tire

Abstract

To provide a tire that can improve resistance to uneven wear while suppressing rib tearing in the shoulder region. [Solution] A tire having a tread portion 2 having a plurality of circumferential main grooves 20 extending in the circumferential direction of the tire, and a belt layer 14 having a plurality of belt plies, wherein the belt layer 14 has a circumferential reinforcing layer 145 disposed between a pair of cross belt layers 142, 143 and formed with a width in the tire width direction narrower than the width of the cross belt layers 142, 143, and the inclination angle of the belt cord with respect to the tire circumferential direction is 5 [deg] or less, and the tread portion 2 has a shoulder portion narrow groove 60 disposed on the outside in the tire width direction of the circumferential main grooves 20 and extending in the tire circumferential direction, and the distance W from the tire equatorial plane CL to the end of the circumferential reinforcing layer 145 in the tire width direction C And the distance W from the tire's equatorial plane CL to the shoulder groove 60. N And, 0.50≦W C / W N The relationship ≤ 0.90 is satisfied.

Description

[Technical Field]

[0001] This invention relates to tires. [Background technology]

[0002] Tires have a belt layer in the tread section, which serves as a reinforcing layer. The tread section is made more rigid by the belt layer, and in conventional tires, performance is improved by modifying the belt layer. For example, in the heavy-duty pneumatic tire described in Patent Document 1, the belt has two or more cord crossing layers closer to the carcass and two or more substantially non-stretchable circumferentially arranged cord layers on its outer circumference. In the tire described in Patent Document 2, the belt layer is made up of multiple belt plies, including a high-angle belt, a pair of crossing belts, and a belt cover. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-250314 [Patent Document 2] Japanese Patent Publication No. 2023-048304 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In long-haul operations, which primarily involve high-speed continuous driving, uneven wear can occur, preventing the tire from being used to its end of life and necessitating premature removal and replacement. One method to improve the resistance to uneven wear of such tires is to place a circumferential reinforcing layer in the belt layer, where cords extend along the tire's circumference, thereby suppressing diameter growth during vehicle operation, reducing slippage at the contact surface, and suppressing uneven wear. Another method involves placing fine grooves communicating in the tire's circumference near the shoulder of the tread, as described in Patent Document 2, to alleviate contact pressure near the shoulder end of the tread and improve uneven wear at the shoulder. Combining these methods can effectively suppress uneven wear in the tread to improve the resistance to uneven wear of tires.

[0005] However, when a circumferential reinforcing layer is placed in the belt layer, the rigidity of the tread increases in the region where the circumferential reinforcing layer is placed in the tire width direction, while the rigidity of the tread decreases relatively in the outer part of the region where the circumferential reinforcing layer is placed in the tire width direction. When a narrow groove communicating in the circumferential direction of the tire is placed near the shoulder, if the rigidity of the outer part of the region where the circumferential reinforcing layer is placed in the tire width direction decreases relatively, the difference in rigidity in the tread tends to increase the load on the rigidity near the shoulder. In this case, there is a risk that damage such as rib tearing, starting from the narrow groove placed in the shoulder, is likely to occur near the shoulder. For this reason, it has been difficult to suppress uneven wear of the tread without causing damage such as rib tearing in the shoulder.

[0006] The present invention has been made in view of the above, and aims to provide a tire that can improve resistance to uneven wear while suppressing rib tearing in the shoulder region. [Means for solving the problem]

[0007] To solve the above-mentioned problems and achieve the objective, the present invention provides a tire comprising: a tread portion having a plurality of circumferential main grooves extending in the tire circumferential direction; and a belt layer disposed on the tread portion and comprising a plurality of belt plies, wherein the belt layer comprises: a pair of cross belt layers in which the inclination direction of the belt cords in the tire width direction relative to the tire circumferential direction is opposite to that of the pair of cross belt layers; and a circumferential reinforcing layer disposed between the pair of cross belt layers, formed with a width in the tire width direction narrower than the width of the cross belt layers, and having an inclination angle of the belt cords in the tire width direction relative to the tire circumferential direction of 5 [deg] or less; wherein the tread portion has a shoulder portion narrow groove that is disposed on the outside of the circumferential main grooves in the tire width direction and extends in the tire circumferential direction, and the distance in the tire width direction from the tire equatorial plane to the end of the circumferential reinforcing layer in the tire width direction is W C Let W be the distance in the tire width direction from the tire's equatorial plane to the inner end of the narrow groove in the shoulder portion in the tire width direction. N In this case, distance W C distance W N This means 0.50 ≤ W C / W N The relationship ≤ 0.90 is satisfied. [Effects of the Invention]

[0008] The tire according to the present invention has the effect of improving resistance to uneven wear while suppressing rib tearing in the shoulder region. [Brief explanation of the drawing]

[0009] [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 schematic diagram of the belt layer shown in Figure 1. [Figure 3] Figure 3 is a plan view of the tread section shown in Figure 1. [Figure 4] Figure 4 is a detailed view of the tread portion shown in Figure 1, showing the region on one side of the tire's equatorial plane in the tire width direction. [Figure 5] Figure 5 is a detailed view of the narrow groove in the shoulder section shown in Figure 4. [Figure 6A] Figure 6A is a chart showing the results of performance evaluation tests for pneumatic tires. [Figure 6B] Figure 6B is a chart showing the results of performance evaluation tests for pneumatic tires. [Modes for carrying out the invention]

[0010] 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.

[0011] [Embodiment] 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.

[0012] Figure 1 is a meridional cross-sectional view of a tire, showing the main part of a pneumatic tire 1 according to an embodiment. In Figure 1, the meridional cross-section of the pneumatic tire 1 according to the embodiment shows a cross-section of one side region of the tire rotation axis in the tire radial direction. In this embodiment, as an example, a heavy-duty pneumatic radial tire mounted on a vehicle for long-distance transport such as a truck or bus will be described.

[0013] In this embodiment, the pneumatic tire 1 has a tread portion 2 located at the outermost part in the radial direction of the tire when viewed in the meridional cross-section of the tire. The tread portion 2 has a tread rubber 4 made of a rubber composition. The surface of the tread portion 2, that is, the part that comes into contact with the road surface when the vehicle (not shown) equipped with the pneumatic tire 1 is running, 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.

[0014] Shoulder portions 5 are located at both outer ends of the tread portion 2 in the tire width direction, and sidewall portions 8 are positioned on the inner side of the shoulder portions 5 in the tire radial direction. In other words, the sidewall portions 8 are located on both sides of the tread portion 2 in the tire width direction. To put it another way, the sidewall portions 8 are located at two locations on both sides of the pneumatic tire 1 in the tire width direction, forming the outermost exposed portion of the pneumatic tire 1 in the tire width direction. The sidewall portions 8 have sidewall rubber 9 made of a rubber composition.

[0015] A bead portion 10 is provided on the radially inner side of each sidewall portion 8 located on both sides in the tire width direction. Similar to the sidewall portion 8, the bead portion 10 is located at two locations on both sides of the tire equatorial plane CL; that is, a pair of bead portions 10 are located on both sides in the tire width direction of the tire equatorial plane CL. A bead core 11 is provided in each bead portion 10, and a bead filler 12 is provided on the radially outer side of the bead core 11.

