tire

Abstract

The goal is to achieve both resistance to belt edge separation and lightweight tires. [Solution] The system includes an outer diameter cross belt 143 having a belt cord 143a with a cord angle θ1 of 45[°] or more in absolute value with respect to the tire circumferential direction, an inner diameter cross belt 141 having a belt cord 141a with a cord angle θ2 of 45[°] or less in absolute value with respect to the tire circumferential direction, which has a different sign from the outer diameter cross belt 143, and is positioned inside the outer diameter cross belt 143 in the tire radial direction, and a circumferential reinforcing layer 142a having a belt cord 142a with a cord angle within ±5[°] of the tire circumferential direction, which is positioned between the inner diameter cross belt 141 and the outer diameter cross belt 143, wherein the width W1 of the circumferential reinforcing layer in the tire width direction, the width W2 of the inner diameter cross belt 141 in the tire width direction, and the width W3 of the outer diameter cross belt 143 in the tire width direction are W1

Description

Technical Field

[0001] This invention relates to a tire.

Background Art

[0002] For example, Patent Document 1 describes a heavy-duty tire that suppresses shoulder edge wear while maintaining plunger durability. This heavy-duty tire includes a first belt layer composed of cords extending obliquely at an angle greater than 45° with respect to the tire circumferential direction, a second belt layer composed of cords extending in the tire circumferential direction, and a third belt layer composed of cords extending obliquely at an angle of 30° or less in the opposite direction to the cords of the first belt layer with respect to the tire circumferential direction. The third belt layer, the second belt layer, and the first belt layer are sequentially disposed from the inner side in the tire radial direction. The width w3 of the third belt layer is set to 80% or more of the tread width w, and when the width of the first belt layer is w1 and the width of the second belt layer is w2, w2 < w1 < w3.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to enhance added values such as an increase in the actual loading capacity of a vehicle and fuel efficiency improvement, weight reduction of a tire is required. Weight reduction of a tire can be achieved by the belt structure of the tire. However, depending on the belt structure, there is a concern that belt edge separation (hereinafter referred to as belt edge separation) may occur due to strain near the belt edge.

[0005] An object of this invention is to provide a tire capable of achieving both belt edge separation resistance performance and weight reduction of the tire.

Means for Solving the Problems

[0006] To achieve the above object, a tire according to one aspect of the present invention includes a carcass layer, a belt layer disposed on the outer side in the tire radial direction of the carcass layer and continuous in the tire circumferential direction, and a tread rubber disposed on the outer side in the tire radial direction of the belt layer. The belt layer includes an outer diameter side cross belt having a belt cord with a cord angle of 45° or more in absolute value with respect to the tire circumferential direction, an inner diameter side cross belt having a belt cord with a cord angle of 45° or less in absolute value and opposite in sign to the outer diameter side cross belt and disposed on the inner side in the tire radial direction of the outer diameter side cross belt, and a circumferential reinforcement layer having a belt cord with a cord angle within a range of ±5° with respect to the tire circumferential direction and disposed between the inner diameter side cross belt and the outer diameter side cross belt. A width W1 of the circumferential reinforcement layer, a width W2 of the inner diameter side cross belt, and a width W3 of the outer diameter side cross belt satisfy the relationship W1 < W3 < W2.

Effect of the Invention

[0007] According to this invention, it is possible to achieve both belt edge separation resistance performance and weight reduction of the tire.

Brief Description of the Drawings

[0008] [Figure 1] FIG. 1 is a meridional cross-sectional view of a pneumatic tire according to an embodiment. [Figure 2] FIG. 2 is a developed view of a belt layer of a pneumatic tire according to an embodiment. [Figure 3] FIG. 3 is a chart showing the results of a performance test of a pneumatic tire according to an embodiment. [Figure 4] FIG. 4 is a chart showing the results of a performance test of a pneumatic tire according to an embodiment. [Figure 5] FIG. 5 is a chart showing the results of a performance test of a pneumatic tire according to an embodiment. [Figure 6] FIG. 6 is a chart showing the results of a performance test of a pneumatic tire according to an embodiment. [Figure 7]Figure 7 is a chart showing the results of a performance test of a pneumatic tire according to the embodiment. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited by these embodiments. Furthermore, the components of these embodiments include those that are substituted and obvious for substitution while maintaining the identity of the invention. In addition, the multiple modifications described in these embodiments can be arbitrarily combined within the scope of what is obvious to those skilled in the art.

