tire

Abstract

To provide a tire that can improve belt edge separation resistance while maintaining the productivity of retreaded tires. [Solution] The tread portion 2 is provided with a belt layer 14 having a plurality of belts 141, 142 on the radially outer side of the carcass layer 13 in the tire. The belt layer 14 consists of a first belt 141, which has the largest width in the tire width direction among the plurality of belts 141, 142, and a second belt 142 adjacent to the radially outer side of the first belt 141, which are a pair of cross belts 141, 142 whose inclination direction of the belt cords 14a is opposite to that of each other. A cushion rubber 15 is placed between the first belt end 141a and the second belt end 142a, and the relationship between the distance A between the second belt 142 and the first belt 141 at the position of the second belt end 142a and the cord diameter g2 of the belt cord 14a of the second belt 142 satisfies 1.5 ≤ A / g2 ≤ 5.

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] A tire has a belt layer as a reinforcing layer in a tread portion. The tread portion is enhanced in rigidity by the belt layer, and in conventional tires, the performance is improved by devising the belt layer. For example, the pneumatic tire described in Patent Document 1 provides a belt edge cushion between the outer end portion in the tire width direction of the second belt disposed second from the outside in the tire radial direction and the outer end portion in the tire width direction of the third belt disposed third from the outside in the tire radial direction, curves the second belt inward in the tire radial direction in the region in the tire width direction of the belt edge cushion, and provides the outer end in the tire width direction of the first belt disposed first from the outside in the tire radial direction at a position in the vicinity in the tire width direction with respect to the inner end in the tire width direction of the belt edge cushion.

[0003] Further, the pneumatic tire described in Patent Document 2 disposes edge rubber having a wedge portion whose thickness gradually decreases toward the tip and a sheet portion having a substantially uniform thickness extending inward in the tire width direction from the tip of the wedge portion between the ends of the first and second belt layers, and sets the distance between the cords in the tire radial direction of the first and second belt layers to be 0.5 times or more the position of the tip of the edge rubber or a position in the vicinity thereof at the tire equatorial plane position. Also, the pneumatic tire described in Patent Document 3 has the first belt layer and the second belt layer each formed by juxtaposing bundles of 5 to 7 monofilament cords in the belt width direction and embedding them in coating rubber, and the gauge of the rubber layer between the monofilament cords of the first belt layer and the second belt layer at the end of the second belt layer is 1.3 to 3.0 times the gauge at the center of the tire, and belt layer intermediate rubber is disposed between the first belt layer and the second belt layer at the end of the second belt.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Patent No. 5278328 [Patent Document 2] Patent No. 4279018 Publication [Patent Document 3] Japanese Patent Publication No. 2007-302203 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] In recent years, there has been growing interest in so-called retreaded tires, which allow for the reuse of tires by replacing the tread rubber when the tread reaches the end of its service life due to the groove depth of the grooves forming in the tread becoming shallower than a predetermined depth. With retreaded tires, if there are defects in parts other than the tread rubber, the tire cannot be used as a retreaded tire. Therefore, it is important to ensure that no defects occur in parts other than the tread even when the tread reaches the end of its service life.

[0006] For example, if a so-called belt edge separation occurs, where the belt layer and the surrounding rubber material separate near the end of the belt layer in the tire width direction, the tire cannot be used as a retreaded tire. To suppress belt edge separation, one possible solution is to place cushioning rubber near the end of the belt between the stacked belts to alleviate the strain between the surrounding rubber material and the belt.

[0007] However, if cushioning rubber is placed between belts near the ends, the ends of belts positioned on the outer side in the tire's radial direction tend to curve upwards in that direction. When the ends of the belts curve upwards in the tire's radial direction, there is a risk of damaging the curved portion of the belt when removing the tread rubber in order to replace the tread rubber in a retreaded tire. If the belt is damaged, the tire cannot be used as a retreaded tire, which can easily reduce the productivity of retreaded tires. For this reason, it has been difficult to achieve both belt edge separation resistance and retreaded tire productivity.

[0008] The present invention has been made in view of the above, and aims to provide a tire that can improve belt edge separation resistance while maintaining the productivity of retreaded tires. [Means for solving the problem]

[0009] To solve the above-mentioned problems and achieve the objective, the tire according to the present invention is characterized in that a belt layer having a plurality of belts made of steel cords is provided on the radially outer side of the carcass layer in the tread portion, and the belt layer is a pair of cross belts in which the inclination direction of the belt cords of the first belt and the belt cords of the second belt are opposite to each other in the tire width direction with respect to the tire circumferential direction, the first belt having the largest width in the tire width direction and the second belt adjacent to the radially outer side of the first belt, a cushion rubber is provided between the first belt end, which is the end of the first belt in the tire width direction and the second belt end, which is the end of the second belt, and the relationship between the distance A between the second belt and the first belt at the position of the second belt end and the cord diameter g2 of the belt cord of the second belt satisfies 1.5 ≤ A / g2 ≤ 5. [Effects of the Invention]

[0010] The tire according to the present invention has the effect of improving belt edge separation resistance while maintaining the productivity of retreaded tires. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a meridional cross-sectional view of a tire showing the main parts of a pneumatic tire according to an embodiment. [Figure 2] Figure 2 is a detailed view of one side of the tread portion shown in Figure 1, from the tire equatorial plane in the tire width direction. [Figure 3] Figure 3 is a detailed view of the area near the end of the belt layer shown in Figure 2 in the tire width direction. [Figure 4] Figure 4 is an explanatory diagram of the cord diameter of the belt cords of the first belt and the second belt shown in Figure 3. [Figure 5] Figure 5 is a detailed view of the area near the end of the belt layer in the tire width direction shown in Figure 2, and is an explanatory diagram of how the first belt and the second belt are separated. [Figure 6] Figure 6 is a detailed view of the area near the end of the belt layer shown in Figure 2 in the tire width direction, and is an explanatory diagram of the amount of outward protrusion of the first belt in the tire width direction relative to the second belt. [Figure 7] Figure 7 is an explanatory diagram showing the relationship between the belt layer and the carcass layer shown in Figure 1. [Figure 8] Figure 8 is a detailed view of the tread section shown in Figure 1, and is an explanatory diagram regarding the thickness of the tread section. [Figure 9] Figure 9 is an explanatory diagram about the retreading of pneumatic tires. [Figure 10A] Figure 10A is a chart showing the results of performance evaluation tests for pneumatic tires. [Figure 10B] Figure 10B is a chart showing the results of performance evaluation tests for pneumatic tires. [Modes for carrying out the invention]

[0012] Hereinafter, embodiments of the present invention will be described in detail based on the drawings. Note that the present invention is not limited by these embodiments. Also, the components of this embodiment include those that can be replaced and whose replacement is obvious while maintaining the identity of the invention. Further, a plurality of modifications described in this embodiment can be arbitrarily combined within the scope obvious to those skilled in the art.

[0013] [Embodiment] In the following description, as an example of a tire according to the present invention, a pneumatic tire 1 will be described. The pneumatic tire 1, which is an example of a tire, can be filled with air, an inert gas such as nitrogen, and other gases.