[0016] 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 has a lower filler 121 and an upper filler 122, which are rubber members, and is positioned on the radially outer side of the bead core 11 to reinforce the bead portion 10.

[0017] A carcass layer 13 containing the cords of radial ply is continuously provided on the inner side of the tread portion 2 in the radial direction of the tire, 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 framework of the tire.

[0018] More specifically, the carcass layer 13 is positioned from one of a pair of bead portions 10 located on both sides in the tire width direction to the other bead portion 10, and is wrapped around the bead core 11 in the tire width direction outward along the bead core 11 so as to enclose the bead core 11 and the bead filler 12. The bead filler 12 is a rubber material that is placed in the space formed on the radially outer side of the bead core 11 when the carcass layer 13 is folded back at the bead portion 10 in this way. Furthermore, the carcass ply of the carcass layer 13 is constructed by covering multiple carcass cords made of steel or organic fiber materials such as aramid, nylon, polyester, or rayon with a coating rubber and rolling it. Multiple carcass cords constituting the carcass ply are arranged side by side at an angle in the tire circumferential direction, while their angle with respect to the tire circumferential direction is along the tire meridian direction.

[0019] Furthermore, a belt layer 14 is arranged in the tread portion 2. Figure 2 is a schematic diagram of the belt layer 14 shown in Figure 1. 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 in the tread portion 2. The belt layer 14 is made up of multiple belt plies 141 to 145 stacked together and is arranged around the outer circumference of the carcass layer 13. The belt plies 141 to 145 include a high-angle belt 141, a pair of cross belts 142 and 143, a belt cover 144, and a circumferential reinforcing layer 145.

[0020] The high-angle belt 141 is constructed by covering multiple belt cords made of steel wire with a coating rubber and rolling them, and has a cord angle (defined as the inclination angle of the belt cord in the longitudinal direction relative to the circumferential direction of the tire) of 45 degrees to 70 degrees in absolute value, preferably 54 degrees to 68 degrees. The high-angle belt 141 is also laminated and arranged on the radially outer side of the carcass layer 13.

[0021] The pair of cross belts 142 and 143 are constructed by covering multiple belt cords made of steel wire with coated rubber and rolling them, and have a cord angle of 10 degrees or more and 45 degrees or less in absolute value, preferably 14 degrees or more and 28 degrees or less. Furthermore, the pair of cross belts 142 and 143 have cord angles of opposite signs to each other and are laminated with the longitudinal directions of the belt cords intersecting each other (having a so-called cross-ply structure). In other words, the inclination direction of the belt cords in the tire width direction relative to the tire circumferential direction of the pair of cross belt layers 142 and 143 is opposite to that of the pair of cross belt layers 142 and 143. In addition, the pair of cross belts 142 and 143 are laminated and arranged on the outer side in the tire radial direction of the high-angle belt 141. Here, the cross belt 142 located on the inner side in the tire radial direction is defined as the inner cross belt, and the cross belt 143 located on the outer side in the tire radial direction is defined as the outer cross belt.

[0022] The belt cover 144 is constructed by covering multiple belt cover cords made of steel wire or organic fiber material with coated rubber and rolling it, and has a cord angle of 10 degrees or more and 45 degrees or less in absolute value, preferably 14 degrees or more and 28 degrees or less. The belt cover 144 is also arranged laminated on the outer side in the tire radial direction of the cross belts 142 and 143. In this embodiment, the belt cover 144 has the same cord angle as the outer cross belt 143 and is arranged as the outermost layer of the belt layer 14.

[0023] The circumferential reinforcement layer 145 is constructed by spirally winding a belt cord made of steel wire covered with coated rubber around the tire circumferentially, and has a cord angle of 5 degrees or less in absolute value. In other words, the circumferential reinforcement layer 145 has a belt cord inclination angle of 5 degrees or less in the tire width direction relative to the tire circumferential direction. The circumferential reinforcement layer 145 is also positioned sandwiched between a pair of cross belts 142 and 143. Furthermore, the circumferential reinforcement layer 145 is formed with a width in the tire width direction that is narrower than the width of the cross belt layers 142 and 143 in the tire width direction. For this reason, the circumferential reinforcement layer 145 is positioned inward in the tire width direction from both ends of the pair of cross belts 142 and 143 in the tire width direction. Specifically, the circumferential reinforcement layer 145 is formed by spirally winding one or more wires around the outer circumference of the inner cross belt 142. Furthermore, the circumferential reinforcement layer 145 is arranged continuously in the tire width direction, straddling the tire equatorial plane CL in the tire width direction.

[0024] In this embodiment, the circumferential reinforcing layer 145 has a number of belt cord ends, i.e., the number of belt cords driven in per unit width, that is, within the range of 15 [cords / 50 mm] to 30 [cords / 50 mm]. The outer diameter of the belt cord is within the range of 1.2 [mm] to 2.2 [mm]. In the case where the belt cord is composed of multiple twisted cords, the diameter of the circumscribed circle of the belt cord is measured as the outer diameter of the belt cord.

[0025] In the bead portion 10, rim cushion rubber 17 is arranged on the inner side in the tire radial direction and the outer side in the tire width direction of the bead core 11 and the reversal portion of the carcass layer 13, forming the contact surface of the bead portion 10 with the rim flange. In addition, an inner liner 16 is formed along the carcass layer 13 on the inside of the carcass layer 13, or on the inner 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.

[0026] Figure 3 is a plan view of the tread portion 2 shown in Figure 1. The tread portion 2 has multiple circumferential main grooves 20 that extend in the circumferential direction of the tire on the tread contact surface 3, and the surface of the tread portion 2 is divided into multiple land areas 30 by the multiple circumferential main grooves 20. In this embodiment, only two circumferential main grooves 20 are provided. The two circumferential main grooves 20 are provided one on each side of the tire equatorial plane CL in the tire width direction.

[0027] The circumferential main groove 20 referred to here is a longitudinal groove that extends in the circumferential direction of the tire and has a wear indicator (slip sign) inside that indicates the end of wear. The circumferential main groove 20 formed in this way has a groove width in the range of 5.0 [mm] to 18.0 [mm] and a groove depth in the range of 10.0 [mm] to 20.0 [mm].

[0028] Furthermore, the tread portion 2 has multiple chamfered circumferential grooves 25 that extend in the circumferential direction of the tire on the tread contact surface 3. The chamfered circumferential grooves 25 are circumferential grooves that extend in the circumferential direction of the tire with a groove width narrower than the circumferential main groove 20, and the openings to the tread contact surface 3 are chamfered. The chamfered circumferential grooves 25 do not have a wear indicator, and the groove width of the portion of the chamfered circumferential groove 25 on the groove bottom side is less than 5.0 [mm].

[0029] Two chamfered circumferential grooves 25 are provided, with one groove on each side of the tire's equatorial plane CL in the tire width direction. More specifically, the chamfered circumferential grooves 25 are positioned inward in the tire width direction compared to the circumferential main grooves 20. In other words, one chamfered circumferential groove 25 is positioned on each side of the tire's equatorial plane CL, and one circumferential main groove 20 is positioned outward in the tire width direction from the two chamfered circumferential grooves 25.

