Pneumatic tire, and method for manufacturing pneumatic tire

Abstract

To improve the durability of a bead part.SOLUTION: In a bead core 50 disposed on a bead part 40, in the case where three layers 52 from a layer 52 positioned on the innermost side in a tire radial direction are a first layer 52a to a third layer 52c, three rows 53 from a row 53 positioned on the innermost side in a tire width direction are a first row 53a to a third row 53c, and of a circulation portion of a bead wire 51, circulation portions from a first circulation to a six circulation of circulation are a first circulation part 55a to a sixth circulation part 55f, the first circulation part 55a is positioned at the second row 53b in the first layer 52a, the second circulation part 55b is positioned at the first row 53a in the first layer 52a, the third circulation part 55c is positioned at the first row 53a in the second layer 52b, the fourth circulation part 55d is positioned at the first row 53a in the third layer 52c, the fifth circulation part 55e is positioned at the second row 53b in the second layer 52b, and the sixth circulation part 55f is positioned at the third row 53c in the first layer 52a.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a pneumatic tire and a method for manufacturing a pneumatic tire. [Background technology]

[0002] A pneumatic tire is mounted on a rim-rimmed wheel by fitting a bead portion, which has a bead core, an annular member formed by bundling multiple bead wires, into the rim of the rim-rimmed wheel. The bead portion is the part that is actually attached to the rim-rimmed wheel when the pneumatic tire is mounted on the rim-rimmed wheel, and is therefore an important part in ensuring the performance of the pneumatic tire. For this reason, some conventional pneumatic tires have implemented various innovations in the bead portion to achieve desired performance. For example, the pneumatic tires described in Patent Documents 1 to 9 each achieve their desired performance by devising ways to wind the bead wires around the bead core. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 08-108714 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-091637 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-091661 [Patent Document 4] Japanese Patent Application Laid-Open No. 2010-000827 [Patent Document 5] Japanese Patent Application Laid-Open No. 2006-137381 [Patent Document 6] Japanese Patent Application Publication No. 07-223412 [Patent Document 7] Japanese Patent Application Laid-Open No. 2006-347375 [Patent Document 8] Japanese Patent Application Laid-Open No. 2004-082767 [Patent Document 9] Japanese Patent Application Laid-Open No. 2002-019428 Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, bead cores have a polygonal shape in a tire meridian cross section, which makes it easy for stress concentration to occur at the corners of the bead core in the tire meridian cross section. In other words, in the bead portion, the carcass is folded back around the bead core in a direction from the inner side of the bead core in the tire width direction to the inner side in the tire radial direction and toward the outer side in the tire width direction. Therefore, when tension acts on the carcass by filling the pneumatic tire with air, a force based on the tension acting on the carcass acts on the bead core. Because the bead core has a polygonal shape in a tire meridian cross section, the force acting on the bead core from the carcass when the pneumatic tire is filled with air acts, for example, at the corners of the bead core in the tire meridian cross section.

[0005] In particular, a large force is likely to act from the carcass on the corner of the bead core located near the bead toe, which is a portion of the bead portion located on the inner side in the tire radial direction and the inner side in the tire width direction. That is, the corner of the bead core located near the bead toe is located near a portion of the carcass where the extension direction of the carcass changes between a portion of the bead core located on the inner side in the tire width direction and a portion of the carcass located on the inner side in the tire radial direction. Therefore, when tension acts on the carcass by filling the pneumatic tire with air, a large force is likely to act from the carcass on the corner of the bead core located near the bead toe, which is located near the portion where the extension direction of the carcass changes.

[0006] When a large force is applied from the carcass to the vicinity of the corner of the bead core, stress concentration occurs near the corner of the bead core due to the force from the carcass, and there is a risk that the bead wire constituting the bead core may be significantly displaced or the bead wire may be easily broken. For this reason, conventional pneumatic tires have had room for improvement in terms of the durability of the bead portion.

[0007] The present invention has been made in view of the above, and has an object to provide a pneumatic tire and a method for manufacturing a pneumatic tire that can improve the durability of a bead portion. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems and achieve the object, a pneumatic tire according to the present invention includes a pair of bead portions disposed on both sides of the tire equatorial plane in the tire width direction, and a bead core disposed in the bead portion and formed by winding a bead wire in a ring shape, the bead core having a layer formed by aligning a plurality of circumferential portions of the bead wire formed by winding the ring shape in the tire width direction, and a row formed by aligning a plurality of circumferential portions in the tire radial direction, the bead core having a plurality of layers and a plurality of rows, the plurality of layers being stacked in the tire radial direction, and the plurality of rows being aligned in the tire width direction, so that the bead wire is arranged in a lattice pattern in a tire meridian cross section, and the plurality of layers are arranged in a lattice pattern from the layer located innermost in the tire radial direction to the outer side in the tire radial direction, the three layers are designated as a first layer, a second layer, and a third layer, respectively; among the plurality of rows, the three rows from the row located innermost in the tire width direction toward the outer side in the tire width direction are designated as a first row, a second row, and a third row, respectively; and among the winding portions of the bead wire, the winding portions from the first turn to the sixth turn are designated as a first winding portion, a second winding portion, a third winding portion, a fourth winding portion, a fifth winding portion, and a sixth winding portion, respectively; the first winding portion is located in the second row in the first layer, the second winding portion is located in the first row in the first layer, the third winding portion is located in the first row in the second layer, the fourth winding portion is located in the first row in the third layer, the fifth winding portion is located in the second row in the second layer, and the sixth winding portion is located in the third row in the first layer.

[0009] In the pneumatic tire, it is preferable that the final turn of the bead wire in the turn portion of the bead core is disposed in a position other than the first row.

[0010] In the pneumatic tire, it is also preferable that the final turn portion of the bead core is arranged in the row located outermost in the tire width direction in the layer located outermost in the tire radial direction among the plurality of layers.

[0011] In the pneumatic tire, the number of rows in the first layer of the bead core is preferably four or more.

[0012] In the pneumatic tire, the number of rows in the first layer of the bead core is preferably six or less.

[0013] In order to solve the above-mentioned problems and achieve the object, a method for manufacturing a pneumatic tire according to the present invention is a method for manufacturing a pneumatic tire including a pair of bead portions disposed on both sides of the tire equatorial plane in the tire width direction, and a bead core disposed in the bead portion and formed by winding a bead wire in a ring shape, wherein the bead core has a plurality of winding portions of the bead wire wound in a ring shape arranged in the tire width direction to form layers, a plurality of winding portions of the bead wire arranged in the tire radial direction to form rows, and the plurality of layers are stacked in the tire radial direction and the plurality of rows are arranged in the tire width direction to arrange the bead wire in a lattice pattern in a tire meridian cross section, and three of the layers are arranged from the layer located innermost in the tire radial direction to the outer side in the tire radial direction among the plurality of layers. The present invention is characterized in that, when the layers are designated as a first layer, a second layer, and a third layer, and among the plurality of rows, the three rows from the row located innermost in the tire width direction to the outer side in the tire width direction are designated as the first row, the second row, and the third row, and the first to sixth winding portions of the winding portion of the bead wire are designated as a first winding portion, a second winding portion, a third winding portion, a fourth winding portion, a fifth winding portion, and a sixth winding portion, the first winding portion is located in the second row in the first layer, the second winding portion is located in the first row in the first layer, the third winding portion is located in the first row in the second layer, the fourth winding portion is located in the first row in the third layer, the fifth winding portion is located in the second row in the second layer, and the sixth winding portion is located in the third row in the first layer. [Effects of the Invention]

