pneumatic tires

Abstract

To provide a pneumatic tire securing air shut-off performance and durability of a rubber chafer, while suppressing molding defect in a bead part.SOLUTION: In the pneumatic tire, an end of a butyl rubber layer is arranged closer to inside in a tire axial direction than an adhesive rubber layer. The end of the butyl rubber layer passes on a point separated away by 7 mm from a bead toe to outside in a tire radial direction and is arranged between a first virtual straight line extending in the tire axial direction and a second virtual straight line passing on both ends in the width direction of the bead core, in a tire meridian cross section. The end of the adhesive rubber layer passes on an inside end in the tire axial direction of a bottom surface of the bead core and is arranged between a third virtual straight line which is orthogonal to the bottom surface and a fourth virtual straight line which contacts an inner end in the tire axial direction of a reinforcement layer, at a side closer to inside in the tire axial direction than the third virtual straight line and is parallel to the third virtual straight line, in tire meridian cross section.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to pneumatic tires. [Background technology]

[0002] Patent Document 1 discloses a pneumatic tire in which the end of the inner liner is positioned between a first imaginary line that passes through the center of the bead core and is perpendicular to the bead base, and a second imaginary line that is parallel to the bead base and is positioned 15 mm away from the bead base.The document states that with this configuration, even if the width of the inner liner is widened and the end of the inner liner approaches the bead toe, it is possible to prevent the occurrence of cracks that could cause cracks or chips in the bead portion between the end of the inner liner and the adjacent rubber chafer, and it is also possible to improve air leakage.

[0003] However, if the end of the inner liner is positioned near the first virtual line, the inner liner may penetrate into the tire radially inward of the bottom surface of the bead core, reducing the thickness of the rubber chafer and potentially reducing the durability of the rubber chafer.

[0004] Furthermore, Patent Document 1 does not describe the position of the butyl rubber layer of the inner liner. Therefore, if the edge of the inner liner is positioned near the second imaginary line, the edge of the butyl rubber layer may be positioned radially outward of the second imaginary line, which may impair the air barrier properties of the inner liner. Furthermore, in this case, air may become trapped between the inner liner and the rubber chafer due to insufficient volume of the inner liner, which may result in poor molding of the bead portion. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-71721 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present disclosure is to provide a pneumatic tire that ensures air barrier properties and durability of rubber chafers while suppressing molding defects in the bead portions. [Means for solving the problem]

[0007] The pneumatic tire of the present disclosure comprises a pair of bead portions each having a bead core with a hexagonal cross section, a carcass ply that is bridged between the pair of bead portions and folded back around the bead core so as to sandwich the bead core, a reinforcing layer that is arranged to cover the bead core and the carcass ply, an inner liner that is arranged axially inward of the carcass ply, and a rubber chafer that forms an inner end of the bead portion in the radial direction of the tire, the inner liner comprising a butyl rubber layer that forms the innermost surface of the tire, and an adhesive rubber layer that is arranged between the butyl rubber layer and the carcass ply, The end of the butyl rubber layer is arranged axially more inward than the end of the adhesive rubber layer, and the end of the butyl rubber layer is arranged, in the tire meridian cross section, between a first imaginary line that passes through a point 7 mm radially outward from the bead toe of the bead portion and extends in the tire axial direction, and a second imaginary line that passes through both ends of the bead core in the width direction, and the end of the adhesive rubber layer is arranged, in the tire meridian cross section, between a third imaginary line that passes through the axially inner end of the bottom surface of the bead core and is perpendicular to the bottom surface, and a fourth imaginary line that is axially more inward than the third imaginary line and is in contact with the axially inner surface of the reinforcing layer and is parallel to the third imaginary line. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a meridian cross-sectional view of a pneumatic tire according to an embodiment; [Figure 2] Enlarged view of area II in Figure 1 [Figure 3] Enlarged view of area II in Figure 1 [Figure 4] Diagram showing the manufacturing process of unvulcanized tires DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of a pneumatic tire will be described with reference to Fig. 1. Note that in each of the figures (Figs. 1 to 4), the dimensional ratios in the drawings do not necessarily match the actual dimensional ratios, and the dimensional ratios between the figures do not necessarily match either.

