TIRES

Abstract

[Task] A tire is provided that can offer improved resistance to uneven wear while also providing suppressed rib cracking in a shoulder area. [Solution] A tire includes: a tread section (2) that includes a plurality of major circumferential grooves (20) extending in a tire circumferential direction; and a belt layer (14) that includes a plurality of belt plies. The belt layer (14) includes a circumferential reinforcement layer (145) arranged between a pair of cross belts (142 and 143) whose width in a tire width direction is less than the width of the cross belts (142 and 143) and whose belt cord angle is 5 degrees or less with respect to the tire circumferential direction. The tread section (2) includes a narrow groove of the shoulder section (60) arranged in the tire width direction on an outside of a major circumferential groove (20) and extending in the tire circumferential direction. A distance W Cfrom a tire equatorial plane (CL) to an end section in the tire width direction of the circumferential reinforcement layer (145) and a distance W N from the tire equatorial plane (CL) to the narrow groove of the shoulder section (60) satisfy the relationship 0.50 ≤ WC / WN ≤ 0.90.

Description

Technical field

[0001] The present invention relates to a tire. State of the art

[0002] A tire has a belt layer as a reinforcing layer in a tread section. Due to the belt layer, the tread section exhibits increased stiffness, and the performance of known tires has been improved by the development of the belt layer. For example, in a heavy-duty pneumatic tire described in Patent Document 1, a belt has two or more intersecting cord layers in the immediate vicinity of a carcass and two or more substantially inextensible, circumferentially arranged cord layers on an outer circumferential side thereof. In a tire described in Patent Document 2, a belt layer is formed by stacking a plurality of belt plies, including a high-angle belt, a pair of cross belts, and a belt cover. List of literature on patent literature Patent Document 1: JP 10-250314 A Patent document 2: JP 2023-048304 A Brief description of the invention: Technical problem

[0003] In long-distance operations primarily involving continuous high-speed driving, uneven wear may prevent the tire from reaching the end of its service life, necessitating early removal and replacement. As an example of a method to improve the resistance of such a tire to uneven wear, a technique for suppressing uneven wear is described. This involves incorporating a circumferential reinforcement layer, in which cord threads extend along the tire's circumference, into a belt layer to suppress radial growth during vehicle travel and prevent slippage of the contact patch.As a further method, a process for improving uneven wear of a shoulder section by arranging narrow grooves connected in the circumferential direction of the tire on or near the shoulder section in a tread section, as described in patent document 2, in order to reduce the ground contact pressure on or in the immediate vicinity of shoulder end sections in the tread section, is explained by way of example. To improve the tire's resistance to uneven wear, it is conceivable to effectively suppress uneven wear of the tread area by combining these methods.

[0004] However, if the circumferential reinforcement layer is located in the belt layer, the stiffness of the tread section increases in the area in the tire width direction where the circumferential reinforcement layer is located, while the stiffness of the tread section decreases relatively in an area on the outside in the tire width direction of the area where the circumferential reinforcement layer is located. If the narrow grooves connected in the tire circumference direction are located at or near the shoulder section, and the stiffness of the section on the outside in the tire width direction of the area where the circumferential reinforcement layer is located decreases relatively, the magnitude of a load is likely to increase with respect to the stiffness at or near the shoulder section due to the difference in stiffness in the tread section.In this case, there is a risk that damage, such as a rib fracture originating from the narrow groove located in the shoulder area, will likely occur at or near the shoulder area. Therefore, it is difficult to prevent uneven wear of the tread without causing damage such as a rib fracture in the shoulder area.

[0005] The present invention was made with regard to the above-mentioned problem, and one object of the present invention is to provide a tire that can provide improved resistance to uneven wear while simultaneously providing suppressed rib cracking in a shoulder area. Solution to the problem

[0006] To solve the problems described above and to fulfill the objective, a tire according to the present invention includes: a tread section with a plurality of main circumferential grooves extending in a tire circumference direction; and a belt layer arranged in the tread section and enclosing a plurality of belt plies. The belt layer includes a pair of cross belts, each enclosing belt cord threads whose inclination directions in a tire width direction are opposite to each other with respect to a tire circumference direction, and a circumferential reinforcement layer arranged between the pair of cross belts, the width of which in the tire width direction is less than the width of the cross belts and the inclination angle of the belt cord threads in the tire width direction with respect to the tire circumference direction is 5 degrees or less.The tread section includes a narrow groove of the shoulder section, which is located on the outside of a major circumferential groove in the tire width direction and extends in the tire circumference direction. A distance in the tire width direction from a tire equatorial plane to an end section in the tire width direction of the circumferential reinforcement layer is denoted as W. C defined as W, a distance in the tire width direction from the tire equatorial plane to an end section on an inside in the tire width direction of the narrow groove of the shoulder section. N defined and a distance W C and a distance W N fulfill a relationship 0.50 ≤ W C / W N ≤ 0.90. Advantageous effects of the invention

[0007] The tire according to an embodiment of the present invention has the effect of providing improved resistance to uneven wear while simultaneously providing suppressed rib cracking in a shoulder area. Brief description of the drawings Fig. Figure 1 is a tire meridian cross-sectional view illustrating a main section of a pneumatic tire according to one embodiment. Fig. 2 is a schematic graphical representation that depicts a Fig. 1 illustrated belt layer illustrated. Fig. 3 is a top view of a Fig. 1 illustrated tread section. Fig. 4 is a detailed view of the tread section, showing an area on one side of a tire equatorial plane in a tire width direction of the Fig. 1 illustrated tread section. Fig. 5 is a detailed view of a Fig. 4 illustrated narrow groove of the shoulder section. Fig. 6A is a table that lists the results of performance evaluation tests of pneumatic tires. Fig. 6B is a table that lists the results of the performance evaluation tests of the pneumatic tires. Description of embodiments

[0008] The embodiments according to the present invention are described in detail below with reference to the drawings. The invention is not limited to these embodiments. Components of the embodiments include elements that are interchangeable while maintaining conformity with the invention, as well as obviously interchangeable elements. The plurality of modified examples described in the embodiments can be combined as required, within the scope obvious to a person skilled in the art. Designs

[0009] In the following description, the term "tire radial direction" refers to a direction perpendicular to the tire axis of rotation (not illustrated), which is an axis of rotation of a pneumatic tire 1 of the embodiment. The term "inside in the tire radial direction" refers to a side in the direction of the tire axis of rotation in the tire radial direction, and the term "outside in the tire radial direction" refers to a side away from the tire axis of rotation in the tire radial direction. The term "tire circumferential direction" refers to a circumferential direction with the tire axis of rotation as its central axis.The term "tire width direction" refers to a direction parallel to the tire's axis of rotation. The term "inside in the tire width direction" refers to a side perpendicular to the tire's equatorial plane (tire equator line) CL in the tire width direction. The term "outside in the tire width direction" refers to a side away from the tire's equatorial plane CL in the tire width direction. The term "tire equatorial plane CL" refers to a plane perpendicular to the tire's axis of rotation and passing through the center of the tire's width. The tire's equatorial plane CL is aligned at a position in the tire width direction on the centerline that corresponds to the tire's center position in the tire width direction. The term "tire equator line" refers to a line in the tire's circumferential direction that lies on the tire's equatorial plane CL.The term “cross-section in the tire meridian direction (meridian cross-section view)” refers to a cross-section of the tire along a plane that includes the axis of rotation of the tire.

[0010] Fig. Figure 1 is a view of the tire meridian cross-section, illustrating a main section of the pneumatic tire 1 according to one embodiment. Fig. Figure 1 illustrates a meridional cross-section of the pneumatic tire 1 according to one embodiment, the cross-section of a lateral region of a tire rotation axis in the tire radial direction. In the present embodiment, a heavy-duty radial pneumatic tire mounted on a long-distance transport vehicle, such as a truck or bus, is described as an example.

[0011] In the pneumatic tire 1 according to the present embodiment, a tread section 2, viewed in a meridional cross-section, is arranged on a section on the outermost side in the tire's radial direction, and the tread section 2 includes a tread rubber layer 4 made of a rubber or rubber compound. A surface of the tread section 2, that is, a section that comes into contact with a road surface during the movement of a vehicle (not illustrated) on which the pneumatic tires 1 are mounted, is formed as a tread ground contact surface 3, and the tread ground contact surface 3 forms a section of a contour of the pneumatic tire 1.

