airless tires

Abstract

An airless tire equipped with a plurality of elastic spokes (12) which are provided so as to radiate from the outer-circumferential side of a wheel (11) connected to a vehicle toward the inner-circumferential side of a tread (15) which contacts the road surface, and an elastic intermediate ring (13) which is provided so as to connect to the plurality of spokes (12) between the wheel (11) and the tread (15), wherein: the spokes (12) have a bending section (16) which is located between the end section (12a) thereof on the wheel side and the end section (12b) thereof on the tread side, and zigzags back and forth relative to the direction connecting said end sections to one another; and the intermediate ring (13) is connected to the bending section (16).

Description

[Technical Field]

[0001] The present invention relates to an airless tire (also called a non-pneumatic tire). [Background technology]

[0002] One example of an airless tire that does not use air is a tire whose support structure for supporting the load from a vehicle includes an inner annular portion, an intermediate annular portion concentrically arranged on the outside of the inner annular portion, an outer annular portion concentrically arranged on the outside of the intermediate annular portion, a plurality of inner connecting portions connecting the inner annular portion and the intermediate annular portion, and a plurality of outer connecting portions connecting the outer annular portion and the intermediate annular portion (Patent Document 1).In this conventional technology, because the intermediate annular portion is interposed between the multiple connecting portions connecting the inner annular portion and the outer annular portion, it is said that fluctuations in stiffness due to the positional relationship between the spoke position and the center position of the contact patch are unlikely to occur. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-35050 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned conventional technology, if the outer annular portion could be made of a rigid body, the amount by which the connecting portions (spokes) near the ground surface contract in response to wheel load would be the same as the amount by which the connecting portions (spokes) on the opposite side, at the top of the tire, expand. However, the outer annular portion cannot be made of a rigid body because it needs to ensure a contact length to generate lateral force in the tire when steering and to absorb small road surface irregularities. Therefore, even in the above-mentioned conventional technology tires, the connecting portions (spokes) near the ground surface are structured so that a large wheel load acts on them, which reduces the durability of the connecting portions (spokes).

[0005] The problem to be solved by the present invention is to provide an airless tire that can distribute the load acting on the tire. [Means for solving the problem]

[0006] The present invention solves the above problem by providing an airless tire comprising a plurality of elastic spokes arranged radially from the outer periphery of the wheel toward the inner periphery of the tread, and an elastic intermediate ring connected to the plurality of spokes between the wheel and the tread, in which a bent portion is provided between the wheel-side end and the tread-side end of the spokes, which bends in the direction connecting these two end portions, and the intermediate ring is connected to the bent portion. [Effects of the Invention]

[0007] According to the present invention, the load acting on the tire is input to the spokes, but the load acting on the bent parts of the spokes is transmitted in the circumferential direction of the tire by the intermediate ring, thereby dispersing the load acting on the tire. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a front view showing the basic structure of an airless tire according to an embodiment of the present invention. [Figure 2A] FIG. 2 is a perspective view showing the rim of the wheel of FIG. 1. [Figure 2B] 2B is an exploded perspective view showing the rim of the wheel of FIG. 2A. FIG. [Figure 3] 1 is a perspective view showing an airless tire according to a first embodiment of the present invention. [Figure 4] FIG. 4 is a front view showing the airless tire according to the first embodiment of FIG. 3. [Figure 5] 5 is an enlarged front view showing a V portion of FIG. 4. FIG. [Figure 6] 6 is a graph showing axial forces acting on an intermediate ring of the airless tire shown in FIG. 5 at different positions on the intermediate ring. [Figure 7]4 is a graph showing the distribution rate of the vertical load transmitted from the spokes to the wheel of the airless tire according to the first embodiment for each angle of the tire. [Figure 8A] FIG. 4 is an enlarged front view showing a comparative example of the first embodiment. [Figure 8B] 8B is a graph showing the distribution rate of the vertical load transmitted from the spokes to the wheel of the airless tire according to the comparative example of FIG. 8A for each angle of the tire. [Figure 9] FIG. 2 is a perspective view showing an airless tire according to a second embodiment of the present invention. [Figure 10] FIG. 10 is a front view showing the airless tire according to the second embodiment of FIG. 9. [Figure 11] 11 is an enlarged front view showing a portion XI in FIG. 10 in an enlarged manner. [Figure 12] FIG. 10 is an enlarged front view showing an airless tire according to still another embodiment of the present invention. [Figure 13] FIG. 10 is an enlarged front view showing an airless tire according to still another embodiment of the present invention. [Figure 14] FIG. 10 is an enlarged front view showing an airless tire according to still another embodiment of the present invention. [Figure 15] FIG. 10 is an enlarged front view showing an airless tire according to still another embodiment of the present invention. [Figure 16] FIG. 10 is an enlarged front view showing an airless tire according to still another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

