Run-flat tire

Abstract

Provided is a non-pneumatic tire that improves the durability of the entire tire. A tire (1) includes an inner annular portion (20), an outer annular portion (30), and a plurality of spokes (40). A pair of inner inclined surfaces (21) are formed on an outer peripheral portion of the inner annular portion that opposes the outer annular portion, and approach the outer annular portion as they move from both ends in the tire width direction toward the center in the tire width direction. A pair of outer inclined surfaces (31) are formed on an inner peripheral portion of the outer annular portion that opposes the inner annular portion, and approach the inner annular portion as they move from both ends in the tire width direction toward the center in the tire width direction. The spokes have an intermediate portion that extends between the inner annular portion and the outer annular portion, an inner connecting portion that connects the intermediate portion and the inner annular portion, and an outer connecting portion that connects the intermediate portion and the outer annular portion. The inner connecting portion includes an inner continuous portion that has a shape that continuously connects to the inner inclined surfaces. The outer connecting portion includes an outer continuous portion that has a shape that continuously connects to the outer inclined surfaces.

Description

Technical Field

[0001] This invention relates to a pneumatic tire. Background Technology

[0002] In recent years, airless tires that do not cause tire blowouts or require air pressure adjustments have been under development. Generally, airless tires are structured by connecting multiple spokes arranged radially to an outer circumferential ring portion with a tread on its outer surface, and an inner circumferential ring portion coaxially arranged inside the outer circumferential ring portion.

[0003] In such pneumatic tires, stress tends to concentrate at the connection points where the spokes meet the annular portions on the inner and outer circumferences, and the strength of these connection points affects the tire's durability. For example, Patent Document 1 discloses a pneumatic tire in which durability is improved by specifying the thickness, length, etc., of these connection points.

[0004] Prior technology literature

[0005] [Patent Documents]

[0006] Patent Document 1: Japanese Patent Application Publication No. 2016-130071 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] Patent document 1 disclosed the possibility of improving durability through the shape of the spokes, but did not describe the durability of the annular portions on the inner and outer circumferences. From the viewpoint of the overall durability of the tire, there is room for improvement.

[0009] Therefore, the object of the present invention is to provide an airless tire that can improve the overall durability of the tire.

[0010] Solution for solving the problem

[0011] The pneumatic tire of the present invention comprises: an inner annular portion; an outer annular portion coaxially disposed on the outer periphery of the inner annular portion; a plurality of spokes connecting the inner annular portion and the outer annular portion and arranged along the tire circumference; and a tread disposed on the outer periphery of the outer annular portion, wherein a pair of inner inclined surfaces are formed on the outer periphery of the inner annular portion opposite to the outer annular portion, which tend to approach the outer annular portion from both ends in the tire width direction toward the center in the tire width direction; and an inner periphery of the outer annular portion opposite to the inner annular portion. The wheel spokes have a pair of outer inclined surfaces that extend from both ends of the tire width direction toward the center of the tire width direction and are close to the inner annular portion. The spokes have a middle portion extending between the inner annular portion and the outer annular portion, an inner connecting portion connecting the middle portion and the inner annular portion, and an outer connecting portion connecting the middle portion and the outer annular portion. The inner connecting portion includes an inner continuous portion that is continuously connected to the inner inclined surface. The outer connecting portion includes an outer continuous portion that is continuously connected to the outer inclined surface.

[0012] Invention Effects

[0013] According to the present invention, it is possible to provide an airless tire that can improve the overall durability of the tire. Attached Figure Description

[0014] Figure 1 This is a side view showing the pneumatic tire involved in the embodiment.

[0015] Figure 2 yes Figure 1 Sectional view II-II.

[0016] Figure 3 It is an oblique observation Figure 2 The image shown is a partial 3D view of a pneumatic tire.

[0017] Figure 4 From and Figure 3 Observing from different directions Figure 2 The image shown is a partial 3D view of a pneumatic tire.

[0018] Figure 5A This is a contour map showing the distribution of Mises stress in the first spoke of the analytical model of Example 1.

[0019] Figure 5B This is a contour plot showing the distribution of Mises stress in the first spoke of the analytical model of Example 2.

[0020] Figure 5CThis is a contour plot showing the distribution of the Mises stress in the first spoke of the analytical model of Comparative Example 1.

[0021] Figure 5D This is a contour plot showing the distribution of the Mises stress in the first spoke of the analytical model of Comparative Example 2.

[0022] Figure 5E This is a contour plot showing the distribution of the Mises stress in the first spoke of the analytical model of Comparative Example 4.

[0023] Figure 6A This is a graph showing the weight of the analytical models of each tire in the comparative embodiments and comparative examples.

[0024] Figure 6B These are graphs showing the rigidity of the analytical models of each tire in the comparative embodiments and comparative examples.

[0025] Figure 6C These are graphs of the Mises stress of the analytical models of each tire in the comparative embodiments and comparative examples.

[0026] Figure 6D This is a graph showing the spoke distance of the analytical models of each tire in the comparative embodiments and comparative examples.

[0027] Figure 6E This is a graph showing the ground contact area of ​​the analytical models of each tire in the comparative embodiments and comparative examples.

[0028] Figure 6F This is a graph showing the maximum ground pressure of the analytical models of each tire in the comparative embodiments and comparative examples.

[0029] Figure 7A This is a graph showing the maximum value of the Mises stress in the inner annular portion of the analytical models of each tire of Comparative Example 1 and Comparative Example 2.

[0030] Figure 7B This is a graph showing the maximum value of the Mises stress in the outer annular portion of the analytical models of each tire of Comparative Example 1 and Comparative Example 2.

[0031] Explanation of reference numerals in the attached figures:

[0032] 1. Airless tire

[0033] 20 Inner circumferential part

[0034] 20a Outer peripheral surface of the inner annular portion

[0035] 21 Inner inclined surface

[0036] 30 Outer ring portion

[0037] 30a Inner circumferential surface of the outer annular portion

[0038] 31 Outer inclined surface

[0039] 40 spokes

[0040] 41 First Radiance

[0041] 42 Second round of radiation

[0042] 50 tread

[0043] 410 First Middle Section (Middle Section)

[0044] 411 First inner connecting part (inner connecting part)

[0045] 411b, 421b First inner transition section (inner continuous section)

[0046] 412 First outer connecting part (outer connecting part)

[0047] 412b, 422b First outer transition section (outer continuous section)

[0048] 420 Second Middle Section (Middle Section)

[0049] 421 Second inner connecting part (inner connecting part)

[0050] 422 Second outer connecting part (outer connecting part). Detailed Implementation

[0051] The embodiments will now be described with reference to the accompanying drawings. Figure 1 It is from the direction parallel to the tire's axis of rotation (tire meridian), that is... Figure 1 A side view of the tire 1 of the airless tire as an embodiment, viewed along the direction from the back of the paper. Figure 1 Tire 1 shown is in an unloaded state. Figure 2 yes Figure 1 Sectional view II-II. Figure 3 It is an oblique observation Figure 2 A partial perspective view of tire 1 shown. Figure 4 From and Figure 3 Observing from different directions Figure 2 A partial perspective view of tire 1 shown.

