Non-pneumatic tires

Abstract

To provide a non-pneumatic tire which suppresses exposure of a reinforcement layer and can maintain rigidity even after being retreaded.SOLUTION: A non-pneumatic tire includes a support structure, and a tread 50 which is positioned outside in a tire radial direction of the support structure and extends in a tire circumferential direction. The support structure includes an inner annular part, an outer annular part 30 which is arranged coaxially with the inner annular part outside in the tire radial direction in the inner annular part, and contains a resin, and a plurality of spokes which connect the inner annular part and the outer annular part 30 and are arrayed in the tire circumferential direction. The outer annular part 30 includes a first colored layer 31 which extends in the tire circumferential direction and exhibits a polishing limit, and a reinforcement layer 32 which is provided inside in the tire radial direction of the first colored layer 31, and extends in the tire circumferential direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a non-pneumatic tire. [Background technology]

[0002] A non-pneumatic tire has been known that includes a support structure containing resin and that supports a load from a vehicle, and a tread that is located radially outward of the support structure and extends along the tire circumferential direction. The support structure includes an inner annular portion, an outer annular portion that is disposed coaxially with the inner annular portion and radially outward of the inner annular portion, and a plurality of spokes that connect the inner and outer annular portions and are arranged along the tire circumferential direction. The outer annular portion is also provided radially inward of the tire and includes a reinforcing layer that extends along the tire circumferential direction.

[0003] On the other hand, it is known to retread used pneumatic tires, that is, to remove the tread from the pneumatic tire by buffing, and then apply a new tread.

[0004] However, when a used pneumatic tire is retreaded, the belt layer is exposed and the peeling resistance of the tread of the retreaded tire is reduced.

[0005] Therefore, Patent Document 1 describes disposing an identification layer made of rubber of a different color from the rubber constituting the tread at a predetermined position in the tire width direction between the belt layer and the tread of the pneumatic tire. Also, Patent Document 2 describes changing the position where the tread is attached in the tire radial direction as the number of times the pneumatic tire is retreaded increases. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-020508 [Patent Document 2] Patent No. 6000516 Summary of the Invention [Problem to be solved by the invention]

[0007] However, as used non-pneumatic tires are retreaded more and more frequently, the outer annular portion is abraded beyond the abrasion limit, which results in the reinforcing layer of the retreaded non-pneumatic tire being exposed or the tire's rigidity being reduced, leading to tread separation or breakage of the outer annular portion.

[0008] An object of the present invention is to provide a non-pneumatic tire that can suppress exposure of a reinforcing layer and maintain rigidity even after retreading. [Means for solving the problem]

[0009] One aspect of the present invention is a non-pneumatic tire comprising a support structure and a tread located radially outward of the support structure and extending circumferentially of the tire, wherein the support structure comprises an inner annular portion, an outer annular portion arranged coaxially with the inner annular portion and radially outward of the inner annular portion, the outer annular portion comprising a resin, and a plurality of spokes connecting the inner annular portion and the outer annular portion and arranged circumferentially of the tire, and the outer annular portion comprises a first colored layer extending circumferentially of the tire and indicating a polishing limit, and a reinforcing layer located radially inward of the first colored layer and extending circumferentially of the tire.

[0010] The outer annular portion may further include at least one colored layer located radially outward of the first colored layer and extending along the tire circumferential direction, the colored layer being colored a different color from the first colored layer.

[0011] The first colored layer and the at least one colored layer may be exposed in the tire width direction. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a non-pneumatic tire that can suppress exposure of the reinforcing layer and maintain rigidity even after retreading. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a side view showing a non-pneumatic tire according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1 showing the structure of the outer annular portion and the tread. [Figure 3] 3 is a cross-sectional view showing a modified example of the outer annular portion of FIG. 2. FIG. [Figure 4] FIG. 2 is a cross-sectional view taken along line II-II of FIG. [Figure 5] FIG. 5 is a partial perspective view of the non-pneumatic tire, as seen obliquely from the portion shown in FIG. 4. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0015] FIG. 1 shows a non-pneumatic tire of this embodiment. The non-pneumatic tire 1 includes a support structure 10 and a tread 50. The support structure 10 includes a resin and supports a load from a vehicle. The tread 50 is located outward of the support structure 10 in the tire radial direction X and extends along the tire circumferential direction C. The support structure 10 also includes an inner annular portion 20, an outer annular portion 30 disposed coaxially with the inner annular portion 20 and outward of the inner annular portion 20 in the tire radial direction X, and a plurality of spokes 40 connecting the inner annular portion 20 and the outer annular portion 30 and arranged along the tire circumferential direction C. Details of the structure of the non-pneumatic tire 1 will be described later.

