pneumatic tires

Abstract

having pneumatic tires (1): four main grooves (3A-3D) formed on a tread surface (2) such that the four main grooves (3A-3D) extend in a tire circumferential direction (Y); a multitude of lateral grooves (4A-4F) formed on the running surface (2); and five block rows (5A-5E), each comprising a plurality of blocks (6, 7, 8, 9, 10) defined by the main grooves (3A-3D) and a pair of lateral grooves (4A-4F) arranged adjacent to each other in the tire circumferential direction (Y), the blocks (6, 7, 8, 9, 10) being grouped in a row (5A-5E) in the tire circumferential direction (Y), wherein a mounting position of a pneumatic tire (1) is shown with regard to a vehicle body in a tire width direction (X), the main grooves (3A-3D) feature: an inner main groove (3A) which is positioned on an innermost side in the tire width direction (X) in a state in which the tire (1) is mounted on the vehicle; an outer main groove (3D) positioned on an outermost side in the tire width direction (X) in a state in which the tire (1) is mounted on the vehicle; a first central main groove (3B) arranged adjacent to an outer side of the inner main groove (3A) in the tire width direction (X); and a second central main groove (3C) which is located adjacent to an inner side of the outer main groove (3D) in the tire width direction (X), where the block rows (5A-5E) exhibit: an inner shoulder row (5A) positioned within the inner main groove (3A) in the tire width direction (X); an outer shoulder row (5E) positioned outside the outer main groove (3D) in the tire width direction (X); an inner middle row (5B) positioned between the inner main groove (3A) and the first central main groove (3B); an outer middle row (5D) positioned between the outer main groove (3D) and the second central main groove (3C); and a central row (5C) positioned between the first central main groove (3B) and the second central main groove (3C), where a groove width (GWb) of the first central main groove (3B) and a groove width (GWc) of the second central main groove (3C) is larger than a groove width (GWa) of the inner main groove (3A) and a groove width (GWd) of the outer main groove (3D), wherein the lateral groove (4A) comprises a plurality of first lateral grooves (4A) formed at intervals in the tire circumferential direction (Y) to define blocks (6) belonging to the inner shoulder row (5A), wherein a first raised part (16) connecting the block pairs (6) belonging to the inner shoulder row (5A) is formed in every second of the first lateral grooves (4A) on the inner main groove side, a depth (GD1') of the first lateral groove (4A) in the first raised part (16) is less than a depth (GD1) of the first lateral groove (4A) in other parts, and the first raised part (16) does not extend into the inner main groove (3A) in the tire width direction (X), wherein a second raised part (17) is formed on the outer main groove (3D) to connect an outer side face of the block (9) belonging to the outer middle row (5D) and an inner side face of the block (10) belonging to the outer shoulder row (5E), and a depth (GD0') of the outer main groove (3D) in the second raised part (17) is less than a depth (GD0) of the outer main groove (3D) in other parts, and wherein a plurality of second slots (10b) which are interconnected in the tire circumferential direction (Y) are formed in the block (10) which belongs to the outer shoulder row (5E).

Description

BACKGROUND OF THE INVENTIONTechnical field

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

[0002] WO 2012 / 111589 A1, Japanese Patent JP 5639461 B2, Japanese Patent JP 3376342 B2, and JP 2012-96782 A disclose a pneumatic tire having a plurality of block rows extending in a tire circumferential direction. Each block row has a plurality of blocks grouped in a row in the tire circumferential direction. However, it is not always the case with these conventional pneumatic tires that the pneumatic tires are successful in improving all of the following: driving performance, braking performance, and turning performance while ensuring tread life.

[0003] Tires with a variety of tread patterns have been proposed for the purpose of improving movement performance (acceleration, braking, turning, and the like) on a dry road surface (a road surface on which no rain or snow has fallen) and a snowy road surface (snowy road).

[0004] For example, on a tread surface of a tire disclosed in Japanese Patent JP 5528208 B2, grooves, each having recessed portions (sipes) on a groove bottom, are formed on a rib formed between two main grooves arranged adjacent to each other at predetermined intervals. With such a configuration, a ground contact area can be reduced, and therefore road noise can be reduced.

[0005] In Japanese patent JP 4718294 B2, sipes are formed on the bottom of a protrusion groove in a shoulder region. The sipes grouped on the groove bottom are minimally raised even when the pneumatic tire is used for a long period of time, and therefore, the on-snow performance provided by the sipes can be maintained for a long period of time.

[0006] According to US 2014 / 0 360 640 A1, blocks on the tread of a pneumatic tire are formed by main grooves extending in the circumferential direction of the tire and by lateral grooves intersecting with the main grooves. The blocks include: center blocks arranged in a central region in the tire width direction; shoulder blocks arranged on both side regions in the tire width direction; and intermediate blocks arranged in an intermediate region between the center blocks and the shoulder blocks. The lateral groove formed between the shoulder blocks and the lateral groove formed between the intermediate blocks, which are offset from each other in the circumferential direction of the tire, are connected to each other via the main groove by an auxiliary block.

[0007] To improve the performance of a tire on snow and wet roads without compromising tire life, JP H06-227 213 A proposes a pneumatic radial tire with center block rows and side part block rows. Each block of the side part block row is divided into sub-blocks on the outer and inner sides across the width by a thin groove extending continuously in the circumferential direction. The sub-block, which is located on the outer side across the width, is divided into substantially two block parts by an auxiliary groove extending across the width. The thin groove is positioned within the range of 5 to 15% of the tread base width from the tread end and has a width smaller than that of the circumferential groove and in the range of 3 to 5 mm. At least one shallow groove per block is provided in this thin groove.

[0008] A pneumatic tire having a block pattern is disclosed in WO 2011 / 087134 A1, which enables improvements in snow performance while reducing uneven wear resulting from rear tire deformation. In a tire, a raised portion traversing a shoulder defining a center side block and a shoulder block, and having a height in the range of 10-20% of the shoulder depth, is disposed on caster grooves extending in the direction intersecting the main groove and the shoulder grooves. This increases the edge components in the circumferential direction of the tire and balances the tread rigidity in the width direction of the tire without reducing fluid drainage performance.

[0009] US 2010 / 0 186 861 A1 discloses a pneumatic tire. Five land portions on the tread are defined by four main grooves extending in the tire circumferential direction. The five land portions include a center land portion between the first main grooves, two center land portions between the first main grooves and the second main grooves, and two shoulder land portions located outside the second main grooves in the tire width direction. Subgrooves and sipes are formed on the land portions. The total groove area ratios of the subgrooves and the sipes in the land portions are different in the center land portion and the shoulder land portion compared to the center land portion, with the total groove area ratio being lower in the center land portion and the shoulder land portion and higher in the center land portion.

