U.S. patent application number 11/871066 was filed with the patent office on 2008-02-07 for tire distortion detecting method, distortion detector, and tire thereof.
This patent application is currently assigned to The Yokohama Rubber Co., Ltd.. Invention is credited to Yutaka Hattori.
Application Number | 20080029192 11/871066 |
Document ID | / |
Family ID | 31492177 |
Filed Date | 2008-02-07 |
United States Patent
Application |
20080029192 |
Kind Code |
A1 |
Hattori; Yutaka |
February 7, 2008 |
TIRE DISTORTION DETECTING METHOD, DISTORTION DETECTOR, AND TIRE
THEREOF
Abstract
The present invention provides a tire distortion detecting
method, a distortion detector, and a tire which can reduce the
occurrence of a deterioration and can be used for a control system
such as a stability control system. That is, series of conductors
composed of a plurality of conductor pieces are provided in two
different layers. The conductor pieces are embedded in lines at
predetermined intervals in the circumferential direction of a tire.
A pulsed electromagnetic wave is radiated to the surfaces of metal
foils in the layers from a monitoring device provided in a tire
house of a vehicle. The monitoring device receives a pulsed
electromagnetic wave reflected from the metal foils in the layers
or a member other than the metal foils. Time from the radiation of
a pulsed electromagnetic wave to the reception of a reflected
pulsed magnetic wave is measured repeatedly, time at which no
distortion occurs on the tire is stored as a reference value, and
the measured time and the stored reference value are compared with
each other to detect a distortion of the tire.
Inventors: |
Hattori; Yutaka;
(Hiratsuka-shi, JP) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET
FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Assignee: |
The Yokohama Rubber Co.,
Ltd.
36-11, Shimbashi 5-chome
Tokyo
JP
105-8685
|
Family ID: |
31492177 |
Appl. No.: |
11/871066 |
Filed: |
October 11, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10505215 |
Aug 20, 2004 |
7302836 |
|
|
PCT/JP03/09169 |
Jul 18, 2003 |
|
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|
11871066 |
Oct 11, 2007 |
|
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|
Current U.S.
Class: |
152/152.1 |
Current CPC
Class: |
G01M 17/02 20130101;
B60T 8/1725 20130101; B60C 13/001 20130101; B60G 2204/113 20130101;
B60C 19/00 20130101; B60C 11/00 20130101; G01S 13/88 20130101; B60C
23/064 20130101; B60C 23/068 20130101; B60T 2240/04 20130101; B60C
23/06 20130101 |
Class at
Publication: |
152/152.1 |
International
Class: |
B60C 19/00 20060101
B60C019/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 2, 2002 |
JP |
226050/2002 |
Claims
1. A tire, characterized in that series of conductors are embedded
in two or more different layers with a part having no overlapping
surfaces, the series of conductors being composed of a plurality of
conductor pieces embedded in lines at predetermined intervals in a
circumferential direction of the tire.
2. The tire according to claim 1, characterized in that the
conductor pieces are embedded in the tire so that the surfaces of
the conductor pieces are almost in parallel with a surface of a
tire tread.
3. The tire according to claim 1, characterized in that the
conductor pieces are embedded in the tire so that the surfaces of
the conductor pieces are almost in parallel with a surface of a
side wall of the tire.
4. The tire according to claim 1, characterized in that at least in
an outermost line of the conductor pieces relative to an axis of
rotation of the tire at the center, the conductor pieces are
arranged at regular intervals in the circumferential direction of
the tire to set a length of the conductor piece in the
circumferential direction of the tire equal to a length of a gap
between the adjacent conductor pieces.
5. The tire according to claim 1, characterized in that the
conductor pieces are arranged so that in a second series of
conductors provided inside a first series of conductors, ends of
the conductor piece in the circumferential direction overlap, by a
predetermined length, ends of the conductor piece in the
circumferential direction of the tire in the first series of
conductors which is outermost relative to an axis of rotation of
the tire at the center.
6. The tire according to claim 1, characterized in that the
conductor pieces are arranged at regular intervals in the same
layer.
7. The tire according to claim 1, characterized in that the
conductor pieces of the layers are arranged so that the conductor
pieces in the two different layers are alternately arranged in the
circumferential direction of the tire.
8. The tire according to claim 7, characterized in that the
conductor pieces of the layers are arranged so that the conductor
pieces partly overlap each other in the circumferential direction
of the tire.
