tire

Abstract

This tire provides excellent snow and wet performance while suppressing a decline in dry performance. [Solution] The tire 10 has a tread surface 14 comprising two circumferential main grooves 16, a plurality of V-shaped grooves 18 arranged inside the tire width direction of the two circumferential main grooves 16 and spaced apart in the tire circumferential direction, and a plurality of lug grooves 26 each provided outside the tire width direction of the two circumferential main grooves 16 and spaced apart in the tire circumferential direction. The plurality of V-shaped grooves 18 and the plurality of lug grooves 26 are connected via the two circumferential main grooves 16. The two circumferential main grooves 16 have a plurality of main groove portions 48 sandwiched in the tire circumferential direction by a plurality of adjacent V-shaped grooves 18. The plurality of main groove portions 48 are connected in the tire circumferential direction via the plurality of V-shaped grooves 18 and the plurality of lug grooves 26. At least a portion of the main groove portion 48 has a raised bottom portion 50 on the treading side in the tire circumferential direction. The groove depth Dr in the raised bottom portion 50 is shallower than the groove depth Dv of the plurality of V-shaped grooves 18 and the plurality of lug grooves 26.

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] In addition to snow performance, winter tires require high wet performance. From this perspective, tires having a pattern in which a plurality of V-shaped grooves are arranged in the tire circumferential direction are known (for example, Patent Document 1). The tire described in Patent Document 1 includes a pair of V-shaped transverse grooves adjacent to each other in the tire circumferential direction, a circumferential groove arranged in the shoulder region, and a communicating transverse groove. The circumferential groove is arranged in the shoulder region and extends in the tire circumferential direction to connect to the V-shaped transverse groove and the communicating transverse groove.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Although tires with a large groove area are excellent in snow performance and wet performance, the block rigidity may decrease and the dry performance may deteriorate.

[0005] An object of the present invention is to provide a tire that is excellent in snow performance and wet performance while suppressing a decrease in dry performance.

Means for Solving the Problems

[0006] A tire according to one aspect of the present invention is as follows.

[0007] The tread surface is provided with two circumferential main grooves, a plurality of V-shaped grooves arranged inside the two circumferential main grooves in the tire width direction and spaced apart in the tire circumferential direction, and a plurality of lug grooves provided outside the two circumferential main grooves in the tire width direction and spaced apart in the tire circumferential direction, and the plurality of V-shaped grooves and the plurality of lug grooves are connected via the two circumferential main grooves. The two circumferential main grooves have multiple main groove sections sandwiched in the circumferential direction of the tire by the multiple adjacent V-shaped grooves. The plurality of main grooves are connected in the circumferential direction of the tire via the plurality of V-shaped grooves and the plurality of lug grooves. At least a portion of the main groove has a raised bottom on the side that is pressed in the circumferential direction of the tire. A tire in which the groove depth in the raised section is shallower than the groove depth of the plurality of V-shaped grooves and the plurality of lug grooves. [Effects of the Invention]

[0008] The tire of the present invention offers excellent snow and wet performance while suppressing a decrease in dry performance. [Brief explanation of the drawing]

[0009] [Figure 1] This is a partial plan view of the tire according to this embodiment. [Figure 2] This is an enlarged plan view of section II-II in Figure 1. [Figure 3] This is a partially enlarged cross-sectional view along line III-III in Figure 2. [Figure 4] This is a partially enlarged cross-sectional view along the line III-III in Figure 2 relating to a modified example (1) of the tire of this embodiment. [Figure 5] This is a partially enlarged cross-sectional view along the line III-III in Figure 2 relating to a modified example (2) of the tire of this embodiment. [Figure 6] This is a partially enlarged cross-sectional view along the line III-III in Figure 2 relating to a modified example (3) of the tire of this embodiment. [Modes for carrying out the invention]

[0010] Embodiments of the present invention relate to the following aspects.

[0011] [Aspect 1] The tread surface includes two circumferential main grooves, a plurality of V-shaped grooves arranged inside the two circumferential main grooves in the tire width direction and spaced apart in the tire circumferential direction, and a plurality of lug grooves provided outside the two circumferential main grooves in the tire width direction and spaced apart in the tire circumferential direction. The plurality of V-shaped grooves and the plurality of lug grooves are connected via the two circumferential main grooves. The two circumferential main grooves have a plurality of main groove portions sandwiched in the tire circumferential direction by the adjacent plurality of V-shaped grooves. The plurality of main groove portions are connected in the tire circumferential direction via the plurality of V-shaped grooves and the plurality of lug grooves. At least a part of the main groove portion has a bottom-raising portion on the indentation side in the tire circumferential direction. The groove depth at the bottom-raising portion is shallower than the groove depths of the plurality of V-shaped grooves and the plurality of lug grooves.

[0012] [Aspect 2] The tire according to Aspect 1, wherein the main groove portion provided with the bottom-raising portion has an increasing groove depth from the indentation side to the kicking-out side in the tire circumferential direction.

[0013] [Aspect 3] The tire according to Aspect 1 or 2, wherein the groove width Wm of the two circumferential main grooves is 3 mm or more.

