JP2009268087A - Ferrite antenna, and tire condition detection system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve full-circumferential power feeding for a tire by suppressing a null point in a property of power feeding to a tire information detection device. <P>SOLUTION: A ferrite antenna 10a is constituted of a horizontal solenoid 6 and a vertical solenoid 7 around which a coated lead wire is wound along a surface of a ferrite core 5 in an approximately cubic shape, a high frequency magnetic field radiated from each of the solenoids generates an induction current of an opposite phase in a conductor wire or conductor mesh 310, generates a high frequency magnetic field of an opposite phase soon, and directly feeds power to an electromagnetic power feeding device such as a small-sized coil, for example, provided as an antenna but since a line B1 of a magnetic force of the horizontal solenoid 6 and a line B4 of magnetic force of the vertical solenoid 7 are brought into an approximately opposite-phase state with respect to each other in the vicinity of a tire information detection device, both the lines are offset, and only the high frequency magnetic field of the opposite phase generated by the induction current of a conductor wire or a conductor mesh 310 feeds power to the small-sized coil of the electromagnetic power feeding device, so that even if a tire information detection device 200 is located at any position, it can be stably supplied with power. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a tire condition detection system using a ferrite antenna and a tire information detection device coupled with a high-frequency magnetic field through a tire.

  First, since the reversibility theorem holds for all antennas in general, the transmission characteristics and reception characteristics are exactly the same, so the following explanation is for all transmissions unless otherwise noted. Since it is the same, description is abbreviate | omitted.

A tire information detection device may be provided inside the tire in order to detect tire information such as air pressure and temperature of the vehicle tire. Since the tire information detection device is provided inside the tire, it is impossible to supply driving power in a wired manner. For this reason, a reader antenna is provided in the vicinity of the tire of the vehicle, and the reader antenna supplies driving power to the tire information detection device by a high-frequency electromagnetic field, and transmits and receives the tire information detection device. For example, Patent Document 1 discloses a tire pressure detection device configured to intermittently send a 134 kHz power pulse from a reader antenna to a sensor antenna.

JP-A-8-136383 (paragraph 0014) JP 2008-230325 A

  FIG. 5 is a configuration diagram of a tire condition detection system using a reader antenna configured with a single solenoid. Here, 20 is a high-frequency power source, 15 is a reader antenna, C1 and C2 are capacitors constituting a matching circuit between the high-frequency power source 20 and the reader antenna 15, 300 is a tire, 320 is a rubber layer of the tire, and 310 is a tire A conductor wire or conductor mesh provided inside the rubber layer, 330 is a wheel rim, 340 is a tire valve, and 200 is a tire information detection device housed in the valve 340.

  In the tire condition detection system of FIG. 5, the reader antenna 15 is installed on the side surface of the rubber layer 320 of the tire 300. The reader antenna 15 is a circular solenoid without a ferrite core, and the central axis is set in the width direction of the tire 300. For this reason, the reader antenna 15 irradiates the magnetic field B <b> 6 in the width direction of the tire 300, and the lines of magnetic force (solid arrows) link the conductor wires 310. Therefore, an induced current that can cancel the magnetic field B6 flows through the conductor wire 310 according to Lorentz's law, and the magnetic field generated by the induced current is an induced magnetic field B8. The induction magnetic field B8 is theoretically opposite in direction to the magnetic field B6 generated by the reader antenna 15, and the strength is determined by the arrangement state of the conductor wire 310, the tire material and the shape, and is theoretically weaker than the magnetic field B6.

  In FIG. 5, the valve 340 housing the tire information detection device 200 is positioned closest to the reader antenna 15 due to rotation of the tire, and the antenna of the tire information detection device 200 irradiates the reader antenna 15. Under the action of the magnetic field B6 and the induction magnetic field B8, since the directions of both magnetic fields are completely opposite and the strengths are substantially the same, they cancel each other, and the tire information detection device 200 is not supplied with power by a high-frequency magnetic field, Signal transmission / reception with the reader antenna 15 cannot be performed normally or is completely interrupted. This is because a null point in the power feeding characteristic of the tire information detecting device 200, that is, a communication poor region with extremely low communication power is generated.

