Airless tire

Abstract

To provide an airless tire that can improve durability performance by suppressing a tread ring and a spoke from coming off when great lateral force acts on as well.SOLUTION: An airless tire 1 comprises a tread ring 2 having a grounding surface, a hub 3 arranged 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 to the hub 3. The spoke 4 includes a plurality of spoke boards 5. The tread ring 2 has an inner peripheral surface 6 facing the inside in the tire radial direction. On the inner peripheral surface 6, a recessed part 7 recessed to the outside in the tire radial direction with respect to a reference straight line BL connecting both ends in a tire shaft direction of the inner peripheral surface 6 is formed on a tire meridian cross section. The recessed part 7 is formed over the whole range in the tire shaft direction of the inner peripheral surface 6.SELECTED DRAWING: Figure 3

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 that suppresses damage to a spoke plate portion by specifying the thickness of the spoke plate portion formed in an S shape of the spoke.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the non-pneumatic tire of Patent Document 1, the adhesive portion between the tread ring and the spoke has a cylindrical shape that is a straight line in the tire meridian cross section, and when a large lateral force such as a sharp turn acts, a shearing force may be generated at the adhesive portion and peeling may occur.

[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 that can suppress peeling between the tread ring and the spoke and improve durability even when a large lateral force acts.

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 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 has an inner circumferential surface facing the inside in the tire radial direction, and a recess recessed outward in the tire radial direction from a reference straight line connecting both ends in the tire axial direction of the inner circumferential surface is formed in the inner circumferential surface in a tire meridian cross section, and the recess is formed over the entire range in the tire axial direction of the inner circumferential surface.

[0007] In the non-pneumatic tire of the present invention, it is desirable that the recess has the largest amount of recess in the tire radial direction at the central position in the tire axial direction.

[0008] In the non-pneumatic tire of the present invention, it is desirable that the maximum amount of recess in the tire radial direction of the recess is 0.5 mm or more.

[0009] In the non-pneumatic tire of the present invention, it is desirable that the maximum amount of recess in the tire radial direction of the recess is 3.0 mm or less.

[0010] In the non-pneumatic tire of the present invention, it is desirable that the recess curves in an arc shape in a tire meridian cross section.

[0011] In the non-pneumatic tire of the present invention, it is desirable that the recess has a single radius of curvature in a tire meridian cross section.

[0012] In the non-pneumatic tire of the present invention, it is desirable that the amount of recess in the tire radial direction of the recess is the same in the tire circumferential direction.

[0013] In the non-pneumatic tire of the present invention, it is desirable that the amount of recess in the tire radial direction of the recess varies in the tire circumferential direction.

[0014] In the non-pneumatic tire of the present invention, the spoke has an outer cylindrical portion having an outer peripheral surface connected to the inner peripheral surface of the tread ring, and it is desirable that a convex portion having a shape corresponding to the concave portion is formed on the outer peripheral surface of the outer cylindrical portion in the tire meridian section.

Advantages of the Invention

[0015] In the non-pneumatic tire of the present invention, the tread ring has an inner peripheral surface facing the inner side in the tire radial direction, and a concave portion recessed outward in the tire radial direction from a reference straight line connecting both ends in the tire axial direction of the inner peripheral surface is formed on the inner peripheral surface in the tire meridian section. In such a non-pneumatic tire, even when a large lateral force acts on the tread ring, the concave portion can disperse the shearing force, so that peeling of the adhesion surface between the tread ring and the spoke can be suppressed.

[0016] In the non-pneumatic tire of the present invention, the concave portion is formed over the entire range in the tire axial direction of the inner peripheral surface. Such a tread ring can disperse the strain when a lateral force acts over the entire range in the tire axial direction, and can also suppress the stress concentration accompanying the shape change, so that the durability performance of the non-pneumatic tire can be improved. Therefore, the non-pneumatic tire of the present invention can suppress the peeling between the tread ring and the spoke and improve the durability performance even when a large lateral force acts.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0018] Hereinafter, an embodiment of the present invention will be described in detail with reference to 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 spokes 4 for connecting the tread ring 2 and the hub 3.