[0014] [Aspect 4] The tire according to any one of Aspects 1 to 3, wherein the groove depth Dr of the main groove portion at the bottom-raising portion is 20% or more and 70% or less of the groove depth Dv of the plurality of V-shaped grooves.

[0015] [Aspect 5] The tire according to any one of Aspects 1 to 4, wherein the tire circumferential length Lr of the bottom-raising portion is 30% or more of the tire circumferential length Lm of the main groove portion.

[0016] [Aspect 6] In the tire according to any one of Aspects 1 to 5, the tire circumferential direction length Lh of the maximum height portion of the bottom raising portion is 30% or more and 60% or less of the tire circumferential direction length Lr of the bottom raising portion.

[0017] [Aspect 7] The tire according to any one of Aspects 1 to 6, wherein the bottom raising portion has a stepped portion with different groove depths in a stepped manner.

[0018] (Definition) The tire radial direction means the direction perpendicular to the tire rotation axis. The tire radial direction inner side means the side facing the tire rotation axis in the tire radial direction, and the tire radial direction outer side means the side away from the tire rotation axis in the tire radial direction. The tire circumferential direction means the circumferential direction with the tire rotation axis as the central axis. The tire width direction means the direction parallel to the tire rotation axis. The tire width direction inner side means the side facing the tire equatorial plane (tire equatorial plane) in the tire width direction, and the tire width direction outer side means the side away from the tire equatorial plane in the tire width direction. The tire equatorial plane means a plane that is perpendicular to the tire rotation axis and passes through the center of the tire width. "Along" a certain reference includes following the direction within a range of less than ±20°, less than ±10°, or less than ±5° with respect to a certain reference. "Center" includes the midpoint where the distances from two certain points are equal, and the range within ±10% of the distance between the two points from the midpoint. A sipe is a cut formed in the land portion and generally has a groove width of less than 1.5 [mm]. The groove width is measured as the maximum value of the distance between the opposing groove walls of the groove opening on the tread surface in a non-loaded state where the tire is mounted on a standard rim and filled with a standard internal pressure. In the case of a configuration having a notch or chamfer at the groove opening, the groove width is taken as the value measured with the intersection of the extension line of the tread surface and the extension line of the groove wall in a cross-sectional view parallel to the groove width direction and the groove depth direction as an end point. Groove depth is measured as the maximum distance from the tread surface to the bottom of the groove when the tire is mounted on a standard rim, filled to the standard internal pressure, and under no load. If the groove in question has partial irregularities or sipes at the bottom of the groove, the groove depth shall be the value measured excluding these irregularities or sipes. The contact end is the maximum position in the tire width direction at the contact surface between the tire and the flat plate when the tire is mounted on a regular rim, subjected to regular internal pressure, and placed perpendicular to the flat plate in a stationary state, with a load corresponding to the regular load (80% of the maximum load capacity) applied. The length along the tread surface in the tire width direction between the two contact points is called the contact width. The length along the tread surface in the tire width direction from the tire equator to one contact point is sometimes called the 1 / 2 contact width.

[0019] In the following explanation, "standard rim" refers to the "applicable rim" as defined by JATMA, the "Design Rim" as defined by TRA, or the "Measuring Rim" as defined by ETRTO.

[0020] Similarly, in the following explanation, "normal internal pressure" refers to the "maximum air pressure" specified by JATMA, the maximum value listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or "INFLATION PRESSURES" specified by ETRTO. Furthermore, "normal load" refers to the "maximum load capacity" specified by JATMA, the maximum value listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or "LOAD CAPACITY" specified by ETRTO.

[0021] (Tire configuration) Embodiments of the present invention will now be described with reference to the drawings. Figure 1 is a plan view of the tire 10 according to this embodiment, seen from the outside in the radial direction of the tire, showing the portions on both sides in the tire width direction with reference to the tire equatorial plane CP. In this figure, the tire portion is shown in a state where it is mounted on a regular rim and subjected to regular internal pressure, and in an unloaded state.

[0022] The tire 10 of this embodiment, although not shown in its entirety, has a meridional cross-sectional shape similar to that of a conventional pneumatic tire. That is, in a meridional cross-sectional view of the tire 10, the tire 10 of this embodiment has a bead portion, a sidewall portion, a shoulder portion, and a tread portion 12 extending from the inside to the outside in the radial direction of the tire. The tire 10 also comprises a carcass layer and a belt layer and optionally a belt cover layer. In a meridional cross-sectional view of the tire, the carcass layer extends from the tread portion 12 to the bead portions on both sides and is wound around a pair of bead cores. The belt layer and belt cover layer are located radially outward from the carcass layer.

[0023] The rotation direction of the tire 10 is specified. The tire 10 is equipped with a rotation direction indicator (not shown) that indicates the tire rotation direction. The tire rotation direction refers to the rotation direction that is most frequently used when the tire is in use, for example, the rotation direction when the vehicle is moving forward. Based on the indication of this rotation direction indicator, the side of the block that makes contact first (the so-called toe side) and the side that makes contact last (the so-called heel side) are defined (see Figure 1). The toe side is the side that makes contact first when the tire rolls in the specified rotation direction, and the heel side is the opposite side to the toe side. The rotation direction indicator is, for example, made by marks or indentations on the sidewall of the tire 10. In Figure 1, the lower side is the toe side. In Figure 1, the upper side is the heel side.

