speed V
and second warning vibration wave data for each vehicle speed V
are, for example, created in advance, and stored in the nonvolatile
memory 34. The first warning vibration wave generator 51 generates
the first warning vibration wave Ie1 based on the vehicle speed V
detected by the vehicle speed sensor 23 and the first warning
vibration wave data stored in the nonvolatile memory 34. The second
warning vibration wave generator 52 generates the second warning
vibration wave Ie2 based on the vehicle speed V detected by the
vehicle speed sensor 23 and the second warning vibration wave data
stored in the nonvolatile memory 34.
[0047] The vibration wave adding unit 45 computes a target current
value I* by adding the first warning vibration wave Ie1 generated
by the first warning vibration wave generator 51 and the second
warning vibration wave Ie2 generated by the second warning
vibration wave generator 52 to the basic target current value Io*
set by the basic target current value setting unit 41. The current
deviation computing unit 46 computes a deviation between the target
current value I* obtained by the vibration wave adding unit 45 and
the actual current value I detected by the current detection
circuit 33 (current deviation .DELTA.I=I*-I).
[0048] By executing P1 computation on the current deviation
.DELTA.I computed by the current deviation computing unit 46, the
PI controller 47 generates a drive command value for adjusting the
current I flowing through the electric motor 18 to the target
current value I*. The PWM controller 48 generates a PWM control
signal having a duty ratio that corresponds to the drive command
value, and supplies this signal to the drive circuit 32. Thus,
electric power corresponding to the drive command value is supplied
to the electric motor 18.
[0049] The current deviation computing unit 46 and the PI
controller 47 constitute a current feedback controller. By the
operation of this current feedback controller, the motor current I
flowing through the electric motor 18 is controlled so as to
approach the target current value I*.
[0050] In the present embodiment, when the lane deviation
determining unit 42 determines that the vehicle is highly likely to
deviate from the lane, the first warning vibration wave generator
51 generates the first warning vibration wave Ie1. This first
warning vibration wave Ie1 is added to the basic target current
value Io*, whereby the target current value I* is computed. The
motor current I flowing through the electric motor 18 is then
controlled so as to approach the target current value I*. Thus,
when the lane deviation determining unit 42 determines that the
vehicle is highly likely to deviate from the lane, the warning
vibration corresponding to the first warning vibration wave Ie1 is
applied to the steering wheel 2. This enables the driver to
recognize that the vehicle is highly likely to deviate from the
lane.
[0051] When the air-pressure drop determining unit 43 determines
that the air pressure of at least one tire is lower than the
threshold A, the second warning vibration wave generator 52
generates the second warning vibration wave Ie2. This second
warning vibration wave Ie2 is added to the basic target current
value Io*, whereby the target current value I* is computed. The
motor current I flowing through the electric motor 18 is then
controlled so as to approach the target current value I*. Thus,
when the air-pressure drop determining unit 43 determines that the
air pressure of at least one tire is lower than the threshold A,
the warning vibration corresponding to the second warning vibration
wave Ie2 is applied to the steering wheel 2. This enables the
driver to recognize that the tire air pressure is low.
[0052] When the air-pressure drop determining unit 43 determines
that the air pressure of at least one tire is lower than the
threshold A under the condition that the lane deviation determining
unit 42 determines that the vehicle is highly likely to deviate
from the lane, the first warning vibration wave Ie1 and the second
warning vibration wave Ie2 are added to the basic target current
value Io*, whereby the target current value I* is computed. Also
when the lane deviation determining unit 42 determines that the
vehicle is highly likely to deviate from the lane under the
condition that the air-pressure drop determining unit 43 determines
that the air pressure of at least one tire is lower than the
threshold A, the first warning vibration wave Ie1 and the second
warning vibration wave Ie2 are added to the basic target current
value Io*, whereby the target current value I* is computed.
[0053] The motor current I flowing through the electric motor 18 is
then controlled so as to approach the target current value I*.
Thus, when the lane deviation determining unit 42 determines that
the vehicle is highly likely to deviate from the lane and the
air-pressure drop determining unit 43 determines that the air
pressure of at least one tire is lower than the threshold A, the
warning vibration corresponding to a wave in which the first
warning vibration wave Ie1 and the second warning vibration wave
Ie2 are superimposed is applied to the steering wheel 2. This
enables the driver to recognize that the vehicle is highly likely
to deviate from the lane and also to recognize that the tire air
pressure is low.
[0054] FIG. 6 is a block diagram illustrating another example of
the electrical configuration of the ECU 12. In FIG. 6, components
corresponding to those in FIG. 2 described above are denoted by the
same numerals as in FIG. 2.
[0055] In the ECU 12 in FIG. 6, the configuration of the warning
vibration wave generator 44A is different from that of the warning
vibration wave generator 44 in FIG. 2.
[0056] The warning vibration wave generator 44A includes a first
warning vibration wave generator 51, a second warning vibration
wave generator 52, a first gate 53, a second gate 54, and a gate
controller 55.