[0012] Shoulder sections 5 are arranged at both ends on the outer sides of the tread section 2 in the tire width direction, and sidewall sections 8 are arranged on the inner sides of the shoulder sections 5 in the tire radial direction. In other words, the shoulder sections 8 are arranged on both sides of the tread section 2 in the tire width direction. In other words, the sidewall sections 8 are arranged in two areas on both sides when viewed in the tire width direction of the pneumatic tire 1, forming sections that are exposed towards the outermost sides of the pneumatic tire 1 in the tire width direction. The sidewall section 8 encloses a sidewall rubber 9, which is made of a rubber compound.

[0013] A bead section 10 is provided on the inner side (in the tire radial direction) of each of the sidewall sections 8, which are located on both sides (in the tire width direction). Similarly to the sidewall sections 8, the bead sections 10 are arranged on both sides of the equatorial plane of the tire CL. That is, a pair of bead sections 10 is arranged on either side of the equatorial plane of the tire CL (viewed in the tire width direction). Each bead section 10 encloses a bead core 11, and a bead filler 12 is provided on the outer side (in the tire radial direction) of the bead core 11.

[0014] The bead core 11 is an annular element formed by bundling and repeatedly winding steel tire bead wires. The bead fillers 12 include a lower filler 121 and an upper filler 122, which are rubber elements, arranged on the outer sides of the bead cores 11 in the tire radial direction and reinforcing the bead sections 10.

[0015] A carcass layer 13, containing cord threads of radial plies, is provided continuously on an inner side in the radial direction of the tread section 2 and on one side of the equatorial plane CL of the sidewall sections 8. Accordingly, the pneumatic tire 1 is configured as a so-called radial tire according to this embodiment. The carcass layer 13 has a single-layer structure consisting of one carcass ply or a multi-layer structure consisting of a plurality of layered carcass plies and runs in a torus shape between the pair of bead sections 10, which are arranged in the width direction of the tire on both sides, to form the frame structure of the tire.

[0016] In particular, the carcass layer 13 is arranged such that it extends from one bead section 10 to the other bead section 10 of the pair of bead sections 10 located on both sides in the tire width direction, and it is folded back on the outer side in the tire width direction along the bead cores 11 at the bead sections 10 such that it wraps around the bead cores 11 and the bead filler 12. The bead filler 12 is a rubber element that is arranged in a space on the outside in the tire radial direction of the bead core 11, the space being formed by folding back the carcass layer 13 at the bead section 10. The carcass layer of carcass layer 13 is produced by coating with coating rubber and rolling up a plurality of carcass cord threads made of steel or an organic fiber material such as aramid, nylon, polyester or rayon.The majority of carcass cord threads forming the carcass layer are arranged parallel at an angle in the tire's circumferential direction, the angle being oriented along a tire meridian direction with respect to the tire's circumferential direction.

[0017] A belt layer 14 is arranged in the tread section 2. Fig. Figure 2 is a schematic graphical representation that shows the Fig. Figure 1 illustrates the belt layer 14. The belt layer 14 is arranged on the outer side, in the tire radial direction, of a section of the carcass layer 13 located in the tread section 2, extending between the pair of bead sections 10. The belt layer 14 is formed by layering a plurality of belt plies 141 to 145 and is arranged around an outer circumference of the carcass layer 13. The belt plies 141 to 145 include a large-angle belt 141, a pair of cross belts 142 and 143, a belt cover 144, and a circumferential reinforcement layer 145.

[0018] The large-angle belt 141 is formed by covering a plurality of steel wire belt cord threads with coating rubber and subjecting them to a rolling process. It has an absolute cord thread angle (defined as an angle of inclination in a longitudinal direction of the belt cord thread with respect to the tire's circumferential direction) of 45 degrees or more and 70 degrees or less, preferably 54 degrees or more and 68 degrees or less. The large-angle belt 141 is arranged layer by layer on an outer surface of the carcass layer 13 in the tire's radial direction.

[0019] The pair of cross belts 142 and 143 is formed by covering a plurality of steel wire belt cord threads with a rubber coating and subsequently carrying out a rolling process on them. The cord thread angles of 10 degrees or more and 45 degrees or less, preferably 14 degrees or more and 28 degrees or less, are absolute values. The pair of cross belts 142 and 143 has cord thread angles that are opposite in direction and is layered such that the belt cord threads overlap in the longitudinal direction (forming a so-called cross-layer structure). That is, the inclination directions of the belt cord threads of the pair of cross belts 142 and 143 are opposite to each other in the direction of the tire width with respect to the tire circumference. The pair of cross belts 142 and 143 is layered on an outer surface in the tire radial direction of the belt at a large angle 141.Here, the cross belt 142 located on the inside in the tire radial direction is defined as the inner cross belt, and the cross belt 143 located on the outside in the tire radial direction is defined as the outer cross belt.

[0020] The belt cover 144 is formed by covering a plurality of belt cover cord threads made of steel wire or organic fiber material with a coating rubber and subsequently carrying out a rolling process on it, and has an absolute cord thread angle of 10 degrees or more and 45 degrees or less, preferably 14 degrees or more and 28 degrees or less. The belt cover 144 is arranged layer by layer on an outer surface in the tire radial direction of the cross belts 142 and 143. In the present embodiment, the belt cover 144 has the same cord thread angle as the outer cross belt 143 and is arranged in the outermost layer of the belt layer 14.

[0021] The circumferential reinforcement layer 145 is manufactured by spirally winding a steel wire belt cord covered with a rubber coating in the tire's circumferential direction and has a cord angle of 5 degrees or less. That is, the inclination angle of the belt cord of the circumferential reinforcement layer 145 in the tire's width direction relative to the tire's circumference is 5 degrees or less. The circumferential reinforcement layer 145 is located between the pair of cross belts 142 and 143. The circumferential reinforcement layer 145 is formed with a width that is narrower than the widths of the cross belts 142 and 143 in the tire's width direction. Therefore, the circumferential reinforcement layer 145 is located on the inner side, in the tire's width direction, of the end sections on both sides of the pair of cross belts 142 and 143.In particular, the circumferential reinforcement layer 145 is formed by spirally winding a wire or a plurality of wires on the outer circumference of the inner cross-belt 142. The circumferential reinforcement layer 145 is arranged continuously in the tire width direction such that it intersects the tire equatorial plane CL in the tire width direction.

[0022] In the present embodiment, the circumferential reinforcement layer 145 has a number of belt cord ends, i.e., a number of belt cords per unit width, in a range of 15 cords / 50 mm or more and 30 cords / 50 mm or less. The outer diameter of the belt cord is in a range of 1.2 mm or more to 2.2 mm or less. In a configuration where the belt cords are made from a plurality of twisted cords, the diameter of a circle circumscribing the belt cords is measured as the outer diameter of the belt cords.

[0023] A rim pad 17, forming a contact surface of the bead section 10 with respect to a rim flange, is arranged on the inside in the tire radial direction and on the outside in the tire width direction of the bead core 11 and a folded-back section of the carcass layer 13. An inner liner 16 is formed along the carcass layer 13 on the inside of the carcass layer 13 or on the inner section side of the carcass layer 13 in the pneumatic tire 1. The inner liner 16 forms a tire inner surface 18, which is a surface on the inside of the pneumatic tire 1.

[0024] Fig. 3 is a top view of the Fig. Figure 1 illustrates tread section 2. A plurality of major circumferential grooves 20, extending in the tire's circumferential direction, are arranged in the tread ground contact surface 3 in tread section 2, and a plurality of rib sections 30 are defined by the plurality of major circumferential grooves 20 on the surface of tread section 2. In the present embodiment, only two major circumferential grooves 20 are arranged. The two major circumferential grooves 20 are each arranged on each side of the tire's equatorial plane CL in the tire's width direction.

[0025] The main circumferential groove 20 referred to herein is a longitudinal groove running in the direction of the tire's circumference and featuring an internal wear indicator (slip mark) that indicates the final stages of wear. The main circumferential grooves 20 formed as described above have a groove width ranging from 5.0 mm or more to 18.0 mm or less and a groove depth ranging from 10.0 mm or more to 20.0 mm or less.

