pneumatic tires

Abstract

pneumatic tires (1), comprising: a carcass layer (13); a belt layer (14) arranged in a tire radial direction on an outer side of the carcass layer (13); a tread rubber (15) arranged in the tire radial direction on an outer side of the belt layer (14); at least three main circumferential grooves (2) running in one tire circumferential direction; and a plurality of raised sections (3) defined by the main circumferential grooves (2); where the belt layer (14) is formed by laminating a pair of cross belts (142, 143) having a belt angle of not less than 10° and not more than 45° as absolute values ​​and having belt angles with opposite signs, and a circumferential reinforcement layer (145) having a belt angle within a range of ± 5° with respect to the tire circumferential direction; a distance Gcc on a tire equator plane from a tread profile to an inner tire circumference surface and a distance Gsh from a tread edge to the inner tire circumference surface have a relationship that satisfies 1.10 ≤ Gsh / Gcc; and a measure of shoulder depression Dt of the tread profile at a contact end of the tire and an outer diameter SH of the tread profile along the tire equator plane have a relationship that satisfies Dt / SH ≤ 0.015.

Description

Technical area

[0001] The present invention relates to a pneumatic tire and, more particularly, to a pneumatic tire having improved wet performance. background

[0002] Recently, heavy-duty tires mounted on trucks, buses, and the like have been able to maintain the shape of the tread portion due to, on the one hand, the tires having a low aspect ratio and, on the other hand, the provision of a circumferential reinforcing layer in the belt layer. The circumferential reinforcing layer is a belt ply having a belt angle of substantially 0° with respect to the tire circumferential direction and is arranged to be laminated on a pair of cross belts. The technologies disclosed in Patent Documents 1 to 3 are known as conventional pneumatic tires configured in this manner. State-of-the-art documents

[0003] JP 4642760 B2, JP 4663638 B2, JP 4663639 B2, DE 11 2012 006 301 B4 and DE 60 2004 010 133 T2 are cited as prior art documents. Summary of the inventionProblem to be solved by the invention

[0004] There is a problem with the pneumatic tire in that an improvement in wet performance is expected.

[0005] Accordingly, in view of the above-mentioned problem, an object of the present invention is to provide a pneumatic tire having improved wet performance. Means to solve the problems

[0006] To achieve the above-mentioned object, the pneumatic tire according to the invention comprises a carcass layer, a belt layer arranged on the outside of the carcass layer in the tire radial direction, and a tread rubber arranged on the outside of the belt layer in the tire radial direction and provided with at least three circumferential main grooves extending in the tire circumferential direction and with a plurality of raised portions defined by the circumferential main grooves; wherein the belt layer is formed by laminating a pair of cross belts having a belt angle of not less than 10° and not more than 45° in absolute values ​​and having belt angles opposite to each other in sign, and a circumferential reinforcing layer having a belt angle within a range of ±5° with respect to the tire circumferential direction;wherein a distance Gcc from the tread pattern to the tire inner peripheral surface along the tire equatorial plane and a distance Gsh from the tread end to the inner peripheral surface have a relationship satisfying 1.10 ≤ Gsh / Gcc; and wherein the amount of shoulder depression Dt of the tread pattern at the contact end of the tire and the outer diameter SH of the tread pattern along the tire equatorial plane have a relationship satisfying Dt / SH ≤ 0.015. Effect of the invention

[0007] In a pneumatic tire design (1) according to the invention, a ratio Gsh / Gcc is increased, whereby the tread as a whole has a flat shape (approximately parallel to the tire rotation axis) and the volume (the distance Gsh) of a tread rubber 15 at the shoulder portion is ensured (see Fig. 1 and Fig. 2). As a result, the amount of deformation of the shoulder portion when the tire is in contact with the ground is reduced, and the rigidity of the shoulder land portion is adequately ensured. Furthermore, (2) an appropriate amount of shoulder depression Dt of the tread pattern at the contact end T of the tire is ensured. As a result, the contact patch pressure of a shoulder land portion 3 when the tire is in contact with the ground is increased, which is beneficial in improving the tire's wet performance. Brief description of the drawings Fig. 1 is a cross-sectional view taken in the tire meridian direction illustrating a pneumatic tire according to an embodiment of the present invention. Fig. 2 is an explanatory view showing a belt layer of the Fig. 1 depicted pneumatic tire. Fig. 3 is an explanatory view showing a belt layer of the Fig. 1 depicted pneumatic tire. Fig. 4 is an explanatory view showing the effect of the Fig. 1 pneumatic tire shown Fig. 5 is an explanatory view showing the effect of the Fig. 1 pneumatic tire shown Fig. 6 is an explanatory view showing a modified example of the Fig. 1 depicted pneumatic tire. Fig. 7 is an explanatory view showing a modified example of the Fig. 1 depicted pneumatic tire. Fig. 8 is a table showing the performance test results of pneumatic tires according to embodiments of the present invention. Best way to carry out the invention

[0008] The present invention will be described in detail below with reference to the accompanying drawings. However, the present invention is not limited to these embodiments. Furthermore, components that can possibly or obviously be replaced while maintaining consistency with the present invention are included in the configurations of the embodiments. Furthermore, a plurality of modified examples described in the embodiment can be freely combined within a range obvious to one skilled in the art. pneumatic tires

[0009] Fig. 1 is a cross-sectional view taken in the tire meridian direction illustrating a pneumatic tire according to an embodiment of the present invention. Fig. 1 shows a heavy-duty radial tire mounted on trucks, buses, and the like for long-distance transportation as an example of the pneumatic tire 1. Note that the symbol CL denotes a tire equatorial plane. Furthermore, a tread end P and a contact end T of the tire correspond in Fig. 1 agree.

[0010] The circumferential reinforcing layer 145 in Fig. 1 is marked by hatching.

[0011] A pneumatic tire 1 comprises a pair of bead cores 11,11, a pair of bead fillers 12,12, a carcass layer 13, a belt layer 14, tread rubber 15 and a pair of sidewall rubbers 16,16 (see Fig. 1).

[0012] The pair of bead cores 11, 11 have annular structures and form cores of the left and right bead portions. The pair of bead fillers 12, 12 are formed by a lower filler 121 and an upper filler 122 and are arranged on the outer periphery of each of the two bead cores 11, 11 in the tire radial direction to reinforce the bead portions.

[0013] The carcass layer 13 extends in a circular shape between the left- and right-side bead cores 11 and 11, forming a support structure for the tire. Furthermore, both ends of the carcass layer 13 are folded and fixed from the inner side to the outer side in the tire width direction, wrapping around the bead cores 11 and the bead fillers 12. Furthermore, the carcass layer 13 is composed of a plurality of carcass cords formed of steel or organic fibers (e.g., nylon, polyester, rayon, or the like) covered with a coating rubber and subjected to a rolling process, and has a carcass angle (an inclination angle of the carcass cord in a fiber direction with respect to the tire circumferential direction) with an absolute value of not less than 85° and not more than 95°.

[0014] The belt layer 14 is formed by laminating a plurality of belt plies 141 to 145 and is arranged to extend over the outer periphery of the carcass layer 13. A detailed configuration of the belt layer 14 will be described below.

[0015] The tread rubber 15 is arranged on an outer periphery of the carcass layer 13 and the belt layer 14 in the tire radial direction, forming a tread portion of the tire. The pair of sidewall rubbers 16, 16 are arranged on the respective outer sides of the carcass layer 13 in the tire width direction, forming left and right sidewall portions of the tire.

