JP2007076506A - Pneumatic tire and tire-wheel assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire and a tire-wheel assembly capable of enhancing transmittance of electric waves, thereby reducing the number of receiving antennas to simplify the configuration of a device and promoting cost reduction. <P>SOLUTION: In this pneumatic tire, a carcass layer 5 wherein metallic cords f extending in the tire radial direction TR are arranged in the tire radial direction TR leaving predetermined clearances x and embedded in a rubber layer 5X is extended between right and left bead parts 3; and belt layers 8 wherein metallic cords inclined to and extending to the tire radial direction TR are arranged at predetermined intervals in the tire circumferential direction TR are provided in the outer peripheral side of the carcass layer 5 in a tread part 1. In a side wall part 2 side, a clearance part 14 specifying the length A (mm) of the carcass layer 5 in the direction where the clearances x between the metallic cords f are extended is provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pneumatic tire and a tire / wheel assembly using the pneumatic tire, and more particularly, a pneumatic tire capable of increasing the transmittance of a radio wave transmitted from a transmitter disposed in a tire cavity. And a tire / wheel assembly.

  In recent years, in order to enhance the safe driving of the vehicle, the tire pressure monitoring device that detects the tire air pressure by monitoring the tire pressure while driving, and the tire temperature by detecting the temperature in the cavity of the tire Various tire monitoring devices that can monitor the state of the tire, such as a tire temperature monitoring device configured to do so, have been proposed.

  Generally, these devices are a tire-side mounting unit including a pressure sensor that detects tire air pressure, a temperature sensor that detects the temperature in the tire, and a transmitter that transmits the detection signal to the vehicle side via a transmission antenna. And a vehicle-side mounting unit that includes a receiver that receives a detection signal transmitted from the transmitter via a reception antenna, and a processor that processes the received detection signal, and is mounted in the cavity of the tire. Communication is performed by electromagnetic waves between the tire side mounting unit and the vehicle side mounting unit (see, for example, Patent Document 1).

  The electromagnetic wave used for communication between the tire side mounting unit and the vehicle side mounting unit is a weak radio wave (for example, 315 MHz) that does not violate the regulations of the Radio Law so that it can be used without license and without delivery. I am trying to use it.

  By the way, heavy-duty pneumatic tires used for heavy trucks and buses, which are currently equipped with tire monitoring devices such as tire pressure monitoring devices, are used not only for belt layer reinforcement cords but also for carcass layer reinforcement cords. A metal cord such as a steel cord is used (for example, see Patent Document 2). Therefore, the tire is almost shielded in terms of radio waves, and the radio wave transmittance is extremely low. Therefore, in order to reliably receive radio waves from the transmitting antenna of the transmitter in the tire cavity, the receiving antenna of the vehicle mounting unit is installed in the tire house near the tire.

Therefore, it is necessary to install at least one receiving antenna for each tire house. As a result, there is a problem that the number of receiving antennas is increased, the configuration of the tire monitoring apparatus is complicated, and the cost is increased.
Japanese Patent Laid-Open No. 7-186633 JP-A-5-155208

  An object of the present invention is to provide a pneumatic tire and a tire / wheel assembly that can increase radio wave transmittance, thereby reducing the number of receiving antennas, simplify the configuration of the device, and reduce the cost. There is.

The pneumatic tire of the present invention that achieves the above object has a carcass layer in which metal cords extending in the tire radial direction are arranged with a predetermined gap in the tire circumferential direction and embedded in a rubber layer with left and right sidewall portions. After that, a pneumatic layer is provided with a belt layer that extends between the right and left bead portions and has metal cords that are inclined and extend in the tire radial direction on the outer periphery side of the carcass layer of the tread portion at predetermined intervals in the tire circumferential direction. The tire is characterized in that a gap portion in which a length A (mm) in a direction in which a gap between metal cords of the carcass layer extends satisfies the following formula is provided on at least one sidewall portion side.
0.7 × λ / 2 × 1 / ε ^1/2 ≦ A ≦ 1.3 × λ / 2 × 1 / ε ^1/2
λ: Wavelength of the radio wave transmitted from the transmitter arranged in the cavity of the pneumatic tire (mm)
ε: Dielectric constant of rubber at the position corresponding to the gap in the window

