Tire and wireless power supply system

Abstract

To provide a tire and a wireless power supply system using the same which can realize excellent power supply efficiency due to selection of an installation portion of a power-receiving coil, or condition of heat dissipation of the installation portion.SOLUTION: In a tire meridian cross sectional view, heat conductivity λ1 of an innerliner of a tire is 0.10 W / m k or more in a tire radial direction area (CW) between perpendicular lines from tire radial direction both ends of a power-receiving coil (40) to the innerliner (12) formed in an inner peripheral side of a carcass (18).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a tire and a wireless power supply system with improved power supply efficiency.

Background Art

[0002] Conventionally, a wireless power reception system has been disclosed in which power is supplied between a power transmission coil buried near a road surface and a power reception coil attached on the center line in the tire width direction of a wheel (for example, Patent Document 1, FIG. 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the wireless power reception system of Patent Document 1, since the power reception coil is usually attached to a metal rim portion, the AC magnetic field is affected by the rim portion, and the power that can be received by the power reception coil tends to decrease. On the other hand, when the power reception coil is installed away from the metal rim portion, the power supply efficiency is improved, but it has been difficult to dissipate the heat generated by the power reception coil.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a tire and a wireless power supply system using the tire that can achieve excellent power supply efficiency due to the selection of the installation location of the power reception coil and the heat dissipation mode at the installation location.

Means for Solving the Problems

[0006] The tire of the present invention has a bead core, a bead filler provided on the outer side in the tire radial direction of the bead core, a carcass folded around the bead core, and a belt provided on the outer side in the tire radial direction of the carcass, and is provided with a power receiving coil on the inner cavity surface for receiving power supplied by an alternating magnetic field from the outside of the tire. In the tire radial direction region between both feet of the perpendicular line drawn from each of both ends in the tire radial direction of the power receiving coil to the inner liner formed on the inner peripheral side of the carcass, the thermal conductivity λ1 of the inner liner is 0.10 W / m·k or more.

Advantages of the Invention

[0007] In the tire according to the present invention, improvements are made to the installation location of the power receiving coil on the inner cavity surface of the tire and the heat dissipation mode at the installation location. As a result, according to the tire of the present invention, the power supply efficiency can be improved.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

DETAILED DESCRIPTION OF THE INVENTION

[0009] Embodiments of the tire according to the present invention (basic form 1 and additional forms 2 to 6 shown below), and embodiments of the wireless power supply system according to the present invention (basic form 7 and additional forms 8 and 9 shown below) will be described in detail with reference to the drawings. Note that these embodiments do not limit the present invention. In addition, the components of each embodiment include those that can be replaced and are easy for those skilled in the art, or those that are substantially the same. Furthermore, each embodiment can be arbitrarily combined within the scope obvious to those skilled in the art.

[0010] In the following description, the tire radial direction refers to the direction perpendicular to the tire rotation axis. The inner side in the tire radial direction refers to the side facing the tire rotation axis in the tire radial direction, and the outer side in the tire radial direction refers to the side away from the tire rotation axis in the tire radial direction. Also, the tire circumferential direction refers to the circumferential direction with the tire rotation axis as the central axis. Furthermore, the tire width direction refers to the direction parallel to the tire rotation axis. The inner side in the tire width direction refers to the side facing the tire equatorial plane (tire equator line) in the tire width direction, and the outer side in the tire width direction refers to the side away from the tire equatorial plane in the tire width direction. Note that the tire equatorial plane refers to a plane that is perpendicular to the tire rotation axis and passes through the center of the tire width.

[0011] Similarly, in the following description, the regular rim refers to the "Applicable Rim" defined by JATMA, the "Design Rim" defined by TRA, or the "Measuring Rim" defined by ETRTO.

[0012] Similarly, in the following description, the regular internal pressure refers to the "Maximum Air Pressure" defined by JATMA, the maximum value described in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" defined by TRA, or the "INFLATION PRESSURES" defined by ETRTO. Also, the regular load refers to the "Maximum Load Capacity" defined by JATMA, the maximum value described in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" defined by TRA, or the "LOAD CAPACITY" defined by ETRTO.

[0013] <Tire> [Basic form 1] FIG. 1 is a meridian cross-sectional view showing a part on one side in the tire width direction with respect to the tire equatorial plane (not shown) for the tire according to the present embodiment. In the figure, the tire part on the side opposite to the ground contact surface is shown in a state where it is mounted on a rim and a normal internal pressure is applied, and a load of 80% of the normal load is applied (hereinafter, the same applies to the invention of the tire).

[0014] As shown in FIG. 1, the tire 10 according to the present embodiment has a bead portion A, a sidewall portion B, a shoulder portion C, and a tread portion D from the inner side to the outer side in the tire radial direction. In the region from the bead portion A to the tread portion D, an inner liner 12 exposed on the inner cavity surface of the tire is provided. On the side opposite to the inner cavity surface of the inner liner 12, a carcass 18 including a main body portion 18a extending along the inner liner 12 and a folded-back portion 18b folded around the bead core 14 and the bead filler 16 is provided. On the outer side in the tire radial direction of the carcass 18 in the tread portion D, a belt 20 (belt layers 20a, 20b) and a belt cover 22 (belt cover layers 22a, 22b, 22c) are sequentially provided on the outer side in the tire radial direction.

[0015] Further, on the outer side in the tire width direction of the folded-back portion 18b of the carcass 18 provided on the outer side in the tire width direction of the bead core 14 and the bead filler 16, a rim cushion 24 is provided. On the outer side in the tire radial direction of the rim cushion 24, a side tread 26, a wing tip 28, and a cap tread 30 are sequentially provided. Note that the tire according to the present embodiment is not limited to the example shown in FIG. 1, and includes, for example, a run-flat tire in which a run-flat liner is provided on the outer side in the tire width direction of the inner liner 12 mainly in the sidewall portion B.

[0016] In the tire 10 configured as described above, the inner liner 12 is a layer for blocking the gas in contact with the inner cavity surface of the tire. The inner liner 12 can be composed of a single inner liner layer, or can also be composed of a plurality of inner liner layers laminated in the tire radial direction at the tire equatorial plane. The inner liner 12 includes at least one layer made of a rubber or resin layer with low air permeability, and as other layers, it can include an adhesive layer at least at the contact portion with the carcass 18.