  However, in FIG. 6, the valve 340 housing the tire information detection device 200 is rotated away from the reader antenna 15 due to rotation of the tire, and the antenna of the tire information detection device 200 is connected to the reader antenna 15. Only the action of the induction magnetic field B8 is received without substantially receiving the action of the magnetic field B6 to be irradiated. As a result, the induced magnetic field B8 generates an induced current in the antenna of the tire information detecting device 200, and becomes a power source of the tire information detecting device 200 through a rectifier circuit or the like. Therefore, the tire information detecting device 200 and the reader Transmission and reception with the antenna 15 can be normally performed.

  Further, the position of the valve 340 housing the tire information detection device 200 is not necessarily the furthest away from the reader antenna 15, and is moved to a position where it is not affected by the irradiation magnetic field B6 from the reader antenna 15. That's fine. That is, if the valve 340 housing the tire information detection device 200 is at a position slightly deviated from the area directly in front of the reader antenna 15, transmission / reception between the tire information detection device 200 and the reader antenna 15 can be performed normally.

  7 to 10 are explanatory diagrams of the tire rotation angle θ and the power feeding characteristics of the tire information detection device 200. FIG.

  In FIG. 7, a zy coordinate system having the origin at the center of the tire 300 is provided, and the valve 340 housing the tire information detection device 200 moves to the position of the angle θ from the z axis by rotation of the tire. Reference numeral 16 denotes a position projected from the reader antenna 15 onto the tire side surface along the broken line 17, and is the strongest region of the irradiation magnetic field B 6 of the reader antenna 15. Here, the valve 340 is separated from the 16 region in the clockwise direction with respect to the z axis at an angle θ, and is only affected by the induced magnetic field B8 without being affected by the magnetic field B6.

  In FIG. 8, it is the figure which looked at FIG. 7 from the front. The bulb 340 is away from the center of the magnetic field B6 irradiation region 16 at an angle θ in the clockwise direction.

  FIG. 9 shows the power feeding characteristics of the tire information detection device 200 expressed by the same zy coordinate system and the tire angle θ. The transmission loss characteristics between the reader antenna 15 and the tire information detection device 200 are expressed as S21 in terms of the S parameter. Equivalent to. Here, the power feeding characteristic 18 of the tire information detecting device 200 is represented by the polar coordinate of θ, and the relative position of the valve 340 and the power feeding characteristic of the tire information detecting device 200 can be easily understood. At a position where θ is around 0 °, S21 is extremely lowered, indicating a null point 19.

  In addition, it is possible to easily calculate the power supplied to the tire information detecting apparatus 200, the induced current, and the like from the S parameter S21.

  FIG. 10 shows the feed characteristics of the polar coordinates shown in FIG. When θ is in the vicinity of 0 or 2π, S21 decreases extremely, indicating a null point 19.

  Strictly speaking, at the null point, power is not supplied to the tire information detection device 200 at all, and the tire information detection device 200 cannot be operated because of insufficient power supply.

  Further, as shown in the power supply characteristic 18 shown in FIG. 9, there is a possibility that the power supply to the tire information detection device 200 is insufficient when θ is in the range of approximately −45 ° to + 45 ° with respect to the z axis. There is. That is, the tire information detection device 200 is likely to malfunction when the valve 340 of the tire 300 that houses the tire information detection device 200 is in a range of approximately −45 ° to + 45 ° with respect to the reader antenna 15 facing the tire. Recognize.