  In the tire / wheel assembly of the present invention, the metal cord extending in the tire radial direction is arranged with a predetermined gap in the tire circumferential direction and the carcass layer embedded in the rubber layer is passed through the left and right sidewall portions. A pneumatic tire provided with a belt layer that extends between the right and left bead portions and has metal cords that are inclined and extend in the tire radial direction on the outer periphery side of the carcass layer of the tread portion at predetermined intervals in the tire circumferential direction. The bead portion of the tire is mounted on the rim of the wheel, and the transmitter is disposed in the hollow portion of the pneumatic tire, and at least one side wall portion side between the metal cords of the carcass layer. A gap portion in which the length A (mm) in the direction in which the gap extends satisfies the above formula is provided.

  According to the present invention described above, the gap between the metal cords of the carcass layer on the side wall portion side is formed in the gap portion having a length suitable for the transmission of the frequency of the radio wave transmitted from the transmitter. Thus, it is possible to effectively increase the transmittance of radio waves transmitted from the transmitter disposed in the cavity. As a result, radio waves transmitted from the transmitter can be sent far away, and there is no need to install a receiving antenna for each tire house, so the number of receiving antennas can be reduced to simplify the configuration of the device and reduce costs. Can do.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
1 shows an embodiment of a pneumatic tire of the present invention, FIG. 2 shows an embodiment of a tire / wheel assembly in which the pneumatic tire T of FIG. 1 is mounted on a rim Wr of a wheel W, 1 is a tread portion, Reference numeral 2 denotes a sidewall portion, 3 denotes a bead portion, 4 denotes a hollow portion, and S denotes a tire-side mounting unit (with a built-in transmitter) of the tire pressure monitoring device.

  As shown in detail in FIG. 3, the pneumatic tire T has a steel cord (metal cord) f extending along the tire radial direction TR and a predetermined gap (gap filled with rubber) in the tire circumferential direction TC. One carcass layer 5 arranged through x and embedded in the rubber layer 5X is provided inside the tire. The carcass layer 5 extends between the left and right bead portions 3 via the left and right sidewall portions 2, and both end portions 5 a sandwich the bead filler 7 around the bead cores 6 embedded in the bead portions 3. It is folded back to the outside.

  On the outer peripheral side of the carcass layer 5 of the tread portion 1, a plurality of belts in which steel cords (metal cords) extending incline in the tire radial direction TR are arranged at predetermined intervals in the tire circumferential direction and embedded in the rubber layer Layer 8 is provided. A tread rubber layer 9 is provided on the outer peripheral side of the belt layer 8.

  An inner liner layer 10 made of butyl rubber or the like is disposed inside the carcass layer 5. Both sidewall portions 2 are provided with side rubber layers 11 outside the carcass layer 5, and rim cushion rubber layers 12 are disposed on the bead portions 3.

In the left and right sidewall portions 2, conductive shielding layers (shielding members) 13 that partially shield the gaps x between the steel cords f of the carcass layer 5 are annularly arranged along the tire circumferential direction. The shielding layer 13 is fixed to the inner surface 10a of the inner liner layer 10, and includes a first shielding layer 13A provided on the tire inner peripheral side and a second shielding layer 13B provided on the tire outer peripheral side. The first shielding layer 13A and the second shielding layer 13B have a gap x between the steel cords f of the carcass layer 5 and a portion xa (length A (mm) in the extending direction of the gap represented by the following formula. (See FIG. 4) and is arranged so as to be shielded, and a gap portion 14 formed of a portion xa of the gap x is formed as a radio wave window portion on the side wall portion 2 side.
0.7 × λ / 2 × 1 / ε ^1/2 ≦ A ≦ 1.3 × λ / 2 × 1 / ε ^1/2

  However, (lambda) is the wavelength (mm) of the electromagnetic wave transmitted from the transmitter arrange | positioned in the cavity 4 of the pneumatic tire T, (epsilon) is the rubber | gum in the position corresponding to the clearance gap x (gap part xa) of the clearance gap part 14. FIG. Is the dielectric constant. In addition, the rubber | gum in the position corresponding to the clearance gap x of this clearance gap part 14 is rubber | gum located between the tire inner surface through the clearance gap x and a tire outer surface, and in embodiment shown in FIG. 5, rubber of the inner liner layer 10 and the side rubber layer 12. When there are a plurality of layers of rubber, the dielectric constant ε is obtained by dividing the sum of the product of the thickness of each layer and the dielectric constant of the rubber by the sum of the thicknesses of the layers.