[0017] The bead core 14 is, for example, a ring-shaped reinforcing material formed by bundling cords, and can have a structure in which a plurality of bead wires made of steel cords or organic fiber cords are coated with rubber. The bead filler 16 is a member for increasing the rigidity of the bead portion A, and the tire width direction dimension at the inner end portion in the tire radial direction thereof is substantially equal to the tire width direction dimension at the outer end portion in the tire radial direction of the bead core 14, and can have a substantially triangular shape as shown in FIG. 1 in which the tire width direction dimension gradually decreases toward the outer side in the tire radial direction.

[0018] The carcass 18 is a member forming the skeleton of the tire 10, and is composed of at least one carcass layer (carcass ply), and each carcass layer has a configuration in which a plurality of carcass cords are coated with rubber. Generally, steel cords or organic fiber cords are used as the carcass cords. However, in the tire 10 according to the present embodiment, as will be described later, in order to prevent the magnetic field generated so as to penetrate the inner cavity surface of the inner liner 12 substantially vertically in the sidewall portion B from being obstructed by a metal member, it is preferable to use a non-magnetic material as the carcass cord. For example, as the non-magnetic material, organic fibers such as rayon, polyester, polyamide, and aramid can be used.

[0019] The belt 20 is a reinforcing layer provided on the outer side in the tire radial direction of the carcass 18, which tightens the carcass 18 to increase the rigidity of the tread portion, improve the handling stability, and reduce the strain deformation to decrease the rolling resistance. The belt 20 can be composed of a plurality of belt layers (two belt layers 20a and 20b in the example shown in FIG. 1) laminated in the tire radial direction in the tread portion D. Each of the belt layers 20a and 20b has a structure in which a plurality of belt cords are coated with rubber. Generally, steel cords or organic fiber cords are used as the belt cords. As the belt cords, not only magnetic materials such as steel cords can be used, but also non-magnetic materials (including paramagnetic materials and diamagnetic materials) can be used.

[0020] The belt cover 22 is a member that reinforces the tightening effect of the carcass 18 by the belt 20, and is particularly a member for preventing the tread portion D from deforming due to the centrifugal force generated during high-speed running of the vehicle. The belt cover 22 can be composed of a plurality of belt cover layers (three belt cover layers 22a, 22b, and 22c in the example shown in FIG. 1) laminated in the tire radial direction on the outer side in the tire radial direction of the belt 20. Each of the belt cover layers 22a, 22b, and 22c has a structure in which a plurality of cords are coated with rubber. Generally, steel cords or organic fiber cords are used as the cords used for the belt cover layer. As this cord, not only magnetic materials such as steel cords can be used, but also non-magnetic materials (including paramagnetic materials and diamagnetic materials) can be used.

[0021] The rim cushion 24 is provided in a region that contacts the rim flange of a wheel (not shown), and the side dredge 26 is arranged to connect the rim cushion 24 and the tread portion D. The wing tips 28 are respectively provided at the boundaries between the tread portions D on the left and right of the tire and the side dredge 26 in a meridional cross-section view of the tire, and the cap tread 30 is formed on the surface of the tread portion D over the entire contact surface of the tire. The run-flat liner (not shown) is formed on the outer peripheral side of the inner liner 12 over at least the sidewall portion B (and may include the bead portion A and / or the shoulder portion C in some cases). Note that for the rim cushion 24, the side tread 26, the wing tips 28, the cap tread 30, and the run-flat liner, rubber members conventionally used can be used according to their respective required characteristics.

[0022] On the premise of the existence of the components 12 to 30 of the tire 10 shown above (including the run-flat liner in some cases), the tire 10 according to the present embodiment includes a power receiving coil 40 (FIG. 1) on its inner cavity surface for receiving AC power transmitted from a power transmission coil (not shown) installed outside the tire 10. The power receiving coil 40 may be provided in contact with the inner liner 12 or may be embedded in the inner liner 12. Further, the power receiving coil 40 may be provided to be fixed to the inner liner 12 via a fixing member other than rubber (for example, made of a non-magnetic material, and in particular, a rubber having a relatively high thermal conductivity such as silicone rubber can be used for the fixing portion). Note that even when a run-flat liner is provided, the power receiving coil 40 can be provided on the inner peripheral side of the inner liner 12 described above.

[0023] Power feeding using the tire 10 according to this embodiment is performed by, for example, once converting a direct current obtained from an in-vehicle battery (not shown) into an alternating current by an AC power supply device, and applying this alternating current to a power transmission coil (attached to, for example, a knuckle or a hub carrier which are parts of a steering axle of a vehicle, or the surface on the tire side of any part constituting a strut structure), thereby generating an alternating magnetic field around the power transmission coil. When this alternating magnetic field intersects the power reception coil 40, an induced electromotive force is generated in the power reception coil 40 and power is supplied.

[0024] In realizing such power feeding, in the tire 10 according to this embodiment, in the tire radial direction region CW between both feet of a perpendicular line drawn from each of both end portions in the tire radial direction of the power reception coil 40 to the inner liner 12 formed on the inner peripheral side of the carcass 18, the thermal conductivity λ1 of the inner liner 12 is 0.10 W / m·k or more.

[0025] In this embodiment, the thermal conductivity is measured by the heat flow meter method defined in JIS A1412-2 and ISO 8301, or the laser flash method defined in JIS R1611, or a method defined in other standards equivalent to these methods.

[0026] (Function, etc.) As described above, conventionally, since the power reception coil was attached to a rim portion made of ordinary metal, the alternating magnetic field was affected by the rim portion, and the power that could be received by the power reception coil tended to decrease (Patent Document 1, FIG. 1). On the other hand, when the power reception coil was installed at a distance from the metal rim portion, although the power feeding efficiency improved, it became difficult to dissipate the heat generated by the power reception coil.

[0027] Therefore, the inventor of the present invention has intensively studied to make the installation location of the power receiving coil a tire component other than a metal member and having as large a surface area as possible (i.e., an area for releasing heat). As a result, the inventors focused on installing the power receiving coil on the inner liner formed on the inner peripheral side of the carcass, and by appropriately adjusting the thermal conductivity in at least a predetermined region of the inner liner, even when a temperature rise occurs in the vicinity of the installation location of the power receiving coil during power reception, heat does not accumulate locally in the rim assembly tire, and the fixed state of the power receiving coil is maintained well, thereby obtaining the knowledge that excellent power supply efficiency can be realized. The specific basis, etc. for the selection of the predetermined region of the inner liner to which a specific thermal conductivity is applied and the selection of the range of the thermal conductivity are as follows.