[0030] The circumferential main grooves 20 and chamfered circumferential fine grooves 25, which are arranged side by side in the tire width direction as described above, are both formed with groove bottoms that extend in the tire width direction while oscillating in the tire width direction. In other words, the openings of both the circumferential main grooves 20 and the chamfered circumferential fine grooves 25 have a constant position in the tire width direction and extend in the tire width direction, while the groove bottoms extend in the tire width direction and oscillate in the tire width direction, thus forming a wave-like shape.

[0031] The chamfered circumferential grooves 25, together with the circumferential main grooves 20, define the land portion 30 of the tread portion 2. The land portion 30, defined by the circumferential main grooves 20 and the chamfered circumferential grooves 25, has a center land portion 31, a middle land portion 32, and a shoulder land portion 33. The center land portion 31 is a land portion 30 positioned between the two chamfered circumferential grooves 25, and both sides in the tire width direction are defined by the chamfered circumferential grooves 25. The center land portion 31 is positioned on the tire equatorial plane CL.

[0032] The middle land section 32 is positioned between adjacent circumferential main grooves 20 and chamfered circumferential narrow grooves 25 in the tire width direction. The inner portion in the tire width direction is demarcated by the chamfered circumferential narrow grooves 25, and the outer portion in the tire width direction is demarcated by the circumferential main grooves 20. For this reason, the middle land section 32 is positioned on both sides of the tire equatorial plane CL in the tire width direction.

[0033] The shoulder land portion 33 is a land portion 30 positioned on the outer side in the tire width direction of the circumferential main groove 20, and the inner portion in the tire width direction is demarcated by the circumferential main groove 20. For this reason, the shoulder land portion 33 is positioned on both sides of the tire equatorial plane CL in the tire width direction.

[0034] Furthermore, the tread portion 2 has a shoulder portion narrow groove 60 that is located on the outside in the tire width direction of the circumferential main groove 20 and extends in the tire circumferential direction. The shoulder portion narrow groove 60 has a groove width of 4.0 [mm] or less at the opening to the tread contact surface 3, and a groove depth within the range of 10.0 [mm] to 20.0 [mm]. The shoulder portion narrow groove 60 is located on the shoulder land portion 33, which is one of the multiple land portions 30 that the tread portion 2 has. Specifically, the shoulder portion narrow groove 60 is located near the outer end in the tire width direction of the shoulder land portion 33.

[0035] Furthermore, multi-sipes 70 are arranged on the land portion 30 of the tread portion 2. Each multi-sipe 70 is a short sipe in each land portion 30, with one end opening into the circumferential groove and the other end terminating within the land portion 30. In this embodiment, the multi-sipe 70 has a groove width in the range of 0.3 [mm] to 1.5 [mm], a groove depth in the range of 2.0 [mm] to 17 [mm], and a length in the extending direction of the multi-sipe 70 in the range of 2.0 [mm] to 10 [mm].

[0036] Multiple multi-sipes 70 are arranged in the center land area 31, the middle land area 32, and the shoulder land area 33. The multiple multi-sipes 70 arranged in the center land area 31 are positioned along two chamfered circumferential grooves 25 that demarcate both sides of the center land area 31 in the tire width direction. In other words, the multiple multi-sipes 70 arranged in the center land area 31 are formed with one end opening into the chamfered circumferential groove 25 and the other end terminating within the center land area 31, and multiple sipes are arranged in a line along the chamfered circumferential groove 25 in the tire circumferential direction.

[0037] Multiple multi-sipes 70 positioned in the middle land portion 32 are arranged along the circumferential main groove 20 and the chamfered circumferential narrow groove 25 that demarcate both sides of the middle land portion 32 in the tire width direction. In other words, multiple multi-sipes 70 positioned in the middle land portion 32 are formed with one end opening into the circumferential main groove 20 or the chamfered circumferential narrow groove 25 and the other end terminating within the middle land portion 32, and multiple sipes are arranged side by side in the tire circumferential direction along the circumferential main groove 20 or the chamfered circumferential narrow groove 25.

[0038] Multiple multi-sipes 70 arranged on the shoulder land portion 33 are positioned along the circumferential main groove 20 that demarcates the inner side of the shoulder land portion 33 in the tire width direction, and along the shoulder portion narrow groove 60 arranged on the shoulder land portion 33. In other words, multiple multi-sipes 70 arranged on the shoulder land portion 33 are formed with one end opening into the circumferential main groove 20 or the shoulder portion narrow groove 60, and the other end terminating within the shoulder land portion 33, and multiple sipes are arranged in a line in the tire circumferential direction along the circumferential main groove 20 or the shoulder portion narrow groove 60.

[0039] In each land section 30, multiple multi-sipes 70 are arranged in a line in the circumferential direction of the tire, and the pitch length between adjacent multi-sipes 70 in the circumferential direction of the tire is in the range of 0.1% to 0.6% of the tire circumference.

[0040] Furthermore, among the multiple land areas 30 arranged on the tread section 2, the center land area 31 and the middle land area 32 are provided with circumferential narrow grooves 40 and lateral grooves 50. The circumferential narrow grooves 40 here have a groove width in the range of 0.1 [mm] to 2.0 [mm], and preferably a groove width in the range of 0.5 [mm] to 1.5 [mm]. Similarly, the lateral grooves 50 also have a groove width in the range of 0.1 [mm] to 2.0 [mm], and preferably a groove width in the range of 0.5 [mm] to 1.5 [mm].

[0041] The center land portion 31 has a circumferential groove 40, which is a center circumferential groove 41, and a lateral groove 50, which is a center lateral groove 51. The center circumferential groove 41 is located near the center of the center land portion 31 in the tire width direction. The center circumferential groove 41 is formed in a zigzag shape by extending in the tire circumferential direction and repeatedly oscillating in the tire width direction. The center lateral groove 51 is located on both sides of the center circumferential groove 41 in the tire width direction on the center land portion 31. One end of the center lateral groove 51 located on both sides of the center circumferential groove 41 in the tire width direction is connected to the center circumferential groove 41, and the other end is connected to a multi-sipe 70 located on the center land portion 31.

[0042] The middle land section 32 is equipped with a middle circumferential groove 42, which is a circumferential groove 40, and a middle lateral groove 52, which is a lateral groove 50. The middle circumferential groove 42 and the middle lateral groove 52 are located in each of the two middle land sections 32, which are located on both sides of the tire equatorial plane CL in the tire width direction. The middle circumferential groove 42 is located near the center of the middle land section 32 in the tire width direction. The middle circumferential groove 42 is formed in a zigzag shape by extending in the tire circumferential direction and repeatedly oscillating in the tire width direction. The middle lateral groove 52 is located on both sides of the middle circumferential groove 42 in the tire width direction in the middle land section 32. The middle lateral grooves 52 located on both sides of the middle circumferential groove 42 in the tire width direction each have one end communicating with the middle circumferential groove 42 and the other end communicating with a multi-sipe 70 located in the middle land section 32.