[0026] In the tread contact surface 3 of the tread section 2, a plurality of chamfered narrow circumferential grooves 25 are arranged, extending in the circumferential direction of the tire. The chamfered narrow circumferential groove 25 is a circumferential groove extending in the circumferential direction of the tire and has a groove width that is narrower than that of the main circumferential groove 20, and an opening section with respect to the tread contact surface 3 is chamfered. The chamfered narrow circumferential groove 25 has no wear indicator, and a section of the chamfered narrow circumferential groove 25 on a groove underside with respect to the chamfered section has a groove width of less than 5.0 mm.

[0027] Two chamfered narrow circumferential grooves 25 are provided, and the two chamfered narrow circumferential grooves 25 are each arranged on each side of the tire equatorial plane CL in the tire width direction. In particular, the chamfered narrow circumferential grooves 25 are arranged on an inside side with respect to the main circumferential groove 20 in the tire width direction. In other words, the two chamfered narrow circumferential grooves 25 are each arranged on each side of the tire equatorial plane CL, and the two main circumferential grooves 20 are each arranged on the outside side of the two chamfered narrow circumferential grooves 25 in the tire width direction.

[0028] The main circumferential grooves 20 and the chamfered narrow circumferential grooves 25, arranged side by side in the tire width direction as described above, are all formed to extend in the tire circumference direction and have groove bottoms that are wavy in the tire width direction. That is, in both the main circumferential groove 20 and the chamfered narrow circumferential groove 25, the opening section extends in the tire circumference direction with respect to the tread base contact surface 3, with the position in the tire width direction being a constant position, while the groove bottom is wavy, extending in the tire circumference direction and following a wave-like pattern in the tire width direction.

[0029] The chamfered narrow circumferential groove 25, together with the main circumferential groove 20, defines a rib section 30 of the tread section 2. The rib section 30 defined by the main circumferential groove 20 and the chamfered narrow circumferential groove 25 includes a central rib section 31, middle rib sections 32, and shoulder rib sections 33. The central rib section 31 is the rib section 30 located between the two chamfered narrow circumferential grooves 25, and both sides in the tire width direction are defined by the chamfered narrow circumferential groove 25. The central rib section 31 is located on the tire equatorial plane CL.

[0030] The central rib section 32 is the rib section 30, which is located between the main circumferential groove 20 and the chamfered narrow circumferential groove 25, adjacent to each other in the tire width direction. A section on the inside in the tire width direction is defined by the chamfered narrow circumferential groove 25, and a section on the outside in the tire width direction is defined by the main circumferential groove 20. Accordingly, the central rib sections 32 are located on both sides of the tire equatorial plane CL in the tire width direction.

[0031] The shoulder rib section 33 is the rib section 30, which is arranged on an outside of the main circumferential groove 20 in the tire width direction, and an inside section in the tire width direction is defined by the main circumferential groove 20. Accordingly, the shoulder rib sections 33 are arranged on both sides of the tire equatorial plane CL in the tire width direction.

[0032] Furthermore, the tread section 2 includes a narrow groove of the shoulder section 60, which is located on the outside of the main circumferential groove 20 in the tire width direction and extends in the tire circumference direction. In the narrow groove of the shoulder section 60, the groove width of an opening section with respect to the tread ground contact surface 3 is 4.0 mm or less, and the groove depth is in a range of 10.0 mm or more to 20.0 mm or less. The narrow groove of the shoulder section 60 is located in the shoulder rib section 33 of the plurality of rib sections 30 contained in the tread section 2. In particular, the narrow groove of the shoulder section 60 is located at a position at or near an end section on the outside of the shoulder rib section 33 in the tire width direction.

[0033] Multiple lamellae 70 are arranged in the web section 30 of the running surface section 2. Each multiple lamella 70 is a short lamella, one end of which is open towards the circumferential groove in each web section 30 and the other end of which terminates within the web section 30. In the present embodiment, the width of the multiple lamella 70 is in a range of 0.3 mm or more to 1.5 mm or less, its depth is in a range of 2.0 mm or more to 17 mm or less, and its length in the direction of extension of the multiple lamella 70 is in a range of 2.0 mm or more to 10 mm or less.

[0034] The majority of multi-sipes 70 are arranged in each of the central rib section 31, the middle rib section 32, and the shoulder rib section 33. The majority of the multi-sipes 70 arranged in the central rib section 31 are arranged along two chamfered narrow circumferential grooves 25 that define both sides of the central rib section 31 in the tire width direction. That is, the majority of the multi-sipes 70 arranged in the central rib section 31 are formed such that one end of them is open towards the chamfered narrow circumferential groove 25 and the other end terminates in the central rib section 31, and the majority of the multi-sipes 70 are arranged side by side in the tire circumferential direction along the chamfered narrow circumferential groove 25.

[0035] The majority of the multiple sipes 70 arranged in the central rib section 32 are arranged along the main circumferential groove 20 and the chamfered narrow circumferential grooves 25, which define both sides of the central rib section 32 in the tire width direction. That is, the majority of the multiple sipes 70 arranged in the central rib section 32 are formed such that one end of them is open towards the main circumferential groove 20 or towards the chamfered narrow circumferential groove 25 and the other end of them terminates in the central rib section 32, and the majority of the multiple sipes 70 are arranged side by side in the tire circumferential direction along the main circumferential groove 20 or the chamfered narrow circumferential groove 25.

[0036] The majority of the multiple sipes 70 arranged in the shoulder rib section 33 are arranged along the main circumferential groove 20, which defines an inner side in the tire width direction of the shoulder rib section 33, and the narrow shoulder section groove 60, which is arranged in the shoulder rib section 33. That is, the majority of the multiple sipes 70 arranged in the shoulder rib section 33 are formed such that one end of them is open towards the main circumferential groove 20 or towards the narrow groove of the shoulder section 60 and the other end of them terminates in the shoulder rib section 33, and the majority of the multiple sipes 70 are arranged side by side in the tire circumferential direction along the main circumferential groove 20 or the narrow groove of the shoulder section 60.

[0037] For the majority of multiple sipes 70, which are arranged next to each other in each of the web sections 30 in the circumferential direction of the tire, the pitch length of the multiple sipes 70 adjacent to each other in the circumferential direction of the tire lies in a range of 0.1% or more and 0.6% or less with respect to a tire circumferential length.

[0038] A narrow circumferential groove 40 and a transverse groove 50 are arranged in the central web section 31 and in the middle web section 32 of the plurality of web sections 30 that are arranged in the running surface section 2. The narrow circumferential groove 40 mentioned herein preferably has a groove width in the range of 0.1 mm or more up to 2.0 mm or less, and the groove width is preferably in the range of 0.5 mm to 1.5 mm. The transverse groove 50 also preferably has a groove width in the range of 0.1 mm or more up to 2.0 mm or less, and the groove width is preferably in the range of 0.5 mm to 1.5 mm.

[0039] A central narrow circumferential groove 41, which is a narrow circumferential groove 40, and a central transverse groove 51, which is a transverse groove 50, are arranged in the central rib section 31. The central narrow circumferential groove 41 is located at or near the center of the central rib section 31 in the tire width direction. The central circumferential groove 41 repeatedly undulates in the tire width direction as it extends in the tire circumference direction, thus forming a zigzag shape. The central transverse grooves 51 are arranged in the tire width direction on both sides of the central narrow circumferential groove 41 in the central rib section 31.The central transverse grooves 51, which are arranged in the tire width direction on both sides of the central narrow circumferential groove 41, are each connected at one end to the central narrow circumferential groove 41 and at the other end to the multiple lamella 70, which is arranged in the central web section 31.

[0040] A central narrow circumferential groove 42, which is a narrow circumferential groove 40, and a central transverse groove 52, which is a transverse groove 50, are arranged in the central rib section 32. The central narrow circumferential groove 42 and the central transverse groove 52 are arranged in each of the two central rib sections 32, which are located on either side of the tire equatorial plane CL in the tire width direction. The central narrow circumferential groove 42 is located at or near the center of the central rib section 32 in the tire width direction. The central narrow circumferential groove 42 is repeatedly undulating in the tire width direction as it extends in the tire circumference direction, thus forming a zigzag shape. The central transverse grooves 52 are arranged on either side of the central narrow circumferential groove 42 in the central rib section 32 in the tire width direction.The central transverse grooves 52, which are arranged in the tire width direction on both sides of the central narrow circumferential groove 42, are each connected at one end to the central narrow circumferential groove 42 and at the other end to the multiple lamella 70, which is arranged in the central web section 32.

