Tire and wireless power supply system

Abstract

To provide a tire and a wireless power supply system using the tire, which enable suppressing reduction in power supply efficiency even on a wet road surface.SOLUTION: A tire 10 with a tread part D having a tread surface 34, a pair of bead parts A, and a pair of side wall parts B provided between the tread part D and the bead parts A, comprises a power receiving coil 40 for receiving electric power supplied from outside the tire 10 via an alternating magnetic field. In a tire meridian cross section view in a non-loaded state, the power receiving coil 40 is provided on an inner side in a tire radial direction from an outermost position OP where a first virtual line L1 forming an angle α of 15° with a tire equator plane CP and a tire side surface come into contact with each other.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Conventionally, a wireless power receiving system has been disclosed in which power is supplied between a power transmission coil buried near a road surface and a power receiving 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 receiving system of Patent Document 1, when water adheres to the tire, for example, in rainy weather, there is a concern that the water adhering to the tire blocks the magnetic field reaching the power receiving coil installed on the tire from the power transmission coil, resulting in a decrease in power supply efficiency.

[0005] An object of the present invention is to provide a tire capable of suppressing a decrease in power supply efficiency even on a wet road surface and a wireless power supply system using the tire.

Means for Solving the Problems

[0006] The tire of the present invention has a tread portion having a tread surface, a pair of bead portions, and a pair of sidewall portions provided between the tread portion and the bead portions, and is a tire including a power receiving coil that receives power supplied by an alternating magnetic field from the outside of the tire. In a tire meridian cross-sectional view in a no-load state, the power receiving coil is provided radially inward of the tire from the outermost position where a first imaginary line having an angle of 15° with the tire equatorial plane contacts the tire side surface.

Advantages of the Invention

[0007] The tire and the wireless power supply system according to the present invention can suppress a decrease in power supply efficiency even on a wet road surface.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0009] Hereinafter, the tire according to the present invention (basic form 1 and additional forms 2 to 8 shown below), and embodiments of the wireless power supply system according to the present invention (basic form 9 and additional forms 10 to 14 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 constituent elements 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 orthogonal 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 centered on the tire rotation 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 orthogonal to the tire rotation axis and passes through the center of the tire width of the tire.

[0011] Similarly, in the following description, the standard 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 standard 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 standard 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] The basic form of the tire according to the embodiment of the present invention will be described below. FIG. 1 is a meridian cross-sectional view of the tire according to this embodiment. In the figure, the tire portion on the ground contact side in a state where the standard internal pressure is applied with the rim mounted and in a non-loaded state is shown.

[0014] As shown in FIG. 1, the tire 10 according to this 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 tire inner cavity surface is provided. On the side opposite to the tire 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) is provided on the outer side in the tire radial direction.

[0015] 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 CP. 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.

[0016] 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 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 inverted 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.

[0017] 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 structure 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 perpendicularly 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.

[0018] The belt 20 is a reinforcing layer provided on the outer side in the tire diameter 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 shear 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 diameter 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.

[0019] The side tread 26 is arranged to connect the bead portion A and the tread portion D. The cap tread 30 is formed on the tread surface 34 which is the surface of the tread portion D over the entire area of the tire contact surface. Note that both the side tread 26 and the cap tread 30 can use rubber members conventionally used according to their respective required characteristics.

[0020] On the premise of the existence of the components 12 to 30 of the tire 10 shown above, the tire 10 according to the present embodiment includes a power receiving coil 40 (FIG. 1) that receives AC power transmitted from a power transmitting coil (not shown) installed outside the tire 10 on the inner side in the tire width direction of the tire inner cavity surface. 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 so as 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) (FIG. 1).

[0021] Power supply using the tire 10 according to the present embodiment converts direct current obtained from an in-vehicle battery (not shown) into alternating current once by an AC power supply device, and applies this alternating current to a power transmission coil (for example, attached to the surface on the tire side of a knuckle, which is a component of the steering axle of a vehicle). By doing so, an alternating magnetic field is generated around the power transmission coil. When this alternating magnetic field links with the power reception coil 40, an induced electromotive force is generated in the power reception coil 40 and power is supplied.

[0022] In the tire 10 according to the present embodiment, in a tire meridian cross-sectional view on the ground contact surface side, the power reception coil 40 is provided radially inward of the tire from the outermost position OP where the first virtual line L1, which forms an angle α of 15° with the tire equatorial plane CP, contacts the tire side surface.

[0023] The first virtual line L1 is inclined by a predetermined angle α toward the tire side surface with respect to the tire equatorial plane CP. When paying attention to the tire side surface on the right side with respect to the paper surface in FIG. 1, the first virtual line L1 is inclined to the right with respect to the tire equatorial plane. Similarly, when paying attention to the tire side surface on the left side with respect to the paper surface in FIG. 1, the first virtual line L1 is inclined to the left with respect to the tire equatorial plane. The angle α formed between the tire equatorial plane CP and the first virtual line L1 may be 10° or 5°.

