Pneumatic tires

Abstract

To provide a pneumatic tire with an excellent balance between traction performance and land rigidity.SOLUTION: A pneumatic tire comprises: shoulder major grooves 25 that divide a tread into a central region 22 in a tire axial direction and both adjacent shoulder lands 21 thereof; and a plurality of major grooves 26 and 27 that divide the central region 22 in the tire axial direction into a plurality of lands 23 and 24. Slits 30 and sipes 31 that divide the lands 23 and 24 by each extending in the tire axial direction are disposed on each of the lands 23 and 24 in the central region 22 in the tire axial direction, a slit bottom sipe 32 is disposed at the bottom of the slit 30, the depth of the slit 30 is 10 to 40% of the depth of the major grooves 26 and 27, and the sum of the depths of the slit 30 and the slit bottom sipe 32 is 60 to 90% of the depth of the major grooves 26 and 27.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a pneumatic tire. [Background technology]

[0002] For example, as described in Patent Document 1, there is known a pneumatic tire in which the tread is divided into an axially central region and adjacent shoulder lands by shoulder main grooves extending in the tire circumferential direction, and the axially central region is further divided into a plurality of lands by other main grooves. As described in Patent Document 1, there is also known a pneumatic tire in which axially extending slits and sipes are provided alternately in the tire circumferential direction on each land in the axially central region of such a pneumatic tire.

[0003] Such pneumatic tires have excellent traction due to the effect of the axially extending slits and sipes. In addition, not all of the grooves extending in the axial direction of the tire are slits, but slits and sipes narrower than the slits are alternately provided in the circumferential direction of the tire, so that when the land deforms, the sipes close and the rigidity of the land is ensured. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-116845 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-mentioned pneumatic tires, it is difficult to achieve a good balance between traction and rigidity on land. For example, the deeper the slits, the better the traction, but the lower the rigidity on land.

[0006] Therefore, an object of the present invention is to provide a pneumatic tire that has an excellent balance between traction performance and rigidity on land. [Means for solving the problem]

[0007] In a pneumatic tire according to an embodiment, a tread is divided into a plurality of lands extending in the tire circumferential direction by a plurality of main grooves extending in the tire circumferential direction, and the main grooves include shoulder main grooves that divide the tread into an axially central region of the tire and shoulder lands on both sides of the central region of the tire, and a plurality of main grooves that divide the axially central region of the tire into a plurality of lands. Each land in the axially central region of the tire is provided with a slit and a sipe that extend in the tire axial direction and divide the land. In the pneumatic tire, the slits and the sipes are provided alternately in the tire circumferential direction. In the pneumatic tire, a slit bottom sipe that is a sipe different from the sipes is provided at the bottom of the slit, and the depth of the slit is 10 to 40% of the depth of the main groove, and the depth of the groove including the slit and the slit bottom sipe is 60 to 90% of the depth of the main groove. The slits and sipes are aligned on a line on both sides of the tire equator and extend in a V-shape when viewed with the side that first touches the ground during normal rotation facing down. It is characterized by: Effect of the Invention

[0008] In the pneumatic tire of the embodiment, due to the above-mentioned characteristics of the slits and sipes, a good balance between traction performance and rigidity on land is achieved. [Brief description of the drawings]

[0009] [Figure 1] 2 shows a tread pattern of a pneumatic tire according to an embodiment. [Diagram 2] Cross section AA of Figure 1. [Diagram 3] An enlarged view of part B in Figure 1. [Figure 4] Cross section taken along CC in Figure 3 . DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The embodiments will be described with reference to the drawings. Note that the embodiments described below are merely examples, and any appropriate modifications that do not depart from the gist of the present invention are included in the scope of the present invention.

[0011] The pneumatic tire of the embodiment has a general cross-sectional structure of a pneumatic tire, except for the tread. Specifically, bead portions (bead portions are portions including a bead core and a bead filler) are provided on both sides in the tire axial direction, and a carcass ply is provided from one bead portion in the tire axial direction to the other bead portion. A belt is provided on the outer diameter side of the carcass ply, and a tread is provided on the outer diameter side of the belt. An inner liner is provided inside the carcass ply, and sidewall rubber is provided on both sides of the carcass ply in the tire axial direction. In addition to the above, a plurality of rubber members are provided to configure the pneumatic tire.

[0012] As shown in Fig. 1, shoulder main grooves 25 extending in the tire circumferential direction are provided on both axial sides of the tread. The shoulder main grooves 25 divide the tread into an axially central region 22 where the tire equator C is located, and shoulder lands 21 on both axially opposite sides of the central region 22.

