Pneumatic tire

Abstract

To provide a pneumatic tire with good drainage performance.SOLUTION: A pneumatic tire 1 is provided with a center main groove 10, shoulder main grooves 11 and 12, and two 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 ribs 13 and 14 are provided with a plurality of sipes 20 and 30. On both opposing walls of the sipes 20 and 30, tapered surfaces 21, 22, 31, and 32 expanding opening width to a grounding surface are formed. The tapered surfaces 21, 22, 31, and 32 have fixed depth in extending directions of the sipes 20 and 30. The sipes 20 and 30 open to the center main groove 10, and the tapered surfaces 21, 22, 31, and 32 reach the center main groove 10.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to pneumatic tires.

Background Art

[0002] As a pneumatic tire mounted on a minivan or the like, a pneumatic tire is known in which three main grooves extending in the tire circumferential direction are provided, and ribs are formed on both sides in the tire axial direction, each sandwiched between two main grooves. There is also known a pneumatic tire in which a plurality of sipes extending in the tire axial direction are provided on these ribs (see, for example, Patent Document 1). The presence of sipes on the ribs improves the frictional force, and the wet performance of the pneumatic tire and the like becomes excellent.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, water that has entered between the road surface and a portion near the center in the tire axial direction of the tread surface of the pneumatic tire is difficult to escape to the outside, which causes the hydroplaning phenomenon. Even if there are sipes on the ribs as described above, the sipes are narrow in width and close when in contact with the ground, so they do not contribute much to drainage.

[0005] Therefore, an object of the present invention is to provide a pneumatic tire having good drainage performance.

Means for Solving the Problems

[0006] The pneumatic tire of the embodiment has, in the tread, at least one center main groove extending in the tire circumferential direction at the center in the tire axial direction, and shoulder main grooves on both sides adjacent to the center main groove, and two ribs extending in the tire circumferential direction are provided between the center main groove and the shoulder main grooves, and a plurality of sipes are provided on each of the two ribs. In the pneumatic tire, In each of the two ribs, Tapered surfaces for widening the opening width to the ground surface are formed on both opposing walls of the sipe, and the tapered surfaces have a constant depth in the extending direction of the sipe. when the tire is mounted on a vehicle, the side that faces the outside of the vehicle In the rib, the sipe opens to both the center main groove and the shoulder main groove, and the tapered surface reaches the center main groove and reaches the shoulder main groove. is not provided with notches, and a pair of notches are provided in the rib on the side that faces the inside of the vehicle when the tire is mounted on the vehicle. The pair of notches includes a first notch that is a groove opening only into the center main groove and a second notch that is a groove opening only into the shoulder main groove. In the rib on the side that faces the inside of the vehicle when the tire is mounted on the vehicle, the sipes and the pair of notches are alternately arranged in the tire circumferential direction. In the rib on the side that faces the outside of the vehicle when the tire is mounted on the vehicle, the pair of notches are not provided, and a plurality of the sipes are provided at predetermined intervals in the tire circumferential direction It is characterized by this.

Advantages of the Invention

[0007] Since the pneumatic tire of the embodiment has the above characteristics, it has good drainage performance.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0009] First, the overall structure of the pneumatic tire 1 of the present embodiment will be described with reference to FIG. 1. Note that only half of the tire in the tire axial direction is shown in FIG. 1, and the actual pneumatic tire 1 is symmetric about the tire center line C. The vertical direction in FIG. 1 is the tire radial direction, the horizontal direction is the tire axial direction, and the direction perpendicular to the paper surface is the tire circumferential direction.

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

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

[0012] Also, one or more belts 4 are provided on the outer side in the tire radial direction of the carcass ply 2, and a belt reinforcing layer 5 is provided on the outer side in the tire radial direction of the belt 4. The belt 4 is a member formed by covering a large number of steel cords with rubber. The belt reinforcing layer 5 is a member formed by covering a large number of cords made of organic fiber with rubber. A tread rubber 6 is provided on the outer side in the tire radial direction of the belt reinforcing layer 5. A large number of grooves are provided in the tread rubber 6 to form a tread pattern.

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

[0014] In addition to these members, members such as an under-belt pad are provided in the pneumatic tire 1 as required.

[0015] Next, the tread pattern of the pneumatic tire 1 will be described with reference to FIGS. 2 to 5. The mounting direction of the pneumatic tire 1 on the vehicle is determined. The mounting direction on the vehicle is indicated by symbols or the like on the tire surface. In FIGS. 2 to 4, the left side is the outside of the vehicle when mounted on the vehicle, and the right side is the inside of the vehicle when mounted on the vehicle.

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

[0017] These main grooves 10, 11, and 12 are partitioned to form four ribs. A rib is a land that extends 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 end on the outer side of the vehicle, and an inner shoulder rib 16 between the inner shoulder main groove 12 and the ground contact end on the inner side of the vehicle. Note that the ground contact end is the tire axial direction end of the ground contact surface when the pneumatic tire 1 contacts the ground.

