Airless tires

Abstract

To provide an airless tire that can suppress buckling deformation of the intermediate ring. [Solution] An airless tire 1 comprises a wheel 2 coupled to a vehicle, a plurality of elastic spokes 31 extending radially from the outer circumference of the wheel 2, periodically arranged in the circumferential direction, and having a bent portion 31a, and an elastic intermediate ring 34 extending in the circumferential direction and connecting adjacent spokes 31, wherein a first convex portion 35 is provided on the wheel-side surface of the intermediate ring 34 between the center 34C of the intermediate ring 34 between adjacent spokes 31 and the bent portion 31a on the acute angle θ1 side of the spoke 31.

Description

Technical Field

[0001] The present invention relates to an airless tire (also referred to as a non-pneumatic tire).

Background Art

[0002] There is known a non-pneumatic tire in which an element (spoke) of one motif is supported by an adjacent element (spoke) via an auxiliary element (intermediate ring) arranged in the circumferential direction (see FIGS. 9a, 9b, 10a, 10b of Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As in the above prior art, providing an intermediate ring in the body portion increases the weight. However, if the intermediate ring is made thinner to reduce the weight of the body portion, there is a problem that the intermediate ring buckles and deforms due to the compressive load.

[0005] The problem to be solved by the present invention is to provide an airless tire that can suppress the buckling deformation of the intermediate ring.

Means for Solving the Problems

[0006] The present invention solves the above problems by providing a first convex portion on the wheel-side surface of the intermediate ring between the center of the intermediate ring between adjacent spokes and the bent portion on the acute angle side of the spoke.

Effects of the Invention

[0007] According to the present invention, the buckling deformation of the intermediate ring can be suppressed. [Brief explanation of the drawing]

[0008] [Figure 1] This is a front view showing an airless tire according to one embodiment of the present invention. [Figure 2] Figure 1 is a perspective view showing the body section. [Figure 3] Figure 1 is a perspective view showing the wheel. [Figure 4] This is a front view illustrating the problems with the conventional structure. [Figure 5] Figure 2 is a perspective view showing a magnified portion of the body. [Figure 6] This is an enlarged front view showing part VI of the body of the airless tire according to the embodiment of Figure 5. [Figure 7] This is a front view showing a part of the body of an airless tire according to another embodiment of the present invention, and corresponds to part VI in Figure 4. [Figure 8] This is a front view showing a part of the body of an airless tire according to yet another embodiment of the present invention, and corresponds to part VI in Figure 4. [Figure 9] This is a front view showing a part of the body of an airless tire according to yet another embodiment of the present invention, and corresponds to part IV of Figure 4. [Figure 10] This is a front view showing a part of the body of an airless tire according to yet another embodiment of the present invention, and corresponds to part IV of Figure 4. [Figure 11] This is a perspective view showing a part of the body of an airless tire according to yet another embodiment of the present invention. [Figure 12] This is a front view showing an enlarged view of section XII of the body of the airless tire according to the embodiment of Figure 11. [Modes for carrying out the invention]

[0009] Hereinafter, examples of embodiments for carrying out the present invention will be described with reference to the drawings. The airless tire according to the embodiments of the present invention shown below can be applied to four-wheeled automobiles, two-wheeled automobiles, industrial vehicles, bicycles and other vehicles, as well as to the wheels of carts and the like.

[0010] Common structure of airless tires Figure 1 is a front view showing a common structure of the airless tire 1 according to an embodiment of the present invention, Figure 2 is a perspective view showing the body portion 3 of Figure 1, and Figure 3 is a perspective view showing the wheel 2 of Figure 1. Referring to Figures 1 to 3, the configurations common to the multiple embodiments described later will be explained first.

[0011] As shown in Figure 1, the airless tire 1 of this embodiment comprises a wheel 2, a body portion 3, and a tread ring 4, the body portion 3 including spokes 31, an inner circumferential ring 32, an outer circumferential ring 33, and an intermediate ring 34.

