pneumatic tires

Abstract

To provide a pneumatic tire that can achieve multi-directional rigidity of the block by combining shapes with different directional specificities in the sipes of the block. [Solution] The tread 2 has a plurality of first main grooves 21 that extend from the first contact end 5 toward the tire equator S1 while being inclined with respect to the tire rotation direction R, a plurality of first sub-grooves 22 connected in a direction intersecting the plurality of main grooves 21, and a plurality of first center blocks 31 partitioned by the first main grooves 21 and the second sub-grooves 22. At least one center block 31 has a first sipe 51 that extends along a front edge 33 in the rotation direction and a rear edge 34 in the rotation direction that are in contact with the first main grooves 21. The first sipe 51 has a surface opening 52 and a bottom surface 53, and has a three-dimensional shape in which the sipe shape in plan view changes in the sipe depth direction.

Description

Technical Field

[0001] The present invention relates to a pneumatic tire having a tread.

Background Art

[0002] A pneumatic tire generally includes a tread that contacts the road surface. The tread is provided with, for example, a block pattern in which a plurality of blocks partitioned by grooves extending in the tire circumferential direction and grooves intersecting therewith are arranged in the tire circumferential direction. In the pneumatic tire described in Patent Document 1, a plurality of sipes are formed in the blocks, and the grip performance of the tire is improved by exerting an edge effect.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By devising the shape of the sipes in the tire pattern, it is possible to control the rigidity of the rubber, the grounding property of the tire, the braking ability of the tire, and the like. For example, regarding the braking ability of the tire, the rubber surface where the edge functions due to the sipes has a greater resistance than a flat rubber surface. However, when the rubber block is cut by the sipes, the rigidity of the block decreases, and therefore the block may bend (hereinafter referred to as "collapse") under the load during braking. The collapse is mainly a deformation in which the block undergoes shear deformation starting from the side of the block bottom surface. When the block collapses, it becomes difficult to contact the ground, and therefore the braking ability of the tire decreases.

[0005] In the shape of the sipes in the conventional block, the direction in which the anti-collapse effect is exerted is limited.

[0006] The present invention aims to provide a pneumatic tire that can impart multidirectional rigidity to a block by combining shapes having different directional specificities in the sipes of the block. [Means for solving the problem]

[0007] A pneumatic tire according to the first view of the present invention is A pneumatic tire having a tread and a specified direction of rotation, The aforementioned tread is Multiple main grooves extend from the contact edge toward the tire equator, while being inclined with respect to the circumferential direction of the tire, Multiple sub-grooves connected in a direction intersecting the multiple main grooves, It has a plurality of blocks partitioned by the main groove and the sub-grooves, At least one of the blocks has a rear edge in the direction of rotation that is in contact with the main groove and a sipe extending along the rear edge in the direction of rotation, The sipe has a surface opening and a bottom surface, and its shape is three-dimensional, with the sipe shape in plan view changing in the direction of the sipe depth. [Effects of the Invention]

[0008] According to the present invention, by combining shapes having different directional specificities in the sipes of the block, it is possible to provide a pneumatic tire that can impart multidirectional rigidity to the block. [Brief explanation of the drawing]

[0009] [Figure 1] This is a diagram showing a portion of the outer surface of a pneumatic tire according to the first embodiment, viewed from above. [Figure 2] This is a plan view of the first center block. [Figure 3] This is a perspective view of the first center block. [Figure 4] This is a perspective view of a sipe. [Figure 5] This is a perspective view of a sipe. [Figure 6] It is a perspective view of a sipe. [Figure 7] It is a perspective view of the first center block of the second embodiment. [Figure 8] It is a perspective view of the first center block of the third embodiment. [Figure 9] It is a perspective view of the first center block of the fourth embodiment. [Figure 10] It is a perspective view of the first center block of the fifth embodiment. [Figure 11] It is a perspective view of the first center block of the sixth embodiment. [Figure 12] It is a perspective view of the first center block of the seventh embodiment. [Figure 13] It is a perspective view of the first center block of the eighth embodiment. [Figure 14] It is a plan view of the first center block of the ninth embodiment. [Figure 15] It is a perspective view of the first center block of the tenth embodiment. [Figure 16] It is a perspective view of the first center block of the eleventh embodiment.

