pneumatic tires

Abstract

We provide pneumatic tires that offer a good balance between snow driving performance and traction. [Solution] The central land bridge 100 has a first central slit 140 that extends from one end of the central land bridge 100 in the axial direction of the tire and intersects with the circumferential direction of the tire, and terminates within the central land bridge 100, and a second central slit 150 that extends from the other end of the central land bridge 100 in the axial direction of the tire and terminates within the central land bridge 100, which are alternately arranged in the circumferential direction of the tire. The first central slit 140 and the second central slit 150 intersect with the tire equator. The first intermediate land bridge 200 has a first intermediate slit 220 that extends in a direction intersect with the circumferential direction of the tire, and the second intermediate land bridge 300 has a third intermediate slit 330 that extends in a direction intersect with the circumferential direction of the tire.

Description

Technical Field

[0001] The present invention relates to pneumatic tires.

Background Art

[0002] Conventionally, pneumatic tires such as studless tires used on snow-covered roads, etc. have a tread that contacts the road surface composed of a plurality of blocks arranged in the tire circumferential direction in order to ensure traction during driving on snow (see Patent Document 1, etc.).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Although the block formation of the tread is effective in improving the driving performance on snow, there is room for improvement because there is a concern that the rigidity of the tread decreases and the grounding performance deteriorates.

[0005] Therefore, an object of the present invention is to provide a pneumatic tire in which the driving performance on snow and the grounding performance are well balanced.

Means for Solving the Problems

[0006] The pneumatic tire of the present invention is a pneumatic tire having a tread that includes a rib-shaped central landform positioned on the tire equator and extending continuously in an annular manner in the tire circumferential direction, a first intermediate landform positioned on one side of the central landform in the tire axial direction, a second intermediate landform positioned on the other side of the central landform in the tire axial direction, a first circumferential groove positioned between the central landform and the first intermediate landform, and a second circumferential groove positioned between the central landform and the second intermediate landform, wherein the central landform has a first central slit that extends from one end of the central landform in the tire axial direction in a direction intersecting the tire circumferential direction and terminates within the central landform, and a second central slit that extends from the other end of the central landform in the tire axial direction in a direction intersecting the tire circumferential direction and terminates within the central landform, which are alternately arranged in the tire circumferential direction, the first central slit and the second central slit intersect the tire equator, the first intermediate landform has a first intermediate slit that extends in a direction intersecting the tire circumferential direction, and the second intermediate landform has a second intermediate slit that extends in a direction intersecting the tire circumferential direction. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a pneumatic tire that ensures a good balance between snow driving performance and ground contact. [Brief explanation of the drawing]

[0008] [Figure 1] This is a perspective view of a tire (pneumatic tire) according to an embodiment, partially showing a portion of the tire in the circumferential direction. [Figure 2] This is a partially enlarged front view showing the tread surface of a tire according to an embodiment. [Figure 3] This is an enlarged view of the area shown in III in Figure 2. [Figure 4] This is an enlarged view of the area shown in IV of Figure 2. [Figure 5] Figure 4 is a VV cross-sectional view. [Figure 6] This is a cross-sectional view taken from VI-VI in Figure 4. [Figure 7] This is a cross-sectional view taken along line VII-VII in Figure 4. [Figure 8]This figure shows a modified example of the buttress of the embodiment, and is a plan view showing a part of the buttress. [Figure 9] This figure shows another modification of the buttress of the embodiment, and is a plan view showing a part of the buttress. [Modes for carrying out the invention]

[0009] The embodiments will be described below with reference to the drawings. Figure 1 is a partial perspective view showing a part of the circumferential direction of tire 1 as a pneumatic tire according to the embodiment. Tire 1 according to the embodiment is, for example, a pneumatic tire for a passenger car. The configuration of tire 1 according to the embodiment can be used for various vehicles other than passenger cars, such as light trucks, trucks, and buses.

[0010] As shown in Figure 1, the tire 1 comprises a tread 2 which includes the outer circumference of the tire and is the part that contacts the road surface, a pair of beads 3 which are the parts that fit onto the rim of a tire wheel (not shown), a pair of sidewalls 4 which are positioned between the tread 2 and each bead 3 and constitute the side wall surface of the tire, and a shoulder 5 between each sidewall 4 and the tread 2. The tread 2 includes a tread surface 2A which contacts the road surface, and a tread pattern 2B is formed on the tread surface 2A by a plurality of types of grooves and other features. The tread pattern 2B in this embodiment is asymmetrical in the tire axial direction. Each of the pair of sidewalls 4 has a buttress 8 on its radially outer side. The buttress 8 is the part that transitions from the sidewall 4 to the shoulder 5, and is the outermost annular part of the sidewall 4 in a side view of the tire, and is a part that is likely to come into contact with the inner wall surface of a rut, for example when driving on snow.

[0011] Figure 2 is a magnified view of a portion of the front view of tire 1, showing the tread surface 2A, a pair of sidewalls 4, a pair of shoulders 5, and a pair of buttresses 8. Figure 3 is a magnified view of the portion indicated by III in Figure 2. Figures 2 and 3 show the tire axial direction X, the tire circumferential direction C, and the tire equator E. The tire equator E is a hypothetical line extending along the tire circumferential direction from the center of the tire axial direction. In Figures 2 and 3, one side of the tire axial direction X (right side in Figures 2 and 3) is indicated by arrow X1, and the other side (left side in Figures 2 and 3) is indicated by arrow X2. Also, in Figures 2 and 3, one side of the tire circumferential direction C (lower side in Figure 1) is indicated by arrow C1, and the other side (upper side in Figure 1) is indicated by arrow C2. The same symbols apply to Figure 4.

[0012] The tread surface 2A has a contact width region in the axial direction of the tire, which is the area that actually contacts the road surface. As shown in Figure 2, the contact width region of the tread surface 2A is the area between the contact ends 2C at both ends of the tread surface 2A in the axial direction of the tire. The contact width region referred to here is the area in the axial direction of the tire that contacts the road surface under the condition that the tire 1, mounted on a regular rim and filled with regular internal pressure, is in contact with the road surface and a regular load is applied to it. Each of the pair of sidewalls 4 extends radially inward from the contact end 2C of the tire.

