pneumatic tires

Abstract

Pneumatic tire (1) comprising: a carcass layer (13); a belt layer (14) arranged on an outer side of the carcass layer (13) in the 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 land portions (3) formed by being divided by the circumferential main grooves (2), wherein, of the main circumferential grooves (2), left and right circumferential main grooves (2) on outermost sides in the tire width direction are referred to as outermost circumferential main grooves (2), and the land portions (3) on an outer side in the tire width direction of the outermost circumferential main grooves (2) on the left and right sides are referred to as shoulder land portions (3), the land portions (3) on an inner side in the tire width direction of the outermost circumferential main grooves (2) on the left and right sides have a first profile (PL1) projecting outward in the tire radial direction, and the shoulder land portions (3) within a ground contact surface have a second profile (PL2) projecting inward in the tire radial direction, a distance d in the tire radial direction between a line extending from the first profile (PL1) and the second profile (PL2) within the ground contact surface of the shoulder land portions (3) becomes larger toward an outer side in the tire width direction, and a distance Gcc from a tread pattern to a tire inner peripheral surface in a tire equatorial plane and a distance Gsh from a tread end to the tire inner peripheral surface have a relationship 1.20 ≤ Gsh / Gcc, wherein the belt layer (14) has a pair of cross belts (142, 143) with belt angles of not less than 10° and not more than 45° as an absolute value, the belt angles having opposite signs, when viewed in cross section from a tire meridian direction, a wear end interface WE is drawn along the main circumferential grooves (2) and a cross belt (143) on an outer side in the tire radial direction of the two cross belts (142, 143) is referred to as an outer side cross belt (143), and a distance Dcc from the outer side cross belt (143) to the wear end interface WE in the tire equatorial plane and a distance De from the outer side cross belt (143) to the wear end interface WE on a groove center line of the outermost circumferential main grooves (2) have a relationship of 0.95 ≤ De / Dcc ≤ 1.30.

Description

Technical field

[0001] The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire having improved resistance to uneven wear. General state of the art

[0002] When a tire used primarily for continuous high-speed driving, such as on main roads, is subjected to free-rolling conditions, uneven wear occurs at land portions in the shoulder regions of the tread portion. A technique for a conventional pneumatic tire to address this problem is described in JP 4553064 B2.

[0003] US 5 616 195 A discloses a pneumatic radial truck tire comprising a tread, one or more radial plies extending between and around two beads, and a belt reinforcing structure disposed radially between the tread and the plies. The tread has a plurality of circumferentially extending continuous grooves defining and defining a plurality of tread ribs. A radius R3 has a center outside the tire and defines an outer surface of a tread shoulder region. A radius R2 has a center inside the tire. The radius R3 is in the range of 0.7 to 2.5 times a radius R1, and the radius R2 is in the range of 1.3 to 2 times the radius R1.

[0004] US 2006 / 0 169 381 A1 discloses a tire having a radial carcass reinforcement anchored in two beads. The carcass reinforcement is wrapped by a crown reinforcement shaped from the inside to the outside. A thickness of the crown block at a shoulder end is defined as a length of an orthogonal projection of the shoulder end onto the radially innermost layer of the rubber compound of the tire, and a thickness of the crown block in the circumferential meridian plane XX' is defined as a distance in the radial direction between (i) a tangent to the crown of the tread in the circumferential meridian plane XX' and (ii) a tangent to the radially innermost layer of the rubber compound 14 of the tire. A ratio between the thickness of the crown block at a shoulder end to the thickness of the shoulder block in the circumferential meridian plane XX' is less than 1.20.

[0005] DE 11 2012 007 267 T5 is a post-published document and discloses a pneumatic tire having a carcass layer, a belt layer disposed on an outer side of the carcass layer in a tire radial direction, and a tread rubber disposed on an outer side of the belt layer in the tire radial direction. A plurality of circumferential main grooves extending in a tire circumferential direction are provided in the tread rubber, the plurality of circumferential main grooves defining a plurality of land portions. Land portions on an inner side of the outermost circumferential main grooves on both sides in the tire width direction have a first profile PL1 protruding outward in the tire radial direction, and shoulder land portions on the outer side of the outermost circumferential main grooves on both sides in the tire width direction have a second profile PL2 protruding inward in the tire radial direction.A distance d in the tire radial direction between a line extending from the first profile PL1 and the second profile PL2 within the ground contact surface of the shoulder land portions increases toward an outer side in the tire width direction. A distance Gcc from a tread pattern to a tire inner peripheral surface in a tire equatorial plane and a distance Gsh from a tread end to the tire inner peripheral surface have a relationship such that 1.20 ≤ Gsh / Gcc. A distance Dcc from a circumferential reinforcing layer to a wear surface in the tire equatorial plane and a distance De from an end portion of the circumferential reinforcing layer to the wear surface have a ratio of De / Dcc ≤ 0.94 to each other. Summary of the inventionProblem to be solved by the invention

[0006] An object of the present invention is to provide a pneumatic tire with improved resistance to uneven wear. Means of solving the task

[0007] The object is achieved by a pneumatic tire according to claim 1. Advantageous developments of the invention are described in the dependent claims 2 to 16. Inventive effect

[0008] The pneumatic tire according to the invention has, within a ground contact surface, the shoulder land portions in which the second profile protrudes inward in the tire radial direction.

[0009] Likewise, the distance d of the first profile of the shoulder land sections within the ground contact area becomes larger towards an outer side in the tire width direction.

[0010] Thus, the ground contact pressure on a ground contact edge side of the shoulder land sections becomes greater when the tire is in ground contact.

[0011] Thus, an amount of slippage of the land portions in the central region and an amount of slippage of the shoulder land portions when the tire is in ground contact are averaged.

[0012] A beneficial consequence of this is that uneven wear of the shoulder land sections is reduced and the tire's resistance to uneven wear is improved. Short description of the drawings Fig. 1 is a cross-sectional view in the tire meridian direction illustrating a pneumatic tire according to an embodiment of the 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 the belt layer of the Fig. 1 depicted pneumatic tire. Fig. 4 is an enlarged view showing a shoulder web portion of the Fig. 1 depicted pneumatic tire. Fig. 5A and Fig. 5B are explanatory views 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 an explanatory view showing a modified example of the Fig. 1 depicted pneumatic tire. Fig. 9 is a table showing performance test results of the pneumatic tire according to the embodiment of the invention. Fig. 10 is a table showing performance test results of the pneumatic tire according to the embodiment of the invention. Best Mode for Carrying Out the Invention[Pneumatic Tires]

[0013] Fig. 1 is a cross-sectional view in the tire meridian direction illustrating a pneumatic tire according to the embodiment of the invention. In Fig. 1 shows, as an example of the pneumatic tire 1, a heavy-duty radial tire mounted on a truck, a bus or the like for long-distance transportation. Herein, the tire equatorial plane is designated by the reference symbol CL. In addition, Fig. 1 a tread end P and a tire ground contact edge T congruent.

