Tire and wheel assembly

Abstract

To provide a tire wheel assembly that can suppress deterioration in power receiving efficiency.SOLUTION: A tire wheel assembly includes a tire and a wheel with a rim part. The tire is fitted to the rim part. The tire wheel assembly includes a power receiving coil. The tire includes a belt including one or more belt layers. A minimum width belt layer has a width W1 in a tire width direction which is smaller than a ground-contact width W2, or the minimum width belt layer has the width W1 in the tire width direction which is equal to the ground-contact width W2.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a tire-wheel assembly. [Background technology]

[0002] In recent years, there has been active development of electric vehicles as vehicles that use electrical energy as their power source (for example, Patent Document 1). In particular, in the field of autonomous driving technology, which is beginning to be fully put into practical use, the use of electric motors provides better response to vehicle operation than the use of engines, and therefore the development of autonomous driving technology using electric vehicles is progressing.

[0003] As power supply methods for supplying power to the power receiving device provided in the tire-wheel assembly, various methods have been proposed, including the overhead line method, which uses a wire, and the electromagnetic induction method and electric field coupling method, which are wireless methods. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-068077 Summary of the Invention [Problem to be solved by the invention]

[0005] Among these, the electromagnetic induction method generates magnetic flux, for example, perpendicular to the road surface, by passing current through a power transmission coil (primary coil) installed on the road surface, and when this magnetic flux passes through a power receiving coil (secondary coil) on the vehicle side, current flows through the power receiving coil, supplying electrical energy from the power transmitting coil to the power receiving coil. The electromagnetic induction method is a technology that has attracted particular attention due to its high power receiving efficiency.

[0006] However, after investigations by the inventors, it was found that if a foreign object enters between the road surface and the tire during power supply (particularly from the leading or trailing side), the foreign object may obstruct the magnetic flux, resulting in a decrease in power receiving efficiency.

[0007] Therefore, the present invention provides: Foreign objects entering from the stepping or kicking side The object is to provide a tire-wheel assembly that can suppress a decrease in power receiving efficiency. [Means for solving the problem]

[0008] The gist and configuration of the present invention are as follows. (1) A tire and a wheel having a rim portion, The tire is mounted on the rim portion, The tire-wheel assembly includes a power receiving coil, The tire has a belt consisting of one or more belt layers, When the tire-wheel assembly is filled with a specified internal pressure and a maximum load is applied, the outermost point in the tire width direction of the contact surface in the load load state is defined as the contact edge E, The tire-wheel assembly is filled with a specified internal pressure and is in a no-load state under standard conditions. A tire-wheel assembly, wherein the width W1 in the tire width direction of a minimum width belt layer, which is the smallest in the tire width direction among the one or more belt layers, is smaller than a contact width W2, which is the distance in the tire width direction between the contact ends E, or the width W1 in the tire width direction of the minimum width belt layer is equal to the contact width W2.

[0009] The "rim portion" of the above "wheel" refers to the standard rim (Measuring Rim in the ETRTO Standards Manual, Design Rim in the TRA Year Book) for the applicable size that is described or will be described in the future, as an industrial standard in effect in the region where the tire is produced and used, such as the JATMA Year Book of the Japan Automobile Tire Manufacturers Association (JATMA) in Japan, the Standards Manual of the European Tyre and Rim Technical Organization (ETRTO) in Europe, or the Year Book of the Tire and Rim Association, Inc. (TRA) in the United States. (In other words, the "rim portion" of the above "wheel" includes not only current sizes but also sizes that may be included in the above industrial standards in the future. An example of a "size to be described in the future" is the size listed as "FUTURE DEVELOPMENTS" in the 2013 edition of the ETRTO.) However, in the case of a size not described in the above industrial standards, it refers to a rim with a width that corresponds to the bead width of the tire. Furthermore, "specified internal pressure" refers to the air pressure (maximum air pressure) that corresponds to the maximum load capacity of a single wheel for the applicable size and ply rating as specified in the above JATMA etc., and in the case of sizes not specified in the above industry standards, "specified internal pressure" refers to the air pressure (maximum air pressure) that corresponds to the maximum load capacity specified for each vehicle on which the tire is fitted. Furthermore, the "maximum load" refers to the load corresponding to the maximum load capacity.

[0010] (2) The ratio W1 / W2 is preferably 0.98 or less.

[0011] (3) The ratio W1 / W2 is preferably 0.9 or less.

[0012] (4) The ratio W1 / W2 is preferably 0.7 or less. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a tire-wheel assembly that can suppress a decrease in power receiving efficiency. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic diagram showing a wireless power receiving system having a tire-wheel assembly according to one embodiment of the present invention, in a tire width direction cross section. FIG. [Figure 2] FIG. 2 is a cross-sectional view of the tire in the tire width direction. [Figure 3] FIG. 3 is a cross-sectional view of the wheel in the width direction. [Figure 4] FIG. 10 is a schematic diagram showing a wireless power receiving system having a modified tire-wheel assembly according to an embodiment of the present invention, in a tire widthwise cross section. [Figure 5] FIG. 2 is a cross-sectional view in the tire width direction for explaining each gauge of the tire and the depth of the circumferential main groove. [Figure 6] FIG. 2 is a plan view showing the configuration of an inclined belt layer. [Figure 7] 1 is a cross-sectional view in the tire width direction of an example tire. [Figure 8] FIG. 10 is a cross-sectional view in the tire width direction of another example of a tire. [Figure 9A] FIG. 9 is a perspective view for explaining the structure of the reinforcing member of the example of FIG. 8. [Figure 9B] FIG. 9 is a perspective view for explaining the structure of the reinforcing member of the example of FIG. 8. [Figure 10] FIG. 2 is a cross-sectional view showing an inclined belt layer and an interlayer rubber. [Figure 11] FIG. 2 is a schematic diagram showing an example of a carcass structure. [Figure 12A] FIG. 4 is a cross-sectional view showing an example of an end of a carcass folded-up portion. [Figure 12B] FIG. 10 is a cross-sectional view showing another example of the end of the carcass folded-up portion. [Figure 12C] FIG. 10 is a cross-sectional view showing another example of the end of the carcass folded-up portion. [Figure 13] FIG. 10 is a cross-sectional view showing an example in which a side reinforcing rubber is arranged. [Figure 14] FIG. 10 is a cross-sectional view showing another example in which a side reinforcing rubber is arranged. [Figure 15] 1 is a cross-sectional view in the tire width direction of an example tire. [Figure 16] 1 is a cross-sectional view in the tire width direction of an example tire. DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Unless otherwise specified, the dimensions and the like refer to the dimensions and the like in the above-mentioned reference state.

[0016] <Wireless power receiving system> FIG. 1 is a schematic diagram showing a wireless power receiving system having a tire-wheel assembly according to one embodiment of the present invention, in a tire width direction cross section. The wireless power receiving system 1 is configured to receive power transmitted wirelessly (i.e., wirelessly) from an external power transmitting device. First, the external configuration of the wireless power receiving system will be described. The power transmitting device 40 includes a power transmitting coil (primary coil) 41. The power transmitting device 40 is installed on the surface of a road or the like, or buried near the road surface. The power transmitting coil 41 generates an AC magnetic field based on an AC current supplied from a power source. The power transmitting coil 41 is configured as a ring, and is positioned so that the axial direction of the ring is approximately perpendicular to the road surface so as to generate an AC magnetic field directed upward toward the road surface. However, in the drawing, the power transmitting coil 41 is shown schematically. The power transmission coil 41 provided in the power transmission device 40 is wound around a core such as a ferrite core, and is configured in a ring shape overall, but is not limited to this and can be any coil capable of generating an AC magnetic field, such as a coil spring or an air-core coil. As shown in Fig. 1, a wireless power receiving system 1 includes a tire-wheel assembly 3 according to one embodiment of the present invention. A power receiving device 30 that receives power supplied wirelessly is accommodated in a housing portion of the tire-wheel assembly 3 (the housing portion is the space inside the tire-wheel assembly 3). The tire-wheel assembly 3 will now be described.

[0017] <Tire and wheel assembly> As shown in Fig. 1, a tire-wheel assembly 3 according to one embodiment of the present invention includes a tire 10 and a wheel 20 having a rim portion 21. The tire 10 is mounted on the rim portion 21 of the wheel 20. Below, the tire 10 and the wheel 20 will be described in order.

[0018] (tire) First, a description will be given of the configuration of an example of a tire 10. Fig. 2 is a cross-sectional view in the tire width direction of the tire 10. As shown in Fig. 2, the tire 10 has a pair of bead portions 11, a pair of sidewall portions 12 connected to the bead portions 11, and a tread portion 13 connected to the pair of sidewall portions 12.

[0019] In this example, the bead portion 11 has a bead core 11A and a bead filler 11B. In this example, the bead core 11A has a plurality of bead wires coated with rubber. In this example, the bead wires are formed of steel cords. The bead filler 11B is made of rubber or the like and is located radially outward of the bead core 11A. In this example, the bead filler 11B has a substantially triangular cross section whose thickness decreases radially outward. However, in the present invention, the tire 10 may have a structure that does not have the bead core 11A or the bead filler 11B.

[0020] In the present invention, the bead wire can also be made of a nonmagnetic material. By making the bead wire of a nonmagnetic material, the magnetic field reaching the power receiving coil 31 from the power transmitting coil 41 can be prevented from being blocked by the bead wire. Here, the term "nonmagnetic material" refers to a material other than a magnetic material, and the magnetic material refers to a material exhibiting ferromagnetic properties (ferromagnetic body). Therefore, nonmagnetic materials include paramagnetic and diamagnetic bodies with low magnetic permeability. Examples of nonmagnetic materials that can be used include resin materials, such as thermoplastic resins such as polyester and nylon, thermosetting resins such as vinyl ester resin and unsaturated polyester resin, and other synthetic resins. The resin material can further contain reinforcing fibers such as glass, carbon, graphite, aramid, polyethylene, and ceramic. The nonmagnetic material is not limited to resin, and any nonmetallic material can be used, including rubber, glass, carbon, graphite, aramid, polyethylene, and ceramic. Furthermore, the nonmagnetic material can be a metal material containing a paramagnetic material such as aluminum or a diamagnetic material such as copper.

[0021] As shown in FIG. 2, the tire 10 has a carcass 14 that straddles a pair of bead portions 11 in a toroidal shape. Ends of the carcass 14 are anchored to bead cores 11A. Specifically, the carcass 14 has a carcass main body 14A disposed between the bead cores 11A and a carcass folded-up portion 14B that is folded back around the bead cores 11A from the inner side in the tire width direction to the outer side in the tire width direction. The extension length of the carcass folded-up portion 14B from the inner side in the tire width direction to the outer side in the tire width direction can be set as appropriate. The carcass 14 may have a structure that does not include the carcass folded-up portion 14B, or may have a structure in which the carcass folded-up portion 14B is wrapped around the bead cores 11A.

[0022] The carcass 14 can be made up of one or more carcass plies. For example, the carcass 14 can be made up of two carcass layers stacked in the tire radial direction at the equatorial plane CL of the tire. In this embodiment, the carcass cords that make up the carcass layer of the carcass 14 are made of a non-magnetic material (organic fiber in this example). Alternatively, the carcass cords that make up the carcass 14 can be made up of steel cords. Non-magnetic materials include paramagnetic and diamagnetic materials with low magnetic permeability. Examples of non-magnetic materials include resin materials, such as thermoplastic resins such as polyester and nylon, thermosetting resins such as vinyl ester resin and unsaturated polyester resin, and other synthetic resins. Resin materials can further contain reinforcing fibers such as glass, carbon, graphite, aramid, polyethylene, and ceramic. Non-magnetic materials are not limited to resins, and any non-metallic material can be used, including rubber, glass, carbon, graphite, aramid, polyethylene, and ceramic. Furthermore, non-magnetic materials can include metal materials, including paramagnetic materials such as aluminum and diamagnetic materials such as copper. In the present invention, although steel cords can be used for the carcass cords, it is preferable to use carcass cords made of a non-magnetic material. This is because the magnetic field from the power transmission coil 41 to the power receiving coil 31 is not blocked by the carcass 14, thereby improving power receiving efficiency. Note that, although the carcass 14 has a radial structure in this embodiment, it is not limited to this and can also have a bias structure.