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

[0010] <Basic structure of airless tires> Fig. 1 is a front view showing the basic structure of an airless tire 1 according to an embodiment of the present invention, and the configuration common to the first and second embodiments described below will first be described with reference to Fig. 1. As shown in Fig. 1, the airless tire 1 of this embodiment includes a wheel 11, spokes 12, an intermediate ring 13, an outer ring 14, and a tread 15.

[0011] The wheel 11 is fixed to a hub of a vehicle (not shown). The wheel 11 is configured to include, for example, a circular disk 111 and a cylindrical rim 112, and is made of metal or other highly rigid materials. In the front view of FIG. 1, the disk 111 of the wheel 11 is shown as a circular member in the center of the airless tire 1, and this disk 111 is fixed to the hub of the vehicle, thereby supporting the airless tire 1 on an axle.

[0012] FIG. 2A is a perspective view showing the rim 112 of the wheel 11 of FIG. 1, and FIG. 2B is an exploded perspective view of the rim 112. For ease of understanding, FIGS. 2A and 2B omit the illustration of the disk 111 of the wheel 11 that connects to the hub of the vehicle, and only show the rim 112 of the wheel 11 to which the spokes 12 are engaged. The rim 112 of the wheel 11 of this embodiment is structured to be divided into two members 112a and 112b in the width direction of the tire. A plurality of grooves 113 are formed on the outer peripheral surface of the rim 112, and the inner ends of the spokes 12 are engaged with these grooves 113. The grooves 113 are provided approximately evenly along the circumferential direction of the outer peripheral surface of the rim 112, and have an anchor-shaped cross section. When attaching the spokes 12 to the rim 112, the rim 112 is disassembled into two members 112a and 112b as shown in Figure 2B, and the inner ends of the spokes 12, which have a cross-sectional shape that matches the anchor shape, are inserted into the grooves 113, the inner ends of the spokes 12 are sandwiched between the two members 112a and 112b, and the two members 112a and 112b are joined with fastening members such as bolts. This binds the multiple spokes 12 to the wheel 11 in both the radial and circumferential directions.

[0013] The means for attaching the spokes 12 to the wheel 11 is not limited to this example as long as robustness can be ensured. For example, the outer peripheral surface of the rim 112 of the wheel 11 and the inner peripheral ends of the spokes 12 may be bonded together using an adhesive. Alternatively, the outer peripheral surface of the rim 112 of the wheel 11 and the inner peripheral ends of the spokes 12 may be directly connected together using bolts without providing grooves 113 in the outer peripheral surface of the rim 112 of the wheel 11. Alternatively, an annular inner ring may be provided to connect the inner peripheral ends of the multiple spokes 12, and this inner ring may be bonded to the outer peripheral surface of the rim 112 of the wheel 11 using an adhesive. In this case, the inner peripheral surface of the inner ring may be provided with protrusions that fit into grooves 113 formed in the rim 112 of the wheel 11, thereby joining the inner peripheral ring to the wheel 11.

[0014] The tread 15 is formed in a cylindrical shape and is provided on the outermost periphery of the airless tire 1. The tread 15 is made of a composite material in which an elastic material such as natural rubber or synthetic rubber is reinforced with metal or resin tire cords. A tread pattern is formed on the outer periphery of the tread 15, similar to that of a conventional pneumatic tire, and forms the contact surface with the road surface.

[0015] The outer ring 14 is a cylindrical member that connects the tread-side ends of the multiple spokes 12, and is fastened to the inner circumferential surface of the above-mentioned tread 15 by means of adhesive or the like. The outer ring 14 is made of an elastic material such as an elastic thermoplastic resin or an elastic thermosetting resin, and may be molded integrally with the spokes 12. Note that in the airless tire 1 of the present invention, the outer ring 14 is not an essential component, and the tread-side ends of the spokes 12 may be fastened directly to the tread 15, thereby eliminating the need for the outer ring 14.

