tire

Abstract

To provide a tire that suppresses shoulder wear, reduces rolling resistance, and ensures traction performance on snow. [Solution] The tread portion 2 has a center land portion 31 demarcated by the outermost main groove 21 and a shoulder land portion 35 located outside the outermost main groove 21 in the tire width direction. The belt layer 14 has a circumferential belt layer 145 in which the inclination angle of the belt cord with respect to the tire circumferential direction is 5 [deg] or less. The ratio of the width CW of the center land portion 31 to the tread expansion width TW is in the range of 0.40 to 0.65. The ratio of the width SW of the shoulder land portion 35 to the value obtained by subtracting the width CW of the center land portion 31 from the tread expansion width TW and dividing by 2 is in the range of 0.50 to 0.90. The end portion 145a of the circumferential belt layer 145 in the tire width direction is located outside the outermost main groove 21 in the tire width direction and within the range of 0.90 or less of the tread expansion width TW.

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] In tires mounted on vehicles, grooves are formed in the tread portion for the purpose of ensuring various performances according to the usage mode of the tire, and a belt layer, which is a reinforcing layer, is disposed in the tread portion. In conventional tires, performance improvement has been attempted by devising the shapes of these grooves or by making improvements to the belt layer.

[0003] For example, the heavy-duty tire described in Patent Document 1 includes a circumferential belt layer, a pair of circumferential main grooves extending in the tire circumferential direction with the tire equatorial plane interposed therebetween, and a plurality of circumferential fine grooves extending in the tire circumferential direction in a central region between the pair of circumferential main grooves. The tire-width direction distance of the circumferential belt layer is larger than the tire-width direction distance between both fine grooves including the groove widths of the two circumferential fine grooves located outermost in the tire-width direction with the tire equator interposed therebetween. Further, the tire described in Patent Document 2 includes at least one high-elongation belt applied as a single cord strip on the radially outer side of the carcass and having a belt cord angle equal to 0°, and an outer tread portion provided with two or more grooves extending in the circumferential direction. The axial-direction widths of both grooves, measured in the axial direction perpendicular to the circumferential direction and parallel to the rotation axis of the tire, are less than 2 millimeters or at least equal to 2 millimeters.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In this case, a tread pattern that divides the land area of ​​the tread with circumferential grooves and centers the land area in the tire width direction can increase the rigidity of the land area located near the center in the tire width direction, thus effectively reducing rolling resistance. However, the rigidity of the land area located near the shoulder of the tread becomes relatively lower. In this case, there is a risk that uneven wear, known as shoulder wear, will occur, where the amount of wear on the land area near the shoulder is greater due to the difference in rigidity of the land areas.

[0006] Furthermore, in recent years, snow performance has sometimes been required even for rib-based tires. However, circumferential grooves can ensure rigidity on the ground surface by closing when the tire makes contact with the ground. In this way, because circumferential grooves ensure rigidity on the ground surface by closing when the tire makes contact with the ground, it becomes difficult to secure sufficient groove volume when the circumferential grooves close when the tire makes contact with the ground, which may make it difficult to ensure snow traction performance. For this reason, it has been extremely difficult to suppress shoulder wear, reduce rolling resistance, and ensure snow traction performance.

[0007] The present invention has been made in view of the above, and aims to provide a tire that can reduce rolling resistance while suppressing shoulder wear and ensuring traction performance on snow. [Means for solving the problem]

[0008] To solve the above-mentioned problems and achieve the objective, the present invention provides a tire comprising: a tread portion having a plurality of circumferential main grooves extending in the tire circumferential direction and a plurality of land portions partitioned by the circumferential main grooves; and a belt layer disposed on the tread portion and comprising a plurality of belt plies, wherein the tread portion comprises a center land portion which is a land portion partitioned by a pair of outermost circumferential main grooves, each of which is located on the outermost side in the tire width direction of the plurality of circumferential main grooves; and a shoulder land portion which is a land portion located on the outer side in the tire width direction of the outermost circumferential main grooves; wherein the center land portion is provided with a plurality of circumferential narrow grooves extending in the tire circumferential direction and a plurality of widthwise narrow grooves extending in the tire width direction; and the belt layer has an inclination of belt cords in the tire width direction with respect to the tire circumferential direction. The tire comprises a pair of cross belt layers whose directions are opposite to each other, and a circumferential belt layer positioned between the pair of cross belt layers, wherein the inclination angle of the belt cords in the tire width direction relative to the tire circumferential direction is 5 degrees or less, the center land portion having a ratio of the width of the center land portion in the tire width direction to the tread deployment width within the range of 0.40 to 0.65, the shoulder land portion having a ratio of the width of the shoulder land portion in the tire width direction to the value obtained by subtracting the width of the center land portion in the tire width direction from the tread deployment width and dividing by 2 within the range of 0.50 to 0.90, and the ends of the circumferential belt layers in the tire width direction are located outside the outermost outermost main groove in the tire width direction and within a range of 0.90 or less of the tread deployment width. [Effects of the Invention]

[0009] The tire according to the present invention has the effect of suppressing shoulder wear, reducing rolling resistance, and ensuring traction performance on snow. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a meridional cross-sectional view of a tire showing the main parts of a pneumatic tire according to an embodiment. [Figure 2] Figure 2 is a schematic diagram of the belt layer shown in Figure 1. [Figure 3] Figure 3 is a detailed view including the location near the edge of the belt layer in Figure 1. [Figure 4] Figure 4 is a plan view of the tread section shown in Figure 1. [Figure 5] Figure 5 is a cross-sectional view of AA in Figure 4. [Figure 6] Figure 6 is a cross-sectional view of BB in Figure 4. [Figure 7] Figure 7 is a detailed view of the blocks located in the land area of ​​the center shown in Figure 4. [Figure 8A] Figure 8A is a chart showing the results of performance evaluation tests for pneumatic tires. [Figure 8B] Figure 8B is a chart showing the results of performance evaluation tests for pneumatic tires. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited by these embodiments. Furthermore, the components of these embodiments include those that are substituted and obvious for substitution while maintaining the identity of the invention. In addition, the multiple modifications described in these embodiments can be arbitrarily combined within the scope of what is obvious to those skilled in the art.

[0012] [Embodiment] In the following description, the tire radial direction refers to the direction perpendicular to the tire rotation axis (not shown), which is the rotation axis of the pneumatic tire 1 of the embodiment. The inner side of the tire radial direction refers to the side toward the tire rotation axis in the tire radial direction, and the outer side of the tire radial direction refers to the side away from the tire rotation axis in the tire radial direction. The tire circumferential direction refers to the direction around the tire rotation axis as the central axis. The tire width direction refers to the direction parallel to the tire rotation axis. The inner side of the tire width direction refers to the side toward the tire equatorial plane (tire equator line) CL in the tire width direction, and the outer side of the tire width direction refers to the side away from the tire equatorial plane CL in the tire width direction. The tire equatorial plane CL is a plane perpendicular to the tire rotation axis and passing through the center of the tire width of the pneumatic tire 1. The position of the tire equatorial plane CL in the tire width direction coincides with the tire width direction center line, which is the center position of the pneumatic tire 1 in the tire width direction. The tire equator line refers to a line on the tire equatorial plane CL that runs along the tire circumferential direction of the pneumatic tire 1. Furthermore, a meridional cross-section of a tire (meridian section) refers to the cross-section obtained when the tire is cut along a plane containing the tire's axis of rotation.