The length A of the portion xa is set such that, for example, the frequency of the radio wave transmitted from the transmitter is 315 MHz, and the dielectric constant ε of the rubber of the sidewall portion 2 (rubber at the position corresponding to the gap x of the gap portion 14) is 17. If it is 4, it will be the range of about 80-147 mm. If the length A of the portion xa is out of the above range, it is difficult to effectively improve the radio wave transmittance. Preferably, 0.9 × λ / 2 × 1 / ε ^1/2 ≦ A ≦ 1.1 × λ / 2 × 1 / ε ^1/2 , and more preferably A = λ / 2 × 1 / ε ^{1 / 2} is good.

  The shielding layer 13 is preferably provided on the left and right sidewall portions 2, but may be provided on any one of the sidewall portions 2, provided that it is disposed on at least one side of the left and right sidewall portions 2. Good.

  The shielding layer 13 may be made of any conductive material as long as it can shield radio waves transmitted from the transmitter, and examples thereof include aluminum foil, conductive paint, and metal plating. Further, the shielding layer 13 may be provided by being embedded in the sidewall portion 2.

  The tire / wheel assembly shown in FIG. 2 has a structure in which the bead portion 3 of the pneumatic tire T described above is mounted on the rim Wr of the wheel W, and the tire-side mounting unit S is mounted on the rim Wr in the cavity 4. ing.

  As a result of intensive studies to improve the transmission of radio waves transmitted from a transmitter disposed in a cavity of a tire that is almost shielded in terms of radio waves, the present inventors have found the following.

  Heavy-duty pneumatic tires used on heavy trucks and buses that are equipped with tire pressure monitoring devices such as tire pressure monitoring devices are radio waved by the belt layer at the tread and the wheel between the beads at the wheel. The portion that is almost completely shielded and not completely shielded is a sidewall portion. A radio wave is transmitted to the outside through a narrow gap between the steel cords of the carcass layer in the sidewall portion. However, since the gap is narrow, the attenuation rate of radio waves when passing through the gap is large, and the radio wave transmittance is extremely low.

  Therefore, when the effective use of this gap was examined, it was found that the same principle as that when the frequency selective shield material was used was established. That is, as shown in FIG. 5, slits 21 having a predetermined length are arranged on the shielding plate 20, and the length of the radio wave frequency λ desired to be transmitted through the length B of the slit 21 is ½ of the wavelength λ. Then, the transmittance of the radio wave desired to be transmitted can be increased.

  For example, if the frequency of the radio wave to be transmitted is 2.45 GHz, by setting the length B of the slit 21 to 61 mm, a high transmittance can be obtained at 2.45 GHz as shown by the graph indicated by F1 in FIG. it can. Moreover, when the frequency of the radio wave to be transmitted is 945 MHz, by setting the length B of the slit 21 to 158.5 mm, a high transmittance can be obtained at 945 MHz, as shown by the graph indicated by F2 in FIG. Further, when the frequency of the radio wave to be transmitted is 315 MHz, by setting the length B of the slit 21 to 476 mm, a high transmittance can be obtained at 315 MHz as shown by the graph F3 in FIG.

The above is the case in the air, but in the case of a pneumatic tire, rubber exists in the sidewall portion through which radio waves are transmitted. In this case, the optimum length B of the slit 21 for the frequency of the radio wave to be transmitted is represented by λ / 2 × 1 / ε ^1/2 .

  The dielectric constant of the rubber can be appropriately changed by adjusting the amount of carbon or the like to be blended, for example. Therefore, the dielectric constant of the rubber is adjusted according to the tire size (the length of the sidewall portion in the tire radial direction), and the length A of the portion xa of the gap x through which radio waves are transmitted is adjusted. This makes it possible to transmit radio waves effectively by optimizing the length of the gap portion between the steel cords of the carcass layer in the sidewall portion.

  For example, if the frequency of the radio wave to be transmitted is 315 MHz and rubber having a dielectric constant of 17.4 is used for the sidewall portion, the length A of the portion xa of the gap x is about 114 mm. If it is a portion, it can be easily formed on the sidewall portion of a heavy duty pneumatic tire currently used for large trucks and buses.

