pneumatic tires

Abstract

To provide a pneumatic tire that can effectively suppress block collapse through the use of bridges. [Solution] The tread 9 of the tire 1 has a first bridge 61 provided in the first main groove 21. The first bridge 61 connects the end portion 331 on the tire equator S1 side in the direction in which the first main groove 21 extends, at the front edge 33 in the rotational direction of the rear first center block 311, and the intermediate portion 341 in the direction in which the first main groove 21 extends, at the second edge 34 of the front first center block 312.

Description

Technical Field

[0007] , ,

[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 therewith 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 to each other. The groove bottom raising portion has a lower structure than the blocks and reinforces one or both of the blocks to be connected.

[0005] When a force acts in a certain direction, the two blocks connected by the bridge are divided into a "reinforced block" and a "reinforcing block" in terms of their roles. The "reinforcing block" may receive a larger load than before the bridge was provided, and in that case, the block may fall over, reducing the contact area with the ground and deteriorating the braking and motion performance.

[0006] An object of the present invention is to provide a pneumatic tire capable of suppressing problems when a load acts on blocks connected to each other 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 second main grooves, a first main groove where the two second main grooves merge, and a plurality of second secondary grooves. The tread further comprises a first bridge provided in the first main groove and a second bridge provided in the second main groove. The first bridge connects the end of the first block on the front edge in the rotational direction of the first block, in the direction in which the first main groove extends, to the end on the tire equator side in the direction in which the first main groove extends, and the intermediate portion of the first block on the rear edge in the rotational direction of the first block, which is located on the front side of the first block in the rotational direction of the first block. The second bridge connects the end of the second block on the front edge in the rotational direction of the second block, which is on the tire equator side in the direction in which the second main groove extends, and the middle portion of the second block located on the rear edge in the rotational direction of the second block, which is on the rear edge in the rotational direction of the second block, which is on the direction in which the second main groove extends. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a pneumatic tire that can suppress malfunctions when block loads connected to each other by bridges are applied. [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 section of Figure 1. [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 first) 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 Figure 1, the tire 1 comprises a tread 2. The tire 1 further comprises 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 transition from the tread 2 to the respective sidewalls (not shown) on both sides in the tire axial direction, and are the shoulder portions of the tire 1.

[0014] The first shoulder 3 and the second shoulder 4 are respectively 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 area that contacts the 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 reach the 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] 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 the boundary.

[0018] (Grooves of the tread pattern) The main grooves include a plurality of first main grooves 21 extending from the first grounding end 5 toward the tire equator S1, and a plurality of second main grooves 22 extending from the second grounding 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 arranged at intervals 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 arranged at intervals in the tire rotation direction R. Here, in the first main grooves 21 and the second main grooves 22, the ends on the first grounding end 5 and the second grounding end 6 sides are respectively used as the base ends, and the ends on the tire equator S1 side are used as the tips.

[0019] The first main grooves 21 are inclined as a whole with respect to the tire axial direction X. More specifically, the first main grooves 21 extend from the first grounding end 5 toward the tire equator S1, gradually curving so as to be convex toward the rear side R2 in the rotation direction and extending toward the front side R1 in the rotation direction. The inclination angle of the first main grooves 21 with respect to the tire axial direction X is larger in the tire equator S1 side portion than in the first grounding end 5 side portion.

[0020] The second main grooves 22 are inclined as a whole with respect to the tire axial direction X. More specifically, the second main grooves 22 extend from the second grounding end 6 toward the tire equator S1, gradually curving so as to be convex toward the rear side R2 in the rotation direction and extending toward the front side R1 in the rotation direction. The inclination angle of the second main grooves 22 with respect to the tire axial direction X is larger in the tire equator S1 side portion than in the second grounding end 6 side portion.

