pneumatic tires

Abstract

To provide a pneumatic tire that is less susceptible to adverse effects on the tread blocks even when a load is applied from the bridge during braking. [Solution] The tread 8 of the pneumatic tire 1 has a first bridge 61 positioned in the first main groove 21 and the second main groove 22 and connected to two sides of the first center block 31, and a second bridge 62 positioned in the first main groove 21 and the second main groove 22 and connected to two sides of the second center block 32.

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 a block pattern in which a plurality of blocks partitioned by grooves extending in the tire circumferential direction and grooves intersecting them are arranged in the tire circumferential direction (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The tire pattern described in Patent Document 1 has a groove bottom raising portion (bridge) that connects blocks. The groove bottom raising portion has a lower structure than the blocks and reinforces one or both of the blocks to be connected.

[0005] The groove bottom raising portion reduces the tilting of the blocks. When the tilting of the blocks is reduced, the block edges are likely to contact the ground, improving the braking and driving abilities of the tire. On the other hand, in the tire pattern described in Patent Document 1, the groove bottom raising portion connects two blocks in the tire circumferential direction and suppresses the tilting of the blocks in the tire circumferential direction, but does not suppress the tilting of the blocks in other directions.

[0006] An object of the present invention is to provide a pneumatic tire capable of effectively suppressing the tilting of blocks by a bridge.

Means for Solving the Problems

[0007] The pneumatic tire according to the present invention is a pneumatic tire having a tread and a specified direction of rotation, The aforementioned tread is Multiple first main grooves extending from the first contact end toward the tire equator, while inclined with respect to the tire axis, It has a plurality of second main grooves that are inclined with respect to the axial direction of the tire and extend from the second contact end toward the tire equator, The tip of the first main groove on the tire's equator side merges with the second main groove. The tip of the second main groove on the tire's equator side merges with the first main groove. The first block is divided by two first main grooves, a second main groove where the two first main grooves merge, and a plurality of first secondary grooves. The second block is divided by two of the aforementioned second main grooves, a first main groove into which the two second main grooves merge, and a plurality of second secondary grooves. The aforementioned tread is A first bridge is positioned in the first main groove and the second main groove and connected to two sides of the first block, The present invention further comprises a second bridge, which is located in the first main groove and the second main groove and is connected to two sides of the second block. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a pneumatic tire that can effectively suppress block collapse by the bridge. [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 magnified view of a portion of Figure 1, showing a part of the tread pattern. [Figure 3]This figure shows a portion of the tread pattern in a pneumatic tire according to the second embodiment. [Figure 4] This figure shows a portion of the tread pattern in a pneumatic tire according to the third embodiment. [Figure 5] This figure shows a portion of the tread pattern in a pneumatic tire according to the fourth embodiment. [Figure 6] This figure shows a portion of the tread pattern in a pneumatic tire according to the fifth embodiment. [Figure 7] This figure shows a portion of the tread pattern in a pneumatic tire according to the sixth embodiment. [Modes for carrying out the invention]

[0010] (First embodiment) The tire 1 according to the first embodiment will be explained using Figure 1. Figure 1 is a diagram showing a portion of the outer surface of a pneumatic tire according to the first embodiment, viewed from above. The tire 1 can be applied to passenger cars, but it can also be applied to tires for various other vehicles such as light trucks, trucks, and buses.

[0011] Tire 1 is a directional tire whose direction of rotation is specified when the vehicle on which it is mounted is moving forward. Figure 1 shows the front side R1 (or the side that is pressed down, the side that lands first) and the rear side R2 (or the side that is pushed out, the side that lands last) of tire 1 in the direction of rotation R (also called the tire circumferential direction).

[0012] Figure 1 shows the tire axis direction X (also called the tire width direction). The tire axis direction X is parallel to the rotation axis of 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 axial sides of the tread 2 in the tire axial direction. The first shoulder 3 and the second shoulder 4 are each a portion that transitions from the tread 2 to each of the sidewalls (not shown) on both axial sides in the tire axial direction and is a portion that contacts the shoulder 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 both axial 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 standard rim and filled with air to a standard internal pressure. In the case of a passenger car tire, the predetermined load is a load corresponding to 88% of the standard 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) defined by these grooves. The block is a portion that protrudes toward the outer side in the tire radial direction and is generally also called land.