[0018] The outer intermediate rib 13 is provided with a first sipe 20 that extends obliquely with respect to the tire axial direction. The first sipe 20 opens to both the center main groove 10 and the outer shoulder main groove 11. Also, the first sipe 20 is slightly curved.

[0019] The first sipe 20 has a width of 0.6 mm or more and 1.2 mm or less (preferably 0.6 mm or more and 1.0 mm or less), and usually closes when contacting the ground. Also, the first sipe 20 has a depth of 50% or more and 100% or less (preferably 75% or more and 90% or less) of the depth of the center main groove 10.

[0020] As shown in FIG. 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 depth of the tapered surfaces 21 and 22 is 10% or more and 30% or less of the depth of the first sipe 20. The depth of the tapered surfaces 21 and 22 is the length of the tapered surfaces 21 and 22 in the depth direction of the first sipe 20, that is, the length indicated by D in FIG. 5. As shown in FIGS. 3 and 4, the depth of the tapered surfaces 21 and 22 is constant in the extension direction of the first sipe 20 (note that only one tapered surface 21 is shown in FIGS. 3 and 4, but the other tapered surface 22 also has a constant depth like the tapered surface 21 in FIGS. 3 and 4). Therefore, the depth of the tapered surfaces 21 and 22 is the same at any location in the extension direction of the first sipe 20.

[0022] As shown in Fig. 2, the inner ends of the tapered surfaces 21 and 22 in the tire axial direction reach the center main groove 10. On the other hand, the outer ends of the tapered surfaces 21 and 22 in the tire axial direction are within the outer intermediate rib 13. Therefore, the outer portion of the first sipe 20 in the tire axial direction is a non-tapered portion 23 where the tapered surfaces 21 and 22 do not exist. The length L1 (see Fig. 2) of the tapered surfaces 21 and 22 in the tire axial direction is 30% or more and 90% or less of the length of the outer intermediate rib 13 in the tire axial direction.

[0023] As shown in Fig. 2, a plurality of first sipers 20 having the above characteristics are arranged in the tire circumferential direction with a predetermined interval in the outer intermediate rib 13. The above-mentioned tapered surfaces 21 and 22 are provided on all the first sipers 20.

[0024] On the other hand, the inner intermediate rib 14 is provided with a second sipe 30 and a pair of notches 34 and 35. As the pair of notches, a first notch 34 and a second notch 35 are provided.

[0025] The second sipe 30 extends linearly in a direction inclined with respect to the tire axial direction. Also, the second sipe 30 is inclined in the same direction (downward in Fig. 2) as the first sipe 20 in the tire circumferential direction starting from the center main groove 10. The second sipe 30 opens into the center main groove 10. On the other hand, the outer end of the second sipe 30 in the tire axial direction is closed within the inner intermediate rib 14.

[0026] The second sipe 30 has a width of 0.6 mm or more and 1.2 mm or less (preferably 0.6 mm or more and 1.0 mm or less) and is usually closed when in contact with the ground. Also, the depth of the second sipe 30 is 50% or more and 100% or less (preferably 75% or more and 90% or less) of the depth of the center main groove 10.

[0027] On both opposing walls of the second sipe 30, tapered surfaces 31, 32 that widen the opening width to the ground plane are formed. 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.

[0028] 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 (only one tapered surface 31 is shown in FIG. 3). Therefore, the depth of the tapered surfaces 31, 32 is the same at any location in the extension direction of the second sipe 30.

[0029] The inner ends of the tapered surfaces 31, 32 in the tire axis direction reach the center main groove 10. On the other hand, the outer ends of the tapered surfaces 31, 32 in the tire axis direction are located more inward in the tire axis direction than the outer ends of the second sipe 30 in the tire axis direction. The length L2 (see FIG. 2) of the tapered surfaces 31, 32 in the tire axis direction is 30% or more and 90% or less of the length of the inner intermediate rib 14 in the tire axis direction.

[0030] The first notch 34 is a short groove that extends in a direction inclined in the tire axis direction and opens only into the center main groove 10. The second notch 35 is a groove that opens only into the inner shoulder main groove 12. The second notch 35 has a bend 36, and the closed side portion 37 on the inner side of the bend 36 in the tire axis direction extends in the same direction as the first notch 34.

[0031] As shown in FIG. 4, the first notch 34 becomes deeper as it approaches the opening end to the center main groove 10. Also, as shown in FIG. 4, the second notch 35 becomes deeper as it approaches the opening end to the inner shoulder main groove 12.

[0032] As shown in FIG. 2, on the inner intermediate rib 14, the second sipe 30 having the above characteristics and a pair of notches 34, 35 are alternately arranged in the tire circumferential direction. The above-mentioned tapered surfaces 31, 32 are provided on all the second sipes 30.