[0052] exist Figure 1 , Figure 3 , Figure 4 In the diagram, arrow C indicates the tire's circumferential direction. Figures 1-4 In the diagram, arrow X indicates the tire's radial direction. Figure 2 , Figure 3 , Figure 4 In the diagram, the arrow Y indicates the tire width direction. Figure 1The tire width direction in the figure is the same as the paper surface direction. Figure 2 The attached diagram shows S1 as the equatorial plane of the tire. Figure 2 The tire's circumferential direction is the same as the paper's surface direction.

[0053] The circumferential direction of the tire is the direction about the tire's axis of rotation and is the same direction as the tire's rotation. The radial direction of the tire is perpendicular to the tire's axis of rotation. The width direction of the tire is parallel to the tire's axis of rotation. Figure 2 , Figure 3 , Figure 4 In the diagram, one side of the tire width direction is shown as Y1, and the other side of the tire width direction is shown as Y2. Figure 2 The tire equatorial plane S1 shown is a plane that is orthogonal to the tire's axis of rotation and located at the center of the tire's width direction.

[0054] The tire 1 of the embodiment includes an inner annular portion 20, an outer annular portion 30, a plurality of spokes 40, and a tread 50.

[0055] It should be noted that, in the following description, the thickness of the inner annular portion 20 and the outer annular portion 30 refers to the dimension along the radial direction of the tire. The width of the inner annular portion 20 and the outer annular portion 30 refers to the dimension along the width direction of the tire.

[0056] The inner annular portion 20 is an annular part along the circumference of the tire 1 that constitutes the inner periphery of the tire 1. The thickness and width of the inner annular portion 20 are set to be constant in order to improve uniformity. A tire wheel (not shown) is arranged in the space on the inner periphery side of the inner annular portion 20. The inner periphery of the inner annular portion 20 is fitted into the outer periphery of the rim of the tire wheel. The inner annular portion 20 is fitted into the rim, thereby the tire 1 is fitted into the tire wheel. In order to fit with the rim of the tire wheel, sometimes a fitting part composed of protrusions, grooves, etc. is provided on the inner periphery surface of the inner annular portion 20.

[0057] The inner annular portion 20 can be formed of, for example, an elastic resin material, but the material is not limited to resin.

[0058] The inner annular portion 20 transmits the rotation of the tire to the spokes 40 and the outer annular portion 30. The thickness of the inner annular portion 20 is determined from the viewpoint of fully transmitting rotational force to the spokes 40 while also achieving lightweight and durability. The thickness of the inner annular portion 20 is not particularly limited; for example, a thickness of 2% to 7% or 3% to 6% of the tire section height can be used. The inner diameter of the inner annular portion 20 is an inner diameter corresponding to the size of the rim of the tire 1 and the purpose of the vehicle. For example, in the case of considering a general pneumatic tire as a substitute, the inner diameter of the inner annular portion 20 can be, for example, 250 mm or more and 500 mm or less, but is not limited to this. The width of the inner annular portion 20 is a width corresponding to the purpose of the vehicle 1 and the length of the axle. For example, when considering a substitute for a general pneumatic tire, the width of the inner annular portion 20 can be between 100 mm and 300 mm, but is not limited to this.

[0059] like Figure 2 As shown, a pair of inner inclined surfaces 21 are formed on the outer periphery of the inner annular portion 20 opposite to the outer annular portion 30, which approach the outer annular portion 30 from both ends in the tire width direction toward the center in the tire width direction. The inner inclined surfaces 21 include a first inner inclined surface 211 extending from the center of the outer peripheral surface 20a of the inner annular portion 20 in the tire width direction toward the tire width direction Y1 side, and a second inner inclined surface 212 extending from the center of the outer peripheral surface 20a in the tire width direction toward the tire width direction Y2 side. The first inner inclined surface 211 extends radially inward toward the end of the outer peripheral surface 20a on the tire width direction Y1 side (in... Figure 2 The inner inclined surface 211 is inclined towards the upper side (center). The second inner inclined surface 212 is inclined towards the radially inward side of the tire as it approaches the end of the outer peripheral surface 20a in the tire width direction Y2. That is, the inner inclined surface 21 has a mountain-shaped cross-section that is inclined towards the radially inward side of the tire as it approaches both sides of the tire width direction from the center in the tire width direction, and is composed of the first inner inclined surface 211 and the second inner inclined surface 212.

[0060] The inner inclined surface 21 is preferably inclined at an angle greater than 0° and less than 3° relative to the tire width direction. That is, the inclination angle θ1 of the first inner inclined surface 211 is preferably greater than 0° and less than 3° relative to the tire width direction. The inclination angle θ2 of the second inner inclined surface 212 is also preferably greater than 0° and less than 3° relative to the tire width direction.

[0061] The inner inclined surface 21 is more preferably inclined at an angle greater than 0° and less than 2° relative to the tire width direction. That is, the inclination angle θ1 of the first inner inclined surface 211 is more preferably greater than 0° and less than 2° relative to the tire width direction. The inclination angle θ2 of the second inner inclined surface 212 is also more preferably greater than 0° and less than 2° relative to the tire width direction.

[0062] The first inner inclined surface 211 and the second inner inclined surface 212 extend to the ends of the outer peripheral surface 20a in the tire width direction. That is, the inner inclined surface 21 extends to both ends of the inner annular portion 20 in the tire width direction. The first inner inclined surface 211 and the second inner inclined surface 212 are flat surfaces along the direction intersecting the tire radial direction and the tire circumferential direction, respectively.

[0063] The outer annular portion 30 is an annular portion along the circumference of the tire 1 that constitutes the outer periphery of the tire 1. The outer annular portion 30 is coaxially disposed on the outer periphery of the inner annular portion 20. The thickness and width of the outer annular portion 30 are set to be constant in order to improve uniformity.

[0064] The outer annular portion 30 can be formed of, for example, an elastic resin material, but the material is not limited to resin.

