pneumatic tires

Abstract

Pneumatic tire (1), comprising: a plurality of main circumferential grooves (21, 22); and a land portion (31, 32) defined by a pair of the plurality of main circumferential grooves (21, 22); wherein the web portion (31, 32) has a plurality of first lug grooves (411), a plurality of second lug grooves (412) which are wider than the first lug grooves (411), and a plurality of recess portions (312) formed only at opening portions of the first lug grooves (411), wherein a circumferential length L1 of edge portions of the land portion (31, 32) defined by the first lug grooves (411) and the second lug grooves (412) adjacent to each other and a circumferential length L2 of the recess portions (312) formed at the edge portions have the relationship 0.30 ≤ L2 / L1 ≤ 0.80.

Description

Technical area

[0001] The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire having good snow performance and noise performance in a compatible manner. State of the art

[0002] To improve snow performance, conventional pneumatic tires are designed with a block pattern to enhance traction. An example of a conventional pneumatic tire configured in this way is the technology described in Patent Document 1. Patent Document 2 describes an improved all-season tire. Patent Document 3 describes a pneumatic tire with an asymmetric tread pattern to improve wet performance. Patent Document 4 describes a pneumatic tire improved in off-road, snow, and cornering performance. Patent Document 5 describes a pneumatic tire capable of improving wetting performance without compromising steering stability. List of citationsPatent literature Patent document 1: JP 4 677 408 B2 Patent document 2: JP H05-229 310 A Patent document 3: DE 698 23 248 T2 Patent document 4: EP 2 048 007 A1 Patent document 5: JP 2002- 240 513 A Summary of the inventionTechnical problem

[0003] However, there is also a need to improve the noise performance of pneumatic tires.

[0004] In view of the foregoing, an object of the present invention is to provide a pneumatic tire having good snow performance and noise performance in a compatible manner. Solution to the problem

[0005] To achieve the above-described object, a pneumatic tire according to an embodiment of the present invention comprises a plurality of circumferential main grooves; and a land portion defined by a pair of the plurality of circumferential main grooves; wherein the land portion includes a plurality of first lug grooves, a plurality of second lug grooves wider than the first lug grooves, and a plurality of recess portions formed only at the opening portions of the first lug grooves. Advantageous effects of the invention

[0006] In a pneumatic tire according to the present invention, since the narrower first lug grooves and the wider second lug grooves are intermingled in the land portion, tread noise during tire rolling is reduced. This is advantageous in improving the noise performance of the tire. Since the recess portions increase the width of the opening portions of the narrower first lug grooves, the snow drainage properties of the lug grooves are improved. This is advantageous in improving the tire's performance on snow. A circumferential length L1 of edge portions of the land portion defined by the first lug grooves and the second lug grooves adjacent to each other and a circumferential length L2 of the recess portions formed at the edge portions have the relationship 0.30 ≤ L2 / L1 ≤ 0.80. Brief description of the drawings Fig. 1 is a cross-sectional view in the tire meridian direction illustrating a pneumatic tire according to an embodiment of the present invention. Fig. 2 is a plan view showing a tread portion of the Fig. 1 illustrates the pneumatic tire. Fig. 3 is an explanatory diagram showing a main section of the Fig. 2 illustrated tread pattern. Fig. 4 is an explanatory diagram showing a center web section shown in Fig. 3 is shown. Fig. 5 is an explanatory diagram showing the center web section shown in Fig. 3 is shown. Fig. 6 is an explanatory diagram showing a recessed portion formed in Fig. 4 is shown. Fig. 7 is an explanatory diagram showing a modified example of the Fig. 4 illustrated recess section. Fig. 8 is an explanatory diagram illustrating an example of a three-dimensional slat. Fig. 9 is an explanatory diagram illustrating an example of a three-dimensional slat. Fig. 10 is a table showing results of performance testing of pneumatic tires according to embodiments of the present invention. Description of embodiments

[0007] Embodiments of the present invention will be explained in detail below with reference to the drawings. However, the present invention is not limited to these embodiments. Furthermore, components of the embodiments include elements that are interchangeable while maintaining consistency with the invention, as well as obviously interchangeable elements. Furthermore, the modified examples described in the embodiments can be combined as needed within the scope obvious to a person skilled in the art. pneumatic tires

[0008] Fig. Figure 1 is a cross-sectional view in the tire meridian direction illustrating a pneumatic tire according to an embodiment of the present invention. The same drawing illustrates a cross-sectional view of a portion to one side in the tire radial direction. The same drawing also illustrates a radial tire for a passenger car as an example of a pneumatic tire.

[0009] Referring to the same drawing, "cross-section in a tire meridian direction" refers to a cross-section of the tire taken along a plane including the tire rotation axis (not illustrated). Reference character "CL" denotes the tire equatorial plane and refers to a plane perpendicular to the tire rotation axis, passing through the tire center in the direction of the tire rotation axis. "Tire transverse direction" refers to the direction parallel to the tire rotation axis. "Tire radial direction" refers to the direction perpendicular to the tire rotation axis.

[0010] The pneumatic tire 1 has a ring structure whose center is the tire rotation axis, and includes a pair of tire bead cores 11, 11, a pair of bead fillers 12, 12, a carcass layer 13, a belt layer 14, a tread rubber 15, a pair of rubber sidewalls 16, 16 and a pair of rim cushion rubbers 17, 17 (see Fig. 1).

[0011] The pair of bead cores 11, 11 are annular members formed by a plurality of bundled tire bead wires. The pair of bead cores 11, 11 form the cores of the left and right bead portions. The pair of bead fillers 12, 12 are arranged on a circumference of the pair of bead cores 11, 11 in the tire radial direction and form the bead portions.

[0012] The carcass layer 13 has a single-layer structure formed by a single carcass layer or a multi-layer structure formed by laminated carcass plies, and extends between the left and right bead cores 11, 11 in a toroidal shape, thereby forming the support structure for the tire. Furthermore, both end portions of the carcass layer 13 are bent back outward in the tire transverse direction so as to be wrapped and fixed around the bead cores 11 and the bead fillers 12. The one or more carcass plies of the carcass layer 13 are formed by a plurality of carcass cords made of steel or an organic fiber material (e.g., aramid, nylon, polyester, rayon, or the like), covered by a coating rubber, and subjected to a rolling process.The one or more carcass plies have a carcass angle (angle of inclination of the fiber direction of the carcass cords with respect to the tire circumferential direction) with an absolute value of 80 degrees to 95 degrees.

[0013] The belt layer 14 is formed by laminating a pair of cross belts 141, 142 and a belt cover 143, and is arranged around the periphery of the carcass layer 13. The pair of cross belts 141, 142 is formed by a plurality of belt cords made of steel or an organic fiber material, covered with a coating rubber, and subjected to a rolling process. The cross belts 141, 142 have a belt angle with an absolute value of 20 degrees to 55 degrees. Furthermore, the pair of cross belts 141, 142 have belt angles (inclination angles of the fiber directions of the belt cords with respect to the tire circumferential direction) with different signs, and the belts are laminated so that the fiber directions of the belt cords cross each other (cross-ply structure).The belt cover 143 is formed by a plurality of cords made of steel or an organic fiber material, covered with a coating rubber, and subjected to a rolling process. The belt cover 143 has a belt angle with an absolute value of 0 to 10 degrees. The belt cover 143 is arranged in a layered manner from the cross belts 141, 142 outward in the tire radial direction.