[0014] The pneumatic tire and the method for manufacturing a pneumatic tire according to the present invention have the effect of improving the durability of the bead portion. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a tire meridian cross-sectional view showing a main part of a pneumatic tire according to an embodiment. [Figure 2]FIG. 2 is a schematic diagram of part A in FIG. [Figure 3] FIG. 3 is an explanatory diagram of the order in which the bead wire is wound around the bead core shown in FIG. [Figure 4] FIG. 4 is a schematic diagram of a ring that winds the bead wire. [Figure 5] FIG. 5 is a cross-sectional view taken along line BB in FIG. [Figure 6] FIG. 6 is an explanatory diagram showing a state in which the bead wire of the bead core starts to be wound from the outermost position in the tire width direction. [Figure 7] FIG. 7 is an explanatory diagram showing a modified example of the pneumatic tire according to the embodiment, in which the bead wires are stacked in three rows. [Figure 8] FIG. 8 is an explanatory diagram showing a modified example of the pneumatic tire according to the embodiment, in which the bead wires are stacked in four rows. [Figure 9] FIG. 9 is an explanatory diagram showing a modified example of the pneumatic tire according to the embodiment, in which bead wires are laminated in three layers, each layer having five rows. [Figure 10] FIG. 10 is an explanatory diagram showing a modified example of the pneumatic tire according to the embodiment, in which the bead wires are laminated in four layers. [Figure 11] FIG. 11 is an explanatory diagram showing a modified example of the pneumatic tire according to the embodiment, in which bead wires are laminated in four layers, each layer having five rows. [Figure 12] FIG. 12 is an explanatory diagram showing a modified example of the pneumatic tire according to the embodiment, in which the bead wires are laminated in five layers. [Figure 13] FIG. 13 is an explanatory diagram showing a modified example of the pneumatic tire according to the embodiment, in which bead wires are stacked in six rows. [Figure 14] FIG. 14 is an explanatory diagram showing a modified example of the pneumatic tire according to the embodiment, in which bead wires are stacked in five layers, each layer consisting of a maximum of six rows. [Figure 15A] FIG. 15A is a chart showing the results of a performance evaluation test of a pneumatic tire. [Figure 15B] FIG. 15B is a chart showing the results of a performance evaluation test of a pneumatic tire. [Figure 15C] FIG. 15C is a chart showing the results of a performance evaluation test of a pneumatic tire. [Figure 15D] FIG. 15D is a chart showing the results of a performance evaluation test of a pneumatic tire. [Figure 15E] FIG. 15E is a chart showing the results of a performance evaluation test of a pneumatic tire. [Figure 16] FIG. 16 is a schematic diagram showing a bead portion of a pneumatic tire according to Comparative Example 1. As shown in FIG. [Figure 17] FIG. 17 is a schematic diagram showing a bead portion of a pneumatic tire according to Conventional Example 2. As shown in FIG. [Figure 18] FIG. 18 is a schematic diagram showing a bead portion of a pneumatic tire according to Comparative Example 2. As shown in FIG. [Figure 19] FIG. 19 is a schematic diagram showing a bead portion of a pneumatic tire according to Conventional Example 3. As shown in FIG. [Figure 20] FIG. 20 is a schematic diagram showing a bead portion of a pneumatic tire according to Comparative Example 3. As shown in FIG. [Figure 21] FIG. 21 is a schematic diagram showing a bead portion of a pneumatic tire according to Conventional Example 4. As shown in FIG. [Figure 22] FIG. 22 is a schematic diagram showing a bead portion of a pneumatic tire according to Comparative Example 4. As shown in FIG. [Figure 23] FIG. 23 is a schematic diagram showing a bead portion of a pneumatic tire according to Conventional Example 5. As shown in FIG. [Figure 24] FIG. 24 is a schematic diagram showing a bead portion of a pneumatic tire according to Comparative Example 5. As shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of a pneumatic tire and a method for manufacturing a pneumatic tire according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to these embodiments. Furthermore, the components in the following embodiments include those that are replaceable and easily conceivable by a person skilled in the art, or those that are substantially the same.

[0017] [Embodiment] In the following description, the tire radial direction refers to the direction perpendicular to the tire rotational axis (not shown), which is the rotational axis of the pneumatic tire 1. The tire radially inner side refers to the side toward the tire rotational axis in the tire radial direction, and the tire radially outer side refers to the side away from the tire rotational axis in the tire radial direction. The tire circumferential direction refers to the direction around the tire rotational axis as the central axis. The tire width direction refers to the direction parallel to the tire rotational axis. The tire width inner side refers to the side toward the tire equatorial plane (tire equator line) CL in the tire width direction, and the tire width outer side refers to the side away from the tire equatorial plane CL in the tire width direction. The tire equatorial plane CL is a plane that is perpendicular to the tire rotational axis and passes through the center of the tire width of the pneumatic tire 1. The tire equatorial plane CL coincides in position in the tire width direction with the tire width centerline, which is the center position of the pneumatic tire 1 in the tire width direction. The tire width is the width in the tire width direction between the outermost portions in the tire width direction, i.e., the distance between the portions farthest from the tire equatorial plane CL in the tire width direction. The tire equator line refers to a line that is on the tire equatorial plane CL and extends along the tire circumferential direction of the pneumatic tire 1. In the following description, the tire meridian section refers to a cross section of the tire cut by a plane that includes the tire rotation axis.

[0018] FIG. 1 is a tire meridian cross-section showing a main portion of a pneumatic tire 1 according to an embodiment. When viewed in a tire meridian cross-section, the pneumatic tire 1 according to this embodiment has a tread portion 2 disposed at the outermost portion in the tire radial direction, and the tread portion 2 has tread rubber 4 made of a rubber composition. The surface of the tread portion 2, i.e., the portion that comes into contact with the road surface when a vehicle (not shown) equipped with the pneumatic tire 1 is traveling, is formed as a tread contact surface 3, and the tread contact surface 3 constitutes part of the contour of the pneumatic tire 1. The tread portion 2 has a plurality of circumferential grooves 30 formed in the tread contact surface 3 and extending in the tire circumferential direction. In this embodiment, four circumferential grooves 30 are arranged side by side in the tire width direction. The surface of the tread portion 2 is partitioned by the plurality of circumferential grooves 30 into a plurality of land portions 20 arranged side by side in the tire width direction.

[0019] The circumferential grooves 30 referred to here are grooves that are required to display a wear indicator as defined by JATMA. The circumferential grooves 30 have a groove width of 3 mm or more and a groove depth of 7 mm or more. The circumferential grooves 30 may extend linearly along the tire circumferential direction, or may be formed in a zigzag shape by repeatedly bending or curving in the tire width direction while extending in the tire circumferential direction. The number of circumferential grooves 30 may be any number other than four.

[0020] In addition to the circumferential grooves 30 extending in the tire circumferential direction, lug grooves (not shown) extending in the tire width direction are provided in the tread contact surface 3. The tread contact surface 3 may also be provided with circumferential narrow grooves (not shown) extending in the tire circumferential direction with a groove width narrower than the circumferential grooves 30, sipes (not shown) formed in the tread contact surface 3 in the form of cuts, and the like.

[0021] Shoulder portions 5 are located at both outer ends of the tread portion 2 in the tire width direction, and sidewall portions 8 are arranged on the tire radially inward side of the shoulder portions 5. That is, the sidewall portions 8 are arranged on both sides of the tread portion 2 in the tire width direction. In other words, the sidewall portions 8 are arranged in two locations on both sides of the pneumatic tire 1 in the tire width direction, and form the outermost exposed portions of the pneumatic tire 1 in the tire width direction.

[0022] A bead portion 40 is located on the tire radially inner side of each sidewall portion 8 located on both sides in the tire width direction. Like the sidewall portions 8, the bead portions 40 are located at two positions on both sides of the tire equatorial plane CL; that is, a pair of bead portions 40 are located on both sides of the tire equatorial plane CL in the tire width direction. A bead core 50 is located in each bead portion 40, and a bead filler 45 is located on the tire radially outer side of the bead core 50. The bead core 50 is an annular member formed by bundling bead wires 51 (see FIG. 2 ), which are steel wires, into a circular shape, and the bead filler 45 is a rubber member located on the tire radially outer side of the bead core 50.