[0014] Also, in the following description, the tire radial direction refers to the direction orthogonal to the tire rotation axis (not shown) which is the rotation axis of the pneumatic tire 1 of the embodiment, the inner side in the tire radial direction refers to the side facing the tire rotation axis in the tire radial direction, and the outer side in the tire radial direction refers to the side away from the tire rotation axis in the tire radial direction. Also, the tire circumferential direction refers to the circumferential direction around the tire rotation axis as the central axis. Also, the tire width direction refers to the direction parallel to the tire rotation axis, the inner side in the tire width direction refers to the side facing the tire equatorial plane (tire equator line) CL in the tire width direction, and the outer side in the tire width direction 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 orthogonal to the tire rotation axis and passes through the center of the tire width of the pneumatic tire 1, and the tire equatorial plane CL coincides with the tire width direction center line which is the central position in the tire width direction of the pneumatic tire 1. The tire equator line refers to a line on the tire equatorial plane CL and along the tire circumferential direction of the pneumatic tire 1. Also, the cross-section in the tire meridian direction (meridian cross-sectional view) refers to the cross-section when the tire is cut by a plane including the tire rotation axis.

[0015] FIG. 1 is a tire meridian cross-sectional view showing a main part of the pneumatic tire 1 according to the embodiment. In FIG. 1, it is a meridian cross-section of the pneumatic tire 1 according to the embodiment, showing a cross-section of one side region of the tire rotation axis in the tire radial direction. In the present embodiment, as an example, a pneumatic radial tire for a light truck will be described.

[0016] In the pneumatic tire 1 according to the present embodiment, when viewed in the tire meridian cross-section, the tread portion 2 is disposed at the outermost portion in the tire radial direction. The tread portion 2 has a tread rubber 4 made of a rubber composition. Further, the surface of the tread portion 2, that is, the portion that contacts the road surface when the vehicle (not shown) equipped with the pneumatic tire 1 travels, is formed as a tread contact surface 3, and the tread contact surface 3 constitutes a part of the contour of the pneumatic tire 1.

[0017] Shoulder portions 5 are located at both outer ends of the tread portion 2 in the tire width direction. A sidewall portion 8 is disposed on the inner side in the tire radial direction of the shoulder portion 5. That is, the sidewall portion 8 is disposed on both sides in the tire width direction of the tread portion 2. In other words, the sidewall portion 8 is disposed at two positions on both sides in the tire width direction of the pneumatic tire 1, forming the outermost exposed portion in the tire width direction of the pneumatic tire 1. The sidewall portion 8 has a sidewall rubber 9 made of a rubber composition.

[0018] Bead portions 10 are provided on the inner side in the tire radial direction of the respective sidewall portions 8 located on both sides in the tire width direction. Similar to the sidewall portion 8, the bead portions 10 are disposed at two positions on both sides of the tire equatorial plane CL. That is, a pair of bead portions 10 are disposed on both sides in the tire width direction of the tire equatorial plane CL. A bead core 11 is disposed in each bead portion 10, and a bead filler 12 is disposed on the outer side in the tire radial direction of the bead core 11.

[0019] The bead core 11 is an annular member formed by bundling steel wires, which are bead wires, and winding them in a ring shape and multiple times. The bead filler 12 is made of a rubber composition and is positioned on the radially outer side of the bead core 11 to reinforce the bead portion 10.

[0020] A carcass layer 13 containing the cords of radial ply is continuously provided on the inner side of the tread portion 2 in the tire radial direction and on the tire equatorial plane CL side of the sidewall portion 8. Therefore, the pneumatic tire 1 according to this embodiment is configured as a so-called radial tire. The carcass layer 13 has a single-layer structure consisting of one carcass ply or a multi-layer structure consisting of multiple carcass ply stacked together, and is toroidally stretched between a pair of bead portions 10 arranged on both sides in the tire width direction to form the tire's skeleton. In the pneumatic tire 1 according to this embodiment, the carcass layer 13 consists of two carcass ply 131 and 132. The two carcass ply 131 and 132 are each arranged between a pair of bead portions 10 located on both sides in the tire width direction.

[0021] Of the two carcass plies 131 and 132, the carcass ply 131 located on the inner side of the tire cavity is wrapped around the bead core 11 and bead filler 12 in the bead portion 10, from the inside in the tire width direction of the bead core 11 to the outside in the tire width direction along the bead core 11. Of the two carcass plies 131 and 132, the carcass ply 132 located on the outer side of the tire is positioned on the outside in the tire width direction of the bead core 11 and bead filler 12 in the bead portion 10, and covers the portion of the carcass ply 131 located on the inner side of the tire cavity that is wrapped around the bead core 11 to the outside in the tire width direction. Furthermore, the carcass plies 131 and 132 of the carcass layer 13 are constructed by covering multiple carcass cords made of steel or organic fibers with a coating rubber and then rolling them. The carcass cords constituting the carcass plies 131 and 132 are arranged at an inclination with respect to the tire circumferential direction. Specifically, the angle of the carcass cords relative to the circumferential direction of the tire is within the range of 80 degrees to 90 degrees in absolute value.

[0022] A belt layer 14 is arranged on the tread portion 2. The belt layer 14 is located on the radially outer side of the portion of the carcass layer 13 that spans between a pair of bead portions 10, specifically the portion located on the tread portion 2. The belt layer 14 is made up of multiple belts 141, 142, and belt covers 143 and belt edge covers 144 that are arranged on the radially outer side of the multiple belts 141, 142, and is wrapped around the outer circumference of the carcass layer 13.

[0023] On the side of the bead portion 10 opposite to the side where the bead core 11 is located in the thickness direction of the carcass layer 13, a rim cushion rubber 17 is arranged, which constitutes the contact surface of the bead portion 10 with respect to the rim flange. The rim cushion rubber 17 is arranged along the carcass layer 13, from the inner side in the tire radial direction to the outer side in the tire width direction of the bead core 11.

[0024] Furthermore, an inner liner 16 is positioned along the carcass layer 13, either on the inside of the carcass layer 13 or on the inner lumen side of the carcass layer 13 in the pneumatic tire 1. The inner liner 16 forms the inner surface 18 of the tire, which is the inner surface of the pneumatic tire 1.

[0025] Figure 2 is a detailed view showing one side of the tread portion 2 shown in Figure 1, in the tire width direction from the tire equatorial plane CL. In this embodiment, the belt layer 14 arranged in the tread portion 2 has two layers of belts 141 and 142. Of the two layers of belts 141 and 142, the belt with the largest width in the tire width direction is the first belt 141, and the first belt 141 is the belt that is positioned furthest inward in the tire radial direction within the belt layer 14. Of the multiple belts 141 and 142, the belt adjacent to the outer side of the first belt 141 in the tire radial direction is provided as the second belt 142, and the second belt 142 has a smaller width in the tire width direction than the first belt 141.

[0026] Furthermore, the second belt 142 is positioned adjacent to the first belt 141 in the radial direction of the tire at most of its positions near the center in the tire width direction, and is spaced apart from the first belt 141 in the radial direction of the tire at positions near both ends in the tire width direction.

[0027] Furthermore, the belt cover 143 and belt edge cover 144 of the belt layer 14 are constructed by covering a belt cover cord made of organic fiber material with a coating rubber. The belt cover 143 is positioned adjacent to the second belt 142 on the outer side in the tire radial direction of the second belt 142, and is positioned over the entire width of the first belt 141 and the second belt 142 in the tire width direction.

[0028] The belt edge covers 144 are positioned near the ends of the first belt 141 and the second belt 142 in the tire width direction, respectively, and cover the ends of the first belt 141 and the second belt 142 in the tire width direction. The belt edge covers 144 are positioned adjacent to the belt cover 143 on the inner side in the tire radial direction. That is, the belt edge covers 144 cover the ends of the first belt 141 and the second belt 142 in the tire width direction at a position on the inner side of the belt cover 143 in the tire radial direction.

[0029] More specifically, the belt cover 143 and the belt edge cover 144 extend inward in the tire radial direction from the position of the second belt 142 on the outer side in the tire radial direction to the position of the second belt end 142a, which is the end of the second belt 142 in the tire width direction, and are positioned on the outer side in the tire width direction of the first belt end 141a and the second belt end 142a, covering the first belt end 141a and the second belt end 142a, which are the ends of the first belt 141 in the tire width direction.