  However, in general, a tire is provided with a belt layer to reinforce the circumferential tension, and a plurality of conductor wires are arranged inside the belt layer, and a conductor mesh formed by braiding the conductor wires into a net-like shape is provided. It is arranged. Conventionally, a loop antenna used as a reader antenna changes the power supply power characteristic to the tire information detection device that indicates the relationship with the rotation angle of the tire by the rotation of the tire. The loop antenna generates an induced current in a conductor wire or a conductor mesh in a tire by radiating a high-frequency magnetic field to radiate a reverse-phase induced magnetic field from the conductor wire or the conductor mesh. The antenna of the tire information detection device generates an electromotive force by the action of the induction magnetic field having the opposite phase and the radiated high frequency magnetic field of the reader antenna, and serves as a power source.

  However, when the tire rotates, the tire information detection device approaches or moves away from the reader antenna, and when it comes close to the reader antenna, it is affected by the opposite-phase induced magnetic field and the radiated high-frequency magnetic field of the reader antenna. However, when it is slightly away from the reader antenna, it is almost only affected by the reversed-phase induced magnetic field. Therefore, when the tire information detection device is at a position away from the reader antenna, it is only affected by the opposite-phase induced magnetic field, so that the power supply power characteristics are stable in a considerably wide tire rotation region, When the tire information detection device is in the vicinity of the reader antenna, the effects of the opposite phase induction magnetic field and the radiated high frequency magnetic field of the reader antenna are simultaneously received, and both cancel each other because they are in the opposite phase state. As a result, there is a problem that a null point is generated in the power supply power characteristic, and power is not received every time the tire information detection device comes close to the reader antenna, that is, there is a poor communication area.

  Then, this invention makes it a subject to provide the ferrite antenna which can suppress or improve the null point of the electric power feeding characteristic of the said reader antenna, and a tire condition detection system using the same.

  In order to solve the above problems, the present invention proposes a substantially cubic ferrite antenna as a reader antenna.

  The ferrite antenna includes a first solenoid wound with a conductor wire along a surface of a substantially cubic ferrite material, and a surface of the ferrite material in a direction substantially orthogonal to the conductor wire with another conductor wire. A second solenoid wound around the first solenoid, wherein a cross section of the first solenoid and a cross section of the second solenoid are substantially orthogonal to each other, and one end of the first solenoid and one end of the second solenoid Are electrically connected to each other, and both the other end of the first solenoid and the other end of the second solenoid are used as input / output terminals.

  As a method of winding the first solenoid and the second solenoid, the direction of the first magnetic field generated by the first solenoid is substantially orthogonal to the tire rotation axis and the tire surface, and the first solenoid When going to the solenoid, the second magnetic field generated by the second solenoid is applied substantially in parallel with the tire rotation axis so as to go from the side without the valve housing the tire information detection device to the side with the valve. . In addition, when the direction of the current is changed because a high-frequency current flows through each of the solenoids, in such a winding method, when the direction of the first magnetic field is directed from the first solenoid toward the tire surface, the second The direction of the magnetic field is directed from the side with the valve housing the tire information detection device to the side without the valve.

  The first magnetic field and the second magnetic field respectively generate a first induced current and a second induced current in a conductor wire or a conductive mesh of a tire, and the first induced current and the second induced current are eventually Although one induction magnetic field and a second induction magnetic field are generated, it is possible to improve the null point of the feeding power characteristic of the reader antenna by adjusting the direction and intensity of each induction magnetic field.

  1 to 4 are configuration diagrams of the first embodiment of the present invention.

  In FIG. 1, the tire condition detection system power supply unit 500 includes a reader antenna system 100, a tire 300, and a tire information detection device 200 housed in a valve 340 of the tire 300. The apparatus 200 is configured to be able to transmit and receive via electromagnetic coupling via a tire. In addition, the tire condition detection system power supply unit 500 includes a signal processing circuit, a control circuit, a directional coupling circuit, and the like.

