Patent ID: 12187078

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of the present invention will be explained with reference to the drawings.

A tire according to the embodiment is a pneumatic tire, which is provided with right and left pair of bead parts and sidewalls, and a tread provided between both sidewalls so as to connect outer end portions in a radial direction of the right and left sidewalls to each other. An internal configuration of the tire is not particularly limited, and the tire is formed by including, for example, annular bead cores embedded in beads, a radial-structured carcass ply extending in a toroidal shape between the pair of beads, a belt, a tread rubber, and the like provided on an outer side in the tire radial direction of the carcass ply on the tread. In the embodiment, a general tire structure can be adopted except for a tread pattern.

Respective shapes and dimensions in this description are measured in a normal state with no load in which the tire is fitted to a normal rim and a normal internal pressure is filled unless otherwise noted. The normal rim corresponds to the “standard rim” in the JATMA standard, “Design Rim” in the TRA standard, or “Measuring Rim” in the ETRTO standard. The normal internal pressure corresponds to the “maximum air pressure” in the JATMA standard, the “maximum value” described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the TRA standard, or “INFLATION PRESSURE” in the ETRTO standard.

(1) Basic Structure of Tread10

FIG.1is a partial development view of a tread10of the tire according to the embodiment. In the drawing, a symbol CL denotes a tire equatorial plane corresponding to the center in the tire width direction. A symbol W denotes the tire width direction (also referred to as a tire axial direction). An inside in the tire width direction W indicates the side closer to the tire equatorial plane CL. An outside in the tire width direction W indicates the side farther from the tire equatorial plane CL. A symbol C denotes a tire circumferential direction which is a direction on a circumference centered at a tire rotation axis.

The tire shown inFIG.1is a tire in which front and back sides are designated when mounted to a vehicle. That is, a surface facing the outside and a surface facing the inside when mounted to the vehicle are designated. Accordingly, an indication for designating a mounting direction to the vehicle is provided on, for example, a sidewall surface of the tire. The tire is mounted to the vehicle so that a side denoted by a symbol OUT faces the outside (vehicle outside) in a vehicle mounted posture and a side denoted by a symbol IN faces the inside (vehicle inside) in the vehicle mounted posture inFIG.1.

As shown inFIG.1, four main grooves12A,12B,12C, and12D extending in a tire circumferential direction C, lateral grooves14A,14B,14C,14D,14E,14F,14G, and14H extending in the tire width direction W, and blocks16A,16B,16C,16D, and16E are provided on the surface of the tread10.

Specifically, a pair of center main grooves12A,12B and a pair of shoulder main grooves12C,12D are provided on the tread10. The pair of center main grooves12A,12B are arranged on both sides of the tire equatorial plane CL. The pair of shoulder grooves12C,12D are respectively arranged on outer sides in the tire width direction of the pair of center main grooves12A,12B.

In the embodiment, the inside center main groove12A in the vehicle inside IN, the inside shoulder main groove12C in the vehicle inside IN, and the outside shoulder main groove12D in the vehicle outside OUT extend in the tire circumferential direction C in an approximately straight shape, and the outside center main groove12B in the vehicle outside OUT extends while bending zigzag in the tire circumferential direction C.

Note that the inside center main groove12A, the inside shoulder main groove12C, and the outside shoulder main groove12D may be zigzag main grooves, and the outside center main groove12B may be a straight-shaped main groove. That is, the main grooves12A,12B,12C, and12D do not always have to be parallel to the tire circumferential direction C as long as the grooves extend in the tire circumferential direction C and may be grooves extending in the tire circumferential direction C while being inclined.

A center block line18A is provided between the inside center main groove12A and the outside main groove12B. The center block line18A includes a plurality of center blocks16A formed by being divided in the tire circumferential direction C by first center lateral grooves14A. The first center lateral groove14A is a groove extending while being inclined with respect to the tire width direction W and opening to the inside center main groove12A and the outside center main groove12B.

The center block16A is provided with a second center lateral groove14B which is inclined to the opposite direction of the first center lateral direction14A. The second center lateral groove14B is a groove in which one end opens to the inside center main groove12A and the other side terminates in the center block16A. The first center lateral grooves14A and the second center lateral grooves14B are alternately provided in the tire circumferential direction C. The first center lateral grooves14A and the second center lateral grooves14B may be straight-line grooves, curved-line grooves, or grooves each having a bending portion as long as the grooves extend while being inclined with respect to the tire width direction W.

