Pneumatic tires

Abstract

The present invention provides a pneumatic tire capable of suppressing damage to the bead portion when removed from a wheel rim. The pneumatic tire (1) comprises a pair of bead portions (4, 4). The pair of bead portions (4, 4) respectively comprises a bead core (5) and a bead chafer rubber (20), wherein the bead chafer rubber (20) is arranged on the inner side of the bead core (5) in the tire axial direction and extends from the bead toe (4t) along the tire inner cavity surface (16) toward the outer side in the tire radial direction. The bead chafer rubber (20) is a rubber composition that does not contain a reinforcing fiber material.

Description

Technical Field

[0001] The present invention relates to pneumatic tires. Background Art

[0002] Patent Document 1 below describes a pneumatic tire having a bead portion with an annular bead core arranged along the tire circumference. A chafer is provided in the bead portion to cover a portion of the inner surface of the tire. The chafer is constructed from cloth and rubber impregnated into the cloth.

[0003] Patent Document 1: Japanese Patent No. 6334932

[0004] The pneumatic tire has a reinforced bead portion with increased bending rigidity due to the chafer fabric. However, when the bead portion is removed from the wheel rim, it cannot smoothly pass over the rim flange. For example, there is a problem that the chafer strongly contacts the rim flange and may peel off. Summary of the Invention

[0005] The present invention has been made in view of the above-mentioned actual situation, and a main object of the present invention is to provide a pneumatic tire capable of suppressing damage to the bead portion when being removed from the rim.

[0006] The present invention is an inflatable tire having a pair of bead portions, characterized in that the pair of bead portions respectively have a bead core and a bead filler rubber, the bead filler rubber is arranged on the inner side of the bead core in the tire axial direction and extends from the bead toe along the tire inner cavity surface to the outer side in the tire radial direction, and the bead filler rubber is a rubber composition that does not contain fiber material for reinforcement.

[0007] In the pneumatic tire of the present invention, it may also be that in the tire meridian section including the tire rotation axis, the ratio Wa / Wb of the first bead width Wa to the second bead width Wb is 0.8 to 1.3, and the first bead width Wa is the bead portion width determined in the tire axial direction of the section center passing through the bead core, and the second bead width Wb is the tire axial width from the bead toe to the axial outer side surface of the bead portion.

[0008] In the pneumatic tire of the present invention, the ratio Wa / Wb may be greater than 1.0.

[0009] In the pneumatic tire of the present invention, the second bead width Wb may be 18.0 mm or less.

[0010] In the pneumatic tire of the present invention, the pair of bead portions may also have a bead bottom surface abutting the rim seat on the inner side of the bead core in the tire radial direction, the bead core has a bead core inner surface opposite to the rim seat, and the shortest distance between the center position of the tire axial direction of the inner surface of the bead core and the bead bottom surface is greater than 3.5 mm.

[0011] In the pneumatic tire of the present invention, the pneumatic tire may include a carcass ply extending across the pair of bead portions, and the shortest distance between the bead toe and the carcass ply may be 6.0 mm or less.

[0012] In the pneumatic tire of the present invention, the chafer rubber may have an elongation at break of 260% or less.

[0013] In the pneumatic tire of the present invention, the chafer rubber may have a complex elastic modulus E* of 12 MPa or less.

[0014] In the pneumatic tire of the present invention, it may also be that, in the tire meridian section including the tire rotation axis, the outline between the intersection of the straight line passing through the cross-section center of the bead core along the tire axial direction in the tire inner cavity surface formed by the bead wrapper rubber and the bead toe is formed into an arc shape.

[0015] In the pneumatic tire of the present invention, the chafer rubber may also include: a first part, which extends outward in the radial direction of the tire along the inner cavity of the tire; a second part, which constitutes at least a part of the bottom surface of the bead that abuts the rim seat; and a third part, which extends outward in the radial direction of the tire on the outer side of the bead core in the axial direction of the tire.

[0016] The pneumatic tire of the present invention may also be used for small trucks.

[0017] The pneumatic tire of the present invention, by adopting the above-described structure, can suppress damage to the bead portion when being removed from the rim. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 FIG1 is a tire meridian cross section showing an example of a pneumatic tire.

[0019] Figure 2 yes Figure 1 An enlarged view of the tire bead portion.

[0020] Figure 3 (a) and (b) are cross-sectional views showing an example of a state where the tire is removed from the wheel rim.