[0016] At the Fig. 1, the pneumatic tire 1 has seven circumferential main grooves 2 extending in the tire circumferential direction and eight raised portions 3 divided and formed by the circumferential main grooves 2. The raised portions 3 are formed by blocks segmented in the tire circumferential direction by ribs or lug grooves (not shown) extending continuously in the tire circumferential direction.

[0017] Here, "circumferential main grooves" refers to circumferential grooves with a groove width of 5.0 mm or more. The groove widths of the circumferential main grooves are measured excluding the notched portions and / or chamfered portions formed at the groove opening portion.

[0018] Furthermore, in the pneumatic tire 1, the left and right circumferential main grooves 2, 2 located at the outermost sides in the tire width direction are referred to as outermost circumferential main grooves. Furthermore, the left and right raised portions 3, 3 on the outer side in the tire width direction, defined by the left and right circumferential main grooves 2, 2, are referred to as shoulder raised portions. [Belt layer]

[0019] Fig. 2 and Fig. 3 are explanatory views showing a belt layer of the Fig. 1. Of these drawings, Fig. 2 represents an area on one side of a tread portion defined by the tire equatorial plane CL, and Fig. 3 shows a layer structure of the belt layer 14. Furthermore, the thin lines in the belt layers 141 to 145 in Fig. 3 schematically shows the respective belt cords of the belt layers 141 to 145.

[0020] The belt layer 14 is formed by laminating a large angle belt 141, a pair of cross belts 142, 143, a belt cover 144 and a circumferential reinforcing layer 145, and is arranged by winding and fixing on the outer circumference of the carcass layer 13 (see Fig. 2).

[0021] The high-angle belt 141 is composed of a plurality of belt cords formed of steel or organic fibers, coated with coating rubber, and subjected to a rolling process. It has a belt angle (an inclination angle of the fiber direction of the belt cords with respect to the tire circumferential direction) with an absolute value of not less than 45° and not more than 70°. Furthermore, the high-angle belt 141 is laminated on the outer side of the carcass layer 13 in the tire radial direction.

[0022] The pair of cross belts 142, 143 consists of a plurality of belt cords formed of steel or organic fibers, coated with a coating rubber, and subjected to a rolling process, and has a belt angle with an absolute value of not less than 10° and not more than 45°. In addition, the pair of cross belts 142, 143 has belt angles of opposite sign and is laminated such that the fiber directions of the belt cords cross each other (a cross-ply structure). In the following description, the cross belt 142 arranged on the inner side in the tire radial direction is referred to as the "inner cross belt," and the cross belt 143 arranged on the outer side in the tire radial direction is referred to as the "outer cross belt." Three or more cross belts may be laminated (not shown).In addition, the pair of cross belts 142, 143 are laminated in the tire radial direction on the outer side of the large angle belt 141.

[0023] The belt cover 144 is composed of a plurality of steel or organic fiber belt cords coated with coating rubber and subjected to a rolling process, and has a belt angle with an absolute value of not less than 10° and not more than 45°. Furthermore, the belt cover 144 is laminated on the outer side of the cross belts 142, 143 in the tire radial direction. In this embodiment, the belt cover 144 has the same belt angle as the outer cross belt 143 and is disposed in the outermost layer of the belt layer 14.

[0024] The circumferential reinforcing layer 145 is composed of belt cords formed of steel and coated with coating rubber, which are spirally wound at an inclination angle within a range of ±5° with respect to the tire circumferential direction. Furthermore, the circumferential reinforcing layer 145 is disposed between the pair of cross belts 142, 143. The circumferential reinforcing layer 145 is arranged on the inner side of the left and right edge portions of the pair of cross belts 142, 143 in the tire width direction. More specifically, the circumferential reinforcing layer 145 is formed by spirally winding one or more wires around the outer periphery of the inner cross belt 142. The circumferential reinforcing layer 145 enhances rigidity in the tire circumferential direction. As a result, the durability of the tire is improved.

[0025] In the pneumatic tire 1, the belt layer 14 may include an edge cover (not shown). Generally, the edge cover is composed of a plurality of belt cords made of steel or organic fibers coated with coating rubber and subjected to a rolling process, and the belt cords have a belt angle with an absolute value of not less than 0° and not more than 5°. Furthermore, the edge covers are arranged on the tire radially outer side of the left and right edge portions of the outer cross belt 143 (or the inner cross belt 142). As a result of the hoop stress effect of the edge cover, the difference in radial expansion between a center tread region and a shoulder region is reduced, and the tire's uneven wear resistance is improved. (Structure with improved wet performance)

[0026] Recently, tires for heavy loads mounted on trucks, buses, and the like maintain the shape of the tread portion due to the fact that the tires have a low aspect ratio, on the one hand, and the disposition of the circumferential reinforcing layer in the belt layer, on the other hand. More specifically, by disposing the circumferential reinforcing layer in the central region of the tread portion and utilizing its hoop stress effect, radial expansion of the tread portion is counteracted, and the shape of the tread portion is maintained.

[0027] Although this design maintains the flat shape of the contact patch due to the circumferential reinforcing layer in the center region of the tread portion, the tread portion is prone to exhibiting a sagging shoulder shape in the region toward the outside in the tire width direction from the edge of the circumferential reinforcing layer. As a result, there is a problem that the contact patch pressure of the shoulder land portion is reduced and the tire's wet performance is degraded.

[0028] Accordingly, the pneumatic tire 1 uses the following design to improve wet performance (see Fig. 1 to 3).

[0029] As in Fig. 2, in the pneumatic tire 1, a distance Gcc from the tread pattern to the tire inner peripheral surface along the tire equatorial plane CL and a distance Gsh from the tread end P to the tire inner peripheral surface have a relationship that satisfies 1.10 ≤ Gsh / Gcc. Preferably, the ratio Gsh / Gcc is in a range that satisfies 1.20 ≤ Gsh / Gcc, as is clear from the performance test results below (see Fig. 8). As a result, the tire's wet performance is effectively improved.

[0030] Although the upper limit of the ratio Gsh / Gcc is not particularly limited, the radius at the tread end P of the tread pattern is preferably equal to or less than the radius at the tire equatorial plane CL when the tire is mounted on a given rim and inflated to a given internal pressure with no load applied. That is, the tread pattern is designed to have a linear shape or an arc shape with its center on the inner side in the tire radial direction so that it does not assume an inverted R shape (an arc shape with its center on the outer side in the tire radial direction). For example, the upper limit of the ratio Gsh / Gss in the design with a square-shaped shoulder portion as shown in Fig. 2 is approximately 1.4 to 1.5. In contrast, the upper limit of the Gsh / Gss ratio is in the design with a rounded shoulder section as in Fig. 6 at about 1.3 to 1.4.

[0031] The distance Gcc is measured as the distance from the intersection point of the tire equatorial plane CL and the tread pattern to the intersection point of the tire equatorial plane CL and the tire inner circumferential surface when viewed in cross section from the tire meridian direction. Therefore, in a design having a main circumferential groove 2 at the tire equatorial plane CL, as shown in the Fig. 1 and Fig. 2, the distance Gcc is measured omitting the main circumferential groove 2. The distance Gsh is measured as the length of a perpendicular line from the tread end P to the tire inner circumferential surface when viewed in cross section from the tire meridian direction.

[0032] At the Fig. In the configuration shown in Figure 2, the pneumatic tire 1 has an inner liner 18 on the inner peripheral surface of the carcass layer 13, and the inner liner 18 is disposed over the entire area of ​​the tire's inner peripheral surface. In such a configuration, the distance Gcc and the distance Gsh are measured from the outer surface of the inner liner 18 (the tire's inner peripheral surface).