[0065] The outer annular portion 30 transmits the rotation of the inner annular portion 20 and the spokes 40 to the road surface via the tread 50. The thickness of the outer annular portion 30 is determined from the viewpoint of fully transmitting rotational force from the spokes 40 to the road surface while also achieving lightweight and durability. The thickness of the outer annular portion 30 is not particularly limited; for example, a thickness of 2% to 7% or more, or 2% to 5% of the tire section height, can be used. The inner diameter of the outer annular portion 30 is an inner diameter corresponding to the size of the rim of the wheel on which the tire 1 is mounted, the purpose of the vehicle, etc. For example, if a general pneumatic tire is considered as an alternative, the inner diameter of the outer annular portion 30 can be 420 mm or more and 750 mm or less, but is not limited to this. The width of the outer annular portion 30 is the same as the width of the inner annular portion 20.

[0066] like Figure 2 As shown, a pair of outer inclined surfaces 31 are formed on the inner circumference of the outer annular portion 30 opposite to the inner annular portion 20, which approach the inner annular portion 20 from both ends in the tire width direction toward the center in the tire width direction. The outer inclined surfaces 31 include a first outer inclined surface 311 extending from the center of the inner circumferential surface 30a of the outer annular portion 30 in the tire width direction toward the tire width direction Y1 side, and a second outer inclined surface 312 extending from the center of the inner circumferential surface 30a in the tire width direction toward the tire width direction Y2 side. The first outer inclined surface 311 extends radially outward (in the tire width direction Y1 side) towards the end of the inner circumferential surface 30a. Figure 2 The second outer inclined surface 312 is inclined radially outward from the end of the inner circumferential surface 30a in the tire width direction Y2. That is, the outer inclined surface 31 has a cross-sectional mountain-shaped shape that is inclined radially outward from the center of the tire width direction toward both sides of the tire width direction, and is composed of the first outer inclined surface 311 and the second outer inclined surface 312.

[0067] The outer inclined surface 31 is preferably inclined at an angle greater than 0° and less than 3° relative to the tire width direction. That is, the inclination angle θ3 of the first outer inclined surface 311 is preferably greater than 0° and less than 3° relative to the tire width direction. The inclination angle θ4 of the second outer inclined surface 312 is also preferably greater than 0° and less than 3° relative to the tire width direction.

[0068] The outer inclined surface 31 is more preferably inclined at an angle greater than 0° and less than 2° relative to the tire width direction. That is, the inclination angle θ3 of the first outer inclined surface 311 is more preferably greater than 0° and less than 2° relative to the tire width direction. The inclination angle θ4 of the second outer inclined surface 312 is also more preferably greater than 0° and less than 2° relative to the tire width direction.

[0069] The first outer inclined surface 311 and the second outer inclined surface 312 extend to the ends of the inner circumferential surface 30a in the tire width direction. That is, the outer inclined surface 31 extends to both ends of the outer annular portion 30 in the tire width direction. The first outer inclined surface 311 and the second outer inclined surface 312 are flat surfaces along the direction intersecting the tire radial direction and the tire circumferential direction, respectively.

[0070] Multiple spokes 40 connect the inner annular portion 20 and the outer annular portion 30. The inner annular portion 20 and the outer annular portion 30, connected by the multiple spokes 40, are coaxially arranged. The multiple spokes 40 are arranged independently along the circumference of the tire. Figure 1 As shown, multiple spokes 40 extend approximately parallel to the radial direction of the tire when the tire 1 is unloaded and viewed from the side. The multiple spokes 40 are arranged at equal intervals along the circumference of the tire.

[0071] like Figures 2-4 As shown, the plurality of spokes 40 in this embodiment include a plurality of first spokes 41 and a plurality of second spokes 42. Any spoke in the first spokes 41 and the second spokes 42 is such that its extension direction is not parallel to the radial direction of the tire when viewed along the tire circumference. The first spokes 41 are inclined toward one side in the tire width direction. The second spokes 42 are inclined toward the opposite side to the first spokes 41. The first spokes 41 and the second spokes 42 are arranged alternately along the tire circumference.

[0072] like Figures 2-4As shown, the first spoke 41 extends obliquely from the tire width direction Y1 side of the outer annular portion 30 toward the tire width direction Y2 side of the inner annular portion 20. The second spoke 42 extends obliquely from the tire width direction Y2 side of the outer annular portion 30 toward the tire width direction Y1 side of the inner annular portion 20.

[0073] The first spoke 41 and the second spoke 42 have the same tilt angle. Therefore, the first spoke 41 and the second spoke 42, which are adjacent along the tire circumference, are arranged in a roughly X-shape when viewed from the direction along the tire circumference. Figure 2 As shown, the first spoke 41 is inclined at an angle θ relative to the tire width direction, which is preferably, for example, 30° or more and 60° or less. The second spoke 42 is also inclined to the opposite side at the same angle θ.

[0074] like Figure 2 As shown, the first spoke 41 and the second spoke 42, viewed from the direction along the tire's circumference, are the same shape that is symmetrical with respect to the tire's equatorial plane S1. Therefore, in the following description, without needing to distinguish between the first spoke 41 and the second spoke 42, the first spoke 41 and the second spoke 42 will be collectively referred to as spoke 40.

[0075] The spokes 40 are formed as plates extending in-plane along the radial and width directions of the tire. The spokes 40 extend obliquely at an angle θ from the inner annular portion 20 toward the outer annular portion 30 as described above. Figure 3 As shown, the thickness t of the spoke 40 is along the tire circumference. Figure 2 and Figure 3 As shown, the width w of the spoke 40 is the width of the first intermediate portion 410 and the second intermediate portion 420 (described later), and is a dimension in a direction orthogonal to the inclined direction of the spoke 40 when viewed along the tire circumference. In this embodiment, the thickness t of all spokes 40 is the same. Furthermore, the width w of all spokes 40 is the same.

[0076] Since the spokes 40 are elongated strips, even if the thickness t is reduced, the durability of the spokes 40 can be improved by setting a wider width w. Furthermore, by reducing the thickness t and increasing the number of spokes 40, the spacing between adjacent spokes 40 along the tire circumference can be reduced while maintaining the overall rigidity of the tire 1. Therefore, the ground pressure is reduced by dispersing the ground pressure during tire rolling based on the spokes 40.

[0077] It should be noted that the spokes 40 of the embodiment are parallel to the tire radial direction when viewed from the side, but the spokes 40 may also be in a form that extends obliquely relative to the tire radial direction when viewed from the side, in a manner that intersects with the tire radial direction.

[0078] The first spoke 41 has a first intermediate portion 410 extending between the inner annular portion 20 and the outer annular portion 30 as an intermediate portion, a first inner connecting portion 411 connecting the first intermediate portion 410 to the inner annular portion 20 as an inner connecting portion, and a first outer connecting portion 412 connecting the first intermediate portion 410 to the outer annular portion 30 as an outer connecting portion.

[0079] The first intermediate portion 410 is the portion of the spoke 40 having a plate width w, and is the portion aligned with the inclination direction of the first spoke 41. The first intermediate portion 410 is located at the radial midpoint of the tire between the inner annular portion 20 and the outer annular portion 30. The first intermediate portion 410 refers to the radial region of the tire having straight portions on both sides facing the tire width direction.