[0016] The above is the basic structure of the airless tire 1 according to the embodiment of the present invention, and below, an embodiment of the configuration of the spokes 12 and intermediate ring 13 provided between the wheel 11 and the tread 15 will be described.

[0017] First Embodiment FIG. 3 is a perspective view of an airless tire 1 according to a first embodiment of the present invention, FIG. 4 is a front view of the airless tire 1 according to the first embodiment of FIG. 3, and FIG. 5 is an enlarged front view of a V-section of FIG. 4. The spokes 12 according to this embodiment are made of an elastic material such as an elastic thermoplastic resin or an elastic thermosetting resin, and extend radially from the outer periphery of the wheel 11 toward the inner periphery of the tread 15, with a plurality of spokes 12 provided at equal intervals along the circumferential direction of the tire. The plurality of spokes 12 are arranged symmetrically about the center axis of the tire. In the enlarged front view of FIG. 5, three spokes 121, 122, and 123 are shown from right to left. The number of spokes 12 provided on one airless tire 1 is not particularly limited and can be set appropriately depending on the tire's contact length, the load-bearing capacity of the spokes 12, vibration resistance, and other required specifications of the tire.

[0018] As shown by the reference numerals 12a and 12b in the rightmost spoke 121 in Fig. 5, each spoke 12 has a bent portion 16 formed between the wheel-side end 12a and the tread-side end 12b, which is bent in the direction connecting these end portions 12a and 12b. This spoke 12 is formed in a zigzag shape when viewed in the direction of the tire's rotational axis (front view in Figs. 4 and 5). The rightmost spoke 121 in Fig. 5 has five bent portions 161, 162, 163, 164, and 165 formed from the wheel-side end 12a toward the tread-side end 12b. Note that although the reference numerals for the bent portions 16 are only given to the rightmost spoke 121 in Fig. 5, bent portions 16 of the same configuration are formed in each spoke 12 around the entire circumference of the tire.

[0019] If the degree of bending of the bent portions 16 of the spokes 12 is extremely small, the spokes 12 will buckle and deform between the bent portions, making it impossible to restrict the amount of deformation in the circumferential direction of the tire. For this reason, the minor angle θ of the bent portions 16 shown in Figure 5 is not particularly limited, but is preferably set to less than 120°.

[0020] The intermediate ring 13 of this embodiment is made of an elastic material, such as an elastic thermoplastic resin or an elastic thermosetting resin, similar to the spokes 12, and is provided between the wheel 11 and the tread 15, connected to the multiple spokes 12. The intermediate ring 13 has a cylindrical shape concentric with the wheel 11 and the tread 15. While two intermediate rings 13 are provided in the front view of the basic configuration shown in FIG. 1, the airless tire 1 of the first embodiment shown in FIGS. 3 to 5 includes five intermediate rings 13. The number of intermediate rings 13 provided in one airless tire 1 is not particularly limited, but by providing two, four, six, or another even number of intermediate rings 13, the balance of forces in the circumferential direction of the tire is maintained. Therefore, the axial force (compressive force and tensile force) acting on the intermediate ring 13 is continuous throughout the circumference of the tire, and the load acting on the bent portions 16 of the spokes 12 can be distributed throughout the entire tire. This results in a reduced rolling resistance coefficient (RRC).

[0021] 3 and 4, one intermediate ring 13 is provided in an annular shape between the wheel 11 and the tread 15, and therefore intersects with a plurality of spokes 12, but in the airless tire 1 of this embodiment, each intermediate ring 13 is connected to each spoke 12 at each bend 16. That is, as shown in the enlarged front view of FIG. 5, the innermost intermediate ring 131 is connected to the innermost bend 161 of each spoke 121, 122, and 123, the next innermost intermediate ring 132 is connected to the next innermost bend 162 of each spoke 121, 122, and 123, and the outermost intermediate ring 135 is connected to the outermost bend 165 of each spoke 121, 122, and 123.

[0022] Furthermore, in the airless tire 1 of this embodiment, the bent portions 16 of the spokes 12 connected to the same intermediate ring 13 are formed to bend in the same direction relative to the circumferential direction of the tire. That is, as shown in the enlarged front view of Fig. 5, when looking at the intermediate ring 131 provided on the innermost side, the bending directions of the bent portions 161 of the three spokes 121, 122, and 123 connected to this intermediate ring 131 are all convex to the left in Fig. 5. Similarly, when looking at the intermediate ring 132 provided next innermost, the bending directions of the bent portions 162 of the three spokes 121, 122, and 123 connected to this intermediate ring 132 are all convex to the right in Fig. 5.