Mode for Carrying Out the Invention

[0010] (First Embodiment) Using FIG. 1, the tire 1 according to the first embodiment will be described. FIG. 1 is a view showing a part of the outer peripheral surface of a pneumatic tire according to the first embodiment when viewed in plan and developed. The tire 1 can be applied to a tire for a passenger car, but in addition, it can also be applied to tires for various vehicles such as light trucks, trucks, and buses.

[0011] The tire 1 is a directional tire in which the rotation direction when the vehicle on which it is mounted moves forward is specified. In FIG. 1, the front side R1 (or the stepping-in side) and the rear side R2 (or the kicking-out side) of the tire 1 in the tire rotation direction R (also referred to as the tire circumferential direction) are shown.

[0012] In FIG. 1, the tire axial direction X (also referred to as the tire width direction) is shown. The tire axial direction X is a direction parallel to the rotation axis of the tire 1.

[0013] As shown in FIG. 1, the tire 1 includes a tread 2. The tire 1 further has a first shoulder 3 and a second shoulder 4 on both sides of the tread 2 in the tire axial direction. The first shoulder 3 and the second shoulder 4 are portions that each transition from the tread 2 to respective sidewalls (not shown) on both sides in the tire axial direction and are portions that contact the shoulders of the tire 1.

[0014] The first shoulder 3 and the second shoulder 4 are each provided with a first grounding end 5 and a second grounding end 6. The first grounding end 5 and the second grounding end 6 are defined as the both ends in the tire axial direction of the region that contacts a flat road surface when a predetermined load is applied in a state where the tire 1 in use is mounted on a regular rim and filled with air to a regular internal pressure. In the case of a passenger car tire, the predetermined load is a load corresponding to 88% of the regular load.

[0015] (Tread pattern) The tread 2 has a tread surface 8 that contacts the road surface. A tread pattern 9 is formed on the tread surface 8. The tread pattern 9 is mainly formed by a plurality of main grooves (described later), a plurality of sub-grooves (described later), and a plurality of blocks (described later) partitioned by these grooves. A block is a portion that protrudes toward the outer side in the tire diameter direction and is generally also called land.

[0016] In FIG. 1, a tire equator S1, which is a virtual line extending along the tire rotation direction R at the center of the tread surface 8 in the tire axial direction, is shown. The tire equator S1 is at an equal distance from the first grounding end 5 and the second grounding end 6.

[0017] The tread surface 8 includes a first tread surface 13 on the side of the first shoulder 3 and a second tread surface 14 on the side of the second shoulder 4 with the tire equator S1 as a boundary.

[0018] (Tread pattern grooves) The main grooves include a plurality of first main grooves 21 extending from the first contact end 5 toward the tire equator S1, and a plurality of second main grooves 22 extending from the second contact end 6 toward the tire equator S1. The first main grooves 21 are mainly formed on the first tread surface 13, and the second main grooves 22 are mainly formed on the second tread surface 14. The first main grooves 21 are grooves extending from one side in the tire axial direction X toward the tire equator S1 and are spaced apart in the tire rotation direction R. The second main grooves 22 are grooves extending from the other side in the tire axial direction X toward the tire equator S1 and are spaced apart in the tire rotation direction R. Here, in the first main grooves 21 and the second main grooves 22, the ends on the first contact end 5 and the second contact end 6 sides are considered the base ends, and the ends on the tire equator S1 side are considered the tip ends.

[0019] The first main groove 21 is inclined with respect to the tire axis X overall. More specifically, the first main groove 21 extends from the first contact end 5 toward the tire equator S1 toward the front side R1 in the direction of rotation, gradually curving so as to be convex toward the rear side R2 in the direction of rotation. The inclination angle with respect to the tire axis X is greater on the tire equator S1 side of the first main groove 21 than on the first contact end 5 side.

[0020] The second main groove 22 is inclined with respect to the tire axis X overall. More specifically, the second main groove 22 extends from the second contact end 6 toward the tire equator S1 toward the front side R1 in the direction of rotation, gradually curving so as to be convex toward the rear side R2 in the direction of rotation. The inclination angle with respect to the tire axis X is greater in the portion of the second main groove 22 toward the tire equator S1 than in the portion toward the second contact end 6.