[0023] A belt layer 14 is also disposed in the tread portion 2. The belt layer 14 has a multi-layer structure in which a plurality of belts 141, 142 and a belt cover 143 are laminated. In this embodiment, two layers of belts 141, 142 are laminated. The belts 141, 142 constituting the belt layer 14 are formed by coating a plurality of belt cords made of steel or organic fiber material such as polyester, rayon, or nylon with coating rubber and rolling the coated belt cords. The belt angle, defined as the inclination angle of the belt cords with respect to the tire circumferential direction, is within a predetermined range (for example, 20° to 55°). The two-layer belts 141, 142 have different belt angles. Therefore, the belt layer 14 has a so-called cross-ply structure in which the two-layer belts 141, 142 are laminated with the inclination directions of the belt cords crossing each other. In other words, the two-layer belts 141, 142 are provided as so-called cross belts in which the belt cords of the respective belts 141, 142 are arranged in a direction in which they cross each other.

[0024] The belt cover 143 is formed by covering a plurality of belt cover cords made of steel or organic fiber material such as polyester, rayon, or nylon with coating rubber and rolling the covered cords, and the belt angle, defined as the inclination angle of the belt cover cords with respect to the tire circumferential direction, is within a predetermined range (for example, 0° to 10°). The belt cover 143 is, for example, a strip material formed by covering one or more belt cover cords with coating rubber, and is formed by winding this strip material spirally around the tire rotation axis from the outer side in the tire radial direction of the two-layered belts 141 and 142.

[0025] A carcass layer 10 containing radial ply cords is provided continuously on the tire radially inward side of the belt layer 14 and on the tire equatorial plane CL side of the sidewall portion 8. For this reason, the pneumatic tire 1 according to this embodiment is configured as a so-called radial tire. The carcass layer 10 has a single-layer structure consisting of one carcass ply or a multi-layer structure consisting of a plurality of carcass plies stacked together, and is toroidally spanned between a pair of bead portions 40 arranged on both sides in the tire width direction to form the framework of the tire.

[0026] More specifically, the carcass layer 10 is disposed from one bead portion 40 to the other of a pair of bead portions 40 located on both sides in the tire width direction, and is wound back along the bead core 50 toward the outside in the tire width direction at the bead portion 40 so as to enclose the bead core 50 and the bead filler 45. Therefore, the carcass layer 10 has a carcass main body portion 10a disposed between the pair of bead portions 40, and a turn-up portion 10b formed continuously from the carcass main body portion 10a and folded back from the inside of the bead core 50 in the tire width direction toward the outside in the tire width direction.

[0027] The carcass main body 10a here is a portion formed across the inner sides of a pair of bead cores 50 in the carcass layer 10 in the tire width direction, and the turnup portion 10b is formed continuously from the carcass main body 10a on the inner side of the bead core 50 in the tire width direction, passing through the inner side of the bead core 50 in the tire radial direction and folded back to the outer side in the tire width direction. The bead filler 45 is arranged on the inner side in the tire width direction of the turnup portion 10b, which is the portion folded back to the outer side of the bead core 50 in the tire width direction, and on the outer side of the bead core 50 in the tire radial direction.

[0028] The bead filler 45 is made of a rubber material and is placed in a space formed radially outward of the bead core 50 by folding back the carcass layer 10 at the bead portions 40. The belt layer 14 is placed radially outward of the tread portion 2 of the carcass layer 10 that is stretched between the pair of bead portions 40. The carcass ply of the carcass layer 10 is formed by coating a plurality of carcass cords made of steel or organic fiber material such as aramid, nylon, polyester, or rayon with a coating rubber and rolling the coated cords. The carcass cords that make up the carcass ply are arranged in parallel at an angle relative to the tire circumferential direction, with the angle being aligned along the tire meridian direction.

[0029] In the bead portion 40, a rim cushion rubber 17 that forms the contact surface of the bead portion 40 with the rim flange is arranged on the tire radially inner side and tire widthwise outer side of the bead core 50 and the turned-up portion of the carcass layer 10. Furthermore, an inner liner 16 is formed along the carcass layer 10 on the inner side of the carcass layer 10 or on the inner side of the carcass layer 10 in the pneumatic tire 1. The inner liner 16 forms a tire inner surface 18, which is the inner surface of the pneumatic tire 1.

[0030] Fig. 2 is a schematic diagram of part A in Fig. 1. In the bead portion 40, as shown in Fig. 2, the carcass layer 10 is folded back around the bead core 50. The bead core 50 is formed to have a cross-sectional shape that is close to a rectangle when viewed in a tire meridian cross section. In this embodiment, the bead core 50 is formed to have a cross-sectional shape that is close to a rectangle with some corners chamfered.

[0031] Specifically, the bead core 50 is formed by winding a bead wire 51 in a ring shape, and by shifting the positions of the respective turns of the bead wire 51, the bead core 50 is formed by winding the bead wire 51 in a plurality of turns. The bead core 50 formed by winding the bead wire 51 in a ring shape has a layer 52 formed by arranging the plurality of turns of the bead wire 51 formed by winding in a ring shape in the tire width direction, and a row 53 formed by arranging the plurality of turns in the tire radial direction.

[0032] The bead core 50 has a plurality of layers 52 and rows 53, and the layers 52 are stacked in the tire radial direction and the rows 53 are aligned in the tire width direction, so that the bead wires 51 are arranged in a lattice pattern in the tire meridian cross section. With the bead wires 51 arranged in a lattice pattern in this way, the bead core 50 has an arrangement that is close to a rectangle when viewed in the tire meridian cross section.

[0033] In the present embodiment, the bead core 50 has three layers 52 formed by arranging the winding portions of the bead wire 51 in the tire width direction, stacked in the tire radial direction. Five rows 53 formed by arranging the winding portions of the bead wire 51 in the tire radial direction are arranged in the tire width direction. Of the three layers 52 stacked in the tire radial direction, the two radially inner layers 52 each have five winding portions of the bead wire 51 arranged in the tire width direction, while the outermost layer 52 in the tire radial direction has four winding portions of the bead wire 51 arranged in the tire width direction.

[0034] In other words, of the multiple rows 53 of the bead wire 51, in the four rows 53 other than the outermost row 53 in the tire width direction, three winding portions of the bead wire 51 are lined up in the tire radial direction, whereas in the outermost row 53 in the tire width direction, there are two winding portions of the bead wire 51 lined up in the tire radial direction. Therefore, the bead core 50 in this embodiment has a cross-sectional shape when viewed in a tire meridian cross section, which is close to a rectangle, with corners located on the outer side in the tire width direction and on the outer side in the tire radial direction being chamfered.

[0035] In this embodiment, the bead core 50 has a structure in which a total of three layers 52 are laminated, in order from the innermost layer in the tire radial direction: a layer 52 including five windings, a layer 52 including five windings, and a layer 52 including four windings. In the following description, such a layered structure of the bead wire 51 in the bead core 50 will be referred to as a "5+5+4 structure." Similarly, in the following description, the layered structure of the bead wire 51 will be appropriately expressed in a similar format in which the number of windings of the bead wire 51 included in each layer 52 is connected with "+" in order from the innermost layer 52 in the tire radial direction.

[0036] Fig. 3 is an explanatory diagram of the order in which the bead wire 51 is wound around the bead core 50 shown in Fig. 2. Note that Fig. 3 shows the order in which the bead wire 51 is wound around the bead core 50 when the bead wire 51 is wound in a ring shape to form the bead core 50, within the bead wire 51 in the figure. That is, Fig. 3 shows the position where the winding starts when winding the bead wire 51 into a ring as 1, and the bead wire 51 is wound in ascending numerical order, with the position where the winding of the bead wire 51 ends as 14.

[0037] In this embodiment, the bead wire 51 is wound around the bead core 50 from a position on the inner side in the tire radial direction and closer to the inner side in the tire width direction. In other words, when the inner end of the bead base portion 41, which is the inner surface of the bead portion 40, in the tire width direction is defined as the bead toe 42 and the outer end thereof in the tire width direction is defined as the bead heel 43, the bead wire 51 is wound around the bead core 50 from a position closer to the bead toe 42.

