JP2005067585A - Tire state measuring rfid system, antenna of tag and wheel equipped with antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire state measuring RFID system capable of surely measuring a tire state of a tire such as a pressure, an antenna of a tag and a wheel equipped with the antenna. <P>SOLUTION: A flexible magnetic material 10 in a shape of a plate is wound around an outer periphery of the wheel 6b for holding a tire 6a of a vehicle, a conductor is wound around thereof so as to form an antenna coil 3a of the tag 3, and a part such as an electric circuit of the tag 3 or a pressure detector is installed on the wheel 6b. Thereby, the antenna coil 3a is prevented from being damaged even when the tire 6a is expanded or contracted at traveling of the vehicle, and the electric circuit of the tag 3 is prevented from being broken by the frictional heat between the tire 6a and a road. The antenna coil 3a and the electric circuit are installed on a part near a rotational shaft of the wheel 6, and thereby influence by the centrifugal force can be also eased. Further, the tag 3 can be used again even when the tire 6a is damaged. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an RFID (Radio Frequency Identification) system that performs non-contact data communication using electromagnetic induction or electromagnetic coupling and an antenna of a tag, and in particular, measures tire conditions such as air pressure and temperature of an automobile tire. The present invention relates to an RFID system for measuring a tire condition, a tag antenna, and a wheel including the antenna.

  For safe operation of automobiles, it is necessary that the tire pressure is normal. Conventionally, a tire pressure measuring device is attached to a valve to measure tire pressure while the automobile is stationary at any time. However, tire pressure measurement is cumbersome and not always performed, and there is an accident in which the tire is damaged by driving in a state where the air from the tire is removed. For this reason, a tire pressure measuring instrument etc. is attached to the tire itself recently and the information is transmitted wirelessly so that the pressure of the tire can be monitored even during driving, and a system that issues a warning by sound, lighting etc. when the tire pressure becomes abnormal It is being considered.

  In order to wirelessly transmit tire pressure information measured by the tire pressure measuring device, a transmitter is required, and the transmitter requires a large number of components such as a signal processing circuit and a battery. For this reason, the structure of the measuring instrument becomes complicated, and it becomes difficult to store it inside the tire. Therefore, an RFID tag (also referred to as a transponder or a responder) that does not require a battery and has a simple circuit configuration has been used as a tire pressure measuring device.

For example, Patent Document 1 listed below includes at least a pair of parallel annular beads, at least a pair of carcass plies surrounding the bead, a tread disposed on the carcass ply in a crown region of a tire, A tag with a continuous wire arranged as a series of loops is disclosed in a crown region of a pneumatic tire comprising a third wall disposed between a tread bead and a circumference thereof. ing.
JP 2001-525284 A (page 11-16, FIG. 1)

  Since the tire pressure measuring system described in the above publication has a structure in which a tag circuit and an antenna are embedded in a tire, there are the following problems.

  The first problem is that the antenna is damaged due to fatigue. That is, since the tire plays a role of absorbing vibration caused by the unevenness of the running road by deforming itself, the tire repeatedly undergoes deformation such as expansion and contraction due to the movement of the automobile. Here, since the antenna of the tag is formed of a conductive wire made of a highly conductive metal such as copper or aluminum, the structure in which the antenna is embedded in the tire repeatedly deforms the conductor in accordance with the deformation of the tire, resulting in fatigue. It will be damaged by. To deal with this problem, a method of manufacturing an antenna using a tough steel wire used for a tire cord is also conceivable, but the steel cord of the tire cord has poor conductivity and is ferromagnetic and therefore suitable as a material for the antenna. is not. In addition, tire cords are provided to improve the strength of the tire, and even if one of the many tire cords is disconnected, there is no problem in use, but if one antenna is disconnected, it will function perfectly. Therefore, the problem of damage due to fatigue cannot always be solved by using a steel wire for a tire cord. Therefore, in the structure in which the antenna is embedded in the tire, the performance of the antenna cannot be maintained and damage due to fatigue cannot be prevented.

  The second problem is that the electric circuit constituting the tag, particularly the IC, is destroyed by heat. For example, the tire pressure is measured by a piezoelectric element and a diaphragm, and the temperature is measured by a resistance thermometer or the like, converted by an electric circuit, and sent to an antenna. This electric circuit includes an IC. Here, since the tire absorbs vibration during driving of the automobile and becomes high temperature, if an electric circuit including the IC is disposed inside the tire or close to the tire, the IC is destroyed by heat. In addition, the process of embedding the tag circuit and antenna inside the tire is also performed at a high temperature, so that the IC may be destroyed by heat during embedding.

  The third problem is that the electric circuit and wiring constituting the tag may not function due to centrifugal force. In other words, since the tire rotates at a high speed, if the electric circuit of the tag is installed on the tire away from the rotation axis, a large centrifugal force is applied, and this centrifugal force destroys the components of the electric circuit or disconnects the wiring. May occur.