[0028] As described above, examples of the installation location of the power transmission coil include a knuckle (not shown) which is a component of the steering axle of a vehicle. This knuckle is usually located on the outer side in the tire width direction of the sidewall portion B (the right side in FIG. 1) in FIG. 1. For this reason, the magnetic field generated between the power transmission coil and the power receiving coil 40 is generated such that the magnetic force lines penetrate the inner cavity surface of the inner liner 12 substantially perpendicularly in the sidewall portion B.

[0029] Also, during power supply, the power receiving coil 40 generates heat. When viewed from the whole tire, the heat generated by the tire 10 includes, in addition to the heat generated by the power receiving coil 40, the heat generated by the rubber member due to tire rolling, the heat generated by the friction between the road surface and the cap tread, etc. In such a harsh environment where there are multiple heat generation causes, it is important to efficiently dissipate the heat generated by the power receiving coil 40.

[0030] Therefore, by setting the thermal conductivity of the inner liner 12 in the tire radial region CW between both feet of the perpendicular lines drawn from both ends of the power receiving coil 40 shown in FIG. 1 to the inner liner 12 to 0.10 W / m·k or more, heat dissipation can be promoted in the inner liner 12 close to the power receiving coil 40 which is the heat source, and the temperature rise of the power receiving coil 40 can be suppressed. As a result, heat can be prevented from accumulating locally in the tire 10, thereby maintaining a good fixed state between the power receiving coil 40 and the inner liner 12, suppressing deformation of the power receiving coil 40, and ultimately achieving excellent power feeding efficiency.

[0031] Here, it is more preferable that the thermal conductivity is 0.11 W / m·k or more, and extremely preferably 0.12 W / m·k or more.

[0032] (Additional Form 2) In Basic Form 1, in the tire meridian cross-sectional view (FIG. 1), it is preferable that the power receiving coil 40 is provided in the tire radial region WH from the outermost position P1 in the tire radial direction of the bead core 14 to the innermost position P2 in the tire radial direction of the belt 20 (Additional Form 2).

[0033] In the above-mentioned Patent Document 1, a wireless power receiving system is known in which power feeding is performed between a power transmission coil buried near the road surface and a power receiving coil attached on the center line in the tire width direction of the wheel (Patent Document 1, FIG. 1). In this wireless power receiving system, the magnetic field reaching the power receiving coil from the power transmission coil may be affected by the belt. For example, in this wireless power receiving system, when a metal (limited to a magnetic material) belt cord is used for the belt, a part of the magnetic field that should reach the power receiving coil from the power transmission coil is blocked by the magnetic material (belt cord) contained in the belt, and ultimately excellent power feeding efficiency may not be achieved.

[0034] Therefore, the inventors earnestly studied a tire 10 that can achieve excellent power supply efficiency without a part of the magnetic field that should reach the power receiving coil 40 from the power transmission coil being blocked by the components of the tire 10 including a magnetic material even when a metal belt cord is used for the belt 20 shown in FIG. 1.

[0035] Specifically, the inventors earnestly studied at which positions the power receiving coil 40 provided on the inner cavity surface of the tire 10 should be formed with respect to a power transmission coil (not shown) provided outside the tire 10.

[0036] First, in FIG. 1, the inventors focused on a plurality of line segments that reach from each point (starting point) on the inner cavity surface of the tire (the same applies when there is a run-flat liner) to each point (ending point) on the outer surface of the tire at the shortest distance, and extracted a region composed of a plurality of line segments that do not include the belt 20 among these line segments. By providing the power receiving coil 40 so as not to deviate from the inner cavity surface of the tire included in this region, the inventors obtained the finding that most of the magnetic field generated between the two coils is not blocked by the belt 20 that may contain a magnetic material.

[0037] Next, in view of the above finding being a finding for defining the radially outer end of the installation region of the power receiving coil 40, the inventors also earnestly studied defining the radially inner end of this installation region. As a result, the inventors focused on the bead core 14 that may be composed of a metal member, extracted a region composed of a plurality of line segments that do not include the bead core 14 among the above line segments, and by providing the power receiving coil 40 so as not to deviate from the inner cavity surface of the tire included in this region, the inventors also obtained the finding that most of the magnetic field generated between the two coils is not blocked by the bead core 14 that may contain a magnetic material.

[0038] Based on the above findings, in the tire 10 according to the present embodiment, the power receiving coil 40 is provided in the tire radial region WH from the outermost position in the tire radial direction of the bead core 14 to the innermost position in the tire radial direction of the belt 20. Thereby, according to the tire 10 according to the present embodiment, since there are no excessive components of the tire 10 that may contain a magnetic material between the power transmission coil and the power receiving coil 40, the power supply efficiency can be improved.

[0039] (Additional Form 3) In the basic form 1 or the form obtained by adding the additional form 2 to the basic form 1, in the tire meridian cross-section (for example, FIG. 1) cut other than the end of the power receiving coil 40, the total wire cross-sectional area S (m 2 ) of the power receiving coil 40, the resistance value r (Ω) of the power receiving coil 40 at the frequency of the above-described alternating current power, and the thermal conductivity λ1 (W / m·k) of the inner liner 12 satisfy the relationship 1×10 5 ≦r / (λ1×S)≦8×10 7 It is preferable to satisfy this (Additional Form 3).

[0040] Here, the power receiving coil 40 is composed of conductive wires physically connected to a connected circuit (such as a resonance circuit and / or a rectifier circuit), and does not include an independent relay circuit or the like if there is one. Further, the resistance value r (Ω) of the power receiving coil 40 is a value measured by an impedance analyzer or a network analyzer when an alternating current power of a specific frequency is applied to both ends of the power receiving coil 40. Here, the specific frequency is the frequency of the alternating current generated by the alternating current power source in the power supply system, in other words, the frequency of the power sent to the power transmission coil, or the frequency of the alternating magnetic field generated between the transmission gaps, that is, the frequency for operating the wireless power supply.