[0038] Here, for the purpose of explaining the order of winding portions when winding the bead wire 51 around the bead core 50 in a ring shape, the three layers 52 of the multiple layers 52 extending from the layer 52 located innermost in the tire radial direction toward the tire radially outer side will be referred to as the first layer 52a, the second layer 52b, and the third layer 52c, respectively. Furthermore, the three rows 53 of the multiple rows 53 extending from the row 53 located innermost in the tire width direction toward the tire width outer side will be referred to as the first row 53a, the second row 53b, and the third row 53c, respectively. Furthermore, the first to sixth winding portions of the winding portion of the bead wire 51 will be referred to as the first winding portion 55a, the second winding portion 55b, the third winding portion 55c, the fourth winding portion 55d, the fifth winding portion 55e, and the sixth winding portion 55f, respectively.

[0039] When each is defined in this manner, in this embodiment, the first winding portion 55a, the second winding portion 55b, the third winding portion 55c, the fourth winding portion 55d, the fifth winding portion 55e, and the sixth winding portion 55f of the winding portion of the bead wire 51 that constitutes the bead core 50 are positioned closer to the bead toe 42.

[0040] Specifically, the first winding portion 55a of the winding portion of the bead wire 51 is located in the second row 53b of the first layer 52a, the second winding portion 55b is located in the first row 53a of the first layer 52a, and the third winding portion 55c is located in the first row 53a of the second layer 52b. Also, the fourth winding portion 55d of the winding portion of the bead wire 51 is located in the first row 53a of the third layer 52c, the fifth winding portion 55e is located in the second row 53b of the second layer 52b, and the sixth winding portion 55f is located in the third row 53c of the first layer 52a.

[0041] The sixth winding portion 55f and subsequent portions of the winding portion of the bead wire 51 are wound sequentially toward the tire radial direction outer side or the tire width direction outer side. In this manner, in the bead core 50 around which the bead wire 51 is wound in a ring shape, the final winding portion 55z of the winding portion of the bead wire 51 is arranged in a position other than the first row 53a. Specifically, in the bead core 50, the final winding portion 55z is arranged in the row 53 that is outermost in the tire width direction in the layer 52 that is outermost in the tire radial direction among the multiple layers 52.

[0042] Next, a method for manufacturing the bead core 50 during the manufacture of the pneumatic tire 1 will be described. Fig. 4 is a schematic diagram of a ring 80 around which the bead wire 51 is wound. Fig. 5 is a cross-sectional view taken along line BB of Fig. 4. Fig. 5(a) is a diagram showing the first winding portion 55a of the bead wire 51 wound, Fig. 5(b) is a diagram showing the second winding portion 55b of the bead wire 51 wound, Fig. 5(c) is a diagram showing the third winding portion 55c of the bead wire 51 wound, and Fig. 5(d) is a diagram showing the fourth winding portion 55d of the bead wire 51 wound. In the manufacturing process of the bead core 50 during the manufacture of the pneumatic tire 1, the bead wire 51 is wound in a ring shape using an annular ring 80, which is a jig used when manufacturing the bead core 50.

[0043] The cross section of the ring 80 when viewed in the circumferential direction of the annular ring 80 is formed in a U-shape, with the open side of the U-shape facing outward in the radial direction of the ring 80 and the closed side of the U-shape positioned inward in the radial direction. Specifically, the ring 80 has an inner circumferential portion 81 that forms the closed side of the U-shape, and side walls 82 that stand outward in the radial direction of the ring 80 from both sides of the inner circumferential portion 81 in the width direction of the ring 80. In this case, the width direction of the ring 80 is the direction along the axial direction of the ring 80, which is formed in an annular shape.

[0044] The inner peripheral portion 81 of the ring 80 has an outer diameter that is approximately the same as the inner diameter of the bead core 50, and a width that is approximately the same as the width of the bead core 50. Recesses 81a are formed on the outer peripheral surface of the inner peripheral portion 81 to align the bead wire 51 when manufacturing the bead core 50 using the ring 80. The recesses 81a are formed in the shape of a recess or groove that extends in the circumferential direction of the ring 80. The number of recesses 81a is the same as the number of turns of the bead wire 51 located in the first layer 52a of the bead core 50, and they are arranged side by side in the width direction of the ring 80.

[0045] The side wall 82 is formed so that its height from the inner circumferential portion 81 in the radial direction of the bead core 50 is at least approximately the same as the height from the inner circumferential surface of the bead core 50 to the third layer 52c.

[0046] When manufacturing the bead core 50 using the ring 80 formed in this manner, the bead wire 51 covered with a coating rubber (not shown) is supplied to the ring 80 in an upstream process, and the bead wire 51 is wound around the ring 80 while the ring 80 is being rotated. When winding the bead wire 51 around the ring 80, the winding of the bead wire 51 begins around the inner periphery 81. When winding the bead wire 51 around the inner periphery 81 of the ring 80, the bead wire 51 is positioned along a recess 81a formed in the inner periphery 81, so that the bead wire 51 is aligned in the width direction while being wound.

[0047] The bead wire 51 wound around the ring 80 is formed into multiple layers 52 and multiple rows 53 by shifting the position where the bead wire 51 is wound in the width direction while rotating the ring 80, or by stacking the bead wire 51 in the radial direction of the ring 80. In this way, the winding portions of the bead wire 51 are aligned in the tire radial direction, and a bead core 50 stacked in the tire radial direction is manufactured.

[0048] When winding the bead wire 51 around the ring 80, first, as shown in Fig. 5(a), winding of the first winding portion 55a around the inner circumferential portion 81 begins at a position spaced apart by one bead wire 51 from the side wall 82 of the ring 80. This positions the first winding portion 55a in the second row 53b of the first layer 52a.

[0049] Next, as shown in Fig. 5(b), the second winding portion 55b of the bead wire 51 is wound around a position between the first winding portion 55a and the side wall 82. As a result, the second winding portion 55b is positioned in the first row 53a of the first layer 52a.

[0050] Next, as shown in Fig. 5(c), the third winding portion 55c of the bead wire 51 is wound around the outer side of the second winding portion 55b in the radial direction of the ring 80. As a result, the third winding portion 55c is positioned in the first row 53a of the second layer 52b.

[0051] Next, as shown in Fig. 5(d), the fourth winding portion 55d of the bead wire 51 is wound around the outside of the third winding portion 55c in the radial direction of the ring 80. As a result, the fourth winding portion 55d is positioned in the first row 53a of the third layer 52c.

[0052] When winding the third winding portion 55c or the fourth winding portion 55d, it is preferable to wind them while adjusting the position between the bead wire 51 supplied to the ring 80 and the ring 80 in a direction that allows the side wall 82 of the ring 80 to be pressed against the bead wire 51.

[0053] After winding up to the fourth winding portion 55d, the bead wire 51 is wound in the order of winding portions indicated by ascending numbers in Fig. 3. For example, the fifth winding portion 55e is wound outside the first winding portion 55a in the radial direction of the ring 80, and the sixth winding portion 55f is wound around the inner circumferential portion 81 of the ring 80 at a position opposite to the side where the second winding portion 55b is located in the width direction of the ring 80. As a result, the fifth winding portion 55e is positioned in the second row 53b of the second layer 52b, and the sixth winding portion 55f is positioned in the third row 53c of the first layer 52a.

[0054] Similarly, the winding portions of the bead wire 51 from the sixth winding portion 55f onwards are wound in the order shown in Fig. 3 while rotating the ring 80. The bead core 50 is manufactured by winding the bead wire 51 into a ring shape in a predetermined order using the ring 80 in this manner.