[0024] The tread portion 12 is formed of rubber material (tread rubber). The tread portion 12 has a tread surface 14 that contacts the road surface when the vehicle is running. The tread surface 14 is annular in shape with respect to the rotation axis of the tire 10, has a predetermined length in the tire width direction, and is continuous in the tire circumferential direction. A tread pattern of a predetermined pattern is engraved on the tread surface 14. The tread pattern is asymmetrical with respect to the tire equatorial plane CP between the two sides in the tire width direction of the tire equatorial plane CP. In Figure 1, the symbol EL indicates the contact edge line (a line connecting continuous contact edges E in the tire circumferential direction).

[0025] The tire 10 has a tread surface 14 equipped with two circumferential main grooves 16, a plurality of V-shaped grooves 18, and a plurality of lug grooves 26.

[0026] The tire 10 is provided with a first circumferential main groove 16L on one side in the tire width direction and a second circumferential main groove 16R on the other side in the tire width direction, relative to the tire equatorial plane CP. The first circumferential main groove 16L and the second circumferential main groove 16R extend in a direction along the tire circumferential direction. That is, the first circumferential main groove 16L and the second circumferential main groove 16R are formed such that an imaginary line parallel to the tire circumferential direction can pass through the groove. Therefore, at least a portion of the water that flows into the first circumferential main groove 16L and the second circumferential main groove 16R can move linearly in the tire circumferential direction through the first circumferential main groove 16L and the second circumferential main groove 16R. In the following description, unless otherwise distinguished, the first circumferential main groove 16L and the second circumferential main groove 16R will be referred to as the circumferential main groove 16.

[0027] The circumferential main groove 16 is a circumferential groove having a wear indicator that shows the end of wear. The groove width of the circumferential main groove 16 is preferably 3 mm or more, more preferably 4 mm or more, preferably 9 mm or less, and more preferably 8 mm or less. The groove depth of the circumferential main groove 16 is preferably 7.5 mm or more, more preferably 8.5 mm or more, preferably 12.0 mm or less, and more preferably 10.0 mm or less.

[0028] With the centerlines of the first circumferential main groove 16L and the second circumferential main groove 16R as boundaries, the area in the tire width direction from the first circumferential main groove 16L to the second circumferential main groove 16R is called the center region Ce, and the area outside the first circumferential main groove 16L in the tire width direction and the area outside the second circumferential main groove 16R in the tire width direction are called the shoulder region Sh, respectively.

[0029] Multiple V-shaped grooves 18 are arranged in the center region Ce and spaced apart in the circumferential direction of the tire. Each V-shaped groove 18 has a tip portion 20 that protrudes in a V-shape toward the tread direction, which is one side of the tire's circumferential direction. The tip portion 20 is located near the tire's equatorial plane CP, that is, within a range of 20%, preferably 10%, of the contact width centered on the tire's equatorial plane CP.

[0030] The V-shaped groove 18 extends from the tip portion 20 toward the kick-off side, which is the other side in the circumferential direction of the tire, and is inclined toward both sides in the tire width direction. The V-shaped groove 18 is connected to the first circumferential main groove 16L and the second circumferential main groove 16R, respectively.

[0031] The groove width of the V-shaped groove 18 is preferably 3 mm or more, more preferably 4 mm or more, preferably 9 mm or less, and more preferably 8 mm or less. The groove depth of the circumferential main groove 16 is preferably 7.5 mm or more, more preferably 8.5 mm or more, preferably 12.0 mm or less, and more preferably 10.0 mm or less.

[0032] The center land area 22 of the tire 10 is defined by a first circumferential main groove 16L, a second circumferential main groove 16R, and adjacent V-shaped grooves 18 in the circumferential direction of the tire. Multiple center land areas 22 are arranged in the circumferential direction of the tire, flanking the V-shaped grooves 18. Multiple sipes 24 may be provided in the center land area 22.

[0033] The tire 10 is provided with lug grooves 26 in the shoulder region Sh. The lug grooves 26 have openings connected to the first circumferential main groove 16L and the second circumferential main groove 16R, respectively, which are positioned to overlap in the tire width direction with the openings of the V-shaped grooves 18 connected to the first circumferential main groove 16L and the second circumferential main groove 16R, respectively. Multiple lug grooves 26 are arranged at predetermined intervals in the tire circumferential direction and extend in the direction along the tire width direction, forming a section of the shoulder land area 28. Multiple sipes 24 may be provided in the shoulder land area 28. The lug grooves 26 may be connected to the contact end EL. The groove depth of the lug grooves 26 is the same as the groove depth Dv of the V-shaped grooves 18. In this specification, "the same" does not only mean that the groove depth of the lug grooves 26 and the groove depth Dv are exactly the same, but also includes the case where the groove depth of the lug grooves 26 is 90% or more and 110% or less of the groove depth Dv.

