Tire for heavy load

Abstract

To provide a tire 2 for a heavy load, which can reduce rolling resistance while suppressing deterioration in wet performance due to abrasion and also reduce a risk that uneven abrasion may occur.SOLUTION: A tire 2 comprises a tread 4. The tread 4 includes a tread surface 6. The tread 4 has a crown part CR and a shoulder land part 22. A circumferential narrow groove 26 is carved in the crown part CR. The circumferential narrow groove 26 comprises a trunk part 28 and a widened part 30. The tread surface 6 includes a land surface 10C of the crown part CR and a land surface 10S of the shoulder land part 22. A contour of the land surface 10C of the crown part CR is represented by a circular arc. A contour of the land surface 10S of the shoulder land part 22 is represented by a circular arc or a straight line. A ratio (D1 / D2) of a distance D1 in a radial direction from an equator to an end TE of the tread surface 6 to a distance D2 in the radial direction from the equator to a reference end BTE of the tread surface 6 is 0.60 or more and 1.70 or less.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present invention relates to a heavy duty tire. [Background technology]

[0002] The tread of the tire has a plurality of circumferential main grooves arranged in parallel in the axial direction, the plurality of circumferential main grooves defining a plurality of land portions in the tread. The land portion of a tire deforms when it comes into contact with the road surface. The deformation of the land portion affects the rolling resistance of the tire. Considering the impact on the environment, there is a strong demand for tires to reduce rolling resistance. By providing circumferential narrow grooves having a groove width narrower than that of the circumferential main grooves, the land portions can support each other when the tread comes into contact with the road surface, suppressing deformation of the land portions. In order to reduce the rolling resistance of tires, the use of circumferential narrow grooves has been considered (for example, Patent Document 1 listed below). The circumferential narrow grooves also affect, for example, the running performance on wet roads (hereinafter also referred to as wet performance). The adoption of the circumferential narrow grooves is being promoted while taking into consideration the influence on various performances. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-094891 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a heavy-duty tire that can reduce rolling resistance while suppressing deterioration of wet performance due to wear, and can also achieve a reduced risk of uneven wear. [Means for solving the problem]

[0005] The heavy-duty tire according to the present invention has a tread. The outer peripheral surface of the tread includes a tread surface that comes into contact with the road surface. A plurality of land portions arranged in the axial direction are formed by carving a plurality of circumferential main grooves extending continuously in the circumferential direction in the tread. The plurality of circumferential main grooves include a pair of shoulder circumferential main grooves located on the outermost side in the axial direction. The plurality of land portions include a pair of shoulder land portions located on the outermost side in the axial direction. In the tread, a portion between a first shoulder circumferential main groove and a second shoulder circumferential main groove, which are a pair of shoulder circumferential main grooves, is a crown portion, and a portion between the shoulder circumferential main groove and an end of the tread surface is the shoulder land portion. At least one circumferential narrow groove is carved in the crown portion. The circumferential narrow groove includes a body portion including a groove mouth of the circumferential narrow groove and a widened portion including a groove bottom of the circumferential narrow groove. The body portion includes a body main body extending straight. The widened portion is connected to the body main body and has a portion showing a maximum groove width between the body main body and the groove bottom. The tread surface includes the land surface of the crown portion and the land surface of the shoulder land portion. The intersection line between the land surface of the crown portion and the equatorial plane is the equator. In the meridian cross section of the tire, the outline of the land surface of the crown portion is represented by an arc having a center on the equatorial plane and a radius of 400 mm or more. The outline of the land surface of the shoulder land portion is represented by an arc having a radius of 0.002 mm or more. -1 When the intersection point of an extension of the arc representing the contour of the land surface of the crown portion and a straight line extending in the radial direction passing through the edge of the tread surface is defined as a reference edge of the tread surface, a ratio (D1 / D2) of a radial distance D1 from the equator to the edge of the tread surface to a radial distance D2 from the equator to the reference edge of the tread surface is 0.60 or more and 1.70 or less. Effect of the Invention

[0006] The present invention can provide a heavy-duty tire that can reduce rolling resistance while suppressing deterioration of wet performance due to wear, and can also reduce the risk of uneven wear. [Brief description of the drawings]

[0007] [Figure 1] 1 is a development view showing a portion of a tread of a heavy duty tire according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Diagram 3] FIG. 2 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 2 is an enlarged development view showing a part of FIG. [Diagram 5] FIG. 5 is a cross-sectional view taken along line VV in FIG. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. [Figure 7] FIG. 2 is an enlarged development view showing a part of FIG. [Figure 8] FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. 7. [Figure 9] FIG. 8 is a cross-sectional view taken along line IX-IX in FIG. [Figure 10] FIG. 2 is a cross-sectional view showing a portion of the contour of the tread surface. [Figure 11] FIG. 2 is a schematic diagram illustrating the shape of the ground contact surface. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The tire of the present invention is mounted on a rim. Air is filled inside the tire, and the internal pressure of the tire is adjusted. The tire mounted on the rim is also called a tire-rim assembly. The tire-rim assembly includes a rim and a tire mounted on the rim.

[0009] In the present invention, a state in which a tire is mounted on a standard rim, the internal pressure of the tire is adjusted to a standard internal pressure, and no load is applied to the tire is called a standard state. The condition in which a tire is mounted on a standard rim, the internal pressure of the tire is adjusted to 5% of the standard internal pressure, and no load is being applied to the tire is called the standard condition.

[0010] In the present invention, unless otherwise specified, the dimensions and angles of each part of the tire are measured in a normal state. The dimensions and angles of each part in the meridian section of the tire, which cannot be measured when the tire is mounted on a regular rim, are measured on the cut surface of the tire obtained by cutting the tire along a plane including the axis of rotation. In this measurement, the tire is set so that the distance between the left and right beads is the same as the distance between the beads of the tire mounted on a regular rim. The tire configuration that cannot be confirmed when the tire is mounted on a regular rim is confirmed on the aforementioned cut surface.

[0011] A genuine rim is a rim that is specified in the standard on which the tire is based. The "standard rim" in the JATMA standard, the "Design Rim" in the TRA standard, and the "Measuring Rim" in the ETRTO standard are genuine rims.

[0012] Normal tire pressure means the internal pressure specified in the standard on which the tire is based. The "maximum air pressure" in the JATMA standard, the "maximum value" listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard are normal tire pressures.

[0013] Normal load refers to the load specified in the standard on which the tire is based. The "maximum load capacity" in the JATMA standard, the "maximum value" listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are normal loads.

[0014] In the present invention, the tread portion of a tire is the portion of the tire that comes into contact with the road surface. The bead portion is the portion of the tire that fits onto the rim. The sidewall portion is the portion of the tire that bridges between the tread portion and the bead portion. A tire has the following portions: a tread portion, a pair of bead portions, and a pair of sidewall portions. The center of the tread is also called the crown. The edges of the tread are also called the shoulders.

[0015] [Foundations underlying the present invention] As mentioned above, by providing circumferential narrow grooves in the tread, deformation of the land portion when the tread comes into contact with the road surface is suppressed, and the apparent rigidity of the land portion is increased. This allows the tire to reduce rolling resistance. As the tread wears, the grooves in the tread disappear. The groove volume of the circumferential narrow groove is smaller than the groove volume of the circumferential main groove. If the tread is provided with a circumferential narrow groove, there is a concern that the groove volume will be insufficient as the tread wears, resulting in a decrease in wet performance. As mentioned above, the circumferential narrow grooves increase the apparent rigidity of the land portion. However, there are concerns that the provision of the circumferential narrow grooves will change the shape of the contact patch, increasing the risk of uneven wear. The present inventors therefore conducted intensive research into technology that can reduce rolling resistance while suppressing the deterioration of wet performance due to wear, and can also reduce the risk of uneven wear, and have completed the invention described below.

[0016] [Overview of the embodiment of the present invention] [Configuration 1] A heavy-duty tire according to one aspect of the present invention is a tire having a tread, an outer peripheral surface of the tread includes a tread surface that comes into contact with a road surface, a plurality of circumferential main grooves extending continuously in a circumferential direction are cut into the tread to form a plurality of land portions aligned in an axial direction, the plurality of circumferential main grooves include a pair of shoulder circumferential main grooves located outermost in the axial direction, the plurality of land portions include a pair of shoulder land portions located outermost in the axial direction, a portion of the tread between a first shoulder circumferential main groove and a second shoulder circumferential main groove, which are the pair of shoulder circumferential main grooves, is a crown portion, and a portion between the shoulder circumferential main groove and an end of the tread surface is the shoulder. a land portion, at least one circumferential narrow groove is formed in the crown portion, the circumferential narrow groove includes a body portion including a groove mouth of the circumferential narrow groove and a widened portion including a groove bottom of the circumferential narrow groove, the body portion includes a body main body extending straight, the widened portion is continuous with the body main body and has a portion showing a maximum groove width between the body main body and the groove bottom, the tread surface includes a land surface of the crown portion and a land surface of the shoulder land portion, an intersection line between the land surface of the crown portion and an equatorial plane is an equator, in a meridian cross section of the tire, an outline of the land surface of the crown portion is represented by an arc having a center on the equatorial plane and a radius of 400 mm or more, and an outline of the land surface of the shoulder land portion is represented by an arc having a center on the equatorial plane and a radius of 400 mm or more, and an outline of the land surface of the shoulder land portion is represented by an arc having a center on the equatorial plane and a radius of 0.002 mm or more. -1 When the reference edge of the tread surface is represented by an arc or a straight line having the following curvature, and the intersection point of an extension of the arc representing the contour of the land surface of the crown portion and a straight line extending radially through the edge of the tread surface is defined as the reference edge of the tread surface, the ratio (D1 / D2) of the radial distance D1 from the equator to the edge of the tread surface to the radial distance D2 from the equator to the reference edge of the tread surface is 0.60 or more and 1.70 or less.