[0055] When manufacturing the pneumatic tire 1, the bead core 50 is manufactured in this manner, and each of the components that make up the pneumatic tire 1, such as the tread rubber 4, carcass layer 10, and belt layer 14, are also manufactured. After each of the components that make up the pneumatic tire 1 is manufactured, they are bonded together and assembled to manufacture a so-called green tire, which is the prototype of the pneumatic tire 1. At this time, the bead core 50 is bonded to other components in an orientation that allows the second circumferential portion 55b to be positioned closer to the bead toe 42. The green tire is then vulcanized using a mold (not shown) and a bladder (not shown) to be molded into the shape of the pneumatic tire 1 that will be the product.

[0056] When mounting the pneumatic tire 1 manufactured in this manner on a vehicle, the bead base portion 41 is fitted to the rim wheel to mount the pneumatic tire 1 on the rim wheel, and the pneumatic tire 1 is assembled to the rim wheel. After the pneumatic tire 1 is assembled to the rim, air is filled inside to inflate the tire, and the rim-assembled and inflated pneumatic tire 1 is mounted on the vehicle.

[0057] When a vehicle equipped with pneumatic tire 1 travels, the pneumatic tire 1 rotates while the lower part of the tread contact surface 3 of the tread portion 2 comes into contact with the road surface. When a vehicle equipped with pneumatic tire 1 travels on a dry road surface, the vehicle travels by transmitting driving force and braking force to the road surface and generating turning force mainly due to the frictional force between the tread contact surface 3 and the road surface.

[0058] Furthermore, when traveling on a wet road surface, water between the tread contact surface 3 and the road surface enters grooves such as the circumferential grooves 30 and lug grooves (not shown), and these grooves drain the water between the tread contact surface 3 and the road surface while traveling. This makes it easier for the tread contact surface 3 to make contact with the road surface, and the frictional force between the tread contact surface 3 and the road surface enables the vehicle to travel.

[0059] When a vehicle equipped with the pneumatic tire 1 is traveling, the frictional force generated between the tread contact surface 3 of the pneumatic tire 1 and the road surface enables the vehicle to travel, but when the vehicle is traveling, loads act in various directions on each part of the pneumatic tire 1. The loads acting on the pneumatic tire 1 are received by the pressure of the air filled inside and the carcass layer 10 provided as the skeleton of the pneumatic tire 1, etc. As a result, tension acts on the carcass layer 10.

[0060] Because the carcass layer 10 is folded around the bead core 50 in the bead portion 40, when tension acts on the carcass layer 10, a force based on the tension acts on the bead core 50. Because the bead core 50 has a cross-sectional shape that is close to a rectangle in the tire meridian cross section, the force that acts on the bead core 50 from the carcass layer 10 when the pneumatic tire 1 is filled with air acts, for example, on a position near a corner of the rectangle that is the shape of the bead core 50 in the tire meridian cross section.

[0061] In particular, a large force is likely to act from the carcass layer 10 near a corner of the bead core 50 located closer to the bead toe 42, which is a portion of the bead portion 40 located on the inner side in the tire radial direction and on the inner side in the tire width direction. That is, the corner of the bead core 50 located closer to the bead toe 42 in the tire meridian cross section is located near a portion of the carcass layer 10 where the extending direction of the carcass layer 10 changes between a portion of the bead core 50 located on the inner side in the tire width direction and a portion of the bead core 50 located on the inner side in the tire radial direction. For this reason, when tension acts on the carcass layer 10 by filling the pneumatic tire 1 with air, a large force is likely to act from the carcass layer 10 near a rectangular corner of the bead core 50 located closer to the bead toe 42 in the tire meridian cross section.

[0062] When a large force from the carcass layer 10 acts near a corner of the rectangular shape of the bead core 50 in the meridian cross section of the tire, stress concentration occurs near the corner of the bead core 50 due to the force from the carcass layer 10. In this case, the bead wire 51 located near the corner of the bead core 50 may be easily displaced or damaged due to the stress concentration.

[0063] Fig. 6 is an explanatory diagram showing a configuration in which the bead wire 51 of the bead core 50 starts to be wound from the outermost position in the tire width direction. As with Fig. 3, Fig. 6 shows the order of winding the bead wire 51 when winding the bead wire 51 into a ring shape to form the bead core 50 by showing ascending numbers inside the bead wire 51 in the figure.

[0064] When forming the bead core 50 by winding the bead wire 51 in a ring shape, if the winding portion of the bead wire 51 is wound while being shifted in the tire width direction for each layer 52, and once wound to the end position in the tire width direction, the bead wire 51 is folded back and wound outward in the tire radial direction to stack multiple layers 52, it may be difficult to ensure the strength of the portion of the bead core 50 located closer to the bead toe 42.

[0065] For example, in the bead core 50 shown in Fig. 6, in the layer 52 located innermost in the tire radial direction, the bead wire 51 is wound from the outer side to the inner side in the tire width direction, and is folded back to the outer side in the tire radial direction at an inner position in the tire width direction to be wound as the bead wire 51 used in the layer 52 laminated on the outer side in the tire radial direction. Also, in the bead core 50 shown in Fig. 6, in the layer 52 located outermost in the tire radial direction, no circumferential portion of the bead wire 51 is arranged in the row 53 located innermost in the tire width direction, and the winding end of the bead wire 51 is located in the second row 53 located outer in the tire width direction from the row 53 located innermost in the tire width direction.

[0066] In the bead core 50 shown in Fig. 6, the bead wire 51 is wound in order from the innermost layer 52 in the tire radial direction to each layer 52. Therefore, even in the innermost part of the bead core 50 in the tire width direction, i.e., in the part of the bead core 50 closer to the bead toe 42 of the bead portion 40, the circumferential portion of the bead wire 51 is wound continuously in the tire width direction for each layer 52. As a result, in the bead core 50 shown in Fig. 6, even in the part closer to the bead toe 42, the tightening force caused by winding the bead wire 51 in a ring shape is approximately the same as in parts other than the part closer to the bead toe 42, such as the part closer to the bead heel 43.

[0067] 6, if a large force from the carcass layer 10 acts on the bead core 50 near the bead toe 42, i.e., near the winding portion of the bead wire 51 indicated by "5" in Fig. 6, the bead wire 51 near this portion may be easily displaced due to stress concentration. In this case, the bead wire 51 may be damaged, or the bead core 50 may be deformed due to the damage to the bead wire 51, and the deformation of the bead core 50 may damage the carcass layer 10 in the bead portion 40.

[0068] In contrast, in the present embodiment, the bead wire 51 constituting the bead core 50 has the second winding portion 55b located in the first row 53a of the first layer 52a, the third winding portion 55c located in the first row 53a of the second layer 52b, and the fourth winding portion 55d located in the first row 53a of the third layer 52c. Therefore, the winding portion of the bead wire 51 near the start of winding can be wound in layers in order from the first layer 52a, which is the innermost layer 52 in the tire radial direction, to the outer side in the tire radial direction in the first row 53a, which is the innermost row 53 in the tire width direction of the bead core 50. This increases the tightening force of the bead wire 51 in the innermost row 53 in the tire width direction of the bead core 50, and increases the strength of the portion of the bead core 50 closer to the inner side in the tire width direction, i.e., the portion of the bead core 50 near the second winding portion 55b located closer to the bead toe 42.

[0069] Furthermore, the fifth winding portion 55e of the bead wire 51 is located in the second row 53b of the second layer 52b, and the sixth winding portion 55f is located in the third row 53c of the first layer 52a. Therefore, the winding portion of the bead wire 51 near the start of winding can be wound around a corner of the rectangular bead core 50 near the bead toe 42 in the tire meridian cross section, thereby increasing the tightening force of the bead wire 51 around the corner of the bead core 50 near the bead toe 42. This further increases the strength of the portion of the bead core 50 near the bead toe 42. Therefore, the strength of the portion of the bead core 50 near the second winding portion 55b, which is the portion near the bead toe 42, can be improved, and even if a large force is applied from the carcass layer 10 to the portion of the bead core 50 near the bead toe 42, the bead wire 51 can be prevented from shifting or being damaged due to stress concentration.