[0010] A tire for vehicle wheels according to EP 2 095 976 A2 comprises a tread band with a tread pattern defined by at least two axially juxtaposed circumferential sections, at least one of which has a first geometric module repeated many times along the circumferential direction of the tire. The first geometric module comprises at least two shoulder blocks circumferentially aligned along a lateral edge of the tread band and delimited by grooves oriented transversely to the circumferential direction of the tire, and an elongate web delimited by two grooves oblique to the circumferential direction and subdivided with respect to the axial extent of the tread band into a plurality of intermediate blocks delimited by a plurality of cuts substantially transversely to the elongate web.

[0011] CN 1 04 943 479 A discloses a tread pattern of an all-season drive wheel. The tread pattern comprises first tread blocks arranged circumferentially on the wheel shoulder portions, wherein adjacent first tread blocks are connected by first reinforcing ribs; fourth tread grooves are formed in the wheel shoulder portions corresponding to the first reinforcing ribs; second tread blocks in the circumferential direction are arranged on the inner sides of the first tread blocks by taking the tread centerline as a line of symmetry; first tread grooves are formed between the first tread blocks and the second tread blocks; third tread blocks in the circumferential direction are arranged on the inner sides of the second tread blocks; second tread grooves are formed between the second tread blocks and the third tread blocks; a third tread groove is formed between every two adjacent third tread blocks.The tread pattern has the advantages of being suitable for medium and long-distance driving wheel transportation, suitable for driving on ordinary and high-grade road surfaces, excellent grip and traction performance due to the mud and snow pattern, excellent one-time mileage and abrasion resistance due to the widened tread design, and excellent water drainage and side slip prevention performance.

[0012] CN 2 04 196 596 U discloses an eccentric high-mileage wear-resistant truck tire. The eccentric high-mileage wear-resistant truck tire comprises a tire tread, the tire tread being defined by a center line, and the left and right surfaces both being provided with at least two stripe-shaped parts arranged side by side and having a certain width; stripe-shaped parts comprise pattern base blocks repeatedly arranged along the circumference of the tire; a reinforcing rib is arranged between the adjacent pattern base blocks along the circumferential direction of the tire and is used to connect the pattern base blocks; shoulder parts are respectively arranged on the two sides of the tire; the shoulder parts comprise shoulder blocks repeatedly arranged along the circumference of the tire;Reinforcing ribs are arranged between the adjacent shoulder blocks along the tire's circumferential direction and are used to connect the shoulder blocks; pattern grooves are arranged to separate adjacent strip-shaped parts and to separate the strip-shaped parts and the shoulder parts along the tire's axial direction. The eccentric high-mileage wear-resistant truck tire disclosed by CN 2 04 196 596 U has the advantageous effects of improving abnormal abrasion caused by inappropriate shear and deformation of the tire surface blocks, improving wear resistance, and reducing the occurrence of abnormal abrasion and noise due to the tread blocks, tread grooves, and shoulders that are ingenious in the structural design.Meanwhile, the eccentric wear-resistant truck tire with high mileage is relatively good in practical use effect and suitable for promotion.;

[0013] To prevent studding by maintaining dry performance and improving snow performance, JP 2005-014859 A proposes a pneumatic tire having, on the tread surface, blocks divided by main grooves and main slits connecting the main grooves, as well as auxiliary slits dividing the blocks into generally two parts in the tire circumferential direction. Corrugated sipes are engraved on both sides of the auxiliary slits in the tire circumferential direction, and linear sipes are engraved at the lower parts of the auxiliary slits. The width of the auxiliary slits is 40 to 60% of the width of the main slits dividing the blocks, and the depth of the auxiliary slits is 40 to 60% of the depth of the main slits dividing the blocks. SUMMARY

[0014] It is a first object of the present invention to provide a pneumatic tire which can improve driving performance, braking performance and turning performance while ensuring the running performance.

[0015] It is a second object of the present disclosure to provide a pneumatic tire that can improve movement performance on both a dry road surface and a snowy road surface.

[0016] A first aspect of the present invention corresponds to the first object. The first aspect of the present invention provides a pneumatic tire as defined in claim 1.

[0017] A first lateral groove is formed between the blocks constituting the inner shoulder row. The first lateral groove allows deformation of these blocks in a tire width direction, so that rigidity in a longitudinal direction (tire circumferential direction) is lower. However, by forming a first raised portion connecting the pair of blocks belonging to the inner shoulder row on the first lateral groove, it becomes possible to cause these blocks to deform integrally against the load in the longitudinal direction. That is, by forming the first raised portion, the rigidity in the longitudinal direction of the blocks constituting the inner shoulder row is increased, and therefore, driving performance and braking performance on a dry road surface can be improved.

[0018] A camber is transmitted for a pneumatic tire (hereinafter referred to as a "tire") mounted on a vehicle. Accordingly, on a dry road surface, a shape of a ground contact region with a road surface tends to expand in a tire circumferential direction at an inner part of a tread in a tire width direction (especially at the time of braking). Accordingly, by increasing the rigidity of connecting the blocks constituting the inner shoulder row at the first raised part, driving performance and braking performance on the dry road surface can be further effectively realized.

[0019] The first raised portion is formed on every other first lateral groove, forming a plurality of first lateral grooves. Accordingly, in the first lateral groove where the first raised portion is not formed, the flow of water is not obstructed by the first raised portion, and therefore priority is given to ensuring drainage performance. That is, by forming the first raised portion on every other first lateral groove, forming a plurality of first lateral grooves, the tire can achieve both ensuring drainage performance and improving driving performance and braking performance on dry road surfaces.

[0020] One side of the block belonging to the outer center row in the tire width direction is defined by the outer main groove. Both sides of the block belonging to the outer center row in the tire circumferential direction are defined by lateral grooves. These outer main grooves and lateral grooves allow the deformation of the blocks belonging to the outer center row in the tire width direction, and therefore, the outer main grooves and lateral grooves reduce the rigidity of the block in the lateral direction (tire width direction). However, by connecting the block belonging to the outer center row and the block belonging to the outer shoulder row together through the second raised part, it is possible to make these blocks deform integrally against a load in the lateral direction.That is, with the formation of the second raised part, the rigidity of the blocks belonging to the outer middle row can be improved in the lateral direction and therefore a steering performance or turning performance on a dry road surface can be improved.