[0010] In the following description, the tire radial direction refers to the direction perpendicular to the tire rotation axis (not shown), which is the rotation axis of the pneumatic tire 1 of the embodiment. The inner side of the tire radial direction refers to the side toward the tire rotation axis in the tire radial direction, and the outer side of the tire radial direction refers to the side away from the tire rotation axis in the tire radial direction. The tire circumferential direction refers to the direction around the tire rotation axis as the central axis. The tire width direction refers to the direction parallel to the tire rotation axis. The inner side of the tire width direction refers to the side toward the tire equatorial plane (tire equator line) CL in the tire width direction, and the outer side of 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 perpendicular to the tire rotation axis and passing through the center of the tire width of the pneumatic tire 1. The position of the tire equatorial plane CL in the tire width direction coincides with the tire width direction center line, which is the center position of the pneumatic tire 1 in the tire width direction. The tire equator line refers to a line on the tire equatorial plane CL that runs along the tire circumferential direction of the pneumatic tire 1. Furthermore, a meridional cross-section of a tire (meridian section) refers to the cross-section obtained when the tire is cut along a plane containing the tire's axis of rotation.

[0011] Figure 1 shows a meridional cross-section of the pneumatic tire 1 of the embodiment, illustrating a cross-section of one side of the tire rotation axis in the tire radial direction. In this embodiment, as an example, a heavy-duty pneumatic radial tire mounted on heavy-duty vehicles such as trucks and buses will be described. The pneumatic tire 1 of this embodiment is particularly suitable for all-season tires.

[0012] The pneumatic tire 1 of this embodiment has an annular structure centered on the tire rotation axis and, although not explicitly shown in the figure, comprises a pair of bead cores, a pair of bead fillers, a pair of rim cushion rubbers, a carcass layer 13, a belt layer 14, a tread rubber 15, and a pair of sidewall rubbers 16, as shown in Figure 1.

[0013] Each pair of bead cores consists of one or more steel bead wires wound in a ring-like and multi-layered manner, and is embedded in the bead portion to form the core of the bead portion on both sides in the tire width direction. Each pair of bead fillers is positioned on the radially outer side of the pair of bead cores to reinforce the bead portion. Each pair of rim cushion rubbers extends from the radially inner side to the radially outer side of each bead core and the winding portion of the carcass layer 13 to form the rim fitting surface of the bead portion.

[0014] The carcass layer 13 has a single-layer structure consisting of one carcass ply or a multi-layer structure consisting of multiple carcass plies stacked together. The carcass layer 13 is toroidally stretched between the two bead cores to form the framework of the tire. The ends of the carcass layer 13 are also wrapped around the bead core and bead filler and secured outwards in the tire width direction. The carcass layer 13 is constructed by rolling out multiple carcass cords made of steel that are covered with a coating rubber, and the cord angle (defined as the longitudinal inclination angle of the carcass cords with respect to the circumferential direction of the tire, also called the belt angle) is 80° to 100° in absolute value for radial tires and 30° to 45° for bias tires.

[0015] The belt layer 14 is made up of at least three belt plies 141 to 143 stacked together and is wrapped around the outer circumference of the carcass layer 13 and arranged continuously in the circumferential direction of the tire. These belt plies 141 to 143 include an inner diameter cross belt 141, an outer diameter cross belt 143, and a circumferential reinforcing layer 142.

[0016] The inner-diameter side crossing belt 141 is arranged on the inner side in the tire diameter direction among the three belt plies. As shown in FIG. 2, the inner-diameter side crossing belt 141 is formed by covering a plurality of belt cords 141a made of steel with a cover rubber 141b and performing rolling processing. The inner-diameter side crossing belt 141 has a cord angle θ2 of the belt cord 141a with an absolute value of 45° or less with respect to the tire circumferential direction. It is preferable that the cord angle θ2 of the belt cord 141a of the inner-diameter side crossing belt 141 has an absolute value of 0° or more and 44° or less.