[0017] By conditioning the tires in this way, it is possible to reduce rolling resistance while suppressing deterioration of wet performance due to wear, and also to reduce the risk of uneven wear.

[0018] [Configuration 2] Preferably, in the heavy duty tire described in the above-mentioned [Configuration 1], the groove width of the body is 2.5 mm or less, and the ratio of the groove width of the body to the maximum groove width of the widened portion is 0.10 or more and 0.40 or less.

[0019] [Configuration 3] Preferably, in the heavy load tire according to the above-mentioned [Configuration 1] or [Configuration 2], a ratio of a groove depth from a groove mouth of the circumferential narrow groove to a position where the widened portion shows the maximum groove width to a groove depth of the circumferential narrow groove is 0.80 or more and 0.90 or less.

[0020] [Configuration 4] Preferably, in a heavy-duty tire according to any one of the above-mentioned [Configuration 1] to [Configuration 3], the tire is mounted on a standard rim, the internal pressure of the tire is adjusted to a standard internal pressure, a standard load is applied to the tire, and the tire is brought into contact with a flat road surface to obtain a contact patch. The length of the contact patch at a position corresponding to 97% of the maximum contact width is contact length L1, and the length of the contact patch at a position corresponding to 70% of the maximum contact width is contact length L2, and the ratio (L2 / L1) of the contact length L2 to the contact length L1 is 0.90 or more and 1.10 or less.

[0021] [Configuration 5] Preferably, in the heavy-duty tire according to any one of the above-mentioned [Configuration 1] to [Configuration 4], the length of the contact patch at a position corresponding to the center of the maximum contact width is a contact length L3, and the ratio of the contact length L3 to the contact length L2 (L3 / L2) is 1.00 or greater and 1.20 or less.

[0022] [Details of the embodiment of the present invention] Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

[0023] 1 shows a part of a tire 2 according to one embodiment of the present invention. This tire 2 is mounted on vehicles such as trucks, buses, etc. This tire 2 is a heavy-duty tire. The direction indicated by the double-headed arrow A represents the axial direction of the tire 2. The direction indicated by the double-headed arrow C represents the circumferential direction of the tire 2. The direction perpendicular to the plane of the paper in FIG. In FIG. 1, a dashed dotted line CL extending in the circumferential direction represents the equatorial plane of the tire 2.

[0024] 1 shows a tread 4. A tire 2 has a tread 4. The tread 4 extends in a circumferential direction. The tread 4 is included in a tread portion of the tire 2. The tread 4 is made of crosslinked rubber.

[0025] Although not shown, the tire 2 includes elements such as sidewalls, beads, and carcass in addition to the tread 4. In the present invention, there is no particular limitation on the internal structure of the tire 2 that is configured with these elements. Although not described in detail, the tire 2 has a general internal structure as an internal structure of a heavy-duty tire.

[0026] The tire 2 comes into contact with the road surface at the tread 4. The outer peripheral surface of the tread 4 includes a tread surface 6 that comes into contact with the road surface. In the present invention, unless otherwise specified, the tread surface 6 means the tread surface of an unused tire 2 that has not been driven. Grooves 8 are formed in the tread 4. This defines a tread pattern. The portion of the tread surface 6 other than the grooves 8 is also called a land surface 10.

[0027] FIG. 1 is a development view of a tread surface 6. In FIG. 1, the two-dot chain line indicated by the symbol TE represents the edge of the tread surface 6. In the tread surface 6 shown in FIG. 1, the edge TE (not shown) of the tread surface 6 located to the left of the equatorial plane is also called a first edge TE1, and the edge TE located to the right of the equatorial plane is also called a second edge TE2. The length indicated by the double arrow TW in FIG. 1 is the width of the tread surface 6. The width TW of the tread surface 6 is the axial distance from the first edge TE1 to the second edge TE2 of the tread surface 6. The width TW of the tread surface 6 is measured along the tread surface 6.

[0028] In the present invention, when the edge TE of the tread surface 6 cannot be identified as a clear edge from the outside, the position on the tread surface 6 corresponding to the axial outer edge (also called the ground contact edge) of the contact surface is specified as the edge TE of the tread surface 6. The contact surface is obtained by applying a load equivalent to the normal load of the tire 2 to the tire 2 with the camber angle of the tire 2 in a normal state set to 0°, and by bringing the tire 2 into contact with a flat road surface.

[0029] The intersection line between the tread surface 6 (specifically, the land surface of the crown portion described later) and the equatorial plane is also called the equatorial PC. When the grooves 8 are located on the equatorial plane as shown in Fig. 1, the equatorial PC is determined based on a virtual outer surface obtained by assuming that the grooves 8 are not on the equatorial plane.

[0030] Fig. 2 shows a cross section of the groove 8 taken along line II-II in Fig. 1. The cross section of the groove 8 shown in Fig. 2 is a cross section of this groove 8 taken along a plane perpendicular to the direction in which the groove 8 extends. Fig. 2 shows an example of a groove 8 formed in the tread 4. Specifically, the cross section of the groove 8 shown in Fig. 2 is a cross section of a crown circumferential main groove, which will be described later. The main configuration of the groove 8 will be described with reference to Fig. 2.

[0031] The groove 8 has a pair of wall surfaces 8W including a groove mouth 8M, and a bottom surface 8B including a groove bottom 8T. Each of the pair of wall surfaces 8W bridges between the groove mouth 8M and the bottom surface 8B. The groove width of the groove 8 is represented by the distance between a pair of wall surfaces 8W, that is, a first wall surface 8W and a second wall surface 8W, that is, the wall-to-wall distance. 2, the length indicated by the double-headed arrow WG is the groove width of the groove 8 at the groove mouth 8M. The groove width WG is represented by the shortest distance from a first edge 8E to a second edge 8E, which are a pair of edges 8E that form the groove mouth 8M. When the edge 8E of the groove opening 8M is chamfered and the groove opening 8M of the groove 8 is tapered, unless otherwise specified, the groove width WG at the groove opening 8M is obtained by virtualally defining the edge as the intersection of the extension of the contour line of the wall surface 8W and the extension of the contour line of the land surface 10. The length indicated by the double-headed arrow DG is the depth of the groove 8. The groove depth DG of the groove 8 is represented as the shortest distance from the line segment connecting the left and right edges 8E to the groove bottom 8T of the groove 8. The line segment DG representing the groove depth is included in the normal line of the line segment connecting the left and right edges 8E, which passes through the groove bottom 8T. The direction of this normal line is the depth direction of the groove 8. The position of the groove 8, the groove width WG, the groove depth DG, etc. are determined appropriately according to the specifications of the tire 2.

[0032] The groove bottom 8T is the deepest position in the cross section of the groove 8. The distance from the line segment connecting the left and right edges 8E that make up the groove opening 8M to the bottom surface 8B is measured along the normal to this line segment. The position where the distance from this line segment to the bottom surface 8B is maximum is the groove bottom 8T. 2 is a curved surface. The bottom surface 8B may include a flat surface, and this flat surface may include the groove bottom 8T. In this case, the width center of the flat surface is used as the groove bottom 8T.

[0033] A groove 8 having a groove width WG of less than 1.0 mm at its groove mouth 8M is also called a sipe. A groove 8 other than a sipe is also called a normal groove, and has a groove width WG of 1.0 mm or more at its groove mouth 8M. The sipe may include a portion having a groove width of 1.0 mm or more between the groove mouth 8M and the groove bottom 8T (hereinafter, a portion equivalent to a normal groove). In this case, the sipe changes to a normal groove when the tread 4 wears and the portion equivalent to the normal groove becomes exposed. The normal groove may include a portion (a portion equivalent to a sipe) having a groove width of less than 1.0 mm between the groove mouth 8M and the groove bottom 8T. In this case, the normal groove changes to a sipe when the tread 4 wears and the portion equivalent to the sipe becomes exposed.

[0034] Among ordinary grooves, ordinary grooves that extend continuously in the circumferential direction and have a groove depth of 0.5 times or more the thickness of the tread 4 are also called circumferential grooves. Ordinary grooves that extend continuously in the circumferential direction and have a groove depth of less than 0.5 times the thickness of the tread 4 are also called longitudinal grooves. Among the circumferential grooves, a circumferential groove in which a pair of wall surfaces 8W do not come into contact with each other even when the tread 4 comes into contact with the road surface is also called a circumferential main groove. The circumferential main groove forms a land portion in the tread 4. A circumferential groove in which a pair of wall surfaces 8W may come into contact with each other when the tread 4 comes into contact with the road surface is also called a circumferential narrow groove.

[0035] The tread pattern of the present invention will be described below based on Fig. 1 which shows the tread pattern in the zone from the equatorial plane to the second end TE2 of the tread surface 6. For convenience of explanation, the circumferential positions of each part of the tread 4 are represented by defining the side indicated by the arrow C1 as the first side and the side indicated by the arrow C2 as the second side. Although not shown, the tread pattern in the zone from the equatorial plane to the first end TE2 of the tread surface 6 also has a configuration similar to that shown in Fig. 1.

[0036] 1, a plurality of circumferential main grooves 12 aligned in the axial direction are formed in the tread 4 of this tire 2. The tread 4 has a plurality of circumferential main grooves 12 aligned in the axial direction and extending continuously in the circumferential direction.

[0037] The groove depth of the circumferential main groove 12 is, for example, 10 mm or more and 21 mm or less. From the viewpoint of enabling the tire 2 to exhibit good wet performance, the groove depth is preferably 13 mm or more and 18 mm or less.

[0038] In the present invention, among the multiple circumferential main grooves 12 engraved in the tread 4, the two circumferential main grooves 12 located on the outermost sides in the axial direction are shoulder circumferential main grooves. The circumferential main grooves 12 located on the equatorial plane (when no circumferential main groove 12 exists on the equatorial plane, the two circumferential main grooves 12 closest to the equatorial plane) are crown circumferential main grooves. When a circumferential main groove 12 is located between the crown circumferential main groove and the shoulder circumferential main groove, this circumferential main groove 12 is also called a middle circumferential main groove.