[0014] The tread rubber 15 is arranged outward from the carcass layer 13 and the belt layer 14 in the tire radial direction and forms a tread portion. The pair of sidewall rubbers 16, 16 are arranged outward from the carcass layer 13 in the tire transverse direction and form left and right sidewall portions. The pair of rim cushion rubbers 17, 17 are arranged inward from the left and right tire bead cores 11, 11 and the bent-back portions of the carcass layer 13 in the tire radial direction. The pair of rim cushion rubbers 17, 17 form the contact surfaces of the left and right bead portions with the rim flanges. Tread pattern

[0015] Fig. 2 is a plan view showing a tread pattern of the Fig. 1. The same drawing illustrates a tread pattern for an all-season tire. Referring to the same drawing, "tire circumferential direction" refers to the direction rotating around the tire's rotational axis. Reference symbol T denotes a ground contact edge of the tire.

[0016] As in Fig. 2, the pneumatic tire 1 is provided in the tread portion with a plurality of circumferential main grooves 21, 22 extending in the tire circumferential direction; a plurality of land portions 31 to 33 defined by the circumferential main grooves 21, 22; and a plurality of lug grooves 411, 412, 421, 422, 43 arranged in the land portions 31 to 33.

[0017] "Main circumferential groove" refers to a circumferential groove with a wear indicator that indicates the final stage of wear and typically has a groove width of 5.0 mm or more and a groove depth of 7.5 mm or more. Furthermore, "lug groove" refers to a lateral groove with a groove width of 2.0 mm or more and a groove depth of 3.0 mm or more. Furthermore, "sipe," described below, refers to a cut formed in a land portion, which typically has a sipe width of less than 1.5 mm.

[0018] The groove width is the maximum distance between the left and right groove walls at the groove opening portion and is measured with the tire mounted on a specified rim, inflated to a predetermined internal pressure, and in an unloaded state. In configurations where the land portions include recessed portions or chamfered portions at the edge portions thereof, the groove width is measured with reference to the points where the tread contact piece and the extension lines of the groove walls meet when viewed in a cross-section perpendicular to the groove longitudinal direction. Furthermore, in a configuration where the grooves extend in a zigzag or wave-like manner in the tire circumferential direction, the groove width is measured with reference to the centerline of the transverse variation of the groove walls. The groove depth is the maximum distance from the

[0019] Tread contact patch to the groove bottom and is measured with the tire mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state. In addition, in configurations where the grooves include an uneven section or sipes on the groove bottom, the groove depth is measured excluding these sections.

[0020] “Specified rim” refers to an applicable rim as defined by the Japan Automobile Tire Manufacturers Association (JATMA), a design rim as defined by the Tire and Rim Association (TRA), or a measuring rim as defined by the European Tire and Rim Technical Organization (ETRTO). Furthermore, “specified internal pressure” refers to a maximum air pressure as defined by JATMA, the maximum value in “tire load limits at various cold inflation pressures” as defined by TRA, and “inflation pressures” as defined by ETRTO.Furthermore, "specified load" refers to a "maximum load capacity" as defined by JATMA, the maximum value in "tire load limits at various cold inflation pressures" as defined by TRA, and a "load capacity" as defined by ETRTO. However, in the case of JATMA, the specified internal pressure for a passenger car tire is 180 kPa, and the specified load is 88% of the maximum load capacity.

[0021] For example, in the configuration of Fig. 2, four main circumferential grooves 21, 22 are arranged with point symmetry around a point in the equatorial plane of the tire CL. Furthermore, five land sections 31 to 33 are defined by the four main circumferential grooves 21, 22. One of the land sections 31 is arranged in the equatorial plane of the tire CL.

[0022] However, the configuration is not limited to this, and five or more circumferential main grooves may be arranged (not illustrated). The circumferential main grooves 21, 22 may be arranged with left-right asymmetry on either side of the equatorial plane of the tire CL (not illustrated). In addition, one circumferential main groove may be arranged on the equatorial plane of the tire CL (not illustrated). Accordingly, the land portion 31 may be arranged at a position away from the equatorial plane of the tire CL.

[0023] In addition, in the configuration of Fig. 2, the four main circumferential grooves 21, 22 have an overall straight shape, and the edge portions of the left and right land portions 31 to 33 protrude toward the main circumferential grooves 21, 22, which gives the groove walls of the main circumferential grooves 21, 22 a step-like shape in the tire circumferential direction.

[0024] However, the present invention is not limited to such a configuration, and the circumferential main grooves 21, 22 may have a simple straight shape or a zigzag shape or a wave-like shape that bends or curves while extending in the tire circumferential direction (not illustrated).

[0025] Here, the left and right circumferential main grooves 22, 22, located at the outermost ends in the tire width direction, are referred to as the outermost circumferential main grooves. Furthermore, the left and right outermost circumferential main grooves 22, 22 define the tread portion center region and the tread portion shoulder regions.

[0026] Furthermore, the outermost left and right land portions 33, 33 in the tire width direction, which are defined by the left and right outermost circumferential main grooves 22, 22, are referred to as shoulder land portions. The left and right shoulder land portions 33, 33 are arranged at the left and right ground contact edges T, T of the tire. In addition, the left and right land portions 32, 32, which are located inward in the tire width direction and which are defined by the left and right outermost circumferential main grooves 22, 22, are referred to as second land portions. Accordingly, the second land portions 32 are adjacent to the outermost circumferential main grooves 22. The land portion 31, which is arranged inward from the left and right second land portions 32, 32 in the tire width direction, is also referred to as the “center land portion.” In the configuration of Fig. 2, only a single center land portion 31 is arranged. However, in configurations with five or more main circumferential grooves, a plurality of center land portions 31 may be arranged.

[0027] In the configuration of Fig. 2, the land portions 31 to 33 enclose a plurality of lug grooves 411, 412, 421, 422, 43 extending in the tire width direction. The lug grooves 411, 412, 421, 422, 43 have an open structure, with the lug grooves 411, 412, 421, 422, 43 extending entirely through the land portions 31 to 33 in the tire width direction, and the lug grooves 411, 412, 421, 422, 43 are arranged at predetermined intervals in the tire circumferential direction. Thus, the land portions 31 to 33 are divided in the tire circumferential direction by the lug grooves 411, 412, 421, 422, 43 into a plurality of blocks forming rows of blocks.