[0033] In addition, a plurality of first transverse grooves 40 extending in the tire axial direction are arranged on the outer shoulder rib 15 at predetermined intervals in the tire circumferential direction. Further, a plurality of second transverse grooves 41 extending in the tire axial direction and a plurality of third sipes 42 extending in the tire axial direction are alternately arranged on the inner shoulder rib 16. A connecting sipe 43 connects the inner end in the tire axial direction of the second transverse groove 41 and the inner shoulder main groove 12.

[0034] The third sipe 42 and the connecting sipe 43 have the same width as the first sipe 20 and the second sipe 30. Further, the first transverse groove 40 and the second transverse groove 41 are wider than the first sipe 20 and the second sipe 30.

[0035] Next, the effects of the present embodiment will be described. As described above, the first sipe 20 is provided on the outer mediate rib 13, the second sipe 30 is provided on the inner mediate rib 14, and tapered surfaces 21, 22, 31, 32 for widening the opening width to the ground surface are provided on both opposing walls of the sipes 20, 30. Then, the sipes 20, 30 open into the center main groove 10, and the tapered surfaces 21, 22, 31, 32 reach the center main groove 10.

[0036] Therefore, the water that has entered between the road surface and the portion near the center in the tire axial direction of the pneumatic tire 1 can not only enter the center main groove 10, but also flow into the space between the center main groove 10 and the road surface and the tapered surfaces 21, 22, 31, 32. Thereby, the drainage performance is improved, so that it is possible to prevent the occurrence of the hydroplaning phenomenon caused by the water between the road surface and the ground contact surface of the pneumatic tire 1.

[0037] Here, since the depths of the tapered surfaces 21, 22, 31, 32 are constant in the extending direction of the sipes 20, 30, the space between the road surface and the tapered surfaces 21, 22, 31, 32 is wide and the drainage performance is improved.

[0038] In addition, since the taper surfaces 21, 22, 31, and 32 are provided on the sipe 20, 30, the ground pressure applied to the edge of the open end to the ground surface of the sipe 20, 30 can be dispersed as compared with the case where the taper surfaces 21, 22, 31, and 32 are not present. Therefore, the ground pressure distribution of the outer intermediate rib 13 and the inner intermediate rib 14 can be made uniform, and uneven wear can be prevented.

[0039] In addition, since the length of each of the taper surfaces 21, 22, 31, and 32 in the tire axial direction is 30% or more and 90% or less of each of the intermediate ribs 13, 14, sufficient drainage performance is ensured, and the rigidity of the portions outside the intermediate ribs 13, 14 in the tire axial direction is ensured.

[0040] The above embodiments are merely examples, and various modifications can be made to the above embodiments. For example, the center line of the center main groove 10 may be slightly shifted (for example, a distance within three times the width of the center main groove 10) in one direction in the tire axial direction from the tire center line. Further, 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, 12 and extend in the tire circumferential direction. Further, four or more main grooves may be provided.

Description of Reference Numerals

[0041] C… Tire center line, 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… Taper surface, 22… Taper surface, 23… Non-tapered portion, 30… Second sipe, 31… Taper surface, 32… Taper surface, 34… First notch, 35… Second notch, 36… Bend, 37… Closed side portion, 40… First transverse groove, 41… Second transverse groove, 42… Third sipe, 43… Connecting sipe

Claims

1. In a pneumatic tire having, in a tread, at least one center main groove extending in the tire circumferential direction at the center in the tire axial direction and shoulder main grooves on both sides adjacent to the center main groove, and having two ribs extending in the tire circumferential direction and sandwiched between the center main groove and the shoulder main grooves, and a plurality of sipes provided in each of the two ribs, in each of the two ribs, tapered surfaces for widening the opening width to the ground surface are formed on both opposing walls of the sipes, and the tapered surfaces have a constant depth in the extending direction of the sipes, in the rib on the vehicle outer side when the tire is mounted on a vehicle, the sipes open to both the center main groove and the shoulder main groove, and the tapered surfaces reach the center main groove but do not reach the shoulder main groove, a pair of notches are provided in the rib on the vehicle inner side when the tire is mounted on a vehicle, and the pair of notches consists of a first notch which is a groove opening only to the center main groove and a second notch which is a groove opening only to the shoulder main groove, in the rib on the vehicle inner side when the tire is mounted on a vehicle, the sipes and the pair of notches are alternately arranged in the tire circumferential direction, in the rib on the vehicle outer side when the tire is mounted on a vehicle, the pair of notches is not provided, and a plurality of the sipes are provided at predetermined intervals in the tire circumferential direction A pneumatic tire, characterized in that.

2. The pneumatic tire according to claim 1, wherein the axial length of the tapered surface in the tire axial direction is 30 to 90% of the axial length of the rib on which the tapered surface is provided.

Images