[0013] The grooves forming the tread pattern 2B include circumferential grooves, slits, lug grooves, sipes, etc., including main grooves and secondary grooves, as described later. The circumferential grooves are basically grooves that run along the circumferential direction of the tire, while the slits, lug grooves, and sipes are basically grooves that extend in a direction intersecting the circumferential direction of the tire. The width of these grooves is largest for the main grooves and smallest for the sipes. In the embodiment, the width of the various sipes is, for example, about 0.3 mm to less than 1.0 mm, and the depth is, for example, about 4 mm to 11 mm, but is not limited to these. The widths of the secondary grooves, slits, and lug grooves are basically smaller than the main grooves and larger than the sipes, but they may have similar widths or there may be differences.

[0014] As shown in FIG. 2, the tread 2 includes a plurality of lands 6 arranged in the tire axial direction and a plurality of circumferential grooves 7 extending in the tire circumferential direction that partition the plurality of lands 6 in the tire axial direction. Each of the plurality of lands 6 extends in the tire circumferential direction. The tubeless 8 includes a first tubeless 8A on one side X1 in the tire axial direction and a second tubeless 8B on the other side X2 in the tire axial direction.

[0015] The plurality of lands 6 includes a central land 100 disposed at the center in the tire axial direction on the tire equator E, a first intermediate land 200 disposed on one side X1 in the tire axial direction of the central land 100, a second intermediate land 300 disposed on the other side X2 in the tire axial direction of the central land 100, a first shoulder land 400 disposed on one side X1 in the tire axial direction of the first intermediate land 200, and a second shoulder land 500 disposed on the other side X2 in the tire axial direction of the second intermediate land 300.

[0016] In the embodiment, the maximum widths of the first intermediate land 200 and the second intermediate land 300 are substantially the same and are larger than the maximum width of the central land 100. The widths of the first shoulder land 400 and the second shoulder land 500 in the embodiment are substantially the same and are larger than the widths of the first intermediate land 200 and the second intermediate land 300. Note that the width of each land 6 is not limited in this way and may be arbitrary.

[0017] The plurality of circumferential grooves 7 includes a sub-groove 600 as a first circumferential groove between the central land 100 and the first intermediate land 200, a first main groove 700 as a second circumferential groove between the central land 100 and the second intermediate land 300, a second main groove 800 between the first intermediate land 200 and the first shoulder land 400, and a third main groove 900 between the second intermediate land 300 and the second shoulder land 500. The maximum width of each of the main grooves 700, 800, 900 is, for example, about 4 mm or more and 8 mm or less, and the depth is, for example, about 8 mm or more and 11 mm or less, but is not limited thereto. The sub-groove 600 has a maximum width and depth smaller than those of the main grooves 700, 800, 900. For example, the maximum width is about 2 to 5 mm, and the depth is about 4 mm or more and 9 mm or less, but is not limited thereto.

[0018] The sub-groove 600 of the embodiment has an overall zigzag shape. The first main groove 700 of the embodiment is linear along the tire circumferential direction and has a substantially constant width. The second main groove 800 and the third main groove 900 of the embodiment have a zigzag shape. The groove shape of these circumferential grooves 7 on the tread surface 2A is not limited and may be arbitrary.

[0019] As shown in FIG. 3, the central land 100 includes a plurality of first central sipes 110, a plurality of second central sipes 120, and a plurality of third central sipes 130.

[0020] The plurality of first central sipes 110 are arranged in a substantially central region in the width direction of the central land 100. The plurality of first central sipes 110 are arranged at intervals in the tire circumferential direction. The first central sipes 110 extend along the tire axial direction as a whole. The first central sipes 110 have a surface shape on the tread surface 2A that can be called a substantially S-shaped or crank-shaped. The first central sipes 110 do not communicate with either the sub-groove 600 or the first main groove 700 on both sides in the tire axial direction, and both ends thereof terminate within the central land 100.

[0021] As shown in FIG. 3, the plurality of second central sipes 120 are arranged on one side X1 and the other side X2 in the tire axial direction of the first central sipes 110, respectively. The plurality of second central sipes 120 are arranged at intervals in the tire circumferential direction. The second central sipes 120 have a portion with a corrugated surface shape on the tread surface 2A. The overall extending direction of the second central sipes 120 is inclined so as to extend toward the one side C1 in the tire circumferential direction as it goes from the end on the other side X2 in the tire axial direction to the end on the one side X1 in the tire axial direction. The second central sipes 120 arranged on the one side X1 in the tire axial direction of the first central sipes 110 communicate with the sub-groove 600. The second central sipes 120 arranged on the other side X2 in the tire axial direction of the first central sipes 110 communicate with the first main groove 700.

[0022] The second central sipe 120 is preferably a 3D sipe. A 3D sipe, as used herein, is a sipe that is three-dimensional in the direction of extension of the second central sipe 120 (the length direction from one end to the other) by being bent in a wave-like shape, and also has a bent portion in the sipe depth direction, making it three-dimensional.

[0023] Multiple third central sipes 130 are located on one side X1 of the tire axial direction of the first central sipe 110. The third central sipes 130 have a wavy surface shape on the tread surface 2A. The third central sipes 130 are located between a predetermined pair of second central sipes 120 that are adjacent in the tire circumferential direction, among the second central sipes 120 located on one side X1 of the tire axial direction of the first central sipe 110. The overall extension direction of the third central sipes 130 is substantially parallel to that of the second central sipes 120. The third central sipes 130 are adjacent to the sub-grooves 600 but do not communicate with the sub-grooves 600, and both ends terminate within the central land 100.

[0024] In this embodiment, the width of the second central sipe 120 and the width of the third central sipe 130 are approximately the same, and the width of the first central sipe 110 is greater than the widths of the second central sipe 120 and the third central sipe 130, but this is not limited to this.

