Pneumatic tires and tire molding dies

Abstract

The present invention provides a pneumatic tire that suppresses the blockage of sipe openings on the tire surface and ensures the water removal effect and edge effect provided by the sipes. [Solution] The first wall surface 160 of the first central sipe 110 has first protrusions 161 that are spaced apart in the sipe depth direction and extend in the sipe length direction, and first recesses 162 that are positioned between the first protrusions 161. The second wall surface 170 of the first central sipe 110 has second recesses 171 that are opposite to each of the first protrusions 161, and second protrusions 172 that are positioned between the second recesses 171 and opposite to the first recesses 162. In the widthwise cross-section of the first central sipe 110, in an unloaded state, a straight space 110S is provided that extends linearly from the opening 110a to the bottom 110b of the first central sipe 110, and the first protrusions 161 and the second protrusions 172 come into contact with each other due to tire deformation that occurs when the tire is pressed down.

Description

Technical Field

[0001] The present invention relates to a pneumatic tire and a tire molding die.

Background Art

[0002] Conventionally, a pneumatic tire having a large number of thin cuts called sipes on the land surface of a tread that contacts the road surface, and the sipes exhibit a water drainage effect and an edge effect to improve traction, is known. Patent Document 1 shows a pneumatic tire in which sipes having different widths in the depth direction are provided on the land.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the width varies in the depth direction as in the sipes shown in Patent Document 1 above, the rigidity of the land in the depth direction (substantially the same direction as the tire diameter direction) becomes non-uniform, so the amount of collapse of the land on both sides of the sipes becomes non-uniform, and as a result, the opening of the sipes on the tire surface is likely to close. If the opening of the sipes closes, the water drainage effect and edge effect, which are the original functions of the sipes, cannot be exerted, so there is room for improvement.

[0005] Therefore, an object of the present invention is to provide a pneumatic tire and a tire molding die therefor that suppress the closing of the opening of the sipes on the tire surface and ensure the water drainage effect and edge effect by the sipes.

Means for Solving the Problems

[0006] The pneumatic tire of the present invention is a pneumatic tire having a tread including a base having sipes extending in a direction intersecting the tire circumferential direction, wherein the sipes are formed between a first wall surface and a second wall surface that are opposite to each other, the first wall surface having first protrusions that are spaced apart in the sipe depth direction and extend in the sipe length direction, and a first recess disposed between the first protrusions, the second wall surface having second recesses opposite to each of the first protrusions, and a second protrusion disposed between the second recesses and opposite to the first recess, the sipe has a straight space in the widthwise cross section of the sipe that extends linearly from the opening to the bottom of the sipe in an unloaded state, and the first protrusions and the second protrusions come into contact with each other due to tire deformation that occurs when the tire is pressed down.

[0007] The tire molding die of the present invention is a tire molding die for molding the pneumatic tire of the present invention described above. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a pneumatic tire and a tire molding die that suppress the blocking of sipe openings on the tire surface and ensure the water removal effect and edge effect provided by the sipes. [Brief explanation of the drawing]

[0009] [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 a plan view showing the first central sipe of the tire according to the embodiment. [Figure 5] This is a cross-sectional view of the tire showing the first central sipe. [Figure 6] This is a cross-sectional view taken from VI-VI in Figure 4. [Figure 7A]This is a schematic cross-sectional diagram illustrating the deformation process of the first central sipe that contacts the road surface, showing the initial state of tire pressure. [Figure 7B] This figure shows the state immediately after the initial stage of tire pressure during the process described above. [Figure 7C] This figure shows the state of the tire during the mid-stage of contact with the ground during the process described above. [Figure 7D] This figure shows the state immediately after the mid-stage of tire contact during the process described above. [Figure 7E] This diagram shows the state of the tire when it is being kicked out during the process described above. [Figure 8] This is an enlarged view of Figure 7B. [Figure 9] This figure shows the contact surface shape of a tire according to an embodiment and illustrates the rectangularity of the contact surface shape. [Figure 10] This is a schematic cross-sectional view showing a tire molding die for forming a tire according to the embodiment. [Modes for carrying out the invention]

[0010] 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.