[0043] Figure 4 is a detailed view of the tread portion 2 shown in Figure 1, showing the region on one side of the tire equatorial plane CL in the tire width direction. The circumferential reinforcing layer 145 of the belt layer 14 is positioned inward in the tire width direction compared to the shoulder groove 60 located on the tread portion 2. Specifically, the distance in the tire width direction from the tire equatorial plane CL to the end of the circumferential reinforcing layer 145 in the tire width direction is W CLet the distance in the tire width direction from the tire equatorial plane CL to the inner end 61 of the shoulder groove 60 in the tire width direction be W. N In the case where C this distance W N and this distance W C satisfy the relationship of 0.50 ≤ W N / W ≤ 0.90.

[0044] Also, when the distance in the tire width direction between the outer end 22 in the tire width direction of the circumferential main groove 20 located most outward in the tire width direction among the plurality of circumferential main grooves 20 and the tire equatorial plane CL is W G in the case where C this distance W G and this distance W C satisfy the relationship of 1.00 ≤ W G / W ≤ 1.40. In this embodiment, since only two circumferential main grooves 20 are arranged, the two circumferential main grooves 20 are both the outermost circumferential main groove 21 located most outward in the tire width direction. Therefore, the distance W in the tire width direction between the outer end 22 in the tire width direction of the circumferential main groove 20 located most outward in the tire width direction and the tire equatorial plane CL G is the distance in the tire width direction between the outer end 22 in the tire width direction of each of the two outermost circumferential main grooves 21 and the tire equatorial plane CL.

[0045] Note that the relationship between the distance W in the circumferential reinforcing layer 145 and the shoulder groove 60 C and this distance W N is preferably within the range of 0.60 ≤ W C / W ≤ 0.80, and the relationship between the distance W in the circumferential reinforcing layer 145 and the outermost circumferential main groove 21 N and this distance W C is preferably within the range of 1.10 ≤ W G / W ≤ 1.30. C / W G is preferably within the range of 1.10 ≤ W / W ≤ 1.30.

[0046] Furthermore, of the pair of cross belt layers 142 and 143, the distance G1 from the end 142a in the tire width direction of the inner cross belt layer 142, which is located on the inside of the circumferential reinforcing layer 145 in the tire radial direction, to the bottom 62 of the shoulder groove 60 is within the range of 7 [mm] ≤ G1 ≤ 17 [mm]. Also, of the pair of cross belt layers 142 and 143, the distance G2 from the end 143a in the tire width direction of the outer cross belt layer 143, which is located on the outside of the circumferential reinforcing layer 145 in the tire radial direction, to the bottom 62 of the shoulder groove 60 is within the range of 10 [mm] ≤ G2 ≤ ​​20 [mm].

[0047] Figure 5 is a detailed view of the shoulder groove 60 shown in Figure 4. The shoulder groove 60, located on the shoulder land portion 33, is positioned near the outer end of the shoulder land portion 33 in the tire width direction. The distance W from the outer end of the shoulder land portion 33 in the tire width direction to the shoulder groove 60 is... R However, 10 [mm] ≤ W R It is within the range of ≤18 [mm].

[0048] The shoulder portion 33 has a shoulder groove 60 positioned near its outer end in the tire width direction, and a thin rib 34 extending outward from the shoulder groove 60 in the tire width direction. The inner portion of the thin rib 34 in the tire width direction is demarcated by the shoulder groove 60, and it is a rib-shaped portion that extends in the tire circumferential direction with a relatively narrow width in the tire width direction.

[0049] The tread contact surface 3 of the thin rib 34 is offset inward in the tire radial direction compared to the portion of the shoulder area 33 that is inward in the tire width direction compared to the shoulder groove 60. The amount F of the offset of the tread contact surface 3 of the thin rib 34 relative to the tread contact surface 3 of the shoulder area 33 that is inward in the tire width direction compared to the shoulder groove 60 is in the range of 1.0 [mm] ≤ F ≤ 4.0 [mm].

[0050] Furthermore, the shoulder groove 60 has a width D in the groove width direction of the shoulder groove 60 at the bottom 62. N The shoulder section has a narrow groove of 60, with a groove width of W. S It has a cylindrical portion 64 that is larger and has a cylindrical shape that extends in the circumferential direction of the tire. The cylindrical portion 64 is formed at a position that includes the bottom 62 of the shoulder groove 60, and is formed by the bottom 62 of the shoulder groove 60 and the groove wall 63 near the bottom 62. In a cross-sectional view taken along the length of the shoulder groove 60, the cylindrical portion 64 formed by the bottom 62 and the groove wall 63 is formed in a shape with a substantially cylindrical diameter by the continuous curvature of the bottom 62 and the groove wall 63.

[0051] More specifically, the cylindrical portion 64 is formed in a curved shape where at least one of the pair of opposing groove walls 63 in the shoulder portion narrow groove 60 is recessed in a direction away from the other groove wall 63, and the bottom portion 62 and the groove wall 63 are continuous. In this embodiment, of the cylindrical portion 64 of the shoulder portion narrow groove 60, of the pair of opposing groove walls 63 with the bottom portion 62 in between, one groove wall 63 is recessed in a curved shape in a direction away from the other groove wall 63, and the other groove wall 63 is curved continuously from the bottom portion 62 without recessing in a direction that increases the distance between the groove walls 63.

[0052] The cylindrical portion 64 of the shoulder groove 60 formed in this manner has a width D in the groove width direction of the shoulder groove 60. N However, the groove width W in the shoulder groove 60 is at a position other than the cylindrical portion 64. S It is larger than this. In this case, the width D of the cylindrical portion 64 N The diameter of the cylindrical portion 64 corresponds to the shape of the cylindrical portion 64. The width D of the cylindrical portion 64 of the shoulder groove 60 N This refers to the groove width W at positions other than the cylindrical portion 64 in the shoulder groove 60. S In contrast, it falls within the range of 1.2 times to 5 times.

[0053] Note that the groove width W is located at positions other than the cylindrical portion 64 in the shoulder groove 60. S 1.0 [mm] ≤ W SPreferably, the width D of the cylindrical portion 64 of the shoulder groove 60 is within the range of ≤3.0 [mm]. N 2.0mm≦D N It is preferable that the range be within ≤5.0 mm.

[0054] The pneumatic tire 1 according to the embodiments configured as described above has an aspect ratio of 80% or less. The aspect ratio, as used here, is the percentage of the ratio of the cross-sectional height of the pneumatic tire 1 to the cross-sectional width of the pneumatic tire 1. The cross-sectional width of the pneumatic tire 1 is the total width of the pneumatic tire 1 in the tire width direction, excluding patterns, letters, etc. on the side of the tire. The cross-sectional height of the pneumatic tire 1 is half the difference between the outer diameter of the pneumatic tire 1 and the diameter of the rim on which the pneumatic tire 1 is mounted.

[0055] 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.

[0056] 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, circumferential fine grooves 40, and lateral grooves 50, and the water between the tread contact surface 3 and the road surface is drained by these grooves as the vehicle drives. 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 allows the vehicle to drive.

[0057] When a vehicle equipped with a pneumatic tire 1 is in motion, the tread contact surface 3 is in contact with the road surface as it moves, so the tread portion 2 gradually wears down from the tread contact surface 3 side on the land portion 30. At that time, the portion of the tread contact surface 3 near the center in the tire width direction tends to have its outer diameter increased by centrifugal force when the pneumatic tire 1 rotates, making it easier for it to make contact with the road under high ground pressure.