[0014] The pneumatic tire 1 includes two bead cores 11, 11, two bead fillers 12, 12, a carcass layer 13, a belt layer 14, a tread rubber 15 and a pair of sidewall rubbers 16, 16 (see Fig. 1).

[0015] Each of the bead cores 11, 11 has an annular structure and forms a respective core of a bead portion on the left and right sides. Each of the bead fillers 12, 12 is formed of a lower filler 121 and an upper filler 122. The bead fillers 12, 12 are arranged on the outer circumference in the tire radial direction with respect to the two bead cores 11, 11 and serve to reinforce the respective bead portions.

[0016] The carcass layer 13 extends annularly between the left and right side tire bead cores 11, 11 and forms a support structure for the tire.

[0017] In addition, both edge portions of the carcass layer 13 are folded and fixed from the tire widthwise inner side to a tire widthwise outer side so as to wrap the corresponding tire bead core 11 and the corresponding tire bead filler 12.

[0018] In addition, the carcass layer 13 is composed of a plurality of carcass cords each formed of steel or an organic fiber material (e.g., nylon, polyester, rayon, or the like) covered by coating rubber and subjected to a rolling process.

[0019] The carcass layer 13 has a carcass angle (inclination angle of a fiber direction of the carcass cords with respect to the tire circumferential direction) as an absolute value of not less than 85° and not more than 95°.

[0020] The belt layer 14 is formed by laminating a plurality of belt plies 141 to 144 and is arranged by wrapping it around the outer periphery of the carcass layer 13. The specific design of the belt layer 14 is described below.

[0021] The tread rubber 15 is arranged on the radially outer periphery of the carcass layer 13 and the belt layer 14 and forms a tread portion. Each of the sidewall rubbers 16, 16 is arranged on the outer side of the carcass layer 13 in the tire width direction. The side wall rubbers 16, 16 form side wall sections on the left and right sides.

[0022] In view of the design in Fig. 1, the pneumatic tire 1 is provided with seven circumferential main grooves 2 extending in the tire circumferential direction and eight land portions 3 divided by the circumferential main grooves 2. Furthermore, the land portions 3 are each formed as a rib continuous in the tire circumferential direction or, alternatively, as a block segmented by lug grooves (not shown in the drawings) in the tire circumferential direction.

[0023] Herein, any circumferential groove having a groove width of not less than 5.0 mm is referred to as a main circumferential groove. The groove width of the main circumferential grooves is measured excluding any notched or chamfered portions formed at the groove opening portion.

[0024] In addition, in this pneumatic tire 1, circumferential main grooves 2, 2 on the left and right sides, which are located outermost in the tire width direction, are called outermost circumferential main grooves. Likewise, the land portions 3, 3 on the left and right sides on the outer side in the tire width direction, which are divided by the outermost circumferential main grooves 2, 2, are called shoulder land portions. [Belt layer]

[0025] Fig. 2 and Fig. 3 are explanatory views showing the belt layer of the Fig. 1 pneumatic tire shown. Of these drawings, Fig. 2 a region on one side of the tread portion bounded by the tire equatorial plane CL. Fig. 3 represents a laminated structure of the belt layer 14. Here, Fig. 3 schematically shows belt cords in each of the belt layers 141 to 144 as thin lines drawn on each of the belt layers 141 to 144.

[0026] The belt layer 14 is formed by laminating a large-angle belt 141, a pair of cross belts 142, 143, and a belt cover 144. The belt layer 14 is arranged by winding and fastening on the outer periphery of the carcass layer 13 (see Fig. 2).

[0027] The large angle belt 141 is composed of a plurality of belt cords formed of steel or organic fiber material, covered with coating rubber, and subjected to a rolling process, with a belt angle (an inclination angle of the fiber direction of the belt cords with respect to the tire circumferential direction) having an absolute value of not less than 45° and not more than 70°. In addition, the large angle belt 141 is laminated and is laminated on the outer side of the carcass layer 13 in the tire radial direction.

[0028] The two cross belts 142, 143 consist of a plurality of belt cords made of steel or organic fiber material, which are covered with a coating rubber and subjected to a rolling process, with a belt angle, as an absolute value, of not less than 10° and not more than 45°. In addition, the two cross belts 142, 143 each have belt angles with opposite signs and are laminated so that they cross each other in the fiber direction of the belt cords (cross-layer structure). Here, the cross belt 142 positioned on the inner side in the tire radial direction is referred to as an inner side cross belt, and the cross belt 143 positioned on the outer side in the tire radial direction is referred to as an outer side cross belt. Three or more cross belts can also be laminated and arranged (not shown in the drawings). Furthermore, in this embodiment, the two cross belts 142, 143 are laminated and arranged on the outer side of the large angle belt 141 in the tire radial direction.

[0029] In addition, the belt cover 144 is composed of a plurality of belt cords made of steel or organic fiber material covered with a coating rubber and subjected to a rolling process, with a belt angle, as an absolute value, of not less than 10° and not more than 45°. Also, the belt cover 144 is laminated and arranged on the outer side of the two cross belts 142, 143 in the tire radial direction. Here, in this embodiment, the belt cover 144 has the same belt angle as the outer cross belt 143 and is arranged as the outermost layer of the belt layer 14.

[0030] In this case, the belt layer 14 in the pneumatic tire 1 may also have an edge cover (not shown in the drawings).

[0031] Typically, such an edge cover consists of a plurality of belt cords made of steel or organic fiber material, which are covered with a coating rubber and subjected to a rolling process, with a belt angle, as an absolute value, of not less than 0° and not more than 5°.

[0032] In addition, the edge cover is arranged on the tire radially outer side of the edge portions on the left and right sides of the outer side cross belt 143 (alternatively, the inner side cross belt 142).

[0033] The difference in radial growth between a center region and a shoulder region of the tread portion is reduced to improve resistance to uneven wear of the tire by the tire effect exhibited by the edge covers. [Improved resistance to uneven wear]

[0034] When a tire used primarily for continuous high-speed driving, such as on main runs, is used under free-rolling conditions, a problem arises that uneven wear usually occurs at the land portions in the shoulder regions of the tread portion.

[0035] Thus, this pneumatic tire 1 uses the following design to counteract the uneven wear of the shoulder land portions (see Fig. 1 to 3).

[0036] In Fig. 2, a wear end interface WE of the circumferential main grooves 2 is drawn in a cross-sectional view along the tire meridian direction. The wear end boundary surface WE is a surface determined from a wear indicator provided in the tire and is a curve drawn parallel to the tire tread and passing through a wear limit indicator (wear indicator) of the outermost main circumferential groove 2. The end-of-wear interface WE is measured using a single tire when the tire is not inflated. In a typical pneumatic tire, the end-of-wear interface WE is a curve that is essentially parallel to the tread pattern.

[0037] Here, according to the invention, a distance De from the outer side cross belt 143 to the wear end interface WE on a center groove line of the outermost circumferential main groove 2 and a distance Dcc from the outermost cross belt 143 to the wear end interface WE on the tire equatorial line CL have a relationship of 0.95 ≤ De / Dcc ≤ 1.30.

