Pneumatic tires

Abstract

To provide a pneumatic tire that is able to sufficiently secure side slip resistance and secure the rigidity of a tread as well.SOLUTION: A pneumatic tire according to an embodiment is provided with a center rib 23, a quarter rib 24 and a shoulder rib 25, and a plurality of slits 30, 40, 50 having a bending point, extending in a tire axial direction and arranged in a circumferential direction of the tire for each rib, where each slit of each rib is staggered from each slit of an adjacent rib in the tire circumferential direction. The pneumatic tire is characterized in that narrow grooves 35, 47 extending in a direction inclined with respect to the tire circumferential direction and connecting the two slits are formed in the center rib 23 and the quarter rib 24, and the inclining directions of the narrow grooves 35, 47 in the center rib 23 and the quarter rib 24 are opposite in the tire circumferential direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] For example, as disclosed in Patent Document 1, a pneumatic tire is known that has five ribs extending circumferentially, with each rib having multiple slits that extend in the axial direction of the tire and bend along the way, and the slits are offset circumferentially from the slits in adjacent ribs.

[0003] In such pneumatic tires, traction is ensured by the effect of the axially extending slits, and traction is provided throughout the entire circumferential direction of the tire because the slits of a given rib are offset from the slits of adjacent ribs in the circumferential direction of the tire. In addition, because the slits not only extend in the axial direction of the tire but also bend along the way, a certain degree of skid resistance is also ensured. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2015-512352 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above pneumatic tire, since the slits extend in the axial direction as a whole, the lateral slip resistance cannot be sufficiently ensured by simply bending the slits. Also, when grooves are provided in the ribs to improve the lateral slip resistance, there is a problem that the rigidity of the tread decreases depending on the way the grooves are provided.

[0006] Therefore, an object of the present invention is to provide a pneumatic tire in which sufficient skid resistance is ensured and tread rigidity is also ensured. [Means for solving the problem]

[0007] In one embodiment, a pneumatic tire is provided with four main grooves extending in a tire circumferential direction and five ribs formed by the main grooves, and the ribs include one center rib on the tire equator, two quarter ribs adjacent to the center rib, and two shoulder ribs on the tire ground contact end side. Each rib is provided with a plurality of slits arranged in the tire circumferential direction and having one or more bending points, the slits of each rib being arranged in a line in the tire circumferential direction, and the slits of each rib are arranged so as to be offset in the tire circumferential direction from the slits of an adjacent rib. In the pneumatic tire, a narrow groove is formed in the center rib and the quarter rib, extending in a direction inclined with respect to the tire circumferential direction and connecting the two slits, and the inclination direction of the narrow groove is opposite to that of the center rib and the quarter rib with respect to the tire circumferential direction. The depth of the slits and the narrow grooves is 10 to 30% of the depth of the main groove. It is characterized by: In addition, a pneumatic tire of an embodiment is provided with four main grooves extending in the tire circumferential direction and five ribs formed by the main grooves, and the ribs include one center rib on the tire equator, two quarter ribs adjacent to the center rib, and two shoulder ribs on the tire ground contact end side, and each rib is provided with a plurality of slits arranged in the tire circumferential direction and having one or more bending points, and each slit of each rib is arranged so as to be offset in the tire circumferential direction from each slit of an adjacent rib, wherein a narrow groove is formed in the center rib and the quarter rib, extending in a direction inclined with respect to the tire circumferential direction and connecting the two slits, the inclination direction of the narrow groove is opposite to that of the tire circumferential direction in the center rib and the quarter rib, and sipes are provided at the bottom of the slit in the center rib and the quarter rib. Effect of the Invention

[0008] In the pneumatic tire of the embodiment, since the slits and narrow grooves are provided as described above, sufficient skid resistance is ensured, and the rigidity of the tread is also ensured. [Brief description of the drawings]

[0009] [Figure 1] Pneumatic tire tread pattern. [Diagram 2] Cross section AA of Figure 1. [Diagram 3] Cross-sectional view of FIG. 1 taken along line B-B. 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, the tread is provided with two center main grooves 21 close to the tire equator C and two shoulder main grooves 22 close to the tire ground contact edge E as main grooves extending in the tire circumferential direction. These main grooves 21, 22 extend straight in the tire circumferential direction without bending. These main grooves 21, 22 have the same depth and are the deepest of the grooves provided in the tread. The center main groove 21 is narrower than the shoulder main grooves 22.