[0028] However, no such limitation is intended, and, for example, a semi-closed structure may be adopted in which the lug grooves 411, 412 of the central land portion 31 or the lug grooves 43 of the shoulder land portions 33 are blindly terminated at an end portion within the land portions 31, 33 (not shown). In such configurations, the land portions 31 to 33 are formed as continuous ribs in the tire circumferential direction. Middle bridge section and second bridge sections

[0029] Fig. 3 is an explanatory diagram showing a main section of the Fig. 2. The same drawing is an enlarged plan view of the center land portion 31 and one of the second land portions 32.

[0030] In the configuration of Fig. 3, the central web portion 31 is provided with the plurality of lug grooves 411, 412 and a plurality of blocks 311.

[0031] The lug grooves 411, 412 are categorized into first lug grooves 411 and second lug grooves 412, which have a larger width than the first lug grooves 411. Specifically, the groove width Wg1 of the first lug grooves 411 (see Fig. 4) and the groove width Wg2 of the second lug grooves 412 (see Fig. 4) the relationship Wg1 < Wg2. In addition, the groove width Wg1 of the first lug grooves 411 and the groove width Wg2 of the second lug grooves 412 preferably have the relationship 1.0 mm ≤ Wg2 - Wg1 ≤ 4.0 mm, and more preferably have the relationship 1.5 mm ≤ Wg2 - Wg1 ≤ 3.5 mm. The first lug grooves 411 and the second lug grooves 412 include a bent portion having a Z-shape or a crank-like shape and extend through the center land portion 31 in the tire width direction, opening toward the left and right circumferential main grooves 21, 21 of the center land portion 31. In addition, the narrower first lug grooves 411 and the wider second lug grooves 412 are alternately arranged at predetermined intervals in the tire circumferential direction. This reduces tread noise as the tire rolls.

[0032] The groove width Wg2 of the wider second lug grooves 412 can be appropriately selected depending on the tire size. For a typical all-season passenger car tire, the groove width Wg2 of the second lug grooves 412 is in the range of 3.8 mm ≤ Wg2 ≤ 5.3 mm.

[0033] The blocks 311 are defined by the first lug grooves 411 and the second lug grooves 412, which are adjacent in the tire circumferential direction, and the left and right circumferential main grooves 21, 21 of the center land portion 31. Furthermore, the plurality of blocks 311 are arranged in a single row in the tire circumferential direction to form a block row.

[0034] In the configuration of Fig. 3, the second land portion 32 is provided with a plurality of lug grooves 421, 422 and a plurality of blocks 321, 322. The lug grooves 421, 422 extend entirely through the second land portion 32 in the tire width direction and open to the left and right circumferential main grooves 21, 22 of the second land portion 32. Furthermore, the lug grooves 421, 422 are arranged at predetermined intervals in the tire circumferential direction. The two types of lug grooves 421, 422 have different inclination angles, groove shapes, and groove widths and are arranged alternately in the tire circumferential direction. The blocks 321, 322 are defined by the lug grooves 421, 422 that are adjacent in the tire circumferential direction. The two types of blocks 321, 322 have different shapes and are arranged in a single row in the tire circumferential direction to form a block row.

[0035] It should be noted that, as described above, in the configuration of Fig. 3, the lug grooves 411, 412 of the central land portion 31 and the lug grooves 421, 422 of the second land portion 32 have a Z-shape or a crank-like shape in which the groove centerline is offset in the tire circumferential direction. Such a configuration is preferable because the edge portion components of the land portions 31, 32 are raised, thereby improving the tire's snow performance.

[0036] However, no such limitation is intended, and the lug grooves 411, 412 of the central land portion 31 and the lug grooves 421, 422 of the second land portion 32 may have a straight shape without a bent portion or an arc shape (not shown). Recess section of the central web section

[0037] As in Fig. 3, in the pneumatic tire 1, the center land portion 31 is provided with a plurality of recess portions 312. The recess portions 312 are formed where the narrower first lug grooves 411 open toward the main circumferential groove 21, and the width of these opening portions of the first lug grooves 411 is increased in the tire circumferential direction. This ensures the drainage properties and the snow drainage properties of the first narrower lug grooves 411. In addition, the recess portions 312 serve to compensate for the groove volume of the narrower lug grooves 411 by making the rigidity of the land portions uniform in the tire circumferential direction.

[0038] The recess portions 312 refer to portions formed at the edge portions of the web portion 31 with a predetermined depth D2 (see Fig. 5, described below). The recessed portions 312 are designed to increase the groove volume of the lug grooves 411, and thus the depth D2 is greater than the depth of the chamfered portions 313 of the recessed portions 312, described below, and the chamfered portions formed at the edge portions of the land portion 31 (not shown). The depth D2 of the recessed portions 312 is described below.

[0039] A chamfered section refers to a section to which the edge portion of adjacent surfaces is adjacent, which is chamfered (for example, square chamfered) or rounded (round chamfered).

[0040] The recess portions 312 are not formed where the wider second lug grooves 412 open toward the circumferential main groove 21. In other words, the wider second lug grooves 412 are not connected to the recess portions 312 and are open at the edge portion of the center land portion 31. Furthermore, the opening portions of the wider second lug grooves 412 and the recess portions 312 may be offset from each other in the tire circumferential direction at the edge portions of the center land portion 31. Accordingly, the opening portions 21 of the second lug grooves 412 are not provided with an increased width by the recess portions 312.

[0041] For example, in the configuration of Fig. 3, when viewing the tread portion in plan view, the recess portions 312 form a V-shaped (or an L-shaped) edge portion. Furthermore, the recess portions 312 are formed at the edge portions of the center land portion 31 on the circumferential main groove 21 side, and the V shape protrudes in the tire circumferential direction and in the inward direction in the width direction of the land portion 31. The V-shaped recessed portions 312 each overlap with an opening portion of one of the lug grooves 411, 412. In other words, the lug grooves 411, 412 are connected to the recessed portions 312 and open to the main circumferential groove 21 through the recessed portions 312. As a result, the recessed portion 312 increases the width of the opening portion of the lug groove 411, 412 to the left and right along the main circumferential groove 21.

[0042] The recessed portions 312 are formed at the left and right edge portions of the center land portion 31. Furthermore, the narrower first lug grooves 411 with the recessed portions 312 are arranged alternately at the left and right opening portions, and the wider second lug grooves 412 without the recessed portions are arranged alternately at the opening portion in the tire circumferential direction. The second lug grooves 412 without the recessed portions 312 are arranged spaced apart from the V-shaped recessed portions 312 in the tire circumferential direction and open to the circumferential main grooves 21 without being connected to the recessed portions 312.

[0043] Furthermore, as described above, a pair of adjacent lug grooves 421, 422 of the second land portion 32 have different inclination angles. Specifically, an intersection angle between the groove centerline of the lug groove 421 and the groove centerline of the circumferential main groove 21 is in the range of 50 degrees to 75 degrees, and an intersection angle between the groove centerline of the lug groove 422 and the groove centerline of the circumferential main groove 21 is in the range of 15 degrees to 40 degrees. In addition, since the pair of lug grooves 421, 422 having the same orientation are inclined with respect to the tire circumferential direction, the extension lines of the groove center lines of the lug grooves 421, 422 meet at the edge portion of the center land portion 31. The recess portions 312 of the center land portion 31 surround the extension lines of the groove center lines of the lug grooves 421, 422.