[0057] The first warning vibration wave generator 51 is the same as
the first warning vibration wave generator 51 in FIG. 2. In other
words, when the lane deviation determining unit 42 determines that
the vehicle is highly likely to deviate from the lane, the first
warning vibration wave generator 51 generates a first warning
vibration wave Ie1 to warn the driver about this likelihood. In the
present embodiment, the first warning vibration wave Ie1 is a
sinusoidal signal having a frequency that varies with the vehicle
speed V. Output of the first warning vibration wave generator 51 is
provided to the first gate 53.
[0058] The second warning vibration wave generator 52 is the same
as the second warning vibration wave generator 52 in FIG. 2. In
other words, when the air-pressure drop determining unit 43
determines that the air pressure of at least one tire is lower than
the threshold A, the second warning vibration wave generator 52
generates a second warning vibration wave Ie2 having a frequency
that is different from that of the first warning vibration wave Ie1
to warn the driver about this air pressure. In the present
embodiment, the second warning vibration wave Ie2 is a sinusoidal
signal having a frequency that varies with the vehicle speed V. The
frequency f2(V) of the second warning vibration wave Ie2 is set
such that the frequency f2(V) of the second warning vibration wave
Ie2 for a certain vehicle speed V is different from the frequency
f1(V) of the first warning vibration wave Ie1 for this vehicle
speed V. Output of the second warning vibration wave generator 52
is provided to the second gate 54.
[0059] Based on the determination result of the lane deviation
determining unit 42 and the determination result of the
air-pressure drop determining unit 43, the gate controller 55
controls the first gate 53 and the second gate 54. Hereinafter, the
condition that the lane deviation determining unit 42 determines
that the vehicle is highly likely to deviate from the lane and the
air-pressure drop determining unit 43 determines that the air
pressure of at least one tire is lower than the threshold A is
referred to as "first determined condition", and the condition
other than the first determined condition is referred to as "second
determined condition".
[0060] Under the second determined condition, the gate controller
55 opens the first gate 53 and the second gate 54. Thus, under the
second determined condition, the output of the first warning
vibration wave generator 51 is provided to the vibration wave
adding unit 45 through the first gate 53, and the output of the
second warning vibration wave generator 52 is provided to the
vibration wave adding unit 45 through the second gate 54.
Consequently, for example, when the lane deviation determining unit
42 determines that the vehicle is highly likely to deviate from the
lane while the air-pressure drop determining unit 43 determines
that the air pressures of all tires are equal to or higher than the
threshold A, the first warning vibration wave Ie1 generated by the
first warning vibration wave generator 51 is provided to the
vibration wave adding unit 45 through the first gate 53.
[0061] When the air-pressure drop determining unit 43 determines
that the air pressure of at least one tire is lower than the
threshold A while the lane deviation determining unit 42 does not
determine that the vehicle is highly likely to deviate from the
lane, the second warning vibration wave Ie2 generated by the second
warning vibration wave generator 52 is provided to the vibration
wave adding unit 45 through the second gate 54.
[0062] Under the first determined condition, the first warning
vibration wave Ie1 is generated by the first warning vibration wave
generator 51, and the second warning vibration wave Ie2 is
generated by the second warning vibration wave generator 52. Under
the first determined condition, the gate controller 55 closes the
first gate 53 and the second gate 54 alternately. In other words,
under the first determined condition, the gate controller 55 opens
the first gate 53 and the second gate 54 alternately. The duration
for which the first gate 53 is open (duration for which the second
gate 54 is closed) and the duration for which the second gate 54 is
open (duration for which the first gate 53 is closed) may be set to
be the same, or may be set to be different. Specifically, under the
first determined condition, the first warning vibration wave Ie1
and the second warning vibration wave Ie2 are alternately
(cyclically) output in a time-divided manner so as not to overlap
temporally. The first warning vibration wave Ie1 and the second
warning vibration wave Ie2 may be generated at the same time, or
may be generated at different times. In this case also, the driver
can recognize that the vehicle is highly likely to deviate from the
lane, and can also recognize that the tire air pressure is low.
[0063] Although one embodiment of the present invention has been
described above, the present invention may be implemented in other
embodiments. For example, in the above embodiment, the case has
been described in which the warning vibration is applied for two
vehicle conditions, the vehicle highly likely to deviate from the
lane and low tire air pressure. However, the present invention may
be applied also to the case in which the warning vibration is
applied for three or more vehicle conditions. In this case as well,
a warning vibration wave having a frequency that varies with the
vehicle speed can be generated for each vehicle condition. Herein,
the frequencies of the warning vibration waves for the
corresponding vehicle conditions are set to be different from each
other at the same vehicle speed.
[0064] The vehicle conditions for which the warning vibration is
applied may be any vehicle conditions about which the driver needs
to be warned. Examples thereof include, in addition to the vehicle
conditions described above, a condition immediately before the time
when the brake is applied in response to a detection of an obstacle
or other objects, a condition that the amount of fuel such as
gasoline falls to or below a predetermined value, and a condition
that a fuel lid is open during traveling.
[0065] In addition, various design changes may be made within the
scope of the matters described in the claims.
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