[0024] The tire side surface is the surface of the tire 10 on the side opposite to the tire inner cavity surface and visible from the outside in the tire width direction. The outermost position OP is a position defined on the tire side surface in a state where the tire is assembled with a rim and a normal internal pressure is applied, and in a no-load state. The outermost position OP is the position on the tire side surface where the first virtual line L1 first touches when the first virtual line L1 is translated parallel from the outside to the inside in the tire width direction of the tire 10. In the case of a tire having a shape in which the tire side surface bulges outward in the tire width direction in the tire meridian section, the outermost position OP may be a position radially outside the tire where the length in the tire width direction is maximum. The power receiving coil 40 is provided radially inside the tire from the outermost position OP. Preferably, at least a part of the conductors included in the power receiving coil 40 is provided radially inside the tire from the outermost position OP, and more preferably, the entire power receiving coil 40 is provided radially inside the tire from the outermost position OP.

[0025] (Function, etc.) Water adheres to the tire 10 in contact with a wet road surface in the range from the contact surface to the tire side surface. However, the tire side surface radially inside the tire from the outermost position OP is relatively far from the wet road surface, so water hardly adheres. When the tire 10 rolls, while rotating in the tire circumferential direction, the water adhering to the tire side surface radially inside the tire from the outermost position OP moves radially outward of the tire by the centrifugal force accompanying the rotation of the tire 10 and can move at least radially outward of the tire from the outermost position OP. Therefore, water hardly adheres to the tire 10 radially inside from the outermost position OP, and during, for example, a 120° rotation in the tire circumferential direction after contacting the wet road surface, the adhering water moves radially outward of the tire. Thus, it is difficult for water to remain on the tire side surface radially inside from the outermost position OP during power reception. Since the power receiving coil 40 is provided radially inside the tire from the outermost position OP, it is hardly affected by water during power reception. Therefore, the tire 10 can suppress a decrease in power supply efficiency even in rainy weather.

[0026] Snow melting agents used particularly in cold regions are generally compounds such as sodium chloride and calcium chloride, which dissolve in water to form an electrolyte solution. Since the electrolyte solution can be regarded as a kind of dielectric, it may affect the magnetic field and further reduce the power supply efficiency.

[0027] On the other hand, even when the tire 10 travels on a wet surface containing a snow melting agent, the power supply efficiency can be suppressed because the power receiving coil 40 is provided on the portion where water hardly adheres, that is, from the outermost position OP to the inner side in the tire radial direction.

[0028] [Additional form 2] In the basic form 1, when the tire radial length from the bead toe 32 to the tread surface 34 is SH in the tire meridian cross-sectional view in the unloaded state, it is preferable that the power receiving coil 40 is provided outside the tire radial direction from the position 15% of the tire radial length SH from the bead toe 32 (Additional form 2), and more preferably outside the tire radial direction from the position 20% of the length SH.

[0029] The power receiving coil 40 is preferably provided outside the tire radial direction from the innermost position MP. The innermost position MP is the position at 15% of the tire radial length SH from the bead toe 32. The length SH is the tire radial length from the bead toe 32 to the tread surface 34 in the state of being assembled with the rim and applying the normal internal pressure and in the unloaded state. The innermost position MP is more preferably the position at 20% of the tire radial length SH from the bead toe 32.

[0030] Since the power receiving coil 40 is provided outside the tire radial direction from the innermost position MP, a sufficient gap is provided between the power receiving coil 40 and the rim 6 in the tire 10 assembled to the rim 6. Since the rim 6 is made of metal, it shields the magnetic field generated when an electric current flows through the power transmission coil. The rim 6 with water adhering thereto may be greatly affected by the magnetic field and further reduce the power supply efficiency.

[0031] When the tire 10 is assembled to the rim 6, the power receiving coil 40 is provided at a position sufficiently separated from the rim 6, so that the magnetic field is less affected by the rim 6, and thus a decrease in power feeding efficiency can be suppressed. It is preferable that at least a part of the conducting wires included in the power receiving coil 40 is provided radially outside the tire diameter from the innermost position MP, and it is more preferable that the entire power receiving coil 40 is provided radially outside the tire diameter from the innermost position MP.

[0032] [Additional Form 3] In the basic form 1 or the form obtained by adding the additional form 2 to the basic form 1, it is preferable that the power receiving coil 40 is provided on the inner surface of the tire opposite to the outer surface of the tire having the tread surface 34 (Additional Form 3).

[0033] The outer surface of the tire has the tread surface 34 and is the surface of the tire 10 that can be visually recognized from the outside when the tire 10 is assembled to the rim. The inner surface of the tire (also referred to as the "inner cavity surface of the tire") is the surface on the opposite side of the outer surface of the tire and is the surface of the tire 10 that cannot be visually recognized from the outside when the tire 10 is assembled to the rim. The power receiving coil 40 is provided on the inner surface of the tire. By providing the power receiving coil 40 on the inner surface of the tire, it is possible to prevent the power receiving coil 40 from coming into contact with rainwater.

[0034] Also, when the power receiving coil 40 is attached to the rim, it is necessary to assemble the rim to the tire without damaging the power receiving coil, and as a result, the workability when assembling the rim may deteriorate.

