Airless tire

Abstract

To provide an airless tire in which the shape change of a tread ring caused by cooling after vulcanization molding is suppressed, and which therefore enables improvement of durability performance thereof.SOLUTION: An airless tire 1 is provided, comprising: a tread ring 2 having a ground contact surface 2a; a hub 3 disposed inside in a tire radial direction, of the tread ring 2 and fixed to an axle; and a spoke 4 for connecting the tread ring 2 and the hub 3 to each other. The tread ring 2 includes an outside reinforcement layer 6 disposed at the side of the ground contact surface 2a and an inside reinforcement layer 7 disposed inside the outside reinforcement layer 6 in the tire redial direction at intervals. The outside reinforcement layer 6 includes at least one outside ply 8 in which an outside reinforcement cord 8a is disposed, and the inside reinforcement layer 7 includes at least one inside ply 9 in which an inside reinforcement cord 9a is disposed. The angle θ2 of the inside reinforcement cord 9a with respect to a tire circumferential direction is larger than the angle θ1 of the outside reinforcement cord 8a with respect to the tire circumferential direction.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a non-pneumatic tire that can support a load by its own structure without using high-pressure air.

Background Art

[0002] Conventionally, various non-pneumatic tires in which a tread ring and a hub are connected by spokes are known. For example, Patent Document 1 below proposes a non-pneumatic tire including a cylindrical tread ring having a ground contact surface, a hub fixed to an axle, and spokes made of a polymer material.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the tread ring of Patent Document 1, due to cooling after vulcanization molding, the rubber contracts, and the inner peripheral surface of the tread ring may be convexly curved outward in the tire radial direction in the tire meridian cross section. Such a tread ring may be subjected to a force that peels the adhesion surface with the spokes, which may reduce the durability performance of the non-pneumatic tire.

[0005] The present invention has been devised in view of the above actual situation, and the main object thereof is to provide a non-pneumatic tire capable of suppressing the shape change of the tread ring due to cooling after vulcanization molding and improving the durability performance.

Means for Solving the Problems

[0006] The present invention relates to a non-pneumatic tire, comprising a tread ring having a ground contact surface, a hub arranged inside the tread ring in the tire radial direction and fixed to an axle, and spokes for connecting the tread ring and the hub. The tread ring includes an outer reinforcing layer arranged on the side of the ground contact surface and an inner reinforcing layer arranged at a distance inside the outer reinforcing layer in the tire radial direction. The outer reinforcing layer includes at least one outer ply in which outer reinforcing cords are arranged, and the inner reinforcing layer includes at least one inner ply in which inner reinforcing cords are arranged. The angle of the inner reinforcing cords with respect to the tire circumferential direction is larger than the angle of the outer reinforcing cords with respect to the tire circumferential direction.

[0007] In the non-pneumatic tire of the present invention, the outer ply includes a first outer ply arranged on the side of the ground contact surface and a second outer ply arranged adjacent to the first outer ply inside the first outer ply in the tire radial direction. It is desirable that the outer reinforcing cords of the first outer ply and the outer reinforcing cords of the second outer ply are inclined in opposite directions at the same angle with respect to the tire circumferential direction.

[0008] In the non-pneumatic tire of the present invention, the inner ply includes a first inner ply arranged on the side of the spokes and a second inner ply arranged adjacent to the first inner ply outside the first inner ply in the tire radial direction. It is desirable that the inner reinforcing cords of the first inner ply and the inner reinforcing cords of the second inner ply are inclined in opposite directions at the same angle with respect to the tire circumferential direction.

[0009] In the non-pneumatic tire of the present invention, the tread ring includes an outer rubber layer on which the ground contact surface is formed, an inner rubber layer in contact with the spokes, and an intermediate rubber layer arranged between the outer rubber layer and the inner rubber layer. The outer reinforcing layer is preferably arranged between the intermediate rubber layer and the outer rubber layer, and the inner reinforcing layer is preferably arranged between the intermediate rubber layer and the inner rubber layer.

[0010] In the non-pneumatic tire of the present invention, it is desirable that the tread ring includes a pair of sidewall rubbers that connect the outer rubber layer and the inner rubber layer on both sides in the tire axial direction of the intermediate rubber layer, the outer reinforcing layer, and the inner reinforcing layer.