[0010] In Figure 1, the first direction D1 is the tire axial direction D1 that is parallel to the tire rotation axis of a pneumatic tire (hereinafter also simply referred to as "tire") 1, and the second direction D2 is the tire radial direction D2 that is the diameter direction of the tire 1.

[0011] In the tire axial direction D1, the inner side is the side closer to the tire equatorial plane S1, and the outer side is the side farther from the tire equatorial plane S1. In the tire radial direction D2, the inner side is the side closer to the tire rotational axis, and the outer side is the side farther from the tire rotational axis. The tire equatorial plane S1 is a plane that is perpendicular to the tire rotational axis and is located at the center of the tire axial direction D1 of the tire 1, and the tire meridian cross section is a cross section that includes the tire rotational axis and is perpendicular to the tire equatorial plane S1.

[0012] The tire 1 according to this embodiment is a heavy-duty tire. Heavy-duty tires are tires that are listed in "Chapter C: For trucks and buses" and "Chapter D: For construction vehicles" of the "JATMA YEAR BOOK 2022 (Japan Automobile Tire Manufacturers Association Standards)."

[0013] 1, a tire 1 according to this embodiment includes a pair of bead portions 2, a pair of sidewalls 3 extending outward in the tire radial direction D2 from each bead portion 2, and a tread 4 continuing to the outer ends in the tire radial direction D2 of each sidewall 3. The tire 1 is mounted on a rim (not shown).

[0014] The bead portion 2 includes an annular bead core 21 and a bead filler 22 extending outward from the bead core 21 in the tire radial direction D2. The bead core 21 has a hexagonal cross section. In this embodiment, the bead core 21 is inclined inward in the tire radial direction D2 toward the inside of the tire axial direction D1, but this is not limited to this. The bead filler 22 has a substantially triangular cross section.

[0015] The tire 1 includes a rubber chafer 23 disposed at a portion that comes into contact with the rim. The rubber chafer 23 forms the inner end of the bead portion 2 in the tire radial direction D2. The rubber chafer 23 is folded back around the bead core 21 so as to sandwich the bead core 21 from the outer side (inner side in the tire radial direction D2) of the reinforcing layer 6 and the inner liner 7 described below, and the outer end of the rubber chafer 23 in the tire axial direction D1 is connected to the sidewall 3. The outer end of the rubber chafer 23 in the tire radial direction D2 on the inner side in the tire axial direction D1 is tapered.

[0016] The tire 1 includes a carcass ply 5 that is laid between a pair of bead portions 2, a reinforcing layer 6 that protects the carcass ply 5 from friction with the rim, and an inner liner 7 that is arranged inside the carcass ply 5 in the tire axial direction D1. The carcass ply 5 and the inner liner 7 are arranged along the inner circumference of the tire 1, spanning the pair of bead portions 2, the pair of sidewalls 3, and the tread 4.

[0017] The carcass ply 5 is formed by covering a plurality of arranged ply cords with rubber. The carcass ply 5 has a turned-up portion 51 that is turned up around the bead core 21 so as to sandwich the bead core 21. An outer end 51a in the tire radial direction D2 of the turned-up portion 51 is disposed outward in the tire radial direction D2 from an outer end 6a in the tire radial direction D2 of the reinforcing layer 6 that is located on the outer side in the tire axial direction D1.

[0018] The reinforcing layer 6 is arranged with a generally U-shaped cross section so as to cover a portion of the carcass ply 5 and the bead core 21. Both ends 6a, 6b of the reinforcing layer 6 are arranged outward of the bead core 21 in the tire radial direction D2. The reinforcing layer 6 is a chafer in which an arrangement of cords such as metal cords or organic fiber cords is covered with rubber. In this embodiment, the reinforcing layer 6 is a steel chafer in which steel cords are arranged, but is not limited to this. The reinforcing layer 6 may also be, for example, a nylon chafer in which nylon cords are arranged.