[0013] Figure 1 is a meridional cross-sectional view of a pneumatic tire 1 according to an embodiment, showing the main part of the tire. In Figure 1, the meridional cross-section of the pneumatic tire 1 according to the embodiment shows a cross-section of one side region of the tire rotation axis in the tire radial direction. In this embodiment, as an example, a heavy-duty pneumatic radial tire mounted on heavy-duty vehicles such as trucks and buses will be described.

[0014] In this embodiment, the pneumatic tire 1 has a tread portion 2 located at the outermost part in the radial direction of the tire when viewed in the meridional cross-section of the tire. The tread portion 2 has a tread rubber 4 made of a rubber composition. The surface of the tread portion 2, that is, the part that comes into contact with the road surface when the vehicle (not shown) equipped with the pneumatic tire 1 is running, is formed as a tread contact surface 3, and the tread contact surface 3 constitutes a part of the contour of the pneumatic tire 1.

[0015] Shoulder portions 5 are located at both outer ends of the tread portion 2 in the tire width direction, and a sidewall portion 8 is disposed on the inner side in the tire radial direction of the shoulder portion 5. That is, the sidewall portion 8 is disposed on both sides in the tire width direction of the tread portion 2. In other words, the sidewall portion 8 is disposed at two positions on both sides in the tire width direction of the pneumatic tire 1, and forms the outermost exposed portion in the tire width direction of the pneumatic tire 1. The sidewall portion 8 has a sidewall rubber 9 made of a rubber composition.

[0016] Bead portions 10 are provided on the inner side in the tire radial direction of the respective sidewall portions 8 located on both sides in the tire width direction. The bead portions 10 are disposed at two positions on both sides of the tire equatorial plane CL, similar to the sidewall portion 8. That is, a pair of bead portions 10 are disposed on both sides in the tire width direction of the tire equatorial plane CL. Each bead portion 10 is provided with a bead core 11, and a bead filler 12 is provided on the outer side in the tire radial direction of the bead core 11.

[0017] The bead core 11 is an annular member formed by bundling bead wires, which are steel wires, into an annular shape and winding them multiple times. The bead filler 12 has a lower filler 121 and an upper filler 122, which are rubber members, and are respectively disposed on the outer side in the tire radial direction of the bead core 11 to reinforce the bead portion 10.

[0018] A carcass layer 13 enclosing cords of a radial ply is continuously provided on the inner side in the tire radial direction of the tread portion 2 and on the tire equatorial plane CL side of the sidewall portion 8. Therefore, the pneumatic tire 1 according to the present embodiment is configured as a so-called radial tire. The carcass layer 13 has a single-layer structure composed of one carcass ply or a multi-layer structure formed by laminating a plurality of carcass plies, and is bridged toroidally between a pair of bead portions 10 disposed on both sides in the tire width direction to constitute the skeleton of the tire.

[0019] More specifically, the carcass layer 13 is positioned from one bead portion 10 to the other of a pair of bead portions 10 located on both sides in the tire width direction, and is wrapped around the bead core 11 in the tire width direction outward along the bead core 11 so as to enclose the bead core 11 and the bead filler 12. The bead filler 12 is a rubber member that is positioned in the space formed on the radially outer side of the bead core 11 when the carcass layer 13 is folded back at the bead portion 10 in this way. Furthermore, the carcass ply of the carcass layer 13 is constructed by covering multiple carcass cords made of steel with a coating rubber and rolling them. The carcass cords constituting the carcass ply are arranged in parallel with an angle in the tire circumferential direction that aligns with the tire meridian direction. Specifically, the angle of the carcass cords with respect to the tire circumferential direction is within the range of 80 degrees to 90 degrees in absolute value.

[0020] In the bead portion 10, rim cushion rubber 17 is arranged on the inner side in the tire radial direction and the outer side in the tire width direction of the bead core 11 and the reversal portion of the carcass layer 13, forming the contact surface of the bead portion 10 with the rim flange. In addition, an inner liner 16 is formed along the carcass layer 13 on the inside of the carcass layer 13, or on the inner side of the carcass layer 13 in the pneumatic tire 1. The inner liner 16 forms the inner surface 18 of the tire, which is the inner surface of the pneumatic tire 1.

[0021] A belt layer 14 is arranged in the tread portion 2. Figure 2 is a schematic diagram of the belt layer 14 shown in Figure 1. Figure 3 is a detailed view including the position near the end of the belt layer 14 in Figure 1. The belt layer 14 is located on the radially outer side of the portion of the carcass layer 13 that spans between a pair of bead portions 10, specifically in the tread portion 2. The belt layer 14 is made up of multiple belt plies 141 to 145 stacked together and is arranged around the outer circumference of the carcass layer 13. The belt plies 141 to 145 include a high-angle belt 141, a pair of cross belts 142 and 143, a belt cover 144, and a circumferential belt layer 145.

[0022] The high-angle belt 141 is constructed by covering multiple belt cords made of steel wire with a coating rubber and rolling them, and has a cord angle (defined as the inclination angle of the belt cord in the longitudinal direction relative to the circumferential direction of the tire) of 45 degrees to 70 degrees in absolute value, preferably 54 degrees to 68 degrees. The high-angle belt 141 is also laminated and arranged on the radially outer side of the carcass layer 13.

[0023] The pair of cross belts 142 and 143 are constructed by covering multiple belt cords made of steel wire with coated rubber and rolling them, and have a cord angle of 10 degrees or more and 45 degrees or less in absolute value, preferably 14 degrees or more and 28 degrees or less. Furthermore, the pair of cross belts 142 and 143 have cord angles of opposite signs to each other and are laminated with the longitudinal directions of the belt cords intersecting each other (having a so-called cross-ply structure). In other words, the inclination direction of the belt cords in the tire width direction relative to the tire circumferential direction of the pair of cross belt layers 142 and 143 is opposite to that of the pair of cross belt layers 142 and 143. In addition, the pair of cross belts 142 and 143 are laminated and arranged on the outer side in the tire radial direction of the high-angle belt 141. Here, the cross belt 142 located on the inner side in the tire radial direction is defined as the inner cross belt, and the cross belt 143 located on the outer side in the tire radial direction is defined as the outer cross belt.

[0024] The belt cover 144 is constructed by covering multiple belt cover cords made of steel wire or organic fiber material with coated rubber and rolling it, and has a cord angle of 10 degrees or more and 45 degrees or less in absolute value, preferably 14 degrees or more and 28 degrees or less. The belt cover 144 is also arranged laminated on the outer side in the tire radial direction of the cross belts 142 and 143. In this embodiment, the belt cover 144 has the same cord angle as the outer cross belt 143 and is arranged as the outermost layer of the belt layer 14.

[0025] The circumferential belt layer 145 is constructed by spirally winding a belt cord made of steel wire covered with coated rubber around the tire circumferentially, and has a cord angle of 5 degrees or less in absolute value. In other words, the circumferential belt layer 145 has an inclination angle of the belt cord in the tire width direction relative to the tire circumferential direction of 5 degrees or less. The circumferential belt layer 145 is also positioned sandwiched between a pair of cross belts 142 and 143. Furthermore, the circumferential belt layer 145 is formed with a width in the tire width direction that is narrower than the width of the cross belt layers 142 and 143 in the tire width direction. For this reason, the circumferential belt layer 145 is positioned inward in the tire width direction from both ends of the pair of cross belts 142 and 143 in the tire width direction. Specifically, the circumferential belt layer 145 is formed by spirally winding one or more wires around the outer circumference of the inner cross belt 142. Furthermore, the circumferential belt layer 145 is arranged continuously in the tire width direction, straddling the tire equatorial plane CL in the tire width direction.

