Airless tires

Abstract

While possessing the function of stress distribution through the intermediate ring, the intermediate ring structure can also be used to improve the rigidity in the circumferential direction of the tire. [Solution] The airless tire 1A comprises an inner circumferential ring 12, a plurality of spokes 13 each extending radially outward from the outer circumferential surface of the inner circumferential ring 12, an outer circumferential ring 14 attached to the radially outward ends of the spokes 13, and at least two intermediate rings 15 provided between the inner circumferential ring 12 and the outer circumferential ring 14. The portions of each intermediate ring 15 that are adjacent in the circumferential direction with respect to the spokes 13 are arranged such that the radial distance from the axle to the center of the thickness of that portion is different from one another.

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a non-pneumatic tire including: a plurality of elastic spokes provided radially from the outer peripheral side of a wheel coupled to a vehicle toward the inner peripheral side of a tread grounded on a road surface; and an elastic intermediate ring provided to connect to the plurality of spokes between the wheel and the tread, the spokes having a bent portion that bends in a direction connecting both end portions thereof between an end portion on the wheel side and an end portion on the tread side, and the intermediate ring being connected to the bent portion.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Since a non-pneumatic tire does not have a sidewall, the torsional rigidity in the circumferential direction of the tire is lower than that of a pneumatic tire. When the torsional rigidity in the circumferential direction is low, the natural frequency of circumferential torsion becomes lower than that of a pneumatic tire, and there is a possibility that the natural vibration of the suspension and the natural vibration of the tire are coupled. When the natural vibration of the suspension and the natural vibration of the tire are coupled, the vibration level increases, which may lead to deterioration of the riding comfort, vehicle interior noise, and durability of the tire. In particular, circumferential torsional vibration is excited when passing through minute irregularities on the road surface and is likely to cause the above problems.

[0005] In the airless tire disclosed in Patent Document 1, the intermediate ring deforms in response to a load in the vertical direction of the tire, i.e., a direction normal to the tire's contact surface, distributing the stress on the spokes. However, in response to a load in the tangential direction to the contact surface, i.e., a circumferential load, the spokes between the intermediate rings deform mainly, and the two intermediate rings rotate relatively within the tire while maintaining their circular shape. In this deformation mode, the intermediate rings do not easily contribute to improving the natural frequency of circumferential torsion.

[0006] The object of the present invention is to provide an airless tire that can improve the circumferential rigidity of the tire while having the function of stress distribution by an intermediate ring. [Means for solving the problem]

[0007] An airless tire according to an aspect of the present invention comprises an inner circumferential ring, a plurality of spokes extending radially outward from the outer circumferential surface of the inner circumferential ring, and an outer circumferential ring attached to the radially outward ends of the spokes. The airless tire further comprises at least two intermediate rings provided between the inner circumferential ring and the outer circumferential ring. The portions of each intermediate ring adjacent in the circumferential direction, with respect to the spokes, are arranged such that the radial distance from the axle to the thickness center of the portion is different from one another. [Effects of the Invention]

[0008] According to the above embodiment of the present invention, it is possible to improve the circumferential rigidity of the tire while having the function of stress distribution by the intermediate ring. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is an overall front view of the airless tire according to the first embodiment. [Figure 2A] Figure 2A is an overall front view of the airless tire according to the comparative example. [Figure 2B] Figure 2B is an overall front view of the airless tire according to the comparative example above, showing deformation due to circumferential load. [Figure 3A]Figure 3A is a partially enlarged view of the airless tire related to the comparative example described above. [Figure 3B] Figure 3B is a partially enlarged view of the airless tire according to the first embodiment described above. [Figure 3C] Figure 3C is a partially enlarged view of the airless tire according to the second embodiment. [Figure 3D] Figure 3D is a partially enlarged view of an airless tire according to a modified example of the first embodiment described above. [Figure 4A] Figure 4A is a partially enlarged view of an airless tire in an unloaded state, relating to a comparative example used to explain the method for evaluating radial compressive stiffness. [Figure 4B] Figure 4B is a partially enlarged view of the wheel load condition of an airless tire related to a comparative example used to explain the method for evaluating radial compressive stiffness. [Figure 5A] Figure 5A is an overall front view of the airless tire according to the first embodiment described above. [Figure 5B] Figure 5B is a partially enlarged view of the airless tire according to the first embodiment described above. [Figure 6] Figure 6 is an overall front view of the airless tire according to the second embodiment described above. [Figure 7A] Figure 7A is an overall front view of the airless tire according to the third embodiment. [Figure 7B] Figure 7B is a partially enlarged view of the airless tire according to the third embodiment described above. [Figure 8] Figure 8 is an overall front view of the airless tire according to the fourth embodiment. [Modes for carrying out the invention]

[0010] An airless tire according to an embodiment will be described with reference to the drawings.