[0025] As shown in Figures 2 and 3, the central land bridge 100 includes a plurality of first central slits 140 and a plurality of second central slits 150 extending in a direction intersecting the tire circumferential direction. Each of the first central slits 140 and the second central slits 150 is spaced apart in the tire circumferential direction. The width of the first central slits 140 and the second central slits 150 is, for example, about 3 mm to 6 mm, but is not limited thereto. The depth is, for example, about 7.0 mm to 8.5 mm for the first slits 140 and about 4.0 mm to 5.5 mm for the second slits 150, but is not limited thereto.

[0026] The first central slit 140 has one end X1 on the tire axial direction that communicates with the sub-groove 600. The first central slit 140 extends from the end communicating with the sub-groove 600 to the other end X2 on the tire axial direction and terminates just before reaching the first main groove 700. The first central slit 140 is inclined with respect to the tire axial direction so that as it moves from the end communicating with the sub-groove 600 toward the other end X2 on the tire axial direction, it extends toward the other end C2 on the tire circumferential direction. The end portion of the first central slit 140 toward the other end X2 on the tire axial direction has a hook-shaped portion 141 that extends toward the other end X2 on the tire axial direction toward the one end C1 on the tire circumferential direction. Preferably, the direction in which the hook-shaped portion 141 extends toward the one end C1 on the tire circumferential direction, that is, the direction from the end of the first central slit 140 toward the tip, is the direction from the tire entry side (first entry side) to the tire exit side (rear entry side), and is inclined with respect to the tire circumferential direction. The first central slit 140 extends across the tire equator E. That is, the first central slit 140 extends in a direction intersecting the tire equator E. In the first central slit 140 of this embodiment, the tire equator E passes near the starting end of the hook-shaped portion 141.

[0027] The second central slit 150 has one end X2 on the other side of the tire axial direction that communicates with the first main groove 700. The second central slit 150 extends from one end communicating with the first main groove 700 toward one side X1 in the tire axial direction and terminates just before reaching the sub-groove 600. The second central slit 150 is inclined with respect to the tire axial direction so that as it moves from one end communicating with the first main groove 700 toward one side X1 in the tire axial direction, it extends toward one side C1 in the tire circumferential direction. The second central slit 150 extends across the tire equator E. That is, the second central slit 150 extends in a direction intersecting the tire equator E.

[0028] The first central slit 140 and the second central slit 150 are arranged alternately in the circumferential direction of the tire. A predetermined number of first central sipes 110, second central sipes 120, and third central sipes 130 are arranged between adjacent first central slits 140 and second central slits 150 in the circumferential direction of the tire. None of the central sipes 110, 120, 130, and none of the central slits 140, 150 cross the central ridge 100 and are in communication with either the sub-groove 600 or the first main groove 700. Therefore, the central ridge 100 has a rib shape that extends continuously in an annular shape in the circumferential direction of the tire.

[0029] As shown in Figures 2 and 3, the first intermediate landform 200 includes a plurality of first intermediate blocks 210 arranged in the circumferential direction of the tire, and a plurality of first intermediate slits 220 extending in a direction intersecting the circumferential direction of the tire. The plurality of first intermediate slits 220 are spaced apart in the circumferential direction of the tire. The first intermediate slits 220 traverse the first intermediate landform 200 and communicate with the secondary groove 600 and the second main groove 800.

[0030] As shown in Figure 3, the first intermediate slit 220 has a first bent portion 221 that protrudes to one side C1 in the tire circumferential direction. The first bent portion 221 is formed in the first intermediate slit 220 at a position closer to one side X1 in the tire axial direction. The first intermediate slit 220 has a first inclined portion 222 that extends from the first bent portion 221 to the second main groove 800, and a second inclined portion 223 that extends from the first bent portion 221 to the sub-groove 600. When viewed from the first bent portion 221 as the starting point, the first inclined portion 222 and the second inclined portion 223 are inclined with respect to the tire axial direction such that they extend to the other side C2 in the tire circumferential direction as they extend away from the first bent portion 221 in the tire axial direction. The first intermediate slit 220 has a first protruding recess 224 on one side C1 in the tire circumferential direction of the first bent portion 221 that protrudes to one side X1 in the tire axial direction.

[0031] As described above, the width of the second main groove 800 is larger than that of the sub-groove 600, which is part of the circumferential groove 7. Also, the width of the first inclined portion 222 and the second inclined portion 223 of the first intermediate slit 220 is smaller for the first inclined portion 222 than for the second inclined portion 223. In the first intermediate slit 220, the first inclined portion 222 on the side with the smaller groove width communicates with the second main groove 800 on the side with the larger groove width in the circumferential groove 7, and the second inclined portion 223 on the side with the larger groove width communicates with the sub-groove 600, which has the smaller groove width in the circumferential groove 7. In other words, the groove width of the first inclined portion 222 communicating with the second main groove 800 is smaller than the groove width of the second inclined portion 223 communicating with the sub-groove 600. The width of the first inclined portion 222 is, for example, about 2.5 mm to 4.5 mm, and its depth is, for example, about 3 mm to 9 mm, but is not limited thereto. The width of the second inclined portion 223, which is larger than the first inclined portion 222, is, for example, about 3 mm to 5 mm, and its depth is, for example, about 7 mm to 9 mm, but is not limited thereto.

