JP2022136377A - pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire with a step part that can suppress stone biting without deteriorating WET performance.SOLUTION: A pneumatic tire includes zigzag main grooves extending in a tire circumferential direction. Main groove wall surfaces of the zigzag main grooves include: a first main groove wall surface 31a formed with a narrow width from a tread surface toward inside in a tire radial direction; and a second main groove wall surface 32a formed with a narrow or constant width from the first main groove wall surface 31a toward a main groove bottom surface. An angle between the second main groove wall surface 32a and the tread surface is smaller than an angle between the first main groove wall surface 31a and the tread surface. The zigzag main groove includes a plurality of step parts 33 joined with the second main groove wall surface 32a and protruding from the main groove bottom surface. The step parts 33 are arranged in a plurality of recess parts 32 formed by the main groove wall surfaces. An angle between a stepped wall surface of the step part 33 and the second main groove wall surface 32a is formed at a right angle or an obtuse angle.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to pneumatic tires.

In Patent Document 1, a zigzag-shaped main groove extending in the tire circumferential direction is provided, and the zigzag-shaped main groove is joined to the main groove wall surface and provided with a plurality of stepped portions protruding from the main groove bottom surface. A pneumatic tire is described which is arranged in a plurality of recesses formed by groove walls. Such a pneumatic tire can suppress stone trapping by providing such a stepped portion.

However, in such a stepped portion, the angle between the stepped wall surface and the main groove wall surface is formed at an acute angle when viewed in the tire radial direction. There is a problem that the WET performance, which is the running performance on the road surface, deteriorates.

JP-A-62-61807

An object of the present disclosure is to provide a pneumatic tire having stepped portions capable of suppressing stone trapping without deteriorating WET performance.

A pneumatic tire of the present disclosure includes a zigzag-shaped main groove extending in the tire circumferential direction, and a main groove wall surface of the zigzag-shaped main groove is narrowed from the tread surface toward the inside in the tire radial direction. a first main groove wall surface and a second main groove wall surface formed with a narrow width or a constant width from the first main groove wall surface toward the main groove bottom surface, and a gap between the second main groove wall surface and the tread surface. The angle is smaller than the angle between the first main groove wall surface and the tread surface, and the zigzag-shaped main groove has a plurality of stepped portions that join with the second main groove wall surface and protrude from the main groove bottom surface. The stepped portion is arranged in a plurality of recesses formed by the main groove wall surface, and the angle formed by the stepped wall surface of the stepped portion and the second main groove wall surface is formed at a right angle or an obtuse angle.

A cross-sectional view of a pneumatic tire according to one embodiment in a tire meridional plane FIG. 2 is an exploded view of the main parts on the tread surface of the pneumatic tire according to the same embodiment; III-III line enlarged cross-sectional view of Fig. 2

An embodiment of a pneumatic tire will be described below with reference to FIGS. 1 to 3. FIG. In each drawing, the dimensional ratio of the drawing and the actual dimensional ratio do not necessarily match, and the dimensional ratio between the drawings does not necessarily match.

In each figure, the first direction D1 is the tire axial direction D1 parallel to the tire rotation axis of the pneumatic tire (hereinafter also simply referred to as "tire") 1, and the second direction D2 is the tire 1. The tire radial direction D2 is the diameter direction, and the third direction D3 is the tire circumferential direction D3 about the tire rotation axis.

In the tire axial direction D1, the inner side is the side closer to the tire equatorial plane S1, and the outer side is the side farther from the tire equatorial plane S1. In addition, in the tire radial direction D2, the inner side is the side closer to the tire rotation axis, and the outer side is the side farther from the tire rotation axis.

The tire equatorial plane S1 is a plane perpendicular to the tire rotation axis and is located at the center of the tire 1 in the tire axial direction D1, and the tire meridional plane is a plane including the tire rotation axis and the tire equator. It is a plane perpendicular to the plane S1. The tire equatorial line L1 is a line where the outer surface of the tire 1 in the tire radial direction D2 (the tread surface 2a described later) intersects with the tire equatorial plane S1.

As shown in FIG. 1, the tire 1 according to the present embodiment includes a pair of beads 11, 11, sidewalls 12, 12 extending outward in the tire radial direction D2 from each bead 11, and a pair of sidewalls 12, 12. and a carcass ply 14 extending so as to bridge between the pair of beads 11, 11.