[0016] 2 shows the structure of the outer annular portion 30. The outer annular portion 30 includes a first colored layer 31 extending along the tire circumferential direction C and indicating a grinding limit, and a reinforcing layer 32 provided inward in the tire radial direction X from the first colored layer 31 and extending along the tire circumferential direction C. This prevents the outer annular portion 30 from being ground beyond the grinding limit, even if the number of times a used non-pneumatic tire 1 is retreaded increases. As a result, exposure of the reinforcing layer 32 of the retreaded non-pneumatic tire 1 is suppressed and rigidity is maintained, thereby suppressing separation of the tread 50 and breakage of the outer annular portion 30.

[0017] Here, the polishing limit is the limit at which polishing is possible without exposing the reinforcing layer 32. The reinforcing layer 32 extends along the tire circumferential direction, contains fiber-reinforced plastic, and is disposed more inward in the tire radial direction X than the first colored layer 31. The presence of the reinforcing layer 32 suppresses the occurrence of buckling, in which the outer annular portion 30 bends in the tire radial direction X at the center in the tire width direction Y. As a result, the rigidity of the non-pneumatic tire 1 is ensured, and the contact of the tread 50 with the road surface is improved.

[0018] The position where the first colored layer 31 is disposed is not particularly limited, as long as it is located outside the reinforcing layer 32 in the tire radial direction X. In FIG. 2 , the first colored layer 31 is provided over the entire area of ​​the outer annular portion 30 in the tire width direction Y, i.e., exposed in the tire width direction Y. However, it does not have to be provided over the entire area of ​​the outer annular portion 30 in the tire width direction Y. When the first colored layer 31 is exposed in the tire width direction Y, the grinding limit can be visually confirmed from both sides of the non-pneumatic tire 1 in the tire width direction Y without grinding the outer annular portion 30. In this case, the ratio of the width of the first colored layer 31 to the width of the outer annular portion 30 is preferably 50% or more, and more preferably 70% or more, taking into consideration visibility and deformation of the outer annular portion 30 during driving. When the ratio of the width of the first colored layer 31 to the width of the outer annular portion 30 is 50% or more, grinding of the outer annular portion 30 beyond the grinding limit is more likely to be prevented, even if the number of times a used non-pneumatic tire 1 is retreaded increases.

[0019] The first colored layer 31 is not particularly limited and contains, for example, a resin and a pigment. The resin is not particularly limited and examples thereof include silicone resin, urethane resin, and epoxy resin. The resin contained in the first colored layer 31 may be the same as or different from the resin contained in the outer annular portion 30. The pigment contained in the first colored layer 31 is not particularly limited as long as it can be colored a color (for example, red) that allows the polishing limit to be visually recognized.

[0020] The thickness of the first colored layer 31, i.e., its length in the tire radial direction X, is preferably 0.5 mm or more and 5 mm or less, and more preferably 1 mm or more and 3 mm or less. If the thickness of the first colored layer 31 is 0.5 mm or more, the outer annular portion 30 is less likely to be polished beyond the polishing limit even if the number of times a used non-pneumatic tire 1 is retreaded increases. On the other hand, if the thickness of the first colored layer 31 is 5 mm or less, the number of times a used non-pneumatic tire 1 is retreaded increases.

[0021] The fiber reinforced plastic contained in the reinforcing layer 32 is not particularly limited, but examples thereof include carbon fiber reinforced plastic, glass fiber reinforced plastic, etc. Among these, CFRP is preferable.

[0022] The thickness of the reinforcing layer 32 is not particularly limited, but is, for example, 1 mm or more and 4 mm or less. The distance between the first colored layer 31 and the reinforcing layer 32, i.e., the distance in the tire radial direction X, is not particularly limited, but is, for example, 1 mm or more and 3 mm or less.