[0041] Fig. Figure 4 is a detailed view of tread section 2, showing an area on one side of the tire equatorial plane CL in the tire width direction. Fig. Figure 1 illustrates tread section 2. The circumferential reinforcement layer 145 contained in the belt layer 14 is arranged in the tire width direction at a position on an inside side in the tire width direction with respect to the narrow groove of the shoulder section 60, which is located in tread section 2. In particular, the circumferential reinforcement layer 145 and the narrow groove of the shoulder section 60 are configured such that a distance W C and a distance W N a relationship 0.50 ≤ W C / W N ≤ 0.90, where W C a distance in the tire width direction from the tire equatorial plane CL to an end section in the tire width direction of the circumferential reinforcement layer 145 is and W Na distance in the tire width direction from the tire equatorial plane CL to an end section 61 on an inside in the tire width direction of the narrow groove of the shoulder section 60.

[0042] A distance in the tire width direction between the tire equatorial plane CL and an end section 22 on an outer side in the tire width direction of the main circumferential groove 20, which is located on the outermost side in the tire width direction of the majority of main circumferential grooves 20, is called W G defined, and the distance W C and the distance W G fulfill a relationship 1.00 ≤ W C / W G ≤ 1.40. In the present embodiment, only two main circumferential grooves 20 are arranged, and therefore the two main circumferential grooves 20 are all the outermost main circumferential grooves 21, which are the main circumferential grooves 20 located on the outermost side in the tire width direction. Therefore, the distance W Ga distance in the tire width direction between the tire equatorial plane CL and the end section 22 on the outside in the tire width direction of the main circumferential groove 20, which is located on the outermost side in the tire width direction, between the tire equatorial plane CL and the end section 22 on the outside in the tire width direction of each of the two outermost main circumferential grooves 21.

[0043] The relationship between the distance W C and the distance W N The distance between the circumferential reinforcement layer 145 and the narrow groove of the shoulder section 60 preferably lies in a range of 0.60 ≤ W C / W N ≤ 0.80, and the relationship between the distance W C and the distance W G The distance between the circumferential reinforcement layer 145 and the outermost circumferential main groove 21 preferably lies in a range of 1.10 ≤ W C / W G ≤ 1.30.

[0044] A distance G1 from an end section 142a in the tire width direction of the inner cross-belt 142 of the pair of cross-belts 142 and 143, which are arranged on the inside in the tire radial direction of the circumferential reinforcement layer 145, to a bottom section 62 of the narrow groove of the shoulder section 60 lies in a range of 7 mm ≤ G1 ≤ 17 mm. A distance G2 from an end section 143a in the tire width direction of the outer cross-belt 143 of the pair of cross-belts 142 and 143, which is arranged on the outside in the tire radial direction of the circumferential reinforcement layer 145, to the bottom section 62 of the narrow groove of the shoulder section 60 lies in a range of 10 mm ≤ G2 ≤ ​​20 mm.

[0045] Fig. 5 is a detailed view of the in Fig. Figure 4 illustrates the narrow groove of the shoulder section 60. The narrow groove of the shoulder section 60, which is located in the shoulder rib section 33, is situated at or near an end section on an outer side in the tire width direction of the shoulder rib section 33. The narrow groove of the shoulder section 60 is configured such that a distance W R from an end section on an outer side in the tire width direction of the shoulder rib section 33 to the narrow groove of the shoulder section 60 in a range of 10 mm ≤ W R ≤ 18 mm.

[0046] The shoulder rib section 33 has a narrow rib 34 on its outer side in the tire width direction relative to the narrow groove of the shoulder section 60, the narrow groove of the shoulder section 60 being located at or near an end section on its outer side in the tire width direction. The narrow rib 34 is a rib-shaped section extending in the tire circumference direction and having a relatively narrow width in the tire width direction, with an inner section in the tire width direction of the narrow rib 34 being defined by the narrow groove of the shoulder section 60.

[0047] The tread contact surface 3 of the narrow rib 34 is offset inwards in the tire radial direction compared to a section of the shoulder rib section 33 on an inner section of the narrow groove of the shoulder section 60 in the tire width direction. The offset F of the tread contact surface 3 of the narrow rib 34 with respect to the tread contact surface 3 of the section of the shoulder rib section 33 on the inner section of the narrow groove of the shoulder section 60 in the tire width direction is in the range of 1.0 mm ≤ F ≤ 4.0 mm.

[0048] The narrow groove of the shoulder section 60 has a cylindrical section 64 on a bottom section 62, which has a width D N in the groove width direction of the narrow groove of the shoulder section 60, which is larger than a groove width W SThe cylindrical section 64 is formed at a position that includes the bottom section 62 of the narrow groove of the shoulder section 60 and is formed by the bottom section 62 of the narrow groove of the shoulder section 60 and a groove wall 63 in the immediate vicinity of the bottom section 62. The cylindrical section 64 formed by the bottom section 62 and the groove wall 63 has a shape with a substantially cylindrical diameter, in that the bottom section 62 and the groove wall 63 are continuously curved in a cross-sectional view along the longitudinal direction of the narrow groove of the shoulder section 60.

[0049] In particular, the cylindrical section 64 is formed in a curved shape, in which at least one of a pair of groove walls 63, facing each other in the narrow groove of the shoulder section 60, is recessed in one direction away from the other groove wall 63, and the bottom section 62 and the groove wall 63 are continuous. In the present embodiment, the cylindrical section 64 of the narrow groove of the shoulder section 60 is formed such that one groove wall 63 of the pair of groove walls 63, facing each other and between which the bottom section 62 is located, is offset in a curved shape in one direction away from the other groove wall 63, and the other groove wall 63 is continuously curved from the bottom section 62 without being offset in a direction in which the distance between the groove walls 63 increases.

[0050] In the cylindrical section 64 of the narrow groove of the shoulder section 60, which is formed in this way, the width D N of the cylindrical section 64 in the groove width direction of the narrow groove of the shoulder section 60 larger than the groove width W S at a different position than the cylindrical section 64 in the narrow groove of the shoulder section 60. The width D N The diameter of the cylindrical section 64 is, in this case, a dimension of the diameter of the cylinder that has the shape of the cylindrical section 64. The width D N of the cylindrical section 64 of the narrow groove of the shoulder section 60 lies in a range of 1.2 times or more and 5 times or less of the groove width W S at a different position than the cylindrical section 64 in the narrow groove of the shoulder section 60.

[0051] The groove width W Sat a position other than the cylindrical section 64 in the narrow groove of the shoulder section 60 preferably lies in a range of 1.0 mm ≤ W S ≤ 3.0 mm, and the width D N The diameter of the cylindrical section 64 of the narrow groove of the shoulder section 60 preferably lies in a range of 2.0 mm ≤ D N ≤ 5.0 mm.

[0052] The pneumatic tire 1 according to the embodiment, configured as described above, has a cross-sectional ratio of 80% or less. The cross-sectional ratio referred to herein is a percentage of the ratio of the cross-sectional height of the pneumatic tire 1 to its cross-sectional width. The cross-sectional width of the pneumatic tire 1 is a value obtained by subtracting any pattern, marking, or the like on a sidewall of the tire from the total width of the pneumatic tire 1 in the tire's width direction. The cross-sectional height of the pneumatic tire 1 is 1 / 2 the difference between the outer diameter of the pneumatic tire 1 and the diameter of a rim on which the pneumatic tire 1 is mounted.

[0053] When the pneumatic tire 1 is mounted on a vehicle according to the present embodiment, the pneumatic tire 1 is mounted on a wheel rim, inflated internally with air, and then mounted on the vehicle. When the vehicle on which the pneumatic tire 1 is mounted is moving, the pneumatic tire 1 rotates, with a lower section of the tread contact surface 3 of the tread section 2 in contact with a road surface. When the vehicle on which the pneumatic tire 1 is mounted is moving on a dry road surface, the vehicle moves primarily by transmitting a driving force and a braking force to the road surface and by generating a rotational force through frictional forces between the tread contact surface 3 and the road surface.