[0023] A belt 15 and tread rubber are provided on the radially outer side of the crown portion of the carcass 14. The belt 15 can be composed of, for example, one or more belt layers. In the illustrated example, a belt layer 15B is disposed on the radially outer side of the belt layer 15A. In this embodiment, the belt cords constituting the belt layers of the belt 15 are made of a non-magnetic material (organic fiber in this example). Alternatively, steel cords can be used for the belt cords constituting the belt 15. Non-magnetic materials include paramagnetic and diamagnetic materials with low magnetic permeability. Examples of non-magnetic materials include resin materials, such as thermoplastic resins such as polyester and nylon, thermosetting resins such as vinyl ester resin and unsaturated polyester resin, and other synthetic resins. Resin materials can further contain reinforcing fibers such as glass, carbon, graphite, aramid, polyethylene, and ceramic. Non-magnetic materials are not limited to resins, and any non-metallic material can be used, including rubber, glass, carbon, graphite, aramid, polyethylene, and ceramic. Furthermore, non-magnetic materials can include metal materials, including paramagnetic materials such as aluminum and diamagnetic materials such as copper. In the present invention, steel cords can be used as the belt cords that make up belt 15, but it is preferable to use belt cords made of a non-magnetic material. This is because belt 15 can prevent the magnetic field that reaches power receiving coil 31 from power transmitting coil 41 from being blocked, thereby improving power receiving efficiency. Note that in the present invention, the number of belt layers (one or more) and the inclination angle of the belt cords are not particularly limited and can be set as appropriate.

[0024] As shown in FIG. 2, the tire 10 has an inner liner 16. The inner liner 16 is arranged to cover the inner surface of the tire 10. The inner liner 16 can be composed of one or more inner liner layers laminated in the tire radial direction at the equatorial plane CL of the tire. The inner liner 16 is composed of, for example, a butyl-based rubber with low air permeability. Butyl-based rubber includes, for example, butyl rubber and its derivative, halogenated butyl rubber. The inner liner 16 is not limited to butyl-based rubber, and can also be composed of other rubber compositions, resins, or elastomers.

[0025] In the present invention, a side reinforcing rubber may be provided in the sidewall portion 12. The side reinforcing rubber may have, for example, a crescent-shaped cross section. This allows the side reinforcing rubber to take on the load in the event of a tire puncture, allowing the vehicle to continue running.

[0026] The tire is preferably a passenger vehicle tire, more preferably a radial passenger vehicle tire.

[0027] Here, when the tire 10 has a section width SW of less than 165 (mm), the ratio SW / OD of the section width SW to the outer diameter OD of the tire 10 is 0.26 or less, and when the tire 10 has a section width SW of 165 (mm) or more, the section width SW (mm) and the outer diameter OD (mm) of the tire 10 are OD(mm)≧2.135×SW(mm)+282.3(mm) (Hereinafter referred to as "relationship (1)") It is preferable that the following is satisfied. By satisfying the above ratio SW / OD or relational expression (1), the cross-sectional width SW of the tire 10 becomes relatively small with respect to the outer diameter OD of the tire 10, thereby reducing air resistance. In addition, since the cross-sectional width is narrow, vehicle space can be secured, and in particular, space for installing drive components can be secured near the inside of the tire where it is mounted on the vehicle. Furthermore, by satisfying the above ratio SW / OD or relational expression (1), the outer diameter OD of the tire 10 becomes relatively large compared to the cross-sectional width SW of the tire 10, thereby reducing rolling resistance. In addition, the larger diameter of the tire 10 increases the height of the wheel axle, thereby expanding the space under the floor, thereby making it possible to secure space for the trunk of the vehicle and space for installing drive components. As described above, by satisfying the above ratio SW / OD or relational expression (1), it is possible to achieve low fuel consumption relative to the supplied electrical energy, and also to ensure a large vehicle space. Further, the tire 10 has a cross-sectional width SW (mm) and an outer diameter OD (mm) of OD(mm)≧-0.0187×SW(mm) 2 +9.15×SW(mm)-380(mm) (Hereinafter referred to as "relationship (2)") It is preferable that the following is satisfied. By satisfying the above relational expression (2), the cross-sectional width SW of the tire becomes relatively small with respect to the outer diameter OD of the tire 10, reducing air resistance. In addition, the narrow cross-sectional width allows for more vehicle space to be secured, and in particular, space for installing drive components can be secured near the inside of the tire 10 where it is mounted on the vehicle. Furthermore, by satisfying the above relational expression (2), the outer diameter OD of the tire becomes relatively large with respect to the cross-sectional width SW of the tire 10, thereby reducing rolling resistance. In addition, the larger diameter of the tire 10 increases the height of the wheel axle, thereby expanding the space under the floor, thereby making it possible to secure space for the trunk of the vehicle and space for installing drive components. As described above, by satisfying the above relational expression (2), it is possible to achieve low fuel consumption relative to the supplied electric energy, and also to ensure a large vehicle space. In each of the above examples, the tire 10 preferably satisfies the ratio SW / OD and / or the relational expression (2), or preferably satisfies the relational expressions (1) and / or (2).

[0028] In addition, it is preferable that the tire width direction cross-sectional area S1 of the bead filler 11B is 1 to 8 times the tire width direction cross-sectional area S2 of the bead core 11A in the tire 10. This makes it possible to preferably achieve both power supply efficiency and low fuel consumption. In the case of a sandwiched bead core structure in which the carcass is sandwiched from the inside and outside in the tire width direction, the total volume of the bead cores on the inside and outside in the carcass width direction is defined as S2. By setting the cross-sectional area S1 of the bead filler 11B within the above range, the volume of the bead filler, which is a highly rigid member, can be reduced, thereby reducing the vertical spring coefficient of the tire and improving ride comfort. In addition, the weight of the bead filler can be reduced, thereby further reducing the rolling resistance of the tire. In particular, in narrow-width, large-diameter tires that satisfy the above-mentioned relational expression (1) or (2), the tensile rigidity of the belt is high and the tensile rigidity of the tire side portion is lower than that of the belt, so the effect of reducing the vertical spring coefficient by setting the cross-sectional area S1 of the bead filler within the specified range as described above is extremely high. Here, by making the tire width direction cross-sectional area S1 of the bead filler 11B 8 times or less the tire width direction cross-sectional area S2 of the bead core 11A, the volume of the bead filler, which is a highly rigid member, is prevented from becoming too large, and the vertical spring coefficient of the tire is prevented from becoming too large, thereby suppressing a decrease in ride comfort. On the other hand, by making the tire width direction cross-sectional area S1 of the bead filler 11B at least one time the tire width direction cross-sectional area S2 of the bead core 11A, the rigidity of the bead portion is ensured, the lateral spring coefficient is not reduced too much, and handling stability can be ensured.

[0029] Here, in the tire 10, when the width in the tire width direction of the bead filler 11B at the tire radial center position is defined as BFW and the maximum width in the tire width direction of the bead core 11A is defined as BDW, 0.1≦BFW / BDW≦0.6 It is preferable that the following is satisfied. This makes it possible to achieve both high power supply efficiency and low fuel consumption. By setting the ratio BFW / BDW to 0.6 or less, the volume of the bead filler can be reduced while maintaining the bead filler height, thereby ensuring rigidity in the tire rotational direction while reducing the vertical spring coefficient, improving ride comfort and reducing the tire weight. On the other hand, by setting the ratio BFW / BDW to 0.1 or more, the rigidity of the bead portion can be ensured, the lateral spring coefficient can be maintained, and steering stability can be further ensured.

[0030] Here, in the tire 10, when the height of the bead filler 11B in the tire radial direction is BFH and the section height (tire cross-sectional height) of the tire is SH, 0.1≦BFH / SH≦0.5 It is preferable that the following is satisfied. This makes it possible to achieve both high power supply efficiency and low fuel consumption. By setting the ratio BFH / SH to 0.5 or less, the radial height of the bead filler, which is a highly rigid member, can be reduced, effectively reducing the vertical spring coefficient of the tire and improving ride comfort. On the other hand, by setting the ratio BFH / SH to 0.1 or more, the rigidity of the bead portion can be ensured, the lateral spring coefficient can be maintained, and steering stability can be further ensured. Here, the tire section height SH refers to half the difference between the outer diameter of the tire and the rim diameter under no load when the tire is mounted on a rim and inflated to the internal pressure specified for each vehicle on which the tire is mounted.

[0031] The height BFH of the bead filler 11B in the tire radial direction is preferably set to 45 mm or less, which makes it possible to achieve both good power supply efficiency and good fuel economy.

[0032] In each of the above examples, the tire 10 preferably has a ratio Ts / Tb of the gauge Ts of the sidewall portion 12 at the tire's widest position (measured in the normal direction of the tangent to a point on the tire surface at the tire's widest position on this cross section) to the bead width Tb (the width of the bead portion 11 in the tire width direction) at the tire's radial center position of the bead core 11A, which is 15% or more and 60% or less. This makes it possible to achieve both power supply efficiency and low fuel consumption. The term "maximum tire width position" refers to the maximum width position in a cross section in the tire width direction under a reference condition. The gauge Ts is the total thickness of all components, including rubber, reinforcing members, and inner liner. By setting the ratio Ts / Tb in the above range, it is possible to appropriately reduce the rigidity at the maximum tire width position where bending deformation under tire load is large, thereby reducing the vertical spring coefficient and improving ride comfort. That is, if the ratio Ts / Tb exceeds 60%, the gauge of the sidewall portion 12 at the tire's maximum width position becomes large, which may increase the rigidity of the sidewall portion 12 and increase the vertical spring coefficient. On the other hand, if the ratio Ts / Tb is less than 15%, the lateral spring coefficient may become too low, making it impossible to ensure steering stability.

[0033] In each of the above examples, the tire 10 preferably has a gauge Ts of 1.5 mm or more at the sidewall portion 12 at the tire's widest point, thereby achieving both power supply efficiency and low fuel consumption. By setting the gauge Ts to 1.5 mm or more, it is possible to maintain an appropriate level of rigidity at the tire's widest point, suppress a decrease in the lateral spring coefficient, and further ensure steering stability.

[0034] In each of the above examples, the diameter Tbc of the bead core 11A (maximum width of the bead core in the tire width direction) of the tire 10 is preferably 3 mm or more and 16 mm or less, thereby making it possible to preferably achieve both power supply efficiency and low fuel consumption. By setting Tbc to 3 mm or more, it is possible to achieve weight reduction while ensuring bending rigidity and torsional rigidity on the rim flange, while by setting Tbc to 16 mm or less, it is possible to ensure handling stability while suppressing weight increase. In the case of a structure in which the bead core is divided into a plurality of small bead cores by the carcass, the distance between the innermost end and the outermost end in the width direction of all the small bead cores may be defined as Tbc.

[0035] In each of the above examples, when the tire 10 is loaded with the maximum load specified for each vehicle on which the tire is mounted, the tire 10 has a ground contact area of ​​8000 mm 2 This makes it possible to achieve both a reduction in tire rolling resistance and a reduction in tire weight, thereby achieving both power supply efficiency and fuel economy. Furthermore, tire axial force can be secured, thereby improving vehicle stability and safety.