[0011] In the non-pneumatic tire of the present invention, it is desirable that the molding shrinkage rate of the outer rubber layer is larger than that of the intermediate rubber layer.

[0012] In the non-pneumatic tire of the present invention, it is desirable that the thickness of the outer rubber layer in the tire radial direction is larger than the thickness of the inner rubber layer in the tire radial direction.

Advantages of the Invention

[0013] In the non-pneumatic tire of the present invention, the tread ring includes an outer reinforcing layer arranged on the side of the ground contact surface and an inner reinforcing layer arranged at a distance inside the outer reinforcing layer in the tire radial direction. The outer reinforcing layer includes at least one outer ply in which outer reinforcing cords are arranged, and the inner reinforcing layer includes at least one inner ply in which inner reinforcing cords are arranged. The angle of the inner reinforcing cords with respect to the tire circumferential direction is larger than the angle of the outer reinforcing cords with respect to the tire circumferential direction.

[0014] Such a tread ring can suppress the shrinkage in the tire axial direction inside in the tire radial direction due to cooling after vulcanization molding, and can maintain the inner peripheral surface in a flat state in the tire meridian cross-section. Therefore, the non-pneumatic tire of the present invention can suppress the shape change of the tread ring due to cooling after vulcanization molding, improve the adhesiveness with the spoke, and improve the durability performance.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0016] Hereinafter, an embodiment of the present invention will be described in detail based on the drawings. FIG. 1 is a perspective view showing the airless tire 1 of the present embodiment, and FIG. 2 is a side view of the airless tire 1. As shown in FIGS. 1 and 2, the airless tire 1 of the present embodiment includes a tread ring 2 having a ground contact surface 2a, a hub 3 disposed inside the tread ring 2 in the tire radial direction, and a spoke 4 for connecting the tread ring 2 and the hub 3.

[0017] The hub 3 preferably includes a fixing portion 3a fixed to an axle (not shown) of a vehicle. Such an airless tire 1 can support the load acting on the tread ring 2 by the hub 3 and the spoke 4 without using high-pressure air. Therefore, the airless tire 1 of the present embodiment has no risk of puncture.

[0018] The spoke 4 includes, for example, a plurality of plate-shaped spoke plates 5 whose width in the tire axial direction is larger than the thickness in the tire circumferential direction. When a load acts on the tread ring 2, such a spoke 4 can support the load by a tensile force acting on the spoke plate 5 located above the hub 3 and a compressive force acting on the spoke plate 5 located below the hub 3.

[0019] FIG. 3 is a partial cross-sectional perspective view of the tread ring 2 and the spoke 4, and FIG. 4 is a tire meridian cross-sectional view of the tread ring 2. As shown in FIGS. 3 and 4, the tread ring 2 of the present embodiment includes an outer reinforcing layer 6 disposed on the side of the ground contact surface 2a between the ground contact surface 2a and the inner circumferential surface 2b, and an inner reinforcing layer 7 disposed at a distance inside the outer reinforcing layer 6 in the tire radial direction.

[0020] FIG. 5 is a developed plan view showing the internal structure of the tread ring 2. As shown in FIGS. 3 to 5, the outer reinforcing layer 6 of the present embodiment includes at least one outer ply 8 in which outer reinforcing cords 8a are arranged. The inner reinforcing layer 7 of the present embodiment includes at least one inner ply 9 in which inner reinforcing cords 9a are arranged.

[0021] The angle θ2 of the inner reinforcing cord 9a of the present embodiment with respect to the tire circumferential direction is larger than the angle θ1 of the outer reinforcing cord 8a with respect to the tire circumferential direction. Such a tread ring 2 can suppress the shrinkage in the tire axial direction on the inner side in the tire radial direction accompanying the cooling after vulcanization molding, and can maintain the inner peripheral surface 2b in a flat state in the tire meridian cross section. Therefore, the non-pneumatic tire 1 of the present embodiment can suppress the shape change of the tread ring 2 due to the cooling after vulcanization molding, improve the adhesiveness with the spoke 4, and improve the durability performance.

[0022] In a more preferable aspect, the outer ply 8 includes a first outer ply 8A arranged on the side of the ground contact surface 2a, and a second outer ply 8B arranged adjacent to the first outer ply 8A on the inner side in the tire radial direction of the first outer ply 8A.