  The fourth problem is that the inductance of the antenna changes. Tires may contain steel wires, and when these steel wires come into contact with each other, the intersections are cut due to wear, so the steel wires are usually arranged in an interdigital shape and are not conductive as a whole. Information can be exchanged even if it is placed inside the. However, when the antenna is close to the steel wire, problems such as change in the inductance of the antenna depending on the relative position with the steel wire and increase in loss occur.

  Furthermore, the fifth problem is that the electric circuit and antenna of the tag are wasted. In other words, tires are consumables and are often replaced due to damage such as punctures. In the structure in which the tag electrical circuit or antenna is embedded in the tire, a new tag electrical circuit or antenna is installed each time the tire is replaced. There must be.

  The present invention has been made in view of the above problems, and its main object is to provide a tire condition measuring RFID system, a tag antenna, and the antenna capable of reliably measuring a tire condition such as a tire pressure. It is in providing a wheel provided with.

  In order to achieve the above object, the tag antenna of the present invention is a tag antenna that communicates with a reader or a reader / writer, and is formed by winding a conducting wire around the outer periphery of a wheel that holds a vehicle tire. The disk portion connected to the wheel center axle made of a metal material is provided with at least one notch, and the magnetic flux of the antenna passes through the notch, or the wheel made of a metal material The antenna can be divided into a plurality of pieces, and each divided piece is coupled via an insulating material, and the magnetic flux of the antenna passes through the insulating material, or the wheel is made of a non-electrically conductive material. .

  The tag antenna of the present invention is a tag antenna that communicates with a reader or a reader / writer, and a conductive wire is wound around the outer periphery of a wheel that holds a tire of a vehicle via a flexible plate-like magnetic material. Is formed.

  The tag antenna of the present invention is a tag antenna that communicates with a reader or a reader / writer, and is made of a magnetic material having a rod shape, a flat plate shape, or a shape having a curvature corresponding to the curvature of a wheel that holds a vehicle tire. The antenna is formed by winding a conducting wire, and the antenna is fixed to the outer periphery of the wheel so that the magnetic axis of the antenna is substantially parallel to the rotation axis of the wheel.

In the present invention, the magnetic material may be composed of a composite material of magnetic powder or magnetic flakes and rubber or plastic, or the magnetic material may be composed of a soft magnetic metal, a soft magnetic amorphous foil, or a laminate thereof. Preferably, the thickness of the soft magnetic metal or soft magnetic amorphous foil or laminated material thereof is about 10 to 50 μm, and the specific resistance is about 50 × 10 ^{−8 to} 150 × 10 ⁻⁸ Ωm.

  In the present invention, a highly conductive metal plate or foil may be disposed between the wheel and the magnetic material or the conductive wire.

  Further, a tire condition measuring system of the present invention is installed in the vicinity of the wheel of the vehicle main body, a tag including at least the antenna described above and an IC having an I / O terminal, a detector for measuring the condition of the tire, and the vehicle body. A reader or reader / writer antenna and a reader or reader / writer circuit unit connected to a control unit for controlling the vehicle.

  In the present invention, the tag and the detector are installed on the wheel of each wheel of the vehicle, and the reader or reader / writer antenna is installed in proximity to each of the tags. The reader or reader / writer antenna is connected to the reader or reader / writer circuit unit via switching means for performing switching operation at predetermined time intervals, and is selected by the reader or reader / writer antenna selected by the switching means. The received pressure information of the tire is transmitted to the reader or the reader / writer circuit unit, or the tag and the detector are installed on the wheel of each wheel of the vehicle. The reader or reader / writer antenna is installed between two wheels, and each of the reader or reader / writer antennas is in place. The tire pressure information received by the reader or reader / writer antenna selected by the switching means is connected to the reader or reader / writer circuit unit via a switching means that performs a switching operation at a time interval of The structure is transmitted to a reader or a reader / writer circuit unit, or the tag and the detector are installed on the wheel of each wheel of the vehicle, and the reader or reader / writer is provided at a substantially central portion of the vehicle. The tire pressure information received by the reader or reader / writer antenna is transmitted to the reader or reader / writer circuit unit, and the tag includes the detector. Means for creating information obtained by adding ID information for identifying the tag to the tire pressure information measured in The reader or writer circuit unit includes means for extracting the ID information from the information received by the reader or reader / writer antenna, and determining the tag by referring to the ID information. You can also.

  The reader or the reader / writer circuit unit may transmit the tire pressure information to the control unit that controls the vehicle, and the control unit may display the pressure information on the instrument panel of the vehicle. The control unit may store the pressure information transmitted from the reader or the reader / writer circuit unit as history information and predict a change in the tire pressure with reference to the history information. .

  The wheel of the present invention is a wheel that holds a tire of a vehicle, and is provided with a tag antenna formed by winding a conductive wire on the outer periphery of the wheel. The disk part connected to the axle of the part is provided with at least one or more cuts through which the magnetic flux of the antenna can pass, or the wheel made of a metal material is divided into a plurality of pieces, and each divided piece is It can be set as the structure couple | bonded through the insulating material which the magnetic flux of the said antenna can pass.