[0021] From the above, the first main grooves 21 and the second main grooves 22 gradually become along the tire axial direction X from the tire equator S1 side toward the first grounding end 5 and the second grounding end 6, and the inclination with respect to the tire axial direction X becomes gentle. The inclination angle of the first main grooves 21 or the second main grooves 22 with respect to the tire axial direction X is, for example, 30° or more and 60° or less or 40° or more and 50° or less in the tire equator S1 side portion.

[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 tire equator S1, 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).

[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 includes a first bridge 61 provided in the first main groove 21 and a second bridge 62 provided in the second main groove 22. Figure 2 is a partially enlarged view of Figure 1. The first bridge 61 is a raised section in the first main groove 21 that raises the bottom of the groove. The second bridge 62 is a raised section in the second main groove 22 that raises the bottom of the groove.

[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 tire rotation direction R. This effectively suppresses the tilting of the first center blocks 31.

[0047] 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. Therefore, the second center blocks 32 and the second bridge 62 are arranged alternately in the tire rotation direction R. This effectively suppresses the tilting of the second center blocks 32.

[0048] In the following description, the first center blocks 31 connected to each other 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. The second center blocks 32 connected to each other 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.

[0049] The first bridge 61 extends between the rear first center block 311 and the front first center block 312 (direction P1) and is inclined with respect to the tire rotation direction R. The second bridge 62 extends between the rear second center block 321 and the front second center block 322 (direction P2) and is inclined with respect to the tire rotation direction R.

[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 second edge 34 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 connected to the first edge 33 of the rear first center block 311. The first bridge 61 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.

[0054] The first bridge 61 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 61 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 the end portion 331), and further connected 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 the intermediate portion 341).

[0055] The end portion 331 is a region that extends a predetermined length along the first main groove 21, including the corner vertex 41 which is the intersection point of the first edge 33 of the rear first center block 311 with the fourth edge 36. The end portion 331 has a length of 20% to 90% of the length of the first edge 33. Furthermore, the end portion 331 may be separated from the edge of the first edge 33. The end portion 331 is provided in a region that is separated from the first edge 33 by a length of 20% or less of the length of the first edge 33.

[0056] In this embodiment, the end portion 331 includes the corner vertex 41 of the rear first center block 311. However, the end portion 331 may be separated from the corner vertex 41.

[0057] The intermediate section 341 is the portion to which the first bridge 61 is connected at the second edge 34 of the front first center block 312. The intermediate section 341 has a length of 20% to 90% of the length of the second edge 34. The intermediate section 341 includes a portion 43 that is further away from the tire equator S1 than the center C1 in the direction in which the first main groove 21 extends.

[0058] As described above, the first bridge 61 is connected to the middle portion 341 of the second edge 34 of the front first center block 312. In other words, the first bridge 61 is connected to a part of the front first center block 312 that has high strength. Therefore, when braking under heavy load, the front first center block 312 functions as a "reinforcing block," and even if a large load is applied from the first bridge 61 to the kicking side portion (the portion on the second edge 34 side) of the front first center block 312 during braking, the front first center block 312 is less likely to tilt.

[0059] As described above, the first bridge 61 extends in a direction P1 that is inclined with respect to the tire rotation direction R. Therefore, during braking when a large load is applied, the tire rotation direction load component acting on the kick-out side portion (the portion on the second edge 34 side) of the front first center block 312 is reduced, thus suppressing a large load acting on the front first center block 312. Also, during acceleration, the rear first center block 311 functions as a "reinforcing block," but during acceleration, the tire rotation direction load component acting from the first bridge 61 to the rear first center block 311 is reduced, thus suppressing a large load acting on the rear first center block 311.

[0060] 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. The first sipe 68 moderately reduces the block rigidity, allowing the tread 2 to make flexible contact with the road surface even if there are protrusions or curvatures such as stone. 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.

[0061] 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.

[0062] 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.

[0063] As shown in Figure 2, the first sipe 68 is open on both sides in the direction in which the first main groove 21 of the first bridge 61 extends.

[0064] The positional relationship between the rear second center block 321 and the front second center block 322, which are connected to each other by the second bridge 62, will be described 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 second edge 34 of the front second center block 322 opposite to the tire equator S1 are facing each other in a direction that intersects the direction in which the second main groove 22 extends.