[0058] On the other hand, the contact pressure in the tread contact surface 3 near the edges in the tire width direction tends to be lower due to the difference in outer diameter between it and the central part in the tire width direction. Therefore, in the tread contact surface 3 near the edges in the tire width direction, slippage is more likely to occur between it and the road surface due to the difference in contact pressure caused by the difference in outer diameter between it and the central part in the tire width direction when the pneumatic tire 1 rotates, and wear is relatively more likely to occur. In this way, the tread contact surface 3 is prone to uneven wear because the ease of wear differs between the central part and the edges in the tire width direction.

[0059] In contrast, the pneumatic tire 1 according to this embodiment has a belt layer 14 that is formed with a width in the tire width direction that is narrower than the width of the pair of intersecting belt layers 142 and 143, and has a belt cord inclination angle of 5 degrees or less. As a result, the belt layer 14 can have its elongation in the tire circumferential direction in the area where the circumferential reinforcing layer 145 is arranged suppressed by the circumferential reinforcing layer 145, and the outer diameter can be prevented from increasing when the pneumatic tire 1 rotates by the circumferential reinforcing layer 145. This makes it possible to suppress the occurrence of uneven wear caused by the outer diameter near the center in the tire width direction increasing when the pneumatic tire 1 rotates.

[0060] On the other hand, if the rigidity near the center in the tire width direction is increased by placing a circumferential reinforcing layer 145 at a position including the center in the tire width direction of the tread portion 2, there is a risk that the rigidity near the ends of the tread portion 2 in the tire width direction, i.e., near the shoulder portion 5 of the tread portion 2, will become too low compared to the rigidity near the center in the tire width direction. In this case, due to the difference in rigidity of the tread portion 2, the load on the rigidity near the shoulder portion 5 of the tread portion 2 will become too large when the vehicle is running, and the contact pressure will become too large locally, which may make it easier for a so-called rib tear to occur, a failure in which the land portion 30 of the tread portion 2 continuously breaks off in the circumferential direction of the tire.

[0061] In contrast, the pneumatic tire 1 according to this embodiment has a shoulder groove 60 extending in the circumferential direction of the tire on the outer side in the tire width direction of the circumferential main groove 20 arranged in the tread portion 2. As a result, near the shoulder portion 5 of the tread portion 2, the tread portion 2 is more easily deformed by the shoulder groove 60 when a load is applied, thereby suppressing a localized increase in the contact pressure of the tread contact surface 3. Therefore, it is possible to suppress the occurrence of rib tears near the shoulder portion 5, which occur when the contact pressure near the shoulder portion 5 increases locally due to the load acting on the shoulder portion 5 of the tread portion 2.

[0062] Furthermore, in the pneumatic tire 1 according to this embodiment, the circumferential reinforcing layer 145 is positioned between the pair of cross belt layers 142 and 143, which can more reliably suppress the increase in the rigidity difference of the tread portion 2. In other words, since the inclination direction of the belt cords in the tire width direction relative to the tire circumferential direction is different for the pair of cross belt layers 142 and 143, when the cross belt layers 142 and 143 are stacked on top of each other, the pair of cross belt layers 142 and 143 can exert a synergistic rigidity by constraining each other's movement.

[0063] However, while stacking the pair of cross belt layers 142 and 143 provides high rigidity, if a circumferential reinforcing layer 145 is added to the pair of cross belt layers 142 and 143, the portion of the belt layer 14 where the circumferential reinforcing layer 145 is located may become too rigid due to the combined rigidity of the pair of cross belt layers 142 and 143 and the circumferential reinforcing layer 145. If the rigidity of the portion of the tire width direction where the circumferential reinforcing layer 145 is located becomes too high, the difference in rigidity between the area near the center of the tread portion 2 and the area near the shoulder portion 5 in the tire width direction will become too large. This makes it difficult to effectively suppress the localized increase in contact pressure near the shoulder portion 5, and may make it difficult to effectively suppress rib tearing that occurs near the shoulder portion 5.

[0064] In contrast, in the pneumatic tire 1 according to this embodiment, the circumferential reinforcing layer 145 is positioned between a pair of cross belt layers 142 and 143. This prevents the rigidity exerted by the pair of cross belt layers 142 and 143 by restraining each other's movement from becoming too high, while appropriately improving the rigidity in the area where the circumferential reinforcing layer 145 is positioned. In other words, the belt layer 14 ensures rigidity over a wide area in the tire width direction of the tread portion 2 by the pair of cross belt layers 142 and 143, while the circumferential reinforcing layer 145, positioned between the cross belt layers 142 and 143 with a narrower width than the pair of cross belt layers 142 and 143, and the cross belt layers 142 and 143, can improve the rigidity near the center in the tire width direction by an appropriate amount without making it too high. This prevents the rigidity difference between the area near the center of the tread portion 2 and the area near the shoulder portion 5 from becoming too large in the tire width direction, and effectively suppresses the occurrence of rib tears originating from the shoulder portion narrow grooves 60 in the shoulder portion 5.

[0065] Furthermore, the circumferential reinforcing layer 145 and the shoulder groove 60 are located at a distance W in the tire width direction from the tire equatorial plane CL to the end of the circumferential reinforcing layer 145 in the tire width direction. CThe distance W in the tire width direction is from the tire equatorial plane CL to the inner end 61 of the shoulder groove 60 in the tire width direction. N And, 0.50≦W C / W N Since the relationship ≤0.90 is satisfied, uneven wear near the shoulder portion 5 of the tread portion 2 can be suppressed, while the occurrence of rib tears near the shoulder portion 5 can also be suppressed.

[0066] In other words, distance W C distance W N The relationship is, W C / W N If <0.50, then distance W N Distance W C Because the width is small and the width of the circumferential reinforcing layer 145 in the tire width direction is too narrow, there is a risk that the rigidity near the center in the tire width direction will not be adequately improved by the circumferential reinforcing layer 145. In this case, it will be difficult for the circumferential reinforcing layer 145 to suppress the increase in the outer diameter near the center in the tire width direction when the pneumatic tire 1 rotates, and there is a risk that it will be difficult to suppress the occurrence of uneven wear near the shoulder portion 5 caused by the increase in the outer diameter near the center in the tire width direction. Also, distance W C distance W N The relationship is, W C / W N If >0.90, then distance W N Distance W C Because the width of the circumferential reinforcing layer 145 in the tire width direction is large, there is a risk that the area in which the rigidity of the tread portion 2 is improved by the circumferential reinforcing layer 145 will extend to the vicinity of the shoulder portion 5. In this case, the part in which the rigidity of the tread portion 2 changes depending on the presence or absence of the circumferential reinforcing layer 145 is located near the shoulder portion 5 of the tread portion 2. As a result, there is a risk that the load on the rigidity will be large in the low-rigidity area due to the location of the part in which the rigidity changes near the shoulder portion 5. Consequently, the contact pressure will be locally large near the shoulder portion 5, which may make it difficult to suppress the occurrence of rib tears starting from the narrow grooves 60 in the shoulder portion.