[0033] The tread end P designates a point of the tread edge section in a design (1) with a square-shaped shoulder section. For example, in the case of Fig. 2, the tread end P and a contact end T of the tire coincide with each other because the shoulder portion has a square shape. In contrast, as shown in (2) in Fig. 6, where the shoulder portion has a round shape, an intersection point P' of the profile of the tread portion and the profile of a sidewall portion as viewed in cross section is taken from the tire meridian direction, and the tread end P is taken as the end point of a perpendicular line drawn from the intersection point P' to the shoulder portion.

[0034] In addition, ‘tire contact point T’ means the position of the maximum width in the tire axial direction of a contact surface between the tire and a flat plate in a design in which the tire is mounted on a predetermined rim, inflated to a predetermined internal pressure, placed vertically on a flat plate in a static state, and loaded with a load corresponding to a predetermined load.

[0035] Herein, "specified rim" means an "applicable rim" as defined by the Japan Automobile Tire Manufacturers Association (JATMA), a "design rim" as defined by the Tire and Rim Association (TRA), or a "measuring rim" as defined by the European Tire and Rim Technical Organization (ETRTO). "Specified internal pressure" means "maximum air pressure" as defined by JATMA, a maximum value in "tire load limits at various cold inflation pressures" as defined by TRA, and "inflation pressures" as defined by ETRTO.Note that "specified load" refers to "maximum load capacity" as defined by JATMA, a maximum value within "tire load limits at various cold inflation pressures" as defined by TRA, and "load capacity" as defined by ETRTO. However, according to JATMA, in the case of passenger car tires, the specified internal pressure is 180 kPa, and the specified load is 88% of the maximum load capacity.

[0036] Fig. 4 and Fig. 5 are explanatory views showing the effects of the Fig. 1. Of these drawings, Fig. 4A and Fig. 4B Ground contact conditions of tires with different Gsh / Gcc ratios, and Fig. Fig. 5 shows dimensions of deviation (distortion of the end portion of the belt cords of the circumferential reinforcing layer 145) of the shoulder portions for each of the Fig. 4 shown tire that has ground contact.

[0037] The ratio Gsh / Gcc from the designs shown in Fig. 1 to 3 is in the tyre of the comparative example shown in Fig. 4A (Gsh / Gcc = 1.06). As a result, the tread pattern has a shoulder drop shape in which the outer diameter is reduced from the tire equatorial plane CL to the tread end P when the tire is not in ground contact (not shown). When the tire is in ground contact, as shown in Fig. Therefore, as shown in Figure 4A, the road surface side (outer side in the tire radial direction) of the tread rubber 15 exhibits a large deviation at the shoulder portion, and the belt plies 141 to 145 of the belt layer 14 exhibit a large degree of deflection on the road surface side (outer side in the tire radial direction). As a result, displacement of the shoulder portion in the radial direction with respect to the road surface increases while the tire is in ground contact, and as a result, the contact pressure of the shoulder land portion decreases, and wet performance deteriorates.

[0038] The ratio Gsh / Gcc from the designs shown in Fig. 1 to 3, is in the tire of the type shown in Fig. 4B. (Gsh / Gcc = 1.20). As a result, the difference in diameter between the outer diameter at the tread end P and the outer diameter along the tire equatorial plane CL in the tread pattern is reduced, and the tread as a whole has a flat shape (approximately parallel to the tire rotation axis) (see Fig. 1 and Fig. 2). The volume of the tread rubber 15 at the shoulder portion (the distance Gsh) is appropriately arranged, thereby reducing displacement of the shoulder portion in the radial direction relative to the road surface when the tire is in contact with the ground. As a result, the contact pressure of the shoulder land portion is increased, and the tire's wet performance is improved.

[0039] A measure of the shoulder depression Dt of the tread pattern at the contact end T in the pneumatic tire 1, which Fig. 2, and an outer diameter SH of the tread pattern at the tire equatorial plane CL have a relationship satisfying 0 ≤ Dt / SH ≤ 0.015. The ratio Dt / SH is preferably in a range satisfying 0.005 ≤ Dt / SH ≤ 0.010. The contact patch pressure of the shoulder land portion 3 when the tire is in contact with the ground is adequately ensured because Dt / SH ≤ 0.010 is satisfied, and any adverse effects due to heat generation in the shoulder portion are reduced because 0.005 ≤ Dt / SH is satisfied.

[0040] When the shoulder drop amount Dt is in a range satisfying 0 ≤ Dt while the tire radial inner side (shoulder drop side) is positive, the outer diameter of the tread pattern at the tire contact patch end T is equal to the outer diameter SH of the tread pattern at the tire equatorial plane CL when Dt = 0. Therefore, the shoulder drop amount Dt is set so that Dt is not less than zero and is in such a range that the tread pattern does not form an inverted R shape.

[0041] The degree of shoulder drop Dt is measured when the tire is mounted on a given rim, inflated to a given internal pressure and no load is applied.

[0042] A shoulder depression amount De of the tread pattern at the end portion of the circumferential reinforcing layer 145 and the shoulder depression amount Dt of the tread pattern at the tire contact end T have a relationship that satisfies 0.25 ≤ De / Dt ≤ 0.65. Therefore, De is smaller than Dt, and the profile of the shoulder land portion 3 has a shape having a shoulder depression toward the outer side in the tire width direction, viewed in a cross section from the tire meridian direction.

[0043] When the lower limit of the shoulder drop amount De is in a range satisfying 0 ≤ De while the inner side (shoulder drop side) in the tire radial direction is positive, the outer diameter of the tread pattern at the end portion of the circumferential reinforcing layer 145 and the outer diameter of the tread pattern at the tire contact end T are equal to the outer diameter SH of the tread pattern at the tire equatorial plane CL when De = Dt = 0.

[0044] As in Fig. 2 and Fig. As shown in Figure 6, the shoulder droop De is measured based on the end point of a perpendicular line drawn from the end portion of the circumferential reinforcing layer 145 to the tread pattern. The shoulder droop De is measured when the tire is mounted on a predetermined rim, inflated to a predetermined internal pressure, and no load is applied.

[0045] A contact width Wsh of the shoulder elevation section 3 and a tread width TW in Fig. 2 have a relationship that satisfies 0.1 ≤ Wsh / TW ≤ 0.2. This ensures a suitable contact width Wsh of the shoulder elevation section 3.

[0046] The contact width Wsh of the shoulder ridge portion 3 is a distance in the tire rotation axis direction from the edge portion on the circumferential main groove 2 side to the tire contact end T of the shoulder ridge portion 3, and is measured when the tire is mounted on a predetermined rim, inflated to a predetermined internal pressure, and no load is applied. The contact width Wsh is calculated as an average value over the entire tire circumference in a design in which the outermost circumferential main groove 2 is zigzagged in the tire circumferential direction, or in a design in which the outermost circumferential main groove 2 has notched portions or chamfered portions at the edge portion.

[0047] The tread width TW is the distance in the direction of the tire rotation axis between the left and right tread ends P, P, measured when the tire is mounted on a specified rim, inflated to a specified internal pressure, and no load is applied.

[0048] A contact width Wcc of the raised portion 3 closest to the tire equator line CL and a contact width Wsh of the shoulder raised portion 3 in Fig. 3 have a relationship that satisfies 0.80 ≤ Wsh / Wcc ≤ 1.20.

[0049] The raised portion 3 closest to the tire equatorial plane CL means the raised portion 3 when the raised portion 3 lies on the tire equatorial line CL. When the circumferential main groove 2 lies on the tire equatorial plane CL, the raised portion 3 closest to the tire equatorial plane CL means the raised portion 3 located on the same side as the shoulder ridge portion 3 used in the comparison between the left and right raised portions 3 delimited by the circumferential main groove 2.The ratio Wsh / Wcc between the contact width Wcc of the land portion 3 closest to the tire equator plane CL and the contact width Wsh of the shoulder land portion 3 is measured in a design having a tread pattern without left-right symmetry (not shown) in a region on one side separated by the tire equator line CL when the circumferential main groove 2 is located on the tire equator line CL.