[0017] The outer-diameter side crossing belt 143 is arranged on the outer side in the tire diameter direction among the three belt plies. As shown in FIG. 2, the outer-diameter side crossing belt 143 is formed by covering a plurality of belt cords 143a made of steel with a cover rubber 143b and performing rolling processing. The outer-diameter side crossing belt 143 has a cord angle θ1 of the belt cord 143a with an absolute value of 45° or more and having a sign opposite to that of the inner-diameter side crossing belt 141 with respect to the tire circumferential direction. The outer-diameter side crossing belt 143 is also simply referred to as a crossing belt together with the inner-diameter side crossing belt 141. It is preferable that the cord angle θ1 of the belt cord 143a of the outer-diameter side crossing belt 143 has an absolute value of 46° or more and 90° or less.

[0018] The circumferential direction reinforcing layer 142 is arranged between the inner-diameter side crossing belt 141 and the outer-diameter side crossing belt 143 among the three belt plies. As shown in FIG. 2, the circumferential direction reinforcing layer 142 is formed by covering a plurality of belt cords 142a made of steel with a cover rubber 142b and performing rolling processing. The circumferential direction reinforcing layer 142 has a cord angle of the belt cord 142a within a range of ±5° with an absolute value with respect to the tire circumferential direction.

[0019] As shown in FIG. 1, the tread rubber 15 is disposed on the radially outer side of the carcass layer 13 and the belt layer 14 of the pneumatic tire 1 to form the tread portion of the pneumatic tire 1. The tread rubber 15 has a tread surface (tread running surface) 15A on the outer peripheral surface that contacts the road surface during running. The outer end of the tread surface 15A in the tire width direction is the grounding end T. Further, the tread rubber 15 has buttress portions 15B on both outer side portions in the tire width direction that do not contact the road surface during running, which are located outside the grounding end T of the tread surface 15A. The buttress portions 15B are provided in the tread rubber 15 from the grounding end T in the outer side in the tire width direction and the inner side in the tire radial direction up to the sidewall rubber 16. The buttress portions 15B are formed in a trapezoidal shape with a larger dimension in the tire width direction from the outer side in the tire radial direction to the inner side in the tire radial direction.

[0020] The grounding end T is defined as the maximum width position in the tire axial direction on the contact surface between the tire and the flat plate when the tire is mounted on a specified rim, filled with a specified internal pressure, placed vertically with respect to the flat plate in a stationary state, and a load corresponding to a specified load is applied.

[0021] [[ID=Z]] The specified rim refers to the "Standard Rim" defined by JATMA, the "Design Rim" defined by TRA, or the "MEASURING RIM" defined by ETRTO. Also, the specified internal pressure refers to the "Maximum Air Pressure" defined by JATMA, the maximum value of the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" defined by TRA, or the "INFLATION PRESSURES" defined by ETRTO. The specified load refers to the "Maximum Load Capacity" defined by JATMA, the maximum value of the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" defined by TRA, or the "LOAD CAPACITY" defined by ETRTO. In the case of the pneumatic tire of the embodiment 1, the specified load is 88[%] of the maximum load capacity at the specified internal pressure.

[0022] The pair of sidewall rubbers 16, 16 are positioned on the outer side of the carcass layer 13 in the tire width direction, respectively, to form the sidewall portions on both sides in the tire width direction.

[0023] As shown in Figure 1, the pneumatic tire 1 of the embodiment includes a circumferential groove 21 extending along the tire's circumferential direction on the tread surface 15A, and a plurality of land portions 31 partitioned by the circumferential groove 21.

[0024] The circumferential groove 21 is provided extending along the circumferential direction of the tire and has an annular structure that extends linearly and continuously around the entire circumference of the tire. The circumferential groove 21 may be defined as a groove that has a wear indicator display obligation as specified by JATMA. The circumferential groove 21 has a groove width of 5 mm to 20 mm and a groove depth of 7 mm to 30 mm.

[0025] Here, the groove width is measured as the maximum distance between opposing groove walls or edges at the opening edge of the tread surface 15A when the tire is mounted on a specified rim and filled to the specified internal pressure in an unloaded state. The groove depth is measured as the maximum distance from the tread surface 15A to the bottom of the groove when the tire is mounted on a specified rim and filled to the specified internal pressure in an unloaded state. Furthermore, in configurations where there are partial irregularities or sipes at the bottom of the groove, these are excluded from the measurement.

