tire

Abstract

The present invention further improves the snow performance in a tire in which a plurality of protrusions are arranged at the groove bottom of a circumferential groove. The tire has a tread portion (2). The tread portion (2) includes a first circumferential groove (5) and a first land portion (11). The groove bottom (5d) of the first circumferential groove (5) includes a groove bottom reference plane (13) and a plurality of protrusions (14) protruding radially outward from the groove bottom reference plane (13). The first land portion (11) is provided with at least one first lateral groove (16) extending from the first circumferential groove (5) and interrupted in the first land portion (11). When the tread is viewed from above, the entire area of ​​the first lateral groove extension region (21) formed by extending the connection portion of the first lateral groove (16) at the first circumferential groove (5) in parallel to the groove bottom (5d) of the first circumferential groove (5) in the tire axial direction is formed by the groove bottom reference plane (13).

Description

Technical Field

[0001] The present invention relates to tires. Background Art

[0002] Patent Document 1 below proposes a tire that improves snow performance by improving the configuration of the main grooves and lateral grooves provided in the tread portion. In addition, Patent Document 2 below proposes a tire that has a plurality of groove bottom ridges provided at the groove bottom of the circumferential groove. The tire of Patent Document 2 can improve snow performance by allowing the groove bottom ridges to sink into the snow.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2017-210105

[0004] Patent Document 2: Japanese Patent Application Publication No. 2019-127104

[0005] In recent years, tires are required to have further improved snow performance. In order to improve the snow performance of tires with circumferential grooves and lateral grooves, it is conceivable to provide a plurality of protrusions at the bottom of the circumferential grooves, but the arrangement of the protrusions may make the snow column in the groove brittle. Summary of the invention

[0006] The present invention has been made in view of the above-mentioned actual situation, and a main object of the present invention is to further improve the on-snow performance in a tire having a plurality of protrusions provided at the groove bottom of a circumferential groove.

[0007] The present invention is a tire having a tread portion, wherein the tread portion includes a first circumferential groove extending continuously in the tire circumferential direction, and a first land portion adjacent to a first side of the first circumferential groove in the tire axial direction, the groove bottom of the first circumferential groove includes a groove bottom reference plane, and a plurality of protrusions protruding radially outward from the groove bottom reference plane, and at least one first lateral groove extending from the first circumferential groove and interrupted in the first land portion is provided in the first land portion, and when the tread is viewed from above, the entire area of ​​the first lateral groove extension region formed by extending the connecting portion of the first lateral groove at the first circumferential groove in parallel to the groove bottom of the first circumferential groove in the tire axial direction is formed by the groove bottom reference plane.

[0008] Preferably, in the tire of the present invention, the first circumferential groove includes, in the tire circumferential direction, first inclined portions inclined with respect to the tire circumferential direction and second inclined portions inclined with respect to the tire circumferential direction at a larger angle than the first inclined portions, alternately.

[0009] Preferably, in the tire of the present invention, the first lateral groove communicates with the second inclined portion.

[0010] Preferably, in the tire of the present invention, the first land portion is provided with at least one second lateral groove that completely crosses the first land portion.

[0011] Preferably, in the tire of the present invention, when the tread is viewed from above, at least a portion of the protrusion overlaps with a second lateral groove extension area formed by extending the connection portion of the second lateral groove at the first circumferential groove toward the groove bottom of the first circumferential groove in parallel in the axial direction of the tire.

[0012] Preferably, in the tire of the present invention, the tread portion includes a second land portion adjacent to a second side of the first circumferential groove in the tire axial direction, and a plurality of third lateral grooves completely crossing the second land portion are provided in the second land portion.

[0013] Preferably, in the tire of the present invention, the third lateral groove faces the first lateral groove across the first circumferential groove.

[0014] Preferably, in the tire of the present invention, the first circumferential groove alternately includes a first inclined portion inclined relative to the tire circumferential direction and a second inclined portion inclined relative to the tire circumferential direction at an angle greater than that of the first inclined portion, and the third lateral groove is connected to the second inclined portion.

[0015] Preferably, in the tire of the present invention, the groove width of the first lateral groove continuously decreases toward the first side in the tire axial direction, and the angle between two groove edges of the first lateral groove is 30 to 50 degrees.

