Pneumatic tires

Abstract

To provide a pneumatic tire in which the stiffness of a part on the outer side in a tire axial direction of a rib that is the outer side of a vehicle when installed to the vehicle.SOLUTION: A pneumatic tire 1 is provided with a center main groove 10, shoulder main grooves 11 and 12, and two mediate ribs 13 and 14 sandwiched between the center main groove 10 and the shoulder main grooves 11 and 12 and extending in a tire circumferential direction. The outer mediate rib 13 that is the outer side of a vehicle when installed to the vehicle is provided with a plurality of sipes 20. On both opposing walls of the sipe 20, tapered surfaces 21 and 22 expanding opening width to a grounding surface are formed. The tapered surfaces 21 and 22 are formed to be deeper as they approach the center main groove 10. The sipe 20 opens to the center main groove 10, and the tapered surfaces 21 and 22 reach the center main groove 10.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] A known pneumatic tire for use on minivans and the like has three circumferentially extending main grooves, with a rib sandwiched between the two main grooves on each of the axially opposite sides of the tire. A pneumatic tire is also known in which a plurality of sipes extending in the axial direction of the tire are provided in these ribs, and a tapered surface (chamfer) is provided at the opening end of the sipes that contacts the ground (see, for example, Patent Document 1). The presence of sipes in the ribs improves friction, giving the pneumatic tire excellent wet performance and the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-94007 A Summary of the Invention [Problem to be solved by the invention]

[0004] Recently, in order to improve drainage and ground contact, tapered surfaces have been considered at the opening ends of the sipes of the ribs. However, depending on how the tapered surfaces are provided on the sipes of the ribs, the rigidity of the portion of the rib that faces the vehicle exterior when installed on the vehicle may be reduced. In terms of steering stability, it is preferable that the rigidity of the portion of the rib that faces the vehicle exterior when installed on the vehicle is high.

[0005] Therefore, an object of the present invention is to provide a pneumatic tire having high rigidity in the portion of the rib that faces the outer side of the vehicle when the tire is mounted on the vehicle. [Means for solving the problem]

[0006] In the pneumatic tire of the embodiment, at least one center main groove in the center of the tire in the tire axial direction and shoulder main grooves on both sides of the center main groove are provided in the tread as main grooves extending in the tire circumferential direction, two intermediate ribs are provided between the center main groove and the shoulder main groove and extending in the tire circumferential direction, and each of the intermediate ribs is provided with a plurality of sipes. In the pneumatic tire of the embodiment, tapered surfaces are formed on both opposing walls of the sipes in the outer intermediate rib, which is the intermediate rib that is on the outer side of the vehicle when mounted on the vehicle, to widen the opening width to the ground contact surface, and the tapered surfaces are formed to become deeper as they approach the center main groove, In the outer intermediate rib, The sipe opens into the center main groove, and the tapered surface reaches the center main groove. A tapered surface is formed on both opposing walls of the sipe in the inner intermediate rib, which is the intermediate rib that is on the inside of the vehicle when the sipe is installed on the vehicle, to widen the opening width to the ground contact surface, and in the inner intermediate rib, the sipe and the tapered surface reach only the center main groove and are closed within the inner intermediate rib, and the depth of the tapered surface is constant in the extension direction of the sipe. It is characterized by: Effect of the Invention

[0007] Since the pneumatic tire of the embodiment has the above-mentioned characteristics, the rigidity of the portion of the rib that faces the outer side of the vehicle when the tire is mounted on the vehicle is high. [Brief description of the drawings]

[0008] [Figure 1] FIG. [Diagram 2] Pneumatic tire tread pattern. [Diagram 3] 3 is a cross-sectional view taken along line AA in FIG. 2 (a cross-sectional view taken along a first sipe and a second sipe). [Figure 4] 3 is a cross-sectional view taken along line BB in FIG. 2 (a cross-sectional view taken along a first sipe, a first notch, and a second notch). [Diagram 5] 3 is a cross-sectional view taken along line CC in FIG. 2 (a cross-sectional view taken along a plane perpendicular to the extension direction of the first sipe). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] First, the overall structure of a pneumatic tire 1 of this embodiment will be described with reference to Fig. 1. Note that Fig. 1 shows only half of the tire in the axial direction, and the actual pneumatic tire 1 is symmetrical with respect to the tire center line C. The up-down direction in Fig. 1 is the tire radial direction, the left-right direction is the tire axial direction, and the direction perpendicular to the paper surface is the tire circumferential direction.