9. The tire according to claim 1, characterized in that the
conductor pieces of the layers are displaced from each other in a
width direction of the tire.
10. The tire according to claim 2, characterized in that the
conductor pieces of the layers are displaced from each other in a
width direction of the tire.
11. The tire according to claim 3, characterized in that the
conductor pieces of the layers are displaced from each other in a
width direction of the tire.
12. The tire according to claim 4, characterized in that the
conductor pieces of the layers are displaced from each other in a
width direction of the tire.
13. The tire according to claim 5, characterized in that the
conductor pieces of the layers are displaced from each other in a
width direction of the tire.
14. The tire according to claim 6, characterized in that the
conductor pieces of the layers are displaced from each other in a
width direction of the tire.
15. The tire according to claim 7, characterized in that the
conductor pieces of the layers are displaced from each other in a
width direction of the tire.
16. The tire according to claim 8, characterized in that the
conductor pieces of the layers are displaced from each other in a
width direction of the tire.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Divisional of U.S. application Ser.
No. 10/505,215 filed Aug. 20, 2004, entitled "TIRE DISTORTION
DETECTING METHOD, DISTORTION DETECTOR, AND TIRE THEREOF."
BACKGROUND OF THE INVENTION
[0002] 1. Technical Field
[0003] The present invention relates to a tire distortion detecting
method, a distortion detector, and a tire thereof that detects a
distortion of the tire during the running of a vehicle.
[0004] 2. Background Art
[0005] Conventionally cautions for the safe driving of a vehicle
include a proper setting of an air pressure in a tire of the
vehicle and attention to the wear of the tire. For example, a
reduced air pressure in a tire increases the occurrence of flat
tires and causes a burst at high speed, resulting in a serious
accident. Therefore, drivers have to check tires on a daily
basis.
[0006] However, even if tires are checked and preferred conditions
are maintained for the tires, when a friction between a road
surface and the tires decreases, for example, when a road surface
is wet on a rainy day, skids occur under braking and move the
vehicle in an unexpected direction, resulting in some
accidents.
[0007] In order to prevent accidents caused by skids and a fast
start, Anti-Lock Brake System (hereinafter referred to as ABS) and
a traction control system are developed, and a stability control
system having a YAW sensor is also developed in addition to these
systems.
[0008] For example, ABS is a system of detecting a rotating state
of each tire and controlling a braking force based on detection
results so as to prevent the tires from locking.
[0009] The number of revolutions, an air pressure, a distortion,
and so forth of each tire are detected as a rotating state of tires
and detection results can be used for control.
[0010] For example, a detector for automatically detecting an air
pressure of a tire is known. Such a detector uses a so-called
"indirect" method of detecting an air pressure of a tire. In this
method, data is inputted from an ABS speed sensor to estimate an
air pressure of a tire.
[0011] As a method of detecting an air pressure of a tire that is
used for the detector, the following methods are known: (a) a
method of calculating a change (distortion) in the rolling radius
of a tire by an angular speed of rotation of a wheel, the change
being caused by a reduced air pressure, and (b) a method of
performing FFT (Fast Fourier Transform) on an input signal and
performing calculations using a change in the natural frequency of
a tire.
[0012] On the other hand, as examples of a sensor and a tire that
are used for the ABS, the traction control system, and the
stability control system, U.S. Pat. No. 5,895,854 (hereinafter
referred to as conventional example 1) and U.S. Pat. No. 6,308,758
(hereinafter referred to as conventional example 2) are known.
[0013] In conventional example 1, magnetic bar codes are provided
which are arranged in lines in the circumferential direction of the
side wall of a tire with adjacent parts alternately changed in
polarity, and the bar codes are read by a sensor fixed on a chassis
and a axis arm. Thus, the rotating speed of the tire can be
detected. Further, the magnetic bar codes are provided in two or
more lines in the radius direction of the tire, thereby calculating
a force and deformation in the radius direction of the tire based
on a phase difference between the detection results of the inner
and outer magnetic bar codes.
[0014] In contrast to conventional example 1 having difficulty in
forming magnetic bands at small intervals, conventional example 2
reduces the difficulty and discloses a tire improved in the
resolution of magnetic bar codes arranged in lines in the
circumferential direction of the side wall of the tire with
adjacent parts alternately changed in polarity.