[0023] In this embodiment, when the bent portions 16 of the spokes 12 connected to the same intermediate ring 13 are formed to bend in the same direction relative to the circumferential direction of the tire (i.e., when the zigzags of the spokes 12 are set in phase), the deformation direction of the bent portions 16 of the spokes 12 in the circumferential direction is the same for adjacent spokes 12. Looking at the innermost intermediate ring 131 shown in Figure 5, the bending directions of the bent portions 161 of the three spokes 121, 122, and 123 connected to this intermediate ring 131 all point to the left, as indicated by the arrows in Figure 5. Looking at the next innermost intermediate ring 132, the bending directions of the bent portions 162 of the three spokes 121, 122, and 123 connected to this intermediate ring 132 all point to the right, as indicated by the arrows in Figure 5. Therefore, the axial force (compressive force and tensile force) acting on the intermediate ring 13 becomes continuous throughout the entire circumference of the tire, and the load acting on the bent portions 16 of the spokes 12 can be distributed throughout the entire tire, resulting in a reduced rolling resistance coefficient.

[0024] Next, the operation will be described. When a wheel load (vehicle weight) acts on the airless tire 1 of this embodiment, each spoke 12 near the road surface bends at each bend 16, causing the spokes 12 to deform in the radial direction of the tire. At this time, the bend 16 deforms in the circumferential direction of the tire as shown by the arrows in Fig. 5, so the vertical load (wheel load) acting on the tire is propagated in the circumferential direction, allowing the load to be distributed throughout the tire.

[0025] In the airless tire 1 of this embodiment, when the spokes 12 near the road surface are compressed and deformed in the radial direction of the tire, the intermediate rings 131, 133, and 135 propagate the load in the clockwise direction as shown by the arrows in FIG. 5, while the intermediate rings 132 and 134 anti The load is transmitted in a clockwise direction. In this way, all of the intermediate rings 13 do not transmit the load in the same rotational direction, but rather offset the rotational forces, making it possible to make tire deformation uniform overall. As mentioned above, by using an even number of intermediate rings 13, the rotational forces are further offset. The bent portions 16 in the spokes 12 are provided so that a portion of the spokes 12 can move in the circumferential direction of the tire in response to deformation of the spokes 12 in the radial direction of the tire.

[0026] FIG. 6 is a graph showing the results of calculating the axial forces acting on each of the intermediate rings 131-135 of the airless tire 1 shown in FIGS. 3-5 (tensile or compressive forces acting on the intermediate rings (here, each beam) connecting the bent portions 16 of each spoke 12) for each position of the intermediate rings 131-135. The horizontal axis represents the position of the intermediate ring [deg], with the center of contact with the ground being 0° and directly above the tire being 180°. The vertical axis represents the axial force [N], with the tensile force acting on the intermediate ring as a positive (+) force and the compressive force as a negative (-) force.

[0027] In the airless tire 1 shown in Figures 3 to 5, it can be seen that not only is the axial force acting on each of the five intermediate rings 131 to 135 large in the range of +90° to -90°, but that the axial force acting has a continuous value throughout the entire tire. This confirms the effect of distributing the load throughout the entire tire in the airless tire 1 shown in Figures 3 to 5. Although not shown, in the case of the first embodiment, compressive and tensile forces act alternately on the five intermediate rings 131 to 135, so it can be said that the load is not distributed throughout the entire tire compared to the configuration of the second embodiment described below. In other words, it can be said that, compared to the second embodiment, there is an effect of transmitting circumferential deformation of the bent portions 16 of the spokes 12 near the contact with the ground to the upper part of the tire.

[0028] Next, the effects of the airless tire 1 according to the first embodiment will be described in comparison with a comparative example. FIG. 7 is a graph showing the distribution rate (Z direction) of the vertical load Pz transmitted from the spokes 12 to the wheel 11 of the airless tire 1 according to the first embodiment shown in FIGS. 3 to 5 for each tire angle [deg]. The tire angle [deg] on the horizontal axis is represented by setting the contact center point at 0° and directly above the tire at 180°. The vertical distribution rate on the vertical axis is represented by a normalized value obtained by dividing the vertical load Pz (Z direction) distributed by each angle range by the wheel load. As shown in FIG. 7, in the airless tire 1 shown in FIGS. 3 to 5, the vertical distribution rate in the vicinity of 0° from the contact center point continuously increases, while the vertical distribution rate in the vicinity of ±180° directly above the tire from the contact center point also distributes approximately 5% of the load.

