Pneumatic tire

Abstract

The invention provides a tire capable of ensuring steering stability and improving driving performance on icy and snowy road surfaces. In the pneumatic tire of the present invention, an inner middle region (14C) divided by an inner center main groove (12B) and an inner shoulder main groove (12D) is provided with: a plurality of inner middle pattern blocks (18C) arranged side by side in the tire circumferential direction (CD); and a plurality of inner middle slits (16C) provided between the inner middle blocks (18C1, 18C2), the plurality of inner middle blocks (18C1, 18C2) being provided with: a first inner middle block (18C1) provided with a first inner middle notch (40) that opens into the inner center main groove (12B); and second inboard middle blocks (18C2) provided with second inboard middle recesses (41) that open on the inboard shoulder main groove (12D) side, the first inboard middle blocks (18C1) and the second inboard middle blocks (18C2) being alternately provided in the tire circumferential direction (CD).

Description

Technical Field

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

[0002] Regarding pneumatic tires, it is known that a sipe pattern is provided in a pattern block formed by a main groove extending in the tire circumferential direction and a slit extending in the tire axial direction (for example, the following patent documents 1 and 2). Regarding such pneumatic tires, although a plurality of grooves and sipe patterns are provided to improve drainage effect, edge effect, and water absorption effect, thereby improving driving performance on icy and snowy roads, the rigidity of the pattern block is reduced, and the steering stability is easily reduced.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2008-105615

[0006] Patent Document 2: Japanese Patent Application Publication No. 2013-71647 Summary of the invention

[0007] The present invention has been made in view of the above problems, and an object of the present invention is to provide a pneumatic tire that can ensure steering stability and improve running performance on icy and snowy roads.

[0008] The present invention includes the following embodiments.

[0009] [1] A pneumatic tire having a tread portion in which three or more main grooves extending in the tire circumferential direction are formed in tread rubber, and having a specified orientation for mounting on a vehicle.

[0010] The tread rubber comprises: an outer central main groove, which is arranged closer to the outer side of the vehicle than the tire equatorial plane; an inner central main groove, which is arranged closer to the inner side of the vehicle than the tire equatorial plane; an inner shoulder main groove, which is adjacent to the inner central main groove on the outer side of the tire axial direction; and an inner middle area, which is divided by the inner central main groove and the inner shoulder main groove, wherein:

[0011] The inner middle region includes: a plurality of inner middle tread blocks arranged in a circumferential direction of the tire; and a plurality of inner middle slits arranged between the inner middle tread blocks.

[0012] The plurality of inner middle tread blocks include: a first inner middle tread block having a first inner middle recess opening in the inner central main groove; and a second inner middle tread block having a second inner middle recess opening in the inner shoulder main groove.

[0013] The first inner middle blocks and the second inner middle blocks are alternately arranged in the tire circumferential direction.

[0014] [2] In the pneumatic tire according to [1], the first inner middle pattern block and the second inner middle pattern block include: inner middle sipes formed in a wave-like shape extending in a direction intersecting with the tire circumferential direction in a manner such that one end opens in the inner central main groove and the other end opens in the inner shoulder main groove;

[0015] The amplitude center line of the inner middle sipe is bent in opposite directions at a first curved portion provided on the inner side of the inner middle pattern block in the tire axial direction and a second curved portion provided on the outer side of the inner middle pattern block in the tire axial direction.

[0016] The inner middle sipe is divided at one of the first bent portion and the second bent portion.

[0017] [3] Based on the pneumatic tire described in [2] above, the inner middle sipe pattern provided in the first inner middle pattern block is divided at the second bending portion, and the inner middle sipe pattern provided in the second inner middle pattern block is divided at the first bending portion.

[0018] [4] Based on the pneumatic tire described in any one of the above [1] to [3], the inner middle slit has: a first slit bent portion, which is bent from one side to the other side of the tire circumference; and a second slit bent portion, which is bent from the other side to the one side of the tire circumference.

[0019] Effects of the Invention

[0020] The present invention has the above-mentioned features, thereby ensuring steering stability and improving running performance on icy and snowy roads. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a cross-sectional view of a pneumatic tire according to one embodiment of the present invention.

[0022] Figure 2 It is shown Figure 1 An expanded view of the tread pattern of a pneumatic tire.

[0023] Figure 3 yes Figure 2 An enlarged plan view of the main part of the tread pattern.

[0024] Figure 4 It is an enlarged plan view of a main part showing the tread pattern in the center area in an enlarged manner.

[0025] Figure 5 It is an enlarged plan view of a main part showing an enlarged view of a tread pattern in an outer middle region.

[0026] Figure 6 It is an enlarged plan view of a main part showing an enlarged view of a tread pattern of an inner middle region.

[0027] Figure 7 yes Figure 2 AA line section view.

[0028] Figure 8 yes Figure 2 BB line cross-sectional view.

[0029] Description of Reference Numerals

[0030] 1…Pneumatic tire, 3…Tread portion, 4…Side portion, 5…Carcass layer, 7…Belt layer, 8…Tread rubber, 9…Belt reinforcement layer, 12A…Outer center main groove, 12B…Inner center main groove, 12C…Outer shoulder main groove, 12D…Inner shoulder main groove, 14A…Center region, 14B…Outer middle region, 14C…Inner middle region, 14D…Outer shoulder region, 14E…Inner shoulder region, 16A1…first center slit, 16A2…second center slit, 16B1…first outer middle slit, 16B1a…bend, 16B2…second outer middle slit, 16B2a…bend, 16C…inner middle slit, 16C1…first slit bend, 16C2…second slit bend, 18A…center rib, 18B…second outer middle pattern block, 18C1…first inner middle Pattern block, 18C2...Second inner middle pattern block, 18D...Outer shoulder pattern block, 18E...Inner shoulder pattern block, 30...Compound sipe, 33...First outer middle notch, 34...Second outer middle notch, 35...First outer middle sipe, 35a...Bend portion, 36...Second outer middle sipe, 36a...Bend portion, 37...Third outer middle sipe, 37a...Bend portion , 38…outer shoulder sipe, 39…inner shoulder sipe, 40…first inner middle notch, 41…second inner middle notch, 42…first inner middle sipe, 42A…first flexure, 42B…second flexure, 42C…inner sipe portion, 42D…outer sipe portion, 43…second inner middle sipe, 43A…first flexure, 43B…second flexure DETAILED DESCRIPTION

[0031] Hereinafter, a pneumatic tire according to an embodiment of the present invention will be described with reference to the drawings.