[0012] The wheel 2 of this embodiment is fixed to a vehicle hub (not shown). As shown in Figure 3, the wheel 2 of this embodiment is composed of, for example, a disc-shaped disc 21 and a cylindrical rim 22, and is made of metal or other highly rigid material. In the front view of Figure 1, the disc 21 of the wheel 2 is shown as a circular member in the center of the airless tire 1, and this disc 21 is fixed to the vehicle hub, thereby supporting the airless tire 1 on the tire rotation axis P.

[0013] As shown in Figure 3, the outer circumferential surface of the rim 22 of the wheel 2 in this embodiment is formed as a flat surface and is joined to the inner circumferential surface 32a of the inner circumferential ring 32 using an adhesive or the like. In addition to joining the wheel 2 and the body portion 3 in this embodiment by adhesive, a protrusion may be formed on one of the outer circumferential surface of the rim 22 of the wheel 2 and the inner circumferential surface 32a of the inner circumferential ring 32, and a groove that fits into the protrusion may be formed on the other, and these may be mechanically fitted together. The fitting of this protrusion and groove may also be joined by an anchoring effect, with their cross-sections forming an anchor shape. As a result, the body portion 3 is constrained to the wheel 2 in both the radial and circumferential directions.

[0014] The tread ring 4 of the present embodiment is formed in a cylindrical shape and provided on the outermost circumference of the airless tire 1. The tread ring 4 of the present embodiment is composed of a composite material in which a material having elasticity such as natural rubber or synthetic rubber is reinforced with a tire cord made of metal or resin. A tread pattern is formed on the outer peripheral surface of the tread ring 4 of the present embodiment, similar to a conventional pneumatic tire, and serves as the ground contact surface with the road surface.

[0015] The inner peripheral ring 32 of the present embodiment is a cylindrical member that connects the ends of the plurality of spokes 31 on the wheel 2 side, and is joined to the outer peripheral surface of the wheel 2 by adhesion or other means as described above. The inner peripheral ring 32 of the present embodiment is composed of an elastic material such as an elastic thermoplastic resin or an elastic thermosetting resin, and may be integrally formed with the spokes 31.

[0016] The outer peripheral ring 33 of the present embodiment is a cylindrical member that connects the ends of the plurality of spokes 31 on the tread ring 4 side, and is fastened to the inner peripheral surface of the tread ring 4 described above by means such as adhesion. The outer peripheral ring 33 of the present embodiment is composed of an elastic material such as an elastic thermoplastic resin or an elastic thermosetting resin, and may be integrally formed with the spokes 31. In the airless tire 1 of the present invention, the outer peripheral ring 33 is not an essential component, and the outer peripheral ring 33 may be omitted by directly fastening the ends of the spokes 31 on the tread ring 4 side to the tread ring 4.

[0017] The spokes 31 of the present embodiment are composed of an elastic material such as an elastic thermoplastic resin or an elastic thermosetting resin, extend radially from the outer peripheral side of the wheel 2 toward the inner peripheral side of the tread ring 4, and are provided in a plurality at equal intervals along the circumferential direction of the tire. The plurality of spokes 31 are provided axially symmetrically with respect to the central axis of the tire. The number of spokes 31 provided in one airless tire 1 is not particularly limited, and can be appropriately set according to the ground contact length of the tire, the load-bearing capacity of the spokes 31, the vibration resistance performance, and other required specifications of the tire.

[0018] In this embodiment, one spoke 31 has a bent portion 31a formed in the intermediate ring 34 between the end on the wheel 2 side and the end on the tread ring 4 side, which bends in the direction connecting these two ends. The bent portion 31a of the spoke 31 restricts the amount of deformation of the tire in the circumferential direction according to its bending angle. Note that the shape and structure of the spoke 31 of the present invention are not limited to the illustrated example, and any appropriate shape or structure can be adopted.