[0044] It should be noted that in the configuration of Fig. 3, the recessed portions 312, 312 are provided at the opening portions of the narrower first lug grooves 411 to the left and right circumferential main grooves 21, 21. However, no such limitation is intended, and the first lug grooves 411 may be provided with the recessed portion 312 only at one opening portion and open to the circumferential main groove 21 at the other opening portion without being connected to the recessed portion 312 (not shown).

[0045] In addition, the configuration of Fig. 3, as described above, the recess portions 312 each form an opening portion of one of the narrower first lug grooves 411. Thus, the opening portion of the first lug grooves 411 is widened to the left and right in the tire circumferential direction. However, no such limitation is intended, and the recess portions 312 may be formed on only one side of the opening portion of the first lug grooves 411 and widen only the opening portion of the first lug grooves 411 in one direction (not shown).

[0046] In addition, the configuration of Fig. 3, the wider second lug grooves 412, without the recess portion 312, are open toward the circumferential main groove 21 with a fixed groove width. Such a configuration is preferable because the rigidity of the land portion 31 can be ensured and the steering stability performance of the tire can be improved to a greater extent than in a configuration in which the recess portions 312 are provided at the opening portions of all the lug grooves 411, 412 of the central land portion 31 (not shown).

[0047] However, no such limitation is intended, and the wider second lug grooves 412 may have a chamfered portion where the left and right corner portions of the opening portions are chamfered (not shown). Such a chamfered portion may have a smaller width and a smaller depth than the recessed portions 312, similar to the chamfered portions 313 of the recessed portions 312 described below. In particular, the width and depth of the chamfered portion are preferably in the range of 1.5 mm to 6.0 mm. Such chamfered portions 313 increase the wear resistance of the center land portion 31.

[0048] Fig. 4 and Fig. 5 are explanatory diagrams that illustrate the Fig. 3 illustrate the central web section. Fig. 4 is an enlarged plan view of the center web section 31. Fig. 5 is a cross-sectional view of the center web portion 31 along the lug groove 41.

[0049] In Fig. 4, a maximum width W1 of the central web portion 31 and a maximum width W2 of the recess portion 312 preferably have the relationship 0.05 ≤ W2 / W1 ≤ 0.25, more preferably the relationship 0.10 ≤ W2 / W1 ≤ 0.15. This appropriately sets the maximum width W2 of the recess portion 312.

[0050] The maximum width of the land section is the maximum value of the width in the tire axial direction of the road contact surface of the land section and is measured with the tire mounted on a given rim, inflated to a given internal pressure and in an unloaded state.

[0051] The maximum width of the recess portion is the maximum value of the width in the tire axial direction of the recess portion and is measured with the tire mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state from the position where the maximum width of the land portion is measured as a standard.

[0052] Furthermore, a circumferential length L1 of the edge portion of the center land portion 31 defined by adjacent lug grooves 411, 412 and a circumferential length L2 of the recess portion 312 formed at the edge portion have the relationship 0.30 ≤ L2 / L1 ≤ 0.80, preferably the relationship 0.45 ≤ L2 / L1 ≤ 0.60. This sets the circumferential length L2 of the recess portion 312 appropriately.

[0053] The circumferential length of the edge portion of the land portion is the length in the tire circumferential direction of the edge portion of the land portion between a pair of lug grooves adjacent in the tire circumferential direction that open to the same circumferential main groove, and is measured with the tire mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state. For example, in the configuration of Fig. 4, the center land portion 31 comprises a series of blocks defined by the lug grooves 411, 412, and the circumferential length L1 of the edge portion of the center land portion 31 is the length of the edge portion of one of the blocks 311 in the tire circumferential direction on the side of the circumferential main groove 21.

[0054] The circumferential length of the recess portion is the tire circumferential length of the recess portion along the edge portion of the land portion, defined by adjacent lug grooves, and is measured with the tire mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state. For example, in the configuration of Fig. 4 the circumferential length L2 of the recess portion 312 the length in the tire circumferential direction of the recess portion 312 formed along the edge portion of one of the blocks 311 of the center land portion 31.

[0055] Furthermore, with reference to Fig. 5, a maximum groove depth D1 of the first lug grooves 411 and a maximum depth D2 of the recessed portions 312 preferably satisfy the relationship 0.30 ≤ D2 / D1 ≤ 1.00, and more preferably the relationship 0.50 ≤ D2 / D1 ≤ 0.80. This appropriately sets the maximum depth D2 of the recessed portion 312.

[0056] The maximum groove depth of the lug groove is the maximum distance from the tread contact surface to the groove bottom and is measured with the tire mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state. In addition, in configurations where the lug grooves partially have a raised bottom section or a sipe at the bottom section, the depth is measured excluding these sections.

[0057] The maximum depth D2 of the recess section is the maximum distance from the tread contact surface to the land portion and is measured with the tire mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state. Furthermore, in configurations where the recess sections have a raised land portion or a sipe at the groove bottom, the groove depth is measured excluding these portions.

[0058] Furthermore, with reference to Fig. 5, a maximum groove depth D0 of the main circumferential groove 21 and the maximum groove depth D1 of the lug grooves 41 of the center land portion 31 preferably satisfy the relationship 0.6 ≤ D1 / D0 ≤ 0.8. This appropriately sets the groove depth D1 of the lug grooves 41, and ensures the drainage characteristics of the lug grooves 411 (412).

[0059] For example, in the configuration of Fig. 5, the groove depth D0 of the main circumferential groove 21, the groove depth D1 of the lug groove 411, and the maximum depth D2 of the recess portion 312 satisfy the relationship D2 < D1 < D0. This provides a raised bottom to the opening portion of the lug groove 41 to the main circumferential groove 21 via the recess portion 312. As a result, the rigidity of the center land portion 31 is ensured where the recess portion 312 is formed. Furthermore, the groove bottom of the lug groove 411 and the bottom portion of the recess portion 312 are connected to each other via a slightly inclined portion. This ensures the drainage properties from the lug groove 411 to the main circumferential groove 21.

[0060] In addition, in the configuration of Fig. 4 and Fig. 5, a groove volume V1 of the narrower first lug groove 411 and a volume Vc of the recessed portion 312 and a groove volume V2 of the wider second lug groove 412 preferably satisfy the relationship 0.70 ≤ (V1 + Vc) / V2 ≤ 1.30, and more preferably the relationship 0.85 ≤ (V1 + Vc) / V2 ≤ 1.15. This allows the groove volume V1 + Vc associated with the first lug groove 411 and the groove volume V2 of the second lug groove 412 to be made uniform.