[0036] In each of the above examples, the tire 10 preferably has a belt cord Young's modulus of 40,000 MPa or more. This allows the carcass structure and belt rigidity to be optimized, ensuring the tire strength that can be used even under high internal pressure. Furthermore, it is possible to achieve both power supply efficiency and low fuel consumption.

[0037] In each of the above examples, the thickness of the inner liner 16 of the tire 10 is preferably 0.6 mm or more. This makes it possible to suppress air leakage under high internal pressure conditions. Furthermore, it is possible to achieve both power supply efficiency and low fuel consumption.

[0038] In each of the above examples, the tire 10 preferably has a ratio Ts / Tc of the gauge Ts of the sidewall portion 12 at the tire maximum width position to the diameter Tc of the carcass cords that is equal to or greater than 4 and equal to or less than 12. This makes it possible to preferably achieve both power supply efficiency and low fuel consumption. By setting the ratio Ts / Tc within the above range, it is possible to appropriately reduce the rigidity at the tire's maximum width position, where bending deformation under tire load is large, thereby reducing the vertical spring coefficient and improving ride comfort. That is, by setting the ratio Ts / Tc to 12 or less, the gauge of the sidewall portion 4 at the tire's widest point is prevented from becoming too large, thereby preventing the rigidity of this portion from becoming too high and the vertical spring coefficient from becoming too high. On the other hand, by setting the ratio Ts / Tc to 4 or more, the lateral spring coefficient is prevented from becoming too low, ensuring steering stability.

[0039] In each of the above examples, when the distance in the tire width direction from the surface of the carcass cord to the outer surface of the tire at the tire maximum width position is Ta, the ratio Ta / Tc of the distance Ta to the diameter Tc of the carcass cord is preferably equal to or greater than 2 and equal to or less than 8. This makes it possible to preferably achieve both power supply efficiency and low fuel consumption. By setting the ratio Ta / Tc to 8 or less, the gauge of the sidewall portion 12 at the tire's widest point can be reduced, lowering the rigidity of the sidewall portion 12 and reducing the vertical spring coefficient, thereby improving ride comfort. On the other hand, by setting the ratio Ta / Tc to 2 or more, the lateral spring coefficient can be ensured, thereby ensuring better handling stability. It should be noted that "Ta" refers to the distance in the tire width direction from the surface of the outermost carcass cord in the width direction to the outer surface of the tire at the maximum width position of the tire. That is, when the carcass folded portion 14B extends radially outward from the maximum tire width position, the distance in the tire width direction from the surface of the carcass cord 14c at the portion forming the carcass folded portion 14B to the outer surface of the tire is defined as Ta.

[0040] In each of the above examples, the diameter Tc of the carcass cord 14c of the tire 10 is preferably 0.2 mm or more and 1.2 mm or less, thereby making it possible to preferably achieve both power supply efficiency and low fuel consumption. By setting Tc to 0.8 mm or less, the vertical spring coefficient can be reduced to improve ride comfort, while by setting Tc to 0.4 mm or more, the lateral spring coefficient can be increased to ensure steering stability.

[0041] Here, the internal pressure of the tire-wheel assembly is preferably 120 to 200 kPa. Setting the internal pressure to 200 kPa or less increases the ground contact area. A small ground contact area creates a gap between the tire and the road surface, allowing water or other foreign objects to enter and obstruct the magnetic flux, reducing power receiving efficiency. However, increasing the ground contact area eliminates the gap between the tire and the road surface, preventing water or other foreign objects from obstructing the magnetic flux and improving power receiving efficiency. Setting the internal pressure to 200 kPa or less also facilitates flexing of the tire sidewall, allowing the power receiving coil and power transmitting coil to be closer, thereby improving power receiving efficiency. Furthermore, the tire-wheel assembly of this embodiment, which has an internal pressure of 120 kPa or more, reduces rolling resistance and improves fuel economy. Here, the internal pressure is more preferably 140 to 180 kPa, because this allows for further improvement in fuel economy and further improvement in power receiving efficiency. Furthermore, the internal pressure is more preferably 150 to 170 kPa, because this allows for further improvement in fuel economy and power receiving efficiency. It is preferable that the above relational expressions (1) and (2) between SW and OD are satisfied when the above internal pressure is filled.

[0042] Alternatively, the internal pressure of the tire-wheel assembly is preferably greater than 200 kPa and less than or equal to 400 kPa. Setting the internal pressure to greater than 200 kPa reduces rolling resistance and improves fuel economy. Setting the internal pressure to 400 kPa or less increases the contact area. A small contact area creates a gap between the tire and the road, allowing water or other foreign objects to penetrate and impede the magnetic flux, reducing power receiving efficiency. Increasing the contact area eliminates the gap between the tire and the road, preventing water or other foreign objects from impeding the magnetic flux and improving power receiving efficiency. Setting the internal pressure to 400 kPa or less also facilitates flexure of the tire's sidewall, allowing the power receiving coil and power transmitting coil to be closer, thereby improving power receiving efficiency. Here, the internal pressure is more preferably 260 to 350 kPa. This can further improve fuel efficiency while further improving power receiving efficiency. Furthermore, the internal pressure is more preferably 300 to 320 kPa. This can further improve fuel efficiency while further improving power receiving efficiency. It is preferable that the above relational expressions (1) and (2) between SW and OD are satisfied when the above internal pressure is filled.

[0043] (wheel) Next, a description will be given of the configuration of the wheel 20. Fig. 3 is a cross-sectional view in the width direction of the wheel 20 according to one embodiment of the present invention.

[0044] As shown in FIG. 3, the wheel 20 has a cylindrical rim portion 21 and a disc portion 22 that is provided radially inside the rim portion 21 and is supported and fixed to a hub 2A of the vehicle 2.

[0045] The rim portion 21 includes, from the outside in the wheel width direction, a pair of flanges 23 (inner flange 23A, outer flange 23B), a pair of bead seats 24 (inner bead seat 24A, outer bead seat 24B), and a well 25. The bead portion 11 of the tire 10 is mounted on the bead seat 24. The flanges 23 extend from the bead seats 24 radially outward and widthwise outward of the wheel to support the bead portion 11 of the tire 10 from the side. The well 25 has a concave shape facing radially inward of the wheel between the pair of bead seats 24 to facilitate tire mounting and dismounting. The well 25 has a bottom and an inclined surface connecting the bottom to the bead seat 24. Furthermore, the bead seat 24 is provided with a pair of humps 26 (inner hump 26A, outer hump 26B) on the inside in the wheel width direction. The hump 26 protrudes radially outward from the wheel to prevent the tire bead from falling into the well 25 .

[0046] The rim portion 21 can be made of, for example, a non-magnetic material. Non-magnetic materials include paramagnetic and diamagnetic materials with low magnetic permeability. Examples of non-magnetic materials include resin materials, such as thermoplastic resins (e.g., polyester and nylon), thermosetting resins (e.g., vinyl ester resin and unsaturated polyester resin), and other synthetic resins. Resin materials can further contain reinforcing fibers (e.g., glass, carbon, graphite, aramid, polyethylene, and ceramic). Non-magnetic materials are not limited to resins, and any non-metallic material can be used, including rubber, glass, carbon, graphite, aramid, polyethylene, and ceramic. Furthermore, non-magnetic materials can include metal materials containing paramagnetic materials (e.g., aluminum) or diamagnetic materials (e.g., copper). This prevents the rim portion 21 from blocking the magnetic field from the transmitting coil 41 to the receiving coil 31, thereby improving power receiving efficiency.

[0047] Furthermore, the rim portion 21 of the wheel 20 is provided with a valve 27 for filling the cavity of the tire 10 with a gas such as air when the tire 10 is mounted. The valve 27 can be made of, for example, the resin material described above. By making the valve 27 out of the non-magnetic material described above, it is possible to prevent the valve 27 from blocking the magnetic field that reaches the power receiving coil 31 from the power transmitting coil 41.

[0048] The disc portion 22 has an annular mounting portion 22A that forms its radially inner end, and a plurality of spokes 22B that extend from the mounting portion 22A radially outward of the wheel. The mounting portion 22A is a portion that is connected and fixed to the hub 2A of the vehicle 2 (see FIGS. 1 and 3), and has mounting holes that penetrate in the width direction of the wheel for inserting bolts or the like that secure the hub 2A and the mounting portion 22A. The radially outer ends of the spokes 22B are connected integrally to the ends of the rim portion 21 on the radially inner surface of the wheel.

[0049] The disk portion 22 may include a magnetic material with high magnetic permeability (e.g., a ferromagnetic material), such as metal or ferrite. This makes it possible to prevent the magnetic field reaching the power receiving coil 31 from being attenuated by the influence of metals and other magnetic fields that exist outside the tire-wheel assembly 3, thereby improving power receiving efficiency. For example, if the disk portion 22 is made of a resin material, the weight of the wheel 20 can be reduced.

[0050] The disk portion 22 of the wheel 20 further includes a wheel cover 28 that covers the outer sides of the spokes 22B in the wheel width direction. The wheel cover 28 may include a magnetic material with high magnetic permeability (e.g., a ferromagnetic material), such as metal or ferrite. This makes it possible to reduce the attenuation of the magnetic field that reaches the power receiving coil 31 from the power transmitting coil 41 due to the influence of metals and other magnetic fields that exist outside the tire-wheel assembly 3, thereby improving power receiving efficiency.

[0051] The wheel 20 includes a housing portion on the tire radially inner side of the rim portion 21, i.e., in the space surrounded by the rim portion 21 and the disc portion 22, that houses a power receiving device 30 (see FIGS. 1 and 4) that receives power supplied wirelessly from the tire radially outer side of the tire 10. For example, when the power receiving device 30 is attached to the hub 2A of the vehicle 2, the wheel 20 is attached to the hub 2A of the vehicle 2, and thereby the power receiving device 30 is housed in the housing portion of the wheel 20.

[0052] <Receiving coil> 1 , the power receiving device 30 is attached to, for example, the hub 2A of the vehicle 2, but is not limited to this and can be attached to any position, such as the drive shaft 2B, as long as the power receiving device 30 is housed inside the rim portion 21 of the wheel 20 in the tire radial direction with the wheel 20 attached to the hub 2A of the vehicle 2. In this example, the power receiving device 30 is configured to be non-rotating relative to the rotation of the tire 10 and the wheel 20. In this embodiment, the power receiving coils (secondary coils) 31 are attached to the outer peripheral surface of the bottom of the well 25, and four power receiving coils 31 are arranged at equal intervals (intervals d (mm)) around the circumference. Therefore, in this example, the power receiving coils 31 are configured to rotate together with the rotation of the tire 10 and the wheel 20. At this time, the circumferential position of the power receiving coils 31 changes as the tire 10 and the wheel 20 rotate, but the power receiving coils 31 are arranged to face the power transmitting coil 41 at least at a certain tire rotation angle when the tire-wheel assembly 3 is positioned above the power transmitting device 40. As a result, when the tire 10 is positioned on the road surface above the power transmitting coils 41 and the power transmitting coils 41 and the power receiving coils 31 face each other, an electromotive force is generated in the power receiving coils 31 based on the AC magnetic field generated by the power transmitting coils 41, causing a current to flow and supplying power. The power receiving coils 31 are configured as a ring, and are arranged so that the axial direction of the ring is approximately perpendicular to the road surface. The receiving coil 31 is, for example, wound around a core such as a ferrite core, and is configured in a ring shape overall, but is not limited to this and can be any coil that can generate an electromotive force based on an AC magnetic field, such as a coil spring or an air-core coil. Here, the power receiving coil 31 may be located in any position so long as it can face the power transmitting coil 41 when the tire 10 is positioned on the road surface above the power transmitting coil 41. For example, the power receiving coil 31 may be attached to the inner circumferential surface of the bottom of the well 25, or to the inner circumferential surface or outer circumferential surface of another part of the rim portion 21. In this case, the power receiving coil 31 also rotates with the rotation of the tire 10 or the wheel 20. Alternatively, the power receiving coil 31 may be attached inside the tire-wheel assembly 3. In this case, the power receiving coil 31 may be configured to be non-rotating relative to the rotation of the tire 10 or the wheel 20, or, for example, a core may be provided that protrudes into the tire cavity fixed to the wheel 20, and the power receiving coil 31 may be attached to the core so that the power receiving coil 31 rotates with the rotation of the tire 10 or the wheel 20. Furthermore, the number of power receiving coils 31 is not particularly limited, and for example, if a continuous series of power receiving coils 31 is used on one circumference, continuous power supply is possible while the tire 10 is rolling when the tire is positioned on the road surface above the power transmitting coil 41, or if the total size of the power receiving coils 31 is reduced by dividing the power receiving coils 31 into multiple pieces, the weight increase due to the power receiving coils 31 can be suppressed and fuel efficiency can be improved. In this embodiment, four power receiving devices 30 are included corresponding to the four power receiving coils 31, but the number of power receiving devices 30 can also be any number depending on the number of power receiving coils 31, or the number of power receiving devices 30 can be different from the number of power receiving coils 31.