[0016] Fig. 1 shows a tire equator S1, which is a virtual line extending along the tire rotation direction R at the axial center of the tread surface 8 in the tire axial direction. 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] (Grooves of the tread pattern) 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-grooves include a first sub-groove 23 connecting a pair of first main grooves 21 adjacent in the tire rotation direction R, and a second sub-groove 24 connecting a pair of second main grooves 22 adjacent in the tire rotation direction R. The first sub-grooves 23 are formed on the first tread surface 13, and the second sub-grooves 24 are 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 tire axis direction X. The first center blocks 31 are divided into a substantially 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] As shown in Figure 2, the first center block 31 is roughly rectangular and has a first edge 33, a second edge 34, a third edge 35, and a fourth edge 36. The first edge 33 and the second edge are opposing long sides, with the first edge 33 being the front edge in the rotational direction and the second edge 34 being the rear edge in the rotational direction. The third edge 35 and the fourth edge 36 are opposing short sides, with the third edge 35 being the rear edge in the rotational direction and the fourth edge 36 being the front edge in the rotational direction. More specifically, the first edge 33 is slightly concave in plan view. The second edge 34 is slightly convex in plan view. The end portion of the first center block 31 (the front portion in the rotational direction including the fourth edge 36) is narrower than the other portions. The first center block 31 has a tapered shape such that the overall distance in the short-side direction decreases as it moves from the rear side in the direction of rotation (the part opposite to the tire equator S1 side, including the third edge 35) to the front side in the direction of rotation (the part on the tire equator S1 side, including the fourth edge 36).

[0033] As shown in Figure 2, the second center block 32 is roughly rectangular and has a first edge 33, a second edge 34, a third edge 35, and a fourth edge 36. The first edge 33 and the second edge are opposing longer sides, with the first edge 33 being the front edge in the rotational direction and the second edge 34 being the rear edge in the rotational direction. The third edge 35 and the fourth edge are opposing shorter sides, with the third edge 35 being the rear edge in the rotational direction and the fourth edge 36 being the front edge in the rotational direction. More specifically, the first edge 33 is slightly concave in plan view. The second edge 34 is slightly convex in plan view. The end portion of the second center block 32 (the front portion in the rotational direction including the fourth edge 36) is narrower than the other portions. The second center block 32 has a tapered shape such that the overall distance in the short-side direction decreases as it moves from the rear side in the direction of rotation (the part opposite to the equator S1 side, including the third edge 35) to the front side in the direction of rotation (the part on the equator S1 side, including the fourth edge 36).

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] Each block has a center sipe 51 formed therein. In the first center block 31, for example, the center sipe 51 extends generally parallel to the first edge 33 and the second edge 34. The center sipe 51 is located approximately midway between the first edge 33 and the second edge 34 and extends in a direction that intersects the tire rotation direction R at an oblique angle.

[0041] The center sipe 51 opens onto the surface of the block, and the depth of the sipe generally aligns with the tire diameter.

[0042] The center sipe 51 is a groove that is narrower in width 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 center sipe 51 has a maximum groove width of 0.3 mm or more and 2.0 mm or less.

[0043] The depth of the center sipe 51 is measured as the straight-line distance from the surface opening to the bottom surface. The sipe depth is set to, for example, 30% to 80% of the depth of the first main groove 21.

[0044] As shown in Figure 2, the center sipe 51 is open on both sides of the first center block 31. Specifically, both ends of the center sipe 51 are open at the third edge 35 and the fourth edge 36 of the first center block 31, respectively.

[0045] (bridge) As shown in Figure 2, the tread pattern 9 further comprises a first bridge 61 and a second bridge 62. Figure 2 is a partial enlargement of Figure 1, and shows a part of the tread pattern. The first bridge 61 and the second bridge 62 are raised sections that create raised groove bottoms in the first main groove 21 and the second main groove 22.

[0046] The first bridge 61 connects the first center blocks 31, which are aligned in the tire rotation direction R, with the first main groove 21 in between. Therefore, the first center blocks 31 and the first bridge 61 are arranged alternately in the circumferential direction of the tire. This effectively suppresses the tilting of the first center blocks 31.

[0047] In the following description, the first center blocks 31 connected to each other by the first bridge 61 will be referred to as the "rear first center block 311" and the "front first center block 312". The front first center block 312 is positioned on the front side R1 in the rotational direction of the rear first center block 311.

[0048] The second bridge 62 connects the second center blocks 32, which are aligned in the tire rotation direction R, with the second main groove 22 in between. As a result, the second center blocks 32 and the second bridge 62 are arranged alternately in the circumferential direction of the tire. This effectively suppresses the tilting of the second center blocks 32.

[0049] In the following description, the second center blocks 32 connected to each other by the second bridge 62 will be referred to as the "rear second center block 321" and the "front second center block 322". The front second center block 322 is positioned on the front side R1 in the rotational direction of the rear second center block 321.