[0035] By providing the power receiving coil 40 on the inner surface of the tire 10, it is possible to prevent the power receiving coil 40 from being damaged when the rim 6 is assembled to the tire 10.

[0036] [Additional Form 4] In the basic form 1 or the form in which additional forms 2 or 3 are added to the basic form 1, in the power receiving vicinity region AR between the intersection point P1 of the tire outer surface and the second virtual line L2 that is inclined 30° inward in the tire radial direction from the inner end in the tire radial direction of the power receiving coil 40 toward the outer side in the tire width direction, and the intersection point P2 of the tire outer surface and the third virtual line L3 that is inclined 30° outward in the tire radial direction from the outer end in the tire radial direction of the power receiving coil 40 toward the outer side in the tire width direction, it is preferable that the height of the unevenness of the tire outer surface is 1 mm or less in 50% or more of the area of the power receiving vicinity region AR (additional form 4).

[0037] The vicinity of the power receiving coil 40 provided in the tire 10 is referred to as the power receiving vicinity region AR (FIG. 1). The power receiving vicinity region AR is a region defined by the second virtual line L2 and the third virtual line L3 in the tire meridian cross section on the ground contact side. The second virtual line L2 is a line that is inclined 30° inward in the tire radial direction from the upper end in the tire radial direction in the tire meridian cross section on the ground contact side of the power receiving coil 40 provided in the tire 10 toward the outer side in the tire width direction. The third virtual line L3 is a line that is inclined 30° outward in the tire radial direction from the lower end in the tire radial direction in the tire meridian cross section on the ground contact side of the power receiving coil 40 provided in the tire 10 toward the outer side in the tire width direction. The power receiving vicinity region AR is a region of the tire outer surface sandwiched between the intersection point P1 of the second virtual line L2 and the tire outer surface and the intersection point P2 of the third virtual line L3 and the tire outer surface. The power receiving vicinity region AR is an annular region centered on the tire rotation axis.

[0038] Tire 10 may have, for example, embossing, decoration, serration, and decorative patterns as irregularities on the tire sidewall. The height of the irregularities formed on the surface (tire sidewall) in the vicinity of power reception region AR of tire 10 is 1 mm or less. The irregularities are the shape of a surface having mountains and valleys. The height of the irregularities refers to the length in the rubber thickness direction between the position where the mountain height is maximum and the position where the valley depth is maximum. Tire 10 may have irregularities, that is, embossing, decoration, serration, and decorative patterns, in a region of 50% or more of the area of the power reception vicinity region AR in the power reception vicinity region AR, and the height of the irregularities in the region having the irregularities is 1 mm or less. Since the height of the above-mentioned irregularities of tire 10 is 1 mm or less, water is less likely to accumulate in the irregularity portions. Therefore, water retention in the irregularity portions on the tire sidewall of tire 10 is suppressed.

[0039] It is preferable that the irregularities are 1 mm or less in 70% or more of the area of the power reception vicinity region AR of tire 10. It is also preferable that the irregularities are 1 mm or less on the tire sidewall other than the power reception vicinity region AR of tire 10.

[0040] [Additional Form 5] In the basic form 1 or the form obtained by adding the additional form 4 to the basic form 1, it is preferable that a coating layer made of a component other than rubber is provided on the outer tire surface of the power reception vicinity region AR (Additional Form 5).

[0041] Since the rubber component constituting tire 10 has high water repellency, water adheres as water droplets on the outer tire surface and tends to remain as water droplets on the outer tire surface. By providing a coating layer on the outer tire surface of the power reception vicinity region AR, the contact angle of the outer tire surface becomes smaller. From the viewpoint of achieving both followability to tire deformation and water repellency, for example, a urethane resin or a silicone resin can be used for the coating layer. As a result, the water droplets that come into contact with the outer tire surface flow while spreading in a film shape, so it is difficult for water droplets to remain on the outer tire surface, and the influence on the magnetic field can be made smaller.

[0042] [Additional Form 6] In the basic form 1 or the form in which any one of the additional forms 2 to 5 is added to the basic form 1, the groove area ratio DR in the tread portion D is 12% or more and 38% or less, and the groove area ratio MR in the region M on the inner side of the vehicle mounting from the tire equatorial plane CP is larger than the groove area ratio ER in the region E on the outer side of the vehicle mounting from the tire equatorial plane CP, and the difference is 3.5 percentage points or more (additional form 6), which is preferable.

[0043] The tire 10 has a pattern formed by a plurality of grooves in the tread portion D. The tire 10 includes, for example, as shown in FIG. 2, three circumferential main grooves 36, one circumferential fine groove 37, and a plurality of lug grooves 38. The tread portion D shown in FIG. 2 only shows an example of the tire 10, and the tire 10 of the present embodiment is not limited to the tread pattern of FIG. 2.

[0044] The groove area ratio is the ratio of the sum of the groove areas arranged in a predetermined region of the tread portion D to the sum of the groove area, the land area, and the groove area within the region (= contact area). The groove area ratio is defined by groove area / contact area. The groove area refers to the opening area of the groove on the contact surface. The groove refers to the circumferential main groove 36, the circumferential fine groove 37, and the lug groove 38 of the tread portion D and does not include the sipe. The land area refers to the contact area between the tire 10 and the contact surface. The groove area and the contact area are measured on the contact surface between the tire and the flat plate when the tire 10 is mounted on a specified rim, a specified internal pressure is applied, and the tire is placed perpendicular to the flat plate in a stationary state and a load corresponding to a specified load (80% of the maximum load capacity) is applied.