[0011] 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 are fitted 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 where it transitions to the shoulder 5.

[0012] 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.

[0013] Examples of grooves forming the tread pattern 2B include circumferential grooves including main grooves and sub-grooves, slits, lug grooves, sipes, etc., as will be described later. The circumferential grooves are basically grooves along the tire circumferential direction, and the slits, lug grooves, and sipes are basically grooves extending in a direction intersecting the tire circumferential direction. The widths of these grooves are such that the width of the main groove is the largest and the width of the sipe is the smallest. The widths of the various sipes in the embodiment are, for example, about 0.3 mm or more and less than 1.0 mm, and the depths are, for example, about 4 mm or more and 11 mm or less, but are not limited thereto. The widths of the sub-grooves, slits, and lug grooves are basically common in that they are smaller than the main groove and larger than the sipe, but they may have the same width or may have 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 buttress 8 includes a first buttress 8A on one side X1 in the tire axial direction and a second buttress 8B on the other side X2 in the tire axial direction.

[0015] The plurality of lands 6 include 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 widths of the respective lands 6 are not limited in this way and may be arbitrary.

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

[0018] The secondary groove 600 of the embodiment has an overall zigzag shape. The first main groove 700 of the embodiment is a groove that is straight along the circumferential direction of the tire 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 Figure 3, the central land 100 comprises a plurality of first central sipes 110, a plurality of second central sipes 120, and a plurality of third central sipes 130, as sipes of this disclosure.

[0020] Multiple first central sipes 110 are arranged in a substantially central region in the width direction of the central ridge 100. Multiple first central sipes 110 are spaced apart in the circumferential direction of the tire. Figure 4 is an enlarged plan view of the first central sipe 110. As shown in Figure 4, the first central sipe 110 has a surface shape on the tread surface 2A that can be described as substantially S-shaped or crank-shaped, and includes a central straight section 111 extending in the axial direction of the tire, a first end straight section 112 extending from one end X1 on the axial side of the central straight section 111 to one end C1 in the circumferential direction of the tire, and a second end straight section 113 extending from the other end X2 on the axial side of the central straight section 111 to the other end C2 in the circumferential direction of the tire. The central straight section 111 is the portion that intersects with the circumferential direction of the tire. The first central sipe 110 does not communicate with either the secondary grooves 600 or the first main groove 700 on either side of the tire axial direction, and both ends terminate within the central land 100.

[0021] The length of the central straight section 111 is, for example, about 5 mm, and preferably between 3 mm and 10 mm. The lengths of the first end straight section 112 and the second end straight section 113 are, for example, about 2.1 mm, and preferably between 1.5 mm and 3 mm.

[0022] As described above, the multiple first central sipes 110 of the embodiment are arranged in a substantially central region in the width direction of the central land 100. This central region may be located within a region that occupies up to 60% of the width of the central land 100, and preferably within a region that occupies 40% of that width.

[0023] The axial length of the first central sipe 110 is preferably 20% to 60% of the width of the central sipe 100.

[0024] As shown in Figure 3, the multiple second central sipes 120 are located on one side X1 and the other side X2 of the first central sipe 110 in the tire axial direction. The multiple second central sipes 120 are spaced apart in the tire circumferential direction. The second central sipes 120 have a wavy surface shape on the tread surface 2A. The overall extending direction of the second central sipes 120 is inclined to extend towards one side C1 in the tire circumferential direction as it moves from the end of the other side X2 in the tire axial direction toward the end of the one side X1 in the tire axial direction. The second central sipes 120 located on one side X1 in the tire axial direction of the first central sipe 110 communicate with the secondary groove 600. The second central sipes 120 located on the other side X2 in the tire axial direction of the first central sipe 110 communicate with the first main groove 700.

[0025] 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.