[0050] The heights of the first bridge 61 and the second bridge 62 are, for example, 20% to 60% of the depth of the first main groove 21 and the second main groove 22. The heights of the first bridge 61 and the second bridge 62 are the heights of the top surfaces relative to the bottom surfaces. The depths of the first main groove 21 and the second main groove 22 are the depths of the bottom surfaces relative to the surfaces of the first center block 31 and the second center block 32.

[0051] The positional relationship between the rear first center block 311 and the front first center block 312, which are connected to each other by the first bridge 61, will be described in detail. The rear first center block 311 and the front first center block 312 are positioned with the first main groove 21 in between them. The rear first center block 311 and the front first center block 312 extend toward the tire equator S1 at an angle in the tire rotation direction R. The front first center block 312 is positioned offset toward the tire equator S1 in the direction in which the first main groove 21 extends relative to the rear first center block 311. As a result, the portion of the first edge 33 of the rear first center block 311 toward the tire equator S1 and the portion of the front first center block 312 opposite to the tire equator S1 are facing each other in a direction that intersects with the direction in which the first main groove 21 extends.

[0052] The structure in which the first bridge 61 connects the rear first center block 311 and the front first center block 312 will be described in more detail.

[0053] The first bridge 61 is positioned in the first main groove 21 and the second main groove 22 and is connected to the first edge 33 and the fourth edge 36, which are two sides of the rear first center block 311.

[0054] More specifically, the first bridge 61 has a first bridge portion 65 and a second bridge portion 66. The first bridge portion 65 and the second bridge portion 66 are connected at an angle where one end of each is approximately perpendicular to the other, and the first bridge 61 as a whole has an L-shape that is inverted left to right.

[0055] The first bridge portion 65 is positioned in the first main groove 21 and connected to the first edge 33 of the rear first center block 311. The first bridge portion 65 is formed across the entire width of the first main groove 21, thereby connecting the rear first center block 311 and the front first center block 312 in the tire rotation direction R.

[0056] The first bridge portion 65 connects the first edge 33 of the rear first center block 311 and the second edge 34 of the front first center block 312. More specifically, the first bridge portion 65 is connected to the end portion 331 in the edge extension direction of the first edge 33 of the rear first center block 311 (hereinafter referred to as "end portion 331") and to the intermediate portion 341 in the edge extension direction of the second edge 34 of the front first center block 312 (hereinafter referred to as "intermediate portion 341").

[0057] The second bridge portion 66 is positioned in the second main groove 22 and connected to the fourth edge 36 of the rear first center block 311. The second bridge portion 66 does not form the entire width of the second main groove 22 and is positioned away from the second center block 32 located on the front R1 in the rotational direction.

[0058] In this embodiment, the first bridge 61 described above is connected to the first edge 33 and the fourth edge 36, which are two sides of the rear first center block 311. In other words, the rear first center block 311 is less likely to tilt in the tire rotation direction R and the tire axis direction X. In other words, the tilting of the rear first center block 311 is effectively suppressed.

[0059] In this embodiment, the first bridge 61 protects the corner 41 of the rear first center block 311, including the intersection of the first edge 33 and the fourth edge 36. Therefore, the corner 41 of the rear first center block 311 is less likely to tilt when subjected to impact from, for example, a rough surface (e.g., muddy ground, rocky terrain).

[0060] The first main groove 21 has a first edge-corresponding region 81 (first region) that corresponds to the first edge 33 of the rear first center block 311. The first bridge 61 has an area of ​​30% or more of the area of ​​the first edge-corresponding region 81. Therefore, the overall strength of the first center block 31 is increased.

[0061] The second main groove 22 has a second edge-corresponding region 82 (third region) that corresponds to the fourth edge 36 of the rear first center block 311. The first bridge 61 has an area of ​​30% or more of the area of ​​the second edge-corresponding region 82. Therefore, the overall strength of the first center block 31 is increased.

[0062] The first bridge 61 has a first sipe 68. The first sipe 68 is located near the boundary with the front first center block 312. Here, "near the boundary with the front first center block 312" refers to the portion in contact with the front first center block 312 and the region slightly away from it. By providing the first sipe 68 near the edge of the first bridge 61, the reinforcing performance of the first bridge 61 is less likely to be reduced.

[0063] The first sipe 68 is a groove that is narrower in width 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 first sipe 68 has a maximum groove width of 0.3 mm or more and 3.0 mm or less.

[0064] The depth of the first sipe 68 is measured as the straight-line distance from the surface opening to the bottom surface. The sipe depth is set to, for example, 20% to 90% of the depth of the first main groove 21.

[0065] The first sipe 68 moderately reduces the block rigidity, allowing the tread 2 to flexibly contact the road surface even if there are protrusions or curvatures such as stones.