[0053] In this example, the power receiving device 30 includes a power conversion circuit 32, a power storage unit 33, and a control unit 34. The power conversion circuit 32 converts the power generated in the power receiving coil 31 into DC power and supplies the DC power to the power storage unit 33 or other on-board devices of the vehicle 2 via conductive wires or the like. The power storage unit 33 stores the power generated in the power receiving coil 31. The power storage unit 33 is, for example, a capacitor, but is not limited thereto and can be any power storage device such as a storage battery. If the power storage unit 33 is a capacitor, it can be charged and discharged in a shorter time than a storage battery. Therefore, the power storage unit 33, which is a capacitor, is advantageous in situations requiring high responsiveness, such as storing power generated in the power receiving coil 31 when the vehicle 2 travels over a power transmission device 40 installed on a road. The control unit 34 may include one or more processors that provide processing for controlling each function of the power receiving device 30. The control unit 34 may be a general-purpose processor such as a CPU (Central Processing Unit) that executes a program that defines a control procedure, or a dedicated processor specialized for processing each function. The control unit 34 may include any means used to control the power receiving device 30, such as a storage means for storing programs and the like, and a communication means for communicating with an external electronic device via wire or wirelessly. Note that, when the power receiving coil 31 is configured to rotate together with the rotation of the tire 10 or the wheel 20 as in this embodiment, the power generated in the power receiving coil 31 can be transmitted to the power conversion circuit 32 or the like via, for example, a slip ring. Alternatively, the power generated in the power receiving coil 31 can be transmitted (via a wire) to the first relay coil, and a magnetic field generated by a current flowing in the first relay coil passes through the second relay coil, causing a current to flow in the second relay coil, and power can be transmitted from the second relay coil to the power conversion circuit 32 or the like. In this case, the first relay coil and the second relay coil are also configured to rotate together with the rotation of the tire 10 or the wheel 20, and in the above example, the relay coils can be attached to the outer circumferential surface of the well 25, for example. On the other hand, when the power receiving coil 31 does not rotate relative to the rotation of the tire 10 or wheel 20 (for example, when the power receiving coil 31 is attached to the hub 2A), power can be transmitted directly from the power receiving coil 31 to the power storage unit 33, etc. In this case, it is particularly preferable from the viewpoint of suppressing a decrease in power receiving efficiency that the carcass 14, the belt cord, and the rim portion 21 of the wheel 20 are made of the non-magnetic material described above.

[0054] FIG. 4 is a schematic diagram showing a cross section in the tire width direction of a wireless power receiving system having a tire-wheel assembly of a modified example according to an embodiment of the present invention. 4, the tire-wheel assembly 1 includes an in-wheel motor 4. The in-wheel motor 4 has a power receiving device 30 attached thereto. As shown in FIG. 4, the power receiving device 30 can also be attached so as to be stationary when the tire 10 or wheel 20 rotates (for example, to the cover of the hub 2A in the illustrated example). In this case, it is particularly possible to place only one power receiving device 30 (power receiving coil 31) in a position facing the road surface. On the other hand, when the power receiving device 30 is attached in a position where it rotates together with the tire 10 and wheel 20 as shown in Fig. 1, it is preferable to install one or more power receiving devices 30 (power receiving coils 31) continuously or intermittently in the circumferential direction of the wheel 20.

[0055] Returning to the explanation of the tire, this embodiment has a belt 15 made up of one or more belt layers (two layers in the illustrated example). When the outermost point in the tire width direction of the ground contact surface in the above-mentioned loaded state is defined as the ground contact edge E, as shown in FIG. 2, in the above-mentioned reference state, the width W1 in the tire width direction of the smallest belt layer (belt layer 15B in the illustrated example) which has the smallest width in the tire width direction among the one or more belt layers is smaller than the ground contact width W2 which is the distance in the tire width direction between the ground contact edges E, or the width W1 in the tire width direction of the smallest belt layer is equal to the ground contact width W2. The following describes the effects of the tire-wheel assembly of this embodiment.

[0056] In the tire-wheel assembly of this embodiment, the width W1 of the minimum width belt layer in the tire width direction is smaller than or equal to the contact width W2. This increases deformation of the shoulder portion of the tire (relatively compared to when W1 > W2), and increases the contact length of the shoulder portion. This makes it difficult for foreign matter to enter between the road surface and the tire (especially from the leading or trailing side) during power supply, thereby suppressing a decrease in power receiving efficiency due to foreign matter interfering with magnetic flux.

[0057] The ratio W1 / W2 is preferably 0.98 or less. This is because the contact length of the shoulder portion is further increased, making it more difficult for foreign matter to enter, and further suppressing a decrease in power receiving efficiency. For the same reason, the ratio W1 / W2 is more preferably 0.9 or less, and even more preferably 0.7 or less. On the other hand, from the viewpoint of increasing the hoop effect of the belt and improving handling stability, the ratio W1 / W2 is preferably 0.5 or more.

[0058] FIG. 5 is a widthwise cross-sectional view of a tire for explaining the gauges and the depth of the circumferential main grooves. FIG. 5 shows only one half of the tire in the widthwise direction, bounded by the tire equatorial plane CL. The other half of the tire in the widthwise direction can have the same gauge (symmetrical with respect to the tire equatorial plane CL). However, the gauges in one half of the tire in the widthwise direction and the other half of the tire bounded by the tire equatorial plane CL can also be asymmetric (at least one of the gauges shown). In this case, it is preferable that the gauges be different within the following gauge range. As shown in FIG. 5, the gauge G1 (measured in the tire radial direction) at the tire equatorial plane CL is preferably 5 to 15 mm. The groove depth OTD1 of the circumferential main groove closest to the tire equatorial plane CL is preferably 2 to 10 mm. The gauge SBG1 from the groove bottom of the circumferential main groove closest to the tire equatorial plane CL to the radially outermost reinforcing member in the tire's widthwise direction is preferably 0.5 to 4.5 mm. The groove depth OTD2 of the outermost circumferential main groove in the tire width direction is preferably 3 to 8 mm. The gauge SBG2 from the groove bottom of the outermost circumferential main groove in the tire width direction to the outermost reinforcing member in the tire radial direction is preferably 0.5 to 4.5 mm. As shown in FIG. 5, the gauge G3 of the entire tread rubber at the tread edge TE (the above-mentioned ground contact edge E) is preferably 5 to 30 mm, and the gauge G4 from the tread surface at the tread edge TE to the outermost reinforcing member in the tire radial direction is preferably 3 to 20 mm. At the tread edge TE, the gauges G3 and G4 are measured in the normal direction to the contour line (or a virtual line if there is a groove) forming the tread surface of the tread portion. However, when the tread edge TE is an end point, the gauge G4 is measured in the direction connecting the tread edge TE and the end of the outermost belt layer in the tire radial direction, and the gauge G3 is also measured in the same direction. 5, the gauge G5 of the entire rubber at the midpoint in the tire width direction between the tread edge TE and the maximum tire width position is preferably 2 to 10 mm, and the gauge G6 from the midpoint to the carcass main body is preferably 1 to 8 mm.Furthermore, the gauge G7 at the maximum tire width position is preferably 1.0 to 8 mm.Also, the gauge G8 from the maximum tire width position to the carcass (the carcass fold-back part in the illustrated example) is preferably 0.5 to 5 mm. Further, the gauge G9 at the outermost point in the tire radial direction (the separation point) that contacts the rim flange in the reference state is preferably 5 to 35 mm. Also, the gauge G10 from the separation point to the carcass fold-back part is preferably 2 to 10 mm. Note that for G5 to G10, each gauge is measured in the normal direction of the outer contour line of the tire.