The tread 13 includes a tread rubber 2 having a tread surface 2 a forming the outer surface of the tread 13 and a belt ply 15 arranged between the tread rubber 2 and the carcass ply 14 . The tread surface 2a has a tire contact surface that actually contacts the road surface, and of the tire contact surface, outer ends in the tire axial direction D1 are referred to as tread contact edges 2b, 2b.

The tire 1 according to the present embodiment is a heavy-duty pneumatic tire used for trucks and the like, and is configured as a regional-use tire suitable for short-distance driving in town, but is not limited to this. In this embodiment, the tread 13 is a wide tread type in which the tread width Wt is 80% or more of the tire maximum width Wm, but is not limited to such a type. The tread width Wt is the maximum width of the tire ground contact surface in the tire axial direction D1, that is, the distance between the tread ground edges 2b, 2b. The maximum tire width Wm is the maximum width in the axial direction D1 of the tire including protrusions such as patterns and letters on the surfaces of the sidewalls 12 .

The tire tread is the portion where the tire 1 is mounted on a regular rim (not shown), the tire 1 is placed vertically on a flat road surface with a regular internal pressure, and the tire 1 touches the road surface when a regular load is applied.

A regular rim is a rim defined for each tire 1 in a standard system including the standard on which the tire 1 is based. For example, JATMA is a standard rim, TRA is a "Design Rim", ETRTO For example, it becomes "Measuring Rim".

The normal internal pressure is the air pressure determined for each tire 1 by each standard in the standard system including the standards on which the tire 1 is based. "INFLATION PRESSURES", or "INFLATION PRESSURE" for ETRTO.

The normal load is the load defined for each tire 1 by each standard in the standard system including the standards on which the tire 1 is based. value, ETRTO is "LOAD CAPACITY".

As shown in FIGS. 2 and 3, the tread rubber 2 has main grooves 21 formed in the tread surface 2a and extending in the tire circumferential direction D3. The main groove 21 includes a pair of shoulder main grooves 4, 4 located on the outermost side in the tire axial direction D1, and a plurality of center main grooves 3 located between the pair of shoulder main grooves 4. are spaced apart. In this embodiment, a pair of center main grooves 3, 3 are arranged across the tire equatorial plane S1.

The center main groove 3 is repeatedly bent to extend in a zigzag shape. A plurality of protrusions 31 and a plurality of recesses 32 are formed by the main groove wall surface 3a of the center main groove 3, and they are alternately repeated along the tire circumferential direction D3. The convex portion 31 protrudes inward from the center main groove 3 . The concave portion 32 is recessed in a direction opposite to the direction in which the convex portion 31 protrudes. The center main grooves 3, 3 are arranged out of phase with each other in the tire circumferential direction D3. That is, as viewed in the tire axial direction D1, the positions of the convex portions 31 and the concave portions 32 of the center main grooves 3, 3 are shifted.

In the present embodiment, the center main grooves 3, 3 are arranged in the tire circumferential direction D3 with a deviation of half or less of the repetition pitch of the recesses 32, but the present invention is not limited to this. The interval from the center of the recessed portion 32 to the center of the recessed portion 32 adjacent in the tire circumferential direction D3 is one pitch in the repeating pitch of the recessed portions 32 . The same applies to "pitch", which will be described later.

The shoulder main groove 4 extends linearly in the tire circumferential direction D3. A plurality of sipes 4 a extending from the shoulder main groove 4 in the tire axial direction D<b>1 are formed in the main groove wall surface of the shoulder main groove 4 . The sipe 4a is provided as a one-side closed sipe 4a having one end opened to the shoulder main groove 4 and the other end closed inland.

As shown in FIG. 3, main groove wall surfaces 3a, 3a of the center main groove 3 include first main groove wall surfaces 31a, 31a which are formed narrower inward in the tire radial direction D2 from the tread surface 2a, and first main groove wall surfaces 31a, 31a. Second main groove wall surfaces 32a, 32a are formed to have a narrow width or a constant width from the main groove wall surface 31a toward the main groove bottom surface 3b. In this embodiment, the second main groove wall surfaces 32a, 32a extend toward the main groove bottom surface 3b with a constant width.