[0045] The tire 10 has a groove area ratio DR in the contact surface area of 12% or more and 38% or less, and the groove area ratio MR in the area M on the inner side of the vehicle mounting from the tire equatorial plane CP is larger than the groove area ratio ER in the area E on the outer side of the vehicle mounting from the tire equatorial plane CP, and the difference (MR - ER (% points)) is 3.5% points or more. The area M is the area from the tire equatorial plane CP to the inner ground contact end of the vehicle mounting. The area E is the area from the tire equatorial plane CP to the outer ground contact end of the vehicle mounting. The ground contact end is the outer edge on the outer side in the tire width direction on the contact surface in a state where the tire is mounted on the rim and the normal internal pressure is applied and a load of 80% of the normal load is applied. A larger groove area ratio can suppress water splash during driving. By having the groove area ratio DR of the entire tread portion D within the above range, the wear performance and wet performance of the vehicle can be maintained. Also, since the groove area MR in the area M on the inner side of the vehicle mounting from the tire equatorial plane CP of the tire 10 is larger, water splash to the inner side of the vehicle mounting can be suppressed. Therefore, when the power receiving coil 40 is installed on the inner side of the vehicle mounting of the tire 10, water adhesion to the side surface of the tire on the inner side of the vehicle mounting can be suppressed, and thus a decrease in power supply efficiency can be suppressed. It is more preferable that the groove area ratio DR is 15% or more and 35% or less, and the difference between the groove area ratio MR and the groove area ratio ER is 4% points or more, and it is preferable that the groove area ratio DR is 17% or more and 33% or less, and the difference between the groove area ratio MR and the groove area ratio ER is 4.5% points or more.

[0046] [Additional Form 7] In the basic form 1 or the form obtained by adding the additional form 6 to the basic form 1, it is preferable that the length Aw between the pair of outermost positions OP and the contact width Tw in a state where a load of 80% of the maximum load is applied satisfy the following formula (1) (Additional Form 7).

[0047] Tw≦0.88×Aw···(1)

[0048] The outermost position OP is, as described above, a position defined on the tire sidewall. The outermost position OP is the position on the tire sidewall where the first virtual line L1 first touches when the first virtual line L1 is translated parallelly from the outside to the inside of the tire 10 in the tire width direction. The length Aw is the distance in the tire width direction between the outermost positions OP defined on the tire sidewalls on both sides of the tire 10, respectively. The ground contact width Tw refers to the maximum dimension in the tire width direction of the region in contact with the road surface in a state where it is assembled to a regular rim, a normal internal pressure is applied, and a load of 80% of the normal load is applied. Note that the outermost position OP is a position defined on the tire sidewall in a state where it is assembled to a rim and a normal internal pressure is applied and in a no-load state.

[0049] When the length Aw between the outermost positions OP and the ground contact width Tw satisfy the above formula (1), the water splash generated between the wet road surface and the ground contact surface of the tire 10 is less likely to adhere to the tire sidewall radially inside the tire than the outermost position OP. That is, in the above formula (1), the smaller the ground contact width Tw is compared to the length Aw between the outermost positions OP, the more the tire 10 has a shape in which the outermost position OP bulges outward in the tire width direction. Therefore, the water splash generated between the wet road surface and the ground contact surface of the tire 10 is less likely to adhere to the tire sidewall radially inside the tire beyond the outermost position OP.

[0050] [Additional Form 8] In the basic form 1 or the form obtained by adding any one of the additional forms 2 to 7 to the basic form 1, it is preferable to be in a state of being assembled to a regular rim (Additional Form 8).

[0051] The tire 10 is used by being assembled to the rim 6. In this case, as shown in FIG. 3, the power receiving coil 40 may be provided on the rim 6. For example, as shown in FIG. 3, the power receiving coil 40 may be provided at a position 40A on the inner surface of the rim facing the inner surface of the tire cavity. The power receiving coil 40 provided at the position 40A has a conductor wound in a cylindrical shape around the tire rotation axis so as to align the conductors in the tire width direction. In another example, the power receiving coil 40 may be provided at a position 40B on the inner surface of the rim so as to align the conductors in the tire diameter direction. In this case, the power receiving coil 40 has a conductor wound in a spiral shape around the tire rotation axis. In yet another example, the power receiving coil 40 may be provided at a position 40C on the outer surface of the rim on the side opposite to the inner surface of the rim facing the inner surface of the tire cavity. The power receiving coil 40 provided at the position 40C has a conductor wound in a cylindrical shape around the tire rotation axis so as to align the conductors in the tire width direction.

[0052] <Wireless power supply system> [Basic form 9] FIG. 4 is a view 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 receiving coil 40 (a portion on one side in the tire width direction with respect to the tire equatorial plane CP in a non-ground contact side tire meridian cross-sectional view). Note that FIG. 4 shows a tire portion on the side opposite to the ground contact surface in a state where the tire is assembled to the rim and 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).