[0026] In this embodiment, the circumferential belt layer 145 has a number of belt cord ends, i.e., the number of belt cords per unit width, that is, within the range of 15 [cords / 50 mm] to 30 [cords / 50 mm]. The outer diameter of the belt cord is within the range of 1.2 [mm] to 2.2 [mm]. In the case where the belt cord consists of multiple twisted cords, the diameter of the circumscribed circle of the belt cord is measured as the outer diameter of the belt cord.

[0027] Figure 4 is a plan view of the tread portion 2 shown in Figure 1. The tread portion 2 has multiple circumferential main grooves 20 that extend in the circumferential direction of the tire on the tread contact surface 3, and the surface of the tread portion 2 is divided into multiple land areas 30 by the multiple circumferential main grooves 20. In this embodiment, only two circumferential main grooves 20 are provided. The two circumferential main grooves 20 are provided one on each side of the tire equatorial plane CL in the tire width direction.

[0028] The circumferential main groove 20 referred to here is a longitudinal groove extending in the circumferential direction of the tire, and has a wear indicator (slip sign) inside that indicates the end of wear. The circumferential main groove 20 formed in this way has a groove width in the range of 10.0 [mm] to 20.0 [mm] and a groove depth in the range of 10.0 [mm] to 25.0 [mm].

[0029] Note that each dimension of the tread pattern is measured in an unloaded state with the tire mounted on a specified rim and filled to the specified internal pressure. The specified rim refers to the "standard rim" specified by JATMA, the "Design Rim" specified by TRA, or the "MEASURING RIM" specified by ETRTO. The specified internal pressure refers to the "maximum air pressure" specified by JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or the "INFLATION PRESSURES" specified by ETRTO. The specified load refers to the "maximum load capacity" specified by JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or the "LOAD CAPACITY" specified by ETRTO.

[0030] The tread portion 2 has a center land portion 31, which is a land portion 30 defined by a pair of outermost outermost main grooves 21, each of which is a circumferential main groove 20 located on the outermost side in the tire width direction, and a shoulder land portion 35, which is a land portion 30 located on the outer side in the tire width direction of the outermost outermost main grooves 21. In this case, the outermost outermost main grooves 21 are circumferential main grooves 20 located on the outermost side in the tire width direction on both sides of the tire equatorial plane CL. In this embodiment, since there is one circumferential main groove 20 on each side of the tire equatorial plane CL in the tire width direction, both of the two circumferential main grooves 20 are outermost outermost main grooves 21.

[0031] The center land portion 31 of the tread portion 2 is positioned across the tire equatorial plane CL in the tire width direction, and both sides in the tire width direction are land portions 30, each demarcated by the outermost outermost main groove 21. The shoulder land portion 35 is positioned outside the outermost outermost main groove 21 in the tire width direction, and the inner side in the tire width direction is land portion 30, demarcated by the outermost outermost main groove 21. Therefore, the outermost outermost main groove 21 is a circumferential main groove 20 that separates the center land portion 31 and the shoulder land portion 35 in the tire width direction, and the center land portion 31 and the shoulder land portion 35 are positioned adjacent to each other in the tire width direction via the outermost outermost main groove 21.

[0032] Of these, the center land portion 31 has multiple circumferential grooves 40 extending in the circumferential direction of the tire. The circumferential grooves 40 do not have wear indicators and have a groove width of less than 5.0 mm. In this embodiment, two circumferential grooves 40 are provided, with one groove on each side of the tire equatorial plane CL in the tire width direction. In other words, the circumferential grooves 40 are located on both sides of the tire equatorial plane CL, between the outermost main groove 21 and the tire equatorial plane CL.

[0033] Multiple circumferential grooves 40 are arranged in the center land area 31, and as a result, the center land area 31 has multiple land area rows 32 that are partitioned by the circumferential grooves 40. Specifically, since two circumferential grooves 40 are arranged in the center land area 31, the center land area 31 has a first land area row 32a, which is a land area row 32 whose both sides in the tire width direction are partitioned by the circumferential grooves 40 and the outermost main groove 21, and a second land area row 32b, which is a land area row 32 whose both sides in the tire width direction are each partitioned by the circumferential grooves 40.

[0034] The first row of land sections 32a is a row of land sections 32 in which the inner side in the tire width direction is demarcated by circumferential narrow grooves 40 and the outer side in the tire width direction is demarcated by outermost main grooves 21, and one row of land sections 32a is located on each side of the tire equatorial plane CL in the tire width direction. The second row of land sections 32b is demarcated on both sides in the tire width direction by two circumferential narrow grooves 40 and is located straddling the tire equatorial plane CL in the tire width direction.

[0035] Furthermore, the center land section 31 is provided with multiple widthwise narrow grooves 50 extending in the tire width direction. The widthwise narrow grooves 50 have a groove width of less than 5.0 [mm]. The widthwise narrow grooves 50 include a first widthwise narrow groove 51 located in the first land section row 32a and a second widthwise narrow groove 52 located in the second land section row 32b.

[0036] The first widthwise narrow groove 51 positioned in the first row of land sections 32a has one end communicating with the circumferential narrow groove 40 and the other end communicating with the outermost main groove 21. Therefore, the first row of land sections 32a has multiple blocks 33, each partitioned on both sides in the tire circumferential direction by the first widthwise narrow groove 51. In other words, the center land section 31 has multiple blocks 33 partitioned by the circumferential narrow groove 40 and the widthwise narrow groove 50.

[0037] Multiple blocks 33 in the first row of land sections 32a are arranged in the circumferential direction of the tire via a first widthwise narrow groove 51. Thus, the first widthwise narrow groove 51, which is arranged in the first row of land sections 32a and demarcates the blocks 33, is formed in a crank shape that extends in the tire width direction and bends at two points.

[0038] The second widthwise narrow groove 52 located in the second land section row 32b has one end communicating with the circumferential narrow groove 40 and the other end terminating within the second land section row 32b. Furthermore, the second widthwise narrow groove 52 located in the second land section row 32b has a second widthwise narrow groove 52 that communicates with one of the two circumferential narrow grooves 40 that demarcate the second land section row 32b, and a second widthwise narrow groove 52 that communicates with the other circumferential narrow groove 40.

[0039] Since one end of the second widthwise groove 52 terminates within the second land section row 32b, the second land section row 32b on which the second widthwise groove 52 is located is formed in a rib-like shape that extends continuously in the circumferential direction of the tire. The second widthwise groove 52 has an opening to the circumferential groove 40 that faces the opening to the circumferential groove 40 in the first widthwise groove 51 located in the first land section row 32a, and a second widthwise groove 52 that does not face the opening to the circumferential groove 40 in the first widthwise groove 51.

[0040] Multiple second widthwise grooves 52 communicating with a single circumferential groove 40 are arranged alternately in the tire circumferential direction, with some second widthwise grooves 52 facing the opening to the circumferential groove 40 in the first widthwise groove 51 located in the first land section row 32a, and others second widthwise grooves 52 that do not face the opening to the circumferential groove 40. The second widthwise grooves 52 facing the opening to the circumferential groove 40 in the first widthwise groove 51 are longer in length than the second widthwise grooves 52 that do not face the opening to the circumferential groove 40 in the first widthwise groove 51.