[0066] The positional relationship between the rear second center block 321 and the front second center block 322 will be explained in detail. The rear second center block 321 and the front second center block 322 are positioned with the second main groove 22 in between them. The rear second center block 321 and the front second center block 322 extend toward the tire equator S1 at an angle in the tire rotation direction R. The front second center block 322 is positioned offset toward the tire equator S1 in the direction in which the second main groove 22 extends relative to the rear second center block 321. As a result, the portion of the first edge 33 of the rear second center block 321 toward the tire equator S1 and the portion of the front second center block 322 opposite to the tire equator S1 are facing each other in a direction that intersects with the direction in which the second main groove 22 extends.

[0067] The structure in which the second bridge 62 connects the rear second center block 321 and the front second center block 322 will be described in more detail.

[0068] The second bridge 62 is positioned in the first main groove 21 and the second main groove 22 and is connected to the first edge 33 and the fourth edge 36, which are two sides of the rear second center block 321.

[0069] More specifically, the second bridge 62 has a first bridge portion 65 and a second bridge portion 66. The first bridge portion 65 and the second bridge portion 66 are connected at an angle where one end of each is approximately perpendicular to the other, and the first bridge 61 as a whole has an L-shape that is inverted left to right.

[0070] The first bridge portion 65 is connected to the first edge 33 of the rear second center block 321. The first bridge portion 65 is formed across the entire width of the second main groove 22, thereby connecting the rear first center block 311 and the front second center block 322 in the tire rotation direction R.

[0071] The first bridge portion 65 connects the first edge 33 of the rear second center block 321 and the second edge 34 of the front second center block 322. More specifically, the first bridge portion 65 is connected to the end portion 331 in the edge extension direction of the first edge 33 of the rear second center block 321 (hereinafter referred to as "end portion 331") and to the intermediate portion 341 in the edge extension direction of the second edge 34 of the front second center block 322 (hereinafter referred to as "intermediate portion 341").

[0072] The second bridge portion 66 is positioned in the second main groove 22 and connected to the fourth edge 36 of the rear second center block 321. The second bridge portion 66 does not form the entire width of the second main groove 22 and is positioned away from the first center block 31 located on the front R1 in the rotational direction.

[0073] In this embodiment, the second bridge 62 described above is connected to the first edge 33 and the fourth edge 36, which are two sides of the rear second center block 321. In other words, the rear second center block 321 is less likely to tilt in the tire rotation direction R and the tire axis direction X. In other words, the tilting of the rear second center block 321 is effectively suppressed.

[0074] In this embodiment, the second bridge 62 protects the corner 41 of the rear second center block 321, including the intersection of the first edge 33 and the fourth edge 36. Therefore, the corner 41 of the rear second center block 321 is less likely to tilt when subjected to impact from, for example, a rough surface (e.g., muddy ground, rocky terrain).

[0075] The second main groove 22 has a third edge-corresponding region 83 (second region) that corresponds to the first edge 33 of the second center block 32. The second bridge 62 has an area of ​​30% or more of the area of ​​the third edge-corresponding region 83. Therefore, the overall strength of the second center block 32 is increased.

[0076] The first main groove 21 has a fourth edge corresponding region 84 (fourth region) that corresponds to the fourth edge 36 of the rear first center block 311. The first bridge 61 has an area of ​​30% or more of the area of ​​the fourth edge corresponding region 84. Therefore, the overall strength of the second center block 32 is increased.

[0077] The second bridge 62 has a second sipe 69. The second sipe 69 has a structure similar to that of the center sipe 51. The second sipe 69 is located near the boundary with the front second center block 322. Here, "near the boundary with the front second center block 322" refers to the portion in contact with the front second center block 322 and the region slightly away from it. By providing the second sipe 69 near the edge of the second bridge 62, the reinforcing performance of the second bridge 62 is less likely to be reduced.

[0078] The second sipe 69 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 second sipe 69 has a maximum groove width of 0.3 mm or more and 2.0 mm or less.

[0079] The depth of the second sipe 69 is measured as the straight-line distance from the surface opening to the bottom surface. The sipe depth is set to, for example, 30% to 80% of the depth of the first main groove 21.

[0080] The second sipe 69 moderately reduces block rigidity, allowing the tread 2 to flexibly contact the road surface even if there are protrusions or curvatures such as stones.

[0081] In the first embodiment, the first bridge 61 can effectively prevent the first center block 31 from tipping over. Furthermore, the second bridge 62 can effectively prevent the second center block 32 from tipping over. Additionally, the corners 41 of the first and second center blocks 31, which are prone to tilting due to shear, are reinforced, preventing a reduction in the contact area due to the tilting of the corners 41.