[0053] The power transmission coil 52 shown in the figure constitutes a resonance circuit by a capacitor and a coil, and is attached to the surface on the tire side of a knuckle or a hub carrier which is a component of a steering axle of a vehicle (not shown), for example, or any component constituting a strut structure.

[0054] Next, the power receiving coil 40 shown in FIG. 4 has the same configuration as the power receiving coil shown in FIG. 1, and forms a resonance circuit with a capacitor and a coil. Note that the tire 10 shown in FIG. 4 is a tire of basic form 1 related to the above-described tire 10 and a tire to which at least any one of additional forms 2 to 8 is added, and its actions, functions, etc. are as described above.

[0055] Under such a premise, the wireless power supply system 50 according to the present embodiment is a magnetic field resonance type wireless power supply using an alternating magnetic field. As shown in FIG. 4, power is supplied to the power transmission coil 52, and power is transmitted to the power receiving coil 40 by the alternating magnetic field. According to such a wireless power supply system 50, as described above, the power supply efficiency can be improved.

[0056] Here, in order to drive sensors and associated electric circuits installed in the tire 10, it is preferable to transmit power of 0.1 to 15 W at a frequency of 1 to 20 MHz. More preferably, AC power with a frequency of 6.78 to 13.56 MHz is supplied to the power transmission coil 52.

[0057] Also, the shortest distance between the power transmission coil 52 and the power receiving coil 40 (hereinafter, may be referred to as "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. The transmission gap G is the shortest distance between the power transmission coil 52 and the power receiving coil 40, that is, in FIG. 4, 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 receiving coil 40.

[0058] By setting the transmission gap G to 10 mm or more, it is possible to suppress the excessive rate of change in received power caused by fluctuations in the relative position between the power transmission coil 52 and the power reception coil 40 shown in FIG. 4 in the direction of power transmission. 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 variation in received power depends on the fact that during the rolling of the tire 10, the tire 10 expands slightly due to centrifugal force, causing the relative position between the two coils 52 and 40 to vary. Specifically, the higher the tire rolling speed, the more the tire 10 expands in the tire radial direction, causing the power reception coil 40 to move outward in the tire radial direction (the upper side in FIG. 4), while the position of the power transmission coil 52 remains unchanged, resulting in a change in the relative position between the two coils 52 and 40.

[0059] 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 the alternating magnetic field can be efficiently performed.

[0060] 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.

[0061] By adopting the above range of the transmission gap G, power range, and frequency band, not only can the temperature rise of the power reception coil 40 be suppressed, but also an increase in the number of turns of the coil, etc. (and thus an increase in coil weight) is not required, the rolling resistance of the tire is not increased, power feeding can be efficiently performed, and thus excellent power feeding efficiency can be realized. In particular, according to the above-mentioned range of the transmission gap G, excellent power feeding efficiency can be obtained when power is transmitted using the tire structure in magnetic field resonance wireless power feeding in the above frequency band.

[0062] In the example shown in FIG. 4, the power transmission coil 52 is arranged to extend in the tire diameter direction. However, 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.

[0063] [Additional Form 10] In the basic form 9, it is preferable that the power receiving coil 40 is arranged inside the vehicle mounting side (Additional Form 10).

[0064] The inner side of the tire 10 where it is mounted on the vehicle faces the wheel house when the tire 10 is mounted on the vehicle. By arranging the power receiving coil 40 on the inner side of the vehicle mounting side, the effect of being less affected by water can be obtained. That is, the inner side of the tire 10 where it is mounted on the vehicle is less likely to be touched by rain or water splashed by an oncoming vehicle during rainy days. Also, when the mounting direction of the tire 10 with respect to the vehicle is specified, the outer surface of the tire on the outer side of the vehicle mounting where it is easily visible to people is often provided with unevenness, such as stamping, commendation, serration, and decorative patterns. Since such unevenness makes it easy for the attached water to stay, the influence on the power receiving coil 40 is large. Therefore, the outer surface of the tire on the inner side of the tire 10 where it is mounted on the vehicle is less likely to be touched by water and has fewer unevennesses compared to the outer surface of the tire on the outer side of the vehicle mounting, so that the retention of the attached water is suppressed. Furthermore, providing the power receiving coil 40 on the inner side of the vehicle mounting provides a higher degree of freedom in the position where the power transmission coil 52 is attached. From the above, it is preferable that the power receiving coil 40 is arranged on the inner side of the vehicle mounting. When the power receiving coil 40 is provided on the inner side of the vehicle mounting, by installing the power transmission coil 52 in the wheel house, the transmission gap G can be easily made within the above range.

[0065] [Additional Form 11] FIG. 5 is a diagram showing that the power receiving coil 40 is located within the power supply area of the power transmission coil 52 in the wireless power supply system 50 according to the present embodiment. (A) and (B) show examples in which the power supply direction is the tire width direction, and (C) and (D) show examples in which the power supply direction is the downward inclined direction with respect to the tire width direction. In FIG. 5, (A) and (C) are examples in which the radially inner portion of the tire diameter of the power receiving coil 40 is included in the power supply area of the power transmission coil 52, and (B) and (D) are examples in which the radially outer portion of the tire diameter of the power receiving coil 40 is included in the power supply area of the power transmission coil 52.