[0041] Furthermore, the second row of land sections 32b has multiple internal grooves 60, each with a groove width of less than 5.0 mm. The internal grooves 60 are arranged in a relatively short length, extending in the circumferential direction of the tire, with both ends in the longitudinal direction terminating within the second row of land sections 32b. The multiple internal grooves 60 are spaced apart from each other and arranged side by side in the circumferential direction of the tire. Each of the multiple internal grooves 60 extends in the circumferential direction of the tire and is inclined in the tire width direction relative to the circumferential direction, with the direction of inclination in the tire width direction relative to the circumferential direction being opposite for adjacent internal grooves 60 in the circumferential direction of the tire.

[0042] The inner groove 60 of the land section is located near the center in the tire width direction of the second row of land sections 32b and is positioned on the tire equatorial plane CL. The inner groove 60 is formed with a length in the tire circumferential direction that is shorter than the pitch in the tire circumferential direction of the second widthwise grooves 52 which are arranged in multiple locations in the second row of land sections 32b, and is positioned in the tire circumferential direction between adjacent second widthwise grooves 52 in the tire circumferential direction.

[0043] Figure 5 is a cross-sectional view of Figure 4, AA. The circumferential narrow groove 40 has a groove width W1 within the range of 0.5 [mm] to 2.0 [mm]. The circumferential narrow groove 40 also has a groove depth D1 of 10 [mm] or more, and a groove depth D1 that is less than or equal to the groove depth of the circumferential main groove 20. Preferably, the groove width W1 of the circumferential narrow groove 40 is within the range of 0.5 [mm] to 1.8 [mm].

[0044] Figure 6 is a cross-sectional view of BB in Figure 4. The widthwise narrow groove 50 has a groove width W2 within the range of 0.5 [mm] to 4.0 [mm]. The widthwise narrow groove 50 also has a groove depth D2 of 1 [mm] or more, and a groove depth D2 that is less than or equal to the groove depth D1 of the circumferential narrow groove 40. Preferably, the groove width W2 of the widthwise narrow groove 50 is within the range of 1.0 [mm] to 4.0 [mm].

[0045] Furthermore, as shown in Figure 4, multiple decorative grooves 65 are arranged on the shoulder land portion 35. The decorative grooves 65 are formed in a triangular shape in plan view. Multiple decorative grooves 65 are arranged in a row along the circumferential direction of the tire. Some of the multiple decorative grooves 65 arranged on the shoulder land portion 35 communicate with the outermost main groove 21, while others are arranged independently within the shoulder land portion 35. The depth of the decorative grooves 65 is within the range of 0.5 [mm] to 5.0 [mm].

[0046] The center land portion 31, which is demarcated on both sides in the tire width direction by the outermost outermost main groove 21, has a ratio of the width CW of the center land portion 31 in the tire width direction to the tread deployment width TW that is within the range of 0.40 to 0.65. Preferably, the ratio of the width CW of the center land portion 31 to the tread deployment width TW is within the range of 0.45 to 0.60. Furthermore, the center land portion 31 is positioned so that its center in the tire width direction is substantially located on the tire equatorial plane CL.

[0047] The tread width TW referred to here is the dimension obtained by unfolding the contact edges T on both sides of the tread contact surface 3 in the tire width direction. The contact edge T is defined as the position of the maximum width in the tire width direction at the contact surface between the pneumatic tire 1 and the flat plate when the pneumatic tire 1 is mounted on a specified rim, a specified internal pressure is applied, and the tire is placed perpendicular to the flat plate and a load corresponding to a specified load is applied. In this embodiment, the contact edge T is at substantially the same position as the shoulder portion 5. Furthermore, the width CW of the center land portion 31 in the tire width direction is the dimension obtained by unfolding the distance between the inner ends in the tire width direction at the openings of the two outermost main grooves 21 that divide both sides of the center land portion 31 in the tire width direction.

[0048] Furthermore, the ratio of the width SW of the shoulder portion 35 in the tire width direction to the value obtained by subtracting the width CW of the center portion 31 in the tire width direction from the tread width TW and dividing by 2 is within the range of 0.50 to 0.90. In other words, the width SW of the shoulder portion 35 satisfies the following equation (1). 0.50 ≤ Shoulder width (35mm) / {(Tread width TW - Center width (31mm)) / 2} ≤ 0.90 ... (1)

[0049] In this case, the value obtained by subtracting the width CW of the center land portion 31 in the tire width direction from the tread width TW and dividing by 2 is, in other words, the width DW (see Figure 4) in the tire width direction between the end of the center land portion 31 in the tire width direction and the contact end T. Therefore, the ratio of the width SW of the shoulder land portion 35 to the width DW is within the range of 0.50 to 0.90. Preferably, the ratio of the width SW of the shoulder land portion 35 to the width DW is within the range of 0.55 to 0.85.

[0050] Furthermore, in the case of a row of land sections 32 having multiple center land sections 31, the ratio of the width CWa of each land section 32 in the tire width direction to the width CW of the center land section 31 in the tire width direction is within the range of 0.1 to 0.49. Note that in the case of a row of land sections 32 having multiple center land sections 31, the width CWa in the tire width direction may differ from one another to the other. In addition, it is preferable that the ratio of the width CWa of the land section 32 in the tire width direction to the width CW of the center land section 31 in the tire width direction is within the range of 0.25 to 0.45.

[0051] Furthermore, the circumferential belt layer 145 (see Figure 3) of the belt layer 14 arranged in the tread portion 2 has an end 145a in the tire width direction that is located outside the outermost main groove 21 in the tire width direction. In addition, the end 145a of the circumferential belt layer 145 in the tire width direction is located within a range of 0.90 or less of the tread development width TW. Preferably, the end 145a of the circumferential belt layer 145 in the tire width direction is located within a range of 0.80 or less of the tread development width TW.

[0052] Figure 7 is a detailed view of the blocks 33 that the center land section 31 has as shown in Figure 4. The blocks 33 that the center land section 31 has multiple of are such that the ratio of the width BW of the block 33 in the tire width direction to the pitch P in the tire circumferential direction between adjacent widthwise narrow grooves 50 in the tire circumferential direction is within the range of 0.3 to 3.0. In this embodiment, since the blocks 33 are arranged in the first land section row 32a, the ratio of the width BW of the block 33 in the tire width direction to the pitch P in the tire circumferential direction between adjacent first widthwise narrow grooves 51 in the tire circumferential direction is within the range of 0.3 to 3.0.

[0053] In this case, the width BW of block 33 in the tire width direction is substantially the same as the width CWa of the land section row 32 in the tire width direction where block 33 is arranged. Furthermore, the ratio of the width BW of block 33 to the pitch P of the narrow groove 50 in the width direction is preferably within the range of 0.7 to 2.0.

[0054] When mounting the pneumatic tire 1 according to this embodiment onto a vehicle, the pneumatic tire 1 is mounted onto a rim wheel, and then inflated by filling it with air before mounting it on the vehicle. When a vehicle equipped with the pneumatic tire 1 is driven, the pneumatic tire 1 rotates while the lower part of the tread contact surface 3 of the tread portion 2 contacts the road surface. When a vehicle equipped with the pneumatic tire 1 is driven on a dry road surface, it is driven mainly by the frictional force between the tread contact surface 3 and the road surface, which transmits driving force and braking force to the road surface and generates turning force.