[0032] Each of the multiple first intermediate blocks 210 is divided into a substantially rectangular shape by a sub-groove 600, a second main groove 800, and a pair of first intermediate slits 220 adjacent in the circumferential direction of the tire. The first central slit 140 of the central land 100 extends on the extension of the first intermediate slits 220, with the sub-groove 600 in between. "0231" first half of claim 2

[0033] As shown in Figure 3, the sub-groove 600 is composed of a plurality of segmented grooves 610 formed in each first intermediate block 210 and divided in the tire circumferential direction, which are continuous in the tire circumferential direction via the first intermediate slit 220. Each of the segmented grooves 610 is inclined with respect to the tire circumferential direction such that it extends to one side X1 in the tire axial direction as it moves from the other side C2 in the tire circumferential direction toward one side C1 in the tire circumferential direction. As a result, the edge of the central land 100 that extends in the tire circumferential direction toward one side X1 in the tire axial direction has a zigzag shape. Claim 3

[0034] As shown in Figure 3, the first intermediate block 210 has a pair of notches, a first notch 211 and a second notch 212, located approximately in the center of the tire circumferential direction and approximately opposite to each other in the tire axial direction. The first notch 211 is formed on the edge of the first intermediate block 210 on one side X1 in the tire axial direction and communicates with the second main groove 800. The second notch 212 is formed on the edge of the first intermediate block 210 on the other side X2 in the tire axial direction and communicates with the sub-groove 600.

[0035] The first intermediate block 210 includes a plurality of first intermediate sipes 213 extending in a direction intersecting the tire circumferential direction. The first intermediate sipes 213 have a wavy surface shape on the tread surface 2A. Overall, the first intermediate sipes 213 are curved so as to be convex on one side C1 in the tire circumferential direction, but the proportion of the inclined portion relative to the tire axial direction on the other side X2 in the tire axial direction is longer.

[0036] The first intermediate sipe 213 includes one end X1 on one side in the tire axial direction communicating with the first notch 211, extending from that end toward the sub-groove 600 and terminating just before reaching the sub-groove 600, one end X2 on the other side in the tire axial direction communicating with the second notch 212, extending from that end toward the second main groove 800 and terminating just before reaching the second main groove 800, and one that communicates with the sub-groove 600 and the second main groove 800. However, the sipe pattern formed by the shape and arrangement of these multiple first intermediate sipes 213 is common to each first intermediate block 210.

[0037] The region of the central land bridge 100 between a pair of first central slits 140 adjacent in the tire circumferential direction corresponds to the region of the two first intermediate blocks 210 of the first intermediate land bridge 200 between a pair of first intermediate slits 220 that are continuous with the first central slits 140 and adjacent in the tire circumferential direction. Therefore, the central land bridge 100 and the first intermediate land bridge 200 in these regions form a single configuration, or a "pair" configuration.

[0038] As shown in Figures 2 and 3, the second intermediate platform 300 includes a plurality of second intermediate blocks 310 arranged in the circumferential direction of the tire, a plurality of second intermediate slits 320 extending in a direction intersecting the circumferential direction of the tire, a plurality of third intermediate slits 330, and a plurality of fourth intermediate slits 340. The width of each slit 320, 330, and 340 is, for example, approximately 2.5 mm to 5.0 mm, but is not limited thereto. The depth is, for example, approximately 7.0 mm to 8.5 mm for slit 320, and approximately 4.0 mm to 5.5 mm for slits 330 and 340, but is not limited thereto.

[0039] Multiple second intermediate slits 320 are arranged at intervals in the circumferential direction of the tire. The second intermediate slits 320 traverse the second intermediate groove 300 and communicate with the first main groove 700 and the third main groove 900.

[0040] As shown in Figure 3, the second intermediate slit 320 has a second bend 321 and a third bend 322 at each end in the tire axial direction. The second bend 321 is formed at the end on one side X1 in the tire axial direction and protrudes to the other side C2 in the tire circumferential direction. The third bend 322 is formed at the end on the other side X2 in the tire axial direction and protrudes to the one side C1 in the tire circumferential direction. The second intermediate slit 320 has a third inclined portion 323 extending from the second bend 321 to the first main groove 700, a fourth inclined portion 324 extending from the third bend 322 to the third main groove 900, and a fifth inclined portion 325 connecting the second bend 321 and the third bend 322.

[0041] The fifth inclined portion 325 is the main part of the second intermediate slit 320 and is longer than the third inclined portion 323 and the fourth inclined portion 324. The fifth inclined portion 325 is inclined with respect to the tire axis so as it extends toward one side C1 in the tire circumferential direction from the second bend portion 321 toward the third bend portion 322. The lengths of the third inclined portion 323 and the fourth inclined portion 324 are approximately the same and are inclined in the opposite direction to the fifth inclined portion 325.

[0042] The second intermediate slit 320 has a second protruding recess 326 on the other side C2 in the tire circumferential direction of the second bent portion 321 that protrudes to the other side X2 in the tire axial direction, and a third protruding recess 327 on one side C1 in the tire circumferential direction of the third bent portion 322 that protrudes to the one side X1 in the tire axial direction.

[0043] Each of the multiple second intermediate blocks 310 is divided into a substantially rectangular shape by a first main groove 700, a third main groove 900, and a pair of second intermediate slits 320 adjacent to each other in the circumferential direction of the tire.

[0044] As shown in Figure 2, the second intermediate block 310 is arranged alternately in the circumferential direction of the tire, with some having a third intermediate slit 330 and others having a fourth intermediate slit 340.

[0045] As shown in Figure 3, the third intermediate slit 330 is formed on the edge of the second intermediate block 310 on one side X1 in the tire axial direction. The third intermediate slit 330 is bent in a hook shape. The third intermediate slit 330 communicates with the first main groove 700, and the end opposite to the communicating end is formed in a tapered shape and terminates within the second intermediate block 310. The fourth intermediate slit 340 is formed on the edge of the second intermediate block 310 on the other side X2 in the tire axial direction. The fourth intermediate slit 340 has the same shape as the third intermediate slit 330 and is bent in a hook shape, but the direction of bending is opposite to that of the third intermediate slit 330. The fourth intermediate slit 340 communicates with the third main groove 900, and the end opposite to the communicating end is formed in a tapered shape and terminates within the second intermediate block 310. The second central slit 150 of the central land 100 extends along the extension of the third intermediate slit 330, with the first main groove 700 in between.