[0070] Furthermore, the first winding portion 55a of the bead wire 51 is located in the second row 53b of the first layer 52a. Therefore, the winding portion of the bead wire 51 near the start of winding can be concentrated around a corner of the bead core 50 closer to the bead toe 42, while the start of winding of the bead wire 51 can be located in a position different from the corner of the bead core 50 closer to the bead toe 42. This makes it possible to prevent the start of winding of the bead wire 51 from being displaced or damaged by the large force from the carcass layer 10, even if a large force acts from the carcass layer 10 on the corner of the bead core 50 closer to the bead toe 42 due to tension acting on the carcass layer 10.

[0071] As a result, even if a large force from the carcass layer 10 based on the tension acting on the carcass layer 10 acts on a corner of the bead core 50 closer to the bead toe 42, deformation or damage to the bead core 50 due to displacement or damage to the bead wire 51 can be suppressed. Therefore, damage to the carcass layer 10 folded around the bead core 50 at the bead portion 40 due to deformation or damage to the bead core 50 can be suppressed. As a result, the durability of the bead portion 40 can be improved.

[0072] Furthermore, because the final winding portion 55z of the bead wire 51 is disposed in a position other than the first row 53a of the bead core 50, the winding end portion of the bead wire 51 can be disposed in a position away from the first row 53a of the bead core 50, where a large force from the carcass layer 10 is likely to act. Therefore, even if a large force from the carcass layer 10 acts on the first row 53a, which is located innermost in the tire width direction of the bead core 50, due to tension acting on the carcass layer 10, the winding end portion of the bead wire 51 can be prevented from being displaced or damaged by the large force from the carcass layer 10. This prevents deformation or damage to the bead core 50 disposed in the bead portion 40 due to displacement or damage of the bead wire 51. As a result, the durability of the bead portion 40 can be improved.

[0073] Furthermore, because the final winding portion 55z of the bead wire 51 is disposed in the row 53 that is outermost in the tire width direction in the layer 52 that is outermost in the tire radial direction, the winding end portion of the bead wire 51 can be disposed at a position significantly spaced outward in the tire width direction from the first row 53a. This more reliably prevents the winding end portion of the bead wire 51 from becoming displaced or damaged, even when a large force from the carcass layer 10 acts on the first row 53a of the bead core 50. This more reliably prevents the bead core 50 disposed in the bead portion 40 from becoming deformed or damaged due to the bead wire 51 becoming displaced or damaged. As a result, the durability of the bead portion 40 can be more reliably improved.

[0074] [Variations] In the above-described embodiment, the bead wire 51 of the bead core 50 has a 5+5+4 layered structure, but the bead wire 51 may be layered in other structures. FIG. 7 is an explanatory diagram showing a modified example of the pneumatic tire 1 according to the embodiment, in which the bead wire 51 is layered in three rows. Similarly to FIG. 3 , FIG. 7 and FIGS. 8 to 14 (described later) show the order of windings of the bead wire 51 when winding the bead wire 51 into a ring shape to form the bead core 50 by indicating ascending numbers within the bead wire 51 in the drawings. For example, as shown in FIG. 7 , the bead wire 51 of the bead core 50 may have a structure in which it is made up of three layers 52 layered in the tire radial direction, and each of the three layers 52 includes three windings. That is, the layered structure of the bead wire 51 may be a 3+3+3 structure.

[0075] Regardless of the layer structure of the bead wire 51 of the bead core 50, the positions at which the first winding portion 55a, the second winding portion 55b, the third winding portion 55c, the fourth winding portion 55d, the fifth winding portion 55e, and the sixth winding portion 55f are arranged may be the same as the positions at which they are arranged in the bead core 50 of the above-described embodiment. Regardless of the layer structure of the bead wire 51, the positions at which the first winding portion 55a to the sixth winding portion 55f are arranged are the same as the positions at which they are arranged in the bead core 50 of the above-described embodiment, thereby increasing the strength of the portion of the bead core 50 closer to the bead toe 42. As a result, even if a large force is applied from the carcass layer 10 to the portion of the bead core 50 closer to the bead toe 42, displacement and damage to the bead wire 51 can be suppressed, thereby suppressing deformation and damage to the bead core 50 and suppressing damage to the carcass layer 10 at the bead portion 40. As a result, the durability of the bead portion 40 can be improved.

[0076] Furthermore, the bead core 50 preferably has four to six rows 53 in the first layer 52a of the bead wire 51. FIG. 8 is an explanatory diagram showing a modified example of the pneumatic tire 1 according to the embodiment, in which the bead wire 51 is laminated in four rows. For example, as shown in FIG. 8, the bead wire 51 of the bead core 50 may have a structure in which the bead wire 51 is made of three layers 52 laminated in the tire radial direction, and each of the three layers 52 includes four winding portions. That is, the bead core 50 may have a 4+4+4 laminated structure in which the first layer 52a of the bead wire 51 has four rows 53.

[0077] Alternatively, the bead core 50 may have five rows 53 in the first layer 52a of the bead wire 51. FIG. 9 is an explanatory diagram showing a modified example of the pneumatic tire 1 according to the embodiment, in which the bead wire 51 is laminated in three layers, each having five rows. For example, as shown in FIG. 9, the bead wire 51 of the bead core 50 may have a structure in which the bead wire 51 is made up of three layers 52 laminated in the tire radial direction, and each of the three layers 52 includes five turns. In other words, the bead core 50 may have a 5+5+5 laminated structure in which the first layer 52a of the bead wire 51 has five rows 53.

[0078] Fig. 10 is an explanatory diagram showing a modified example of the pneumatic tire 1 according to the embodiment, in which the bead wire 51 is laminated in four layers. Alternatively, the bead wire 51 of the bead core 50 may have a structure in which, from the innermost layer to the outermost layer in the tire radial direction, three layers 52 each including five turns and one layer 52 each including four turns are laminated in this order, as shown in Fig. 10. That is, the bead core 50 may have a laminated structure of a 5+5+5+4 structure in which the number of rows 53 in the first layer 52a of the bead wire 51 is five.

[0079] Fig. 11 is an explanatory diagram showing a modified example of the pneumatic tire 1 according to the embodiment, in which the bead wire 51 is laminated in four layers, each consisting of five rows. Alternatively, the bead wire 51 of the bead core 50 may be made up of four layers 52 laminated in the tire radial direction, with each of the four layers 52 including five turns, as shown in Fig. 11. That is, the bead core 50 may have a 5+5+5+5 laminated structure in which the first layer 52a of the bead wire 51 has five rows 53.

[0080] Fig. 12 is an explanatory diagram showing a modified example of the pneumatic tire 1 according to the embodiment, in which the bead wire 51 is laminated in five layers. Alternatively, the bead wire 51 of the bead core 50 may have a structure in which, from the innermost layer to the outermost layer in the tire radial direction, four layers 52 each including five turns and one layer 52 each including four turns are laminated in this order, for example, as shown in Fig. 12. That is, the bead core 50 may have a laminated structure of a 5+5+5+5+4 structure in which the number of rows 53 in the first layer 52a of the bead wire 51 is five.

[0081] Alternatively, the bead core 50 may have six rows 53 in the first layer 52a of the bead wire 51. FIG. 13 is an explanatory diagram showing a modified example of the pneumatic tire 1 according to the embodiment, in which the bead wire 51 is laminated in six rows. For example, as shown in FIG. 13, the bead wire 51 of the bead core 50 may have a structure in which a total of four layers 52 are laminated, in order from the innermost side to the outer side in the tire radial direction, including three layers 52 each including six turns and one layer 52 each including five turns. That is, the bead core 50 may have a 6+6+6+5 laminated structure in which the first layer 52a of the bead wire 51 has six rows 53.