  The reader antenna system 100 includes a ferrite antenna 10a, a high-frequency power source 20, and capacitors C1 and C2 that constitute the reader antenna. In the ferrite antenna 10a, a coated conductor is wound around the surface of the ferrite core 5, and a horizontal solenoid 6 as a first solenoid and a vertical solenoid 7 as a second solenoid are formed orthogonal to each other. The ferrite core 5 is formed in a cube in which two opposing surfaces are parallel and adjacent surfaces are orthogonal to each other. Note that the combination of the horizontal solenoid 6 and the vertical solenoid 7 is a two-terminal composite solenoid in which one coated conductor is divided and wound and electrically connected in series. That is, one end of the horizontal solenoid 6 and one end of the vertical solenoid 7 are electrically connected by a single coated conductor, and both the other end of the horizontal solenoid 6 and the other end of the solenoid 7 serve as input / output terminals. used. The ferrite core 5 may be a rectangular parallelepiped instead of a cube.

  The ferrite antenna 10a is connected to the high frequency power supply 20 via the capacitor C2 and the capacitor C1. C1 and C2 constitute a matching circuit, which matches the impedance between the ferrite antenna 10a and the high-frequency power source 20. The high frequency power supply 20 uses a frequency of 13.56 MHz, for example. Further, the total length of the conductor wires of the horizontal solenoid 6 and the vertical solenoid 7 is desirably 0.05 times or less of the wavelength of the high-frequency power source 20, and this is expressed as cos (0.05 × 360 °) = cos ( 18 °) = 0.95, the phase difference of the high-frequency magnetic field generated by each solenoid can be ignored. The maximum dimension of the ferrite core 5 is preferably not more than (0.05 / (2 × 4 × N)) times the wavelength of the high-frequency current input to the input / output terminal, where N is the first value. The number of turns of the solenoid 6 and the second solenoid 7 is smaller.

  The tire 300 includes a wheel rim 330, a rubber layer 320, and a valve 340, and a plurality of conductor wires 310 are provided inside the rubber layer 320. The rubber layer 320 is radially arranged on the inner surface, serves as a tire skeleton, and supports the radial force. The plurality of conductor wires 310 support the circumferential force and form a belt layer. The valve 340 is for injecting air into the tire 300 through a valve inlet penetrating the edge of the wheel rim 330, and an information detection device 200 for detecting tire information such as air pressure and temperature is disposed inside the valve 340. is doing.

  In FIG. 1, the tire 300 only shows a cross-sectional view of the upper half, but a lower half also exists and is not shown for convenience.

  The ferrite antenna 10a is arranged so that the direction of each ridge line of the core 5 of isotropic ferrite material substantially coincides with or substantially orthogonal to the direction of the conductor wire 310. That is, the horizontal solenoid 6 is wound in the x direction (6a) which is the width direction of the tire 300 and the y direction (6b) which is the direction of the conductor wire 310, and the vertical solenoid 7 is wound in the y direction (7b) and the radial direction. Are wound in the z direction (7a). That is, the magnetic field B12 of the horizontal solenoid 6 is generated in the z direction (normal direction of the outer peripheral surface of the tire 300), and the magnetic field B4 of the vertical solenoid 7 is parallel to the outer peripheral surface of the tire 300 and rotates the tire 300. Occurs in the direction of the axis).

  2 and 3 are diagrams for explaining the influence of the magnetic field generated by the ferrite antenna. The influence of the positional relationship between the winding direction of each solenoid of the ferrite antenna and the direction of the conductor wire 310 is described. Yes.

  FIG. 2 shows a ferrite antenna 10b wound with a coated conducting wire along the x direction and the y direction, and FIG. 3 shows a ferrite antenna 10c wound along the y direction and the z direction. It can be said that the ferrite antenna 10a in FIG. 1 is a combination of the horizontal solenoid of the ferrite antenna 10b in FIG. 2 and the vertical solenoid of the ferrite antenna 10c in FIG.