[0013] The tire axially central region 22 is provided with a center main groove 26 that overlaps with the tire equator C and extends in the tire circumferential direction, and a quarter main groove 27 that extends in the tire circumferential direction between the center main groove 26 and the shoulder main grooves 25.

[0014] The center main groove 26, the quarter main groove 27, and the shoulder main groove 25 are zigzag main grooves. The axial deviation of the zigzag groove is greatest in the center main groove 26, followed by the quarter main groove 27 and the shoulder main groove 25. Conversely, the shoulder main groove 25 is closest to being straight, followed by the quarter main groove 27 and the center main groove 26.

[0015] Moreover, the center main groove 26 and the quarter main grooves 27 in the tire axially central region 22 are narrower than the shoulder main grooves 25. Specifically, the widths of the center main groove 26 and the quarter main grooves 27 are 30 to 70% of the width of the shoulder main groove 25.

[0016] The tire axially central region 22 is divided into a center main groove 26 and a quarter main groove 27, so that four lands extending in the tire circumferential direction are formed in the tire axially central region 22. The four lands are a center land 23 between the center main groove 26 and the quarter main groove 27, and a quarter land 24 between the quarter main groove 27 and the shoulder main groove 25.

[0017] As described above, since each of the main grooves 25, 26, 27 is zigzag, the center land 23, the quarter land 24, and the shoulder land 21 are formed with wide portions 23a, 24a, 21a and narrow portions 23b, 24b, 21b.

[0018] Looking at the center land 23, in the wide portion 23a, the main grooves on both sides of the center land 23 (center main groove 26 and quarter main groove 27) are bent in the direction of widening the width of the center land 23, and in the narrow portion 23b, the main grooves on both sides of the center land 23 are bent in the direction of narrowing the width of the center land 23.

[0019] Looking at the quarter land 24, in the wide portion 24a, the main grooves on both sides of the quarter land 24 (quarter main groove 27 and shoulder main groove 25) are bent in a direction that widens the width of the quarter land 24, and in the narrow portion 24b, the main grooves on both sides of the quarter land 24 are bent in a direction that narrows the width of the quarter land 24.

[0020] Looking at the shoulder land 21, in the wide portion 21a, the shoulder main groove 25 is bent in a direction that widens the width of the shoulder land 21, and in the narrow portion 21b, the shoulder main groove 25 is bent in a direction that narrows the width of the shoulder land 21.

[0021] In each of the lands 23, 24 of the tire axial center region 22, slits 30 and sipes 31, which are a type of groove, are alternately provided in the tire circumferential direction. That is, in each of the two center lands 23, the slits 30 and sipes 31 are alternately provided in the tire circumferential direction, and in each of the two quarter lands 24, the slits 30 and sipes 31 are alternately provided in the tire circumferential direction. As a result, a plurality of blocks are formed in each of the center lands 23 and the quarter lands 24. Here, the slits 30 and the sipes 31 are grooves that extend in the tire axial direction and divide the lands. The slits 30 are grooves with a width greater than 1.5 mm. The sipes 31 are grooves with a width of 1.5 mm or less.

[0022] In the center land 23, the slit 30 is provided in the narrow portion 23b and connects the bent portion of the center main groove 26 and the bent portion of the quarter main groove 27. In addition, in the center land 23, the sipe 31 is provided in the wide portion 23a and connects the bent portion of the center main groove 26 and the bent portion of the quarter main groove 27.

[0023] Also in the quarter land 24, the slit 30 is provided in the narrow portion 24b, connecting the bent portion of the center main groove 26 and the bent portion of the quarter main groove 27. Also in the quarter land 24, the sipe 31 is provided in the wide portion 24a, connecting the bent portion of the center main groove 26 and the bent portion of the quarter main groove 27.

[0024] In the center land 23 and the quarter land 24, the depth of the slit 30 is 10 to 40% of the depth of the center main groove 26 and the quarter main groove 27. Also, as shown in Fig. 2, in the center land 23 and the quarter land 24, a slit bottom sipe 32 having a width of 1.5 mm or less is provided at the groove bottom of the slit 30. Also, in the center land 23 and the quarter land 24, the total depth of the slit 30 and the slit bottom sipe 32 is 60 to 90% of the depth of the center main groove 26 and the quarter main groove 27.