[0039] The tread 4 shown in Fig. 1 has three circumferential main grooves 12 aligned in the axial direction. Of the three circumferential main grooves 12, the two circumferential main grooves 12 located on the outermost sides in the axial direction are shoulder circumferential main grooves 14. The circumferential main groove 12 located on the equatorial plane is a crown circumferential main groove 16. This tread 4 has the crown circumferential main groove 16 and a pair of shoulder circumferential main grooves 14.

[0040] As described above, the cross section of the groove 8 shown in Fig. 2 is a cross section of the crown circumferential main groove 16. The crown circumferential main groove 16 has a pair of wall surfaces 16W including a groove mouth 16M, and a bottom surface 16B including a groove bottom 16T.

[0041] As shown in FIG. 1, the crown circumferential main groove 16 of the tire 2 extends in a zigzag manner in the circumferential direction. The crown circumferential main groove 16 includes a first apex 16a close to a first end TE1 (not shown) of the tread surface 6 and a second apex 16b close to a second end TE2 of the tread surface 6. The crown circumferential main groove 16 extends in a zigzag manner, passing through the first apex 16a and the second apex 16b alternately in the circumferential direction. A pair of edges 16E constituting a groove mouth 16M of the crown circumferential main groove 16 each extend in a zigzag manner in the circumferential direction. The crown circumferential main groove 16 may be configured such that a pair of edges 16E constituting the groove mouth 16M each extend straight in the circumferential direction, similar to the shoulder circumferential main groove 14 described later.

[0042] FIG. 3 shows a cross section of the shoulder circumferential main groove 14 taken along line III-III in FIG. The shoulder circumferential main groove 14 has a pair of wall surfaces 14W including a groove mouth 14M and a bottom surface 14B including a groove bottom 14T. As shown in Fig. 1, a pair of edges 14E constituting the groove mouth 14M of the shoulder circumferential main groove 14 each extend straight in the circumferential direction. The shoulder circumferential main groove 14 may be configured such that the pair of edges 14E constituting the groove mouth 14M each extend in a zigzag manner in the circumferential direction, similar to the above-mentioned crown circumferential main groove 16.

[0043] 1, the length indicated by the double arrow WGc is the groove width at the groove mouth 16M of the crown circumferential main groove 16. The length indicated by the double arrow WGs is the groove width at the groove mouth 14M of the shoulder circumferential main groove 14.

[0044] The ratio (WGc / TW) of the groove width WGc of the crown circumferential main groove 16 to the width TW of the tread surface 6 exceeds 2.0%. Specifically, the ratio (WGc / TW) is preferably 4.0% or more and 10% or less. 1, the groove width WGs of the shoulder circumferential main groove 14 is wider than the groove width WGc of the crown circumferential main groove 16. The ratio (WGs / TW) of the groove width WGs of the shoulder circumferential main groove 14 to the width TW of the tread surface 6 is preferably 5.0% or greater and 11% or less.

[0045] The length indicated by the double arrow DGc in Fig. 2 is the groove depth of the crown circumferential main groove 16. The length indicated by the double arrow DGs in Fig. 3 is the groove depth of the shoulder circumferential main groove 14. The groove depth DGs of the shoulder circumferential main groove 14 is the same as the groove depth DGc of the crown circumferential main groove 16. The shoulder circumferential main groove 14 may be shallower than the crown circumferential main groove 16, or the shoulder circumferential main groove 14 may be deeper than the crown circumferential main groove 16.

[0046] A protrusion 18 protruding from the bottom surface is provided on the bottom surface of the crown circumferential main groove 16 shown in Fig. 1. A plurality of protrusions 18 are arranged at predetermined intervals in the circumferential direction. The protrusions 18 prevent stones from getting caught in the crown circumferential main groove 16.

[0047] As described above, a plurality of circumferential main grooves 12 are formed in the tread 4. As a result, a plurality of land portions 20 aligned in the axial direction are formed in the tread 4. The plurality of circumferential main grooves 12 form a plurality of land portions 20 in the tread 4.

[0048] In the present invention, among the multiple land portions 20 formed in the tread 4, the two land portions 20 located on the outermost sides in the axial direction are shoulder land portions. The shoulder land portions include the end TE of the tread surface 6. The land portion 20 located on the equatorial plane (when no land portion 20 exists on the equatorial plane, the two land portions 20 closest to the equatorial plane) is the crown land portion. When the land portion 20 is located between the crown land portion and the shoulder land portion, this land portion 20 is also called a middle land portion.

[0049] The tread 4 shown in FIG. 1 has four land portions 20 arranged in the axial direction. Of the four land portions 20, the two land portions 20 located outermost in the axial direction are shoulder land portions 22. In this tread 4, no land portion 20 exists on the equatorial plane. The two land portions 20 closest to the equatorial plane are crown land portions 24. This tread 4 has a pair of crown land portions 24 and a pair of shoulder land portions 22. Each of the pair of shoulder land portions 22 includes an edge TE of the tread surface 6.

[0050] In the tire 2, the portion of the tread 4 between a pair of shoulder circumferential main grooves 14, that is, a first shoulder circumferential main groove 14 (not shown) and a second shoulder circumferential main groove, is the crown portion Cr. The portion between the shoulder circumferential main groove 14 and an end of the tread surface 6 located near the shoulder circumferential main groove 14 is the shoulder land portion 22. The two shoulder circumferential main grooves 14 form the crown portion Cr and the two shoulder land portions 22 in the tread 4.

[0051] 1 includes two crown land portions 24 and a crown circumferential main groove 16 located between the two crown land portions 24. The crown portion Cr is composed of one circumferential main groove 12 and two land portions 20. The crown portion Cr may be composed of only one land portion 20. The crown portion Cr may be composed of two circumferential main grooves 12 and three land portions 20. The crown portion Cr may be composed of three circumferential main grooves 12 and four land portions 20. The configuration of the crown portion CR is appropriately determined in consideration of the specifications of the tire 2. The greater the number of circumferential main grooves 12 included in the crown portion Cr, the more difficult it becomes to maintain the rigidity of the crown portion Cr at a high level. From the viewpoint of effectively reducing rolling resistance, the fewer the number of circumferential main grooves 12 included in the crown portion Cr, the more preferable. Specifically, the number of circumferential main grooves 12 included in the crown portion Cr is preferably two or less, and more preferably one or zero.

[0052] At least one circumferential narrow groove 26 is formed in the crown portion Cr of the tire 2. As described above, the crown portion Cr includes two crown land portions 24. In the tire 2, one circumferential narrow groove 26 is formed in each crown land portion 24. Two circumferential narrow grooves 26 are formed in the crown portion Cr of the tire 2. The crown circumferential main groove 16 is located between the two circumferential narrow grooves 26. In the tire 2, there is no particular limit to the number of circumferential narrow grooves 26 formed in one land portion 20 included in the crown portion Cr. Two or more circumferential narrow grooves 26 may be formed in one land portion 20. The number of circumferential narrow grooves 26 formed in one land portion 20 is appropriately determined according to the specifications of the tire 2.

[0053] Fig. 4 shows a portion of the tread surface 6 shown in Fig. 1. Fig. 4 shows the crown land portion 24. 4, the length indicated by the double arrow WLC is the maximum width of the crown land portion 24. In the crown land portion 24 of the tire 2, the ratio (WLC / TW) of the maximum width WLC to the width TW of the tread surface 6 is 17% or more and 27% or less.

[0054] In FIG. 4, the dashed dotted line LCM is the maximum width center line of the crown land portion 24. The circumferential narrow groove 26 is located on the maximum width center line LCM. In other words, the circumferential narrow groove 26 is disposed so as to overlap with the maximum width center line LCM in the radial direction. The circumferential narrow groove 26 may be provided axially inside the maximum width center line LCM, or the circumferential narrow groove 26 may be provided axially outside the maximum width center line LCM. The position of the circumferential narrow groove 26 is determined appropriately according to the specifications of the tire 2.

[0055] FIG. 5 shows a cross section of the circumferential narrow groove 26 taken along line VV in FIG. The circumferential narrow groove 26 has a pair of wall surfaces 26W including a groove mouth 26M, and a bottom surface 26B including a groove bottom 26T.

[0056] The circumferential narrow groove 26 includes, as geometric elements, a body portion 28 and a widened portion 30. The body portion 28 of the circumferential narrow groove 26 shown in FIG.

[0057] The tapered portion 32 includes the groove opening 26M of the circumferential narrow groove 26. The tapered portion 32 tapers inward from the groove opening 26M. The contour of the wall surface 26W of the tapered portion 32 shown in Fig. 5 is represented by a straight line. This contour may be represented by one or more circular arcs. The body body 34 is located radially inside the tapered portion 32. The body body 34 is continuous with the tapered portion 32. The body body 34 extends straight in the depth direction of the circumferential narrow groove 26. The contour of the wall surface 26W of the body body 34 is represented by a straight line.

[0058] The position indicated by the symbol PU in Fig. 5 is the boundary between the tapered portion 32 and the barrel main body 34. The boundary PU is represented by the intersection of the wall contour line of the tapered portion 32 and the wall contour line of the barrel main body 34. When the boundary between the tapered portion 32 and the barrel main body 34 is rounded as shown in Fig. 5, the boundary PU is represented by the intersection of an extension of the wall contour line of the tapered portion 32 and an extension of the wall contour line of the barrel main body 34.

[0059] The circumferential narrow groove 26 does not necessarily have to be provided with the tapered portion 32. In this case, the body portion 28 is composed of only the body portion main body 34. From the viewpoint of effectively suppressing the concentration of strain at the groove opening 26M of the circumferential narrow groove 26 while ensuring the groove volume of the circumferential narrow groove 26, it is preferable that the circumferential narrow groove 26 is provided with a tapered portion 32, as shown in FIG. 5.