[0015] However, in conventional examples 1 and 2, since the
magnetic bands are formed on the side wall when the tire is
manufactured, it is quite troublesome to set the magnetic force of
the magnetic band at the optimum value. That is, when the magnetic
force of the magnetic band is much higher than the optimum value, a
magnetic substance such as iron sand and an iron piece on a road
surface may be adsorbed. Further, when the magnetic force of the
magnetic band is lower than the optimum value, the detection of the
sensor becomes difficult.
[0016] Moreover, the magnetic bands may gradually decrease in
magnetization due to heat generated on the tire during the running
of a vehicle and the detection of the sensor may become more
difficult as running time increases.
[0017] In view of the above problems, an object of the present
invention is to provide a tire distortion detecting method, a
distortion detector, and a tire that can reduce the occurrence of a
deterioration and can be used for a control system such as a
stability control system.
DISCLOSURE OF THE INVENTION
[0018] A tire distortion detecting method of the present invention
uses a tire, in which a plurality of conductor pieces embedded in
lines at predetermined intervals in the circumferential direction
of the tire are embedded in two or more different layers, and a
monitoring device which has a scanner unit provided in a tire house
of a vehicle. When a distortion of a rotating tire is detected by
using the tire and the monitoring device, a pulsed electromagnetic
wave is radiated to the surface of the conductor piece along the
lines of the conductor pieces in each of the layers. Further, the
scanner unit receives the pulsed electromagnetic wave reflected
from the conductor piece in each of the layers and a member other
than the conductor pieces. The monitoring device repeatedly
measures time from when the scanner unit radiates the pulsed
electromagnetic wave to when the scanner unit receives the
reflected pulsed electromagnetic wave. The monitoring device
stores, as a reference value, time at which no distortion occurs on
the tire and compares an actually measured time with the stored
reference value to detect a distortion of the tire.
[0019] According to the tire distortion detecting method of the
present invention, the pulsed electromagnetic wave radiated from
the scanner unit is reflected by the conductor piece or another
member having a characteristic of reflecting an electromagnetic
wave, and the reflected pulsed electromagnetic wave is received by
the scanner unit.
[0020] Time from when the scanner unit radiates a pulsed
electromagnetic wave to when the scanner unit receives the
reflected wave, i.e., the round-trip time of the pulsed
electromagnetic wave changes according to a distance between the
scanner unit and a reflector for reflecting the pulsed
electromagnetic wave. Further, when a distortion of the tire
changes, a difference in the round-trip time of a pulsed
electromagnetic wave also changes that corresponds to each of the
conductor pieces embedded in the different layers. Moreover, when a
distortion of the tire changes, the conductor pieces are displaced
according to the distortion and a pulsed electromagnetic wave
radiated from the scanner unit is reflected to the scanner unit by
a member other than the conductor pieces. Therefore, it is possible
to detect a distortion of the tire by the round-trip time of a
pulsed electromagnetic wave or a difference in the round-trip time
of the different layers.
[0021] Besides, according to the tire distortion detecting method
of the present invention, the monitoring device radiates one or
more pulsed electromagnetic waves in an interval of a smaller
distance or length, out of a distance between the conductor pieces
adjacent to each other in the circumferential direction of the tire
or the length of the conductor piece arranged in the
circumferential direction of the tire, so that time measurement is
conducted on all the conductor pieces and between the adjacent
conductor pieces. The tire distortion detecting method of the
present invention can obtain resolutions more than the number of
the conductor pieces arranged in lines along the circumferential
direction of the tire, thereby detecting a distortion with high
accuracy.
[0022] Additionally, according to the tire distortion detecting
method of the present invention, the monitoring device uses a
frequency of 1 GHz or higher to radiate a pulsed electromagnetic
wave. Thus, it is possible to reduce the influence of reflection
made by a reinforcing metal in the tire, the reinforcing metal
having a gap larger than the wavelength of the frequency.
[0023] Besides, a tire distortion detector is constituted of a
tire, in which a plurality of conductor pieces embedded in lines at
predetermined intervals in the circumferential direction of the
tire are embedded in two or more different layers, and a monitoring
device which has a scanner unit provided in a tire house of a
vehicle.
[0024] The monitoring device comprises means for radiating a pulsed
electromagnetic wave from the scanner unit to a surface of the
conductor piece along the line of the conductor pieces in each of
the layers of the tire, means which is provided in the scanner unit
and receives the pulsed electromagnetic wave reflected by the
conductor piece in each of the layers of the tire and a member
other than the conductor piece, means for measuring time from the
radiation of the pulsed electromagnetic wave to the reception of
the reflected pulsed electromagnetic wave, means for alternately
repeating the radiation of the pulsed electromagnetic wave and the
reception of the reflected pulsed electromagnetic wave, means for
storing, as a reference value, time at which no distortion occurs
on the tire, and means for comparing the measured time and the
stored reference value to detect a distortion of the tire.