[0050] The contact width Wcc of the raised portion 3 is measured when the tire is mounted on a specified rim, inflated to a specified internal pressure, and no load is applied. The contact width Wcc is calculated as an average value over the entire tire circumference in a design in which the outermost circumferential main groove 2 is zigzagged in the tire circumferential direction, or in a design in which the outermost circumferential main groove 2 has notched portions or chamfered portions at the edge portion.

[0051] The tread width TW and the width Ws of the circumferential reinforcing layer 145 in Fig. 1 preferably have a relationship that satisfies 0.70 ≤ Ws / TW ≤ 0.90.

[0052] The width Ws of the circumferential reinforcing layer 145 is a distance in the direction of the tire rotation axis between the left and right portions of the circumferential reinforcing layer 145 and is measured when the tire is mounted on a predetermined rim, inflated to a predetermined internal pressure, and no load is applied. The width Ws of the circumferential reinforcing layer 145 is the distance between the outermost end portions of the divided portions when the circumferential reinforcing layer 145 has a structure divided in the tire width direction (not shown).

[0053] A pneumatic tire generally has a left-right symmetrical structure, with a center on the tire equator plane CL, as in Fig. 1. Consequently, the distance from the tire equatorial plane CL to the tread end P is TW / 2, and the distance from the tire equatorial plane CL to the circumferential reinforcing layer 145 is Ws / 2.

[0054] In contrast, in a pneumatic tire having a structure without left-right symmetry (not shown), the range of the above-mentioned ratio Ws / TW between the tread width TW and the width Ws of the circumferential reinforcing layer is defined by converting the widths into half-widths from the tire equatorial plane CL. Specifically, a distance TW' from the tire equatorial plane CL to the tread end P (not shown) and a distance Ws' from the tire equatorial plane CL to the end portion of the circumferential reinforcing layer 145 are set to have a relationship satisfying 0.70 ≤ Ws' / TW' ≤ 0.90.

[0055] A groove area ratio A in the contact patch in the pneumatic tire 1 lies in a range that satisfies 0.20 ≤ A ≤ 0.30.

[0056] The groove area ratio is defined as groove area / (groove area + contact area). "Groove area" refers to the opening area of ​​the grooves in the contact patch. "Groove" refers to the circumferential grooves and lug grooves in the tread portion and excludes sipes, cuts, and notches. "Contact area" refers to the contact area between the tire and the road surface. It should be noted that the groove area and contact area are measured at a contact surface between a tire and a flat plate in a design in which the tire is mounted on a specified rim, inflated to a specified internal pressure, placed vertically with respect to the flat plate in a static state, and loaded with a load equal to a specified load.

[0057] A loss angle tangent tanδ of the tread rubber 15 in the pneumatic tire 1 lies in a range satisfying 0.10 ≤ tanδ.

[0058] The loss angle tangent tanδ is measured using a viscoelastic spectrometer under the conditions of a temperature of 20 °C, a shear strain of 10% and a frequency of 20 Hz.

[0059] In addition, a width Wb1 of the large angle belt 141 and a width Wb3 of the narrower cross belt 143 of the pair of cross belts 142, 143 preferably have a relationship satisfying 0.85 ≤ Wb1 / Wb3 ≤ 1.05 (see Fig. 3). As a result, an appropriate Wb1 / Wb3 ratio is ensured.

[0060] The width Wb1 of the large angle belt 141 and the width Wb3 of the cross belt 143 are measured as distances in the tire width direction when the tire is mounted on a given rim, inflated to a given internal pressure, and no load is applied.

[0061] When designing in Fig. 1, the belt layer 14 has a structure which is left-right symmetrical about the tire equatorial plane CL, as in Fig. 3, and the width Wb1 of the large angle belt 141 and the width Wb3 of the narrower cross belt 143 have a relationship that Wb1 <Wb3 erfüllt. Infolgedessen wird ein Randabschnitt des Gürtels mit großem Winkel 141 in einer Region auf jeder Seite der Reifenäquatorebene CL in Reifenbreitenrichtung weiter innen angeordnet als der Randabschnitt des schmäleren Kreuzgürtels 143. Jedoch ist die Gestaltung nicht darauf beschränkt, und die Breite Wb1 des Gürtels mit großem Winkel 141 und die Breite Wb3 des schmäleren Kreuzgürtels 143 können eine Beziehung aufweisen, die Wb1 ≥ Wb3 erfüllt (nicht dargestellt).

[0062] Furthermore, the belt cords of the large angle belt 141 are preferably steel wire and the number of ends is preferably not less than 15 ends / 50 mm and not more than 25 ends / 50 mm (see Fig. 4). The belt cords of the pair of cross belts 142, 143 are preferably steel wire, and the number of ends is preferably not less than 18 ends / 50 mm and not more than 28 ends / 50 mm. The belt cords of the circumferential reinforcing layer 145 are steel wire, and the number of ends is preferably not less than 17 ends / 50 mm and not more than 30 ends / 50 mm. As a result, the strength of the belt layers 141, 142, 143, 145 is adequately ensured.

[0063] In addition, a modulus E1 at 100% elongation of the coating rubber of the large-angle belt 141 and a modulus Es at 100% elongation of the coating rubber of the circumferential reinforcing layer 145 preferably have a relationship satisfying 0.90 ≤ Es / E1 ≤ 1.10 (see Fig. 4). Furthermore, the moduli E2, E3 at 100% elongation of the coating rubbers of the pair of cross belts 142, 143 and the modulus Es at 100% elongation of the coating rubber of the circumferential reinforcing layer 145 preferably have relationships that satisfy 0.90 ≤ Es / E2 ≤ 1.10 and 0.90 ≤ Es / E3 ≤ 1.10. Furthermore, the modulus Es at 100% elongation of the coating rubber of the circumferential reinforcing layer 145 preferably lies in a range that satisfies 4.5 MPa ≤ Es ≤ 7.5 MPa. As a result, appropriate moduli of the belt layers 141, 142, 143, 145 are ensured.

[0064] The modulus at 100% elongation is measured in a tensile test at ambient temperature according to JIS K6251 (using dumbbell No. 3).

[0065] In addition, a breaking elongation λ1 of the coating rubber of the large angle belt 141 is preferably at least 200% (see Fig. 4). Furthermore, the breaking elongations λ2, λ3 of the coating rubbers of the pair of cross belts 142, 143 are preferably within ranges satisfying 200% ≤ λ2 and 300% ≤ λ3. Furthermore, the breaking elongation λs of the coating rubber of the circumferential reinforcing layer 145 is preferably equal to or greater than 200%. As a result, the durability of the belt plies 141, 142, 143, 145 is adequately ensured.

[0066] The elongation at break is measured by performing a tensile test on a specimen of the 1B shape according to specification JIS-K7162 (dumbbell shape with a thickness of 3 mm) at a tensile speed of 2 mm / min using a tensile testing machine (INSTRON 5585H, manufactured by Instron Corp.) conforming to JIS-K7161.

[0067] The elongation of the belt cords constituting the circumferential reinforcing layer 145 when the belt cords are constituent parts is preferably not less than 1.0% and not more than 2.5% when the tensile load is 100 N to 300 N, and when the belt cords are from a tire (when removed from the tire), it is preferably not less than 0.5% and not more than 2.0% when the tensile load is 500 N to 1000 N. The belt cords (high elongation steel wire) have a good elongation ratio when a low load is applied compared to ordinary steel wire, so that the belt cords can withstand loads applied to the circumferential reinforcing layer 145 during the period from manufacture to use of the tire, so that it is possible to counteract damage to the circumferential reinforcing layer 145, which is desirable.