[0023] The position where the reinforcing layer 32 is disposed is not particularly limited as long as it is located more inward in the tire radial direction X than the first colored layer 31. Although the reinforcing layer 32 is provided over the entire area in the tire width direction Y in FIG. 2 , it does not have to be provided over the entire area in the tire width direction Y.

[0024] The resin contained in the outer annular portion 30 is not particularly limited, but examples thereof include thermoplastic elastomers, cross-linked rubbers, and other resins. Among these, urethane resins are preferred. As the urethane resin, known urethane resins used in the support structure 10 can be used. The resins contained in the inner annular portion 20 and the spokes 40 may be the same as or different from the resin contained in the outer annular portion 30.

[0025] The thickness of the outer annular portion 30 is not particularly limited, but is, for example, 4 mm or more and 15 mm or less.

[0026] The outer annular portion 30 is obtained, for example, by molding each layer sequentially into a cylindrical shape using a mold.

[0027] 3 shows a modified structure of the outer annular portion 30. The outer annular portion 30A is similar to the outer annular portion 30 except that it is colored a different color from the first colored layer 31 and is located further outward in the tire radial direction X than the first colored layer 31, and includes a second colored layer 33 and a third colored layer 34 extending along the tire circumferential direction C and continuing from the first colored layer 31. This makes it possible to visually confirm the amount of grinding of the outer annular portion 30A before it reaches its grinding limit, and as a result, to grasp the number of times a used non-pneumatic tire 1 has been retreaded.

[0028] The second colored layer 33 is similar to the first colored layer 31 except that it is colored a different color (for example, blue) from the first colored layer 31. The third colored layer 34 is similar to the first colored layer 31 except that it is colored a different color (for example, green) from the first colored layer 31. The resins contained in the first colored layer 31, the second colored layer 33, and the third colored layer 34 may be the same or different. The number of colored layers colored a different color from the first colored layer 31 is not particularly limited.

[0029] The non-pneumatic tire 1 is obtained by vulcanizing and bonding the support structure 10 and the rubber composition for the tread together using, for example, a vulcanization adhesive.

[0030] The rubber composition for a tread is not particularly limited, but for example, contains natural rubber and carbon black, and may further contain sulfur, silica, etc. Here, the rubber composition for a tread may contain synthetic rubber such as polyisoprene rubber or styrene-butadiene rubber together with or instead of natural rubber.

[0031] When retreading a used non-pneumatic tire 1, the tread 50 is removed from the non-pneumatic tire 1, for example, by buffing, and then the support structure 10 and the rubber composition for the tread are vulcanized and bonded together using a vulcanizing adhesive.

[0032] The structure of the non-pneumatic tire 1 (see FIG. 1) will be described in detail below. FIG. 1 is a side view of the non-pneumatic tire 1 of this embodiment, viewed from the side in a direction parallel to the tire rotation axis (tire meridian), i.e., in a direction along the front-to-back direction of the paper in FIG. 1. The non-pneumatic tire 1 shown in FIG. 1 is in an unloaded state. FIG. 4 is a cross-sectional view taken along II-II in FIG. 1. FIG. 5 is a partial perspective view of the non-pneumatic tire 1, when the portion shown in FIG. 4 is viewed obliquely.

[0033] In Fig. 1 and Fig. 5, arrow C indicates the tire circumferential direction. In Fig. 1, Fig. 4, and Fig. 5, arrow X indicates the tire radial direction. In Fig. 4 and Fig. 5, arrow Y indicates the tire width direction. In Fig. 1, the tire width direction Y is the front-to-back direction of the page. In Fig. 4, symbol E is the tire equatorial plane. In Fig. 4, the tire circumferential direction C is the front-to-back direction of the page.

[0034] The tire circumferential direction C is a direction around the tire rotational axis and is the same direction as the rotational direction of the non-pneumatic tire 1. The tire radial direction X is a direction perpendicular to the tire rotational axis. The tire width direction Y is a direction parallel to the tire rotational axis. In FIGS. 4 and 5, one side of the tire width direction Y is indicated as Y1, and the other side of the tire width direction Y is indicated as Y2. The tire equatorial plane E shown in FIG. 4 is a plane perpendicular to the tire rotational axis and located at the center of the tire width direction Y.

[0035] In the following description, the thickness of the inner annular portion 20 and the outer annular portion 30 refers to the dimension in the tire radial direction X. The width of the inner annular portion 20 and the outer annular portion 30 refers to the dimension in the tire width direction Y shown in FIG.