[0082] As a variation, the sipe may be provided on the opposite edge of the first bridge portion 65.

[0083] (Second embodiment) The tread pattern 9A of the tire 1A according to the second embodiment will be explained using Figure 3. Figure 3 is a diagram showing a part of the tread pattern in a pneumatic tire according to the second embodiment. Note that the basic structure of the tread pattern 9A is the same as the basic structure of the tread pattern 9 of the first embodiment, so the following explanation will focus on the differences. Also, in the second embodiment, for ease of understanding, the same or corresponding components as in the first embodiment are denoted with the same number followed by A as reference numerals.

[0084] The first bridge 61A has a first sipe 68A. Specifically, the first sipe 68A extends in the direction in which the first main groove 21A extends in the first bridge portion 65A. Both ends of the first sipe 68A are open to the first main groove 21A. The first sipe 68A has a bent portion near the corner 41A of the rear first center block 311A.

[0085] The second bridge 62A has a second sipe 69A. Specifically, the second sipe 69A extends in the direction in which the second main groove 22A extends in the first bridge portion 65A. Both ends of the second sipe 69A are open to the second main groove 22A. The second sipe 69A has a bent portion near the corner 41A of the front second center block 321A.

[0086] The second embodiment also provides the same effects as the first embodiment, and can more effectively suppress the collapse of the blocks.

[0087] (Third embodiment) The tread pattern 9B of the tire 1B according to the third embodiment will be explained using Figure 4. Figure 4 is a diagram showing a part of the tread pattern in a pneumatic tire according to the third embodiment. Note that the basic structure of the tread pattern 9B is the same as the basic structure of the tread pattern 9 of the first embodiment, so the following explanation will focus on the differences. Also, in the third embodiment, for ease of understanding, the same or corresponding components as those in the first embodiment are denoted with the letter B as reference numerals.

[0088] In the first and second embodiments, the bridge connects two blocks. In the third embodiment, an example in which the bridge connects three blocks will be described. In the following, the first bridge 61B will be described, and the description of the second bridge 62B will be omitted as it has a similar configuration.

[0089] The first bridge 61B connects the two first center blocks 31B and the one second center block 32B. Hereinafter, the two first center blocks 31B will be referred to as the "rear first center block 311B" and the "front first center block 312B". The one second center block 32B will be referred to as the "front second center block 323B".

[0090] The front first center block 312B is positioned on the front R1 in the rotational direction of the rear first center block 311B. The front second center block 323B is positioned on the front R1 in the rotational direction of the rear first center block 311B.

[0091] The first bridge 61B connects the rear first center block 311B and the front first center block 312B, which are aligned in the tire rotation direction R with the first main groove 21B in between. Furthermore, the first bridge 61B connects the rear first center block 311B and the front first center block 312B to the front second center block 323B. This effectively suppresses the tilting of the first center block 31B.

[0092] The structure in which the first bridge 61B connects the rear first center block 311B, the front first center block 312B, and the front second center block 323B will be described in more detail.

[0093] The positional relationship between the rear first center block 311B and the front first center block 312B will be explained in detail. The rear first center block 311B and the front first center block 312B are positioned with the first main groove 21B in between them. The rear first center block 311B and the front first center block 312B extend toward the tire equator S1 at an angle in the tire rotation direction R. The front first center block 312B is positioned offset toward the tire equator S1 in the direction in which the first main groove 21B extends relative to the rear first center block 311B. As a result, the portion of the first edge 33B of the rear first center block 311B toward the tire equator S1 and the portion of the second edge 34B of the front first center block 312B opposite to the tire equator S1 are facing each other in a direction that intersects the direction in which the first main groove 21B extends.

[0094] The positional relationship between the front second center block 323B, the rear first center block 311B, and the front first center block 312B will be explained in detail. The front second center block 323B faces the front first center block 312B across the first main groove 21B, and faces the rear first center block 311B across the second main groove 22B. More specifically, the portion of the second edge 34B of the front second center block 323B on the tire equator S1 side and the fourth edge 36B of the rear first center block 311B face each other in a direction that intersects the direction in which the second main groove 22B extends. Furthermore, the fourth edge 36B of the front second center block 323B and the tire equator S1 side portion of the second edge 34B of the front first center block 312B are facing each other in a direction that intersects the direction in which the first main groove 21B extends.

[0095] The first bridge 61B is positioned in the first main groove 21B and the second main groove 22B and is connected to the first edge 33B and the fourth edge 36B, which are two sides of the rear first center block 311B. Furthermore, the first bridge 61B is connected to the second edge 34B and the fourth edge 36B, which are two sides of the front second center block 323B.