[0030] The belt cover 143 and the belt edge cover 144 are positioned in such a way that they protrude from the first belt end 141a toward the opposite side of where the second belt end 142a is located. The amount of protrusion W4 of the belt cover 143 and the belt edge cover 144 toward the opposite side of where the second belt end 142a is located is within the range of 0.5 mm ≤ W4 ≤ 5.0 mm.

[0031] The amount of protrusion W4 from the first belt end 141a of the belt cover 143 and belt edge cover 144 is measured at the meridional cross-section of the tire in an unloaded state with the tire mounted on the specified rim and filled to the specified internal pressure. The same applies to other dimensions described herein unless otherwise specified. The specified rim refers to the "standard rim" as defined by JATMA, the "Design Rim" as defined by TRA, or the "MEASURING RIM" as defined by ETRTO. The specified internal pressure refers to the "maximum air pressure" as defined by JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" as defined by TRA, or the "INFLATION PRESSURES" as defined by ETRTO. Furthermore, the specified load refers to the "maximum load capacity" specified by JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or the "LOAD CAPACITY" specified by ETRTO.

[0032] The belt cover 143 and belt edge cover 144, arranged in this manner, have a cord angle such that the belt cover cords are aligned with the circumferential direction of the tire. The belt cover 143 and belt edge cover 144 are constructed, for example, by wrapping a strip material, which consists of one or more belt cover cords covered with coated rubber, around the outer surface of the second belt 142 multiple times in a spiral manner in the circumferential direction of the tire.

[0033] Furthermore, the first belt 141 and the second belt 142, which are stacked in the tire diameter direction, are separated in the tire diameter direction near both ends in the tire width direction, and cushion rubber 15 is placed between the separated portions of the first belt 141 and the second belt 142 near both ends in the tire width direction. In other words, cushion rubber 15 is placed between the first belt end 141a, which is the end of the first belt 141, and the second belt end 142a, which is the end of the second belt 142.

[0034] More specifically, the first belt 141 and the second belt 142 are spaced radially apart from predetermined positions on the inside of the tire width direction compared to the first belt end 141a and the second belt end 142a. The belt cover 143 and the belt edge cover 144 extend radially inward from the position on the outside of the second belt 142a in the tire width direction, and are positioned on the outside of the first belt end 141a and the second belt end 142a in the tire width direction, covering the first belt end 141a and the second belt end 142a.

[0035] The cushion rubber 15 is positioned in the portion of the first belt 141 and second belt 142 that is separated in the tire diameter direction near both ends in the tire width direction, and in the portion demarcated by the belt cover 143 and belt edge cover 144. As a result, the cushion rubber 15 is positioned between the first belt 141 and the second belt 142 near both ends in the tire width direction.

[0036] Figure 3 is a detailed view of the area near the end of the belt layer 14 in the tire width direction, as shown in Figure 2. The first belt 141 and the second belt 142 of the belt layer 14 are each constructed by covering multiple belt cords 14a made of steel cord with cord-covered rubber 14b and then rolling them. The first belt 141 and the second belt 142 are a pair of cross belts 141 and 142, where the inclination direction of the belt cords 14a of the first belt 141 and the inclination direction of the belt cords 14a of the second belt 142 are opposite to each other in the tire width direction relative to the tire circumferential direction. In other words, the first belt 141 and the second belt 142 have a so-called cross-ply structure in which the belt cords 14a have cord angles with opposite signs relative to the tire circumferential direction and are stacked in a cross-ply configuration.

[0037] Furthermore, the inclination angle of the belt cord 14a of the first belt 141 in the tire width direction with respect to the tire circumferential direction is within the range of 15° to 30°, and preferably within the range of 16° to 26°. Also, the inclination angle of the belt cord 14a of the second belt 142, which is inclined in the opposite direction to the inclination direction of the belt cord 14a of the first belt 141, in the tire width direction with respect to the tire circumferential direction is also within the range of 15° to 30°, and preferably within the range of 16° to 26°.

[0038] Furthermore, the cushion rubber 15 positioned between the first belt 141 and the second belt 142 has a modulus at 100% elongation that is within the range of 65% to 90% of the modulus of the cord-covered rubber 14b of the belt layer 14 at 100% elongation. The modulus referred to here is measured by a tensile test at a temperature of 20°C using a dumbbell-shaped test piece in accordance with JIS K6251 (using a No. 3 dumbbell).

[0039] The first belt 141 and the second belt 142, which are separated in the tire diameter direction near both ends in the tire width direction, satisfy the relationship between the distance A between the second belt 142 and the first belt 141 at the position of the second belt end 142a and the cord diameter g2 of the belt cord 14a of the second belt 142, which is 1.5 ≤ A / g2 ≤ 5.

[0040] In this case, distance A is the distance in the tire meridional cross-section, and the same applies to all distances and lengths in the following explanation. Furthermore, distance A in this case is the distance between the belt cord 14a of the second belt 142 that is located closest to the second belt end 142a, and the tangent line 14c that is in contact with the portion of the multiple belt cords 14a of the first belt 141 that are arranged in the tire width direction and are on the second belt 142 side. That is, distance A is the distance along a perpendicular line drawn from the portion of the belt cord 14a of the second belt 142 that is located closest to the second belt end 142a on the first belt 141 side to the tangent line 14c of the multiple belt cords 14a of the first belt 141.

[0041] Furthermore, it is preferable that the relationship between the distance A between the second belt 142 and the first belt 141 at the position of the second belt end 142a and the cord diameter g2 of the belt cord 14a of the second belt 142 satisfies 1.5 ≤ A / g2 ≤ 3.

[0042] Furthermore, the first belt 141 and the second belt 142 use belt cords 14a of substantially the same size. For this reason, the distance A between the second belt 142 and the first belt 141 at the position of the second belt end 142a is within the range of 1.5 ≤ A / g1 ≤ 5 with respect to the cord diameter g1 of the belt cord 14a of the first belt 141, and preferably within the range of 1.5 ≤ A / g1 ≤ 3. In addition, in a configuration in which the belt cord 14a consists of multiple twisted cords, the diameter of the circumscribed circle of the belt cord 14a is measured as the cord diameter of the belt cord 14a.

[0043] Here, the belt cords 14a of the first belt 141 and the second belt 142 may have a flattened cross-sectional shape when the belt cords 14a are cut in a direction perpendicular to the extending direction of the belt cords 14a.

[0044] Figure 4 is an explanatory diagram of the cord diameter of the belt cords 14a of the first belt 141 and the second belt 142 shown in Figure 3. Figure 4(a) is an explanatory diagram of the cord diameter of the belt cords 14a of the first belt 141, and Figure 4(b) is an explanatory diagram of the cord diameter of the belt cords 14a of the second belt 142. When the belt cords 14a of the first belt 141 are formed in a flattened shape, if the minor axis of the flattened shape of the belt cords 14a of the first belt 141 is g1 and the major axis is h1, it is preferable that the ratio of the minor axis g1 to the major axis h1 of the belt cords 14a of the first belt 141 is within the range of 0.5 ≤ g1 / h1 ≤ 1. Similarly, when the belt cord 14a of the second belt 142 is formed in a flattened shape, and the minor axis of the flattened shape of the belt cord 14a of the second belt 142 is g2 and the major axis is h2, it is preferable that the ratio of the minor axis g2 to the major axis h2 of the belt cord 14a of the second belt 142 is within the range of 0.5 ≤ g2 / h2 ≤ 1.