[0068] The elongation of the belt cord is measured according to JIS G3510.

[0069] As in Fig. 3, the circumferential reinforcing layer 145 is preferably disposed on the tire widthwise inner side of the left and right edge portions of the narrower cross belt 143 of the pair of cross belts 142, 143. Furthermore, the width Wb3 of the narrower cross belt 143 and a distance S from an edge portion of the circumferential reinforcing layer 145 to an edge portion of the narrower cross belt 143 are preferably within a range satisfying 0.03 ≤ S / Wb ≤ 0.12. As a result, the distance between the end portions of the width Wb3 of the cross belt 143 and the end portions of the circumferential reinforcing layer 145 is adequately secured. This point is the same even when the circumferential reinforcing layer 145 has a split structure (not shown).

[0070] The distance S of the circumferential reinforcing layer 145 is measured as a distance in the tire width direction when the tire is mounted on a prescribed rim, inflated to a prescribed internal pressure, and no load is applied.

[0071] In addition, the design in Fig. 1 the circumferential reinforcing layer 145 consists of a spirally wound single steel wire, as in Fig. 3. However, the configuration is not limited thereto, and the circumferential reinforcing layer 145 may also be composed of a plurality of wires wound spirally and parallel to each other (multi-winding structure). In this case, the number of wires is preferably 5 or less. In addition, when five wires are wound in multiple layers, the winding width per unit is preferably not more than 12 mm. As a result, a plurality of wires (not less than two and not more than five wires) can be properly wound with an inclination within a range of ±5° with respect to the tire circumferential direction.

[0072] In addition, the design in Fig. 2 the circumferential reinforcing layer is arranged so that it lies between the pair of cross belts 142, 143 (see Fig. 2). However, the circumferential reinforcing layer 145 is not limited to this, and it may also be disposed on the outer side of the pair of cross belts 142, 143 in the tire radial direction (not shown). Furthermore, the circumferential reinforcing layer 145 may also be disposed on the inner side of the pair of cross belts 142, 143. For example, the circumferential reinforcing layer 145 may be disposed (1) between the high-angle belt 141 and the inner cross belt 142, or (2) between the carcass layer 13 and the high-angle belt 141 (not shown).

[0073] The elongation at break of the tread rubber 15 in the pneumatic tire 1 is preferably in a range of 350% or more. As a result, the strength of the tread rubber 15 is ensured and tearing of the outermost circumferential main groove 2 is prevented. Although the upper limit of the elongation at break of the tread rubber 15 is not limited, the elongation at break is limited due to the nature of the rubber compound of the tread rubber 15.

[0074] The hardness of the tread rubber 15 in the pneumatic tire 1 is preferably in a range of 70 or less. As a result, the strength of the tread rubber 15 is ensured and tearing of the outermost circumferential main groove 2 is prevented. Although the upper limit for the hardness of the tread rubber 15 is not limited, the hardness is limited due to the nature of the rubber compound of the tread rubber 15.

[0075] Here, “rubber hardness” refers to JIS-A hardness according to JIS-K6263. [Rounded shoulder section]

[0076] Fig. 6 is an explanatory view of a modified example of the pneumatic tire shown in Fig. 1 is shown. Fig. 6 illustrates a design having a shoulder portion with a rounded shape.

[0077] In the design in Fig. 1, the shoulder portion has a square shape in which the contact end T of the tire and the tread end P coincide, as in Fig. 2 shown.

[0078] However, the shoulder section is not limited to this and can also have a rounded shape, as in Fig. 6. In such a case, when viewed in cross-section from the tire meridian direction, an intersection point P' of the tread portion profile and the sidewall portion profile is formed, and the tread end P is taken as the end point of a perpendicular line drawn from the intersection point P' to the shoulder portion. Therefore, the tire contact end T and the tread end P are normally located at different positions from each other. [Two-tone structure of the belt edge padding]

[0079] Fig. Fig. 7 is an explanatory view of a modified example of the pneumatic tire shown in Fig. 1 is shown. Fig. Fig. 7 is an enlarged view of an end portion of the belt layer 14 on the outer side in the tire width direction. The circumferential reinforcing layer 145 and the belt edge cushion 19 are shown in Fig. 6 marked by hatching.

[0080] In the Fig. 1, the circumferential reinforcing layer 145 is disposed on the inner side of the left and right edge portions of the narrower cross belt 143 of the pair of cross belts 142, 143 in the tire width direction. The belt edge cushion 19 is arranged to be located between the pair of cross belts 142, 143 at a position corresponding to the edge portions of the pair of cross belts 142, 143. Specifically, the belt edge cushion 19 is arranged on the outer side of the circumferential reinforcing layer 145 in the tire width direction so as to be adjacent to the circumferential reinforcing layer 145 and to extend from the end portion on the outer side of the circumferential reinforcing layer 145 in the tire width direction to the end portion on the outer side of the pair of cross belts 142, 143 in the tire width direction.

[0081] At the Fig. 1, the belt edge cushion 19 has a structure that is thicker as a whole than the circumferential reinforcing layer 145 because the thickness increases toward the outer side in the tire width direction. The belt edge cushion 19 has a modulus E at 100% elongation that is lower than that of the coating rubber of the cross belts 142, 143. Specifically, the modulus E at 100% elongation of the belt edge cushion 19 and a modulus Eco of the coating rubber have a relationship that satisfies 0.60 ≤ E / Eco ≤ 0.95. As a result, there is an advantage in suppressing the occurrence of separation of rubber materials between the pair of cross belts 142, 143 and in a region located on the outer side of the circumferential reinforcing layer 145 in the tire width direction.

[0082] On the other hand, the belt edge pad 19 has, according to the Fig. 7 shown design in the Fig. 1, the tire has a two-tone structure formed of a stress relief rubber 191 and an end-portion relief rubber 192. The stress relief rubber 191 is disposed between the pair of cross belts 142, 143 on the outer side in the tire width direction of the circumferential reinforcing layer 145 so as to be adjacent to the circumferential reinforcing layer 145. The end-portion relief rubber 192 is disposed between the pair of cross belts 142, 143 on the outer side in the tire width direction of the stress relief rubber 191 at a position corresponding to the edge portion of the pair of cross belts 142, 143 so as to be adjacent to the stress relief rubber 191.Therefore, when viewed in cross section from the tire meridian direction, the belt edge cushion 19 has a structure formed by disposing the stress relief rubber 191 and the edge portion relief rubber 192 side by side in the tire width direction to fill up an area from the end portion of the circumferential reinforcing layer 145 on the outer side in the tire width direction to the end portion of the pair of cross belts 142, 143.

[0083] In addition, the design in Fig. 7, a modulus Ein at 100% elongation of the stress relief rubber 191 and the modulus Es at 100% elongation of the coating rubber of the circumferential reinforcing layer 145 have a relationship that satisfies Ein < Es. Specifically, the modulus Ein of the stress relief rubber 191 and the modulus Es of the circumferential reinforcing layer 145 preferably have a relationship that satisfies 0.6 ≤ Ein / Es ≤ 0.9.

[0084] Furthermore, the Fig. 7, the modulus Ein at 100% elongation of the stress relief rubber 191 and the modulus Eco at 100% elongation of the coating rubber of the cross belts 142, 143 have a relationship that Ein <Eco erfüllt. Insbesondere weisen der Modul Ein des Spannungsabbaugummis 191 und der Modul Eco des Beschichtungsgummis vorzugsweise eine Beziehung auf, die 0,6 ≤ Ein / Eco ≤ 0,9 erfüllt.