[0046] The second intermediate block 310 includes a plurality of second intermediate sipes 311 extending in a direction intersecting the tire circumferential direction. The second intermediate sipes 311 have a wavy surface shape on the tread surface 2A. There are multiple types of second intermediate sipes 311, differing in their length, direction of extension, position, and the grooves or slits they communicate with. For example, some second intermediate sipes 311 have a substantially straight extension direction, while others have a curved extension direction. Furthermore, some second intermediate sipes 311 terminate within the second intermediate block 310 by communicating only with the first main groove 700 or only with the third main groove 900. In addition, some second intermediate sipes 311 communicate with either the first main groove 700 or the third main groove 900 and with the second intermediate slit 320. However, the sipe pattern formed by the shape and arrangement of these multiple second intermediate sipes 311 is common to each second intermediate block 310.

[0047] The region of the central ramp 100 between a pair of adjacent first central slits 140 in the tire circumferential direction corresponds to the region of two adjacent second intermediate blocks 310 in the second intermediate ramp 300, one having a third intermediate slit 330 and the other not having a third intermediate slit 330. Therefore, the central ramp 100 and the second intermediate ramp 300 in these regions form a single configuration, or a "pair" configuration.

[0048] As shown in Figure 2, the first shoulder block 400 includes a plurality of first shoulder blocks 410 arranged in the circumferential direction of the tire, and a plurality of first lug grooves 420 extending in a direction intersecting the circumferential direction of the tire. The width of the first lug grooves 420 is, for example, about 3.5 mm to 6 mm, and the depth is, for example, about 6.5 mm to 8.5 mm, but is not limited thereto.

[0049] In this embodiment, the first shoulder land area 400 is the land area in the tire axial direction between the second main groove 800 and the contact end 2C on one side X1 in the tire axial direction. A first buttress 8A is provided on one side X1 in the tire axial direction from this contact end 2C, in a manner that is continuous with the first shoulder land area 400.

[0050] Multiple first lug grooves 420 are arranged at intervals in the circumferential direction of the tire. The first lug grooves 420 communicate with the second main groove 800 and are continuous with the first buttress slit 820, which will be described later. The majority of the first lug grooves 420 on the side communicating with the second main groove 800 is slightly inclined with respect to the tire axis.

[0051] Multiple first shoulder blocks 410 are partitioned in a substantially rectangular shape in plan view between a pair of first lug grooves 420 adjacent to each other in the circumferential direction of the tire, and are arranged in the circumferential direction of the tire.

[0052] The first shoulder block 410 includes a first shoulder slit 411 and a plurality of first shoulder sipes 412. Both the first shoulder slit 411 and the first shoulder sipes 412 extend in a direction intersecting the circumferential direction of the tire.

[0053] The first shoulder slit 411 has a shape that is bent in a roughly Z-shape. The first shoulder slit 411 does not communicate with any grooves other than the sipes and terminates within the first shoulder block 410. The width of the first shoulder slit 411 is, for example, about 0.5 mm to 2.0 mm, and the depth is, for example, about 0.5 mm to 2.0 mm, but is not limited to these values.

[0054] Multiple first shoulder sipes 412 are arranged at intervals in the circumferential direction of the tire. Each first shoulder sipe 412 has a wavy shape. Each first shoulder sipe 412 communicates with the second main groove 800, extends from its communicating end toward the shoulder 5, and communicates with the dimples 414 provided on the shoulder 5.

[0055] As shown in Figure 2, the configuration of the second shoulder ramp 500 and the second buttress 8B on the other side X2 in the tire axial direction from the third main groove 900 is almost point-symmetric to the configuration of the first shoulder ramp 400 and the first buttress 8A on the other side X1 in the tire axial direction from the second main groove 800 described above, and has a similar configuration as follows. Note that the width and depth of the corresponding slits and grooves are approximately the same due to the point symmetry.

[0056] The second shoulder land 500 includes a plurality of second shoulder blocks 510 arranged in the circumferential direction of the tire, and a plurality of second lug grooves 520 extending in a direction intersecting the circumferential direction of the tire. In this embodiment, the second shoulder land 500 is the land in the region between the third main groove 900 and the contact end 2C on the other side X2 in the tire axial direction. A second buttress 8B is provided on the other side X2 in the tire axial direction from this contact end 2C in a manner continuous with the second shoulder land 500.

[0057] Multiple second lug grooves 520 are arranged at intervals in the circumferential direction of the tire. The second lug grooves 520 communicate with the third main groove 900 and are continuous with the second buttress slit 920, which will be described later. The majority of the second lug grooves 520 that communicate with the third main groove 900 are slightly inclined with respect to the tire axis.

[0058] Multiple second shoulder blocks 510 are divided into a roughly rectangular shape in plan view by a pair of adjacent second lug grooves 520 in the circumferential direction of the tire, and are arranged in the circumferential direction of the tire.

[0059] The second shoulder block 510 includes a second shoulder slit 511 and a plurality of second shoulder sipes 512. Both the second shoulder slit 511 and the second shoulder sipes 512 extend in a direction intersecting the circumferential direction of the tire.

[0060] The second shoulder slit 511 has a shape that is bent in a roughly Z-shape. The second shoulder slit 511 does not communicate with any grooves other than the sipe and terminates within the second shoulder block 510.

[0061] Multiple second shoulder sipes 512 are arranged at intervals in the circumferential direction of the tire. The second shoulder sipes 512 have a wavy shape. The second shoulder sipes 512 communicate with the third main groove 900, extend from the end communicating with it toward the shoulder 5, and communicate with the dimples 514 provided on the shoulder 5.

[0062] As shown in Figure 2, the first buttress 8A includes a plurality of first buttress blocks 810 arranged in the circumferential direction of the tire, and a plurality of first buttress slits 820 extending in a direction intersecting the circumferential direction of the tire, and extending in the axial direction of the tire and the radial direction of the tire.

[0063] Each first buttress slit 820 has its other side X2 in the tire axial direction communicating with the first lug groove 420 of the first shoulder 400 near the contact end 2C, and its other side X1 in the tire axial direction communicating with the first annular groove 9A. The first annular groove 9A is an annular groove along the tire circumferential direction and is formed on the radially inner side of the first buttress 8A. The first lug groove 420 and the first buttress slit 820 form a continuous slit. Multiple first buttress blocks 810 are partitioned in a substantially rectangular shape between adjacent first buttress slits 820 in the tire circumferential direction and are arranged in the tire circumferential direction.