[0016] Preferably, in the tire of the present invention, the length of the first lateral groove in the tire axial direction is 15% to 30% of the maximum width of the first land portion in the tire axial direction.

[0017] Preferably, in the tire of the present invention, the tread portion includes a second land portion adjacent to the second side of the first circumferential groove in the tire axial direction, and the second land portion is provided with a plurality of fourth lateral grooves connected to the first circumferential groove and interrupted in the second land portion.

[0018] Preferably, in the tire of the present invention, in a cross section along the longitudinal direction of the first circumferential groove, the protrusion includes a first surface extending in the tire radial direction and a second surface extending at a larger angle than the first surface with respect to the tire radial direction.

[0019] Preferably, in the tire of the present invention, the tread portion includes a second circumferential groove adjacent to the first side of the first land portion and extending in the circumferential direction of the tire, and the groove bottom of the second circumferential groove includes a groove bottom reference plane and a plurality of protrusions protruding radially outward from the tire compared to the groove bottom reference plane.

[0020] Preferably, in the tire of the present invention, in the cross-section along the length direction of the above-mentioned first circumferential groove or the above-mentioned second circumferential groove, the above-mentioned protrusion of the above-mentioned first circumferential groove and the above-mentioned protrusion of the above-mentioned second circumferential groove respectively include a first surface extending in the tire radial direction, and a second surface extending at a larger angle than the above-mentioned first surface relative to the tire radial direction.

[0021] Preferably, in the tire of the present invention, the first surface of the protrusion of the first circumferential groove faces the first side in the tire circumferential direction, and the first surface of the protrusion of the second circumferential groove faces the second side in the tire circumferential direction.

[0022] The tire of the present invention can exhibit excellent on-snow performance by adopting the above-mentioned structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a development view of the tread portion of the tire according to one embodiment of the present invention.

[0024] Figure 2 yes Figure 1 Enlarged view of the first circumferential groove, the first land portion and the second land portion.

[0025] Figure 3 yes Figure 2 A cross-sectional view along the length direction of the first circumferential groove.

[0026] Figure 4 Yes means Figure 2 An enlarged view of the profile of the first circumferential groove.

[0027] Figure 5 This is an enlarged view of the first circumferential groove of the comparative example.

[0028] Description of Reference Numerals

[0029] 2... tread portion; 5... first circumferential groove; 5d... groove bottom; 11... first land portion; 13... groove bottom reference surface; 14... protrusion; 16... first lateral groove; 21... groove bottom reference surface. DETAILED DESCRIPTION

[0030] Hereinafter, one embodiment of the present invention will be described based on the drawings.

[0031] Figure 1 FIG. 2 is a development diagram of the tread portion 2 of the tire 1 according to the present embodiment. Figure 1 As shown, the tire 1 of this embodiment is used as a pneumatic tire for a passenger car that is used in winter, for example. However, the tire 1 of the present invention is not limited to such a form.

[0032] The tire 1 of the present embodiment includes, for example, a tread portion 2 in which the orientation for mounting on a vehicle is specified. For example, the orientation for mounting on a vehicle is indicated by characters or marks on a sidewall portion or the like (not shown).

[0033] The tread portion 2 is composed of four circumferential grooves 3 extending continuously in the tire circumferential direction between the outer tread end To and the inner tread end Ti, and five land portions 4 divided by the circumferential grooves 3. That is, the tire 1 of the present invention is a so-called five-rib tire. However, the tire 1 of the present invention is not limited to such a form, and for example, it may be a so-called four-rib tire composed of three circumferential grooves 3 and four land portions 4.

[0034] The outer tread end To is the tread end intended to be located on the outer side of the vehicle when installed on the vehicle, and the inner tread end Ti is the tread end intended to be located on the inner side of the vehicle when installed on the vehicle. The outer tread end To and the inner tread end Ti are respectively equivalent to the outermost ground contact position of the tire axial direction when a normal load is applied to the tire 1 in a normal state and the tire contacts the flat surface at a camber angle of 0°.

[0035] "Normal state" means a state where the tire is assembled on a regular rim, filled with a regular internal pressure and unloaded, in the case of a pneumatic tire with various specifications specified. In the case of a tire with no specifications specified or a non-pneumatic tire, the normal state means a standard usage state corresponding to the purpose of use of the tire and an unloaded state. In this specification, unless otherwise specified, the dimensions of various parts of the tire are values ​​measured in the normal state.