[0034] The tire 10 is equipped with inclined narrow grooves 30, and a first branch groove 32 and a second branch groove 34. The inclined narrow grooves 30, and the first branch groove 32 and the second branch groove 34 are formed in each center land portion 22.

[0035] Multiple inclined narrow grooves 30 are provided between the tire equatorial plane CP and the first circumferential main groove 16L, and between the tire equatorial plane CP and the second circumferential main groove 16R. The groove width of the inclined narrow grooves 30 is smaller than that of the first circumferential main groove 16L and the second circumferential main groove 16R.

[0036] Four inclined grooves 30 are provided in total: two between the tire equatorial plane CP and the first circumferential main groove 16L within one center land area 22, and two between the tire equatorial plane CP and the second circumferential main groove 16R. The inclined grooves 30 are inclined outward in the tire width direction from the push-off side to the push-off side in the tire circumferential direction. Each inclined groove 30 is connected to an adjacent V-shaped groove 18 in the tire circumferential direction.

[0037] The first branch groove 32 and the second branch groove 34 extend from the tip 20 of the V-shaped groove 18 toward the tread direction in the circumferential direction of the tire. The first branch groove 32 extends from the tip 20 toward the tread direction in the circumferential direction of the tire, inclined toward the other side in the tire width direction, and terminates within the center land portion 22. The second branch groove 34 extends from the tip 20 toward the tread direction in the circumferential direction of the tire, inclined toward one side in the tire width direction, and connects to the V-shaped groove 18 adjacent to the tread direction in the circumferential direction of the tire.

[0038] Furthermore, the tire 10 may have a notch 36. The notch 36 is provided between the tip 20 of the V-shaped groove 18 and the inclined narrow groove 30. The notch 36 is on the extension of the second branch groove 34 connected to the kicking side of the V-shaped groove 18, extends toward the center land portion 22 on the stepping side of the V-shaped groove 18, and terminates within the center land portion 22.

[0039] The multiple inclined grooves 30 include substantially straight inclined grooves 38 and curved inclined grooves 40. The straight inclined grooves 38 extend linearly from the V-shaped groove 18 on the push-off side toward the stepping side, inclined outward in the tire width direction, and connect to adjacent V-shaped grooves 18 in the tire circumferential direction.

[0040] The curved inclined narrow groove 40 has an inclined portion 42, a curved portion 44, and a circumferential portion 46. The inclined portion 42 extends linearly from the V-shaped groove 18 on the kicking side toward the footing side, inclined outward in the tire width direction. The curved portion 44 has a shape that is convex outward in the tire width direction and connects the inclined portion 42 and the circumferential portion 46. The circumferential portion 46 extends linearly from the curved portion 44 in a direction along the tire circumferential direction and connects to the adjacent V-shaped groove 18 on the footing side in the tire circumferential direction.

[0041] The tire 10 shown in Figure 1 has a total of two inclined grooves 30, one straight inclined groove 38 and one curved inclined groove 40, located within one center land portion 22, between the tire equatorial plane CP and the first circumferential main groove 16L, and between the tire equatorial plane CP and the second circumferential main groove 16R. The tire 10 has the straight inclined groove 38 and the curved inclined groove 40 in order from the tire equatorial plane CP outward in the tire width direction. That is, the straight inclined groove 38 is located between the tire equatorial plane CP and the curved inclined groove 40, and the curved inclined groove 40 is located between the straight inclined groove 38 and the circumferential main groove 16.

[0042] As shown in Figure 2, the circumferential main groove 16 has a plurality of main groove sections 48. The plurality of main groove sections 48 are grooves that extend in a direction along the tire circumferential direction, separated by V-shaped grooves 18. Each of the plurality of main groove sections 48 is sandwiched in the tire circumferential direction by the plurality of V-shaped grooves 18. The plurality of main groove sections 48 have a raised base section 50. The raised base section 50 is provided on the tread-in side in the tire circumferential direction of the main groove section 48.

[0043] As shown in Figure 3, the main groove 48 has a main base 52 and a raised base 50. The groove depth of the main groove 48 in the raised base 50 is shallower than the groove depth of the main groove 48 in the main base 52. The kicking end of the raised base 50 is connected to the treading end of the main base 52 in the tire circumferential direction. The treading end of the raised base 50 is connected to a V-shaped groove 18 located on the treading side of the main groove 48.

[0044] The raised section 50 has an inclined surface 54 as the bottom surface of the groove and a flat surface 56 as the maximum height section. The inclined surface 54 extends from the tip of the footing side of the main bottom section 52 toward the V-shaped groove 18 and is inclined outward in the radial direction of the tire. The flat surface 56 extends from the tip of the footing side of the inclined surface 54 toward the V-shaped groove 18 in a direction along the tread surface 14. Due to the presence of the inclined surface 54, the groove depth of the main groove section 48 increases from the footing side toward the push-off side.