A second main groove wall angle θ2 between the second main groove wall surface 32a and the tread surface 2a is smaller than a first main groove wall angle θ1 between the first main groove wall surface 31a and the tread surface 2a. By making the second main groove wall angle θ2 smaller than the first main groove wall angle θ1, it becomes difficult for pebbles and the like to enter the second main groove wall surface 32a side, and stone trapping in the center main groove 3 can be suppressed. This makes it difficult for pebbles and the like to reach the main groove bottom surface 3b, and damage to the center main groove 3 can be suppressed. In this embodiment, the first main groove wall angle θ1 is 103.5 degrees and the second main groove wall angle θ2 is 90 degrees, but the angles are not limited to such angles.

In this embodiment, the width of the main groove bottom surface 3b in the tire axial direction D1 is ensured by setting the second main groove wall angle θ2 to 90 degrees, that is, by making the opposing second main groove wall surfaces 32a, 32a parallel to each other. can be done. As a result, the width of the stepped portion 33, which will be described later, in the axial direction D1 of the tire can be ensured, and the effect of suppressing stone trapping can be improved.

As shown in FIGS. 2 and 3, the center main groove 3 includes a plurality of stepped portions 33 that join with the second main groove wall surface 32a and protrude from the main groove bottom surface 3b. By providing the stepped portion 33 in the center main groove 3, it becomes difficult for small stones or the like to enter the center main groove 3, and stone entrapment in the center main groove 3 can be suppressed. The stepped portion 33 is arranged in each of the plurality of recessed portions 32 . By disposing the stepped portion 33 in the recessed portion 32, the recessed portion 32 having weak rigidity in the tire circumferential direction D3 can be reinforced, and uneven wear in the recessed portion 32 can be suppressed.

The stepped portion 33 includes a first stepped portion 331 joined to one of the second main groove wall surfaces 32a (in this embodiment, the second main groove wall surface 32a on the outer side in the tire axial direction D1), and the other of the second main groove wall surfaces 32a. (In this embodiment, the second main groove wall surface 32a on the inner side in the tire axial direction D1) and a second stepped portion 332 that joins. The first stepped portion 331 and the second stepped portion 332 are arranged in a zigzag pattern along the tire circumferential direction D3. Note that the first stepped portion 331 may be arranged on the inner side in the tire axial direction D1, and the second stepped portion 332 may be arranged on the outer side in the tire axial direction D1.

As shown in FIG. 2, the stepped wall surface of the stepped portion 33 intersects with a first stepped wall surface 33a that intersects with the second main groove wall surface 32a (surface along the tire axial direction D1) and the second main groove wall surface 32a. and a second stepped wall surface 33b that is a surface (a surface along the tire circumferential direction D3) that does not extend. The angle formed by the first stepped wall surface 33a and the second main groove wall surface 32a is formed at a right angle or an obtuse angle. That is, the step wall surface angle θ3 between the first step wall surface 33a and the second main groove wall surface 32a is 90 degrees or more.

By making the angle formed by the first stepped wall surface 33a and the second main groove wall surface 32a a right angle or an obtuse angle, it is possible to prevent water from stagnation between the first stepped wall surface 33a and the second main groove wall surface 32a. Smooth drainage can be promoted. As a result, the stepped portion 33 can suppress stone trapping without deteriorating wet performance. In addition, it is possible to prevent strain from concentrating on the portion where the first stepped wall surface 33a and the second main groove wall surface 32a intersect and causing cracks to occur. Wet performance refers to running performance on a wet road surface.

In this embodiment, the angle formed by the first stepped wall surface 33a and the second main groove wall surface 32a is a right angle. The first stepped wall surface 33a extends vertically from the main groove bottom surface 3b, but is not limited to this. The second stepped wall surface 33b is formed parallel to the second main groove wall surface 32a. That is, the second stepped wall surface 33b is recessed in the direction opposite to the direction in which the projection 31 protrudes. The second stepped wall surface 33b extends vertically from the main groove bottom surface 3b, but is not limited to this.

In the present embodiment, the first stepped portion 331 and the second stepped portion 332 do not intersect when viewed in the tire circumferential direction D3. A see-through region 3S is formed between the first stepped portion 331 and the second stepped portion 332 . Here, the see-through region 3S refers to a region within the center main groove 3 in which the field of vision can be seen through without being obstructed by the first stepped portion 331 and the second stepped portion 332 when viewed in the tire circumferential direction D3.