[0025] As shown in Fig. 1, the slits 30 and sipes 31 in the axially central region 22 of the tire are arranged alternately in the tire axial direction, and are aligned on a line. For example, next to the slit 30 in the quarter land 24 on one side in the tire axial direction is the sipe 31 in the center land 23 on one side in the tire axial direction, next to the sipe 31 is the slit 30 in the center land 23 on the other side in the tire axial direction, and next to the sipe 31 is the sipe 31 in the quarter land 24 on the other side in the tire axial direction. These slits 30, sipes 31, slits 30 and sipes 31 are aligned on a line.

[0026] The slits 30 and sipes 31 aligned on a line in this manner extend in a direction inclined with respect to the tire axial direction so as to be line-symmetrical with respect to the tire equator C. That is, the slits 30 and sipes 31 on one side in the tire axial direction are aligned on a straight line inclined with respect to the tire axial direction, and the slits 30 and sipes 31 on the other side in the tire axial direction are aligned on a straight line inclined with respect to the tire axial direction. The straight lines on one side and the other side in the tire axial direction are connected at the tire equator C and are line-symmetrical with respect to the tire equator C. In FIG. 1, the bottom is the side that touches the ground first when the tire is rotating forward (when the tire rolls to move the vehicle forward), and as shown in this figure, the straight line consisting of the slits 30 and sipes 31 is V-shaped.

[0027] Notches 28, 29 are formed at the ends of the sipes 31 facing the slits 30 across the main grooves 25, 26, 27. In detail, at the locations where the sipes 31 of the center land 23 open to the center main groove 26 and the quarter main groove 27, respectively, a notch 28 having a triangular shape is formed in the center land 23. This notch 28 partially widens the width of the sipes 31.

[0028] In addition, at the places where the sipes 31 of the quarter land 24 open into the quarter main groove 27 and the shoulder main groove 25, triangular notches 29 are formed in the quarter land 24. The notches 29 partially widen the width of the sipes 31.

[0029] Slits 33 and sipes 34 are also provided alternately in the circumferential direction of the tire on the shoulder land 21. The slits 33 are grooves having a width greater than 1.5 mm. The sipes 34 are grooves having a width of 1.5 mm or less.

[0030] The slits 33 and sipes 34 of the shoulder land 21 are bent and extend in a direction that forms a V shape when viewed with the side that first touches the ground during normal rotation facing down.

[0031] One end of the slit 33 in the shoulder land 21 (the end on the tire equator C side) opens into the shoulder main groove 25, and the other end is located beyond the tire ground contact edge E. Therefore, the slits 33 divide the shoulder land 21 into multiple blocks. The slits 33 in the shoulder land 21 do not have sipes at the slit bottom.

[0032] Moreover, one end of the sipe 34 of the shoulder land 21 (the end on the tire equator C side) opens to the shoulder main groove 25, but the other end is closed at a position closer to the tire equator C than the tire ground contact edge E. In other words, the other end of the sipe 34 is closed within the shoulder land 21.

[0033] In the shoulder land 21, the slit 33 is provided in the narrow portion 21b and opens into the bent portion of the shoulder main groove 25. In the shoulder land 21, the sipe 34 is provided in the wide portion 21a and opens into the bent portion of the shoulder main groove 25.

[0034] An opening end of the slit 33 of the shoulder land 21 facing the shoulder main groove 25 faces an opening end of the sipe 31 of the quarter land 24 facing the shoulder main groove 25 across the shoulder main groove 25. In addition, an opening end of the sipe 34 of the shoulder land 21 facing the shoulder main groove 25 faces an opening end of the slit 30 of the quarter land 24 facing the shoulder main groove 25 across the shoulder main groove 25.

[0035] At the location where the sipe 34 of the shoulder land 21 opens into the shoulder main groove 25, a notch 35 having a triangular shape is formed in the shoulder land 21. Due to this notch 35, the width of the sipe 34 is partially wider.

[0036] As shown in Figures 3 and 4, at the location of the notch 28, an inclined surface 36 is formed that is inclined with respect to the ground contact surface from the ground contact surface of the center land 23 to the bottom surface of the quarter main groove 27. Although not shown, at the locations of all of the notches 28, 29, and 35, an inclined surface is formed from the ground contact surface of the land to the bottom surface of the main groove as shown in Figures 3 and 4.

[0037] A pneumatic tire having the above characteristics is mounted, for example, on the drive side of a vehicle.

[0038] As described above, in the pneumatic tire of the present embodiment, the slits 30 and sipes 31 that divide the center land 23 and the quarter land 24 of the tire axial central region 22 are provided. The presence of the slits 30 and sipes 31 provides the pneumatic tire with excellent traction.