[0011] While referring to FIG. 1, the airless tire 1A according to the first embodiment will be described. The airless tire 1A shown in FIG. 1 is assembled to a wheel 11 made of a highly rigid material such as metal. The vehicle axle is fixed to the center of the wheel 11. The airless tire 1A includes, from its inner peripheral side, an inner peripheral ring 12 that contacts the outer periphery of the wheel 11, a plurality of spokes 13, an outer peripheral ring 14, and a tread ring 16 formed on the outer peripheral surface of the outer peripheral ring 14. The airless tire 1A contacts the ground with the tread surface of the tread ring 16. The inner peripheral ring 12 is attached to the wheel 11. The spokes 13 are provided substantially radially in the radially outward direction from the outer peripheral surface of the inner peripheral ring 12 and are arranged at substantially equal intervals in the circumferential direction. The outer peripheral ring 14 is connected to the radially outward ends of the spokes 13. The airless tire 1A includes two intermediate rings 15 between the inner peripheral ring 12 and the outer peripheral ring 14. The portion excluding the wheel 11 and the tread ring 16 is also referred to as the body portion.

[0012] Each spoke 13 is connected to the intermediate ring 15. The inner peripheral ring 12, the spokes 13, the intermediate ring 15, the outer peripheral ring 14, and the tread ring 16 are formed of an elastic material. They may be formed of the same material, or may be formed of different materials as long as they are bonded, and are mainly formed of rubber or resin. In particular, the inner peripheral ring 12, the spokes 13, the outer peripheral ring 14, and the intermediate ring 15 can use various existing materials such as thermoplastic resins and thermosetting resins. The tread ring 16 is provided on the outer peripheral surface of the outer peripheral ring 14 and preferably has a composite structure that encapsulates reinforcing fibers such as steel cords. The airless tire 1A having the above overall configuration is mounted on a vehicle, supports the vehicle, and transmits the driving and braking forces to the ground.

[0013] Figures 2A and 2B show the comparative example airless tire 1X. Figure 2A shows the unloaded state. Figure 2B shows the state when circumferential torsional input occurs, i.e., when a circumferential load is applied to the tread surface, such as during vehicle operation, as obtained from structural analysis using the finite element method. Since the airless tire 1X is sandwiched between a relatively rigid wheel 11 (see Figure 1, not shown in Figures 2A and 2B) and a tread ring 16, the spokes 13 deform mainly in the area surrounding the intermediate ring 15. As shown in Figure 2B, the deformation mode of the airless tire 1X is such that the two intermediate rings 15 rotate relative to each other inside the tire while maintaining their circular shape, and the spokes 13 deform mainly. At this time, because the rotation angles of the two intermediate rings 15 are different, the spokes 13 between the two intermediate rings 15 bend in the circumferential direction, and as a result the spokes 13 exhibit a deformation mode in which bending and compression are combined.

[0014] Next, Figures 3A to 3D show the spokes 13 and intermediate rings 15 of the comparative example and the first embodiment (including modified versions) and the second embodiment. Figure 3A is a partially enlarged view of the airless tire 1X of the comparative example shown in Figure 2A. In the airless tire 1X of the comparative example, as shown in Figure 2B, the two intermediate rings 15 are displaced relative to each other in the circumferential direction, so the spokes 13 between the two intermediate rings 15 deform to tilt in the circumferential direction. In this comparative example, the intermediate rings 15 are displaced in the circumferential direction along with the tilting of the spokes 13, so their contribution to improving circumferential rigidity is small.