[0054] When driving on a wet road surface, water enters the grooves between the tread contact surface 3 and the road surface, such as the main circumferential grooves 20, the narrow circumferential grooves 40, and the transverse grooves 50. As the vehicle travels, the water is channeled away through these grooves. This allows the tread contact surface 3 to easily engage with the road surface, and the vehicle can then travel due to the frictional force between the tread contact surface 3 and the road surface.

[0055] The vehicle, on which the pneumatic tires 1 are mounted, travels with the tread contact surface 3 in contact with the road surface, as described above, and therefore the tread section 2 gradually wears down from the side of the tread contact surface 3 in the rib section 30. At this point, it is likely that the outer diameter of a section of the tread contact surface 3 near the center in the tire width direction increases due to the centrifugal force during the rotation of the pneumatic tire 1, and it comes into contact with the ground with a high ground contact pressure.

[0056] On the other hand, it is likely that the ground contact pressure of the section of the tread contact surface 3 in the immediate vicinity of the end section in the tire width direction decreases due to a difference in the outer diameter compared to the section at or near the center in the tire width direction. Therefore, in the section of the tread contact surface 3 near the end section in the tire width direction, slippage between the tread contact surface 3 and the road surface can easily occur during the rotation of the pneumatic tire 1 due to a difference in ground contact pressure caused by the difference in the outer diameter compared to the section near the center in the tire width direction, and wear can occur relatively easily.The tread contact surface 3 is prone to uneven wear because the section at or near the center and the section at or near the end of the tire are differently susceptible to wear in the direction of tire width.

[0057] In contrast, in the pneumatic tire 1 according to the present embodiment, the belt layer 14 includes the circumferential reinforcement layer 145, which has a narrower width in the tire width direction than the width of the pair of cross belts 142 and 143, and in which the inclination angle of the belt cord threads is 5 degrees or less. Therefore, the belt layer 14 can suppress the expansion of the area in which the circumferential reinforcement layer 145 is located in the tire width direction and can suppress the increase in the outer diameter caused by the circumferential reinforcement layer 145 during the rotation of the pneumatic tire 1. This can suppress the occurrence of uneven wear caused by the increase in the outer diameter of the section at or near the center in the tire width direction during the rotation of the pneumatic tire 1.

[0058] On the other hand, if the stiffness at or near the center in the tire width direction is increased by arranging the circumferential reinforcement layer 145 in a position that includes the center in the tire width direction of the tread section 2, there is a risk that the stiffness at or near the end section in the tire width direction of the tread section 2, i.e. at or near the shoulder section 5 of the tread section 2, will be excessively lower than the stiffness at or near the center in the tire width direction.In this case, due to the different stiffness of the tread section 2, the stress in relation to the stiffness during the journey of the vehicle at or near the shoulder section 5 of the tread section 2 becomes excessively high and the ground contact pressure becomes locally excessive, so that there is a risk of a so-called rib crack occurring, which is a defect in which the rib section 30 of the tread section 2 is continuously torn off in the circumferential direction of the tire.

[0059] In contrast, according to the present embodiment, the pneumatic tire 1 includes the narrow groove of the shoulder section 60, which is located in the tire width direction on an outside of the main circumferential groove 20 arranged in the tread section 2 and extending in the tire circumference direction. This allows the tread section 2 to deform at or near the shoulder section 5 of the tread section 2 due to the narrow groove of the shoulder section 60 when a load is applied, thus preventing a local increase in the ground contact pressure of the tread ground contact surface 3. Therefore, it is possible to suppress the occurrence of rib cracking that would otherwise occur at or near the shoulder section 5 due to the local increase in ground contact pressure at or near the shoulder section 5 caused by the load acting on the immediate vicinity of the shoulder section 5 of the tread section 2.

[0060] Furthermore, in the pneumatic tire 1 according to the present embodiment, the circumferential reinforcement layer 145 is arranged between the pair of cross belts 142 and 143, and therefore an increase in the stiffness difference of the tread section 2 can be more reliably suppressed. That is, since the belt cord threads of the pair of cross belts 142 and 143 have different inclination directions in the direction of the tire width with respect to the tire's circumferential direction, the pair of cross belts 142 and 143 can, when the cross belts 142 and 143 overlap each other, exhibit synergistic stiffness by mutually restricting movement.

[0061] However, if the circumferential reinforcement layer 145 overlaps with the pair of cross belts 142 and 143 and thereby exhibits a high stiffness due to the overlap of the pair of cross belts 142 and 143, there is a risk that the stiffness will become excessively high in the section of the belt layer 14 in which the circumferential reinforcement layer 145 is arranged, due to the stiffness of the pair of cross belts 142 and 143 and the stiffness of the circumferential reinforcement layer 145.If the stiffness of the section in which the circumferential reinforcement layer 145 is arranged in the tire width direction becomes excessively high, the stiffness difference between the immediate vicinity of the center of the tread section 2 in the tire width direction and the immediate vicinity of the shoulder section 5 becomes excessively large, making it difficult to effectively suppress the local increase in ground contact pressure at or near the shoulder section 5, and thus there is a risk that it will be difficult to effectively suppress the rib cracking that occurs at or near the shoulder section 5.

[0062] In contrast, in the pneumatic tire 1 according to the present embodiment, the circumferential reinforcement layer 145 is arranged between the pair of cross belts 142 and 143. This allows the stiffness of the area in which the circumferential reinforcement layer 145 is arranged to be suitably improved by the circumferential reinforcement layer 145, while at the same time suppressing the excessive increase in stiffness that the pair of cross belts 142 and 143 exhibit by mutually restricting their movement.This means that the belt layer 14 can provide a suitably improved stiffness in the tire width direction at or near the center, without excessively increasing the stiffness of the circumferential reinforcement layer 145, which is arranged between the cross belts 142 and 143 with a width narrower than that of the pair of cross belts 142 and 143, while ensuring the stiffness of the tread section 2 over a wide area in the tire width direction by the pair of cross belts 142 and 143. This prevents an excessive increase in the stiffness difference between the immediate vicinity of the center of the tread section 2 in the tire width direction and the immediate vicinity of the shoulder section 5, and effectively suppresses the occurrence of rib cracks originating from the narrow groove of the shoulder section 60 in the shoulder section 5.

[0063] Furthermore, the circumferential reinforcement layer 145 and the narrow groove of the shoulder section 60 are configured such that the distance W C in the tire width direction from the tire equatorial plane CL to the end section in the tire width direction of the circumferential reinforcement layer 145 and the distance W N in the tire width direction from the tire equatorial plane CL to the end section 61 on the inside in the tire width direction of the narrow groove of the shoulder section 60 the relationship 0.50 ≤ W C / W N ≤ 0.90, and therefore the occurrence of rib fractures at or near shoulder section 5 can be suppressed, while uneven wear at or near shoulder section 5 of running surface section 2 is suppressed.

[0064] That is, if the relationship between the distance W C and the distance W N W C / W N If the distance is less than 0.50, then W is the distance. Csmall in relation to the distance W N , and the width of the circumferential reinforcement layer 145 in the tire width direction is excessively narrow, and therefore there is a risk that it will be difficult to adequately improve the stiffness at or near the center in the tire width direction by the circumferential reinforcement layer 145. In this case, it is difficult to suppress the increase in the outer diameter at or near the center in the tire width direction by the circumferential reinforcement layer 145 during the rotation of the pneumatic tire 1, and thus there is a risk that it will be difficult to suppress the occurrence of uneven wear at or near the shoulder section 5 caused by the increase in the outer diameter at or near the center in the tire width direction. If the relationship between the distance W C and the distance W N W C / W N If the distance W is greater than 0.90, then it is a distance of 0.90. Clarge in relation to the distance W NThe width of the circumferential reinforcement layer 145 in the tire width direction is excessively wide, and therefore there is a risk that the area where the stiffness of the tread section 2 is improved by the circumferential reinforcement layer 145 extends into the immediate vicinity of the shoulder section 5. In this case, the section of the tread section 2 where the stiffness changes depending on the presence or absence of the circumferential reinforcement layer 145 is located at or near the shoulder section 5 of the tread section 2, and therefore there is a risk that, due to the fact that the section where the stiffness changes is located at or near the shoulder section 5, the stress in terms of stiffness in the section with low stiffness is likely to increase.This results in the ground contact pressure likely increasing locally at or near shoulder segment 5, and it may therefore be difficult to suppress the occurrence of rib fractures originating from the narrow groove of shoulder segment 60.