[0026] Preferably, the sum of the sipe lengths of all the second central sipes 120 on the surface of the central landmass 100, i.e., the total length, is longer than the sum of the sipe lengths of the first central sipes 110 on the surface of the central landmass 100, i.e., the total length. Here, sipe length refers to the total length tracing the shape of the sipes on the surface of the central landmass 100.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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. As a result, the central ridge 100 has a rib shape that extends continuously in an annular manner in the tire circumferential direction. The first central slit 140 is inclined with respect to the tire axial direction so that it extends to the other end C2 on the tire circumferential direction as it moves from the end communicating with the sub-groove 600 toward the other end X2 on the tire axial 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 one end C1 on the tire circumferential direction as it moves toward the other end X2 on the tire axial direction. The first central slit 140 extends across 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.

[0031] 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.

[0032] 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.

[0033] As shown in Figures 2 and 3, the first intermediate ridge 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 ridge 200 and communicate with the secondary groove 600 and the second main groove 800. The width and depth of the first intermediate slits 220 are equivalent to those of the first central slit 140.

[0034] 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.

[0035] Each of the multiple first intermediate blocks 210 is partitioned into a roughly rectangular shape by a sub-groove 600, a second main groove 800, and a pair of first intermediate slits 220 adjacent to each other 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.

[0036] 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 towards 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] Multiple first lug grooves 420 are arranged at intervals in the circumferential direction of the tire. The first lug grooves 420 traverse the first shoulder ridge 400 and the first buttress 8A and communicate with the second main groove 800 and the first annular groove 9A. The first annular groove 9A is an annular groove along the circumferential direction of the tire and is formed on the radially inward side of the first buttress 8A.

[0051] The first shoulder block 410 is provided extending from the first shoulder base 400 to the first buttress 8A. The first shoulder block 410 is divided into a substantially rectangular shape in plan view by a second main groove 800, a first annular groove 9A, and a pair of first lug grooves 420 adjacent 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] The region of the first buttress 8A in the first shoulder block 410 includes a pair of opposing first hook-shaped grooves 81 and second hook-shaped grooves 82 in the tire axial direction, and a shoulder groove 86 provided near the shoulder 5. 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 widths of the first hook-shaped groove 81, the second hook-shaped groove 82, and the shoulder groove 86 are, for example, about 1.0 mm to 3.5 mm, and the depths are, for example, about 0.5 mm to 1.5 mm, but are not limited thereto.

[0056] The first hook-shaped groove 81 and the second hook-shaped groove 82 have the same shape. Each of the hook-shaped grooves 81 and 82 has a hook-shaped bent tip portion 81b and 82b at the end of a circumferentially inclined groove portion 81a and 82a that is inclined with respect to the circumferential direction of the tire. The hook-shaped grooves 81 and 82 are arranged in the first shoulder block 410 in a manner in which the tip portions 81b and 82b engage with each other, and the circumferentially inclined groove portions 81a and 82a are parallel, and are arranged in opposite directions in the circumferential direction of the tire. The first hook-shaped groove 81, located on one side X1 in the axial direction of the tire, has its base end in communication with the first annular groove 9A and the first lug groove 420, and its tip portion 81b terminates within the first shoulder block 410. The second hook-shaped groove 82, located on the other side X2 of the tire axial direction, has its base end in communication with a first lug groove 420 that is different from the first lug groove 420 that the base end of the first hook-shaped groove 81 communicates with.

[0057] The shoulder groove 86 is located within the first shoulder block 410 on one side C1 in the tire circumferential direction of the second hook-shaped groove 82. The shoulder groove 86 communicates with the first lug groove 420, which is connected to the base end of the first hook-shaped groove 81, and extends from that communicating end to the other side C2 in the tire circumferential direction, terminating without reaching the second hook-shaped groove 82.

[0058] 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.

[0059] The second shoulder block 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.

[0060] Multiple second lug grooves 520 are arranged at intervals in the circumferential direction of the tire. The second lug grooves 520 traverse the second shoulder land 500 and the second buttress 8B and communicate with the third main groove 900 and the second annular groove 9B. The second annular groove 9B is an annular groove along the circumferential direction of the tire and is formed on the radially inward side of the second buttress 8B.