An inside intermediate block line18B is provided between the inside center main groove12A and the inside shoulder main groove12C. The inside intermediate block line18B includes a plurality of inside intermediate blocks16B formed by being divided in the tire circumferential direction C by inside intermediate lateral grooves14C.

The inside intermediate lateral groove14C is a groove extending while being inclined with respect to the tire width direction W and opening to the inside center main groove12A and the inside shoulder main groove12C. A plurality of inside intermediate lateral grooves14C are provided at intervals in the tire circumferential direction C. The inside intermediate lateral grooves14C are formed in a straight shape. The inside intermediate lateral grooves14C may be straight-line grooves, curved-line grooves, or grooves each having a bending portion as long as the grooves extend while being inclined with respect to the tire width direction W.

Since the inside intermediate lateral grooves14C extend while being inclined with respect to the tire width direction W, each of the inside intermediate blocks16B has an acute angle portion16B1and an obtuse angle portion16B2. The acute angle portion16B1is a corner portion formed by the inside intermediate lateral groove14C crossing the inside shoulder main groove12C at an acute angle. The obtuse angle portion16B2is a corner portion formed by the inside intermediate lateral groove14C crossing the inside shoulder main groove12C at an obtuse angle. The acute angle portions16B1and the obtuse angle portions16B2are alternately provided in the tire circumferential direction C.

An inside shoulder block line18C is provided on an outer side in the tire width direction of the inside shoulder main groove12C (namely, between the inside shoulder main groove12C and a ground contact end). The inside shoulder block line18C includes a plurality of inside shoulder blocks16C formed by being divided in the tire circumferential direction C by inside shoulder lateral grooves14D.

The inside shoulder lateral groove14D is a groove extending while being inclined with respect to the tire width direction W and opening to the inside shoulder main groove12C and the ground contact end. An opening of the inside shoulder lateral groove14D opening to the inside shoulder main groove12C is formed on an extended line of the inside intermediate lateral groove14C. The inside shoulder lateral groove14D is a groove having a bending portion. The inside shoulder lateral grooves14D may be straight-line grooves, curved-line grooves, or grooves each having a bending portion as long as the grooves extend while being inclined with respect to the tire width direction W.

Since the inside shoulder lateral grooves14D extend while being inclined with respect to the tire width direction W, each of the inside shoulder blocks16C has an acute angle portion16C1and an obtuse angle portion16C2. The acute angle portion16C1is a corner portion formed by the inside shoulder lateral groove14D crossing the inside shoulder main groove12C at an acute angle. The obtuse angle portion16C2is a corner portion formed by the inside shoulder lateral groove14D crossing the inside shoulder main groove12C at an obtuse angle.

The acute angle portions16C1and the obtuse angle portions16C2of the inside shoulder blocks16C are alternately provided in the tire circumferential direction C in the same manner as the acute angle portions16B1and the obtuse angle portions16B2of the inside intermediate blocks16B. The acute angle portion16C1of the inside shoulder block16C faces the obtuse angle portion16B2of the inside intermediate block16B in a direction in which the inside intermediate lateral groove14C are extended. The obtuse angle portion16C2of the inside shoulder block16C faces the acute angle portion16B1of the inside intermediate block16B in a direction in which the inside intermediate lateral groove14C are extended.

An outside intermediate block line18D is provided between the outside center main groove12B and the outside shoulder main groove12D. The outside intermediate block line18D includes a plurality of outside intermediate blocks16D formed by being divided in the tire circumferential direction C by first outside intermediate lateral grooves14E. The first outside intermediate lateral groove14E is a groove extending while being inclined with respect to the tire width direction W and opening to the outside center main groove12B and the outside shoulder main groove12D.

The outside intermediate block16D is provided with second outside intermediate lateral grooves14F which is inclined to an opposite direction of the first outside intermediate lateral groove14E. The second outside intermediate lateral groove14F is a groove in which one end opens to the outside shoulder main groove12D and the other end terminates in the outside intermediate block16D. The first outside intermediate lateral grooves14E and the second outside intermediate lateral grooves14F are alternately provided in the tire circumferential direction C. The first outside intermediate lateral grooves14E and the second outside intermediate lateral grooves14F may be straight-line grooves, curved-line grooves, or grooves each having a bending portion as long as the grooves extend while being inclined with respect to the tire width direction W. The second outside intermediate lateral groove14F may be a groove in which one end opens to the outside shoulder main groove12D and the other end opens to the outside center main groove12B as shown inFIG.7.