[0015] Figure 3B is a partially enlarged view of the airless tire 1A of the first embodiment shown in Figure 1. As shown in Figure 3B, in the airless tire 1A, the cells partitioned by spokes 13 between two intermediate rings 15 are alternately offset towards the outer or inner circumference along the circumferential direction. Furthermore, the intermediate rings 15 are not connected to the bent portions of the spokes 13. In other words, the portions of each intermediate ring 15 partitioned by spokes 13 are alternately offset radially along the circumferential direction. Alternatively, in each intermediate ring 15, the circumferentially adjacent portions separated by a single spoke 13 are arranged such that the radial distance from the axle to the center of the thickness of that portion is different from one another.

[0016] Therefore, when a circumferential load is input, the deformation modes of the spoke 13 and the intermediate ring 15 in the first embodiment are different from those of the comparative example. In the non-pneumatic tire 1A of the first embodiment, when a circumferential load is input, the intermediate ring 15 functions as a member that suppresses the deformation of the spoke 13. That is, the intermediate ring 15 functions as a member that improves the circumferential rigidity. Note that the intermediate ring 15 of the non-pneumatic tire 1X according to the comparative example had a function of dispersing the radial load in the circumferential direction, and the intermediate ring 15 of the non-pneumatic tire 1A of the first embodiment also has this function.

[0017] For example, in the non-pneumatic tire 1A of the first embodiment, in each cell partitioned by the spoke 13 between the intermediate rings 15, the radial distance between the intermediate rings 15 is equal, but this distance may be different between each cell. FIG. 3C shows a non-pneumatic tire 1B according to the second embodiment. In the non-pneumatic tire 1B according to the second embodiment, the radial distance between the intermediate rings 15 is set to alternately increase and decrease along the circumferential direction. In other words, the radial dimensions of the cells partitioned by the spoke 13 between two intermediate rings 15 are set to alternately increase and decrease along the circumferential direction. Here too, the intermediate ring 15 is not connected to the bent portion of the spoke 13.

[0018] The effect of improving the circumferential torsional rigidity by the non-pneumatic tire 1B according to the second embodiment is equivalent to that of the non-pneumatic tire 1A according to the first embodiment. However, when cells with different distances between the intermediate rings 15 are arranged adjacent to each other in the circumferential direction, when the non-pneumatic tire 1B rotates, a new problem arises that the radial rigidity varies depending on the grounding position of the tire, and the amount of deformation with respect to the radial load varies according to the rotation angle of the tire. Therefore, a structure in which cells with equal distances between the intermediate rings 15 are arranged in the circumferential direction, like the non-pneumatic tire 1A of the first embodiment shown in FIGS. 1 and 3B, is more preferable.

[0019] Figure 3D shows an airless tire 1A' according to a modification of the first embodiment. In this modified airless tire 1A', the angle of the spokes 13 between the intermediate rings 15 with respect to the radial direction (the straight line passing through the center O of the airless tire 1A') is smaller than the angle of the airless tire 1A of the first embodiment. As a result, the radial compressive rigidity of the cells partitioned by the spokes 13 between the intermediate rings 15 is improved. In this case, bending and compressive deformation of the spokes 13 between the intermediate rings 15 is suppressed when circumferential torsional input is applied. As a result, the circumferential torsional rigidity is improved. Furthermore, in this modification, by reducing the angle of the spokes 13 between the intermediate rings 15 with respect to the radial direction, the angle of the line connecting the connection point between the spokes 13 and the inner circumferential ring 12 and the connection point between the spokes 13 and the outer circumferential ring 14 with respect to the radial direction (see θ1 in Figure 5B) is reduced. As a result, the circumferential torsional rigidity can be improved more effectively.

[0020] The angle of spoke 13 refers to the largest angle among the angles formed by the line segment connecting the connection point between the inner intermediate ring 15 and the spoke 13, the connection point between the outer intermediate ring 15 and the spoke 13, and the radial direction, in the case of a cell between the intermediate ring 15 and the inner ring 12. Similarly, in the case of a cell between the intermediate ring 15 and the inner ring 12, it refers to the largest angle among the angles formed by the line segment connecting the connection point between the inner ring 12 and the spoke 13, the connection point between the intermediate ring 15 and the spoke 13, and the radial direction, in the case of a cell between the intermediate ring 15 and the outer ring 14. Furthermore, in the case of a cell between the intermediate ring 15 and the outer ring 14, it refers to the largest angle among the angles formed by the line segment connecting the connection point between the outer ring 14 and the spoke 13, the connection point between the intermediate ring 15 and the spoke 13, and the radial direction. Each connection point is defined as the intersection of the plate thickness centerlines of the spoke 13 connected at that connection point and the rings 12, 14, or 15. Unless otherwise specified, "angle" refers to the size of a corner.