[0010] The pneumatic tire 1 has bead portions 9 on both axial sides of the tire (only the right side in FIG. 1). The bead portion 9 is composed of a bead core 9a made of a steel wire and a rubber bead filler 9b provided radially outside the bead core 9a.

[0011] One or more carcass plies 2 are laid across the bead portions 9 on both axial sides of the tire. The carcass ply 2 is a sheet-like member in which numerous ply cords arranged in a direction perpendicular to the tire circumferential direction are covered with rubber. The carcass ply 2 forms the skeleton shape of the pneumatic tire 1 between the bead portions 9 on both axial sides of the tire. Furthermore, the carcass ply 2 is folded back from the axially inner side to the outer side around the bead portions 9 and wound up radially outward. A rubber chafer 3 is provided at a location axially outward of the radially outward wound-up portion 2a of the carcass ply 2.

[0012] Furthermore, one or more belts 4 are provided on the radially outer side of the carcass ply 2, and a belt reinforcing layer 5 is provided on the radially outer side of the belt 4. The belt 4 is a member made of many steel cords covered with rubber. The belt reinforcing layer 5 is a member made of many organic fiber cords covered with rubber. A tread rubber 6 is provided on the radially outer side of the belt reinforcing layer 5. The tread rubber 6 has many grooves formed therein to form a tread pattern.

[0013] In addition, sidewall rubber 7 is provided on both sides of the carcass ply 2 in the tire axial direction. The tread rubber 6 and the sidewall rubber 7 overlap at the buttress, but either the tread rubber 6 or the sidewall rubber 7 may be on the tire surface side. In the buttress of FIG. 1, the tread rubber 6 is on the tire surface side. Although not shown, wing rubber may be provided on the buttress. The inner part of the sidewall rubber 7 in the tire radial direction extends close to the bead portion 9, and covers part of the rubber chafer 3 from the outer side in the tire axial direction.

[0014] In addition to these members, the pneumatic tire 1 may be provided with members such as an under-belt pad as necessary.

[0015] Next, the tread pattern of the pneumatic tire 1 will be described with reference to Fig. 2 to Fig. 5. The orientation of the pneumatic tire 1 when mounted on a vehicle is fixed. The orientation when mounted on a vehicle is indicated by symbols or the like on the tire surface. In Fig. 2 to Fig. 4, the left side is the outer side of the vehicle when mounted on the vehicle, and the right side is the inner side of the vehicle when mounted on the vehicle.

[0016] The tread rubber 6 is provided with three wide main grooves 10, 11, 12 extending in the tire circumferential direction. The three main grooves 10, 11, 12 include a center main groove 10 in the center of the three, an outer shoulder main groove 11 located on the outer side of the vehicle than the center main groove 10, and an inner shoulder main groove 12 located on the inner side of the vehicle than the center main groove 10. These main grooves 10, 11, 12 extend linearly in the tire circumferential direction. The center main groove 10 is on the tire center line C (see FIG. 1).

[0017] Four ribs are formed by dividing the main grooves 10, 11, and 12. The ribs are lands extending in the tire circumferential direction. The four ribs are an outer intermediate rib 13 sandwiched between the center main groove 10 and the outer shoulder main groove 11, an inner intermediate rib 14 sandwiched between the center main groove 10 and the inner shoulder main groove 12, an outer shoulder rib 15 between the outer shoulder main groove 11 and the ground contact edge on the outer side of the vehicle, and an inner shoulder rib 16 between the inner shoulder main groove 12 and the ground contact edge on the inner side of the vehicle. The ground contact edge refers to the axial end of the ground contact surface when the pneumatic tire 1 touches the ground.