[0041] FIG. 2 is a schematic diagram showing the winding mode of the power receiving coil 40 in the tire circumferential direction shown in FIG. 1. In the tire meridian section along the line A-A' shown in FIG. 2, the shape of the power receiving coil 40 is as shown in FIG. 1. On the other hand, in most of the region X surrounded by the dotted line in FIG. 2 (especially the central region in the vertical direction of the drawing), in the case of the tire meridian section cut in the tire width direction, compared with the case of FIG. 1, the power receiving coil 40 becomes longer in the tire width direction. Therefore, in the present embodiment, the tire meridian section cut in the tire width direction in the region X surrounded by the dotted line in FIG. 2 is excluded.

[0042] Here, [r / (λ1×S)] considered in the present embodiment is an index indicating the degree of temperature rise during heat generation in the region including the power receiving coil 40 and the inner liner 12 in its vicinity. That is, if the resistance value (r / S) of the power receiving coil 40 per unit total cross-sectional area S (m 2 ) of the wire of the power receiving coil 40 is high, the heat generation amount is large, so the temperature rise is high. If the thermal conductivity λ1 (W / m·k) of the inner liner 12 is low, the heat dissipation is not promoted, so the temperature rise is high.

[0043] By setting the upper limit value of the above [r / (λ1×S)] to 8×10 7 or less, it is possible to suppress the temperature rise during heat generation in the region including the power receiving coil 40 and the inner liner 12 in its vicinity. As a result, the fixing state between the power receiving coil 40 and the inner liner 12 can be maintained better, and the durability of the tire 10 can be further improved.

[0044] On the other hand, if the total cross-sectional area S (m 2 ) of the wire of the power receiving coil 40 is made excessively large, as the weight of the power receiving coil 40 increases, the rolling resistance increases and the fuel consumption decreases. Therefore, the total cross-sectional area S (m 2 ) of the wire of the power receiving coil 40 is not made excessively large, and thus by setting the lower limit value of the above [r / (λ1×S)] to 1×10 5 or more, good fuel consumption can be realized and power supply can be performed efficiently. As a result, excellent transmission efficiency can be realized.

[0045] Incidentally, the upper limit value of the above [r / (λ1×S)] is 6×10 7 It is more preferably 4×10 7 or less, and extremely preferably 4×10 5 or less. On the other hand, the lower limit value is more preferably 2×10 5 or more, and extremely preferably 4×10

[0046] (Additional form 4) In the basic form 1 or the form obtained by adding at least one of the additional forms 2 and 3 to the basic form 1, in the above-mentioned tire radial region WH (the tire radial region from the outermost tire radial position of the bead core 14 to the innermost tire radial position of the belt 20), it is preferable that the thermal conductivity λ2 of the rubber layer other than the inner liner 12 is 0.13 W / m·k or more (Additional form 4).

[0047] Here, the rubber layer other than the inner liner 12 includes the rim cushion 24, the side tread 26, the bead filler 16, the wing tip 28, a run-flat liner (not shown), etc. In addition, this rubber layer includes a second filler (not shown) that is located outside the tire width direction of the folded portion 18b of the carcass 18 and inside the tire width direction of the rim cushion 24 and the side tread 26.

[0048] By setting the thermal conductivity λ2 of the above rubber layer to 0.13 W / m·k or more in the tire radial region WH centered on the sidewall portion B shown in FIG. 1 and reaching the bead portion A and the shoulder portion C in the vicinity thereof, heat dissipation in this region can be further promoted, and the temperature rise of the power receiving coil 40 can be further suppressed. As a result, heat can be prevented from accumulating more locally in the tire 10, and furthermore, the fixing state between the power receiving coil 40 and the inner liner 12 can be maintained better, and the durability of the tire 10 can be further improved.

[0049] (Additional form 5) FIG. 3 is a schematic diagram showing a specific example of the installation ratio [(Σθ2) / θ1] of the fixing member 41 with respect to the power receiving coil 40 shown in FIG. 1. (A) shows an example in which a plurality of fixing members 41a are installed at regular intervals, and (B) shows an example in which one fixing member 41b is installed.

[0050] In the basic form 1 or the form in which at least one of the additional forms 2 to 4 is added to the basic form 1, a fixing member 41 (41a, 41b) for fixing the power receiving coil 40 to the inner cavity surface of the tire is provided. The ratio [(Σθ2) / θ1] of the total sum Σθ2 of the circumferential installation angle θ2 of the fixing member with respect to the circumferential arrangement angle θ1 of the power receiving coil 40 in the tire circumferential direction, with the tire center as a reference, and the thermal conductivity λ3 (W / m·k) of the fixing member satisfy 0.14×[(Σθ2) / θ1]+0.13≦λ3≦0.38×[(Σθ2) / θ1]+0.42 (Additional form 5), which is preferable.

[0051] For both examples in FIGS. 3(A) and (B), since the circumferential arrangement angle θ1 of the power receiving coil 40 is 360°, in the examples shown in FIGS. 3(A) and (B), the above ratio can be described as [(Σθ2) / 360°].

[0052] By setting the thermal conductivity λ3 of the fixing member 41 within the range of the lower limit value or more of the above-described formula, it is possible to suppress the temperature rise of the power receiving coil 40 that generates heat by power supply, and thus to maintain the fixing state between the power receiving coil 40 and the inner liner 12 better and further improve the durability of the tire 10.

[0053] On the other hand, by setting the thermal conductivity λ3 of the fixing member 41 within the range of the upper limit value or less of the above-described formula, when the tire is deformed during rolling, the fixing member 41 can follow the inner liner 12 well, and thus the fixing state between the power receiving coil 40 and the inner liner 12 can be maintained better and the durability of the tire 10 can be further improved.

[0054] In addition, in the present embodiment, when the power receiving coil 40 is embedded in the inner liner 12, the inner liner 12 is considered as the fixing member 41.

[0055] Further, regarding the thermal conductivity λ1 of the inner liner 12 and the thermal conductivity λ3 of the fixing member 41 described above, it is preferable that λ3 is greater than λ1 from the viewpoint of heat dissipation. The relationship between the thermal conductivities λ1 and λ3 is more preferably λ3 > 1.1 × λ1, and extremely preferably λ3 > 1.2 × λ1.