[0021] The second raised portion is not formed over the entire outer main groove, but is partially formed in the region defined by the imaginary line connecting the block belonging to the outer middle row and the block belonging to the outer shoulder row. Accordingly, the effect of the second raised portion on the water flow in the outer main groove is limited, thus ensuring drainage performance.

[0022] A second aspect of the present disclosure corresponds to the second object. The second aspect of the present disclosure provides a pneumatic tire comprising: at least three main grooves extending in a tire circumferential direction and formed on a tread; between at least a pair of the main grooves arranged adjacent to each other among the three main grooves, a plurality of blocks separated from a periphery by the main grooves and deep grooves are grouped in a row in the tire circumferential direction; and all of the plurality of blocks are formed of a composite block in which a surface is divided by one or a plurality of shallow grooves having sipes that the sipes have on a groove bottom.

[0023] According to a pneumatic tire according to the second aspect of the present disclosure, the pneumatic tire can improve snow performance while preventing a decrease in dry performance by utilizing a characteristic of a “composite block”.

[0024] A third aspect of the present disclosure also corresponds to the second objective. The third aspect of the present disclosure provides a pneumatic tire having at least three main grooves extending in a tire circumferential direction and formed on a tread surface, wherein a rib positioned between a pair of main grooves positioned on an innermost side in a state where a tire is mounted on the vehicle is configured so that the rib is not divided into blocks by deep grooves, and a sipe or a shallow groove with sipes having the sipes on a groove bottom is formed on a surface of the rib, wherein a plurality of blocks separated from a periphery by the main grooves and the deep grooves are grouped in a row in the tire circumferential direction in at least one of other regions, each of which is arranged between the main grooves.and wherein all of the plurality of blocks are formed from a composite block having a surface divided by one or more shallow grooves with slats having the slats on a groove bottom.,

[0025] First, a rib is grouped in the region sandwiched between two main grooves, in a region between a pair of main grooves positioned on the innermost side in a state where a tire is mounted on a vehicle (a basic contact length in the tire circumferential direction is assumed to be the longest in this region when a camber is assumed). The rib is not divided into blocks by deep grooves, and the groove has sipes on one surface thereof or has a shallow groove with sipes that has the sipes on the groove bottom thereof.

[0026] Such a rib has high rigidity as a whole and can increase grip force due to the sipes or shallow grooves with sipes formed on the surface of the rib. That is, by forming the rib with high rigidity and high grip force in the region with a long ground contact length (inner center region), the pneumatic tire can achieve high traction and braking performance on dry road surfaces.

[0027] Furthermore, the pneumatic tire can increase snow performance while preventing a reduction in dry performance by utilizing the “composite block” characteristic. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The foregoing and other features of the present invention will become apparent from the following description and drawings of an illustrative embodiment of the invention, in which: Fig.1 shows a development of a tread structure of a tire according to a first embodiment of the present invention; Fig. 2 a partially enlarged view of Fig. 1 shows; Fig. Figure 3 shows a schematic sectional view of the various grooves described; Fig. 4 is a schematic sectional view taken along a line IV-IV in Fig. 2 shows; Fig. 5 is a schematic sectional view taken along a line VV in Fig. 2 shows; Fig. 6 shows a developed view of a tread structure of a tire according to a second embodiment of the present disclosure; Fig. 7 a partially enlarged view of Fig. 6 shows; Fig. 8 shows a developed view of a tread structure of a tire according to a third embodiment of the present disclosure; Fig.9A is a partially enlarged view of Fig. 8 shows; Fig. 9B is a partially enlarged view of Fig. 8 shows; Fig. 10 shows a developed view of a tread structure of a tire according to a fourth embodiment of the present disclosure; Fig. 11A is a partially enlarged view of Fig. 10 shows; Fig. 11B is a partially enlarged view of Fig. 10 shows; Fig. 11C a partially enlarged view of Fig. 10 shows; Fig. 12 shows a set of developed views of a tread structure of tires according to Comparative Examples 3 to 6; Fig. 13 shows a development of a tread structure of a tire according to a fifth embodiment of the present disclosure; Fig. 14A is a partially enlarged view of Fig. 13 shows; Fig.14B is a partially enlarged view of Fig. 13 shows; Fig. 15 shows a developed view of a tread structure of a tire according to a sixth embodiment of the present disclosure; Fig. 16A is a partially enlarged view of Fig. 15 shows; Fig. 16B is a partially enlarged view of Fig. 15 shows; Fig. 16C a partially enlarged view of Fig. 15 shows; Fig. 17 shows a development of a tread structure of a tire according to a seventh embodiment of the present disclosure; Fig. 18A is a partially enlarged view of Fig. 17 shows; Fig. 18B is a partially enlarged view of Fig. 17 shows; Fig. 18C a partially enlarged view of Fig. 17 shows; Fig.19 shows a development of a tread structure of a tire according to a comparative example 7. DETAILED DESCRIPTION OF EMBODIMENTS

[0029] An embodiment of the present invention will be described with reference to the attached drawings.

[0030] The first embodiment corresponds to the first aspect of the present invention.

[0031] Referring to Fig. 1 and Fig. 2, on a tread 2 of a pneumatic tire 1 which is a rubber-made winter tire according to this embodiment (hereinafter referred to as “tire”), four main grooves 3A to 3D are formed such that the main grooves 3A to 3D extend in a tire circumferential direction (denoted by symbol Y in Fig. 1 and Fig.2). A plurality of lateral grooves (projection grooves) 4A to 4F are formed on the tread 2 such that lateral grooves 4A to 4F extend in a tire width direction (denoted by symbol X in Fig. 1 and Fig. 2) extend.

[0032] A mounting position of a tire 1 in a tire width direction is designated with respect to a vehicle (not shown in the drawing). In the following description, the terms "inside" and "outside" in the tire width direction are defined with respect to the case where the tire 1 is mounted on the vehicle in a normal position. Fig. 1 and Fig. 2, a center line (equator line) in the tire width direction of the tread 2 is denoted by symbol CL. Ground contact edges of the tread 2, inside and outside on the tread 2 in the tire width direction, are denoted by symbols GEi and GEo, respectively.

[0033] Also referring to Fig.3, the inner main groove 3A, positioned innermost in the tire width direction, is a linear groove having a groove depth GD0 and a substantially fixed groove width GWa. The outer main groove 3, positioned outermost in the tire width direction, is a gently winding, zigzag-shaped groove having a groove depth GD0 and a groove width GWd. A first central main groove 3B, located adjacent to an outer side of the inner main groove 3A in the tire width direction, is a linear groove having a groove depth GD0 and a substantially fixed groove width GWb. A second central main groove 3C, which is arranged adjacent to an inner side of the outer main groove 3D in the tire width direction and adjacent to an outer side of the first central main groove 3B in the tire width direction, is a linear groove having a groove depth GD0 and having a substantially fixed groove width GWc.