[0066] In the form in which the additional form 10 is added to the basic form 9, as shown in FIGS. 5(A) to 5(D), in the tire meridian cross-sectional view, at least a part of the power receiving coil 40 is located within the power supply area extending in the winding axis direction of the power transmission coil 52 between both longitudinal ends of the power transmission coil 52 (additional form 11).

[0067] 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 attached and stopped on a flat ground. More preferably, the power transmission coil radial direction area defined by the length between both tire diameter direction ends of the power transmission coil 52 is arranged so as to overlap at least a part of the power receiving coil radial direction area defined by the length between both tire diameter direction ends of the power receiving coil 40. By such an arrangement, higher power supply efficiency can be realized.

[0068] The power transmission coil 52 shown in FIGS. 5(A) and 5(B) is disposed at a position outside in the tire width direction and corresponding to a partial region in the tire circumferential direction. The power reception coil 40 provided on the inner cavity surface of the tire extends over the entire circumference in the tire circumferential direction. At least a part of the power reception coil 40 is provided in a region obtained by projecting the power transmission coil radial direction region onto the inner cavity surface of the tire, that is, a region between points where virtual lines parallel to the winding axis of the power transmission coil 52 extending from the outer end and the inner end of the power transmission coil 52 in the tire radial direction intersect the inner cavity surface of the tire. The power reception coil 40 provided on the inner cavity surface of the tire is preferably such that a part of the power reception coil 40 in the tire radial direction is included in the region obtained by projecting the above power transmission coil radial direction region, and more preferably, the entire part of the power reception coil 40 in the tire radial direction is included in the region obtained by projecting the above power transmission coil radial direction region.

[0069] 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 (located outside the tire width direction of the sidewall portion B) which is a component of the steering axle of the vehicle, or the tire-side surface of any component constituting the strut structure. Therefore, 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. 5(A) and 5(B), it is desirable that the direction of the magnetic field lines penetrating the tire in the sidewall portion B, and thus the power supply direction Dp, be substantially in the tire width direction.

[0070] In accordance with such findings, as shown in FIGS. 5(A) and 5(B), when the power supply direction Dp is substantially in the tire width direction, power supply can be performed more efficiently, and thus excellent power supply efficiency can be realized.

[0071] Further, in the example shown in FIGS. 5(B) and 5(C), for each of the power transmission coil 52 and the power reception coil 40, the constituent surfaces (planes having the winding axes of the respective coils as normal lines in FIGS. 5(B) and 5(C)) are parallel to each other. Therefore, compared with the example shown in FIGS. 5(A) and 5(D), power supply can be performed more efficiently, and thus excellent transmission efficiency can be realized.

[0072] Note that, as shown in FIGS. 5(A) and 5(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 the alternating magnetic field, and there is no constraint on the relative orientation between the above-mentioned surfaces.

[0073] [Additional Form 12] In the form obtained by adding Additional Form 10 or Additional Form 11 to the basic form 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 (Additional Form 12).

[0074] Normally, when the tire 10B rolls, at the grounding portion of the tire 10, the power reception coil 40 deforms along with the deformation, while at a portion away from the grounding portion of the tire 10 (the upper portion of the tire 10 in FIG. 6), almost no deformation of the power reception coil 40 due to the tire deformation is observed. For this reason, 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 (the tire circumferential direction range R of 60° on both sides of the imaginary line extending vertically upward from the tire center O), during tire rolling, the variation of the above-mentioned transmission gap G can be suppressed, power supply can be performed more efficiently, and thus more excellent power supply efficiency can be realized. Note that the example shown in FIG. 6 is an example of attaching the power transmission coil 52 to the wheel house 54, and the above-mentioned tire circumferential direction range R is applied within the wheel house 54.

[0075] It is more preferable that the power transmission coil 52 is installed within a tire circumferential direction range of 55° on both sides of an imaginary line extending vertically upward from the tire center O, and it is extremely preferable that the power transmission coil 52 is installed within a tire circumferential direction range of 50° on both sides of the imaginary line.

[0076] Also, the shape of the power transmission coil 52 is not particularly limited, but when the power transmission coil 52 is installed in the wheel house, for example, it is preferable to use a so-called spiral coil that can reduce the overall thickness.

[0077] [Additional form 13] In a form in which any one of additional forms 10 to 12 is added to the basic form 9, it is preferable that the power transmission side surface 60 facing the power reception coil 40 of the power transmission coil unit 56 including the power transmission coil 52 has a contact angle of 50° or more (additional form 13).

[0078] As shown in FIG. 7, the power transmission coil unit 56 has a power transmission coil 52 and a case 58 that houses the power transmission coil 52. The case 58 is formed of a non-magnetic material. The case 58 is fixed to a vehicle, for example, a wheel house 54, with the power transmission coil 52 housed therein. The case 58 has a power transmission side surface 60 facing the power reception coil 40 provided on the tire 10. The power transmission side surface 60 has a contact angle of 50° or more.