[0036] "Regular rims" are rims whose specifications are specified for each tire in a standard system that includes the specifications that the tire complies with. For example, JATMA means "standard rim", TRA means "design rim", and ETRTO means "measuring rim".

[0037] "Normal internal pressure" is the air pressure specified for each tire in the specification system including the specifications to which the tire is based. If it is JATMA, it means "maximum air pressure". If it is TRA, it means the maximum value recorded in the table "TIRE LOAD LIMITS ATVARIOUS COLD INFLATION PRESSURES". If it is ETRTO, it means "INFLATION PRESSURE".

[0038] "Normal load" refers to the load specified for each specification for each tire in the specification system including the specifications based on which the tire is specified when various specifications of pneumatic tires are specified. If it is JATMA, it means "maximum load capacity", if it is TRA, it means the maximum value recorded in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and if it is ETRTO, it means "LOAD CAPACITY". In addition, in the case of tires that do not specify various specifications or non-pneumatic tires, "Normal load" refers to the load acting on a tire under the standard use state of the tire. The above-mentioned "standard use state" refers to the state in which the tire is installed on a standard vehicle corresponding to the purpose of use of the tire and the above-mentioned vehicle is stationary on a flat road surface in a state where it can travel.

[0039] The circumferential groove 3 includes, for example, a first circumferential groove 5, a second circumferential groove 6, a third circumferential groove 7, and a fourth circumferential groove 8. The first circumferential groove 5 is provided between the tire equator C and the outer tread end To. The second circumferential groove 6 is provided on the first side (the right side in each drawing of this specification) of the first circumferential groove 5 in the tire axial direction, and in this embodiment, is provided between the tire equator C and the inner tread end Ti. The third circumferential groove 7 is provided between the first circumferential groove 5 and the outer tread end To. The fourth circumferential groove 8 is provided between the second circumferential groove 6 and the inner tread end Ti.

[0040] The circumferential groove 3 can be in various forms such as a groove extending in a straight line in the tire circumferential direction, a groove extending in a zigzag shape, etc. In the present embodiment, the first circumferential groove 5 extends in a zigzag shape. On the other hand, the second circumferential groove 6, the third circumferential groove 7, and the fourth circumferential groove 8 extend in parallel in a straight line in the tire circumferential direction. However, the tire 1 of the present invention is not limited to such a form.

[0041] The distance L1 in the tire axial direction from the groove center line of the first circumferential groove 5 or the second circumferential groove 6 to the tire equator C is, for example, 3% to 15% of the tread width TW. In a preferred embodiment, the distance in the tire axial direction from the groove center line of the second circumferential groove 6 to the tire equator C is greater than the distance in the tire axial direction from the groove center line of the first circumferential groove 5 to the tire equator C. In addition, the distance L2 in the tire axial direction from the groove center line of the third circumferential groove 7 or the fourth circumferential groove 8 to the tire equator C is, for example, 20% to 35% of the tread width TW. In addition, the tread width TW is the distance in the tire axial direction from the outer tread end To to the inner tread end Ti in the above-mentioned normal state.

[0042] The groove width W1 of the circumferential groove 3 is preferably at least 3 mm. In a preferred embodiment, the groove width W1 of the circumferential groove 3 is 2.0% to 5.0% of the tread width TW. In this embodiment, among the four circumferential grooves 3, the second circumferential groove 6 has the largest groove width.

[0043] The land portion 4 includes a first land portion 11. The first land portion 11 is adjacent to the first side of the first circumferential groove 5 in the tire axial direction, and is divided between the first circumferential groove 5 and the second circumferential groove 6 in the present embodiment. In addition, the land portion 4 includes a second land portion 12. The second land portion 12 is adjacent to the second side of the first circumferential groove 5 in the tire axial direction (the side opposite to the first side, the left side in each of the drawings of this specification), and is divided between the first circumferential groove 5 and the third circumferential groove 7 in the present embodiment.