[0019] The hub 3 preferably includes a fixing portion 3a that is fixed to an axle (not shown) of the vehicle. Such an airless tire 1 can support the load acting on the tread ring 2 by the hub 3 and the spokes 4 without using high-pressure air. Therefore, the airless tire 1 of the present embodiment has no risk of puncture.

[0020] The spoke 4 of the present embodiment includes a plurality of spoke plates 5 spaced apart in the tire circumferential direction. The spoke plate 5 is formed in a plate shape, for example, having a width in the tire axial direction larger than the thickness in the tire circumferential direction. 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 when a load acts on the tread ring 2.

[0021] FIG. 3 is a cross-sectional view taken along line A-A of FIG. 2. As shown in FIG. 3, the tread ring 2 of the present embodiment has an inner peripheral surface 6 facing the inside in the tire radial direction. A recess 7 is formed on the inner peripheral surface 6 of the present embodiment, recessed outward in the tire radial direction from a reference straight line BL connecting both ends 6a in the tire axial direction of the inner peripheral surface 6 in the tire meridian cross-section.

[0022] Such an airless tire 1 can suppress the peeling of the adhesive surface between the tread ring 2 and the spokes 4 because the recess 7 can disperse the shearing force even when a large lateral force acts on the tread ring 2.

[0023] The recess 7 of this embodiment is formed over the entire range of the tire axial direction of the inner peripheral surface 6. Such a tread ring 2 can disperse the strain when a lateral force acts over the entire range in the tire axial direction, and can also suppress the stress concentration associated with the shape change of the inner peripheral surface 6, so that the durability performance of the airless tire 1 can be improved. For this reason, the airless tire 1 of this embodiment can suppress the peeling between the tread ring 2 and the spoke 4 and improve the durability performance even when a large lateral force acts.

[0024] As a more preferable aspect, in the recess 7, the amount of recess a1 in the tire radial direction is the largest at the center position C in the tire axial direction. Such a recess 7 can disperse the shear force with respect to the lateral forces in both directions, and can improve the durability performance of the airless tire 1. Here, the center position C is the central position in the tire axial direction of the width W of the tread ring 2, and is also called the tire equator.

[0025] In the recess 7, the maximum amount of recess a1 in the tire radial direction is preferably 0.5 mm or more. By the maximum amount of recess a1 being 0.5 mm or more, the shear force can be reliably dispersed, and the durability performance of the airless tire 1 can be improved. From such a viewpoint, the maximum amount of recess a1 is more preferably 0.7 mm or more, and still more preferably 1.0 mm or more.

[0026] In the recess 7, the maximum amount of recess a1 in the tire radial direction is preferably 3.0 mm or less. By the maximum amount of recess a1 being 3.0 mm or less, excessive distortion of the tread ring 2 due to the recess 7 when a compressive force acts on the spoke plate 5 can be suppressed, and the durability performance of the airless tire 1 can be improved. From such a viewpoint, the maximum amount of recess a1 is more preferably 2.7 mm or less, and still more preferably 2.5 mm or less.

[0027] The recess 7 of this embodiment is curved in an arc shape in the tire meridian cross-section. Such a recess 7 can more reliably suppress stress concentration associated with the shape change of the inner peripheral surface 6, and can further improve the durability performance of the non-pneumatic tire 1.

[0028] The recess 7 preferably has a single radius of curvature R1 in the tire meridian cross-section. Such a recess 7 can more reliably suppress stress concentration associated with the shape change of the inner peripheral surface 6, and can further improve the durability performance of the non-pneumatic tire 1.

[0029] In the recess 7 of this embodiment, the amount of recess a1 in the tire radial direction is the same in the tire circumferential direction. Such a tread ring 2 has no change in thickness in the tire circumferential direction, and can suppress the generation of vibration and noise.

[0030] The recess 7 may, for example, have a variable amount of recess a1 in the tire radial direction in the tire circumferential direction. In this case, even when a large longitudinal force acts on the tread ring 2 of the non-pneumatic tire 1, the recess 7 can disperse the shear force, so that the peeling of the adhesion surface between the tread ring 2 and the spoke 4 can be more reliably suppressed.

