Airless tires

Abstract

While possessing the function of stress distribution through the intermediate ring, it can also distribute stress and strain concentrated in the radially outer cells. [Solution] The airless tire 1A comprises an inner circumferential ring 12, a plurality of spokes 13 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 inner circumferential ring 12, intermediate rings 15 and outer circumferential ring 14 and the spokes 13 define a cell. With respect to radially adjacent cells, the spoke 13 of the outermost cell has a bend point PX, and if the angle with respect to the radial direction of the portion of the spoke 13 radially outward from the bend point PX is θ11, and the angle with respect to the radial direction of the portion of the spoke 13 radially inward from the bend point PX is θ12, then θ11

Description

Technical Field

[0004] , ,

[0005] , ,

[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 contacting the road surface, and an elastic intermediate ring provided connected to the plurality of spokes between the wheel and the tread. The spokes have a bent portion that bends in a direction connecting both end portions thereof between the wheel-side end portion and the tread-side end portion, and the intermediate ring is 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] When a wheel load of a vehicle is applied, the elastic body portion and the tread ring of a non-pneumatic tire deform, and the load is supported by the reaction force during deformation. The body portion generally has a radial spoke structure. In a state where the non-pneumatic tire contacts the ground and supports the load, the plurality of radial spokes buckle near the ground contact surface, and stress and strain increase at the buckled portion. When stress and strain concentrate and occur, durability deteriorates.

[0005] In the airless tire disclosed in Patent Document 1, when a wheel load is applied, the spokes and intermediate rings deform simultaneously, and the deformation of the spokes is propagated to adjacent spokes by the intermediate rings. Therefore, compared to an airless tire with simple radial spokes, the stress and strain due to buckling near the contact surface are distributed. On the other hand, because it has a structure in which cell structures partitioned by spokes and each ring are stacked, the stress and strain of the spokes are not continuously distributed in the radial direction, but rather discontinuously distributed between adjacent cells. In particular, when focusing on the amount of deformation of radially adjacent cells, the amount of deformation tends to be relatively large in the radially outer cells, and stress and strain tend to concentrate there.

[0006] The object of the present invention is to provide an airless tire that has the function of stress distribution by an intermediate ring, while also being able to distribute stress and strain concentrated in the radially outer cells. [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. A cell is defined by the inner circumferential ring, the intermediate rings and the outer circumferential ring and the spokes. With respect to radially adjacent cells, the spoke of the outermost cell has a bend point, and if the angle with respect to the radial direction of the portion of the spoke radially outward from the bend point is θ11, and the angle with respect to the radial direction of the portion of the spoke radially inward from the bend point is θ12, then θ11 < θ12. [Effects of the Invention]

[0008] According to the above airless tire, while having the function of stress distribution by the intermediate ring, it is possible to distribute the stress and strain that are concentrated in the radially outer cells. [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 an overall front view of the airless tire according to the first embodiment 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 first embodiment described above. [Figure 4A] Figure 4A is an overall front view of the airless tire according to the second embodiment. [Figure 4B] Figure 4B is a partially enlarged view of the airless tire according to the second embodiment described above. [Figure 4C] Figure 4C is a partially enlarged view of the airless tire according to the second embodiment described above. [Modes for carrying out the invention]

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

[0011] The airless tire 1A according to the first embodiment will be described with reference to Figure 1. The airless tire 1A shown in Figure 1 is assembled on a wheel 11 made of a highly rigid material such as metal. The airless tire 1A comprises, from its inner circumference side, an inner circumference ring 12 that contacts the outer circumference of the wheel 11, a plurality of spokes 13, an outer circumference ring 14, and a tread ring 16 formed on the outer circumference surface of the outer circumference ring 14. The airless tire 1A contacts the ground with the tread surface of the tread ring 16. The inner circumference ring 12 is attached to the wheel 11. The spokes 13 are arranged substantially radially outward from the outer circumference surface of the inner circumference ring 12 and are arranged at substantially equal intervals in the circumferential direction. The outer circumference ring 14 is connected to the radially outward ends of the spokes 13. The airless tire 1A has two intermediate rings 15 between the inner circumference ring 12 and the outer circumference ring 14. The part excluding the wheel 11 and the tread ring 16 is also called the body part.