[0029] In contrast, FIG. 8A is a front view (enlarged front view corresponding to FIG. 5) showing an airless tire as a comparative example of the airless tire 1 according to the first embodiment, in which a honeycomb structure is employed in the spokes. FIG. 8B is a graph showing the distribution rate (Z direction) of the vertical load Pz transmitted from the spokes 12 to the wheel 11 of the airless tire according to the comparative example shown in FIG. 8A for each tire angle α [deg]. As with the graph of FIG. 7, the tire angle α [deg] on the horizontal axis is represented by setting the contact point at 0° and directly above the tire at 180°. The vertical distribution rate on the vertical axis is represented by a normalized value obtained by dividing the vertical load Pz (Z direction) distributed by each angle range by the wheel load. As shown in FIG. 8B, in the airless tire according to the comparative example, the vertical distribution rate is high near the 0° contact point, and the vertical distribution rate near ±180°, directly above the tire from the contact point, is only about 1%. Moreover, it can be seen that the waveform of the vertical contribution rate shows discrete values throughout.

[0030] Another effect of the airless tire 1 according to this embodiment, that is, the rolling resistance of the tire, will now be described. The rolling resistance coefficient (RRC) of the tire can be calculated using the following equation.

number

number

[0031] In the above formulas 1 and 2, ENt represents the tire's loss energy, Lt represents the tire's effective circumference, Fz represents the wheel load, Si represents the strain energy of each portion, tanδi represents the material's loss coefficient, and Vi represents the volume of each portion. The structure of the airless tire 1 according to this embodiment was modeled, a structural analysis was performed, the strain energy Si of each portion of the tire was derived, and the product of the material's tanδi and volume was calculated. This made it possible to derive the tire's overall loss energy ENt, from which the RRC could be calculated. The rolling resistance coefficient RRC of the tire was calculated by applying this method to the results of the structural analysis. It was confirmed that the rolling resistance coefficient RRC of the airless tire 1 according to the first embodiment shown in FIGS. 3 to 5 was 48% of the rolling resistance coefficient RRC of the airless tire according to the comparative example having a honeycomb shape shown in FIG. 8A.

[0032] The strain energy Si in the above formula 2 can also be considered as follows:

number

[0033] In the above formula 3, σi represents the stress at each portion, and Ei represents the Young's modulus of the material at each portion. As is clear from the above formula 3, the strain energy Si is proportional to the square of the stress σi at each portion, so reducing stress contributes greatly to the strain energy, which also leads to a reduction in the rolling resistance coefficient RRC in the above formulas 1 and 2. From the load distribution ratios in the vertical direction shown in Figures 7 and 8B, it can be seen that the less the load is concentrated near the contact center point, the more the stress near the contact center point can be reduced, which explains the effect of reducing the rolling resistance coefficient RRC according to the present invention.

[0034] Second Embodiment Fig. 9 is a perspective view showing an airless tire 1 according to a second embodiment of the present invention, Fig. 10 is a front view showing the airless tire 1 according to the second embodiment of Fig. 9, and Fig. 11 is an enlarged front view showing an enlarged portion XI of Fig. 10. The airless tire 1 of this embodiment differs from the configuration of the first embodiment described above in that the bent portions 16, 16 of two spokes 12, 12 that are adjacent in the circumferential direction of the tire and connected to the same intermediate ring 13 are formed so as to bend in opposite directions relative to the circumferential direction of the tire. The other configurations are the same as those of the first embodiment, and therefore the description thereof is incorporated herein by reference.

[0035] That is, in the airless tire 1 of the first embodiment shown in Fig. 5, when looking at the intermediate ring 131 provided on the innermost side, the bending directions of the bending portions 161 of the three spokes 121, 122, and 123 connected to this intermediate ring 131 are all convex to the left in Fig. 5. Similarly, when looking at the intermediate ring 132 provided next innermost, the bending directions of the bending portions 162 of the three spokes 121, 122, and 123 connected to this intermediate ring 132 are all convex to the right in Fig. 5.