[0021] As described above, the first main groove 21 and the second main groove 22 gradually align with the tire axial direction X from the tire equator S1 side toward the first contact end 5 and the second contact end 6, and the inclination with respect to the tire axial direction X becomes gentler. The inclination angle of the first main groove 21 or the second main groove 22 with respect to the tire axial direction X is, for example, 30° to 60° or 40° to 50° in the portion on the tire equator S1 side.

[0022] The tips of the multiple first main grooves 21 terminate in such a manner that they merge with the second main groove 22 just before the tire equator S1.

[0023] The tips of the multiple second main grooves 22 terminate in such a manner that they merge with the first main groove 21 just before the tire equator S1.

[0024] The sub-groove 11 includes a first sub-groove 23 that connects a pair of first main grooves 21 adjacent in the tire rotation direction R, and a second sub-groove 24 that connects a pair of second main grooves 22 adjacent in the tire rotation direction R. The first sub-groove 23 is formed on the first tread surface 13, and the second sub-groove 24 is formed on the second tread surface 14.

[0025] The first sub-groove 23 and the second sub-groove 24 are grooves that are narrower in width (maximum width) than the first main groove 21 and the second main groove 22. The first sub-groove 23 is inclined with respect to the tire rotation direction R such that it gradually moves away from the first contact end 5 from the front side R1 in the rotation direction to the rear side R2 in the rotation direction. The second sub-groove 24 is inclined with respect to the tire rotation direction R such that it gradually moves away from the second contact end 6 from the front side R1 in the rotation direction to the rear side R2 in the rotation direction. The first sub-groove 23 and the second sub-groove 24 may be shallower than the first main groove 21 and the second main groove 22, or they may be the same depth.

[0026] The first main groove 21 and the second main groove 22 have similar configurations, and the first secondary groove 23 and the second secondary groove 24 have similar configurations.

[0027] (Tread pattern blocks) The multiple blocks include multiple first center blocks 31 positioned in the center in the direction of the tire axis. The first center blocks 31 are divided into a roughly rectangular shape by two first main grooves 21, a second main groove 22 where the two first main grooves 21 merge, and a first secondary groove 23.

[0028] The multiple blocks include multiple second center blocks 32 positioned in the center in the tire axis direction X. The second center blocks 32 are divided into a roughly rectangular shape by two second main grooves 22, a first main groove 21 where the two second main grooves 22 merge, and a second secondary groove 24.

[0029] The first center block 31 and the second center block 32 are arranged alternately in a staggered pattern along the tire rotation direction R. More specifically, the first center block 31 and the second center block 32 are arranged so as to span both the first tread surface 13 and the second tread surface 14. That is, the tire equator S1 passes through the first center block 31 and the second center block 32.

[0030] Multiple first center blocks 31 are mainly located on the first tread surface 13. Multiple second center blocks 32 are mainly located on the second tread surface 14.

[0031] In the tread pattern 9, in a plan view, for example, the first center block 31 and the second center block 32 are arranged symmetrically with respect to the tire equator S1, offset by a predetermined pitch in the tire rotation direction R. The shape of the first center block 31 is the same as the shape of the second center block 32 when it is inverted with respect to the tire equator S1 (the same applies to the first main groove 21 and the second main groove 22). The tread pattern 9 of this embodiment has good left-right balance and is effective in improving handling stability.

[0032] The plurality of blocks further comprises a plurality of first shoulder blocks 37 and second shoulder blocks 38 positioned outward in the tire axial direction. The plurality of blocks further comprises a plurality of first intermediate blocks 39 and second intermediate blocks 40 positioned in the middle in the tire axial direction.

[0033] The first shoulder block 37 is divided into a substantially rectangular shape by a pair of first main grooves 21 and a first sub-groove 23 adjacent to each other in the tire rotation direction R. The edge of the first shoulder block 37 on the first shoulder 3 side is continuous with the outer surface of the first shoulder 3.

[0034] The second shoulder block 38 is divided into a substantially rectangular shape by a pair of second main grooves 22 and a second sub-groove 24 adjacent to each other in the tire rotation direction R. The edge of the second shoulder block 38 on the second shoulder 4 side is continuous with the outer surface of the second shoulder 4.

[0035] The first intermediate block 39 is positioned on the first tread surface 13. The second intermediate block 40 is positioned on the second tread surface 14.

[0036] The first intermediate block 39 is divided into a substantially rectangular shape by a pair of first main grooves 21 and a pair of first sub-grooves 23 adjacent to each other in the tire rotation direction R. Multiple first intermediate blocks 39 are arranged in the tire rotation direction R with the first main grooves 21 in between.