[0021] Description of labels

[0022] 1: Pneumatic tire; 4: Bead portion; 5: Bead core; 16: Tire inner cavity surface; 20: Chafer rubber. DETAILED DESCRIPTION

[0023] The following describes embodiments of the present invention based on the accompanying drawings. To facilitate understanding of the present invention, the accompanying drawings must be understood to include exaggerated representations and representations that differ from the actual dimensional ratios. Furthermore, throughout the various embodiments, identical or common elements are denoted by the same reference numerals, and repeated descriptions are omitted. Furthermore, the specific structures shown in the embodiments and the accompanying drawings are provided for understanding the present invention; the present invention is not limited to the specific structures shown in the drawings.

[0024] exist Figure 1 An example of a tire meridian cross section including the tire rotation axis in a normal state of the pneumatic tire (hereinafter sometimes simply referred to as "tire") of this embodiment is shown in FIG. Figure 1 In FIG, a dashed line indicates the tire equator (equatorial plane) C. The tire 1 of this embodiment is configured for a small truck. The tire 1 is not necessarily for a small truck, and may be configured for heavy loads such as passenger cars, buses, and trucks.

[0025] Here, the "normal state" refers to the unloaded state in which the tire 1 is assembled on a normal rim (hereinafter sometimes referred to as "rim") 18 and adjusted to a normal internal pressure. In this specification, unless otherwise specified, the dimensions of various parts of the tire 1 are values measured in this normal state.

[0026] A "regular rim" is a rim whose standard is determined for each tire within a system of standards that includes the standards to which the tire 1 conforms. For example, a regular rim is a "standard rim" under JATMA, a "design rim" under TRA, or a "measuring rim" under ETRTO.

[0027] "Regulated internal pressure" refers to the air pressure determined for each tire within the standards system that includes the standards to which tire 1 conforms. For JATMA, this refers to the "maximum air pressure." For TRA, this refers to the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table. For ETRTO, this refers to the "INFLATION PRESSURE."

[0028] The tire 1 of this embodiment includes a tread portion 2, a pair of sidewall portions 3, 3, and a pair of bead portions 4, 4. Furthermore, the tire 1 of this embodiment includes a carcass 6 having a bead core 5 extending from the tread portion 2 through the pair of sidewall portions 3, 3 to the pair of bead portions 4, 4, and a belt layer 7 disposed radially outward of the carcass 6.

[0029] The carcass 6 is composed of at least one, or in this embodiment, two, carcass plies 6A and 6B arranged radially inward and outward from the tire. Each carcass ply 6A or 6B includes carcass cords (not shown) arranged at an angle of, for example, 75° to 90° relative to the tire equator C. The carcass cords are preferably made of organic fiber cords such as nylon, polyester, or rayon.

[0030] Each carcass ply 6A, 6B extends across the pair of bead portions 4, 4. Each carcass ply 6A, 6B includes a main body portion 6a that spans annularly between the pair of bead cores 5, 5, and a pair of turnback portions 6b, 6b that are connected to both sides of the main body portion 6a and turn back around the bead core 5 from the axial inside to the outside of the tire.

[0031] The belt layer 7 is arranged radially outward from the carcass 6 and within the tread portion 2. The belt layer 7 is composed of at least one belt ply, or in this embodiment, two belt plies 7A and 7B, arranged radially inward and outward from the tire. Each belt ply 7A and 7B is formed, for example, by coating an array of belt cords (not shown) with topping rubber. The belt cords are preferably highly elastic, such as steel cords.

[0032] The tire 1 of the present embodiment is provided with a tread rubber 11 , a pair of sidewall rubbers 12 , 12 , a pair of bead apex rubbers 13 , 13 , an inner liner rubber 14 , and a pair of bead rubbers 15 , 15 .

[0033] The tread rubber 11 is disposed radially outward of the belt layer 7 in the tread portion 2. The sidewall rubbers 12, 12 are disposed axially outward of the carcass 6, extending radially inward from the axially outer end of the tread rubber 11. The bead apex rubbers 13, 13 are each made of hard rubber and extend radially outward from the bead core 5 between the main body portions 6a, 6a and the turnback portions 6b, 6b of the carcass plies 6A, 6B.

[0034] The inner liner rubber 14 is non-air-permeable and is provided inside the carcass 6. The inner liner rubber 14 of this embodiment extends annularly between the pair of bead portions 4, 4. The inner liner rubber 14 forms the tire inner cavity surface 16 together with the chafer rubber 20 described later.

[0035] A pair of sidewall rubbers 15, 15 are respectively arranged on the outer side of the tire in the axial direction of the tire carcass 6, and extend from the inner end of the tire radial direction of the sidewall rubber 12 to the inner side of the tire in the radial direction. When the tire 1 is mounted on the rim (wheel rim) 18, these sidewall rubbers 15, 15 constitute at least a portion of the bead outer surface 4o that abuts against the rim flange 18f of the rim 18.