[0031] As shown in FIGS. 1 and 3, the tread ring 2 is formed in a substantially cylindrical shape by an elastic body such as rubber, for example. The tread ring 2 may be provided with a reinforcing layer or a rubber layer (not shown) inside, for example. A plurality of grooves 8 are preferably formed in the ground contact surface 2a of the tread ring 2 that contacts the road surface during running. The ground contact surface 2a is not limited to such a mode, and may be, for example, block-shaped or may have a plurality of recesses formed therein.

[0032] The ground contact surface 2a of the present embodiment includes a profile parallel to the reference straight line BL in the tire meridian cross-section. Such a ground contact surface 2a has good grip performance and can improve the handling stability performance of the non-pneumatic tire 1. The ground contact surface 2a is not limited to such a mode, and for example, it may include a profile parallel to the inner peripheral surface 6.

[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 3c 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 for example, it may be attachable to a dedicated axle with one touch.

[0034] The spoke 4 is formed of a polymer material having elasticity, for example. The polymer material is preferably selected from a single elastomer, a composite elastomer of two or more kinds, or a fiber-containing elastomer. Such a spoke 4 is excellent in the balance of weight reduction, flexibility, and strength, and helps to improve the fuel efficiency performance, riding comfort performance, and durability performance of the non-pneumatic tire 1 in a well-balanced manner.

[0035] The spoke 4 of the present embodiment includes a plurality of spoke plates 5, an inner cylindrical portion 9 connected to the hub 3, and an outer cylindrical portion 10 connected to the tread ring 2. Thereby, each of the spoke plates 5 is indirectly connected to the tread ring 2 and the hub 3. 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 non-pneumatic tire 1.

[0036] As shown in FIG. 3, it is desirable that the outer cylindrical portion 10 has its outer peripheral surface 11 adhered to the inner peripheral surface 6 of the tread ring 2. The outer peripheral surface 11 of the outer cylindrical portion 10 of the present embodiment has a convex portion 12 formed in a shape corresponding to the concave portion 7 in the tire meridian cross section. Such an outer cylindrical portion 10 can combine the convex portion 12 with the concave portion 7 of the tread ring 2, and can suppress the peeling of the adhesion surface between the tread ring 2 and the spoke 4 even when a large lateral force acts on the tread ring 2.

[0037] Each of the spoke plates 5 of the present embodiment has a first end portion 13 extending in the tire radial direction at one end side in the tire axial direction and a second end portion 14 extending in the tire radial direction at the other end side in the tire axial direction. Thereby, the spoke plate 5 of the present embodiment has a spoke width w measured along the surface 5a of the spoke plate 5 from the first end portion 13 to the second end portion 14 at the same tire radial position.

[0038] The spoke width w of the spoke plate 5 is preferably smaller than the width W of the tread ring 2. Such a spoke plate 5 is useful for weight reduction and can improve the low fuel consumption performance of the non-pneumatic tire 1.

[0039] FIG. 4 is an end view of the spoke plate 5 viewed from the direction of the spoke width w. As shown in FIGS. 3 and 4, the spoke plate 5 of the present embodiment has a spoke thickness t orthogonal to the spoke width w and the surface 5a of the spoke plate 5.

[0040] Each of the spoke plates 5 of the present embodiment includes a first curved portion 15 that curves so as to protrude in one direction in the tire circumferential direction on the hub 3 side and a second curved portion 16 that curves so as to protrude in the other direction in the tire circumferential direction on the tread ring 2 side when viewed from the direction of the spoke width w. Such a spoke plate 5 can improve the riding comfort performance of the non-pneumatic tire 1 by the first curved portion 15 and the second curved portion 16.

[0041] The amplitude a2 of the first curved portion 15 and the amplitude a3 of the second curved portion 16 of this embodiment are different from each other. Such a spoke plate 5 can limit the direction of deformation when a large compressive force acts on the spoke plate 5, such as when passing through a step, to the side with the larger amplitude among the first curved portion 15 and the second curved portion 16. Thereby, even when passing through a step, the spoke 4 can suppress the contact between the adjacent spoke plates 5 in the tire circumferential direction due to deformation.