[0025] According to the tire distortion detector of the present
invention, the pulsed electromagnetic wave radiated from the
scanner unit is reflected by the conductor piece or another member
having a characteristic of reflecting an electromagnetic wave, and
the reflected pulsed electromagnetic wave is received by the
scanner unit.
[0026] Time from when the scanner unit radiates a pulsed
electromagnetic wave to when the scanner unit receives the
reflected wave, i.e., the round-trip time of the pulsed
electromagnetic wave changes according to a distance between the
scanner unit and a reflector for reflecting the pulsed
electromagnetic wave.
[0027] Further, when a distortion of the tire changes, a difference
in the round-trip time of a pulsed electromagnetic wave also
changes that corresponds to each of the conductor pieces embedded
in the different layers. Moreover, when a distortion of the tire
changes, the conductor pieces are displaced according to the
distortion and a pulsed electromagnetic wave radiated from the
scanner unit is reflected to the scanner unit by a member other
than the conductor pieces.
[0028] The monitoring device repeatedly measures the round-trip
time of a pulsed electromagnetic wave and stores, as a reference
value, time at which no distortion occurs on the tire. Further, the
monitoring device compares time measured in the running of the
vehicle with the stored reference value to detect a distortion of
the tire. Therefore, it is possible to detect a distortion of the
tire by the round-trip time of a pulsed electromagnetic wave or a
difference in the round-trip time of a pulsed electromagnetic wave
in the different layers of the tire.
[0029] Moreover, according to the tire distortion detector of the
present invention, when a distortion is made detectable mainly on
the tread of the tire, the conductor pieces are embedded in the
tire so that the surfaces of the conductor pieces are almost in
parallel with the surface of the tire tread.
[0030] Besides, according to the tire distortion detector of the
present invention, when a distortion is made detectable mainly on
the side wall of the tire, the conductor pieces are embedded in the
tire so that the surfaces of the conductor pieces are almost in
parallel with the surface of the side wall of the tire.
[0031] Additionally, according to the tire distortion detector of
the present invention, the pulsed electromagnetic wave is set at a
frequency of 1 GHz or higher in order to reduce the influence of
reflection made by the reinforcing metal in the tire, the
reinforcing metal having a gap larger than the wavelength of the
frequency.
[0032] Moreover, according to the tire distortion detector of the
present invention, at least in the outermost line of the conductor
pieces relative to the axis of rotation of the tire at the center,
the conductor pieces are arranged at regular intervals in the
circumferential direction of the tire to set the length of the
conductor piece in the circumferential direction of the tire equal
to the length of a gap between the adjacent conductor pieces, so
that measurement time changes at regular intervals when the tire
having no distortion rotates at a fixed number of revolutions.
[0033] Besides, according to the tire distortion detector of the
present invention, the conductor pieces are arranged so that in a
second series of conductors provided inside a first series of
conductors, the ends of the conductor piece in the circumferential
direction of the tire overlap, by a predetermined length, the ends
of the conductor piece in the circumferential direction of the tire
in the first series of conductors which is outermost relative to
the axis of rotation of the tire at the center.
[0034] According to the tire distortion detector of the present
invention, when a distortion of the tire is larger than a
predetermined amount, an overlap disappears between the conductor
piece of the first series of conductors and the conductor piece of
the second series of conductors and a gap appears between the
series of conductors. The occurrence of the gap largely changes the
round-trip time of a pulsed electromagnetic wave and thus it is
possible to detect that a distortion of the tire has become larger
than the predetermined amount.
[0035] Further, according to the present invention, as a tire used
for the tire distortion detector, a tire is configured so that
series of conductors are embedded in two or more different layers
with a part having no overlapping surface, the series of conductors
being composed of a plurality of conductor pieces embedded in lines
at predetermined intervals in the circumferential direction of the
tire.
[0036] Moreover, according to the tire of the present invention,
when a distortion is made detectable mainly on the tread of the
tire, the conductor pieces are embedded in the tire so that the
surfaces of the conductor pieces are almost in parallel with the
surface of the tire tread.