[0059] Here, as shown in FIG. 2, the tire 10 has one or more (four in the illustrated example) circumferential main grooves 17 extending in the tire circumferential direction on the tread surface of the tread portion 13. When the groove depth of the circumferential main groove 17 is OTD and the gauge from the groove bottom of the circumferential main groove 17 to the outermost reinforcing member in the tire radial direction (the outer belt layer 15B of the two-layer belt layer in the illustrated example) is SBG, at least one circumferential main groove satisfies, in the above reference state, OTD≧SBG is satisfied. According to this, for at least one circumferential main groove 17, since OTD≧SBG is satisfied, among the magnetic fluxes generated from the power transmission coil 41, the magnetic flux passing through the position of the circumferential main groove 17 is less likely to be obstructed by the tread rubber compared to the case where OTD<SBG, and more magnetic flux can reach the power reception coil 31. Therefore, in automatic power supply using the electromagnetic induction method, high power reception efficiency can be achieved. Here, the ratio OTD / SBG is preferably 1.05 or more. This is because higher power reception efficiency can be achieved in automatic power supply using the electromagnetic induction method. For the same reason, the ratio OTD / SBG is preferably 1.3 or more. On the other hand, from the viewpoint of ensuring wear resistance, the ratio OTD / SBG is preferably 1.5 or less. Note that when two or more circumferential main grooves satisfy OTG≧SBG, the value of the ratio OTD / SBG can be the same or different depending on the positions of the circumferential main grooves. In addition, when there is a circumferential main groove with OTD < SBG, for this circumferential main groove, from the perspective of ensuring drainage, the ratio OTD / SBG is preferably 0.8 or more. Also, it is preferable that the at least one circumferential main groove (satisfying OTD ≧ SBG) is located in a region obtained by projecting the surface of the power receiving coil in a direction orthogonal to the surface. This is because in automatic power feeding using the electromagnetic induction method, even higher power receiving efficiency can be achieved. Note that the at least one circumferential main groove can be located, for example, on the tire equatorial plane CL or be the circumferential main groove closest to the tire equatorial plane CL in correspondence with the projected region. Alternatively, for example, it can be the circumferential main groove located at the outermost side in the tire width direction. Also, it is preferable that all circumferential main grooves located within the region obtained by projecting the surface of the power receiving coil in a direction orthogonal to the surface satisfy OTD ≧ SBG in order to further improve the power receiving efficiency. OTD is preferably 2 mm or more and 10 mm or less. When OTD is 2 mm or more, in automatic power feeding using the electromagnetic induction method, higher power receiving efficiency can be achieved. On the other hand, when OTD is 10 mm or less, handling stability can be ensured. For the same reason, OTD is more preferably 3 mm or more and 8 mm or less. Also, SBG is preferably 0.5 mm or more and 4.5 mm or less. When the tread thickness is the same, when SBG is 0.5 mm or more, cut resistance can be ensured. On the other hand, when SBG is 4.5 mm or less, in automatic power feeding using the electromagnetic induction method, higher power receiving efficiency can be achieved. For the same reason, SBG is more preferably 1.0 to 3.5 mm. Most preferably, the circumferential main groove extends straight in the tire circumferential direction. On the other hand, the circumferential main groove may extend in a zigzag shape or while curving in the tire circumferential direction. In this case, in order to improve the power receiving efficiency, it is preferable that the circumferential main groove has a groove portion that extends straight and continuously in the tire circumferential direction (has a see-through portion (a portion where the kick-out side can be seen without being blocked by the groove wall when looking from the depression side to the kick-out side during grounding)). Here, the groove width (opening width) of the circumferential main groove is preferably 2% or more of the tread width TW. This can improve drainage. For the same reason, the groove width of the circumferential main groove is more preferably 4% or more of the tread width TW. On the other hand, from the viewpoint of ensuring the rigidity of the land portion and improving wear resistance, the groove width of the circumferential main groove is preferably 20% or less of the tread width TW. For the same reason, the groove width of the circumferential main groove is more preferably 15% or less of the tread width TW. Here, "tread width" refers to the distance in the tire width direction between the tread ends when the tire-wheel assembly is inflated to a specified internal pressure and is in an unloaded state. Although not particularly limited, the groove width (opening width) of the circumferential main groove is preferably 3 mm or more. This is because it is possible to further improve the power receiving efficiency. For the same reason, although not particularly limited, the groove width of the circumferential main groove is more preferably 5 mm or more. On the other hand, from the viewpoint of ensuring the rigidity of the land portion and improving the wear resistance, although not particularly limited, the groove width of the circumferential main groove is preferably 30 mm or less. For the same reason, the groove width of the circumferential main groove 17 is more preferably 20 mm or less. The tread surface of the tread portion 13 may have no widthwise grooves extending in the tire width direction, or may have one or more widthwise grooves. The tread surface of the tread portion 13 may have no circumferential sipes extending in the tire circumferential direction or widthwise sipes extending in the tire width direction, or may have one or more circumferential sipes and / or one or more widthwise sipes. Note that a widthwise groove refers to a groove extending in the tire width direction that has a groove width (opening width) of 2 mm or more when the tire-wheel assembly is inflated to a specified internal pressure and is under no load. A circumferential sipe refers to a groove extending in the tire circumferential direction that has a groove width (opening width) of less than 2 mm when the tire-wheel assembly is inflated to a specified internal pressure and is under no load. A widthwise sipe refers to a groove width (opening width) of less than 2 mm when the tire-wheel assembly is inflated to a specified internal pressure and is under no load. The groove width (opening width) of the widthwise grooves is not particularly limited in order to achieve both drainage performance and cornering performance, but may be, for example, 1 to 15 mm. For the same reason, the groove width of the widthwise grooves is more preferably 2 to 10 mm. The groove depth (maximum depth) of the widthwise grooves is not particularly limited in order to achieve both wear performance and steering stability, but may be, for example, 2 to 10 mm. For the same reason, the groove depth of the widthwise grooves is more preferably 3 to 8 mm. In addition, grooves that run continuously from one circumferential side to the other in the tire tread surface without being interrupted along the way are referred to as circumferential grooves (including circumferential main grooves), and other grooves are referred to as widthwise grooves. The negative ratio of the entire tread surface of the tread portion 13 is not particularly limited, but can be set to 8 to 40%. By setting the negative ratio of the entire tread surface of the tread portion 13 to 8% or more, drainage performance can be further improved, while by setting the negative ratio of the entire tread surface of the tread portion 13 to 40% or less, wear resistance can be further improved. For the same reason, the negative ratio of the entire tread surface of the tread portion 13 is more preferably 15 to 35%. Here, "tread surface" refers to the entire circumferential surface of the tire that comes into contact with the road when the tire-wheel assembly is inflated to the specified internal pressure and subjected to the maximum load. In addition, "circumferential main groove" refers to a groove that extends in the circumferential direction of the tire and has a groove width (opening width) of 2 mm or more when the tire-wheel assembly is filled with the specified internal pressure and is under no load. In addition, the "groove depth OTD of the circumferential main groove" refers to the maximum depth of the circumferential main groove measured in the normal direction of the contour line (or imaginary line if there is a groove) that forms the tread surface of the tread portion in the above-mentioned reference condition. Furthermore, the "gauge SBG from the groove bottom of the circumferential main groove to the radially outermost reinforcing member" refers to the distance from the groove bottom of the circumferential main groove to the radially outermost reinforcing member on the extension line of the line segment forming the OTD when the internal pressure of the tire-wheel assembly is 0 kPa and there is no load. The reinforcing member may be, for example, a belt, or may be, for example, a belt reinforcing layer disposed radially outward of the belt.

[0060] After careful consideration, the inventors have found that because the tire-wheel assembly described above is equipped with a power receiving coil (and in some cases an in-wheel motor), the load supported by the tire increases, causing significant distortion in the shoulder portion of the tire, generating heat and potentially reducing the durability of the tire. Therefore, the tire 10 preferably has a reinforcing member (the belt 15 in this example) made up of one or more reinforcing layers (two belt layers 15A and 15B in this example) made up of rubberized cord layers. Here, in the above-mentioned reference state, the shoulder regions are regions that are outward in the tire width direction from positions spaced inward in the tire width direction from both ends in the tire width direction of the widest reinforcing layer (in this example, the radially innermost belt layer 15A) that has the largest width in the tire width direction among the one or more reinforcing layers. In this case, in the present embodiment, in the above-mentioned reference state, cord ends (not shown in FIG. 2 ) of at least one reinforcing layer (in this example, both belt layers 15A and 15B) are located more inward in the tire width direction than the shoulder regions. Accordingly, in the tire 10 in the above-mentioned reference state, cord ends (not shown in FIG. 2 ) of at least one reinforcing layer (in this example, both belt layers 15A and 15B) are located more inward in the tire width direction than the shoulder regions. Therefore, by not positioning the cord end, which is likely to become the nucleus of failure, in the shoulder region where distortion increases due to the increased load caused by the presence of the power receiving coil 31, failures occurring at the cord end can be suppressed, thereby improving the durability of the tire. Note that, if the cord end of at least one reinforcing layer is positioned more inward in the tire width direction than the shoulder region, the above-mentioned effect can be obtained for that reinforcing layer. Also, if at least one of the cord start and end ends is positioned more inward in the tire width direction than the shoulder region, the above-mentioned effect can be obtained for that end, and if both the cord start and end ends are positioned more inward in the tire width direction than the shoulder region, the above-mentioned effect can be obtained for both ends. Here, as in the above example, in the standard state, it is preferable that the cord ends of all reinforcing layers are located more inward in the tire width direction than the shoulder regions, because this can suppress failures occurring from the cord ends of all reinforcing layers and further improve tire durability. In addition, in the standard state, it is preferable that the cord ends of at least one reinforcing layer be located more inward in the tire width direction than positions in the tire width direction that are spaced inward in the tire width direction from both ends of the widest reinforcing layer in the standard state by 10% of the width of the widest reinforcing layer in the tire width direction. This is because by moving the cord ends further away from the shoulder regions, failures occurring at the cord ends can be suppressed and tire durability can be further improved. In addition, in the standard state, it is preferable that the cord ends of all reinforcing layers are located more inward in the tire width direction than positions in the tire width direction that are spaced inward in the tire width direction from both ends of the widest reinforcing layer in the standard state by 10% of the width of the widest reinforcing layer in the tire width direction. This is because, for all reinforcing layers, by moving the cord ends farther away from the shoulder regions, it is possible to suppress failures that occur from the cord ends and further improve tire durability. FIG. 6 is a plan view showing the configuration of the inclined belt layer. As shown in FIG. 6, the reinforcing member (inclined belt) is preferably in a state where the strip member 15a is spirally wound in the tire circumferential direction so that it extends from one widthwise end to the other widthwise end, is folded back at the other widthwise end, extends from the other widthwise end to one widthwise end, is folded back at the one widthwise end, and extends from the one widthwise end to the other widthwise end, repeating this process (so-called endless belt structure). In this case, the ends (starting and / or ending ends) of the strip member are separated in the width direction from the widthwise ends of the reinforcing layer (belt layer) by an appropriate distance (winding can start or end from a separated position) so that they are not located in the shoulder regions, thereby allowing the cord ends to be located more inward in the tire width direction than the shoulder regions. Note that the tire width direction position of the starting end of the cord end can be the same as or different from the tire width direction position of the ending end of the cord end. Here, it is preferable that the reinforcing layer is an inclined belt layer in which cords are inclined with respect to the tire circumferential direction, and the reinforcing member is an inclined belt. When the reinforcing layer is an inclined belt, failure from the cord ends of the inclined belt can be suppressed, thereby improving tire durability. The inclination angle of the cords with respect to the tire circumferential direction is not particularly limited, but can be 5 to 45 degrees with respect to the tire circumferential direction. Alternatively, it is also preferable that the reinforcing layer is a circumferential belt layer in which cords extend along the tire circumferential direction, and the reinforcing member is a circumferential belt. In this case, the width of the circumferential belt layer in the tire width direction can be adjusted so that the outermost cords in the tire width direction are located more inward in the tire width direction than the shoulder regions. This can suppress failures from the cord ends of the circumferential belt when the reinforcing layer is a circumferential belt, thereby improving tire durability. Alternatively, it is also preferable that the reinforcing layer is an inclined belt layer in which cords are inclined with respect to the tire circumferential direction, and a circumferential belt layer arranged on the outer or inner side in the tire radial direction of the inclined belt layer, in which cords extend along the tire circumferential direction, and the reinforcing member is an inclined belt and a circumferential belt arranged on the outer or inner side in the tire radial direction of the inclined belt. This is because, even in a configuration in which the circumferential belt is arranged on the outer or inner side in the tire radial direction of the inclined belt, failure from the cord ends of the inclined belt layer and / or the circumferential belt layer can be suppressed, thereby improving tire durability.