[0042] It is desirable that the amplitude a3 of the second curved portion 16 is larger than the amplitude a2 of the first curved portion 15. The amplitude a3 of the second curved portion 16 of this embodiment is 1 to 3 mm larger than the amplitude a2 of the first curved portion 15. Such a spoke plate 5 has a good vibration absorption effect by increasing the deformation of the second curved portion 16 located on the outer side in the tire radial direction, and can improve the riding comfort performance of the non-pneumatic tire 1.

[0043] The amplitude a2 of the first curved portion 15 of this embodiment is the same throughout the entire range of the spoke width w. Also, the amplitude a3 of the second curved portion 16 of this embodiment is the same throughout the entire range of the spoke width w. Such a spoke plate 5 can disperse the strain when a compressive force acts in the direction of the spoke width w, and can further improve the durability performance of the non-pneumatic tire 1.

[0044] It is desirable that the radius of curvature R2 of the first curved portion 15 and the radius of curvature R3 of the second curved portion 16 are equal to each other. Such a spoke plate 5 can limit the direction of change when a compressive force acts to the direction based on the amplitude. Also, this spoke plate 5 can disperse the strain when a compressive force acts to the first curved portion 15 and the second curved portion 16, and can further improve the durability performance of the non-pneumatic tire 1. Here, the radius of curvature R2 of the first curved portion 15 and the radius of curvature R3 of the second curved portion 16 are the radii of curvature of the center line 5c of the spoke thickness t.

[0045] As shown in FIG. 3, each of the spoke plates 5 of the present embodiment includes an inner end portion 17 which is the end portion on the hub 3 side and an outer end portion 18 which is the end portion on the tread ring 2 side. The spoke plate 5 is formed such that, for example, the inner end portion 17 is integrally formed with the inner cylindrical portion 9 via the curved surface portion 5b. Further, the spoke plate 5 is formed such that, for example, the outer end portion 18 is integrally formed with the outer cylindrical portion 10 via the curved surface portion 5b.

[0046] As shown in FIG. 4, the center line 5c of the spoke thickness t at the inner end portion 17 of the present embodiment extends parallel to the tire radial direction. The center line 5c of the spoke thickness t at the outer end portion 18 of the present embodiment also extends parallel to the tire radial direction, similar to the inner end portion 17. Such a spoke plate 5 can reduce the distortion when a tensile force acts, and can further improve the durability performance of the airless tire 1.

[0047] It is desirable that the center line 5c of the spoke thickness t of the inner end portion 17 and the center line 5c of the spoke thickness t of the outer end portion 18 are located on the same straight line when viewed from the spoke width w direction. Such a spoke plate 5 can limit the direction of change when a compressive force acts to the direction based on the amplitude. Further, such a spoke plate 5 can reduce the distortion when a compressive force acts, and can further improve the durability performance of the airless tire 1.

[0048] As shown in FIGS. 1 to 3, the spoke plate 5 of the present embodiment includes a first spoke plate 5A arranged on one side in the tire axial direction and a second spoke plate 5B arranged on the other side in the tire axial direction. The first spoke plate 5A and the second spoke plate 5B are arranged alternately in the tire circumferential direction, for example. Such a spoke plate 5 can achieve both weight reduction and balance in the tire axial direction, and can achieve both low fuel consumption performance and handling stability performance of the airless tire 1.

[0049] FIG. 5 is a cross-sectional view taken along line B-B of FIG. 2. As shown in FIG. 5, the inner end portion 17 of the present embodiment extends obliquely with respect to the tire axis direction. Although not shown, it is desirable that the outer end portion 18 extends obliquely in the same direction as the inner end portion 17 with respect to the tire axis direction.

[0050] The inclination angles of the inner end portion 17 and the outer end portion 18 with respect to the tire axis direction are preferably 2 to 10°. By the inclination angle being 2° or more, the rigidity in the tire circumferential direction can be improved, and the durability performance of the non-pneumatic tire 1 can be improved. By the inclination angle being 10° or less, it is possible to suppress an excessive increase in rigidity in the tire circumferential direction and improve the ride comfort performance of the non-pneumatic tire 1.

[0051] It is desirable that the inner end portion 17 of the first spoke plate 5A and the inner end portion 17 of the second spoke plate 5B incline in opposite directions with respect to the tire axis direction. Such a spoke 4 has good balance in the tire axis direction and can improve the ride comfort performance of the non-pneumatic tire 1.