[0045] If the belt cords 14a of the first belt 141 and the second belt 142 are formed in a flattened shape, the belt cords 14a are arranged such that their minor axes g1 and g2 are aligned with the thickness direction of the first belt 141 and the second belt 142, and their major axes h1 and h2 are aligned with the width direction of the first belt 141 and the second belt 142.

[0046] Furthermore, if the belt cords 14a of the first belt 141 and the second belt 142 are formed in a flattened shape, the distance A between the second belt 142 and the first belt 141 at the position of the second belt end 142a is formed within the range of 1.5 ≤ A / g1 ≤ 5 and 1.5 ≤ A / g2 ≤ 5 with respect to the minor diameters g1 and g2 of the belt cords 14a of the first belt 141 and the second belt 142.

[0047] Figure 5 is a detailed view of the area near the end of the belt layer 14 in the tire width direction, as shown in Figure 2, and is an explanatory diagram of how the first belt 141 and the second belt 142 are separated. The second belt 142 is separated radially outward from the first belt 141 by the outer portion in the tire width direction from the separation portion 142b, which is located inward in the tire width direction from the second belt end 142a. The separation portion 142b is the boundary between the portion of the second belt 142 that contacts the first belt 141 in the tire radial direction and the portion that separates it in the tire radial direction. That is, the second belt 142 is in contact with the first belt 141 in the tire width direction inward from the separation portion 142b, and separates radially outward from the first belt 141 in the tire radial direction outward from the separation portion 142b.

[0048] In the first belt 141 and second belt 142 formed in this manner, when the distance A on the first belt 141 is measured between the measuring section 141b and the separation section 142b, and W2 is the distance between the measuring section 141b and the separation section 142b, the relationship between the distance B between the first belt 141 and the second belt 142 at a position where W2 / 2 is the distance from the measuring section 141b toward the separation section 142b satisfies 0.4 ≤ B / A ≤ 1.0.

[0049] In this case, the measuring section 141b is located on the tangent line 14c that contacts the portion of the multiple belt cords 14a of the first belt 141 that is on the second belt 142 side. Furthermore, the distance B between the first belt 141 and the second belt 142 is the shortest distance between the portion of the multiple belt cords 14a of the first belt 141 that is W2 / 2 toward the side where the separation section 142b is located from the measuring section 141b, and the tangent line 14c that contacts the portion of the multiple belt cords 14a of the second belt 142 that is on the first belt 141 side.

[0050] Furthermore, it is preferable that the distance B defined in this manner and the distance A mentioned above are within the range of 0.5 ≤ B / A ≤ 0.8.

[0051] FIG. 6 is a detailed view near the end in the tire width direction of the belt layer 14 shown in FIG. 2, and is an explanatory view of the amount of protrusion of the first belt 141 outward in the tire width direction with respect to the second belt 142. The first belt 141 and the second belt 142 are such that the distance W1 between the first belt end 141a and the second belt end 142a in the direction along the first belt 141 in the tire meridian section is within the range of 0 mm < W1 ≦ 18 mm.

[0052] In this case, the distance W1 is the distance between the tangent lines 14d that are tangent to the belt cords 14a and are perpendicular to the extending direction of the first belt in the tire meridian section from the outside in the tire width direction, with respect to the belt cord 14a that is arranged at the position closest to the first belt end 141a among the belt cords 14a of the first belt 141 and the belt cord 14a that is arranged at the position closest to the second belt end of the second belt 142.

[0053] The first belt 141 and the second belt 142 are such that at both ends in the tire width direction, the distance W1 is within the range of 0 mm < W1 ≦ 18 mm. Also, the distance W1 is preferably within the range of 2 mm ≦ W1 ≦ 13 mm. ​​​​​​Figure 7 is an explanatory diagram showing the relationship between the belt layer 14 and the carcass layer 13 shown in Figure 1. The relationship between the belt layer 14 and the carcass layer 13 is such that the relationship between the width Wb1 of the first belt 141 in the tire width direction and the maximum cross-sectional width Wt of the carcass layer 13 in the tire width direction is within the range of 0.5 ≤ Wb1 / Wt ≤ 1. In this embodiment, since the carcass layer 13 is made up of a carcass ply 131 located on the inner side of the tire and a carcass ply 132 located on the outer side of the tire, the maximum cross-sectional width Wt of the carcass layer 13 in the tire width direction is equal to the maximum cross-sectional width Wt of the carcass ply 132 located on the outer side of the tire.

[0056] Furthermore, it is preferable that the relationship between the width Wb1 of the first belt 141 in the tire width direction and the maximum cross-sectional width Wt of the carcass layer 13 in the tire width direction is within the range of 0.6 ≤ Wb1 / Wt ≤ 0.95.

[0057] Figure 8 is a detailed view of the tread portion 2 shown in Figure 1, and is an explanatory diagram of the thickness of the tread portion 2. The tread portion 2 has multiple circumferential main grooves 20 that extend in the circumferential direction of the tire. The tread portion 2 also has multiple land portions 30 that are partitioned by the multiple circumferential main grooves 20. The circumferential main grooves 20 here are longitudinal grooves that extend in the circumferential direction of the tire and have wear indicators (slip signs) inside that indicate the end of wear.

[0058] In this embodiment, there are three circumferential main grooves 20, one center main groove 21 located on the tire equatorial plane CL, and two shoulder main grooves 22 located on both sides of the center main groove 21 in the tire width direction.

[0059] Furthermore, the land area 30, which is partitioned by the circumferential main grooves 20, has a center land area 31 and a shoulder land area 32. The center land area 31 is located between adjacent center main grooves 21 and shoulder main grooves 22 and is part of the land area 30 partitioned by the center main grooves 21 and shoulder main grooves 22. The shoulder land area 32 is located on the outside of the shoulder main grooves 22 in the tire width direction and is part of the land area 30 whose inside in the tire width direction is partitioned by the shoulder main grooves 22.

[0060] In the tread portion 2, among the multiple land portions 30 partitioned by the circumferential main groove 20, the relationship between the thickness Ga from the tread contact surface 3 at the center in the tire width direction of the land portion 30 closest to the tire equatorial plane CL, to the outermost belt in the tire radial direction in the belt layer 14, and the thickness Gb from the tread contact surface 3 at the position of the second belt end 142a to the outermost belt in the tire radial direction in the belt layer 14, is within the range of 0.9 ≤ Ga / Gb ≤ 1.2.

[0061] In this case, the land portion 30 closest to the tire equatorial plane CL is the center land portion 31, and the belt located furthest outward in the tire radial direction in the belt layer 14 is the second belt 142. In other words, the relationship between the thickness Ga from the tread contact surface 3 at the center of the center land portion 31 in the tire width direction to the second belt 142 and the thickness Gb from the tread contact surface 3 to the second belt 142 at the second belt end 142a is within the range of 0.9 ≤ Ga / Gb ≤ 1.2.

[0062] In this case, the thicknesses Ga and Gb include the thicknesses of the belt cover 143 and the belt edge cover 144. Furthermore, the thickness Gb from the tread contact surface 3 to the second belt 142 at the position of the second belt end 142a is the thickness from the tread contact surface 3 to the second belt 142 at the position of the belt cord 14a, which is located closest to the second belt end 142a. In addition, it is preferable that the relationship between the thickness Ga from the tread contact surface 3 to the second belt 142 at the center position in the tire width direction of the center land portion 31 and the thickness Gb from the tread contact surface 3 to the second belt 142 at the position of the second belt end 142a is within the range of 0.9 ≤ Ga / Gb ≤ 1.0.