[0018] The outer intermediate rib 13 is provided with a first sipe 20 extending at an angle with respect to the tire axial direction. The first sipe 20 opens into both the center main groove 10 and the outer shoulder main groove 11. The first sipe 20 is slightly curved.

[0019] The first sipes 20 have a width of 0.6 mm to 1.2 mm (preferably 0.6 mm to 1.0 mm) and usually close when the tire contacts the ground. The first sipes 20 have a depth of 50% to 100% (preferably 75% to 90%) of the depth of the center main groove 10.

[0020] 5, tapered surfaces 21 and 22 are formed on both opposing walls of the first sipe 20 so as to widen the opening width to the ground contact surface. The tapered surfaces 21 and 22 are provided along the first sipe 20.

[0021] The tapered surfaces 21, 22 have a gradually changing depth along the first sipe 20, becoming deeper as they approach the center main groove 10 (one of the tapered surfaces 21 is shown in Figs. 3 and 4). The depth of the tapered surfaces 21, 22 refers to the length of the tapered surfaces 21, 22 in the depth direction of the first sipe 20. The depth of the tapered surfaces 21, 22 is indicated by D in Fig. 5.

[0022] The axially inner ends of the tapered surfaces 21, 22 reach the center main groove 10. The axially outer ends of the tapered surfaces 21, 22 reach the outer shoulder main groove 11. In other words, the tapered surfaces 21, 22 are provided over the entire first sipe 20 in the extension direction.

[0023] The tapered surfaces 21, 22 are deepest at the intersection with the center main groove 10. The depth of the tapered surfaces 21, 22 at the intersection with the center main groove 10 is 10% to 30% of the depth of the first sipe 20. The tapered surfaces 21, 22 have a depth and width of 0 mm at the intersection with the outer shoulder main groove 11. Therefore, it can be said that the tapered surfaces 21, 22, which become shallower as they approach the outer shoulder main groove 11, disappear at the intersection with the outer shoulder main groove 11. The width of the tapered surface refers to the length in a direction perpendicular to the extension direction of the sipe when viewed from the outside in the tire radial direction.

[0024] A plurality of first sipes 20 having the above characteristics are arranged at predetermined intervals in the tire circumferential direction on the outer intermediate rib 13. All of the first sipes 20 are provided with the tapered surfaces 21, 22 described above.

[0025] The inner intermediate rib 14 is provided with a second sipe 30 and a pair of notches 34, 35. As the pair of notches, a first notch 34 and a second notch 35 are provided.

[0026] The second sipes 30 extend linearly in a direction inclined relative to the tire axial direction. The second sipes 30 start from the center main groove 10 and incline in the tire circumferential direction in the same direction as the first sipes 20 (downward in FIG. 2 ). The second sipes 30 open into the center main groove 10. Meanwhile, the axially outer ends of the second sipes 30 are closed within the inner intermediate rib 14.

[0027] The second sipes 30 have a width of 0.6 mm to 1.2 mm (preferably 0.6 mm to 1.0 mm) and usually close when the tire contacts the ground. The second sipes 30 have a depth of 50% to 100% (preferably 75% to 90%) of the depth of the center main groove 10.

[0028] Tapered surfaces 31, 32 that widen the opening width to the ground contact surface are formed on both opposing walls of the second sipe 30. The shapes of the tapered surfaces 31, 32 are the same as the shapes of the tapered surfaces 21, 22 of the first sipe 20 shown in Fig. 5. The tapered surfaces 31, 32 are provided along the second sipe 30.

[0029] The depth of the tapered surfaces 31, 32 is 10% or more and 30% or less of the depth of the second sipe 30. The depth of the tapered surfaces 31, 32 refers to the length of the tapered surfaces 31, 32 in the depth direction of the second sipe 30. The depth of the tapered surfaces 31, 32 is constant in the extension direction of the second sipe 30 (one of the tapered surfaces, 31, is shown in FIG. 3). Therefore, the depth of the tapered surfaces 31, 32 is the same at any location.