[0036] The inner annular portion 20 is an annular portion along the tire circumferential direction C that constitutes the inner circumferential portion of the non-pneumatic tire 1. The thickness and width of the inner annular portion 20 are set to be constant to improve uniformity. A tire wheel (not shown) is placed in the space on the inner circumferential side of the inner annular portion 20. The inner circumferential portion of the inner annular portion 20 is fitted onto the outer circumferential portion of the rim of the tire wheel. The inner annular portion 20 is fitted onto the rim, and the non-pneumatic tire 1 is then fitted onto the tire wheel. The inner circumferential surface of the inner annular portion 20 may be provided with a fitting portion consisting of a protrusion, a groove, etc. for fitting with the rim.

[0037] The inner annular portion 20 can be made of, for example, a resin material having elasticity, but the material is not limited to resin.

[0038] The inner annular portion 20 transmits the rotation of the tire wheel to the spokes 40 and the outer annular portion 30. The thickness of the inner annular portion 20 is determined from the viewpoint of achieving light weight and durability while fulfilling the function of sufficiently transmitting rotational force to the spokes 40. The thickness of the inner annular portion 20 is not particularly limited, but is preferably 2% to 7% of the tire cross-sectional height H shown in FIG. 4, for example, and more preferably 3% to 6%.

[0039] The inner diameter of the inner annular portion 20 is determined depending on the dimensions of the rim of the tire wheel on which the non-pneumatic tire 1 is mounted, the use of the vehicle, etc. For example, when assuming a replacement for a general pneumatic tire, the inner diameter of the inner annular portion 20 may be, for example, a dimension of 250 mm or more and 500 mm or less, but is not limited to this.

[0040] The width of the inner annular portion 20 is determined appropriately depending on the use of the vehicle on which the non-pneumatic tire 1 is mounted, the length of the axle, etc. For example, when assuming a replacement for a general pneumatic tire, the width of the inner annular portion 20 may be, but is not limited to, a dimension of 100 mm or more and 300 mm or less.

[0041] The outer annular portion 30 is an annular portion along the tire circumferential direction C that constitutes the outer periphery of the non-pneumatic tire 1. The outer annular portion 30 is disposed on the outer circumferential side of the inner annular portion 20 and concentric with the inner annular portion 20. The thickness and width of the outer annular portion 30 are set to be constant to improve uniformity.

[0042] The outer annular portion 30 transmits the rotation of the inner annular portion 20 and the spokes 40 to the road surface via the tread 50. The thickness of the outer annular portion 30 is determined from the viewpoint of achieving light weight and durability while also fulfilling the function of sufficiently transmitting rotational force from the spokes 40 to the road surface. The thickness of the outer annular portion 30 is not particularly limited, but is preferably, for example, 2% to 7% of the tire cross-sectional height H shown in FIG. 4, and more preferably 2% to 5%.

[0043] The inner diameter of the outer annular portion 30 is determined appropriately depending on the dimensions of the rim of the tire wheel on which the non-pneumatic tire 1 is mounted, the use of the vehicle, etc. For example, when assuming a replacement for a general pneumatic tire, the inner diameter of the outer annular portion 30 may be, but is not limited to, a dimension of 420 mm or more and 750 mm or less.

[0044] The width of the outer annular portion 30 is determined appropriately depending on the application of the vehicle on which the non-pneumatic tire 1 is mounted, etc. For example, when assuming a replacement for a general pneumatic tire, the width of the outer annular portion 30 may be, but is not limited to, a dimension of 100 mm or more and 300 mm or less.

[0045] The plurality of spokes 40 connect the inner annular portion 20 and the outer annular portion 30. The inner annular portion 20 and the outer annular portion 30, connected by the plurality of spokes 40, are arranged concentrically with each other. The plurality of spokes 40 are arranged independently along the tire circumferential direction C. As shown in FIG. 1 , when the non-pneumatic tire 1 is in an unloaded state, the plurality of spokes 40 extend linearly in the radial direction substantially parallel to the tire radial direction X in a side view.