[0019] The inner liner 7 is disposed on the innermost surface of the tire and faces the internal space of the tire 1, which is filled with air. As shown in FIG. 2 , the inner liner 7 includes a butyl rubber layer 71 that forms the innermost surface of the tire, and an adhesive rubber layer 72 that is disposed between the butyl rubber layer 71 and the carcass ply 5. The butyl rubber layer 71 is formed of butyl rubber, which has excellent air barrier properties. The adhesive rubber layer 72 is formed of adhesive rubber, which has better adhesiveness than butyl rubber. When the adhesiveness to a metal plate is measured using a measuring device (product name "Tack Tester II") manufactured by Toyo Seiki Seisakusho, Ltd., the adhesive rubber exhibits adhesiveness that is, for example, 1.5 times or more that of butyl rubber. The adhesive rubber layer (also referred to as an adhesive rubber layer) 72 bonds the butyl rubber layer 71 and the carcass ply 5 together.

[0020] An end 71a of the butyl rubber layer 71 is tapered. The end 71a of the butyl rubber layer 71 is in contact with the surface of the adhesive rubber layer 72. In the tire meridian cross section, the end 71a of the butyl rubber layer 71 is located between a first imaginary line L1 that passes through a point 7 mm outward in the tire radial direction D2 from the bead toe 2a of the bead portion 2 and extends along the tire axial direction D1, and a second imaginary line L2 that passes through both ends of the bead core 21 in the width direction. The first imaginary line L1 and the second imaginary line L2 are included between the first imaginary line L1 and the second imaginary line L2.

[0021] The end 71a of the butyl rubber layer 71 is disposed more inward in the tire axial direction D1 than the end 72a of the adhesive rubber layer 72. In this embodiment, the end 71a of the butyl rubber layer 71 is disposed more outward in the tire radial direction D2 than the end 72a of the adhesive rubber layer 72, but is not limited to this.

[0022] In the tire meridian cross section, the end 72a of the adhesive rubber layer 72 is disposed between a third imaginary line L3 that passes through the inner end of the bottom surface 21a of the bead core 21 in the tire axial direction D1 and is perpendicular to the bottom surface 21a, and a fourth imaginary line L4 that is located more inward in the tire axial direction D1 than the third imaginary line L3 and is parallel to the third imaginary line L3. The fourth imaginary line L4 is in contact with the inner surface of the reinforcing layer 6 in the tire axial direction D1. The third imaginary line L3 and the fourth imaginary line L4 are included between the third imaginary line L3 and the fourth imaginary line L4.

[0023] 3, in the tire meridian cross section, the end 71a of the butyl rubber layer 71 is preferably located on a fifth imaginary line L5 extending in the tire axial direction D1 at a position 13 mm outward in the tire radial direction D2 from the bead toe 2a, or on the inside in the tire radial direction D2 of the fifth imaginary line L5. That is, the end 71a of the butyl rubber layer 71 is preferably located between the first imaginary line L1 and the fifth imaginary line L5.

[0024] In the tire meridian cross section, the end 71a of the butyl rubber layer 71 is preferably located on a sixth imaginary line L6 extending along the bottom surface 21a of the bead core 21 or further outward in the tire radial direction D2 than the sixth imaginary line L6. That is, the end 71a of the butyl rubber layer 71 is preferably located between the second imaginary line L2 (see FIG. 2) and the sixth imaginary line L6, and more preferably located between the fifth imaginary line L5 and the sixth imaginary line L6.

[0025] An end 72a of the adhesive rubber layer 72 is in contact with the surface of the carcass ply 5. In the tire meridian cross section, the end 72a of the adhesive rubber layer 72 is preferably located on a seventh imaginary line L7 that extends parallel to the third imaginary line L3 and is 3 mm away from the third imaginary line L3, or further outward in the tire axial direction D1 than the seventh imaginary line L7. In other words, the end 72a of the adhesive rubber layer 72 is preferably located between the third imaginary line L3 and the seventh imaginary line L7.