[0096] More specifically, the first bridge 61B includes a first bridge section 65B, a second bridge section 66B, and a third bridge section 67B.

[0097] The first bridge portion 65B is positioned in the first main groove 21B and connected to the first edge 33B of the rear first center block 311B. The first bridge portion 65B is formed across the entire width of the first main groove 21B, thereby connecting the rear first center block 311B and the front first center block 312B in the tire rotation direction R.

[0098] The first bridge portion 65B connects the first edge 33B of the rear first center block 311B and the second edge 34B of the front first center block 312B. More specifically, the first bridge portion 65B is connected to the end portion 331B in the edge extension direction of the first edge 33B of the rear first center block 311B (hereinafter referred to as "end portion 331B") and to the intermediate portion 341B in the edge extension direction of the second edge 34B of the front first center block 312B (hereinafter referred to as "intermediate portion 341B").

[0099] The second bridge portion 66B is positioned in the second main groove 22B and connected to the fourth edge 36B of the rear first center block 311B. The second bridge portion 66B is formed across the entire width of the second main groove 22B, thereby connecting the rear first center block 311B and the front second center block 323B in the tire rotation direction R.

[0100] The second bridge section 66B connects the fourth edge 36B of the rear first center block 311B to the second edge 34B of the front second center block 323B. More specifically, the second bridge section 66B is connected to a part of the fourth edge 36B of the rear first center block 311B (the part on the front first center block 312B side) and a part of the front second center block 323B (the part on the front first center block 312B side).

[0101] The third bridge portion 67B is positioned in the first main groove 21 and connects the fourth edge 36B of the front second center block 323B to the second edge 34B of the front first center block 312B. More specifically, the third bridge portion 67B is connected to the rear R2 side portion in the rotational direction of the fourth edge 36B of the front second center block 323B and to the intermediate portion 341B of the second edge 34B of the front first center block 312B.

[0102] The first bridge 61B protects the corner 41B including the intersection of the first edge 33B and the fourth edge 36B of the rear first center block 311B, and protects the corner 42B including the intersection of the second edge 34B and the fourth edge 36B of the front second center block 323B. Therefore, the corners 41B and 42B are less likely to tilt when subjected to impact from, for example, a rough surface (e.g., muddy ground, rocky terrain).

[0103] The same effects as in the first embodiment can be obtained in the third embodiment, and the collapse of the blocks can be suppressed more effectively.

[0104] (Fourth embodiment) The tread pattern 9C of the tire 1C according to the fourth embodiment will be explained using Figure 5. Figure 5 is a diagram showing a part of the tread pattern in a pneumatic tire according to the fourth embodiment. Note that the basic structure of the tread pattern 9C is the same as the basic structure of the tread pattern 9B of the third embodiment, so the following explanation will focus on the differences. Also, in the fourth embodiment, for ease of understanding, components that are the same as or corresponding to the configuration of the third embodiment are denoted with C instead of B for the same numbers.

[0105] The first bridge 61C has a first sipe 68C. The first sipe 68C extends from the second bridge portion 66C toward the space between the first bridge portion 65C and the third bridge portion 67C. One end of the first sipe 68C is open to the second main groove 22C, and the other end extends to the second edge 34C of the front first center block 312C. The first sipe 68C has a bent portion near the corner 41C of the rear first center block 311C.

[0106] The second bridge 62C has a second sipe 69C. The second sipe 69C is the same as the first sipe 68C, so its description is omitted.

[0107] The same effects as in the first embodiment can be obtained in the fourth embodiment, and the collapse of the blocks can be suppressed more effectively.

[0108] (Fifth embodiment) The tread pattern 9D of the tire 1D according to the fifth embodiment will be explained using Figure 6. Figure 6 is a diagram showing a part of the tread pattern in a pneumatic tire according to the fifth embodiment. Note that the basic structure of the tread pattern 9D is the same as the basic structure of the tread pattern 9B of the third embodiment, so the following explanation will focus on the differences. Also, in the third embodiment, for ease of understanding, components that are the same as or corresponding to the configuration of the third embodiment are denoted with D instead of B for the same numbers.

[0109] The first bridge 61D has a first groove 68D. The first groove 68D extends from the second bridge portion 66D toward the space between the first bridge portion 65D and the third bridge portion 67D. The first groove 68D has a first portion 681D and a second portion 682D. The first portion 681D is an elongated groove that is sipe and opens to the second main groove 22D. The second portion 682D is continuous with the first portion 681D. The second portion 682D has a shape that widens as it approaches the front first center block 312D and extends to the second edge 34D of the front first center block 312D.