[0055] Furthermore, when driving on a wet road surface, water between the tread contact surface 3 and the road surface enters grooves such as the circumferential main grooves 20, circumferential narrow grooves 40, and lateral narrow grooves 50, and these grooves drain the water between the tread contact surface 3 and the road surface as the vehicle drives. As a result, the tread contact surface 3 makes contact with the road surface more easily, and the frictional force between the tread contact surface 3 and the road surface allows the vehicle to drive.

[0056] Furthermore, the tread portion 2 is divided into a center land portion 31 and a shoulder land portion 35 by multiple circumferential main grooves 20, and the circumferential grooves located in the center land portion 31 are circumferential narrow grooves 40, thus ensuring the rigidity of the center land portion 31. In other words, when the center land portion 31 makes contact with the ground and a load is applied to the center land portion 31, the circumferential narrow grooves 40 close, allowing the land portion rows 32 divided by the circumferential narrow grooves 40 to come into contact with each other. As a result, when the center land portion 31 makes contact with the ground, the land portion rows 32 can support each other, thereby increasing the rigidity of the center land portion 31. This ensures the rigidity of the tread portion 2 closer to the center in the tire width direction, which is prone to receiving large loads when the vehicle is running. Consequently, deformation of the land portion 30 when the vehicle is running can be suppressed, and rolling resistance caused by deformation of the land portion 30 can be reduced.

[0057] Furthermore, since multiple narrow grooves 50 extending in the tire width direction are arranged in the center land portion 31, it is possible to ensure the rigidity of the center land portion 31 while also ensuring an edge component in the tire circumferential direction. This makes it possible to reduce rolling resistance while ensuring snow traction performance, which is the traction performance on snowy road surfaces.

[0058] Furthermore, the ratio of the width CW of the center land portion 31 in the tire width direction to the tread width TW is within the range of 0.40 to 0.65, which allows for ensuring the rigidity of the center land portion 31 while suppressing the rigidity difference between the center land portion 31 and the shoulder land portion 35 from becoming too large. In other words, if the ratio of the width CW of the center land portion 31 to the tread width TW is less than 0.40, the width CW of the center land portion 31 is too narrow, making it difficult to ensure the rigidity of the center land portion 31 and potentially making it difficult to reduce rolling resistance.

[0059] Furthermore, if the ratio of the width CW of the center landing area 31 to the tread width TW is greater than 0.65, the width CW of the center landing area 31 is too wide, which may cause the width SW of the shoulder landing area 35 to become relatively too narrow. In this case, the rigidity of the shoulder landing area 35 will be reduced, and shoulder wear, a type of uneven wear where the amount of wear on the shoulder landing area 35 increases due to the difference in rigidity between the center landing area 31 and the shoulder landing area 35, may be more likely to occur.

[0060] In contrast, if the ratio of the width CW of the center landing area 31 to the tread width TW is within the range of 0.40 to 0.65, the width SW of the shoulder landing area 35 becomes narrower, which can prevent the difference in rigidity between the center landing area 31 and the shoulder landing area 35 from becoming too large, while still ensuring the rigidity of the center landing area 31. This makes it possible to reduce rolling resistance while suppressing shoulder wear.

[0061] Furthermore, the ratio of the width SW of the shoulder land portion 35 in the tire width direction to the value obtained by subtracting the width CW of the center land portion 31 from the tread deployment width TW and dividing by 2 is within the range of 0.50 to 0.90. This ensures that the groove width of the outermost main groove 21 is maintained while suppressing the excessive difference in rigidity between the center land portion 31 and the shoulder land portion 35. In other words, if the value of the width SW of the shoulder land portion 35 / {(tread deployment width TW - width CW of the center land portion 31) / 2} is less than 0.5, the width SW of the shoulder land portion 35 is too narrow, which may result in excessively low rigidity of the shoulder land portion 35. In this case, the difference in rigidity between the center land portion 31 and the shoulder land portion 35 tends to become large, which may increase the likelihood of shoulder wear due to the difference in rigidity.

[0062] Furthermore, if the value of the width SW of the shoulder land area 35 / {(tread width TW - width CW of the center land area 31) / 2} is greater than 0.9, the width SW of the shoulder land area 35 will become too wide, which may make it difficult to secure the groove width of the outermost main groove 21 that demarcates the shoulder land area 35. In this case, the amount of water that enters the outermost main groove 21 when driving on a wet road surface, and the amount of snow that enters the outermost main groove 21 when driving on a snowy road surface will decrease, which may make it difficult to secure wet performance, which is the driving performance on a wet road surface, and snow performance, which is the driving performance on a snowy road surface.

[0063] In contrast, if the value of the width SW / {(tread width TW - width CW of the center land area 31) / 2} of the shoulder land area 35 is within the range of 0.50 to 0.90, it is possible to suppress the groove width of the outermost main groove 21 from becoming too narrow, thereby ensuring the groove width of the outermost main groove 21, while also suppressing the rigidity difference between the center land area 31 and the shoulder land area 35 from becoming too large. This makes it possible to suppress shoulder wear while ensuring wet performance and snow performance.

[0064] Here, when a vehicle equipped with a pneumatic tire 1 is in motion, the tread contact surface 3 is in contact with the road surface as it moves, so the tread portion 2 gradually wears down from the tread contact surface 3 side on the land portion 30. At that time, the portion of the tread contact surface 3 near the center in the tire width direction tends to have its outer diameter increased by centrifugal force when the pneumatic tire 1 rotates, making it easier for it to make contact with the road under high ground pressure.

[0065] On the other hand, the contact pressure in the area of ​​the tread contact surface 3 near the shoulder portion 5 tends to be lower due to the difference in outer diameter between this area and the area near the center in the tire width direction. Therefore, in the area of ​​the tread contact surface 3 near the shoulder portion 5, slippage is more likely to occur between this area and the road surface due to the difference in contact pressure caused by the difference in outer diameter between this area and the area near the center in the tire width direction when the pneumatic tire 1 rotates, and wear is relatively more likely to occur. In other words, shoulder wear is also likely to occur due to the difference in contact pressure caused by the difference in outer diameter between the area near the center in the tire width direction and the area near the shoulder portion 5 in the tread contact surface 3.

[0066] In contrast, in the pneumatic tire 1 according to this embodiment, the belt layer 14 has a circumferential belt layer 145 positioned between a pair of intersecting belt layers 142 and 143, with a belt cord inclination angle of 5 degrees or less. Therefore, the belt layer 14 can suppress elongation in the tire circumferential direction in the area where the circumferential belt layer 145 is positioned in the tire width direction, and the circumferential belt layer 145 can suppress the increase in outer diameter when the pneumatic tire 1 rotates. As a result, the occurrence of shoulder wear caused by the increase in outer diameter near the center in the tire width direction when the pneumatic tire 1 rotates can be suppressed.

[0067] Furthermore, the circumferential belt layer 145 has an end 145a in the tire width direction that is located outside the outermost main groove 21 in the tire width direction, and within a range of 0.90 or less of the tread width TW, thus more reliably suppressing the occurrence of shoulder wear. In other words, if the end 145a of the circumferential belt layer 145 is located inside the outermost main groove 21 in the tire width direction, the width of the circumferential belt layer 145 in the tire width direction is too narrow, which may make it difficult to suppress the increase in the outer diameter of the portion near the center of the tread contact surface 3 in the tire width direction when the pneumatic tire 1 rotates. In this case, it becomes difficult to reduce the difference in outer diameter between the portion near the center in the tire width direction and the portion near the shoulder 5 when the pneumatic tire 1 rotates, and it becomes difficult to reduce the difference in contact pressure between the two portions, which may make it difficult to obtain the effect of suppressing shoulder wear by arranging the circumferential belt layer 145.