[0021] Here, the method for evaluating the radial compressive stiffness between the intermediate rings 15 will be explained below. Figure 4A shows the airless tire 1X of the comparative example in an unloaded state. Figure 4B shows the state of the airless tire 1X when a vehicle wheel load is applied, i.e., when a radial load is applied, as obtained from structural analysis using the finite element method.

[0022] As shown in Figures 4A and 4B, the airless tire 1X deforms under the input of a wheel load, and the radial distance d11 between the inner ring 12 and the inner intermediate ring 15, the radial distance d21 between the intermediate rings 15, and the radial distance d31 between the outer intermediate ring 15 and the outer ring 14 at the center of contact change to radial distances d12, d22, and d32, respectively. The contact center line Y in Figure 4B is a straight line passing through the center of contact of the tread surface and the center O of the airless tire 1X, and the radial distances d12, d22, and d32 are the distances along this straight line Y.

[0023] Each radially adjacent cell can be considered as a series spring, and when evaluating the compressive stiffness of a cell, it can be represented and replaced by the radial deformation under wheel load. Therefore, by making the deformation between the intermediate rings 15 (d21-d22) less than the deformation between the inner ring 12 and the inner intermediate ring 15 (d11-d12), and less than the deformation between the outer ring 14 and the outer intermediate ring 15 (d31-d32) (i.e., satisfying (d21-d22) < (d11-d12) and (d21-d22) < (d31-d32)), the radial compressive stiffness of the cells between the intermediate rings 15 can be improved.

[0024] As described above, in airless tires 1A, 1A', and 1B having an intermediate ring 15, the torsional rigidity can be improved by utilizing the intermediate ring 15 as a component for improving torsional rigidity and by optimizing the arrangement of cells between the intermediate ring 15 and the other cells.

[0025] The following provides a more detailed explanation of each embodiment.

[0026] (First Embodiment) Figures 5A and 5B show the airless tire 1A according to the first embodiment shown in Figures 1 and 3B. Note that the wheel 11 and tread ring 16 are not shown in Figures 5A and 5B. In this embodiment, each intermediate ring 15 is not a single continuous circle, but is composed of arcs of different radii having the same center point, and cells with equal distances between intermediate rings 15 are arranged alternately radially offset along the circumferential direction. With this structure, the intermediate rings 15 function as members that improve circumferential rigidity, thereby improving the circumferential rigidity of the airless tire 1B.

[0027] Furthermore, in this embodiment, each spoke 13 has an even number of vertices in its zigzag shape, specifically two. The vertices of the zigzag shape are the bending points of the spoke 13, and refer to the points where the angle with respect to the radial direction changes from positive to negative, or from negative to positive, when counterclockwise rotation is considered positive with respect to the radial direction (a straight line passing through the center of the airless tire). Also, in this embodiment, as shown in Figure 5B, the line connecting the connection point P1 between the spoke 13 and the inner ring 12 and the connection point P4 between the spoke 13 and the outer ring 14 is inclined at an angle θ1 with respect to the radial direction. In the illustrated example, θ1 = 20°. By having an even number of vertices in the zigzag shape, the inclination direction of the spoke 13 at the connection point with the inner ring 12 can be aligned with the inclination direction of the spoke 13 at the connection point with the outer ring 14. In other words, the angle θ1 can be set to a large value without locally bending the spoke 13 significantly at the vertices of the zigzag shape. As the entire spoke 13 is inclined at an angle θ1, the spoke 13 resists circumferential torsional input with its compressive stiffness, thereby improving the circumferential stiffness of the airless tire 1A. In other words, according to this embodiment, the circumferential stiffness of the tire can be improved while distributing stress with the zigzag-shaped spoke 13 and the intermediate ring 15.