[0060] 5, the length indicated by the double-headed arrow WD is the groove width of the body 34. The groove opening 26M of the circumferential narrow groove 26 is tapered. The groove width of the circumferential narrow groove 26 at the groove opening 26M is represented by the groove width WD of the body 34. The groove width WD of the body 34 is narrower than half the maximum groove width of the widened portion 30, which will be described later.

[0061] The widened portion 30 is located on the radially inner side of the body 28, specifically, the body main body 34. The widened portion 30 is continuous with the body main body 34. The widened portion 30 includes a groove bottom 26T of the circumferential narrow groove 26.

[0062] 5, the length indicated by the double-headed arrow WM is the maximum groove width of the widened portion 30. The position indicated by the symbol PM is the position where the widened portion 30 exhibits the maximum groove width WM. The widened portion 30 has a portion exhibiting a maximum groove width WM between the body 34 and the groove bottom 26T. The widened portion 30 has a groove width wider than the groove width WD of the body 34. 5, the widened portion 30 tapers outward from the portion showing the maximum groove width WM. In the portion from the maximum groove width position PM to the boundary PS, the widened portion 30 curves so as to recess inward from its outer side. The widened portion 30 tapers inward from the portion showing the maximum groove width WM. In the portion from the maximum groove width position PM to the groove bottom 26T, the widened portion 30 has a rounded contour. In this portion, the widened portion 30 curves so as to bulge outward from its inside. In the widened portion 30, the boundary between the portion that curves inwardly from the outside and the portion that curves outwardly from the inside is located radially outside the maximum groove width position PM.

[0063] In the circumferential narrow groove 26 of the tire 2, the contour of the portion including the maximum groove width position PM and the groove bottom 26T of the widened portion 30 is represented by a circular arc. In Fig. 5, the arrow Rh indicates the radius of the circular arc representing the contour of the portion including the maximum groove width position PM and the groove bottom 26T.

[0064] 5 is the boundary between the body main body 34 and the widened portion 30. As described above, in the cross section of the circumferential narrow groove 26, the wall surface contour line of the body main body 34 is a straight line. In the present invention, the position where the wall surface contour line of the widened portion 30 converges to the wall surface contour line of the body main body 34 is the boundary PS between the body main body 34 and the widened portion 30. Specifically, in the groove width from the body main body 34 to the widened portion 30, the position showing a groove width 1.1 times the groove width WD of the body main body 34 is represented as the boundary PS between the body main body 34 and the widened portion 30.

[0065] In FIG. 5, the length indicated by the double-headed arrow HT is the groove depth of the circumferential narrow groove 26. The length indicated by the double-headed arrow HS is the groove depth of the body portion 28. The groove depth HS is represented by the distance from the groove opening 26M to the position PS. The length indicated by the double-headed arrow HU is the groove depth of the tapered portion 32. The groove depth HU is represented by the distance from the groove opening 26M to the position PU. The length indicated by the double-headed arrow HM is the groove depth up to the portion where the widened portion 30 exhibits the maximum groove width WM. The groove depth HM is represented by the distance from the groove opening 26M to the maximum groove width position PM. The groove depth HS, the groove depth HU and the groove depth HM are measured along a line segment representing the groove depth HT of the circumferential narrow groove 26.

[0066] From the viewpoint of enabling the tire 2 to effectively suppress the concentration of strain at the groove openings 26M of the circumferential narrow grooves 26 while ensuring the groove volume of the circumferential narrow grooves 26, it is preferable that the ratio (HU / HT) of the groove depth HU of the tapered portion 32 to the groove depth HT of the circumferential narrow grooves 26 be 0.12 or greater and 0.14 or less.

[0067] As described above, the crown land portion 24 has the circumferential narrow groove 26. The circumferential narrow groove 26 divides the crown land portion 24 into two crown narrow land portions 36. Of the two crown narrow land portions 36, the crown narrow land portion 36 closer to the equatorial plane is the inner crown narrow land portion 38, and the crown narrow land portion 36 closer to the end TE of the tread surface 6 is the outer crown narrow land portion 40.

[0068] Each of the two crown narrow land portions 36 has a plurality of crown sipes 42 that traverse the crown narrow land portion 36. The plurality of crown sipes 42 divide the crown narrow land portion 36 into a plurality of crown blocks 44. The crown sipes 42 provided in the inner crown narrow portion 38 are also referred to as inner crown sipes 46. The crown blocks 44 of the inner crown narrow portion 38 are also referred to as inner crown blocks 48. The crown sipes 42 provided in the outer crown narrow portion 40 are also referred to as outer crown sipes 50. The crown blocks 44 of the outer crown narrow portion 40 are also referred to as outer crown blocks 52.

[0069] FIG. 6 shows a cross section of the inner crown sipe 46 taken along line VI-VI in FIG. The cross-sectional shape of the outer crown sipes 50 is the same as that of the inner crown sipes 46. Taking the cross-sectional shape of the inner crown sipes 46 as an example, the cross-sectional shape of the crown sipes 42 will be described.

[0070] The crown sipe 42 extends straight in the depth direction. The crown sipe 42 has a pair of wall surfaces 42W including a groove mouth 42M, and a bottom surface 42B including a groove bottom 42T. 6, the double arrow WGp indicates the groove width at the groove mouth 42M of the crown sipe 42. The double arrow DGp indicates the groove depth of the crown sipe 42. The groove width WGp of the crown sipe 42 of the tire 2 is less than 1.0 mm. When a load acts on the crown narrow land portion 36 and the crown narrow land portion 36 is deformed, the wall surfaces 42W of the crown sipes 42 come into contact with each other and support each other.

[0071] Fig. 7 shows a portion of the tread surface 6 shown in Fig. 1. Fig. 7 shows the shoulder land portion 22. The length indicated by the double arrow WLS in Fig. 7 is the maximum width of the shoulder land portion 22. In this shoulder land portion 22 of the tire 2, the ratio (WLS / TW) of the maximum width WLS to the width TW of the tread surface 6 is 15% or more and 25% or less. In FIG. 7, the dashed dotted line LSM is the center line of the maximum width of the shoulder land portion 22.

[0072] The tread 4 of the tire 2 is provided with two shoulder land portions 22. Each of the two shoulder land portions 22 has a shoulder lateral groove 54. The shoulder lateral groove 54 connects between the shoulder circumferential main groove 14 and the end TE of the tread surface 6. The shoulder lateral groove 54 crosses the shoulder land portion 22. The shoulder lateral groove 54 is inclined with respect to the axial direction. The end of the shoulder lateral groove 54 on the second end TE2 side of the tread surface 6 shown in FIG. 7 is located on the first side in the circumferential direction with respect to the end of the shoulder lateral groove 54 on the equatorial plane side. The shoulder lateral groove 54 may be configured to extend in the axial direction. The shoulder land portion 22 has a plurality of shoulder lateral grooves 54. The plurality of shoulder lateral grooves 54 form a plurality of shoulder blocks 56 in the shoulder land portion 22.

[0073] The shoulder lateral grooves 54 function as edge components. The shoulder lateral grooves 54 can contribute to improving wet performance. From this viewpoint, it is preferable that the shoulder lateral grooves 54 are inclined with respect to the axial direction.

[0074] FIG. 8 shows a cross section of the shoulder lateral groove 54 taken along line VIII-VIII in FIG. The shoulder lateral groove 54 extends straight in the depth direction. The shoulder lateral groove 54 has a pair of wall surfaces 54W including a groove mouth 54M, and a bottom surface 54B including a groove bottom 54T.

[0075] 8, the double-headed arrow WGy indicates the groove width at the groove mouth 54M of the shoulder lateral groove 54. The double-headed arrow DGy indicates the groove depth of the shoulder lateral groove 54. The groove width WGy of the shoulder lateral groove 54 of this tire 2 is 1.0 mm or more.

[0076] The shoulder lateral grooves 54 are shallower than the crown sipes 42 provided in the crown narrow land portion 36. Even though the shoulder lateral grooves 54 are provided in the shoulder land portion 22, the rigidity of the shoulder land portion 22 is appropriately maintained. From this viewpoint, it is preferable that the shoulder lateral grooves 54 are shallower than the crown sipes 42. Specifically, the ratio (DGy / DGp) of the groove depth DGy of the shoulder lateral grooves 54 to the groove depth DGp of the crown sipes 42 is preferably 0.50 or less, and more preferably 0.30 or less. From the viewpoint that the shoulder lateral grooves 54 can effectively contribute to improving wet performance, this ratio (DGy / DGp) is preferably 0.10 or more.

[0077] As shown in FIG. 7, the shoulder land portion 22 has a shoulder longitudinal groove 58 that extends continuously in the circumferential direction. FIG. 9 shows a cross section of the shoulder flute 58 taken along line IX-IX in FIG. The shoulder longitudinal groove 58 extends straight in the depth direction. The shoulder longitudinal groove 58 has a pair of wall surfaces 58W including a groove mouth 58M, and a bottom surface 58B including a groove bottom 58T. 9, a double-headed arrow WGt indicates the groove width at a groove mouth 58M of the shoulder longitudinal groove 58. A double-headed arrow DGt indicates the groove depth of the shoulder longitudinal groove 58. The groove width WGt of the shoulder longitudinal groove 58 of this tire 2 is 1.0 mm or more.

[0078] The shoulder longitudinal grooves 58 of the tire 2 are shallower than the crown sipes 42 provided in the crown narrow land portion 36. Although the shoulder longitudinal grooves 58 are provided in the shoulder land portion 22 in addition to the shoulder lateral grooves 54, the rigidity of the shoulder land portion 22 is appropriately maintained. From this viewpoint, it is preferable that the shoulder longitudinal grooves 58 are shallower than the crown sipes 42. Specifically, the ratio (DGt / DGp) of the groove depth DGt of the shoulder longitudinal grooves 58 to the groove depth DGp of the crown sipes 42 is preferably 0.50 or less, and more preferably 0.30 or less. From the viewpoint that the shoulder longitudinal grooves 58 can effectively contribute to improving wet performance, it is preferable that the ratio (DGt / DGp) is 0.10 or more.