[0068] Furthermore, if the end portion 145a of the circumferential belt layer 145 is located outside the range of 0.90 of the tread width TW, the width of the circumferential belt layer 145 in the tire width direction becomes wider, making it easier for the range in which the rigidity of the tread portion 2 is improved by the circumferential belt layer 145 to extend to the vicinity of the shoulder portion 5. In this case, the shoulder land portion 35 can also withstand a large load, but in the portion of the shoulder land portion 35 near the shoulder portion 5 where the circumferential belt layer 145 is not placed, the load on the rigidity may become too large, making it prone to wear and potentially making it difficult to suppress the occurrence of shoulder wear.

[0069] In contrast, if the end portion 145a of the circumferential belt layer 145 is located outside the outermost main groove 21 in the tire width direction and within a range of 0.90 or less of the tread width TW, then it is possible to suppress excessive load on rigidity in the area near the shoulder portion 5 of the shoulder land area 35 where the circumferential belt layer 145 is not placed, while improving the rigidity near the center in the tire width direction with the circumferential belt layer 145. As a result, both shoulder wear caused by the difference in the outer diameter of the tread contact surface 3 during rotation of the pneumatic tire 1 and shoulder wear caused by excessive load on rigidity near the shoulder portion 5 can be suppressed.

[0070] Furthermore, since the circumferential grooves 40 have a groove width W1 within the range of 0.5 [mm] to 2.0 [mm], rolling resistance can be reduced while ensuring wet performance and snow performance. In other words, if the groove width W1 of the circumferential grooves 40 is less than 0.5 [mm], the groove width W1 of the circumferential grooves 40 is too narrow, which may reduce the amount of water that enters the circumferential grooves 40 when driving on a wet road surface, and the amount of snow that enters the circumferential grooves 40 when driving on a snowy road surface, making it difficult to ensure wet performance and snow performance. Also, if the groove width W1 of the circumferential grooves 40 is greater than 2.0 [mm], the groove width W1 of the circumferential grooves 40 is too wide, which may make it difficult for the circumferential grooves 40 to close when the center land portion 31 makes contact. In this case, the land portion rows 32 may not make contact with each other when the center land portion 31 makes contact, which may make it difficult to increase the rigidity of the center land portion 31.

[0071] In contrast, if the groove width W1 of the circumferential groove 40 is within the range of 0.5 [mm] to 2.0 [mm], the circumferential groove 40 can be closed when the center land area 31 makes contact with the ground, while maintaining the groove width W1 of the circumferential groove 40, thereby increasing the rigidity of the center land area 31. As a result, rolling resistance can be reduced while maintaining wet performance and snow performance.

[0072] Furthermore, since the widthwise narrow grooves 50 have a groove width W2 within the range of 0.5 [mm] to 4.0 [mm], rolling resistance can be reduced more reliably, and traction performance on snow can be ensured. In other words, if the groove width W2 of the widthwise narrow grooves 50 is less than 0.5 [mm], the groove width W2 of the widthwise narrow grooves 50 is too narrow, making it difficult for snow to enter the widthwise narrow grooves 50 when driving on a snowy road surface, which may make it difficult to ensure traction performance on snow. Also, if the groove width W2 of the widthwise narrow grooves 50 is greater than 4.0 [mm], the groove width W2 of the widthwise narrow grooves 50 is too wide, which may easily reduce the rigidity of the center land area 31 where the widthwise narrow grooves 50 are located. In this case, the center land area 31 is more likely to deform when it makes contact with the ground, which may easily worsen rolling resistance.

[0073] In contrast, if the groove width W2 of the lateral narrow groove 50 is within the range of 0.5 [mm] to 4.0 [mm], it is possible to maintain the groove width W2 of the lateral narrow groove 50 while suppressing a decrease in the rigidity of the center land area 31 where the lateral narrow groove 50 is located. This suppresses deformation of the center land area 31 when it makes contact with the ground, and makes it easier for snow to enter the lateral narrow groove 50 when driving on a snowy road surface. As a result, rolling resistance can be reduced more reliably, and traction performance on snow can be ensured.

[0074] Furthermore, since the circumferential grooves 40 have a groove depth D1 of 10 mm or more, rolling resistance can be reduced more reliably. In other words, if the groove depth D1 of the circumferential grooves 40 is less than 10 mm, the groove depth D1 of the circumferential grooves 40 is too shallow, and there is a risk that the circumferential grooves 40 will not close properly when the center land portion 31 on which the circumferential grooves 40 are located makes contact with each other. In this case, there is a risk that the land portion rows 32 will not make contact with each other when the center land portion 31 makes contact with each other, and therefore it will be difficult to increase the rigidity of the center land portion 31.

[0075] In contrast, if the circumferential groove 40 has a groove depth D1 of 10 mm or more, the circumferential groove 40 is more likely to close when the center land area 31 on which the circumferential groove 40 is located makes contact with the ground, thereby increasing the rigidity of the center land area 31. As a result, rolling resistance can be reduced more reliably.

[0076] Furthermore, since the widthwise narrow grooves 50 have a groove depth D2 of 1 [mm] or more, they can more reliably reduce rolling resistance and ensure traction performance on snow. In other words, if the groove depth D2 of the widthwise narrow grooves 50 is less than 1 [mm], the groove depth D2 of the widthwise narrow grooves 50 is too shallow, making it difficult to ensure a sufficient amount of snow to enter the widthwise narrow grooves 50 when driving on a snowy road surface, which may make it difficult to ensure traction performance on snow. Also, if the groove depth D2 of the widthwise narrow grooves 50 is less than 1 [mm], the groove depth D2 of the widthwise narrow grooves 50 is too shallow, which may make it difficult for the widthwise narrow grooves 50 to close when the center land area 31 on which the widthwise narrow grooves 50 are located makes contact with the ground.

[0077] In contrast, if the widthwise narrow groove 50 has a groove depth D2 of 1 mm or more, it is possible to ensure that a sufficient amount of snow enters the widthwise narrow groove 50 when driving on a snowy road surface. Also, if the widthwise narrow groove 50 has a groove depth D2 of 1 mm or more, the portion of the widthwise narrow groove 50 near the bottom of the groove is more likely to close when the center land area 31 on which the widthwise narrow groove 50 is located makes contact with the ground, thereby increasing the rigidity of the center land area 31. As a result, rolling resistance can be reduced more reliably, and traction performance on snow can be ensured.

[0078] Furthermore, in the center land area 31, the multiple rows of land areas 32 partitioned by the circumferential grooves 40 have a ratio of width CWa of the land area 32 to width CW of the center land area 31 that is within the range of 0.1 to 0.49, thus ensuring wet performance and snow performance while reducing rolling resistance. In other words, if the ratio of width CWa of the land area 32 to width CW of the center land area 31 is less than 0.1, the width CWa of the land area 32 is too narrow, which may make it difficult to ensure the rigidity of the land area 32. In this case, the amount of deformation of the land area 32 when the center land area 31 makes contact with the ground will be large, which may make it difficult to reduce rolling resistance. Also, if the ratio of width CWa of the land area 32 to width CW of the center land area 31 is greater than 0.49, the width CWa of the land area 32 is too wide, which may result in an area of ​​the center land area 31 where the circumferential grooves 40 are not provided becoming too large. In this case, it may become difficult to ensure drainage in the circumferential grooves 40 on the center land section 31, and the amount of snow that enters the circumferential grooves 40 when driving on a snowy road surface may decrease, which could make it difficult to ensure wet performance and snow performance.