[0037] The second intermediate block 40 is divided into a roughly rectangular shape by a pair of second main grooves 22 adjacent to each other in the tire rotation direction R, a second sub-groove 24, and another second main groove 22. Multiple second intermediate blocks 40 are arranged in the tire rotation direction R with the second main grooves 22 in between.

[0038] (Sipes on the block) The first center block 31 will be described in detail using Figures 2 to 6. Figure 2 is a plan view of the first center block. Figure 3 is a perspective view of the first center block. Figures 4 to 6 are perspective views of the sipes. Note that the structure of the second center block 32 is the same as that of the first center block, so its explanation will be omitted.

[0039] The first center block 31 has a front edge 33 in the direction of rotation, a rear edge 34 in the direction of rotation, and a sipe 51. The front edge 33 in the direction of rotation is located at a front R1 in the direction of rotation relative to the rear edge 34 in the direction of rotation. The front edge 33 in the direction of rotation is slightly concave in plan view. The rear edge 34 in the direction of rotation is slightly convex in plan view.

[0040] The sipes 51 extend generally parallel to the front edge 33 and the rear edge 34 in the direction of rotation, and one sipe is provided on each first center block 31. The sipes 51 are located approximately midway between the front edge 33 and the rear edge 34 in the direction of rotation, and extend in a direction that intersects the tire rotation direction R at an angle.

[0041] The sipe 51 is preferably located in the interior of the first center block 31. The interior of the first center block 31 is, for example, the area 5 mm or more inward from the front edge 33 and the rear edge 34 in the rotational direction of the first center block 31.

[0042] The sipe 51 opens onto the surface of the first center block 31, and the depth of the sipe generally aligns with the tire diameter. More specifically, the sipe 51 has a surface opening 52 and a bottom surface 53. The surface opening 52 is a gap at the same height as the surface of the first center block 31. The bottom surface 53 is a flat bottom inside the first center block 31. Therefore, the depth of the sipe 51 is constant throughout. Note that the surface opening 52 and the bottom surface 53 have different shapes (described later).

[0043] Sipe 51 is a groove that is narrower than the first main groove 21, the second main groove 22, the first secondary groove 23, and the second secondary groove 24. For example, the average groove width of sipe 51 is 1.5 to 2.0 mm.

[0044] The depth of the sipe 51 is measured as the straight-line distance from the surface opening 52 to the bottom surface 53. The sipe 51 has a maximum depth of, for example, 2.0 mm to 3.0 mm or more. The sipe depth is set to, for example, 40 to 80% of the depth of the first main groove 21.

[0045] The surface opening 52 has a curved shape that is convex towards the rear side R2 in the rotational direction when viewed from above. This allows the surface opening 52 to achieve high edge capability.

[0046] The base surface 53 has a curved shape that is convex towards the front side R1 in the rotational direction when viewed from above. This allows the base surface 53 to suppress tilting and shearing of the first center block 31.

[0047] As shown in Figure 2, in a plan view, the surface opening 52 and the bottom surface 53 overlap. That is, the middle part of the surface opening 52 is located R2 further back in the rotational direction than the middle part of the bottom surface 53, and both ends of the surface opening 52 are located R1 further forward in the rotational direction than both ends of the bottom surface 53. In this case, the area that acts as the pivot point on the tire side becomes larger.

[0048] In the structure described above, the sipe 51 as a whole is tilted towards the rear side R2 in the direction of rotation. Therefore, after tilting, the block wall surface approaches vertical, resulting in improved rigidity against vertical loads.

[0049] As shown in Figures 4 to 6, the sipe 51 is continuous in the depth direction from the surface opening 52 to the bottom surface 53 while maintaining a smooth curved surface. Thus, the sipe 51 is a three-dimensional sipe in which the sipe shape in plan view changes in the sipe depth direction. Therefore, when the first center block 31 tries to deform in the front-rear direction during starting or braking, the three-dimensionally formed wall surfaces engage with each other, suppressing the deformation. Similarly, when the first center block 31 tries to deform in the lateral direction during turning, the three-dimensionally formed wall surfaces engage with each other, suppressing the deformation. In this way, the sipe 51 suppresses the tilting of the first center block 31.