  Further, the wheel of the present invention is a wheel for holding a tire of a vehicle, and a tag antenna formed by winding a conductive wire through a flexible plate-like magnetic material on the outer periphery thereof. It is.

  The wheel of the present invention is a wheel that holds a tire of a vehicle, and is formed by winding a conductive wire around a magnetic material having a rod shape, a flat plate shape, or a shape corresponding to the curvature of the wheel on the outer periphery thereof. The antenna of the tag may be fixed, and the antenna may be fixed so that the magnetic axis of the antenna is substantially parallel to the rotation axis of the wheel.

  As described above, the present invention is characterized in that the antenna of the tag is not installed in the vicinity of the tire or embedded in the tire, but is installed in the wheel that holds the tire. Since the wheel is made of a rigid metal and does not substantially deform during the operation of the automobile, the antenna coil installed on the wheel is not damaged by fatigue. In addition, one side of the wheel is in contact with the tire that becomes hot during driving, but the other side is in contact with the outside air, so the temperature does not rise so much, so the IC that constitutes the electric circuit may be destroyed by heat. Absent. In addition, since the tag's electrical circuit and antenna are installed on a wheel that is closer to the rotating shaft than the tire, the influence of centrifugal force can be reduced, preventing destruction of the electrical circuit and disconnection of the wiring. be able to. Furthermore, even if the tire is damaged due to puncture or the like, the electric circuit and antenna of the tag installed on the wheel can be used as they are, so that waste of parts can be reduced.

  As described above, the tire condition measurement RFID system, the RFID tag antenna, and the wheel including the antenna according to the present invention have the following effects.

  The first effect of the present invention is that the antenna is damaged due to fatigue caused by the expansion and contraction of the tire during traveling, the electric circuit is destroyed by heat caused by the friction of the tire, the electric circuit is broken by the rotational centrifugal force, and the wiring is cut. It can be prevented.

  The reason is that the antenna coil is not installed close to the tire or embedded in the tire, but is installed on the outer peripheral portion of the wheel, so that it is not affected by the expansion and contraction of the tire during traveling. In addition, by installing the tag's electrical circuit and pressure detector on the wheel, the effect of tire temperature rise due to friction can be suppressed, and the centrifugal force can be reduced by shortening the distance from the rotating shaft. This is because it can be made smaller.

  The second effect of the present invention is that existing tires and wheels can be used.

  The reason for this is that a dedicated tire must be manufactured in a structure in which a tag circuit or an antenna coil is installed or embedded in the tire, whereas in the present invention, the antenna coil is only wound around the wheel. This is because the tires and wheels can be used. And even if a tire is damaged by puncture or the like, a tag, a pressure detector, and the like can be used as they are, so that the tire pressure measurement system can be used effectively.

  As shown in the prior art, the RFID system is used to measure the tire pressure of the car in real time, but the conventional system has a structure in which the electric circuit of the tag and the antenna are embedded in the tire of the car. Due to the expansion and contraction of the tires, the wires are fatigued and damaged, the IC included in the electric circuit is destroyed due to the temperature during traveling and the temperature at the time of embedding, the electric circuit is destroyed or the wiring is disconnected due to the centrifugal force during traveling There is a problem that the electric circuit of the tag, the antenna, the pressure detector, and the like are wasted when the tire is damaged.

  In order to solve these problems, the tag may be installed on a portion other than the tire, that is, on the wheel. However, if the antenna is disposed on a metal wheel that is a highly conductive material, the antenna current is canceled in the wheel. Eddy current flows and the antenna does not operate normally. Therefore, in the present invention, any of the following methods is adopted to prevent the influence of the wheel.

  In the first method, a cut (for example, a cut extending in the radial direction) is provided in the wheel. A plurality of slits are preferable, and it is preferable to fill the slit with a two-component adhesive in order to prevent strength reduction due to the slit. Further, the wheel may be divided and the divided pieces may be joined with bolts or the like via an insulating material. And a coil is wound around the outer periphery of the wheel which provided the notch, or the wheel which divided | segmented / joined. In this way, the magnetic flux generated by the coil can be suppressed and the influence of eddy currents generated in the wheel through the insulating material can be suppressed.

  In the second method, a flexible plate-like magnetic material is wound around the outer periphery of the wheel, and a coil is wound thereon. In this way, the magnetic flux generated by the coil passes through the magnetic material and does not pass through the wheel, so that eddy currents can be avoided.

  The third method is: A coil is wound around a magnetic material having a curvature corresponding to the curvature of a flat plate or wheel, and is installed in a predetermined direction on the outer periphery of the wheel. Even if it does in this way, since the magnetic flux by a coil passes through a magnetic material and magnetic flux does not pass to a wheel, the bad effect of an eddy current is avoided.

  If the wheel itself is made of a non-conductive material such as fiber reinforced plastic, any antenna can be arranged on the wheel. Hereinafter, a specific configuration of the method will be described with reference to the drawings.