The minimum gap W1 between the first stepped portion 331 and the second stepped portion 332 is 0.0 of the width W2 of the first stepped portion 331 (or the second stepped portion 332) in a cross section perpendicular to the second main groove wall surface 32a. 67 times to 1.5 times. In this embodiment, the gap W3 between the first stepped portion 331 (or the second stepped portion 332) and the opposing second main groove wall surface 32a is equal to the width W2 of the first stepped portion 331 (or the second stepped portion 332). 0.67 to 1.5 times the

As shown in FIG. 3, the second main groove wall height H2 in the tire radial direction D2 of the second main groove wall surface 32a is greater than the first main groove wall height H1 in the tire radial direction D2 of the first main groove wall surface 31a. is also small. That is, the ratio of the first main groove wall height H1 and the second main groove wall height H2 to the overall height of the center main groove 3 (first main groove wall height H1 + second main groove wall height H2) is , the second main groove wall height H2 is smaller. The ratio of the first main groove wall height H1 is preferably 60 to 80% of the total height of the center main groove 3. The ratio of the second main groove wall height H2 is preferably 20 to 40% of the total height of the center main groove 3. If the ratio of the second main groove wall height H2 is less than 20%, the effect of suppressing stone trapping by the stepped portion 33 provided on the second main groove wall surface 32a tends to decrease. If the ratio of the second main groove wall height H2 exceeds 40%, the volume of the center main groove 3 will be reduced, possibly deteriorating the wettability. In this embodiment, the ratio between the first main groove wall height H1 and the second main groove wall height H2 is 75% to 25%, but is not limited to this.

A step height H3 of the step portion 33 in the tire radial direction D2 is equal to or less than the second main groove wall height H2. In this embodiment, the step height H3 is the same as the second main groove wall height H2. Here, the second main groove wall height H2 is obtained as the distance in the tire radial direction D2 from the main groove bottom surface 3b to the intersection of the first main groove wall surface 31a and the second main groove wall surface 32a. The first main groove wall height H1 is obtained as the distance in the tire radial direction D2 from the intersection of the first main groove wall surface 31a and the second main groove wall surface 32a to the tread surface 2a. The step height H3 is obtained as a distance in the tire radial direction D2 from the main groove bottom surface 3b to the top surface of the stepped portion 33. As shown in FIG.

As shown in FIG. 2, the tire 1 has a center land 5 formed between the center main grooves 3 and a pair of quarter lands 6, 6 formed between the center main groove 3 and the shoulder main grooves 4. , and shoulder lands 7, 7 formed outside the shoulder main groove 4 in the tire axial direction D1. The center land 5 is arranged on the inner region of the tread surface 2a in the tire axial direction D1 and on the tire equator line L1. The quarter land 6 is arranged between the center land 5 and the shoulder land 7 . The shoulder land 7 is arranged at the outer end of the tread surface 2a in the tire axial direction D1.

The tire 1 of this embodiment employs a wide center structure, and the center land width Wc of the center land 5 in the tire axial direction D1 is 15% or more, more preferably 18% or more of the total land width. By enlarging the center land width Wc in this manner, the pressure applied to the center land 5 can be dispersed, and uneven wear in the center land 5 can be suppressed to improve uneven wear resistance performance.

The total land width is the width in the tire axial direction D1 excluding the main groove 21, that is, the sum of the center land width Wc, the quarter land width Wq of the quarter land 6, and the shoulder land width Ws of the shoulder land 7. be. The land widths Wc, Wq, Ws are the maximum widths of the lands 5, 6, 7 in the tire axial direction D1.

The tire 1 includes a slit 8 extending from the recess 32 along the tire axial direction D1. Slits 8 are arranged in center land 5 and quarter land 6 . By extending the slit 8 from the concave portion 32 in which the stepped portion 33 is provided, the stepped portion 33 can suppress the decrease in rigidity of the lands 5 and 6 due to the provision of the slit 8 .

The angle formed by the center main groove 3 and the slit 8 is a right angle or an obtuse angle. That is, the corner angle θ4 of the corner portion C1 formed by the center main groove 3 and the slit 8 in the center land 5 and the quarter land 6 exceeds 90 degrees.

The slit 8 includes a center slit 81 arranged in the center land 5 and a quarter slit 82 arranged in the quarter land 6. - 特許庁The center land 5 includes a plurality of center blocks 51 partitioned by the center main grooves 3 and the center slits 81 . The quarter land 6 includes a plurality of quarter blocks 61 partitioned by the center main groove 3 , shoulder main grooves 4 and quarter slits 82 . In this embodiment, the depths of the center slit 81 and the quarter slits 82 are small (for example, 2 mm or less), and the center land 5 and the quarter land 6 are shaped like ribs.