[0036] In contrast, in the airless tire 1 of this embodiment, as shown in Figs. 9 to 11, two adjacent spokes (for example, spokes 121 and 122, and spokes 123 and 124 in Fig. 11) form a pair of spokes, and this pair of spokes 12, 12 is provided at equal intervals around the entire circumference of the tire. In the airless tire 1 of this embodiment, as shown in Fig. 11, when looking at the intermediate ring 131 provided on the innermost side, of the bent portions 161 of the four spokes 121, 122, 123, 124 connected to this intermediate ring 131, the bending direction of the bent portions 161 of the spokes 121, 123 is convex to the left in Fig. 11, and the bending direction of the bent portions 161 of the spokes 122, 124 is convex to the right in Fig. 11. Similarly, when looking at the intermediate ring 132 provided next on the inner circumference side, 4 Spokes 121, 122, 123 ,124 Among the bent portions 162, the bent portions of the spokes 121 and 123 162The bending direction of the spokes 122 and 124 is convex to the right in FIG. 162 The bending direction is convex to the left in FIG.

[0037] In this embodiment, when the bent portions 16 of the spokes 12 connected to the same intermediate ring 13 are bent in opposite directions relative to the circumferential direction of the tire (i.e., the zigzags of the spokes 12 are set out of phase), when a wheel load (vehicle weight) acts on the tire, not only is there a dispersion effect due to the transmission of the load by the intermediate ring 13, but the radial rigidity of the spokes 12 near the center of contact with the ground is also increased. As a result, the thickness of the spokes 12 and the intermediate ring 13 can be reduced, thereby achieving a lighter tire.

[0038] Other Embodiments FIG. 12 is an enlarged front view of an airless tire according to yet another embodiment of the present invention, and is an enlarged front view corresponding to FIG. 5 when viewed from the entire tire. In the airless tire 1 of this embodiment, the minor angles θ of the multiple bends 16 formed in one spoke 12 are formed so that they decrease from the wheel-side end 12a toward the tread-side end 12b (some of the angles may be equal). That is, as shown in FIG. 12, when the minor angles θ of the multiple bends 16 formed in one spoke 122 are θ1, θ2, θ3, θ4, and θ5 from the wheel-side end 12a to the tread-side end 12b, the minor angles are set so that the relationship θ1 ≥ θ2 ≥ θ3 ≥ θ4 ≥ θ5 holds. The smaller the minor angle θ of the bends 16, the more easily the structure bends under the same load. Therefore, in the airless tire 1 of this embodiment, the bends 16 closer to the outer periphery are structured to be more easily bendable.

[0039] When the spokes 12 near the center point of contact with the ground are compressed and deformed in the radial direction, the spokes 12 deform circumferentially at the bends 16, as shown in Figure 5, and the intermediate rings 13 transmit the load in the circumferential direction. In this case, in the airless tire 1 of this embodiment, the bends 16 closer to the outer periphery are designed to bend more easily, so the amount of circumferential displacement increases for intermediate rings 13 located closer to the outer periphery. As a result, the difference in circumferential length is absorbed, and force transmission by the inner intermediate ring 13 and the outer intermediate ring 13 can be made uniform.

[0040] Fig. 13 is an enlarged front view of an airless tire according to still another embodiment of the present invention, and is an enlarged front view of the entire tire corresponding to Fig. 5. In the airless tire 1 of this embodiment, directions L1, L2, and L3 connecting the wheel-side end 12a and the tread-side end 12b of the spokes 12 are inclined in the circumferential direction of the tire by a predetermined angle γ that exceeds 0 with respect to each of the radial directions R1, R2, and R3 of the tire.

[0041] In the airless tire 1 of this embodiment configured as described above, when the spokes 12 near the contact center point deform in the radial direction, the spokes 12 also generate a component force in the circumferential direction of the tire, i.e., in the front-to-rear direction of the vehicle. Therefore, by providing an angle γ between the direction L1, L2, L3 connecting the wheel-side end 12a and the tread-side end 12b of the spokes 12 and the radial directions R1, R2, R3 of the tire, as in the airless tire 1 of this embodiment, it is possible to reduce rolling resistance by the component force in the circumferential direction of the tire (the front-to-rear direction of the vehicle) generated by the spokes 12 while the tire is rotating.