[0032] In this specification, the ground contact state refers to a state in which the pneumatic tire is assembled on a regular rim and filled with a regular internal pressure, and is placed vertically on a flat road surface, and a regular load is applied. The ground contact ends Ei and Eo refer to the axial ends of the tire tread surface that are in contact with the road surface in the ground contact state. In addition, the sipe pattern refers to a groove whose opening toward the ground contact surface is closed in the ground contact state, for example, it means a narrow groove with a width of less than 2 mm. The main groove and slit extending in the circumferential direction are grooves with a width greater than the sipe pattern and whose opening toward the ground contact surface is not closed in the ground contact state, for example, it means a groove with a width of more than 2 mm.

[0033] A regular rim is a rim that is specified for each tire in accordance with the specification in the specification system including the specification to which the tire is based. For example, a regular rim is a "standard rim" in the JATMA specification, a "design rim" in the TRA specification, or a "measurement rim" in the ETRTO specification.

[0034] The normal internal pressure is the air pressure specified for each tire in accordance with each specification in the specification system including the specification to which the tire is based. For example, the normal internal pressure is the maximum value of the "maximum air pressure" in the JATMA specification, the "tire load limit at various cold inflation pressures" in the TRA specification, or the "inflation pressure" in the ETRTO specification.

[0035] The normal load is the load specified for each tire in accordance with each specification in the specification system including the specification to which the tire is based. For example, the normal load is the maximum value of the "maximum load capacity" in the JATMA specification, the "tire load limit at various cold inflation pressures" in the TRA specification, or the "load capacity" in the ETRTO specification.

[0036] In addition, in the accompanying drawings, reference numeral CL represents the tire equatorial plane corresponding to the axial center of the tire. Reference numeral AD represents the tire axial direction (also referred to as the tire width direction). The tire axial inner side ADi refers to the direction approaching the tire equatorial plane CL, and the tire axial outer side ADo refers to the direction away from the tire equatorial plane CL. Reference numeral CD represents the direction on the circumference centered on the tire rotation axis, i.e., the tire circumferential direction. In addition, the tire radial inner side RDi refers to the direction approaching the tire rotation axis, and the tire radial outer side RDo refers to the direction away from the tire rotation axis.

[0037] (1) Cross-sectional structure of pneumatic tire 1

[0038] Figure 1 The pneumatic tire 1 according to the embodiment shown includes: a pair of left and right bead portions 2; a pair of left and right sidewall portions 4 extending radially outward from the bead portions 2; and a tread portion 3 connecting radially outer ends of the sidewall portions 4 to form a ground contact surface 8a.

[0039] The pneumatic tire 1 is a tire with a specified orientation for mounting on a vehicle. That is, the surface to be mounted on the inside of the vehicle and the surface to be mounted on the outside of the vehicle are predetermined. Therefore, a mark for specifying the orientation for mounting on the vehicle is provided on the surface of the tire, for example, the sidewall portion. Figure 1 and Figure 2 In the figure, the left side of the tire equatorial plane CL indicated by reference numeral OUT is arranged on the vehicle outer side in the vehicle mounting posture, and the right side of the tire equatorial plane CL indicated by reference numeral IN is arranged on the vehicle inner side in the vehicle mounting posture.

[0040] An annular bead core 2a is embedded in each of the pair of bead portions 2. A bead outer rubber 2b is provided on the tire radial direction outer side RDo of the bead core 2a and is tapered toward the tire radial direction outer side RDo.

[0041] The pneumatic tire includes a carcass layer 5 extending in a circular line across a pair of bead portions 2. The carcass layer 5 reaches the bead portion 2 from the tread portion 3 via the sidewall portions 4 on both sides, and is folded back from the tire axial inner side ADi to the outer side ADo around the bead portion 2 and the bead core 2a, thereby locking both ends of the carcass layer 5.

[0042] The carcass layer 5 is composed of at least one carcass ply. In this example, the carcass layer 5 is composed of one carcass ply, but the carcass layer may be composed of two or more carcass plies.

[0043] The carcass fabric constituting the carcass layer 5 is a rubber member formed by covering carcass cords composed of organic fiber cords arranged substantially at right angles to the tire circumferential direction CD with rubber. A sheet-like inner liner 6 composed of rubber with low air permeability is attached to the inner side of the carcass layer 5.

[0044] The tread portion 3 includes a belt layer 7 provided on the outer peripheral side of the carcass layer 5 , a tread rubber 8 having a ground contact surface 8 a that contacts the road surface, and a belt reinforcing layer 9 provided between the belt layer 7 and the tread rubber 8 .

[0045] The belt layer 7 is composed of at least two cross belt cords arranged at an inclination angle of 23° or more and 29° or less relative to the tire circumferential direction CD. In this example, the belt layer 7 is a two-layer structure of a first belt cord 7A arranged on the inner side of the tire radial direction and a second belt cord 7B arranged on the outer peripheral side thereof. Among them, the first belt cord 7A is a maximum width belt cord with the largest width. The outer end of the first belt cord 7A in the tire axial direction is equivalent to the belt end 7C which is the tire axial end of the belt layer 7.

[0046] like Figure 2As shown, the surface of the tread rubber 8 is provided with: more than 3 (4 in the present embodiment) main grooves 12A, 12B, 12C, 12D, which extend along the circumferential direction CD of the tire; and slits 16A1, 16A2, 16B1, 16B2, 16C, 16D, 16E, which extend along the axial direction AD of the tire, thereby forming a tread pattern.