An outside shoulder block line18E is provided on an outer side in the tire width direction of the outside shoulder main groove12D (namely, between the outside shoulder main groove12D and a ground contact end). The outside shoulder block line18E includes a plurality of outside shoulder blocks16E formed by being divided in the tire circumferential direction C by the first outside shoulder lateral grooves14G. The first outside shoulder lateral groove14G is a groove extending while being inclined with respect to the tire width direction W and opening to the outside shoulder main groove12D and the ground contact end.

The outside shoulder block16E is provided with the second outside shoulder lateral groove14H extending in parallel to the first outside shoulder lateral groove14G. The second outside shoulder lateral groove14H is a groove in which one end opens to the ground contact end and the other end terminates in the outside shoulder block16E. The first outside shoulder lateral grooves14G and the second outside shoulder lateral grooves14H are alternately provided in the tire circumferential direction C. The first outside shoulder lateral grooves14G and the second outside shoulder lateral grooves14H may be straight-line grooves, curved-line grooves, or grooves each having a bending portion as long as the grooves extend while being inclined with respect to the tire width direction W.

(2) Inside Intermediate Block16B and Inside Shoulder Block16C

Next, the inside intermediate block16B and the inside shoulder block16C will be explained. As shown inFIG.1andFIG.2, the inside intermediate block16B and the inside shoulder block16C are respectively provided with reinforcing protrusions20,22.

The reinforcing protrusion20protrudes from the acute angle portion side in a side wall16B3of the inside intermediate block16B which faces the shoulder main groove12C toward the center of the shoulder main groove12C (toward a side wall16C3of the inside shoulder block16C which faces the side wall16B3). The reinforcing protrusion20is provided from a tread surface16B4of the inside intermediate block16B toward a groove bottom12C1of the shoulder main groove12C as shown inFIG.3.

The reinforcing protrusion20includes a tread-surface side inclined surface20aconnected to the tread surface16B4of the inside intermediate block16B and extending toward the groove bottom12C1side and a groove-bottom side inclined surface20bconnected to the tread-surface side inclined surface20aand further extending toward the groove bottom12C1side as shown inFIG.3.

The tread-surface side inclined surface20ais inclined with respect to the tire radial direction. The groove-bottom side inclined surface20bis provided approximately in parallel to the tire radial direction. That is, an inclination angle θ1of the tread-surface side inclined surface20awith respect to the tire radial direction is larger than an inclination angle of the groove-bottom side inclined surface20bwith respect to the tire radial direction. θ1is, for example, 25 degrees or more and 65 degrees or less.

Note that the groove-bottom side inclined surface20bmay be inclined with respect to the tire radial direction as long as the inclination angle with respect to the tire radial direction is smaller than the inclination angle θ1of the tread-surface side inclined surface20a. The inclination angle of the groove-bottom side inclined surface20bwith respect to the tire radial direction can be 10 degrees or less.

At a place closer to the groove bottom12C1than the groove-bottom side inclined surface20b, a curved surface smoothly connecting the groove-bottom side inclined surface20band the groove bottom12C1is provided.

The reinforcing protrusion22protrudes from the acute angle portion side in the side wall16C3of the inside shoulder block16C which faces the shoulder main groove12C toward the center of the inside shoulder main groove12C (toward the side wall16B3of the inside intermediate block16B). The reinforcing protrusion22is provided from a tread surface16C4of the inside shoulder block16C toward the groove bottom12C1of the shoulder main groove12C. The above reinforcing protrusions22and the reinforcing protrusions20provided in the inside intermediate blocks16B are alternately arranged in the tire circumferential direction C (seeFIG.1andFIG.2).

The reinforcing protrusion22includes a tread-surface side inclined surface22aconnected to the tread surface16C4of the inside shoulder block16C and extending toward the groove bottom12C1side and a groove-bottom side inclined surface22bconnected to the tread-surface side inclined surface22aand further extending toward the groove bottom12C1side.

The tread-surface side inclined surface22ais inclined with respect to the tire radial direction. The groove-bottom side inclined surface22bis provided approximately in parallel to the tire radial direction. That is, an inclination angle θ2of the tread-surface side inclined surface22awith respect to the tire radial direction is larger than an inclination angle of the groove-bottom side inclined surface22bwith respect to the tire radial direction. θ2is, for example, 25 degrees or more and 65 degrees or less.