[0050] Generally, the collapse of a block is a deformation in which the block undergoes shear deformation, starting from the edge of its base. Since collapse is a deformation in one dimension, it is more difficult to bend an object along a curve than along a straight line. Specifically, if the base is curved, it interferes with the starting point of the curve, creating distortion, or a "resistance to collapse." Therefore, in this embodiment, the shape of the base 53 of the sipe 51, which is the starting point of collapse, is curved rather than straight, thereby suppressing the collapse of the first center block 31.

[0051] As described above, the sipe 51 has a curved shape throughout its entire depth (its longitudinal cross-section is a smooth curve). In this embodiment, the sipe 51 has a complex shape that changes in the depth direction. Specifically, the shape of the depth-direction changes in each part of the sipe 51 are different from each other. By combining shapes with different directional specificities in this way, rigidity in multiple directions can be obtained. Furthermore, since the sipe 51 does not have sharp bends at corners in the depth direction, stress concentration is less likely to occur.

[0052] As a variation, the sipe only needs to have a curved shape in at least a portion of the depth direction in the longitudinal section, and therefore may include a straight section in the longitudinal section. However, it is preferable that the sipe has a curved shape over 60% or more of the longitudinal section.

[0053] As shown in FIGS. 2 and 3, the sipe 51 is open on both sides of the first center block 31. Specifically, both ends of the sipe 51 are open at the first side surface 35 and the second side surface 36 of the first center block 31, respectively.

[0054] As shown in FIGS. 2 and 3, let the length of the front edge 33 in the rotation direction be L0, the length of the surface opening 52 be L1, and the length of the bottom surface 53 be L2. Each length is the length along the curve. In this case, L0 < L1 < L2 holds. That is, in the sipe 51, the surface opening 52 is longer than the front edge 33 in the rotation direction, and further, the bottom surface 53 is longer than the surface opening 52.

[0055] By making the length L1 of the surface opening 52 longer than the length L0 of the front edge 33 in the rotation direction, an edge effect can be obtained. By making the length L2 of the bottom surface 53 longer than the length L1 of the surface opening 52, excessive tilting of the sipe 51 during braking and turning can be suppressed, and braking and turning performance can be improved.

[0056] As shown in FIG. 3, let the length of the 50% depth sipe of the sipe 51 be L3. In this case, L1 < L3 < L2 holds. That is, the 50% depth sipe is longer than the surface opening 52, and further, the bottom surface 53 is longer than the 50% depth sipe. In this embodiment, the sipe length increases from the surface opening 52 to the bottom surface 53.

[0057] In the first embodiment, the sipe 51 is formed in all of the first shoulder block 37, the second shoulder block 38, the first intermediate block 39, and the second intermediate block 40.

[0058] In the first embodiment, the bottom surface 53 is a flat surface, and the sipe 51 has a constant depth along its entire length. In a modification of the first embodiment, the bottom surface 53 may have portions of varying depths. For example, the bottom surface may have a maximum depth portion and a raised portion (shallow groove portion). The number and location of the raised portions are not limited. In this modification, the length of the bottom surface is the total length assuming that the raised portions extend to the maximum depth portion.

[0059] As a modification of the first embodiment, the sipes 51 may be formed on only some of the blocks. For example, the sipes 51 may be formed only on the first center block 31 and the second center block 32.

[0060] (Second embodiment) The sipe 51A of the first center block 31A according to the second embodiment will be explained using Figure 7. Figure 7 is a perspective view of the first center block of the second embodiment. Note that the basic configuration of the second embodiment is the same as that of the first embodiment, so only the differences will be explained (the same applies hereafter).

[0061] As shown in Figure 7, the bottom surface 53A of the sipe 51A of the first center block 31A is convex toward the rear side R2 in the rotational direction, in a plan view, just like the surface opening 52A. In other words, the surface opening 52A and the bottom surface 53A have curved shapes that are convex to the same side.

[0062] In a plan view, the bottom surface 53A is located on the front side R1 in the rotational direction relative to the surface opening 52A.

[0063] In this embodiment as well, the bottom surface 53A has a different shape from the surface opening 52A, and the bottom surface 53A is longer than the surface opening 52A.

[0064] (Third embodiment) The sipe 51B of the first center block 31B according to the third embodiment will be explained using Figure 8. Figure 8 is a perspective view of the first center block according to the third embodiment.