  In the ferrite antenna 10b of FIG. 2, since the coated conductor wire constituting the horizontal solenoid 6 is wound along the x direction and the y direction, the first magnetic field B12 is generated in the z direction when the current I12 flows. At this time, the lines of magnetic force generated from one xy plane of the ferrite core 5 go around the outside of the ferrite core 5 and return to the facing surface. Further, the current flowing through the conductor wire 310 when the magnetic field lines of the first magnetic field B12 are linked is referred to as a first induced current, and a first induced magnetic field is generated by the first induced current. However, since the direction of the first magnetic field B12 is substantially perpendicular to the tire surface, the first induced current and the first induced magnetic field are compared with the second induced current and the second induced magnetic field described below. Weak and negligible. Here, for the sake of convenience, before the first magnetic field B12 passes through the horizontal solenoid 6, the magnetic field on the side where the valve 340 for housing the tire information detection device 200 is located is called B1, and the magnetic field on the opposite side is called B2. In particular, it is substantially the same as the first magnetic field B12. In the drawing, it is described that the magnetic force lines interlinking the conductor wire 310 circulate in the xz plane. However, the magnetic field lines circulate in all the planes passing through the z axis passing through the center. Although there are magnetic field lines in the yz plane that do not link 310, the description will be omitted because it hardly contributes to the generation of the first induced current.

  Therefore, the magnetic field generated by the horizontal solenoid 6 acting on the tire information detection device may be considered to be only B1.

  In the ferrite antenna 10c of FIG. 3, since the coated conductor wire constituting the vertical solenoid 7 is wound along the y direction and the z direction, the second magnetic field B4 is generated along the x direction when the current I4 flows. In particular, the magnetic field lines in the xz plane are linked to the conductor wire 310. Further, the current flowing through the conductor wire 310 due to the linkage of the magnetic lines of force is referred to as a second induced current I42, and the second induced magnetic field B42 is generated by the second induced current. The magnetic field in the xy plane does not interlink the conductor wire 310.

  Further, in FIG. 1, when the first magnetic field B <b> 12 moves from the tire outer peripheral side surface toward the horizontal solenoid 6 (in the + z direction) through the inside of the tire, the second magnetic field B <b> 4 is a valve in which the information detection device 200 is accommodated. However, when the phase of the high-frequency power supply 20 is reversed, the first magnetic field B12 passes from the horizontal solenoid 6 to the tire outer peripheral side (in the -z direction) through the inside of the tire. ), The second magnetic field B4 is directed from the valve side in which the information detection apparatus 200 is stored toward the opposite side of the valve (in the + x direction).

  Further, the magnetic field B1 and the magnetic field B2 generated by the horizontal solenoid 6 are always in opposite directions on the left and right side surfaces of the tire, and become the magnetic field B12 so as to be bundled in the same direction around the center in the tire. Therefore, the directions of the first induced currents I1 and I2 of the tire conductor wire and the conductor mesh generated by the linkage of the magnetic field B1 and the magnetic field B2 are also opposite to each other, resulting in the respective induced currents. The directions of the first induction magnetic fields B11 and B21 are also opposite to each other. For this reason, it can be considered that the induction magnetic fields of the horizontal solenoids 6 in the space inside the tire are almost canceled out and do not exist. That is, the induced magnetic field existing in the space inside the tire is the second induced current I4 of the tire conductor wire or conductor mesh generated by the induction of the second magnetic field B4 of the vertical solenoid 7, and the second induction generated thereby. Only the magnetic field B42.

In other words, the high-frequency magnetic fields (magnetic fields B1, B2, and B4) radiated from the horizontal solenoid 6 and the vertical solenoid 7 generate an induced current in the conductor wire 310, and this induced current generates an induced magnetic field and directly serves as an antenna. It also acts on the antenna of the provided tire information detection apparatus 200. However, as described above, since the magnetic field induced by the horizontal solenoid 6 does not exist in the space inside the tire, the magnetic field B1 of the horizontal solenoid 6 and the vertical solenoid substantially act on the antenna of the information detecting device 200. The second induction magnetic field B42 generated by acting on the conductor wire or the conductor mesh of the tire by induction of the second magnetic field B4 and the second magnetic field B4. The directions of these magnetic fields are as follows:
1- First magnetic field B1 is opposite in direction to second magnetic field B4
2- The first magnetic field B1 has the same direction as the second induction magnetic field B42
3- The second magnetic field B4 has the opposite direction to the second induction magnetic field B42