[0019] The intermediate ring 34 in this embodiment is made of an elastic material such as an elastic thermoplastic resin or an elastic thermosetting resin, similar to the spokes 31, inner ring 32, and outer ring 33, and is provided between the inner ring 32 and the outer ring 33, connected to a plurality of spokes 31. The intermediate ring 34 in this embodiment has a cylindrical shape concentric with the inner ring 32 and the outer ring 33, and in the front view of Figure 1, the body portion 3 includes three intermediate rings 34, but it may include one, two, or four or more intermediate rings 34.

[0020] The number of intermediate rings 34 provided in a single airless tire 1 is not particularly limited, but by setting the number of intermediate rings 34 to 2, 4, 6, or other even numbers, the balance of forces in the circumferential direction of the tire can be maintained. As a result, the axial force (compressive force and tensile force) acting on the intermediate rings 34 becomes continuous throughout the entire circumference of the tire, and the load acting on the bent parts of the spokes 31 can be distributed across the entire tire. As a result, there is an effect of reducing the rolling resistance coefficient (RRC).

[0021] In this embodiment, one intermediate ring 34 is provided in an annular shape between the inner ring 32 and the outer ring 33, as shown in Figure 1, and therefore intersects with multiple spokes 31. In the airless tire 1 of this embodiment, each intermediate ring 34 is connected to each spoke 31 at each bent portion 31a. Furthermore, in the airless tire 1 of this embodiment, the bent portions 31a of the spokes 31 connected to the same intermediate ring 34 are formed to bend in the same direction with respect to the circumferential direction of the tire. That is, looking at the intermediate ring 34 provided on the innermost side of the three intermediate rings 34 in the front view of Figure 1, the bending direction of the bent portion 31a of the spokes 31 connected to this intermediate ring 34 is convex to the right in Figure 1. In contrast, looking at the intermediate ring 34 provided in the center of the three intermediate rings 34, the bending direction of the bent portion 31a of the spokes 31 connected to this intermediate ring 34 is convex to the left in Figure 1. Furthermore, looking at the outermost of the three intermediate rings 34, the bending direction of the bent portion 31a of the spoke 31 connected to this intermediate ring 34 is convex to the right in Figure 1.

[0022] In this way, by forming the bent portions 31a of the spokes 31 connected to the same intermediate ring 34 so that they bend in the same direction with respect to the circumferential direction of the tire (i.e., setting the zigzag of the spokes 31 in phase), the deformation direction of the bent portion 31a of the spokes 31 toward the circumferential direction becomes the same for adjacent spokes 31. As a result, the axial force (compressive force and tensile force) acting on the intermediate ring 34 becomes continuous throughout the entire circumference of the tire, and the load acting on the bent portion of the spokes 31 can be distributed across the entire tire. As a result, there is an effect of reducing the rolling resistance coefficient.

[0023] In this invention, the inner ring 32 and the outer ring 33 are not essential components. Since these inner ring 32 and outer ring 33 are provided to hold a plurality of spokes 31, for example, the plurality of spokes 31 may be directly joined to the wheel 2 and the tread ring 4 respectively, and at least one of the inner ring 32 and the outer ring 33 may be omitted. Also, in this invention, the tread ring 4 is not an essential component, and the outer ring 33 may incorporate the function of the tread ring 4, and the tread ring 4 may be omitted.

[0024] The above describes the structure common to the airless tire 1 according to the embodiment of the present invention. Below, embodiments of the configuration of the first protrusion 35, second protrusion 36, first recess 37, and second recess 38 provided on the intermediate ring 34 will be described.

[0025] Before describing each embodiment of the present invention, the problems of the present invention will be explained with reference to Figure 4. Figure 4 is a front view illustrating the problems of a conventional airless tire, showing the state in which a wheel load is applied to the airless tire 1. When a vertically upward load from the road surface, i.e., the wheel load which is the weight of the vehicle, is applied to the airless tire 1, the spokes 31 directly below the ground deform radially, and the reaction force supports the wheel load.