[0045] The groove depth of the main groove 48 in the main base 52 may be the same as or different from the groove depth Dv of the V-shaped groove 18. The groove depth of the main groove 48 is preferably 7.5 mm or more, more preferably 8.5 mm or more, preferably 12.0 mm or less, and more preferably 10.0 mm or less. The groove depth Dr of the main groove 48 in the raised base 50 is preferably 20% to 70% of the groove depth Dv of the V-shaped groove 18, more preferably 30% to 50%. The groove depth Dr of the main groove 48 in the raised base 50 is the groove depth of the shallowest part of the groove, and in the case of Figure 3, it is the groove depth on the flat surface 56. The deeper the groove depth Dr of the main groove 48 in the raised base 50, the better the drainage and the better the snow column shear force, while the shallower the groove, the better the reduction in block rigidity can be suppressed.

[0046] The tire circumferential length Lr of the raised section 50 (Figure 2) is preferably 30% or more, more preferably 40% or more, preferably 90% or less, and more preferably 70% or less of the tire circumferential length Lm of the main groove section 48. The tire circumferential length Lr of the raised section 50 is the distance between the tip on the kicking side and the tip on the stepping side. The kicking side tip of the raised section 50 is the midpoint of the groove width of the main groove section 48 at the intersection of the inclined surface 54 and the bottom surface of the main bottom section 52. The stepping side tip of the raised section 50 is the midpoint of the groove width of the main groove section 48 at the intersection of the flat surface 56 and the V-shaped groove 18. The tire circumferential length Lr of the raised section 50 shown in Figure 3 is the sum of the lengths of the inclined surface 54 and the flat surface 56.

[0047] If a chamfer is formed between the raised section 50 and the main base 52, in the cross-section shown in Figure 3, the intersection of the extension of the inclined surface 54 and the extension of the bottom surface of the main base 52 shall be the tip of the raised section 50 on the kicking side. The tip of the raised section 50 on the stepping side shall be the intersection with the side wall 19 of the V-shaped groove 18. If a chamfer is formed between the tip of the raised section 50 on the stepping side and the side wall 19 of the V-shaped groove 18, the intersection of the extension of the flat surface 56 of the raised section 50 and the extension of the side wall 19 shall be the tip of the raised section 50 on the stepping side.

[0048] The tire circumferential length Lm of the main groove 48 is the length in the tire circumferential direction between the intersection of the main groove 48 with the side wall 19 of the V-shaped groove 18 on the kicking side and the intersection of the main groove 48 with the side wall 19 of the V-shaped groove 18 on the stepping side. The intersection of the main groove 48 and the side wall 19 of the V-shaped groove 18 is the midpoint of the groove width of the V-shaped groove 18 at the opening of the main groove 48 connected to the V-shaped groove 18. The tire circumferential length of the raised base 50 is such that the longer it is relative to the tire width direction length of the main groove 48, the more the reduction in block rigidity can be suppressed, and the shorter it is, the better the drainage performance.

[0049] The length Lf of the flat surface 56 in the tire circumferential direction is preferably 30% or more, more preferably 40% or more, preferably 60% or less, and more preferably 50% or less of the tire circumferential length Lr of the raised base portion 50. The length Lf of the flat surface 56 in the tire circumferential direction is the distance between the tip on the kicking side and the tip on the stepping side. The tip on the kicking side of the flat surface 56 is the midpoint of the groove width of the main groove portion 48 at the intersection of the inclined surface 54 and the flat surface. As described above, the tip on the stepping side of the flat surface 56 is the midpoint of the groove width of the main groove portion 48 at the intersection of the flat surface 56 and the V-shaped groove 18. If a chamfer is formed between the inclined surface 54 and the flat surface 56, in the cross section in Figure 3, the intersection of the extension of the inclined surface 54 and the extension of the flat surface 56 is the tip on the kicking side of the flat surface 56. The longer the circumferential length Lf of the flat surface 56 is compared to the circumferential length Lr of the raised base 50, the more the reduction in block rigidity can be suppressed, while the shorter the length Lf, the better the drainage performance.

[0050] The tires according to the embodiments described above are obtained through the usual manufacturing processes, namely, the mixing process of tire materials, the processing process of tire materials, the molding process of green tires, the vulcanization process, and the inspection process after vulcanization. When manufacturing the tires of the embodiments, for example, protrusions and recesses corresponding to the tread pattern shown in Figure 1 are formed on the inner wall of the vulcanization mold, and vulcanization is performed using this mold.

[0051] (Mechanism of Action and Effects) The tire 10 has multiple V-shaped grooves 18 and multiple lug grooves 26, which compact snow that enters the grooves on a snowy road surface. When driving force, braking force, or lateral force during turning is applied to the tire 10 in this state, a so-called snow column shear force is generated on the snow in the grooves. Therefore, the tire 10 has excellent snow performance.

[0052] Since the tire 10 has circumferential main grooves 16 that extend in a direction along the tire's circumference, water flows easily in the circumferential direction. In addition, the tire 10 has V-shaped grooves 18 that extend inclined to both sides in the tire width direction from near the tire's equatorial plane CP toward the push-off side, so water flows easily outward in the tire width direction from the tire's equatorial plane CP. Furthermore, since the V-shaped grooves 18 are each connected to the circumferential main grooves 16, water can be easily discharged in the tire's circumferential direction.