[0047] The belt reinforcement layer 9 is composed of a covering cord having reinforcing cords such as organic fiber cords extending substantially parallel to the tire circumferential direction CD. Figure 1 As shown, the belt reinforcing layer 9 is provided in at least a portion of the shoulder regions 14D and 14E so as to cover the belt layer 7 in the tire axial direction outer side ADo from the tire radial direction outer side RDo, and is not provided in the central region 14A and the intermediate regions 14B and 14C.

[0048] (2) Structure of tread pattern

[0049] like Figure 1 and Figure 2 As shown, on the surface of the tread rubber 8, there are provided main grooves extending along the circumferential direction CD of the tire: an outer central main groove 12A, which is provided closer to the outer side OUT of the vehicle than the tire equatorial plane CL; an inner central main groove 12B, which is provided closer to the inner side IN of the vehicle than the tire equatorial plane CL; an outer shoulder main groove 12C, which is adjacent to the outer central main groove 12A on the axially outer side ADo of the tire; and an inner shoulder main groove 12D, which is adjacent to the inner central main groove 12B on the axially outer side ADo of the tire.

[0050] The inner central main groove 12B extends substantially straight along the tire circumferential direction CD. The outer central main groove 12A, the outer shoulder main groove 12C, and the inner shoulder main groove 12D extend in the tire circumferential direction CD in a zigzag shape while bending in the tire axial direction AD. The outer central main groove 12A is composed of a groove having a smaller groove width and a shallower depth than the other main grooves (the inner central main groove 12B, the outer shoulder main groove 12C, and the inner shoulder main groove 12D).

[0051] For example, the groove widths of the outer central main groove 12A, the inner central main groove 12B, the outer shoulder main groove 12C and the inner shoulder main groove 12D are preferably 1.5mm~4.5mm, 3.5mm~7.5mm, 4.5mm~8.0mm and 4.0mm~7.5mm, respectively, and more preferably 2.0mm~3.9mm, 3.8mm~7.2mm, 4.7mm~7.5mm and 4.5mm~6.8mm. The groove depths of the outer central main groove 12A, the inner central main groove 12B, the outer shoulder main groove 12C and the inner shoulder main groove 12D are preferably 6.0mm~7.5mm, 8.0mm~9.5mm, 8.0mm~9.5mm and 8.0mm~9.5mm, respectively, and more preferably 6.2mm~7.2mm, 8.2mm~9.2mm, 8.2mm~9.2mm and 8.2mm~9.2mm.

[0052] The ratio of the width of the outer central main groove 12A to the width of the inner central main groove 12B is preferably 0.45 to 0.60, more preferably 0.50 to 0.55. The ratio of the depth of the outer central main groove 12A to the depth of the inner central main groove 12B is preferably 0.70 to 0.85, more preferably 0.75 to 0.80.

[0053] The ratio of the groove width of the outer central main groove 12A to the groove width of the outer shoulder main groove 12C is preferably 0.35 to 0.65, more preferably 0.40 to 0.60. The ratio of the groove depth of the outer central main groove 12A to the groove depth of the outer shoulder main groove 12C is preferably 0.70 to 0.85, more preferably 0.75 to 0.80.

[0054] The ratio of the groove width of the outer central main groove 12A to the groove width of the inner shoulder main groove 12D is preferably 0.35 to 0.65, more preferably 0.40 to 0.60. The ratio of the groove depth of the outer central main groove 12A to the groove depth of the inner shoulder main groove 12D is preferably 0.70 to 0.85, more preferably 0.75 to 0.80.

[0055] A central region 14A is provided between the outer central main groove 12A and the inner central main groove 12B, an outer intermediate region 14B is provided between the outer central main groove 12A and the outer shoulder main groove 12C, and an inner intermediate region 14C is provided between the inner central main groove 12B and the inner shoulder main groove 12D.

[0056] In addition, an outer shoulder area 14D is provided on the axially outer side of the outer shoulder main groove 12C (i.e., between the outer shoulder main groove 12C and the ground contact end Eo on the outer side of the vehicle), and an inner shoulder area 14E is provided on the axially outer side of the inner shoulder main groove 12D (i.e., between the inner shoulder main groove 12D and the ground contact end Ei on the inner side of the vehicle).

[0057] (3) Central Area 14A

[0058] like Figure 2 to Figure 4 As shown, the central area 14A provided between the outer central main groove 12A and the inner central main groove 12B includes: a central rib 18A which is continuous in the tire circumferential direction CD; a plurality of first central slits 16A1 which extend in a direction intersecting with the tire circumferential direction CD; and a plurality of second central slits 16A2.

[0059] The first central slit 16A1 is a concave groove extending in a direction intersecting the tire circumferential direction CD, one end of which opens in the outer central main groove 12A and the other end of which terminates in the central rib 18A. A central recess 16A3 having a triangular shape in a plan view and composed of a recessed portion having a shallower depth than the first central slit 16A1 is provided on the other end side (the inner central main groove 12B side) of the first central slit 16A1.

[0060] The second central slit 16A2 is a groove extending in a direction intersecting the tire circumferential direction CD, one end of which opens at the inner central main groove 12B and the other end of which terminates in the central rib 18A. Figure 7 The first central slits 16A1 and the second central slits 16A2 are alternately provided on the central rib 18A in the tire circumferential direction CD.

[0061] In addition, the central rib 18A is provided with a plurality of composite sipes 30 composed of a central sipe 31 and a pair of left and right end sipes 32 arranged in the tire circumferential direction CD. The central sipe 31 is provided at the central portion of the central rib 18A in the tire axial direction AD. The pair of left and right end sipes 32 are provided on both sides of the central sipe 31 in the tire axial direction AD. In the present embodiment, the composite sipes 30 are arranged in parallel with each other at intervals in the tire circumferential direction CD.