[0080] The first inner connecting portion 411 is provided in half of the inner annular portion 20 on the Y2 side of the tire width direction. The first inner connecting portion 411 has a first inner transition portion 411b disposed on the inner side of the tire width direction and continuously transitioning from the first intermediate portion 410 to the inner annular portion 20, and a second inner transition portion 411a disposed on the outer side of the tire width direction and continuously transitioning from the first intermediate portion 410 to the inner annular portion 20. The first inner transition portion 411b is disposed on the side where the angle formed by the first intermediate portion 410 and the inner annular portion 20 is an acute angle. The second inner transition portion 411a is disposed on the side where the angle formed by the first intermediate portion 410 and the inner annular portion 20 is an obtuse angle.

[0081] The first inner transition portion 411b is disposed on the inner side in the tire width direction (tire equatorial plane S1 side). The first inner transition portion 411b is formed in a concave arc shape from the position of the first intermediate portion 410 to the tire equatorial plane S1 of the inner annular portion 20, and connects to the first inner inclined surface 211. That is, the first inner connecting portion 411 includes the first inner transition portion 411b, which has a shape that is continuously connected from the first intermediate portion 410 to the first inner inclined surface 211. The first inner transition portion 411b is disposed on the side where the angle formed between the first intermediate portion 410 and the inner annular portion 20 in the first inner connecting portion 411 is an acute angle. The first inner transition portion 411b of the embodiment is an example of the inner continuous portion involved in this disclosure that is continuously connected to the first inner inclined surface 211.

[0082] It should be noted that, in the embodiment, the first inner transition portion 411b is formed to connect to the first inner inclined surface 211 at the position of the tire equator surface S1, but it can also be formed to connect to the second inner inclined surface 212 at a position closer to the first inner connecting portion 411 than the tire equator surface S1, or to connect to the first inner inclined surface 211 beyond the tire equator surface S1.

[0083] The second inner transition portion 411a is disposed on the outer side in the tire width direction. The second inner transition portion 411a extends to the end of the inner annular portion 20 on the tire width direction Y2 side while gently curving.

[0084] Through the first inner transition portion 411b and the second inner transition portion 411a, the first inner connecting portion 411 has a shape that widens along the tire width direction as it approaches the inner annular portion 20.

[0085] The first outer connecting portion 412 is disposed in half of the outer annular portion 30 on the tire width direction Y1 side. The first outer connecting portion 412 has a first outer transition portion 412b disposed on the inner side in the tire width direction and continuously transitioning to the outer annular portion 30 from the first middle portion 410, and a second outer transition portion 412a disposed on the outer side in the tire width direction and continuously transitioning to the outer annular portion 30 from the first middle portion 410. The first outer transition portion 412b is disposed on the side where the angle formed by the first middle portion 410 and the outer annular portion 30 is an acute angle. The second outer transition portion 412a is disposed on the side where the angle formed by the first middle portion 410 and the outer annular portion 30 is an obtuse angle.

[0086] The first outer transition portion 412b is disposed on the inner side in the tire width direction (tire equatorial plane S1 side). The first outer transition portion 412b is formed in a concave arc shape from the position of the first intermediate portion 410 to the tire equatorial plane S1 of the outer annular portion 30, and connects to the second outer inclined surface 312. That is, the first outer connecting portion 412 includes the first outer transition portion 412b, which has a shape that continuously connects from the first intermediate portion 410 to the second outer inclined surface 312. The first outer transition portion 412b is disposed on the side where the angle formed by the first intermediate portion 410 and the outer annular portion 30 in the first outer connecting portion 412 is an acute angle. The first outer transition portion 412b of the embodiment is an example of the outer continuous portion involved in this disclosure that is continuously connected to the second outer inclined surface 312.

[0087] It should be noted that the first outer transition portion 412b in the embodiment is formed to connect to the second outer inclined surface 312 at the position of the tire equatorial surface S1, but it can also be formed to connect to the first outer inclined surface 311 at a position closer to the first outer connecting portion 412 than the tire equatorial surface S1, or to connect to the second outer inclined surface 312 beyond the tire equatorial surface S1.

[0088] The second outer transition portion 412a is disposed on the outer side in the tire width direction. The second outer transition portion 412a extends to the end of the outer annular portion 30 on the tire width direction Y1 side while gently curving.

[0089] The first outer connecting portion 412 has a shape that widens along the tire width direction as it approaches the outer annular portion 30 via the first outer transition portion 412b and the second outer transition portion 412a.

[0090] The second spoke 42 has the same shape as the first spoke 41, and the second spoke 42 is a symmetrical shape with respect to the tire equatorial plane S1 and the first spoke 41.

[0091] like Figure 2 and Figure 3 As shown, the second spoke 42 has a second intermediate portion 420 extending between the inner annular portion 20 and the outer annular portion 30 as an intermediate portion, a second inner connecting portion 421 connecting the second intermediate portion 420 to the inner annular portion 20 as an inner connecting portion, and a second outer connecting portion 422 connecting the second intermediate portion 420 to the outer annular portion 30 as an outer connecting portion.

[0092] The second intermediate portion 420 is the portion of the spoke 40 having a plate width w, and is the portion that is inclined in the same direction as the second spoke 42. The second intermediate portion 420 is located in the radial middle of the tire between the inner annular portion 20 and the outer annular portion 30. The second intermediate portion 420 refers to the radial region of the tire having straight portions on both sides facing the tire width direction.

[0093] The second inner connecting portion 421 is provided in half of the inner annular portion 20 on the tire width direction Y1 side. The second inner connecting portion 421 has a first inner transition portion 421b disposed on the inner side in the tire width direction and continuously transitioning from the second middle portion 420 to the inner annular portion 20, and a second inner transition portion 421a disposed on the outer side in the tire width direction and continuously transitioning from the second middle portion 420 to the inner annular portion 20. The first inner transition portion 421b is disposed on the side where the angle formed by the second middle portion 420 and the inner annular portion 20 is an acute angle. The second inner transition portion 421a is disposed on the side where the angle formed by the second middle portion 420 and the inner annular portion 20 is an obtuse angle.

[0094] The first inner transition portion 421b is disposed on the inner side in the tire width direction (tire equatorial plane S1 side). The first inner transition portion 421b is formed in a concave arc shape from the position of the second intermediate portion 420 to the tire equatorial plane S1 of the inner annular portion 20, and connects to the second inner inclined surface 212. That is, the second inner connecting portion 421 includes the first inner transition portion 421b, which has a shape that is continuously connected from the second intermediate portion 420 to the second inner inclined surface 212. The first inner transition portion 421b is disposed on the side where the angle formed between the second intermediate portion 420 and the inner annular portion 20 in the second inner connecting portion 421 is an acute angle. The first inner transition portion 421b of the embodiment is an example of the inner continuous portion involved in this disclosure that is continuously connected to the second inner inclined surface 212.