[0044] exist Figure 2 FIG. 2 shows an enlarged view of the first circumferential groove 5, the first land portion 11, and the second land portion 12. Figure 3 2 shows a cross-sectional view of the first circumferential groove 5 along the length direction. Figure 2 and Figure 3 As shown in FIG. 1 , the groove bottom 5d of the first circumferential groove 5 includes a groove bottom reference surface 13 and a plurality of protrusions 14 protruding outward in the tire radial direction relative to the groove bottom reference surface 13. Figure 2 In the figure, the above-mentioned protrusions 14 are colored.

[0045] like Figure 2 As shown, the first land portion 11 is provided with at least one first lateral groove 16 extending from the first circumferential groove 5 and interrupted within the first land portion 11 .

[0046] exist Figure 4 An enlarged view showing the outline of the first circumferential groove 5 is shown in FIG. Figure 4 The sipes configured on the land portion are omitted. Figure 4 As shown in FIG. 1 , when the tread is viewed from above, the first lateral groove 16 is connected to the first circumferential groove 5 by extending the first lateral groove extension area 21 (at the bottom 5d of the first circumferential groove 5) in parallel with the tire axial direction. Figure 4 The entire area of ​​) is formed by the groove bottom reference surface 13. In other words, no protrusion 14 is formed in the first lateral groove extension area 21 (in Figure 4 In, with Figure 2 The tire 1 of the present invention can exhibit excellent snow performance by adopting the above-mentioned structure. The following mechanism is presumed as the reason for this.

[0047] When the tire of the present invention runs on snow, the protrusions 14 provided at the groove bottom of the first circumferential groove 5 push away the snow column pressed in the first circumferential groove 5 to generate a large reaction force in the tire circumferential direction, thereby being able to exhibit excellent performance on snow.

[0048] On the other hand, when driving on snow, there is a tendency for harder snow pillars to be generated in the first lateral groove extension area 21 than in other parts. In the present invention, the entire area of ​​the first lateral groove extension area 21 is formed by the groove bottom reference surface 13, so a large amount of snow is easy to enter the first lateral groove extension area 21, and a large snow pillar shearing force may be generated. Such an action can exert excellent snow performance. In addition, with such a structure, the movement of water from the first circumferential groove 5 to the first lateral groove 16 is not hindered by the protrusion 14, so that the wet performance can be maintained.

[0049] The following describes a more detailed structure of the present embodiment. In addition, each structure described below represents a specific form of the present embodiment. Therefore, it goes without saying that the present invention can exert the above-mentioned effects even if it does not have the structure described below. In addition, even if any one of the structures described below is applied alone to the tire of the present invention that does not have the above-mentioned characteristics, it is possible to expect an improvement in performance corresponding to each structure. Moreover, in the case where several of the structures described below are applied in combination, it is possible to expect an improvement in performance corresponding to the combination of each structure.

[0050] like Figure 2 As shown, the first circumferential groove 5 includes first inclined portions 26 inclined with respect to the tire circumferential direction and second inclined portions 27 inclined with respect to the tire circumferential direction at a larger angle than the first inclined portions 26 alternately in the tire circumferential direction.

[0051] The angle of the first inclined portion 26 relative to the tire circumferential direction is, for example, less than 10°. The angle of the second inclined portion 27 relative to the tire circumferential direction is, for example, 60 to 80°. The first inclined portion 26 and the second inclined portion 27 are inclined in opposite directions relative to the tire circumferential direction. The angle between the first inclined portion 26 and the second inclined portion 27 is, for example, 100 to 120°. The length of the second inclined portion 27 is smaller than the length of the first inclined portion 26. As a result, when driving on snow, hard snow columns are generated on the second inclined portion 27, thereby improving the performance on snow. In addition, in this specification, the angle of the groove and the length of the groove are measured at the center line of the groove.

[0052] like Figure 3As shown in FIG. 1 , in a cross section of the first circumferential groove 5 along the longitudinal direction, the protrusion 14 provided at the groove bottom 5d of the first circumferential groove 5 includes a first surface 28 extending in the tire radial direction, and a second surface 29 extending at a larger angle than the first surface 28 relative to the tire radial direction. In the present embodiment, the first surface 28 at least partially includes an area orthogonal to the tire circumferential direction. The first surface 28 of the protrusion 14 of the first circumferential groove 5 faces the first side in the tire circumferential direction (at the first side). Figure 3 In addition, the first surface 28 and the second surface 29 are connected via a ridgeline 30 extending in the tire axial direction. The ridgeline 30 extends over the entire width of the groove bottom of the first circumferential groove 5. Such a protrusion 14 effectively improves the traction performance or braking performance on snow.