[0063] When mounting the pneumatic tire 1 according to this embodiment onto a vehicle, the pneumatic tire 1 is mounted onto a rim wheel, and then inflated by filling it with air before mounting it on the vehicle. When a vehicle equipped with the pneumatic tire 1 is driven, the pneumatic tire 1 rotates while the lower part of the tread contact surface 3 of the tread portion 2 contacts the road surface. When a vehicle equipped with the pneumatic tire 1 is driven on a dry road surface, it is driven mainly by the frictional force between the tread contact surface 3 and the road surface, which transmits driving force and braking force to the road surface and generates turning force.

[0064] Furthermore, when driving on a wet road surface, water between the tread contact surface 3 and the road surface enters grooves such as the circumferential main grooves 20, and the vehicle drives while draining the water between the tread contact surface 3 and the road surface through these grooves. As a result, the tread contact surface 3 makes contact with the road surface more easily, and the frictional force between the tread contact surface 3 and the road surface enables the vehicle to drive.

[0065] When a vehicle is in motion, the pneumatic tire 1 has its tread contact surface 3 on the road surface, and it runs using the frictional force between the tread contact surface 3 and the road surface, so the tread surface 2 gradually wears down. When the tread surface 2 wears down and reaches the end of its service life, the pneumatic tire 1 generally becomes unusable for driving a vehicle.

[0066] In contrast, the pneumatic tire 1 according to this embodiment can be used as a so-called retreaded tire, in which the tread rubber 4 can be replaced and reused when the tread portion 2 reaches the end of its service life. For example, when the tread portion 2 is worn down to the extent that the wear indicators located in the circumferential main grooves 20 are exposed, it is determined that the tread portion 2 has reached the end of its service life, and the pneumatic tire 1 is retreaded by replacing the tread rubber 4. Next, the method for retreading the pneumatic tire 1 will be described.

[0067] Figure 9 is an explanatory diagram of the retreading of a pneumatic tire 1. When retreading a pneumatic tire 1, first, the tread rubber 4 located on the tread portion 2 of the pneumatic tire 1, which has reached the end of its service life, is removed by buffing using a buffing device. The buffing is performed, for example, along a buffing section 40 set near the belt layer 14 and on the outside of the belt layer 14, as shown in Figure 9. The buffing section 40 is shaped to allow for proper buffing by a buffing device (not shown) while leaving a small amount of tread rubber 4. By performing the buffing work along the buffing section 40 in this way, a so-called basting tire (not shown) is produced, from which most of the tread rubber 4 in the tread portion 2, which has reached the end of its service life, has been removed.

[0068] After removing most of the tread rubber 4 through buffing, the tread rubber 4 is revitalized by placing new tread rubber 4 on the buffed area 40 of the base tire. Remolding or pre-cure methods are used for revitalizing the tread rubber 4. The remolding method involves attaching unvulcanized tread rubber 4 to the base tire and vulcanizing it in a mold with a pattern engraved on it. The pre-cure method involves attaching pre-vulcanized tread rubber 4 to the base tire and then vulcanizing it. By revitalizing the tread rubber 4 using these remolding or pre-cure methods, the pneumatic tire 1, which has reached the end of its service life for the tread section 2, can be reused as a revitalized tire.

[0069] Retreaded tires allow pneumatic tires 1 that have reached the end of their service life (tread portion 2) to be reused by replacing the tread rubber 4 in this manner. However, if a failure occurs in any part of the pneumatic tire 1 other than the tread rubber 4, it becomes impossible to reuse it as a retreaded tire. For example, if a failure occurs in the belt layer 14, the pneumatic tire 1 becomes impossible to reuse as a retreaded tire.

[0070] One example of a failure in the belt layer 14 is the separation of the belt near its end from the surrounding rubber material, known as belt edge separation. In other words, when the vehicle is running, both the belt layer 14 and the rubber material deform in accordance with the load acting on them, but the rigidity of the belt in the belt layer 14 and the rubber material arranged around the belt are different.

[0071] Therefore, when a load is applied to the belt layer 14 while the vehicle is in motion, the belt layer 14 and the rubber member deform in different ways in response to the load. This causes stress concentration in the portion of the rubber member adjacent to the belt layer 14, making the rubber member prone to distortion. In particular, near the ends of the belt layer 14 in the tire width direction, the rubber member is prone to significant distortion when a load is applied. This makes the rubber member more likely to separate from the end of the belt, thus making belt edge separation more likely.

[0072] In contrast, in the pneumatic tire 1 according to this embodiment, a cushion rubber 15 is placed between the first belt end 141a of the first belt 141 and the second belt end 142a of the second belt 142 of the belt layer 14. Therefore, even when a load is applied to the belt layer 14 during vehicle operation, causing deformation of the belt layer 14 and the surrounding rubber members, the cushion rubber 15 adjacent to the first belt end 141a and the second belt end 142a can follow the movement of the first belt 141 and the second belt 142. As a result, large distortions are less likely to occur in the cushion rubber 15, thus suppressing the separation of the cushion rubber 15 from the first belt end 141a and the second belt end 142a due to distortion of the cushion rubber 15, and thus suppressing belt edge separation.

[0073] Furthermore, the relationship between the first belt 141 and the second belt 142 of the belt layer 14, where A is the distance between the second belt 142 and the first belt 141 at the position of the second belt end 142a, and g2 is the cord diameter of the belt cord 14a of the second belt 142, satisfies 1.5 ≤ A / g2 ≤ 5. Therefore, it is possible to improve belt edge separation resistance while maintaining the productivity of retreaded tires. In other words, if the relationship between the distance A between the second belt 142 and the first belt 141 and g2 is A / g2 < 1.5, there is a risk that the distance A between the second belt 142 and the first belt 141 at the position of the second belt end 142a is too small. In this case, the amount of cushioning rubber 15 placed between the first belt end 141a and the second belt end 142a is reduced, making it difficult for the cushioning rubber 15 to follow the movement of the first belt 141 and the second belt 142 when a load is applied. This can easily cause significant distortion in the cushioning rubber 15, potentially making it difficult to suppress belt edge separation.

[0074] Furthermore, if the relationship between the distance A between the second belt 142 and the first belt 141 and the cord diameter g2 of the belt cord 14a of the second belt 142 is A / g2 > 5, there is a risk that the distance A between the second belt 142 and the first belt 141 at the position of the second belt end 142a is too large. In this case, the area near the second belt end 142a of the second belt 142 will be farther outward from the first belt 141 in the tire radial direction, which may easily lead to a deterioration in the productivity of retreaded tires.

[0075] In other words, if the vicinity of the second belt end 142a is significantly farther outward from the first belt 141 in the tire radial direction, the distance between the buffing portion 40, which is set on the outside of the belt layer 14 during the retreading of the pneumatic tire 1, and the second belt 142 becomes shorter. As a result, it becomes difficult to secure the necessary thickness of the original tread rubber 4 for attaching new tread rubber 4 near the second belt end 142a. In this case, there is a risk that new tread rubber 4 cannot be properly attached near the second belt end 142a during the retreading of the pneumatic tire 1. Alternatively, if the vicinity of the second belt end 142a is significantly farther outward from the first belt 141 in the tire radial direction, there is a risk that the vicinity of the second belt end 142a of the second belt 142 will be exposed from the buffing portion 40 during the buffing work during the retreading of the pneumatic tire 1. In this case, it will become impossible to attach new tread rubber 4, and there is a risk that the tire cannot be reused as a retreaded tire.