[0095] It should be noted that, in the embodiment, the first inner transition portion 421b is formed to connect to the second inner inclined surface 212 at the position of the tire equator surface S1, but it can also be formed to connect to the first inner inclined surface 211 at the position of the second inner connecting portion 421 closer to the tire equator surface S1, or to connect to the second inner inclined surface 212 beyond the tire equator surface S1.

[0096] The second inner transition portion 421a is disposed on the outer side in the tire width direction. The second inner transition portion 421a extends to the end of the inner annular portion 20 on the tire width direction Y1 side while gently curving.

[0097] The second inner connecting portion 421 has a shape that widens along the tire width direction as it approaches the inner annular portion 20 via the first inner transition portion 421b and the second inner transition portion 421a.

[0098] The second outer connecting portion 422 is disposed in half of the outer annular portion 30 on the Y2 side of the tire width direction. The second outer connecting portion 422 has a first outer transition portion 422b disposed on the inner side of the tire width direction and continuously transitioning from the second middle portion 420 to the outer annular portion 30, and a second outer transition portion 422a disposed on the outer side of the tire width direction and continuously transitioning from the second middle portion 420 to the outer annular portion 30. The first outer transition portion 422b is disposed on the side where the angle formed by the second middle portion 420 and the outer annular portion 30 is an acute angle. The second outer transition portion 422a is disposed on the side where the angle formed by the second middle portion 420 and the outer annular portion 30 is an obtuse angle.

[0099] The first outer transition portion 422b is disposed on the inner side in the tire width direction (tire equatorial plane S1 side). The first outer transition portion 422b is formed in a concave arc shape from the position of the second intermediate portion 420 to the tire equatorial plane S1 of the outer annular portion 30, and connects to the first outer inclined surface 311. That is, the second outer connecting portion 422 includes the first outer transition portion 422b, which has a shape that is continuously connected from the second intermediate portion 420 to the first outer inclined surface 311. The first outer transition portion 422b is disposed on the side where the angle formed between the second intermediate portion 420 and the outer annular portion 30 in the second outer connecting portion 422 is an acute angle. The first outer transition portion 422b of the embodiment is an example of the outer continuous portion involved in this disclosure that is continuously connected to the first outer inclined surface 311.

[0100] It should be noted that the first outer transition portion 422b in the embodiment is formed to connect to the first outer inclined surface 311 at the position of the tire equatorial surface S1, but it can also be formed to connect to the second outer inclined surface 312 at the position of the second outer connecting portion 422 closer to the tire equatorial surface S1, or connect to the first outer inclined surface 311 beyond the tire equatorial surface S1.

[0101] The second outer transition portion 422a is disposed on the outer side in the tire width direction. The second outer transition portion 422a extends to the end of the outer annular portion 30 on the Y2 side in the tire width direction while curving gently.

[0102] The second outer connecting portion 422 has a shape that widens along the tire width direction as it approaches the outer annular portion 30 via the first outer outer transition portion 422b and the second outer outer transition portion 422a.

[0103] As described above, all spokes 40 in the embodiment have the same plate thickness t. The plate thickness t of the spokes 40 is not particularly limited, but in order for the spokes 40 to fully withstand the rotational force from the inner annular portion 20 and the outer annular portion 30 and to be able to flex and deform appropriately when subjected to load, the plate thickness t of the spokes 40 is preferably 1 mm or more and 30 mm or less, more preferably 5 mm or more and 25 mm or less.

[0104] As described above, all spokes 40 in the embodiment have the same plate width w. The plate width w of the spokes 40 is the width of the first intermediate portion 410 and the second intermediate portion 420. The plate width w of the spokes 40 is not particularly limited, but in order to fully withstand the rotational force from the inner annular portion 20 and the outer annular portion 30 and to be able to flex appropriately under load, the plate width w of the spokes 40 is preferably 5 mm or more and 25 mm or less, more preferably 10 mm or more and 20 mm or less. In addition, from the viewpoint of improving durability while dispersing grounding pressure, the plate width w is preferably 110% or more of the plate thickness t, more preferably 115% or more.

[0105] From the viewpoint that the number of spokes 40 can adequately support the load from the vehicle, reduce weight, and improve power transmission and durability, it is preferable to have 80 or more and 300 or less, and more preferably 100 or more and 200 or less.

[0106] The tire circumferential spacing of the plurality of spokes 40 is preferably set to be 1.0 mm or more and 4.1 mm or less. It should be noted that, in the embodiments, the tire circumferential spacing of the plurality of spokes 40 is equal, but it may also be unequal.

[0107] The radial dimension of a tire with 40 spokes can be between 45mm and 75mm, but is not limited to this.

[0108] The spokes 40 can be formed from the following elastic materials. First, as a characteristic of this elastic material, from the viewpoint of ensuring sufficient durability and imparting appropriate rigidity, a tensile test is conducted based on JIS K7312, and the tensile modulus calculated from the tensile stress at 10% elongation is preferably 3 MPa or more and 12 MPa or less.

[0109] In the spokes 40, if the tensile modulus calculated based on the tensile stress at 10% elongation is less than 3 MPa, sufficient rigidity cannot be obtained, and adjacent spokes 40 along the tire circumference may come into contact with each other. On the other hand, if the tensile modulus calculated based on the tensile stress at 10% elongation is greater than 12 MPa, the rigidity is too high, and the ride comfort deteriorates.

[0110] Examples of elastic materials that can be used as the base material for spoke 40 include thermoplastic elastomers, cross-linked rubbers, and other resins.

[0111] Examples of thermoplastic elastomers include polyester elastomers, polyolefin elastomers, polyamide elastomers, polystyrene elastomers, polyvinyl chloride elastomers, and polyurethane elastomers.

[0112] As the rubber material constituting cross-linked rubber, any rubber from natural rubber and synthetic rubber can be used. Examples of synthetic rubbers include styrene-butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IIR), nitrile rubber (NBR), hydrogenated nitrile rubber (hydrogenated NBR), chloroprene rubber (CR), ethylene propylene rubber (EPDM), fluororubber, silicone rubber, acrylic rubber, and polyurethane rubber. These rubber materials can also be combined with two or more materials as needed.

[0113] Other examples of resins include thermoplastic resins and thermosetting resins. Examples of thermoplastic resins include polyethylene resin, polystyrene resin, and polyvinyl chloride resin. Examples of thermosetting resins include epoxy resin, phenolic resin, polyurethane resin, silicone resin, polyimide resin, and melamine resin.