[Embodiment 1]
First, a tire condition measurement RFID system, an RFID tag antenna, and a wheel including the antenna according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 5. FIG. 1 is a diagram schematically showing a configuration of a tire pressure measurement system according to the first embodiment, and FIG. 2 is a configuration of a tag and a reader or a reader / writer (hereinafter referred to as a reader / writer). It is a figure shown typically. 3 and 4 are diagrams showing an example of an antenna installation structure according to the present embodiment, and FIG. 5 is a diagram showing an example of installation of a tag and a pressure detector. In the following description, an automobile having four wheels will be described as an example. However, the present invention can be similarly applied to a motorcycle having two wheels, a truck having four or more wheels, a trailer, and the like. it can.

  As shown to Fig.1 (a), the tire pressure measuring system 1 of this embodiment is a tire on each wheel 6 of a vehicle 7 (in this specification, what combined a tire and a wheel is called a wheel). A pressure measuring unit 2 is attached. A reader / writer antenna 5a is installed near the wheel 6 of the vehicle 7 body, and each reader / writer antenna 5a is connected to the vehicle body 7 body via switching means 11 such as a switch or a relay. It is connected to the writer circuit unit 5b. Although not shown, the reader / writer circuit unit 5b is connected to a control unit that controls the vehicle 7, and the tire pressure information detected by the tire pressure measurement unit 2 is sent to the control unit. Is displayed on the instrument panel.

  As shown in FIG. 2, the reader / writer 5 includes a reader / writer antenna 5a and a reader / writer circuit unit 5b, and the reader / writer circuit unit 5b converts a transmission / reception signal into a communication circuit unit 5c. And an arithmetic processing unit 5d for decoding the transmission / reception signal. The tire pressure measurement unit 2 includes a tag 3 and a pressure detector 4 including a diaphragm and a piezoelectric element. The tag 3 includes an antenna coil 3a and a capacitor 3b (capacitor built in the IC 3c) constituting a resonance circuit. And an IC 3c having an I / O terminal to which an external device such as the pressure detector 4 can be connected, and using a built-in power source or a power source supplied from the reader / writer 5 Driven. Then, the resonance frequency of the tag 3 and the reader / writer antenna 5a is adjusted to the carrier frequency, and the switching means 11 is sequentially switched to provide a time difference to operate the reader / writer antenna 5a. The detected tire pressure information is sent to the reader / writer circuit unit 5b in the order set by the switching means 11.

  In FIG. 1A, a pair of a tag 3 and a reader / writer antenna 5a is installed on each wheel 6. However, a single reader / writer antenna 5a transmits data from a plurality of tags 3. Information can also be read. For example, as shown in FIG. 1 (b), a pair of reader / writer antennas 5a is provided between the front wheels and between the rear wheels, or between the right wheels 6 and as shown in FIG. 1 (c). A pair of reader / writer antennas 5a is provided between the left wheels 6, and the information of the tags 3 installed on the two wheels 6 can be read by each of the reader / writer antennas 5a. FIG. As shown in FIG. 5, one reader / writer antenna 5a is provided at the center of the four wheels 6, and information of the tags 3 installed on the four wheels 6 can be read by one reader / writer antenna 5a. In this case, since it is necessary to determine which tag 3 information, for example, in the tag 3, ID information for identifying the tag 3 is added to the tire pressure information detected by the tire pressure measuring means 4. In the reader / writer circuit unit 5b, ID information is extracted from information received via the reader / writer antenna 5a, and information from the tag 3 installed on any wheel 6 with reference to the ID information. It can also be determined. In the case of the configuration shown in FIG. 1A, the reader / writer antenna 5a may receive information from tags 3 other than the tag 3 installed in the vicinity. The sensitivity is adjusted so that only the information of the tag 3 that is closest to the writer circuit unit 5b is read, or the ID information of the tag 3 is added to the tire pressure information in the same manner as in FIGS. You can also. Further, the tire pressure information is displayed on the instrument panel or the like as described above. At this time, the previously measured tire pressure information is stored in the control unit as history information so that the history information can be displayed. It is also possible to perform control such as calculating a change in tire pressure with reference to history information and issuing a warning when the tire pressure gradually decreases. Further, in FIGS. 1A to 1D, the tire pressure measuring unit 2 is installed on all the wheels 6, but it is sufficient that the tire pressure measuring unit 2 is installed on at least one wheel 6. 1 (a) to 1 (d), all reader / writer antennas 5a are connected to one reader / writer circuit unit 5b. However, a separate reader / writer circuit is connected to each reader / writer antenna 5a. It is good also as a structure connected to the part 5b.

  Here, since the tag 3 and the antenna coil 3a of the conventional tire pressure measuring device are installed close to the tire or embedded in the tire, the antenna coil 3a is damaged due to fatigue accompanying the expansion and contraction of the tire, and the temperature rises due to friction. However, in the present embodiment, as shown in FIG. 3, the wheel 6b that holds the tire 6a (more than More precisely, the antenna coil 3a of the tag 3 is wound along the outer periphery of the rim). Thereby, even when the wheel 6 rotates, the antenna coil 3a does not expand and contract, and damage due to fatigue can be prevented. In addition, the diameter of the winding of the antenna coil 3a and the number of turns are not limited to the configuration shown in the figure, and can be appropriately set according to the performance required for the tag 3. Further, the shape of the wheel 6b is not limited to the configuration shown in the drawing, and depending on the shape of the wheel 6b, a spacer having a predetermined thickness may be interposed between the wheel 6b and the antenna coil 3a.