[0028] In this embodiment, the number of intermediate rings 15 is equal to the number of vertices in the zigzag shape of the spokes 13, and the intermediate rings 15 are connected near the vertices. This structure effectively improves circumferential rigidity. In this embodiment, if the smallest thickness of the intermediate rings 15 is denoted as d, the connection between the spokes 13 and the intermediate rings 15 is positioned within a range of ±d radially from the vertices. This configuration also further effectively improves circumferential rigidity.

[0029] (Modified version of the first embodiment, and the second embodiment) The airless tire 1A', a modified version of the first embodiment shown in Figure 3D, can also achieve the same effects as the first embodiment. However, as described above, in the modified airless tire 1A', the angle of the spokes 13 between the intermediate rings 15 with respect to the radial direction is smaller than the angle of the airless tire 1A of the first embodiment. As a result, the radial compressive rigidity of the cells partitioned by the spokes 13 between the intermediate rings 15 is improved.

[0030] Figure 6 shows the airless tire 1B according to the second embodiment shown in Figure 3C. The airless tire 1B according to the second embodiment shown in Figure 6 can also obtain the same effects as the first embodiment. However, as described above, the airless tire 1B is prone to a new problem in which the amount of deformation in response to radial load varies depending on the contact position. Therefore, a structure in which cells with equal distances between intermediate rings 15 are arranged in the circumferential direction, as in the airless tire 1A of the first embodiment, is more preferable.

[0031] (Third embodiment) Figures 7A and 7B show an airless tire 1C according to the third embodiment. In this embodiment, the radial compressive stiffness of the cells between the intermediate rings 15 is set higher than the compressive stiffness of the other cells. As shown in Figure 7B, the angle θa of the spokes 13 between the intermediate rings 15 with respect to the radial direction is smaller than the angle θb of the spokes 13 between the outer ring 14 and the outer intermediate ring 15 with respect to the radial direction. Also, the angle θa of the spokes 13 between the intermediate rings 15 with respect to the radial direction is smaller than the angle θc of the spokes 13 between the inner ring 12 and the inner intermediate ring 15 with respect to the radial direction. In the illustrated example, θa = 0.3θb and θb = θc.

[0032] Furthermore, as shown in Figure 7B, the thickness d2 of the spokes 13 between the intermediate rings 15 is greater than the thickness d1 of the spokes 13 between the outer ring 14 and the outer intermediate ring 15. Moreover, the thickness d2 of the spokes 13 between the intermediate rings 15 is greater than the thickness d3 of the spokes 13 between the inner ring 12 and the inner intermediate ring 15. In the illustrated example, d2 = 1.25d1 and d1 = d3.

[0033] By reducing the angle θa of the spokes 13 between the intermediate rings 15 with respect to the radial direction, the angle θ1 of the entire spoke 13 with respect to the radial direction (see Figure 5B) can be set to be larger. In this embodiment, since only the spokes 13 between the intermediate rings 15 have a different inclination direction, the smaller the angle θa, the larger the angle θ1. Therefore, the circumferential torsional rigidity can be improved more effectively. In the illustrated example, θ1 = 40°. In addition, in this embodiment, the radial compressive rigidity of the cells between the intermediate rings 15 is set higher than the compressive rigidity of the other cells. This setting of compressive rigidity for each cell can be confirmed by the fact that, under wheel load, the amount of radial deformation of the cells between the intermediate rings 15 is smaller than the amount of radial deformation of the other cells. According to the airless tire 1C of this embodiment, when circumferential torsional input is applied, the compressive deformation of the cells between the intermediate rings 15 can be reduced, thereby improving the circumferential rigidity of the airless tire 1C.

[0034] (Fourth Embodiment) Figure 8 shows an airless tire 1D according to the third embodiment. In this embodiment, reinforcing spokes 13A are added to each cell between the intermediate rings 15 to improve compressive rigidity, compared to the airless tire 1C of the third embodiment shown in Figures 7A and 7B. Therefore, in the region between the intermediate rings 15, there are more spokes 13 (including 13A) arranged in the circumferential direction than in the region between the inner ring 12 and the inner intermediate ring 15, or between the outer ring 14 and the outer intermediate ring 15. According to this embodiment, the radial compressive rigidity of the cells between the intermediate rings 15 is higher than that of the other cells, so the circumferential torsional rigidity can be effectively improved.

[0035] The effects and benefits of the airless tires mentioned above will now be explained.