[0026] In the pneumatic tire 1 of this embodiment, the circumferential grooves 21 are arranged within the range of the center region CE on the tread surface 15A and within the range of the shoulder region SE on the tread surface 15A, as shown in Figure 1. In this embodiment, one circumferential groove 21 is arranged in each center region CE separated by the tire equatorial plane CL, and one groove is arranged in each shoulder region SE separated by the tire equatorial plane CL.

[0027] The center region CE is a region within a range of 1 / 4 from the tire equatorial plane CL to both outer sides in the tire width direction with respect to the grounding width Wt (measurement dimension in the unloaded state where the tire is mounted on a specified rim and filled with a specified internal pressure) of the tread surface 15A (tread rubber 15) between both grounding ends T. The shoulder region SE is a region within a range of 1 / 4 from each grounding end T to the inner side in the tire width direction with respect to the grounding width Wt of the tread surface 15A between both grounding ends T.

[0028] The land portion 31 extends over the entire circumference of the tire and constitutes an annular tread surface (ground contact surface). The land portion 31 includes a center land portion disposed in the center region CE, a middle land portion straddling the center region CE and the shoulder region SE, and a shoulder land portion at the outermost side in the tire width direction disposed in the shoulder region SE.

[0029] The pneumatic tire 1 of the embodiment is characterized in that, as shown in FIGS. 1 and 2, it includes a carcass layer 13, a belt layer 14 disposed on the outer side in the tire radial direction of the carcass layer 13 and continuous in the tire circumferential direction, and a tread rubber 15 disposed on the outer side in the tire radial direction of the belt layer 14. The belt layer 14 includes an outer diameter side cross belt 143 having a belt cord 143a with a cord angle θ1 of 45° or more in absolute value with respect to the tire circumferential direction, an inner diameter side cross belt 141 having a belt cord 141a with a cord angle θ2 of 45° or less in absolute value and opposite in sign to the outer diameter side cross belt 143 and disposed on the inner side in the tire radial direction of the outer diameter side cross belt 143, and a circumferential reinforcement layer 142 having a belt cord 142a with a cord angle within a range of ±5° with respect to the tire circumferential direction and disposed between the inner diameter side cross belt 141 and the outer diameter side cross belt 143. The width W1 of the circumferential reinforcement layer in the tire width direction, the width W2 of the inner diameter side cross belt 141 in the tire width direction, and the width W3 of the outer diameter side cross belt 143 in the tire width direction satisfy the relationship W1 < W3 < W2. Here, each belt width W1, W2, W3 is a value measured in the unloaded state where the tire is mounted on a specified rim and filled with a specified internal pressure.

[0030] According to this pneumatic tire 1, the outer diameter side cross belt 143 functions as a belt ply having a belt cord 143a at a relatively high angle, ensuring the rigidity in the tire width direction. Also, according to this pneumatic tire 1, the circumferential reinforcing layer 142 and the inner diameter side cross belt 141 function as belt plies having belt cords 142a, 141a at a relatively low angle, ensuring the rigidity in the tire circumferential direction. And this pneumatic tire 1 regulates the arrangement of each belt ply 141 - 143 and the cord angle of the belt cord within a specified range, thereby alleviating the fluctuation of the rigidity of the tread portion in the tire width direction. Since the strain near the belt edge is shared by the edges of each belt ply 141 - 143, the tire durability performance is improved from the perspective of belt edge separation. Moreover, this pneumatic tire 1 sets the relationship of the widths W1, W2, W3 of each belt ply 141 - 143 as W1 < W3 < W2, so that a sufficient rubber layer can be secured from the end portions of each belt ply 141 - 143 in the tire width direction to the outer profile of the buttress portion 15B, and the tire durability is improved from the perspective of belt edge separation.