[0065] 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.

[0066] The second bridge 62 is positioned in the second main groove 22 and connects to the first edge 33 of the rear second center block 321. The second bridge 62 is formed across the entire width of the second main groove 22, thereby connecting the rear second center block 321 and the front second center block 322 in the tire rotation direction R.

[0067] The second bridge 62 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 second bridge 62 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 the end portion 331), and further connected 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 the intermediate portion 341).

[0068] The end portion 331 is a region that extends a predetermined length along the second main groove 22, including the corner vertex 41 which is the intersection point of the first edge 33 of the rear second center block 321 with the fourth edge 36. The end portion 331 has a length of 20% to 90% of the length of the first edge 33. Furthermore, the end portion 331 may be separated from the edge of the first edge 33. The end portion 331 is provided in a region that is separated from the first edge 33 by a length of 20% or less of the length of the first edge 33.

[0069] In this embodiment, the end portion 331 includes the corner vertex 41 of the rear second center block 321. However, the end portion 331 may be separated from the corner vertex 41 of the first edge 33.

[0070] The intermediate section 341 is the portion to which the second bridge 62 is connected at the second edge 34 of the front second center block 322. The intermediate section 341 has a length of 20% to 90% of the length of the second edge 34. The intermediate section 341 includes a portion 43 that is further away from the tire equator S1 than the center C2 in the direction in which the second main groove 22 extends.

[0071] As described above, the second bridge 62 is connected to the middle portion 341 of the second edge 34 of the front second center block 322. In other words, the second bridge 62 is connected to a part of the front second center block 322 that has high strength. Therefore, when braking under heavy load, the front second center block 322 functions as a "reinforcing block," and even if a large load is applied from the second bridge 62 to the kicking side portion (the portion on the second edge 34 side) of the front second center block 322 during braking, the front second center block 322 is less likely to tilt.

[0072] As described above, the second bridge 62 extends in a direction P2 that is inclined with respect to the tire rotation direction R. Therefore, during braking when a large load is applied, the tire rotation direction load component acting on the kick-out side portion (the portion on the second edge 34 side) of the front second center block 322 is reduced, thus suppressing a large load acting on the front second center block 322. Also, during acceleration, the rear second center block 321 functions as a "reinforcing block," but during acceleration, the tire rotation direction load component acting from the second bridge 62 to the rear second center block 321 is reduced, thus suppressing a large load acting on the rear second center block 321.

[0073] The second bridge 62 has a second sipe 69. The second sipe 69 is located near the boundary with the front second center block 322. The second sipe 69 moderately reduces the block rigidity, allowing the tread 2 to make flexible contact with the road surface even if there are protrusions or curvatures such as stone. 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.

[0074] 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.

[0075] 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.

[0076] The second sipe 69 is open on both sides in the direction in which the second main groove 22 of the second bridge 62 extends, as shown in Figure 2.

[0077] (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 6 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 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 is partitioned 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. The tread further comprises a first bridge 61 provided in a first main groove 21 and a second bridge 62 provided in a second main groove 22. The first bridge 61 connects the end portion 331 on the tire equator S1 side in the direction in which the first main groove 21 extends at the first edge 33 (front edge in the direction of rotation) of the rear first center block 311 (first center block) and the intermediate portion 341 in the direction in which the first main groove 21 extends at the second edge 34 (rear edge in the direction of rotation) of the front first center block 312 (front block in the direction of rotation) located on the front R1 in the direction of rotation of the rear first center block 311. The second bridge 62 connects the end portion 331 (end) of the first edge 33 (front edge in the rotational direction) of the rear second center block 321 in the direction in which the second main groove 22 extends, on the tire equator S1 side, and the intermediate portion 341 (intermediate portion) of the second edge 34 (rear edge in the rotational direction) of the front second center block 322 (front block in the rotational direction) located on the front R1 in the rotational direction of the second center block 321 in the direction in which the second main groove 22 extends. This makes it possible to suppress malfunctions that occur when a load is applied to blocks connected to each other by a bridge in a tire with a specified rotation direction.