The center slit 81 has a pair of center intersection portions 81a, 81a that intersect the center main groove 3 and extend along the tire axial direction D1, and a center inclined portion 81b that does not intersect the center main groove 3 and is inclined with respect to the tire axial direction D1. And prepare. The quarter slit 82 includes a pair of quarter intersection portions 82a that intersect the center main groove 3 or the shoulder main groove 4 and extend along the tire axial direction D1, and a quarter slope portion 82b that slopes with respect to the .

The pair of center crossing portions 81a, 81a are arranged to be shifted in the tire circumferential direction D3. According to such a configuration, the center inclined portion 81b can be provided between the pair of center intersection portions 81a, 81a, and the end portion of the center block 51 in the tire circumferential direction D3 (the portion formed by the center slit 81) can be provided. can be tilted with respect to the tire axial direction D1. As a result, the rigidity of the center block 51 in the tire circumferential direction D3 can be increased, and uneven wear of the center block 51 can be suppressed. In the present embodiment, the pair of center crossing portions 81a, 81a are arranged in the tire circumferential direction D3 with a shift of less than half of the repetition pitch of the recesses 32, but the present invention is not limited to this.

In the present embodiment, the center crossing portions 81a are arranged two pitches apart from each other to the adjacent center crossing portions 81a in the tire circumferential direction D3, but this is not restrictive. By arranging the center intersections 81a two pitches apart, the protrusions 31 can be included at two locations on one side of each center block 51 in the tire axial direction D1, and the traction performance of each center block 51 can be improved.

The pair of quarter intersections 82a, 82a are arranged to be offset in the tire circumferential direction D3. According to such a configuration, the quarter inclined portion 82b can be provided between the pair of quarter intersection portions 82a, 82a, and the end portion of the quarter block 61 in the tire circumferential direction D3 (the portion formed by the quarter slit 82) can be provided. can be tilted with respect to the tire axial direction D1. As a result, the rigidity of the quarter block 61 in the tire circumferential direction D3 can be increased, and uneven wear of the quarter block 61 can be suppressed. In the present embodiment, the pair of quarter crossing portions 82a, 82a are arranged in the tire circumferential direction D3 with a shift of half or more of the repetition pitch of the recesses 32, but the present invention is not limited to this.

The deviation of the pair of quarter intersections 82a, 82a is greater than the deviation of the pair of center intersections 81a, 81a. Of the pair of quarter intersection portions 82a, 82a, the quarter intersection portion 82a that intersects the shoulder main groove 4 overlaps the center inclined portion 81b as viewed in the tire axial direction D1. The center inclined portion 81b and the quarter inclined portion 82b are inclined in opposite directions with respect to the tire axial direction D1.

The quarter slit 82 has a quarter sipe 82c. The quarter sipe 82c is a closed sipe whose both ends are closed without being connected to the main groove. The quarter sipe 82c is arranged on the slit bottom surface of the quarter inclined portion 82b. The quarter sipe 82c is arranged at a position overlapping the first stepped portion 331 or the second stepped portion 332 as viewed in the tire axial direction D1.

The center block 51 has a center sipe 51a. The center sipe 51a is a closed sipe with both ends closed without being connected to the main groove. The center sipe 51 a is arranged on the center block 51 at a position that does not cross the center main groove 3 and the center slit 81 . The center sipes 51a and the center inclined portions 81b are alternately arranged along the tire equator line L1. In this embodiment, the center sipe 51 a is inclined in the same direction as the center inclined portion 81 b and arranged in each center block 51 . By arranging the center inclined portion 81b at an angle, traction performance in the tire axial direction D1 can be ensured, and side slip in the tire axial direction D1 during cornering can be suppressed.

The center sipe 51a and the quarter sipe 82c are arranged at positions overlapping the first stepped portion 331 and/or the second stepped portion 332 as viewed in the tire axial direction D1.

The sipes 4a, 5a, 82c are cuts having a groove width of 1.5 mm or less. The depth of the center sipe 51a is smaller than the depth of the quarter sipe 82c from the tread surface 2a. In this embodiment, the depth of the center sipe 51a is 35% of the depth of the center main groove 3, but it is not limited to this. Also, the depth of the quarter sipe 82c from the tread surface 2a is 70% of the depth of the center main groove 3, but is not limited to this.