Note that the groove-bottom side inclined surface22bmay be inclined with respect to the tire radial direction as long as the inclination angle with respect to the tire radial direction is smaller than the inclination angle θ2of the tread-surface side inclined surface22a. The inclination angle of the groove-bottom side inclined surface22bwith respect to the tire radial direction can be 10 degrees or less.

At a place closer to the groove bottom12C1from the groove-bottom side inclined surface22b, a curved surface smoothly connecting the groove-bottom side inclined surface22band the groove bottom12C1is provided.

A height H of the groove-bottom side inclined surfaces20b,22bof the reinforcing protrusions20,22from the groove bottom12C1of the inside shoulder main groove12C is preferably 50% or more of a depth D0of the inside shoulder main groove12C. That is, it is preferable that the tread-surface side inclined surfaces20a,22aare provided closer to the tread surface side than a position of 50% of the depth D0of the inside shoulder main groove12C. For example, the depth D0of the inside shoulder main groove12C may be 5 to 10 cm, the height H of the groove-bottom side inclined surfaces20b,22bmay be 5 to 8.5 cm, and a height of the tread-surface side inclined surfaces20a,22a(length in the tire radial direction) may be 1 to 3 cm.

Additionally, sipes may be provided on the inside intermediate blocks16B and the inside shoulder blocks16C. In the embodiment, three sipes24a,24b, and24care provided on the inside intermediate block16B, and three sipes24d,24e, and24fare provided on the inside shoulder block16C.

In this description, the sipes are cuts formed on the blocks, which have a minute groove width. The groove width of the sipes is not particularly limited, and may be, for example, 0.1 to 1.5 mm, 0.2 to 1.0 mm or 0.3 to 0.8 mm. The sipes do not always have to be parallel to the tire width direction W as long as the sipes are narrow grooves extending in the tire width direction W and may be narrow grooves extending in the tire width direction W while being inclined. The sipes may be straight-line sipes, curved-line sipes, or sipes each having a bending portion.

As shown inFIG.2andFIG.4, the three sipes24a,24b, and24cprovided on the inside intermediate block16B extend while being inclined with respect to the tire width direction W and open to the inside shoulder main groove12C.

Specifically, the sipe24ais an acute-angle side sipe opening to the reinforcing protrusion20. As shown inFIG.3, a depth D1of the inside intermediate block acute-angle side sipe24amay be the same as, or may be shallower than the depth D0of the inside shoulder main groove12C. The depth D1of the inside intermediate block acute-angle side sipe24amay be constant in an extension direction thereof, or may vary in the extension direction. For example, the inside intermediate block acute-angle side sipe24amay be formed to be shallow at an opening end part to the inside shoulder main groove12C and may be formed to be deeper at the central part in the extension direction than at the opening end part.

A depth D11at the opening end part may be shallower than a lower end position of the tread-surface side inclined surface20a(an upper end position of the groove-bottom side inclined surface20b), which may be, for example, 10% or more and 90% or less of the depth D0of the inside shoulder main groove12C. The inside intermediate block acute-angle side sipe24amay open to the tread-surface side inclined surface20a, not opening to the groove-bottom side inclined surface20b.

Moreover, the depth D1of the inside intermediate block acute-angle side sipe24aat the central part in the extension direction may be deeper than the lower end position of the tread-surface side inclined surface20a, which may be, for example, 50% or more and 90% or less of the depth D0of the inside shoulder main groove12C.

The sipe24bis a sipe provided at the central part in the tire circumferential direction C of the inside intermediate block16B, which corresponds to the intermediate sipe24bopening to a boundary portion with respect to the reinforcing protrusion20protruding from the side wall16B3of the inside intermediate block16B. In other words, the intermediate sipe24bis disposed between the acute-angle side sipe24aand the obtuse-angle side sipe24c, which opens to a root portion of the reinforcing protrusion20.

The sipe24cis the inside intermediate block obtuse-angle side sipe24copening to the obtuse angle portion side in the side wall16B3of the inside intermediate block16B (namely, a position facing the reinforcing protrusion22of the inside shoulder block16C in the tire width direction W).

The inside intermediate block acute-angle side sipe24a, the inside intermediate block intermediate sipe24b, and the inside intermediate block obtuse-angle side sipe24care provided in parallel to the inside intermediate lateral groove14C; however, these sipes can be grooves extending while being inclined with respect to the inside intermediate lateral groove14C. The inside intermediate block acute-angle side sipe24aand the inside intermediate block obtuse-angle side sipe24calso open to the inside center main groove12A and are provided so as to completely traverse the inside intermediate block16B; however, these sipes do not always have to completely traverse the block. Moreover, the inside intermediate block intermediate sipe24bdo not have to completely traverse the inside intermediate block16B as in the shown example, but can completely traverse the block.