[0061] The second shoulder block 510 is provided extending from the second shoulder base 500 to the second buttress 8B. The second shoulder block 510 is divided into a substantially rectangular shape in plan view by a third main groove 900, a second annular groove 9B, and a pair of second lug grooves 520 adjacent in the circumferential direction of the tire.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] The region of the second buttress 8B in the second shoulder block 510 includes a pair of third hook-shaped grooves 83 and a fourth hook-shaped groove 84 facing each other in the tire axial direction, and a shoulder groove 87 provided near the shoulder 5. The fourth hook-shaped groove 84 is located on one side X1 in the tire axial direction of the third hook-shaped groove 83.

[0066] The third hook-shaped groove 83 and the fourth hook-shaped groove 84 have the same shape. Each of the hook-shaped grooves 83 and 84 has a hook-shaped bent tip portion 83b and 84b at the end of a circumferentially inclined groove portion 83a and 84a that is inclined with respect to the tire circumferential direction. The hook-shaped grooves 83 and 84 are arranged in the second shoulder block 510 in opposite directions in the tire circumferential direction, with the tip portions 83b and 84b engaging with each other and the circumferentially inclined groove portions 83a and 84a being parallel. The third hook-shaped groove 83, located on the other side X2 in the tire axial direction, has its base end communicating with the second annular groove 9B and the second lug groove 520, and its tip portion 83b terminates within the second shoulder block 510. The fourth hook-shaped groove 84, located on one side X1 of the tire axial direction, has its base end in communication with a second lug groove 520 that is different from the second lug groove 520 to which the base end of the third hook-shaped groove 83 communicates.

[0067] The shoulder groove 87 is located within the second shoulder block 510 on the other side C2 in the tire circumferential direction of the fourth hook-shaped groove 84. The shoulder groove 87 communicates with the second lug groove 520, which is connected to the base end of the third hook-shaped groove 83, and extends from that communicating end to one side C1 in the tire circumferential direction, terminating without reaching the fourth hook-shaped groove 84.

[0068] As mentioned above, the central rib 100 of the embodiment has a rib shape that extends continuously in an annular manner in the circumferential direction of the tire. This ensures a contact length of the central rib 100 and increases the contact area, thereby improving ice driving performance. In addition, the first central sipe 110 provided on the central rib 100 improves the water removal effect, which also improves ice driving performance. The first central sipe 110 will be described in detail below.

[0069] Figure 5 is a cross-sectional view of a tire showing the first central sipe 110 located on the central land surface 100, and in Figure 5, VA shows an enlarged view of the cross-section of multiple first central sipes 110 in the sipe depth direction (tire radial direction).

[0070] Figure 6 is a cross-sectional view of the VI-VI section of Figure 4, in which the opening 110a of the first central sipe 110 is positioned on the lower side and the bottom 110b is positioned on the upper side. Figure 6 shows a cross-sectional view of the first central sipe 110 in the sipe width direction when the tire 1 is unloaded. As shown in Figure 6, the first central sipe 110 is formed between the first wall surface 160 and the second wall surface 170, which are opposite each other in the central landform 100. In other words, the first central sipe 110 as a groove has an opening 110a, a bottom 110b, a first wall surface 160, and a second wall surface 170, with a space between the first wall surface 160 and the second wall surface 170. The first central sipe 110 is also a 3D sipe, similar to the second central sipe 120.

[0071] The first wall surface 160 is provided at two locations spaced apart in the sipe depth direction (vertical direction in Figure 6) and has a first protrusion 161 extending in the sipe length direction and a first recess 162 positioned between the first protrusions 161. Each of the first protrusions 161 projects toward the second wall surface 170. The first protrusions 161 and the first recess 162 are provided along the entire length of the first central sipe 110 in the extending direction.