[0079] 7, the shoulder groove 58 extends vertically through the shoulder block 56. As a result, the shoulder block 56 is formed with an inner shoulder block 60 and an outer shoulder block 62. The shoulder longitudinal groove 58 intersects with the shoulder lateral groove 54. As a result, the shoulder lateral groove 54 is formed with an inner shoulder lateral groove 64 and an outer shoulder lateral groove 66. The shoulder lateral groove 54 includes the inner shoulder lateral groove 64 and the outer shoulder lateral groove 66. The inner shoulder lateral groove 64 connects between the shoulder circumferential main groove 14 and the shoulder longitudinal groove 58. The outer shoulder lateral groove 66 connects between the shoulder longitudinal groove 58 and the edge TE of the tread surface 6.

[0080] Since the shoulder longitudinal grooves 58 intersect with the shoulder lateral grooves 54, water present between the wet road surface and the tire 2 is effectively discharged through the shoulder lateral grooves 54. This tire 2 can improve the wet performance. From this viewpoint, it is preferable that the shoulder longitudinal grooves 58 intersect with the shoulder lateral grooves 54.

[0081] As described above, at least one circumferential narrow groove 26 is formed in the crown portion CR of the tread 4. When the tread 4 comes into contact with the road surface, the crown land portion 24 included in the crown portion Cr is deformed. In the tire 2, a pair of wall surfaces 26W of the circumferential narrow groove 26 contact each other in the body portion 28 (more specifically, the body portion main body 34).

[0082] In this tire 2, when the tread 4 contacts the road surface, the crown narrow land portions 36 come into contact with each other and support each other. The circumferential narrow groove 26 increases the apparent rigidity of the crown land portion 24. The crown portion Cr includes two crown land portions 24. Since deformation of the crown portion Cr is suppressed, the tire 2 can reduce the rolling resistance and improve the wear resistance.

[0083] As described above, the circumferential narrow groove 26 has the widened portion 30 on the inside of the body portion 28. When the body portion 28 disappears due to wear, the widened portion 30 is exposed. As described above, the widened portion 30 has a groove width wider than the groove width WD of the body main body 34. The widened portion 30 of the circumferential narrow groove 26 can contribute to an increase in groove volume. The circumferential narrow groove 26 having the widened portion 30 can effectively discharge water present between the road surface and the tread surface 6 compared to a circumferential narrow groove not having the widened portion 30. Although the rigidity of the land portion 20 appears to increase due to wear, the widened portion 30 suppresses a sudden increase in rigidity, so that the tire 2 can maintain good wet performance and low rolling resistance even if the tread 4 is worn. The tire 2 can reduce the rolling resistance while suppressing deterioration of wet performance due to wear.

[0084] As described above, the circumferential narrow groove 26 increases the apparent rigidity of the crown land portion 24. Since the deformation of the crown land portion 24 is suppressed, there is a concern that the shape of the ground contact surface may change. Specifically, since the ground contact length of the crown portion Cr is shortened, the ground contact length of the shoulder portion becomes relatively longer, which may increase the risk of uneven wear. The inventors have conducted extensive research into the risk of uneven wear, focusing on the contour of the tread surface 6, and have found that the risk of uneven wear can be reduced by controlling the contact length of the shoulder portion by adjusting the radial distance from the equator to the end TE of the tread surface 6. This has led to the completion of the present invention. The technology for reducing the risk of uneven wear will be described below.

[0085] Fig. 10 shows a part of the contour line of the tire 2 in a meridian cross section of the tire 2 shown in Fig. 1. Fig. 10 shows a part of the contour line TL of the tread surface 6. In the present invention, the meridian cross section means a cross section of the tire 2 taken along a plane including the rotation axis of the tire 2. 10, the direction indicated by the double-headed arrow A represents the axial direction of the tire 2. The direction indicated by the double-headed arrow R represents the radial direction of the tire 2. The direction perpendicular to the plane of the paper in FIG.

[0086] The contour line TL shown in FIG. 10 is obtained by measuring the outer surface shape of the tire 2 in a reference state with a displacement sensor. The contour line of the outer surface of the tire 2 is formed by connecting a plurality of contour lines made of straight lines or circular arcs, assuming that there are no grooves 8, decorations, etc. in the measured outer surface shape.

[0087] Although not described in detail, the outer surface of the tire 2 is shaped by pressing an unvulcanized tire (the raw tire 2, also called a raw cover) against a cavity surface of a mold (not shown). The contour line TL of the tread surface 6 shown in Fig. 10 coincides with the contour line of the portion of the cavity surface of the mold that corresponds to the tread surface 6.

[0088] As described above, in the tread 4, the portion between a pair of shoulder circumferential main grooves 14, that is, the first shoulder circumferential main groove 14 (not shown) and the second shoulder circumferential main groove, is the crown portion Cr, and the portion between the shoulder circumferential main groove 14 and the end TE of the tread surface 6 located near the shoulder circumferential main groove 14 is the shoulder land portion 22. The tread surface 6 of the tire 2 includes a land surface 10C of the crown portion Cr and a land surface 10S of a pair of shoulder land portions 22. The contour line TL of the tread surface 6 includes a contour line of the land surface 10C of the crown portion Cr (hereinafter, crown contour line TLC) and a contour line of the land surface 10S of the pair of shoulder land portions 22 (hereinafter, shoulder contour line TLS).

[0089] The crown contour line TLC of the tire 2 bridges between an inner edge 14E1 (not shown) of the shoulder circumferential main groove 14 located on the first end TE1 side of the tread surface 6 and an inner edge 14E1 of the shoulder circumferential main groove 14 located on the second end TE2 side thereof, and includes the equator PC. The crown contour line TLC also includes the groove mouths 26M of the circumferential narrow grooves 26. On the crown contour line TLC, the equator PC is located at the outermost position in the radial direction, and the inner edge 14E1 of the shoulder circumferential main groove 14 is located at the innermost position in the radial direction. The crown contour line TLC is configured such that the distance from the rotation axis (not shown) of the tire 2 gradually decreases from the equator PC toward the inner edge 14E1. The crown contour line TLC is an arc that bulges outward. The arrow indicated by the symbol R1 in FIG. 10 indicates the radius of the crown contour line TLC. Although not shown, the center of the crown contour line TLC is located on the equatorial plane. The contour of the land surface 10C of the crown portion Cr is represented by an arc with its center on the equatorial plane.

[0090] The shoulder contour line TLS of the tire 2 bridges between the outer edge 14E2 of the shoulder circumferential main groove 14 and the end TE of the tread surface 6. In the shoulder contour line TLS, the outer edge 14E2 of the shoulder circumferential main groove 14 is located at the outermost position in the radial direction, and the end TE of the tread surface 6 is located at the innermost position in the radial direction. The shoulder contour line TLS is configured such that the distance from the rotation axis (not shown) gradually decreases from the outer edge 14E2 toward the end TE of the tread surface 6. The shoulder contour line TLS of the tire 2 is a straight line. The shoulder contour line TLS may be a circular arc. In other words, the contour of the land surface 10S of the shoulder land portion 22 is represented by a straight line or a circular arc. When the shoulder contour line TLS is a circular arc, the circular arc may be an outwardly bulging arc having a center on the inside of the tread surface 6, or an inwardly bulging arc having a center on the outside of the tread surface 6.

[0091] In the contour line TL of the tread surface 6 of the tire 2, the transition between the crown contour line TLC and the shoulder contour line TLS is located between a pair of wall surfaces 14W of the shoulder circumferential main groove 14. As shown in Fig. 10, the outer edge 14E2 of the shoulder circumferential main groove 14 is located radially inward of the inner edge 14E1. If the radial distance from the inner edge 14E1 to the outer edge 14E2, indicated by the double arrow d in Fig. 10, is 2.0 mm or less, the extension line of the crown contour line TLC and the extension line of the shoulder contour line TLS may be in contact with each other, may intersect with each other, or may be separated from each other without intersecting.

[0092] In FIG. 10, the solid line RL is a radial reference line. The radial reference line RL is a straight line extending in the radial direction through the edge TE of the tread surface 6. The solid line EXL is an extension of the crown contour line TLC, that is, an extension of the circular arc representing the contour of the land surface 10C of the crown portion CR. The position indicated by the symbol BTE is the intersection of the radial reference line RL and the extension line EXL. This intersection point BTE is the reference edge of the tread surface 6.

[0093] 10, the length indicated by the double-headed arrow D1 is the radial distance from the equator PC to the edge TE of the tread surface 6. The radial distance D1 is also called the drop amount of the tread surface 6. The length indicated by the double-headed arrow D2 is the radial distance from the equator PC to the reference edge BTE of the tread surface 6. The radial distance D2 is also called the reference drop amount of the tread surface 6. The ratio (D1 / D2) of the drop amount D1 to the reference drop amount D2 represents the position of the tread surface 6 relative to the extension line EXL and how far the tread surface 6 is from the extension line EXL. Specifically, the closer the ratio (D1 / D2) is to 1.00, the closer the tread surface 6 is to the extension line EXL. When the ratio (D1 / D2) is greater than 1.00, the tread surface 6 is located radially inside the extension line EXL. When the tread surface 6 is located radially inside the extension line EXL, the tread surface 6 is said to be located on the negative side. When the ratio (D1 / D2) is less than 1.00, the tread surface 6 is said to be located radially outside the extension line EXL. When the tread surface 6 is located radially outside the extension line EXL, the tread surface 6 is said to be located on the positive side. 6, the drop amount D1 of the tread surface 6 is smaller than the reference drop amount D2, in other words, the ratio (D1 / D2) is smaller than 1.00. Therefore, the tread surface 6 is located on the positive side.