[0042] 14 is an enlarged front view showing an airless tire according to still another embodiment of the present invention, and is an enlarged front view corresponding to a part of FIG. 5 when viewed from the entire tire. In the airless tire 1 of this embodiment, the bending rigidity of the spokes 12 is set to a value greater than the bending rigidity of the intermediate ring 13.

[0043] That is, when the modulus of longitudinal elasticity of the material of the spokes 12 is Es, the modulus of longitudinal elasticity of the material of the intermediate ring 13 is Erc, the thickness of the spokes 12 is ts, the thickness of the intermediate ring 13 is trc, the width of the spokes 12 in the width direction of the tire is ws, and the width of the intermediate ring 13 in the width direction of the tire is wrc, Es·ts 3 ·ws≧Erc·trc 3 These values are set so that wrc is equal to 1. If the bending rigidity of the spokes 12 is smaller than that of the intermediate ring 13, the amount of deformation near the center point of contact with the ground increases, but by setting the bending rigidity of the spokes 12 to a value greater than that of the intermediate ring 13, as in the airless tire 1 of this embodiment, the effect of the spokes 12 in supporting the wheel load increases, and the load can be supported by the entire tire.

[0044] 15 is an enlarged front view showing an airless tire according to still another embodiment of the present invention, and is an enlarged front view corresponding to FIG. 5 when viewed from the entire tire. The airless tire 1 of this embodiment is provided with an even number of intermediate rings 13, that is, four. As described above, in the airless tire 1 of this embodiment, when the spokes 12 near the road surface are compressed and deformed in the radial direction of the tire, the intermediate rings 131, 133, and 135 transmit the load in the clockwise direction as shown by the arrows in FIG. 5, while the intermediate rings 132 and 134 transmit the load in the clockwise direction. anti The load is transmitted in a clockwise direction. In this way, all of the intermediate rings 13 do not transmit the load in the same rotational direction, but rather offset the rotational forces, making it possible to make the tire deformation uniform overall. However, by using an even number of intermediate rings 13, the rotational forces are further offset.

[0045] In the airless tire 1 according to the embodiment shown in Fig. 15, as in the first embodiment, the bent portions 16 of the spokes 12 connected to the same intermediate ring 13 are formed so as to bend in the same direction relative to the circumferential direction of the tire, and as in the embodiment shown in Fig. 12, the minor angle θ of the multiple bent portions 16 formed in one spoke 12 is formed so as to decrease from the wheel-side end 12a to the tread-side end 12b. In the airless tire 1 according to the embodiment shown in Fig. 15, as in the embodiment shown in Fig. 13, the directions L1, L2, and L3 connecting the wheel-side end 12a and the tread-side end 12b of the spoke 12 are inclined in the circumferential direction of the tire by a predetermined angle γ that exceeds 0 with respect to each of the radial directions R1, R2, and R3 of the tire.

[0046] FIG. 16 is an enlarged front view of an airless tire according to yet another embodiment of the present invention, and is an enlarged front view corresponding to FIG. 5 when viewed from the entire tire. In the airless tire 1 of this embodiment, as in the second embodiment, the bent portions 16 of the spokes 12 connected to the same intermediate ring 13 are formed so as to bend in the opposite direction to the circumferential direction of the tire, and an even number of intermediate rings 13 is provided, four. Also, as in the embodiment shown in FIG. 12, the minor angle θ of the multiple bent portions 16 formed in one spoke 12 is formed so as to decrease from the wheel-side end 12a to the tread-side end 12b. Also, in the airless tire 1 according to the embodiment shown in FIG. 15, as in the embodiment shown in FIG. 13, the directions L1, L2, and L3 connecting the wheel-side end 12a and the tread-side end 12b of the spoke 12 are inclined in the circumferential direction of the tire by a predetermined angle γ that exceeds 0 with respect to each of the radial directions R1, R2, and R3 of the tire.

[0047] As described above, according to the airless tire 1 of this embodiment, the spokes 12 have the bent portions 16, and the intermediate ring 13 is connected to the bent portions 16. Therefore, the load acting on the bent portions 16 of the spokes 12 from the tire is transmitted in the circumferential direction of the tire by the intermediate ring 13, thereby dispersing the load acting on the tire. As a result, the rolling resistance coefficient can be reduced.