[0065] As shown in Figure 8, the surface opening 52B of the sipe 51B of the first center block 31B is convex toward the front side R1 in the rotational direction, in a plan view, just like the bottom surface 53B. In other words, the surface opening 52B and the bottom surface 53B have curved shapes that are convex to the same side.

[0066] In a plan view, the bottom surface 53B is located on the front side R1 in the rotational direction relative to the surface opening 52B.

[0067] In this embodiment as well, the bottom surface 53B has a different shape from the surface opening 52B, and the bottom surface 53B is longer than the surface opening 52B.

[0068] (Fourth embodiment) The sipe 51C of the first center block 31C according to the fourth embodiment will be explained with reference to Figure 9. Figure 9 is a perspective view of the first center block according to the fourth embodiment.

[0069] As shown in Figure 9, the surface opening 52C of the sipe 51C of the first center block 31C has, in plan view, a first curved portion 52C1, a second curved portion 52C2, and a connecting portion 52C3.

[0070] The first curved section 52C1 and the second curved section 52C2 have similar shapes and extend along the front edge 33C in the direction of rotation. However, the first curved section 52C1 is located on the first side, closer to the front edge 33C in the direction of rotation, while the second curved section 52C2 is located on the second side, closer to the rear edge 34C in the direction of rotation. The connecting section 52C3 connects the ends of the first curved section 52C1 and the second curved section 52C2 in the middle of the direction in which the edge extends. Thus, the surface opening 52C has discontinuous curved sections.

[0071] In this embodiment as well, the bottom surface 53C has a different shape from the surface opening 52C, and the bottom surface 53C is longer than the surface opening 52C.

[0072] (Fifth embodiment) The sipe 51D of the first center block 31D according to the fifth embodiment will be described with reference to Figure 10. Figure 10 is a perspective view of the first center block according to the fifth embodiment.

[0073] As shown in Figure 10, the sipe 51D of the first center block 31D is wavy in the depth direction.

[0074] In this embodiment as well, the bottom surface 53D has a different shape from the surface opening 52D, and the bottom surface 53D is longer than the surface opening 52D.

[0075] (Sixth embodiment) The sipe 51E of the first center block 31E according to the sixth embodiment will be described with reference to Figure 11. Figure 11 is a perspective view of the first center block according to the sixth embodiment.

[0076] As shown in Figure 11, the bottom surface 53E of the sipe 51E of the first center block 31E is wave-shaped in plan view.

[0077] In this embodiment as well, the bottom surface 53E has a different shape from the surface opening 52E, and the bottom surface 53E is longer than the surface opening 52E.

[0078] (Seventh Embodiment) The sipe 51F of the first center block 31F according to the seventh embodiment will be explained with reference to Figure 12. Figure 12 is a perspective view of the first center block according to the seventh embodiment.

[0079] As shown in Figure 12, the bottom surface 53F of the sipe 51F of the first center block 31F has a curved portion 53F1 and a flat stepped portion 53F2 provided in the center of the curved portion 53F1. The curved section 53F1 is curved and convex toward the front side R1 in the direction of rotation. The planar stepped section 53F2 is convex in the direction away from the front edge 33F in the direction of rotation.

[0080] In this embodiment as well, the bottom surface 53F has a different shape from the surface opening 52F, and the bottom surface 53F is longer than the surface opening 52F.

[0081] (Eighth Embodiment) Using FIG. 13, the sip 51G of the first center block 31G according to the eighth embodiment will be described. FIG. 13 is a perspective view of the first center block of the eighth embodiment.

[0082] As shown in FIG. 13, the sip 51G of the first center block 31G has a bottom surface 53G. The bottom surface 53G has a pair of first bottom surfaces 53G1, a second bottom surface 53G2 (bottom raising portion), and a third bottom surface 53G3 (bottom raising portion). The pair of first bottom surfaces 53G1 are curved and convex in the front side R1 of the rotation direction. The second bottom surface 53G2 is a shallower groove (a groove that bulges in the tire diameter direction) than the first bottom surface 53G1 and is provided at both outer ends in the length direction of the first bottom surface 53G1. The third bottom surface 53G3 is a shallower groove (a groove that bulges in the tire diameter direction) than the first bottom surface 53G1 and is provided between the pair of first bottom surfaces 53G1. The pair of second bottom surfaces 53G2 open to the first side surface 35G and the second side surface 36G, respectively.