  Here, since the wheel 6b is usually made of a highly conductive metal, the magnetic flux 9 cannot pass through the wheel 6b simply by winding the antenna coil 3a along the outer periphery of the wheel 6b. It is not possible to communicate with the reader / writer antenna 5a. Therefore, in the present embodiment, a notch 8a (through hole) is provided in the disk part (the part connected to the axle) in the center of the wheel 6b so that the magnetic flux 9 can pass through the notch 8a.

  The larger the notch 8a is, the easier it is to pass the magnetic flux 9. On the other hand, if the notch 8a is too large, the strength of the wheel 6b may be reduced. In particular, a shape extending in the radial direction is preferable because the magnetic flux 9 can be passed efficiently. Note that a cut is provided in advance to reduce the weight and improve heat dissipation like an aluminum wheel, and if the communication with the reader / writer antenna 5a is possible through the cut, it is not necessary to provide the cut 8a separately. .

  Further, instead of providing the notch 8a, the wheel 6b is divided into a plurality of parts (divided into two in the figure) as shown in FIG. 4, and the divided wheel 6b is joined with a bolt or the like with the insulating material 8b interposed therebetween. It can also be configured. Even in such a structure, since the magnetic flux 9 can be passed through the insulating material 8b, communication with the reader / writer antenna 5a becomes possible. Further, instead of providing the notch 8a or dividing the wheel 6b, the wheel 6b itself can be manufactured using a non-conductive material such as fiber reinforced plastic.

  And as shown in FIG. 5, components, such as the pressure detector 4, the capacitor | condenser 3b, and IC3c, are installed in the area | region which connects the inside and outside of the tire 6a provided in the predetermined part of the wheel 6b, and it wound around the outer periphery of the wheel 6b The tire pressure measuring unit 2 is formed by connecting to the antenna coil 3a. In addition, this invention has the characteristics in the structure of the antenna coil 3a of the tag 3, The structure of the said components, an installation place, the connection method with the antenna coil 3a, etc. can be set arbitrarily, for example, to a tire The above parts can also be mounted on a valve portion for introducing air.

[Embodiment 2]
Next, a tire condition measurement RFID system, an RFID tag antenna, and a wheel including the antenna according to a second embodiment of the present invention will be described with reference to FIG. FIG. 6 is a diagram illustrating an example of an antenna installation structure according to the second embodiment.

  In the first embodiment described above, the antenna coil 3a is wound around the outer periphery of the wheel 6b, and the insulating member 8b installed between the notch 8a provided in the wheel 6b with the magnetic flux 9 of the antenna coil 3a or between the divided wheels 6b. Can be communicated with the reader / writer antenna 5a through this, but in this method, since it is necessary to perform processing such as providing or dividing the wheel 6b with a cut 8a, the existing wheel 6b should be used as it is. I can't. Therefore, in this embodiment, in order to make it possible to use the existing wheel 6b as it is, a magnetic material 10 (and a spacer if necessary) is interposed between the wheel 6b and the antenna coil 3a. Yes.

  Specifically, as shown in FIG. 6, a flexible plate-like magnetic material 10 is wound around the outer periphery of the wheel 6b, and the antenna coil 3a is wound thereon. With such a configuration, the magnetic flux 9 generated in the antenna coil 3a passes through the magnetic material 10, and the magnetic flux 9 does not pass through the wheel 6b. / Communication with the writer antenna 5a is possible.

  Examples of the flexible magnetic material 10 include amorphous foil, laminated material of amorphous foil, metal powder, carbonyl iron powder, reduced iron powder, atomized powder (iron containing pure iron, Si, Cr, Al, permalloy, Co-Fe, etc. Etc.), amorphous powders (produced by water or gas atomization of iron, cobalt, nickel containing B, P, Si, Cr, etc.), etc., and composite materials of organic substances such as plastics and rubber Or a coating film of a paint containing the above powder or flakes.

  As a method for producing the composite material, for example, the granular powder is flattened by an attractor, a ball mill, a stamp mill or the like to form flakes, and then a coating containing flakes or granular powder is repeatedly applied / dried on the film. In this case, by applying a magnetic field during coating, flakes can be oriented in a certain direction, and the characteristics can be improved.

  As the plastic in the composite material, a thermoplastic plastic having good processability or a thermosetting plastic having a good heat resistance can be used, and insulating acrylic, polyester, polychlorinated Resins such as vinyl, polyethylene, polystyrene, and epoxy can also be used.