[0110] The second bridge 62D has a second groove 69D. The second groove 69D is the same as the first groove 68D, so its description is omitted.

[0111] The fifth embodiment also provides the same effects as the first embodiment, and can more effectively suppress the collapse of the blocks.

[0112] (Sixth embodiment) The tread pattern 9E of the tire 1E according to the second embodiment will be explained using Figure 7. Figure 7 is a diagram showing a part of the tread pattern in a pneumatic tire according to the sixth embodiment. Note that the basic structure of the tread pattern 9E is the same as the basic structure of the tread pattern 9B of the third embodiment, so the following explanation will focus on the differences. Also, in the sixth embodiment, for ease of understanding, the same or corresponding components as in the third embodiment are denoted with E instead of B for the same numbers.

[0113] The first bridge 61E has a first groove 68E. The first groove 68E extends from the second bridge portion 66E toward the space between the first bridge portion 65E and the third bridge portion 67E. One end of the first groove 68E terminates at the second main groove 22E, and the other end extends to the second edge 34E of the front first center block 312E.

[0114] The first groove 68E has a first portion 681E and a second portion 682E. The first portion 681E is an elongated groove that is a sipe and extends to near the second main groove 22E but terminates before reaching it. The second portion 682E is continuous with the first portion 681E. The second portion 682E has a shape that widens as it approaches the front first center block 312E and then extends at a constant width, extending to the second edge 34E of the front first center block 312E.

[0115] The second bridge 62E has a second groove 69E. The second groove 69E is the same as the first groove 68E, so its description is omitted.

[0116] The sixth embodiment also provides the same effects as the first embodiment, and can more effectively suppress the collapse of the blocks.

[0117] (Summary of this embodiment) <1> A tire 1 (pneumatic tire) having a tread 2 and a specified direction of rotation, Tread 2 is Multiple first main grooves 21 extend from the first contact end 5 toward the tire equator S1, while being inclined with respect to the tire axis X, It has a plurality of second main grooves 22 that are inclined with respect to the tire axis X and extend from the second contact end toward the tire equator S1, The tip of the first main groove 21 on the tire equator S1 side merges with the second main groove 22. The tip of the second main groove 22 on the tire equator S1 side merges with the first main groove 21. The first center block 31 (first block) is divided by two first main grooves 21, a second main groove 22 where the two first main grooves 21 merge, and a plurality of first sub-grooves 23. The second center block 32 (second block) is divided by two second main grooves 22, a first main groove 21 where the two second main grooves 22 merge, and a plurality of second sub-grooves 24. Tread 2 is A first bridge 61 is positioned in the first main groove 21 and the second main groove 22 and is connected to two sides of the first center block 31, It further comprises a second bridge 62 positioned in the first main groove 21 and the second main groove 22, and connected to two sides of the second center block 32. As a result, the first bridge 61 effectively suppresses the tilting of the first center block 31. Similarly, the second bridge 62 effectively suppresses the tilting of the second center block 32. By effectively suppressing the tilting of the blocks not only in the circumferential direction of the tire but also in other directions, the block edges can make better contact with the ground, improving the braking and driving capabilities of the tire. In addition, the corners 41 of the first center block 31 and the second center block 32, which are prone to tilting due to shear, are reinforced, preventing a reduction in the contact area due to the tilting of the corners 41.

[0118] <2> The first bridge 61 connects two first center blocks 31 that are aligned with the first main groove 21 in between. The second bridge 62 connects two second center blocks 32 that are aligned with the second main groove 22 in between. <1> The tire described is tire 1 (pneumatic tire). This makes it possible to more effectively suppress the collapse of the first center block 31 and the second center block 32.

[0119] <3> The first center block 31 has a first edge 33 (first main groove side edge) that is in contact with the first main groove 21, The first main groove 21 has a first edge corresponding region 81 (first region) corresponding to the first edge 33, The first bridge 61 has an area of ​​30% or more of the area of ​​the first edge-compatible region 81 in the first edge-compatible region 81. The second center block 32 has a first edge 33 (second main groove side edge) that is in contact with the second main groove 22. The second main groove 22 has a third edge corresponding region 83 (second region) that corresponds to the second edge 34. The second bridge 62 has an area of ​​30% or more of the area of ​​the third edge-compatible region 83 in the third edge-compatible region 83. <1> or <2> Tire 1 (pneumatic tire) as described. This makes it possible to more effectively suppress the collapse of the first center block 31 and the second center block 32.