[0036] Figure 2 yes Figure 1 An enlarged view of the bead portion 4. Figure 2 In the figure, the enlarged Figure 1 One of the pair of bead portions 4, 4 shown is Figure 1 The pair of bead portions 4, 4 each includes a bead core 5 and a chafer rubber 20.

[0037] The bead core 5 is formed into a rectangular (trapezoidal) shape in a tire meridian cross-section (hereinafter sometimes referred to as a "tire meridian cross-section") that includes the tire's rotation axis. The bead core 5 of this embodiment has a bead core inner surface 5i that faces the rim seat 18s and a bead core outer surface 5o that faces radially outward from the tire. The shape of the bead core 5 is not limited to this; for example, it may be formed into a hexagonal or circular shape. The bead core 5 is formed, for example, by winding a steel bead wire (not shown) in multiple rows and multiple layers.

[0038] The chafer rubber 20 is composed of a rubber composition that does not contain a reinforcing fiber material. The fiber material, for example, corresponds to the cloth that constitutes the chafer described in Patent Document 1 (e.g., canvas composed of organic fibers, etc.). Such fiber material (cloth) exhibits low elasticity and a high reinforcing effect. Therefore, the chafer rubber 20 of this embodiment can prevent the rigidity of the bead portion 4 from becoming excessively high compared to chafers containing fiber material.

[0039] The rubber composition of the chafer rubber 20 can be appropriately set. The rubber composition of the present embodiment is constituted by containing a polymer and a compounding agent, and employs a rubber composition having excellent wear resistance.

[0040] The polymer and compounding agent can be polymers and compounding agents commonly used in the manufacture of rubber materials. The polymer can be appropriately selected from natural rubber (NR), butadiene rubber (BR) or styrene butadiene rubber (SBR), etc. The compounding material can be appropriately selected from cushion rubber such as carbon, silica, oil, processing aid, sulfur or vulcanization accelerator, etc. The chafer rubber 20 is formed by vulcanizing the unvulcanized rubber composition containing these polymers and compounding materials. In addition, these compounds can be appropriately adjusted based on the previous manufacturing process of rubber materials so that the chafer rubber 20 has the physical properties (elongation at break EB, complex elastic modulus E*) described later.

[0041] The chafer rubber 20 of this embodiment is configured to include a first portion 21 extending radially outward along the tire inner surface 16. The first portion 21 is arranged axially inward of the bead core 5 and extends radially outward from the bead toe 4t of the bead portion 4 along the tire inner surface 16.

[0042] The outer end 21o of the first portion 21 in the tire radial direction is aligned with the inner end 14i of the inner liner rubber 14 in the tire radial direction ( Figure 1 Thus, the first portion 21 can continuously form the tire inner cavity surface 16 together with the inner liner rubber 14.

[0043] The chafer rubber 20 of the present embodiment further includes a second portion 22 and a third portion 23. In addition, the chafer rubber 20 is not limited to this form.

[0044] The second portion 22 of this embodiment extends from the inner end (bead toe 4t) of the first portion 21 in the tire radial direction to the outer side of the tire axial direction. The outer end of the second portion 22 in the tire axial direction is connected to the inner end side of the bead rubber 15 in the tire radial direction. Such second portion 22 forms a rim seat 18s ( Figure 1 At least a portion of the bead bottom surface 4b abutted by the tire (shown).

[0045] The third portion 23 of the present embodiment extends outward in the radial direction of the tire from the outer side of the bead core 5 in the tire axial direction. The third portion 23 of the present embodiment is arranged on the inner side of the bead rubber 15 in the tire axial direction. The inner end of the third portion 23 in the tire radial direction is connected to the outer end of the second portion 22 in the tire axial direction. The outer end 23o of the third portion 23 in the tire radial direction is arranged at a position that is closer to the outside than the outer end (outermost end) 5o of the bead core 5 in the tire radial direction. In addition, the outer end 23o of the third portion 23 is arranged at a position that is closer to the inside than the outer end 15o of the bead rubber 15 in the tire radial direction. In this way, the outer end 23o of the third portion 23 is staggered with the outer surface 5o of the bead core and the outer end 15o of the bead rubber 15 in the tire radial direction. In this way, the bending rigidity of the bead portion 4 can be prevented from becoming higher.

[0046] The chafer rubber 20 of this embodiment is continuously provided with a first portion 21, a second portion 22, and a third portion 23. As a result, the chafer rubber 20 is formed into a substantially U-shaped (or J-shaped) shape in the tire meridian cross-section. This chafer rubber 20 protects the bead portion 4 (preventing damage from friction with the rim 18) and effectively prevents rim runout.