[0023] The outer reinforcing cord 8a of the first outer ply 8A and the outer reinforcing cord 8a of the second outer ply 8B of the present embodiment are inclined in opposite directions to each other at the same angle θ1 with respect to the tire circumferential direction. The outer reinforcing cord 8a is formed of, for example, a metal cord, an organic fiber cord, or the like. It is desirable that the outer reinforcing cord 8a of the first outer ply 8A and the outer reinforcing cord 8a of the second outer ply 8B are formed of the same material. Such an outer reinforcing layer 6 is excellent in balance in the tire axial direction, and can improve the handling stability performance of the non-pneumatic tire 1.

[0024] The inner ply 9 preferably includes a first inner ply 9A arranged on the side of the inner peripheral surface 2b in contact with the spoke 4, and a second inner ply 9B arranged adjacent to the first inner ply 9A on the outer side in the tire radial direction of the first inner ply 9A.

[0025] The inner reinforcing cords 9a of the first inner ply 9A and the inner reinforcing cords 9a of the second inner ply 9B in this embodiment are inclined in opposite directions to each other at the same angle θ2 with respect to the tire circumferential direction. The inner reinforcing cord 9a is formed of, for example, a metal cord, an organic fiber cord, or the like. It is desirable that the inner reinforcing cords 9a of the first inner ply 9A and the inner reinforcing cords 9a of the second inner ply 9B be formed of the same material. Such an inner reinforcing layer 7 is excellent in balance in the tire axial direction and can improve the handling stability performance of the non-pneumatic tire 1.

[0026] As shown in FIGS. 3 to 5, the tread ring 2 includes an outer rubber layer 10 on which a ground contact surface 2a is formed, an inner rubber layer 11 on which an inner peripheral surface 2b in contact with the spoke 4 is formed, and an intermediate rubber layer 12 disposed between the outer rubber layer 10 and the inner rubber layer 11. Such a tread ring 2 can achieve both the durability performance and the riding comfort performance of the non-pneumatic tire 1 by adjusting the rubber materials of the outer rubber layer 10, the inner rubber layer 11, and the intermediate rubber layer 12.

[0027] The outer reinforcing layer 6 of this embodiment is disposed between the intermediate rubber layer 12 and the outer rubber layer 10. The inner reinforcing layer 7 of this embodiment is disposed between the intermediate rubber layer 12 and the inner rubber layer 11. Such outer and inner reinforcing layers 6 and 7 can increase the rigidity of the tread ring 2 and improve the durability performance and the handling stability performance of the non-pneumatic tire 1.

[0028] The tread ring 2 includes a sidewall rubber 13 that connects the outer rubber layer 10 and the inner rubber layer 11 on at least one side in the tire axial direction of the intermediate rubber layer 12, the outer reinforcing layer 6, and the inner reinforcing layer 7.

[0029] The tread ring 2 of the present embodiment includes a pair of sidewall rubbers 13 that connect the outer rubber layer 10 and the inner rubber layer 11 on both sides in the tire axial direction of the intermediate rubber layer 12, the outer reinforcing layer 6, and the inner reinforcing layer 7. Such a tread ring 2 can improve the durability performance of the airless tire 1 because the intermediate rubber layer 12, the outer reinforcing layer 6, and the inner reinforcing layer 7 are not likely to come into contact with external obstacles or the like.

[0030] The molding shrinkage rate of the outer rubber layer 10 of the present embodiment is larger than that of the intermediate rubber layer 12. Here, the molding shrinkage rate is the ratio at which the rubber shrinks as it cools after vulcanization molding. Such a tread ring 2 helps to suppress the shrinkage in the tire axial direction on the inner side in the tire radial direction due to the cooling after vulcanization molding, and to maintain the inner peripheral surface 2b in a flat state in the tire meridian cross section.

[0031] As shown in FIG. 4, the thickness t1 in the tire radial direction at the tire equator C of the outer rubber layer 10 of the present embodiment is larger than the thickness t2 in the tire radial direction of the inner rubber layer 11. Such a tread ring 2 can create a difference in the shrinkage force due to the difference in thickness even when using rubber materials with the same molding shrinkage rate for the outer rubber layer 10 and the inner rubber layer 11, and helps to maintain the inner peripheral surface 2b in a flat state in the tire meridian cross section.