[0030] The axially inner ends of the tapered surfaces 31, 32 reach the center main groove 10. On the other hand, the axially outer ends of the tapered surfaces 31, 32 are axially more inward than the axially outer end of the second sipe 30. The axial length L of the tapered surfaces 31, 32 (see FIG. 2 ) is 30% or more and 90% or less of the axial length of the inner intermediate rib 14.

[0031] The first notch 34 is a short groove that extends in a direction inclined to the tire axial direction and opens only into the center main groove 10. The second notch 35 is a groove that opens only into the inboard shoulder main groove 12. The second notch 35 has a bend 36, and a closed side portion 37 on the axially inner side of the bend 36 extends in the same direction as the first notch 34.

[0032] 4, the first notch 34 becomes deeper as it approaches the end opening to the center main groove 10. Also, the second notch 35 becomes deeper as it approaches the end opening to the inboard shoulder main groove 12.

[0033] 2, the second sipes 30 and pairs of notches 34, 35 each having the above characteristics are alternately arranged in the tire circumferential direction on the inner intermediate rib 14. All of the second sipes 30 are provided with the tapered surfaces 31, 32 described above.

[0034] A plurality of first lateral grooves 40 extending in the tire axial direction are arranged at a predetermined interval in the tire circumferential direction in the outer shoulder rib 15. A plurality of second lateral grooves 41 extending in the tire axial direction and a plurality of third sipes 42 extending in the tire axial direction are arranged alternately in the inner shoulder rib 16. Axial inner ends of the second lateral grooves 41 and the inner shoulder main groove 12 are connected by a connecting sipe 43.

[0035] The third sipes 42 and the connecting sipes 43 have the same width as the first sipes 20 and the second sipes 30. In addition, the first lateral grooves 40 and the second lateral grooves 41 are wider than the first sipes 20 and the second sipes 30.

[0036] Additionally, the ground contact area of ​​the outer intermediate rib 13 and the outer shoulder rib 15 is larger than that of the inner intermediate rib 14 and the inner shoulder rib 16. The ground contact area here refers to the area per pitch of the tread pattern on the tire surface excluding sipes, tapered surfaces, and grooves.

[0037] Next, the effect of this embodiment will be described. As described above, the outer intermediate rib 13, which is on the outer side of the vehicle when the tire is mounted on the vehicle, is provided with a plurality of first sipes 20, and the opposing walls of the first sipes 20 are provided with tapered surfaces 21, 22 that widen the opening width to the ground contact surface. Therefore, the ground contact length (the length of the ground contact surface in the tire circumferential direction) of the outer intermediate rib 13 is long, and the concentration of ground contact pressure at the opening end of the first sipe 20 on the ground contact surface is unlikely to occur, and the ground contact property of the outer intermediate rib 13 is good.

[0038] The first sipe 20 opens into the center main groove 10, and the tapered surfaces 21, 22 reach the center main groove 10, but the tapered surfaces 21, 22 become deeper as they approach the center main groove 10 and shallower as they approach the outer shoulder main groove 11. Therefore, the rigidity of the portion of the outer intermediate rib 13 that faces the outer side of the vehicle is high, and the steering stability of the pneumatic tire is good.

[0039] In addition, the axial length of the first sipe 20 and the tapered surfaces 21, 22 is the same as the axial length of the outer intermediate rib 13, and the first sipe 20 and the tapered surfaces 21, 22 are provided over the entire outer intermediate rib 13 in the axial direction. Therefore, unlike a case where the tapered surfaces 21, 22 are provided only on the inner side of the outer intermediate rib 13, no extreme difference in rigidity occurs between the inner side and outer side of the outer intermediate rib 13. This results in effects such as suppression of uneven wear.