[0053] The tire 10 has lug grooves 26 in the shoulder region Sh, which allows water that has flowed from the V-shaped grooves 18 into the circumferential main grooves 16 to flow outward in the tire width direction and be discharged to the outside of the tire 10 from the contact edge. Therefore, the tire 10 has excellent wet performance.

[0054] The main groove section 48 has a raised section 50 on the foot-pressure side, which helps to suppress a decrease in block rigidity of the center foot section 22. Therefore, the tire 10 can suppress a decrease in dry performance.

[0055] As a result, tire 10 offers superior wet and snow performance while suppressing a decline in dry performance.

[0056] The main groove 48 has an increasing groove depth from the foot-stepping side to the kick-off side, making it less likely to obstruct water flow. Furthermore, the raised bottom section 50 increases the surface pressure on the foot-stepping side of the main groove 48. As a result, the main groove 48 can more smoothly drain water that has flowed into it towards the kick-off side.

[0057] The groove width of the circumferential main groove 16 is 3 mm or more, which allows water to flow more reliably in the circumferential direction of the tire. The circumferential main groove 16 has a groove width of 3 mm or more and a raised bottom portion 50, which provides excellent drainage and suppresses a decrease in block rigidity.

[0058] The groove depth Dr of the main groove 48 in the raised bottom section 50 is 20% to 70% of the groove depth Dv of the V-shaped groove 18, thereby providing excellent drainage and suppressing a decrease in block rigidity.

[0059] The circumferential length Lr of the raised section 50 is 30% or more of the circumferential length Lm of the main groove section 48, thereby more reliably suppressing the decrease in block rigidity. The circumferential length Lf of the flat surface 56 of the raised section 50 is 30% to 60% of the circumferential length Lr of the raised section 50, thereby providing excellent drainage and suppressing the decrease in block rigidity.

[0060] The tire 10 has multiple inclined narrow grooves 30 that connect adjacent V-shaped grooves 18 in the circumferential direction of the tire, and a first branch groove 32 and a second branch groove 34 provided at the tip 20. As a result, it has more edge components than conventional tires, and therefore has superior snow performance. Furthermore, because the tire 10 has multiple inclined narrow grooves 30, it has a larger groove area than conventional tires, and therefore has superior drainage performance.

[0061] As described above, tire 10 can improve wet and snow performance compared to conventional tires. The groove area of ​​the inclined narrow grooves 30 is small in proportion to the entire tire because the groove width is sufficiently smaller than that of the circumferential main grooves 16, and therefore has little effect on block rigidity. Thus, although tire 10 has an increased groove area compared to conventional tires by the amount of the inclined narrow grooves 30, the proportion of the inclined narrow grooves 30 in the entire tire is small, so the decrease in block rigidity is limited and the decrease in dry performance can be suppressed.

[0062] Furthermore, the tire 10 can improve its snow performance by having a notch 36, which increases the edge component.

[0063] Since the tire 10 has circumferential main grooves 16 that extend in a direction along the tire's circumference, water flows easily in the circumferential direction. In addition, the tire 10 has V-shaped grooves 18 that extend inclined to both sides in the tire width direction from near the tire's equatorial plane CP toward the push-off side, so water flows easily outward in the tire width direction from the tire's equatorial plane CP. Furthermore, since the V-shaped grooves 18 are each connected to the circumferential main grooves 16, water can be easily discharged in the tire's circumferential direction. Therefore, the tire 10 has excellent drainage properties.

[0064] The tire 10 has multiple inclined narrow grooves 30 that connect adjacent V-shaped grooves 18 in the circumferential direction of the tire, and a first branch groove 32 and a second branch groove 34 provided at the tip 20. As a result, it has more edge components than conventional tires, and therefore has superior snow performance. Furthermore, because the tire 10 has multiple inclined narrow grooves 30, it has a larger groove area than conventional tires, and therefore has superior drainage performance.

[0065] The tire 10 can improve snow performance by increasing the edge component through the provision of multiple inclined grooves 30. Since the groove width of the inclined grooves 30 is sufficiently smaller than the groove width of the circumferential main grooves 16, the proportion of the inclined grooves 30 to the entire tire is small. Therefore, the influence of the inclined grooves 30 on block rigidity is small. Consequently, although the groove area of ​​the tire 10 increases by the amount of the inclined grooves 30 compared to a conventional tire, the proportion of the inclined grooves 30 to the entire tire is small, so the decrease in block rigidity is limited, and the decrease in dry performance can be suppressed.

[0066] The tire 10 has lug grooves 26 in the shoulder area Sh, which allows water that has flowed from the V-shaped grooves 18 into the circumferential main grooves 16 to flow outward in the tire width direction and be discharged to the outside of the tire 10 from the contact edge. Furthermore, the tire 10 has notches 36, which increases the edge component and further improves snow performance.

[0067] The curved and inclined narrow groove 40 has a curved portion 44, which forms an edge in the block that is partitioned by the curved and inclined narrow groove 40. Therefore, the tire 10 has a greater edge component due to the presence of the curved and inclined narrow groove 40, resulting in superior snow performance.