[0052] It is desirable that the angle θ1 of the inner end portion 17 of the first spoke plate 5A with respect to the tire axis direction and the angle θ2 of the inner end portion 17 of the second spoke plate 5B with respect to the tire axis direction are equal. Such a spoke 4 has good balance in the tire axis direction and can improve the ride comfort performance of the non-pneumatic tire 1. Note that the angle θ1 of the inner end portion 17 of the first spoke plate 5A with respect to the tire axis direction and the angle θ2 of the inner end portion 17 of the second spoke plate 5B with respect to the tire axis direction may be different from each other, for example.

[0053] 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

[0054] A non-pneumatic tire having the basic structure of FIGS. 1 to 5 was prototyped based on the specifications in Table 1, and its durability performance was tested. The main common specifications and test methods are as follows.

[0055] <Common specifications> Tread ring width: 165 mm Outer diameter of tread ring: 502 mm Inner diameter of tread ring: 489 mm Outer diameter of hub: 304 mm Number of spokes: 20 pairs Inclination angle of spoke part: 2°

[0056] <Durability performance> Using a drum tester, the vehicle was run under the conditions of a load of 3.8 kN, a speed of 60 km / h, and a slip angle of 1.5°. The running distance until the vehicle became inoperable due to the peeling between the tread ring and the spokes or the damage of the tread ring was measured. The result is an index with the comparative example set to 100. The larger the numerical value, the longer the running distance, indicating excellent durability performance.

[0057] The test results are shown in Table 1.

Table 1

[0058] As a result of the test, it was confirmed that the airless tire of the example had a smaller degree of abrasion and improved durability performance compared to the comparative example.

Explanation of symbols

[0059] 1 Airless tire 2 Tread ring 3 Hub 4 Spoke 5 Spoke plate 6 Inner peripheral surface 7 Recess

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 has an inner peripheral surface facing the inside in the tire radial direction; a recess recessed outward in the tire radial direction from a reference straight line connecting both ends in the tire axial direction of the inner peripheral surface is formed in the inner peripheral surface in a tire meridian cross section; the recess is formed over the entire range in the tire axial direction of the inner peripheral surface; the ground contact surface includes a profile parallel to the reference straight line in a tire meridian cross section; the spokes include a plurality of spoke plates; each of the spoke plates includes an inner end portion which is an end portion on the hub side; the inner end portion extends obliquely with respect to the tire axial direction; the inclination angle of the inner end portion with respect to the tire axial direction is 2 to 10°; a non-pneumatic tire.

2. The non-pneumatic tire according to claim 1, wherein the recess has the largest amount of recess in the tire radial direction at the center position in the tire axial direction.

3. The non-pneumatic tire according to claim 2, wherein the maximum amount of recess in the tire radial direction of the recess is 0.5 mm or more.

4. The non-pneumatic tire according to claim 2 or 3, wherein the maximum amount of recess in the tire radial direction of the recess is 3.0 mm or less.

5. The non-pneumatic tire according to any one of claims 1 to 4, wherein the recess is curved in an arc shape in a tire meridian cross section.

6. The non-pneumatic tire according to claim 5, wherein the recess has a single radius of curvature in a tire meridian cross section.

7. The non-pneumatic tire according to any one of claims 1 to 6, wherein the amount of recess in the tire radial direction of the recess is the same in the tire circumferential direction.

8. The non-pneumatic tire according to any one of claims 1 to 6, wherein the amount of recess in the tire radial direction of the recess varies in the tire circumferential direction.

9. The spokes have an outer cylindrical portion having an outer peripheral surface connected to the inner peripheral surface of the tread ring; The non-pneumatic tire according to any one of claims 1 to 8, wherein a convex portion having a shape corresponding to the recess is formed on the outer peripheral surface of the outer cylindrical portion in a tire meridian cross section.

10. The spoke plate includes a first spoke plate arranged on one side in the tire axial direction and a second spoke plate arranged on the other side in the tire axial direction, wherein the first spoke plate and the second spoke plate are alternately arranged in the tire circumferential direction. The non-pneumatic tire according to any one of Claims 1 to 9.

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