tire

Abstract

We provide a tire that improves durability by suppressing rearward displacement. [Solution] The tire 1 includes a bead portion 2 fixed to a rim 20. The tire 1 includes a bead core 9 and a carcass 6 having a down ply 8 containing an organic fiber cord and a turn-up ply 7. The rim-mounting rubber 17, which is positioned outward in the tire axial direction from the down ply 8, is provided with a reinforcing layer 10 that extends from the inside in the tire radial direction to the outside in the tire radial direction, straddling the rim separation point P0 where contact between the tire 1 and the rim 20 ends, and has higher rigidity than the rim-mounting rubber 17.

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] Regarding conventional tires, attention has been paid to the fact that tensile stress and compressive stress are generated in the vicinity of the bead portion when a load is applied to the tire, and the carcass ply is positioned near a portion that hardly generates stress called the neutral zone. There is known a pneumatic tire for a light truck in which the shape of the rim-attached rubber is dimensionally defined (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, as a result of intensive test research, the inventors of the present application have found that when a large load is applied to a tire attached to a rim, a large compressive stress occurs in, for example, the contact area between the rim-attached rubber of the tire and the rim. It has been recognized that the contact area may be displaced outward in the tire radial direction along the rim surface as a back displacement, and such a back displacement bulges the contact area outward in the tire width direction from the rim separation point where the contact between the rim-attached rubber and the rim ends. As a result, a bulge portion is formed as a back bulge, and it has been found that there is room for improvement in terms of the durability of the tire.

[0005] An object of the present invention is to provide a tire having improved durability by suppressing back displacement.

Means for Solving the Problems

[0006] (1) The tire of the present invention is a tire having a bead portion fixed to a rim, comprising a bead core and a carcass having a down ply and a turn-up ply containing organic fiber cords, and a reinforcing layer having a rigidity higher than the rim-mounting rubber which is located outward in the tire axial direction from the carcass and extends from the inside in the tire radial direction to the outside in the tire radial direction, straddling the rim separation point where contact between the tire and the rim ends.

[0007] (2) In the tire described in (1) above, it is preferable that the reinforcing layer extends in the tire radial direction to a position in the tire radial direction that is equal to the tire radial center of the bead core.

[0008] (3) In the tire described in (2) above, it is more preferable that the reinforcing layer extends in the tire radial direction to a position equal to the tire radial position of the inner end of the bead core in the tire radial direction.

[0009] (4) In any one of the tires described in (1) to (3) above, the reinforcing layer contains organic fiber cords, the down ply is positioned furthest outward in the tire axial direction of the carcass, and the angle on the acute side between the extending direction of the organic fiber cords in the reinforcing layer and the extending direction of the organic fiber cords in the down ply is preferably 0° to 20°.

[0010] (5) In the tire described in (4) above, it is more preferable that the acute angle is 0°.

[0011] (6) In any one of the tires described in (1) to (5) above, it is preferable that the rigidity of the reinforcing layer is the same as that of the carcass. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a tire whose durability is improved by suppressing rearward displacement. [Brief explanation of the drawing]

[0013] [Figure 1] This is a cross-sectional view showing one side of the tire's equatorial plane, which is one embodiment of the present invention, along the tire's rotation axis. [Figure 2] Figure 1 is an enlarged cross-sectional view schematically showing the main parts of the tire together with the rim. [Figure 3] This is an enlarged cross-sectional view showing a further magnified view of the area around the bead portion in Figure 2. [Figure 4A] This is a schematic diagram illustrating the function that the organic fiber cords contained in the reinforcing layer exert on the organic fiber cords contained in the down ply. [Figure 4B] This is a schematic diagram illustrating the relationship between the arrangement of organic fiber cords contained in the reinforcing layer and organic fiber cords contained in the down ply. [Modes for carrying out the invention]

[0014] Hereinafter, with reference to the drawings, a tire 1, which is one embodiment of the present invention, will be described. In this disclosure, tire 1 is a pneumatic tire. In particular, in this disclosure, tire 1 is a light truck tire used in high-load areas.