[0037] Besides, according to the tire of the present invention,
when a distortion is made detectable mainly on the side wall of the
tire, the conductor pieces are embedded in the tire so that the
surfaces of the conductor pieces are almost in parallel with the
surface of the side wall of the tire.
[0038] Additionally, according to the tire of the present
invention, at least in the outermost line of the conductor pieces
relative to the axis of rotation of the tire at the center, the
conductor pieces are arranged at regular intervals in the
circumferential direction of the tire to set the length of the
conductor piece in the circumferential direction of the tire equal
to the length of a gap between the adjacent conductor pieces.
[0039] Further, according to the tire of the present invention, the
conductor pieces are arranged so that in a second series of
conductors provided inside a first series of conductors, the ends
of the conductor piece in the circumferential direction of the tire
overlap, by a predetermined length, the ends of the conductor piece
in the circumferential direction of the tire in the first series of
conductors which is outermost relative to the axis of rotation of
the tire at the center.
[0040] According to the tire of the present invention, the
conductor pieces are arranged at regular intervals in the same
layer.
[0041] According to the tire of the present invention, the
conductor pieces of the layers are arranged so that the conductor
pieces in the two different layers are alternately arranged in the
circumferential direction of the tire.
[0042] According to the tire of the present invention, the
conductor pieces of the layers in the tire are arranged so that the
conductor pieces partly overlap each other in the circumferential
direction of the tire.
[0043] According to the tire of the present invention, the
conductor pieces of the layers in the tire are displaced from each
other in the width direction of the tire.
BRIEF DESCRIPTION OF THE DRAWINGS
[0044] FIG. 1 is a schematic diagram showing a state of mounting a
tire distortion detector into a vehicle according to Embodiment 1
of the present invention;
[0045] FIG. 2 is a top view showing the tire according to
Embodiment 1 of the present invention;
[0046] FIG. 3 is cutaway view showing a state of embedding metal
foils in the tire according to Embodiment 1 of the present
invention;
[0047] FIG. 4 is a diagram for explaining an overlapping state of
the metal foils of different layers according to Embodiment 1 of
the present invention;
[0048] FIG. 5 is a structural diagram showing a specific example of
an electrical circuit of a monitoring device according to
Embodiment 1 of the present invention.
[0049] FIG. 6 is a diagram for explaining a method of detecting a
distortion of the tire according to Embodiment 1 of the present
invention;
[0050] FIG. 7 is a diagram for explaining the method of detecting a
distortion of the tire according to Embodiment 1 of the present
invention;
[0051] FIG. 8 is a timing chart for explaining the method of
detecting a distortion of the tire according to Embodiment 1 of the
present invention;
[0052] FIG. 9 is a timing chart for explaining the method of
detecting a distortion of the tire according to Embodiment 1 of the
present invention;
[0053] FIG. 10 is a timing chart for explaining the method of
detecting a distortion of the tire according to Embodiment 1 of the
present invention;
[0054] FIG. 11 is a diagram for explaining the method of detecting
a distortion of the tire according to Embodiment 1 of the present
invention;
[0055] FIG. 12 is a timing chart for explaining the method of
detecting a distortion of the tire according to Embodiment 1 of the
present invention;
[0056] FIG. 13 is a diagram for explaining a use example of the
tire distortion detector according to Embodiment 1 of the present
invention;
[0057] FIG. 14 is a schematic diagram showing a state of mounting a
tire distortion detector into a vehicle according to Embodiment 2
of the present invention;
[0058] FIG. 15 is cutaway view showing a state of embedding metal
foils in the tire according to Embodiment 3 of the present
invention; and
[0059] FIG. 16 is a top view for explaining a state of embedding
the metal foils in the tire according to Embodiment 3 of the
present invention.
BEST MODES FOR CARRYING OUT THE INVENTION
[0060] The following will describe embodiments of the present
invention in accordance with the accompanying drawings.
[0061] FIG. 1 is a schematic view showing a mounting state of a
tire distortion detector into a vehicle according to Embodiment 1
of the present invention. In FIG. 1, reference numerals 101 and 102
denote metal foils (conductor piece), reference numeral 200 denotes
a monitoring device, reference numeral 300 denotes a tire, and
reference numeral 400 denotes a tire house.
[0062] The metal foils 101 and 102 are made of a metal such as an
aluminum foil, which reflects an electromagnetic wave and is shaped
like a rectangle with a predetermined width and a predetermined
length.