[0120] <4> The first center block 31 has a fourth edge 36 (third main groove side edge) that is in contact with the second main groove 22, The second main groove 22 has a second edge-corresponding region 82 (third region) corresponding to the third edge 35, The first bridge 61 has an area of ​​30% or more of the area of ​​the second edge-compatible region 82 in the second edge-compatible region 82. The second center block 32 has a fourth edge 36 (fourth main groove side edge) that is in contact with the first main groove 21. The first main groove 21 has a fourth edge corresponding region 84 that corresponds to the fourth edge 36, The second bridge 62 has an area of ​​30% or more of the area of ​​the fourth edge-compatible region 84. <1> ~ <3> Tire 1 (pneumatic tire) as described in any of the following. This makes it possible to more effectively suppress the collapse of the first center block 31 and the second center block 32.

[0121] <5> The first bridge 61B connects two first center blocks 31B and one second center block 32B. The second bridge connects two second center blocks 32B to one first center block 31B. <1> ~ <4> Tire 1 (pneumatic tire) as described in any of the following. This makes it possible to more effectively suppress the collapse of the first center block 31 and the second center block 32.

[0122] The first bridge 61 has a first sipe 68 located near the boundary with the first center block 31. The second bridge 62 has a second sipe 69 located near the boundary with the second center block 32. <1> ~ <5> A pneumatic tire as described in any of the following. This allows for a moderate reduction in block rigidity, enabling the tread 2 to flexibly contact the road surface even if there are protrusions or curvatures such as stones.

[0123] (Other embodiments and variations) Although several embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications are possible without departing from the spirit of the invention. In particular, the multiple embodiments and modifications described herein can be arbitrarily combined as needed.

[0124] The blocks are generally formed in a rectangular shape when viewed from above, but are not limited to this.

[0125] The block may have other sipes or shallow grooves formed in it.

[0126] The bridge does not need to have sipes. [Explanation of Symbols]

[0127] 1: Tires 2: Tread 5: First grounding end 6: Second grounding end 21: First main groove 22: Second main trench 23: First auxiliary groove 24: Second auxiliary groove 31: First center block (first block) 32: Second center block (second block) 33: First edge (first main groove side edge, second main groove side edge) 36: Fourth edge (third main groove side edge, fourth main groove side edge) 61: The First Bridge 62: The Second Bridge 65: First bridge section 66: Second bridge section 68: Sipes 69: Sipes 81: First edge-compatible region (first region) 82: Second edge-compatible area (third area) 83: Third edge-compatible area (second area) 84: Fourth edge-enabled region (fourth region) R: Tire rotation direction 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 first main grooves extending from the first contact end toward the tire equator, while inclined with respect to the tire axis, It has a plurality of second main grooves that are inclined with respect to the tire axis and extend from the second contact end toward the tire equator, The tip of the first main groove on the tire's equator side merges with the second main groove. The tip of the second main groove on the tire equator side merges with the first main groove. The first block is divided by two first main grooves, a second main groove where the two first main grooves merge, and a plurality of first secondary grooves. The second block is divided by two of the aforementioned second main grooves, a first main groove into which the two second main grooves merge, and a plurality of second secondary grooves. The aforementioned tread is A first bridge is positioned in the first main groove and the second main groove and connected to two sides of the first block, The present invention further comprises a second bridge, which is positioned in the first main groove and the second main groove and connected to two sides of the second block, Pneumatic tires.

2. The first bridge connects two first blocks that are aligned with the first main groove in between, The pneumatic tire according to claim 1, wherein the second bridge connects two second blocks that are aligned with the second main groove in between.

3. The first block has a first main groove side edge that is in contact with the first main groove, The first main groove has a first region corresponding to the edge on the first main groove side, The first bridge has an area of ​​30% or more of the area of ​​the first region in the first region. The second block has a second main groove side edge that is in contact with the second main groove, The second main groove has a second region corresponding to the second main groove side edge, The pneumatic tire according to claim 1 or 2, wherein the second bridge has an area of ​​30% or more of the area of ​​the second region in the second region.

4. The first block has a third main groove side edge that is in contact with the second main groove, The second main groove has a third region corresponding to the edge of the third main groove, The first bridge has an area of ​​30% or more of the area of ​​the third region in the third region. The second block has a fourth main groove side edge that is in contact with the first main groove, The first main groove has a fourth region corresponding to the fourth main groove side edge, The pneumatic tire according to claim 1 or 2, wherein the second bridge has an area of ​​30% or more of the area of ​​the fourth region in the fourth region.

5. The first bridge connects two of the first blocks and one of the second blocks. The pneumatic tire according to claim 1 or 2, wherein the second bridge connects two of the first blocks to one of the first blocks.

6. The first bridge has a first sipe located near the boundary with the first block, The pneumatic tire according to claim 1 or 2, wherein the second bridge has a second sipe located near the boundary with the second block.

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