[0015] Here, "tire axis direction" refers to the direction parallel to the rotation axis of tire 1. In Figure 1, it refers to the direction indicated by the arrow W in the horizontal direction of the paper. In the following explanation, the direction toward the outside of the tire is referred to as "tire axis outward," and the direction toward the inside of the tire is referred to as "tire axis inward." Also, "tire radial direction" refers to the direction perpendicular to the rotation axis of tire 1, and in Figure 1, it refers to the direction indicated by the arrow R in the vertical direction of the paper. In the following explanation, the direction toward the tread portion 5 is referred to as "tire radial outward," and the direction toward the rotation axis of the tire is referred to as "tire radial inward."

[0016] As shown in Figure 1, the tire 1 is mainly composed of a bead section 2, a side section 3, a shoulder section 4, and a tread section 5. The carcass 6 has a turn-up ply 7 and a down ply 8. The turn-up ply 7 and the down ply 8 are both of a general structure in which multiple cords (organic fiber cords) made of organic fibers are covered with rubber. "Organic fiber cords" include, for example, multiple organic fibers twisted together, multiple organic fibers tied together (bundled), or a single organic fiber.

[0017] The turn-up ply 7 is a ply that extends across the tread portion 5 between two bead portions 2 located on both sides of the tire axial direction and is folded back around the bead core 9. In this disclosure, the widthwise end portion of the turn-up ply 7 is folded back from the inner side of the tire axial direction to the outer side of the tire axial direction of the bead core 9. The portion extending from one of the two bead cores 9 (only one side is shown in Figure 1) located on both sides of the tire axial direction corresponds to the main body portion 7A of the turn-up ply 7. The portion of the bead core 9 that is folded back to the outer side of the tire axial direction corresponds to the folded portion 7B of the turn-up ply 7.

[0018] The down ply 8 extends across the tread portion 5 between two bead portions 2 located on both sides of the tire axial direction and is a ply that is not folded back around the bead core 9. The down ply 8 is located on the tire axial side of the turn-up ply 7. The widthwise end of the down ply 8 is in close contact with the tire axial side surface of the folded portion 7B of the turn-up ply 7. In this disclosure, the widthwise end of the down ply 8 terminates on the tire axial side of the bead core 9.

[0019] Between the main body portion 7A of the turn-up ply 7, the folded-back portion 7B of the turn-up ply 7, and the down ply 8, a first bead filler 11 made of a hard rubber extending in a tapered shape from the outer peripheral surface of the bead core 9 toward the outer side in the tire diameter direction is provided. In the present disclosure, the first bead filler 11 is composed of a high-hardness rubber portion 11A on the side of the bead core 9 and a low-hardness rubber portion 11B disposed on the outer side in the tire diameter direction of the high-hardness rubber portion 11A. The low-hardness rubber portion 11B is made of a rubber having a softer hardness compared to the rubber constituting the high-hardness rubber portion 11A. Note that both the rubber constituting the high-hardness rubber portion 11A and the rubber constituting the low-hardness rubber portion 11B are harder than the rubber of the side rubber layer 14. The side rubber layer 14 is disposed on the outer side in the tire axial direction of the carcass 6. The side rubber layer 14 constitutes the tire side portion 3.

[0020] Also, in the present disclosure, a reinforcing cord layer 12 is provided between the bead core 9 and the turn-up ply 7 and between the first bead filler 11 and the turn-up ply 7 so as to fold back the bead core 9. A plurality of cords intersecting the cords of the turn-up ply 7 are embedded in the reinforcing cord layer 12.

[0021] On the other hand, a rubber chafer 13 extending from the bead heel 2A toward the outer side in the tire diameter direction is disposed on the outer side in the tire axial direction of the bead portion 2. The vicinity of the inner end in the tire diameter direction of the side rubber layer 14 is covered by the vicinity of the outer end in the tire diameter direction of this rubber chafer 13. In the present disclosure, the rubber chafer 13 and the side rubber layer 14 constitute the side portion of the tire 1.

[0022] Furthermore, in this disclosure, a second bead filler 15 is positioned on the tire axial outer side of the down ply 8, radially outward from the bead core 9 and facing the first bead filler 11. The second bead filler 15 is provided together with the first bead filler 11 to reinforce the bead portion 2. The second bead filler 15 is made of rubber that is harder than the rubber constituting the side rubber layer 14, similar to the first bead filler 11. The thickness of the second bead filler 15 gradually decreases toward the tire radial outer side and the tire radial inner side. A barrier member 16 having water-resistant permeability is positioned on the tire axial outer side of the second bead filler 15.