[0036] (1) When an airless tire having an intermediate ring 15 is subjected to a load normal to the contact surface, i.e., a radial load, the spokes 13 near the contact surface are bent and compressed in the radial direction, and at the same time, the intermediate ring 15 also deforms. The deformation of the intermediate ring 15 causes adjacent spokes 13 to deform as well, and as a result, the radial load applied to the spokes 13 is distributed in the circumferential direction, allowing the entire tire to support the load. In the airless tires 1A to 1D and 1A' of the above embodiments, the portions of each intermediate ring 15 demarcated by the spokes 13 are further offset radially alternately along the circumferential direction. Alternatively, in each intermediate ring 15, the portions adjacent in the circumferential direction with respect to a single spoke 13 are arranged such that the radial distance from the axle to the center of the thickness of that portion is different from each other. Therefore, even when a load tangential to the contact surface, i.e., a circumferential load, is applied, the intermediate ring 15 functions as a member that suppresses the deformation of the spokes 13. As a result, deformations like those shown in Figure 2B are suppressed, and the circumferential rigidity of the tire is improved. In other words, the airless tire of the above embodiment can improve the circumferential rigidity of the tire while having the function of stress distribution by the intermediate ring 15. It is preferable that the intermediate ring 15, which is alternately offset radially along the circumferential direction, be located on two concentric circles, from the viewpoint of maximizing both stress distribution and circumferential rigidity. However, the shape of the intermediate ring 15 is not limited to this shape.

[0037] (2) In the airless tires of the above embodiments (1A to 1D and 1A'), the spokes 13 have a zigzag shape. Furthermore, each spoke 13 has a zigzag shape with an even number of vertices, and the line connecting the connection point P1 with the inner ring 12 and the connection point P4 with the outer ring 14 forms an angle θ1 (>0) with respect to the radial direction. If the number of vertices were odd and the entire spoke 13 were inclined with respect to the radial direction, the spoke 13 would bend significantly locally at the vertices, which could become a cause of stress concentration. If the number of vertices is even, for example, when counterclockwise is considered positive with respect to the radial direction, the angles of the spokes 13 are arranged in the order of positive, negative, ..., positive from the cells on the inside of the radial direction. As a result, the spokes 13 can be inclined such that the line connecting the connection points P1 and P4 forms an angle θ1 with respect to the radial direction, while suppressing significant local bending of the spokes 13 at the vertices. The inclination of the spokes 13 can improve circumferential rigidity. Here, setting θ1 > 20 degrees is preferable because it effectively improves rigidity when a circumferential load is applied, and setting θ1 > 30 degrees is more preferable.

[0038] (3) In the airless tires of the above embodiments (1A to 1D and 1A'), the number of intermediate rings 15 is equal to the number of vertices of the zigzag shape. Therefore, by connecting the intermediate rings 15 near the vertices, deformation of the spokes 13 originating from the vertices can be more effectively suppressed, and circumferential rigidity can be effectively improved. When the smallest thickness of the intermediate rings 15 is denoted as d, it is effective for the connection between the intermediate rings 15 and the spokes 13 to be positioned within ±2d in the radial direction from the vertices of the zigzag shape of the spokes 13, and it is even more effective to position it within ±d.

[0039] (4) In the deformation of the airless tire 1X according to the comparative example shown in Figure 2B, the two intermediate rings 15 are displaced relative to each other in the circumferential direction, so the spokes 13 between the intermediate rings 15 tilt in a direction that increases the angle with respect to the radial direction (see Figure 2B). As a result, the cells between the intermediate rings 15 are compressed and the distance between the intermediate rings 15 becomes smaller. In the airless tires of the above embodiments (1A to 1D and 1A'), when a wheel load is applied, the amount of radial deformation of the cells between the intermediate rings 15 is smaller than the amount of radial deformation of the other cells. That is, the radial compressive stiffness of the cells partitioned by the spokes 13 between the intermediate rings 15 is higher than the compressive stiffness of the other cells. By improving the compressive stiffness of the cells between the intermediate rings 15, the torsional stiffness is also improved. Note that radially adjacent cells can be considered as series springs, so when evaluating the compressive stiffness of the cells, it is reasonable to evaluate it by representing it with the amount of radial deformation of each cell on the ground contact center line Y when a wheel load is applied.