[0026] On the other hand, the intermediate ring 34 has the function of restraining the deformation of adjacent spokes 31 and transmitting load in the circumferential direction, so a tensile or compressive force acts on the intermediate ring 34 in the circumferential direction depending on the rotation angle of the tire. As shown in Figure 4, the intermediate ring 34 is subjected to a compressive load Fx in the circumferential direction of the tire and a load Fy in the vertical direction of the tire. When subjected to these loads Fx and Fy, the intermediate ring 34 is subjected to a bending moment M in the direction shown in the figure, causing a curved deformation. That is, the intermediate ring 34 on the side where the angle θ1 between the spoke 31 and the intermediate ring 34 is acute curves outward, and the intermediate ring 34 on the side where the angle θ2 between the spoke 31 and the intermediate ring 34 is obtuse curves inward.

[0027] If the thickness of the intermediate ring 34 is reduced to lower the weight, it becomes more susceptible to this deformation mode, weakening the force that the intermediate ring 34 exerts on the adjacent spokes 31, making it difficult for the airless tire 1 to hold a large wheel load. If the overall thickness of the intermediate ring 34 is increased to avoid this, another problem arises: increased weight, resulting in reduced fuel efficiency and dynamic performance. To solve the above problems, the airless tire 1 of this embodiment has the following configuration.

[0028] 《First Embodiment》 Figure 5 is a perspective view showing an enlarged portion of the body portion 3 in Figure 2, and Figure 6 is a front view showing an enlarged portion VI of the body portion 3 of the airless tire 1 according to the embodiment of Figure 4. As shown in Figure 6, in the bent portion 31a where the spoke 31 and the intermediate ring 34 are joined, the acute angle between the spoke 31 and the intermediate ring 34 is called the acute-side spoke inclination angle θ1, and the obtuse-side angle is called the obtuse-side spoke inclination angle θ2.

[0029] In the airless tire 1 of this embodiment, as shown in Figure 6, a first protrusion 35 is provided on the wheel-side surface of the intermediate ring 34, located between the center 34C of the intermediate ring 34 between adjacent spokes 31, 31 and the bent portion 31a on the acute angle θ1 side of the spoke 31. Furthermore, in the airless tire 1 of this embodiment, as shown in Figure 6, a second protrusion 36 is provided on the non-wheel-side surface of the intermediate ring 34, located between the center 34C of the intermediate ring 34 between adjacent spokes 31, 31 and the bent portion 31a on the obtuse angle θ2 side of the spoke 31. Note that the center 34C of the intermediate ring 34 between adjacent spokes 31, 31 refers to the midpoint of the length of the intermediate ring 34 in the extending direction between two adjacent spokes 31, 31.

[0030] In this embodiment, the intermediate ring 34 is a plate-shaped member that extends in the width direction of the tire along the tire rotation axis P of the body portion 3. Therefore, the first protrusion 35 formed on the wheel-side surface of the intermediate ring 34 and the second protrusion 36 formed on the non-wheel-side surface of the intermediate ring 34 are each formed to extend in the width direction of the tire along the tire rotation axis P of the body portion 3.

[0031] As explained with reference to Figure 4, in the airless tire 1 directly above the ground, the intermediate ring 34 near the acute-angle spoke inclination angle θ1 curves convexly toward the wheel side, and the intermediate ring 34 near the obtuse-angle spoke inclination angle θ2 curves convexly toward the wheel side. Therefore, by providing a first protrusion 35 on the wheel-side surface of the intermediate ring 34 near the acute-angle spoke inclination angle θ1, and a second protrusion 36 on the non-wheel-side surface of the intermediate ring 34 near the obtuse-angle spoke inclination angle θ2, it is possible to resist the curvature deformation, and as a result, buckling deformation of the intermediate ring 34 can be suppressed.

[0032] Furthermore, in this embodiment, it is more preferable that the height H2 of the second protrusion 36 is lower than the height H1 of the first protrusion 35, as shown in Figure 6. The height H1 of the first protrusion 35 refers to the distance from the wheel-side surface of the intermediate ring 34 to the maximum height position of the first protrusion 35 (distance perpendicular to the wheel-side surface), and the height H2 of the second protrusion 36 refers to the distance from the non-wheel-side surface of the intermediate ring 34 to the maximum height position of the second protrusion 36 (distance perpendicular to the non-wheel-side surface). By making the height H2 of the second protrusion 36 lower than the height H1 of the first protrusion 35, the bending rigidity of the intermediate ring 34 that is close to the acute-angle spoke inclination angle θ1 becomes greater than the bending rigidity of the intermediate ring 34 that is close to the obtuse-angle spoke inclination angle θ2. As a result, the overall buckling deformation of the intermediate ring 34 can be further suppressed.