[0034] With four main grooves 3A to 3D and the lateral grooves 4A to 4F, five block rows are formed extending in the tire circumferential direction. That is, the inner shoulder row 5A, the inner center row 5B, the center row 5C, the outer center row 5D, and the outer shoulder row 5E are formed.

[0035] Among the block rows, the inner shoulder row 5A, which is positioned innermost in the tire width direction, is positioned within the inner main groove 3A in the tire width direction. The inner shoulder row 5A extends toward the inner side in the tire width direction (a side part side of the tire 1 not shown in the drawings) beyond the inner ground contact edge GEi. The inner shoulder row 5A includes a plurality of inner shoulder blocks 6 defined by the inner main groove 3A and the plurality of lateral grooves 4A (first lateral grooves) formed at intervals in the tire circumferential direction. In other words, the inner shoulder row 5A is formed by the plurality of inner shoulder blocks 6 grouped in a row in the tire circumferential direction. Two sipes 6a extending in the tire width direction are formed on each individual inner shoulder block 6.A zigzag-shaped slit 6b extending in the tire width direction is formed on an innermost part of each individual inner shoulder block 6 in the tire width direction. Further, three inner longitudinal slits (first slits) 6c, 6d, 6e are formed on each individual inner shoulder block 6, as described in detail later.

[0036] Among the block rows, the outermost shoulder row 5E in the tire width direction is positioned outside the outer main groove 3D in the tire width direction. The outer shoulder row 5E extends toward the outer side in the tire width direction (a side part side of the tire 1 not shown in the drawings) beyond the outer ground contact edge GEo. The outer shoulder row 5E includes a plurality of outer shoulder blocks 10 defined by the outer main groove 3D and the plurality of lateral grooves 4F (second lateral grooves) formed at intervals in the tire circumferential direction. In other words, the outer shoulder row 5E is formed by the plurality of outer shoulder blocks 10 grouped in a row in the tire circumferential direction. Three sipes 10a extending in the tire width direction are formed on each individual outer shoulder block 10.An outer longitudinal slit (second slit) 10b is formed on each individual outer shoulder block 10, as described in detail later. A pair of lateral grooves 4F arranged adjacent to each other in the tire circumferential direction are connected to each other by short longitudinal grooves 11 in a region further outward from the outer ground contact edge GEo.

[0037] The inner center row 5B is arranged adjacent to an outer side of the inner shoulder row 5A in the tire width direction and is positioned between the inner main groove 3A and the first central main groove 3B. The inner center row 5B includes a plurality of inner center blocks 7 defined by the inner main groove 3A, the first central main groove 3B, and a plurality of lateral grooves 4B formed at intervals in the tire circumferential direction. In other words, the inner center row 5B is formed by the plurality of inner center blocks 7 grouped in a row in the tire circumferential direction. A lateral slit 7a, which intersects the individual inner center block 7 in the tire width direction, is formed near the center of the inner center block 7 in the tire circumferential direction.Further, on the inner center block 7, two sipes 7b extending in the tire width direction are formed on both sides of the lateral slit 7a, respectively.

[0038] The outer center row 5D is arranged adjacent to an inner side of the outer shoulder row 5E in the tire width direction and is positioned between the outer main groove 3D and the second center main groove 3C. The outer center row 5D includes a plurality of outer center blocks 9 defined by the outer main groove 3D, the second center main groove 3C, and a plurality of lateral grooves (third lateral grooves) 4D, 4E alternately formed at intervals in the tire circumferential direction. In other words, the outer center row 5D is formed by the plurality of outer center blocks 9 grouped in a row in the tire circumferential direction. Three sipes 9a extending in the tire width direction are formed on each individual outer center block 9.

[0039] The central row 5C is formed on the center line CL. The central row 5C is arranged adjacent to the inner center row 5B and the outer center row 5D and is positioned between the first center main groove 3B and the second center main groove 3C. The central row 5C includes a plurality of center blocks 8 defined by the first center main groove 3B, the second center main groove 3C, and a plurality of lateral grooves 4C formed at intervals in the tire circumferential direction. In other words, the central row 5C is formed from the plurality of center blocks 8 grouped in a row in the tire circumferential direction. A plurality of sipes 8a extending in the tire width direction are formed on each individual center block 8.

[0040] The lateral grooves 4A to 4F are designed with respect to Fig.3. The lateral groove 4A formed on the inner shoulder row 5A, the lateral groove 4D formed on the outer middle row 5D, and the lateral groove 4F formed on the outer shoulder row 5E are each formed of a "deep lateral groove." On the other hand, the lateral groove 4B formed on the inner middle row 5B, the lateral groove 4C formed on the central row 5C, and the lateral groove 4E formed on the outer middle row 5D are each formed of a "shallow groove with sipes."

[0041] The lateral grooves 4A, 4D, 4F, which are the "deep lateral grooves," have a substantially rectangular cross-section. A groove depth GD1 of these lateral grooves 4A, 4D, 4F is set to 0.85 to 1.0 times inclusive of the groove depth GD0 of the main grooves 3A to 3D (0.85 GD0 ≤ GD1 ≤ 1.0 GD0). The groove width GW1 of these lateral grooves 4A, 4D, 4F is preferably set to a value falling within a range of 2.5 mm to 8 mm inclusive.

[0042] The lateral grooves 4B, 4C, 4E formed of the "shallow groove with sipes" are formed in a shape in which sipes 14 are formed on a groove bottom of the shallow groove 13. In this specification, grooves having a groove depth GD2 that is 0.4 to 0.6 times inclusive of the groove depth GD0 of the main grooves 3A to 3D are referred to as "shallow grooves" (0.4 GD0 ≤ GD2 ≤ 0.6 GD0). A groove width GW2 of a "shallow groove" is preferably equal to or less than the groove width GW1 of a "deep lateral groove" (GW2 ≤ GW1). Further, in this specification, "sipe" is referred to as a sipe having a narrower width than the "main groove," "deep lateral groove," and "shallow groove." Generally, the width GW3 is set to a value falling within a range of 0.8 mm to 1.5 mm inclusive, and the depth is 2 mm or less.It is preferable that the groove depth GD3 of the "shallow groove with sipes" be 0.6 to 1.0 times inclusive of the groove depth GD0 of the main grooves 3A to 3D (0.6 GD0 ≤ GD3 ≤ 1.0 GD0). The concept of a "sipe" encompasses the sipes 6a of the inner shoulder block 6, the sipes 10a of the outer shoulder block 10, the sipes 7b of the inner center block 7, the sipes 9a of the outer center block 9, and the sipes 8a of the center block 8.