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

[0013] Figures 2A and 2B show the comparative airless tire 1X. Figure 2A shows the unloaded state. Figure 2B shows the state when a wheel load is applied, obtained from structural analysis using the finite element method. From Figure 2B, it can be seen that the amount of deformation of the spokes 13 when a wheel load is applied differs from cell to cell, with the outermost cell having a larger deformation and stress and strain concentrating near the contact surface. Therefore, as in the embodiment described below, setting a bend point PX in the spokes 13 of the outermost cell and appropriately setting the radial stiffness of the spokes 13 is effective in improving stress and strain concentration near the contact surface.

[0014] The following describes each embodiment.

[0015] (First Embodiment) Figures 3A to 3C show the airless tire 1A of the first embodiment shown in Figure 1. Note that the wheel 11 and tread ring 16 are not shown in Figures 3A to 3C. In the airless tire 1A, cells are divided by rings 12, 14, 15 and spokes 13. The cells are stacked in three layers in the radial direction. The spoke 13 of the outermost cell has a bend point PX. The portion of the spoke 13 radially inward from the bend point PX is approximately straight or slightly curved convexly to the left in the figure, as shown in Figure 3B. The portion of the spoke 13 radially outward from the bend point PX is curved convexly to the right in the figure. If the angle of the portion radially outward from the bend point PX with respect to the radial direction (the straight line passing through the center O of the airless tire) is θ11, and the angle of the portion radially inward from the bend point PX with respect to the radial direction is θ12, then θ12 is greater than θ11 (θ11 < θ12). Therefore, the extension direction of the portion of the spoke 13 closer to the outer ring 14 approaches the radial direction, improving the radial rigidity of the spoke 13. This improves the radial rigidity of the outer circumference of the airless tire 1A, and can alleviate stress concentration near the contact surface. In the illustrated example, θ11 = 0.5θ12.

[0016] Note that the angle θ11 with respect to the radial direction of the portion on the radially outer side of the bending point PX of the spoke 13 refers to the angle formed by the line segment connecting the connection point between the outer peripheral ring 14 and the spoke 13 and the bending point PX, and the radial direction. Also, the angle θ12 with respect to the radial direction of the portion on the radially inner side of the bending point PX of the spoke 13 refers to the angle formed by the line segment connecting the connection point between the intermediate ring 15 and the spoke 13 and the bending point PX, and the radial direction. Each connection point is defined as the intersection point of the center line of the plate thickness of the spoke 13 and the ring 12, 14, or 15 connected at that connection point. The bending point PX is the point where the curvature of the center line of the plate thickness of the spoke 13 is maximum. Also, "angle" refers to the magnitude of the angle, unless otherwise specified.

[0017] As shown in FIG. 3B, when the distance between the connection point of the spoke 13 of the outermost peripheral side cell with the outer peripheral ring 14 and the bending point PX is L11, and the distance between the connection point of the spoke 13 with the intermediate ring 15 and the bending point PX is L12, L12 is larger than L11 (L11 < L12). That is, in the spoke 13, the portion on the radially outer side of the bending point PX is shorter than the portion on the radially inner side of the bending point PX. Thereby, since the bending point PX is set near the ground surface where stress and strain tend to concentrate, that is, near the outer peripheral ring 14, buckling and large deformation of the spoke 13 can be prevented, and stress concentration can be effectively suppressed. In the illustrated example, L11 = 0.3L12.

[0018] As shown in FIG. 3B, the distance between the connection point of the spoke 13 of the outermost peripheral side cell having the bending point PX with the intermediate ring 15 and the connection point with the outer peripheral ring 14 is set as L1. Similarly, the distance between the connection points of the spoke 13 of the other cells is set as Ln (n = 2, 3,...). Also, the maximum value among Ln is set as Lnmax. In the present embodiment, L1 > Lnmax. That is, in the cells adjacent in the radial direction, the distance L1 between the connection points of the spoke 13 of the outermost peripheral side cell is longer than the longest Lnmax among the distances Ln between the connection points of the spoke 13 of the other cells. For this reason, local stress and strain concentration can be alleviated. In the illustrated example, L1 = 1.15Ln (n = 2, 3). <>

[0019] Also, in the present embodiment, as shown in FIG. 4C, a line connecting the connection point P1 between the spoke 13 and the inner peripheral ring 12 and the connection point P4 between the spoke 13 and the outer peripheral ring 14 is inclined at an angle θa with respect to the radial direction (θa > 0). By inclining the entire spoke 13 at the angle θa, an equivalent spoke length can be set longer, and stress concentration can be alleviated. In the illustrated example, the angle θa = 40°.