[0033] Modified version of the first embodiment In the airless tire 1 of the embodiment shown in Figures 5 and 6, both the first protrusion 35 and the second protrusion 36 are formed as smooth convex ridges, but the first and second protrusions of the present invention are not limited to these shapes. A modified example of the airless tire 1 according to the first embodiment will be described below.

[0034] Figure 7 is a front view showing a part of the body portion 3 of an airless tire 1 according to another embodiment of the present invention, and corresponds to portion VI of Figure 4. The airless tire 1 according to the illustrated embodiment is similar to the airless tire 1 of the first embodiment shown in Figure 6, in which a first convex portion 35 is provided on the wheel-side surface of the intermediate ring 34 between the center 34C of the intermediate ring 34 between adjacent spokes 31, 31 and the bent portion 31a on the acute angle θ1 side of the spoke 31, and a second convex portion 36 is provided on the non-wheel-side surface of the intermediate ring 34 between the center 34C of the intermediate ring 34 between adjacent spokes 31, 31 and the bent portion 31a on the obtuse angle θ2 side of the spoke 31.

[0035] However, in the airless tire 1 of the embodiment shown in Figure 6, both the first protrusion 35 and the second protrusion 36 are smooth protrusions, whereas in the airless tire 1 of the embodiment shown in Figure 7, both the first protrusion 35 and the second protrusion 36 are steep protrusions with a semicircular cross-section. Even with the first protrusion 35 and the second protrusion 36 having such shapes, they produce the same effects as the airless tire 1 of the embodiment shown in Figure 6.

[0036] Figure 8 is a front view showing a part of the body portion 3 of an airless tire 1 according to yet another embodiment of the present invention, and corresponds to portion VI of Figure 4. The airless tire 1 according to the illustrated embodiment, like the airless tire 1 of the first embodiment shown in Figure 6, has a first protrusion 35 on the wheel-side surface of the intermediate ring 34, between the center 34C of the intermediate ring 34 between adjacent spokes 31, 31 and the bent portion 31a on the acute angle θ1 side of the spoke 31. However, there is no second protrusion 36 on the non-wheel-side surface of the intermediate ring 34, between the center 34C of the intermediate ring 34 between adjacent spokes 31, 31 and the bent portion 31a on the obtuse angle θ2 side of the spoke 31. Even with only the first protrusion 35 provided in this way, buckling deformation of the intermediate ring 34 can be suppressed in the same way as the airless tire 1 of the embodiment shown in Figure 6.

[0037] Figure 9 is a front view showing a part of the body portion 3 of an airless tire 1 according to yet another embodiment of the present invention, and corresponds to portion VI in Figure 4. The airless tire 1 according to the illustrated embodiment is similar to the airless tire 1 of the first embodiment shown in Figure 6, in which a first protrusion 35 is provided on the wheel-side surface of the intermediate ring 34 between the center 34C of the intermediate ring 34 between adjacent spokes 31, 31 and the bent portion 31a on the acute angle θ1 side of the spoke 31. However, the first protrusion 35 is provided further away from the bent portion 31a than the first protrusion 35 shown in Figure 6. Therefore, the plate thickness T0 of the intermediate ring 34 between the bent portion 31a of the spoke 31 and the first protrusion 35 is thinner than the plate thickness T1 of the intermediate ring 34 including the first protrusion 35.