[0072] The second wall surface 170 has second recesses 171 facing each of the first protrusions 161 of the first wall surface 160, and a second protrusion 172 positioned between these second recesses 171 and facing the first recess 162 of the first wall surface 160. The second protrusions 172 project toward the first wall surface 160. The second recesses 171 and the second protrusions 172 are provided along the entire length of the first central sipe 110 in the extending direction.

[0073] As shown in Figure 6, the first central sipe 110 has a straight space 110S in its cross-section in the width direction of the sipe, which extends linearly from the opening 110a to the bottom 110b when unloaded. This straight space 110S allows for a clear view of the bottom 110b from the opening 110a to the bottom 110b in the depth direction of the sipe, without being obstructed by the first protrusion 161 of the first wall surface 160 and the second protrusion 172 of the second wall surface 170.

[0074] In the first central sipe 110, the distance between the first wall surface 160 and the second wall surface 170 is approximately equal from the opening 110a to the bottom 110b. The distance between the first wall surface 160 and the second wall surface 170 referred to here is the distance in the sipe width direction between the main first wall surface 160 and the second wall surface 170, between the portion of the first wall surface 160 where the first protrusion 161 and the first recess 162 are not provided, and between the portion of the second wall surface 170 where the second recess 171 and the second protrusion 172 are not provided, as well as the distance in the sipe width direction between the first protrusion 161 and the second recess 171, and the distance in the sipe width direction between the first recess 162 and the second protrusion 172. At both ends of the first recess 162 and the second recess 171 in the depth direction, the gap between them and the opposing wall surface is partially larger, but the spacing in the width direction of the sipe in that portion is excluded from the spacing between the first wall surface 160 and the second wall surface 170, which is considered to have equal spacing.

[0075] The spacing between the first wall surface 160 and the second wall surface 170, i.e., the sipe width of the first central sipe 110, is, for example, about 0.6 mm, and preferably between 0.5 mm and 1.0 mm. The protruding height of the first protrusion 161 and the second protrusion 172 is, for example, about 0.3 mm, and preferably between 0.2 mm and 0.5 mm. The width of the straight space 110S is, for example, about 0.3 mm, and preferably between 0.1 mm and 0.5 mm.

[0076] Preferably, the length of the first protrusion 161 of the first wall surface 160 in the sipe depth direction is 40% or more and 70% or less of the length of the second recess 171 of the second wall surface 170 in the sipe depth direction.

[0077] The operation of the first central sipe 110 having this configuration will now be explained. Figures 7A to 7E schematically show the deformation process when the central contact surface 100 of a rotating tire 1, which rotates in the G direction, makes contact with the road surface R while the vehicle is traveling forward on the road surface R. Here, the central straight portion 111 extending in the tire axis direction of the three first central sipes 110 arranged in the circumferential direction of the tire is shown. The contact surface of the tire 1 has a tire-pressing side (first contact side) that makes contact with the road surface R first, and a tire-kicking side (rear contact side) that moves away from the road surface R. In the embodiment of the tire 1, the first wall surface 160 is located on the tire-pressing side, and the second wall surface 170 is located on the tire-kicking side.

[0078] Figures 7A and 7B show the state when the tire is pressed down, illustrating how the width of the central sipe 110 narrows from the side where the tire is pressed down (right side). Figure 8 is an enlarged view of Figure 7B.

[0079] As shown in Figure 8, when the tire is pressed down, the rubber of the central rim 100 on the tire-pressing side deforms more than the first wall surface 160 on the tire-pressing side, causing the first wall surface 160 to approach the second wall surface 170 and reducing the width of the first central sipe 110. At this time, the first protrusion 161 fits into the second recess 171, and the second protrusion 172 fits into the first recess 162. Furthermore, of the two first protrusions 161, the first protrusion 161 on the opening 110a side comes into contact with the second protrusion 172, and the first protrusion 161 on the bottom 110b side comes into contact with the edge 171c of the second recess 171 on the bottom 110b side. In this state, in the tire 1 of the embodiment, a gap 105 is formed between the first protrusion 161 and the second protrusion 172 in the sipe depth direction.