[0040] In addition, the depth of the tapered surfaces 21, 22 and the width when viewed from the outside in the tire radial direction become 0 at the vehicle outer end of the outer intermediate rib 13 (in other words, the tapered surfaces 21, 22 terminate at the vehicle outer end of the outer intermediate rib 13). Therefore, when the pneumatic tire 1 touches the ground, the first sipe 20 closes completely at the vehicle outer end, and the rigidity of the portion of the outer intermediate rib 13 that is on the vehicle outer side becomes high.

[0041] In addition, since the first sipes 20 open into the center main groove 10 and the tapered surfaces 21, 22 reach the center main groove 10, water that has entered between the road surface and the tread surface near the axial center of the tire can move into the center main groove 10 and between the road surface and the tapered surfaces 21, 22. This provides good drainage.

[0042] In addition, the inner intermediate rib 14 is also provided with a second sipe 30, and since the second sipe 30 has tapered surfaces 31, 32, the contact length of the inner intermediate rib 14 is long and concentration of ground pressure on the open end of the contact surface of the second sipe 30 is unlikely to occur, resulting in good ground contact performance of the inner intermediate rib 14.

[0043] In addition, the ground contact area of ​​the outer intermediate rib 13 and the outer shoulder rib 15 is larger than the ground contact area of ​​the inner intermediate rib 14 and the inner shoulder rib 16, so that the steering stability of the pneumatic tire 1 is good.

[0044] The above embodiment is merely an example, and various modifications are possible to the above embodiment. For example, the center line of the center main groove 10 may be slightly offset from the tire center line in one axial direction of the tire (for example, a distance within three times the width of the center main groove 10). In addition, the outer shoulder rib 15 and the inner shoulder rib 16 may be provided with sub-grooves that are narrower than the main grooves 10, 11, and 12 and extend in the tire circumferential direction. In addition, four or more main grooves may be provided. [Explanation of symbols]

[0045] C...tire centerline, 1...pneumatic tire, 2...carcass ply, 2a...turned-up portion, 3...rubber chafer, 4...belt, 5...belt reinforcing layer, 6...tread rubber, 7...sidewall rubber, 9...bead portion, 9a...bead core, 9b...bead filler, 10...center main groove, 11...outer shoulder main groove, 12...inner shoulder main groove, 13...outer intermediate rib, 14...inner intermediate rib, 15...outer shoulder rib, 16...inner shoulder rib, 20...first sipe, 21...tapered surface, 22...tapered surface, 30...second sipe, 31...tapered surface, 32...tapered surface, 34...first notch, 35...second notch, 36...bend, 37...occluded side portion, 40...first lateral groove, 41...second lateral groove, 42...third sipe, 43...connecting sipe

Claims

1. A pneumatic tire having a tread including at least one center main groove at the center in the tire axial direction and shoulder main grooves on both sides of the center main groove as main grooves extending in the tire circumferential direction, two intermediate ribs extending in the tire circumferential direction and sandwiched between the center main groove and the shoulder main groove, and each of the intermediate ribs having a plurality of sipes, A tapered surface is formed on both opposing walls of the sipe in the outer intermediate rib, which is the intermediate rib that is on the outer side of the vehicle when the sipe is installed on the vehicle, to widen the opening width to the ground contact surface, and the tapered surface is formed so as to become deeper as it approaches the center main groove, In the outer intermediate rib, the sipe opens into the center main groove, and the tapered surface reaches the center main groove, A tapered surface is formed on both opposing walls of the sipe in the inner intermediate rib, which is the intermediate rib that is on the inside of the vehicle when the sipe is installed on the vehicle, to widen the opening width to the ground contact surface, In the inner intermediate rib, the sipe and the tapered surface reach only the center main groove and are closed within the inner intermediate rib, and the depth of the tapered surface is constant in the extension direction of the sipe. A pneumatic tire characterized by:

2. A pneumatic tire as described in claim 1, wherein, in the outer intermediate rib, the axial length of the sipe and the axial length of the tapered surface are the same as the axial length of the outer intermediate rib.

3. A pneumatic tire as described in claim 2, wherein, in the outer intermediate rib, the tapered surface terminates at an end portion of the outer intermediate rib opposite the center main groove.

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