[0061] Fig. 6 is an explanatory diagram showing the recess portion shown in Fig. 4 is shown. Fig. 7 is an explanatory diagram showing a modified example of the Fig. 4. These drawings illustrate the edge portion of the center land portion 31 and the profile line of the recess portion 312 when the tread is viewed from above.

[0062] In the configuration of Fig. 4, the recess portion 312 has a V-shape that protrudes in the tire circumferential direction when the tread is viewed in plan view. In addition, as shown in Fig. 6, the two sides of the V-shape of the recess portion 312 have a shorter straight line located on the protruding side of the V-shape and a longer arc on the other side. The two sides are inclined in the same direction with respect to the tire circumferential direction. A bending angle θ of the V-shape of the recess portion 312 is preferably in the range of 10 degrees ≤ θ ≤ 70 degrees, more preferably in the range of 15 degrees ≤ θ ≤ 55 degrees, and even more preferably in the range of 20 degrees ≤ θ ≤ 43 degrees. Since the recess portion 312 has a V-shape with such an acute angle protruding in the tire circumferential direction, as shown in Fig. 3, the recess portions 312 may extend around where the extension lines of the groove center lines of the lug grooves 421, 422 of the second web portion 32 meet.

[0063] The bending angle θ of the recess portion 312 is measured when observing the tread in plan view using the profile line of the wall surface of the recess portion 312 and is measured with the tire mounted on a specified rim, inflated to a predetermined internal pressure, and in an unloaded state. In addition, as shown in Fig. As shown in Figure 6, in configurations where the recess portion 312 has a curved side, the bend angle θ is measured using the tangent of the curved side at the apex of the V-shape as a standard. Note that the bend angle θ can be appropriately adjusted in relation to the pitch length of a tread pattern with pitch variation.

[0064] However, no such limitation is intended, and the two sides of the V-shape of the recess portion 312 may be either straight lines (see Fig. 7) or both arcs (not shown). Furthermore, the recess portion 312 may have a shape such as a circular, elliptical, triangular, rectangular, or trapezoidal shape (not shown).

[0065] Chamfered section of the recess section As shown in Fig. 4 and Fig. As shown in Figure 5, the center ridge portion 31 is provided with the chamfered portion 313. The chamfered portion 313 is formed along the edge portion of the recessed portion 312. This improves the wear resistance of the edge portion of the center ridge portion 31.

[0066] For example, in the configuration of Fig. 4, the chamfered portion 313 is formed along the entire area of ​​the edge portion of the V-shaped recessed portion 312. Furthermore, the chamfered portion 313 is formed at all recessed portions 312 of the center web portion 31.

[0067] The maximum width W2 of the recess portion 312 and a width W3 of the chamfered portion 313 preferably have the relationship of 0.30 ≤ W3 / W2 ≤ 1.80, and more preferably the relationship of 0.80 ≤ W3 / W2 ≤ 1.20. Furthermore, the width W3 of the chamfered portion 313 is preferably in the range of 1.5 mm ≤ W3 ≤ 6.0 mm. This appropriately sets the width W3 of the chamfered portion 313.

[0068] The width W2 of the chamfered portion is the distance between the profile line of the cut-out portion and the tread contact surface when the tread is viewed from above and is measured with the tire mounted on a specified rim, inflated to a specified internal pressure and in an unloaded condition (see Fig. 4).

[0069] In addition, as in Fig. 5, a depth D3 of the chamfered portion 313 and a maximum depth D2 of the recessed portion 312 preferably satisfy the relationship 0.50 ≤ D3 / D2 ≤ 0.80. The depth D3 of the chamfered portion 313 is preferably in the range of 1.3 mm ≤ D3 ≤ 5.5 mm. This appropriately sets the depth D3 of the chamfered portion 313.

[0070] The chamfer depth D3 is the distance from the tread contact surface to the deepest point of the chamfer and is measured with the tire mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded condition. As shown in Fig. 5, the boundary between the recess portion and the sloped portion is defined by the point where the extension line of the wall surface of the recess portion 312 on the ground portion side and the inclined surface of the sloped portion 313 connected to the road contact surface of the land portion 31 meet.

[0071] It should be noted that in the configuration of Fig. 5, the chamfered portion 313 may have a corner chamfer, but no such limitation is intended. The chamfered portion 313 may have a round chamfer (not shown). Slats of the web sections

[0072] As in Fig. As shown in Figure 3, the center land portion 31 and the second land portions 32 are provided with a plurality of sipes 5. The sipes 5 are divided into two-dimensional sipes (flat sipes) and three-dimensional sipes (cubic sipes). The sipes 5 secure the edge components in the land portions 31, 32. As a result, the traction properties of the tire are improved.

[0073] The two-dimensional fins have a fin wall surface with a straight shape when viewed in cross-section along the normal direction of the fin length direction (a cross-section showing the fin width direction and the fin depth direction). The two-dimensional fins only need to have a straight shape when viewed in the cross-section described above and can extend in a straight shape, a zigzag shape, a wave-like shape, or an arc shape in the fin length direction.

[0074] The three-dimensional sipes have a sipe wall surface with a curved shape with lateral variation in the sipe width direction when viewed in cross-section along the normal direction of the sipe length direction and a cross-section along the normal direction of the sipe depth direction. Compared with the two-dimensional sipes, three-dimensional sipes have a greater engagement force between opposing sipe wall surfaces and therefore act to enhance the rigidity of the land portions. The three-dimensional sipes need only have the above-described structure on the sipe wall surface and may have a straight shape, a zigzag shape, a wave-like shape, or an arc shape on the tread contact surface. The following are examples of such three-dimensional sipes (see Fig. 8 and Fig. 9).

[0075] Fig. 8 and Fig. Figure 9 are explanatory diagrams showing examples of three-dimensional fins. These drawings are perspective views of three-dimensional fins with a pyramid-shaped fin wall surface.

[0076] In the configuration of Fig. 8, the sipe wall surface has a structure in which pyramids and inverted pyramids are connected in the sipe length direction. In other words, the sipe wall surface is formed by mutually offsetting, in the tire width direction, the pitches of a zigzag shape located proximal to the tread surface and a zigzag shape located on the land portion side, so that opposing depressions and protrusions are formed by the zigzag shapes on the tread surface side and the land side.In addition, in these depressions and projections, when viewed in the tire rotation direction, the sipe wall surface is formed by connecting a projection curvature point on the tread surface side with a depression curvature point on the ground side, a depression curvature point on the tread surface side with a projection curvature point on the ground side, and projection curvature points each adjacent to the projection curvature point on the tread surface side and the projection curvature point on the ground side with ridge lines, and connecting these ridge lines to successive planes in the tire width direction.Furthermore, a first sipe wall surface has an uneven surface with convex pyramids and inverted pyramids arranged alternately in the tire transverse direction; and a second sipe wall surface has an uneven surface with concave pyramids and inverted pyramids arranged alternately in the tire transverse direction. Furthermore, the uneven surface of the sipe wall surface is oriented toward the outside of the blocks at at least the outer ends of the sipe. Note that examples of such a three-dimensional sipe include the technology described in Japanese Patent No. 3894743.