[0080] As shown in Figure 7C, during the mid-tire contact period when the sipe depth direction of the first central sipe 110 is approximately perpendicular to the road surface R, the first wall surface 160 and the second wall surface 170 are separated, the first protrusion 161 does not fit into the second recess 171, and the first recess 162 does not fit into the second protrusion 172.

[0081] Figures 7D to 7E show the tire kick-out process. During this process, the rubber of the central land 100 on the tire kick-out side (left side) of the second wall 170 deforms, causing the second wall 170 to separate from the first wall 160 and increasing the width of the first central sipe 110.

[0082] In this embodiment, the first central sipe 110 comes into contact with each other due to tire deformation that occurs when the tire is pressed down, as described above. As a result, the opening 110a of the first central sipe 110 remains open, making it difficult for blockage to occur on the tire surface. Therefore, a water-removing effect is ensured as moisture enters the first central sipe 110 from the opening 110a, resulting in improved ice driving performance.

[0083] There are no particular restrictions on the dimensions of the first central sipe 110, but as shown in Figure 6, for example, the spacing Wa in the sipe width direction between the first protrusion 161 and the second recess 171 is 0.6 mm, and the maximum spacing Wb between the first protrusion 161 and the edge 171c of the second recess 171, which are in contact with each other, is 0.5 mm. These dimensions are just examples, and it is preferable that the ratio of Wa to Wb, Wb / Wa, is, for example, 0.5 or more and 1 or less. By having such a dimensional relationship, the first protrusion 161 can easily come into contact with the edge 171c of the second recess 171, and the water removal effect described above can be ensured.

[0084] The tread 2, including the central ridge 100, is made of tread rubber, and the hardness of this tread rubber is preferably 50 to 65 on the durometer hardness type A of JIS K6253-3:2012. When the tread rubber has such hardness, the first convex portion 161 can easily come into proper contact with the edge 171c of the second concave portion 171, thereby ensuring the water removal effect described above.

[0085] Figure 9 is a diagram showing an example of the contact surface shape of the tread surface 2A of the tire 1 of the embodiment, and is a diagram for explaining the rectangularity of the contact surface. Figure 9 is a diagram corresponding to the contact mark left by the tire 1 when it makes contact with the ground. In Figure 9, L1 is shown as the tread contact length in the circumferential direction of the tire on the tire equator E, and L2 is shown as the tread contact length in the circumferential direction of the tire at a position 10 mm inward from both ends of the contact width W1, and the rectangularity is L2 / L1. Note that the actual L2 may differ on the left and right sides, so the average of both is taken.

[0086] In the embodiment, when tire 1 is mounted on a standard rim and filled to the standard internal pressure, the rectangular ratio L2 / L1 at 70% of the maximum load is between 70% and 92%. This relatively high rectangular ratio of the contact surface, resulting in a square-shaped contact surface, improves ice driving performance due to the increased contact area.

[0087] Figure 10 shows one embodiment of a tire molding die used for vulcanizing the tire 1 of the embodiment. Figure 10 is a meridian cross-sectional view of the tire molding die 10 along the axial direction of the tire 1 being molded.

[0088] The tire molding die 10 shown in Figure 10 comprises a plurality of sectors 11 arranged circumferentially along the outer circumference of the tire 1, a pair of side plates 12 positioned on both sides of the axial direction of the annular body formed by the combination of the plurality of sectors 11, and a pair of bead rings (not shown). During vulcanization molding, an unvulcanized tire, which will become the tire 1, is set inside the tire molding die 10. The combination of sectors 11, side plates 12, and bead rings forms the mold for forming the tire 1, and the outer surface of the entire tire 1 is formed by the inner surface of the mold, i.e., the inner surface 11a of the sectors 11, the inner surface 12a of the side plates 12, and the inner surface of the bead rings. Also, during vulcanization molding, a bladder (not shown) is placed inside the unvulcanized tire to press the unvulcanized tire against the inner surface of the tire molding die 10. The plurality of sectors 11 mainly form the tread 2, shoulder 5, and buttress 8, and the pair of side plates 12 mainly form the sidewall 4. The pair of bead rings forms the bead 3, and the bladder forms the entire inner surface of the tire 1.