[0053] Angle θ1 between first surface 28 and second surface 29 is, for example, 80 to 110°. Maximum height h1 of protrusion 14 is, for example, 5% to 15% of maximum depth of first circumferential groove 5. Such protrusion 14 can maintain drainage of first circumferential groove 5 and improve on-snow performance.

[0054] like Figure 2 As shown in FIG. 1 , the protrusion 14 is provided on the first inclined portion 26 and is not provided on the second inclined portion 27. In addition, the number of protrusions 14 provided on one first inclined portion 26 is, for example, 2 to 6, preferably 3 to 5. In addition, the arrangement pitch P1 of adjacent protrusions 14 in the tire circumferential direction (e.g. Figure 3 20% to 30% of the length of the first inclined portion 26 in the tire circumferential direction. Such an arrangement of the protrusions 14 helps to improve the wet performance and the on-snow performance in a well-balanced manner.

[0055] At least one first lateral groove 16 is connected to the second inclined portion 27 of the first circumferential groove 5. Specifically, Figure 4 As shown, the first lateral groove extension area 21 overlaps at least a portion of the second inclined portion 27. Thus, the second inclined portion 27 and the first lateral groove 16 cooperate with each other to generate a harder snow column, thereby improving the on-snow performance. In this embodiment, the first lateral groove 16 communicating with the second inclined portion 27 and the first lateral groove 16 communicating with the first inclined portion 26 are alternately provided in the tire circumferential direction.

[0056] like Figure 2 As shown, the first lateral groove 16 is interrupted, for example, at a position closer to the first circumferential groove 5 than the center position of the first land portion 11 in the tire axial direction. The length L3 of the first lateral groove 16 in the tire axial direction is, for example, 15% to 30% of the maximum width W2 of the first land portion 11 in the tire axial direction. Such first lateral groove 16 can maintain the rigidity of the first land portion 11 and improve the on-snow performance.

[0057] The groove width of the first lateral groove 16 decreases, for example, toward the first side in the axial direction of the tire. In the present embodiment, the two groove edges of the first lateral groove 16 are non-parallel, and the groove width of the first lateral groove 16 continuously decreases toward the first side in the axial direction of the tire. One groove edge of the first lateral groove 16 is inclined in the same direction as the second inclined portion 27 of the first lateral groove 16 relative to the axial direction of the tire, and the other groove edge of the first lateral groove 16 is inclined in the opposite direction to the above-mentioned one groove edge relative to the axial direction of the tire. The angle between the two groove edges of the first lateral groove 16 is, for example, 30 to 50 degrees. Such a first lateral groove 16 can strongly compact the snow inside it by compressing the snow from the side of the second inclined portion 27.

[0058] The first land portion 11 is provided with at least one second lateral groove 17 that completely crosses the first land portion 11. In the present embodiment, a plurality of second lateral grooves 17 are provided in the first land portion 11. Thus, the first land portion 11 includes a first block 31 defined by the plurality of second lateral grooves 17.

[0059] The second lateral groove 17 is inclined, for example, in a direction opposite to the second inclined portion 27 of the first circumferential groove 5 with respect to the tire axial direction. An angle θ2 of the second lateral groove 17 with respect to the tire axial direction is, for example, 10 to 30 degrees.

[0060] It is preferred that the groove width of the connecting portion of the second lateral groove 17 at the first circumferential groove 5 increases toward the first circumferential groove 5. Thus, the second lateral groove 17 and the first circumferential groove 5 can cooperate with each other to form a hard snow column. In addition, when running on wet land, water in the first circumferential groove 5 easily moves to the second lateral groove 17, thereby improving wet performance.

[0061] like Figure 4 As shown, it is preferred that at least a portion of the protrusion 14 is connected to a second lateral groove extension region 22 (at the bottom of the first circumferential groove 5) formed by extending the connecting portion of the second lateral groove 17 at the first circumferential groove 5 in parallel with the tire axial direction toward the groove bottom of the first circumferential groove 5. Figure 4 As a result, it is possible to prevent snow from clogging the above-mentioned connecting portion of the second lateral groove 17, thereby continuously exerting excellent on-snow performance.