[0065] In contrast, if the relationship between the distance W C and the distance W N in the range of 0.50 ≤ W C / W N≤ 0.90, the section in which the stiffness of the tread section 2 changes depending on the presence or absence of the circumferential reinforcement layer 145 does not occur at or near the shoulder section 5, and the stiffness at or near the center in the tire width direction can be improved by the circumferential reinforcement layer 145. This can suppress the occurrence of rib cracking caused by a local increase in ground contact pressure at or near the shoulder section 5, while simultaneously suppressing uneven wear, in which the area near the shoulder section 5 of the tread section 2 wears down earlier than the section at or near the center in the tire width direction.This makes it possible to improve resistance to uneven wear and at the same time suppress rib cracks in the shoulder area, that is, in an area at or near the shoulder section 5 of the running surface section 2.

[0066] The circumferential reinforcement layer 145 and the outermost circumferential main groove 21 are configured such that the distance W C in the tire width direction from the tire equatorial plane CL to the end section in the tire width direction of the circumferential reinforcement layer 145 and the distance W G in the tire width direction between the tire equatorial plane CL and the end section 22 on the outside in the tire width direction of the outermost main circumferential groove 21 the relationship 1.00 ≤ W C / W G≤ 1.40, and therefore the occurrence of rib fractures at or near shoulder section 5 can be suppressed, while uneven wear at or near shoulder section 5 of running surface section 2 is suppressed.

[0067] That is, if the relationship between the distance W C and the distance W G W C / W G If the distance is less than 1.00, then W is the distance. C small in relation to the distance W G, and the width of the circumferential reinforcement layer 145 in the tire width direction is excessively narrow, and therefore there is a risk that it will be difficult to adequately improve the stiffness at or near the center in the tire width direction by the circumferential reinforcement layer 145. In this case, it is difficult to suppress the increase in the outer diameter at or near the center in the tire width direction by the circumferential reinforcement layer 145 during the rotation of the pneumatic tire 1, and thus there is a risk that it will be difficult to suppress the occurrence of uneven wear at or near the shoulder section 5 caused by the increase in the outer diameter at or near the center in the tire width direction. If the relationship between the distance W C and the distance W G W C / W G If the distance is > 1.40, then W is the distance. C large in relation to the distance W GThe width of the circumferential reinforcement layer 145 in the tire width direction is excessively wide, and therefore there is a risk that the area where the stiffness of the tread section 2 is improved by the circumferential reinforcement layer 145 extends into the immediate vicinity of the shoulder section 5. In this case, the section of the tread section 2 where the stiffness changes depending on the presence or absence of the circumferential reinforcement layer 145 is located at or near the shoulder section 5 of the tread section 2, and therefore there is a risk that, due to the fact that the section where the stiffness changes is located at or near the shoulder section 5, the stress in terms of stiffness in the section with low stiffness is likely to increase.This results in the ground contact pressure likely increasing locally at or near shoulder segment 5, and it may therefore be difficult to suppress the occurrence of rib fractures originating from the narrow groove of shoulder segment 60.

[0068] In contrast, if the relationship between the distance W C and the distance W G Range from 1.00 ≤ W C / W G≤ 1.40, the section in which the stiffness of the tread section 2 changes depending on the presence or absence of the circumferential reinforcement layer 145 does not occur at or near the shoulder section 5, and the stiffness at or near the center in the tire width direction can be improved by the circumferential reinforcement layer 145. This can suppress the occurrence of rib cracking caused by a local increase in ground contact pressure at or near the shoulder section 5, while simultaneously suppressing uneven wear, in which the area near the shoulder section 5 of the tread section 2 wears down earlier than the section at or near the center in the tire width direction. This makes it possible to improve resistance to uneven wear while simultaneously suppressing rib cracking in the shoulder area.

[0069] The pair of cross belts 142 and 143 is configured such that the distance G1 from the end section 142a in the tire width direction of the inner cross belt 142 to the bottom section 62 of the narrow groove of the shoulder section 60 is in the range 7 mm ≤ G1 ≤ 17 mm and the distance G2 from the end section 143a in the tire width direction of the outer cross belt 143 to the bottom section 62 of the narrow groove of the shoulder section 60 is in the range 10 mm ≤ G2 ≤ ​​20 mm, and therefore it is possible to prevent the occurrence of rib cracks starting from the narrow groove of the shoulder section 60 and at the same time to suppress uneven wear on or near the shoulder sections 5 of the tread section 2.

[0070] This means that if the distance G1 from the end section 142a of the inner cruciate girdle 142 to the base section 62 of the narrow groove of the shoulder section 60 G1 is < 7 mm, or if the distance G2 from the end section 143a of the outer cruciate girdle 143 to the base section 62 of the narrow groove of the shoulder section 60 G2 is < 10 mm, the distance between the inner cruciate girdle 142 or the outer cruciate girdle 143 and the narrow groove of the shoulder section 60 is excessively small, and thus there is a risk that stresses will likely concentrate between the inner cruciate girdle 142 or the outer cruciate girdle 143 and the narrow groove of the shoulder section 60. In this case, there is a risk that a rib fracture originating from the narrow groove of the shoulder section 60 will occur due to the stress concentration.

[0071] If the distance G1 from the end section 142a of the inner cross belt 142 to the bottom section 62 of the narrow groove of the shoulder section 60 G1 > 17 mm or the distance G2 from the end section 143a of the outer cross belt 143 to the bottom section 62 of the narrow groove of the shoulder section 60 G2 > 20 mm, the distance between the inner cross belt 142 or the outer cross belt 143 and the narrow groove of the shoulder section 60 is excessively large and thus there is a risk that the width of the cross belts 142, 143 is excessively narrow in the direction of the tire width.In this case, the area where the stiffness of the tread section 2 is ensured by the cross belts 142 and 143 is narrowed, and it becomes difficult to ensure stiffness at or near the center in the tire width direction by the cross belts 142 and 143, and therefore there is a risk that it will be difficult to suppress the increase in the outer diameter at or near the center in the tire width direction by the cross belts 142 and 143 during the rotation of the pneumatic tire 1, and it will be difficult to suppress the occurrence of uneven wear at or near the shoulder section 5.

[0072] In contrast, if the distance G1 from the end section 142a of the inner cross belt 142 to the bottom section 62 of the narrow groove of the shoulder section 60 is in the range 7 mm ≤ G1 ≤ 17 mm and the distance G2 from the end section 143a of the outer cross belt 143 to the bottom section 62 of the narrow groove of the shoulder section 60 is in the range 10 mm ≤ G2 ≤ ​​20 mm, it is possible to improve the stiffness at or near the center in the tire width direction by the cross belts 142 and 143 while suppressing the occurrence of a stress concentration between the inner cross belt 142 or the outer cross belt 143 and the narrow groove of the shoulder section 60.This suppresses the occurrence of rib cracking originating from the narrow groove of the shoulder section 60, while simultaneously suppressing uneven wear, where the area immediately surrounding the shoulder section 5 of the tread section 2 wears down earlier than the section at or near the center in the tire width direction. This makes it possible to improve resistance to uneven wear and simultaneously suppress rib cracking in the shoulder area.