[0056] Furthermore, as in the example shown in FIG. 3(A), when a plurality of fixing members 41a are installed at intervals, with the tire center as a reference, the tire circumferential direction angle α between adjacent fixing members is preferably 35° or less. According to such a configuration, in a region where the fixing member 41a is not arranged during tire rolling (when the vehicle is running), the frictional heat that may occur between the wire constituting the power receiving coil 40 and the rubber member in its vicinity can be reduced, and further heat generation of the entire tire can be suppressed. As a result, the fixing state between the power receiving coil 40 and the inner liner 12 can be maintained better, and the durability of the tire 10 can be further improved.

[0057] Note that, with the tire center as a reference, the tire circumferential direction angle between adjacent fixing members is more preferably 33° or less, and extremely preferably 30° or less.

[0058] (Additional Form 6) FIG. 4 is a cross-sectional view showing the wire 42 that constitutes the power receiving coil 40. As shown in the figure, the wire 42 includes an electric wire 42a and a coating layer 42b that coats the electric wire 42a. The electric wire 42a is composed of a conductor, and when used in a high-frequency AC circuit as in the present embodiment, a conductor with a particularly low resistance value is suitable. Further, when the condition of being used as a coil that further receives a magnetic field is added to the electric wire 42a, copper is optimal as a non-magnetic metal with a low magnetic permeability.

[0059] The covering layer 42b is made of an insulating material, and particularly when adding flexibility to achieve compatibility with processability, it is made of a resin material. In particular, in this embodiment, since it is desired that the covering layer 42b has a high thermal conductivity, it is preferably made of a resin material such as polyurethane, polyester, polyvinyl formal, polyethylene, nylon, polyvinyl chloride, polyamideimide, polyesterimide, polyimide, etc.

[0060] In the basic form 1 or the form in which at least one of the additional forms 2 to 5 is added to the basic form 1, the wire 42 constituting the power receiving coil 40 includes the electric wire 42a and the covering layer 42b covering the electric wire 42a. The thermal conductivity λ4 (W / m·k) of the covering layer 42b is preferably greater than the thermal conductivity λ1 (W / m·k) of the inner liner 12, and the thickness of the covering layer 42b is preferably 10 to 100 μm (additional form 6).

[0061] By making the thermal conductivity λ4 (W / m·k) of the covering layer 42b greater than the thermal conductivity λ1 (W / m·k) of the inner liner 12 and / or making the thickness of the covering layer 42b 100 μm or less, the dissipation of heat generated in the electric wire 42a to the inner liner 12 through the covering layer 42b can be promoted more efficiently. Thereby, the fixed state between the power receiving coil 40 and the inner liner 12 can be maintained better, and the durability of the tire 10 can be further improved. Note that it is more preferable that the thermal conductivity λ4 of the covering layer 42b is 0.15 (W / m·k) or more in terms of further promoting the above-mentioned heat dissipation, more preferably 0.16 (W / m·k) or more, and extremely preferably 0.17 (W / m·k) or more. Similarly, it is more preferable that the thickness of the covering layer 42b is 90 μm or less in terms of further promoting the above-mentioned heat dissipation, and extremely preferably 80 μm or less.

[0062] On the other hand, by setting the thickness of the coating layer 42b to 10 μm or more, the formability of the wire 42 can be ensured, the durability of the wire 42 itself can be guaranteed, and thus the durability of the tire 10 itself can be improved. This effect is more preferable by setting the thickness of the coating layer 42b to 12 μm or more, and extremely preferable by setting it to 15 μm or more.

[0063] <Wireless power supply system> [Basic form 7] FIG. 5 is a diagram showing a wireless power supply system 50 according to the present embodiment, a power transmission coil 52, and a tire 10 provided with a power reception coil 40 (on one side in the tire width direction with respect to the tire equatorial plane CP in a tire meridian cross-sectional view). In the figure, the tire portion on the side opposite to the ground contact surface is shown in a state where it is assembled to a rim and a normal internal pressure is applied, and a load of 80% of the normal load is applied (hereinafter, the same applies to the invention of the wireless power supply system). The power transmission coil 52 shown in the figure is a coil wound around the tire width direction. In particular, with respect to the portion extending in the tire diameter direction, it may extend only in the tire diameter direction, or may also extend in at least one of the tire circumferential direction and the tire width direction in addition to the tire diameter direction.

[0064] The power transmission coil 52 shown in the figure forms a resonance circuit with a capacitor and a coil, and is attached to the surface on the tire side of, for example, a knuckle or a hub carrier that is a component of a steering axle of a vehicle (not shown), or any component that constitutes a strut structure. The position where the power transmission coil 52 is installed will be described in detail below.

[0065] The power transmission coil 52 is preferably installed on a lower spring member of the vehicle. The lower spring member includes, for example, a knuckle, a brake caliper, and a damper case of a strut suspension. By providing the power transmission coil 52 on the lower spring member, even when the vehicle moves up and down due to unevenness of the road surface, the distance between the power transmission coil 52 and the power reception coil 40 provided on the tire 10 can be kept constant.

[0066] FIG. 6(A), (B) and FIG. 7 are diagrams showing positions where the power transmission coil 52 is installed in the wireless power feeding system 50 shown in FIG. 5. As shown in FIGS. 6(A) and 6(B), the power transmission coil 52 may be provided in the damper case 60 of the strut suspension. FIG. 6(A) shows an example in which the power transmission coil 52 is provided in the damper case 60 of the front wheel, and FIG. 6(B) shows an example in which the power transmission coil 52 is provided in the damper case 60 of the rear wheel. Thereby, even when the tire 10 moves up and down due to unevenness of the road surface, the power transmission coil 52 faces the power reception coil 40 in the tire width direction, avoids the belt and the bead core, and can transmit power in the tire width direction. Therefore, the wireless power feeding system 50 can improve the power feeding efficiency.

[0067] Also, the power transmission coil 52 may be provided on a member that moves with the tire 10 in conjunction with steering, such as a knuckle of a multi-link type suspension. FIG. 7 shows a front wheel of a multi-link type suspension, and the knuckle 70 rolls with the tire 10 with respect to the upper arm 72 in conjunction with steering. Thereby, even during steering, the distance between the power transmission coil 52 and the power reception coil 40 provided on the tire 10 can be kept constant. Therefore, the tire 10 can be stably power-fed during traveling.