The one-side closed sipes 4a are arranged on both sides of the shoulder main groove 4 in the axial direction D1 of the tire and are arranged side by side in the circumferential direction D3 of the tire. The one-side closed sipe 4a extends widely from the shoulder main groove 4 along the tire axial direction D1. As a result, concentration of pressure on the tip of the one-side closed sipe 4a can be suppressed, and cracks can be suppressed from occurring in the tip of the one-side closed sipe 4a.

As described above, like the present embodiment, the tire 1 includes a zigzag main groove (center main groove 3) extending in the tire circumferential direction D3, and the main groove of the zigzag main groove (center main groove 3) The wall surface 3a includes a first main groove wall surface 31a formed narrower inward in the tire radial direction D2 from the tread surface 2a, and a narrow or constant width from the first main groove wall surface 31a toward the main groove bottom surface 3b. and a second main groove wall surface 32a formed, wherein the angle between the second main groove wall surface 32a and the tread surface 2a is smaller than the angle between the first main groove wall surface 31a and the tread surface 2a, and the zigzag-shaped main groove is formed. The groove (center main groove 3) has a plurality of stepped portions 33 that are joined to one of the second main groove wall surfaces 32a and protrude from the main groove bottom surface 3b. It is preferable that the stepped wall surface (first stepped wall surface 33a) of the stepped portion 33 and the second main groove wall surface 32a form a right angle or an obtuse angle.

According to such a configuration, the angle between the stepped wall surface (first stepped wall surface 33a) of the stepped portion 33 and the second main groove wall surface 32a is a right angle or an obtuse angle. It is possible to suppress the retention of water between the second main groove wall surface 32a. As a result, the stepped portion 33 can suppress stone trapping without deteriorating wet performance.

Further, as in the present embodiment, in the tire 1, the stepped portion 33 includes a first stepped portion 331 that joins one of the second main groove wall surfaces 32a and a second stepped portion that joins the other of the second main groove wall surfaces 32a. 332, and the first stepped portion 331 and the second stepped portion 332 do not intersect with each other when viewed in the tire circumferential direction D3.

With such a configuration, the see-through region 3S can be secured between the first stepped portion 331 and the second stepped portion 332, and the wet performance of the zigzag-shaped main groove (center main groove 3) can be ensured. can be done.

Further, as in the present embodiment, in the tire 1, the minimum gap W1 between the first stepped portion 331 and the second stepped portion 332 is the width W2 of the first stepped portion 331 in the cross section orthogonal to the second main groove wall surface 32a. is preferably 0.67 to 1.5 times.

According to such a configuration, it is possible to ensure the groove capacity of the zigzag-shaped main groove (the center main groove 3), thereby ensuring the WET performance. In addition, the width W2 of the first stepped portion 331 can be secured, and stone trapping can be appropriately suppressed.

Further, as in the present embodiment, the tire 1 is provided with the slit 8 extending from the recess 32 along the tire axial direction D1, and the angle formed by the zigzag-shaped main groove (center main groove 3) and the slit 8 is a right angle or a A preferred configuration is an obtuse angle.

According to such a configuration, it is possible to suppress concentration of pressure on the corner portions C1 of the center block 51 and the quarter block 61 formed by the center main groove 3 and the slits 8, thereby preventing uneven wear at the corner portions C1. can be suppressed.

Further, as in the present embodiment, in the tire 1, among the main grooves 21 formed in the tread surface 2a, the pair of shoulder main grooves 4 located on the outermost side in the tire axial direction D1 and the pair of shoulder main grooves 4 are arranged. a plurality of center main grooves 3 positioned therebetween, a center land 5 formed between the plurality of center main grooves 3, and a quarter land 6 formed between the center main groove 3 and the shoulder main groove 4; The center main groove 3 is a zigzag main groove, the slit 8 includes a center slit 81 arranged in the center land 5 and a quarter slit 82 arranged in the quarter land 6, and the center slit 81 includes a center inclined portion 81b that does not intersect the center main groove 3 and is inclined with respect to the tire axial direction D1, and quarter slits 82 are provided that do not intersect with the center main groove 3 and the shoulder main groove 4 and are inclined with respect to the tire axial direction D1. It is preferable that the quarter inclined portion 82b be inclined, and the center inclined portion 81b and the quarter inclined portion 82b are inclined in opposite directions with respect to the tire axial direction D1.