[0078] <2> The direction P1 in which the first bridge 61 extends between the first center blocks 31 is inclined with respect to the tire rotation direction R (tire circumferential direction). The direction P2 in which the second bridge 62 extends between the second center blocks 32 is inclined with respect to the tire rotation direction R (tire circumferential direction). <1> The pneumatic tire described above. This makes it possible to more effectively suppress malfunctions that occur when a load is applied to blocks connected to each other by a bridge in a tire with a specified rotation direction.

[0079] <3> The intermediate portion 341 (the portion to which the first bridge 61 is connected at the second edge 34 of the first center block 31) includes the portion that is further away from the tire equator S1 than the center C1 in the direction in which the first main groove 21 extends. The intermediate portion 341 (the portion to which the second bridge 62 is connected at the second edge 34 of the second center block 32) includes the portion that is further away from the tire equator S1 than the center C2 in the direction in which the second main groove 22 extends. <1> or <2> Tire 1 (pneumatic tire) as described. This makes it possible to more effectively suppress malfunctions that occur when a load is applied to blocks connected to each other by a bridge in a tire with a specified rotation direction.

[0080] <4> 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> ~ <3> Tire 1 (pneumatic tire) as described in any of the following. This allows for a moderate reduction in block rigidity, enabling the tread to flexibly contact the road surface even when there are protrusions or curvatures such as stones.

[0081] (Other embodiments and variations) Although the first embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, 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.

[0082] The blocks are generally formed in a rectangular shape when viewed from above, but are not limited to this.

[0083] The block may have sipes or shallow grooves formed in it.

[0084] The bridge sipes may be formed near the boundary with the end of the center block located on the rear side R2 in the rotational direction.

[0085] The bridge may have other sipes or shallow grooves formed on it. The bridge may not have any sipes at all. [Explanation of Symbols]

[0086] 1: Tire (pneumatic tire) 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) 311: Rear first center block (first block) 312: Front first center block (front block in the direction of rotation) 32: Second center block (second block) 321: Rear second center block (second block) 322: Front second center block (front block in the direction of rotation) 33: First edge (front edge in the direction of rotation) 34: Second edge (rear edge in the direction of rotation) 35: The Third Edge 36: The Fourth Edge 61: The First Bridge 62: The Second Bridge 331: Edge extension direction end (end) 341: Intermediate portion in the edge extension direction (intermediate portion) 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 partitioned 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 second main grooves, a first main groove where the two second main grooves merge, and a plurality of second sub-grooves. The tread further comprises a first bridge provided in the first main groove and a second bridge provided in the second main groove. The first bridge connects the end of the first block on the front edge in the rotational direction of the first block, in the direction in which the first main groove extends, to the end on the tire equator side in the direction in which the first main groove extends, and the intermediate portion of the first block on the rear edge in the rotational direction of the first block, which is located on the front side of the first block in the rotational direction of the first block. The second bridge connects the end of the second block on the front edge in the rotational direction of the second block, in the direction in which the second main groove extends, to the middle portion of the second block located on the rear edge in the rotational direction of the second block, in the direction in which the second main groove extends. Pneumatic tires.

2. The direction in which the first bridge extends between the first blocks is inclined with respect to the tire circumferential direction. The pneumatic tire according to claim 1, wherein the direction in which the second bridge extends between the second blocks is inclined with respect to the tire circumferential direction.

3. The portion of the first block to which the first bridge is connected at the rear edge in the rotational direction includes the portion that is further away from the tire equator than the center in the direction in which the first main groove extends. The pneumatic tire according to claim 1 or 2, wherein the portion of the second block to which the second bridge is connected at the rear edge in the rotational direction includes a portion that is further away from the tire equator than the center in the direction in which the second main groove extends.

4. 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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