[0067] In contrast, distance W C distance W N The relationship is 0.50 ≤ W C / W N If the value is within the range of ≤0.90, the stiffness of the tread portion 2 does not change due to the presence or absence of the circumferential reinforcing layer 145, and the stiffness of the area near the center in the tire width direction can be improved by the circumferential reinforcing layer 145 without the area near the shoulder portion 5 being located there. As a result, uneven wear, where the area near the shoulder portion 5 of the tread portion 2 wears out earlier than the area near the center in the tire width direction, can be suppressed, while the occurrence of rib tear caused by locally high contact pressure near the shoulder portion 5 can be suppressed. As a result, resistance to uneven wear can be improved while suppressing rib tear in the shoulder region, which is the area near the shoulder portion 5 of the tread portion 2.

[0068] Furthermore, the circumferential reinforcing layer 145 and the outermost main groove 21 are located at a distance W in the tire width direction from the tire equatorial plane CL to the end of the circumferential reinforcing layer 145 in the tire width direction. C The distance W in the tire width direction is between the outermost end 22 of the outermost main groove 21 in the tire width direction, the tire equatorial plane CL, and the tire width direction. G And, 1.00 ≤ W C / W G Since the relationship ≤1.40 is satisfied, uneven wear near the shoulder portion 5 of the tread portion 2 can be suppressed, while the occurrence of rib tears near the shoulder portion 5 can also be suppressed.

[0069] In other words, distance W C distance W G The relationship is W C / W G If <1.00, then distance W G Distance W CBecause the width is small and the width of the circumferential reinforcing layer 145 in the tire width direction is too narrow, there is a risk that the rigidity near the center in the tire width direction will not be adequately improved by the circumferential reinforcing layer 145. In this case, it will be difficult for the circumferential reinforcing layer 145 to suppress the increase in the outer diameter near the center in the tire width direction when the pneumatic tire 1 rotates, and there is a risk that it will be difficult to suppress the occurrence of uneven wear near the shoulder portion 5 caused by the increase in the outer diameter near the center in the tire width direction. Also, distance W C distance W G The relationship is W C / W G If >1.40, then distance W G Distance W C Because the width of the circumferential reinforcing layer 145 in the tire width direction is large, there is a risk that the area in which the rigidity of the tread portion 2 is improved by the circumferential reinforcing layer 145 will extend to the vicinity of the shoulder portion 5. In this case, the part in which the rigidity of the tread portion 2 changes depending on the presence or absence of the circumferential reinforcing layer 145 is located near the shoulder portion 5 of the tread portion 2. As a result, there is a risk that the load on the rigidity will be large in the low-rigidity area due to the location of the part in which the rigidity changes near the shoulder portion 5. Consequently, the contact pressure will be locally large near the shoulder portion 5, which may make it difficult to suppress the occurrence of rib tears starting from the narrow grooves 60 in the shoulder portion.

[0070] In contrast, distance W C distance W G The relationship is 1.00 ≤ W C / W G If the value is within the range of ≤1.40, the stiffness of the tread portion 2 does not change due to the presence or absence of the circumferential reinforcing layer 145, and the stiffness of the central part in the tire width direction can be improved by the circumferential reinforcing layer 145 without the part near the shoulder portion 5 being located there. As a result, uneven wear, where the area near the shoulder portion 5 of the tread portion 2 wears out earlier than the central part in the tire width direction, can be suppressed, while the occurrence of rib tear caused by locally high contact pressure near the shoulder portion 5 can be suppressed. As a result, resistance to uneven wear can be improved while suppressing rib tear in the shoulder region.

[0071] Furthermore, the pair of cross belt layers 142 and 143 have a distance G1 from the end 142a in the tire width direction of the inner cross belt layer 142 to the bottom 62 of the shoulder groove 60 within the range of 7 [mm] ≤ G1 ≤ 17 [mm], and a distance G2 from the end 143a in the tire width direction of the outer cross belt layer 143 to the bottom 62 of the shoulder groove 60 within the range of 10 [mm] ≤ G2 ≤ ​​20 [mm]. Therefore, uneven wear near the shoulder portion 5 of the tread portion 2 can be suppressed, while the generation of rib tears originating from the shoulder groove 60 can be suppressed.

[0072] In other words, if the distance G1 from the end 142a of the inner cross belt layer 142 to the bottom 62 of the shoulder groove 60 is G1 < 7 [mm], or if the distance G2 from the end 143a of the outer cross belt layer 143 to the bottom 62 of the shoulder groove 60 is G2 < 10 [mm], then the distance between the inner cross belt layer 142 or outer cross belt layer 143 and the shoulder groove 60 is too small, which may easily cause stress concentration between the inner cross belt layer 142 or outer cross belt layer 143 and the shoulder groove 60. In this case, stress concentration may easily cause rib tearing starting from the shoulder groove 60.

[0073] Furthermore, if the distance G1 from the end 142a of the inner cross belt layer 142 to the bottom 62 of the shoulder groove 60 is G1 > 17 [mm], or if the distance G2 from the end 143a of the outer cross belt layer 143 to the bottom 62 of the shoulder groove 60 is G2 > 20 [mm], the distance between the inner cross belt layer 142 or outer cross belt layer 143 and the shoulder groove 60 is too large, which may result in the cross belt layers 142 and 143 being too narrow in the tire width direction. In this case, the range over which the rigidity of the tread portion 2 is ensured by the cross belt layers 142 and 143 becomes narrower, making it difficult to ensure rigidity near the center in the tire width direction by the cross belt layers 142 and 143. As a result, it becomes difficult for the cross belt layers 142 and 143 to suppress the increase in the outer diameter near the center in the tire width direction when the pneumatic tire 1 rotates, which may make it difficult to suppress uneven wear near the shoulder portion 5.

[0074] In contrast, if the distance G1 from the end 142a of the inner cross belt layer 142 to the bottom 62 of the shoulder groove 60 is within the range of 7[mm]≦G1≦17[mm], and the distance G2 from the end 143a of the outer cross belt layer 143 to the bottom 62 of the shoulder groove 60 is within the range of 10[mm]≦G2≦20[mm], then it is possible to improve the rigidity near the center in the tire width direction using the cross belt layers 142 and 143 while suppressing the occurrence of stress concentration between the inner cross belt layer 142 and the outer cross belt layer 143 and the shoulder groove 60. This suppresses uneven wear where the area near the shoulder 5 of the tread 2 wears out earlier than the area near the center in the tire width direction, and also suppresses the occurrence of rib tear starting from the shoulder groove 60. As a result, it is possible to improve resistance to uneven wear while suppressing rib tear in the shoulder region.

[0075] Furthermore, since the circumferential reinforcing layer 145 has a belt cord end count of 15 [cords / 50mm] to 30 [cords / 50mm], it can suppress uneven wear near the shoulder portion 5 of the tread portion 2 while suppressing the occurrence of rib tears originating from the shoulder portion narrow groove 60. In other words, if the number of belt cord ends of the circumferential reinforcing layer 145 is less than 15 [cords / 50mm], the number of belt cord ends is too small, which may make it difficult to ensure the rigidity of the circumferential reinforcing layer 145. In this case, it becomes difficult to appropriately improve the rigidity near the center in the tire width direction with the circumferential reinforcing layer 145, and it becomes difficult to suppress the increase in the outer diameter near the center in the tire width direction when the pneumatic tire 1 rotates with the circumferential reinforcing layer 145. As a result, it may become difficult to suppress the occurrence of uneven wear near the shoulder portion 5 caused by the increase in the outer diameter near the center in the tire width direction. Furthermore, if the number of belt cord ends in the circumferential reinforcing layer 145 is greater than 30 [belt cords / 50 mm], there is a risk that the rigidity of the circumferential reinforcing layer 145 will become too high due to the excessive number of belt cord ends. In this case, the difference in rigidity between the part of the tire width where the circumferential reinforcing layer 145 is located and the part where the circumferential reinforcing layer 145 is not located will become too large, which may result in an excessive load on the rigidity near the shoulder part 5 of the tread part 2, making it difficult to suppress the occurrence of rib tears originating from the narrow grooves 60 in the shoulder part.