[0062] The groove width of the first central slit 16A1 and the second central slit 16A2 is preferably 3.0 mm to 6.0 mm, and more preferably 3.3 mm to 5.4 mm. The groove depth of the first central slit 16A1 and the second central slit 16A2 is preferably 4.0 mm to 8.5 mm, and more preferably 4.4 mm to 8.2 mm. The maximum width of the central recess 16A3 (the length of the portion connected to the first central slit 16A1) is preferably 2.0 mm to 5.0 mm, and more preferably 2.3 mm to 4.5 mm. The depth of the central recess 16A3 is preferably 1.0 mm to 5.5 mm, and more preferably 1.3 mm to 5.2 mm. In addition, the groove width of the central sipe 31 and the end sipe 32 is preferably 0.15 mm to 1.0 mm, and more preferably 0.3 mm to 0.6 mm. The groove depth of the center sipe 31 and the end sipe 32 is preferably 3.5 mm to 7.0 mm, and more preferably 4.0 mm to 6.5 mm.

[0063] (4) Outer middle area 14B

[0064] like Figure 2 , Figure 3 and Figure 5 As shown, the outer middle area 14B provided between the outer center main groove 12A and the outer shoulder main groove 12C includes: a plurality of outer middle blocks 18B arranged in the tire circumferential direction CD; and a plurality of outer middle slits 16B1, 16B2 provided between the outer middle blocks 18B.

[0065] The outer middle region 14B includes a plurality of first outer middle slits 16B1 provided on the extension line of the first central slit 16A1, and a plurality of second outer middle slits 16B2 provided on the extension line of the second central slit 16A2. The first outer middle slits 16B1 and the second outer middle slits 16B2 are grooves extending in a direction intersecting with the tire circumferential direction CD so as to open in the outer central main groove 12A and the outer shoulder main groove 12C, and are alternately provided in the tire circumferential direction CD.

[0066] Specifically, the first outer middle slit 16B1 is arranged such that at least a portion of the opening portion opening to the outer central main groove 12A is opposite to the opening portion of the first central slit 16A1 toward the outer central main groove 12A in a direction in which the first central slit 16A1 is extended. The first outer middle slit 16B1 constitutes a continuous groove connected to the first central slit 16A1.

[0067] like Figure 3 and Figure 5As shown, the first outer middle slit 16B1 is provided with a bent portion 16B1a at the center of the outer middle tread block 18B in the tire axial direction AD. The portion of the first outer middle slit 16B1 closer to the outer central main groove 12A than the bent portion 16B1a extends in a direction parallel to the first central slit 16A1, and the portion closer to the outer shoulder main groove 12C than the bent portion 16B1a is inclined in the opposite direction of the first central slit 16A1 with respect to the tire axial direction AD.

[0068] The groove depth of the first outer middle slit 16B1 closer to the outer shoulder main groove 12C than the bending portion 16B1a is set to be shallower than the groove depth of the portion closer to the outer center main groove 12A than the bending portion 16B1a or the groove depth of the second outer middle slit 16B2.

[0069] In the present embodiment, the groove depth of the first outer middle slit 16B1 closer to the outer shoulder main groove 12C side than the curved portion 16B1a is set to the same depth as the groove depth of the second central slit 16A2. The groove depth of the first outer middle slit 16B1 closer to the outer central main groove 12A side than the curved portion 16B1a is set to the same depth as the groove depth of the first central slit 16A1 or the second outer middle slit 16B2.

[0070] The second outer middle slit 16B2 is provided so that, although it is not connected to the second central slit 16A2, at least a part of the opening portion opened to the outer central main groove 12A exists on an extension line obtained by extending the second central slit 16A2.

[0071] The second outer middle slit 16B2 is provided with a bent portion 16B2a at a position overlapping with the bent portion 16B1a of the first outer middle slit 16B1 in the tire axial direction AD. The portion of the second outer middle slit 16B2 closer to the outer central main groove 12A than the bent portion 16B2a extends in a direction parallel to the second central slit 16A2, and the portion closer to the outer shoulder main groove 12C than the bent portion 16B2a is inclined in the opposite direction of the second central slit 16A2 with respect to the tire axial direction AD. In the present embodiment, the second outer middle slit 16B2 is composed of a groove extending in a direction parallel to the first outer middle slit 16B1.

[0072] The second outer middle block 18B is provided with a first outer middle recess 33 at the center of the sidewall in the tire circumferential direction CD facing the outer central main groove 12A, and a second outer middle recess 34 at the center of the sidewall in the tire circumferential direction CD facing the outer shoulder main groove 12C. The outer middle recesses 33 and 34 are recesses cut from the upper surface of the block toward the groove bottom of the main grooves 12A and 12C to the bottom of the block, and are formed in a triangular shape in a plan view, the front end of which becomes thinner as it approaches the tire axial center of the outer middle block 18B (the farther away from the sidewall of the block).

[0073] In addition, the outer middle block 18B is provided with a first outer middle sipe 35 and a second outer middle sipe 36 in the center in the tire circumferential direction CD, and third outer middle sipes 37 and 37 are provided outside the first outer middle sipe 35 and the second outer middle sipe 36 in the tire circumferential direction CD.

[0074] The first outer middle sipe 35 is a sipe extending in a direction intersecting the tire circumferential direction CD, one end of which is connected to the first outer middle notch 33 and opens in the outer central main groove via the first outer middle notch 33, and the other end of which terminates in the outer middle pattern block 18B. The second outer middle sipe 36 is a sipe extending in a direction intersecting the tire circumferential direction CD, one end of which is connected to the second outer middle notch 34 and opens in the outer shoulder main groove 12C via the second outer middle notch 34, and the other end of which terminates in the outer middle pattern block 18B.

[0075] The third outer middle sipes 37 are provided at positions further outward in the tire circumferential direction CD of the outer middle block 18B than the first outer middle sipes 35, and further outward in the tire circumferential direction CD of the outer middle block 18B than the second outer middle sipes 36. That is, the first outer middle sipe 35 and the second outer middle sipe 36 are provided between a pair of third outer middle sipes 37 provided at a distance in the tire circumferential direction CD in the outer middle block 18B.