[0076] In contrast, if the relationship between the distance A between the second belt 142 and the first belt 141 and the cord diameter g2 of the belt cord 14a of the second belt 142 is within the range of 1.5 ≤ A / g2 ≤ 5, then the amount of cushion rubber 15 to be placed between the first belt end 141a and the second belt end 142a can be secured, thereby suppressing large distortion in the cushion rubber 15 when a load is applied, and thus suppressing the occurrence of belt edge separation. Furthermore, since it is possible to suppress the area near the second belt end 142a of the second belt 142 from moving far outward in the tire radial direction from the first belt 141, the second belt end 142a can be positioned radially inward at an appropriate distance from the buff portion 40 during the retreading of the pneumatic tire 1. As a result, new tread rubber 4 can be properly attached to the buff portion 40, and pneumatic tires 1 that have reached the end of their service life of the tread portion 2 can be produced as retreaded tires. As a result, it is possible to improve belt edge separation resistance while maintaining the productivity of retreaded tires.

[0077] Furthermore, if W2 is the distance between the measuring portion 141b of the first belt 141 and the separation portion 142b, which is the boundary between the portion of the second belt 142 that contacts the first belt 141 and the portion that separates in the tire radial direction, then the relationship between the distance B and distance A at a position where W2 / 2 is reached from the measuring portion 141b toward the separation portion 142b satisfies 0.4 ≤ B / A ≤ 1.0. This suppresses a deterioration in the productivity of retreaded tires and also suppresses the occurrence of belt edge separation. In other words, if the relationship between distance B and distance A is B / A < 0.4, then distance A is too large relative to distance B, and there is a risk that the area near the second belt end 142a of the second belt 142 will be too far outward in the tire radial direction relative to the first belt 141. In this case, the second belt 142 may have an end 142a that is too close to the buff portion 40 which is set on the outside of the belt layer 14 when the pneumatic tire 1 is retreaded, or the second belt end 142a may be located radially outward from the buff portion 40, which could easily lead to a decrease in the productivity of the retreaded tire. Also, if the relationship between distance B and distance A is B / A > 1.0, distance A is too small compared to distance B, which could make it difficult to secure enough cushion rubber 15 to be placed between the first belt end 141a and the second belt end 142a. In this case, the cushion rubber 15 may have difficulty following the movement of the first belt 141 and the second belt 142 when a load is applied, which could easily cause large distortion in the cushion rubber 15, making it difficult to suppress belt edge separation.

[0078] In contrast, if the relationship between distance B and distance A is within the range of 0.4 ≤ B / A ≤ 1.0, it is possible to suppress the large outward separation of the second belt end 142a of the second belt 142 from the first belt 141 in the radial direction of the tire. This suppresses a deterioration in the productivity of retreaded tires, and also ensures that the amount of cushion rubber 15 placed between the first belt end 141a and the second belt end 142a is secured, thereby suppressing the occurrence of belt edge separation. As a result, it is possible to improve belt edge separation resistance while maintaining the productivity of retreaded tires.

[0079] Also, since the distance W1 between the first belt end portion 141a and the second belt end portion 142a in the direction along the first belt 141 is within the range of 0 mm < W1 ≦ 18 mm, the productivity of the retread tire can be improved. That is, when the distance W1 between the first belt end portion 141a and the second belt end portion 142a in the direction along the first belt 141 is W1 > 18 mm, the distance between the first belt end portion 141a and the second belt end portion 142a is too large, so there is a possibility that the vicinity of the second belt end portion 142a of the second belt 142 will be greatly separated from the first belt 141 toward the outer side in the tire radial direction. In this case, the second belt 142 may cause the second belt end portion 142a to be too close to the buff portion 40 set outside the belt layer 14 during retreading of the pneumatic tire 1, or the second belt end portion 142a may be located outside the buff portion 40 in the tire radial direction, which may easily deteriorate the productivity of the retread tire.

[0080] On the other hand, when the distance W1 between the first belt end portion 141a and the second belt end portion 142a in the direction along the first belt 141 is within the range of 0 mm < W1 ≦ 18 mm, it is possible to suppress the vicinity of the second belt end portion 142a in the second belt 142 from being greatly separated from the first belt 141 toward the outer side in the tire radial direction, so it is possible to suppress the deterioration of the productivity of the retread tire. As a result, the productivity of the retread tire can be improved.

[0081] Furthermore, since the relationship between the width Wb1 of the first belt 141 in the tire width direction and the maximum cross-sectional width Wt of the carcass layer 13 in the tire width direction is within the range of 0.5 ≤ Wb1 / Wt ≤ 1, it is possible to suppress the occurrence of belt edge separation while suppressing deterioration of wear resistance and uneven wear resistance. In other words, if the relationship between the width Wb1 of the first belt 141 in the tire width direction and the maximum cross-sectional width Wt of the carcass layer 13 in the tire width direction is Wb1 / Wt < 0.5, then the width Wb1 of the first belt 141 is too narrow, and when inflated, the outer part of the tread portion 2 in the tire width direction where the belt layer 14 is located is likely to bulge outward in the tire radial direction relative to the part where the belt layer 14 is located. In this case, the difference in bulging of the tread portion 2 during inflation may easily lead to deterioration of wear resistance and uneven wear resistance. Furthermore, if the relationship between the width Wb1 of the first belt 141 in the tire width direction and the maximum cross-sectional width Wt of the carcass layer 13 in the tire width direction is Wb1 / Wt > 1, then the width Wb1 of the first belt 141 is too wide, and the first belt end 141a is likely to separate significantly in the tire radial direction from the portion of the belt layer 14 in the carcass layer 13 that is located on the tire radial side. In this case, the movement of the first belt end 141a is likely to increase when a load is applied to the pneumatic tire 1, and the concentration of strain may make belt edge separation more likely to occur.

[0082] In contrast, if the relationship between the width Wb1 of the first belt 141 in the tire width direction and the maximum cross-sectional width Wt of the carcass layer 13 in the tire width direction is within the range of 0.5 ≤ Wb1 / Wt ≤ 1, the portion of the belt layer 14 located on the outer side in the tire width direction in the tread portion 2 can be reduced. This suppresses deterioration of wear resistance and uneven wear resistance, and also suppresses strain concentration near the first belt end 141a, thereby suppressing belt edge separation. As a result, it is possible to improve belt edge separation resistance while suppressing deterioration of wear resistance and uneven wear resistance.

[0083] Furthermore, the relationship between the distance measurement portion 141b of the first belt 141 and the separation portion 142b, which is the boundary between the portion of the second belt 142 that contacts the first belt 141 and the portion that separates in the tire radial direction, and the distance W1 between the first belt end 141a and the second belt end 142a in the direction along the first belt 141, satisfies 1 ≤ W2 / W1 ≤ 5, which suppresses deterioration in the productivity of retreaded tires and suppresses the occurrence of belt edge separation. In other words, if the relationship between distance W2 and distance W1 is W2 / W1 < 1, the distance W1 is too large, which may result in the area near the second belt end 142a of the second belt 142 being significantly separated from the first belt 141 in the tire radial direction. In this case, the productivity of retreaded tires may be reduced if the second belt end 142a is too close to the buff portion 40, which is set on the outside of the belt layer 14 when retreading the pneumatic tire 1, or if the second belt end 142a is located radially outward from the buff portion 40. Also, if the relationship between distance W2 and distance W1 is W2 / W1 > 5, the distance W1 is too small, which may cause the first belt end 141a and the second belt end 142a to be too close. In this case, even if a cushion rubber 15 is placed between the first belt end 141a and the second belt end 142a, it may be difficult to suppress belt edge separation due to the large distortion that occurs in the cushion rubber 15 when a load is applied.