[0079] In contrast, if the ratio of the width CW of the center land area 31 to the width CW of the land area row 32 is within the range of 0.1 to 0.49, it is possible to ensure the rigidity of the land area row 32 while suppressing the widening of the area in the center land area 31 where the circumferential grooves 40 are not arranged. This reduces the amount of deformation of the land area row 32 when the center land area 31 makes contact with the ground, while ensuring drainage in the circumferential grooves 40 in the center land area 31 and making it easier for snow to enter the circumferential grooves 40 when driving on a snowy road surface. As a result, it is possible to reduce rolling resistance while ensuring wet performance and snow performance.

[0080] Furthermore, the center land portion 31 has multiple blocks 33 demarcated by circumferential narrow grooves 40 and lateral narrow grooves 50, and the ratio of the width BW of the block 33 to the pitch P of adjacent lateral narrow grooves 50 in the tire circumferential direction is within the range of 0.3 to 3.0, so that rolling resistance can be reduced more reliably. In other words, if the ratio of the width BW of the block 33 to the pitch P of the lateral narrow grooves 50 is less than 0.3, there is a risk that the width BW of the block 33 will be too narrow relative to the length of the block 33 in the tire circumferential direction. In this case, it becomes difficult to ensure the rigidity of the block 33 in the tire width direction, and the block 33 will be more prone to deformation when the center land portion 31 makes contact with the ground, so there is a risk that rolling resistance will be difficult to reduce. Also, if the ratio of the width BW of the block 33 to the pitch P of the lateral narrow grooves 50 is greater than 3.0, there is a risk that the length of the block 33 in the tire circumferential direction will be too short relative to the width BW of the block 33. In this case, it becomes difficult to ensure the rigidity of the blocks 33 in the circumferential direction of the tire, and the blocks 33 are more likely to deform when the center ground portion 31 makes contact with the ground, which may make it difficult to reduce rolling resistance.

[0081] In contrast, when the ratio of the width BW of the block 33 to the pitch P of the narrow groove 50 in the width direction is within the range of 0.3 to 3.0, the rigidity of the block 33 in the tire width direction and tire circumferential direction can be appropriately ensured, and the amount of deformation of the block 33 when the center land portion 31 makes contact with the ground can be reduced. As a result, rolling resistance can be reduced more reliably.

[0082] [Differentiation] In the embodiment described above, the number of circumferential main grooves 20 arranged in the tread portion 2 is two, but there may be other than two circumferential main grooves 20. For example, a circumferential main groove 20 different from the outermost main grooves 21 may be arranged between the two outermost main grooves 21.

[0083] Furthermore, in the embodiment described above, two circumferential grooves 40 are arranged on the center land portion 31, but the number of circumferential grooves 40 arranged on the center land portion 31 may be other than two. The number of circumferential grooves 40 arranged on the center land portion 31 may be one, three or more.

[0084] Furthermore, in the embodiment described above, the block 33, which is partitioned by the circumferential groove 40 and the widthwise groove 50 in the center land area 31, is present in the first land area row 32a, but the block 33 may be present in all land area rows 32 of the center land area 31.

[0085] Furthermore, although the above-described embodiment used a pneumatic tire 1 as an example of a tire according to the present invention, the tire according to the present invention may be other than a pneumatic tire 1. The tire according to the present invention may be, for example, a so-called airless tire that can be used without filling with gas.

[0086] [Examples] Figures 8A and 8B are charts showing the results of performance evaluation tests for pneumatic tires. Below, we will describe the performance evaluation tests conducted on the above-mentioned pneumatic tire 1, comparing it with a conventional pneumatic tire, the pneumatic tire 1 according to the present invention, and a comparative example pneumatic tire used for comparison with the pneumatic tire 1 according to the present invention. The performance evaluation tests included tests for snow traction performance, rolling resistance performance, and shoulder wear resistance performance.

[0087] The performance evaluation test was conducted by mounting a pneumatic tire 1, with a nominal size of 385 / 65R22.5 as defined by ETRTO, onto a rim wheel with a specified rim size of 22.5”×11.75” as defined by ETRTO, adjusting the air pressure to the maximum air pressure (900kPa) as defined by ETRTO, and then mounting it on a trailer axle and conducting a real-world test under the maximum load (49.03kN) as defined by ETRTO.

[0088] The evaluation method for each test item was as follows: For snow traction performance, the evaluation was conducted in accordance with UN R117-04 (UN Regulation No. 117 Revision 4). The distance required to accelerate from the specified initial speed to the terminal speed on a snowy road surface was measured using a test vehicle equipped with the test tire, and the acceleration was calculated. Snow traction performance was evaluated by expressing the calculated acceleration as an index with the conventional example described later set to 100. A higher value indicates better acceleration performance on snowy roads and higher snow traction performance. In addition, a snow traction performance index of 96 or higher is considered to maintain a level comparable to the conventional example, and snow traction performance that is in no way inferior to the conventional example is ensured.

[0089] Furthermore, evaluation tests for rolling resistance performance were conducted in accordance with UN R117-04 (UN Regulation No. 117 Revision 4), measuring the average rolling resistance coefficient (ratio of rolling resistance to load on the test tire) in both forward and reverse directions at a speed of 80 km / h and a specified load of 85%. The evaluation of rolling resistance performance was performed by expressing the measured rolling resistance coefficient as an index with the conventional example described later set to 100. A higher value indicates lower rolling resistance and superior rolling resistance performance.

[0090] Furthermore, the evaluation test for shoulder wear resistance was conducted by measuring the difference between the wear amount of the groove located closest to the tire's equatorial plane CL and the wear amount of the outermost main groove 21 after a test vehicle equipped with the test tire has traveled 100,000 km. Shoulder wear resistance was evaluated by expressing the measured shoulder wear as an index with the conventional example described later set to 100. A larger index indicates less shoulder wear and superior shoulder wear resistance.

[0091] Performance evaluation tests were conducted on 24 types of pneumatic tires, including a conventional pneumatic tire (an example of a conventional pneumatic tire), Examples 1 to 17 (pneumatic tire 1 according to the present invention), and Comparative Examples 1 to 6 (pneumatic tires compared to pneumatic tire 1 according to the present invention). Of these, the conventional pneumatic tire and Comparative Examples 1 to 3 all lacked a circumferential belt layer, differing only in the presence or absence of circumferential and widthwise narrow grooves located in the center land area. Furthermore, although the pneumatic tires of Comparative Examples 4 to 6 each have a circumferential belt layer and have circumferential and lateral narrow grooves arranged in the center land area, they do not satisfy at least one of the following conditions: the ratio of the width CW of the center land area to the tread expansion width TW is within the range of 0.40 to 0.65; the ratio of the width SW of the shoulder land area to the value obtained by subtracting the width CW of the center land area from the tread expansion width TW and dividing by 2 is within the range of 0.50 to 0.90; the edge of the circumferential belt layer is located outside the tire width direction of the outermost main groove; or the edge of the circumferential belt layer is located within a range of 0.90 or less of the tread expansion width TW.