[0077] In the configuration of Fig. 9, the sipe wall surface has a structure in which a plurality of prism shapes having a block shape are connected in the sipe depth direction and the sipe length direction while being inclined with respect to the sipe depth direction. In other words, the sipe wall surface has a zigzag shape in the tread surface. Furthermore, the sipe wall surface has bent portions at at least two locations in the tire radial direction in the blocks, which are bent in the tire circumferential direction and connected in the tire transverse direction. Furthermore, these bent portions have a zigzag shape with lateral variation in the tire radial direction.Furthermore, while the lateral variation in the tire circumferential direction is constant in the sipe wall surface, an inclination angle in the tire circumferential direction with respect to a normal direction of the tread surface is smaller in a portion on the sipe bottom side than in a portion on the tread surface side; and the lateral variation of the bent portion in the tire radial direction is larger in a portion on the sipe bottom side than in a portion on the tread surface side. Note that examples of such a three-dimensional sipe include the technology described in Japanese Patent No. 4316452.

[0078] For example, in the configuration of Fig. 4, the blocks 311 of the center land portion 31 each have the plurality of sipes 5, wherein each of the sipes 5 is a three-dimensional sipe. In addition, the sipe 5 terminates within the block 311 at one end portion and is connected to the circumferential main groove 21 at the other end, which is open at the edge portion of the block 311. The sipes 5 are inclined with respect to the tire circumferential direction in the same orientation as the lug grooves 41 and extend in the tire width direction such that they intersect the center line of the center land portion 31 (the equatorial plane of the tire CL in Fig. 4). The sipes 5 and the lug grooves 41 are arranged at equal intervals in the tire circumferential direction, thus defining the blocks 311 in rectangular areas with substantially equal widths. Furthermore, in the blocks 311, 311 adjacent in the tire circumferential direction, the sipes 5 are inclined in the same orientation with respect to the tire circumferential direction and open at the edge portion on different sides.

[0079] The sipes 5 are each open at the edge portion of the blocks 311 without being connected to the recess portions 312. Accordingly, the opening portion of the sipe 5 and the recess portion 312 at the edge portion of the block 311 are offset from each other in the tire circumferential direction. At the edge portion of the block 311, a distance g1 (reference symbol for dimension omitted from drawings) between the opening portion of the sipe 5 and the recess portion 312 is preferably in the range of 2.0 mm ≤ g1. This ensures that the distance g1 between the opening portion of the sipes 5 and the recess portion 312 is appropriate.

[0080] In addition, at least one of the slats 5 extends completely through the beveled portion 313 of the recess portion 312 and is open at the edge portion of the block 311. In particular, as shown in Fig. As shown in Figure 4, the recessed portion 312 and the chamfered portion 313 have a V-shape that protrudes in the tire circumferential direction and extends beyond the lug groove 41 over two of the blocks 311, 311. In the block 311 having the V-shaped recessed portion 312 and the chamfered portion 313, all the sipes 5 are arranged at a distance from the recessed portion 312 and the chamfered portion 313. In the other block 311, at least one of the sipes 5 extends completely through the chamfered portion 313 and is open at the edge portion of the block 311.

[0081] Furthermore, as described above, the blind end portion of the sipes 5 is disposed within the blocks 311 at a distance from the recessed portion 312 and the chamfered portion 313. In such a configuration, the road contact surface of the blocks 311 is not divided by the sipes 5, the recessed portion 312, or the chamfered portion 313, and is continuous in the tire circumferential direction. This ensures the road contact surface of the blocks 311. In addition, a distance g2 (reference symbol for dimension omitted from drawings) between the blind end portion of the sipe 5 and the chamfered portion 313 is preferably in the range of 2.0 mm ≤ g2. This ensures that the distance g2 between the blind end portion of the sipes 5 and the chamfered portion 313 is appropriate.

[0082] It should be noted that in the configuration of Fig. 4, as described above, at least one of the slats 5 extends entirely through the tapered portion 313 of the recess portion 312. However, no such limitation is intended, and all of the slats 5 may be arranged at a distance from the recess portions 312 and the tapered portions 313. As a result, the rigidity of the center web portion 31 is ensured. Effects

[0083] As described above, the pneumatic tire 1 has the plurality of circumferential main grooves 21, 22 and the land portion 31 defined by the circumferential main grooves 21, 21 (see Fig. 2). In addition, the land portion 31 is provided with the plurality of first lug grooves 411, the plurality of second lug grooves 412 which are wider than the first lug grooves 411, and the plurality of recess portions 312 formed only at the opening portions of the first lug grooves 411 (see Fig. 4).

[0084] In such a configuration the following applies: (1) Since the narrower first lug grooves 411 and the wider second lug grooves 412 are intermingled in the land portion 31, the tread noise when the tire is rolling is reduced. This is advantageous because the noise performance of the tire is improved. (2) Since the recess portions 312 increase the width of the opening portions of the narrower first lug grooves 411, the drainage properties and snow drainage properties of the first lug grooves 411 are improved. This is advantageous because the wet performance and snow performance of the tire are improved. In addition, (2) the recess portions 312 serve to balance the groove volume of the first narrower lug grooves 411 by making the rigidity of the land portion 31 uniform in the tire circumferential direction. This is advantageous because the steering stability performance of the tire is improved.

[0085] In addition, in the pneumatic tire 1, the groove width Wg1 of the first lug grooves 411 and the groove width Wg2 of the second lug grooves 412 have the relationship 1.0 mm ≤ Wg2 - Wg1 ≤ 4.0 mm (see Fig. 4). This is advantageous because the difference Wg2 - Wg1 between the groove width Wg1 of the narrower first lug grooves 411 and the wider second lug grooves 412 is appropriately adjusted. In other words, when 1.0 mm ≤ Wg2 - Wg1 is satisfied, the difference Wg2 - Wg1 between the groove widths of the lug grooves 411, 412 is ensured and the tread noise during tire rolling is reduced. In addition, when Wg2 - Wg1 ≤ 4.0 mm is satisfied, the uneven rigidity of the land portion 31 caused by the excessive difference Wg2 - Wg1 between the groove widths of the lug grooves 411, 412 is alleviated.

[0086] Furthermore, in the pneumatic tire 1, the groove volume V1 of the first lug grooves 411 and the volume Vc of the recess portions 312, and the groove volume V2 of the second lug grooves 412 have the relationship 0.70 ≤ (V1 + Vc) / V2 ≤ 1.30. With such a configuration, the sum V1 + Vc of the volume of the narrower first lug grooves 411 and the recess portions 312 and the groove volume V2 of the wider second lug grooves 412 are made uniform. This is advantageous because the rigidity of the land portion 31 is made uniform in the tire circumferential direction.