[0038] In this embodiment, the airless tire 1 has a structure in which the spokes 31 near the ground deform radially to support the wheel load. However, if the intermediate ring 34 is provided with a first protrusion 35 and a second protrusion 36, and these are placed close to the bent portion 31a, the thickness of the intermediate ring 34 in the portion close to the bent portion 31a also increases. As a result, the length of the spokes 31 between the intermediate rings 34 becomes shorter, and in addition, the rigidity of the bent portion 31a increases. Consequently, the radial length of the spokes near the ground becomes smaller (rigidity increases) relative to the wheel load. This means that instead of the entire tire supporting the load, the load on the spokes 31 near the ground increases, which contradicts the intended purpose. Therefore, as in the airless tire 1 of this embodiment, the rigidity of the joint portion between the spoke 31 and the intermediate ring 34 (the bent portion 31a of the spoke 31) is not increased, and in order to make this portion easily deformable, the plate thickness T0 of the intermediate ring 34 adjacent to the bent portion 31a is made thinner than the plate thickness T1 of the intermediate ring 34 including the first protrusion 35.

[0039] Figure 10 is a front view showing a part of the body portion 3 of an airless tire 1 according to yet another embodiment of the present invention, and corresponds to portion VI of Figure 4. The airless tire 1 according to the illustrated embodiment differs from the airless tire 1 shown in Figure 9 in the shape of the first protrusion 35. In the airless tire 1 of this embodiment, similar to the airless tire 1 shown in Figure 9, the first protrusion 35 is provided on the wheel-side surface of the intermediate ring 34, between the center 34C of the intermediate ring 34 between adjacent spokes 31, 31 and the bent portion 31a on the acute angle θ1 side of the spoke 31. However, the first protrusion 35 is provided further away from the bent portion 31a than the first protrusion 35 shown in Figure 6. Therefore, the plate thickness T0 of the intermediate ring 34 between the bent portion 31a of the spoke 31 and the first protrusion 35 is thinner than the plate thickness T1 of the intermediate ring 34 including the first protrusion 35. Even with this shape of first protrusion 35, it provides the same effects as the airless tire 1 of the embodiment shown in Figure 9.

[0040] In addition, in Figures 6 and 7, the rigidity of the joint portion between the spoke 31 and the intermediate ring 34 (the bent portion 31a on the obtuse angle θ2 side of the spoke 31) is not increased, and in order to make this portion easily deformable, the plate thickness T0 of the intermediate ring 34 adjacent to the bent portion 31a may be made thinner than the plate thickness T2 of the intermediate ring 34 including the second protrusion 36.

[0041] 《Second Embodiment》 Figure 11 is a perspective view showing a part of the body portion 3 of an airless tire 1 according to yet another embodiment of the present invention, and Figure 12 is an enlarged front view showing portion XII of the body portion 3 of the airless tire 1 according to the embodiment of Figure 11.

[0042] In the airless tire 1 of this embodiment, as shown in Figure 12, a first protrusion 35 is provided on the wheel-side surface of the intermediate ring 34, located between the center 34C of the intermediate ring 34 between adjacent spokes 31, 31 and the bent portion 31a on the acute angle θ1 side of the spoke 31. Furthermore, in the airless tire 1 of this embodiment, as shown in Figure 12, a second protrusion 36 is provided on the non-wheel-side surface of the intermediate ring 34, located between the center 34C of the intermediate ring 34 between adjacent spokes 31, 31 and the bent portion 31a on the obtuse angle θ2 side of the spoke 31.

[0043] In addition, in the airless tire 1 of this embodiment, as shown in Figure 12, a first recess 37 is provided on the wheel-side surface of the intermediate ring 34, between the center 34C of the intermediate ring 34 between adjacent spokes 31, 31 and the bent portion 31a on the acute angle θ1 side of the spoke. Furthermore, in the airless tire 1 of this embodiment, as shown in Figure 12, a second recess 38 is provided on the wheel-side surface of the intermediate ring 34, between the center 34C of the intermediate ring 34 between adjacent spokes 31, 31 and the bent portion 31a on the obtuse angle θ2 side of the spoke 31.