[0082] Fig. 14 is an explanatory diagram showing a modified example of the pneumatic tire 1 according to the embodiment, in which the bead wire 51 is laminated in five layers, each consisting of a maximum of six rows. Alternatively, the bead wire 51 of the bead core 50 may have a structure in which, from the innermost layer to the outermost layer in the tire radial direction, four layers 52 each consisting of six turns and one layer 52 each consisting of five turns are laminated in this order, as shown in Fig. 14. That is, the bead core 50 may have a 6+6+6+6+5 laminated structure in which the number of rows 53 in the first layer 52a of the bead wire 51 is six.

[0083] The bead core 50 has four or more rows 53 in the first layer 52a, thereby ensuring the strength of the first layer 52a. This prevents the bead wires 51 from shifting or being damaged, even when a large force is applied to the bead core 50 from the carcass layer 10, thereby preventing the bead core 50 from being deformed or damaged. Furthermore, the bead core 50 has six or fewer rows 53 in the first layer 52a, thereby preventing the width of the first layer 52a in the tire width direction from becoming too large. This prevents a large force from acting between the carcass layer 10 and the ends of the first layer 52a on both sides in the tire width direction of the bead core 50 when a large tension is applied to the carcass layer 10, thereby preventing damage to the carcass layer 10 and the bead core 50. As a result, the durability of the bead portion 40 can be improved.

[0084] [Example] 15A to 15E are tables showing the results of performance evaluation tests of the pneumatic tire 1. Below, we will explain performance evaluation tests conducted on the conventional pneumatic tire 1, the pneumatic tire 1 according to the present invention, and a comparative pneumatic tire 1 compared to the pneumatic tire 1 according to the present invention. The performance evaluation tests were conducted by burst pressure tests.

[0085] The performance evaluation test was carried out using a pneumatic tire 1 having a tire nominal size of 195 / 65R15 91H as specified by JATMA.

[0086] The burst pressure test involves placing a rim-mounted tire in a water tank, gradually filling the tire with pressurized water while deflating, and measuring the pressure at which the tire bursts. The burst pressure test was also evaluated for each number of rows of the first layer of bead wires 51, with evaluations being conducted for each of five, six, seven, four, and three rows of the first layer. The burst pressure test results are expressed as an index, with Conventional Examples 1 to 5 (described below), which have different numbers of rows in the first layer, being indexed as 100. The higher the index, the less likely the carcass layer 10 and bead core 50 located in the bead portion 40 are to be damaged, indicating superior durability of the bead portion 40.

[0087] FIG. 16 is a schematic diagram showing a bead portion 40 of a pneumatic tire 1 according to Comparative Example 1. FIG. 17 is a schematic diagram showing a bead portion 40 of a pneumatic tire 1 according to Conventional Example 2. FIG. 18 is a schematic diagram showing a bead portion 40 of a pneumatic tire 1 according to Comparative Example 2. FIG. 19 is a schematic diagram showing a bead portion 40 of a pneumatic tire 1 according to Conventional Example 3. FIG. 20 is a schematic diagram showing a bead portion 40 of a pneumatic tire 1 according to Comparative Example 3. FIG. 21 is a schematic diagram showing a bead portion 40 of a pneumatic tire 1 according to Conventional Example 4. FIG. 22 is a schematic diagram showing a bead portion 40 of a pneumatic tire 1 according to Comparative Example 4. FIG. 23 is a schematic diagram showing a bead portion 40 of a pneumatic tire 1 according to Conventional Example 5. FIG. 24 is a schematic diagram showing a bead portion 40 of a pneumatic tire 1 according to Comparative Example 5. 16 to 24, similar to FIG. 3, the order in which the bead wire 51 is wound around the bead core 50 by winding the bead wire 51 in a ring shape is shown by indicating ascending numbers within the bead wire 51 in the figures.

[0088] The performance evaluation test was conducted on 20 types of pneumatic tires 1, including pneumatic tires 1 of Conventional Examples 1 to 5, which are examples of conventional pneumatic tires, pneumatic tires 1 of Examples 1 to 10 according to the present invention, and comparative examples 1 to 5, which are pneumatic tires compared to pneumatic tire 1 according to the present invention. Of these, pneumatic tire 1 of Conventional Example 1 has a bead core 50 arranged in a bead portion 40 configured in the form shown in Fig. 6. That is, pneumatic tire 1 of Conventional Example 1 has five rows of bead wire 51 in the first layer, with the first winding portion of bead wire 51 located in the fifth row, which is the fifth row 53 counting from the innermost row 53 in the tire width direction to the outer side in the tire width direction, and the second winding portion located in the fourth row, which is the fourth row 53.

[0089] 16, the bead core 50 disposed in the bead portion 40 of the pneumatic tire 1 of Comparative Example 1 has five rows of the first layer of the bead wire 51. That is, in the pneumatic tire 1 of Comparative Example 1, the first winding portion of the bead wire 51 is located in the second row, which is the second row 53 counting from the innermost row 53 in the tire width direction to the outer side in the tire width direction, and the third winding portion is located in the third row, which is the third row 53.

[0090] Furthermore, Conventional Example 2 and Comparative Example 2 have six rows of bead wires 51 in the first layer, and the pneumatic tire 1 of Conventional Example 2 has bead cores 50 arranged in the bead portions 40 configured in the form shown in Fig. 17, while the pneumatic tire 1 of Comparative Example 2 has bead cores 50 arranged in the bead portions 40 configured in the form shown in Fig. 18. Furthermore, Conventional Example 3 and Comparative Example 3 have seven rows of bead wires 51 in the first layer, and the pneumatic tire 1 of Conventional Example 3 has bead cores 50 arranged in the bead portions 40 configured in the form shown in Fig. 19, while the pneumatic tire 1 of Comparative Example 3 has bead cores 50 arranged in the bead portions 40 configured in the form shown in Fig. 20.

[0091] Furthermore, Conventional Example 4 and Comparative Example 4 have four rows of bead wires 51 in the first layer, and the pneumatic tire 1 of Conventional Example 4 has bead cores 50 arranged in the bead portions 40 configured in the form shown in Fig. 21, while the pneumatic tire 1 of Comparative Example 4 has bead cores 50 arranged in the bead portions 40 configured in the form shown in Fig. 22. Furthermore, Conventional Example 5 and Comparative Example 5 have three rows of bead wires 51 in the first layer, and the pneumatic tire 1 of Conventional Example 5 has bead cores 50 arranged in the bead portions 40 configured in the form shown in Fig. 23, while the pneumatic tire 1 of Comparative Example 5 has bead cores 50 arranged in the bead portions 40 configured in the form shown in Fig. 24.

[0092] In contrast to these, in Examples 1 to 10, which are examples of the pneumatic tire 1 according to the present invention, the first winding portion 55a of the bead wire 51 is located in the second row 53b in the first layer 52a, and the second winding portion 55b is located in the first row 53a in the first layer 52a. Furthermore, the pneumatic tires 1 according to Examples 1 to 10 are different from each other in the row 53 in which the final winding portion 55z of the bead wire 51 is arranged and the number of rows 53 in the first layer 52a. Specifically, among Examples 1 to 10, Examples 1 and 2 have five rows 53 in the first layer 52a of the bead wire 51, Examples 3 and 4 have six rows 53 in the first layer 52a of the bead wire 51, Examples 5 and 6 have seven rows 53 in the first layer 52a of the bead wire 51, Examples 7 and 8 have four rows 53 in the first layer 52a of the bead wire 51, and Examples 9 and 10 have three rows 53 in the first layer 52a of the bead wire 51.

[0093] 15A to 15E, performance evaluation tests were conducted using these pneumatic tires 1. As a result, it was found that the pneumatic tires 1 according to Examples 1 to 10 were able to improve the results of the burst pressure test compared to Conventional Examples 1 to 5 and Comparative Examples 1 to 5, which have the same number of rows 53 in the first layer 52a. In other words, the pneumatic tires 1 according to Examples 1 to 10 are less likely to damage the carcass layer 10 and bead cores 50 located in the bead portion 40 than the conventional examples and comparative examples, and the durability of the bead portion 40 can be improved.