[0031] Moreover, according to this pneumatic tire 1, since the tire durability is improved as described above, it becomes possible to make the belt layer 14 into a three - ply structure of an inner diameter side cross belt 141, a circumferential reinforcing layer 142, and an outer diameter side cross belt 143, and the weight reduction of the tire can be achieved. For example, although not shown in the figure, it is possible to arrange a low - angle belt on the outer side in the tire diameter direction of the outer diameter side cross belt 143 and arrange a high - angle belt on the inner side in the tire diameter direction of the inner diameter side cross belt 141, but these low - angle belts and high - angle belts can be made unnecessary.

[0032] Here, the low-angle belt has a width range in the tire width direction that includes the position of the circumferential groove 21 in the center region CE, and is less than 90% of the width W3 of the outer diameter cross belt 143. The low-angle belt is constructed by rolling a plurality of belt cords made of steel covered with coated rubber. The additional belt has belt cords with the same sign as the outer diameter cross belt 143 and a cord angle of 10° to 45° (preferably 20°) in absolute value with respect to the tire circumferential direction. The low-angle belt protects the outer diameter cross belt 143 from, for example, the occurrence of stones getting into the bottom of the circumferential groove 21.

[0033] Furthermore, the high-angle belt has a width range in the tire width direction that includes the positions of the circumferential grooves 21 in the center region CE and the shoulder region, and is less than 100% of the width W3 of the outer diameter cross belt 143 and less than 95% of the width W2 of the inner diameter cross belt 141. The high-angle belt has, for example, a belt cord with the same symbol as the inner diameter cross belt 141 and an absolute value of 45° to 70° (preferably 60°) with respect to the tire circumferential direction. The high-angle belt ensures, for example, rigidity in the tire width direction.

[0034] Furthermore, in the pneumatic tire 1 of this embodiment, the width W1 of the circumferential reinforcing layer 142 and the cross-sectional width Wp of the carcass layer 13 satisfy the relationship 0.50 ≤ W1 / Wp ≤ 0.70.

[0035] The cross-sectional width Wp of the carcass layer 13 is the largest cross-sectional dimension in the tire width direction of the carcass cords, excluding the coating rubber of the carcass layer 13, and is the dimension between the two outermost carcass cords in the tire width direction.

[0036] With this pneumatic tire 1, by setting the width W1 of the circumferential reinforcing layer 142 within the above range, the internal pressure distribution between the belt layer 14 and the carcass layer 13 during inflation can be balanced, improving the overall tire durability. In order to obtain the above effect, it is preferable that this pneumatic tire 1 satisfies the relationship 0.55 ≤ W1 / Wp ≤ 0.67.

[0037] Furthermore, in the pneumatic tire 1 of the embodiment, the width W1 of the circumferential reinforcing layer 142 and the width W2 of the inner diameter cross belt 141 satisfy the relationship 1.25 ≤ W2 / W1 ≤ 1.55, and the width W2 of the inner diameter cross belt 141 and the width W3 of the outer diameter cross belt 143 satisfy the relationship W2 - W3 ≤ 30 [mm].

[0038] With this pneumatic tire 1, setting the width W1 of the circumferential reinforcing layer 142 within the above range is effective in increasing the rigidity of the tire in the circumferential direction. Moreover, with this pneumatic tire 1, by setting the difference between the width W2 of the inner diameter cross belt 141 and the width W3 of the outer diameter cross belt 143 within the above range, a sufficient rubber layer can be secured in the radial direction of the tire at the ends of the cross belts consisting of the inner diameter cross belt 141 and the outer diameter cross belt 143, and the difference in cross belt width can be reduced, thereby widening the range of the cross belt's binding effect and further improving the tire's durability. In order to obtain the above effects, it is preferable that this pneumatic tire 1 satisfies the relationships 1.30 ≤ W2 / W1 ≤ 1.45 and W2 - W3 ≤ 20 [mm].

[0039] Furthermore, in the pneumatic tire 1 of the embodiment, the outer diameter cross belt 143 is positioned adjacent to the tread rubber 15. That is, in the pneumatic tire 1 of the embodiment, there is no belt having belt cords (for example, the low-angle belt described above) between the outer diameter cross belt 143 and the tread rubber 15 on the outer side in the tire radial direction.

[0040] With this pneumatic tire 1, the presence of a circumferential reinforcing layer 142 ensures rigidity in the circumferential direction of the tire, eliminating the need for a low-angle belt and thus resulting in weight reduction.