[0064] The first buttress block 810 includes a pair of opposing first hook-shaped grooves 81 and second hook-shaped grooves 82 in the tire axial direction. The second hook-shaped groove 82 is located on the other side X2 in the tire axial direction of the first hook-shaped groove 81. The first buttress block 810 also has a first groove 830 and a second groove 840.

[0065] As shown in Figure 2, the second buttress 8B includes a plurality of second buttress blocks 910 arranged in the circumferential direction of the tire, and a plurality of second buttress slits 920 extending in a direction intersecting the circumferential direction of the tire, and extending in the axial direction and radial direction of the tire.

[0066] Each second buttress slit 920 has one side X1 in the tire axial direction that communicates with the second lug groove 520 of the second shoulder 500 near the contact end 2C, and the other side X2 in the tire axial direction that communicates with the second annular groove 9B. The second annular groove 9B is an annular groove along the tire circumferential direction and is formed on the radially inner side of the second buttress 8B. The second lug groove 520 and the second buttress slit 920 form a continuous slit. Multiple second buttress blocks 910 are partitioned in a substantially rectangular shape between adjacent second buttress slits 920 in the tire circumferential direction and are arranged in the tire circumferential direction.

[0067] The second buttress block 910 includes a pair of opposing first hook-shaped grooves 83 and second hook-shaped grooves 84 in the tire axial direction. The second hook-shaped groove 84 is located on one side X1 of the first hook-shaped groove 83 in the tire axial direction. The second buttress block 910 also has a first groove 930 and a second groove 940.

[0068] The first buttress 8A will be described in detail below. As mentioned above, the first buttress 8A and the second buttress 8B are almost point-symmetrical and have similar configurations, so by explaining the first buttress 8A, the explanation of the second buttress 8B will be omitted.

[0069] Figure 4 is an enlarged view of the portion shown in IV of Figure 2, and shows a part of the first buttress 8A. As described above, the first buttress 8A has a first buttress block 810 provided between each of the multiple first buttress slits 820 arranged in the circumferential direction of the tire. In the second buttress 8B, the first buttress block 810 and the first buttress slits 820 correspond to the second buttress block 910 and the second buttress slits 920, respectively.

[0070] The first hook-shaped groove 81 and the second hook-shaped groove 82 included in the first buttress block 810 have the same shape. The width of the first hook-shaped groove 81 and the second hook-shaped groove 82 is, for example, about 1.0 mm to 3.5 mm, and the depth is, for example, about 0.5 mm to 1.5 mm, but is not limited thereto. In the second buttress 8B, the first hook-shaped groove 81 and the second hook-shaped groove 82 correspond to the first hook-shaped groove 83 and the second hook-shaped groove 84, respectively.

[0071] The first hook-shaped groove 81 includes a first circumferential inclined groove 861 and a first bent groove 862. The base end of the first circumferential inclined groove 861 communicates with one of a pair of adjacent first buttress slits 820 in the tire circumferential direction (the lower one in Figure 4) and the first annular groove 9A. From these first buttress slits 820 and the first annular groove 9A, it extends toward the other side C2 in the tire circumferential direction, inclined with respect to the tire circumferential direction, and terminates within the first buttress block 810 without reaching the first buttress slit 820 in the direction of extension. The first annular groove 9A corresponds to the second annular groove 9B on the second buttress 8B side. As the first circumferential inclined groove 861 moves toward the other side C2 in the tire circumferential direction, it inclins to extend inward in the tire axial direction. The first bent groove 862 bends at an acute angle from the tip 861a, which is the end of the first circumferential inclined groove 861, toward the inside in the tire axial direction and toward one side C1 in the tire circumferential direction.

[0072] The second hook-shaped groove 82 includes a second circumferential inclined groove 865 and a second bent groove 866. The base end of the second circumferential inclined groove 865 communicates with the other (upper in Figure 4) of a pair of adjacent first buttress slits 820 in the tire circumferential direction, and extends from that first buttress slit 820 toward one side C1 in the tire circumferential direction, in the opposite direction to the first circumferential inclined groove 861 and inclined with respect to the tire circumferential direction, and terminates within the first buttress block 810 without reaching the first buttress slit 820 in the direction of extension. The second circumferential inclined groove 865 is inclined to extend outward in the tire axial direction as it approaches one side C1 in the tire circumferential direction. The second bent groove 866 bends at an acute angle outward in the tire axial direction and toward the other side C2 in the tire circumferential direction from its tip 865a, which is the end of the second circumferential inclined groove 865.

[0073] The first hook-shaped groove 81 and the second hook-shaped groove 82 are arranged in opposite directions in the tire circumferential direction, such that the circumferential inclined grooves 861 and 865 are parallel to each other and the bent grooves 862 and 866 are engaged with each other. Preferably, the inclination angle θ of each circumferential inclined groove 861 and 865, which extends inclined with respect to the tire circumferential direction, is 5° or more and 22° or less.

[0074] Figure 5 is a cross-sectional view of VV in Figure 4. Figure 6 is a cross-sectional view of VI-VI in Figure 4. Figure 7 is a cross-sectional view of VII-VII in Figure 4.

[0075] Figure 5 shows the cross-sectional shape of the second circumferential inclined groove 865 of the second hook-shaped groove 82, and Figure 6 shows the cross-sectional shape of the tip 865a of the second circumferential inclined groove 865. As shown in Figures 5 and 6, the bottom 870 of the second circumferential inclined groove 865 has an arc portion 871 and an inclined surface 872 that slopes to one side in the groove width direction from the arc portion 871 along its entire length. The inclined surface 872 is located on the side of the second bent groove 866. Figure 7 shows the cross-sectional shape of the tip portion of the second bent groove 866 in the second hook-shaped groove 82. As shown in Figure 7, the bottom 880 of the second bent groove 866 has an arc portion 881 and an inclined surface 882 that slopes to one side in the groove width direction from the arc portion 881 along its entire length. The inclined surface 882 is located on the side of the second bent groove 866. The arc portion 871 of the second circumferential inclined groove 865 and the arc portion 881 of the second bent groove 866 are continuous, and the inclined surface 872 of the second circumferential inclined groove 865 and the inclined surface 882 of the second bent groove 866 are continuous. The first hook-shaped groove 81 also has the same cross-sectional shape as the second hook-shaped groove 82.