[0023] In this disclosure, in the bead portion 2, the rubber chafer 17 that forms the bead toe 2B is positioned inward in the tire axial direction from the inner end of the rubber chafer 13 in the tire radial direction. However, in this disclosure, the outer surface of the rubber chafer 17 is covered with a cover rubber 18.

[0024] In this disclosure, a belt 21 is arranged on the radially outer side of the carcass 6. In this disclosure, the belt 21 has a first belt ply 22 and a second belt ply 23. On the radially outer side of the belt 21, there is a first belt reinforcing layer 24 that covers substantially the entire belt, and a second belt reinforcing layer 25 that is arranged on the radially outer side of the first belt reinforcing layer 24 near its widthwise end. In addition, in this disclosure, a tread rubber layer 26 that forms the tread portion 5 is provided on the radially outer side of the first belt reinforcing layer 24 and the second belt reinforcing layer 25. Furthermore, in this disclosure, a cushion rubber 27 with a substantially triangular cross-section is arranged between the widthwise end of the first belt ply 22 and the down ply 8 of the carcass 6.

[0025] An inner liner 28 is provided on the inner surface of the tire 1. The inner liner 28 is made of a rubber that has better air impermeability than the rubber that forms the side rubber layer 14 and the rubber that forms the tread rubber layer 26. In this disclosure, the inner liner 28 terminates radially outward from the bead core 9, but it may extend to the bead toe 2B. The inner liner 28 uses a butyl-based rubber composition that is commonly used in pneumatic tires.

[0026] As shown in Figure 2, the tire 1 includes a bead portion 2 fixed to the rim 20. The tire 1 includes a bead core 9 and a carcass 6 having a down ply 8 and a turn-up ply 7 containing organic fiber cords. The tire 1 includes a rubber chafer (rim-mounting rubber) 13 positioned outward in the tire axial direction from the carcass 6 (down ply 8 in this disclosure), and a reinforcing layer 10 that extends from the inside to the outside in the tire radial direction, straddling the rim separation point P0 where contact between the tire 1 and the rim 20 ends, on the outer surface of the bead portion 2 in the tire width direction, and has higher rigidity than the rubber chafer 13.

[0027] Here, "sandwiching the rim separation point P0" means that the reinforcing layer 10 extends longitudinally (or transversely) across the rim separation point P0 in the tire radial direction. Referring to Figure 3 described later, it is sufficient that the region of the reinforcing layer 10 extending in the tire radial direction between the inner end 10e1 of the reinforcing layer 10 and the outer end 10e2 of the reinforcing layer 10 in the tire radial direction includes the tire radial position of the rim separation point P0.

[0028] The rim separation point P0 is determined appropriately according to, for example, the dimensions, specifications, and application of the tire 1 and rim 20, the internal pressure of the tire 1, etc.

[0029] Unless otherwise specified, the positional relationships and dimensions of each element shall be measured under standard conditions, with the tire mounted on the applicable rim, filled to the specified internal pressure, and unloaded. Furthermore, the outer circumference of the tire that comes into contact with the road surface when the tire is mounted on the applicable rim, filled to the specified internal pressure, and under maximum load is referred to as the "tread surface" (however, it may also be called the "tread face"), and the edges at both ends of the tread surface in the tire width direction are referred to as the "tread edges".

[0030] In this specification, "applicable rim" refers to the standard rim (Measuring Rim in the ETRTO STANDARDS MANUAL, Design Rim in the TRA YEAR BOOK) for the applicable size, which is listed or will be listed in the industrial standards valid in the region where the tire is produced and used, such as the JATMA YEAR BOOK of JATMA (Japan Automobile Tire Manufacturers Association) in Japan, the STANDARDS MANUAL of ETRTO (The European Tyre and Rim Technical Organisation) in Europe, and the YEAR BOOK of TRA (The Tire and Rim Association, Inc.) in the United States. However, for sizes not listed in these industrial standards, it refers to a rim with a width corresponding to the bead width of a pneumatic tire. "Applicable rim" includes not only current sizes but also sizes that will be listed in the aforementioned industrial standards in the future. An example of "sizes that will be listed in the future" is the size listed as "FUTURE DEVELOPMENTS" in the ETRTO 2013 edition.