  As described above, in the present invention, the gap x between the steel cords f of the carcass layer 5 of the sidewall portion 2 is partially shielded by the shielding member 13 and is suitable for transmission of the frequency of the radio wave transmitted from the transmitter. 14 is formed, the transmittance of the radio wave transmitted from the transmitter of the tire-side mounting unit S disposed in the cavity 4 can be increased, whereby the radio wave transmitted from the transmitter is conventionally transmitted. Since it is possible to fly farther, there is no need to install a receiving antenna for each tire house. Therefore, the number of receiving antennas of the tire pressure monitoring device can be reduced, the configuration of the device can be simplified, and the cost can be reduced.

  FIG. 7 shows another embodiment of the pneumatic tire of the present invention. In the pneumatic tire T of this embodiment, the gap portion 14 is formed without providing the above-described shielding layer 13. That is, the bead portion 3 where the rim Wr starts to come into contact with the perpendicular U1 drawn from the edge e of the belt layer 8 (belt layer 8X having the widest belt width) to the inner surface (tire inner surface) 10a of the inner liner layer 10 and the rim. The length n in the extending direction of the gap x between the steel cords f of the carcass layer 5 in the region Z between the tire outer surface position OP and the perpendicular line U2 drawn on the inner surface 10a of the inner liner layer 10 is the length A. The entire gap x located in the region Z is the gap 14.

  1 and 2 described above, by using a rubber having a high dielectric constant with the dielectric constant adjusted as appropriate, the gap portion having an increased radio wave transmittance without the shielding layer 13 being disposed. 14 can be provided, and the same effects as described above can be obtained also in the pneumatic tire T of FIG. 7 and the tire / wheel assembly using the same.

  In the present invention, the width m of the gap x between the steel cords f of the carcass layer 5 is set to 2/1000 times or more the wavelength of the radio wave transmitted from the transmitter to effectively increase the radio wave transmittance. Preferred above.

  However, if the width m of the gap x is 2/1000 times or more of the wavelength of the radio wave, the distance between the steel cords f becomes wider than the currently used tire. Shear force decreases. Therefore, the strength and shearing force of the carcass layer can be increased by increasing the diameter of the steel cord f and increasing the thickness of the carcass layer 5 and / or using a rubber having a higher elastic modulus for the carcass layer 5. Can be prevented. For example, assuming that the distance between the steel cords f (the width m of the gap x) is twice that of the conventional case, at least one of the rubber thickness and the elastic modulus of the carcass layer 5 can be about twice that of the conventional case. . The upper limit value of the width m of the gap x is preferably 8/1000 times or less of the wavelength of the radio wave from the viewpoint of maintaining air pressure. The width m of the gap x is more preferably 3/1000 times to 5/1000 times.

  In the tire / wheel assembly, the antenna of the transmitter of the tire side mounting unit S disposed in the cavity 4 of the pneumatic tire T is a radio wave Q transmitted from the antenna K as shown in FIGS. The direction P of the electric field of the carcass layer 5 should be installed so that it intersects the direction of the gap x between the steel cords f of the carcass layer 5 (the tire radial direction TR in the example of the figure) at 45 ° or more, preferably perpendicular. It is preferable for improving the radio wave transmittance. In FIG. 9, QD is the traveling direction of the radio wave Q.

  In the above embodiment, the tire side mounting unit S of the tire pressure monitoring device is provided in the tire cavity 4 in the above embodiment, but the tire side mounting unit (built-in transmitter) of the tire temperature monitoring device is installed. Any device may be used as long as a transmitter for transmitting radio waves to the outside is disposed in the tire cavity 4.