[0087] Furthermore, in the pneumatic tire 1 according to the invention, the circumferential length L1 of the edge portions of the center land portion 31 defined by adjacent first lug grooves 411 and second lug grooves 412 and the circumferential length L2 of the recess portions 312 formed at the edge portions have the relationship 0.30 ≤ L2 / L1 ≤ 0.80 (see Fig. 4). This is advantageous because the circumferential length L2 of the recessed portions 312 is set appropriately. In other words, when 0.30 ≤ L2 / L1 is satisfied, the circumferential length L2 of the recessed portions 312 is ensured, the drainage properties and snow drainage properties of the narrower first lug grooves 411, and the noise properties are improved. When L2 / L1 ≤ 0.80 is satisfied, a decrease in the rigidity of the land portion 31 caused by the excessively large recessed portions 312 is suppressed.

[0088] In addition, in the pneumatic tire 1, the maximum width W1 of the land portion 31 and the maximum width W2 of the recess portions 312 have the relationship 0.05 ≤ W2 / W1 ≤ 0.20 (see Fig. 4). This is advantageous because the maximum width W2 of the recessed portions 312 is set appropriately. In other words, when 0.05 ≤ W2 / W1 is satisfied, the maximum width W2 of the recessed portions 312 is ensured, the drainage and snow drainage properties of the narrower first lug grooves 411 and the noise characteristics are improved. When W2 / W1 ≤ 0.20 is satisfied, a decrease in the rigidity of the land portion 31 caused by the excessively large recessed portions 312 is suppressed.

[0089] In addition, in the pneumatic tire 1, the maximum groove depth D1 of the first lug grooves 411 and the maximum depth D2 of the recess portions 312 have the relationship 0.30 ≤ D2 / D1 ≤ 1.00 (see Fig. 5). This is advantageous because the maximum depth D2 of the recessed portions 312 is set appropriately. In other words, when 0.30 ≤ D2 / D1 is satisfied, the maximum depth D2 of the recessed portions 312 is ensured, the drainage and snow drainage properties of the first lug grooves 411 and the noise characteristics are improved. When D2 / D1 ≤ 1.00 is satisfied, a decrease in the rigidity of the land portion 31 caused by the excessively deep recessed portions 312 is suppressed.

[0090] In addition, in the pneumatic tire 1, the maximum groove depth D1 of the first lug grooves 411 and the maximum depth D2 of the recess portions 312 have the relationship D2 / D1 ≤ 0.80 (see Fig. 5). In other words, when the recess portions 312 have the maximum depth D2 smaller than the maximum groove depth D1 of the first lug grooves 411, the opening portions of the first lug grooves 411 are provided with a raised bottom. This is advantageous in ensuring the rigidity of the land portion 31 and improving the steering stability performance of the tire.

[0091] In addition, in the pneumatic tire 1, the recess portions 312 have an edge portion having a V-shape protruding in the tire circumferential direction (see Fig. 4). This is advantageous because the edge length of the land portion 31 is increased, thus improving snow performance and driving performance on poor roads.

[0092] In addition, in the pneumatic tire 1, the bending angle θ of the V-shape of the recess portions 312 is in the range of 10 degrees ≤ θ ≤ 70 degrees (see Fig. 6). This is advantageous because the bending angle θ of the recessed portions 312 is set appropriately. In other words, when 10 degrees ≤ θ is satisfied, the size of the recessed portions 312 is ensured, the drainage and snow drainage properties of the narrower first lug grooves 411, and the noise characteristics are improved. When θ ≤ 70 degrees is satisfied, a decrease in the rigidity of the land portion 31 caused by the excessively large recessed portions 312 is suppressed.

[0093] In addition, in the pneumatic tire 1, the recess portions 312 overlap with the opening portion of the first lug grooves 411 (see Fig. 4). In other words, the recessed portions 312 are each arranged on one side of one of the first lug grooves 411 across the edge portions of a pair of adjacent portions of the land portion 31 (the blocks 311, 311). This is advantageous because the opening portion of the narrower first lug grooves 411 is widened to the left and right by the recessed portions 312, thereby improving the drainage characteristics of the first lug grooves 411.

[0094] In addition, in the pneumatic tire 1, the land portion 31 is referred to as a first land portion, and the land portions 32 on the other side of the circumferential main groove 21 from the first land portion 31 are referred to as second land portions (see Fig. 3). The second land portions 32 include pairs of lug grooves 421, 422 inclined at different inclination angles, and the extension lines of the groove center lines of the pairs of lug grooves 421, 422 meet at the edge portion of the first land portion 31. Furthermore, the recess portions 312 of the first land portion 31 are formed to surround the extension lines of the groove center lines of the pair of lug grooves 421, 422. With such a configuration, a water drainage channel is formed from the recess portion 312 of the first land portion 31 to the circumferential main groove 22 outside the second land portion 32 in the tire width direction through the lug grooves 421, 422 of the second land portion 32. This is advantageous in improving the drainage characteristics of the tread portion center region and the wet performance of the tire.

[0095] In addition, the web portion 31 in the pneumatic tire 1 includes three-dimensional sipes 5 (see Fig. 4). This is advantageous because the edge components of the land portion 31 are increased, thereby improving the tire's performance on snow. Furthermore, compared to configurations with two-dimensional sipes, the rigidity of the land portion 31 is ensured and the tire's steering stability performance is maintained.

[0096] Furthermore, in the pneumatic tire 1, the land portion 31 includes three-dimensional sipes 5 which extend entirely through the chamfered portion 313 and are open to the main circumferential groove 21 (see Fig. 4). Such a configuration is advantageous because the stiffness of the web portion 31 can be adjusted by the three-dimensional sipes 5 and the stiffness distribution in the tire contact surface can be optimized.

[0097] In addition, in the pneumatic tire 1, the opening portions of the three-dimensional sipes 5 to the main circumferential groove 21 and the recess portions 312 at the edge portion of the land portion 31 are arranged spaced apart from each other (see Fig. 4). This ensures the distance g1 (reference symbol for dimension omitted from drawings) between the opening portion of the three-dimensional slat 5 and the recess portion 312 and suppresses cracking starting from the slats 5.

[0098] In addition, the land portion 31 in the pneumatic tire 1 includes the three-dimensional sipes 5 which are blindly terminated within the land portion 31 at one end portion and open at the edge portion of the land portion 31 at the other end portion (see Fig. 4). The blind end portions of the three-dimensional slats 5 are spaced apart from the chamfered portions 313. This ensures the distance g2 (dimension omitted from drawings) between the blind end portion of the three-dimensional slat 5 and the chamfered portion 313 and suppresses cracking starting from the slats 5. Examples

[0099] Fig. 10 is a table showing results of performance testing of pneumatic tires according to embodiments of the present invention.

[0100] In the performance testing, a variety of pneumatic tires were evaluated for (1) snow performance, (2) noise performance, and (3) steering stability performance. The test tires, measuring 265 / 65R17 112H, were mounted on a 17 × 8J rim, inflated to an air pressure of 230 kPa, and a maximum load as defined by JATMA was applied to the pneumatic tires. The test tires were then mounted on the wheels of a test vehicle, a 3.5-liter four-wheel-drive recreational vehicle (RV).