[0047] Figure 3(a) and (b) are cross-sectional views showing an example of a state where the tire 1 is removed from the wheel rim (rim) 18. Figure 3 In (a) and (b), the bead portion 4 on one side (in Figure 1 The left side) has been removed from the rim flange 18f on one side (in Figure 1 Remove the bead portion 4 on the other side ( Figure 1 The right side is to be crossed over the rim flange 18f on one side (in Figure 1 (center is the left side).

[0048] like Figure 3 As shown in (a), when the tire 1 is removed from the wheel rim (rim) 18, the tire inner cavity surface 16 of the bead portion 4 composed of the chafer rubber 20 (first portion 21) abuts (hooks) against the rim flange 18f. Therefore, it is necessary to deform the bead portion 4 so that it can pass over the rim flange 18f. At this time, for example, in a chafer (not shown) composed of a fiber material such as in Patent Document 1 mentioned above, when the chafer comes into strong contact with the rim flange 18f, the fibers constituting the fiber material may be cut, thereby damaging the bead portion 4. In particular, in tires for small trucks that have a large tightening force to the rim 18, there is a tendency for the chafer rubber 20 to come into strong contact with the rim flange 18f.

[0049] In this embodiment, the chafer rubber 20 that contacts the rim flange 18f is composed of a rubber composition that does not contain a reinforcing fiber material. Figure 3 As shown in (b), compared to a chafer (not shown) made of fiber material, as in Patent Document 1, the chafer rubber 20 is more flexible and deformable. Consequently, the tire 1 of this embodiment allows the bead portion 4 to smoothly pass over the rim flange 18f, preventing the chafer rubber 20 from strongly contacting the rim flange 18f. Consequently, the tire 1 of this embodiment can minimize damage to the bead portion 4 when removed from the rim 18.

[0050] exist Figure 2 In the tire meridian cross section shown, the contour 26 between the intersection 25 of the tire inner cavity surface 16 formed by the chafer rubber 20 and the straight line L1 that passes through the cross-sectional center 5c of the bead core 5 in the tire axial direction and the bead toe 4t is preferably formed into an arc shape. Figure 3 As shown in Figures (a) and (b), when the tire 1 is removed from the rim 18, the contact area between the profile 26 of the chafer rubber 20 (first portion 21) and the rim flange 18f is reduced. This prevents the chafer rubber 20 from coming into strong contact with the rim flange 18f and being separated. To effectively achieve this function, the profile 26 is preferably formed into an arc shape that bulges inward in the tire axial direction.

[0051] like Figure 2 As shown, the outer end 21o of the first portion 21 is preferably arranged between the outer surface 5o of the bead core 5 and the inner surface 5i of the bead core in the radial direction of the tire. As a result, the deformation of the boundary portion (near the outer end 21o) between the first portion 21 and the inner liner rubber 14 can be suppressed by the bead core 5 with high rigidity arranged on the outer side in the tire axial direction. Figure 3 As shown in (a) and (b), when the tire 1 is removed from the rim 18, it is possible to prevent the rubber from breaking in the first portion 21 (the chafer rubber 20), and to suppress damage to the bead portion 4. In addition, in order to suppress such rubber breakage, it is preferred that the shortest distance D3 between the outer end 21o of the first portion 21 and the bead toe 4t in the radial direction of the tire bead be set to be greater than 10 mm. On the other hand, it is preferred that the shortest distance D3 be set to be less than 40 mm. By setting the shortest distance D3 to be less than 40 mm, it is possible to prevent the strain of the first portion 21 from increasing when a load is applied, and to prevent peeling from occurring between the first portion 21 (the chafer rubber 20) and the inner liner rubber 14 (the portion at the outer end 21o).

[0052] like Figure 2 As shown, in the tire meridian section including the tire rotation axis, the ratio Wa / Wb of the first bead width Wa to the second bead width Wb is preferably set to 0.8 to 1.3. In addition, the first bead width Wa is the bead portion width determined in the tire axial direction (in this example, on the straight line L1) passing through the cross-sectional center 5c of the bead core 5. On the other hand, the second bead width Wb is the width from the bead toe 4t to the outer side surface of the bead portion 4 in the tire axial direction ( Figure 1 The width in the tire axial direction (bead base width) from the bead outer surface 4o shown.