[0044] In this embodiment, the intermediate ring 34 is a plate-shaped member that extends in the width direction of the tire along the tire rotation axis P of the body portion 3. Therefore, the first recess 37 formed on the side of the intermediate ring 34 opposite to the wheel and the second recess 38 formed on the side of the intermediate ring 34 on the wheel side are each formed to extend in the width direction of the tire along the tire rotation axis P of the body portion 3.

[0045] In this embodiment, the first protrusion 35 and the first recess 37 are provided at the same position on the intermediate ring 34 between adjacent spokes 31, 31. Similarly, in this embodiment, the second protrusion 36 and the second recess 38 are provided at the same position on the intermediate ring 34 between adjacent spokes 31, 31. Therefore, as shown in Figure 12, between two adjacent spokes 31, 31, the centerline of the thickness of the intermediate ring 34 curves toward the wheel side and the opposite side of the wheel with respect to the straight line connecting two adjacent bent portions 31a.

[0046] As explained with reference to Figure 4, in the airless tire 1 directly above the ground, the intermediate ring 34 near the acute-angle spoke inclination angle θ1 curves convexly toward the wheel side, while the intermediate ring 34 near the obtuse-angle spoke inclination angle θ2 curves convexly toward the wheel side. To counteract these bending moments M, it is necessary to increase the bending rigidity of the intermediate ring 34.

[0047] Here, the further the center line of the thickness of the intermediate ring 34 is from the line connecting the joint portion (the two bent portions 31a) between the intermediate ring 34 and the spoke 31, the higher the bending rigidity. This can be achieved by the first convex portion 35 and the first concave portion 37, and the second convex portion 36 and the second concave portion 38, respectively. As a result, the bending deformation of the intermediate ring 34 can be suppressed. In addition, compared to the airless tire 1 of the first embodiment, the weight can be reduced by the amount by which the first concave portion 37 and the second concave portion 38 are provided.

[0048] As described above, the airless tire 1 of this embodiment comprises a wheel 2 connected to a vehicle, a plurality of elastic spokes 31 extending radially from the outer circumference of the wheel 2, arranged periodically in the circumferential direction, and provided with a bent portion 31a, and an elastic intermediate ring 34 extending in the circumferential direction and connecting adjacent spokes 31. In this airless tire 1, a first convex portion 35 is provided on the wheel-side surface of the intermediate ring 34 between the center 34C of the intermediate ring 34 between adjacent spokes 31 and the bent portion 31a on the acute angle θ1 side of the spoke 31. As a result, the rigidity between the center 34C of the intermediate ring 34 and the bent portion 31a on the acute angle θ1 side of the spoke 31 is increased, and buckling deformation of this portion can be suppressed.

[0049] Furthermore, according to the airless tire 1 of this embodiment, a second convex portion 36 is provided on the surface of the intermediate ring 34 that is not on the wheel side, between the center 34C of the intermediate ring 34 between adjacent spokes 31 and the bent portion 31a on the obtuse angle θ2 side of the spoke 31. This increases the rigidity between the center 34C of the intermediate ring 34 and the bent portion 31a on the obtuse angle θ2 side of the spoke 31, thereby suppressing buckling deformation of the entire intermediate ring 34.

[0050] Furthermore, according to the airless tire 1 of this embodiment, the height H2 of the second protrusion 36 is lower than the height H1 of the first protrusion 35. Therefore, the bending rigidity of the intermediate ring 34 that is closer to the acute-angle spoke inclination angle θ1 is greater than the bending rigidity of the intermediate ring 34 that is closer to the obtuse-angle spoke inclination angle θ2. As a result, the overall buckling deformation of the intermediate ring 34 can be further suppressed.

[0051] Furthermore, according to the airless tire 1 of this embodiment, a first recess 37 is provided on the surface of the intermediate ring 34 that is not on the wheel side, between the center 34C of the intermediate ring 34 between adjacent spokes 31 and the bent portion 31a on the acute angle θ1 side of the spoke 31, so that the airless tire 1 can be made lighter.

[0052] Furthermore, according to the airless tire 1 of this embodiment, a second recess 38 is provided on the wheel-side surface of the intermediate ring 34, between the center 34C of the intermediate ring 34 between adjacent spokes 31 and the bent portion 31a on the obtuse angle θ2 side of the spoke 31, so that the airless tire 1 can be made lighter.