[0089] The tire molding die 10 vulcanizes the unvulcanized tire to form the overall rubber shape of the tire 1, and also forms a tread pattern 2B on the tread 2.

[0090] The tire 1 and tire molding die 10 according to the embodiments described above provide the following effects.

[0091] (1) The tire 1 according to the embodiment is a pneumatic tire having a tread 2 including a central ridge 100 having a first central sipe 110 as a sipe extending in a direction intersecting the tire circumferential direction, wherein the first central sipe 110 is formed between a first wall surface 160 and a second wall surface 170 that are opposite to each other, and the first wall surface 160 has first protrusions 161 that are spaced apart in the sipe depth direction and extend in the sipe length direction, and a first recess 162 disposed between the first protrusions 161, The wall surface 170 has a second recess 171 facing each of the first protrusions 161, and a second protrusion 172 positioned between the second recesses 171 and facing the first recess 162. The first central sipe 110 has a straight space 110S in its widthwise cross-section that extends linearly from the opening 110a to the bottom 110b in an unloaded state, and the first protrusion 161 and the second protrusion 172 come into contact with each other due to tire deformation that occurs when the tire is pressed down.

[0092] In this embodiment, the first central sipe 110 comes into contact with each other due to tire deformation that occurs when the tire is pressed down, as described above. As a result, the opening 110a of the first central sipe 110 remains open, making it difficult for blockage to occur on the tire surface. Therefore, a water-removing effect is ensured as moisture enters the first central sipe 110 from the opening 110a, and an edge effect is also ensured. As a result, ice driving performance is improved.

[0093] (2) In the tire 1 of the embodiment described in (1) above, it is preferable that the distance between the first wall surface 160 and the second wall surface 170 is substantially equal from the opening 110a of the first central sipe 110 to the bottom 110b.

[0094] This results in uniform block rigidity in the central 100 section, which in turn equalizes the ground pressure, thereby improving ice driving performance.

[0095] (3) In the tire 1 according to the embodiment described in (1) and (2) above, it is preferable that the first wall surface 160 is positioned on the tire pressing side and the second wall surface 170 is positioned on the tire kicking side.

[0096] As a result, when a forward and backward force is applied, the first protrusion 161 of the first wall surface 160 and the second protrusion 172 of the second wall surface 170 come into contact on the side away from the opening 110a of the first central sipe 110, as shown in Figure 8. This makes it easier to create a space on the opening 110a side between the first protrusion 161 and the second protrusion 172 in the sipe depth direction. Therefore, the sipe volume is more easily secured, and the water removal effect is improved.

[0097] (4) In the tire 1 according to the embodiment described in (1) to (3) above, when the tire is pressed down, the first protrusion 161 and the second recess 171 fit together with each other, and the first recess 162 and the second protrusion 172 fit together, and in that state, a gap 105 is formed between the first protrusion 161 and the second protrusion 172 in the sipe depth direction.

[0098] This allows the gap 105 in the sipe depth direction to move, enabling the central land surface 100 to deform, thus improving road surface following ability. As a result, ice driving performance is improved.

[0099] (5) In the tire 1 according to the embodiment described in (1) to (4) above, it is preferable that the length of the first protrusion 161 in the sipe depth direction is 40% or more and 70% or less of the length of the second recess 171 in the sipe depth direction.

[0100] This increases the likelihood that the first wall surface 160, on which the first protrusion 161 is formed, and the second wall surface 170, on which the second protrusion 172 is formed, will come into contact with each other when the tire is pressed down, thereby suppressing excessive tilting of the block. In addition, while the first wall surface 160, on which the first protrusion 161 is formed, and the second wall surface 170, on which the second protrusion 172 is formed, are in contact with each other, an appropriate gap space is more easily formed. Furthermore, even when the sipes are closed, it is possible to ensure movement in the radial direction of the tire and improve road surface following ability by making the block easier to move.