As shown inFIG.2, the three sipes24d,24e, and24fprovided on the inside shoulder block16C extend while being inclined with respect to the tire width direction W and open to the inside shoulder main groove12C.

Specifically, the sipe24dis an inside shoulder block acute-angle side sipe opening to the reinforcing protrusion22. The inside shoulder block acute-angle side sipe24dmay be provided on an extension of the inside intermediate block obtuse-angle side sipe24cprovided in the inside intermediate block16B as shown inFIG.2.

A depth D2of the inside shoulder block acute-angle side sipe24dmay be the same as, or may be shallower than the depth D0of the inside shoulder main groove12C in the same matter as the inside intermediate block acute-angle side sipe24aprovided in the inside intermediate block16B. The depth D2of the inside shoulder block acute-angle side sipe24dmay be constant in an extension direction thereof, or may vary in the extension direction. For example, the inside shoulder block acute-angle side sipe24dmay be formed to be shallow at an opening end part to the inside shoulder main groove12C and may be formed to be deeper at the central part in the extension direction than at the opening end part.

The depth D21at the opening end part may be shallower than a lower end position of the tread-surface side inclined surface22a(an upper end position of the groove-bottom side inclined surface22b), which may be, for example, 10% or more and 90% or less of the depth D0of the inside shoulder main groove12C. The inside shoulder block acute-angle side sipe24dmay open to the tread-surface side inclined surface22a, not opening to the groove-bottom side inclined surface22b.

Moreover, the depth D2of the inside shoulder block acute-angle side sipe24dat the central part in the extension direction may be deeper than the lower end position of the tread-surface side inclined surface22a, which may be, for example, 50% or more and 90% or less of the depth D0of the inside shoulder main groove12C.

The sipe24eis a sipe provided at the central part in the tire circumferential direction C of the inside shoulder block16C, which corresponds to the intermediate sipe24eopening to a boundary portion with respect to the reinforcing protrusion22protruding from the side wall16C3of the inside shoulder block16C. In other words, the intermediate sipe24eis disposed between the inside shoulder block acute-angle side sipe24dand the inside shoulder block obtuse-angle side sipe24f, which opens to a root portion of the reinforcing protrusion22. The intermediate sipe24emay be provided on an extension of the intermediate sipe24bprovided in the inside intermediate block16B as shown inFIG.2.

The sipe24fis the inside shoulder block obtuse-angle side sipe24fopening to the obtuse angle portion side in the side wall16C3of the inside shoulder block16C (namely, a position facing the reinforcing protrusion20of the inside intermediate block16B in the tire width direction W). The inside shoulder block obtuse-angle side sipe24fmay be provided on an extension of the inside intermediate block acute-angle side sipe24aprovided in the inside intermediate block16B as shown inFIG.2.

The inside shoulder block acute-angle side sipe24d, the inside shoulder block intermediate sipe24e, and the inside shoulder block obtuse-angle side sipe24fare provided in parallel to the inside shoulder lateral groove14D; however, these sipes can be grooves extending while being inclined with respect to the inside shoulder lateral groove14D.

(3) Center Block16A and Outside Intermediate Block16D

Next, the center block16A and the outside intermediate block16D will be explained. As shown inFIG.1andFIG.5, a plurality of sipes extending while being inclined with respect to the tire width direction W and connecting portions connecting the sipes are provided respectively in the center block16A and the outside intermediate block16D.

Specifically, a first intermediate sipe24g, a second intermediate sipe24h, a third intermediate sipe24i, a fourth intermediate sipe24j, a first intermediate connecting portion26a, and a second intermediate connecting portion26bare provided in the outside intermediate block16D.

As shown inFIG.5, the first intermediate sipe24gextends while being inclined in an opposite direction to the first outside intermediate lateral groove14E with respect to the tire width direction W. In the first intermediate sipe24g, one end24g1is connected to the first intermediate connecting portion26aprovided in the outside intermediate block16D and the other end opens on a side wall16D1of the outside intermediate block16D which faces the first outside intermediate lateral groove14E.