[0083] Let the total length of the second bottom surface 53G2 and the third bottom surface 53G3 be L4. Let the virtual length of the bottom surface 53G of the sip 51G (the bottom surface length when the second bottom surface 53G2 is extrapolated to the first bottom surface 53G1) be L5.

[0084] In the above case, L4 < L5 holds.

[0085] In the above structure, mainly, the first bottom surface 53G1 becomes the support point on the tire side, and the portion of the surface opening 52G corresponding to the second bottom surface 53G2 becomes the support point on the ground side. Note that the number, depth, and shape of the bottom raising portions are not particularly limited.

[0086] Also in this embodiment, the bottom surface 53G has a different shape from the surface opening 52G, and the bottom surface 53G is longer than the surface opening 52G.

[0087] (Ninth Embodiment) The sipe 51H of the first center block 31H according to the eighth embodiment will be described with reference to Figure 14. Figure 14 is a perspective view of the first center block according to the ninth embodiment.

[0088] As shown in Figure 14, the sipe 51H of the first center block 31H has a bottom surface 53H. The bottom surface 53H has a first bottom surface 53H1 and a second bottom surface 53H2 (raised bottom portion). The first bottom surface 53H1 is curved and convex toward the front side R1 in the rotational direction. The second bottom surface 53H2 is a shallower groove (a groove that rises in the tire diameter direction) compared to the first bottom surface 53H1 and is provided at both ends of the first bottom surface 53H1. The pair of second bottom surfaces 53H2 open to the first side surface 35H and the second side surface 36H, respectively.

[0089] In this embodiment as well, the bottom surface 53H has a different shape from the surface opening 52H, and the bottom surface 53H is longer than the surface opening 52H.

[0090] (Tenth embodiment) The sipe 51I of the first center block 31I according to the tenth embodiment will be explained using Figure 15. Figure 15 is a plan view of the first center block according to the tenth embodiment.

[0091] As shown in Figure 15, the bottom surface 53I of the sipe 51I of the first center block 31I is located on the front side R1 in the rotational direction relative to the surface opening 52I. In this case, the area that acts as a pivot point on the tire side when the block collapses becomes larger.

[0092] In this embodiment as well, the bottom surface 53I has a different shape from the surface opening 52I, and the bottom surface 53I is longer than the surface opening 52I.

[0093] (11th embodiment) The sipe 51J of the first center block 31J according to the 11th embodiment will be described with reference to Figure 16. Figure 16 is a perspective view of the first center block according to the 11th embodiment.

[0094] As shown in FIG. 16, let the length of the virtual line drawn straight at both ends of the surface opening 52 be L6. Let the depth, which is the length from the surface opening 52J of the sipe 51J to the bottom surface 53J, be L7. In this case, in 50% or more of the length of the surface opening 52, L6 < L7 holds. Thereby, the force applied to the sipe 51J is dispersed following the curve, and the phenomenon that the first center block 31J is peculiarly distorted (falls over) in one direction can be reduced. Even when the sipe has a bottom-raising portion as in the eighth and ninth embodiments, the same effect can be obtained if the above conditions are satisfied.

[0095] (Features of this embodiment) <1>A pneumatic tire provided with a tread and having a specified rotational direction, wherein the tread has a plurality of main grooves that extend from the grounding end toward the tire equator while being inclined with respect to the tire circumferential direction, and a plurality of sub grooves connected in a direction intersecting the plurality of main grooves, and a plurality of blocks partitioned by the main grooves and the sub grooves, at least one of the blocks has a sipe that extends along the front edge in the rotational direction and the rear edge in the rotational direction that contact the main groove, the sipe has a surface opening and a bottom surface, and has a three-dimensional shape in which the sipe shape in plan view changes in the sipe depth direction, a pneumatic tire.

[0096] <2>If the length of the front edge in the rotational direction is L0, the length of the surface opening is L1, and the length of the bottom surface is L2, the pneumatic tire according to <1>, in which L0 < L1 < L2 holds.

[0097] <3>If the length of the 50% depth sipe of the sipe is L3, the pneumatic tire according to <2>, in which L1 < L3 < L2 holds.

[0098] <4>The bottom surface of the sipe has a first bottom surface and a second bottom surface shallower than the first bottom surface, Let the length of the second bottom surface be L4, and let the total length L5 be the sum of the lengths of the first bottom surface and the second bottom surface. The pneumatic tire according to <1>, wherein L4 < L5 holds.