[0061] Furthermore, the tire 10 preferably has a reinforcing member (in this example, the inclined belt 15) made up of two or more reinforcing layers (in this example, the inclined belt layers) made up of rubberized cord layers. As shown in Fig. 7, a cord end (for example, when the cord end and the tire width direction end of the reinforcing layer are located at the same tire width direction position) of at least one reinforcing layer (in the illustrated example, the belt layer 15B that is the outermost in the tire radial direction of the two belt layers) is surrounded by the other reinforcing layer (in the illustrated example, the belt layer 15B) by folding back an end of another reinforcing layer (in the illustrated example, the belt layer 15A) located more inward in the tire radial direction than the at least one reinforcing layer (in the illustrated example, the belt layer 15B) from the inner side in the tire radial direction to the outer side, and terminating more outward in the tire radial direction than the at least one belt layer (in the illustrated example, the belt layer 15B). (Note that a configuration may also be adopted in which an end of another reinforcing layer located more outward in the tire radial direction than the at least one belt layer is folded back from the outer side in the tire radial direction to the inner side, and terminating more inward in the tire radial direction than the at least one reinforcing layer, and thereby surrounded by the other reinforcing layer.) In this example, the cord ends of at least one reinforcing layer are surrounded by another reinforcing layer as the other reinforcing layer is folded back from the inner side to the outer side in the tire radial direction or from the outer side to the inner side in the tire radial direction. According to this, in the tire 10, the cord ends of at least one reinforcing layer are surrounded by other reinforcing layers by folding back the other reinforcing layers from the inner side to the outer side in the tire radial direction or from the outer side to the inner side in the tire radial direction. As a result, even if the cord ends are located in a shoulder region where distortion increases due to an increase in load caused by the presence of the power receiving coil 31, the cord ends can be protected from distortion because they are surrounded by other reinforcing layers as described above, thereby suppressing failures that occur from the cord ends and improving tire durability. 7, it is particularly preferable that the cord ends of at least one reinforcing layer (in the illustrated example, the outermost belt layer 15B in the tire radial direction of the two belt layers) are surrounded by the other reinforcing layer (in the illustrated example, the belt layer 15A) located radially inward of the at least one reinforcing layer (in the illustrated example, the belt layer 15B) by folding back the end portion of the other reinforcing layer (in the illustrated example, the belt layer 15A) located radially inward of the at least one reinforcing layer (in the illustrated example, the belt layer 15B) from the inner side to the outer side in the tire radial direction, and terminate radially outward of the at least one belt layer (in the illustrated example, the belt layer 15B). This can improve maneuverability such as cornering performance. As in the present embodiment, the reinforcing layer is preferably an inclined belt layer in which cords are inclined with respect to the tire circumferential direction. In this case, the inclination angle of the cords with respect to the tire circumferential direction is not particularly limited, but may be, for example, 5 to 45 degrees with respect to the tire circumferential direction. At least one reinforcing layer surrounding the cord ends may be a circumferential belt layer in which cords extend along the tire circumferential direction, and in this case too, failure from the cord ends of the circumferential belt layer can be suppressed, thereby improving tire durability. In addition, in the above example, the tire width direction positions of the cord end and the tire width direction end of the reinforcing layer are the same, but they may be different, and in this case too, the above-mentioned effect can be obtained as long as the cord end is surrounded by another reinforcing layer as described above. Fig. 8 is a cross-sectional view in the tire width direction of another example of a tire. Figs. 9A and 9B are perspective views for explaining the reinforcing member of Fig. 8. 8, 9A, and 9B, at least one reinforcing layer (belt layer 15C in FIG. 8) is a circular core reinforcing layer, and the other reinforcing layer (belt layer 15D in FIG. 8) is a sheath reinforcing layer that is spirally wound around the tire circumferential direction so as to extend from one widthwise end of the core reinforcing layer 15C to the other widthwise end, be turned back at the other widthwise end from the inner side to the outer side in the tire radial direction, extend from the other widthwise end to one widthwise end, be turned back at one widthwise end from the outer side to the inner side in the tire radial direction, and extend from one widthwise end to the other widthwise end (FIG. 9B shows the completed state). The core reinforcing layer can be composed of one or more reinforcing layers made of rubberized organic fiber cords or rubber alone, and is preferably a rubberized cord layer. Even with this configuration, the cord ends of at least one reinforcing layer of the tire 10 are surrounded by other reinforcing layers by folding back the other reinforcing layers from the inner side to the outer side in the tire radial direction or from the outer side to the inner side in the tire radial direction. As a result, even if the cord ends are located in the shoulder region where distortion increases due to an increase in load caused by the presence of the power receiving coil 31, the cord ends can be protected from distortion because they are surrounded by other reinforcing layers as described above, thereby suppressing failures that occur from the cord ends and improving tire durability. In particular, as in this example, it is also preferable that at least one reinforcing layer (belt layer 15C) is an annular core reinforcing layer, and the other reinforcing layers (belt layers 15D) are sheath reinforcing layers that are spirally wound in the tire circumferential direction so as to extend from one width direction end of the core reinforcing layer to the other width direction end, be folded back at the other width direction end from the inner side to the outer side in the tire radial direction, extend from the other width direction end to one width direction end, be folded back at one width direction end from the outer side to the inner side in the tire radial direction, and extend from one width direction end to the other width direction end, repeating this process. This can improve belt durability. 8, 9A, and 9B, the core reinforcing layer is preferably a core belt layer having cords extending along the tire circumferential direction or extending at an inclination angle of 30 to 90° with respect to the tire circumferential direction, and the sheath reinforcing layer is preferably a sheath belt layer having cords extending at an inclination angle of 45° or less with respect to the tire circumferential direction.Moreover, the inclination angle of the cords of the core belt layer with respect to the tire circumferential direction is more preferably smaller than the inclination angle of the cords of the sheath belt layer with respect to the tire circumferential direction.

[0062] Here, the tire 10 preferably has a reinforcing member (in this example, the inclined belt 15) made up of two or more reinforcing layers (in this example, the inclined belt layers) made up of rubberized cord layers. Fig. 10 is a cross-sectional view showing the inclined belt layers and the interlayer rubber. As shown in FIG. 10 , an interlayer rubber 19 is disposed between at least one of two reinforcing layers adjacent in the tire radial direction (between the belt layer 15A and the belt layer 15B in the example shown in FIG. 10 ), extending in a region in the tire width direction including the tire width direction end of the reinforcing layer (belt layer 15B in the illustrated example) that is located on the outer side in the tire radial direction of the two reinforcing layers. As a result, even if the cord end of the belt layer is located in a shoulder region where strain increases due to an increase in load caused by the presence of the power receiving coil 31, for example, the interlayer rubber 19 can absorb the strain, and the distance between the cord ends of the two belt layers can be secured by the distance where the interlayer rubber 19 is disposed. This makes it possible to suppress failures that occur from the cord end (particularly the cord end of the belt layer 15B that is on the outer side in the tire radial direction) and improve tire durability. In this example, the cord end and the tire width direction end of each inclined belt layer are located at the same position in the tire width direction. The interlayer rubber may extend from the tire width direction end of the reinforcing layer located on the inner side in the tire radial direction of the two reinforcing layers to the outer side in the tire width direction, or may extend to the inner side in the tire width direction, or may be located at the same position in the tire width direction. The interlayer rubber may cover the end face of the reinforcing layer located on the outer side in the tire radial direction out of the two reinforcing layers, or may not cover it as shown in the drawing. Here, the 100% modulus of the interlayer rubber is preferably 3.0 MPa or more. This is because it is possible to sufficiently absorb strain that may occur, further suppress failures that occur at the cord ends, and further improve tire durability. For the same reason, the 100% modulus of the interlayer rubber is preferably 5.0 MPa or more. On the other hand, from the viewpoint of reducing the difference in rigidity with the surrounding rubber, the 100% modulus of the interlayer rubber is preferably 20.0 MPa or less. Furthermore, the interlayer rubber is preferably in the form of a sheet, and the maximum thickness in the tire radial direction is preferably 3 mm or less. This is because it is possible to suppress the weight increase due to the interlayer rubber. For the same reason, the maximum thickness of the interlayer rubber is more preferably 2 mm or less. On the other hand, from the viewpoint of sufficiently absorbing strain that may occur, the maximum thickness of the interlayer rubber is preferably 0.5 mm or more. In addition, in a cross section in the tire width direction, it is preferable that the thickness of the interlayer rubber in the tire radial direction gradually increases from the inner side toward the outer side in the tire width direction. This is because the distance between the belt layers can be further secured on the end side of the belt layers, which further suppresses failures occurring from the cord ends and further improves tire durability. On the other hand, the thickness of the interlayer rubber can also be constant when viewed in a cross section in the tire width direction. Here, the two reinforcing layers with interlayer rubber disposed between them are preferably two inclined belt layers in which cords extend at an inclination angle of 20 to 70° with respect to the tire circumferential direction. When the reinforcing layers are inclined belt layers, failures occurring from the cord ends of the inclined belt layers can be suppressed, thereby improving the durability of the tire. Alternatively, the two reinforcing layers with interlayer rubber disposed between them are preferably one inclined belt layer in which cords extend at an inclination angle of 20 to 70° with respect to the tire circumferential direction, and one circumferential belt layer in which cords extend along the tire circumferential direction. This is because, when the reinforcing layers are the inclined belt layer and the circumferential belt layer, failures occurring at the cord ends of the inclined belt layer and the circumferential belt layer can be suppressed, thereby improving the durability of the tire. Alternatively, the two reinforcing layers with interlayer rubber disposed between them are preferably two circumferential belt layers in which cords extend along the tire circumferential direction. This is because, when the reinforcing layers are circumferential belt layers, failures occurring from the cord ends of the circumferential belt layers can be suppressed, thereby improving the durability of the tire.

[0063] 2, in the above-described reference state, it is also preferable that the tire width direction end of the minimum width belt layer (belt layer 15B in the illustrated example) which has the smallest width in the tire width direction among the one or more belt layers is located outward in the tire width direction from the outermost circumferential main groove 17 which is located outermost in the tire width direction among the one or more circumferential main grooves 17. This suppresses deformation of the shoulder portion of the tire (relatively compared to when the tire width direction end of the minimum width belt layer is located more inward in the tire width direction than the outermost circumferential main groove), reduces the contact length of the shoulder portion, and increases the contact width. This makes it difficult for foreign matter to enter between the road surface and the tire (particularly from the width direction) during power supply, and can suppress a decrease in power receiving efficiency caused by foreign matter interfering with magnetic flux. Here, in the above-mentioned standard state, it is preferable that the tire width direction end of the minimum width belt layer is located 2 mm or more outward in the tire width direction from the outermost circumferential main groove. By making it 2 mm or more, the ground contact width is further increased, making it more difficult for foreign matter to enter between the road surface and the tire (particularly from the width direction), and it is possible to further suppress a decrease in power receiving efficiency due to foreign matter interfering with magnetic flux. For the same reason, it is even more preferable that the tire width direction end of the minimum width belt layer is located 5 mm or more outward in the tire width direction from the outermost circumferential main groove in the above-mentioned standard state. On the other hand, from the viewpoint of suppressing an increase in weight due to the belt layer, it is preferable that the tire width direction end of the minimum width belt layer is located 20 mm or less outward in the tire width direction from the outermost circumferential main groove.

[0064] Furthermore, the tire 10 has a belt made up of one or more belt layers each made of a rubber-coated layer of cords made of organic fiber (aramid fiber in this example), and the end count of the cords in each belt layer is preferably 10 to 50 cords / 50 mm. If the end count of the cords in the belt layer exceeds 50 cords / 50 mm, the rate at which strain between the cords develops increases, which may result in breakdown. On the other hand, if the end count of the cords in the belt layer is less than 10 cords / 50 mm, rubber has a lower magnetic permeability than organic fiber and is more likely to obstruct the magnetic flux from the power transmission coil 31, which may result in reduced power receiving efficiency. In contrast, by setting the end count of the cords in the belt layer within the above range, it is possible to improve power receiving efficiency while also improving tire durability. In some cases, it may be preferable for the cord count of the belt layer to be 15 to 45 cords per 50 mm. For example, in a tire-wheel assembly used for autonomous driving, the vehicle can travel sufficiently even if the hoop effect of the belt is not so great, and improved power receiving efficiency is particularly desired. Therefore, by setting the cord count of the belt layer to 15 cords per 50 mm or more, high power receiving efficiency can be achieved, while by setting the cord count of the belt layer to 45 cords per 50 mm or less, tire durability can be further improved while sufficient tire running performance can be ensured. A tire-wheel assembly used for autonomous driving may be equipped with, for example, an in-wheel motor. As the organic fiber, for example, aramid fiber, PET fiber, nylon fiber, etc. can be used.