[0101] (6) In the tire 1 according to the embodiment described in (1) to (5) above, when mounted on a regular rim and filled with regular internal pressure, it is preferable that the rectangular ratio at 70% of the maximum load is 70% or more and 92% or less. However, the rectangular ratio here is L2 / L1, where L1 is the circumferential length of the tire on the tire equator E in the tire contact surface shape, and L2 is the circumferential length of the tire at a position 10 mm inward from both ends of the contact width of the tire contact surface shape.

[0102] This results in a relatively high rectangularity and a square-shaped contact surface. Consequently, the increased contact area improves ice driving performance. (7) In the tire 1 according to the embodiment described in (1) to (6) above, the hardness of the rubber constituting the tread 2 is preferably 50 or more and 65 or less on the durometer hardness type A of JIS K6253-3:2012.

[0103] When the rubber constituting the tread 2 has such hardness, the first protrusion 161 can easily come into proper contact with the edge 171c of the second recess 171, thereby ensuring the water removal effect and edge effect described above.

[0104] (8) The tire molding die 10 according to the embodiment can mold the tire 1 described in (1) to (7) above.

[0105] As a result, the tire molding die 10 of the embodiment can suitably manufacture the tire 1 of the embodiment.

[0106] 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. [Explanation of symbols]

[0107] 1. Tire (pneumatic tire) 2 tread 6 land 10 Tire molding dies 100 Chuo Riku 105 gap 110 First Central Sipe (Sipe) 110a aperture 110b bottom 110S Straight Space 160 First Wall 161 First protrusion 162 First recess 170 Second Wall 171 Second recess 172 Second protrusion E-Tire Equator C Tire circumferential direction X Tire Axle

Claims

1. A pneumatic tire having a tread including land with sipes extending in a direction intersecting the circumferential direction of the tire, The sipe is formed between a first wall surface and a second wall surface that are opposite to each other. The first wall surface has first protrusions that are spaced apart in the sipe depth direction and extend in the sipe length direction, and first recesses that are positioned between the first protrusions. The second wall surface has second recesses facing each of the first protrusions, and second protrusions positioned between the second recesses and facing the first recesses. In the cross-section of the sipe in the width direction, a straight space is provided that extends linearly from the opening to the bottom of the sipe in an unloaded state. A pneumatic tire in which the first and second protrusions come into contact with each other due to tire deformation that occurs when the tire is pressed down.

2. The pneumatic tire according to claim 1, wherein the distance between the first wall surface and the second wall surface is substantially equal from the opening of the sipe to the bottom.

3. The pneumatic tire according to claim 1 or 2, wherein the first wall surface is positioned on the tire-pressing side and the second wall surface is positioned on the tire-kicking side.

4. The pneumatic tire according to claim 1 or 2, wherein when the tire is pressed down, the first convex portion and the second recess portion engage with each other, and the first recess portion and the second convex portion engage with each other, and in that state, a gap is formed between the first convex portion and the second convex portion in the sipe depth direction.

5. The pneumatic tire according to claim 1 or 2, wherein the length of the first protrusion in the sipe depth direction is 40% or more and 70% or less of the length of the second recess in the sipe depth direction.

6. A pneumatic tire according to claim 1 or 2, wherein, when mounted on a standard rim and filled to the standard internal pressure, the rectangularity at 70% of the maximum load is 70% or more and 92% or less. However, the aforementioned rectangular ratio is L2 / L1, where L1 is the circumferential length of the tire at the tire equator in the tire contact surface shape, and L2 is the circumferential length of the tire at a position 10 mm inward from both ends of the contact width of the tire contact surface shape.

7. The pneumatic tire according to claim 1 or 2, wherein the hardness of the rubber constituting the tread is 50 or more and 65 or less on the durometer hardness type A of JIS K6253-3:2012.

8. A tire molding die for molding a pneumatic tire according to claim 1 or 2.

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