  Further, the information detection device 200 housed in the valve 340 also rotates due to the rotation of the tire, and the position of the information detection device 200 moves away from or approaches the ferrite antenna 10a. When approaching the ferrite antenna 10a, the first magnetic field B1, the second magnetic field B4 and the second induction magnetic field B42 simultaneously act on the antenna of the tire information detection device 200, but when separated from the ferrite antenna 10a, There is no action of the first magnetic field B1 and the second magnetic field B4, and only the second induction magnetic field B42 acts on the antenna of the information detection apparatus 200. However, the first magnetic field B1 and the second magnetic field B4 have substantially the same strength and are opposite in direction, so that they cancel each other, and as a result, only the second induction magnetic field B42 that hardly changes in strength is the only feature of the information detecting device 200. It will act on the antenna. As a result, it can be seen that the power supply characteristic to the information detection apparatus 200 is almost circular.

  FIG. 4 shows a transmission loss characteristic S21, which is one of S parameters between the ferrite antenna of the present invention and the tire information detection apparatus, as a feeding characteristic. FIG. 4- (a) shows the above-mentioned feeding characteristics drawn in polar coordinates, and FIG. A broken line 18 is a power feeding characteristic (FIG. 9) between the reader antenna 15 and the tire information detection device 200 in the tire condition detection system shown in FIGS. 5 and 6, and has a null point 19. Is a feeding characteristic between the ferrite antenna 10a of the present invention from which the null point is removed and the tire information detection apparatus 200.

  Since the ferrite antenna 10a, which is the reader antenna of the present invention, is arranged away from the outer peripheral surface of the tire 300 as shown in FIG. 1, it is arranged away from the side surface of the tire as shown in FIGS. Although the strength of the power supply characteristic 21 is slightly lower than that in the case of doing so, it is almost stable regardless of the rotation of the tire. Since the power feeding characteristic is substantially a transmission loss characteristic S21 between the reader antenna and the tire information detecting device, if the output power of the high-frequency power source 20 is increased, the power necessary for the tire information detecting device from the reader antenna regardless of the rotation of the tire. Can be stably fed.

Explanation of operation

  First, a description will be given with reference to FIG.

  A high-frequency power, for example, a signal of 13.56 MHz is fed from a high-frequency power source 20 to a reader antenna 10a composed of a horizontal solenoid 6, a vertical solenoid 7 and a ferrite core 5 through a matching circuit formed by capacitors C1 and C2, and the reader The antenna 10a is disposed away from the outer peripheral surface of the tire 300, and generates a first magnetic field B12 and a second magnetic field B4. Here, B12 on the left side of the drawing, that is, the valve 340 side that houses the tire information device is B1, and B12 on the right side on the opposite side is B2. The first magnetic field B12 and the second magnetic field B4 act on the conductor wire 310 of the tire 300 to generate a first induced current and a second induced current I42, and the first induced current and the second induced current I42. As a result, the first induction magnetic field and the second induction magnetic field B42 are generated in the space in the tire. Regardless of the rotation of the tire 300, the relative position between the reader antenna 10a and the tire 300 does not change, so the intensity of the first induced current and the second induced current I42 does not change, and as a result, the first The strengths of the induction magnetic field and the second induction magnetic field B42 are not changed.

  It is the first magnetic field B1, the second magnetic field B4, and the second induction magnetic field B42 that these magnetic fields generated by the power supply from the high frequency power supply 20 substantially act on the tire information detection apparatus 200. As the tire rotates, the information detection device 200 housed in the valve 340 also rotates and moves away from or close to the ferrite antenna 10a. When approaching the ferrite antenna 10a, the first magnetic field B1, the second magnetic field B4, and the second induction magnetic field B42 simultaneously act on the antenna of the tire information detecting device 200. There is no action of the magnetic field B1 and the second magnetic field B4, and only the second induction magnetic field B42 acts on the antenna of the information detection apparatus 200. However, since the first magnetic field B1 and the second magnetic field B4 have substantially the same strength and are opposite in direction, they cancel each other, and as a result, only the second induction magnetic field B42 that hardly changes in strength is applied to the antenna of the information detection apparatus 200. Will work. As a result, it can be seen that the power supply characteristic to the information detection apparatus 200 is almost circular.