[0038] The distance Dcc and the distance De are each measured using a single tire when the tire is deflated. Furthermore, the measurement point on the outer side cross belt 143 side is defined by a curve connecting, in cross section, the respective centers of the belt cords constituting the outer side cross belt 143 as viewed in the tire meridian direction.

[0039] Here, the term "specified rim" refers to 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 Standards (ETRTO). Furthermore, the term "specified internal pressure" refers to a "maximum air pressure" as required 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. Likewise, the term “specified load” refers to a “maximum load capacity” as defined by JATMA, a maximum value in “tire load limits at various cold inflation pressures” as defined by TRA and “load capacity” as defined by ETRTO. However, in the case of passenger car tires, at JATMA, the specified internal pressure is an air pressure of 180 kPa, and a specified load is 88% of the maximum load capacity.

[0040] In addition, according to the invention, the distance Gcc from the tread pattern to the tire inner peripheral surface at the tire equatorial plane CL and the distance Gsh from the tread end P to the tire inner peripheral surface have a relationship of 1.20 ≤ Gsh / Gcc.

[0041] There is no specific restriction on the upper limit of the Gsh / Gcc ratio.

[0042] However, the upper limit of the ratio Gsh / Gcc is preferably defined such that the radius at the tread end P of the tread pattern is equal to or smaller than the radius at the tire equatorial plane CL when the tire is mounted on a given rim, inflated to the given internal pressure and in an unloaded state.

[0043] That is, the upper limit of the ratio Gsh / Gcc is preferably defined so that the tread pattern has an arc shape or a linear shape with a center on the inner side in the tire radial direction and does not have an inverted R shape (no arc shape with a center on the outer side in the tire radial direction).

[0044] For example, in a design having an angular shaped shoulder portion, as in Fig. 2, the upper limit of the relationship Gsh / Gcc is approximately 1.4 to 1.5.

[0045] In contrast, in a design described below, which has a round-shaped shoulder section, as in Fig. 6, the upper limit of the relationship Gsh / Gcc is approximately 1.3 to 1.4.

[0046] 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. Thus, in the design of Fig. 1 and Fig. 2, in which one of the main circumferential grooves 2 lies in the tire equatorial plane CL, the distance Gcc is measured excluding this main circumferential groove 2. The distance Gsh is measured as the length of a vertical line drawn from the tread end P to the tire inner circumferential surface when viewed in cross section from the tire meridian direction.

[0047] When designing Fig. 2 of the pneumatic tire 1 has an inner liner 18 on the inner circumferential surface of the carcass layer 13. The inner liner 18 is arranged over the entire inner circumferential surface of the tire. In such a configuration, the distance Gcc and the distance Gsh are measured using the surface of the inner liner 18 as a reference (tire inner peripheral surface).

[0048] The tread end P is (1) a point on the edge portion in a design having the shoulder sections in a square shape. For example, in the design in Fig. 2 the tread end P and the tire ground contact edge T coincide with each other because the shoulder portion has a square shape.

[0049] On the other hand, (2) in a design where the shoulder portion has the round shape, as in the modified example of Fig. 6, which will be described later, the profile of the tread portion and the profile of the sidewall portion have an intersection point P', 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 when viewed in cross section from the tire meridian direction.

[0050] Here, the ground contact edge T of the tire is a position of a maximum width of a contact surface between the tire and a flat plate in the tire axial direction when the tire is mounted on a given rim, inflated to a given internal pressure, perpendicular to the flat plate in a static state, and loaded with a load equal to a given load.

[0051] Fig. 4 is an enlarged view showing the shoulder web portion of the Fig. 1 depicted pneumatic tire. Fig. 4 also shows the relationship between a line extending from a first profile PL1 of the web portion 3 in a central region and a second profile PL2 of the shoulder web portion 3.

[0052] As in Fig. 4, in this pneumatic tire 1, a middle land portion 3 and a second land portion 3 disposed inward of the outermost circumferential main grooves 2, 2 have the first profile PL1 and thus protrude outward in the tire radial direction when viewed from the tire meridian direction in cross section. In addition, the shoulder land portions 3, which are located further outward in the tire width direction than the outermost circumferential main grooves 2, have the second profile PL2 and thus protrude inward within the ground contact surface in the tire radial direction.

[0053] Both the first profile PL1 and the second profile PL2 are preferably gentle curves formed from a single arc or from a plurality of arcs combined with one another. However, no such limitation is intended. The first profile PL1 and the second profile PL2 can also have a design that partly includes straight lines.

[0054] In addition, a distance d in the tire radial direction from a line extending from the first profile PL1 to the second profile PL2 within the ground contact surface of the shoulder land portion 3 becomes larger toward the outer side in the tire width direction.

[0055] For example, in the design of Fig. 4 the first profile PL1 of the central land portion 3 and the second land portion 3 is formed by a single arc projecting outward in the tire radial direction, having a maximum diameter D1 in the tire equatorial plane CL (see Fig. 2) and whose diameter in the tire radial direction becomes smaller towards the outer side in the tire width direction. In contrast, the second profile PL2 of the shoulder land portion 3 is formed by a single arc protruding inward in the tire radial direction, which has a minimum diameter at an end portion of the shoulder land portion 3 on the inner side in the tire width direction and whose diameter becomes larger toward the outer side in the tire width direction. As a result, the shoulder land portion 3 has a ground contact surface shape that gradually increases in the tire radial direction toward the tire width direction outer side. Therefore, the second profile PL2 of the shoulder land portion 3 is increasingly separated from the line extending from the first profile PL1 of the middle land portion 3 and the second land portion 3 from the outer side in the tire radial direction to the outer side in the tire width direction. In addition, the distance d between the profiles PL1, PL2 increases monotonically from the edge portion on the inner side of the shoulder land portion 3 in the tire width direction to the outer side in the tire width direction.

[0056] According to this configuration, the shoulder land portion 3 within the ground contact surface has the second profile PL2 projecting inward in the tire radial direction. Also, the distance d between the profiles PL1, PL2 within the ground contact surface of the shoulder land portion 3 increases toward the outer side in the tire width direction. Thus, the ground contact pressure on the side of the shoulder land portion where the tire ground contact edge T is located becomes larger when the tire is in ground contact. Thus, the amount of slippage of the land portions 3 in the central region and the amount of slippage of the shoulder land portions 3 when the tire is in ground contact are averaged. As a result, uneven wear in the shoulder web section 3 is effectively counteracted.

[0057] This involves measuring the tread shape and tread diameter when the tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded condition. Furthermore, the tread diameter is measured as a diameter centered on the tire's axis of rotation.

[0058] Furthermore, in the configuration described above, the diameter D1 of the first profile PL1 in the tire equatorial plane CL and the diameter D2 of the second profile PL2 at the tire ground contact edge T preferably have a relationship of -0.015 ≤ (D1 ≤ D2) / D1 ≤ 0.015. That is, the diameter of the profile for the entire tire is preferably substantially the same at the tire equatorial plane CL and at the tire ground contact edge T.