The second intermediate sipe24hextends while being inclined in an opposite direction to the second outside intermediate lateral groove14F with respect to the tire width direction W. The second intermediate sipe24hextends while being inclined in an opposite direction to the first intermediate sipe24gwith respect to the tire width direction W. One end24h1of the second intermediate sipe24his arranged at a position shifted from the one end24g1of the first intermediate sipe24gin the tire circumferential direction C and connected to the first intermediate connecting portion26aprovided in the outside intermediate block16D. The other end of the second intermediate sipe24hopens on a side wall16D2of the outside intermediate block16D which faces the second outside intermediate lateral groove14F.

The third intermediate sipe24iextends while being inclined in an opposite direction to the second outside intermediate lateral groove14F with respect to the tire width direction W. One end24i1of the third intermediate sipe24iis connected to the second intermediate connecting portion26bprovided in the outside intermediate block16D. The other end of the third intermediate sipe24iopens on a side wall16D3of the outside intermediate block16D which faces the outside center main groove12B. It is also preferable that, as shown inFIG.7, the second outside intermediate lateral groove14F is provided so as to pierce through the outside intermediate block16D, and that the other end of the third intermediate sipe24iopens on the side wall16D2of the outside intermediate block16D which faces the second outside intermediate lateral groove14F.

The fourth intermediate sipe24jextends while being inclined in an opposite direction to the first outside intermediate lateral groove14E with respect to the tire width direction W. That is, the fourth intermediate sipe24jextends while being inclined in an opposite direction to the third intermediate sipe24iwith respect to the tire width direction W. One end24j1of the fourth intermediate sipe24jis arranged at a position shifted from the one end24i1of the third intermediate sipe24iin the tire circumferential direction C and connected to the second intermediate connecting portion26bprovided in the outside intermediate block16D. The other end of the fourth intermediate sipe24jopens on the side wall16D1of the outside intermediate block16D which faces the first outside intermediate lateral groove14E.

The first intermediate connecting portion26ais formed by a recessed portion recessed from a tread surface of the outside intermediate block16D, which has a trapezoidal shape in planar view as shown inFIG.5. The first intermediate connecting portion26aconnects the one end24g1of the first intermediate sipe24gand the one end24h1of the second intermediate sipe24hwhich are arranged apart from each other in the tire circumferential direction C.

As shown inFIG.6, a depth of the first intermediate connecting portion26ais shallower than depths of the first intermediate sipe24gand the second intermediate sipe24h. For example, the depth of the first intermediate connecting portion26acan be set to 1.0 to 4.0 mm. The first intermediate connecting portion26ahas an inclined bottom surface26a1which becomes deep as coming close to tip ends of the first intermediate sipe24gand the second intermediate sipe24h(as coming close to the inside in the tire width direction W).

The second intermediate connecting portion26bis formed by a recessed portion recessed from the tread surface of the outside intermediate block16D, which has a trapezoidal shape in planar view as shown inFIG.5in the same manner as the first intermediate connecting portion26a. The second intermediate connecting portion26bconnects the one end24i1of the third intermediate sipe24iand the one end24j1of the fourth intermediate sipe24jwhich are arranged apart from each other in the tire circumferential direction C.

A depth of the second intermediate connecting portion26bis shallower than depths of the third intermediate sipe24iand the fourth intermediate sipe24j. For example, the depth of the second intermediate connecting portion26bcan be set to 1.0 to 4.0 mm. The second intermediate connecting portion26bhas an inclined bottom surface26b1which becomes deep as coming close to tip ends of the third intermediate sipe24iand the fourth intermediate sipe24j(as coming close to the inside in the tire width direction W).

The first intermediate connecting portion26aand the second intermediate connecting portion26bdescribed above are arranged to be shifted in the tire width direction W and are alternately arranged in the tire circumferential direction C.

Moreover, a first center sipe24k, a second center sipe24l, a third center sipe24m, a fourth center sipe24n, a first center connecting portion28a, and a second center connecting portion28bare provided in the center block16A in the embodiment.

As shown inFIG.5, the first center sipe24kextends while being inclined in an opposite direction to the first center lateral groove14A with respect to the tire width direction W. In the first center sipe24k, one end24k1is connected to the first center connecting portion28aprovided in the center block16A and the other end opens on a side wall16A1of the center block16A which faces the outside center main groove12B.

The first center sipe24lextends while being inclined in an opposite direction to the second center lateral groove14B with respect to the tire width direction W. The second center sipe24lextends while being inclined in an opposite direction to the first center sipe24kwith respect to the tire width direction W. One end24l1of the second center sipe24lis arranged at a position shifted from the one end24k1of the first center sipe24kin the tire circumferential direction C and connected to the first center connecting portion28aprovided in the center block16A. The other end of the second center sipe24lopens on the side wall16A1of the center block16A which faces the outside center main groove12B.