[0043] In general, a "shallow groove with sipes" exhibits strong resistance to block drop caused by ground surface reaction compared to grooves with the same full depth. Accordingly, it is possible to also prevent a reduction in rigidity while preventing a reduction in snow column shear force. In order to obtain a snow performance improvement effect by adding the sipes 14 to the groove bottom of the shallow groove 13, it is preferable that the depth of the sipes 14 per se be 0.2 mm or more as a minimum. On the other hand, when the width GW3 of "sipes" is less than 0.8 mm, a snow performance improvement effect is small, while when the width GW3 exceeds 1.5 mm, a tread rigidity is largely reduced, and therefore both cases are undesirable.

[0044] As previously described, the zigzag-shaped slot 6b is formed on the inner shoulder block 6. The inner longitudinal slots 6c, 6d, 6e are formed on the inner shoulder block 6.

[0045] The outer longitudinal slot 10b is formed on the outer shoulder block 10. The lateral slot 7a is formed on the inner center block 7. In this specification, these "slots" are referred to as cuts with a smaller groove depth and a narrower groove width than the "main grooves," the "deep lateral grooves," and the "shallow grooves," while they have a deeper groove depth and a wider groove width than the "sipes."

[0046] Referring to Fig.2, in the inner center block 7 constituting the inner center row 5B, a tire circumferential direction length IHc is greater than a tire width direction length IHw. That is, the inner center block 7 has an elongated shape in the tire circumferential direction. It is preferable that, for example, the tire circumferential direction length IHc be set to 1.3 to 1.9 times inclusive as large as the tire width direction length IHw (1.3 ≤ IHc / IHw ≤ 1.9). A wheel camber is imposed on the tire 1 mounted on a vehicle. There is a tendency for a shape of a ground contact region on a road surface to expand in a tire circumferential direction on an inner part of the tread 2 in a tire width direction (especially at the time of applied braking). Accordingly, by forming the inner center block 7 in an elongated shape in the tire circumferential direction, the driving performance and braking performance on a dry road surface can be improved.Further, by forming the inner center block 7 in an elongated shape in the tire circumferential direction, the sensitivity to a steering angle is improved when a steering wheel is turned during driving.

[0047] Referring to Fig.2, in the outer center block 9 constituting the outer center row 5D, a tire width direction length OHw is greater than a tire circumferential direction length OHc. That is, the outer center block 9 has an elongated shape in the tire width direction. It is preferable that, for example, the tire width direction length OHw be set to 1.1 to 1.5 times inclusive as large as the tire circumferential direction length OHc (1.1≤OHw / OHc≤1.5). By forming the outer center block 9 in an elongated shape in the tire width direction, rigidity of the outer center block 9 against a load in a lateral direction (tire width direction) is increased, and therefore, turning performance on a dry road surface is improved.Furthermore, the outer center block 9 is formed in an elongated shape in the tire width direction, and therefore, an edge component in a tire width direction in a region outside the tread 2 is increased in the tire width direction. As a result, driving performance and braking performance on a snowy road surface are also improved.

[0048] In this embodiment, the total number Na of the inner shoulder blocks 6 is set larger than the total number Ne of the outer shoulder blocks 10 (Na>Ne). Further, the total number Nb of the inner middle blocks 7 is set smaller than the total number Nd of the outer middle blocks 9 (Nb<Nd). In this embodiment, the total number Nd of the outer shoulder blocks 9 and the total number Ne of the outer shoulder blocks 10 are set equal to each other (Nd=Ne). In short, in this embodiment, the total numbers of the blocks Na, Nb, Nd, Ne satisfy the following relationship. Na>Nd=Ne>Nb

[0049] The total number Nc of the central blocks 8 is set smaller than the total numbers Na, Nb, Nd, Ne of the blocks in the block rows that are not the central row C.

[0050] The total number Na of the inner shoulder blocks 6 can be set to 1.8 to 2.5 times inclusive as large as the total number Nb of the inner middle blocks 7. The total number Nc of the center blocks 8 can be set to 1.0 to 1.4 times inclusive as large as the total number Nb of the inner middle blocks 7. The total number Nd of the outer middle blocks 9 can be set to 1.3 to 1.7 times inclusive as large as the total number Nb of the inner middle blocks 7. The total number Ne of the outer shoulder blocks 10 can be set to 1.3 to 1.7 times inclusive as large as the total number Nb of the inner middle blocks 7.

[0051] By setting the total number Na of the inner shoulder blocks 6 larger than the total number Ne of the outer shoulder blocks 10, the road grip generated by a snow column shear force is increased, particularly at an inner side part of the tread 2 in a tire width direction, and therefore, snow performance is improved. Further, setting the total number Na of the inner shoulder blocks 6 larger than the total number Ne of the outer shoulder blocks 10 means that the outer shoulder block 10 is relatively larger than the inner shoulder block 6 in size. Accordingly, the rigidity of the outer shoulder block 10 against a load in a lateral direction becomes relatively higher compared to the rigidity of the inner shoulder block 6 against a load in a lateral direction, and therefore, turning performance on a dry road surface is improved.

[0052] By setting the total number Nb of the inner center blocks 7 smaller than the total number Nd of the outer center blocks 9 as described above, the tire circumferential direction length IHc of the inner center block 7 is set relatively large compared to the tire circumferential direction length OHc of the outer center block. As a result, as described above, driving performance and braking performance on a dry road surface are improved, and at the same time, sensitivity to a steering angle is also improved.

[0053] Referring to Fig.2, the tire circumferential direction length CHc of the center block 8 is set larger than any of the tire circumferential direction lengths ISHc, IHc, OHc, OSHc of the inner shoulder block 6, the inner middle block 7, the outer middle block 9, and the outer shoulder block 10. The center row 5C includes a central part in a tire width direction in the ground contact region with a road surface, and therefore, by setting the tire circumferential direction length IHc of the center block 8 large, sensitivity to a steering angle can be further improved.

[0054] With such technical features, the tire according to this embodiment can improve driving performance and braking performance and can improve turning performance at the same time.