[0046] As shown in Figures 4 and 5, the multiple spokes 40 of this embodiment include multiple first spokes 41 and multiple second spokes 42. The extension direction of both the first spokes 41 and the second spokes 42 is not parallel to the tire radial direction X when viewed in a direction along the tire circumferential direction C. The first spokes 41 are inclined toward one side in the tire axial direction, i.e., the tire width direction Y. The second spokes 42 are inclined toward the opposite side to the first spokes 41. The first spokes 41 and the second spokes 42 are arranged alternately in the tire circumferential direction C.

[0047] 4 and 5, the first spokes 41 extend at an angle from the Y1 side, which is one side in the tire width direction Y of the outer annular portion 30, toward the Y2 side, which is the other side in the tire width direction Y of the inner annular portion 20. The second spokes 42 extend at an angle from the Y2 side, which is the other side in the tire width direction Y of the outer annular portion 30, toward the Y1 side, which is one side in the tire width direction Y of the inner annular portion 20.

[0048] The inclination angles of the first spokes 41 and the second spokes 42 are the same. Therefore, the first spokes 41 and the second spokes 42 that are adjacent in the tire circumferential direction C are arranged in a substantially X-shape when viewed from a direction along the tire circumferential direction C. As shown in FIG. 4 , the first spokes 41 and the second spokes 42 are inclined at an angle θ with respect to the tire width direction Y, and the angle θ is preferably, for example, equal to or greater than 30° and equal to or less than 60°.

[0049] As shown in Fig. 4, the first spokes 41 and the second spokes 42 have the same shape as each other and are symmetrical with respect to the tire equatorial plane E when viewed in the direction along the tire circumferential direction C. Therefore, in the following, when there is no need to distinguish between the first spokes 41 and the second spokes 42 and they can be described together, the first spokes 41 and the second spokes 42 will be collectively referred to as spokes 40.

[0050] The spokes 40 are plate-shaped and extend obliquely at the angle θ from the inner annular portion 20 toward the outer annular portion 30 as described above. As shown in FIG. 5 , the thickness t of the spokes 40 along the tire circumferential direction is smaller than the width w, and the direction of the thickness t is along the tire circumferential direction C. That is, the spokes 40 are formed in a plate shape extending in a plane of the tire radial direction X and the tire width direction Y. Note that the width w here refers to the dimension in a direction perpendicular to the oblique direction in which the spokes 40 extend when viewed from a direction along the tire circumferential direction C, as also shown in FIG. 4 . In this embodiment, all of the spokes 40 have the same thickness t. All of the spokes 40 also have the same width w.

[0051] Because the spokes 40 are long and plate-shaped, the durability of the spokes 40 can be improved by widening the plate width w even if the plate thickness t is thin. Furthermore, by thinning the plate thickness t and increasing the number of spokes 40, the distance between adjacent spokes 40 in the tire circumferential direction C can be reduced while maintaining the rigidity of the entire non-pneumatic tire 1. This distributes the ground contact pressure when the tire rolls through the spokes 40, thereby reducing the ground contact pressure.

[0052] Although the spokes 40 in this embodiment are parallel to the tire radial direction X in a side view, the spokes 40 may be disposed obliquely with respect to the tire radial direction X so as to intersect with the tire radial direction X in a side view.

[0053] 4 and 5 , the first spoke 41 has a first inner connection portion 411 connected to the tire width direction Y2 side of the inner annular portion 20, and a first outer connection portion 412 connected to the tire width direction Y1 side of the outer annular portion 30. The second spoke 42 has a second inner connection portion 421 connected to the tire width direction Y1 side of the inner annular portion 20, and a second outer connection portion 422 connected to the tire width direction Y2 side of the outer annular portion 30. The first outer connection portion 412 and the second outer connection portion 422 are each an example of a connection portion of the spoke 40 connected to the outer annular portion 30 in this embodiment.

[0054] 4, the first inner connection portion 411 of the first spoke 41 has a shape that widens in the tire width direction Y as it approaches the inner annular portion 20. A side surface 411a on the tire width direction Y2 side of the first inner connection portion 411 extends while gently curving to an end portion 20b of the inner annular portion 20 on the tire width direction Y2 side. A side surface 411b on the tire width direction Y1 side of the first inner connection portion 411 extends while curving toward the tire width direction Y1 side to the position of the tire equatorial plane E of the inner annular portion 20.