[0094] The present disclosure encompasses the following inventions. Invention[1] a pair of bead portions disposed on both sides of the tire equatorial plane in the tire width direction; a bead core disposed in the bead portion and formed by winding a bead wire in a ring shape; Equipped with The bead core has a layer formed by arranging a plurality of winding portions of the bead wire, which is formed by winding the bead wire in a ring shape, in the tire width direction, and a row formed by arranging a plurality of winding portions in the tire radial direction, the bead core has a plurality of layers and a plurality of rows, the layers being stacked in the tire radial direction, and the rows being aligned in the tire width direction, so that the bead wires are arranged in a lattice pattern in a tire meridian cross section, Among the plurality of layers, three layers from the layer located innermost in the tire radial direction toward the outer side in the tire radial direction are designated as a first layer, a second layer, and a third layer, respectively; Among the plurality of rows, three rows from the row located innermost in the tire width direction toward the outer side in the tire width direction are designated as a first row, a second row, and a third row, respectively; When the first to sixth winding portions of the winding portion of the bead wire are designated as a first winding portion, a second winding portion, a third winding portion, a fourth winding portion, a fifth winding portion, and a sixth winding portion, respectively, the first winding portion is located in the second row in the first layer, the second winding portion is located in the first row in the first layer, the third winding portion is located in the first row in the second layer, the fourth winding portion is located in the first row in the third layer, the fifth winding portion is located in the second row in the second layer, The pneumatic tire is characterized in that the sixth winding portion is located in the third row of the first layer. Invention[2] The pneumatic tire according to the invention [1], wherein the final turn of the bead wire in the turn portion of the bead core is arranged at a position other than the first row. Invention[3] The pneumatic tire according to invention [2], wherein the final turn of the bead core is arranged in the row located outermost in the tire width direction in the layer located outermost in the tire radial direction among the plurality of layers. Invention[4] The pneumatic tire according to any one of the inventions [1] to [3], wherein the number of rows in the first layer of the bead core is four or more. Invention[5] The pneumatic tire according to any one of the inventions [1] to [4], wherein the number of rows in the first layer of the bead core is six or less. Invention[6] a pair of bead portions disposed on both sides of the tire equatorial plane in the tire width direction; a bead core disposed in the bead portion and formed by winding a bead wire in a ring shape; A method for manufacturing a pneumatic tire comprising: The bead core is configured such that a layer is formed by arranging a plurality of winding portions of the bead wire wound in a ring shape in the tire width direction, and a row is formed by arranging a plurality of winding portions of the bead wire in the tire radial direction, and the bead wire is arranged in a lattice pattern in the tire meridian cross section by stacking a plurality of the layers in the tire radial direction and arranging a plurality of the rows in the tire width direction, Among the plurality of layers, three layers from the layer located innermost in the tire radial direction toward the outer side in the tire radial direction are designated as a first layer, a second layer, and a third layer, respectively; Among the plurality of rows, three rows from the row located innermost in the tire width direction toward the outer side in the tire width direction are designated as a first row, a second row, and a third row, respectively; When the first to sixth winding portions of the winding portion of the bead wire are designated as a first winding portion, a second winding portion, a third winding portion, a fourth winding portion, a fifth winding portion, and a sixth winding portion, respectively, the first winding portion is positioned in the second row in the first layer, the second winding portion is positioned in the first row in the first layer, the third winding portion is positioned in the first row in the second layer, the fourth winding portion is positioned in the first row in the third layer, the fifth winding portion is positioned in the second row in the second layer, a sixth winding portion positioned in the third row of the first layer; [Explanation of symbols]

[0095] 1 pneumatic tire 2 Tread section 3 Tread contact surface 4 Tread rubber 5 Shoulder section 8 Sidewall 10 Carcass layer 10a Carcass main body 10b Turn-up section 14 Belt Layer 141, 142 Belt 143 Belt cover 16 Inner liner 17 Rim cushion rubber 18 Tire inner surface 20 Land 30 Circumferential groove 40 Bead section 41 Bead base part 42 Bead Toe 43 Bead Heel 45 Bead Filler 50 bead core 51 Bead wire 52 layers 52a 1st layer 52b 2nd layer 52c 3rd layer 53 columns 53a 1st row 53b 2nd row 53c 3rd row 55a 1st lap 55b 2nd lap section 55c 3rd lap 55d 4th lap 55e 5th lap 55f 6th lap 55z Final lap 80 Ring 81 Inner circumference 81a Recess 82 Side wall

Claims

1. a pair of bead portions disposed on both sides of the tire equatorial plane in the tire width direction; a bead core disposed in the bead portion and formed by winding a bead wire in a ring shape; Equipped with The bead core has a layer formed by arranging a plurality of winding portions of the bead wire, which is formed by winding the bead wire in a ring shape, in the tire width direction, and a row formed by arranging a plurality of winding portions in the tire radial direction, the bead core has a plurality of layers and a plurality of rows, the layers being stacked in the tire radial direction, and the rows being aligned in the tire width direction, so that the bead wires are arranged in a lattice pattern in a tire meridian cross section, Among the plurality of layers, three layers from the layer located innermost in the tire radial direction toward the outer side in the tire radial direction are designated as a first layer, a second layer, and a third layer, respectively; Among the plurality of rows, three rows from the row located innermost in the tire width direction toward the outer side in the tire width direction are designated as a first row, a second row, and a third row, respectively; When the first to sixth winding portions of the winding portion of the bead wire are designated as a first winding portion, a second winding portion, a third winding portion, a fourth winding portion, a fifth winding portion, and a sixth winding portion, respectively, the first winding portion is located in the second row in the first layer, the second winding portion is located in the first row in the first layer, the third winding portion is located in the first row in the second layer, the fourth winding portion is located in the first row in the third layer, the fifth winding portion is located in the second row in the second layer, The pneumatic tire is characterized in that the sixth winding portion is located in the third row of the first layer.

2. The pneumatic tire according to claim 1 , wherein the final turn of the bead wire in the turn portion of the bead core is disposed at a position other than the first row.

3. 3. The pneumatic tire according to claim 2, wherein the final turn portion of the bead core is disposed in the row located outermost in the tire width direction in the layer located outermost in the tire radial direction among the plurality of layers.

4. The pneumatic tire according to claim 1 or 2, wherein the number of rows in the first layer of the bead core is four or more.

5. The pneumatic tire according to claim 4 , wherein the number of rows in the first layer of the bead core is six or less.

6. a pair of bead portions disposed on both sides of the tire equatorial plane in the tire width direction; a bead core disposed in the bead portion and formed by winding a bead wire in a ring shape; A method for manufacturing a pneumatic tire comprising: The bead core is configured such that a layer is formed by arranging a plurality of winding portions of the bead wire wound in a ring shape in the tire width direction, and a row is formed by arranging a plurality of winding portions of the bead wire in the tire radial direction, and the bead wire is arranged in a lattice pattern in the tire meridian cross section by stacking a plurality of the layers in the tire radial direction and arranging a plurality of the rows in the tire width direction, Among the plurality of layers, three layers from the layer located innermost in the tire radial direction toward the outer side in the tire radial direction are designated as a first layer, a second layer, and a third layer, respectively; Among the plurality of rows, three rows from the row located innermost in the tire width direction toward the outer side in the tire width direction are designated as a first row, a second row, and a third row, respectively; When the first to sixth winding portions of the winding portion of the bead wire are designated as a first winding portion, a second winding portion, a third winding portion, a fourth winding portion, a fifth winding portion, and a sixth winding portion, respectively, the first winding portion is positioned in the second row in the first layer, the second winding portion is positioned in the first row in the first layer, the third winding portion is positioned in the first row in the second layer, the fourth winding portion is positioned in the first row in the third layer, the fifth winding portion is positioned in the second row in the second layer, The method for manufacturing a pneumatic tire, wherein the sixth winding portion is positioned in the third row in the first layer.

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