[0032] As shown in FIGS. 1, 3 to 5, the tread ring 2 has a plurality of, in this embodiment, two circumferential grooves 14 extending in the tire circumferential direction formed in the ground contact surface 2a that contacts the road surface during running. Such a tread ring 2 has good drainage performance and can improve the wet performance of the airless tire 1. The ground contact surface 2a is not limited to such a mode, and for example, it may be block-shaped or may have a plurality of recesses formed therein.

[0033] As shown in FIGS. 1 and 2, the hub 3 is formed of a non-elastic body such as metal, for example. The hub 3 preferably has a disk-shaped fixing portion 3a fixed to the axle and a cylindrical portion 3b connected to the spoke 4. The fixing portion 3a of the hub 3 has, for example, a plurality of fixing holes formed therein. The fixing portion 3a of the hub 3 is not limited to such a mode, and may be, for example, attachable to a dedicated axle with one touch.

[0034] As shown in FIGS. 1 to 3, the spoke 4 is formed of, for example, a polymer material having elasticity. The polymer material is preferably appropriately selected from a single elastomer, two or more composite elastomers, an elastomer containing fibers, and the like. Such a spoke 4 is excellent in the balance of weight reduction, flexibility, and strength, and helps to improve the low fuel consumption performance, riding comfort performance, and durability performance of the airless tire 1 in a well-balanced manner.

[0035] The spoke 4 of the present embodiment includes a plurality of spoke plates 5, an outer cylindrical portion 15 connected to the tread ring 2, and an inner cylindrical portion 16 connected to the hub 3. Thereby, each of the spoke plates 5 is indirectly connected to the tread ring 2 and the hub 3.

[0036] Such a spoke 4 can be firmly connected to the hub 3 and the tread ring 2, and can improve the durability performance of the airless tire 1. Note that, for example, the outer cylindrical portion 15 and the inner cylindrical portion 16 of the spoke 4 may be omitted, and each of the spoke plates 5 may be directly connected to the tread ring 2 and the hub 3.

[0037] Each of the spoke plates 5 is preferably curved in a substantially S shape when viewed in the tire axial direction. Such a spoke 4 can be easily deformed when a compressive force acts thereon and can mitigate the impact at the time of grounding, so that the riding comfort performance of the airless tire 1 can be improved.

[0038] The spoke plate 5 includes a first spoke plate 5A arranged on one side in the tire axis direction and a second spoke plate 5B arranged on the other side when viewed from the thickness direction of the spoke plate 5. The first spoke plate 5A and the second spoke plate 5B are alternately arranged, for example, in the tire circumferential direction. Such a spoke plate 5 can achieve both weight reduction and balance in the tire axis direction, and can achieve both low fuel consumption performance and handling stability performance of the non-pneumatic tire 1.

[0039] Each of the spoke plates 5 preferably extends obliquely with respect to the tire axis direction. Such a spoke 4 can improve the rigidity in the tire circumferential direction and improve the durability performance of the non-pneumatic tire 1.

[0040] As described above, the particularly preferred embodiments of the present invention have been described in detail. However, the present invention is not limited to the above-described embodiments and can be implemented in various forms.

Example

[0041] A tread ring of a non-pneumatic tire shown in FIGS. 1 to 5 was prototyped based on the specifications in Table 1. In Table 1, the inclination of each reinforcing cord in one direction with respect to the tire circumferential direction is indicated by +, and the inclination in the other direction is indicated by -. Using the prototyped tread ring, the shape change of the tread ring due to cooling after vulcanization molding with a neutral core having a flat tire meridian cross section was tested. The main common specifications and test methods are as follows.

[0042] <Common specifications> Tread ring width: 155.0 mm Tread ring outer diameter: 524.0 mm Tread ring inner diameter: 476.8 mm Outer rubber layer thickness: 7.0 mm Inner rubber layer thickness: 0.8 mm

[0043] <Test method> The tread ring cooled after vulcanization molding was photographed by CT, and the radius of curvature of the inner peripheral surface in the tire meridian cross-section was measured. The results are expressed as an index with Comparative Example 1 being 100, indicating that the larger the numerical value, the larger the radius of curvature and the closer it is to being flat.