[0053] By setting the ratio Wa / Wb to 0.8 or greater, the second bead width Wb on the bead toe 4t side, which is more likely to contact the rim flange 18f, can be prevented from becoming excessively larger than the first bead width Wa on the bead core 5 side. This prevents the bead portion 4 on the bead toe 4t side from strongly contacting the rim flange 18f when the tire 1 is removed from the wheel rim 18, and prevents the chafer rubber 20 from peeling off. Furthermore, since the rubber thickness of the bead portion 4 on the bead core 5 side can be prevented from decreasing, insufficient rubber (improper molding) can be prevented in this portion during vulcanization molding. From this perspective, the ratio Wa / Wb is preferably set to 1.0 or greater, and more preferably greater than 1.0.

[0054] On the other hand, by setting the ratio Wa / Wb to 1.3 or less, the first bead width Wa on the bead core 5 side can be prevented from becoming excessively larger than the second bead width Wb on the bead toe 4t side. This prevents the rubber thickness of the bead portion 4 on the bead core 5 side from becoming excessively larger, thereby preventing the generation of rubber residue (molding defects) in this portion during vulcanization molding. From this perspective, the ratio Wa / Wb is preferably set to 1.2 or less.

[0055] The second bead width Wb is preferably set to 18.0 mm or less. By setting the second bead width Wb to 18.0 mm or less, it is possible to prevent the bending rigidity of the bead portion 4 from increasing. Figure 3 As shown in (b), the bead portion 4 can smoothly pass over the rim flange 18f. From this perspective, the second bead width Wb is preferably set to 17.0 mm or less. On the other hand, if the second bead width Wb is excessively reduced, it becomes difficult to maintain the rim run prevention effect. Therefore, the second bead width Wb is preferably set to 15 mm or more.

[0056] like Figure 2 As shown, the shortest distance D1 between the center position 28 of the tire axial direction of the bead core inner surface 5i and the bead bottom surface 4b is preferably set to 3.5 mm or more. By setting the shortest distance D1 to 3.5 mm or more, the bead bottom surface 4b can be separated from the bead core inner surface 5i in the tire radial direction. This can prevent the bead portion 4 assembled to the rim 18 from being excessively tightened ( Figure 1 The rim seat 18s and rim flange 18f shown in the figure are in contact with each other. Furthermore, the chafer rubber 20 can be prevented from strongly contacting the rim flange 18f. Therefore, the bead portion 4 can be easily removed from the wheel rim (rim) 18, and the chafer rubber 20 can be effectively prevented from peeling off. From this perspective, the shortest distance D1 is preferably set to 4.0 mm or greater.

[0057] On the other hand, if the shortest distance D1 becomes excessively large, the force with which the bead portion 4 fastens the rim 18 becomes weak, and rim shifting, rim separation, etc. are more likely to occur. From this viewpoint, the shortest distance D1 is preferably set to 5.5 mm or less.

[0058] The shortest distance D2 between the bead toe 4t and the carcass ply 6A, 6B (in this example, the inner carcass ply 6A) is preferably set to 6.0 mm or less. By setting the shortest distance D2 to 6.0 mm or less, the tire 1 can be removed from the wheel rim 18 ( Figure 3 (a) and (b) of FIG), the contact area (hooking amount) of the rim flange 18f can be reduced in the bead toe 4t of the bead portion 4. As a result, the bead portion 4 can smoothly pass over the rim flange 18f ( Figure 3(b) shows), it is possible to prevent damage to the bead portion 4. From this viewpoint, the shortest distance D2 is preferably set to 5.5 mm or less.

[0059] On the other hand, when the shortest distance D2 becomes excessively small, rim displacement, rim separation, etc. are likely to occur. From such a viewpoint, the shortest distance D2 is preferably set to 4.0 mm or more.

[0060] The elongation at break EB of the chafer rubber 20 is preferably set to 260% or less. By setting the elongation at break EB to 260% or less, the elongation at break can be suppressed. Figure 3 The chafer rubber 20 (first portion 21) is greatly stretched by contact with the rim flange 18f shown in (b), thereby preventing separation of the chafer rubber 20. From this viewpoint, the elongation at break EB is preferably set to 250% or less.

[0061] On the other hand, if the elongation at break EB of the chafer rubber 20 is excessively low, the tightening force of the bead portion 4 to the rim 18 decreases, making rim shifting and rim separation more likely to occur. From this perspective, the elongation at break EB is preferably set to 220% or greater. In this specification, elongation at break can be measured, for example, in accordance with JIS K6251, "Rubber, vulcanized and thermoplastic rubber - Methods of determining tensile properties."

[0062] The complex elastic modulus E* of the chafer rubber 20 is preferably set to 12 MPa or less. By setting the complex elastic modulus E* to 12 MPa or less, it is possible to prevent the bead portion 4 assembled to the rim 18 from being strongly fastened to the rim 18 ( Figure 1 The rim seat 18s and the rim flange 18f shown are in contact with each other. This allows the bead portion 4 to be easily removed from the wheel rim 18, and prevents the chafer rubber 20 from peeling off. From this perspective, the complex elastic modulus E* is preferably set to 10 MPa or less.