[0055] Each of the inner center blocks 7 constituting the inner center row 5B is defined by the lateral grooves 4, which are "shallow grooves with sipes." From this point of view, it could also be safe to say that the inner center row 5B is not a block row, but essentially a rib row. As described previously, due to an effect of camber, there is a tendency for a shape of a ground contact region with a road surface to widen in a tire circumferential direction at an inner part of the tread 2 in the tire width direction (especially at the time of applied braking). Accordingly, by essentially constituting the inner center row 5B into a rib row, braking performance on a dry road surface is improved, and sensitivity to a steering angle is improved.

[0056] Each of the outer center blocks 9 constituting the outer center row 5D is defined by alternately forming the lateral groove 4D, which is a "deep lateral groove," and the lateral groove 4E, which is a "shallow groove with sipes." As described previously, with respect to the outer center block 9, the tire width direction length OHw is greater than the tire circumferential direction length OHc. In other words, the outer center row 5D has a large size in the tire width direction. By forming the lateral groove 4D, which is a "deep lateral groove," on the outer center row 5D with a large size in the tire width direction, road grip on a snowy road surface can be increased, and therefore, driving performance and braking performance on the snowy road surface can be improved.A pair of outer center blocks 9 arranged on both sides of the lateral groove 4E, which is a "shallow groove with sipes," in the tire circumferential direction can be regarded as one large block. Accordingly, the rigidity of the outer center row 5D in the longitudinal direction (tire circumferential direction) can be improved, so that steering stability can be improved.

[0057] Various other technical features of the tire 1 according to this embodiment will be described below.

[0058] Referring to Fig. 1 and Fig. 2, the groove width GWb of the first central main groove 3B and the groove width GWc of the second central main groove 3C are set larger than the groove width GWa of the inner main groove 3A and the groove width GWd of the outer main groove 3D.

[0059] The first central main groove 3B and the second central main groove 3C are positioned at the center of the tread 2 in the tire width direction. At the center of the tread 2 in the tire width direction, a boundary portion of a ground contact region with a road surface extends in the tire width direction (lateral direction) on both a step-in side and a kick-out side. Therefore, water penetrating the ground contact region at the center of the tread 2 in the tire width direction has a velocity vector directed in the tire circumferential direction.Accordingly, by setting the groove widths GWb, GWc of the first central main groove 3B and the second central main groove 3C located at the center of the tread 2 in the tire width direction to be large, water intruding into the ground contact region can be effectively introduced into the first central main groove 3B and the second central main groove 3C, and therefore, water can be effectively drained. That is, by setting the groove widths GWb, GWc of the first central main groove 3B and the second central main groove 3C to be large, drainage performance can be improved.

[0060] Referring to Fig. 1 and Fig.2, a first raised portion 16 is formed on every other of the plurality of lateral grooves 4A arranged on the inner shoulder row 5A. The first raised portion 16 is formed on an inner side of the main grooves 3A of the lateral groove 4A, so that a pair of outer shoulder blocks 10A positioned adjacent to both sides of the lateral groove 4A in the tire circumferential direction are connected to each other. A length of the first raised portion 16 in the tire width direction is set sufficiently smaller than a length of the lateral groove 4A in the tire width direction. Also referring to Fig. 4, a top surface of the first raised portion 16 is substantially flat. A groove depth GD1' of the lateral groove 4A in the first raised portion 16 is set shallower than a groove depth GD1 of the lateral groove 4A (which is a "deep lateral groove" as described above) in portions other than the first raised portion 16.

[0061] Due to the effect of camber, the shape of the ground contact region with the road surface tends to expand in the tire circumferential direction at an inner portion of the tread 2 in the tire width direction (particularly at the time of braking). Accordingly, by connecting the inner shoulder blocks 6 constituting the inner shoulder row 5A to each other through the first raised portion 16, the rigidity of the inner shoulder blocks 6 in both the longitudinal and lateral directions can be improved, thereby improving driving performance and braking performance on a dry road surface.

[0062] The first raised portion 16 is formed on every other one of a plurality of lateral grooves 4A. Accordingly, in the lateral grooves 4A on which the first raised portion 16 is not formed, the flow of water is not obstructed by the first raised portion 16, and therefore, priority is given to ensuring drainage performance. That is, by forming the first raised portion 16 on every other one of the plurality of lateral grooves 4A, the tire 1 can achieve both ensuring drainage performance and improving driving performance and braking performance on a dry road surface.

[0063] It is preferable that the groove depth GD1' of the lateral groove 4A in the first raised portion 16 be set to 0.4 to 0.6 times inclusive as large as the groove depth GD1 of the other portions of the lateral groove 4A. If the groove depth GD1' exceeds 0.6 times the groove depth GD1, the height of the first raised portion 16 becomes short, so that a rigidity improvement effect in the longitudinal direction brought about by connecting the inner shoulder blocks 6 by the first raised portion 16 cannot be sufficiently obtained. On the other hand, if the groove depth GD1' becomes less than 0.4 times the groove depth GD1, the groove depth of the lateral groove 4A becomes short, and therefore, the drainage performance of the lateral groove 4A is remarkably deteriorated.

[0064] Referring to Fig. 1 and Fig.2, a second raised portion 17 is formed on the outer main groove 3D in a region defined by an imaginary line connecting the outer center block 9 forming the outer center row 5D and the outer shoulder block 10 forming the outer shoulder row 5E. An outer side surface of the outer center block 9 in the tire width direction and an inner side surface of the outer center block 10 in the tire width direction are connected to each other by the second raised portion 17. Further referring to Fig. 5, an edge surface of the second raised portion 17 is substantially flat. A groove depth GW0' of the outer main groove 3D in the second raised portion 17 is set shallower than a groove depth GW0 of the outer main groove 3D in portions other than the second raised portion 17.

[0065] One side in the tire width direction of the outer center block 9, which forms the outer center row 5D, is defined by the outer main groove 3D. Both sides of the outer center block 9 in the tire circumferential direction are defined by the lateral grooves 4D, 4E. These outer main grooves 3D and lateral grooves 4D, 4E allow the deformation of the outer center block 9 in the tire width direction, and therefore, the outer center grooves 3D and lateral grooves 4D, 4E reduce the rigidity in the lateral direction (tire width direction). However, by connecting the outer center block 9 and the outer shoulder block 10 to each other through the second raised part 17, it is possible to make these blocks 9, 10 deform integrally against a load in the lateral direction.That is, with the formation of the second raised part 17, the rigidity of the outer center block 9 in the lateral direction can be improved and therefore a steering performance or turning performance on a dry road surface can be improved.

[0066] The second raised portion 17 is not formed on the entire outer main groove 3D, but is partially formed in the region defined by the imaginary line connecting the outer middle block 9 and the outer shoulder block 10. Accordingly, an effect that the second raised portion 17 exerts on the flow of water in the outer main groove 3D is limited, and therefore, drainage performance is ensured.