[0084] In contrast, if the relationship between distance W2 and distance W1 is within the range of 1 ≤ W2 / W1 ≤ 5, it is possible to suppress the large outward separation of the second belt end 142a of the second belt 142 from the first belt 141 in the tire radial direction, thereby suppressing a deterioration in the productivity of retreaded tires. Furthermore, it is possible to suppress the occurrence of belt edge separation by making it less likely for large distortions to occur in the cushion rubber 15 placed between the first belt end 141a and the second belt end 142a. As a result, it is possible to improve belt edge separation resistance while maintaining the productivity of retreaded tires.

[0085] Furthermore, the relationship between the thickness Ga from the tread contact surface 3 to the second belt 142 at the center of the center land portion 31 in the tire width direction and the thickness Gb from the tread contact surface 3 to the second belt 142 at the second belt end 142a is within the range of 0.9 ≤ Ga / Gb ≤ 1.2, which improves the productivity of retreaded tires. In other words, if the relationship between the thickness Ga and thickness Gb of the tread portion 2 is Ga / Gb < 0.9 or Ga / Gb > 1.2, the thickness of the tread portion 2 changes significantly depending on the position in the tire width direction, which may make it difficult to set the buffing portion 40 when retreading the pneumatic tire 1, and may make buffing work difficult.

[0086] In contrast, if the relationship between the thickness Ga and thickness Gb of the tread portion 2 is within the range of 0.9 ≤ Ga / Gb ≤ 1.2, the change in the thickness of the tread portion 2 due to its position in the tire width direction is small. This makes it easier to set the buffing portion 40 when retreading the pneumatic tire 1, improving the workability of the buffing operation. As a result, the productivity of retreaded tires can be improved.

[0087] Furthermore, since the belt layer 14 has belt covers 143 made of organic fibers on the outer side of the multiple belts 141 and 142 in the tire radial direction, the movement of the first belt end 141a and the second belt end 142a when a load is applied can be suppressed by the belt covers 143. As a result, the resistance to belt edge separation can be improved.

[0088] Furthermore, since the modulus of the cushion rubber 15 when fully stretched is within the range of 65% to 90% of the modulus of the cord-coated rubber 14b of the belt layer 14 when fully stretched, the resistance to belt edge separation can be improved. In other words, if the modulus of the cushion rubber 15 when fully stretched is less than 65% of the modulus of the cord-coated rubber 14b of the belt layer 14 when fully stretched, the modulus of the cushion rubber 15 is too low, which may cause the movement of the first belt end 141a and the second belt end 142a to become too large when a load is applied. In this case, the distortion of rubber members other than the cushion rubber 15 located near the first belt end 141a and the second belt end 142a will increase, which may make belt edge separation more likely to occur between these rubber members. Furthermore, if the modulus of the cushion rubber 15 when fully extended is 90% higher than the modulus of the cord-covered rubber 14b of the belt layer 14 when fully extended, the cushion rubber 15 may have difficulty following the movement of the first belt end 141a and the second belt end 142a when a load is applied. In this case, the cushion rubber 15 is more likely to experience significant strain, which may make it difficult to suppress belt edge separation.

[0089] In contrast, if the modulus of the cushion rubber 15 when fully extended is within the range of 65% to 90% of the modulus of the cord-covered rubber 14b of the belt layer 14 when fully extended, then the deformation of the rubber members, including the cushion rubber 15 located near the first belt end 141a and the second belt end 142a, can be suppressed when a load is applied. As a result, the belt edge separation resistance can be improved.

[0090] [Differentiation] In the embodiment described above, the belt layer 14 consists of two layers of belts, a first belt 141 and a second belt 142. However, the belt layer 14 may have more than two layers, including three or more layers.

[0091] Furthermore, in the embodiments described above, the belt layer 14 has a belt cover 143 and a belt edge cover 144, but the belt layer 14 does not necessarily have a belt cover 143 or a belt edge cover 144. Also, in the embodiments described above, the carcass layer 13 has two carcass plies 131 and 132, but the carcass layer 13 may be formed from a single carcass ply.

[0092] Furthermore, although the above-described embodiment used a pneumatic tire 1 as an example of a tire according to the present invention, the tire according to the present invention may be other than a pneumatic tire 1. The tire according to the present invention may be, for example, a so-called airless tire that can be used without filling with gas.

[0093] [Examples] Figures 10A and 10B are charts showing the results of performance evaluation tests for pneumatic tires. Below, we will describe the performance evaluation tests conducted on the above-mentioned pneumatic tire 1, comparing it with a conventional pneumatic tire, the pneumatic tire 1 according to the present invention, and a comparative example pneumatic tire used for comparison with the pneumatic tire 1 according to the present invention. The performance evaluation tests focused on resistance to belt edge separation and retreaded tire productivity.

[0094] The performance evaluation test was conducted by mounting a pneumatic tire (size 205 / 85R16 LT151R) onto a rim wheel with a specified rim size of 16×5.5.

[0095] For each test item, the evaluation method for belt edge separation resistance involved filling the drum with air at 75% of the specified internal pressure, applying a load at 75% of the specified load, and conducting a drum durability test at a speed of 81 km / h. After 8 steps of this test, a sialography inspection, an internal damage inspection performed in a vacuum atmosphere using sialography equipment, was conducted to detect the locations of belt edge separation. The evaluation of belt edge separation resistance was performed by expressing the reciprocal of the number of belt edge separation locations detected by the sialography inspection as an index with the conventional example described later set to 100. A higher value indicates fewer belt edge separation locations and superior belt edge separation resistance.

[0096] Furthermore, regarding retreaded tire productivity, after driving to the wear limit in the market, the locations of belt edge separation were detected by siaro inspection, and then buffing work was performed to determine whether or not the belt was exposed from the buffed area. The evaluation of retreaded tire productivity was made by comprehensively judging the number of locations of belt edge separation detected by siaro inspection and whether or not the belt was exposed after buffing work, and expressed as an index with the conventional example described later set to 100. In the evaluation of retreaded tire productivity, a higher index value indicates fewer locations of belt edge separation and less belt exposure from the buffed area, and thus better retreaded tire productivity.

[0097] Performance evaluation tests were conducted on 22 types of pneumatic tires, including a conventional pneumatic tire (an example of a conventional pneumatic tire), Examples 1 to 19 (pneumatic tire 1 according to the present invention), and Comparative Examples 1 and 2 (pneumatic tires compared to pneumatic tire 1 according to the present invention). Of these, the conventional pneumatic tire does not have a cushion rubber between the first belt end and the second belt end. In addition, in the comparative example pneumatic tire, the relationship between the distance A between the second belt and the first belt at the position of the second belt end and the cord diameter g2 of the belt cord of the second belt does not satisfy 1.5 ≤ A / g2 ≤ 5.

[0098] In contrast, in all of the Examples 1 to 19, which are examples of the pneumatic tire 1 according to the present invention, a cushion rubber 15 is placed between the first belt end 141a and the second belt end 142a, and the relationship between the distance A between the second belt 142 and the first belt 141 at the position of the second belt end 142a and the cord diameter g2 of the belt cord 14a of the second belt 142 satisfies 1.5 ≤ A / g2 ≤ 5. Furthermore, in the pneumatic tire 1 according to Examples 1 to 19, the ratio B / A of the distance B between the first belt 141 and the second belt 142 at a position where the distance A is W2 / 2 toward the separation portion 142b from the measuring portion 141b of the first belt 141, the distance W1 (mm) between the first belt end 141a and the second belt end 142a in the direction along the first belt 141, and the width Wb1 of the first belt 141 in the tire width direction and the tire width direction of the carcass layer 13 The maximum cross-sectional width Wt and its ratio Wb1 / Wt in the direction, the distance W2 between the measuring point and the separation point 142b of the first belt 141, the distance W1 and its ratio W2 / W1 between the first belt end 141a and the second belt end 142a in the direction along the first belt 141, the ratio Ga / Gb between the thickness Ga of the tread portion 2 at the position of the center land portion 31 and the thickness Gb of the tread portion 2 at the position of the second belt end 142a, and the presence or absence of the belt cover 143 are all different.