[0094] In the tire 2, a contour line TL of the tread surface 6 in a meridian cross section includes a crown contour line TLC and a pair of shoulder contour lines TLS. The crown contour line TLC is a circular arc having a center on the equatorial plane and a radius of 400 mm or more, and each of the shoulder contour lines TLS is a circular arc having a radius of 0.002 mm or more. -1 It is a circular arc or a straight line having the following curvature: If the radius R1 of the arc of the crown contour line TLC is less than 400 mm, the roundness of the land surface 10C of the crown portion CR is emphasized, and the land surface 10C of the crown portion CR is pressed against the road surface so that the groove width is expanded rather than the circumferential narrow groove 26 is crushed. In this case, the circumferential narrow groove 26 cannot fully exert its effect. However, since the crown contour line TLC of this tire 2 is an arc having a center on the equatorial plane and a radius of 400 mm or more, the land surface 10C of the crown portion CR is pressed against the road surface so that the circumferential narrow groove 26 is crushed. The circumferential narrow groove 26 of this tire 2 can fully exert its effect. From this viewpoint, it is preferable that the crown contour line TLC is an arc having a center on the equatorial plane and a radius of 500 mm or more. Shoulder contour line TLS is 0.002mm -1 When expressed as an arc with a larger curvature, if this arc bulges outward, the land surface 10S of the shoulder land portion 22 bulges, and the volume of the shoulder land portion 22 increases. In this case, there is a risk of increased rolling resistance. On the other hand, if this arc bulges inward, the land surface 10S of the shoulder land portion 22 sinks, and the entire land surface 10S cannot come into contact with the road surface, so there is a risk of localized increase in ground contact pressure, for example, at the edge TE of the tread surface 6. In this case, there is an increased risk of uneven wear. However, the shoulder contour line TLS of this tire 2 is 0.002 mm -1 Since the shoulder contour line TLS is a circular arc or straight line having a curvature of 0.001 mm or less, the volume of the shoulder land portion 22 is appropriately maintained. Since the entire land surface 10S is in contact with the road surface, local increases in ground pressure are suppressed. Increases in rolling resistance and uneven wear caused by the shoulder land portion 22 are suppressed. From this perspective, the shoulder contour line TLS is within a range of 0.001 mm or less. -1 It is preferable that the curvature of the arc is a straight line or a circular arc. The ratio (D1 / D2) of the drop amount D1 to the reference drop amount D2 is equal to or greater than 0.60 and equal to or less than 1.70. If the ratio (D1 / D2) is less than 0.60, the contact length at the shoulder portion becomes longer, and there is a risk that the contact pressure at the end TE of the tread surface 6 increases locally. In this case, the risk of uneven wear increases. If the ratio (D1 / D2) is greater than 1.70, the contact length at the shoulder portion becomes too short, and the end TE of the tread surface 6 may become more slippery on the road surface. In this case, the risk of uneven wear also increases. However, in this tire 2, the ratio (D1 / D2) is 0.60 or more and 1.70 or less, so that this tire 2 can control the contact state of the shoulder portion so that the contact length corresponds to the contact length of the crown portion CR that has been shortened by providing the circumferential narrow groove 26. Moreover, since the widened portion 30 provided on the groove bottom 26T side of the circumferential narrow groove 26 suppresses excessive increase in the rigidity of the crown portion CR, this tire 2 can effectively control the contact state of the shoulder portion. This tire 2 can reduce the risk of uneven wear. In this respect, the ratio (D1 / D2) is preferably greater than or equal to 0.65 and less than or equal to 1.65.

[0095] As described above, the tire 2 can reduce the rolling resistance while suppressing the deterioration of wet performance due to wear. The tire 2 can reduce the rolling resistance while suppressing the deterioration of wet performance due to wear, and can also reduce the risk of uneven wear.

[0096] Figure 11 shows an example of the shape of a tire's contact patch (contact shape). In Figure 11, the direction indicated by the double-headed arrow L is the length direction of the contact patch. The length direction corresponds to the circumferential direction of the tire. The direction indicated by the double-headed arrow W is the width direction of the contact patch. The width direction corresponds to the axial direction of the tire. As described above, the contact shape is obtained by using a contact shape measuring device (not shown) to apply a normal load to a tire in a normal state, set the camber angle to 0 degrees, and bring the tire into contact with a flat road surface, and then photographing the contact surface with a camera or transferring the image. Using the schematic diagram of the ground contact shape shown in FIG. 11, an index for evaluating the ground contact shape will be explained below.

[0097] 11, the dashed dotted line CLa is a reference line indicating the center position in the width direction of the contact shape. This reference line CLa usually coincides with the equatorial plane of the tire. The position indicated by the symbol GE is the widthwise outer end of the ground contact surface. The widthwise distance from the first widthwise outer end GE to the second widthwise outer end GE is the maximum ground contact width of the ground contact surface. The length indicated by the double-headed arrow W100 is the widthwise distance from the reference line CLa to the widthwise outer end GE. This widthwise distance W100 is also called the reference width. The maximum ground contact width described above is equal to twice the reference width W100. The solid line indicated by the symbol L70 is a straight line located between the reference line CLa and the widthwise outer end GE and extending in the length direction. The length indicated by the symbol W70 is the widthwise distance from the reference line CLa to the solid line L70. In the present invention, the ratio (W70 / W100) of the widthwise distance W70 to the reference width W100 is 70%. The solid line L70 represents a position corresponding to 70% of the maximum ground contact width. The solid line indicated by the symbol L97 is located between the solid line L70 and the widthwise outer end GE, and is a straight line extending in the length direction. The length indicated by the symbol W97 is the widthwise distance from the reference line CLa to the solid line L97. In the present invention, the ratio (W97 / W100) of the widthwise distance W97 to the reference width W100 is 97%. The solid line L97 represents a position corresponding to 97% of the maximum ground contact width. The length indicated by the double-headed arrow L1 is the length of the intersection line between the solid line L97 and the ground contact shape. In the present invention, this length L1 is the length of the ground contact surface at a position corresponding to 97% of the maximum ground contact width, and is represented as the ground contact length L1. The length indicated by the double-headed arrow L2 is the length of the intersection line between the solid line L70 and the ground contact shape. In the present invention, this length L2 is the length of the ground contact surface at a position corresponding to 70% of the maximum ground contact width, and is represented as the ground contact length L2. The length indicated by the double-headed arrow L3 is the length of the intersection line between the reference line CLa and the ground contact shape. In the present invention, this length L3 is the length of the ground contact surface at the position corresponding to the center of the maximum ground contact width, and is represented as the ground contact length L3.

[0098] In the tire 2, the ratio (L2 / L1) of the contact length L2 to the contact length L1 is preferably equal to or greater than 0.90 and equal to or less than 1.10. By making the ratio (L2 / L1) 0.90 or more, the contact length of the inner part of the shoulder portion is prevented from becoming shorter relative to the contact length of the outer part, that is, the part of the edge PE of the tread surface 6. Since the local increase in contact pressure is prevented, the tire 2 can reduce the risk of uneven wear. From this viewpoint, it is more preferable that the ratio (L2 / L1) is 0.95 or more. By setting the ratio (L2 / L1) to 1.10 or less, the contact length of the inner part of the shoulder portion is prevented from becoming relatively long compared to the contact length at the edge PE of the tread surface 6. Since the shoulder land portion 22 is less likely to slip on the road surface, the risk of uneven wear can also be reduced in this case. From this perspective, it is more preferable that the ratio (L2 / L1) is 1.05 or less.

[0099] In the tire 2, the ratio (L3 / L2) of the contact length L3 to the contact length L2 is preferably equal to or greater than 1.00 and equal to or less than 1.20. By making the ratio (L3 / L2) 1.00 or more, the contact length of the crown portion Cr is prevented from becoming shorter relative to the contact length of the end PE portion of the tread surface 6. Since the crown portion Cr is less likely to slip on the road surface, the tire 2 can reduce the risk of uneven wear. From this viewpoint, it is more preferable that the ratio (L3 / L2) is 1.05 or more. By setting the ratio (L3 / L2) to 1.20 or less, the contact length of the crown portion Cr is prevented from becoming relatively longer than the contact length of the portion of the edge PE of the tread surface 6. Since a local increase in contact pressure is prevented, even in this case, the tire 2 can reduce the risk of uneven wear. From this perspective, it is more preferable that the ratio (L3 / L2) is 1.15 or less.

[0100] In the tire 2, from the viewpoint of reducing the risk of occurrence of uneven wear, the ratio (L2 / L1) is more preferably equal to or greater than 0.90 and equal to or less than 1.10, and the ratio (L3 / L2) is more preferably equal to or greater than 1.00 and equal to or less than 1.20.

[0101] As described above, when the crown land portion 24 included in the crown portion Cr is deformed, a pair of wall surfaces 26W of the circumferential narrow groove 26 contact each other in the trunk body 34. This suppresses deformation of the crown portion Cr, and reduces rolling resistance. In the tire 2, the groove width WD of the body portion 34 is preferably equal to or less than 2.5 mm. This allows the body portion 34 of the circumferential narrow groove 26 to effectively contribute to reducing rolling resistance. From this viewpoint, the groove width WD is more preferably equal to or less than 2.0 mm.

[0102] As described above, the circumferential narrow groove 26 has, on the inside of the barrel body 34 , the widened portion 30 having a groove width wider than the groove width of the barrel body 34 . In the tire 2, the ratio (WD / WM) of the groove width WD of the trunk main body 34 to the maximum groove width WM of the widened portion 30 is preferably equal to or greater than 0.10 and equal to or less than 0.40. By setting the ratio (WD / WM) to 0.10 or more, the widened portion 30 does not become too large, and its size is appropriately maintained. Since the effect of the widened portion 30 on the rigidity is suppressed, the circumferential narrow groove 26 can effectively contribute to reducing the rolling resistance. From this viewpoint, it is more preferable that the ratio (WD / WM) is 0.15 or more. By setting the ratio (WD / WM) to 0.40 or less, the widened portion 30 does not become too small, and its size is appropriately maintained. When the widened portion 30 is exposed, the widened portion 30 can effectively contribute to improving wet performance. From this viewpoint, it is more preferable that the ratio (WD / WM) is 0.35 or less.