[0073] Since the number of ends of the belt cord threads of the circumferential reinforcement layer 145 is in the range of 15 cord threads / 50 mm or more and 30 cord threads / 50 mm or less, it is possible to suppress the occurrence of rib cracks originating from the narrow groove of the shoulder section 60 and simultaneously suppress uneven wear at or near the shoulder section 5 of the tread section 2. That is to say, if the number of ends of the belt cord threads of the circumferential reinforcement layer 145 is less than 15 cord threads / 50 mm, the number of ends of the belt cord threads is excessively small, and thus there is a risk that it will be difficult to ensure the stiffness of the circumferential reinforcement layer 145.In this case, it is difficult to adequately improve the stiffness at or near the center in the tire width direction by the circumferential reinforcement layer 145 and to suppress the increase in the outer diameter at or near the center in the tire width direction by the circumferential reinforcement layer 145 during the rotation of the pneumatic tire 1. Therefore, there is a risk that it will be difficult to suppress the occurrence of uneven wear at or near the shoulder section 5, which is caused by the increase in the outer diameter at or near the center in the tire width direction. If the number of ends of the belt cord threads of the circumferential reinforcement layer 145 exceeds 30 cord threads / 50 mm, the number of ends of the belt cord threads is excessive, and thus there is a risk that the stiffness of the circumferential reinforcement layer 145 will become excessive.In this case, the difference in stiffness between the section in which the circumferential reinforcement layer 145 is arranged and the section that is not the section in which the circumferential reinforcement layer 145 is arranged becomes excessively large in the tire width direction, and thus the stress in terms of stiffness at or near the shoulder section 5 of the tread section 2 becomes excessive, and there is a risk that it will be difficult to suppress the occurrence of rib cracks starting from the narrow groove of the shoulder section 60.

[0074] If, on the other hand, the number of ends of the belt cord threads of the circumferential reinforcement layer 145 is in the range of 15 cord threads / 50 mm or more and 30 cord threads / 50 mm or less, the stiffness of the circumferential reinforcement layer 145 is ensured, and it can be suppressed that the stiffness difference between the section where the circumferential reinforcement layer 145 is located and the section that is not the section where the circumferential reinforcement layer 145 is located will not become excessively large. This can suppress the occurrence of rib cracking originating from the narrow groove of the shoulder section 60, while simultaneously suppressing uneven wear, in which the area immediately surrounding the shoulder section 5 of the tread section 2 wears down earlier than the section at or near the center in the tire width direction.This makes it possible to improve resistance to uneven wear while simultaneously providing suppressed rib tearing in the shoulder area.

[0075] Since the narrow groove of the shoulder section 60 at the base section 62 has the cylindrical section 64, the cylindrical section 64 can mitigate the load-induced deformation at the base section 62 of the narrow groove of the shoulder section 60, even when a load is applied to or near the narrow groove of the shoulder section 60 while the vehicle is in motion. That is, the stress concentration that occurs at the base section 62 when a load is applied to or near the narrow groove of the shoulder section 60 can be suppressed by the cylindrical section 64. This can suppress the formation of rib cracks originating from the base section 62 of the narrow groove of the shoulder section 60, even when a load is applied to or near the shoulder section 5 of the tread section 2. This can suppress the formation of rib cracks in the shoulder area.

[0076] Since only two main circumferential grooves 20 are arranged in the tread section 2, the ground contact area at or near the center in the tire width direction can be increased. This allows the majority of the load applied to tread section 2 in the tire width direction to be absorbed at or near the center, and the load absorbed at or near the shoulder section 5 can be relatively reduced, thereby reducing the ground contact pressure at or near the shoulder section 5. This prevents the area immediately surrounding the shoulder section 5 of tread section 2 from wearing down earlier than the area at or near the center in the tire width direction. This, in turn, prevents uneven wear caused by premature wear of the shoulder area.

[0077] Since the aspect ratio of the pneumatic tire 1 according to the embodiment is 80% or less, uneven wear of the tread section 2 can be effectively suppressed by the circumferential reinforcement layer 145. That is, in a pneumatic tire 1 with an aspect ratio of 80% or less, the inflation pressure is high, and thus the proportion of the inflation pressure borne by the belt layer 14 tends to increase, and the contribution of the belt layer 14 to the stiffness of the tread section 2 tends to increase. Therefore, the stiffness of the belt layer 14 can be effectively improved by arranging the circumferential reinforcement layer 145 within the belt layer 14, and thus, even in a pneumatic tire 1 with an aspect ratio of 80% or less, it is possible to suppress an increase in the outer diameter at or near the center in the tire's width direction during rotation.This can suppress uneven wear, where the area immediately surrounding the shoulder section 5 of the tread section 2 wears down earlier than the section at or near the center in the tire's width direction, even in the case of a pneumatic tire 1 with an aspect ratio of 80% or less. As a result, resistance to uneven wear can be improved. Modified examples

[0078] In the embodiment described above, the narrow groove of the shoulder section 60 has the cylindrical section 64 on the bottom section 62; however, the narrow groove of the shoulder section 60 may not have the cylindrical section 64. The narrow groove of the shoulder section 60 can be formed such that it has a constant groove width.

[0079] In the embodiment described above, the number of main circumferential grooves 20 arranged in the running surface section 2 is two; however, the number of main circumferential grooves 20 can also be other than two. For example, the chamfered narrow main circumferential groove 25 can be replaced by the main circumferential groove 20 in the embodiment, so that four main circumferential grooves 20 can be arranged.

[0080] Although in the embodiment described above, the pneumatic tire 1 is used as an example of the tire according to the embodiment of the present invention, the tire according to the embodiment of the present invention can be a different tire than the pneumatic tire 1. For example, the tire according to the embodiment of the present invention can be a so-called airless tire, which can be used without being filled with a gas. Examples

[0081] Fig. 6A and Fig. Table 6B contains the results of performance evaluation tests of pneumatic tires. With regard to the pneumatic tire 1 described above, performance evaluation tests are described that were carried out on a pneumatic tire according to a prior art example, on pneumatic tires 1 according to embodiments of the present invention, and on pneumatic tires according to comparative examples for comparison with pneumatic tires 1 according to embodiments of the present invention. The performance evaluation tests performed were tests for resistance to uneven shoulder wear and resistance to rib cracking.

[0082] The performance evaluation tests were carried out by mounting the pneumatic tires 1 with a nominal size of 295 / 75R22.5 according to TRA specification onto rim wheels with regular rims according to TRA specification, setting the air pressure to the maximum air pressure specified by TRA and mounting the rim wheels on a 2-DD test vehicle (semi-trailer truck) to carry out a test drive.

[0083] The evaluation procedure for each test item was as follows: After a 100,000 km drive with the test vehicle on which the test tires were mounted, the degree of uneven shoulder wear was measured, i.e., uneven wear of the shoulder rib section 33 in relation to the central rib section 31 and the middle rib section 32. The measured degree of uneven shoulder wear was expressed as an index, where the value of the prior art example described below is 100. The resistance to uneven shoulder wear indicates that the higher the index value, the lower the degree of uneven shoulder wear, thus indicating excellent resistance to uneven shoulder wear.

[0084] Rib crack resistance was assessed by driving the test vehicle, fitted with the test tires, over a 50 cm high step twenty times and measuring the number of rib cracks that formed in shoulder rib section 33, as well as the size of the rib cracks. Rib crack resistance was evaluated by comprehensively expressing the number of rib cracks generated and the reciprocal of the rib crack size as indices, where the value for the prior art example described below is 100. The rib crack resistance indicates that the higher the index, the lower the number of rib cracks generated and the smaller the rib crack size, thus indicating excellent rib crack resistance.

[0085] The performance evaluation tests were carried out on twenty-eight types of pneumatic tires, including a prior art pneumatic tire, pneumatic tires of Examples 1 to 25 corresponding to pneumatic tire 1 according to an embodiment of the present invention, and pneumatic tires of Comparative Examples 1 and 2 compared to pneumatic tire 1 according to an embodiment of the present invention. Among these, the prior art pneumatic tire has the narrow groove of the shoulder section but lacks the circumferential reinforcement layer. In the pneumatic tires of Comparative Examples 1 and 2, the distance W meets C from the tire equatorial plane to the end section of the circumferential reinforcement layer and the distance W N from the tire equatorial plane to the narrow groove of the shoulder section, the relationship 0.50 ≤ W does not apply. C / W N ≤ 0.90.