[0026] As shown in Fig. 2, the rubber chafer 23 covers the end 71a of the butyl rubber layer 71 from the inside in the tire axial direction D1. The covering distance H1 of the butyl rubber layer 71 by the rubber chafer 23 is preferably 10 mm or more in the tire meridian cross section. The covering distance H1 is more preferably 20 mm or less. The covering distance H1 is the shortest length from the outer end of the rubber chafer 23 in the tire radial direction D2 on the inside in the tire axial direction D1 to the end 71a of the butyl rubber layer 71.

[0027] The above dimensions are values ​​measured, for example, when the tire 1 is mounted on a standard rim and inflated to the standard internal pressure under no load. The standard rim is the rim specified for each tire by the standard system including the standard on which the tire is based, such as the standard rim for JATMA, or the measuring rim for TRA and ETRTO. The standard internal pressure is the air pressure specified for each tire by the standard system including the standard on which the tire is based, such as the maximum air pressure for JATMA, the maximum value listed in the table "IRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and the inflation pressure for ETRTO.

[0028] The above dimensions may be values ​​measured with the tire 1 removed from the rim. Specifically, the tire 1 removed from the rim is cut along the tire meridian cross section, and the bead toes 2a on both sides are connected with adhesive tape. At this time, adhesive tape is attached to each bead toe 2a so that the adhesive tape coincides with the tire axial direction D1, and the distance between the bead toes 2a coincides with the distance when the tire is attached to the rim. Then, the above dimensions can be confirmed by measuring the cut cross section with a measuring tool. The tire radial direction D2 is the direction on the cut cross section that is perpendicular to the adhesive tape.

[0029] [Manufacturing method of pneumatic tires] Next, an example of a method for manufacturing a pneumatic tire will be described with reference to FIG.

[0030] As shown in Fig. 4, first, a sidewall rubber 102 and a rubber chafer rubber 103 having a triangular cross section are placed on a forming drum 101. Next, a sheet-shaped adhesive rubber 105 is attached to a sheet-shaped butyl rubber 104, and the butyl rubber 104 and the adhesive rubber 105 are placed on the forming drum 101 so that they overlap the rubber chafer rubber 103.

[0031] The width dimension of the adhesive rubber 105 is larger than the width dimension of the butyl rubber 104. That is, the end 105a of the adhesive rubber 105 protrudes in the width direction beyond the end 104a of the butyl rubber 104, and a step is formed by the butyl rubber 104 and the adhesive rubber 105. This reduces the gap between the adhesive rubber 105 and the rubber chafer rubber 103, thereby preventing air from being trapped in the gap. In this embodiment, the protruding length W1 of the adhesive rubber 105 is 10 mm, but is not limited to this. The protruding length W1 is set appropriately depending on the positions of the end 71a of the butyl rubber layer 71 and the end 72a of the adhesive rubber layer 72 in FIG. 2.

[0032] The end 104a of the butyl rubber 104 has a shape that follows the thickness direction of the butyl rubber 104. That is, the butyl rubber 104 is formed to have a rectangular cross section. The end 104a of the butyl rubber 104 may be inclined, for example, along the contact surface with the rubber chafer rubber 103. The corners of the butyl rubber 104 may be rounded.

[0033] The edge 105a of the adhesive rubber 105 preferably has a shape that follows the thickness direction of the adhesive rubber 105. That is, the adhesive rubber 105 is preferably formed to have a rectangular cross section. This prevents a gap from forming between the adhesive rubber layer 72 and the rubber chafer 23 due to insufficient volume of the adhesive rubber layer 72, and prevents air from pooling between them. The corners of the adhesive rubber 105 may be rounded.

[0034] The overlap width W2 between the butyl rubber 104 and the rubber chafer rubber 103 is preferably 10 mm to 20 mm, thereby ensuring the covering width H1 of the butyl rubber layer 71 by the rubber chafer 23 in FIG.

[0035] Next, the bead cores, carcass plies, etc. are placed on the building drum 101, and the carcass plies are folded back around the bead cores. Then, similar to a general tire manufacturing process, other tire components are attached to form an unvulcanized tire. Finally, the unvulcanized tire is vulcanized in a vulcanization mold to manufacture a tire.