[0040] (5) In the airless tire 1C of the third embodiment and the airless tire 1D of the fourth embodiment, the angle θa of the spokes 13 with respect to the radial direction between the intermediate rings 15 is smaller than the angles θb and θc of the other spokes 13 with respect to the radial direction. In order to achieve the effects of (4) above, and to increase the radial compressive rigidity of the cells between the intermediate rings 15 compared to the other cells while suppressing an increase in overall mass, it is effective to make the angle θa smaller than the angles θb and θc. Here, it is preferable that θa < 0.5θb and θa < 0.5θc.

[0041] (6) In the airless tire 1C of the third embodiment and the airless tire 1D of the fourth embodiment, the thickness d2 of the spokes 13 between the intermediate rings 15 is greater than the thicknesses d1 and d3 of the other spokes 13. In order to achieve the effects of (4) above, it is effective to make the thickness d2 greater than the thicknesses d1 and d3 in order to make the radial compressive stiffness of the cells between the intermediate rings 15 higher than the compressive stiffness of the other cells. Here, it is preferable that d2 > 1.1d1 and d2 > 1.1d3. If the thickness of the spokes 13 is non-uniform, the average value of the thickness of the spokes 13 surrounding that cell is used.

[0042] (7) In the airless tire 1D of the fourth embodiment described above, reinforcing spokes 13A are added between adjacent spokes 13 only between the intermediate rings 15. In order to achieve the effects of (4) described above, it is effective to add reinforcing spokes 13A in this way in order to make the radial compressive stiffness of the cells between the intermediate rings 15 higher than the compressive stiffness of the other cells.

[0043] As described above, embodiments of the present invention have been presented, but the statements and drawings that constitute part of this disclosure should not be understood as limiting the invention. Various alternative embodiments, examples, and operational techniques will become apparent to those skilled in the art from this disclosure. For example, in the above embodiments, the airless tire 1A and the wheel 11 were separate parts, but they may be integrated. In this case, the airless tire 1A and the wheel 11 would have a hub similar to that of the wheel 11 in its center, and the outer circumference of this hub would become the inner ring 12. In this case, a metal hub may be insert-molded during the resin molding of the spokes 13 and the outer ring 14. [Explanation of symbols]

[0044] 1A, 1A', 1B, 1C, 1D Airless Tires 11 wheels 12 Inner ring 13 spokes 13A Reinforced Spokes 14 Outer ring 15 Intermediate ring 16 Tread Rings

Claims

1. It is an airless tire, A wheel with an axle fixed to the center, A body portion having an inner circumferential ring attached to the wheel, a plurality of spokes extending radially outward from the outer circumferential surface of the inner circumferential ring, an outer circumferential ring connected to the radially outward ends of the spokes, and at least two intermediate rings provided between the inner circumferential ring and the outer circumferential ring, which connect the plurality of spokes in the circumferential direction, A tread ring provided on the outer surface of the outer ring, Equipped with, An airless tire in which, in each of the intermediate rings, the portions adjacent to each other in the circumferential direction with respect to the spokes are arranged such that the radial distance from the axle to the center of the thickness of the portion is different from that of the other portion.

2. An airless tire according to claim 1, An airless tire in which each of the spokes has a zigzag shape with an even number of vertices, and the line connecting the connection point with the inner ring and the connection point with the outer ring forms an angle with respect to the radial direction.

3. An airless tire according to claim 2, An airless tire in which the number of intermediate rings is equal to the number of vertices of the zigzag shape.

4. An airless tire according to claim 3, An airless tire in which the radial compressive stiffness of the cells partitioned by the spokes between the intermediate rings is higher than that of the other cells, and when a wheel load is applied, the amount of radial deformation of the cells between the intermediate rings is smaller than that of the other cells.

5. An airless tire according to claim 3 or 4, An airless tire in which the angle of the spokes with respect to the radial direction between the intermediate rings is smaller than the angle of the other spokes with respect to the radial direction.

6. An airless tire according to claim 3 or 4, An airless tire in which the thickness of the spokes between the intermediate rings is greater than the thickness of the other spokes.

7. An airless tire according to claim 3 or 4, An airless tire in which reinforcing spokes are added between adjacent spokes only between the intermediate rings.

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