The width, thickness, and shape of the magnetic material 10 are not limited to the configuration shown in the figure, and it is sufficient that the magnetic material 10 is interposed at least between the wheel 6b and the antenna coil 3a. Alternatively, when the laminated material is used, a material having a thickness of about 10 μm or less is difficult to obtain, and if the thickness is about 50 μm or more, the eddy current increases and the product cannot be used. , unusable increased eddy current is less resistivity of about 50 × ^{10 -8} Ωm, since about 150 × ^{10 -8} Ωm or more of it is difficult to obtain, the resistivity of about 50 × ^{10 -8} ~ 150 × 10 ⁻⁸ Ωm is preferred.

  Further, when iron is used as the material of the wheel 6b, the electromagnetic characteristics of the iron are not constant, so that the performance of the antenna coil 3a varies. Therefore, in order to ensure the operation of the tag 3, a highly conductive material such as aluminum or copper may be disposed between the wheel 6b and the magnetic material 10 to shield the influence of iron.

[Embodiment 3]
Next, an RFID system for tire condition measurement according to a third embodiment of the present invention, an antenna of an RFID tag, and a wheel including the antenna will be described with reference to FIGS. 7 and 8 are diagrams illustrating examples of the antenna installation structure according to the third embodiment.

  In the first and second embodiments described above, the antenna coil 3a is wound around the entire outer periphery of the wheel 6b in order to increase the antenna area. However, the antenna coil 3a and the reader / writer antenna 5a When the distance between them can be shortened, communication with the reader / writer antenna 5a is possible without necessarily winding the antenna coil 3a around the entire circumference of the wheel 6b.

  For example, as shown in FIG. 7, a rod-shaped or flat magnetic material 10 is used as a magnetic core, and a conductive wire is wound around the magnetic core 10 to create an antenna coil 3a. The coil axis of the antenna coil 3a, that is, the magnetic material 10 A configuration in which the longitudinal direction is substantially parallel to the rotation axis of the wheel 6 (a spacer, a highly conductive metal plate or foil may be disposed between the wheel 6b and the antenna coil 3a as necessary. .). With such a configuration, the magnetic flux 9 generated in the antenna coil 3a passes through the magnetic material 10, and the magnetic flux 9 does not pass through the wheel 6b. Therefore, it is necessary to provide a cut 8a in the wheel 9b or divide the wheel 6b. Furthermore, since it is only necessary to fix the antenna coil 3a manufactured in advance to the wheel 6b, the manufacturing can be facilitated.

  Further, as shown in FIG. 8, a flexible magnetic material 10 having a shape that partially covers the outer periphery of the wheel 6b (for example, a flat shape or a shape having a curvature corresponding to the curvature of the wheel 6b) is used. A structure in which a magnetic wire 10 is used as a magnetic core and a conductive wire is wound along the outer circumferential direction of the wheel 6b to create the antenna coil 3a, and the coil axis of the antenna coil 3a is installed so as to be substantially parallel to the rotation axis of the wheel 6. (Similarly, a spacer or a highly conductive metal plate or foil may be disposed between the wheel 6b and the antenna coil 3a as necessary). Even in such a configuration, the magnetic flux 9 generated in the antenna coil 3a passes through the magnetic material 10, and the magnetic flux 9 does not pass through the wheel 6b. Therefore, it is not necessary to provide the notch 8a in the wheel 6b or to divide the wheel 6b. Moreover, since it is only necessary to fix the antenna coil 3a manufactured in advance to the wheel 6b, the manufacturing can be facilitated.

  However, in this configuration, depending on the size, shape, and installation location of the reader / writer antenna 5a, there are positions where communication is possible and positions where communication is impossible, so the tire pressure is reduced particularly when the vehicle 7 is stationary. There may be cases where measurement is not possible. Therefore, when the tire pressure is always measured, as shown in FIGS. 7 and 8, the reader / writer antenna 5a is made larger than the wheel 6b, and its antenna axis substantially coincides with the rotation axis of the wheel 6b. It is preferable to arrange in such a manner.

  Even if there is a position where communication is impossible, the rotation speed of the tire can be detected by enabling periodic communication, and this rotation speed can be actively used. In that case, the coil axis of the antenna coil 3a and the rotation axis of the wheel 6b do not need to be substantially parallel. For example, the antenna axis is set so that the coil axis of the antenna coil 3a faces the tangential direction of the outer periphery of the wheel 6b. / The writer antenna 5a can also be installed in a mudguard.

  In order to confirm the effect of the antenna of the above-described embodiment, a steel wheel having a diameter of about 380 mm and a width of 160 mm was prepared, and the following experiment was performed using an RFID system that operates at a frequency of 125 kHz. The specific contents and results will be described.

[Comparative example]
First, as a comparative example, a coated copper wire having a diameter of 1 mm was wound 100 times around the outer periphery of the steel wheel 6b having the above shape to produce an antenna coil 3a, and an IC 3c was connected to the antenna coil 3a to create a tag 3. .