[0099] <5> Let the length of the virtual line drawn by connecting both ends of the surface opening with a straight line be L6, and let the depth, which is the length from the surface opening of the sipe to the bottom surface, be L7. The pneumatic tire according to any one of <1> to <4>, wherein L6 < L7 holds for 50% or more of the length of the surface opening.

[0100] <6> The pneumatic tire according to any one of <1> to <5>, wherein the shape of the sipe in the depth direction has a curved shape at least in part.

[0101] <7> The pneumatic tire according to any one of <1> to <6>, wherein the sipe is open on both sides of the block.

[0102] <8> The pneumatic tire according to any one of <1> to <7>, wherein the length of the bottom surface located on the front side in the rotational direction in the tire circumferential direction with respect to the surface opening is longer than the length located on the rear side in the rotational direction in the tire circumferential direction with respect to the surface opening.

[0103] (Other embodiments and modifications) Although multiple embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various changes are possible without departing from the gist of the invention. In particular, the multiple embodiments and modifications described in this specification can be arbitrarily combined as needed.

[0104] The block is generally formed in a substantially rectangular shape in plan view, but is not limited thereto.

[0105] Other sipes or shallow grooves may be formed in the block. The other sipes or shallow grooves may merge with the sipe of this embodiment.

[0106] The sipe in this embodiment may have an interrupted portion. [Explanation of Symbols]

[0107] 1: Tires 2: Tread 9: Tread Pattern 21: First main groove 22: Second main trench 23: First auxiliary groove 24: Second auxiliary groove 31, 31A, 31B, 31C, 31D, 31E, 31F, 31G, 31H, 31I: First center block (block) 32: Second center block (block) 33: Front edge in the direction of rotation 51, 51A, 51B, 51C, 51D, 51E, 51F, 51G, 51I: Sipes 52, 52A, 52B, 52C, 52G, 52H, 52I: Surface opening 53, 53A, 53B, 53E, 53F, 53G, 53I: Bottom R1: Front side in the direction of rotation R2: Rear side in the direction of rotation S1: Tire Equator X: Tire axis

Claims

1. A pneumatic tire having a tread and a specified direction of rotation, The aforementioned tread is Multiple main grooves extend from the contact edge toward the tire equator, while being inclined with respect to the circumferential direction of the tire, Multiple sub-grooves connected in a direction intersecting the multiple main grooves, It has a plurality of blocks partitioned by the main groove and the sub-grooves, At least one of the blocks has a sipe extending along a front edge in the rotational direction and a rear edge in the rotational direction that are in contact with the main groove, The sipe has a surface opening and a bottom surface, and its shape in plan view is a three-dimensional shape that changes in the direction of the sipe's depth. Pneumatic tires.

2. If the length of the front edge in the rotational direction is L0, the length of the surface opening is L1, and the length of the bottom surface is L2, The pneumatic tire according to claim 1, wherein L0 < L1 < L2 is satisfied.

3. If the length of the sipe at 50% depth is L3, The pneumatic tire according to claim 2, wherein L1 < L3 < L2 is satisfied.

4. The bottom surface of the sipe has a first bottom surface and a second bottom surface that is shallower than the first bottom surface. Let L4 be the length of the second base, and let L5 be the total length, which is the sum of the lengths of the first base and the second base. The pneumatic tire according to claim 1, wherein L4 < L5 is satisfied.

5. If we let L6 be the length of the imaginary line drawn by a straight line from both ends of the surface opening, and L7 be the depth of the sipe, which is the length from the surface opening to the bottom surface, A pneumatic tire according to any one of claims 1 to 3, wherein L6 < L7 is satisfied in the length of 50% or more of the surface opening.

6. The pneumatic tire according to any one of claims 1 to 3, wherein the shape of the sipe in the depth direction is curved in at least a portion of it.

7. The pneumatic tire according to any one of claims 1 to 3, wherein the sipes are open on both sides of the block.

8. The pneumatic tire according to any one of claims 1 to 3, wherein the length of the bottom surface located on the front side in the rotational direction of the tire circumferential direction relative to the surface opening is longer than the length of the bottom surface located on the rear side in the rotational direction of the tire circumferential direction relative to the surface opening.

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