[0041] Furthermore, in the pneumatic tire 1 of this embodiment, the inner diameter cross belt 141 is positioned adjacent to the carcass layer 13. That is, there is no belt with belt cords (for example, the high-angle belt described above) between the inner diameter cross belt 141 and the carcass layer 13 on the inner side in the tire radial direction.

[0042] In the belt structure of a general heavy-duty tire, a high-angle belt for ensuring the rigidity in the tire width direction is arranged on the inner side in the tire radial direction of the cross belt. However, according to this pneumatic tire 1, since the outer diameter side cross belt 143 functions as a high-angle belt, the rigidity in the tire width direction is ensured, and since a high-angle belt is not required, the weight is reduced.

[0043] Also, in the pneumatic tire 1 of the embodiment, the belt cords 142a of the circumferential reinforcing layer 142 are steel wires, and the number of ends is 15 [ends / 50 mm] or more and 30 [ends / 50 mm] or less.

[0044] The number of ends is the number of belt cords per 50 [mm] in the tire circumferential direction when the pneumatic tire is mounted on a regular rim and filled with a regular internal pressure in a non-loaded state, and the unit is [ends / 50 mm].

[0045] According to this pneumatic tire 1, by setting the number of ends of the circumferential reinforcing layer 142 within a specified range, the rigidity of the tread portion is optimized, and the strain of the groove bottom of the circumferential groove 21 and the belt edge of the belt layer 14 is reduced, thereby improving the tire durability from the viewpoint of belt edge separation.

[0046] Also, the pneumatic tire 1 of the embodiment further includes at least two circumferential grooves 21 extending in the tire circumferential direction in the tread rubber 15. The circumferential grooves 21 are present in the center region CE and the shoulder region SE of the tread surface 15A. As shown in FIG. 1, the thickness D from the circumferential groove 21 in the center region CE to the belt layer 14 and the thickness d from the circumferential groove 21 in the shoulder region SE to the belt layer 14 satisfy the relationship of 0.8 < D / d < 1.3. Here, D and d are values measured in a non-loaded state where the tire is mounted on a specified rim and filled with a specified internal pressure.

[0047] According to this pneumatic tire 1, by making the distance from the groove bottom of the circumferential groove 21 to the belt cord of the belt layer 14 equal at the positions of the circumferential grooves 21 in the center region CE and the shoulder region SE, the strain in the tire width direction of the tread surface 15A is evenly dispersed, thereby improving the tire durability from the viewpoint of belt edge separation. In order to obtain the above effects, this pneumatic tire 1 preferably satisfies the relationship of 0.9 < D / d < 1.1.

[0048] Further, in the pneumatic tire 1 of the embodiment, the contact width Wt of the tread surface 15A (tread rubber 15) and the cross-sectional width Wp of the carcass layer 13 satisfy the relationship of 0.60 ≤ Wt / Wp ≤ 0.95. Here, Wp is a value measured in a no-load state where the tire is mounted on a specified rim and filled with a specified internal pressure.

[0049] According to this pneumatic tire 1, by setting the relationship between the contact width Wt of the tread surface 15A and the cross-sectional width Wp of the carcass layer 13 within a predetermined range, an appropriate balance can be maintained for the carcass internal pressure sharing ratio of the outer portion in the tire width direction of the tread rubber 15 (also referred to as the shoulder portion) during inflation, and an improvement in the overall durability of the tire can be expected in terms of reducing the strain during deflection at the time of grounding. In order to obtain the above effects, this pneumatic tire 1 preferably satisfies the relationship of 0.70 ≤ Wt / Wp ≤ 0.85.

[0050] Further, in the pneumatic tire 1 of the embodiment, the belt layer 14 is composed of three belt plies including an inner diameter side cross belt 141, an outer diameter side cross belt 143, and a circumferential reinforcing layer 142.

[0051] According to this pneumatic tire 1, weight reduction is achieved by reducing the number of belt plies.