  As Example 1, an antenna coil 3a is manufactured by winding a coated copper wire having a diameter of 1 mm around a vinyl chloride cylinder having a diameter of 380 mm, a width of 160 mm, and a thickness of 5 mm, and an IC 3c is connected to the antenna coil 3a. 3 was created.

  As Example 2, as shown in the first embodiment (FIG. 3), two notches 8a having a length of 150 mm are formed in the steel wheel 6b in the radial direction, and a coated copper wire having a diameter of 1 mm is formed on the outer periphery of the wheel 6b. Was wound 45 times to produce an antenna coil 3a, and an IC 3c was connected to the antenna coil 3a to produce a tag 3.

  As Example 3, as shown in the second embodiment (FIG. 6), a magnetic material in which a lacquer is coated for insulation on the surface of an iron-based amorphous foil having a width of 100 mm and a thickness of 20 μm on the outer periphery of a steel wheel 6b. 10 was wound to a thickness of 1 mm, and a coated copper wire having a diameter of 1 mm was wound thereon 45 times to produce an antenna coil 3a, and an IC 3c was connected to the antenna coil 3a to produce a tag 3.

  As Example 4, as shown in the third embodiment (FIG. 8), 100 sheets of magnetic material 10 in which lacquer is applied for insulation on the surface of an iron-based amorphous foil having a width of 20 mm, a length of 150 mm, and a thickness of 20 μm. The antenna coil 3a was manufactured by stacking 450 turns of a coated copper wire having a diameter of 0.2 mm around it, and the tag 3 was formed by connecting the IC 3c to the antenna coil 3a.

  The inductances of the antenna coil 3a of the comparative example and Examples 1 to 4 were almost equal and in the range of 7 mH to 8 mH. Further, in the comparative example, the tag 3 did not operate, whereas in Examples 1 to 4, all the tags 3 operated. From the above results, the tag 3 does not operate only by winding the coated copper wire around the outer circumference of the steel wheel 6b (comparative example), whereas the notch 8a is made in the steel wheel 6b (Example 2). ), Interposing the magnetic material 10 between the steel wheel 6b and the coated copper wire (Example 3), or winding the coated copper wire around the plate-like magnetic material 10 (Example 4) It was possible to operate, and the effect of the present invention could be confirmed.

  In the above description, the RFID system of the present invention has been described as a system for measuring tire pressure. However, the present invention is not limited to the above-described embodiments, and a system for measuring the state of a tire, for example, a tire The present invention can be similarly applied to a system for measuring the temperature of the tire and a system for measuring tire wear.

It is a figure showing typically composition of a tire state measuring system concerning a 1st embodiment of the present invention. It is a figure showing typically other composition of the tire condition measuring system concerning a 1st embodiment of the present invention. It is a figure showing typically other composition of the tire condition measuring system concerning a 1st embodiment of the present invention. It is a figure showing typically other composition of the tire condition measuring system concerning a 1st embodiment of the present invention. It is a figure which shows typically the structure of the RFID tag and reader / writer of this invention. It is a figure which shows typically the structure of the antenna and wheel of a tag which concern on the 1st Embodiment of this invention. It is a figure which shows typically the other structure of the antenna and wheel of the tag which concerns on the 1st Embodiment of this invention. It is a figure which shows the example of installation of the tag which concerns on the 1st Embodiment of this invention, and a pressure detector. It is a figure which shows typically the structure of the antenna and wheel of a tag which concern on the 2nd Embodiment of this invention. It is a figure which shows typically the structure of the antenna and wheel of a tag which concern on the 3rd Embodiment of this invention. It is a figure which shows typically the other structure of the antenna and wheel of the tag which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tire pressure measuring system 2 Tire pressure measuring part 3 Tag 3a Antenna coil 3b Capacitor 3c IC
4 pressure detector 5 reader / writer 5a reader / writer antenna 5b reader / writer circuit unit 5c communication circuit unit 5d arithmetic processing unit 6 wheel 6a tire 6b wheel 7 vehicle 8a notch 8b insulating material 9 magnetic flux 10 magnetic material 11 switching means

Claims (28)