[0114] From the viewpoints of molding, processability, and cost, polyurethane resin, one of the aforementioned elastic materials, is preferred for use in the spokes 40. It should be noted that foamed materials can also be used as elastic materials. That is, materials obtained by foaming the aforementioned thermoplastic elastomers, cross-linked rubbers, or other resins can be used.

[0115] It should be noted that the elastic material used as the base material for the spokes 40 can also be reinforced with reinforcing fibers. Examples of reinforcing fibers include long fibers, short fibers, woven fabrics, and non-woven fabrics. Types of reinforcing fibers include rayon cords, polyamide cords such as nylon 66, polyester cords such as polyethylene terephthalate, aramid cords, glass fiber cords, carbon fiber, and steel wire cords.

[0116] It should be noted that the reinforcement of elastic materials is not limited to reinforcement based on reinforcing fibers. For example, reinforcement based on the addition of granular fillers can also be carried out. Examples of granular fillers to be added include carbon black, silica, alumina, and other inorganic materials.

[0117] Furthermore, the inner annular portion 20 and the outer annular portion 30 are preferably formed of the same resin material as the spokes 40. In this case, the inner annular portion 20, the outer annular portion 30 and the spokes 40 can be integrally formed by, for example, injection molding.

[0118] The tread 50 is disposed on the outer peripheral surface of the outer annular portion 30. The tread 50 constitutes the outermost peripheral portion of the tire 1. The tread 50 includes tread rubber 51. The tread rubber 51 has a tread surface 51a that contacts the road surface on its outer peripheral surface. The type of rubber material used as the tread rubber 51 is not particularly limited, and general vulcanized rubber or the like, which are used as rubbers for the tread of vehicle tires, can be used. The tread surface 51a of the tread rubber 51 is provided with a tread pattern formed by multiple grooves and grooves, similar to that of conventional pneumatic tires. It should be noted that the tread rubber 51 can also be a structure obtained by laminating multiple rubber layers with different compositions and properties (for example, two or three layers). In addition, the tread 50 can also be formed of resin.

[0119] It should be noted that the tire 1 of the embodiment may further be provided with a reinforcing layer around the entire circumference of the tire to improve the rigidity and ground contact of the tire 1. The reinforcing layer is provided around the entire circumference of the tire, for example, it may be embedded inside the outer annular portion 30, or it may be provided between the outer annular portion 30 and the tread 50.

[0120] The tire 1 according to the embodiment can achieve the following effects.

[0121] (1) The tire 1 according to the embodiment is a pneumatic tire, which includes: an inner annular portion 20; an outer annular portion 30, which is coaxially disposed on the outer periphery of the inner annular portion 20; a plurality of spokes 40, which connect the inner annular portion 20 and the outer annular portion 30 and are arranged along the tire circumference; and a tread 50, which is disposed on the outer periphery of the outer annular portion 30, wherein a pair of inner inclined surfaces 21 are formed on the outer periphery of the inner annular portion 20 opposite to the outer annular portion 30, which approach the outer annular portion 30 from both ends in the tire width direction toward the center in the tire width direction; and a pair of inner inclined surfaces 21 are formed on the inner periphery of the outer annular portion 30 opposite to the inner annular portion 20, which approach the inner annular portion 20 from both ends in the tire width direction toward the center in the tire width direction. The wheel spokes 40 have a pair of outer inclined surfaces 31, a middle portion (first middle portion 410 and second middle portion 420) extending between the inner annular portion 20 and the outer annular portion 30, an inner connecting portion (first inner connecting portion 411 and second inner connecting portion 421) connecting the middle portion to the inner annular portion 20, and an outer connecting portion (first outer connecting portion 412 and second outer connecting portion 422) connecting the middle portion to the outer annular portion 30. The inner connecting portion includes an inner continuous portion (first inner transition portion 411b and 421b) which has a shape that is continuously connected to the inner inclined surface 21. The outer connecting portion includes an outer continuous portion (first outer transition portion 412b and 422b) which has a shape that is continuously connected to the outer inclined surface 31.

[0122] In the spoke 40 of the embodiment, the inner connecting portion connected to the inner annular portion 20 has an inner continuous portion that is continuously connected to the inner inclined surface 21 of the inner annular portion 20, and the outer connecting portion connected to the outer annular portion 30 has an outer continuous portion that is continuously connected to the outer inclined surface 31 of the outer annular portion 30. Thus, stress concentration at the root portion of the spoke 40 relative to the inner annular portion 20 and the outer annular portion 30 is suppressed by the inner and outer continuous portions, resulting in increased rigidity and durability of the spoke 40. By suppressing deformation of the spoke 40 along with increased rigidity, the spacing between spokes 40 can be maintained, and contact between adjacent spokes 40 in the tire circumferential direction can be suppressed. Therefore, the spokes 40 are less prone to damage. As a result, the overall durability of the tire 1 can be improved. Furthermore, the deformation suppression effect of the spoke 40 along with increased rigidity reduces rolling resistance.

[0123] The inner annular portion 20 has an inner inclined surface 21, which increases its rigidity and thus improves its fit with the rim. The outer annular portion 30 has an outer inclined surface 31, which increases its rigidity and makes it less prone to buckling. Consequently, it can suppress the formation of flat spots on the tread 50.

[0124] By having an inner inclined surface 21 and an outer inclined surface 31, when the tire 1 is molded, the inner inclined surface 21 and the outer inclined surface 31 become a draft angle, which can easily demold the tire from the mold.

[0125] (2) In the tire 1 of this embodiment, the inner inclined surface 21 and the outer inclined surface 31 are inclined at an angle greater than 0° and less than 3° relative to the tire width direction.

[0126] Therefore, there is a tendency for ride comfort to decrease when the rigidity of tire 1 is excessively increased, but the inclination angles of the inner inclined surface 21 and the outer inclined surface 31 relative to the tire width direction are less than 3°, so good ride comfort can be maintained.

[0127] (3) In the tire 1 of this embodiment, the inner inclined surface 21 and the outer inclined surface 31 are inclined at an angle of less than 2° relative to the tire width direction.

[0128] Therefore, the overall durability of tire 1 can be improved while maintaining good ground contact and wear resistance.

[0129] (4) In the tire 1 according to the embodiment, the middle part of the spoke 40 extends obliquely relative to the radial direction of the tire when viewed from the circumferential direction of the tire, the angle between the middle part of the inner continuous part provided in the inner connecting part and the inner annular part 20 is an acute angle, and the angle between the middle part of the outer continuous part provided in the outer connecting part and the outer annular part 30 is an acute angle.