[0020] (Second Embodiment) FIGS. 4A to 4C show the airless tire 1B of the second embodiment. Also in this embodiment, a folding point PX is set on the spoke 13 of the cell on the outermost peripheral side, and θ11 < θ12, L11 < L12, Lnmax < L1, and θa > 0 are satisfied. Further, in this embodiment, as shown in FIG. 4B, the relationship between the angle θn of the spoke 13 of the cell on the innermost peripheral side with respect to the radial direction and the angle θ1 of the spoke 13 of the outermost peripheral side with respect to the radial direction is θn > θ1. That is, the spoke 13 of the cell on the outermost peripheral side extends in a direction closer to the radial direction than the spoke 13 of the cell on the innermost peripheral side. Therefore, the radial rigidity of the spoke 13 on the outermost peripheral side can be increased compared to the radial rigidity of the spoke 13 on the innermost peripheral side, and the concentration of stress and strain in the vicinity of the ground contact surface can be alleviated. In the illustrated example, θ1 = 0.8 × θn.

[0021] The angle θn (n = 1, 2, 3 ···) of the spoke 13 means an angle formed by a line segment connecting the connection point between the inner peripheral intermediate ring 15 and the spoke 13 and the connection point between the outer peripheral intermediate ring 15 and the spoke 13 and the radial direction in the case of a cell between the intermediate rings 15. Also, in the case of a cell between the intermediate ring 15 and the inner peripheral ring 12, it means an angle formed by a line segment connecting the connection point between the inner peripheral ring 12 and the spoke 13 and the connection point between the intermediate ring 15 and the spoke 13 and the radial direction. Further, in the case of a cell between the intermediate ring 15 and the outer peripheral ring 14, it means an angle formed by a line segment connecting the connection point between the outer peripheral ring 14 and the spoke 13 and the connection point between the intermediate ring 15 and the spoke 13 and the radial direction.

[0022] Furthermore, in this embodiment, as shown in Figure 4C, θn > θ12 holds true. In the illustrated example, θn > θ12 > θ1 holds true. This makes it possible to alleviate the concentration of stress and strain around the connection point P3 between the spoke 13 and the intermediate ring 15 in the outermost cell. In addition, the portion of the spoke 13 closer to the outer ring 14 can be extended in a direction closer to the radial direction, further improving rigidity against radial load input.

[0023] The effects and benefits of the airless tires mentioned above will now be explained.

[0024] (1) In airless tires, stress and strain tend to concentrate in the outermost cells. Therefore, it is desirable to improve the radial rigidity of the spokes 13 near the connection point between the spokes 13 and the outer ring 14 to prevent stress concentration. To improve the radial rigidity of the spokes 13, it is effective to reduce the angle of the spokes 13 with respect to the radial direction, thereby bringing the extension direction of the spokes 13 closer to the radial direction. However, if the angle of the spokes 13 is reduced in the outermost cells, including the portion radially inward from the bending point PX near the intermediate ring 15, the radial rigidity of the entire tire becomes excessively high, which is undesirable. In the outermost cells, a bending point PX is set in the spokes 13, and the relationship between the angle θ11 of the portion radially outward from the bending point PX and the angle θ12 of the portion radially inward from the bending point PX is set to θ11 < θ12. In this way, stress concentration can be mitigated while optimizing the overall rigidity of the tire. In other words, according to the airless tires 1A and 1B of the above embodiment, the intermediate ring provides a stress distribution function while distributing the stress and strain concentrated in the radially outer cells. It is preferable that θ11 ≤ 0.5θ12.

[0025] (2) In a non-pneumatic tire having an intermediate ring, the deformation of the spokes is restricted by the intermediate ring, so stress and strain tend to increase in the vicinity of the connection between the intermediate ring and the spokes. Therefore, if the folding point PX is located near the connection between the intermediate ring 15 and the spoke 13, the folding point PX will be located at a site with large stress and strain, and buckling or deformation may occur in the spoke 13 near the folding point PX. After satisfying the condition of θ11 < θ12, as shown in FIG. 3B, let L11 < L12. L11 is the distance between the connection point of the outer peripheral ring 14 of the portion radially outside the folding point PX and the folding point PX. L12 is the distance between the connection point of the intermediate ring 15 of the portion radially inside the folding point PX and the folding point PX. Thereby, the folding point PX is set closer to the outer peripheral ring 14, and buckling and large deformation of the spoke 13 in the outermost peripheral cell can be prevented, and stress concentration can be effectively suppressed. It is more preferable that L11 < 0.5L12.