[0013] The main groove is a groove that extends in the circumferential direction of the tire and has a width that is at least half the width of the widest groove in the tread. Therefore, the width of the center main groove 21 is at least half the width of the shoulder main grooves 22.

[0014] Five ribs are formed in the tread by these main grooves 21, 22. The five ribs are a center rib 23 located on the tire equator C, quarter ribs 24 on both sides of the center rib 23, and shoulder ribs 25 on both axial sides of the tire at the tire ground contact ends E.

[0015] Each of the ribs 23, 24, and 25 has a slit that has one or more bending points and extends in the tire axial direction. The slit is a groove that is narrower than the main grooves 21 and 22.

[0016] First, a plurality of center slits 30 are provided at intervals in the tire circumferential direction in the center rib 23. The center slits 30 open into the center main groove 21 on both sides of the center rib 23. The depth of the center slits 30 is 10 to 30% of the depth of the main grooves 21, 22.

[0017] The center slit 30 has two bending points 31, and is composed of a first straight line portion 32 from the bending point 31 to the bending point 31, and two second straight line portions 33 from the bending point 31 to the opening end to the center main groove 21. The first straight line portion 32 and the second straight line portion 33 are inclined with respect to the tire axial direction, but the second straight line portion 33 is inclined in the opposite direction to the first straight line portion 32 with respect to the tire axial direction.

[0018] As shown in FIG. 2, a center sipe 34 narrower than the center slit 30 is provided at the groove bottom of the center slit 30. As shown in FIG. 1, the center sipe 34 also opens into the center main groove 21 on both sides of the center rib 23. The center sipe 34 also bends at the same position as the center slit 30. The total depth of the center slit 30 and the center sipe 34 (i.e., the length from the opening end of the center slit 30 facing the ground contact surface to the bottom of the center sipe 34) is 50 to 90% of the depth of the main grooves 21, 22.

[0019] Further, a plurality of quarter slits 40 are provided at intervals in the tire circumferential direction in the quarter rib 24. The quarter slits 40 open to the center main groove 21 and the shoulder main grooves 22. The depth of the quarter slits 40 is 10 to 30% of the depth of the main grooves 21, 22.

[0020] The quarter slit 40 has two bending points 41, 42, and is made up of a first straight portion 43 from the opening end to the center main groove 21 to the first bending point 41, a second straight portion 44 from the first bending point 41 to the second bending point 42, and a third straight portion 45 from the second bending point 42 to the opening end to the shoulder main groove 22. The first straight portion 43 and the second straight portion 44 are inclined with respect to the tire axial direction and arranged in a V shape. The third straight portion 45 extends in the tire axial direction.

[0021] As shown in Fig. 3, a quarter sipe 46 narrower than the quarter slit 40 is provided at the groove bottom of the quarter slit 40. As shown in Fig. 1, the quarter sipe 46 also opens into the center main groove 21 and the shoulder main groove 22. The quarter sipe 46 is also bent at the same position as the quarter slit 40. The total depth of the quarter slit 40 and the quarter sipe 46 (i.e., the length from the opening end of the quarter slit 40 facing the ground contact surface to the bottom of the quarter sipe 46) is 50 to 90% of the depth of the main grooves 21, 22.

[0022] Additionally, the shoulder rib 25 is provided with a plurality of shoulder slits 50 spaced apart in the tire circumferential direction. One end of the shoulder slits 50 opens into the shoulder main groove 22. The other end of the shoulder slit 50 (hereinafter, this end will be referred to as the "closed end 51") is closed within the shoulder rib 25, and is located closer to the tire equator C than the tire ground contact edge E. The depth of the shoulder slit 50 is 10 to 30% of the depth of the main grooves 21, 22.