[0039] In addition, not all of the grooves provided in the center land 23 and the quarter land 24 are wide slits 30, but half of the grooves are narrow sipes 31, so that the sipes 31 are easily closed when the lands 23, 24 are deformed, ensuring the rigidity of the lands 23, 24. In addition, since the slits 30 and the sipes 31 are alternately arranged in the tire circumferential direction, the rigidity of the center land 23 and the quarter land 24 is relatively uniform in the tire circumferential direction.

[0040] In addition, the depth of the slits 30 is 10% or more of the depth of the center main groove 26 and the quarter main groove 27, so that traction is ensured. In addition, the depth of the slits 30 is 40% or less of the depth of the center main groove 26 and the quarter main groove 27, so that the slits 30 are not too deep, so that the rigidity of the center land 23 and the quarter land 24 is ensured.

[0041] In addition, although the slits 30 are relatively shallow, the slit bottom sipes 32 are provided at the bottom of the slits 30, so that even if the center land 23 and the quarter land 24 wear and the slits 30 become shallower or disappear, the slit bottom sipes 32 ensure traction.

[0042] In addition, the traction performance is ensured because the total depth of the slits 30 and the slit bottom sipes 32 is 60% or more of the depth of the center main groove 26 and the quarter main groove 27. In addition, the total depth of the slits 30 and the slit bottom sipes 32 is 90% or less of the depth of the center main groove 26 and the quarter main groove 27, so the rigidity of the center land 23 and the quarter land 24 is ensured.

[0043] As described above, the pneumatic tire of this embodiment has an excellent balance between traction and the rigidity of the lands 23, 24. Since the rigidity of the lands 23, 24 is ensured, the resistance to uneven wear of the lands 23, 24 is improved, and the deformation of the lands 23, 24 is small, which reduces energy loss and improves fuel efficiency.

[0044] Such pneumatic tires have excellent traction properties and are therefore particularly effective when mounted on the drive side of a vehicle.

[0045] In this embodiment, the sipes 31, 34 are provided in the wide portions 23a, 24a, 21a of the lands 23, 24, 21, and the slits 30, 33 are provided in the narrow portions 23b, 24b, 21b, so that the sipes 31, 34 are longer than the slits 30, 33. Therefore, the rigidity of the lands 23, 24, 21 is increased.

[0046] In this embodiment, the ends of the slits 30 and 33 and the ends of the sipes 31 and 34 face each other across the main grooves 25, 26 and 27, and notches 28, 29 and 35 are provided at one of the two facing ends by cutting out the lands 21, 23 and 24. At the ends of the slits 30 and 33 and the ends of the sipes 31 and 34, small angle corners such as acute angles are formed in the lands 21, 23 and 24, but by providing the notches 28, 29 and 35 in this way, small angle corners are eliminated. Therefore, the rigidity of the corners of the lands 21, 23 and 24 can be secured, and the occurrence of cracks due to the corners of the lands 21, 23 and 24 moving significantly can be prevented.

[0047] Further, the wide portions 23a, 24a, 21a of the lands 23, 24, 21 have corners that are smaller in angle than the narrow portions 23b, 24b, 21b of the lands 23, 24, 21. The notches 28, 29, 35 are provided at the ends of the sipes 31, 34 in the wide portions 23a, 24a, 21a, thereby ensuring the rigidity of the corners of the wide portions 23a, 24a, 21a.

[0048] The axial center region 22 of the tire is subjected to a larger ground pressure than the shoulder land 21. Therefore, the widths of the center main groove 26 and the quarter main groove 27 are narrower than the width of the shoulder main groove 25, specifically, 70% or less, so that the rigidity of the axial center region 22 of the tire is ensured, and the center land 23 and the quarter land 24 are less likely to deform even when a large ground pressure is applied, thereby ensuring low fuel consumption.

[0049] In addition, the widths of the center main groove 26 and the quarter main groove 27 are 30% or more of the width of the shoulder main groove 25, thereby ensuring skid resistance and drainage.

[0050] In the tire axial center region 22, the slits 30 and sipes 31 are aligned on a line on both sides of the tire equator C (that is, they are aligned on a line on both sides of the tire equator C, and the lines on both sides of the tire equator C are connected at the tire equator C), and extend in a direction that forms a V shape when viewed with the side that touches the ground first downward during forward tire rotation. Therefore, resistance is less likely to occur during forward tire rotation, resulting in good fuel efficiency.