[0059] Also, the diameter D2 of the second profile PL2 at the tire ground contact edge T and the diameter D3 of the second profile PL2 at the edge portions on the tire widthwise inner side of the shoulder land portions 3 preferably have a relationship D3 < D2. In addition, the diameters D2, D3 preferably have a relationship 0.0 ≤ D3 - D2 ≤ 15.0, where the values are given in millimeters. As in Fig. 4, the shoulder land portions 3 preferably have a ground contact surface shape which gradually increases in the tire radial direction toward the outer side in the tire width direction.

[0060] However, no such limitation is intended as long as the diameter D2 of the second profile PL2 at the tire ground contact edge T and the diameter D3 of the second profile PL2 at the edge portion on the tire widthwise inner side of the shoulder land portion 3 have a relationship D2 ≤ D3. Thus, the shoulder land portion 3 may also have a flat ground contact surface shape and may have a ground contact surface shape that slopes toward the outer side in the tire width direction.

[0061] Fig. 5A and Fig. 5B are explanatory views showing the effect of the Fig. 1 pneumatic tire shown. Fig. 5A and Fig. 5B each show a ground contact state of the tire having different values for the De / Dcc ratio and the Gsh / Gcc ratio.

[0062] In the tire of the comparison example of Fig. 5A is the ratio De / Dcc with respect to the design in Fig. 1 to Fig. 3 is set equal (De / Dcc = 1.00), and the relationship Gsh / Gcc is set smaller (Gsh / Gcc = 1.06). When the tire is not in contact with the ground, the tread pattern according to such a design has a sloping shape in which an outer diameter decreases from the tire equatorial plane CL toward the profile end P (not shown in the drawings). As a result, the shoulder region of the tread portion, as shown in Fig. 5A, is greatly deformed on the road surface side (the outer side in the tire radial direction) when the tire contacts the ground. Here, the distances Dcc, De from the outer side cross belt 143 to the wear end interface WE are uniform (De / Dcc = 1.00). Thus, the end portion of the outer side cross belt 143 is strongly bent toward the road surface side (the outer side in the tire radial direction) due to the deformation of the shoulder region in the tread portion. As a result, the outer side cross belt 143 is subjected to a strong load when the tire is in contact with the ground.

[0063] In contrast, in the tire of the application example of Fig. 5B with regard to the design in Fig. 1 to Fig. 3 the ratio De / Dcc is set equal (De / Dcc = 1.00), and the ratio Gsh / Gcc is set larger (Gsh / Gcc = 1.20). According to such a design, the difference in diameter between the outer diameter of the tread pattern at the tire equatorial plane CL and the outer diameter at the tread end P is small when the tire is not in contact with the ground, and the tread pattern has an overall flat shape (substantially parallel to the tire rotation axis) (see Fig. 1 and Fig. 2). As a result, the shoulder region in the tread section, as shown in Fig. 5B, the tire undergoes little deformation when in contact with the ground. Furthermore, the inflated state of the tire typically causes a drop in the tire profile due to internal pressure, producing a difference in diameter between the shoulder region in the tread portion and the shoulder regions. Thus, a higher setting of the Gsh / Gcc ratio (Gsh / Gcc = 1.20) results in the shoulder region in the tread portion having an inverted R-shape (becoming higher outward in the tire radial direction) before inflation. Thus, the drop of the tread pattern in the inflated state is limited, and the outer side cross belt 143 has a flat shape overall. As a result, the stress on the outer side cross belt 143 during tire-ground contact is reduced.

[0064] As described above, compared to the design of Fig. 5A the design of Fig. 5B, a small amount of deformation occurs in the shoulder region in the tread portion when the tire is in ground contact, and the outer side cross belt 143 is under a small amount of stress. As a result, the amount of slippage of the land portion 3 in the central region and the amount of slippage of the shoulder land portion 3 are averaged when the tire is in contact with the ground, thereby counteracting uneven wear of the shoulder land portion 3.

[0065] Furthermore, the shoulder web section 3 has in the design of Fig. 5B due to the presence of the design of Fig. 4, the second profile PL2 protrudes inward in the tire radial direction within the ground contact surface. Also, the distance d between the profiles PL1, PL2 within the ground contact surface of the shoulder land portion 3 increases toward the outer side in the tire width direction. According to this configuration, the tire contact pressure of the shoulder land portion 3 on the tire ground contact edge T side becomes larger when the tire contacts the ground. Likewise, the amount of slippage of the land portions 3 in the central region and the amount of slippage of the shoulder land portions 3 when the tire is in ground contact are averaged. As a result, uneven wear in the shoulder web section 3 is counteracted. [Rounded shoulder sections]

[0066] Fig. 6 is an explanatory view showing a modified example of the Fig. 1 depicted pneumatic tire.

[0067] Fig. 6 shows a design in which the shoulder sections have a rounded shape.

[0068] In the design of Fig. 1, the shoulder portion has a square shape in which the tire ground contact edge T and the tread edge P coincide, as in Fig. 2 shown.

[0069] However, no such limitation is intended. As in Fig. 6, the shoulder section may also have a rounded shape. In such a situation, the profile of the tread portion and the profile of the sidewall portion have an intersection point P' as described above, 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 when viewed in cross section from the tire meridian direction. Therefore, the tire ground contact edge T and the tread end P are usually located at different positions relative to each other. [Additional information]

[0070] As in Fig. 1, the tread width TW and a tire overall width SW preferably have a relationship of 0.79 ≤ TW / SW ≤ 0.89.

[0071] Tire overall width SW means a linear distance (including all sections such as letters and patterns on the tire sidewall) between the sidewalls when the tire is mounted on a specified rim and inflated to a specified internal pressure and is in an unloaded state.

[0072] In addition, Fig. 1 and Fig. 2 the ground contact width Wsh of each shoulder land portion 3 and the tread width TW preferably have a relationship 0.1 ≤ Wsh / TW ≤ 0.2.

[0073] Since this relationship is satisfied, a suitable ground contact width Wsh is created for the shoulder web section 3.

[0074] The ground contact width is measured as the maximum linear distance of a contact surface between the tire and a flat plate in a design where the tire is mounted on a given rim and inflated to a given internal pressure, placed perpendicularly on the flat plate while in a static state, and applied with a load corresponding to a given load in the axial direction.

[0075] Furthermore, Fig. 1, a width Wb2 of a wider cross belt 142 and the cross-sectional width Wca of the carcass layer 13 preferably have a relationship of 0.70 ≤ Wb2 / Wca ≤ 0.93, and more specifically have a relationship in a range of 0.78 ≤ Wb2 / Wca ≤ 0.83.

[0076] In addition, the tread width TW and the cross-sectional width Wca of the carcass layer 13 preferably have a relationship of 0.82 ≤ TW / Wca ≤ 0.92.

[0077] The tread width TW is a distance in the direction of the tire rotation axis between the left and right tread ends, P, P, which is measured when the tire is mounted on a given rim, inflated to a given internal pressure and in an unloaded state.