[0092] In contrast, all of the following conditions are met in Examples 1 to 17, which are examples of the pneumatic tire 1 according to the present invention: the belt layer 14 has a circumferential belt layer 145, the center land portion 31 has circumferential narrow grooves 40 and widthwise narrow grooves 50, the ratio of the width CW of the center land portion 31 to the tread development width TW is within the range of 0.40 to 0.65, the ratio of the width SW of the shoulder land portion 35 to the value obtained by subtracting the width CW of the center land portion 31 from the tread development width TW and dividing by 2 is within the range of 0.50 to 0.90, the end 145a of the circumferential belt layer 145 is located outside the tire width direction of the outermost outermost main groove 21, and the end 145a of the circumferential belt layer 145 is located within a range of 0.90 or less of the tread development width TW. Furthermore, the pneumatic tire 1 according to Examples 1 to 17 differs in the following aspects: the groove width W1 [mm] of the circumferential groove 40, the groove width W2 [mm] of the lateral groove 50, the groove depth D1 [mm] of the circumferential groove 40, the groove depth D2 [mm] of the lateral groove 50, the minimum ratio of the width CWa of the land section row 32 to the width CW of the center land section 31, and the ratio of the width BW of the block 33 to the pitch P of the lateral groove 50.

[0093] As a result of evaluation tests conducted using these pneumatic tires 1, as shown in Figures 8A and 8B, it was found that the pneumatic tires 1 according to Examples 1 to 17 can improve rolling resistance and shoulder wear resistance while minimizing the decrease in snow traction performance compared to conventional examples. In other words, the pneumatic tires 1 according to Examples 1 to 17 can reduce rolling resistance while suppressing shoulder wear and ensuring snow traction performance.

[0094] This disclosure encompasses the following inventions: Invention [1] A tire having a tread portion having a plurality of circumferential main grooves extending in the circumferential direction of the tire and a plurality of land portions partitioned by the circumferential main grooves, and a belt layer disposed on the tread portion and comprising a plurality of belt plies, The aforementioned tread portion is The center land area is defined by a pair of outermost circumferential main grooves, each of which is located on the outermost side in the tire width direction among the multiple circumferential main grooves, The shoulder land portion, which is the land portion located on the outer side in the tire width direction of the outermost main groove, It has, The aforementioned center land portion is provided with a plurality of circumferential grooves extending in the tire's circumferential direction and a plurality of widthwise grooves extending in the tire's width direction. The aforementioned belt layer is A pair of cross belt layers in which the inclination directions of the belt cords in the tire width direction relative to the tire circumferential direction are in opposite directions, A circumferential belt layer is disposed between a pair of the aforementioned cross belt layers, wherein the inclination angle of the belt cords in the tire width direction relative to the tire circumferential direction is 5 degrees or less, It has, The aforementioned center land portion has a ratio of the width of the center land portion in the tire width direction to the tread width that is within the range of 0.40 to 0.65. The ratio of the width of the shoulder portion in the tire width direction to the value obtained by subtracting the width of the center portion in the tire width direction from the tread width and dividing by 2 is within the range of 0.50 to 0.90. The tire is characterized in that the circumferential belt layer has an end in the tire width direction that is located outside the outermost circumferential main groove in the tire width direction and within a range of 0.90 or less of the tread width. invention[2] The tire according to invention [1], wherein the circumferential grooves have a groove width within the range of 0.5 [mm] to 2.0 [mm]. Invention [3] The tire according to invention [1] or invention [2], wherein the narrow grooves in the width direction have a groove width within the range of 0.5 [mm] to 4.0 [mm]. invention [4] The tire according to any one of inventions [1] to [3], wherein the circumferential groove has a groove depth of 10 [mm] or more. invention [5] The tire according to any one of inventions [1] to [4], wherein the narrow groove in the width direction has a groove depth of 1 [mm] or more. invention [6] The aforementioned center land area has a plurality of land area rows partitioned by the aforementioned circumferential narrow grooves, The tire according to any one of inventions [1] to [5], wherein the ratio of the width of the row of land portions in the tire width direction to the width of the center row of land portions in the tire width direction is within the range of 0.1 to 0.49. invention [7] The aforementioned center land area has a plurality of blocks partitioned by the circumferential groove and the widthwise groove, The tire according to any one of the inventions [1] to [6], wherein the block has a ratio of the width of the block in the tire width direction to the pitch of adjacent widthwise narrow grooves in the tire width direction in the tire width direction, which is in the range of 0.3 to 3.0. [Explanation of symbols]

[0095] 1. Pneumatic tire 2 Tread section 3. Tread contact surface 5 Shoulder section 8 Sidewall section 10 Bead section 11 Bead core 12 Bead Fillers 13. Carcass layer 14 Belt Layer 142, 143 Cross belt 145 Circumferential belt layer 145a End 17 Rim cushion rubber 16 Inner liner 20 Circumferential main groove 21 Main grooves in the outermost direction 30 Land 31 Center Track and Field Club 32 Rikubu row 33 blocks 35 Shoulder Track and Field Club 40 Circumferential thin groove 50 Width direction thin groove 60 Inland groove 65 Decorative grooves

Claims

1. A tire having a tread portion having a plurality of circumferential main grooves extending in the circumferential direction of the tire and a plurality of land portions partitioned by the circumferential main grooves, and a belt layer disposed on the tread portion and comprising a plurality of belt plies, The aforementioned tread portion is The center land area is defined by a pair of outermost circumferential main grooves, each of which is located on the outermost side in the tire width direction among the multiple circumferential main grooves, The shoulder land portion, which is the land portion located on the outer side in the tire width direction of the outermost main groove, It has, The aforementioned center land portion is provided with a plurality of circumferential grooves extending in the tire's circumferential direction and a plurality of widthwise grooves extending in the tire's width direction. The aforementioned belt layer is A pair of cross belt layers in which the inclination directions of the belt cords in the tire width direction relative to the tire circumferential direction are in opposite directions, A circumferential belt layer is disposed between a pair of the aforementioned cross belt layers, wherein the inclination angle of the belt cords in the tire width direction relative to the tire circumferential direction is 5 [deg] or less, It has, The center land portion has a ratio of the width of the center land portion in the tire width direction to the tread width that is within the range of 0.40 to 0.

65. The ratio of the width of the shoulder portion in the tire width direction to the value obtained by subtracting the width of the center portion in the tire width direction from the tread width and dividing by 2 is within the range of 0.50 to 0.

90. The tire is characterized in that the circumferential belt layer has an end in the tire width direction that is located outside the outermost circumferential main groove in the tire width direction and within a range of 0.90 or less of the tread width.

2. The tire according to claim 1, wherein the circumferential groove has a groove width within the range of 0.5 mm to 2.0 mm.

3. The tire according to claim 1, wherein the narrow groove in the width direction has a groove width within the range of 0.5 mm to 4.0 mm.

4. The tire according to claim 1, wherein the circumferential groove has a groove depth of 10 mm or more.

5. The tire according to claim 1, wherein the narrow groove in the width direction has a groove depth of 1 [mm] or more.

6. The aforementioned center land area has a plurality of land area rows partitioned by the aforementioned circumferential narrow grooves, The tire according to claim 1, wherein the ratio of the width of the row of land portions in the tire width direction to the width of the center land portion in the tire width direction is within the range of 0.1 to 0.

49.

7. The aforementioned center land area has a plurality of blocks partitioned by the circumferential groove and the widthwise groove, The tire according to claim 1, wherein the ratio of the width of the block in the tire width direction to the pitch of adjacent narrow grooves in the tire width direction in the tire width direction is within the range of 0.3 to 3.0.

Images