The third center sipe24mextends while being inclined in an opposite direction to the second center lateral groove14B with respect to the tire width direction W. One end24m1of the third center sipe24mis connected to the second center connecting portion28bprovided in the center block16A. The other end of the third center sipe24mopens on a side wall16A2of the center block16A which faces the inside center main groove12A.

The fourth center sipe24nextends while being inclined in an opposite direction to the first center lateral groove14A with respect to the tire width direction W. That is, the fourth center sipe24nextends while being inclined in an opposite direction to the third center sipe24mwith respect to the tire width direction W. One end24n1of the fourth center sipe24nis arranged at a position shifted from the one end24m1of the third center sipe24min the tire circumferential direction C and connected to the second center connecting portion28bprovided in the center block16A. The other end of the fourth center sipe24nopens on the side wall16A2of the center block16A which faces the inside center main groove12A.

The first center connecting portion28ais formed by a recessed portion recessed from the tread surface of the center block16A, which has a trapezoidal shape in planar view as shown inFIG.5. The first center connecting portion28aconnects the one end24k1of the first center sipe24kand the one end24l1of the second center sipe24lwhich are arranged apart from each other in the tire circumferential direction C.

As shown inFIG.6, a depth of the first center connecting portion28ais shallower than depths of the first center sipe24kand the second center sipe24l. For example, the depth of the first center connecting portion28acan be set to 1.0 to 4.0 mm. The first center connecting portion28ahas an inclined bottom surface28a1which becomes deep as coming close to tip ends of the first center sipe24kand the second center sipe24l.

A length of the first center connecting portion28aalong the tire circumferential direction C is longer than a length of the first intermediate connecting portion26aprovided in the outside intermediate block16D along the tire circumferential direction C. For example, the length of the first intermediate connecting portion26aalong the tire circumferential direction C can be set to 1.0 to 5.0 mm, and the length of the first center connecting portion28aalong the tire circumferential direction C can be set to 5.0 to 10.0 mm. The first center connecting portion28ais arranged so as to overlap at least part of the first intermediate connecting portion26ain the tire width direction W.

The second center connecting portion28bis formed by a recessed portion recessed from the tread surface of the center block16A, which has a trapezoidal shape in planar view as shown inFIG.5in the same manner as the first center connecting portion28a. The second center connecting portion28bconnects the one end24m1of the third center sipe24mand the one end24n1of the fourth center sipe24nwhich are arranged apart from each other in the tire circumferential direction C. A depth of the second center connecting portion28bis shallower than depths of the third center sipe24mand the fourth center sipe24n. For example, the depth of the second center connecting portion28bcan be set to 1.0 to 4.0 mm. The second center connecting portion28bhas an inclined bottom surface28b1which becomes deep as coming close to tip ends of the third center sipe24mand the fourth center sipe24n(as coming close to the inside in the tire width direction W).

The second center connecting portion28bis arranged so as to overlap at least part of the second intermediate connecting portion26bin the tire width direction W.

In the embodiment, the first intermediate sipe24gand the fourth intermediate sipe24jare provided in parallel to the second outside intermediate lateral groove14F, and the second intermediate sipe24hand the third intermediate sipe24iare provided in parallel to the first outside intermediate lateral groove14E.

Moreover, the first center sipe24kand the fourth center sipe24nare arranged in parallel to the second center lateral groove14B, and are arranged in parallel to the first intermediate sipe24g, the fourth intermediate sipe24j, and the second outside intermediate lateral groove14F. The second center sipe24land the third center sipe24mare arranged in parallel to the first center lateral groove14A, and are arranged in parallel to the second intermediate sipe24h, the third intermediate sipe24i, and the first outside intermediate lateral groove14E.

(4) Advantageous Effects

In the above-described pneumatic tire according to the embodiment, a pair of sipes connected by the connecting portion are provided in the outside intermediate block16D or the center block16A so as to be inclined in opposite directions to each other with respect to the tire width direction W; therefore, at least one of the pair of sipes makes a large angle which is almost perpendicular to a traveling direction of the vehicle at the time of turning of the vehicle when a large force acts. Accordingly, edge effect due to sipes can be maintained in the outside intermediate block16D and the center block16A not only during straight traveling but also at the time of turning of the vehicle.