[0048] Furthermore, according to the airless tire 1 of this embodiment, the spokes 12 are formed in a zigzag shape when viewed in the direction of the tire's rotation axis, which clarifies the deformation mode at the bent portions 16 of the spokes 12. As a result, the load acting on the tire can be further distributed.

[0049] Furthermore, according to the airless tire 1 of this embodiment, the bent portions 16 of the spokes 12 connected to the same intermediate ring 13 are formed so as to bend in the same direction relative to the circumferential direction of the tire, so that the direction of deformation of the bent portions 16 in the circumferential direction is the same as that of the adjacent spokes 12. This makes the axial force (compressive force and tensile force) acting on the intermediate ring 13 continuous over the entire circumference of the tire, thereby further dispersing the load acting on the tire.

[0050] Furthermore, according to the airless tire 1 of this embodiment, the bent portions 16 of two spokes 12 that are adjacent in the circumferential direction of the tire and that are connected to the same intermediate ring 13 are formed so as to bend in opposite directions relative to the circumferential direction of the tire, thereby increasing the apparent rigidity of the spokes 12 near the center point of contact with the ground. This allows the spokes 12 and intermediate ring 13 to be made of less material, thereby reducing the weight of the airless tire 1.

[0051] Furthermore, according to the airless tire 1 of this embodiment, the minor angle θ of the bent portion 16 is formed to decrease from the wheel-side end 12a toward the tread-side end 12b, so that the deformation of the bent portion 16 in response to radial deformation of the spokes 12 increases toward the outer periphery. This makes the acting force of the intermediate ring 13 uniform, further distributing the load acting on the tire.

[0052] Furthermore, according to the airless tire 1 of this embodiment, the directions L1, L2, and L3 connecting the wheel-side end 12a and the tread-side end 12b of the spokes 12 are inclined in the circumferential direction of the tire by a predetermined angle γ that exceeds 0 with respect to each of the tire radial directions R1, R2, and R3, so that a force can be generated in the fore-and-aft direction of the vehicle when the tire rotates. This reduces the rolling resistance of the airless tire 1.

[0053] Furthermore, according to the airless tire 1 of this embodiment, the bending rigidity of the spokes 12 is set to a value greater than the bending rigidity of the intermediate ring 13, so that the load acting on the tire can be further distributed.

[0054] Furthermore, according to the airless tire 1 of this embodiment, an even number of intermediate rings 13 are provided, so that the balance of the forces in the circumferential direction is maintained by the intermediate rings 13, and the load acting on the tire can be further distributed. [Explanation of symbols]

[0055] 1. Airless tires 11...Wheels 111...Disc 112…Rim 113...Groove 12,121~124...Spokes 12a...Wheel side end 12b...Tread side edge 13,131~135...Intermediate ring 14...Outer ring 15...Tread 16,161~165...Bend R1, R2, R3... Radial direction of tire L1, L2, L3...Direction connecting the wheel-side end of the spoke with the tread-side end

Claims

1. a plurality of elastic spokes arranged radially from an outer periphery of a wheel coupled to a vehicle toward an inner periphery of a tread that comes into contact with a road surface; an elastic intermediate ring provided between the wheel and the tread and connected to the plurality of spokes; the spoke has a bent portion between the wheel-side end and the tread-side end, the bent portion being bent in a direction connecting the two end portions, the intermediate ring is connected to the bent portion; an angle of the bent portion that decreases from the wheel-side end toward the tread-side end;

2. The airless tire according to claim 1 , wherein the spokes are formed in a zigzag shape when viewed in the direction of the rotation axis of the tire.

3. 3. The airless tire according to claim 1, wherein the bent portions of the spokes connected to the same intermediate ring are formed so as to bend in the same direction relative to the circumferential direction of the tire.

4. 3. The airless tire according to claim 1, wherein the bent portions of two spokes that are connected to the same intermediate ring and adjacent to each other in the circumferential direction of the tire are formed so as to bend in opposite directions relative to the circumferential direction of the tire.

5. 5. The airless tire according to claim 1, wherein a direction in which the wheel-side end portion and the tread-side end portion of the spoke are connected is inclined in a circumferential direction of the tire by a predetermined angle greater than 0 with respect to a radial direction of the tire.

6. The airless tire according to any one of claims 1 to 5, wherein the flexural rigidity of the spokes is set to a value greater than the flexural rigidity of the intermediate ring.

7. The airless tire according to any one of claims 1 to 6, wherein an even number of the intermediate rings are provided.

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