[0078] Sectional width Wca of the carcass layer 13 denotes a linear distance between the left and right positions of the maximum width of the carcass layer 13 when the tire is mounted on a predetermined rim, inflated to a predetermined internal pressure, and in a no-load state.

[0079] In addition, in the pneumatic tire 1, a width Wb1 of the large angle belt 141 and a width Wb3 of the wider cross belt 143 of the two cross belts 142, 143 preferably have a relationship of 0.85 ≤ Wb1 / Wb3 ≤ 1.05 (see Fig. 3). The result is a suitable ratio Wb1 / Wb3.

[0080] The width Wb1 of the large angle belt 141 and the width Wb3 of the cross belt 143 are measured as the respective distances in the tire width direction when the tire is mounted on a given rim, inflated to a given internal pressure and in an unloaded state.

[0081] In this case, the design of Fig. 1, as in Fig. 3, the belt layer 14 has a design which has a lateral symmetry around the center of the tire equatorial plane CL, as shown in Fig. 3. Likewise, the width Wb1 of the large-angle belt 141 and the width Wb3 of the wider cross belt 143 have a relationship of Wb1 < Wb3. As a result, in a side region of the tire equatorial plane CL, the edge portion of the large-angle belt 141 is located further inward in the tire width direction than the edge portion of the wider cross belt. However, no such limitation is intended. The width Wb1 of the large angle belt 141 and the width Wb3 of the wider cross belt 143 may also have a relationship Wb1 ≥ Wb3 (not shown in the drawings).

[0082] In addition, Fig. 1, a diameter Ya at the position of a maximum height of the carcass layer 13, a diameter Yc at the position of a maximum width of the carcass layer 13, and a diameter Yd of the carcass layer 13 along a groove center line of the outermost circumferential main groove 2 preferably have the following relationships: 0.80 ≤ Yc / Ya ≤ 0.90 and 0.95 ≤ Yd / Ya ≤ 1.02. As a result, a suitable shape of the carcass layer 13 is obtained.

[0083] The diameter Ya at the point where the carcass layer 13 has the maximum height is measured as a distance from the tire rotation axis to the intersection point of the tire equatorial plane CL and the carcass layer 13 when the tire is mounted on a predetermined rim, inflated to the predetermined internal pressure, and in an unloaded state.

[0084] The diameter Yc at the position where the carcass layer 13 has the maximum width is measured as a distance from the tire rotation axis to the position of the maximum width of the carcass layer 13 when the tire is mounted on the predetermined rim, inflated to the predetermined internal pressure, and in an unloaded state.

[0085] A diameter Yd of the carcass layer 13 along the groove centerline of the outermost circumferential main groove is measured when a point Q3 (not shown in the drawings) at the intersection of the groove centerline of the outermost circumferential main groove and the carcass layer 13 is measured as a distance from the tire rotation axis to the point Q3 when the tire is mounted on a predetermined rim, inflated to a predetermined internal pressure, and in an unloaded state.

[0086] In addition, Fig. 1, the actual tire ground contact width Wg (not shown in the drawings) and the cross-sectional width Wca of the carcass layer 13 preferably have a relationship of 0.64 ≤ Wg / Wca ≤ 0.84. As a result, a suitable ratio Wg / Wca of the actual tire ground contact width Wg and the cross-sectional width Wca of the carcass layer 13 is obtained.

[0087] The actual tire ground contact width Wg is calculated as the difference between the ground contact width of the entire tire and the sum of the groove widths of all main circumferential grooves 2.

[0088] In addition, the belt cords of the large angle belt 141 are preferably steel wire, and the number of ends in the large angle belt 141 is preferably not less than 15 ends / 50 mm and not more than 25 ends / 50 mm. In addition, the belt cords of the two cross belts 142, 143 are preferably steel wire. The number of ends in each of the two cross belts 142, 143 is preferably not less than 18 ends / 50 mm and not more than 28 ends / 50 mm, and the number of ends is more preferably not less than 20 ends / 50 mm and not more than 25 ends / 50 mm. As a result, sufficient strength of the belt layers 141, 142, 143 can be ensured.

[0089] Furthermore, a breaking elongation λ 1 of the coating rubber of the large-angle belt 141 is preferably in a range of λ 1 ≥ 200%. Furthermore, the corresponding breaking elongations λ 2 , λ 3 of the coating rubber of the two cross belts 142, 143 are preferably in a range of λ 2 ≥ 200% and λ 3 ≥ 200%. As a result, sufficient durability of the belt layers 141, 142, 143 is ensured.

[0090] The elongation at break is measured by conducting a tensile test according to JIS-K7161 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.).

[0091] In addition, in the pneumatic tire 1, the elongation at break of the tread rubber 15 is preferably in a range of not less than 350%. Therefore, the strength of the tread rubber 15 is ensured, and the occurrence of cracks at the outermost circumferential main groove 2 is prevented. There is no particular limitation on the upper limit of the elongation at break of the tread rubber 15. However, there are some limitations due to the type of rubber compound used in the tread rubber 15.

[0092] Furthermore, in this pneumatic tire 1, the hardness of the tread rubber 15 is preferably within a range of not more than 60.

[0093] As a result, sufficient durability of the tread rubber 15 is ensured.

[0094] There are no special restrictions set for the upper limit of the hardness of the tread rubber 15.

[0095] However, there are some limitations due to the type of rubber compound used in the tread rubber 15.

[0096] Here, the term rubber hardness refers to a JIS-A hardness according to JIS-K6263.

[0097] In addition, in the pneumatic tire 1, a loss angle tangent tan δ of the tread rubber 15 is preferably in a range where 0.10 ≤ tan δ.

[0098] The loss angle tangent tan δ 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. [Beveled sections of the shoulder bar section]

[0099] Fig. 7 is an explanatory view showing a modified example of the Fig. 1 depicted pneumatic tire. Fig. Figure 7 shows an enlarged cross-sectional view of the shoulder web section.

[0100] As in Fig. 7, in this pneumatic tire 1, the shoulder land portion 3 on the outermost side in the tire width direction preferably has a chamfered portion 31 at an edge portion on the circumferential main groove 2 side. The chamfered portion 31 may be a square chamfer or a rounded chamfer formed continuously in the tire circumferential direction along the circumferential main groove 2, and may also be a notch formed discontinuously in the tire circumferential direction.

[0101] For example, when designing in Fig. 7, the land portions 3, 3 on the left and right sides divided by the outermost circumferential main groove 2 are ribs each having the chamfered portion 31 at an edge portion on the side of the outermost circumferential main groove 2. In addition, the chamfered portion 31 is an angular chamfer formed continuously in the tire circumferential direction.

[0102] According to this configuration, the ground contact pressure at the edge portion on the side of the shoulder land portion 3 where the circumferential main groove 2 is located is reduced by the presence of the chamfered portion 31 at the edge portion on the side of the shoulder land portion 3 where the circumferential main groove 2 is located. As a result, the tire's resistance to uneven wear is improved. [Narrow groove on the flank section]

[0103] Fig. 8 is an explanatory view showing a modified example of the Fig. 1 depicted pneumatic tire. Fig. 8 shows an enlarged cross-sectional view of a flank section.