[0063] On the other hand, if the complex elastic modulus E* of the chafer rubber 20 becomes excessively small, the tightening force of the bead portion 4 to the rim 18 decreases, which can easily cause rim shifting and rim separation. From this perspective, the complex elastic modulus E* is preferably set to 8 MPa or more.

[0064] In this specification, the complex elastic modulus E* is a value measured using a viscoelasticity spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. under the following conditions based on the provisions of JIS-K6394.

[0065] Initial strain: 10%

[0066] Amplitude: ±2%

[0067] Frequency: 10Hz

[0068] Deformation Mode: Stretch

[0069] Measurement temperature: 70°C

[0070] As mentioned above, although the particularly preferred embodiment of the present invention has been described in detail, the present invention is not limited to the illustrated embodiment, and can be implemented in various modified forms.

[0071] [Example]

[0072] [Example A]

[0073] Hereinafter, more specific and non-limiting examples of the present invention will be described.

[0074] Trial-produced Figure 1 Pneumatic tires with the basic structure shown above and chafer rubber that do not include reinforcing fiber material (Examples 1 to 5). For comparison, a pneumatic tire with a chafer that includes reinforcing fiber material was trial-produced (Comparative Example). Each pneumatic tire was evaluated for damage resistance to the bead portion when removed from the rim to which it was mounted, the number of vulcanization molding defects, and the tightening force to the rim. Common specifications are as follows.

[0075] Tire size: 195 / 75R15 109 / 107N

[0076] Rim size: 15×5.5J

[0077] 2nd bead width Wb: 17.0mm

[0078] The shortest distance between the center of the inner surface of the bead core and the bottom surface of the bead D1: 4.0mm

[0079] The shortest distance between the tire toe and the carcass ply D2: 5.5mm

[0080] Chafer rubber:

[0081] Elongation at break EB: 250%

[0082] Complex elastic modulus E*: 10.1 MPa

[0083] The test method is as follows.

[0084] <Damage resistance of the bead section>

[0085] Each pneumatic tire mounted on the rim was removed from the rim using a mechanical tire changer. The extent of chafer rubber peeling was then visually inspected and evaluated on a 5-point scale. A score of 1 indicated significant peeling, while a score of 5 indicated no peeling at all. Therefore, a higher score is better; a score of 2 or higher indicates no issues with the bead area's damage resistance.

[0086] <Number of Vulcanization Molding Defects>

[0087] 1,000 pneumatic tires of each type were manufactured, and the number of pneumatic tires with molding defects, such as insufficient rubber or residual rubber in the bead area, was calculated. Fewer tires with molding defects were considered better. A number of 10 or fewer tires was considered within the acceptable range.

[0088] <Tightening force to the rim>

[0089] Using a bead holding force tester (Hoffmann, Model WKM-B4), the bead of a pneumatic tire was expanded in eight sections, and the holding force (expansion force) was measured when the sections were expanded to the standard values for the rim. The results were expressed as an index, with the holding force of Example 3 set at 100. A higher index indicates a higher holding force. An index of 80 or higher indicates that rim shifting and rim separation are unlikely to occur. On the other hand, to effectively prevent chafer rubber peeling, an index of 120 or lower is preferred.

[0090] The test results are shown in Table 1.

[0091]

Table 1

[0092]

[0093] The test results showed that, compared to the comparative example, Examples 1-5 were able to suppress damage to the bead portion during removal from the rim. Furthermore, Examples 2-4, where the ratio Wa / Wb of the first bead width Wa to the second bead width Wb was within the preferred range, suppressed the occurrence of molding defects (rubber residue and rubber deficiency) caused by vulcanization compared to Examples 1 and 5, which were outside the preferred range. Furthermore, Examples 2-4 optimized the tightening force to the rim, effectively suppressing bead damage, rim shifting, and rim separation.

[0094] [Example B]

[0095] Trial-produced Figure 1 Pneumatic tires (Examples 3 and Examples 6-9) with the basic structure shown above and having chafer rubber without reinforcing fiber material were evaluated. Each pneumatic tire was evaluated for damage resistance of the bead portion when removed from the rim to which it was mounted, the number of vulcanization molding defects, and the tightening force to the rim. The common specifications were the same as those of Example A (except for the second bead width Wb), except as noted below. The testing method was the same as that described in Example A. The test results are shown in Table 2.