[0023] The shoulder slit 50 has two bending points 52, 53, and is composed of a first straight line portion 54 from the shoulder main groove 22 to the first bending point 52, a second straight line portion 55 from the first bending point 52 to the second bending point 53, and a third straight line portion 56 from the second bending point 53 to the closed end 51. The second straight line portion 55 is inclined with respect to the tire axial direction, while the first straight line portion 54 and the third straight line portion 56 extend in the tire axial direction. No grooves such as sipes are provided at the groove bottom of the shoulder slit 50.

[0024] These slits are arranged with a circumferential offset from the slits of the adjacent ribs. Specifically, the center slit 30 and the quarter slit 40 are arranged with a circumferential offset from each other in the tire circumferential direction and do not overlap in the tire axial direction. Also, the quarter slit 40 of the quarter rib 24 and the shoulder slit 50 of the adjacent shoulder rib 25 are arranged with a circumferential offset from each other in the tire circumferential direction and do not overlap in the tire axial direction.

[0025] On the other hand, the slits of non-adjacent ribs may have an overlapping area in the tire axial direction. However, the circumferential length of the axially overlapping area of ​​the slits is 10% or less of the pitch length. Here, the pitch length means the circumferential length of one repeating unit of the tread pattern, and is, for example, the circumferential distance P between the closed ends 51 of two circumferentially adjacent shoulder slits 50 (see the right shoulder rib 25 in FIG. 1).

[0026] For example, the center slit 30 and the shoulder slit 50 have an axially overlapping region, but the circumferential length L (see FIG. 1) of the axially overlapping region of the slits 30, 50 is 10% or less of the pitch length.

[0027] Furthermore, the quarter slits 40 of one quarter rib 24 have an area that overlaps in the tire axial direction with the quarter slits 40 of another quarter rib 24 and the shoulder slits 50 of the non-adjacent shoulder rib 25. However, the length in the tire circumferential direction of such an area that overlaps in the tire axial direction is 10% or less of the pitch length.

[0028] The center rib 23 and the quarter ribs 24 are provided with narrow grooves extending at a slight incline with respect to the circumferential direction of the tire. The narrow grooves are narrower than the main grooves 21, 22.

[0029] The center rib 23 is provided with a center narrow groove 35 extending in a direction inclined with respect to the tire circumferential direction. The center narrow groove 35 connects two center slits 30 adjacent in the tire circumferential direction. The center narrow groove 35 does not open into the center main groove 21, but opens into the center slit 30. The depth of the center narrow groove 35 is 10 to 30% of the depth of the main grooves 21, 22. The center narrow groove 35 and the center slit 30 may have the same depth or different depths.

[0030] Further, each of the two quarter ribs 24 is provided with a quarter narrow groove 47 extending in a direction inclined with respect to the tire circumferential direction. The quarter narrow groove 47 connects two quarter slits 40 adjacent in the tire circumferential direction. The quarter narrow groove 47 does not open to the main grooves 21, 22 but opens to the quarter slit 40. The depth of the quarter narrow groove 47 is 10 to 30% of the depth of the main grooves 21, 22. The quarter narrow groove 47 and the quarter slit 40 may have the same depth or different depths.

[0031] The quarter narrow groove 47 is inclined in the opposite direction to the center narrow groove 35 with respect to the tire circumferential direction. Therefore, the extension line of the quarter narrow groove 47 intersects with the extension line of the center narrow groove 35. The quarter narrow groove 47 of the quarter rib 24 on one side in the tire axial direction is parallel to the quarter narrow groove 47 of the quarter rib 24 on the other side in the tire axial direction. The shoulder ribs 25 are not provided with narrow grooves extending in the tire circumferential direction.

[0032] A pneumatic tire having such characteristics is attached, for example, to the front side of a vehicle.