[0031] In this specification, "specified internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity of a single wheel in the applicable size and ply rating as described in the aforementioned industrial standards such as the JATMA YEAR BOOK. For sizes not listed in the aforementioned industrial standards, it refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity specified for each vehicle on which the tire is mounted. Furthermore, in this specification, "maximum load" refers to the load corresponding to the maximum load capacity of a tire of the applicable size as described in the aforementioned industrial standards, or, for sizes not listed in the aforementioned industrial standards, the load corresponding to the maximum load capacity specified for each vehicle on which the tire is mounted.

[0032] As shown in Figure 2, when a reinforcing layer 10 with higher rigidity than the rubber chafer 13 is provided on the rubber chafer 13 so as to sandwich the rim separation point P0, the reinforcing layer 10 has higher rigidity than the rubber chafer 13, and therefore can suppress the movement of the rubber chafer 13 to displace outward in the tire radial direction from the rim separation point P0. For this reason, by providing a reinforcing layer 10 with higher rigidity than the rubber chafer 13 so as to sandwich the rim separation point P0 on the rubber chafer 13, it is possible to suppress the occurrence of a back bulge from the rim separation point P0 (for example, a bulge that bulges outward in the tire axial direction from the rim separation point P0 as the rubber chafer 13 is compressed between the down ply 8 and the rim 20 and displaced outward in the tire radial direction).

[0033] Therefore, according to tire 1, it is possible to provide a tire whose durability is improved by suppressing rearward displacement.

[0034] Figure 3 shows a more magnified view of the area around the bead portion 2 in Figure 2.

[0035] Preferably, the reinforcing layer 10 extends to a position P1 in the tire radial direction that is equal to the tire radial center O1 of the bead core 9. In this case, the reinforcing layer 10 can suppress the movement of the rubber chafer 13 that follows the movement of the center O1 of the bead core 9. This makes it possible to further suppress the generation of a back bulge from the rim separation point P0, which may occur when the rubber chafer 13 is displaced on its back side radially outward along the holding surface of the rim 20.

[0036] As shown in Figure 3, in this disclosure, the reinforcing layer 10 extends in the tire radial direction to a position equal to the tire radial position P2 of the inner end 9e of the bead core 9 in the tire radial direction. In this case, the reinforcing layer 10 can suppress the movement of the rubber chafer 13 that follows the overall movement of the bead core 9. Therefore, it is possible to further suppress the generation of a back bulge from the rim separation point P that may occur due to the back displacement of the rubber chafer 13 outward in the tire radial direction along the holding surface of the rim 20.

[0037] In this disclosure, the reinforcing layer 10 includes organic fiber cords C10. In this disclosure, the down ply 8 is positioned furthest outward in the tire axial direction of the carcass 6. Furthermore, in this disclosure, the acute angle α between the extending direction of the organic fiber cords C10 included in the reinforcing layer 10 and the extending direction of the organic fiber cords C8 included in the down ply 8 is preferably 0° to 20°. More preferably, the acute angle α is 0°. In this disclosure, when the tread surface is viewed in plane, the angle between the organic fiber cords C8 of the down ply 8 and the tire circumferential direction is 0°. Furthermore, in this disclosure, the angle between the organic fiber cords of the turn-up ply 7 and the tire circumferential direction is also 0° when the tread surface is viewed in plane. However, the angle between the organic fiber cords C8 of the down ply 8 and the organic fiber cords of the turn-up ply 7 and the tire circumferential direction can be, for example, 0° to 30° when the tread surface is viewed in plane.

[0038] In this disclosure, when the reinforcing layer 10 includes an organic fiber cord C10, the reinforcing layer 10 tends to expand and contract along the organic fiber cord C10. Therefore, as shown in Figure 4A, if the down ply 8 and the reinforcing layer 10 are positioned so that the organic fiber cord C10 of the reinforcing layer 10 is parallel to the organic fiber cord C8 of the down ply 8, the displacement of the down ply 8 can be effectively suppressed.

[0039] Figure 4A shows a state where the organic fiber cord C8 of the downply 8 and the organic fiber cord C10 of the reinforcing layer 10 are arranged in parallel (α=0°). In this case, the displacement of the downply 8 can be effectively suppressed by the reinforcing layer 10. However, as shown in Figure 4B, even when the organic fiber cord C8 of the downply 8 and the organic fiber cord C10 of the reinforcing layer 10 intersect at an angle α, the effect of suppressing the displacement of the downply 8 can be achieved as long as the angle α is 20° or less.