[0026] (3) To relieve the concentration of stress and strain, it is effective to increase the length of the spoke 13, that is, to increase the length of the beam equivalent to the spoke. Here, as shown in FIG. 3B, the relationship between the distance L1 between the connection point of the spoke 13 of the outermost peripheral cell and the outer peripheral ring 14 and the distance Ln between the connection points of the spokes 13 of the other cells is set to L1 > Lnmax. Lnmax is the largest value among Ln (n = 2, 3, ···). In this way, by making the length of the spoke 13 of the outermost peripheral cell the longest among the cells adjacent in the radial direction, the concentration of stress and strain in the spoke 13 can be relieved. It is more preferable that L1 > 1.2Lnmax.

[0027] (4) As described above, to improve stress and strain concentration, it is effective to increase the length of the spokes 13, that is, to increase the length of the beam equivalent to the spokes. On the other hand, in an airless tire having an intermediate ring 15, the rigidity of the cells on the radially outward side of the cells partitioned by the rings 12, 14, 15 and the spokes 13 decreases locally, which can result in stress concentration. In the airless tires 1A and 1B according to the above embodiment, the condition θ11 < θ12 is satisfied, and the straight line connecting connection point P1 and connection point P4 has an angle θa (θa > 0) with respect to the radial direction. Therefore, stress concentration can be suppressed. It is more preferable that the angle θa > 30°.

[0028] (5) In airless tires, stress and strain tend to concentrate in the outermost cells, and it is desirable to appropriately set the stiffness and dimensions of the cells. Since radially adjacent cells can be considered as springs connected in series, improving the radial stiffness of the outermost cells relative to the radial stiffness of the innermost cells is effective in mitigating the concentration of stress and strain. By setting θn > θ1, the angle of the spoke 13 with respect to the radial direction can be made smaller in the outermost cells than in the innermost cells. That is, the radial stiffness of the outermost cells can be improved by utilizing the compressive stiffness of the spoke 13. It is preferable to set θn > 1.2θ1.

[0029] (6) In the second embodiment described above, θn > θ12 is set (see Figure 4C). This further suppresses the concentration of stress and strain in the spoke 13 in the outermost cell. If θ12 ≥ θn, the amount of deformation becomes large in the part of the spoke 13 on the radial side of the bending point PX in the outermost cell, and stress and strain concentration may occur around the connection point P3 with the intermediate ring 15. This can be avoided by setting θn > θ12.

[0030] 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]

[0031] 1A, 1B Airless tire, 11 Wheel, 12 Inner ring, 13 Spoke, 14 Outer ring, 15 Intermediate ring, 16 Tread ring, PX Fold point

Claims

1. It is an airless tire, It consists of a body, a tread ring, and a wheel. The aforementioned body portion is An inner circumferential ring attached to the wheel, A plurality of spokes extending radially outward from the outer surface of the inner ring, An outer ring connected to the radially outward end of the spoke, on which the tread ring is provided on the outer surface, The system comprises at least two intermediate rings provided between the inner ring and the outer ring, which connect the multiple spokes in the circumferential direction. An airless tire in which, with respect to radially adjacent cells among the cells partitioned by the inner ring, the intermediate ring, the outer ring and the spokes, the spoke of the outermost cell has a bend point, and if the angle with respect to the radial direction of the portion of the spoke 13 radially outward from the bend point is θ11 and the angle with respect to the radial direction of the portion radially inward from the bend point is θ12, then θ11 < θ12.

2. An airless tire according to claim 1, An airless tire in which, L11 is the distance between the connection point with the outer ring in the portion radially outward from the bending point and the bending point, and L12 is the distance between the connection point with the intermediate ring in the portion radially inward from the bending point and the bending point, such that L11 < L12.

3. An airless tire according to claim 1 or 2, An airless tire in which, with respect to radially adjacent cells, L1 is the distance between the connection point of the spoke of the outermost cell with the intermediate ring and the connection point with the outer ring, and Ln (n = 2, 3, ...) is the distance between the connection points of the spokes 13 of the other cells, and Lnmax is the maximum value of Ln, such that Lnmax < L1.

4. An airless tire according to claim 1 or 2, An airless tire in which the straight line connecting the connection point of the spoke with the inner ring and the connection point of the spoke with the outer ring is at an angle with respect to the radial direction.

5. An airless tire according to claim 1 or 2, An airless tire in which, with respect to radially adjacent cells, the angles of the spokes with respect to the radial direction are denoted as θ1, θ2, ... starting from the outermost cell, and the angle of the innermost cell is denoted as θn, such that θn > θ1.

6. An airless tire according to claim 5, An airless tire where θn > θ12.

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