[0055] The first outer connection portion 412 of the first spoke 41 has a shape similar to that of the first inner connection portion 411, and has a shape that widens in the tire width direction as it approaches the outer annular portion 30. A side surface 412a on the tire width direction Y1 side of the first outer connection portion 412 extends in a gently curved manner to an end portion 30a of the outer annular portion 30 on the tire width direction Y1 side. A side surface 412b on the tire width direction Y2 side of the first outer connection portion 412 extends in a curved manner toward the tire width direction Y2 to the position of the tire equatorial plane E of the outer annular portion 30.

[0056] The first inner connecting portion 411 is provided in a half region on the tire width direction Y2 side of the inner annular portion 20. The first outer connecting portion 412 is provided in a half region on the tire width direction Y1 side of the outer annular portion 30.

[0057] 4, the second inner connection portion 421 of the second spoke 42 has a shape that widens in the tire width direction Y as it approaches the inner annular portion 20. A side surface 421a on the tire width direction Y1 side of the second inner connection portion 421 extends in a gently curved manner to an end portion 20a of the inner annular portion 20 on the tire width direction Y1 side. A side surface 421b on the tire width direction Y2 side of the second inner connection portion 421 extends in a curved manner toward the tire width direction Y2 to the position of the tire equatorial plane E of the inner annular portion 20.

[0058] The second outer connection portion 422 of the second spoke 42 has a shape similar to that of the second inner connection portion 421, and has a shape that widens in the tire width direction as it approaches the outer annular portion 30. A side surface 422a on the tire width direction Y2 side of the second outer connection portion 422 extends in a gently curved manner to an end portion 30b of the outer annular portion 30 on the tire width direction Y2 side. A side surface 422b on the tire width direction Y1 side of the second outer connection portion 422 extends in a curved manner toward the tire width direction Y1 side to the position of the tire equatorial plane E of the outer annular portion 30.

[0059] The second inner connecting portion 421 is provided in a half region on the tire width direction Y1 side of the inner annular portion 20. The second outer connecting portion 422 is provided in a half region on the tire width direction Y2 side of the outer annular portion 30.

[0060] As described above, in this embodiment, all of the spokes 40 have the same thickness t. The dimension of the thickness t is not particularly limited, but is preferably 1 mm or more and 30 mm or less, and more preferably 5 mm or more and 25 mm or less, so that the spokes 40 can fully receive the rotational force from the inner annular portion 20 and the outer annular portion 30 and can be appropriately flexibly deformed when subjected to a load.

[0061] As described above, all spokes 40 in this embodiment have the same width w. The width w of the spokes 40 is not particularly limited, but is preferably 5 mm to 25 mm, more preferably 10 mm to 20 mm, so as to be able to adequately withstand rotational forces from the inner annular portion 20 and the outer annular portion 30 while also being able to flex appropriately when subjected to a load. Furthermore, the width w is preferably 110% or more of the thickness t, more preferably 115% or more, so as to be able to distribute ground pressure while improving durability.

[0062] The number of spokes 40 is preferably 80 to 300, and more preferably 100 to 200, from the viewpoint of being able to adequately support the load from the vehicle while being lightweight and achieving both improved power transmission and durability.

[0063] The spokes 40 can be made of any of the following elastic materials. First, in terms of the properties of the elastic material, from the viewpoint of imparting appropriate rigidity while ensuring sufficient durability, it is preferable that the tensile modulus calculated from the tensile stress at 10% elongation in a tensile test conducted in accordance with JIS K7312:1996 be 3 MPa or more and 12 MPa or less.

[0064] If the tensile modulus of the spokes 40 calculated from the tensile stress at 10% elongation is less than 3 MPa, sufficient rigidity cannot be obtained, and there is a possibility that adjacent spokes 40 in the tire circumferential direction C may come into contact with each other. On the other hand, if the tensile modulus calculated from the tensile stress at 10% elongation exceeds 12 MPa, the rigidity becomes excessively high, resulting in a deterioration in ride comfort.

[0065] The elastic material used as the base material of the spokes 40 may be a thermoplastic elastomer, a crosslinked rubber, or other resin.

[0066] Examples of thermoplastic elastomers include polyester elastomers, polyolefin elastomers, polyamide elastomers, polystyrene elastomers, polyvinyl chloride elastomers, and polyurethane elastomers.