[0079] Since the power transmission coil 52 is fixed to the vehicle, centrifugal force does not act on it like the tire 10. For this reason, since the power transmission side surface 60 of the case 58 housing the power transmission coil 52 has water repellency, it is easy to drop water from the power transmission side surface 60.

[0080] The case where the power transmission coil unit 56 includes the case 58 has been described, but the present invention is not limited to this. The power transmission coil unit 56 may have a power transmission coil 52 and a resin film that coats the power transmission coil 52. In this case, the power transmission side surface refers to the surface of the resin film on the side facing the power reception coil 40. Further, the power transmission coil unit 56 may be composed of only the power transmission coil 52. In this case, the power transmission side surface refers to the surface of the power transmission coil 52 on the side facing the power reception coil 40.

[0081] [Additional form 14] In the form in which any one of the additional forms 10 to 13 is added to the basic form 9, the power transmission side surface 60 of the power transmission coil unit 56 including the power transmission coil 52 facing the power reception coil 40 has an angle β formed with the tire radial direction as viewed from the tire meridian cross section within a range of 70° toward the side close to the tire 10 and 30° toward the side away from the tire 10 around the inner end 57 in the tire radial direction of the power transmission coil unit 56 (Additional form 14), which is preferable.

[0082] As described above, the power transmission coil unit 56 may have the power transmission coil 52 and a case 58 that encloses the power transmission coil 52. As shown in FIG. 7, the case 58 has a power transmission side surface 60, and the angle formed between the power transmission side surface 60 centered on the lower end in the tire radial direction of the power transmission coil unit 56 and the tire radial direction is β. The angle β is within a range of 70° toward the side close to the tire 10 and 30° toward the side away from the tire with respect to the tire radial direction.

[0083] Since the angle β formed between the power transmission side surface 60 of the power transmission coil unit 56 facing the power reception coil 40 and the tire circumferential direction as viewed from the tire meridian cross section is within the above range, it is difficult to get wet with water, and it is easy to install the power transmission coil unit 56 at an angle and position where power can be efficiently supplied to the power reception coil 40.

[0084] <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.

[0085] The carbon content of the inner liner 12, which is a component of the tire 10, is 45 to 75 parts by mass (parts by mass when the rubber is 100, the same applies hereinafter), the carbon content of the side tread is 25 to 65 parts by mass, the carbon content of the bead filler 16 is 40 to 80 parts by mass, and the carbon content of the covering rubber of the carcass 18 is preferably 35 to 70 parts by mass. By adopting these respective compounding amounts, desired rubber physical properties can be realized in each rubber layer. Usually, the carbon compounded in the rubber has an ultraviolet absorption ability in addition to the reinforcing effect, and has an effect of suppressing the deterioration of the rubber. Therefore, even when the compounding amounts of the anti-aging agent and wax are reduced, while maintaining the contact angle of the tire surface within the desired range, it is possible to achieve compatibility with the necessary rubber properties of the tire 10.

[0086] Regarding the wireless power supply system 50 shown in FIG. 4, the power receiving coil 40 is preferably provided in the tire inner cavity of the sidewall portion B of the tire 10B so that the configuration surface faces in the tire width direction. As described above, as shown in FIGS. 5(A) and (B), when the power supply 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 supply can be performed more efficiently, and thus excellent power supply efficiency can be realized.

[0087] FIG. 8 is a diagram showing the arrangement mode of the power receiving coil 40. (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.

[0088] As shown in FIGS. 8(A) to 8(H), the power receiving coil 40 may be formed of 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.

[0089] FIG. 9 is a tire meridian cross-sectional view (however, half in the tire width direction) showing a power supply mode for supplying power from the power receiving coil 40 to the electronic device 46 attached to the inner surface of the tire cavity via the power line 44 in the tire 10.

[0090] According to what is shown in FIG. 9, the power receiving coil 40 is connected to a capacitor (not shown) as a resonant circuit, and further supplies power to an electronic device 46 (sensor, signal processing circuit, communication circuit, etc.) attached to the inner surface of the tire cavity via the power line 44 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, no trouble occurs 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 in the sidewall portion B where the power supply efficiency can be increased, and these 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 less 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

[0091] Hereinafter, a comparison of the predetermined effects of the present application among the inventions defined in the claims of the present application (hereinafter referred to as "Invention Examples 1 to 5") will be described.

[0092] A tire having a tire size of 245 / 40R19 (defined by JATMA) was manufactured, and the tire shown in FIG. 1 was produced. The conditions of the tires 10 in Examples 1 to 10 are as shown in Table 1 below.

[0093] [Table 1]

[0094] The "position in the tire radial direction of the power receiving coil with respect to the outermost position", "position in the tire radial direction of the power receiving coil with respect to the position at 15% of the length SH from the bead toe", "coating layer", "groove area ratio in the region inside the vehicle mounting side from the tire equatorial plane", and "Tw / Aw" in Table 1 conform to the definitions described in this specification.