[0036] [1] As described above, the pneumatic tire 1 according to this embodiment comprises a pair of bead portions 2 each having a bead core 21 with a hexagonal cross section, a carcass ply 5 that is bridged between the pair of bead portions 2 and folded back around the bead core 21 so as to sandwich the bead core 21, a reinforcing layer 6 that is arranged to cover the bead core 21 and the carcass ply 5, an inner liner 7 that is arranged inside the carcass ply 5 in the tire axial direction D1, and a rubber chafer 23 that forms an inner end of the bead portion 2 in the tire radial direction D2, and the inner liner 7 comprises a butyl rubber layer 71 that forms the innermost surface of the tire, and an adhesive rubber layer 72 that is arranged between the butyl rubber layer 71 and the carcass ply 5, and an end 71a of the butyl rubber layer 71 is The adhesive rubber layer 72 is disposed between a first imaginary straight line L1 that passes through a point 7 mm outward in the tire radial direction D2 from the bead toe 2a of the bead portion 2 and extends in the tire axial direction D1, and a second imaginary straight line L2 that passes through both ends of the bead core 21 in the width direction (tire axial direction D1), and is disposed more inward in the tire axial direction D1 than an end 72a of the adhesive rubber layer 72; in the tire meridian cross section, the end 72a of the adhesive rubber layer 72 is disposed between a third imaginary straight line L3 that passes through the inner end of the bottom surface 21a of the bead core 21 in the tire axial direction D1 and is perpendicular to the bottom surface 21a, and a fourth imaginary straight line L4 that is located more inward in the tire axial direction D1 than the third imaginary line L3 and is parallel to the third imaginary line L3; and the fourth imaginary line L4 is in contact with the inner surface of the reinforcing layer 6 in the tire axial direction D1.

[0037] According to this configuration, by positioning the end 71a of the butyl rubber layer 71 at a position not exceeding the first imaginary line L1 and more inward in the tire axial direction D1 than the end 72a of the adhesive rubber layer 72, it is possible to prevent a gap from forming between the rubber chafer 23 and the adhesive rubber layer 72, thereby preventing air pockets from forming in the gap. Positioning the end 71a of the butyl rubber layer 71 at a position exceeding the second imaginary line L2 ensures airtightness. Positioning the end 72a of the adhesive rubber layer 72 between the third imaginary line L3 and the fourth imaginary line L4 prevents the adhesive rubber layer 72 from penetrating into the bottom surface 21a of the bead core 21, preventing the thickness of the rubber chafer 23 from becoming thin. This ensures the durability of the rubber chafer 23. Furthermore, it is possible to prevent air pockets from forming between the rubber chafer 23 and the adhesive rubber layer 72, thereby preventing molding defects in the bead portion 2. As a result, molding defects in the bead portion 2 can be suppressed, and the air barrier properties and durability of the rubber chafer 23 can be ensured.

[0038] [2] Furthermore, with regard to the pneumatic tire 1 according to [1] above, it is preferable that the end 71a of the butyl rubber layer 71 is positioned on a fifth imaginary line L5 extending in the tire axial direction D1 at a position 13 mm outward in the tire radial direction D2 from the bead toe 2a in the tire meridian cross section, or positioned more inward in the tire radial direction D2 than the fifth imaginary line L5.

[0039] With this configuration, the air barrier properties of the pneumatic tire 1 can be further ensured.

[0040] [3] Furthermore, with respect to the pneumatic tire 1 according to [1] or [2] above, it is preferable that the end 71a of the butyl rubber layer 71 is positioned on a sixth imaginary line L6 extending along the bottom surface 21a of the bead core 21 in the tire meridian cross section or further outward in the tire radial direction D2 than the sixth imaginary line L6.

[0041] According to this configuration, it is possible to further prevent a gap from being formed between the rubber chafer 23 and the adhesive rubber layer 72, and it is possible to further prevent air from being trapped in the gap.