[0065] Here, depending on the arrangement of the power receiving coil and the power transmitting coil, there are cases where the inside of the tire-wheel assembly when mounted on a vehicle becomes the path through which the magnetic flux passes. As shown in FIG. 15 , the tire 10 has a belt made up of one or more belt layers each made of a rubberized layer of cords made of organic fiber, and in the above-mentioned reference state, it is preferable that a minimum width belt layer (belt layer 15B in the illustrated example) having the smallest width in the tire width direction among the one or more belt layers has a width Wa in the tire width direction of the minimum width belt layer in a half portion in the tire width direction that is on the inner side when mounted on a vehicle, which is larger than a width Wb in the tire width direction of the minimum width belt layer in the half portion in the tire width direction that is on the outer side when mounted on a vehicle. In this example, the belt layer is made of cords made of organic fiber, which has a higher magnetic permeability than rubber, so the magnetic flux from the power transmission coil 31 is less likely to be obstructed when the belt layer is provided. Therefore, in this example, the magnetic flux from the power transmission coil 31 is less likely to be obstructed in the half portion in the tire width direction on the inner side where the tire is mounted on the vehicle. Therefore, according to this example, high power receiving efficiency can be achieved in automatic power feeding using the electromagnetic induction method. Here, the width of the minimum width belt layer in the tire width direction is preferably 102% or more of the ground contact width. As described above, the magnetic flux from the power transmission coil 31 is less likely to be obstructed when a belt layer is disposed, and therefore, by making this tire width direction region 102% or more of the ground contact width, power receiving efficiency can be further improved. For the same reason, the width of the minimum width belt layer in the tire width direction is more preferably 105% or more of the ground contact width, and even more preferably 125% or more. On the other hand, from the viewpoint of suppressing the weight increase due to the belt layer, the width of the minimum width belt layer in the tire width direction is preferably 135% or less of the ground contact width. Furthermore, the ratio Wa / Wb is preferably 1.1 or greater. This is because the magnetic flux from the power transmission coil 31 is less likely to be obstructed in the half portion in the tire width direction on the inner side where the tire is mounted on the vehicle, thereby further improving power receiving efficiency. For the same reason, the ratio Wa / Wb is more preferably 1.2 or greater, and even more preferably 1.3 or greater. On the other hand, from the viewpoint of suppressing the weight increase due to the belt layer, the ratio Wa / Wb is preferably 1.5 or less. When magnetic flux can pass through the inner side of the belt layer mounted on the vehicle during power supply, the above-mentioned effect can achieve high power supply efficiency. This is particularly effective when, for example, part or all of the power receiving coil 31 is arranged on the inner side mounted on the vehicle, or when, for example, part or all of the power receiving coil 31 is arranged on the outer side mounted on the vehicle but the axial direction perpendicular to the plane of the power receiving coil is inclined inward when mounted on the vehicle, moving from the inner side to the outer side in the tire radial direction. As the organic fiber, for example, aramid fiber, PET fiber, nylon fiber, etc. can be used.

[0066] On the other hand, depending on the arrangement of the power receiving coil and the power transmitting coil, there are cases where the magnetic flux passes through the outside of the tire-wheel assembly when it is mounted on a vehicle. As shown in FIG. 16 , the tire 10 has a belt made up of one or more belt layers each made of a rubberized layer of cords made of organic fiber, and in the above-mentioned reference state, it is also preferable that a minimum width belt layer (belt layer 15B in the illustrated example) having the smallest width in the tire width direction among the one or more belt layers has a width Wb in the tire width direction of the minimum width belt layer in a half portion in the tire width direction that is on the outer side when mounted on a vehicle, which is larger than a width Wa in the tire width direction of the minimum width belt layer in a half portion in the tire width direction that is on the inner side when mounted on a vehicle. In this example, the width Wb of the minimum width belt layer in the tire width direction in the half portion on the outer side of the tire when mounted on the vehicle is larger than the width Wa of the minimum width belt layer in the tire width direction in the half portion on the inner side of the tire when mounted on the vehicle. In this embodiment, the cords of the belt layer are made of organic fiber, which has a higher magnetic permeability than the tread rubber. Therefore, the magnetic flux from the power transmission coil 31 is less likely to be obstructed when the belt layer is disposed. Therefore, in this example, the magnetic flux from the power transmission coil 31 is less likely to be obstructed in the outer half of the tire width direction on the vehicle mounting side. Therefore, according to this example, high power receiving efficiency can be achieved in automatic power feeding using the electromagnetic induction method. Here, the width of the minimum width belt layer in the tire width direction is preferably 102% or more of the ground contact width. As described above, the magnetic flux from the power transmission coil 31 is less likely to be obstructed when a belt layer is disposed, and therefore, by making this tire width direction region 102% or more of the ground contact width, power receiving efficiency can be further improved. For the same reason, the width of the minimum width belt layer in the tire width direction is more preferably 105% or more of the ground contact width, and even more preferably 125% or more. On the other hand, from the viewpoint of suppressing the weight increase due to the belt layer, the width of the minimum width belt layer in the tire width direction is preferably 135% or less of the ground contact width. Furthermore, the ratio Wb / Wa is preferably 1.1 or greater. This is because the magnetic flux from the power transmission coil 31 is less likely to be obstructed in the outer half of the tire width direction on the vehicle mounting side, thereby further improving power receiving efficiency. For the same reason, the ratio Wb / Wa is more preferably 1.2 or greater, and even more preferably 1.3 or greater. On the other hand, from the viewpoint of suppressing the weight increase due to the belt layer, the ratio Wb / Wa is preferably 1.5 or less. When magnetic flux can pass through the outer side of the belt layer mounted on the vehicle during power supply, the above-mentioned effect can achieve high power supply efficiency. This is particularly effective when, for example, part or all of the power receiving coil 31 is arranged on the outer side mounted on the vehicle, or when, for example, part or all of the power receiving coil 31 is arranged on the inner side mounted on the vehicle but the axial direction perpendicular to the plane of the power receiving coil is inclined outward from the inner side in the tire radial direction to the outer side when mounted on the vehicle. As the organic fiber, for example, aramid fiber, PET fiber, nylon fiber, etc. can be used.

[0067] Furthermore, the tire 10 preferably includes a carcass 14 made up of one or more carcass plies, and the cords of the carcass ply are inclined at an inclination angle of 80° or more relative to the tire circumferential direction. This allows the cords of the carcass ply to be inclined at an inclination angle of 80° or more relative to the tire circumferential direction. This reduces tire deflection when a load is applied to the tire-wheel assembly (compared to when the cords of the carcass ply are inclined at an inclination angle of less than 80° relative to the tire circumferential direction), suppresses fluctuations in the distance between the power transmitting coil and the power receiving coil, and improves power receiving efficiency. From the viewpoint of reducing the deflection of the tire under load and improving the power receiving efficiency, it is more preferable that the cords of the carcass ply are inclined at an inclination angle of 85° or more relative to the tire circumferential direction, and it is even more preferable that they are inclined at an inclination angle of 90°. From the viewpoint of reducing the deflection of the tire under load and improving the power receiving efficiency, the number of carcass plies is preferably more than one, for example, 2 or 3. On the other hand, from the viewpoint of suppressing the increase in weight due to the carcass, the number of carcass plies is preferably one. FIG. 11 is a schematic diagram showing an example of a carcass structure. As shown in Fig. 11, the carcass preferably has one or more (two in the example shown in Fig. 11) up-plies 14C, 14D each consisting of a carcass main body portion toroidally spanning a pair of bead portions and a carcass wrap portion consisting of a carcass wrap portion extending from the carcass main body portion and wrapping from the inner side to the outer side of the bead core in the tire width direction. This combination can achieve a good balance between suppressing the weight increase due to the carcass and improving power receiving efficiency. The bead core may have an inner bead core on the inner side in the tire width direction and an outer bead core on the outer side in the tire width direction, and the carcass may be interposed between the inner bead core and the outer bead core. As shown in the figure, it is preferable that the end of the up ply, whose turned-up portion is located on the inner side in the tire width direction, is located radially outward of the end of the up ply, whose turned-up portion is located on the outer side in the tire width direction, but they may be located radially inward in the tire width direction or at the same position.

[0068] As a result of investigations by the present inventors, it was found that, in consideration of the fact that a power receiving coil is mounted, it is necessary to improve the external damage resistance of the tire. The tire 10 preferably includes a carcass 14 made of one or more carcass plies toroidally straddling a pair of bead cores, and the carcass ply preferably includes a carcass main body 14A toroidally straddling the pair of bead cores and a carcass folded-up portion 14B extending from the carcass main body and folded back around the bead cores from the inner side in the tire width direction to the outer side, thereby extending radially outward in the tire. According to this, the carcass ply includes the carcass main body 14A toroidally straddling the pair of bead cores and the carcass folded-up portion 14B extending from the carcass main body and folded back around the bead cores from the inner side in the tire width direction to the outer side, thereby extending radially outward in the tire. This allows the carcass folded-up portion 14B to protect components such as the carcass main body and the power receiving coil from external damage to the tire (particularly to the sidewalls), thereby improving the tire's resistance to external damage. Fig. 12A is a schematic diagram showing an example of a carcass structure. As shown in Fig. 12A, in the reference state, the end of the carcass folded-up portion is preferably located in a region extending from the radially inner end of a region corresponding to the tire cross-sectional height SH to a position radially outward from the radially inner end of the tire. This is because, as described above, the weight increase due to the carcass can be suppressed while improving external damage resistance. 12B is a schematic diagram showing another example of a carcass structure. As shown in FIG. 12B, in the above-mentioned reference state, it is also preferable that the end of the carcass folded-up portion is located in a tire radial direction region from a position spaced radially outward from the tire radially inner end of the tire radial direction region that forms the tire cross-sectional height SH by at least ¼ of the tire cross-sectional height SH to a position spaced radially outward from the tire radially inner end by less than ¾ of the tire cross-sectional height SH. Compared to the case shown in FIG. 12A, the tire radial direction region that can be protected from external damage by the carcass folded-up portion is larger, thereby further improving the tire's resistance to external damage. In the carcass structure shown in FIG. 12B, the tire radial direction position of the end of the carcass folded-up portion can be the tire radial direction position of the tire maximum width position P, or it can be located radially inward from the tire maximum width position P as shown, or it can be located radially outward from the tire maximum width position P. Fig. 12C is a schematic diagram showing another example of a carcass structure. As shown in Fig. 12C, it is also preferable that the end of the carcass folded-up portion is located radially outward of a position spaced 3 / 4 of the tire cross-sectional height SH from the radially inner end of the tire radial region that forms the tire cross-sectional height SH in the reference state. Compared to the case shown in Fig. 12B, the tire radial region that can be protected from external damage by the carcass folded-up portion is further enlarged, thereby further improving the tire's resistance to external damage. In this case, a so-called envelope structure can be used in which the end of the carcass folded-up portion is located inward in the tire width direction from the end in the tire width direction of the widest belt layer that has the largest width in the tire width direction among the one or more belt layers, and this can particularly improve the external damage resistance of the tire. Here, in a cross section in the tire width direction in the above-mentioned reference state, the gauge of the sidewall rubber measured from the tire outer surface at the tire maximum width position in the normal direction to the contour line of the tire outer surface is preferably 0.5 to 5 mm. When transmitting power from the transmitting coil to the receiving coil by electromagnetic induction, it is possible to make the gauge relatively thin, between 0.5 and 5 mm, in order to reduce the amount of magnetic flux obstructed by the sidewall rubber and to reduce the tire weight. However, it has been discovered that in such cases, damage to components such as the carcass main body and the receiving coil can become a significant problem. Therefore, when the gauge is 5 mm or less, having a carcass folded portion (for example, as shown in each of the above examples) is particularly effective in increasing the tire's resistance to external damage. From the viewpoint of generating appropriate deflection and the like in the sidewall portion of a tire, the gauge is preferably set to 1.0 mm or more.