[0052] By the way, in this embodiment, as described above, a pneumatic tire 1 was described as an example of a tire. This pneumatic tire 1 can be filled with air, an inert gas such as nitrogen, or other gases. However, the tread pattern configuration of the pneumatic tire 1 described in this embodiment can be arbitrarily applied to other tires within the scope of what is obvious to those skilled in the art. Other tires include, for example, airless tires and solid tires. [Examples]

[0053] Figures 3 to 7 are charts showing the results of performance tests of the pneumatic tire according to the embodiment. Below, we will describe the performance evaluation tests conducted on the conventional pneumatic tire, the comparative pneumatic tire, and the pneumatic tire according to the embodiment. The performance evaluation tests focused on weight reduction and belt edge separation resistance (durability).

[0054] The weight reduction evaluation test involved measuring the mass of a pneumatic tire (green tire) with a tire size of 275 / 80R22.5, and then indexing its reciprocal. This evaluation was performed using an index based on the conventional example as the baseline (100), with a higher value indicating a more desirable result.

[0055] The evaluation test for belt edge separation resistance involved mounting a pneumatic tire of size 275 / 80R22.5 onto a standard rim specified by JATMA, and applying the JATMA-specified internal pressure. A cambered drum testing machine with a drum diameter of 1707 mm was used, and the load was increased from the specified load at regular intervals. The mileage at the time of failure was calculated and evaluated. This evaluation was performed using an index evaluation with the conventional example as the baseline (100), and a higher value is preferable.

[0056] Conventional pneumatic tires have a three-layer belt structure with a pair of crossing belts, but they lack a circumferential reinforcing layer between the crossing belts, and the cord angle of the belt cords of the crossing belts does not meet the specified requirements.

[0057] The pneumatic tire of Comparative Example 1 has a three-layer belt structure with a pair of cross belts and a circumferential reinforcing layer between the cross belts, but the relationship between the cord angle and widths W1, W2, W3 of the belt cords of the outer diameter cross belts does not meet the specifications. The pneumatic tire of Comparative Example 2 has a three-layer belt structure with a pair of cross belts and a circumferential reinforcing layer between the cross belts, but the relationship between the cord angle and widths W1, W2, W3 of the belt cords of the inner diameter cross belts does not meet the specifications. The pneumatic tire of Comparative Example 3 has a three-layer belt structure with a pair of cross belts and a circumferential reinforcing layer between the cross belts, and the cord angle of the belt cords of the cross belts meets the specifications, but the relationship between the widths W1, W2, W3 does not meet the specifications.

[0058] The pneumatic tire of the embodiment has a three-layer belt structure, with a pair of cross belts, a circumferential reinforcing layer between the cross belts, and the relationship between the cord angle and widths W1, W2, W3 of the belt cords of the cross belts satisfies the specifications.

[0059] As the test results show, the pneumatic tire of this embodiment is lighter and has improved belt edge separation resistance compared to the conventional example.

[0060] This disclosure includes the following inventions: [Invention 1] Carcass layer and A belt layer is arranged on the radially outer side of the carcass layer and is continuous in the circumferential direction of the tire, The tread rubber arranged on the radially outer side of the belt layer, Equipped with, The aforementioned belt layer is An outer diameter cross belt having belt cords with a cord angle of 45° or more in absolute value with respect to the circumferential direction of the tire, An inner diameter cross belt is positioned inside the outer diameter cross belt in the tire radial direction, having belt cords with a different sign than the outer diameter cross belt and a cord angle of 45° or less in absolute value with respect to the tire circumferential direction, It has a belt cord with a cord angle within a range of ±5° with respect to the tire circumferential direction, and a circumferential reinforcing layer disposed between the inner diameter side intersecting belt and the outer diameter side intersecting belt, including where a width W1 of the circumferential reinforcing layer, a width W2 of the inner diameter side intersecting belt, and a width W3 of the outer diameter side intersecting belt satisfy the relationship W1 < W3 < W2, tire. [Invention 2] where the width W1 of the circumferential reinforcing layer and a cross-sectional width Wp of the carcass layer satisfy the relationship 0.50 ≦ W1 / Wp ≦ 0.70, the tire according to Invention 1. [Invention 3] where the width W1 of the circumferential reinforcing layer and the width W2 of the inner diameter side intersecting belt satisfy the relationship 1.25 ≦ W2 / W1 ≦ 1.55, and the width W2 of the inner diameter side intersecting belt and the width W3 of the outer diameter side intersecting belt satisfy the relationship W2 - W3 ≦ 30 [mm], the tire according to Invention 1 or 2. [Invention 4] where the outer diameter side intersecting belt is disposed adjacent to the tread rubber, the tire according to any one of Inventions 1 to 3. [Invention 5] where the inner diameter side intersecting belt is disposed adjacent to the carcass layer, the tire according to any one of Inventions 1 to 4. [Invention 6] where the belt cord of the circumferential reinforcing layer is a steel wire and the number of ends is 15 [ends / 50 mm] or more and 30 [ends / 50 mm] or less, the tire according to any one of Inventions 1 to 5. [Invention 7] further comprising at least two circumferential grooves extending in the tire circumferential direction in the tread rubber, where the circumferential grooves are present in a center region and a shoulder region of the tread surface, The thickness D of the tread rubber from the groove bottom of the circumferential groove in the center region to the belt layer and the thickness d of the tread rubber from the groove bottom of the circumferential groove in the shoulder region to the belt layer satisfy the relationship 0.8 < D / d < 1.3. The tire according to any one of Inventions 1 to 6. [Invention 8] The grounding width Wt of the tread rubber and the cross-sectional width Wp of the carcass layer satisfy the relationship 0.60 ≤ Wt / Wp ≤ 0.95. The tire according to any one of Inventions 1 to 7.