[0076] The third outer middle sipe 37 is a sipe which opens at one end in the outer center main groove 12A and opens at the other end in the outer shoulder main groove 12C and is provided to penetrate the outer middle block 18B in the tire axial direction AD.

[0077] In the present embodiment, the first outer middle sipe 35, the second outer middle sipe 36, and the third outer middle sipe 37 are repeatedly bent or curved in a plan view while extending in the sipe length direction, and the cross-sectional shape parallel to the tread surface is formed into a waveform having an amplitude in the sipe width direction. The amplitude center lines of the first outer middle sipe 35, the second outer middle sipe 36, and the third outer middle sipe 37 are bent at the curved portions 35a, 36a, and 37a provided at positions overlapping with the curved portion 16B1a of the first outer middle slit 16B1 or the curved portion 16B2a of the second outer middle slit 16B2 in the tire axial direction AD, and extend in a direction parallel to the first outer middle slit 16B1 and the second outer middle slit 16B2.

[0078] In addition, the first outer middle sipe 35, the second outer middle sipe 36 and the third outer middle sipe 37 may be: Figure 4 The sipes extending linearly in the bent portions 35a, 36a, and 37a as shown may be formed in the bent portions 35a, 36a, and 37a in a waveform having an amplitude in the sipe width direction similarly to other portions.

[0079] The groove width of the first outer middle slit 16B1 and the second outer middle slit 16B2 is preferably 2.5 mm to 5.5 mm, more preferably 3.0 mm to 5.0 mm. The groove depth of the first outer middle slit 16B1 and the second outer middle slit 16B2 is preferably 7.0 mm to 8.5 mm, more preferably 7.2 mm to 8.2 mm.

[0080] The groove width of the first outer middle recess 33 and the second outer middle recess 34 is preferably 2.5 mm to 5.0 mm, more preferably 2.8 mm to 4.6 mm. The groove depth of the first outer middle recess 33 and the second outer middle recess 34 is preferably 1.0 mm to 5.5 mm, more preferably 1.3 mm to 5.2 mm.

[0081] The groove width of the first outer middle sipe 35, the second outer middle sipe 36, and the third outer middle sipe 37 is preferably 0.15 mm to 1.0 mm, and more preferably 0.3 mm to 0.4 mm. The groove depth of the first outer middle sipe 35, the second outer middle sipe 36, and the third outer middle sipe 37 is preferably 4.0 mm to 7.0 mm, and more preferably 6.0 mm to 6.5 mm.

[0082] In addition, if Figure 3As shown, when the following are set: the axial length W from the outer shoulder main groove 12C to the inner center main groove 12B, the length L in the circumferential direction CD from the first outer middle slit 16B1 to the first outer middle slit 16B1 adjacent on one side in the circumferential direction CD of the tire, the circumferential length L1 from the first outer middle slit 16B1 to the second outer middle slit 16B2 adjacent on one side in the circumferential direction CD of the tire, and the length L2 in the circumferential direction CD from the second outer middle slit 16B2 to the first outer middle slit 16B1 adjacent on one side in the circumferential direction CD of the tire, it is preferred that each length W, L, L1, and L2 satisfy the following formula (1) to

[0083] (4) All relations.

[0084] 1.0≤L / W≤2.0 Formula (1)

[0085] 0.4≤L1 / L≤0.5 Formula (2)

[0086] 0.4≤L2 / L≤0.5 Formula (3)

[0087] 0.9≤L1 / L2≤1.1 Formula (4)

[0088] (5) Inner middle area 14C

[0089] like Figure 2 , Figure 3 and Figure 6 As shown, the inner middle area 14C arranged between the inner center main groove 12B and the inner shoulder main groove 12D includes: a plurality of inner middle blocks 18C1, 18C2, which are arranged in the tire circumferential direction CD; and a plurality of inner middle slits 16C, which are arranged between the inner middle blocks 18C1, 18C2.

[0090] Specifically, the inner middle region 14C includes a plurality of first inner middle blocks 18C1 provided with first inner middle notches 40 and a plurality of second inner middle blocks 18C2 provided with second inner middle notches 41. The first inner middle blocks 18C1 and the second inner middle blocks 18C2 are alternately provided in the tire circumferential direction CD.

[0091] The first inner middle notch 40 is a transverse groove-shaped notch that opens at one end in the inner central main groove 12B and terminates at the other end in the inner middle region 14C, and is inclined with respect to the tire axial direction AD so as to extend in a direction parallel to the second central slit 16A2 provided in the central rib 18A. The first inner middle notch 40 is provided so that at least a portion of the opening portion that opens to the inner central main groove 12B faces the opening portion of the second central slit 16A2 that faces the inner central main groove 12B in the direction in which the second central slit 16A2 is extended.

[0092] The second inner middle recess 41 is a transverse groove-shaped incision with one end of its extension direction opening in the inner shoulder main groove 12D and the other end forming a terminal in the inner middle area 14C, and is inclined relative to the tire axial direction AD in a manner extending in a direction parallel to the second central slit 16A2 provided in the central rib 18A, or the first inner middle recess 40.

[0093] The plurality of inner middle slits 16C provided in the inner middle region 14C are grooves extending in a direction intersecting with the tire circumferential direction CD so as to open in the inner central main groove 12B and the inner shoulder main groove 12D. The inner middle slit 16C is provided with a first slit bent portion 16C1 on the inner central main groove 12B side, and a second slit bent portion 16C2 is provided on the inner shoulder main groove 12D side at a distance from the first slit bent portion 16C1 on the tire axially outer side AWo. The inner middle slit 16C is bent from one side to the other side in the tire circumferential direction at the first slit bent portion 16C1, and is bent from the other side to one side in the tire circumferential direction at the second slit bent portion 16C2.