[0063] As shown in FIGS. 2 to 4, the plurality of metal foils 101
are arranged in lines at regular intervals along the
circumferential direction, which has the axis of rotation of the
tire 300 at the center, in a layer between a cap tread 301 and an
under tread 302 so that the surfaces of the metal foils 101 are
almost in parallel with the surface of the cap tread 301 and the
long sides of the metal foils 101 match the circumferential
direction which has the axis of rotation of the tire 300 at the
center. Further, a distance between the adjacent metal foils 101
(length L12 of a gap) is set equal to a length L11 of the metal
foil 101.
[0064] Moreover, the plurality of metal foils 102 are arranged in
lines at regular intervals L22 along the circumferential direction,
which has the axis of rotation of the tire 300 at the center,
between a carcass 304 and a belt 303B so that the surfaces of the
metal foils 102 are almost in parallel with the surface of the cap
tread 301 and the long sides of the metal foils 102 match the
circumferential direction which has the axis of rotation of the
tire 300 at the center. Additionally, as shown in FIG. 4, a length
L21 of the long side of the metal foil 102 is set so that the both
ends in the longitudinal direction of the metal foil 102 each
overlap the ends of the different metal foils 101 by a length
L3.
[0065] Further, the metal foils 101 and 102 are arranged so that
the center in the width direction of a series of conductors
composed of the plurality of metal foils 101 substantially overlaps
the center in the width direction of a series of conductors
composed of the plurality of metal foils 102.
[0066] The monitoring device 200 is provided in the tire house 400
of the vehicle so as to correspond with the top of the tire 300.
The tire distortion detector of the present embodiment is
constituted of the tire 300, which has the metal foils 101 and 102
embedded therein, and the monitoring device 200.
[0067] As shown in FIG. 5, the monitoring device 200 is constituted
of a radiation unit 210, a receiving unit 220, a control section
230, an arithmetic section 240, and a distortion detecting section
250.
[0068] The radiation unit 210 is constituted of an antenna 211,
which radiates an electromagnetic wave at a predetermined frequency
of 2.45 GHz, and an oscillation section 212. In response to an
instruction from the control section 230, an electromagnetic wave
at the above frequency is radiated like a pulse from the antenna
211.
[0069] The oscillation section 212 is constituted of an oscillator
circuit 213 and a power amplifier circuit 214. The oscillator
circuit 213 is constituted of a known PLL circuit and so on and
outputs a carrier wave at a frequency of 2.45 GHz in response to an
instruction from the control section 230.
[0070] The power amplifier 214 amplifies a carrier wave having been
outputted from the oscillator circuit 131 and feeds the carrier
wave as a pulse to the antenna 211. Thus, a pulsed electromagnetic
wave at 2.45 GHz is radiated from the antenna 211. Additionally,
high-frequency power outputted from the power amplifier circuit 214
is set at a value enabling the metal foils 101 and 102 to reflect
the pulsed electromagnetic wave, which has been radiated from the
antenna 211 for radiating an electromagnetic wave in the monitoring
device 200, as shown in FIG. 1 and enabling the antenna 221, which
will be described later, to receive the reflected pulsed
electromagnetic wave.
[0071] The receiving unit 220 is constituted of an antenna 221,
which receives an electromagnetic wave at a frequency of 2.45 GHz,
and a detecting section 222. In response to an instruction from the
control section 230, the receiving unit 220 converts the
high-frequency energy of an electromagnetic wave, received by the
antenna 221 in a predetermined frequency band width including 2.45
GHz into direct-current voltage and outputs the voltage as a
detection voltage Vout.
[0072] The detecting section 222 is constituted of a tuned circuit
223 and a detector circuit 224.
[0073] The tuned circuit 223 is tuned to an electromagnetic wave in
a frequency band of .+-..DELTA.f1 having its center at 2.45 GHz,
and the turned circuit 223 converts high-frequency energy into
electric energy and outputs the electric energy.
[0074] The detector circuit 224 converts the electric energy having
been outputted from the tuned circuit 223 into direct-current
voltage and outputs the voltage as the detection voltage Vout.
[0075] The control section 230 makes initial settings when
receiving an initial setting instruction from a host device (not
shown) and the control section 230 detects a distortion when
receiving an instruction to detect distortion from the host
device.
[0076] The initial settings are made when the tire 300 rotates with
no distortion during the running of the vehicle.