[0069] The tire 10 also includes a pair of bead portions and a carcass consisting of one or more carcass plies toroidally straddling the pair of bead portions. The cords of the carcass ply are made of organic fiber, and the end count of the cords of the carcass ply is preferably 10 to 50 per 50 mm. If the end count of the cords of the carcass ply exceeds 50 per 50 mm, the rate at which strain between the cords develops increases, which may result in a breakdown. On the other hand, if the end count of the cords of the carcass ply is less than 10 per 50 mm, rubber has a lower magnetic permeability than organic fiber and is likely to obstruct the magnetic flux from the power transmission coil 31, resulting in a decrease in power receiving efficiency. In contrast, by setting the end count of the cords of the carcass ply within the above range, it is possible to improve power receiving efficiency while also improving tire durability. Here, it may be preferable for the cord count of the carcass ply to be 15 to 45 per 50 mm. For example, in a tire-wheel assembly used for autonomous driving, the strength of the carcass as a tire frame does not need to be particularly high to be sufficient for the vehicle to run, and improved power receiving efficiency is particularly desired. Therefore, by setting the cord count of the carcass ply to 15 per 50 mm or more, high power receiving efficiency can be achieved, while by setting the cord count of the carcass ply to 45 per 50 mm or less, tire durability can be further improved while sufficient tire running performance can be ensured. A tire-wheel assembly used for autonomous driving may be equipped with, for example, an in-wheel motor. As the organic fiber, for example, aramid fiber, PET fiber, nylon fiber, etc. can be used.

[0070] The inventors have conducted research and found that it is preferable to protect the tire components and the power receiving coil from external damage, particularly when the tire has an aspect ratio of 75% or less. Therefore, as shown in FIG. 13 , it is preferable that the aspect ratio of the tire 10 is 75% or less and that a side reinforcing rubber 60 is disposed on the sidewall portion 12 of the tire 10. In this example, because the aspect ratio of the tire 10 is 75% or less, the distance between the ground contact surface and the wheel 20 is shorter (relatively compared to tires with a larger aspect ratio). For this reason, when the tire deforms significantly, for example when running over a curb, a large load may be applied to the wheel 20. In contrast, in this embodiment, the side reinforcing rubber 60 is disposed on the sidewall portion 12 of the tire 10, and the side reinforcing rubber 60 reinforces the sidewall portion 12 of the tire, thereby reducing the load on the wheel 20. In particular, when the power receiving coil 31 is provided on the rim portion, damage to the power receiving coil 31 can be suppressed. In this way, external damage resistance can be improved. Here, the aspect ratio of the tire is preferably 70% or less, more preferably 65% ​​or less, even more preferably 60% or less, and particularly preferably 55% or less, because the problem of a large load being applied to the wheel as described above becomes more pronounced, and therefore, as described above, it is particularly effective to arrange side reinforcing rubber in the sidewall portion of the tire 10 to reduce the load on the wheel. Here, the tire preferably includes a pair of bead portions and a carcass toroidally straddling the pair of bead portions, and the side reinforcing rubber is preferably disposed between the carcass and the tire inner surface (inner liner in the illustrated example) in the tire width direction, thereby protecting the carcass with the side reinforcing rubber and improving the tire's resistance to external damage. In addition, it is preferable that the side reinforcing rubber has a crescent-shaped cross section in a cross section in the tire width direction, so that the side reinforcing rubber can take on the load in the event of a tire puncture, allowing the tire to continue running.

[0071] According to the inventor's investigation, run-flat durability is considered to be required even in the technology using the electromagnetic induction system. 13, it is preferable that the sidewall portion 12 of the tire 10 is provided with a side reinforcing rubber 60, and in the above-mentioned standard state, the inner end of the side reinforcing rubber 60 in the tire width direction is located more inward in the tire width direction than the ground contact edge E. This allows the side reinforcing rubber 60 to fully exert its effect of shouldering the load when the tire is punctured, thereby improving run-flat durability. Here, it is preferable that the inner end of the side reinforcing rubber in the tire width direction is located 3 mm or more inward from the ground contact edge in the tire width direction. This is because run-flat durability can be further improved. For the same reason, it is more preferable that the inner end of the side reinforcing rubber in the tire width direction is located 5 mm or more inward from the ground contact edge in the tire width direction. On the other hand, from the viewpoint of suppressing a decrease in power receiving efficiency due to the side reinforcing rubber interfering with magnetic flux, it is preferable that the inner end of the side reinforcing rubber in the tire width direction is located within a range of 20 mm or less inward from the ground contact edge in the tire width direction. Here, it is preferable that the tire includes a pair of bead portions and a carcass toroidally straddling the pair of bead portions, and the side reinforcing rubber is disposed between the carcass and the tire inner surface in the tire width direction, thereby protecting the carcass with the side reinforcing rubber and improving the tire's resistance to external damage. In addition, it is preferable that the side reinforcing rubber has a crescent-shaped cross section in a cross section in the tire width direction, because this is suitable for running when the tire has a flat by taking over the load of the tire.

[0072] 14, it is also preferable that the sidewall portion 12 of the tire 10 is provided with a side reinforcing rubber 60, and in the above-mentioned reference state, the inner end of the side reinforcing rubber 60 in the tire width direction is located at the tire width direction position of the ground contact edge E or outward in the tire width direction from the ground contact edge E. This prevents the magnetic flux from being obstructed by the side reinforcing rubber 60 when transmitting power from the power transmitting coil 41 to the power receiving coil 31 via the ground contact surface. This can suppress a decrease in power receiving efficiency. Here, it is preferable that the inner end of the side reinforcing rubber in the tire width direction is located 3 mm or more outward from the ground contact edge in the tire width direction. This is because this can further suppress a decrease in power receiving efficiency. For the same reason, it is more preferable that the inner end of the side reinforcing rubber in the tire width direction is located 5 mm or more outward from the ground contact edge in the tire width direction. On the other hand, from the viewpoint of improving run-flat performance, it is preferable that the inner end of the side reinforcing rubber in the tire width direction is located 20 mm or less outward from the ground contact edge in the tire width direction. Here, it is preferable that the tire includes a pair of bead portions and a carcass toroidally straddling the pair of bead portions, and the side reinforcing rubber is disposed between the carcass and the tire inner surface in the tire width direction, thereby protecting the carcass with the side reinforcing rubber and improving the tire's resistance to external damage. In addition, it is preferable that the side reinforcing rubber has a crescent-shaped cross section in a cross section in the tire width direction, because this is suitable for running when the tire has a flat by taking over the load of the tire.

[0073] The inventors have conducted research and found that in technology using the electromagnetic induction method, it is necessary to ensure power receiving efficiency not only during normal driving but also during run-flat driving. Therefore, as shown in FIG. 13 , the sidewall portion 12 of the tire 10 is provided with a side reinforcing rubber 60, and in the reference state, the width w of the side reinforcing rubber 60 in the tire width direction at the tire's maximum width position is preferably 4 mm or more and 12 mm or less. If the width w is less than 4 mm, the tire may not be able to fully shoulder and support the load during run-flat driving, causing the tire to flex, which may result in the position of the power receiving coil 31 becoming too close to the road surface (for example, from a state designed to maximize power receiving efficiency based on normal driving), resulting in reduced power receiving efficiency. On the other hand, if the width w exceeds 12 mm, the side reinforcing rubber may obstruct magnetic flux during power supply during normal driving, reducing power receiving efficiency. In contrast, by setting the width w to 4 mm or more and 12 mm or less, power receiving efficiency can be achieved both during normal driving and during run-flat driving. Here, in the reference state, the width w of the side reinforcing rubber in the tire width direction at the tire radial position of the tire's widest point is preferably 6 mm or more and 10 mm or less. By making the width w 6 mm or more, it is possible to sufficiently shoulder and support the load during run-flat driving, suppressing fluctuations in the distance between the power receiving coil and the road surface (from normal driving), and further suppressing a decrease in power receiving efficiency during run-flat driving. Furthermore, by making the width w 10 mm or less, magnetic flux is less obstructed by the side reinforcing rubber during power supply during normal driving, and further suppressing a decrease in power receiving efficiency during normal driving. For the same reason, it is more preferable that the width w be 7 mm or more and 9 mm or less. Here, it is preferable that the tire includes a pair of bead portions and a carcass toroidally straddling the pair of bead portions, and the side reinforcing rubber is disposed between the carcass and the tire inner surface in the tire width direction, thereby protecting the carcass with the side reinforcing rubber and improving the tire's resistance to external damage. In addition, it is preferable that the side reinforcing rubber has a crescent-shaped cross section in a cross section in the tire width direction, because this is suitable for running when the tire has a flat by taking over the load of the tire.

[0074] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, in the present invention, the vehicle 2 has been described as an automobile, but this is not limited thereto. The vehicle 2 may include any vehicle whose wheels and tires are driven by a power source such as a motor, such as an agricultural vehicle such as a tractor, a construction vehicle such as a dump truck, an electric bicycle, or an electric wheelchair, in addition to automobiles such as passenger cars, trucks, buses, and motorcycles. Furthermore, the vehicle 2 may be electrically driven or may be a power source for use within the vehicle.

[0075] For example, in the present invention, the tire is described as being filled with air, but this is not limited thereto. For example, the tire can be filled with a gas such as nitrogen. For example, the tire can be filled with any fluid, including not only gas but also liquid, gel-like substance, or powder or granular material.

[0076] Furthermore, for example, in the present invention, the tire has been described as a tubeless tire having an inner liner, but this is not limiting, and the tire may be, for example, a tube-type tire having a tube.

[0077] In addition, for example, in the present invention, the tire may be a non-pneumatic tire. In this case, too, the power receiving coil may be disposed in a position that allows it to face the power transmitting coil.

[0078] In particular, the present invention is preferably a tire having a contact patch width of 120 mm or more. [Explanation of symbols]

[0079] 1: Wireless power receiving system; 2: Vehicle; 2A: Hub, 2B: Drive shaft, 3: tire-wheel assembly, 4: in-wheel motor, 10: tire; 11: bead portion; 12: Sidewall portion, 13: Tread portion, 13a: Tread surface, 14: Carcass; 14A: Carcass main body; 14B: Carcass folded-back portion; 15: Belt, 16: Inner liner, 17: circumferential main groove, 19: interlayer rubber, 20: Wheel, 21: Rim part, 22: disc portion; 22A: mounting portion; 22B: spokes; 23: flange, 24: bead seat, 25: well, 26: Hump, 27: Valve, 28: Wheel cover, 30: power receiving device; 31: power receiving coil; 32: power conversion circuit; 33: power storage unit; 34: control unit; 40: power transmission device; 41: power transmission coil; 60: Side reinforcement rubber

Claims

1. A tire-wheel assembly including a tire and a wheel having a rim portion, The tire is a passenger vehicle tire, The tire is mounted on the rim portion, the tire-wheel assembly includes a power receiving coil; The tire has a belt consisting of one or more belt layers, When the tire-wheel assembly is inflated to a specified internal pressure and a maximum load is applied, the outermost point in the tire width direction of the contact surface in a loaded state is defined as a contact edge E, In a standard state where the tire-wheel assembly is filled with a specified internal pressure and is unloaded, a width W1 in the tire width direction of a minimum width belt layer that has the smallest width in the tire width direction among the one or more belt layers is smaller than a contact width W2 that is a distance in the tire width direction between the contact ends E, The ratio W1 / W2 is 0.98 or less, the power receiving coil is attached to the rim portion, the power receiving coil is positioned so as to face a power transmitting coil placed on a road surface, such that when the power transmitting coil and the power receiving coil face each other, an AC magnetic field generated upward from the power transmitting coil crosses the tread portion of the tire and reaches the power receiving coil, generating an electromotive force in the power receiving coil, causing a current to flow and supplying power.

2. 2. The tire-wheel assembly according to claim 1, wherein the ratio W1 / W2 is equal to or less than 0.

9.

3. 3. The tire-wheel assembly according to claim 2, wherein the ratio W1 / W2 is equal to or less than 0.7.

Images