[0085] In addition, the design in Fig. 7, a modulus Eout at 100% elongation of the end portion relief rubber 192 and the modulus Ein at 100% elongation of the stress relief rubber 191 preferably have a relationship satisfying Eout < Ein. In addition, the modulus Ein at 100% elongation of the stress relief rubber 191 is preferably within a range satisfying 4.0 MPa ≤ Ein ≤ 5.5 MPa.

[0086] Since the tension relief rubber 191 is Fig. 7, the end portion relief rubber 192 is disposed on the outer side of the circumferential reinforcing layer 145 in the tire width direction, the shear strain of the peripheral rubbers between the edge portions of the circumferential reinforcing layer 145 and the cross belts 142, 143 is reduced. Furthermore, since the end portion relief rubber 192 is disposed at a position corresponding to the edge portions of the cross belts 142, 143, the shear strain of the peripheral rubbers at the edge portions of the cross belts 142, 143 is reduced. Accordingly, separation of the peripheral rubbers of the circumferential reinforcing layer 145 is suppressed. Effect

[0087] As described above, the pneumatic tire 1 includes the carcass layer 13, the belt layer 14 arranged on the outer side of the carcass layer 13 in the tire radial direction, and the tread rubber 15 arranged on the outer side of the belt layer 14 in the tire radial direction (see Fig. 1). Further, the belt layer 14 is formed by laminating the pair of cross belts 142, 143 having a belt angle with an absolute value of not less than 10° and not more than 45° and having belt angles of opposite signs, and the circumferential reinforcing layer 145 having a belt angle within a range of ± 5° with respect to the tire circumferential direction (see Fig. 3). The distance Gcc from the tread pattern to the inner circumferential surface of the tire along the tire equatorial plane CL and the distance Gsh from the tread end P to the inner circumferential surface of the tire have a relationship that satisfies 1.10 ≤ Gsh / Gcc (see Fig. 2). The shoulder drop Dt of the tread pattern at the tire contact end T and the outer diameter SH of the tread pattern at the tire equatorial plane CL have a relationship that satisfies 0 ≤ Dt / SH ≤ 0.015.

[0088] According to this design (1), the ratio Gsh / Gcc is increased, whereby the tread as a whole has a flat shape (approximately parallel to the tire rotation axis) and the volume (distance Gsh) of a tread rubber 15 at the shoulder portion is ensured (see Fig. 1 and Fig. 2). As a result, the amount of deformation of the shoulder portion when the tire is in contact with the ground is reduced, and the rigidity of the shoulder land portion is adequately ensured. Furthermore, (2) an appropriate amount of shoulder depression Dt of the tread pattern at the contact end T of the tire is ensured. As a result, the contact patch pressure of a shoulder land portion 3 when the tire is in contact with the ground is increased, which is beneficial in improving the tire's wet performance.

[0089] The degree of shoulder depression De of the tread pattern at the end portion of the circumferential reinforcing layer 145 and the degree of shoulder depression Dt of the tread pattern at the tire contact end T in the pneumatic tire 1 have the relationship satisfying 0.25 ≤ De / Dt ≤ 0.65 (see Fig. 2) There is an advantage in that, according to this design, an appropriate De / Dt ratio is ensured. That is, the contact pressure of the shoulder land portion 3 when the tire is in contact with the ground is increased, resulting in improved tire performance in wet conditions because the De / Dt ratio is equal to or greater than 0.25. Since the De / Dt ratio is equal to or less than 0.65, an increase in heat generation is counteracted because the tread rubber is not applied in an excessive amount, thus ensuring tire durability.

[0090] The contact width Wsh of the shoulder ridge portion 3 and the tread width TW in the pneumatic tire 1 have a relationship that satisfies 0.1 ≤ Wsh / TW ≤ 0.2 (see Fig. 2). As a result, this design provides the advantage of ensuring an appropriate contact width Wsh of the shoulder land portion 3. That is, since the ratio Wsh / TW is equal to or greater than 0.1, the contact patch area of ​​the shoulder land portion 3 is maintained, and the tire's resistance to uneven wear is ensured. The contact patch pressure of the shoulder land portion 3 when the tire is in contact with the ground is increased because the ratio Wsh / TW is equal to or less than 0.2, resulting in improved tire performance in wet conditions.

[0091] The contact width Wcc of the land portion 3 closest to the tire equatorial plane CL and the contact width Wsh of the shoulder land portion 3 in the pneumatic tire 1 have the relationship satisfying 0.80 ≤ Wsh / Wcc ≤ 1.20 (see Fig. 2). This has the advantage of ensuring a suitable Wsh / Wc ratio. That is, since the Wsh / Wcc ratio is equal to or greater than 0.80, the contact patch pressure of the shoulder land portion 3 is adequately ensured, and the tire's resistance to uneven wear is suppressed. However, even if the relationship 1.20 < Wsh / Wcc is satisfied, the effect of increasing the contact patch pressure in the shoulder land portion 3 is small because the contact width Wsh is increased.

[0092] In addition, the tread width TW and the width Ws of the circumferential reinforcing layer 145 in the pneumatic tire 1 have the relationship that satisfies 0.70 ≤ Ws / TW ≤ 0.90 (see Fig. 1). According to this configuration, there is an advantage in that the degree of deviation of the shoulder portion 3 when the tire is in contact with the ground is effectively reduced due to the appropriate ratio Ws / TW between the tread width TW and the width Ws of the circumferential reinforcing layer 145 (see Fig. 4B and Fig. 5). That is, the width Ws of the circumferential reinforcing layer 145 is adequately secured, and the degree of deviation of the shoulder portion 3 when the tire is in contact with the ground is reduced because the ratio Ws / TW is equal to or greater than 0.70. However, even when the ratio Ws / Tw is less than or equal to 0.90, deformation at the belt layer end portions is reduced because the deformation of the belt end portions is suppressed when the tire is in contact with the ground.

[0093] The groove area ratio A in the tire contact patch in the pneumatic tire 1 is within a range of 0.20 ≤ A ≤ 0.30. As a result, there is an advantage in ensuring an appropriate groove area ratio A. That is, the groove area is appropriately ensured and the tire performance in wet conditions is improved because the groove area ratio A is equal to or greater than 0.20. Meanwhile, excessive increase in the groove area is suppressed, and the tire's uneven wear resistance is appropriately ensured because the groove area ratio A is less than or equal to 0.30.

[0094] A loss angle tangent tanδ of the tread rubber 15 in the pneumatic tire 1 is within a range satisfying 0.10 ≤ tanδ. As a result, there is an advantage in that the loss angle tangent tanδ of the tread rubber 15 is adequately ensured and the tire performance in wet conditions is improved.

[0095] Furthermore, in the pneumatic tire 1, the belt cords constituting the circumferential reinforcing layer 145 are made of steel wire, and the number of ends in the circumferential reinforcing layer 145 is not less than 17 ends / 50 mm and not more than 30 ends / 50 mm. As a result, there is an advantage in ensuring an appropriate number of ends of the belt cords in the circumferential reinforcing layer 145. More specifically, since the circumferential reinforcing layer 145 has at least 17 ends / 50 mm, the strength of the circumferential reinforcing layer 145 is appropriately ensured. In addition, the amount of coating rubber of the circumferential reinforcing layer 145 is appropriately ensured, and separation of the rubber materials between the adjacent belt layers (the pair of cross belts 142, 143 and the circumferential reinforcing layer 145 in Fig. 3) is suppressed because the circumferential reinforcing layer 145 has no more than 30 ends / 50 mm.