[0077] In the initial settings, the control section 230 notifies
the distortion detecting section 250 of the initial settings and
then drives the oscillation section 212 to radiate the pulsed
electromagnetic wave with a pulse width of time t1 at predetermined
time intervals, and the control section 230 notifies the arithmetic
section 240 of the timing of radiating the pulsed electromagnetic
wave. Besides, it is preferable that the time intervals for
radiating the pulsed electromagnetic wave are set so as to obtain
one or more reflected waves from each of the metal foils 101 and
102. It is needless to say that a distortion can be accurately
detected by reducing the time intervals for radiating the pulsed
electromagnetic wave.
[0078] The arithmetic section 240 measures time T from when the
notification about the timing of radiation is received to when the
detection voltage Vout exceeds a predetermined threshold value,
that is until the reception of the pulsed electromagnetic wave
having been reflected from the metal foils 101 and 102 and so on,
and the arithmetic section 240 outputs the value to the distortion
detecting section 250.
[0079] In the initial settings, the distortion detecting section
250 stores measurement time periods, which are outputted from the
arithmetic section 240, sequentially in time sequence and stores a
round-trip time T1 of a pulsed electromagnetic wave reflected from
the metal foil 101 and a round-trip time T2 of a pulsed
electromagnetic wave reflected from the metal foil 102, based on
the stored values at the completion of the initial settings.
Further, the distortion detecting section 250 calculates an average
value T avg of measurement times T in initial setting time and
stores the average value T avg. Furthermore, the distortion
detecting section 250 outputs the round-trip times T1 and T2 and
the average value T avg to the host device.
[0080] In the initial settings, when the settings may be changed by
the speed of the vehicle, i.e., the number of revolutions of the
tire 300, it is preferable to make the settings at a plurality of
speeds and determine round-trip times T1 and T2 and an average
value T avg at each of the speeds.
[0081] Further, in the distortion detection, the control section
230 notifies the distortion detecting section 250 of distortion
detection and then drives the oscillation section 212 to radiate a
pulsed electromagnetic wave with a pulse width of time t1.
Moreover, the control section 230 notifies the arithmetic section
250 of the timing of radiating the pulsed electromagnetic wave.
[0082] The arithmetic section 240 measures time T from when the
notification about the timing of radiation is received to when the
detection voltage Vout exceeds the predetermined threshold value,
that is until the reception of the pulsed electromagnetic wave
having been reflected from the metal foils 101 and 102 and so on,
and the arithmetic section 240 outputs the value to the distortion
detecting section 250.
[0083] The distortion detecting section 250 calculates a difference
T dif (=T-T avg) between the measurement time T, which is outputted
from the arithmetic section 240, and the stored average value T
avg, and the distortion detecting section 250 outputs the
difference T dif and the measurement time T sequentially in time
sequence to the host device.
[0084] The difference T dif and the measurement time T may be
outputted to the host device at other predetermined time intervals
and may not be outputted every time a measurement is performed.
This setting is preferably made as necessary according to the
diameter of the tire 300, the length L11 and L21 and the intervals
L12 and L22 of the metal foils 101 and 102, the processing speed of
the arithmetic section 240, or the requests from the host
device.
[0085] The following will describe a tire distortion detecting
method using the detector configured thus.
[0086] When no distortion occurs on the tire 300, as shown in FIGS.
6 and 7, a pulsed electromagnetic wave P1 radiated from the
monitoring device 200 is reflected on the metal foil 101 or the
metal foil 102 and is received as a reflected wave P2 by the
monitoring device 200.
[0087] At this point, the round-trip time T of the pulsed
electromagnetic wave that is measured by the monitoring device 200
repeatedly changes between the time T1 and the time T2 as shown in
FIG. 8. Further, time T.sub.L1 keeping the measurement time T1 and
time T.sub.L2 keeping the measurement time T2 are maintained almost
constant according to the length L11 of the metal foil 101, the
interval L12 thereof, and the number of revolutions of the tire
300.
[0088] On the other hand, when the tire 300 has the same number of
revolutions and a pressure is applied from the front and back to
the top of the tire 300 so as to compress the top of the tire 300,
the length L11 and the interval L12 of the metal foil 101 are
reduced. Hence, as shown in FIG. 9, time T.sub.L1A keeping the
measurement time T1 and time T.sub.L2A keeping the measurement time
T2 are smaller than the time T.sub.L1 and the time T.sub.L2 during
which no distortion occurs.