[0094] Therefore, with respect to the inner middle slit 16C, the portion from the inner center main groove 12B to the first slit bend portion 16C1 is inclined relative to the tire axial direction AD in the same direction as the second center slit 16A2, the portion from the first slit bend portion 16C1 to the second slit bend portion 16C2 is inclined relative to the tire axial direction AD in the opposite direction to the second center slit 16A2, and the portion from the second slit bend portion 16C2 to the inner shoulder main groove 12D is inclined relative to the tire axial direction AD in the same direction as the second center slit 16A2.

[0095] In addition, the first inner middle block 18C1 and the second inner middle block 18C2 are provided with a first inner middle sipe 42 and a second inner middle sipe 43 extending in a direction intersecting with the tire circumferential direction CD so that one end opens in the inner central main groove 12B and the other end opens in the inner shoulder main groove 12D. Figure 6As shown, the first inner middle sipe 42 and the second inner middle sipe 43 extend in the sipe length direction while repeatedly bending or flexing, and the cross-sectional shape parallel to the tread surface is formed into a waveform having an amplitude in the sipe width direction.

[0096] The amplitude center line of the first inner middle sipe 42 is provided with a first curved portion 42A on the inner central main groove 12B side, and a second curved portion 42B is provided on the inner shoulder main groove 12D side at a distance from the first curved portion 42A on the outer side AWo in the tire axial direction. The amplitude center line of the first inner middle sipe 42 is bent from one side to the other side in the tire circumferential direction at the first curved portion 42A, and is bent from the other side to one side in the tire circumferential direction at the second curved portion 42B.

[0097] The first inner middle sipe 42 is divided at the second curved portion 42B. That is, the first inner middle sipe 42 includes an inner sipe portion 42C extending from the inner central main groove 12B to the outer side AWo in the tire axial direction, and an outer sipe portion 42D extending from the inner shoulder main groove 12D to the inner side AWi in the tire axial direction. The inner sipe portion 42C and the outer sipe portion 42D are arranged to face each other in the tire axial direction AD at a distance in the tire axial direction AD at a position closer to the inner shoulder main groove 12D than the tire axial center of the first inner middle block 18C1 so that the projections projected in the tire circumferential direction CD overlap each other at least partially.

[0098] The amplitude center line of the second inner middle sipe 43 is provided with a first curved portion 43A on the inner central main groove 12B side, and a second curved portion 43B is provided on the inner shoulder main groove 12D side at a distance from the first curved portion 43A on the outer side AWo in the tire axial direction. The amplitude center line of the second inner middle sipe 43 is bent from one side to the other side in the tire circumferential direction at the first curved portion 43A, and is bent from the other side to one side in the tire circumferential direction at the second curved portion 43B.

[0099] The second inner middle sipe 43 is divided at the first curved portion 43A. That is, the second inner middle sipe 43 includes an inner sipe portion 43C extending from the inner central main groove 12B to the outer side AWo in the tire axial direction, and an outer sipe portion 43D extending from the inner shoulder main groove 12D to the inner side AWi in the tire axial direction. The inner sipe portion 43C and the outer sipe portion 43D are arranged to face each other in the tire axial direction AD at a distance in the tire axial direction AD at a position closer to the inner central main groove 12B than the tire axial center of the first inner middle block 18C1 so that the projections projected in the tire circumferential direction CD overlap each other at least partially.

[0100] In addition, in the first inner middle pattern block 18C1, a plurality of third inner middle sipes 44 extending in a direction intersecting with the tire circumferential direction CD are provided at intervals in the tire circumferential direction CD on both sides of the first inner middle sipe 42. Figure 6 As shown, the third inner middle sipe 44 repeatedly bends or curves while extending in the sipe length direction, and the cross-sectional shape parallel to the tread surface is formed into a waveform having an amplitude in the sipe width direction. Regarding the third inner middle sipe 44, the amplitude center line of the third inner middle sipe 44 extends in a direction parallel to the first inner middle sipe 42.

[0101] In the second inner middle pattern block 18C2, and on both sides of the second inner middle sipe 43 in the tire circumferential direction CD, a plurality of fourth inner middle sipes 45 extending in a direction intersecting with the tire circumferential direction CD are provided at intervals in the tire circumferential direction CD. Figure 6 As shown, the fourth inner middle sipe 45 repeatedly bends or curves while extending in the sipe length direction, and the cross-sectional shape parallel to the tread surface is formed into a waveform having an amplitude in the sipe width direction. Regarding the fourth inner middle sipe 45, the amplitude center line of the fourth inner middle sipe 45 extends in a direction parallel to the second inner middle sipe 43.

[0102] The groove width of the inner middle slit 16C is preferably 2.5 mm to 4.5 mm, more preferably 2.5 mm to 4.2 mm. The groove depth of the inner middle slit 16C is preferably 7.0 mm to 8.5 mm, more preferably 7.2 mm to 8.2 mm. The groove width of the first inner middle notch 40 and the second inner middle notch 41 is preferably 2.0 mm to 5.0 mm, more preferably 2.6 mm to 4.5 mm. The groove depth of the first inner middle notch 40 and the second inner middle notch 41 is preferably 1.0 mm to 5.5 mm, more preferably 1.3 mm to 5.2 mm. The groove width of the first inner middle sipe 42, the second inner middle sipe 43, the third inner middle sipe 44 and the fourth inner middle sipe 45 is preferably 0.15 mm to 1.0 mm, more preferably 0.3 mm to 0.4 mm. The groove depths of the first inner middle sipe 42 , the second inner middle sipe 43 , the third inner middle sipe 44 , and the fourth inner middle sipe 45 are preferably 4.0 mm to 7.0 mm, and more preferably 6.0 mm to 6.5 mm.

[0103] (6) Outer shoulder area 14D

[0104] like Figure 2As shown, the outer shoulder region 14D includes: a plurality of outer shoulder blocks 18D arranged in the tire circumferential direction CD; and a plurality of outer shoulder slits 16D provided between the outer shoulder blocks 18D.