[0076] In contrast, if the number of belt cord ends of the circumferential reinforcing layer 145 is within the range of 15 [cords / 50mm] to 30 [cords / 50mm], it is possible to ensure the rigidity of the circumferential reinforcing layer 145 while suppressing the excessive difference in rigidity between the area where the circumferential reinforcing layer 145 is located and the area where it is not located. This suppresses uneven wear where the area near the shoulder 5 of the tread 2 wears out earlier than the area near the center in the tire width direction, and also suppresses the generation of rib tears starting from the narrow grooves 60 in the shoulder area. As a result, it is possible to improve resistance to uneven wear while suppressing rib tears in the shoulder area.

[0077] Furthermore, since the shoulder groove 60 has a cylindrical portion 64 at its bottom 62, even when a load is applied near the shoulder groove 60 during vehicle operation, the strain generated at the bottom 62 of the shoulder groove 60 due to the load can be mitigated by the cylindrical portion 64. In other words, the stress concentration that occurs at the bottom 62 when a load is applied near the shoulder groove 60 can be suppressed by the cylindrical portion 64. As a result, even when a load is applied near the shoulder 5 of the tread portion 2, the generation of rib tears starting from the bottom 62 of the shoulder groove 60 can be suppressed.

[0078] Furthermore, since only two circumferential main grooves 20 are arranged in the tread portion 2, the contact area near the center in the tire width direction can be increased. As a result, a large portion of the load acting on the tread portion 2 can be received near the center in the tire width direction, and the load received near the shoulder portion 5 is relatively reduced, thus reducing the contact pressure near the shoulder portion 5. Therefore, it is possible to suppress premature wear of the shoulder portion 5 of the tread portion 2 compared to the portion near the center in the tire width direction during vehicle operation. As a result, uneven wear caused by premature wear in the shoulder region can be suppressed.

[0079] Furthermore, since the pneumatic tire 1 according to the embodiment has an aspect ratio of 80% or less, uneven wear of the tread portion 2 can be effectively suppressed by the circumferential reinforcing layer 145. In other words, in a pneumatic tire 1 with an aspect ratio of 80% or less, the filling internal pressure becomes high, so the contribution of the belt layer 14 to the internal pressure tends to increase, and the contribution of the belt layer 14 to the rigidity of the tread portion 2 tends to increase. Therefore, by arranging the circumferential reinforcing layer 145 on the belt layer 14, the rigidity of the belt layer 14 can be effectively improved, so even in a pneumatic tire 1 with an aspect ratio of 80% or less, it is possible to suppress the increase in the outer diameter near the center in the tire width direction when the pneumatic tire 1 rotates. Consequently, even in a pneumatic tire 1 with an aspect ratio of 80% or less, uneven wear caused by the shoulder portion 5 of the tread portion 2 wearing out earlier than the portion near the center in the tire width direction can be suppressed. As a result, resistance to uneven wear can be improved.

[0080] [Differentiation] In the embodiment described above, the shoulder groove 60 has a cylindrical portion 64 at its bottom 62, but the shoulder groove 60 does not necessarily have to have a cylindrical portion 64. The shoulder groove 60 may also be formed with a constant groove width.

[0081] Furthermore, in the embodiment described above, the number of circumferential main grooves 20 arranged in the tread portion 2 is two, but the number of circumferential main grooves 20 may be other than two. For example, the chamfered circumferential fine grooves 25 in the embodiment may be replaced with circumferential main grooves 20, so that there are four circumferential main grooves 20.

[0082] 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.

[0083] [Examples] Figures 6A and 6B 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 uneven shoulder wear and resistance to rib tearing.

[0084] The performance evaluation test was conducted by mounting a pneumatic tire 1, with a tire nominal size of 295 / 75R22.5 as specified by TRA, onto a rim wheel with a rim specified by TRA, adjusting the air pressure to the maximum air pressure specified by TRA, and then mounting it on a 2-DD test vehicle (tractor head) for a test run.

[0085] For each test item, the evaluation method for shoulder uneven wear resistance was as follows: After driving a test vehicle equipped with the test tire for 100,000 km, the degree of shoulder uneven wear, which is uneven wear of the shoulder area 33 relative to the center area 31 and middle area 32, was measured. The measured degree of shoulder uneven wear was then expressed as an index, with the conventional example described later set to 100, for evaluation. A higher index indicates less shoulder uneven wear and superior shoulder uneven wear resistance.

[0086] Furthermore, the rib tear resistance was evaluated by having a test vehicle equipped with the test tire go on and off a 50 cm high step 20 times, and measuring the number and size of rib tears that occurred on the shoulder land portion 33. Rib tear resistance was evaluated by comprehensively expressing the reciprocal of the number and size of rib tears as an index, with the conventional example described later set to 100. A higher index indicates that the number and size of rib tears are smaller, and that the rib tears are of superior quality.

[0087] The performance evaluation test was conducted on 28 types of pneumatic tires, including a conventional pneumatic tire as an example of a conventional pneumatic tire with air, Examples 1 to 25 of the pneumatic tire 1 according to the present invention, and Comparative Examples 1 and 2 which are pneumatic tires for comparison with the pneumatic tire 1 according to the present invention. Among these, the conventional pneumatic tire has shoulder grooves but no circumferential reinforcing layer. Also, for the pneumatic tires of Comparative Examples 1 and 2, the distance W C from the tire equatorial plane to the end of the circumferential reinforcing layer and the distance W N from the tire equatorial plane to the shoulder groove do not satisfy the relationship of 0.50 ≦ W C / W N ≦ 0.90.

[0088] On the other hand, all of Examples 1 to 25, which are examples of the pneumatic tire 1 according to the present invention, have a circumferential reinforcing layer 145 and shoulder grooves 60, and the distance W C from the tire equatorial plane CL to the end of the circumferential reinforcing layer 145 and the distance W N from the tire equatorial plane CL to the shoulder groove 60 satisfy the relationship of 0.50 ≦ W C / W N ≦ 0.90. Further, for the pneumatic tire 1 according to Examples 1 to 25, the ratio (W C / W G ) of the distance W from the tire equatorial plane CL to the end of the circumferential reinforcing layer 145 and the distance W from the tire equatorial plane CL to the end 22 of the outermost circumferential main groove 21, the distance G1 [mm] from the end 142a of the inner cross belt layer 142 to the shoulder groove 60, the distance G2 [mm] from the end 143a of the outer cross belt layer 143 to the shoulder groove 60, the number of ends of the circumferential reinforcing layer 145 [per 50 mm], the presence or absence of the cylindrical portion 64 of the shoulder groove 60, the width D C / W G ) [mm] of the cylindrical portion 64 of the shoulder groove 60, and the number of circumferential main grooves 20 are all different.