[0096] In the pneumatic tire 1, the elongation of the belt cords constituting the circumferential reinforcing layer 145, when the belt cords are constituents, is preferably not less than 1.0% and not more than 2.5% when the tensile load is 100 N to 300 N. As a result, there is an advantage that the effect of suppressing radial expansion in the central region due to the circumferential reinforcing layer 145 is appropriately ensured.

[0097] In the pneumatic tire 1, the elongation of the belt cords constituting the circumferential reinforcing layer 145, when the belt cords are of a tire, is preferably not less than 0.5% and not more than 2.0% when the tensile load is 500 N to 1000 N. As a result, there is an advantage that the effect of suppressing radial expansion in the central region is appropriately ensured due to the circumferential reinforcing layer 145.

[0098] In the pneumatic tire 1, the circumferential reinforcing layer 145 is arranged on the inner side of the left and right edge portions of the narrower cross belt 143 of the pair of cross belts 142, 143 in the tire width direction (see Fig. 3). The pneumatic tire 1 includes the stress relief rubber 191 disposed between the pair of cross belts 142, 143 and on the outer side of the circumferential reinforcing layer 145 in the tire width direction so as to be adjacent to the circumferential reinforcing layer 145, and the end portion relief rubber 192 disposed between the pair of cross belts 142, 143 and on the outer side of the stress relief rubber 191 in the tire width direction and at a position corresponding to the end portions of the pair of cross belts 142, 143 so as to be adjacent to the stress relief rubber 191 (see Fig. 7).

[0099] Such a configuration has the advantage of suppressing fatigue fracture of the peripheral rubbers at the edge portion of the circumferential reinforcing layer 145 by disposing the circumferential reinforcing layer 145 on the inner side of the left and right edge portions of the narrower cross belt 143 of the pair of cross belts 142, 143 in the tire width direction. Since the stress relief rubber 191 is disposed on the outer side of the circumferential reinforcing layer 145 in the tire width direction, the shear strain of the peripheral rubbers between the edge portions of the circumferential reinforcing layer 145 and the cross belts 142, 143 is reduced. Furthermore, since the end portion relief rubber 192 is arranged at a position corresponding to the edge portions of the cross belts 142, 143, the shear strain of the peripheral rubbers at the edge portions of the cross belts 142, 143 is reduced.Accordingly, there is an advantage that separation of the peripheral rubbers of the circumferential reinforcing layer 145 is suppressed.

[0100] The modulus Ein at 100% elongation of the stress relief rubber 191 and the modulus Eco at 100% elongation of the coating rubber of the pair of cross belts 142, 143 in the pneumatic tire 1 have a relationship that Ein <Eco erfüllt. Infolgedessen besteht der Vorteil, dass für einen angemessenen Modul Ein des Spannungsabbaugummis 191 gesorgt wird und die Scherdehnung der peripheren Gummis zwischen den Randabschnitten der Umfangsverstärkungsschicht 145 und den Kreuzgürteln 142, 143 gemildert wird.

[0101] The modulus Ein at 100% elongation of the stress relief rubber 191 and the modulus Eco at 100% elongation of the coating rubber of the pair of cross belts 142, 143 in the pneumatic tire 1 have the relationship that satisfies 0.6 ≤ Ein / Eco ≤ 0.9. As a result, there is an advantage of ensuring an appropriate Ein / Eco ratio and mitigating the shear strain of the peripheral rubbers between the edge portions of the circumferential reinforcing layer 145 and the cross belts 142, 143.

[0102] In addition, in the pneumatic tire 1, the modulus Ein at 100% elongation of the stress relief rubber 191 is within a range satisfying 4.0 MPa ≤ Ein ≤ 5.5 MPa (see Fig. 7). As a result, there is an advantage in ensuring an appropriate modulus Ein of the stress relief rubber 191 and mitigating the shear strain of the peripheral rubber between the edge portions of the circumferential reinforcing layer 145 and the cross belts 142, 143.

[0103] The belt layer 14 in the pneumatic tire 1 has the large angle belt 141 having a belt angle of not less than 45° and not more than 70° as an absolute value (see Fig. 1 and Fig. 3). As a result, there is an advantage that the belt layer 14 is reinforced and the distortion of the end portions of the belt layer 14 when the tire is in contact with the ground is suppressed.

[0104] In addition, in the pneumatic tire 1, the width Wb1 of the large angle belt 141 and the width Wb3 of the narrower cross belt 143 of the pair of cross belts 142, 143 satisfy the relationship that 0.85 ≤ Wb1 / Wb3 ≤ 1.05 (see Fig. 3) According to this design, an appropriate ratio Wb1 / Wb3 is ensured between the width Wb1 of the large-angle belt 141 and the width Wb3 of the narrower cross belt 143. As a result, there is an advantage in suppressing the distortion of the end portions of the belt layer 14 when the tire is in contact with the ground.

[0105] In the pneumatic tire 1, the circumferential reinforcing layer 145 is arranged on the inner side of the left and right edges of the narrower cross belt 143 of the pair of cross belts 142, 143 in the tire width direction (see Fig. 3). Also, the width Wb3 of the narrower cross belt 143 and the distance S from the edge portion of the circumferential reinforcing layer 145 to the edge portion of the narrower cross belt 143 are preferably in the range satisfying 0.03 ≤ S / Wb ≤ 0.12. This has the advantage of ensuring an appropriate positional relationship S / Wb3 between the edge portions of the cross belts 142, 143 and the edge portions of the circumferential reinforcing layer 145. In particular, the relationship satisfying 0.03 ≤ S / Wb3 ensures an appropriate distance between the end portions of the circumferential reinforcing layer 145 and the end portions of the cross belt 143 to suppress the separation of the peripheral rubbers at the end portions of the belt plies 145 and 143. In addition, the relationship satisfying S / Wb3 ≤ 0.12 ensures the width Ws of the circumferential reinforcing layer 145 relative to the width Wb3 of the cross belt 143 to ensure an appropriate hoop stress effect of the circumferential reinforcing layer 145. (Area of ​​application)

[0106] The pneumatic tire 1 is preferably applied to a heavy-duty tire having an aspect ratio of not less than 40% and not more than 70% when mounted on a regular rim and inflated with regular internal pressure and a regular load is applied. A heavy-duty tire experiences greater loads in use than a passenger tire. As a result, the difference in diameters between the region where the circumferential reinforcing layer 145 is disposed in the tread and the region on the outer side of the circumferential reinforcing layer 145 in the tire width direction tends to increase. Furthermore, a ground contact shape having an hourglass shape is likely to occur in the tire having the above-mentioned low aspect ratio. As a result, by applying such a heavy-duty tire, remarkable uneven wear resistance and wet performance of the above-mentioned tire are achieved. Examples

[0107] Fig. 8 is a table showing performance test results of pneumatic tires according to embodiments of the present invention.

[0108] Wet performance evaluations of several different pneumatic tires were conducted for the performance test (see Fig. 8). Pneumatic tires of size 285 / 60R22.5 were mounted on rims measuring 22.5 x 8.25, and the pneumatic tires were inflated to an air pressure of 900 kPa during the evaluations. The pneumatic tires were mounted on a 2D vehicle (2 front wheels - rear wheel drive) as the test vehicle, and a load of 28.44 kN was applied to the pneumatic tires.

[0109] Wet performance evaluations involved driving the vehicle with the pneumatic tires on a wet road surface and measuring the braking distance from an initial speed of 60 km / h. Based on the measurement results, index evaluations were conducted using the prior art example as the standard (100). A higher numerical value is better in the evaluations. In particular, a rating of 115 or higher indicates an effect that is significantly better than that of the prior art example.