[0130] When the middle part of the spoke 40 is inclined, greater stress is applied to the side where the angle between the inner and outer connecting parts and each annular part 20, 30 forms an acute angle. Here, in the embodiment, an inner continuous part and an outer continuous part that continue to each inclined surface are provided in this part, so that stress is not easily concentrated and rigidity can be improved.

[0131] (5) In the tire 1 of the embodiment, it is preferable that the inner inclined surface 21 extends to both ends of the inner annular portion 20 in the tire width direction, and the outer inclined surface 31 extends to both ends of the outer annular portion 30 in the tire width direction.

[0132] As a result, the overall durability of the tire 1 is improved due to the increased rigidity of the inner inclined surface 21 and the outer inclined surface 31.

[0133] (6) In the tire 1 of the embodiment, it is preferable that the inner inclined surface 21 and the outer inclined surface 31 are flat.

[0134] Therefore, the stress applied to the inner inclined surface 21 and the outer inclined surface 31 is easily dispersed, and the effect of improving rigidity is easily obtained.

[0135] (7) In the tire 1 of the embodiment, the spoke 40 includes: a first spoke 41 with its middle portion inclined toward one side of the tire axis; and a second spoke 42 with its middle portion inclined toward the opposite side of the first spoke 41, the first spoke 41 and the second spoke 42 being alternately arranged along the tire circumference.

[0136] Therefore, the first spoke 41 and the second spoke 42 are configured in a roughly X-shape when viewed from the direction along the tire circumference. Since the first spoke 41 and the second spoke 42 are inclined along the tire axial direction respectively, excessive rigidity can be suppressed, thereby improving ride comfort.

[0137]

Example

[0138] Using an analytical model of a tire with the same structure as the embodiments described above based on FEM, the tire's stiffness, Mises stress, spoke spacing, contact patch, and maximum contact pressure when a load of 200 kg is applied were calculated. As Example 1, a tire with an inclination angle of 2° relative to the tire width direction for the inner inclined surface 21 and the outer inclined surface 31 was used. As Example 2, a tire with an inclination angle of 3° relative to the tire width direction for the inner inclined surface 21 and the outer inclined surface 31 was used. As comparative examples, Comparative Example 1, which has the same dimensions and structure as Examples 1 and 2 but does not have an inclined surface (inner inclined surface and outer inclined surface) in either the inner annular portion 20 or the outer annular portion 30; Comparative Examples 2 and 3, which have an inclined surface (inner inclined surface) only in the inner annular portion 20; and Comparative Example 4, which has an inclined surface (outer inclined surface) only in the outer annular portion 30, were used. In Comparative Example 2, the inclination angle of the inner inclined surface 21 relative to the tire width direction is 2°, and in Comparative Example 3, the inclination angle of the inner inclined surface 21 relative to the tire width direction is 5°. Furthermore, in Comparative Example 4, the inclination angle of the outer inclined surface 31 relative to the tire width direction is 2°. For Comparative Examples 1 to 4, the same items as in Examples 1 and 2 were calculated using the analytical models of these tires.

[0139] Figure 5A This is a contour map showing the distribution of Mises stress on the first spoke 41 of the analytical model of Example 1, with varying shades of black. Figure 5B This is a contour map showing the distribution of Mises stress on the first spoke 41 of the analytical model of Example 2, with varying shades of black representing different levels of black. Figure 5C This is a contour map showing the distribution of Mises stress on the first spoke 41 of the analytical model of Comparative Example 1, with varying shades of black representing different levels of black. Figure 5D The contour map is a diagram of the distribution of Mises stress on the first spoke 41 of the analytical model of Comparative Example 2, with the shades of black representing the distribution. Figure 5E This is a contour map showing the distribution of Mises stress on the first spoke 41 of the analytical model of Comparative Example 4, with the shades of black representing the intensity of the stress. In any map, lighter shades of black indicate a more stressed state. When comparing Examples 1 and 2 with Comparative Examples 1, 2, and 4, the results are... Figure 5A Example 1 and Figure 5B Compared to Example 2, in Figure 5C Comparative Example 1 Figure 5D Comparative Example 2 and Figure 5E In Comparative Example 4, the range of stress applied is wide and the stress is large. Compared with Comparative Example 1, the stress applied to the inner annular portion 20 side in Comparative Example 2 is small, and the stress applied to the outer annular portion 30 side in Comparative Example 4 is small compared with Comparative Example 1. However, compared with Comparative Example 1, the stress applied to the entire first wheel spoke 41 in Examples 1 and 2 is small. Therefore, it can be seen that if the inner annular portion 20 and the outer annular portion 30 have an inner inclined surface 21 and an outer inclined surface 31 respectively, the stress generated when a load is applied is dispersed, and the rigidity is improved. In addition, comparing Examples 1, 2 and Comparative Example 1, it can be seen that the stress generated when a load is applied to the first wheel spoke 41 decreases in the order of Comparative Example 1, Example 1 and Example 2. That is, it can be seen that it is preferable for the inner annular portion 20 and the outer annular portion 30 to have inclined surfaces, and there is a tendency for the stress generated when a load is applied to be smaller when the inclination angle of the inner inclined surface 21 and the outer inclined surface 31 relative to the tire width direction is large.

[0140] Table 1

[0141]

[0142] Table 1 shows the measured values ​​of weight, rigidity, Mises stress generated at the first spoke 41, spoke spacing, ground contact area, and maximum ground contact pressure for Examples 1, 2, and Comparative Examples 1 to 4. Based on these measurements, the evaluation results for spoke durability, rolling resistance, ground contact, tire-rim fit, buckling and flat spot suppression, ride comfort, and processability (indicating ease of tire processing) are also presented. The measured values ​​shown in Table 1 are obtained by exponentially evaluating Examples 1, 2, and 1 to 4 relative to Comparative Example 1, with Comparative Example 1 as the index of 100. The evaluation results for spoke durability, rolling resistance, ground contact, rim fit, buckling and flat spot suppression, ride comfort, and processability are marked as "◎" if higher than Comparative Example 1 and particularly good, "○" if good, "equal" if equal to Comparative Example 1, and "△" if lower than Comparative Example 1.

[0143] Figures 6A to 6F The weight, rigidity, Mises stress generated at the first inner transition portion 411b of the first spoke 41, spoke spacing, grounding area, and maximum grounding voltage of Examples 1, 2, and Comparative Examples 1 to 4 shown in Table 1 are presented graphically. In these graphs, the vertical axis represents the values ​​of Examples 1, 2, and Comparative Examples 2 to 4 evaluated with the measured value of Comparative Example 1 as an index of 100 relative to Comparative Example 1, and the horizontal axis represents angles. It should be noted that in each graph, solid lines represent approximate curves of each tilt angle relative to the measured value when both the inner annular portion 20 and the outer annular portion 30 have tilted surfaces, dashed lines represent approximate curves of each tilt angle relative to the measured value when only the inner annular portion 20 has a tilted surface, and dashed lines represent approximate curves of each tilt angle relative to the measured value when only the outer annular portion 30 has a tilted surface. In addition, Figure 7A This is a graph obtained by exponentially evaluating the maximum value of the Mises stress generated in the inner annular portion 20 relative to the measured value of Comparative Example 1 versus Example 1. Figure 7B This is a graph obtained by exponentially evaluating the maximum value of the Mises stress generated in the outer annular portion 30 relative to the measured value of Comparative Example 1 versus Example 1.