[0104] According to the design of Fig. 8, the pneumatic tire 1 is provided with a narrow groove 4.

[0105] This narrow groove 4 is arranged in the sidewall section and runs in the tire circumferential direction.

[0106] When viewed in cross-section from the tire meridian direction, the narrow groove is also located further outward in the tire radial direction than the wear end interface WE of the main circumferential direction groove 2.

[0107] The sidewall portion is a non-ground contact region of a connecting portion between the profile of the tread portion and the profile of the sidewall portion and forms a sidewall surface on the tire widthwise outer side of the shoulder land portion 3.

[0108] For example, according to the design of Fig. 8, a narrow groove 4 is arranged in a non-ground contact region from the tread end P (from the tire ground contact edge T), which is the sidewall portion, to the wear end interface WE of the main circumferential groove 2. In addition, the narrow groove 4 has a shape such that it is inclined towards the tire interior with respect to the tire radial direction.

[0109] According to this configuration, the narrow groove 4 in the sidewall portion is closed when the tire is in ground contact, and then the ground contact pressure at the shoulder land portion 3 is reduced. As a result, the tire's resistance to uneven wear is improved. [Effects]

[0110] As described above, the pneumatic tire 1 includes a carcass layer 13, a belt layer 14 disposed on the tire radially outer side of the carcass layer 13, a tread rubber 15 disposed on the tire radially outer side of the belt layer 14, at least three circumferential main grooves 2 extending in the tire circumferential direction, and a plurality of land portions 3 divided by the circumferential main grooves 2 (see Fig. 1).

[0111] In addition, the land portions 3 on the inner side in the tire width direction with respect to the outermost circumferential main groove 2 on the left and right sides each have a first profile PL1 which projects outward in the tire radial direction.

[0112] In addition, the shoulder web sections 3 each have a second profile PL2 within the ground contact area, which projects inwards in the tire radial direction (see Fig. 4).

[0113] In addition, a distance d in the tire radial direction from a line extending from the first profile PL1 to the second profile PL2 within the ground contact surface of the shoulder land portions 3 becomes larger toward the outer side in the tire width direction.

[0114] Likewise, the distance Gcc from the tread pattern (from the first pattern PL1) to the inner peripheral surface of the tire along the tire equatorial plane CL and the distance Gsh from the tread end P to the inner peripheral surface of the tire have a relationship 1.10 ≤ Gsh / Gcc, wherein a relationship 1.20 ≤ Gsh / Gcc is according to the invention (see Fig. 2)

[0115] According to this configuration, the shoulder land portion 3 within the ground contact surface has the second profile PL2 projecting inward in the tire radial direction. Also, the distance d between the first and second profiles, PL1, PL2 within the ground contact surface of the shoulder land portion 3 increases toward the outer side in the tire width direction. Thus, the ground contact pressure on the tire ground contact edge T side of the shoulder land portion becomes larger when the tire is in ground contact. Thus, the amount of slippage of the land portions 3 in the central region and the amount of slippage of the shoulder land portions 3 when the tire is in ground contact are averaged. As a result, there is an advantage that uneven wear of the shoulder land portions 3 is reduced and the tire's resistance to uneven wear is improved.

[0116] Furthermore, in this pneumatic tire 1, the distance Dcc from the outer side cross belt 143 to the wear end interface WE in the tire equatorial plane CL and the distance De from the outer side cross belt 143 to the wear end interface WE on the groove center line of the outermost circumferential main groove 2 have a relationship of 0.70 ≤ De / Dcc ≤ 1.30 (see Fig. 2). Only designs with a relationship of 0.95 ≤ De / Dcc ≤ 1.30 are in accordance with the invention. According to this configuration, the De / Dcc ratio is appropriate. This has the advantage of averaging the amount of slip of the land portion 3 in the central region and the amount of slip of the shoulder land portion 3 when the tire is in contact with the ground, thereby limiting uneven wear of the shoulder land portion 3.

[0117] Furthermore, in the pneumatic tire 1, the belt layer 14 has a belt angle of not less than 10° and not more than 45° as an absolute value and is provided with the two cross belts 142, 143 having belt angles of opposite signs (see Fig. 2). Likewise, the distance Dcc from the outer side cross belt 143 to the wear-end interface WE in the tire equatorial plane CL and the distance De from the outer side cross belt 143 to the wear-end interface WE on the groove centerline of the outermost circumferential main groove 2 have a relationship of 0.70 ≤ De / Dcc ≤ 1.30. Only designs having a relationship of 0.95 ≤ De / Dcc ≤ 1.30 are according to the invention. This design has the advantage that the distances Dcc, De of the outer side cross belt 143 are appropriate with respect to the wear end interface WE. That is, given that 0.70 ≤ De / Dcc, the tread thickness at the groove bottom of the outermost circumferential main groove 2 is ensured, and the groove crack resistance is ensured. Furthermore, given that De / Dcc ≤ 1.30, the load on the outer side cross belt 143 is reduced when the tire is in ground contact (see for comparison Fig. 5A, Fig. 5B). As a result, the amount of slippage of the land portion 3 in the central region and the amount of slippage of the shoulder land portion 3 are averaged when the tire is in ground contact, thereby counteracting uneven wear of the shoulder land portion 3.

[0118] In addition, in the pneumatic tire 1, the diameter D1 of the first profile PL1 in the tire equatorial plane CL and the diameter D2 of the second profile PL2 at the tire ground contact edge T have a relationship -0.015 ≤ (D1 ≤ D2) / D1 ≤ 0.015 (see Fig. 4). As a result, an appropriate degree of drop of the tire ground contact edge T is obtained. This has the advantage that the extent of slippage of the land sections 3 in the central region and the extent of slippage of the shoulder land section 3 when the tire is in ground contact are averaged.

[0119] In addition, in the pneumatic tire 1, the diameter D2 of the second profile PL2 at the tire ground contact edge T and the diameter D3 of the second profile PL2 at the edge portions on the inner side in the tire width direction of the shoulder land portions 3 have a relationship D3 < D2 (see Fig. 4). As a result, this relationship has the advantage that the profile shape of the shoulder web sections 3 is appropriate.

[0120] In addition, in this pneumatic tire 1, the width Wb2 of the wider cross belt 142 and the cross-sectional width Wca of the carcass layer 13 have a relationship 0.70 ≤ Wb2 / Wca ≤ 0.93 (see Fig. 1). As a result, an appropriate width Wb2 of the wider cross belt 142 is obtained, which has the advantage of ensuring the stiffness of the tread section.

[0121] In addition, in the pneumatic tire 1, the diameter Ya of the carcass layer 13 at the position of maximum height and the diameter Yc of the carcass layer 13 at the position of maximum width have a relationship of 0.80 ≤ Yc / Ya ≤ 0.90 (see Fig. 1). Consequently, this relationship has the advantage of maintaining a suitable shape of the carcass layer 13.