It is a tire meridian half section view showing one embodiment of a pneumatic tire of the present invention. It is sectional drawing which shows one Embodiment of the tire and wheel assembly which has the pneumatic tire of FIG. It is a principal part expanded sectional view of a carcass layer. It is the elements on larger scale of the side wall part seen from the tire cavity part side. It is explanatory drawing explaining the relationship between the slit provided in the shielding board, and the transmittance | permeability of an electromagnetic wave. It is a graph which shows the relationship between the frequency of a radio wave, and the transmittance | permeability. It is a tire meridian half section view showing other embodiments of the pneumatic tire of the present invention. It is explanatory drawing which shows direction of the antenna in the cavity part of a tire. It is explanatory drawing which shows the direction of the electric field direction of the electromagnetic wave transmitted from an antenna.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Cavity part 5 Carcass layer 5X Rubber layer 8 Belt layer 10 Inner liner layer 11 Side rubber layer 13 Shielding layer (shielding member)
14 Gap K Antenna P Direction of electric field direction of radio wave Q Radio wave S Tire side wearing unit (transmitter)
T Pneumatic tire TC Tire circumferential direction TR Tire radial direction W Wheel Wr Rim Z area f Steel cord (metal cord)
m width x gap xa part

Claims (9)

A carcass layer in which metal cords extending in the tire radial direction are arranged through a predetermined gap in the tire circumferential direction and embedded in the rubber layer is extended between the left and right bead portions through the left and right sidewall portions, and the tread portion In a pneumatic tire provided with a belt layer in which metal cords that are inclined and extended in the tire radial direction on the outer circumferential side of the carcass layer are arranged at predetermined intervals in the tire circumferential direction,
A pneumatic tire in which a gap portion in which a length A (mm) in a direction in which a gap between metal cords of the carcass layer extends satisfies the following formula is provided on at least one sidewall portion side.
0.7 × λ / 2 × 1 / ε ^1/2 ≦ A ≦ 1.3 × λ / 2 × 1 / ε ^1/2
λ: Wavelength of the radio wave transmitted from the transmitter arranged in the cavity of the pneumatic tire (mm)
ε: Dielectric constant of rubber at the position corresponding to the gap of the gap   2. The pneumatic tire according to claim 1, wherein a conductive shielding member that shields the gap leaving the gap is disposed on the side of the at least one sidewall.   Between the metal cords of the carcass layer in the region between the perpendicular drawn from the edge of the belt layer to the tire inner surface and the perpendicular drawn to the tire inner surface from the tire outer surface position of the bead portion where the rim starts to contact when the rim is assembled The pneumatic tire according to claim 1, wherein the length A is a length in a direction in which the gap extends.   The pneumatic tire according to claim 1, 2, or 3, wherein a width of a gap between metal cords of the carcass layer is 2/1000 times or more of a wavelength of the radio wave. A carcass layer in which metal cords extending in the tire radial direction are arranged through a predetermined gap in the tire circumferential direction and embedded in the rubber layer is extended between the left and right bead portions through the left and right sidewall portions, and the tread portion A bead portion of a pneumatic tire provided with a belt layer in which metal cords extending in the tire radial direction on the outer circumferential side of the carcass layer are arranged at predetermined intervals in the tire circumferential direction is attached to a rim of the wheel, A tire / wheel assembly in which a transmitter is disposed in a cavity of a pneumatic tire,
A tire / wheel assembly in which at least one sidewall portion is provided with a gap portion in which a length A (mm) in a direction in which a gap between metal cords of the carcass layer extends satisfies the following formula.
0.7 × λ / 2 × 1 / ε ^1/2 ≦ A ≦ 1.3 × λ / 2 × 1 / ε ^1/2
λ: Wavelength of the radio wave transmitted from the transmitter arranged in the cavity of the pneumatic tire (mm)
ε: Dielectric constant of rubber at the position corresponding to the gap of the gap   The tire / wheel assembly according to claim 5, wherein a conductive shielding member that shields the gap while leaving the gap is disposed on the side of the at least one sidewall.   Between the metal cords of the carcass layer in the region between the perpendicular drawn from the edge of the belt layer to the tire inner surface and the perpendicular drawn to the tire inner surface from the tire outer surface position of the bead portion where the rim starts to contact when the rim is assembled The tire / wheel assembly according to claim 5, wherein the length A in the direction in which the gap extends is the length A.   The tire / wheel assembly according to claim 5, 6, or 7, wherein a width of a gap between metal cords of the carcass layer is 2/1000 times or more of a wavelength of the radio wave.   The tire / wheel according to any one of claims 5 to 8, wherein the antenna is installed such that a direction of an electric field of a radio wave transmitted from an antenna of the transmitter is perpendicular to a direction in which the gap extends. Assembly.

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