[0042] [4] Furthermore, with respect to the pneumatic tire 1 according to any one of the above [1] to [3], it is preferable that the end 72a of the adhesive rubber layer 72 is positioned on a seventh imaginary line L7 extending parallel to the third imaginary line L3 at a position 3 mm away from the third imaginary line L3 in the tire meridian cross section, or positioned further outward in the tire axial direction D1 than the seventh imaginary line L7.

[0043] According to this configuration, it is possible to further prevent air from being trapped between the rubber chafer 23 and the adhesive rubber layer 72, and it is possible to further prevent molding defects in the bead portion 2.

[0044] [5] In addition, with regard to the pneumatic tire 1 according to any one of the above [1] to [4], it is preferable that the covering distance H1 of the butyl rubber layer 71 by the rubber chafer 23 is 10 mm or more in the tire meridian cross section.

[0045] According to this configuration, by setting the covering distance H1 to 10 mm or more, it is possible to prevent air from entering the gap that occurs between the butyl rubber layer 71 and the rubber chafer 23.

[0046] The pneumatic tire 1 is not limited to the configuration of the above-described embodiment, nor is it limited to the above-described effects and advantages. Of course, various modifications can be made to the pneumatic tire 1 without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0047] DESCRIPTION OF SYMBOLS 1... tire, 2... bead portion, 2a... bead toe, 21... bead core, 21a... bottom surface, 22... bead filler, 23... rubber chafer, 3... sidewall, 4... tread, 5... carcass ply, 51... folded portion, 6... reinforcing layer, 7... inner liner, 71... butyl rubber layer, 72... adhesive rubber layer, 101... molding drum, 102... sidewall rubber, 103... rubber chafer rubber, 104... butyl rubber, 105... adhesive rubber, L1... first imaginary line, L2... second imaginary line, L3... third imaginary line, L4... fourth imaginary line, L5... fifth imaginary line, L6... sixth imaginary line, L7... seventh imaginary line, S1... tire equatorial plane

Claims

1. a pair of bead portions each having a bead core with a hexagonal cross section; a carcass ply that is bridged between the pair of bead portions and folded back around the bead core so as to sandwich the bead core; a reinforcing layer disposed so as to cover the bead core and the carcass ply; an inner liner disposed axially inside the carcass ply; a rubber chafer that forms an inner end of the bead portion in the tire radial direction, the inner liner includes a butyl rubber layer forming the innermost surface of the tire, and an adhesive rubber layer disposed between the butyl rubber layer and the carcass ply, an end of the butyl rubber layer is disposed axially more inward than an end of the adhesive rubber layer, an end of the butyl rubber layer is disposed, in the tire meridian cross section, between a first imaginary line that passes through a point 7 mm away from a bead toe of the bead portion toward the outside in the tire radial direction and extends in the tire axial direction, and a second imaginary line that passes through both ends of the bead core in the width direction, a third imaginary line that passes through an axially inner end of a bottom surface of the bead core and is perpendicular to the bottom surface, and a fourth imaginary line that is axially more inward than the third imaginary line and is in contact with an axially inner surface of the reinforcing layer and is parallel to the third imaginary line, in a tire meridian cross section.

2. 2. The pneumatic tire according to claim 1, wherein an end of the butyl rubber layer is located on a fifth imaginary line extending in the tire axial direction at a position 13 mm away from the bead toe radially outward in the tire direction, or located radially inward of the fifth imaginary line, in the tire meridian cross section.

3. The pneumatic tire according to claim 1 , wherein an end of the butyl rubber layer is positioned on a sixth imaginary line extending along the bottom surface or on an outer side in the tire radial direction than the sixth imaginary line in the tire meridian cross section.

4. 2. The pneumatic tire according to claim 1, wherein an end of the adhesive rubber layer is located on a seventh imaginary line extending parallel to the third imaginary line at a position 3 mm away from the third imaginary line, or axially outward of the seventh imaginary line, in the tire meridian cross section.

5. The pneumatic tire according to any one of claims 1 to 4, wherein a covering area of ​​the butyl rubber layer by the rubber chafer is 10 mm or more in a tire meridian cross section.

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