[0122] In addition, in the pneumatic tire 1, the diameter Ya of the carcass layer 13 at the position of maximum height and the diameter Yd of the carcass layer 13 at the groove center line of the outermost circumferential main groove 2 have a relationship of 0.95 ≤ Yc / Ya ≤ 1.02 (see Fig. 1). Consequently, a suitable shape of the carcass layer 13 is obtained. This has the advantage that the extent of deformation of the carcass layer 13 at the groove bottom of the outermost main circumferential groove 2 is reduced when the tire is in ground contact. That is, given 0.95 ≤ Yd / Ya, the amount of deformation of the carcass layer 13 at the groove bottom of the outermost circumferential main groove 2 when the tire is in contact with the ground is reduced. Given Yd / Ya ≤ 1.02, the appropriate tire shape is ensured.

[0123] Furthermore, in the pneumatic tire 1, the tread width TW and the total tire width SW have a relationship of 0.79 ≤ TW / SW ≤ 0.89 (see Fig. 1). According to this design, since the TW / SW relationship is within the range described above, the difference in radial increment between the center region and the shoulder region is reduced. As a result, this design has the advantage of averaging the tire ground contact pressure distribution. This means that given 0.79 ≤ TW / SW, the air volume in the tire is ensured and deflection is counteracted. Furthermore, given TW / SW ≤ 0.89, a rise in the shoulder region is counteracted and deflection is limited when the tire is in ground contact.

[0124] In addition, in the pneumatic tire 1, the tread width TW and the section width Wca of the carcass layer 13 have a relationship of 0.82 ≤ TW / Wca ≤ 0.92 (see Fig. 1). According to this configuration, since the relationship TW / Wca is in the above-described range, the difference in radial increment between the center region and the shoulder region is reduced, and the distribution of ground contact pressure is averaged in the tire width direction. As a result, this design has the advantage of averaging the tire ground contact pressure distribution. That is, given 0.82 ≤ TW / Wca, the air volume in the tire is ensured and the deflection is counteracted. Furthermore, given TW / Wca ≤ 0.92, an increase in the shoulder section is counteracted and the ground contact pressure distribution is averaged.

[0125] Furthermore, in the pneumatic tire 1, the belt layer 14 has the large angle belt 141 having, as an absolute value, a belt angle of not less than 45° and not more than 70° (see Fig. 1 and Fig. 3). As a result, the belt layer 14 is reinforced, which has the advantage of reducing the load at the end portions of the belt layer 14 when the tire is in contact with the ground.

[0126] In addition, in the pneumatic tire 1, the width Wb1 of the large angle belt 141 and the width Wb3 of a narrower cross belt 143 of the two cross belts 142, 143 have a relationship 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 belt with the large angle 141 and the width Wb3 of the narrower cross belt 143. As a result, there is the advantage that the load at the end portions of the belt layer 14 is limited when the tire is in ground contact.

[0127] In addition, in the pneumatic tire 1, the ground contact width Wsh of the shoulder land portions 3 and the tread width TW have a relationship 0.1 ≤ Wsh / TW ≤ 0.2 (see Fig. 1 and Fig. 2). According to this design, there is an advantage in obtaining an appropriate ground contact width Wsh of the shoulder elevation portion 3. That is, given 0.1 ≤ Wsh / TW, the ground contact area of the shoulder land portions 3 is ensured, and resistance to uneven wear of the tire is ensured. In addition, given Wsh / TW ≤ 0.2, the ground contact surface pressure of the shoulder land portions 3 is increased when the tire is in ground contact, and the wet performance of the tire is improved.

[0128] In addition, in the pneumatic tire 1, the actual tire ground contact width Wg (not shown in the drawings) and the section width Wca of the carcass layer 13 have a relationship of 0.64 ≤ Wg / Wca ≤ 0.84 (see Fig. 1). As a result, this relationship has the advantage of obtaining a suitable cross-sectional width Wca of the carcass layer 13. This means that given 64 ≤ Wg / Wca, an adequate ground contact area of the tire is ensured. In addition, given that Wg / Wca ≤ 0.84, the tread width TW is designed so that it is not excessively large and an appropriate ground contact surface pressure of the shoulder land sections 3 is ensured.

[0129] In addition, in the pneumatic tire 1, the rubber hardness of the tread rubber 15 is in a range of not less than 60. As a result, there is an advantage that the strength of the tread rubber 15 is adequately ensured and the resistance of the tire to uneven wear is improved.

[0130] Furthermore, in the pneumatic tire 1, the shoulder land portion 3 has a chamfered portion 31 at an edge portion on the side where the circumferential main groove 2 is located (see Fig. 7). As a result, the ground contact pressure at the edge portion on the side of the shoulder land portion 3 where the main circumferential groove 2 is located is reduced. The advantage of reducing the ground contact pressure is that the tire's resistance to uneven wear is improved.

[0131] In addition, the pneumatic tire 1 is provided with a narrow groove 4 which is arranged in the sidewall portion and which runs in the tire circumferential direction (see Fig. 8). When viewed in cross-section from the tire meridian direction, the narrow groove is also located further outward in the tire radial direction than the end-of-wear interface WE of the main circumferential groove 2. According to this configuration, the narrow groove 4 in the sidewall portion is closed when the tire is in ground contact, and then the ground contact pressure at the shoulder land portion 3 is reduced. As a result, this has the advantage of improving the tire's resistance to uneven wear. (Area of application)

[0132] In addition, 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 the tire is mounted on a standard rim, inflated to a regular internal pressure, and applied with a regular load. In a tire having the aspect ratio described above, the amount of drop when inflated (the difference in diameter between the center region and the shoulder region at the Tread surface) is rather elevated, and the ground contact shape is more hourglass-shaped when the tire is in contact with the ground. Thus, when the application target is a heavy-duty tire with a low profile, a remarkable effect is achieved in improving the tire's resistance to uneven wear, as described above. Example

[0133] Fig. 9 and Fig. 10 are tables showing the results of performance tests of pneumatic tires according to the embodiments of the present invention. The embodiments 1, 2, and 3 in Fig. 9 are not in accordance with the invention.

[0134] In the performance tests, an evaluation was carried out with regard to resistance to uneven wear on a number of pneumatic tires that differed from each other (see Fig. 9 and Fig. 10). In the evaluation, pneumatic tires, each with a tire size of 315 / 60R22.5, were mounted on rims, each with a rim size of 22.5 × 9.00.

[0135] The pneumatic tires were inflated to an air pressure of 900 kPa. Furthermore, the pneumatic tires were mounted on the front axle of a test vehicle, which was a 4×2 tractor with a trailer, and a load of 34.81 kN was applied.

[0136] After the test vehicle had been driven for 100,000 km, the evaluation was then carried out by measuring the shoulder drop wear of the shoulder land portions (the difference between the amount of wear at the edge portion of the shoulder land portions and the amount of wear at the outermost main circumferential groove).