[0040] The rigidity of the reinforcing layer 10 is preferably higher than that of the carcass 6. However, the rigidity of the reinforcing layer 10 can be the same as that of the carcass 6. In this case, for example, the reinforcing layer 10 can be used as a reinforcing layer for the carcass 6, so there is no need to add new material for the reinforcing layer of the carcass 6. Also, when introducing a new member as a reinforcing layer for the carcass 6, it is necessary to check the workability (for example, whether there are any manufacturing defects), but if the reinforcing layer 10 is used as a reinforcing layer for the carcass 6, the need to check the workability when introducing a new member as a reinforcing layer for the carcass 6 is reduced. Therefore, it is advantageous in terms of manufacturing if the rigidity of the reinforcing layer 10 is higher than that of the carcass 6. Note that the organic fiber cord reinforcing layer C10 of the reinforcing layer 10 may be, for example, a metal fiber cord reinforcing layer, a hard rubber layer, etc.

[0041] As described above, exemplary embodiments of the present invention have been stated, but the present invention is not limited to these embodiments and can be modified in various ways without departing from the spirit of the invention. For example, the reinforcing layer 10 can be provided in a region where the contact pressure is at least 0.5 MPa or higher. The reinforcing layer 10 can also be embedded in the rubber chafer 17, for example. In this case, the reinforcing layer 10 may be embedded so as to be exposed from the rubber chafer 17. Furthermore, the reinforcing layer 10 can also be attached to the surface of the rubber chafer 17 by means of adhesive or other means.

[0042] [Contribution to the United Nations-led Sustainable Development Goals (SDGs)] The SDGs have been proposed to realize a sustainable society. Each embodiment of the present invention is considered to be a technology that can contribute to "No. 9 - Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation" and "No. 12 - Ensure responsible consumption and production," among others. [Industrial applicability]

[0043] The tire according to the present invention can be suitably used for any type of pneumatic tire, for example, pneumatic tires for passenger cars, pneumatic tires for trucks and buses, etc. [Explanation of Symbols]

[0044] 1: Tire, 2: Bead section, 2A: Bead heel, 2B: Bead toe, 3: Side section, 4: Shoulder section, 5: Tread section, 6: Carcass, 7: Turn-up ply, 7A: Main body section, 8: Down ply, 9: Bead core, 9e: Inner end of tire in radial direction, 10: Reinforcement layer, 11: First bead filler, 11A: High-hardness rubber section, 11B: Low-hardness rubber section, 12: Reinforcement cord layer, 13: Rubber chafer (rim mounting side rubber), 14: Side rubber layer, 15: Second bead filler, 17: Rubber chafer, 18: Cover rubber, 20: Rim, 21: Belt, 22: First belt ply, 23: Second belt ply, 24: First belt reinforcement layer, 25: Second belt reinforcement layer, 26: Tread rubber layer, 27: Cushion rubber, 28: Inner liner, P0: Rim separation point

Claims

1. A tire having a bead portion that is fixed to the rim, The structure comprises a bead core and a carcass having down plies and turn-up plies containing organic fiber cords, A tire comprising a rim-mounting rubber positioned axially outward from the carcass, the rim-mounting rubber having a reinforcing layer that extends from the radially inner side to the radially outer side of the tire, straddling the rim separation point where contact between the tire and the rim ends, and having a higher rigidity than the rim-mounting rubber.

2. The tire according to claim 1, wherein the reinforcing layer extends in the tire radial direction to a position in the tire radial direction that is equal to the tire radial center of the bead core.

3. The tire of the invention according to claim 3, wherein the reinforcing layer extends in the tire radial direction to a position equal to the tire radial position of the inner end of the bead core in the tire radial direction.

4. The reinforcing layer contains organic fiber cords, and the downply is positioned furthest outward in the tire axial direction of the carcass. The tire according to claim 1, wherein the acute angle formed by the extending direction of the organic fiber cords contained in the reinforcing layer and the extending direction of the organic fiber cords contained in the down ply is 0° to 20°.

5. The tire according to claim 4, wherein the angle on the acute side is 0°.

6. The tire according to claim 1, wherein the rigidity of the reinforcing layer is equivalent to that of the carcass.

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