[0103] From the viewpoint of enabling the tire 2 to reduce rolling resistance while suppressing deterioration of wet performance due to wear, it is more preferable that the groove width WD of the body 34 is 2.0 mm or less, and the ratio (WD / WM) of the groove width WD of the body 34 to the maximum groove width WM of the widened portion 30 is 0.10 or more and 0.40 or less.

[0104] In the tire 2, the position PM where the widened portion 30 shows the maximum groove width WM is preferably located between the groove bottom 26T and a position corresponding to 3 / 4 of the groove depth of the circumferential narrow groove 26. Specifically, the ratio (HM / HT) of the groove depth HM from the groove mouth 26M of the circumferential narrow groove 26 to the position PM where the widened portion 30 shows the maximum groove width WM to the groove depth HT of the circumferential narrow groove 26 is preferably 0.80 or more and 0.90 or less. By setting the ratio (HM / HT) to 0.80 or more, the widened portion 30 is disposed at an appropriate distance from the groove opening 26M. Since the length of the trunk body 34 is ensured, the circumferential narrow groove 26 can effectively contribute to reducing rolling resistance. From this viewpoint, it is more preferable that the ratio (HM / HT) is 0.82 or more. By setting the ratio (HM / HT) to be equal to or less than 0.90, the exposed widened portion 30 can effectively contribute to improving the wet performance. From this viewpoint, the ratio (HM / HT) is more preferably equal to or less than 0.88.

[0105] The groove depth HT of the circumferential narrow groove 26 of this tire 2 is the same as the groove depth DGc of the crown circumferential main groove 16, or the circumferential narrow groove 26 is shallower than the crown circumferential main groove 16. As described above, the circumferential narrow groove 26 has a widened portion 30 on the groove bottom 26T side. The widened portion 30 of the circumferential narrow groove 26 can effectively contribute to compensating for the reduced groove volume until the tread 4 wears down to a state where the tire 2 needs to be replaced (hereinafter, the end-of-wear state). This tire 2 can effectively suppress deterioration of wet performance due to wear. From this viewpoint, it is preferable that the groove depth HT of the circumferential narrow groove 26 is the same as the groove depth DGc of the crown circumferential main groove 16, or that the circumferential narrow groove 26 is shallower than the crown circumferential main groove 16. In other words, it is preferable that the ratio (HT / DGc) of the groove depth HT of the circumferential narrow groove 26 to the groove depth DGc of the crown circumferential main groove 16 is 1.0 or less. From the viewpoint that the entire circumferential narrow groove 26 does not disappear in the final stage of wear, and the widened portion 30 can effectively contribute to compensating for the reduced groove volume, it is preferable that the ratio (HT / DGc) is 0.75 or more.

[0106] The ratio (HS / HT) of the groove depth HS of the body portion 28 of the circumferential narrow groove 26 to the groove depth HT of the circumferential narrow groove 26 is preferably 0.20 or more and 0.50 or less. By setting the ratio (HS / HT) to 0.20 or more, the tire 2 can effectively suppress the influence of the widened portion 30 on the rigidity of the crown land portion 24. The circumferential narrow groove 26 can effectively contribute to increasing the apparent rigidity of the crown land portion 24. The tire 2 can further reduce the rolling resistance. From this viewpoint, it is more preferable that the ratio (HS / HT) is 0.25 or more. By setting the ratio (HS / HT) to 0.50 or less, the widened portion 30 can effectively contribute to compensating for the groove volume reduced by wear. From this viewpoint, the ratio (HS / HT) is more preferably 0.45 or less.

[0107] The circumferential narrow grooves 26 of this tire 2 are deeper than the crown sipes 42. The crown sipes 42 disappear before the circumferential narrow grooves 26. From the viewpoint of minimizing the influence on rolling resistance and wet performance due to the transition from the crown sipes 42 to the widened portions 30 of the circumferential narrow grooves 26, the ratio (DGp / HT) of the groove depth DGp of the crown sipes 42 to the groove depth HT of the circumferential narrow grooves 26 is preferably 0.30 or more, and more preferably 0.50 or more. From the same viewpoint, this ratio (DGp / HT) is preferably 0.85 or less.

[0108] In the tire 2, the crown sipes 42 are preferably deeper than the trunk portions 28 of the circumferential narrow grooves 26. This allows the tire 2 to reduce the effects on rolling resistance and wet performance caused by the transition from the crown sipes 42 to the widened portions 30 of the circumferential narrow grooves 26. From this viewpoint, it is more preferable that the ratio (HS / HT) of the groove depth HS of the trunk portions 28 of the circumferential narrow grooves 26 to the groove depth HT of the circumferential narrow grooves 26 is 0.20 or more and 0.50 or less, the ratio (DGp / HT) of the groove depth DGp of the crown sipes 42 to the groove depth HT of the circumferential narrow grooves 26 is 0.30 or more and 0.85 or less, and the crown sipes 42 are deeper than the trunk portions 28 of the circumferential narrow grooves 26.

[0109] As described above, the groove depth HT of the circumferential narrow groove 26 is the same as the groove depth DGc of the crown circumferential main groove 16, or the circumferential narrow groove 26 is shallower than the crown circumferential main groove 16. The crown sipes 42 are shallower than the crown circumferential main groove 16.

[0110] In this tire 2, the position of the shoulder circumferential main groove 14 relative to the end TE of the tread surface 6 and the position of the circumferential narrow groove 26 closest to the shoulder circumferential main groove 14 are controlled so that the circumferential narrow groove 26 can fully exert its function. 10, the length indicated by the double-headed arrow WS is the axial distance from the end TE of the tread surface 6 to the groove bottom 14T of the shoulder circumferential main groove 14. The length indicated by the double-headed arrow WH is the axial distance from the end TE of the tread surface 6 to the groove bottom 26T of the circumferential narrow groove 26.

[0111] In this tire 2, the position of the groove bottom 14T of the shoulder circumferential main groove 14 coincides with the position of half the axial distance WH from the end TE of the tread surface 6 to the groove bottom 26T of the circumferential narrow groove 26 in the axial direction, or the groove bottom 14T of the shoulder circumferential main groove 14 is preferably located axially inward of the position of half the axial distance WH. This allows the outer crown narrow land portion 40 located between the shoulder circumferential main groove 14 and the circumferential narrow groove 26 to be configured with an appropriate volume. As soon as a load is applied to the outer crown narrow land portion 40, the outer crown narrow land portion 40 is deformed, and a pair of wall surfaces 26W of the circumferential narrow groove 26 can contact with the trunk body 34. Since the deformation of the crown portion Cr is effectively suppressed, the tire 2 can reduce the rolling resistance.

[0112] In this tire 2, the outer crown narrow land portion 40 located between the shoulder circumferential main groove 14 and the circumferential narrow groove 26 does not have a longitudinal groove extending continuously in the circumferential direction. In this case, as shown in Fig. 10, it is more preferable that the groove bottom 14T of the shoulder circumferential main groove 14 is located axially inside the position of half the axial distance WH. Specifically, it is more preferable that the ratio of the axial distance WS to the axial distance WH (WS / WH) is 0.60 or more. From the viewpoint of ensuring the rigidity of the outer crown narrow land portion 40, it is preferable that this ratio (WS / WH) is 0.80 or less.

[0113] 4, the circumferential narrow groove 26 extends in a circumferential direction while meandering rather than straight. In particular, the circumferential narrow groove 26 of the tire 2 includes an inner narrow groove 68 close to the equatorial plane, an outer narrow groove 70 close to the edge TE of the tread surface 6, and a connecting narrow groove 72 connecting the inner narrow groove 68 and the outer narrow groove 70. The inner narrow groove 68 and the outer narrow groove 70 are arranged so as to overlap with the maximum width center line LCM.

[0114] Of the connecting narrow grooves 72, the connecting narrow groove 72 connecting the inner narrow groove 68 and the outer narrow groove 70 located on a first side of the inner narrow groove 68 in the circumferential direction is also called a first connecting narrow groove 72a. The connecting narrow groove 72 connecting the inner narrow groove 68 and the outer narrow groove 70 located on a second side of the inner narrow groove 68 in the circumferential direction is also called a second connecting narrow groove 72b. When a groove unit is formed by connecting the first connecting narrow groove 72a, the inner narrow groove 68, the second connecting narrow groove 72b, and the outer narrow groove 70 in this order, the circumferential narrow groove 26 is formed by connecting a plurality of such groove units in the circumferential direction. The inner narrow groove 68 and the outer narrow groove 70 are alternately arranged in the circumferential direction.

[0115] When a force acts on the crown land portion 24 and the crown land portion 24 is deformed, the wall surfaces of the circumferential narrow grooves 26 come into contact with each other in the trunk body 34. The circumferential narrow grooves 26 extend in a circumferential direction while meandering, so that the wall surfaces effectively mesh with each other. The crown narrow land portions 36 located on both sides of the circumferential narrow groove 26 constrain each other. The rigidity of the crown land portion 24 is apparently increased. The deformation of the crown land portion 24 is effectively suppressed. The tire 2 can further reduce the rolling resistance. From this viewpoint, the circumferential narrow groove 26 includes an inner narrow groove 68, an outer narrow groove 70, and a connecting narrow groove 72 connecting the inner narrow groove 68 and the outer narrow groove 70, and it is preferable that the inner narrow groove 68 and the outer narrow groove 70 are arranged alternately in the circumferential direction.

[0116] The inner crown sipes 46 shown in Figure 4 are inclined relative to the axial direction. The outer crown sipes 50 are also inclined relative to the axial direction. The crown sipes 42 are inclined relative to the axial direction. The crown sipes 42 may extend in the axial direction. The crown sipes 42 extending in the axial direction or inclined with respect to the axial direction can effectively function as edge components. The tire 2 can improve wet performance. From this viewpoint, it is preferable that the crown sipes 42 extend in the axial direction or inclined with respect to the axial direction. It is more preferable that the crown sipes 42 inclined with respect to the axial direction.