[0068] Next, the power reception coil 40 shown in FIG. 5 has the same configuration as the power reception coil 40 shown in FIG. 1, and forms a resonance circuit with a capacitor and a coil. The tire 10 shown in FIG. 5 is a tire of the basic form 1 regarding the tire 10 described above and a tire to which at least any one of the additional forms 2 to 6 is added to the basic form 1, and its actions, functions, etc. are as described above.

[0069] Under such a premise, the wireless power feeding system 50 according to the present embodiment is wireless power feeding of a magnetic field resonance method using an alternating magnetic field. As shown in FIG. 5, power is supplied to the power transmission coil 52, and power is transmitted to the power reception coil 40 by the alternating magnetic field. According to such a wireless power feeding system 50, as described above, the power feeding efficiency can be improved.

[0070] Here, in order to drive sensors and associated electric circuits installed within the tire 10, it is preferable to transmit power at a frequency of 1 to 20 MHz with a power of 0.1 to 15 W.

[0071] Also, the shortest distance between the power transmission coil 52 and the power reception coil 40 (hereinafter sometimes referred to as the "transmission gap G") is preferably 10 mm or more and 80 mm or less. Here, the transmission gap G is a value measured in a state where the tire 10 is rim-mounted, normal internal pressure is applied, and the vehicle is attached and stopped on flat ground. Also, in FIG. 5, the transmission gap G refers to the shortest distance between the power transmission coil 52 and the power reception coil 40, that is, in FIG. 5, the distance between the innermost position in the tire width direction of the power transmission coil 52 and the outermost position in the tire width direction of the power reception coil 40.

[0072] By setting the transmission gap G to 10 mm or more, it is possible to suppress the power reception power fluctuation rate from becoming excessive due to the relative position fluctuation between the power transmission coil 52 and the power reception coil 40 shown in FIG. 5 in the power transmission direction, and the circuit configuration connected to the power reception coil 40 can be made simple, and thus stable power can be easily supplied to the electronic device. Here, the power reception power fluctuation depends on the relative position between the two coils 52 and 40 changing due to the tire 10 expanding slightly due to centrifugal force during the rolling of the tire 10. Specifically, the higher the tire rolling speed, the more the power reception coil 40 moves radially outward of the tire (upper side in FIG. 5) due to the tire 10 expanding in the tire diameter direction, while the position of the power transmission coil 52 remains unchanged, so the relative position between the two coils 52 and 40 changes.

[0073] On the other hand, by setting the transmission gap G to 80 mm or less, the strength of the magnetic field generated between the two coils 52 and 40 does not become excessively small, and power feeding by electromagnetic induction can be efficiently performed.

[0074] Note that the transmission gap G is more preferably 12 mm or more and 75 mm or less, and extremely preferably 15 mm or more and 70 mm or less.

[0075] By adopting the range of the transmission gap G, the power range, and the frequency band as described above, not only can the temperature rise of the power receiving coil 40 be suppressed, but also an increase in the number of turns of the coil or the like (and thus an increase in the coil weight) is not required, the rolling resistance of the tire is not increased, power feeding can be performed efficiently, and thus excellent transmission efficiency can be realized. In particular, according to the range of the transmission gap G described above, excellent power feeding efficiency can be obtained when power is transmitted using the tire structure in the magnetic field resonance type wireless power feeding in the above frequency band.

[0076] In the example shown in FIG. 5, the power transmission coil 52 is arranged to extend in the tire diameter direction, but the present embodiment is not limited to such an arrangement form. That is, if the above-described transmission gap G is within a predetermined range, the extending direction of the power transmission coil 52 may be inclined with respect to the tire diameter direction.

[0077] [Additional Form 8] FIG. 8 is a diagram showing that at least a part of the power receiving coil 40 is located within the power feeding region of the power transmission coil 52 for the wireless power feeding system 50 according to the present embodiment. (A) and (B) show examples in which the power feeding direction is the tire width direction, and (C) and (D) show examples in which the power feeding direction is inclined with respect to the tire width direction. In FIG. 8, (A) and (C) are examples in which the inner portion in the tire diameter direction of the power receiving coil 40 is included in the power feeding region of the power transmission coil 52, and (B) and (D) are examples in which the outer portion in the tire diameter direction of the power receiving coil 40 is included in the power feeding region of the power transmission coil 52.

[0078] In Basic Form 7, as shown in FIGS. 8(A) to 8(D), in a tire meridian cross-sectional view, it is preferable that at least a part of the power receiving coil 40 is located within the power feeding region extending in the winding axis direction of the power transmission coil 52 between both longitudinal ends of the power transmission coil 52 (Additional Form 8). Here, the positional relationship between the power receiving coil 40 and the power transmission coil 52 is measured in a state where the tire 10 is rim-mounted, a normal internal pressure is applied, and the vehicle is mounted and stopped on a flat ground.

[0079] In the wireless power supply system 50 according to the present embodiment, the power transmission coil 52 is attached to a knuckle or a hub carrier that is a component of the steering axle of the vehicle (located on the outer side in the tire width direction of the sidewall portion B), or to the tire-side surface of any component constituting the strut structure. Therefore, when considering the power supply efficiency in view of the shape of the tire, particularly the sidewall portion B of the tire 10, as shown in FIGS. 8(A) and 8(B), it is desirable that the direction of the magnetic field lines passing through the tire in the sidewall portion B, and thus the power supply direction Dp, be substantially the tire width direction.

[0080] In accordance with such findings, as shown in FIGS. 8(A) and 8(B), when the power supply direction Dp is substantially the tire width direction, power supply can be performed more efficiently, and thus excellent transmission efficiency can be achieved.

[0081] Also, in the examples shown in FIGS. 8(B) and 8(C), for each of the power transmission coil 52 and the power reception coil 40, the constituent surfaces (the planes perpendicular to the winding axes of the respective coils in FIGS. 8(B) and 8(C)) are parallel to each other. Therefore, compared with the examples shown in FIGS. 8(A) and 8(D), power supply can be performed more efficiently, and thus excellent transmission efficiency can be achieved.

[0082] Note that, as shown in FIGS. 8(A) and 8(D), the power transmission coil 52 and the power reception coil 40 do not necessarily have their constituent surfaces parallel to each other. The reason is that if the magnetic field generated by the power transmission coil 52 links with the power reception coil 40, an electromotive force is generated by electromagnetic induction, and there is no constraint on the relative orientation of the above-mentioned surfaces.