According to such a configuration, by making the inclination directions of the center inclined portion 81b and the quarter inclined portion 82b opposite to the tire axial direction D1, the rigidity of the center land 5 and the quarter land 6 is reduced in the direction (the inclined portion 81b , 82b) can be different. As a result, the directions in which the center land 5 and the quarter land 6 are weak in rigidity can be reinforced, and the uneven wear of the center land 5 and the quarter land 6 can be suppressed.

Further, as in the present embodiment, the tire 1 preferably has a configuration in which the quarter sipes 82c are arranged on the bottom surface of the slit of the quarter inclined portion 82b. According to such a configuration, even if the tread surface 2a is worn down to the bottom surface of the quarter slit 82, the quarter sipe 82c can ensure traction performance.

Moreover, it is preferable that the tire 1 has a configuration in which the center sipe 51a is arranged on the center land 5 as in the present embodiment. According to such a configuration, by arranging the center sipe 51a on the center land 5, the traction performance of the tire 1 during rolling can be enhanced.

Further, as in the present embodiment, the tire 1 preferably has a configuration in which the center sipe 51a is arranged in the center land 5, and the center sipe 51a and the quarter sipe 82c overlap the stepped portion 33 as viewed in the tire axial direction D1. .

According to such a configuration, by arranging the center sipe 51a and the quarter sipe 82c at the position overlapping the stepped portion 33, local rigidity reduction of the lands 5 and 6 due to the provision of the center sipe 51a and the quarter sipe 82c is suppressed. , and uneven wear of the tread rubber 2 can be suppressed.

In addition, the tire 1 is not limited to the configuration of the embodiment described above, and is not limited to the effects described above. Moreover, it goes without saying that the tire 1 can be modified in various ways without departing from the gist of the present invention. For example, it is of course possible to arbitrarily select one or a plurality of configurations, methods, etc., according to various modified examples described below and employ them in the configurations, methods, etc., according to the above-described embodiment.

(1) In the present embodiment, as the main grooves 21, a pair of center main grooves 3 are arranged across the tire equatorial plane S1. However, the main groove 21 is not limited to such a configuration. For example, as the main groove 21, the center main groove 3 may be arranged along the tire equator line L1.

(2) In the present embodiment, the shoulder main groove 4 extends linearly in the tire circumferential direction D3. However, the shoulder main groove 4 is not limited to such a configuration. For example, the shoulder main groove 4 may be configured to repeatedly bend and extend in a zigzag shape. Further, the shoulder main groove 4 may be configured to repeat bending and extend in a wavy shape, for example.

(3) In the present embodiment, the stepped portion 33 includes a first stepped portion 331 joined to one side of the second main groove wall surface 32a and a second stepped portion 332 joined to the other side of the second main groove wall surface 32a. It is a configuration that is prepared. However, the stepped portion 33 is not limited to such a configuration. For example, the stepped portion 33 may be configured to include only the first stepped portion 331 that joins with one of the second main groove wall surfaces 32a. That is, the stepped portion 33 may be configured without the second stepped portion 332 that joins the other of the second main groove wall surfaces 32a.

(4) In the present embodiment, in the stepped portion 33, the first stepped portion 331 and the second stepped portion 332 do not intersect when viewed in the tire circumferential direction D3. The configuration is such that a see-through region 3S is formed. However, the stepped portion 33 is not limited to such a configuration. For example, in the stepped portion 33, the first stepped portion 331 and the second stepped portion 332 intersect when viewed in the tire circumferential direction D3, and the see-through region 3S is not formed between the first stepped portion 331 and the second stepped portion 332. may be configured as follows.

(5) In the present embodiment, the tread rubber 2 is configured to have the slits 8 extending from the recessed portions 32 along the tire axial direction D1. However, the tread rubber 2 is not limited to such a configuration. For example, the tread rubber 2 may be configured to have slits 8 extending from the protrusions 31 along the tire axial direction D1.

(6) In the present embodiment, in the center slit 81 and the quarter slits 82, the center crossing portion 81a and the quarter crossing portion 82a extend parallel to the tire axial direction D1. However, the center slit 81 and the quarter slits 82 are not limited to such configurations. For example, in the center slit 81 and the quarter slits 82, the center crossing portion 81a and/or the quarter crossing portion 82a may extend obliquely with respect to the tire axial direction D1.

(7) In the present embodiment, in the center slit 81 and the quarter slits 82, the center slant portion 81b and the quarter slant portion 82b are arranged in opposite directions with respect to the tire axial direction D1. 81 and quarter slit 82 are not limited to such a configuration. For example, in the center slit 81 and the quarter slit 82, the center inclined portion 81b and the quarter inclined portion 82b may have the same inclination direction with respect to the tire axial direction D1.