Moreover, sipes inclined in opposite directions with respect to the tire width direction W are connected by the connecting portions26a,26b,28a, and28bformed by the recessed portion shallower than these sipes; therefore, distortion and heat generation occurring at ends of the sipes can be reduced to thereby improve durability performance, and reduction of rigidity in the outside intermediate blocks16D and the center blocks16A can be suppressed to thereby suppress uneven wear.

Since the connecting portions26a,26b,28a, and28bhave the inclined bottom surfaces26a1,26b1,28a1, and28b1which become deep as coming close to the tip ends of the sipes in the embodiment, distortion and heat generation occurring at ends of the sipes can be efficiently suppressed.

In the embodiment, the first intermediate sipe24gextends while being inclined in the opposite direction to the first outside intermediate lateral groove14E with respect to the tire width direction W and opens on the side wall16D1of the outside intermediate block16D which faces the first outside intermediate lateral groove14E. Moreover, the second intermediate sipe24hextends while being inclined in the opposite direction to the second outside intermediate lateral groove14F with respect to the tire width direction W and opens on the side wall16D2of the outside intermediate block16D which faces the second outside intermediate lateral groove14F; therefore, the rigidity of the blocks at the time of turning of the vehicle can be secured and uneven wear can be suppressed.

In particular, the first intermediate sipe24gis provided in parallel to the second outside intermediate lateral groove14F, and the second intermediate sipe24his provided in parallel to the first outside intermediate lateral groove14E in the embodiment. Accordingly, when a force in which the outside intermediate block16D leans against the first outside intermediate lateral groove14E or the second outside intermediate lateral groove14F acts, groove widths of the second intermediate sipe24hand the first intermediate sipe24gwhich are provided in parallel to the grooves are expanded to make the edge effect easy to produce, which can improve performance on a slippery road surface such as an icy and snowy road.

Although a large force tends to act on an outside area of the vehicle outside OUT on an outer side than the tire equatorial plane CL at the time of turning of the vehicle in the vehicle mounted posture, the first intermediate sipe24g, the second intermediate sipe24h, the third intermediate sipe24i, the fourth intermediate sipe24j, the first intermediate connecting portion26a, and the second intermediate connecting portion26bdescribed above are provided on the outside area in the embodiment; therefore, the outside intermediate block16D does not easily lean against the groove to thereby suppress uneven wear.

Moreover, the sipes24a,24b,24c,24d,24e, and24fwhich are parallel to the inside intermediate lateral groove14C or the inside shoulder lateral groove14D are provided on the inside intermediate blocks16B and the inside shoulder blocks16C positioned in the area of the vehicle inside IN on the inner side of the tire equatorial plane CL in the vehicle mounted posture; therefore, the groove widths of the sipes are easily expanded at the time of contacting the ground to thereby exert high edge effect.

The present invention is not at all limited by the above embodiment, and various modifications and alterations may occur within a scope not departing from the gist of the invention.

REFERENCE SIGNS LIST

10: tread12A: inside center main groove12B: outside center main groove12C: inside shoulder main groove12C1: groove bottom12D: outside shoulder main groove14A: first center lateral groove14B: second center lateral groove14C: inside intermediate lateral groove14D: inside shoulder lateral groove14E: first outside intermediate lateral groove14F: second outside intermediate lateral groove14G: first outside shoulder lateral groove14H: second outside shoulder lateral groove16A: center block16B: inside intermediate block16B1: acute angle portion16B2: obtuse angle portion16B3: side wall16B4: tread surface16C: inside shoulder block16C1: acute angle portion16C2: obtuse angle portion16C3: side wall16D: outside intermediate block16E: outside shoulder block18A: center block line18B: inside intermediate block line18C: inside shoulder block line18D: outside intermediate block line18E: outside shoulder block line20: reinforcing protrusion20a: tread-surface side inclined surface20b: groove-bottom side inclined surface22: reinforcing protrusion22a: tread-surface side inclined surface22b: groove-bottom side inclined surface24a: inside intermediate block acute-angle side sipe24b: inside intermediate block intermediate sipe24c: inside intermediate block obtuse-angle side sipe24d: inside shoulder block acute-angle side sipe24e: inside shoulder block intermediate sipe24f: inside shoulder block obtuse-angle side sipe24g: first intermediate sipe24h: second intermediate sipe24i: third intermediate sipe24j: fourth intermediate sipe24k: first center sipe24l: second center sipe24m: third center sipe24n: fourth center sipe26a: first intermediate connecting portion26b: second intermediate connecting portion28a: first center connecting portion28a1: inclined bottom surface28b: second center connecting portion28b1: inclined bottom surface