[0083] [Additional Form 9] FIG. 9 is a schematic diagram showing the installation position of the power transmission coil 52 for the wireless power supply system 50 according to the present embodiment.

[0084] In the basic form 7 or the form obtained by adding the additional form 8 to the basic form 7, as shown in FIG. 9, it is preferable that the power transmission coil 52 is installed within a range of 60° on both sides in the tire circumferential direction centered on an imaginary line extending vertically upward from the tire center O (additional form 9).

[0085] Normally, when the tire 10 rolls, at the grounding portion of the tire 10, the power receiving coil 40 deforms along with the deformation of the tire 10. On the other hand, at the portion away from the grounding portion of the tire 10 (the upper portion of the tire 10 in FIG. 9), almost no deformation of the power receiving coil 40 due to tire deformation is observed. Therefore, by installing the power transmission coil 52 arranged outside the tire 10 near the upper part of the tire away from the installation portion of the tire 10 (range R of 60° on both sides in the tire circumferential direction centered on an imaginary line extending vertically upward from the tire center O), when the tire rolls, the variation of the above-described transmission gap G can be suppressed, power supply can be performed more efficiently, and ultimately, more excellent transmission efficiency can be realized. Note that the example shown in FIG. 9 is an example of attaching the power transmission coil 52 to the wheel house 54, and the above-described range R is applied within the wheel house 54.

[0086] It is more preferable that the power transmission coil 52 is installed within a range of 55° on both sides in the tire circumferential direction centered on the above imaginary line, and it is extremely preferable that the power transmission coil 52 is installed within a range of 50° on both sides in the tire circumferential direction centered on the above imaginary line.

[0087] Also, the shape of the power transmission coil 52 is not particularly limited. However, when the power transmission coil 52 is installed in, for example, the wheel house, it is preferable to use a so-called spiral coil that can reduce the overall thickness.

[0088] <Other forms of the tire and the wireless power supply system> The above is the description of the tire and the wireless power supply system according to the present invention. Hereinafter, other matters regarding the tire and the wireless power supply system according to the present invention will be listed.

[0089] The carbon content of the inner liner 12, which is a component of the tire 10 shown in FIG. 1, is 45 to 75 parts by mass (parts by mass when the rubber is 100, the same hereinafter). The carbon content of the side tread is 25 to 65 parts by mass, the carbon content of the rim cushion is 60 to 90 parts by mass, the carbon content of the bead filler 16 is 40 to 80 parts by mass, the carbon content of the covering rubber of the carcass 18 is 35 to 70 parts by mass, and the carbon content of the run-flat liner is preferably 45 to 75 parts by mass. By adopting these respective compounding amounts, while realizing the desired physical properties (such as hardness and elastic modulus) and thermal conductivity in each rubber layer, the above-described excellent power feeding efficiency can be realized. Usually, it is most preferable to adjust the carbon content to achieve the thermal conductivity of the rubber because it is effective and it is easy to balance with the characteristics of the rubber required for the tire.

[0090] Regarding the wireless power feeding system 50 shown in FIG. 5, the power receiving coil 40 is preferably provided on the inner cavity surface of the sidewall portion B of the tire 10 so that the configuration surface faces in the tire width direction. As described above, as shown in FIGS. 8(A) and (B), when the power feeding direction by the power transmission coil 52 is in the substantially tire width direction, by providing the power receiving coil 40 so that its configuration surface faces in the tire width direction, the power transmission surface of the power transmission coil 52 and the configuration surface of the power receiving coil 40 become parallel. Thereby, power feeding can be performed more efficiently, and thus excellent transmission efficiency can be realized.

[0091] FIG. 10 is a view showing an arrangement mode of the power receiving coil 40 (a mode in which the power receiving coil 40 is not continuous in the tire circumferential direction, different from the case of FIG. 2). (A) to (F) are examples showing the power receiving coil 40 composed of 2 sets, 3 sets, 4 sets, 5 sets, 6 sets, and 8 sets of power receiving coil elements 40a respectively. (G) is an example in which a plurality of power receiving coil elements 40a are laminated in the tire radial direction, and (H) is an example in which a part of the plurality of power receiving coil elements 40a extends obliquely with respect to the tire radial direction.

[0092] As shown in FIGS. 10(A) to 10(H), the power receiving coil 40 may be formed from a plurality of power receiving coil elements 40a. On the inner surface of the tire cavity where the power receiving coil 40 is provided, during the rolling of the tire 10, the deformation and release of the tire 10 are repeated. When one power receiving coil 40 is provided around the entire circumference of the tire 10, this power receiving coil 40 has a portion that is deformed and distorted (near the ground contact portion of the tire 10) and a portion that is not deformed (the upper portion of the tire 10) during the rolling of the tire 10, and the power receiving coil 40 is likely to peel off from the inner surface of the tire cavity. Therefore, by dividing the tire circumference into a plurality of regions and arranging the power receiving coil elements 40a in each of the divided regions, it is possible to suppress the peeling of the power receiving coil 40 from the inner peripheral surface of the tire.

[0093] FIG. 11 is a tire meridian sectional view (however, half in the tire width direction) showing a power supply mode for supplying power from the power receiving coil 40 to an electronic device 46 attached to the inner surface of the tire cavity via a power line 44 in the tire 10 shown in FIG. 1.

[0094] According to what is shown in the figure, the power receiving coil 40 is connected to a capacitor (not shown) as a resonance circuit, and further, via a power line 44 attached to the inner surface of the tire cavity, it is possible to supply power to an electronic device 46 (sensor, signal processing circuit, communication corridor, etc.) attached to the inner surface of the tire cavity. The electronic device 46 has lower durability against deformation than the power receiving coil 40, and on the other hand, even if it is installed near the belt 20 which is a magnetic body, there is no problem due to the influence of the magnetic field. For this reason, the electronic device 46 is arranged on the inner surface of the tire cavity in the tire width direction region where the belt 20 having high rigidity is formed in the tire 10, the power receiving coil 40 is arranged on the inner surface of the tire cavity of the sidewall portion B where the power supply efficiency can be increased, and the two are wired-connected by the power line 44. Thereby, the power received by the power receiving coil 40 can be supplied to the electronic device 46 with little loss and high power supply efficiency, and at the same time, the durability of the electronic device 46 can be ensured. Further, by arranging all these components (power receiving coil 40, capacitor, power line 44, and electronic device 46) on the inner surface of the tire cavity, an increase in the manufacturing cost and manufacturing difficulty of the tire 10 is suppressed.