[0062] like Figure 2 As shown, the first block 31 is provided with an interrupted short groove 32 extending from the second circumferential groove 6 and interrupted in the first block 31. The interrupted short groove 32 is interrupted at a position closer to the second circumferential groove 6 than the center position of the first land portion 11 in the tire axial direction. The length L4 of the interrupted short groove 32 in the tire axial direction is, for example, 15% to 30% of the maximum width W2 of the first land portion 11 in the tire axial direction. Such an interrupted short groove 32 can maintain the rigidity of the first land portion 11 and improve the on-snow performance.

[0063] The interrupted short groove 32 is inclined, for example, relative to the tire axial direction. The interrupted short groove 32 of this embodiment is inclined in the same direction as the second inclined portion 27 of the first circumferential groove 5, and the angle difference between these grooves is, for example, 10° or less. In addition, the angle of the interrupted short groove 32 relative to the tire axial direction is, for example, 10 to 30°. Such an interrupted short groove 32 improves the traction performance on snow and the cornering performance in a well-balanced manner.

[0064] A plurality of sipes 33 are provided in the first pattern block 31. In the present specification, a "sipe" refers to a cutout element having a small width, and the width between two sipe walls facing each other is 1.5 mm or less. The width of the sipe is preferably 0.1 to 1.0 mm, and more preferably 0.2 to 0.4 mm. For the sipe of the present embodiment, the width is within the above range throughout the entire depth. In addition, in the present specification, in a cross section of a certain cutout element, a cutout element including an area with a width of 1.5 mm or less at more than 50% of its entire depth is treated as a sipe (a sipe including a groove element) even if it partially includes an area with a width of more than 1.5 mm. In addition, in a cross section of a certain cutout element, a cutout element including an area with a width of more than 1.5 mm at more than 50% of its entire depth is treated as a groove (a groove including a sipe element) even if it partially includes an area with a width of less than 1.5 mm.

[0065] The sipe 33 is inclined, for example, in the same direction as the second inclined portion 27 with respect to the tire axial direction. In addition, when the tread is viewed from above, the sipe 33 of the present embodiment extends in a zigzag shape. The sipe 33 may be configured as a so-called 3D (three-dimensional) sipe extending in a zigzag shape in the length direction and the depth direction thereof, for example. Such a sipe 33 can maintain the rigidity of the first land portion 11 and improve the performance on ice.

[0066] The second land portion 12 is provided with a plurality of third lateral grooves 18 that completely cross the second land portion 12 , and a plurality of fourth lateral grooves 19 that are connected to the first circumferential grooves 5 and are interrupted in the second land portion 12 .

[0067] The third lateral groove 18 is inclined, for example, with respect to the tire axial direction. The third lateral groove 18 is inclined with respect to the tire axial direction in the same direction as the second inclined portion 27 of the first circumferential groove 5. Thus, the second lateral groove 17 and the third lateral groove 18 are inclined with respect to the tire axial direction in opposite directions. The angle θ3 of the third lateral groove 18 with respect to the tire axial direction is, for example, 15 to 30 degrees. Such a third lateral groove 18 improves the traction performance on snow and the cornering performance in a well-balanced manner.

[0068] At least one third lateral groove 18 communicates with, for example, the second inclined portion 27. In the present embodiment, the third lateral grooves 18 communicating with the second inclined portion 27 and the third lateral grooves 18 communicating with the first inclined portion 26 are alternately provided in the tire circumferential direction.

[0069] The third lateral groove 18 faces the first lateral groove 16 across the first circumferential groove 5. In addition, this structure refers to a form in which an imaginary area formed by extending the third lateral groove 18 along its length direction toward the first land portion 11 overlaps at least a portion of the first lateral groove 16. As a result, the third lateral groove 18, the first circumferential groove 5, and the first lateral groove 16 can cooperate with each other to form a hard snow column, thereby further improving the on-snow performance.

[0070] The fourth lateral groove 19 is inclined, for example, with respect to the tire axial direction. The fourth lateral groove 19 is inclined with respect to the tire axial direction in the same direction as the second inclined portion 27 of the first circumferential groove 5. Thus, the fourth lateral groove 19 is inclined with respect to the tire axial direction in the same direction as the third lateral groove 18. The angle θ4 of the fourth lateral groove 19 with respect to the tire axial direction is, for example, 15 to 30 degrees.