[0089] ​​As a result of conducting an evaluation test using these pneumatic tires 1, as shown in FIGS. 6A and 6B, it was found that the pneumatic tires 1 according to Examples 1 to 25 can improve both the shoulder uneven wear resistance and the rib tear resistance with respect to the conventional example and Comparative Examples 1 and 2. That is, the pneumatic tires 1 according to Examples 1 to 25 can improve the uneven wear resistance while suppressing rib tears in the shoulder region.

[0090] The present disclosure includes the following inventions. Invention [1] A tire having a tread portion with a plurality of circumferential main grooves extending in the tire circumferential direction, and a belt layer disposed in the tread portion and including a plurality of belt plies, wherein the belt layer includes a pair of intersecting belt layers in which the inclination directions of the belt cords in the tire width direction with respect to the tire circumferential direction are opposite to each other, a circumferential reinforcing layer disposed between the pair of intersecting belt layers and formed with a width narrower than the width of the intersecting belt layers in the tire width direction, and having an inclination angle of the belt cord in the tire width direction with respect to the tire circumferential direction of 5° or less, and the tread portion has shoulder portion fine grooves disposed outside the circumferential main grooves in the tire width direction and extending in the tire circumferential direction, where a distance in the tire width direction from the tire equatorial plane to an end portion of the circumferential reinforcing layer in the tire width direction is W C and a distance in the tire width direction from the tire equatorial plane to an inner end portion of the shoulder portion fine grooves in the tire width direction is W N in which case distance W C and distance W N satisfy the relationship of 0.50 ≦ W C / W N ≦ 0.90. Invention [2] A distance in the tire width direction between an outer end portion of the circumferential main groove located most outside in the tire width direction among the plurality of circumferential main grooves, the tire equatorial plane, andG In that case, Distance W C distance W G This means that 1.00 ≤ W C / W G A tire according to the invention [1] that satisfies the relationship ≤ 1.40. Invention [3] Of the pair of cross belt layers, G1 is defined as the distance from the end of the cross belt layer in the tire width direction to the bottom of the shoulder groove, which is located on the inner side of the circumferential reinforcement layer in the tire radial direction. When G2 is defined as the distance from the end of the cross belt layer in the tire width direction to the bottom of the narrow groove in the shoulder portion, among the pair of cross belt layers, which is located on the outer side of the circumferential reinforcing layer in the tire radial direction, The distance G1 is within the range of 7[mm] ≤ G1 ≤ 17[mm]. The tire according to invention [1] or invention [2], wherein the distance G2 is within the range of 10 [mm] ≤ G2 ≤ ​​20 [mm]. invention [4] The circumferential reinforcing layer is made of steel wire belt cords. The tire according to any one of inventions [1] to [3], wherein the number of ends of the belt cords in the circumferential reinforcing layer is within the range of 15 [cords / 50 mm] to 30 [cords / 50 mm]. invention [5] The tire according to any one of the inventions [1] to [4], wherein the shoulder groove has a cylindrical portion at its bottom that is cylindrical in shape and extends in the circumferential direction of the tire, with a width in the groove width direction of the shoulder groove being greater than the groove width of the shoulder groove. invention [6] The tire according to any one of the inventions [1] to [5], wherein only two circumferential main grooves are arranged. invention [7] The tire is the tire according to any one of inventions [1] to [6], wherein the aspect ratio is 80[%] or less. [Explanation of Symbols]

[0091] 1. Pneumatic tire 2 Tread section 3. Tread contact surface 5 Shoulder section 8 Sidewall section 10 Bead section 11 Bead core 12 Bead Fillers 13. Carcass layer 14 Belt Layer 142, 143 Cross belt 145 Circumferential reinforcement layer 17 Rim cushion rubber 16 Inner liner 20 Circumferential main groove 21 Main grooves in the outermost direction 25 Chamfered circumferential fine groove 30 Land 31 Center Track and Field Club 32 Middle Track and Field Club 33 Shoulder Track and Field Club 34 Fine Rib 40 Circumferential thin groove 41 Center circumferential narrow groove 42 Medium circumferential fine grooves 50 Yokomizo 51 Center horizontal groove 52 Middle Horizontal Groove 60 Fine grooves on the shoulder section 62 Bottom 63 Ditch wall 64 Cylindrical section 70 Multi-Sipes

Claims

1. A tire having a tread portion having a plurality of circumferential main grooves extending in the circumferential direction of the tire, and a belt layer disposed on the tread portion and comprising a plurality of belt plies, The aforementioned belt layer is A pair of cross belt layers in which the inclination directions of the belt cords in the tire width direction relative to the tire circumferential direction are in opposite directions, A circumferential reinforcing layer is disposed between a pair of the aforementioned cross belt layers, and is formed with a width in the tire width direction that is narrower than the width of the aforementioned cross belt layers, and the inclination angle of the belt cord in the tire width direction with respect to the tire circumferential direction is 5 [deg] or less. It has, The tread portion has a shoulder portion with a narrow groove that is located on the outside of the circumferential main groove in the tire width direction and extends in the tire circumferential direction. W is the distance in the tire width direction from the tire's equatorial plane to the end of the circumferential reinforcement layer in the tire width direction. Ｃ Let W be the distance in the tire width direction from the tire's equatorial plane to the inner end of the narrow groove in the shoulder portion in the tire width direction. Ｎ In that case, Distance W Ｃ distance W Ｎ This means that 0.50 ≤ W Ｃ / W Ｎ A tire characterized by satisfying the relationship ≤ 0.

90.

2. The distance in the tire width direction between the outermost end of the circumferential main groove, which is located in the tire width direction among multiple circumferential main grooves, and the tire equatorial plane is W. Ｇ In that case, Distance W Ｃ and the distance W Ｇ are such that 1.00 ≤ W Ｃ / W Ｇ ≤ 1.40, for the tire according to claim 1

3. Of the pair of cross belt layers, the distance from the end of the cross belt layer located on the inner side of the circumferential reinforcement layer in the tire radial direction to the bottom of the shoulder groove is G. １ year, Of the pair of cross belt layers, the distance from the end of the cross belt layer located on the outer side of the circumferential reinforcement layer in the tire radial direction to the bottom of the shoulder groove is G. ２ In that case, distance G １ 7 [mm] ≤ G １ It is within the range of ≤17 [mm]. distance G ２ For 10 [mm] ≤ G ２ The tire according to claim 1, wherein the dimensions are within the range of ≤20 [mm].

4. The circumferential reinforcing layer is made of steel wire belt cords. The tire according to claim 1, wherein the number of ends of the belt cords in the circumferential reinforcing layer is within the range of 15 [cords / 50 mm] or more and 30 [cords / 50 mm] or less.

5. The tire according to claim 1, wherein the shoulder groove has a cylindrical portion at its bottom that has a cylindrical shape and extends in the circumferential direction of the tire, and whose width in the groove width direction of the shoulder groove is greater than the groove width of the shoulder groove.

6. The tire according to claim 1, wherein only two circumferential main grooves are arranged.

7. The tire according to claim 1, wherein the aspect ratio of the tire is 80% or less.

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