[0105] The outer shoulder slits 16D are grooves extending in a direction intersecting the tire circumferential direction CD so as to open at the outer shoulder main groove 12C and the ground contact end Eo, and are alternately arranged in the tire circumferential direction CD. The outer shoulder slits 16D are arranged so that at least a portion of the opening portion opening at the outer shoulder main groove 12C is opposite to the opening portions of the first outer middle slit 16B1 and the second outer middle slit 16B2 facing the outer shoulder main groove 12C in the tire axial direction AD.

[0106] The outer shoulder block 18D is provided with a plurality of (e.g., three) outer shoulder sipes 38 spaced apart in the tire circumferential direction CD. The outer shoulder sipe 38 is a sipe extending in a direction intersecting the tire circumferential direction CD, with one end opening at the outer shoulder main groove 12C and the other end opening at the ground contact end Eo. Figure 2 As shown, the outer shoulder sipe 38 extends in the longitudinal direction of the sipe while repeatedly bending or flexing, and the cross-sectional shape parallel to the tread surface is formed into a waveform having an amplitude in the sipe width direction.

[0107] (7) Inner shoulder area 14E

[0108] like Figure 2 As shown, the inner shoulder region 14E includes: a plurality of inner shoulder blocks 18E arranged in the tire circumferential direction CD; and a plurality of inner shoulder slits 16E provided between the inner shoulder blocks 18E.

[0109] The inner shoulder slits 16E are grooves extending in a direction intersecting the tire circumferential direction CD so as to open at the inner shoulder main groove 12D and the ground contact end Ei, and are alternately arranged in the tire circumferential direction CD. The inner shoulder slits 16E are arranged so that at least a portion of the opening portion opening at the inner shoulder main groove 12D is opposed to the opening portion of the inner middle slit 16C facing the inner shoulder main groove 12D in the tire axial direction AD.

[0110] In the inner shoulder block 18E, a plurality of (e.g., three) inner shoulder sipes 39 are provided at intervals in the tire circumferential direction CD. The inner shoulder sipe 39 is a sipe extending in a direction intersecting the tire circumferential direction CD, with one end opening at the inner shoulder main groove 12D and the other end opening at the ground contact end Ei. Figure 2As shown, the inner shoulder sipe 39 repeatedly bends or flexes while extending in the length direction of the sipe, and the cross-sectional shape parallel to the tread surface is formed as a waveform having an amplitude in the sipe width direction. In addition, in the present embodiment, the inner shoulder sipe 39 is composed of a sipe having a waveform with a longer bending or flexing repetition period than the outer shoulder sipe 38.

[0111] (8) Effect

[0112] Regarding the pneumatic tire 1 of this embodiment, the outer central main groove 12A is arranged to be closer to the outer side of the vehicle than the tire equatorial plane, and is a groove with a smaller groove width and a shallower depth than the inner central main groove 12B, the outer shoulder main groove 12C and the inner shoulder main groove 12D. Therefore, it is possible to suppress the reduction in the rigidity of the tread portion in the axial center portion of the tire near the outer side of the vehicle of the pneumatic tire 1 and ensure handling stability.

[0113] In the pneumatic tire 1 of the present embodiment, the central slits 16A1 opening in the outer central main groove 12A and the central slits 16A2 opening in the inner central main groove 12B are alternately provided on the extension line of the outer middle slits 16B1 and 16B2 of the central region 14A in the tire circumferential direction CD. Thus, the rigidity of the central region 14A can be ensured, and a high edge effect can be obtained by the central slits 16A1 and 16A2, so that both steering stability and running performance on icy and snowy roads can be achieved.

[0114] Regarding the pneumatic tire 1 of the present embodiment, a first outer middle sipe 35 and a second outer middle sipe 36 are provided in the central portion of the outer middle tread block 18B in the tire circumferential direction CD. Therefore, a higher edge effect based on the sipes 35 and 36 can be obtained, and the central portion of the outer middle tread block 18B in the tire circumferential direction CD is not divided by the sipes, so that the rigidity of the tread block can be ensured, thereby achieving both handling stability and driving performance on icy and snowy roads.

[0115] The pneumatic tire 1 of the present embodiment is provided with the third outer middle sipe 37 penetrating the outer middle pattern block 18B in the tire axial direction AD, so that a high edge effect can be obtained. Moreover, the third outer middle sipe 37 is provided at a position closer to the outer side of the outer middle pattern block 18B in the tire circumferential direction than the first outer middle sipe 35 and the second outer middle sipe 36, so that the rigidity of the outer middle pattern block 18B can be suppressed from decreasing.

[0116] Regarding the pneumatic tire 1 of the present embodiment, when the above-mentioned lengths W, L, L1, and L2 satisfy all the relationships of the above-mentioned formulas (1) to (4), the shape of the ground contact surface of the land portion sandwiched by the outer shoulder main groove 12C and the inner center main groove 12B in the tire axial direction AD and sandwiched by adjacent first outer middle slits 16B1 in the tire circumferential direction CD is not formed into a shape that is elongated in either the tire circumferential direction CD or the tire axial direction AD, but is formed into a shape that is roughly approximate to a square. Therefore, even if the slits are provided, the reduction in the rigidity of the land portion can be suppressed.

[0117] That is, in the present embodiment, the outer central main groove 12A is composed of a groove having a smaller groove width and a shallower depth than the other main grooves 12B, 12C, and 12D, and the second central slit 16A2 is not connected to the second outer middle slit 16B2. Therefore, the land portion sandwiched by the outer shoulder main groove 12C and the inner central main groove 12B in the tire axial direction AD and sandwiched by the adjacent first outer middle slits 16B1 in the tire circumferential direction CD can simulate and function as one land portion. When the length L is close to the length W (when L / W is close to 1), the land portion is formed in a shape close to a square, and the rigidity of the land portion is unlikely to decrease. In addition, when the length L is greater than the length W and L / W is close to 2, the outer middle pattern block 18B is formed in a shape close to a square, and therefore, the rigidity of the land portion is unlikely to decrease.