[0076] Figure 4 shows the dimples 414 described above. Multiple dimples 414 are arranged at intervals in the circumferential direction of the tire on the shoulder 5 portion extending from the tread 2 to the buttress 8, on the contact edge 2C of the tread 2. On the second buttress 8B side, multiple dimples 514 are also arranged at intervals in the circumferential direction of the tire on the contact edge 2C, similar to the dimples 414. The dimples 414 and 415 have a roughly rectangular shape with their length extending in the direction of the tire axis when viewed from above the tire.

[0077] As shown in Figure 4, the first buttress block 810 has the first groove 830 and the second groove 840 described above. In the second buttress 8B, the first groove 830 and the second groove 840 correspond to the first groove 930 and the second groove 940, respectively.

[0078] The first groove 830 is located on the inner side (tire equator E side, left side in Figure 4) of the first buttress block 810 in the tire axial direction. The base end of the first groove 830 communicates with one side (lower side in Figure 4) of a pair of adjacent first buttress slits 820 in the tire circumferential direction, and extends from the first buttress slits 820 to the other side C2 in the tire circumferential direction. The first groove 830 is close to the second circumferential inclined groove 865 of the second hook-shaped groove 82. The width of the first groove 830 is, for example, about 1.0 mm to 3.0 mm, and the depth is, for example, about 0.5 mm to 1.5 mm, but is not limited thereto.

[0079] The second groove 840 is located on the outer side (away from the tire equator E, to the right in Figure 4) of the first buttress block 810 in the tire axial direction. The second groove 840 is notched to communicate with the other side (upper side in Figure 4) of a pair of adjacent first buttress slits 820 in the tire circumferential direction and with the first annular groove 9A. The second groove 840 is close to the first circumferential inclined groove 861 of the first hook-shaped groove 81. The width of the second groove 840 is, for example, approximately 0.5 mm to 2.0 mm at most, and the depth is, for example, approximately 0.5 mm to 1.5 mm at most, but is not limited thereto.

[0080] As shown in Figure 2, on one side X1 of the tread surface 2A in the tire axial direction, four slits and grooves—the first buttress slit 820 of the first buttress 8A, the first lug groove 420 of the first shoulder 400, the first intermediate slit 220 of the first intermediate 200, and the first central slit 140 of the central 100—extend continuously in a direction intersecting the tire circumferential direction. Here, these four slits are referred to as a single continuous slit, the first continuous slit 10.

[0081] On the other hand, as shown in Figure 2, on the other side X2 of the tread surface 2A in the tire axial direction, three slits and grooves—the second buttress slit 920 of the second buttress 8B, the second lug groove 520 of the second shoulder 500, and the second intermediate slit 320 of the second intermediate 300—extend continuously in a direction intersecting the tire circumferential direction. Here, these three slits are referred to as a single continuous slit, the second continuous slit 20.

[0082] The lengths of the first continuous slit 10 and the second continuous slit 20 are different. Note that the slit length referred to here is the total length traced along the shape of the slit on the tire surface.

[0083] Of the slits and grooves that make up the first continuous slit 10, the first buttress slit 820, the first lug groove 420, and the first intermediate slit 220 traverse the first buttress 8A, the first shoulder land 400, and the first intermediate land 200 in the tire axial direction, respectively, but the first central slit 140 intersects with the tire equator E and terminates within the central land 100. In other words, the first continuous slit 10 terminates within a single land 6.

[0084] On the other hand, the second buttress slit 920, the second lug groove 520, and the second intermediate slit 320, which constitute the second continuous slit 20, traverse the second buttress 8B, the second shoulder land 500, and the second intermediate land 300 in the tire axis direction, respectively, and do not terminate within each land. In other words, the second continuous slit 20 traverses multiple land 6 in the tire axis direction and does not terminate within each land 6.

[0085] The second central slit 150 of the central land 100 extends in the opposite direction to the first continuous slit 10, that is, from the other side X2 in the tire axial direction, and terminates within the central land 100.

[0086] The first intermediate slit 220 constituting the first continuous slit 10 has a first bent portion 221 that bends within the first intermediate land 200. In other words, the first continuous slit 10 has a first bent portion 221 that bends within the first intermediate land 200. Furthermore, the first continuous slit 10 has a first protruding recess 224 that protrudes from the first bent portion 221.

[0087] The second intermediate slit 320, which constitutes the second continuous slit 20, has a second bent portion 321 and a third bent portion 322 that bend within the second intermediate land 300. In other words, the second continuous slit 20 has a second bent portion 321 and a third bent portion 322 that bend within the second intermediate land 300. Furthermore, the second continuous slit 20 has a second protruding recess 326 that protrudes from the second bent portion 321 and a third protruding recess 327 that protrudes from the third bent portion 322.

[0088] The tire 1 according to the embodiment described above provides the following effects.

[0089] (1) The tire 1 according to the embodiment is a pneumatic tire having a tread 2 that includes a central rib 100 which is arranged on the tire equator E and extends in an annular shape continuously in the tire circumferential direction, a first intermediate rib 200 which is arranged on one side of the central rib 100 in the tire axial direction, a second intermediate rib 300 which is arranged on the other side of the central rib 100 in the tire axial direction, a sub-groove 600 which is arranged between the central rib 100 and the first intermediate rib 200 as a first circumferential groove, and a first main groove 700 which is arranged between the central rib 100 and the second intermediate rib 300 as a second circumferential groove, wherein the central rib 100 is located on the tire axial direction of the central rib 100 A first central slit 140 extends from one end in a direction intersecting the tire circumferential direction and terminates within the central land 100, and a second central slit 150 extends from the other end of the central land 100 in the tire axial direction in a direction intersecting the tire circumferential direction and terminates within the central land 100, are alternately arranged in the tire circumferential direction. The first central slit 140 and the second central slit 150 intersect the tire equator E. The first intermediate land 200 has a first intermediate slit 220 extending in a direction intersecting the tire circumferential direction, and the second intermediate land 300 has a third intermediate slit 330 extending in a direction intersecting the tire circumferential direction.