A tag antenna that communicates with a reader or reader / writer,
A tag antenna characterized by being formed by winding a conducting wire around an outer periphery of a wheel for holding a tire of a vehicle.   2. The tag antenna according to claim 1, wherein at least one notch is provided in a disk part connected to the wheel center axle made of a metal material, and the magnetic flux of the antenna passes through the notch. 3.   The tag antenna according to claim 1, wherein the wheel made of a metal material is divided into a plurality of pieces, each divided piece is coupled via an insulating material, and the magnetic flux of the antenna passes through the insulating material.   The tag antenna according to claim 1, wherein the wheel is made of a non-electrically conductive material. A tag antenna that communicates with a reader or reader / writer,
An antenna for a tag, wherein the antenna is formed by winding a conductive wire around a wheel holding a vehicle tire via a flexible plate-like magnetic material. A tag antenna that communicates with a reader or reader / writer,
It is formed by winding a conducting wire around a magnetic material having a curvature corresponding to the curvature of the wheel holding the tire of the rod, flat plate or vehicle,
The antenna of a tag, wherein the antenna is fixed to an outer periphery of the wheel so that a magnetic axis of the antenna is substantially parallel to a rotation axis of the wheel.   The tag antenna according to claim 5 or 6, wherein the magnetic material is a composite material of magnetic powder or magnetic flake and rubber or plastic.   The tag antenna according to claim 5 or 6, wherein the magnetic material is a soft magnetic metal, a soft magnetic amorphous foil, or a laminated material thereof. The thickness of the soft magnetic metal or soft magnetic amorphous foil or laminated material thereof is approximately 10 to 50 μm, and the specific resistance is approximately 50 × 10 ^{−8 to} 150 × 10 ⁻⁸ Ωm. Tag antenna.   The tag antenna according to any one of claims 1 to 9, wherein a highly conductive metal plate or foil is disposed between the wheel and the magnetic material or the conductive wire.   A tag comprising at least the antenna according to any one of claims 1 to 10 and an IC having an I / O terminal, a detector for measuring a state of the tire, and a wheel of the vehicle main body that are installed in the vicinity of the wheel. A tire condition measurement system comprising at least a reader or reader / writer antenna and a reader or reader / writer circuit unit connected to a control unit for controlling the vehicle.   The tag and the detector are installed on the wheel of each wheel of the vehicle, and the reader or reader / writer antenna is installed in proximity to each tag, and each of the reader or reader / writer An antenna for the tire is connected to the reader or reader / writer circuit unit via switching means for performing switching operation at a predetermined time interval, and the tire antenna received by the reader or reader / writer antenna selected by the switching means. The tire condition measuring system according to claim 11, wherein pressure information is transmitted to the reader or the reader / writer circuit unit.   The tag and the detector are installed on the wheel of each wheel of the vehicle, and the reader or reader / writer antenna is installed between the front and rear or left and right wheels, and the reader or reader The / writer antenna is connected to the reader or reader / writer circuit unit via switching means that performs switching operation at a predetermined time interval, and is received by the reader or reader / writer antenna selected by the switching means. The tire pressure measurement system according to claim 11, wherein tire pressure information is transmitted to the reader or reader / writer circuit unit.   The tag and the detector are installed on the wheel of each wheel of the vehicle, the reader or reader / writer antenna is installed at a substantially central portion of the vehicle, and the reader or reader / writer antenna is used. 12. The tire condition measuring system according to claim 11, wherein the received tire pressure information is transmitted to the reader or reader / writer circuit unit.   The tag includes means for creating information in which ID information for identifying the tag is added to pressure information of the tire measured by the detector, and the reader or the reader / writer circuit unit includes the information 15. The apparatus according to claim 12, further comprising means for extracting the ID information from the information received by a reader or a reader / writer antenna and determining the tag by referring to the ID information. The described tire condition measuring system.   The reader or the reader / writer circuit unit transmits pressure information of the tire to the control unit that controls the vehicle, and the control unit displays the pressure information on an instrument panel of the vehicle. The tire condition measuring system according to any one of 12 to 15.   The control unit stores the pressure information transmitted from the reader or the reader / writer circuit unit as history information, and predicts a change in the tire pressure with reference to the history information. 16. The tire condition measuring system according to 16. A wheel for holding a vehicle tire,
A wheel characterized in that an antenna of a tag formed by winding a conductive wire on its outer periphery is installed.   The wheel according to claim 18, wherein at least one notch through which a magnetic flux of the antenna can pass is provided in a disk portion connected to an axle at a central portion of the wheel made of a metal material.   The wheel according to claim 18, wherein the wheel made of a metal material is divided into a plurality of pieces, and each divided piece is coupled via an insulating material through which the magnetic flux of the antenna can pass.   The wheel according to claim 18, wherein the wheel is made of a non-electrically conductive material. A wheel for holding a vehicle tire,
A wheel comprising a tag antenna formed by winding a conductive wire through a flexible plate-like magnetic material on an outer periphery thereof. A wheel for holding a vehicle tire,
A wheel characterized in that a tag antenna formed by winding a conducting wire around a magnetic material having a rod shape, a flat plate shape, or a shape corresponding to the curvature of the wheel is fixed to the outer periphery thereof.   The wheel according to claim 23, wherein the antenna is fixed so that a magnetic axis of the antenna is substantially parallel to a rotation axis of the wheel.   The wheel according to any one of claims 21 to 24, wherein the magnetic material is a composite of magnetic powder or magnetic flakes and rubber or plastic.   The wheel according to any one of claims 21 to 24, wherein the magnetic material is a soft magnetic metal, a soft magnetic amorphous foil, or a laminated material thereof. The soft magnetic metal or soft magnetic amorphous foil or thickness substantially 10 to 50μm of the laminate, resistivity of claim 26 which is a substantially 50 × ^{10 -8} to 0.99 × ^{10 -8} [Omega] m wheel.   The wheel according to any one of claims 18 to 27, wherein a highly conductive metal plate or foil is disposed between the wheel and the magnetic material or the conductive wire.

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