[0068] The bent portion 44 has a shape that is convex outward in the tire width direction, which prevents the surface area of ​​the outermost block 23 (Figure 1) in the tire width direction in the center region Ce, which is partitioned by the bent inclined narrow groove 40 and the main groove in the tire circumferential direction, from becoming too small. Therefore, the tire 10 can improve snow performance while suppressing a decrease in the rigidity of the outermost block in the center region Ce.

[0069] (modified version) The present invention is not limited to the embodiments described above and can be modified as appropriate within the scope of the spirit of the invention. In the above embodiments, the raised portion 50 was described as having an inclined surface 54, but the present invention is not limited to this. For example, the raised portion does not have to have an inclined surface. The raised portion 50A shown in Figure 4 has a wall surface 58 and a flat surface 56. The wall surface 58 extends in a direction substantially perpendicular to the bottom surface 49 of the main groove portion 48, that is, in a direction along the tire diameter direction, and is connected to the flat surface 56 at its outer tip in the tire diameter direction. The raised portion 50A has an edge 60 between the wall surface 58 and the flat surface 56 that extends in a direction along the tire width direction. The tire 10 can obtain snow column shear force by having the edge 60 on the main groove portion 48.

[0070] As shown in Figure 5, the raised section 50B may have stepped sections 62. The stepped sections 62 change the groove depth of the main groove section 48 in a stepped manner. The groove depth of the stepped sections 62 increases in a stepped manner from the stepping side to the kicking side. The raised section 50B may have multiple stepped sections 62, in the case of Figure 5, three. The height of the stepped sections 62, i.e., the length in the tire radial direction, is preferably 1 mm to 4 mm, more preferably 1.5 mm to 3 mm. Each stepped section 62 of the raised section 50B has an edge 60 extending in the direction along the tire width direction. By providing multiple edges 60 in the main groove section 48, the tire 10 can more reliably obtain snow column shear force.

[0071] The present invention has described a case in which the raised portion 50 has a flat surface 56, but the present invention is not limited to this. For example, as shown in Figure 6, the raised portion 50C does not have to have a flat surface 56. The raised portion 50C shown in Figure 6 has only an inclined surface 54. The inclined surface 54 slopes outward in the tire radial direction from the tip of the stepping side of the main base 52 toward the kicking side and is connected to the side wall 19 of the V-shaped groove 18. The maximum height of the raised portion 50C shown in Figure 6 is the tip that is connected to the side wall 19 of the V-shaped groove 18 on the stepping side.

[0072] In the above embodiment, the case in which multiple main grooves 48 have raised bottom portions 50 has been described, but the present invention is not limited to this. That is, some of the multiple main grooves 48 may be main grooves that do not have raised bottom portions 50.

[0073] The main groove 48 provided with the raised base 50 is not limited to cases where the groove depth increases from the foot-in side to the kick-out side in the tire circumferential direction. The main groove 48 provided with the raised base 50 may have a constant groove depth from the foot-in side to the kick-out side in the tire circumferential direction. The main groove 48 provided with the raised base 50 may include a portion where the groove depth gradually decreases from the foot-in side to the kick-out side in the tire circumferential direction. The groove width of the circumferential main groove 16 may be less than 3 mm. The groove depth of the main groove 48 in the raised base 50 may be less than 20% of the groove depth of the plurality of V-shaped grooves 18, or it may be more than 70%. The tire circumferential length of the raised base 50 may be less than 30% of the tire circumferential length of the main groove 48. The tire circumferential length of the maximum height portion of the raised base 50 may be less than 30% of the tire circumferential length of the raised base 50, or it may be more than 60%.

[0074] (Examples) The following examples were evaluated using pneumatic tires. Tires according to Examples 1 to 13, as well as comparative examples, were manufactured with a tire size of 205 / 55R16 91H and having the tread pattern shown in Figure 1 (or a tread pattern similar to the tread pattern shown in Figure 1). The detailed specifications of these tires are shown in Table 1 below.

[0075] In Table 1, the descriptions in each column of the first row are as described in the specification above. In particular, "groove depth Dr" refers to the groove depth of the main groove section having a raised base. When the raised base is formed along the entire length of the main groove section, it is indicated as "constant," and when the groove depth Dr increases from the foot-in side to the kick-off side, it is indicated as "increasing." The column "Dr / Dv × 100 (%)" shows the ratio of the groove depth Dr of the main groove in the raised section to the groove depth Dv of the V-shaped groove. The column "Lr / Lm × 100 (%)" shows the ratio of the circumferential length Lr of the raised section to the circumferential length Lm of the main groove section. The column "Lf / Lr × 100 (%)" shows the ratio of the tire circumferential length Lf of the flat surface to the tire circumferential length Lr of the raised section. In the "Stepped Section" column, if the raised section has the stepped section shown in Figure 5, it is indicated as "Yes". In other words, the raised sections of Examples 2 to 12 have a flat surface and an inclined surface as shown in Figure 3. The raised section of Example 13 has a stepped section as shown in Figure 5.

[0076] The tires created in Examples 1 to 10, as well as the comparative example tires, were mounted on 16 x 6.5J aluminum rims with an air pressure (F / R) of 250kPa / 250kPa. Each test tire was mounted on a front-wheel-drive test vehicle (engine displacement: 1500cc), and the handling stability on compacted snow, wet, and dry surfaces was evaluated according to the following procedure to confirm snow performance, wet performance, and dry performance.