[0044] The test results are shown in Table 1.

Table 1

[0045] As a result of the test, it was confirmed that the tread ring of the example is closer to being flat in the tire meridian cross-section compared to the comparative example, suppresses the shape change of the tread ring due to cooling after vulcanization molding, improves the adhesion with the spoke, and can improve the durability performance of the non-pneumatic tire.

Explanation of Signs

[0046] 1 Non-pneumatic tire 2 Tread ring 2a Contact surface 3 Hub 4 Spoke 6 Outer reinforcing layer 7 Inner reinforcing layer 8 Outer ply 8a Outer reinforcing cord 9 Inner ply 9a Inner reinforcing cord

Claims

1. A non-pneumatic tire, comprising: a tread ring having a ground contact surface, a hub disposed inside the tread ring in the tire radial direction and fixed to an axle, and spokes for connecting the tread ring and the hub; the tread ring includes an outer reinforcing layer disposed on the side of the ground contact surface and an inner reinforcing layer disposed at a distance inside the outer reinforcing layer in the tire radial direction; the outer reinforcing layer includes at least one outer ply in which outer reinforcing cords are disposed; the inner reinforcing layer includes at least one inner ply in which inner reinforcing cords are disposed; an angle of the inner reinforcing cords with respect to the tire circumferential direction is larger than an angle of the outer reinforcing cords with respect to the tire circumferential direction; the inner ply includes a first inner ply disposed on the side of the spokes and a second inner ply disposed adjacent to the first inner ply outside the first inner ply in the tire radial direction; the inner reinforcing cords of the first inner ply and the inner reinforcing cords of the second inner ply are inclined in opposite directions at the same angle with respect to the tire circumferential direction; A non-pneumatic tire.

2. The tread ring includes an outer rubber layer on which the ground contact surface is formed, an inner rubber layer in contact with the spokes, and an intermediate rubber layer disposed between the outer rubber layer and the inner rubber layer; the outer reinforcing layer is disposed between the intermediate rubber layer and the outer rubber layer; The non-pneumatic tire according to claim 1, wherein the inner reinforcing layer is disposed between the intermediate rubber layer and the inner rubber layer.

3. A non-pneumatic tire, comprising: a tread ring having a ground contact surface, a hub disposed inside the tread ring in the tire radial direction and fixed to an axle, and spokes for connecting the tread ring and the hub; the tread ring includes an outer reinforcing layer disposed on the side of the ground contact surface and an inner reinforcing layer disposed at a distance inside the outer reinforcing layer in the tire radial direction; the outer reinforcing layer includes at least one outer ply in which outer reinforcing cords are disposed; the inner reinforcing layer includes at least one inner ply in which inner reinforcing cords are disposed; an angle of the inner reinforcing cords with respect to the tire circumferential direction is larger than an angle of the outer reinforcing cords with respect to the tire circumferential direction; The tread ring includes an outer rubber layer on which the ground contact surface is formed, an inner rubber layer in contact with the spoke, and an intermediate rubber layer disposed between the outer rubber layer and the inner rubber layer. The outer reinforcing layer is disposed between the intermediate rubber layer and the outer rubber layer. The inner reinforcing layer is disposed between the intermediate rubber layer and the inner rubber layer. The molding shrinkage rate of the outer rubber layer is larger than that of the intermediate rubber layer. Puncture-proof tire.

4. The tread ring includes a pair of sidewall rubbers that connect the outer rubber layer and the inner rubber layer on both sides of the intermediate rubber layer, the outer reinforcing layer, and the inner reinforcing layer in the tire axial direction. The puncture-proof tire according to claim 2 or 3.

5. The puncture-proof tire according to any one of claims 2 to 4, wherein the thickness of the outer rubber layer in the tire radial direction is larger than the thickness of the inner rubber layer in the tire radial direction.

6. The outer ply includes a first outer ply disposed on the side of the ground contact surface, and a second outer ply disposed adjacent to the first outer ply inside the first outer ply in the tire radial direction. The outer reinforcing cords of the first outer ply and the outer reinforcing cords of the second outer ply are inclined in opposite directions to each other at the same angle with respect to the tire circumferential direction. The puncture-proof tire according to any one of claims 1 to 5.

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