[0067] It is preferable that the groove depth GD0' of the outer main groove 3D in the second raised portion 17 be set to 0.5 to 0.7 times inclusive as large as the groove depth GD0 of other parts of the outer main groove 3D. If the groove depth GD0' exceeds 0.7 times the groove depth GD0, the height of the second raised portion 17 becomes short, so that a rigidity improvement effect in the lateral direction brought about by connecting the outer center block 9 to the outer shoulder block 10 through the second raised portion 17 cannot be sufficiently obtained. On the other hand, if the groove depth GD0' becomes less than 0.5 times the groove depth GD0, the groove depth of the outer main groove 3D becomes short, and therefore, a drainage performance of the outer main groove 3D is remarkably deteriorated.

[0068] Referring to Fig. 1 and Fig.2, as previously described, three inner longitudinal slots 6c to 6e are formed in the inner shoulder block 6 constituting the inner shoulder row 5A. These inner longitudinal slots 6c to 6e are grouped in the tire circumferential direction so that the slots 6c to 6e do not overlap with each other. One end of the inner longitudinal slots 6c, 6e terminates in the inner shoulder block 6, and the other end of the inner longitudinal slots 6c, 6e intersects a side surface of the inner shoulder block 6 in the tire circumferential direction. Both other ends of the inner longitudinal slots 6c, 6e terminate in the shoulder block 6. The inner longitudinal slots 6c, 6e are set at substantially the same position in the tire width direction.The inner longitudinal slit 6d, which is grouped between the inner longitudinal slits 6c, 6e in the tire circumferential direction, is arranged at a position offset toward the inside with respect to the inner longitudinal slits 6c, 6e in the tire width direction. In other words, three inner longitudinal slits 6c to 6e are grouped in a staggered manner in the circumferential direction.

[0069] Caused by an effect of wheel camber, there is a tendency for a shape of a ground contact region with a road surface to widen in a tire circumferential direction at an inner part of the tread in the tire width direction, that is, at a part where the inner shoulder row 5A is formed (particularly at the time of applied braking). By forming the inner longitudinal slits 6c to 6b grouped in a staggered manner on the inner shoulder block 6, it becomes possible to disperse the deformation and ground contact pressure in the inner shoulder block 6 at the time of applied braking. As a result, braking performance on a dry road surface can be improved.

[0070] Referring to Fig. 1 and Fig.2, as previously described, three inner longitudinal slits 6c to 6e are formed in the inner shoulder block 6 constituting the inner shoulder row 5A. The inner longitudinal slits 6c to 6e are grouped in the tire circumferential direction so that slits 6c to 6e do not overlap with each other. One end of the inner longitudinal slits 6c, 6e terminate in the inner shoulder block 6, and the other ends of the inner longitudinal slits 6c, 6e intersect with a side surface of the inner shoulder block 6 in the tire circumferential direction. Both ends of the inner longitudinal slit 6d terminate in the shoulder block 6. The inner longitudinal slits 6c, 6e are set at substantially the same position in the tire width direction.The inner longitudinal slot 6d, which is grouped between the inner longitudinal slots 6c, 6e in the tire circumferential direction, is positioned at a position offset toward the inside with respect to the inner longitudinal slots 6c, 6e in the tire width direction. In other words, three inner longitudinal slots 6c to 6e are grouped in a staggered manner in the circumferential direction.

[0071] The outer center block 9 and the outer shoulder block 10 are connected to each other by the second raised portion 17. Accordingly, when the outer center block 9 is deformed in the lateral direction against a load when a vehicle turns, the load in the lateral direction (the deformation in the tire width direction) is transmitted to the outer shoulder block 10 from the outer center block 9. By forming the outer longitudinal slits 10b in the outer shoulder block 10, the load in the lateral direction (the deformation in the tire width direction) transmitted to the outer shoulder block 10 from the outer center block 9 when a vehicle turns can be reduced. As a result, turning performance on a dry road surface can be improved.

[0072] With the above-mentioned technical features, the tire 1 according to this embodiment can improve driving performance, braking performance and turning performance while ensuring drainage performance.

[0073] As previously described, in the outer center row 5D, the lateral groove 4D forming a "deep lateral groove" and the lateral groove 4E forming a "shallow groove with sipes" are alternately formed. Compared with the pair of outer center blocks 9 positioned on both sides of the lateral groove 4D forming a "deep lateral groove," the pair of outer center blocks 9 positioned on both sides of the lateral groove 4E forming a "shallow groove with sipes" are relatively strongly connected to each other in the tire circumferential direction. In other words, there is a tendency for the pair of outer center blocks 9 positioned on both sides of the lateral groove 4E to be deformed integrally in the tire circumferential direction against a load in a longitudinal direction and a load in a lateral direction.Further, as described above, by connecting the outer center block 9 and the outer shoulder block 10 together using the second raised part 17, these blocks 9 and 10 are integrally deformed against a load in a lateral direction. Due to such a structure, as indicated by symbol U in . Fig.1, it can be assumed that the pair of outer center blocks 9 positioned on both sides of the lateral groove 4E forming a "shallow groove with sipes" in the tire circumferential direction and the pair of outer shoulder blocks 10 connected to this pair of outer center blocks 9 using the second raised part 17 constitute a unit. The unit U tends to be integrally deformed against a load in a longitudinal direction and a load in a lateral direction due to the lateral groove 4E forming a "shallow groove with sipes" and the second raised part 17. Since the unit U is provided on an outer part of the tread 2 in the tire width direction, turning performance on a dry road surface is particularly improved. (Evaluation Test 1)

[0074] With respect to tires of Comparative Examples 1 and 2 and tires of Example 1 shown in Table 1 below, evaluation tests were conducted on driving performance (dry driving performance), braking performance (dry braking performance), and turning performance (dry turning performance) on a dry road surface. Data not specifically referred to below are data common to the tires of Comparative Examples 1 and 2 and the tires of Example 1. Specifically, with respect to all of the tires of Comparative Examples 1 and 2 and the tires of Example 1, the evaluation was conducted under conditions where a tire size was 225 / 50R17 and the tire was mounted on a 2000cc FF sedan. [Table 1] Comparison example 1 Comparison example 2 Example 1 Remarks Characteristic 1 GWb, GWc = GWa, GWd GWb, GWc = GWa, GWd GWb, GWc > GWa, GWd Characteristic 2 present not present present Characteristic 3 not present present present Characteristic 4 not present not present present Mileage 100 100 103 Braking performance 100 100 102 Turning performance 100 103 104