  Since the second induction magnetic field B42 is a high-frequency magnetic field, when passing through an antenna provided in the tire information detection apparatus 200, for example, a small loop antenna, an induction high-frequency current is generated due to fluctuation of magnetic flux, and the rectifier circuit provided with this induction current Is converted into a direct current and becomes a power source for various sensor circuits and control circuits of the tire information detection apparatus 200. The measurement results of the various sensors become transmission signals having tire information through a modulation circuit, and return to the reader antenna 10a through the small loop antenna, but do not return to the high-frequency power source 20, and the transmission signal is not transmitted to the reader antenna. The signal is input to the signal processing circuit from the terminal 10a through a circuit that changes the propagation direction of the signal, such as a circulator, for example, where tire information is detected by demodulation and displayed on the display device. The driver can know the condition of the tire from this display device.

Effect description

  According to the present invention, the second magnetic field B4 acting on the antenna of the tire information detection device is relaxed by the first magnetic field B1 in the reverse direction, and is caused by the second induced current I42 flowing in the conductor wire or conductor mesh of the tire. Only the generated second induction magnetic field B42 acts on the antenna of the tire information detection device. As a result, the generation of null points in the power feeding characteristics of the tire information detection system is suppressed, and power feeding around the entire tire is realized.

  Therefore, the power supplied to the tire information detection device that moves relative to the reader antenna is relatively stable due to the rotation of the tire, and power supply and transmission / reception of tire information between the reader antenna and the tire information detection device are always performed. Will be possible.

Explanation of usage

  The first embodiment of the present invention is to provide the driver with information related to the tire air pressure and temperature at the same time as in the tire air pressure and temperature detection device that operates on conventional batteries. In other words, the fineness and accuracy are much more reliable than the former, and may be applied to automatic driving of future vehicles.

Description of modification

  The present invention is not limited to the above-described embodiments, and various modifications such as those described below are possible.

  The ferrite core 5 of the above embodiment has a cubic shape, but is a rectangular parallelepiped, a substantially cylindrical shape having a substantially equal diameter and height, a substantially spherical shape, and a substantially elliptical shape whose major axis is approximately 4 times or less than 4 times the minor axis. It may be either a body or a substantially hen egg shape.

  Instead of the ferrite core 5 having any shape in the above-described embodiment, a ferrite material powder or fragments may be hardened with a resin or plastic having the same shape to form the core.

It is a figure which shows the electric power feeding principle of a tire condition detection system. It is explanatory drawing of the magnetic field which a ferrite antenna provided with a horizontal solenoid generate | occur | produces. It is explanatory drawing of the magnetic field which the ferrite antenna provided with the vertical solenoid derives. It is a figure which shows the electric power feeding characteristic of the reader antenna and tire information detection apparatus of a present Example. Description of a conventional tire condition detection system in which a reader antenna is disposed on the side of a tire (1) Description of a conventional tire condition detection system in which a reader antenna is disposed on the side of a tire (2) It is a figure which shows arrangement | positioning of the tire seen from diagonally, a tire information detection apparatus, and a reader antenna. It is a figure which shows arrangement | positioning of the tire seen from the front, a tire information detection apparatus, and a reader antenna. It is a figure which shows the electric power feeding characteristic (polar coordinate) between a reader antenna and a tire information detection apparatus. It is a figure which shows the electric power feeding characteristic (orthogonal coordinate) between a reader antenna and a tire information detection apparatus.