[0144] according to Figure 6A , Figure 6B , Figure 6CAs shown in Table 1, in Examples 1, 2, and Comparative Examples 2 to 4, the greater the inclination angle of the inner inclined surface 21 and the outer inclined surface 31, the greater the increase in rigidity, the greater the decrease in the Mises stress generated in the spokes 40, and the greater the improvement in spoke durability. It can be seen that by increasing tire rigidity and reducing Mises stress in this way, the spacing between spokes 40 can be maintained. This is believed to be because the inner annular portion 20 and the outer annular portion 30 each have inclined surfaces (inner inclined surface and outer inclined surface), and the spokes 40 have a shape where they are continuous with these inclined surfaces via inner and outer continuous portions, respectively. Furthermore, according to... Figure 7A and Figure 7B It can be recognized that because the inner annular portion 20 and the outer annular portion 30 each have an inner inclined surface 21 and an outer inclined surface 31 with an inclination angle of 2° relative to the tire width direction, the Mises stress generated in the inner annular portion 20 and the outer annular portion 30 is also reduced. Based on these results, an improvement in the overall durability of the tire can be confirmed.

[0145] According to Table 1, regarding rolling resistance, in Example 1, which has an inner inclined surface 21 and an outer inclined surface 31 with an inclination angle of 2°, the rolling resistance is reduced compared to Comparative Example 1 due to the increased rigidity. On the other hand, in Example 2, where the inclination angle of the inner inclined surface 21 and the outer inclined surface 31 is 3°, although the tire rigidity is increased and the Mises stress is reduced compared to Example 1, the rolling resistance suppression effect is reduced due to the increased tire weight. Furthermore, in Example 2, compared to Example 1, the contact area is reduced and the maximum contact pressure is increased, resulting in decreased contact contact and reduced ride comfort. Based on these results, it can be confirmed that by forming inclined surfaces (inner inclined surface 21 and outer inclined surface 31) on both the inner annular portion 20 and the outer annular portion 30, and making the inclination angle of the inner inclined surface 21 and the outer inclined surface 31 greater than 0° and less than 3°, it is possible to improve the overall durability of the tire while maintaining good ride comfort.

[0146] In addition, according to Figure 6A , Figure 6B , Figure 6C As shown in Table 1, compared with Comparative Examples 2 and 4, which have inclined surfaces with an inclination angle of 2° relative to the tire width direction on either the inner annular portion 20 or the outer annular portion 30, Example 1 exhibits improved tire rigidity, thereby reducing Mises stress and maintaining the spacing between the spokes 40. According to Table 1, this improvement in rigidity, etc., yields particularly good results for spoke durability and rolling resistance.

[0147] Furthermore, as shown in Table 1, compared to Comparative Example 1, the fit with the rim is improved in Comparative Example 2, and compared to Comparative Example 1, buckling and flattening are suppressed in Comparative Example 4. In contrast, the embodiment having an inner inclined surface 21 and an outer inclined surface 31 achieves both the effects of "improving the fit with the rim" and "suppressing buckling and flattening".

[0148] The above describes the embodiments of the present invention, but the present invention is not limited to the above embodiments. Even modifications and improvements made within the scope of achieving the purpose of the present invention are included in the scope of the present invention.

[0149] For example, the spokes 40 can be straight along the tire radial direction, except that they are inclined relative to the tire radial direction. In this case, the inner connecting portion has an inner continuous portion that extends to the inner inclined surface 21 on both sides of the tire width direction relative to the inner annular portion 20, and the outer connecting portion has an outer continuous portion that extends to the outer inclined surface 31 on both sides of the tire width direction relative to the outer annular portion 30.

Claims

1. A pneumatic tire, comprising: Inner annular portion; An outer annular portion is coaxially disposed on the outer periphery of the inner annular portion; Multiple spokes connecting the inner annular portion to the outer annular portion and arranged circumferentially along the tire; and The tread is located on the outer peripheral surface of the outer annular portion. in, The outer peripheral portion of the inner annular portion, which is opposite to the outer annular portion, has a pair of inner inclined surfaces that move closer to the outer annular portion as they extend from both ends of the tire width direction toward the center of the tire width direction. The inner circumferential portion of the outer annular portion, which is opposite to the inner annular portion, has a pair of outwardly inclined surfaces that move closer to the inner annular portion as they extend from both ends in the tire width direction toward the center in the tire width direction. The spokes have a middle portion extending between the inner annular portion and the outer annular portion, an inner connecting portion connecting the middle portion to the inner annular portion, and an outer connecting portion connecting the middle portion to the outer annular portion. The inner connecting portion includes an inner continuous portion, which has a shape that is continuously connected to the inner inclined surface. The outer connecting portion includes an outer continuous portion having a shape that is continuously connected to the outer inclined surface.

2. The pneumatic tire according to claim 1, wherein, The inner inclined surface and the outer inclined surface are inclined at an angle greater than 0° and less than 3° relative to the tire width direction.

3. The pneumatic tire according to claim 2, wherein, The inner inclined surface and the outer inclined surface are inclined at an angle of less than 2° relative to the tire width direction.

4. The pneumatic tire according to any one of claims 1 to 3, wherein, The middle portion of the spokes extends at an angle relative to the tire radially when viewed from the tire circumferential direction. The inner continuous portion is disposed on the side where the angle between the middle portion and the inner annular portion in the inner connecting portion is an acute angle. The outer continuous portion is disposed on the side where the angle between the middle portion and the outer annular portion in the outer connecting portion is an acute angle.

5. The pneumatic tire according to any one of claims 1 to 3, wherein, The inner inclined surface extends to both ends of the inner annular portion in the tire width direction. The outer inclined surface extends to both ends of the outer annular portion in the tire width direction.

6. The pneumatic tire according to any one of claims 1 to 3, wherein, The inner inclined surface and the outer inclined surface are both flat.

7. The pneumatic tire according to any one of claims 1 to 3, wherein, The spokes include: The first spoke, whose middle portion is inclined toward one side of the tire axial direction; and The second spoke, whose middle portion is inclined to the side opposite to the first spoke, The first spoke and the second spoke are arranged alternately along the tire circumference.

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