[0090] In this embodiment, the central rib 100 has a rib shape that extends continuously in an annular manner in the circumferential direction of the tire, thereby improving the block rigidity of the tread 2 and consequently improving contact with the ground. Furthermore, the first central slit 140 and the second central slit 150 of the central rib 100 that intersect with the tire equator E, and the first intermediate slit 220 and the third intermediate slit 330 of each intermediate rib 200 and 300, improve the shear force in the snow and enhance snow driving performance. Therefore, according to the tire 1 of this embodiment, a good balance between snow driving performance and contact with the ground is ensured.

[0091] (2) In the tire 1 of the embodiment described in (1) above, the first central slit 140 extends on the extension of the first intermediate slit 220, sandwiching the sub-groove 600 which serves as the first circumferential groove, and the second central slit 150 extends on the extension of the third intermediate slit 330, sandwiching the first main groove 700 which serves as the second circumferential groove.

[0092] With this configuration, a cross-shaped groove is formed by a sub-groove 600 extending in the circumferential direction of the tire, and a first central slit 140 and a first intermediate slit 220 extending in a direction intersecting the circumferential direction of the tire, flanking the sub-groove 600. Additionally, a cross-shaped groove is formed by a first main groove 700 extending in the circumferential direction of the tire, and a second central slit 150 and a third intermediate slit 330 extending in a direction intersecting the circumferential direction of the tire, flanking the first main groove 700. These cross-shaped grooves improve the shear force in snow and enhance snow driving performance.

[0093] (3) In the tire 1 according to the embodiments of (1) and (2) above, the edge of the central land 100 that extends in the tire circumferential direction on at least one end in the tire axial direction has a zigzag shape.

[0094] This improves the rigidity of the central 100, and the zigzag edge enhances the shear force in the snow, resulting in improved snow driving performance.

[0095] (4) In the tire 1 according to the embodiment described in (1) to (3) above, the first central slit 140 has a hook-shaped portion 141 that bends into a hook shape from its end.

[0096] The hook-shaped section 141 that bends from the end of the first central slit 140 improves the shear force in the snow, thereby improving snow driving performance.

[0097] (5) In the tire 1 according to the embodiment described in (4), it is preferable that the hook-shaped portion 141 is inclined with respect to the tire circumferential direction, with the direction from the end of the first central slit 140 toward the tip being in the direction from the tire pressing side toward the tire kicking side.

[0098] This further enhances the effect of the hook-shaped section 141 in improving shear force in snow, thereby improving snow driving performance.

[0099] Furthermore, the present invention is not limited to the embodiments described above, and modifications, improvements, etc., made to the extent that the objectives of the present invention can be achieved are also included within the scope of the present invention.

[0100] For example, in the embodiment, the central ridge 100 has a zigzag edge extending in the circumferential direction of the tire on the side of the sub-groove 600 in the tire axial direction, but the edge extending in the circumferential direction of the tire on the side of the first main groove 700 may also have a zigzag shape, or both edges may have a zigzag shape.

[0101] In this embodiment, the first central slit 140 is provided with a hook-shaped portion 141, but the second central slit 150 may also be provided with a similar hook-shaped portion, or both central slits may be provided with them. [Explanation of Symbols]

[0102] 1...Tire (pneumatic tire), 2...Tread, 100...Central surface, 140...First central slit, 141...Hook-shaped section, 150...Second central slit, 200...First intermediate surface, 220...First intermediate slit, 300...Second intermediate surface, 600...Sub-groove (First circumferential groove), 700...First main groove (Second circumferential groove), 330...Third intermediate slit, E...Tire equator, C...Tire circumferential direction, X...Tire axial direction.

Claims

1. A central rib-shaped landmass positioned on the tire equator, extending continuously in a ring shape in the circumferential direction of the tire, The first intermediate land, which is located on one side of the tire axial direction of the central land, A second intermediate landmass is located on the other side of the central landmass in the tire axial direction, A first circumferential groove is provided between the central landmass and the first intermediate landmass, A pneumatic tire having a tread including a second circumferential groove positioned between the central land and the second intermediate land, The central landmass has a first central slit extending from one end of the central landmass in the tire axial direction in a direction intersecting the tire circumferential direction and terminating within the central landmass, and a second central slit extending from the other end of the central landmass in the tire axial direction in a direction intersecting the tire circumferential direction and terminating within the central landmass, which are alternately arranged in the tire circumferential direction. The first central slit and the second central slit intersect the tire equator, The first intermediate land has a first intermediate slit extending in a direction intersecting the tire circumferential direction, The aforementioned second intermediate slit is a pneumatic tire having a third intermediate slit extending in a direction intersecting the tire circumferential direction.

2. The first central slit extends along the extension of the first intermediate slit, with the first circumferential groove in between. The pneumatic tire according to claim 1, wherein the second central slit extends on the extension of the third intermediate slit, straddling the second circumferential groove.

3. The pneumatic tire according to claim 1 or 2, wherein at least one end of the central landmass extending in the tire circumferential direction on the tire axis side has a zigzag shape.

4. The pneumatic tire according to claim 1 or 2, wherein at least one of the first central slit and the second central slit has a hook-shaped portion that bends in a hook shape from its end.

5. The pneumatic tire according to claim 4, wherein the direction from the end to the tip of the hook-shaped portion is inclined with respect to the tire circumferential direction, from the tire treading side to the tire kicking side.

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