[0096] Ratio of the first bead width Wa to the second bead width Wb Wa / Wb: 1.1

[0097]

Table 2

[0098]

[0099] The test results showed that compared to the comparative example of Example A (shown in Table 1), Example 3 and Examples 6-9 were able to suppress damage to the bead portion during removal from the rim. Furthermore, compared to Example 6 and Example 9, which were outside the preferred range, Examples 3, 7, and 8, whose second bead widths Wb were within the preferred range, were able to suppress bead portion damage and vulcanization molding defects (rubber residue and rubber deficiency). Furthermore, Examples 3, 7, and 8 were able to optimize the tightening force to the rim, effectively suppressing bead portion damage, rim shifting, and rim separation.

[0100] [Example C]

[0101] Trial-produced Figure 1 Pneumatic tires having the basic structure shown and having chafer rubber that does not include a reinforcing fiber material (Example 3 and Examples 10 to 17). Furthermore, for each pneumatic tire, the damage resistance of the bead portion when removed from the rim to which it was mounted, the number of vulcanization molding defects, and the tightening force to the rim were evaluated. The common specifications are the same as those of Example A (except for the shortest distance D1 between the center position of the inner surface of the bead core and the bottom surface of the bead, and the shortest distance D2 between the bead toe and the carcass ply), except as shown below. Furthermore, the test method is the same as that described in Example A. The test results are shown in Table 3.

[0102] Ratio of the first bead width Wa to the second bead width Wb Wa / Wb: 1.1

[0103]

Table 3

[0104]

[0105] The test results showed that compared to the comparative example of Example A (shown in Table 1), Example 3 and Examples 10-17 were able to suppress damage to the bead portion during removal from the rim. Furthermore, compared to the other examples, Example 3, Examples 11-12, and Examples 15-16, whose shortest distances D1 and D2 fell within the preferred range, were able to suppress damage to the bead portion and the occurrence of vulcanization molding defects (rubber residue and rubber deficiency), thereby optimizing the tightening force to the rim.

[0106] [Example D]

[0107] Trial-produced Figure 1Pneumatic tires (Examples 3 and Examples 18 to 25) with the basic structure shown above and having chafer rubber that does not include a reinforcing fiber material were evaluated. Each pneumatic tire was evaluated for damage resistance to the bead portion when removed from the rim to which it was mounted, the number of vulcanization molding defects, and the tightening force to the rim. The common specifications were the same as those of Example A (except for the elongation at break EB and complex elastic modulus E* of the chafer rubber), except as noted below. The testing method was the same as that described in Example A. The test results are shown in Table 4.

[0108] Ratio of the first bead width Wa to the second bead width Wb Wa / Wb: 1.1

[0109]

Table 4

[0110]

[0111] The test results showed that compared to the comparative example of Example A (shown in Table 1), Example 3 and Examples 18-25 were able to suppress damage to the bead portion during removal from the rim. Furthermore, Example 3, Examples 19-20, and Examples 23-24, whose chafer rubber had an elongation at break EB and complex elastic modulus E* within the preferred range, suppressed bead damage compared to the other examples, achieving optimal tightening force to the rim.

Claims

1. A pneumatic tire having a pair of bead portions, wherein: The pneumatic tire includes an inner liner rubber extending annularly between the pair of bead portions. The pair of bead portions each include a bead core and a chafer rubber, the chafer rubber being arranged on the inner side of the bead core in the tire axial direction and extending from the bead toe along the tire inner cavity toward the outer side in the tire radial direction. The chafer rubber is a rubber composition that does not contain a reinforcing fiber material, and the chafer rubber includes a first portion extending along the tire inner cavity toward the outer side in the tire radial direction. The outer end of the first part in the tire radial direction is connected to the inner end of the inner liner rubber in the tire radial direction, and the outer end of the first part in the tire radial direction is arranged between the outer surface of the bead core in the tire radial direction and the inner surface of the bead core in the tire radial direction.

2. The pneumatic tire according to claim 1, wherein In a tire meridian section that includes the tire's axis of rotation, The ratio Wa / Wb of the first bead width Wa to the second bead width Wb is 0.8 to 1.

3. The first bead width Wa is the width of the bead portion determined in the tire axial direction through the cross-sectional center of the bead core, and the second bead width Wb is the width in the tire axial direction from the bead toe to the axially outer side of the bead portion.

3. The pneumatic tire according to claim 2, wherein: The ratio Wa / Wb is greater than 1.

0.