[0077] (Handling stability on compacted snow surfaces) A subjective evaluation was conducted by test drivers when vehicles equipped with each test tire were driven on a test course with a compacted snow surface. Based on these results, an index evaluation was performed using the comparative example as the baseline (100). The evaluation results are shown in Table 1. In this evaluation, a higher index indicates better handling stability on a compacted snow surface.

[0078] (Handling stability on wet surfaces) A subjective evaluation was conducted by test drivers when vehicles equipped with each test tire were driven on a wet road surface (1 mm water film) test course. Based on these results, an index evaluation was performed using the comparative example as the baseline (100). The evaluation results are shown in Table 1. In this evaluation, a higher index indicates better handling stability on wet road surfaces.

[0079] (Handling stability on dry surfaces) A test vehicle was driven on a dry, flat test track at speeds ranging from 10 km / h to 180 km / h. A test driver conducted subjective evaluations of steering performance during lane changes and cornering, as well as stability during straight-line driving. Based on these results, an index evaluation was performed using a comparative example as the baseline (100). The evaluation results are shown in Table 1. A higher index indicates superior handling stability on dry surfaces.

[0080] [Table 1]

[0081] (result) Table 1 shows that in Reference Example 1, the lack of a raised base in the main groove reduced block rigidity, resulting in decreased dry performance. In contrast, in all embodiments, the presence of a raised base in the main groove suppressed the reduction in block rigidity and improved dry performance. In Embodiment 1, the formation of a raised base along the entire length of the main groove reduced snow and wet performance, but this was within an acceptable range. In Embodiments 3 and 4, the groove width of the circumferential main groove was 3 mm or more, which improved wet performance. In Embodiments 5 to 7, the groove depth Dr of the main groove in the raised base was 20% to 70% of the groove depth Dv of the V-shaped groove, which improved wet and dry performance. In Embodiments 8 and 9, the tire circumferential length Lr of the raised base was 30% or more of the tire circumferential length Lm of the main groove, which improved dry performance. Examples 10-12 showed improved wet and dry performance by having the tire circumferential length Lf of the flat surface of the raised section be between 30% and 60% of the tire circumferential length Lr of the raised section. Example 13 showed improved wet performance by having a stepped section in the raised section. [Explanation of Symbols]

[0082] 10 tires 12 Tread section 14 Tread surface 16 Circumferential main groove 16C Centerline of the circumferential main groove 16E Opening of circumferential main groove 16L 1st circumferential main groove 16R 2nd circumferential main groove 18 V-shaped groove 19 Groove wall (V-shaped groove) 20 Tip 22 Center Track and Field Club 24 sipes 26 lug grooves 28 Shoulder Track and Field Club 30 Slanted narrow groove 32. First branch groove 34. Second branching groove 36 Notch 38 Straight inclined narrow groove 40 Bend inclined narrow groove 42 Slope 44. Bending section 46 Circumferential section 48 Main groove 49 Bottom (main groove) 50, 50A, 50B, 50C Raised base 52 Main bottom 54 Slope 56 Flat surface 58 Wall surface 60 Edge 62 Stepped section CP Tire Equatorial Plane Ce Center Area Sh shoulder region Dr. Groove depth (raised bottom section) Dv groove depth (V-shaped groove)

Claims

1. The tread surface is provided with two circumferential main grooves, a plurality of V-shaped grooves arranged inside the two circumferential main grooves in the tire width direction and spaced apart in the tire circumferential direction, and a plurality of lug grooves arranged outside the two circumferential main grooves in the tire width direction and spaced apart in the tire circumferential direction, and the plurality of V-shaped grooves and the plurality of lug grooves are connected via the two circumferential main grooves. The two circumferential main grooves have multiple main groove sections sandwiched in the circumferential direction of the tire by the multiple adjacent V-shaped grooves. The plurality of main grooves are connected in the circumferential direction of the tire via the plurality of V-shaped grooves and the plurality of lug grooves. At least a portion of the main groove has a raised bottom on the side that is pressed in the circumferential direction of the tire. A tire in which the groove depth in the raised section is shallower than the groove depth of the plurality of V-shaped grooves and the plurality of lug grooves.

2. The tire according to claim 1, wherein the main groove portion, on which the raised base portion is provided, has an increasing groove depth from the foot-in side to the kick-out side in the circumferential direction of the tire.

3. The tire according to claim 1, wherein the groove width Wm of the two circumferential main grooves is 3 mm or more.

4. The tire according to claim 1, wherein the groove depth Dr of the main groove in the raised base portion is 20% or more and 70% or less of the groove depth Dv of the plurality of V-shaped grooves.

5. The tire according to claim 1, wherein the circumferential length Lr of the raised base portion is 30% or more of the circumferential length Lm of the main groove portion.

6. The tire according to claim 1, wherein the tire circumferential length Lh of the maximum height portion of the raised base is 30% or more and 60% or less of the tire circumferential length Lr of the raised base.

7. The raised portion has stepped portions in which the groove depths differ in a stepped manner, as described in claim 1.

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