Example

[0095] Hereinafter, a comparison of the predetermined effects of the present application among the inventions defined in claims 1 to 6 of the present application (hereinafter referred to as "Invention Examples 1 to 6") will be described. Regarding the comparison between Invention Examples 1 to 6 and the conventional example (the example described in Patent Document 1), as described above, since the difference in the predetermined effects of the present application is obvious in terms of the configuration, it will not be particularly mentioned.

[0096] The tire size was set to 245 / 40R19 (specified by JATMA), and a wireless power supply system 50 (Invention Examples 1 to 6) shown in FIG. 5 was manufactured, and the power supply efficiency from the power transmission coil 52 to the power reception coil 40 was investigated. The conditions of the tire 10 included in each of the wireless power supply systems 50 of Invention Examples 1 to 6 are as shown in Table 1 below.

[0097]

Table 1

[0098] In Table 1, the thermal conductivities λ1 to λ4, r, S, θ1, θ2, etc. conform to the definitions described in this specification.

[0099] Regarding the wireless power supply systems of Invention Examples 1 to 6 manufactured in this way, the ratio (power transmission efficiency) of the power 2 received by the power reception coil (and the resonance circuit of the capacitor) to the power 1 transmitted from the power transmission coil 52 was measured, and these ratios were expressed as indices when Invention Example 1 was set to 100. The measurement of the ratio of the above-mentioned powers 1 and 2 was performed using a vector network analyzer. The results are also shown in Table 1. In this specification, it is considered that the ratio of the transmitted power (power transmission efficiency) is good at 95 or more.

[0100] According to Table 1, it can be seen that all the wireless power supply systems belonging to the technical scope of the present invention show excellent power transmission efficiency, and thus achieve excellent power supply efficiency.

Explanation of Reference Numerals

[0101] 10 Tire 12 Inner liner 14 Bead core 16 Bead filler 18 Carcass 18a Body part 18b Folded-back part 20 Belt 20a, 20b Belt layers 22 Belt cover 22a, 22b, 22c Belt cover layers 24 Rim cushion 26 Side tread 28 Wing tip 30 Cap tread 40 Power receiving coil 41, 41a, 41b Fixing members 42 Wire 44 Power line 46 Electronic device 50 Wireless power supply system 52 Power transmission coil 54 Wheel house 60 Tamper case 70 Knuckle 72 Upper arm A Bead part B Sidewall part C Shoulder part CW Tire radial direction region between both feet of the perpendicular line drawn from each of both end parts in the tire radial direction of the power receiving coil 40 to the inner liner 12 D Tread part Dp Power supply direction G Transmission gap O Tire center P1 Outermost position in the tire radial direction of the bead core 14 P2 Innermost position in the tire radial direction of the belt 20 R Range of 60° on both sides in the tire circumferential direction centered on an imaginary line extending vertically upward from the tire center O X Region surrounded by a dotted line Tire radial region from the outermost position in the tire radial direction of the WH bead core 14 to the innermost position in the tire radial direction of the belt 20

Claims

1. A tire having a bead core, a bead filler provided on the outer side in the tire radial direction of the bead core, a carcass folded around the bead core, and a belt provided on the outer side in the tire radial direction of the carcass, the tire comprising a power receiving coil on the inner cavity surface for receiving power supplied by an alternating magnetic field from outside the tire, in the tire radial direction region between both feet of a perpendicular line drawn from each of both ends in the tire radial direction of the power receiving coil to the inner liner formed on the inner peripheral side of the carcass in a tire meridian cross-sectional view, the thermal conductivity λ1 of the inner liner is 0.10 W / m·k or more. A tire characterized by this.

2. The tire according to claim 1, wherein in a tire meridian cross-sectional view, the power receiving coil is provided in a tire radial direction region from the outermost position in the tire radial direction of the bead core to the innermost position in the tire radial direction of the belt.

3. In the tire meridian cross section cut other than the end of the power receiving coil, the relationship between the total wire cross-sectional area S (m ２ ), the resistance value r (Ω) of the power receiving coil at the frequency of the AC power, and the thermal conductivity λ1 (W / m·k) of the inner liner is 1×10 ５ ≦ r / (λ1 × S) ≦ 8×10 ７ The tire according to claim 1 or 2, satisfying

4. In the tire radial direction region from the outermost position in the tire radial direction of the bead core to the innermost position in the tire radial direction of the belt, the thermal conductivity λ2 of the rubber layer other than the inner liner is 0.13 W / m·k or more. The tire according to claim 1 or 2.

5. Comprising a fixing member for fixing the power receiving coil to the inner cavity surface of the tire, The ratio [(Σθ2) / θ1] of the total sum Σθ2 of the tire circumferential installation angle θ2 of the fixing member to the tire circumferential arrangement angle θ1 of the power receiving coil 40 with respect to the tire center, and the thermal conductivity λ3 (W / m·k) of the fixing member, 0.14×[(Σθ2) / θ1] + 0.13 ≤ λ3 ≤ 0.38×[(Σθ2) / θ1] + 0.42 The tire according to claim 1 or 2, satisfying

6. The wire constituting the power receiving coil includes a wire and a coating layer covering the wire, the thermal conductivity λ4 (W / m·k) of the coating layer is greater than the thermal conductivity λ1 (W / m·k) of the inner liner, and the thickness of the coating layer is 10 to 100 μm. The tire according to claim 1 or 2.

7. A wireless power supply system that applies AC power to a power transmission coil that constitutes a resonance circuit with a capacitor and a coil, and transmits power to the power receiving coil that constitutes a resonance circuit with a capacitor and a coil, characterized by including the tire according to claim 1 or 2. A wireless power supply system.

8. The wireless power supply system according to claim 7, wherein at least a part of the power receiving coil is located in a power supply region that extends in the winding axis direction of the power transmission coil across both longitudinal ends of the power transmission coil in a tire meridian cross-sectional view.

9. The wireless power supply system according to claim 7 or 8, wherein the power transmission coil is installed within a range of 60° on both sides in the tire circumferential direction centered on an imaginary line extending vertically upward from the tire center.

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