4. The pneumatic tire according to claim 2 or 3, wherein: The second bead width Wb is 18.0 mm or less.

5. The pneumatic tire according to any one of claims 1 to 3, wherein: The pair of bead portions each have a bead bottom surface that abuts against the rim seat on the inner side of the bead core in the tire radial direction. The bead core has a bead core inner surface facing the rim seat, The shortest distance between the center position of the inner surface of the bead core in the tire axial direction and the bottom surface of the bead is greater than or equal to 3.5 mm.

6. The pneumatic tire according to any one of claims 1 to 3, wherein: The pneumatic tire includes a carcass ply extending across the pair of bead portions. The shortest distance between the bead toe and the carcass ply is 6.0 mm or less.

7. The pneumatic tire according to any one of claims 1 to 3, wherein: The chafer rubber has an elongation at break of 260% or less.

8. The pneumatic tire according to any one of claims 1 to 3, wherein: The complex elastic modulus E* of the chafer rubber is 12 MPa or less.

9. The pneumatic tire according to any one of claims 1 to 3, wherein: In a tire meridian section that includes the tire's axis of rotation, The contour between the bead toe and an intersection point of the tire inner cavity surface formed of the chafer rubber with a straight line passing through the cross-sectional center of the bead core in the tire axial direction is formed in an arc shape.

10. The pneumatic tire according to any one of claims 1 to 3, wherein: The pneumatic tire further comprises: a carcass extending from a tread portion through a pair of sidewall portions to the bead core of the pair of bead portions; and A pair of edge rubbers, the pair of edge rubbers are arranged on the tire axial outer side of the carcass, The chafer rubber comprises: a second portion constituting at least a portion of the bead bottom surface that abuts against the rim seat; and The third part extends outward in the radial direction of the tire from the outer side of the bead core in the tire axial direction. The first portion is arranged from the inner cavity surface of the tire to the inner surface of the carcass in the tire axial direction. The third portion is arranged from the outer surface of the carcass in the tire axial direction to the inner surface of the bead rubber in the tire axial direction.

11. The pneumatic tire according to any one of claims 1 to 3, wherein: This pneumatic tire is for small trucks.

12. A pneumatic tire having a pair of bead portions, wherein: The pair of bead portions each include a bead core and a chafer rubber, the chafer rubber being arranged on the inner side of the bead core in the tire axial direction and extending from the bead toe along the tire inner cavity toward the outer side in the tire radial direction. The chafer rubber is a rubber composition that does not contain a reinforcing fiber material, The pneumatic tire includes a carcass ply extending across the pair of bead portions. The shortest distance between the bead toe and the carcass ply is 6.0 mm or less to reduce a contact area of a rim flange in the bead toe of the bead portion when the pneumatic tire is removed from a rim.

13. The pneumatic tire according to claim 12, wherein: In a tire meridian section that includes the tire's axis of rotation, The ratio Wa / Wb of the first bead width Wa to the second bead width Wb is 0.8 to 1.

3. The first bead width Wa is the width of the bead portion determined in the tire axial direction through the cross-sectional center of the bead core, and the second bead width Wb is the width in the tire axial direction from the bead toe to the axially outer side of the bead portion.

14. The pneumatic tire according to claim 13, wherein: The ratio Wa / Wb is greater than 1.

0.

15. The pneumatic tire according to claim 13 or 14, wherein: The second bead width Wb is 18.0 mm or less.

16. The pneumatic tire according to any one of claims 12 to 14, wherein: The pair of bead portions each have a bead bottom surface that abuts against the rim seat on the inner side of the bead core in the tire radial direction. The bead core has a bead core inner surface facing the rim seat, The shortest distance between the center position of the inner surface of the bead core in the tire axial direction and the bottom surface of the bead is greater than or equal to 3.5 mm.

17. The pneumatic tire according to any one of claims 12 to 14, wherein: The chafer rubber has an elongation at break of 260% or less.

18. The pneumatic tire according to any one of claims 12 to 14, wherein: The complex elastic modulus E* of the chafer rubber is 12 MPa or less.

19. The pneumatic tire according to any one of claims 12 to 14, wherein: In a tire meridian section that includes the tire's axis of rotation, The contour between the bead toe and an intersection point of the tire inner cavity surface formed of the chafer rubber with a straight line passing through the cross-sectional center of the bead core in the tire axial direction is formed in an arc shape.

20. The pneumatic tire according to any one of claims 12 to 14, wherein: The chafer rubber comprises: The first portion extends along the inner cavity of the tire and outward in the radial direction of the tire; a second portion constituting at least a portion of the bead bottom surface that abuts against the rim seat; and The third portion extends outward in the tire radial direction from the outer side of the bead core in the tire axial direction.

21. The pneumatic tire according to any one of claims 12 to 14, wherein: This pneumatic tire is for small trucks.

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