[0117] In Fig. 4, angle θuc represents the angle that the inner crown sipes 46 make with respect to the axial direction. The angle θuc is also referred to as the inclination angle of the inner crown sipes 46. Angle θsc represents the angle that the outer crown sipes 50 make with respect to the axial direction. The angle θsc is also referred to as the inclination angle of the outer crown sipes 50. From the viewpoint of allowing the inner crown sipes 46 to effectively function as edge components, the inclination angle θuc of the inner crown sipes 46 is preferably equal to or greater than 0 degrees, and more preferably equal to or greater than 5 degrees. From the same viewpoint, the inclination angle θuc is preferably equal to or less than 45 degrees. From the viewpoint of allowing the outer crown sipes 50 to effectively function as edge components, the inclination angle θsc of the outer crown sipes 50 is preferably 0 degrees or more, and more preferably 5 degrees or more. From the same viewpoint, the inclination angle θsc is preferably 45 degrees or less.

[0118] 4, the end TE side of the tread surface 6 of the inner crown sipe 46 is located on the second side in the circumferential direction relative to the equatorial plane side end of the inner crown sipe 46. The end TE side of the tread surface 6 of the outer crown sipe 50 is located on the first side in the circumferential direction relative to the equatorial plane side end of the outer crown sipe 50. The inclination direction of the inner crown sipe 46 is opposite to that of the outer crown sipe 50. In this tire 2, when a force acts on the crown land portion 24 from the equatorial plane side toward the end TE of the tread surface 6, the wall surfaces of the outer crown sipe 50 come into contact with each other and support each other. The outer crown narrow land portion 40 can effectively restrain the movement of the inner crown narrow land portion 38. This increases the apparent rigidity of the crown land portion 24. When a force acts on the crown land portion 24 from the end TE of the tread surface 6 toward the equatorial plane, the wall surfaces of the inner crown sipe 46 come into contact with each other and support each other. The inner crown narrow land portion 38 can effectively restrain the movement of the outer crown narrow land portion 40. In this case, the apparent rigidity of the crown land portion 24 also increases. In either case, the deformation of the crown land portion 24 is effectively suppressed. This tire 2 can further reduce the rolling resistance. From this viewpoint, it is preferable that the inclination direction of the crown sipe 42 in the inner crown narrow land portion 38 is opposite to the inclination direction of the crown sipe 42 in the outer crown narrow land portion 40.

[0119] From the viewpoint of effectively suppressing deterioration of wet performance due to wear while reducing rolling resistance, it is more preferable that the crown sipes 42 provided in each of the two crown narrow land portions 36 are inclined with respect to the axial direction, the direction of inclination of the inner crown sipes 46 is opposite to the direction of inclination of the outer crown sipes 50, the inner crown sipes 46 connect between the second apex 14b of the crown circumferential main groove 16 and the outer narrow groove 70 of the circumferential narrow groove 26, and the outer crown sipes 50 connect between the inner narrow groove 68 of the circumferential narrow groove 26 and the shoulder circumferential main groove 14.

[0120] 7, each of the inner shoulder lateral groove 64 and the outer shoulder lateral groove 66 is inclined with respect to the axial direction. The shoulder land portion 22 may be configured so that the inner shoulder lateral groove 64 extends in the axial direction. The shoulder land portion 22 may be configured so that the outer shoulder lateral groove 66 extends in the axial direction.

[0121] Each of the inner shoulder lateral groove 64 and the outer shoulder lateral groove 66 functions as an edge component. The shoulder lateral groove 54 having the inner shoulder lateral groove 64 and the outer shoulder lateral groove 66 can contribute to improving wet performance. From the viewpoint of improving the wet performance of the tire 2, it is preferable that the shoulder land portion 22 has a shoulder lateral groove 54 crossing the shoulder land portion 22, the shoulder lateral groove 54 includes an inner shoulder lateral groove 64 located on the equatorial plane side and an outer shoulder lateral groove 66 located on the end TE side of the tread surface 6, and that each of the inner shoulder lateral groove 64 and the outer shoulder lateral groove 66 extends in the axial direction or is inclined with respect to the axial direction.

[0122] In Figure 7, angle θuy represents the angle that the inboard shoulder lateral groove 64 makes with respect to the axial direction. The angle θuy is also referred to as the inclination angle of the inboard shoulder lateral groove 64. Angle θsy represents the angle that the outboard shoulder lateral groove 66 makes with respect to the axial direction. The angle θsy is also referred to as the inclination angle of the outboard shoulder lateral groove 66. From the viewpoint of enabling the inner shoulder lateral groove 64 to effectively function as an edge component, the inclination angle θuy of the inner shoulder lateral groove 64 is preferably 0 degrees or more, and more preferably 5 degrees or more. From the same viewpoint, the inclination angle θuy is preferably 45 degrees or less. From the viewpoint of enabling the outer shoulder lateral groove 66 to effectively function as an edge component, the inclination angle θsy of the outer shoulder lateral groove 66 is preferably 0 degrees or more, and more preferably 5 degrees or more. From the same viewpoint, the inclination angle θsy is preferably 45 degrees or less.

[0123] As shown in Fig. 7, the inclination angle θuy of the inner shoulder lateral groove 64 is larger than the inclination angle θsy of the outer shoulder lateral groove 66. This allows the shoulder lateral groove 54 as a whole to effectively function as an edge component. The tire 2 can effectively improve wet performance. From this viewpoint, it is preferable that the inclination angle θuy of the inner shoulder lateral groove 64 is larger than the inclination angle θsy of the outer shoulder lateral groove 66. In this case, it is more preferable that the shoulder lateral groove 58 is located closer to the end TE of the tread surface 6 than the maximum width center line LSM of the shoulder land portion 22.

[0124] As is clear from the above description, according to the present invention, a heavy-duty tire can be obtained that can reduce rolling resistance while suppressing deterioration of wet performance due to wear, and can also achieve a reduced risk of uneven wear. [Industrial Applicability]

[0125] The technology described above that can reduce rolling resistance while suppressing deterioration of wet performance due to wear, and can also reduce the risk of uneven wear, can be applied to various tires. [Explanation of symbols]

[0126] 2. Tires 4. Tread 6. Tread surface 8...Groove 10...land surface 12...Circumferential main groove 14. Shoulder circumferential main groove 16. Crown circumferential main groove 20... Rikubu 22. Shoulder land section 24. Crown Land Division 26... Circumferential narrow groove 28...Torso 30... Widening section 32 Tapered section 34... Body 68...Inner narrow groove 70...Outside longitudinal groove 72...Connected narrow groove

Claims

1. A tire having a tread, The outer peripheral surface of the tread includes a tread surface that comes into contact with a road surface, A plurality of land portions arranged in an axial direction are formed by forming a plurality of circumferential main grooves extending continuously in a circumferential direction in the tread, The plurality of circumferential main grooves include a pair of shoulder circumferential main grooves located outermost in the axial direction, The plurality of land portions include a pair of shoulder land portions located outermost in the axial direction, In the tread, a portion between a pair of the shoulder circumferential main grooves, that is, a first shoulder circumferential main groove and a second shoulder circumferential main groove, is a crown portion, and a portion between the shoulder circumferential main groove and an edge of the tread surface is the shoulder land portion, The crown portion has at least one circumferential groove therein; The circumferential narrow groove includes a body portion including a groove mouth of the circumferential narrow groove and a widened portion including a groove bottom of the circumferential narrow groove, The body portion includes a body main body that extends straight, The widening portion is connected to the body and has a portion that exhibits a maximum groove width between the body and the groove bottom, The tread surface includes a land surface of the crown portion and a land surface of the shoulder land portion, The intersection line between the land surface of the crown portion and the equatorial plane is the equator, In a meridian cross section of the tire, the outline of the land surface of the crown portion is represented by an arc having a center on the equatorial plane and a radius of 400 mm or more, and the outline of the land surface of the shoulder land portion is represented by an arc having a radius of 0.002 mm or more. －１ It is represented by a circular arc or a straight line having the following curvature: When an intersection point between an extension line of a circular arc representing the contour of the land surface of the crown portion and a straight line passing through an edge of the tread surface and extending in a radial direction is defined as a reference edge of the tread surface, a ratio (D1 / D2) of a radial distance D1 from the equator to the edge of the tread surface to a radial distance D2 from the equator to the reference edge of the tread surface is 0.60 or more and 1.70 or less. Heavy duty tires.

2. The groove width of the body is 2.5 mm or less, The ratio of the groove width of the body to the maximum groove width of the widening portion is 0.10 or more and 0.40 or less.

2. A heavy duty tire according to claim 1.

3. A ratio of a groove depth from a groove opening of the circumferential narrow groove to a position where the widened portion shows the maximum groove width to a groove depth of the circumferential narrow groove is 0.80 or more and 0.90 or less.

3. A heavy duty tire according to claim 2.

4. The tire is mounted on a standard rim, the internal pressure of the tire is adjusted to a standard internal pressure, a standard load is applied to the tire, and the tire is brought into contact with a flat road surface. In the contact patch obtained, the length of the contact patch at a position corresponding to 97% of the maximum contact width is the contact length L1, and the length of the contact patch at a position corresponding to 70% of the maximum contact width is the contact length L2. A ratio (L2 / L1) of the contact length L2 to the contact length L1 is 0.90 or more and 1.10 or less. The heavy duty tire according to any one of claims 1 to 3.

5. The length of the ground contact surface at a position corresponding to the center of the maximum ground contact width is a ground contact length L3, A ratio (L3 / L2) of the contact length L3 to the contact length L2 is 1.00 or greater and 1.20 or less.

5. A heavy duty tire according to claim 4.

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