[0089] Moreover, when the tire 300 has the same number of
revolutions and a pressure is applied from the top of the tire 300
to the front and back so as to expand the top of the tire 300, the
length L11 and the interval L12 of the metal foil 101 are
increased. Hence, as shown in FIG. 10, time T.sub.L1B keeping the
measurement time T1 and time T.sub.L2B keeping the measurement time
T2 are larger than the time T.sub.L1 and the time T.sub.L2 during
which no distortion occurs.
[0090] Furthermore, when the pressure from the top of the tire 300
to the front and back increases, a part having the metal foil 101
and the metal foil 102 overlapping in the circumferential direction
of the tire (an overlap with the length L3) disappears and a gap
103 with a length L4 appears between the metal foil 101 and the
metal foil 102. When the pulsed electromagnetic wave P1 radiated
from the monitoring device 200 is caused to be incident into the
gap 103, the pulsed electromagnetic wave P1 is reflected by an
electromagnetic reflector, for example, a rim 305 positioned closer
to the axis of rotation of the tire than the metal foil 102, and
the reflected wave P2 is received by a monitor unit 200.
[0091] At this point, as shown in FIG. 12, the round-trip time T of
the pulsed electromagnetic wave is equal to time T3 which is larger
than the round-trip time T2 of the reflection from the metal foil
102.
[0092] Therefore, a distortion of the tire 300 can be detected by
using the difference T dif (=T-T avg) outputted from the distortion
detecting section 205.
[0093] For example, the tire distortion detector is applicable to a
stability controller 500 shown in FIG. 13. A conventional and
typical stability controller captures detection results outputted
from sensors 510 and 520, which detect the number of revolutions of
the tire 300 mounted in the vehicle, to perform stability control.
By adding the stability controller 500, in which the tire 300 and
the monitoring device 200 are provided and detection results
outputted from the monitoring device 200 are captured to perform
stability control, to the conventional configuration, it is
possible to perform control with higher accuracy. In this case, an
instruction from the monitoring device 200 to the control section
230 is outputted from the stability controller 500.
[0094] Further, as shown in FIG. 14, Embodiment 2 of the present
invention has two monitoring devices 200A and 200B at the front and
back of the top of a tire house 400. In this case, an
electromagnetic wave may be radiated and received in a time-sharing
manner by the monitoring devices 200A and 200B. Thus, a distortion
can be detected on two points of a tire 300. Additionally a
monitoring device 200 may be provided on three or more points of
the tire house 400 so as to detect a distortion on three points of
the tire 300.
[0095] Moreover, according to Embodiment 3 of the present
invention, as shown in FIGS. 15 and 16, a tire 300A is provided
instead of the tire 300 of Embodiment 1. Embodiment 3 is different
from Embodiment 1 only in the tire 300A.
[0096] In the tire 300A, a series of conductors composed of a
plurality of metal foils 101 and a series of conductors composed of
a plurality of metal foils 102 are displaced in opposite directions
along the width of the tire 300A. Besides, the widths of the metal
foil 101 and the metal foil 102 are set as Embodiment 1 and only a
width L5 of an overlap of the metal foil 101 and the metal foil 102
is set smaller than that of Embodiment 1. Therefore, it is possible
to increase the accuracy of detecting a distortion in the width
direction of the tire 300A.
[0097] The above-described embodiments are specific examples of the
present invention and thus the present invention is not limited to
these embodiments. For example, it is needless to say that the same
effect can be obtained by a configuration having the metal foils
101 and 102 on the side wall of the tire.
[0098] Further, although a pulsed electromagnetic wave has a
frequency of 2.45 GHz in the above-described embodiments, the
frequency is not particularly limited. As described above, a
frequency at 1 GHz or higher can remarkably reduce the influence of
a reinforcing metal in the tire that reflects and interrupts an
electromagnetic wave, thereby detecting a distortion of the tire
with high accuracy. Moreover, it is preferable to properly set a
frequency of a pulsed electromagnetic wave in consideration of the
influence of the reinforcing metal and so on in designing.
[0099] Moreover, it is needless to say that these embodiments are
applicable to sensors for a traction controller or a device which
performs active control on a suspension, a stabilizer in the
suspension, and so on.
INDUSTRIAL APPLICABILITY
[0100] As described above, according to the present invention, a
workload for manufacturing a tire can be reduced as compared with
the conventional art, applicability is widened to a control system
such as a stability control system, a deterioration and a damage in
a sensor unit can be reduced that are caused by heat generated on
the tire during the running of the vehicle, and a distortion of the
tire can be detected with high accuracy.
* * * * *