[0110] The pneumatic tires 1 of the embodiments 1 to 21 have a configuration shown in Fig. 1 and Fig. 3. All raised portions 3 are ribs that run continuously in the tire circumferential direction. The main dimensions are set as TW = 245 mm, SH = 916 mm, Gcc = 30 mm, and Wcc = 30 mm.

[0111] A part of the numerical ranges in the pneumatic tire of the prior art example is different from that in Fig. Structure shown in 1 to 3.

[0112] As shown in the test results, the pneumatic tires 1 of Embodiments 1 to 21 exhibit improved wet tire performance. In particular, comparing Embodiments 1 to 13, it can be seen that a remarkably superior wet performance effect is achieved because the relationships of 1.20 ≤ Gsh / Gcc, 0.25 ≤ De / Dt, and 0.1 ≤ Wsh / TW ≤ 0.2 are satisfied. REFERENCE SYMBOL 1 pneumatic tire 2 main circumferential grooves 3 Sublime Section 11 Tire bead core 12 tire bead inflators 121 Lower filler 122 Upper filler 13 carcass layers 14 Belt layer 141 Belt with large angle 142, 143 Cross belt 144 Belt cover 145 circumferential reinforcement layer 15 Tread rubber 16 sidewall rubber 18 inner liners 19 belt edge pads 191 Tension relief rubber 192 Edge section relief rubber

Claims

[1] Pneumatic tire (1), comprising: a carcass layer (13); a belt layer (14) arranged on an outer side of the carcass layer (13) in a tire radial direction; a tread rubber (15) arranged on an outer side of the belt layer (14) in the tire radial direction; at least three main circumferential grooves (2) extending in a tire circumferential direction; and a plurality of raised portions (3) defined by the main circumferential grooves (2); where the belt layer (14) is formed by laminating a pair of cross belts (142, 143) having a belt angle of not less than 10° and not more than 45° as absolute values and having belt angles of opposite signs, and a circumferential reinforcing layer (145) having a belt angle within a range of ± 5° with respect to the tire circumferential direction; a distance Gcc on a tire equatorial plane from a tread pattern to a tire inner peripheral surface and a distance Gsh from a tread edge to the tire inner peripheral surface have a relationship satisfying 1.10 ≤ Gsh / Gcc; and a degree of shoulder depression Dt of the tread pattern at a contact end of the tire and an outer diameter SH of the tread pattern along the tire equatorial plane have a relationship satisfying Dt / SH ≤ 0.

015. [2] The pneumatic tire (1) according to claim 1, wherein a shoulder drop amount De of the tread pattern at an end portion of the circumferential reinforcing layer (145) and the shoulder drop amount Dt of the tread pattern at the tire contact end have a relationship satisfying 0.25 ≤ De / Dt. [3] Pneumatic tire (1) according to one of claims 1 or 2, wherein, when the left and right circumferential main grooves (2) which are outermost in a tire width direction are referred to as outermost circumferential main grooves (2) and the left and right raised portions (3) on the outer side in the tire width direction which are defined by the outermost circumferential main grooves (2) are referred to as shoulder raised portions (3), a contact width Wsh of the shoulder land portion (3) and a tread width Tw have a relationship satisfying 0.1 ≤ Wsh / TW ≤ 0.

2. [4] Pneumatic tire (1) according to one of claims 1 to 3, wherein, when the left and right circumferential main grooves (2) which are outermost in the tire width direction are referred to as outermost circumferential main grooves (2) and the left and right raised portions (3) on the outer side in the tire width direction which are defined by the outermost circumferential main grooves (2) are referred to as shoulder raised portions (3), a contact width Wcc of the raised portion (3) closest to the tire equator line and the contact width Wsh of the shoulder raised portion (3) have a relationship satisfying 0.80 ≤ Wsh / Wcc ≤ 1.

20. [5] A pneumatic tire (1) according to any one of claims 1 to 4, wherein a groove area ratio A in a tire contact patch is in a range satisfying 0.20 ≤ A. [6] A pneumatic tire (1) according to any one of claims 1 to 5, wherein a loss angle tangent tanδ of the tread rubber (15) is in a range satisfying 0.10 ≤ tanδ. [7] A pneumatic tire (1) according to any one of claims 1 to 6, wherein belt cords of the circumferential reinforcing layer (145) are steel wire, and the belt cords have a number of ends not less than 17 ends / 50 mm and not more than 30 ends / 50 mm. [8] A pneumatic tire (1) according to any one of claims 1 to 7, wherein an elongation of the belt cords constituting the circumferential reinforcing layer (145) when the belt cords are constituents is not less than 1.0% and not more than 2.5% when a tensile load is 100 N to 300 N. [9] A pneumatic tire (1) according to any one of claims 1 to 8, wherein an elongation of the belt cords constituting the circumferential reinforcing layer (145) when the belt cords are from a tire is not less than 0.5% and not more than 2% when a tensile load is 500 N to 1000 N. [10] The pneumatic tire (1) according to any one of claims 1 to 9, wherein the circumferential reinforcing layer (145) is disposed on an inner side in the tire width direction of left and right edge portions of a narrower cross belt (143) of the pair of cross belts (142, 143), and a stress relief rubber (191) is disposed between the pair of cross belts (142, 143) and is disposed on the outer side in the tire width direction of the circumferential reinforcing layer (145) so as to be adjacent to the circumferential reinforcing layer (145); and an end portion relief rubber (192) is arranged between the pair of cross belts (142, 143) and is arranged on the outer side of the stress relief rubber (191) in the tire width direction and at a position corresponding to an edge portion of the pair of cross belts (142, 143) so as to be adjacent to the stress relief rubber (191). [11] A pneumatic tire (1) according to claim 10, wherein a modulus Ein at 100% elongation of the stress relief rubber (191) and a modulus Eco at 100% elongation of the coating rubber of the pair of cross belts (142, 143) have a relationship that Ein <Eco erfüllt. [12] A pneumatic tire (1) according to claim 10 or 11, wherein the modulus Ein at 100% elongation of the stress relief rubber (191) and the modulus Eco at 100% elongation of the coating rubber of the pair of cross belts (142, 143) have a relationship satisfying 0.6 ≤ Ein / Eco ≤ 0.

9. [13] A pneumatic tire (1) according to any one of claims 10 to 12, wherein the modulus Ein at 100% elongation of the stress relief rubber (191) is in a range satisfying 4.0 MPa ≤ Ein ≤ 5.5 MPa. [14] A pneumatic tire (1) according to any one of claims 1 to 13, wherein the belt layer (14) comprises the large angle belt (141) having a belt angle of not less than 45° and not more than 70° as an absolute value. [15] A pneumatic tire (1) according to claim 14, wherein a width Wb1 of the large angle belt (141) and a width Wb3 of the narrower cross belt (143) of the pair of cross belts (142, 143) have a relationship satisfying 0.85 ≤ Wb1 / Wb3 ≤ 1.

05. [16] The pneumatic tire (1) according to any one of claims 1 to 15, wherein the circumferential reinforcing layer (145) is disposed on the inner side in the tire width direction of the left and right edge portions of the narrower cross belt (143) of the pair of cross belts (142, 143), and the width Wb3 of the narrower cross belt (143) and a distance S from an edge portion of the circumferential reinforcing layer (145) to the edge portion of the narrower cross belt (143) have a relationship satisfying 0.03 ≤ S / Wb3. [17] A pneumatic tire (1) according to any one of claims 1 to 16, which is applied to a heavy-duty tire having an aspect ratio of 70% or less.

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