[0051] In this embodiment, the center main groove 26, the quarter main groove 27, and the shoulder main groove 25 are zigzag main grooves, but the axial deviation of the zigzag shape is larger in the order of the center main groove 26, the quarter main groove 27, and the shoulder main groove 25. Therefore, the main groove in the area with the larger ground pressure has a larger zigzag shape, and thus exhibits greater traction when the tread comes into contact with the ground.

[0052] In this embodiment, the shoulder land 21 is also provided with slits 33 and sipes 34, ensuring traction. The slits 33 and sipes 34 are alternately arranged in the circumferential direction of the tire, so that the rigidity of the shoulder land 21 is relatively uniform in the circumferential direction of the tire. Therefore, uneven wear of the shoulder land 21 is unlikely to occur.

[0053] In addition, the shoulder land 21 is susceptible to large lateral forces, but the ends of the sipes 34 of the shoulder land 21 on the tire ground contact edge E side are closed within the shoulder land 21, ensuring the rigidity of the shoulder land 21. Therefore, uneven wear is unlikely to occur on the shoulder land 21.

[0054] In addition, the slits 33 and sipes 34 of the shoulder land 21 are bent and extend in a V-shape when viewed with the side that touches the ground first when the tire is rotating forward facing downwards. Therefore, resistance is less likely to occur when the tire is rotating forward, and fuel efficiency is good.

[0055] Various modifications can be made to the above embodiment.

[0056] For example, in the center land 23, the quarter land 24 and the shoulder land 21, the slits 30, 33 may be provided in the wide portions 23a, 24a, 21a, and the sipes 31, 34 may be provided in the narrow portions 23b, 24b, 21b, in contrast to the above embodiment.

[0057] In the center land 23, the quarter land 24, and the shoulder land 21, the notches 28, 29, and 35 in the above embodiment may be provided at the opening ends of the slits 30 and 33 instead of the sipes 31 and 34. In a preferred embodiment, when the wide portions 23a, 24a, and 21a are provided with the slits 30 and 33 and the sipes 31 and 34, the notches are preferably formed in the wide portions 23a, 24a, and 21a. However, the notches may be formed in the narrow portions 23b, 24b, and 21b. [Explanation of symbols]

[0058] C... tire equator, E... tire ground contact edge, 21... shoulder land, 21a... wide portion, 21b... narrow portion, 22... tire axial center region, 23... center land, 23a... wide portion, 23b... narrow portion, 24... quarter land, 24a... wide portion, 24b... narrow portion, 25... shoulder main groove, 26... center main groove, 27... quarter main groove, 28... notch, 29... notch, 30... slit, 31... sipe, 32... slit bottom sipe, 33... slit, 34... sipe, 35... notch, 36... inclined surface

Claims

1. A plurality of main grooves extending in the tire circumferential direction divide the tread into a plurality of lands extending in the tire circumferential direction, As the main grooves, a shoulder main groove that divides the tread into an axially central region of the tire and shoulder lands on both sides of the shoulder lands, and a plurality of main grooves that divide the axially central region of the tire into a plurality of lands are provided, Each land in the tire axial center region is provided with a slit and a sipe extending in the tire axial direction and dividing the land, In a pneumatic tire in which the slits and the sipes are alternately provided in the tire circumferential direction on each land, A slit bottom sipe, which is a sipe different from the sipe, is provided at the bottom of the slit, The depth of the slit is 10 to 40% of the depth of the main groove, The depth of the groove including the slit and the slit bottom sipe is 60 to 90% of the depth of the main groove, The pneumatic tire is characterized in that the slits and the sipes are aligned on a line on both sides of the tire equator and extend in a direction forming a V shape when viewed with the side that first comes into contact with the ground during normal rotation facing down.

2. An end of the slit and an end of the sipe face each other across the main groove, 2. The pneumatic tire according to claim 1, wherein a notch is provided in one of the two opposing ends.

3. 3. The pneumatic tire according to claim 1, wherein a width of the main groove in the axial center region of the tire is 30 to 70% of a width of the shoulder main groove.

4. As the main grooves in the tire axial center region, a center main groove overlapping with a tire equator and quarter main grooves adjacent to the center main groove are provided, the center main groove, the quarter main groove, and the shoulder main groove are zigzag main grooves, The pneumatic tire according to any one of claims 1 to 3, wherein the zigzag axial swing width of the tire is greatest in the center main groove, greatest in the quarter main groove, and greatest in the shoulder main groove.

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