[0033] As described above, in the pneumatic tire of this embodiment, the center rib 23, the quarter rib 24, and the shoulder rib 25 are provided with the slits 30, 40, and 50 extending in the tire axial direction. These slits 30, 40, and 50 allow the pneumatic tire to exhibit traction. Since these slits 30, 40, and 50 each have a bending point and a portion inclined with respect to the tire axial direction, the pneumatic tire also exhibits skid resistance. In addition, since the slits 30, 40, and 50 of each of the ribs 23, 24, and 25 are arranged to be offset from the slits of the adjacent ribs in the tire circumferential direction, the pneumatic tire exhibits traction over the entire tire circumferential direction.

[0034] In addition, the center rib 23 is provided with a center narrow groove 35 extending in the tire circumferential direction, and the quarter rib 24 is provided with a quarter narrow groove 47 extending in the tire circumferential direction, further improving the skid resistance of the pneumatic tire. Here, the center narrow groove 35 connects the two center slits 30, and the quarter narrow groove 47 connects the two quarter slits 40, so these narrow grooves 35, 47 are longer and the center rib 23 and the quarter rib 24 are more likely to deform. This also improves the skid resistance of the pneumatic tire.

[0035] Furthermore, the center narrow groove 35 and the quarter narrow groove 47 are inclined in opposite directions with respect to the tire circumferential direction. Therefore, when a force is applied to the tread in a direction in which the center narrow groove 35 is easily closed and the center rib 23 is easily deformed (i.e., a direction perpendicular to the extension direction of the center narrow groove 35), the quarter narrow groove 47 is difficult to close and the quarter rib 24 is difficult to deform. Conversely, when a force is applied to the tread in a direction in which the quarter narrow groove 47 is easily closed and the quarter rib 24 is easily deformed (i.e., a direction perpendicular to the extension direction of the quarter narrow groove 47), the center narrow groove 35 is difficult to close and the center rib 23 is difficult to deform. Therefore, regardless of the direction of force applied, the rigidity of each rib 23, 24, 25 is ensured, and the rigidity of the entire tread is ensured.

[0036] Furthermore, since the rigidity of the tread is ensured, the abrasion resistance and resistance to uneven wear are improved, and since the deformation of the tread is small and energy loss is reduced, fuel efficiency is also improved.

[0037] In addition, the depth of each of the slits 30, 40, 50 and each of the narrow grooves 35, 47 is 10% or more of the depth of the main grooves 21, 22, improving traction and skid resistance. In addition, the depth of each of the slits 30, 40, 50 and each of the narrow grooves 35, 47 is 30% or less of the depth of the main grooves 21, 22, ensuring the rigidity of the tread and improving wear resistance, uneven wear resistance, and fuel economy.

[0038] In addition, since a center sipe 34 is provided at the groove bottom of the center slit 30 and a quarter sipe 46 is provided at the groove bottom of the quarter slit 40, even if the center slit 30 or the quarter slit 40 becomes shallow or disappears due to the progress of tread wear, the center sipe 34 and the quarter sipe 46 remain, and the traction of the pneumatic tire is maintained.

[0039] On the other hand, although a large force is applied to the shoulder rib 25, since no sipes are provided at the groove bottom of the shoulder slit 50, excessive deformation of the shoulder rib 25 is suppressed.

[0040] In addition, traction is improved because the combined depth of the center slit 30 and the center sipes 34 is 50% or more of the depth of the main grooves 21, 22. In addition, the combined depth of the center slit 30 and the center sipes 34 is 90% or less of the depth of the main grooves 21, 22, so the rigidity of the center rib 23 is ensured, improving wear resistance, uneven wear resistance, and fuel economy.

[0041] In addition, traction is improved because the combined depth of the quarter slits 40 and the quarter sipes 46 is 50% or more of the depth of the main grooves 21, 22. In addition, the combined depth of the quarter slits 40 and the quarter sipes 46 is 90% or less of the depth of the main grooves 21, 22, so the rigidity of the quarter rib 24 is ensured, improving wear resistance, uneven wear resistance, and fuel economy.