[0118] In the present embodiment, the belt reinforcement layer 9 is provided in the shoulder regions 14D and 14E, and no belt reinforcement layer is provided in the central region 14A, so that it is easy to touch the ground near the tire equatorial plane CL, and the steering stability can be improved. In addition, in the present embodiment, the inclination angle of the belt cords of the belt fabrics 7A and 7B constituting the belt layer 7 relative to the tire circumferential direction is set to be greater than 23 degrees and less than 29 degrees, thereby improving the steering stability.

[0119] In the present embodiment, the first inner middle blocks 18C1 provided with the first inner middle recesses 40 opening to the inner center main groove 12B and the second inner middle blocks 18C2 provided with the second inner middle recesses 41 opening to the inner shoulder main groove 12D are alternately provided in the inner middle region 14C in the tire circumferential direction. Thus, the recesses 40 and 41 are evenly arranged in the inner middle region 14C on both sides in the tire axial direction AD, so that the edge effect based on the recesses 40 and 41 can be obtained, and the block rigidity can be made uniform to disperse the ground contact pressure.

[0120] The inner middle blocks 18C1 and 18C2 are provided with inner middle sipes 42 and 43 which are formed into waveforms extending in a direction intersecting the tire circumferential direction CD in a manner that one end opens at the inner central main groove 12B and the other end opens at the inner shoulder main groove 12D. Since the inner middle sipes 42 and 43 are divided at the bending portions 42B and 43A, the reduction in the rigidity of the inner middle blocks 18C1 and 18C2 caused by the inner middle sipes 42 and 43 can be suppressed, and the edge effect can be improved.

[0121] In addition, in the first inner middle block 18C1, the inner middle notch 40 is provided on the inner central main groove 12B side, and the bent portion 42B that divides the sipe 42 is provided on the inner shoulder main groove 12D side, and in the second inner middle block 18C2, the inner middle notch 41 is provided on the inner shoulder main groove 12D side, and the bent portion 43A that divides the sipe 43 is provided on the inner central main groove 12B side. Thus, the reduction in rigidity of the inner middle blocks 18C1 and 18C2 caused by the inner middle notches 40 and 41 and the inner middle sipes 42 and 43 can be suppressed, and the edge effect can be improved.

[0122] In addition, in the present embodiment, the outer central main groove 12A is provided with a smaller groove width and a shallower depth than the inner central main groove 12B, but the first central slit 16A1 connected to the outer central main groove 12A is deeper than the second central slit 16A2 connected to the inner central main groove 12B. Therefore, the rigidity of the central region 14A on the vehicle outer side and the vehicle inner side can be made uniform, and the drainage performance of the central region 14A on the vehicle outer side can be ensured.

[0123] (9) Example of changes

[0124] Next, the modification examples are described. For the above embodiments, various modifications can be made within the scope of the main purpose of the invention. The modification examples are described below. In addition, in addition to the following modification examples, various omissions, substitutions, and changes can also be made within the scope of the main purpose of the invention.

[0125] In the above embodiment, the belt reinforcement layer 9 is provided in the shoulder regions 14D and 14E, but not in the central region 14A and the middle regions 14B and 14C. However, the belt reinforcement layer 9 may be provided in the central region 14A, the middle regions 14B and 14C and the shoulder regions 14D and 14E in a manner that covers the entire belt layer 7. In the case where the belt reinforcement layer 9 is provided to cover the entire belt layer 7, it is preferred that a belt reinforcement layer 9 thinner than the belt reinforcement layer 9 provided in the shoulder regions 14D and 14E is provided in the central region 14A. By making the thickness of the belt reinforcement layer 9 in the central region 14A thinner than that in the shoulder regions 14D and 14E, it is easy to contact the ground near the tire equatorial plane CL, and the steering stability can be improved.

Claims

1. A pneumatic tire having a tread portion in which three or more main grooves extending in the tire circumferential direction are formed in the tread rubber, and a direction in which the tire is to be mounted on a vehicle is specified, The tread rubber comprises: an outer central main groove, which is arranged closer to the outer side of the vehicle than the tire equatorial plane; an inner central main groove, which is arranged closer to the inner side of the vehicle than the tire equatorial plane; an inner shoulder main groove, which is adjacent to the inner central main groove on the outer side of the tire axial direction; and an inner middle area, which is divided by the inner central main groove and the inner shoulder main groove, wherein: The inner middle region includes: a plurality of inner middle tread blocks arranged in a circumferential direction of the tire; and a plurality of inner middle slits arranged between the inner middle tread blocks. The plurality of inner middle tread blocks include: a first inner middle tread block having a first inner middle recess opening in the inner central main groove; and a second inner middle tread block having a second inner middle recess opening in the inner shoulder main groove. The first inner middle blocks and the second inner middle blocks are alternately arranged in the tire circumferential direction.

2. The pneumatic tire according to claim 1, wherein: The first inner middle block and the second inner middle block include inner middle sipes formed in a corrugated shape extending in a direction intersecting with the tire circumferential direction so that one end opens in the inner central main groove and the other end opens in the inner shoulder main groove. The amplitude center line of the inner middle sipe is bent in opposite directions at a first curved portion provided on the inner side of the inner middle block in the tire axial direction and a second curved portion provided on the outer side of the inner middle block in the tire axial direction. The inner middle sipe is divided at one of the first bent portion and the second bent portion.

3. The pneumatic tire according to claim 2, wherein: The inner middle sipe provided in the first inner middle block is divided at the second bent portion, and the inner middle sipe provided in the second inner middle block is divided at the first bent portion.

4. The pneumatic tire according to claim 1, wherein: The inner middle slit includes a first slit bent portion bent from one side to the other side in the tire circumferential direction, and a second slit bent portion bent from the other side to the one side in the tire circumferential direction.

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