5 Ferrite core 6 6a 6b Horizontal solenoid 7 7a 6b Vertical solenoid 10a 10b 10c Ferrite antenna 15 Leader antenna 18 Feeding characteristic 19 of tire information detecting device 19 Null point 20 High frequency power supply 21 Feeding characteristic 100 of ferrite antenna of the present invention Leader antenna system 200 Tire information Detection device 300 Tire 310 Conductor wire or mesh 320 provided inside tire rubber layer 330 Tire rubber layer 330 Wheel rim 340 Tire valve 500 Tire condition detection system power supply unit B1 B2 B4 B8 B12 B42 Magnetic field C1 C2 Capacitor I12 I42 Current

Claims (10)

A substantially cubic ferrite material;
A first solenoid wound with a conductor wire along the surface of the ferrite material;
A second solenoid wound along the surface of the ferrite material in a direction substantially perpendicular to the conductor wire with another conductor wire,
A cross section of the first solenoid and a cross section of the second solenoid are substantially orthogonal to each other;
One end of the first solenoid and one end of the second solenoid are electrically connected to each other;
A ferrite antenna, wherein both the other end of the first solenoid and the other end of the second solenoid are used as input / output terminals.   The ferrite antenna according to claim 1, wherein both the first solenoid and the second solenoid are formed by a single conductor wire.   The ferrite antenna according to claim 1 or 2, wherein both of the first solenoid and the second solenoid are covered with an insulating coating of these conductor wires.   Both the first solenoid and the second solenoid are characterized in that the total length of these conductor wires is not more than 0.05 times the wavelength of the high-frequency current input to the input / output terminal. The ferrite antenna according to claim 1. Ferrite material,
A first solenoid wound with a conductor wire along the ferrite material;
A second solenoid wound along the surface of the ferrite material in a direction substantially perpendicular to the conductor wire with another conductor wire,
The ferrite material has a substantially cylindrical shape, a substantially spherical shape, and a substantially elliptical shape or a substantially hen egg shape whose major axis is approximately 4 times or less than 4 times the minor axis,
A cross section of the first solenoid and a cross section of the second solenoid are substantially orthogonal to each other;
One end of the first solenoid and one end of the second solenoid are electrically connected;
A ferrite antenna, wherein both the other end of the first solenoid and the other end of the second solenoid are used as input / output terminals. When the smaller number of turns in the first solenoid and the second solenoid is N,
2. The ferrite material according to claim 1, wherein a maximum dimension of the ferrite material is not more than (0.05 / (2 × 4 × N)) times a wavelength of a high-frequency current input to the input / output terminal. Ferrite antenna. In the ferrite antenna according to any one of claims 1 to 6,
The ferrite antenna is characterized in that the core of the ferrite antenna is formed of a ferrite material powder or debris which is hardened with resin or plastic. A tire having a conductor wire or a conductor mesh;
The ferrite antenna according to any one of claims 1 to 7, which is disposed apart from an outer peripheral surface of the tire,
A tire information detection device that is arranged inside the tire, detects information in the tire, and transmits the detected information;
The direction of the first magnetic field generated by the first solenoid is a normal direction of the outer peripheral surface of the tire,
The direction of the second magnetic field generated by the second solenoid is substantially parallel to the rotation axis of the tire,
The tire state detection system, wherein the first magnetic field and the second magnetic field act on an antenna of the tire information detection device to become a power source, thereby driving the tire information detection device. The conductor wire or conductor mesh is provided on the outer periphery of the tire,
9. The tire condition detection system according to claim 8, wherein the information in the tire is information such as a pressure of air in the tire, a temperature of air in the tire, an acidity of air in the tire, an acceleration, and the like. The direction of the first magnetic field generated by the first solenoid is:
The normal direction of the outer peripheral surface of the tire,
When the first magnetic field is directed from the outer peripheral surface of the tire toward the first solenoid, the second magnetic field passes through the tire from the side without the tire information detection device, and the side with the tire information detection device Or head to
When the first magnetic field is directed from the first solenoid toward the tire outer peripheral surface, the second magnetic field passes through the tire from the side where the tire information detection device is present, and the side where the tire information detection device is not present 10. The tire state detection system according to claim 8, wherein the ferrite antenna is configured to go to

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