[0099] Performance evaluation tests were conducted using these pneumatic tires 1, and as shown in Figures 10A and 10B, it was found that the pneumatic tires 1 according to Examples 1 to 19 can improve belt edge separation resistance without reducing retread tire productivity compared to conventional examples. In other words, the pneumatic tires 1 according to Examples 1 to 19 can improve belt edge separation resistance while maintaining retread tire productivity.

[0100] This disclosure encompasses the following inventions: Invention [1] The tread portion of the carcass layer has a belt layer on the radially outer side of the tire, which has multiple belts made of steel cords. The belt layer includes a first belt having the largest width in the tire width direction among the plurality of belts, and a second belt adjacent to the outside of the first belt in the tire radial direction. The inclination direction of the belt cord of the first belt in the tire width direction with respect to the tire circumferential direction and the inclination direction of the belt cord of the second belt are a pair of crossed belts in opposite directions. A cushion rubber is disposed between a first belt end portion that is an end portion of the first belt in the tire width direction and a second belt end portion that is an end portion of the second belt. A tire characterized in that the relationship between the distance A between the second belt and the first belt at the position of the second belt end portion and the cord diameter g2 of the belt cord of the second belt satisfies 1.5 ≦ A / g2 ≦ 5. Invention [2] The outside portion in the tire width direction of the second belt is separated from the first belt in the tire radial direction outside from a separation portion located inside the second belt end portion in the tire width direction. In the tire according to Invention [1], when the distance between the measurement portion of the distance A in the first belt and the separation portion is W2, the relationship between the distance B between the first belt and the second belt at the position that becomes W2 / 2 from the measurement portion toward the separation portion and the distance A satisfies 0.4 ≦ B / A ≦ 1.0. Invention [3] In the tire according to Invention [1] or Invention [2], the distance W1 between the first belt end portion and the second belt end portion in the direction along the first belt is within the range of 0 mm < W1 ≦ 18 mm. Invention [4] In the tire according to any one of Invention [1] to Invention [3], the relationship between the width Wb1 of the first belt in the tire width direction and the maximum cross-sectional width Wt of the carcass layer is within the range of 0.5 ≦ Wb1 / Wt ≦ 1. Invention [5] The outside portion in the tire width direction of the second belt is separated from the first belt in the tire radial direction outside from a separation portion located inside the second belt end portion in the tire width direction. A tire according to any one of the inventions [1] to [4], wherein the relationship between the distance W2 between the distance measuring portion and the separation portion of the first belt and the distance W1 between the end of the first belt and the end of the second belt in the direction along the first belt is 1 ≤ W2 / W1 ≤ 5. invention [6] The tread portion has a plurality of land areas that are divided by a plurality of circumferential main grooves that extend in the circumferential direction of the tire. A tire according to any one of inventions [1] to [5], wherein the relationship between the thickness Ga from the tread contact surface at the center of the land portion closest to the tire equatorial plane among a plurality of land portions to the belt located furthest radially outward in the belt layer and the thickness Gb from the tread contact surface at the second belt end to the belt located furthest radially outward in the belt layer is in the range of 0.9 ≤ Ga / Gb ≤ 1.2. invention [7] The tire according to any one of the inventions [1] to [6], wherein the belt layer has a belt cover made of organic fibers on the outer side of the plurality of belts in the tire radial direction. invention [8] The belt layer has a cord covering rubber that covers the belt cord, The tire according to any one of Inventions [1] to [7], wherein the modulus of the cushion rubber when stretched to 100% is within the range of 65% to 90% of the modulus of the cord-covered rubber when stretched to 100%. [Explanation of symbols]

[0101] 1. Pneumatic tire (tire) 2 Tread section 3. Tread contact surface 4 Tread Rubber 5 Shoulder section 8 Sidewall section 9 Sidewall rubber 10 Bead section 11 Bead core 12 Bead Fillers 13. Carcass layer 14 Belt Layer 14a Belt Cord 14b Cord insulation rubber 141 First Belt 141a First belt end 142 Second Belt 142a Second belt end 143 Belt cover 144 Belt Edge Cover 15 Cushion rubber 17 Rim cushion rubber 16 Inner liner 18 Tire interior 20 Circumferential main groove 21 Center main groove 22 Shoulder main groove 30 Land 31 Center Track and Field Club 32 Shoulder Track and Field Club 40 Buffing section

Claims

1. The tread portion of the carcass layer has a belt layer on the radially outer side of the tire, which has multiple belts made of steel cords. The belt layer consists of a first belt, which has the largest width in the tire width direction among the multiple belts, and a second belt, which is adjacent to the radially outer side of the first belt, and the two intersecting belts such that the inclination direction of the belt cords of the first belt and the inclination direction of the belt cords of the second belt are opposite to each other in the tire width direction with respect to the tire circumferential direction. A cushioning rubber is placed between the first belt end, which is the end of the first belt in the tire width direction, and the second belt end, which is the end of the second belt. A tire characterized in that the relationship between the distance A between the second belt and the first belt at the position of the second belt end and the cord diameter g2 of the belt cord of the second belt satisfies 1.5 ≤ A / g2 ≤ 5.

2. The second belt has a separation portion located inward in the tire width direction from the end of the second belt, and the outer portion in the tire width direction is separated from the first belt in the tire radial direction. The tire according to claim 1, where W2 is the distance between the measuring portion and the separation portion of the first belt, and the relationship between the distance B between the first belt and the second belt at a position where W2 / 2 is the distance from the measuring portion to the separation portion, and the distance A, satisfies 0.4 ≤ B / A ≤ 1.

0.

3. The tire according to claim 1, wherein the distance W1 between the end of the first belt and the end of the second belt in the direction along the first belt is within the range of 0 mm < W1 ≤ 18 mm.

4. The tire according to claim 1, wherein the relationship between the width Wb1 of the first belt in the tire width direction and the maximum cross-sectional width Wt of the carcass layer in the tire width direction is within the range of 0.5 ≤ Wb1 / Wt ≤ 1.

5. The second belt has a separation portion located inward in the tire width direction from the end of the second belt, and the outer portion in the tire width direction is separated from the first belt in the tire radial direction. The tire according to claim 1, wherein the relationship between the distance W2 between the distance measuring portion A and the separation portion in the first belt and the distance W1 between the end of the first belt and the end of the second belt in the direction along the first belt satisfies 1 ≤ W2 / W1 ≤ 5.

6. The tread portion has a plurality of land areas that are divided by a plurality of circumferential main grooves that extend in the circumferential direction of the tire. The tire according to claim 1, wherein the relationship between the thickness Ga from the tread contact surface at the center of the land portion closest to the tire equatorial plane in the tire width direction to the belt located furthest radially outward in the belt layer and the thickness Gb from the tread contact surface at the second belt end to the belt located furthest radially outward in the belt layer is within the range of 0.9 ≤ Ga / Gb ≤ 1.

2.

7. The tire according to claim 1, wherein the belt layer has a belt cover made of organic fibers on the outer side of the plurality of belts in the tire radial direction.

8. The belt layer has a cord covering rubber that covers the belt cord, The tire according to claim 1, wherein the modulus of the cushion rubber when stretched to 100% is within the range of 65% to 90% of the modulus of the cord-covered rubber when stretched to 100%.

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