[0086] In contrast, all examples 1 to 25, which are examples of the pneumatic tire 1 according to the present invention, include the circumferential reinforcement layer 145 and the narrow groove of the shoulder section 60, and the distance W C from the tire equatorial plane CL to the end section of the circumferential reinforcement layer 145 and the distance W N From the tire equatorial plane CL to the narrow groove of the shoulder section 60, the relationship 0.50 ≤ W is satisfied. C / W N ≤ 0.90. Furthermore, the pneumatic tires 1 according to examples 1 to 25 differ from each other with regard to the ratio (W C / W G ) of the distance W C from the tire equatorial plane CL to the end section of the circumferential reinforcement layer 145 to the distance W Gfrom the tire equatorial plane CL to the end section 22 of the outermost main circumferential groove 21, the distance G1 (mm) from the end section 142a of the inner cross belt 142 to the narrow groove of the shoulder section 60, the distance G2 from the end section 143a of the outer cross belt 143 to the narrow groove of the shoulder section 60, the number of ends (ends / 50 mm) of the circumferential reinforcement layer 145, the presence or absence of the cylindrical section 64 of the narrow groove of the shoulder section 60, the width D N of the cylindrical section 64, the narrow groove of the shoulder section 60, and the number of main circumferential grooves 20.

[0087] As a result of conducting the evaluation test using these pneumatic tires 1, as described in Fig. 6A and Fig.As stated in 6B, it was found that the pneumatic tires 1 according to Examples 1 to 25, compared to the prior art example and comparative examples 1 and 2, can exhibit improved resistance to uneven shoulder wear and improved resistance to rib fractures. That is, the pneumatic tires 1 according to Examples 1 to 25 can provide improved resistance to uneven wear and simultaneously suppress rib fractures in the shoulder area.

[0088] The present disclosure includes the following inventions. Invention [1]

[0089] Tires, including: a tread section, including a plurality of main circumferential grooves extending in a tire circumferential direction; and a belt layer that is arranged in the tread section and includes a plurality of belt layers, the belt layer has a pair of cross belts, each enclosing belt cord threads whose inclination directions in a tire width direction are opposite to each other with respect to a tire circumference direction, and a circumferential reinforcement layer arranged between the pair of cross belts and having a width in the tire width direction that is smaller than the width of the cross belts, and having an inclination angle of the belt cord threads in the tire width direction with respect to the tire circumference direction of 5 degrees or less, wherein the tread section includes a narrow groove of the shoulder section which is arranged in the tire width direction on an outside of a main circumferential groove of the main circumferential grooves and extends in the tire circumferential direction, where a distance in the tire width direction from a tire equatorial plane to an end section in the Tire width direction of the circumferential reinforcement layer as W C is defined as a distance in the tire width direction from the tire equatorial plane to an end section on an inside in the tire width direction of the narrow groove of the shoulder section as W N is defined and where a distance W C and a distance W N a relationship 0.50 ≤ W C / W N ≤ 0.90 Invention [2]

[0090] The tire according to the invention [1], wherein a distance in the tire width direction between the tire equatorial plane and an end section on an outer side in the tire width direction of the outermost side in the tire width direction of the majority of main circumferential grooves as W G is defined and the distance W C and the distance W G a relationship 1.00 ≤ W C / W G ≤ 1.40 Invention [3]

[0091] The tire according to invention [1] or [2], wherein a distance from an end section in the tire width direction of a cross belt of the pair of cross belts, which are arranged on an inside in a tire radial direction of the circumferential reinforcement layer, to a bottom section of the narrow groove of the shoulder section is defined as G1, a distance from an end section in the tire width direction of a cross belt of the pair of cross belts, which are arranged on an outer side in the tire radial direction of the circumferential reinforcement layer, to the bottom section of the narrow groove of the shoulder section is defined as G2, the distance G1 is in the range 7 mm ≤ G1 ≤ 17 mm and the distance G2 is in the range 10 mm ≤ G2 ≤ ​​20 mm. Invention [4]

[0092] The tire according to one of the inventions [1] to [3], wherein the belt cord threads of the circumferential reinforcement layer are made of steel wire and The number of ends of the belt cord threads of the circumferential reinforcement layer is in a range of 15 cord threads / 50 mm or more and 30 cord threads / 50 mm or less. Invention [5]

[0093] The tire according to one of the inventions [1] to [4], wherein the narrow groove of the shoulder section on a bottom section has a cylindrical section whose width in a groove width direction of the narrow groove of the shoulder section is greater than a groove width of the narrow groove of the shoulder section, which has a cylindrical shape and extends in the circumferential direction of the tire. Invention [6]

[0094] The tire according to one of the inventions [1] to [5], wherein only two of the main circumferential grooves are arranged. Invention [7]

[0095] The tire according to one of the inventions [1] to [6], wherein the tire has a cross-sectional ratio of 80% or less. List of reference symbols 1 pneumatic tire 2. Tread section 3 Running surface floor contact surface 5 Shoulder section 8 Side wall section 10 bead section 11 bead core 12 bead fillers 13 Carcass layer 14 Belt layer 142, 143 Cross belt 145 Perimeter reinforcement layer 17 Wheel rim pad rubber 16 Inner Soul 20 Main circumferential groove 21 outermost main circumferential groove 25 beveled narrow circumferential grooves 30 Bridge section 31 central bridge section 32 middle bridge section 33 Shoulder strap section 34 narrow rib 40 narrow circumferential groove 41 central narrow circumferential groove 42 medium narrow circumferential groove 50 transverse groove 51 central transverse groove 52 middle transverse groove 60 narrow groove of the shoulder section 62 Floor section 63 grooved wall 64 cylindrical section 70 multiple lamellae QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 10-250314 A

[0002] JP 2023-048304 A

[0002]

Claims

A tire comprising: a tread section comprising a plurality of main circumferential grooves extending in a tire circumferential direction; and a belt layer arranged in the tread section comprising a plurality of belt plies; wherein the belt layer comprises: a pair of cross belts, each comprising belt cord threads whose inclination directions in a tire width direction with respect to a tire circumferential direction are opposite to each other, and a circumferential reinforcement layer arranged between the pair of cross belts, having a width in the tire width direction that is less than the width of the cross belts, and having an inclination angle of the belt cord threads in the tire width direction with respect to the tire circumferential direction of 5 degrees or less, wherein the tread section comprises a narrow groove of the shoulder section.which is arranged in the tire width direction on an outside of a main circumferential groove of the main circumferential grooves and extends in the tire circumference direction, wherein a distance in the tire width direction from a tire equatorial plane to an end section in the tire width direction of the circumferential reinforcement layer is defined as WC, a distance in the tire width direction from the tire equatorial plane to an end section on an inside in the tire width direction of the narrow groove of the shoulder section is defined as WN, and wherein a distance WC and a distance W satisfy a relationship 0.50 ≤ WC / WN ≤ 0.

90. Tires according to claim 1, wherein a distance in the tire width direction between the tire equatorial plane and an end section on an outer side in the tire width direction of the outermost side in the tire width direction of the plurality of main circumferential grooves is defined as WG and the distance WC and the distance WG satisfy a relationship 1.00 ≤ WC / WG≤ 1.

40. Tires according to claim 1, wherein a distance from an end section in the tire width direction of a cross belt of the pair of cross belts, which are arranged on an inside in a tire radial direction of the circumferential reinforcement layer, to a bottom section of the narrow groove of the shoulder section is defined as G1, a distance from an end section in the tire width direction of a cross belt of the pair of cross belts, which are arranged on an outside in a tire radial direction of the circumferential reinforcement layer, to the bottom section of the narrow groove of the shoulder section is defined as G2, the distance G1 is in the range 7 mm ≤ G1 ≤ 17 mm and the distance G2 is in the range 10 mm ≤ G2 ≤ ​​20 mm. Tires according to claim 1, wherein the belt cord threads of the circumferential reinforcement layer are made of steel wire and the number of ends of the belt cord threads of the circumferential reinforcement layer is in a range of 15 cord threads / 50 mm or more and 30 cord threads / 50 mm or less. Tire according to claim 1, wherein the narrow groove of the shoulder section on a bottom section comprises a cylindrical section which, in a groove width direction of the narrow groove of the shoulder section, has a width which is greater than a groove width of the narrow groove of the shoulder section which has a cylindrical shape and extends in the circumferential direction of the tire. Tires according to claim 1, wherein only two of the main circumferential grooves are arranged. Tires according to claim 1, wherein the tire has a cross-sectional ratio of 80% or less.

Images