Explanation of Reference Numerals

[0061] 1 Pneumatic tire (tire) 13 Carcass layer 14 Belt layer 15 Tread rubber 15A Tread surface 21 Circumferential groove 141 Inner diameter side cross belt 142 Circumferential reinforcement layer 143 Outer diameter side cross belt 141a, 142a, 143a Belt cord

Claims

1. Carcass layer and A belt layer is arranged on the radially outer side of the carcass layer and is continuous in the circumferential direction of the tire, The tread rubber arranged on the radially outer side of the belt layer, Equipped with, The aforementioned belt layer is An outer diameter cross belt having belt cords with a cord angle of 45° or more in absolute value with respect to the circumferential direction of the tire, An inner diameter crossing belt is positioned inside the outer diameter crossing belt in the tire radial direction, having belt cords with a different sign than the outer diameter crossing belt and a cord angle of 45° or less in absolute value with respect to the tire circumferential direction, A belt cord having a cord angle within ±5° with respect to the circumferential direction of the tire, and a circumferential reinforcing layer disposed between the inner diameter cross belt and the outer diameter cross belt, Includes, The width W1 of the circumferential reinforcing layer, the width W2 of the inner diameter cross belt, and the width W3 of the outer diameter cross belt satisfy the relationship W1 < W3 < W2. tire.

2. The width W1 of the circumferential reinforcing layer and the cross-sectional width Wp of the carcass layer satisfy the relationship 0.50 ≤ W1 / Wp ≤ 0.

70. The tire according to claim 1.

3. The width W1 of the circumferential reinforcing layer and the width W2 of the inner diameter cross belt satisfy the relationship 1.25 ≤ W2 / W1 ≤ 1.

55. The width W2 of the inner diameter crossing belt and the width W3 of the outer diameter crossing belt satisfy the relationship W2 - W3 ≤ 30 [mm]. The tire according to claim 1.

4. The outer diameter cross belt is positioned adjacent to the tread rubber. The tire according to claim 1.

5. The inner diameter cross belt is arranged adjacent to the carcass layer. The tire according to claim 1.

6. The belt cord of the circumferential reinforcing layer is made of steel wire and has 15 [wires / 50 mm] or more and 30 [wires / 50 mm] or less ends. The tire according to claim 1.

7. The tread rubber further comprises at least two circumferential grooves extending in the circumferential direction of the tire, The aforementioned circumferential grooves are present in the center region and shoulder region of the tread surface. The thickness D of the tread rubber from the bottom of the circumferential groove in the center region to the belt layer, and the thickness d of the tread rubber from the bottom of the circumferential groove in the shoulder region to the belt layer, satisfy the relationship 0.8 < D / d < 1.

3. The tire according to claim 1.

8. The contact width Wt of the tread rubber and the cross-sectional width Wp of the carcass layer satisfy the relationship 0.60 ≤ Wt / Wp ≤ 0.

95. The tire according to claim 1.

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