[0042] Furthermore, large lateral forces are applied to the front tires of a vehicle when the vehicle turns, but the pneumatic tire of this embodiment has excellent skid resistance and is therefore suitable as a front tire.

[0043] As described above, the circumferential length of the area where the center slit 30 and the shoulder slit 50 overlap in the tire axial direction is 10% or less of the pitch length. In this way, the center slit 30 and the shoulder slit 50 are arranged in a dispersed manner without concentrating in one place in the tire circumferential direction, so that traction performance is exhibited throughout the entire tire circumferential direction.

[0044] As described above, the quarter slits 40 of one quarter rib 24 have an area that overlaps with the quarter slits 40 of another quarter rib 24 and the shoulder slits 50 of the non-adjacent shoulder rib 25 in the tire axial direction, but the length of the area that overlaps in the tire axial direction is 10% or less of the pitch length. In this way, the slits are arranged in a dispersed manner without concentrating in one place in the tire circumferential direction, so that traction is exhibited throughout the entire tire circumferential direction.

[0045] Various modifications can be made to the above embodiment. For example, some or all of the center slit, quarter slit, and shoulder slit may have one or more bends, which can improve not only traction but also skid resistance.

[0046] Further, a part or all of the center main groove and the shoulder main grooves may be main grooves extending in the tire circumferential direction in a zigzag shape. [Explanation of symbols]

[0047] C...tire equator, E...tire ground contact edge, 21...center main groove, 22...shoulder main groove, 23...center rib, 24...quarter rib, 25...shoulder rib, 30...center slit, 31...bending point, 32...first straight section, 33...second straight section, 34...center sipe, 35...center narrow groove, 40...quarter slit, 41...bending point, 42...bending point, 43...first straight section, 44...second straight section, 45...third straight section, 46...quarter sipe, 47...quarter narrow groove, 50...shoulder slit, 51...closed end, 52...bending point, 53...bending point, 54...first straight section, 55...second straight section, 56...third straight section

Claims

1. The tire has four main grooves extending in a circumferential direction and five ribs formed by the main grooves, The ribs include one center rib on the tire equator, two quarter ribs adjacent to the center rib, and two shoulder ribs on the tire ground contact end side. Each rib has one or more bending points and is provided with a plurality of slits arranged in the tire circumferential direction, the slits having one or more bending points and extending in the tire axial direction, In a pneumatic tire in which each slit of each rib is arranged to be shifted from each slit of an adjacent rib in the tire circumferential direction, A narrow groove is formed in each of the center rib and the quarter rib, the narrow groove extending in a direction inclined with respect to the tire circumferential direction and connecting the two slits, The inclination directions of the narrow grooves of the center rib and the quarter rib are opposite to each other with respect to the tire circumferential direction, A pneumatic tire, characterized in that the depth of the slits and the narrow grooves is 10 to 30% of the depth of the main groove.

2. A tire having four circumferentially extending main grooves and five ribs formed by the main grooves, The ribs include one center rib on the tire equator, two quarter ribs adjacent to the center rib, and two shoulder ribs on the tire ground contact end side. Each rib has one or more bending points and is provided with a plurality of slits arranged in the tire circumferential direction, the slits having one or more bending points and extending in the tire axial direction, In a pneumatic tire in which each slit of each rib is arranged to be shifted from each slit of an adjacent rib in the tire circumferential direction, A narrow groove is formed in each of the center rib and the quarter rib, the narrow groove extending in a direction inclined with respect to the tire circumferential direction and connecting the two slits, The inclination directions of the narrow grooves of the center rib and the quarter rib are opposite to each other with respect to the tire circumferential direction, A pneumatic tire, wherein sipes are provided at bottoms of the slits in the center rib and the quarter ribs.

3. The pneumatic tire according to claim 2, wherein a combined depth of the slits and the sipes is 50 to 90% of a depth of the main groove.

4. The pneumatic tire according to claim 2 or 3, wherein a bottom of the slit of the shoulder rib has no sipes.

Images