(8) In the present embodiment, the center sipe 51a is inclined in the same direction as the center inclined portion 81b. However, the center sipe 51a is not limited to such a configuration. For example, the center sipe 51a may be configured to be inclined in the same direction as the quarter inclined portion 82b.

(9) In the present embodiment, an example was shown in which the tire 1 has a tread pattern that is symmetrical about a point on the tire equator line L1, but the present invention is not limited to this. For example, the tire 1 may have a symmetrical tread pattern centered on the tire equator L1, an asymmetrical tread pattern, or a directional tread pattern in which the tire rotation direction is specified.

REFERENCE SIGNS LIST 1 tire 2 tread rubber 21 main groove 2a tread surface 2b tread edge 3 center main groove 3a main groove wall surface 31a first main groove wall surface 32a second main groove wall surface Groove wall surface 3b... Main groove bottom surface 31... Convex part 32... Concave part 33... Stepped part 33a... First stepped wall surface 33b... Second stepped wall surface 331... First stepped part 332... Second stepped part , 3S... See-through area, 4... Shoulder main groove, 4a... One side closed sipe, 5... Center land, 51... Center block, 51a... Center sipe, 6... Quarter land, 61... Quarter block, 7... Shoulder land, 8... Slit 81...Center slit 81a...Center intersection part 81b...Center inclined part 82...Quarter slit 82a...Quarter intersection part 82b...Quarter inclined part 82c...Quarter sipe 11...Bead 12...Sidewall, 13... Tread, 14... Carcass ply, 15... Belt ply, C1... Corner part

Claims (8)

Equipped with a zigzag-shaped main groove extending in the tire circumferential direction,
The main groove wall surface of the zigzag-shaped main groove includes a first main groove wall surface formed narrower inward in the tire radial direction from the tread surface, and a first main groove wall surface narrower in width from the first main groove wall surface toward the main groove bottom surface. or a second main groove wall surface formed with a constant width,
The angle between the second main groove wall surface and the tread surface is smaller than the angle between the first main groove wall surface and the tread surface,
The zigzag-shaped main groove has a plurality of stepped portions that join with the second main groove wall surface and protrude from the main groove bottom surface,
The stepped portion is arranged in a plurality of recesses formed by the main groove wall surface, and the angle formed by the stepped wall surface of the stepped portion and the second main groove wall surface is formed at a right angle or an obtuse angle. . The stepped portion includes a first stepped portion that joins one of the second main groove wall surfaces, and a second stepped portion that joins the other of the second main groove wall surfaces,
The pneumatic tire according to claim 1, wherein the first stepped portion and the second stepped portion do not intersect when viewed in the tire circumferential direction. The minimum gap between the first stepped portion and the second stepped portion is 0.67 to 1.5 times the width of the first stepped portion in a cross section perpendicular to the wall surface of the second main groove. 2. The pneumatic tire according to 2. A slit extending along the tire axial direction from the recess,
The pneumatic tire according to any one of claims 1 to 3, wherein the angle formed by the zigzag main groove and the slit is a right angle or an obtuse angle. Of the main grooves formed on the tread surface, a pair of shoulder main grooves positioned on the outermost side in the tire axial direction, a plurality of center main grooves positioned between the pair of shoulder main grooves, and the plurality of center main grooves a center land formed between grooves and a quarter land formed between the center main groove and the shoulder main groove;
The center main groove is the zigzag main groove,
The slit includes a center slit arranged on the center land and a quarter slit arranged on the quarter land,
The center slit has a center inclined portion that does not cross the center main groove and is inclined with respect to the tire axial direction,
The quarter slit has a quarter inclined portion that does not cross the center main groove and the shoulder main groove and that is inclined with respect to the tire axial direction,
5. The pneumatic tire according to claim 4, wherein the center inclined portion and the quarter inclined portion have opposite inclination directions with respect to the tire axial direction. The pneumatic tire according to claim 5, wherein a quarter sipe is arranged on the slit bottom surface of the quarter inclined portion. The pneumatic tire according to claim 5 or 6, wherein a center sipe is arranged on said center land. A center sipe is arranged on the center land,
The pneumatic tire according to claim 6, wherein the center sipe and the quarter sipe overlap with the step portion when viewed in the axial direction of the tire.

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