[0067] The rubber material constituting the crosslinked rubber can be either natural rubber or synthetic rubber. Examples of synthetic rubber include styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IIR), nitrile rubber (NBR), hydrogenated nitrile rubber (hydrogenated NBR), chloroprene rubber (CR), ethylene propylene rubber (EPDM), fluororubber, silicone rubber, acrylic rubber, and urethane rubber. Two or more of these rubber materials may be used in combination as needed.

[0068] Other resins include thermoplastic resins and thermosetting resins. Thermoplastic resins include polyethylene resins, polystyrene resins, polyvinyl chloride resins, etc. Thermosetting resins include epoxy resins, phenolic resins, polyurethane resins, silicone resins, polyimide resins, melamine resins, etc.

[0069] Of the above elastic materials, urethane resin is preferably used for the spokes 40 from the viewpoints of moldability, processability, and cost. However, foamed materials can also be used as the elastic material. That is, foamed materials made from the above thermoplastic elastomers, crosslinked rubber, and other resins can be used.

[0070] The elastic material used as the base material of the spokes 40 may be reinforced with reinforcing fibers. Examples of reinforcing fibers include long fibers, short fibers, woven fabrics, and nonwoven fabrics. Examples of reinforcing fibers include rayon cords, polyamide cords such as nylon-6,6, polyester cords such as polyethylene terephthalate, aramid cords, glass fiber cords, carbon fibers, and steel cords.

[0071] The reinforcement of the elastic material is not limited to reinforcement with reinforcing fibers. For example, reinforcement may be performed by adding granular fillers. Examples of the granular fillers that can be added include carbon black, ceramics such as silica and alumina, and other inorganic fillers.

[0072] Incidentally, it is preferable that the inner annular portion 20 and the outer annular portion 30 are formed from the same resin material as the spokes 40. In this case, the inner annular portion 20, the outer annular portion 30 and the spokes 40 can be integrally molded, for example, by a cast molding method.

[0073] The tread 50 is provided on the outer peripheral surface of the outer annular portion 30 and constitutes the outermost peripheral portion of the non-pneumatic tire 1. The tread 50 is formed by vulcanization bonding the support structure 10 and a rubber composition for a tread. The tread 50 has a tread surface 51 on its outer peripheral surface that comes into contact with the road surface. The tread surface 51 of the tread 50 is provided with a tread pattern formed of a plurality of grooves and land portions, similar to that of a conventional pneumatic tire.

[0074] The tread 50 may be configured by laminating a plurality of vulcanized rubber layers having different components and properties (for example, two or three layers).

[0075] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and the above-described embodiments may be modified as appropriate within the scope of the spirit of the present invention. [Explanation of symbols]

[0076] 1 Non-pneumatic tires 10 Support structure 20 Inner annular portion 20a, 20b end 30, 30A outer annular part 30a, 30b end 31 First colored layer 32 Reinforcement layer 33 Second colored layer 34 Third colored layer 40 spokes 41 First Spoke 42 Second Spoke 411 First inner connection 411a, 411b side 412 first outer connection 412a, 412b side 421 Second inner connection 421a, 421b side 422 Second outer connection 422a, 422b side 50 tread 51 tread C Circumferential direction of tire E Tire equatorial plane O axis center X radial direction of tire Y Tire width direction

Claims

1. A non-pneumatic tire comprising: a support structure; and a tread located radially outward of the support structure and extending along a tire circumferential direction, the support structure includes an inner annular portion, an outer annular portion that is disposed coaxially with the inner annular portion and outward in the tire radial direction from the inner annular portion and that contains a resin, and a plurality of spokes that connect the inner annular portion and the outer annular portion and are arranged along the tire circumferential direction, the outer annular portion includes a first colored layer extending along the tire circumferential direction and indicating a polishing limit, and a reinforcing layer provided radially inward of the first colored layer and extending along the tire circumferential direction, A non-pneumatic tire, wherein the distance between the first colored layer and the reinforcing layer is 1 mm or more.

2. 2. The non-pneumatic tire according to claim 1, wherein the outer annular portion further includes at least one colored layer that is colored a different color from the first colored layer and extends along the tire circumferential direction, and is located radially outward of the first colored layer.

3. The non-pneumatic tire according to claim 2 , wherein the first colored layer and the at least one colored layer are exposed in the tire width direction.

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