[0071] The length L5 of the fourth lateral groove 19 in the tire axial direction is, for example, 40% to 60% of the maximum width W3 of the second land portion 12 in the tire axial direction. In addition, the maximum groove width of the fourth lateral groove 19 is smaller than the maximum groove width of the third lateral groove 18. Such fourth lateral groove 19 can maintain the rigidity of the second land portion 12 and improve the on-snow performance.

[0072] like Figure 4 As shown in FIG. 1 , when the tread is viewed from above, it is preferred that the fourth lateral groove 19 is connected to the first circumferential groove 5 by extending the fourth lateral groove extension region 24 (at the bottom 5d of the first circumferential groove 5) in parallel with the tire axial direction. Figure 4 ), the entire area of ​​the first circumferential groove 5 is formed by the groove bottom reference surface 13. Thus, a hard snow column can be generated in the fourth lateral groove extension area 24. In addition, the above structure makes it easy for water to move from the first circumferential groove 5 to the fourth lateral groove 19 side, which also helps to improve wetland performance.

[0073] like Figure 2 As shown, the second land portion 12 includes a plurality of second blocks 34 divided by a plurality of third lateral grooves 18. A plurality of sipes 35 are provided in the second blocks 34. The sipes 35 provided in the second blocks 34 are inclined in a direction opposite to the second inclined portion 27 with respect to the tire axial direction. For other structures, the structure of the sipes 33 provided in the above-mentioned first blocks 31 can be applied to the sipes 35 provided in the second blocks 34.

[0074] The groove width of the second circumferential groove 6 is larger than the groove width of the first circumferential groove 5. Preferably, the groove width of the second circumferential groove 6 is 1.5 to 2.0 times the groove width of the first circumferential groove 5. Such second circumferential groove 6 contributes to improving the on-snow performance and wet performance.

[0075] The groove bottom 6d of the second circumferential groove 6 includes a groove bottom reference surface 38 and a plurality of protrusions 39 protruding outward in the tire radial direction relative to the groove bottom reference surface 38. The structure of the protrusion 14 of the first circumferential groove 5 described above can be applied to the protrusion 39 of the second circumferential groove 6. The second circumferential groove 6 having such protrusions 39 can improve traction performance or braking performance on snow.

[0076] In a more preferred embodiment, the first surface 28 of the protrusion 14 of the first circumferential groove 5 faces the first side in the tire circumferential direction, and the first surface of the protrusion 39 of the second circumferential groove 6 faces the second side in the tire circumferential direction opposite to the first side. Thus, the traction performance and braking performance on snow are improved in a well-balanced manner.

[0077] It is preferred that the protrusion 39 of the second circumferential groove 6 overlaps at least a portion of a region formed by extending the connecting portion of the second lateral groove 17 or the interrupted short groove 32 at the second circumferential groove 6 in parallel to the tire axial direction toward the groove bottom of the second circumferential groove. Such an arrangement of the protrusion 39 can prevent snow from clogging the second lateral groove 17 and the interrupted short groove 32, thereby continuously exhibiting excellent on-snow performance.

[0078] As mentioned above, although the tire which concerns on one embodiment of this invention was demonstrated in detail, this invention is not limited to the said specific embodiment, It can be implemented by changing into various forms.

[0079] [Example]

[0080] Based on the specifications in Table 1, we have produced Figure 1 A tire with a basic tread pattern of 195 / 65R15 was produced as a comparative example. Figure 5 The tire has the first circumferential groove a shown in FIG. Figure 5 As shown, the projection b of the first circumferential groove a overlaps with the first lateral groove extension region formed by extending the first lateral groove c of the comparative example in parallel to the tire axial direction toward the groove bottom of the first circumferential groove a. The tire of the comparative example has the same Figure 1 The tires shown have substantially the same tread pattern. For each test tire, snow performance and wet performance were tested. The general specifications and test methods of each test tire are as follows.

[0081] Installed rim: 15×6.0JJ

[0082] Tire internal pressure: front wheel 230kPa, rear wheel 230kPa

[0083] Test vehicle: 1500cc displacement, front-wheel drive

[0084] Tire installation position: All wheels

[0085] <Snow performance>

[0086] The on-snow performance of the test vehicle when driving on snow was evaluated by the driver's senses. The results were scored with the comparative example as 100, and a larger value indicated a better on-snow performance.