[0095] The tires of Invention Examples 1 to 5 manufactured in this way were mounted on a test vehicle (a passenger car with a displacement of 3000 cc) equipped with a power transmission coil, and the ratio of the power 2 received by the power receiving coil (and the resonance circuit of the capacitor) to the power 1 transmitted from the power transmission coil when traveling at a speed of 60 km / h on a wet road test course sprinkled to a water depth of 2 mm was measured. These ratios were expressed as indices when Invention Example 1 was set to 100. The measurement of the ratio of powers 1 and 2 was performed using a power meter. The results are also shown in Table 1.

[0096] According to Table 1, it can be seen that all of the wireless power supply systems belonging to the technical scope of the present invention exhibit excellent power transmission efficiency, and thus realize excellent power supply efficiency. [Explanation of Signs]

[0097] 6 Rim 8 Rim Flange 10 Tire 12 Inner Liner 14 Bead Core 16 Bead Filler 18 Carcass 18a Body Part 18b Folded-back Part 20 Belt 26 Side Tread 30 Cap Tread 32 Bead Tow 34 Tread Surface 36 Circumferential Main Groove 37 Circumferential Fine Groove 38 Lug Groove 40 Power Receiving Coil 40A Power Receiving Coil 40B Power Receiving Coil 40C Power Receiving Coil 40D Power Receiving Coil 40a Power Receiving Coil Element 44 Power Line 46 Electronic Device 50 Power Supply System 52 Power Transmission Coil 54 Wheel House 56 Power Transmission Coil Unit 58 Case 60 Power Transmission Side Surface A Bead Part B Side Wall Part C Shoulder Part D Tread Part CP Tire Equator Plane Dp Power Supply Direction α Angle β Angle L1 First Virtual Line L2 Second Virtual Line L3 Third Virtual Line OP Outermost Position MP Innermost Position P1 Intersection Point P2 Intersection Point AR Power Receiving Nearby Region M Region Inside Vehicle Mounting E Region Outside Vehicle Mounting

Claims

1. A tire having a tread portion with a tread surface, a pair of bead portions, and a pair of sidewall portions provided between the tread portion and the bead portions, the tire comprising a power receiving coil for receiving power supplied by an alternating magnetic field from outside the tire, The tire, wherein the power receiving coil is provided radially inward of the outermost position where a first virtual line, which forms an angle of 15° with the tire equatorial plane in a meridional cross-section view of the tire in an unloaded state, contacts the tire side surface.

2. The tire according to claim 1, wherein the power receiving coil is provided radially outward of a position that is 15% of the radial length SH of the tire from the bead toe to the tread surface in a meridional cross-section view of the tire in an unloaded state.

3. The tire according to claim 1, wherein the power receiving coil is provided on the inner surface of the tire opposite to the outer surface of the tire having the tread surface.

4. The intersection of the tire outer surface and a second virtual line inclined 30° radially inward from the inner end of the power receiving coil in the tire radial direction toward the outer side in the tire width direction, The tire according to claim 1, wherein in the power receiving vicinity region between the intersection of the tire outer surface and a third virtual line inclined 30° radially outward from the outer end of the power receiving coil in the tire radial direction toward the outer side in the tire width direction, the height of the unevenness of the tire outer surface is 1 mm or less in 50% or more of the area of the power receiving vicinity region.

5. The tire according to claim 4, wherein a coating layer made of a component other than rubber is provided on the tire outer surface in the power receiving vicinity region.

6. The tire according to claim 1, wherein the groove area ratio in the tread portion is 12% or more and 38% or less, and the groove area ratio in the region inside the vehicle mounting side from the tire equatorial plane is larger than the groove area ratio in the region outside the vehicle mounting side from the tire equatorial plane, and the difference is 3.5% points or more.

7. The tire according to claim 1, wherein the length Aw between the pair of outermost positions and the grounding width Tw in a state where a load of 80% of the maximum load is applied satisfy the following formula (1). Tw ≦ 0.88 × Aw... (1)

8. The tire according to any one of claims 1 to 6 when assembled to a standard rim.

9. A wireless power supply system that supplies AC power to a power transmission coil that forms a resonance circuit with a capacitor and a coil, and transmits power to the power receiving coil that forms a resonance circuit with the capacitor and the coil, the wireless power supply system including the tire according to claim 1 or 2.

10. The wireless power supply system according to claim 9, wherein the power receiving coil is disposed inside the vehicle mounting.

11. The wireless power supply system according to claim 10, wherein at least a part of the power receiving coil is located within 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.

12. The wireless power supply system according to claim 10, wherein the power transmission coil is installed in a range of 60° on both sides in the tire circumferential direction centered on an imaginary line extending vertically upward from the tire center.

13. The wireless power supply system according to claim 10, wherein the power transmission side surface of the power transmission coil unit including the power transmission coil that faces the power receiving coil has a contact angle of 50° or more.

14. The wireless power supply system according to claim 10, wherein the angle formed by the power transmission side surface of the power transmission coil unit including the power transmission coil and the tire radial direction, as viewed from the tire meridian cross-section, is in a range of 70° toward the side close to the tire and 30° toward the side away from the tire, with the inner end in the tire radial direction of the power transmission coil unit as the center.

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