[0137] In this evaluation, a larger value is preferred.

[0138] The pneumatic tire 1 of application example 1 had the Fig. 1 to Fig. 4 described design.

[0139] In addition, the belt angle of the cross belts was 142, 143 ±19°. Furthermore, the main dimensions were set as follows: TW = 275mm, Gcc = 32.8mm, Dcc = 11.2mm, Ya = 446mm, Wca = 320mm, D2 < D1 and D3 < D2.

[0140] The pneumatic tires 1 in each of Application Examples 2 to 22 were modified examples of the pneumatic tires of Application Example 1.

[0141] A conventional pneumatic tire had the design of Fig. 1 to Fig. 4, wherein the shoulder land portions 3 had a profile that protruded outwardly in the tire radial direction within the ground contact surface.

[0142] As indicated by the test results, the pneumatic tire 1 of each of the application examples 1 to 22 provides significantly improved resistance to uneven tire wear. REFERENCE SYMBOL: 1 pneumatic tire 2 main circumferential grooves 3 bridge section 31 Beveled section 4 Narrow groove 11 Bead core 12 bead filling 121 Lower filling 122 Upper filling 13 carcass layers 14 belt layer 141 Belt with large angle 142 inner cross belt 143 Outer cross belt 144 Belt cover 15 Tread rubber 16 sidewall rubber PL1 First Profile PL2 Second Profile WE wear end interface

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 the 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 land portions (3) formed by being divided by the circumferential main grooves (2), wherein, of the main circumferential grooves (2), left and right circumferential main grooves (2) on outermost sides in the tire width direction are referred to as outermost circumferential main grooves (2), and the land portions (3) on an outer side in the tire width direction of the outermost circumferential main grooves (2) on the left and right sides are referred to as shoulder land portions (3), the land portions (3) on an inner side in the tire width direction of the outermost circumferential main grooves (2) on the left and right sides have a first profile (PL1) projecting outward in the tire radial direction, and the shoulder land portions (3) within a ground contact surface have a second profile (PL2) projecting inward in the tire radial direction, a distance d in the tire radial direction between a line extending from the first profile (PL1) and the second profile (PL2) within the ground contact surface of the shoulder land portions (3) becomes larger toward an outer side in the tire width direction, and a distance Gcc from a tread pattern to a tire inner peripheral surface in a tire equatorial plane and a distance Gsh from a tread end to the tire inner peripheral surface have a relationship 1.20 ≤ Gsh / Gcc, wherein the belt layer (14) has a pair of cross belts (142, 143) with belt angles of not less than 10° and not more than 45° as an absolute value, the belt angles having opposite signs, when viewed in cross section from a tire meridian direction, a wear end interface WE is drawn along the main circumferential grooves (2) and a cross belt (143) on an outer side in the tire radial direction of the two cross belts (142, 143) is referred to as an outer side cross belt (143), and a distance Dcc from the outer side cross belt (143) to the wear end interface WE in the tire equatorial plane and a distance De from the outer side cross belt (143) to the wear end interface WE on a groove center line of the outermost circumferential main grooves (2) have a relationship of 0.95 ≤ De / Dcc ≤ 1.

30. [2] A pneumatic tire (1) according to claim 1, wherein the distance Dcc and the distance De have a relationship of 0.98 ≤ De / Dcc ≤ 1.

30. [3] A pneumatic tire (1) according to claim 1 or claim 2, wherein a diameter D1 of the first tread (PL1) in the tire equatorial plane and a diameter D2 of the second tread (PL2) at the tire ground contact edge have a relationship of -0.015 ≤ (D1 ≤ D2) / D1 ≤ 0.

015. [4] A pneumatic tire (1) according to any one of claims 1 to 3, wherein a diameter D2 of the second profile (PL2) at the tire ground contact edge and a diameter D3 of the second profile (PL2) at the edge portion on the tire widthwise inner side of the shoulder land portions (3) have a relationship of D3 < D2. [5] The pneumatic tire (1) according to any one of claims 1 to 4, wherein the belt layer (14) has the two cross belts (142, 143) with the belt angles of not less than 10° and not more than 45° as an absolute value, the belt angles having opposite signs, and a width Wb2 of the wider cross belt among the two cross belts (142, 143) and a cross-sectional width Wca of the carcass layer (13) have a relationship of 0.70 ≤ Wb2 / Wca ≤ 0.

93. [6] A pneumatic tire (1) according to any one of claims 1 to 5, wherein a diameter Ya at a position of a greatest height of the carcass layer (13) and a diameter Yc at a position of the greatest width of the carcass layer (13) have a relationship of 0.80 ≤ Yc / Ya ≤ 0.

90. [7] A pneumatic tire (1) according to any one of claims 1 to 6, wherein the diameter Ya at the position of the greatest height of the carcass layer (13) and a diameter Yd of the carcass layer (13) at the groove center line of the outermost circumferential main grooves (2) have a relationship of 0.95 ≤ Yd / Ya ≤ 1.

02. [8] A pneumatic tire (1) according to any one of claims 1 to 7, wherein a tread width TW and a tire overall width SW have a relationship of 0.79 ≤ TW / SW ≤ 0.

89. [9] A pneumatic tire (1) according to any one of claims 1 to 8, wherein the tread width TW and the cross-sectional width Wca of the carcass layer (13) have a relationship of 0.82≤TW / Wca≤0.

92. [10] A pneumatic tire (1) according to any one of claims 1 to 9, wherein the belt layer (14) comprises a high-angle belt (141) having a belt angle of not less than 45° and not more than 70° as an absolute value. [11] A pneumatic tire (1) according to claim 10, wherein a width Wb1 of the large angle belt (141) and a width Wb3 of a narrower cross belt of the pair of cross belts (142, 143) have a relationship of 0.85 ≤ Wb1 / Wb3 ≤ 1.

05. [12] A pneumatic tire (1) according to any one of claims 1 to 11, wherein a ground contact width Wsh of the shoulder land portion and the tread width Tw have a relationship of 0.1 ≤ Wsh / TW ≤ 0.

2. [13] A pneumatic tire (1) according to any one of claims 1 to 12, wherein an actual tire ground contact width Wg and the cross-sectional width Wca of the carcass layer (13) have a relationship of 0.64 ≤ Wg / Wca ≤ 0.

84. [14] A pneumatic tire (1) according to any one of claims 1 to 13, wherein a rubber hardness of the tread rubber (15) is in a range of not less than 60. [15] A pneumatic tire (1) according to any one of claims 1 to 14, wherein the edge portion of the shoulder land portions has a chamfered portion (31) on a side where the circumferential main groove (2) is located. [16] A pneumatic tire (1) according to any one of claims 1 to 15, wherein a narrow groove (4) is arranged in a sidewall portion and extends in the tire circumferential direction, and the narrow groove (4) is located on an outer side in the tire radial direction of the wear end interface WE of the circumferential main grooves (2) when viewed in cross section from the tire meridian direction. [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 not more than 70%.

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