[0053] Furthermore, according to the airless tire 1 of this embodiment, the first convex portion 35 and the first concave portion 37, and the second convex portion 36 and the second concave portion 38, respectively, cause the center line of the thickness of the intermediate ring 34 to be further away from the line connecting the joint portion (two bent portions 31a) between the intermediate ring 34 and the spoke 31, thereby increasing the bending rigidity. As a result, buckling deformation of the intermediate ring 34 can be further suppressed.

[0054] Furthermore, according to the airless tire 1 of this embodiment, the plate thickness T0 of the intermediate ring 34 between the bent portion 31a of the spoke 31 and the first protrusion 35 is thinner than the plate thickness T1 of the intermediate ring 34 including the first protrusion 35, so that the spoke 31 is more easily deformed in the radial direction. As a result, the tire is more easily deformed even when driving on an uneven road surface, and shock absorption is improved.

[0055] Furthermore, according to the airless tire 1 of this embodiment, the plate thickness T0 of the intermediate ring 34 between the bent portion 31a of the spoke 31 and the second protrusion 36 is thinner than the plate thickness T2 of the intermediate ring 34 including the second protrusion 36, so that the spoke 31 is more easily deformed in the radial direction. As a result, the tire is more easily deformed even when driving on an uneven road surface, and shock absorption is improved. [Explanation of symbols]

[0056] 1…Airless tires 2... Wheels 21…Disk 22...rim 3…Body part 31…Spokes 31a...Bending part 32…Inner ring 32a…Inner peripheral surface 33…Outer ring 34…Intermediate ring 35...First protrusion 36...Second protrusion 37…First recess 38...Second recess 4...Tread Ring P...Tire rotation axis θ1…Acute-angle spoke inclination angle θ2… Obtuse angle of spoke inclination H1...Height of the first protrusion H2...Height of the second protrusion T0... Thickness of the intermediate ring between the bent portion and the first protrusion. T1…Thickness of the intermediate ring including the first protrusion. T2…Thickness of the intermediate ring including the second protrusion.

Claims

1. Wheels that are attached to the vehicle, The wheel comprises a plurality of spokes that extend radially outward, are periodically arranged in the circumferential direction, and are elastic. It comprises an elastic intermediate ring that extends in the circumferential direction and connects adjacent spokes, At the point where the spoke and the intermediate ring intersect, the spoke has a bent portion. In an airless tire, the aforementioned bent portion is such that adjacent angles between the intermediate ring and the spokes are an acute angle and an obtuse angle, An airless tire having a first convex portion, which is larger in thickness than other parts, on the wheel-side surface of the intermediate ring, between the center of the intermediate ring between adjacent spokes and the sharp-angled bend of the spoke.

2. The airless tire according to claim 1, wherein a second convex portion is provided on the surface of the intermediate ring opposite the wheel, between the center of the intermediate ring between adjacent spokes and the bent portion on the obtuse angle side of the spoke.

3. The airless tire according to claim 2, wherein the height of the second protrusion is lower than the height of the first protrusion.

4. The airless tire according to any one of claims 1 to 3, wherein the first recess is provided on the surface of the intermediate ring opposite the wheel, between the center of the intermediate ring between adjacent spokes and the sharp-angled bend of the spoke.

5. An airless tire according to any one of claims 1 to 3, wherein a second recess is provided on the wheel-side surface of the intermediate ring, between the center of the intermediate ring between adjacent spokes and the bent portion on the obtuse angle side of the spoke.

6. The airless tire according to any one of claims 1 to 3, wherein the thickness of the intermediate ring between the bent portion of the spoke and the first protrusion is thinner than the thickness of the intermediate ring including the first protrusion.

7. The airless tire according to any one of claims 1 to 3, wherein the thickness of the intermediate ring between the bent portion of the spoke and the second protrusion is thinner than the thickness of the intermediate ring including the second protrusion.

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