[0101] (1) Snow performance evaluation: The test vehicle was driven on a snowy road surface at a snow-covered road test site, and the braking distance was measured at a driving speed of 40 km / h. The measurement results were then expressed as index values, with the result of the prior art example defined as the reference value (100). Higher values ​​are preferable for this evaluation.

[0102] (2) Noise performance evaluation: The test vehicle was driven on a test track according to the International Organization for Standardization (ISO) at a speed of 80 km / h, and the sound pressure levels of the pass-by noise (exterior noise) were measured. The evaluation results were expressed as index values, with the result of the prior art example 1 defined as the reference value (100). In this evaluation, higher values ​​are preferred and indicate lower sound pressure levels.

[0103] (3) Steering stability performance evaluation: The test vehicle was driven at a speed of 60 km / h to 100 km / h on a flat test circuit with a dry road surface. The test driver then performed a sensory evaluation of steering during lane changes and cornering, and forward stability. The evaluation results were expressed as index values, with the result of the prior art example 1 defined as the reference value (100). In this evaluation, higher values ​​are preferable.

[0104] The test tires of examples 1 to 11 have the Fig. 1 to 5, wherein the center land portion 31 includes the lug grooves 41, the recess portions 312, and the chamfered portions 313. The width W1 of the center land portion 31 is 30.0 mm, the groove depth D0 of the circumferential main groove 21 is 6.0 mm, and the groove depth D1 of the first lug grooves 411 and the second lug grooves 412 is 4.0 mm. Furthermore, in Examples 1 to 9, the two sides of the V-shape are inclined with different orientations with respect to the tire circumferential direction, so that the V-shape of the recess portions 312 does not protrude in the tire circumferential direction. In Examples 10 and 11, the two sides of the V-shape are inclined with the same orientation with respect to the tire circumferential direction, so that the V-shape of the recess portions 312 protrudes in the tire circumferential direction (see Fig. 4).

[0105] The test tires of the prior art example and the comparative example have the Fig. 1 to 5, however, the center web portion 31 does not include the recess portions 312 or the beveled portions 313.

[0106] As shown in the test results, it can be seen that the tires of Examples 1 to 8 have good snow performance, noise performance and steering stability performance in a compatible manner. List of reference symbols 1 pneumatic tire 21, 22 Main circumferential groove 31 Central bridge section 311 Block 312 recess section 313 Beveled section 32 Second bridge section 321, 322 Block 33 shoulder bar section 411, 412, 421, 422, 43 lug groove 5 slats 11 Tire bead core 12 bead fillers 13 carcass layers 14 Belt layer 141, 142 Cross belt 143 Belt cover 15 Tread rubber 16 sidewall rubber 17 Wheel rim cushion rubber

Claims

[1] Pneumatic tyre (1), comprising: a plurality of main circumferential grooves (21, 22); and a land portion (31, 32) defined by a pair of the plurality of main circumferential grooves (21, 22); wherein the web portion (31, 32) has a plurality of first lug grooves (411), a plurality of second lug grooves (412) which are wider than the first lug grooves (411), and a plurality of recess portions (312) formed only at opening portions of the first lug grooves (411), wherein a circumferential length L1 of edge portions of the land portion (31, 32) defined by the first lug grooves (411) and the second lug grooves (412) adjacent to each other and a circumferential length L2 of the recess portions (312) formed at the edge portions have the relationship 0.30 ≤ L2 / L1 ≤ 0.

80. [2] A pneumatic tire (1) according to claim 1, wherein a groove width Wg1 of the first lug grooves (411) and a groove width Wg2 of the second lug grooves (412) have the relationship 1.0 mm ≤ Wg2 - Wg1 ≤ 4.0 mm. [3] A pneumatic tire (1) according to claim 1 or 2, wherein a groove volume V1 of the first lug grooves (411) and a volume Vc of the recess portions (312) and a groove volume V2 of the second lug grooves (412) have the relationship 0.70 ≤ (V1 + Vc) / V2 ≤ 1.

30. [4] A pneumatic tire (1) according to any one of claims 1 to 3, wherein a maximum width W1 of the land portion (31, 32) and a maximum width W2 of the recess portions (312) have the relationship 0.05 ≤ W2 / W1 ≤ 0.

20. [5] A pneumatic tire (1) according to any one of claims 1 to 4, wherein a maximum groove depth D1 of the first lug grooves (411) and a maximum depth D2 of the recess portions (312) have the relationship 0.30 ≤ D2 / D1 ≤ 1.

00. [6] A pneumatic tire (1) according to claim 5, wherein the maximum groove depth D1 of the first lug grooves (411) and the maximum depth D2 of the recess portions (312) have the relationship D2 / D1 ≤ 0.

80. [7] A pneumatic tire (1) according to any one of claims 1 to 6, wherein the recess portions (312) include an edge portion having a V-shape protruding in a tire circumferential direction. [8] A pneumatic tire (1) according to claim 7, wherein a bending angle θ of the V-shape of the recess portions (312) is in the range of 10 degrees ≤ θ ≤ 70 degrees. [9] A pneumatic tire (1) according to any one of claims 1 to 8, wherein the recess portions (312) are arranged to overlap the opening portions of the first lug grooves (411). [10] The pneumatic tire (1) according to any one of claims 1 to 9, wherein the land portion (31, 32) is referred to as a first land portion (31), and the land portions (31, 32) on the other side of the circumferential main grooves (21, 22) from the first land portion (31) are referred to as second land portions (32), and the second land portions (32) each include a pair of lug grooves (421, 422) inclined at different inclination angles, and extension lines of groove center lines of the pair of lug grooves (421, 422) meet at the edge portion of the first land portions (31), and the recess portions (312) of the first land portion (31) are formed so as to surround the extension lines of the groove center lines of the pair of lug grooves (421, 422). [11] Pneumatic tire (1) according to one of claims 1 to 10, wherein the web portion (31, 32) comprises a three-dimensional sipe (5). [12] Pneumatic tire (1) according to claim 11, wherein the web portion (31, 32) comprises a chamfered portion (313) at the edge portion on the main circumferential groove side, and the three-dimensional lamella (5) extends completely through the bevelled section (313) and is open towards the main circumferential groove (21, 22). [13] A pneumatic tire (1) according to claim 11 or 12, wherein an opening portion of the three-dimensional sipe (5) to the main circumferential groove (21, 22) and the recess portions (312) are arranged spaced apart from each other in the tire circumferential direction at the edge portion of the land portion (31, 32). [14] Pneumatic tire (1) according to one of claims 11 to 13, wherein the web portion (31, 32) comprises a chamfered portion (313) at the edge portion on the main circumferential groove side, the three-dimensional slat (5) ends blindly within the web section (31, 32) at one end section and is open to the edge section of the web section (31, 32) at the other end section, and the blind end portion of the three-dimensional slat (5) and the beveled portion (313) are arranged at a distance from each other.

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