[0087] <Wetland Performance>

[0088] The wet performance of the test vehicle when driving on a wet road was evaluated by the driver's senses using the test vehicle. The results were scored with the comparative example as 100, and a larger value indicated a better wet performance.

[0089] The test results are shown in Table 1.

[0090]

Table 1

[0091]

[0092] As shown in Table 1, it was confirmed that the tires of the examples exhibited excellent on-snow performance. In addition, it was also confirmed that the tires of the examples maintained their wet performance.

Claims

1. A tire having a tread portion, The tire is characterized in that The tread portion includes a first circumferential groove extending continuously in the tire circumferential direction and a first land portion adjacent to a first side of the first circumferential groove in the tire axial direction. The groove bottom of the first circumferential groove includes a groove bottom reference surface and a plurality of protrusions protruding outward in the tire radial direction relative to the groove bottom reference surface. The first land portion is provided with at least one first lateral groove extending from the first circumferential groove and interrupted in the first land portion. When the tread is viewed from above, the entire first lateral groove extension region formed by extending the connection portion of the first lateral groove at the first circumferential groove in parallel to the groove bottom of the first circumferential groove in the tire axial direction is formed by the groove bottom reference plane. The first circumferential groove alternately includes, in the tire circumferential direction, first inclined portions inclined relative to the tire circumferential direction and second inclined portions inclined relative to the tire circumferential direction at a larger angle than the first inclined portions. The first land portion is provided with at least one second lateral groove which completely crosses the first land portion, wherein the second lateral groove is inclined in a direction opposite to the second inclined portion of the first circumferential groove with respect to the tire axial direction. When the tread is viewed from above, at least a portion of the protrusion overlaps with a second lateral groove extension region formed by extending a connection portion of the second lateral groove at the first circumferential groove toward the groove bottom of the first circumferential groove in parallel in the tire axial direction.

2. The tire according to claim 1, characterized in that The first lateral groove communicates with the second inclined portion.

3. The tire according to claim 1 or 2, characterized in that: The tread portion includes a second land portion adjacent to a second side of the first circumferential groove in the tire axial direction. The second land portion is provided with a plurality of third lateral grooves that completely cross the second land portion.

4. The tire according to claim 3, characterized in that The third lateral groove faces the first lateral groove across the first circumferential groove.

5. The tire according to claim 3, characterized in that The third lateral groove communicates with the second inclined portion.

6. The tire according to claim 1 or 2, characterized in that: The groove width of the first lateral groove continuously decreases toward the first side in the tire axial direction. The angle between the two groove edges of the first transverse groove is 30 to 50 degrees.

7. The tire according to claim 1 or 2, characterized in that: The length of the first lateral groove in the tire axial direction is 15% to 30% of the maximum width of the first land portion in the tire axial direction.

8. The tire according to claim 1 or 2, characterized in that: The tread portion includes a second land portion adjacent to a second side of the first circumferential groove in the tire axial direction. The second land portion is provided with a plurality of fourth lateral grooves which are connected to the first circumferential grooves and are interrupted in the second land portion.

9. The tire according to claim 1 or 2, characterized in that: In a cross section along the longitudinal direction of the first circumferential groove, the protrusion includes a first surface extending in the tire radial direction and a second surface extending at a larger angle than the first surface with respect to the tire radial direction.

10. The tire according to claim 1 or 2, characterized in that: The tread portion includes a second circumferential groove adjacent to the first side of the first land portion and extending in the tire circumferential direction. The groove bottom of the second circumferential groove includes a groove bottom reference surface and a plurality of protrusions that protrude outward in the tire radial direction relative to the groove bottom reference surface.

11. The tire according to claim 10, characterized in that In the cross-section along the length direction of the first circumferential groove and the second circumferential groove, the protrusion of the first circumferential groove and the protrusion of the second circumferential groove respectively include a first surface extending in the tire radial direction, and a second surface extending at a larger angle than the first surface relative to the tire radial direction.

12. The tire according to claim 11, characterized in that The first surface of the protrusion of the first circumferential groove faces the first side in the tire circumferential direction. The first surface of the protrusion of the second circumferential groove faces the second side in the tire circumferential direction.

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