[0075] In Table 1, "Characteristic 1" is a size relationship between groove widths GWb, GWc of the first and second central main grooves 3B, 3C and groove widths GWa, GWd of the inner and outer main grooves 3A, 3D. As described previously, in the first embodiment, the groove widths GWb, GWc are larger than the groove widths GWa, GWd. Next, "Characteristic 2" is a structure in which lateral grooves 4F formed on a shoulder row 5E extend outward in the tire width direction beyond an outer ground contact edge GEo located on the outer side in the tire width direction. “Characteristic 3” is a second raised part 17 formed in a region defined by an imaginary line connecting outer middle blocks 9 forming an outer middle row 5D and outer shoulder blocks 10 forming an outer shoulder row 5E.“Characteristic 4” is the configuration in which the lateral grooves 4D, 4E on the outer middle row 5 are positionally aligned with the lateral grooves 4F, so that the lateral grooves 4D, 4E communicate with the lateral grooves 4F over a range from the second central main groove 3C to the base contact edge GEo.

[0076] For performance, each tire was mounted on a vehicle, and the time required for acceleration from a stationary position to 60 km / h on a dry road surface was measured. The evaluation was conducted by expressing the result of the tire of Comparative Example 1 as a reference number out of 100. In Table 1, the larger the reference number, the better the tire's performance.

[0077] For braking performance, each tire was mounted on a vehicle, and the braking distance required to stop the vehicle after ABS braking was applied at a speed of 100 km / h on a dry road surface was measured. The evaluation was conducted by expressing the result of the tire of Comparative Example 1 as a reference number out of 100. In Table 1, the larger the reference number, the better the tire's braking performance.

[0078] For turning performance, each tire was mounted on a vehicle, and the vehicle moved while turning in a smooth circle with a radius of R20 on a dry road surface under a load condition with a person in the vehicle. The lap time was evaluated using a reference number. The evaluation was performed by expressing a result of the tire of Comparative Example 1 as a reference number out of 100. In Table 1, the larger the reference number, the more excellent the tire's dry braking performance.

[0079] With respect to the tire of Example 1, all of a comparative number of driving performance, a comparative number of braking performance, and a comparative number of turning performance are 102 or more, so the tire of Example 1 has preferable driving performance, preferable braking performance, and preferable turning performance. On the other hand, with respect to the tires of Comparative Examples 1 and 2, all of a comparative number of driving performance, a comparative number of braking performance, and a comparative number of turning performance are smaller than corresponding comparative numbers of the tire of Example 1. Particularly, with respect to the tire of Comparative Example 2 having "Characteristic 3" but not having "Characteristic 2," that is, the tire of Comparative Example 2 in which a second raised portion 17 is formed but lateral grooves 4F on an outer shoulder row 5E do not reach a ground contact edge GEo, a comparative number of hydroplaning performance was 98.That is, the aquaplaning performance of the tire of Comparative Example 2 was mostly worse than that of the tire of Example 1.

[0080] As described above, from the result of comparison between the tires of Comparative Examples 1, 2 and the tire of Example 1, it can be understood that the pneumatic tire according to this embodiment can improve driving performance, braking performance and turning performance while ensuring tread life performance.

[0081] Second to seventh embodiments will be described below. In the drawings relating to these embodiments, fundamental elements that are substantially the same or similar to corresponding fundamental elements of the first embodiment are given the same or similar symbols. The structures that are not particularly limited in these embodiments are substantially the same or similar to the corresponding structures of the first aspect of the present invention. The second to fourth embodiments correspond to the second aspect of the present disclosure, and the fifth to seventh embodiments correspond to the third aspect of the present disclosure. The second to seventh embodiments do not fall under the scope of the claims, but are helpful in understanding the present invention. (Second embodiment)

[0082] Referring to Fig.6, on a tread 2 of a tire 1 according to a second embodiment, none of the inner longitudinal slots 6c, 6d, 6e on an inner shoulder block 6, none of the first raised parts 16 and second raised parts 17 are formed (see also Fig. 1 and Fig. 2 with regard to these basic elements). The same applies to the third to seventh embodiments, which will be described later with regard to this point.

[0083] On an outer middle row 5D located between a second central main groove 3C and an outer main groove 3D, a lateral groove 4D, which is a "deep groove," and a lateral groove 4E, which is a "shallow groove with sipes," are alternately formed. In the first embodiment, each outer middle block 9 constituting the outer middle row 5D is defined as a block defined by the second central main groove 3C, the outer main groove 3D, the lateral groove (deep groove) 4D, and the lateral groove (shallow groove with sipes) 4E. However, the lateral groove 4E, which is a "shallow groove with sipes," has a smaller groove volume than the lateral groove 4D, which is a "deep groove." By taking into account that the lateral groove 4E has the smaller groove volume than the lateral groove 4D, it can be considered that the outer middle row 5D is formed only from composite blocks 21 (see also Fig.7). That is, a "composite block" can be defined as a block that satisfies the following two conditions. This definition is also applicable to the third to seventh embodiments described later.

[0084] First, a “composite block” is defined by two “main grooves” arranged adjacent to each other in the tire width direction and two “deep grooves” arranged adjacent to each other in the tire circumferential direction.

[0085] Next, one or a plurality of shallow slatted grooves are formed on the surface of a composite block. The composite block is divided into a plurality of subregions by shallow slatted grooves.

[0086] Advantageous effects obtained by forming the composite blocks 21 will be described hereinafter.

[0087] First, "block" refers to an island-shaped portion separated from the surrounding area by the main grooves and the lateral grooves. Assuming that only a plurality of simple blocks are formed on the tread 2, each block has a high degree of independence, and therefore, the rigidity of the tread is reduced. As a result, dry performance (i.e., movement performance such as acceleration, braking, and turning on a dry road surface) is also reduced.

[0088] Second, to mitigate the reduction in dry performance, some "lateral grooves" are replaced with "shallow grooves," thus increasing the rigidity of the tread surface. However, when a vehicle drives on a snowy road, the snow column shear force is reduced by a portion of the groove volume difference caused by replacing "lateral grooves" with "shallow grooves," thus reducing snow performance (i.e., movement performance such as acceleration, braking, and turning on a snowy road).

[0089] Third, in the present disclosure, a "shallow groove" is formed on a "block," and a "sipe" is formed on a groove bottom of a "shallow groove." That is, a "shallow groove with sipes" is formed on a "block" (composite block). By forming a "sipe" on the groove bottom of a "shallow groove," the shallow groove can be largely opened, compared to a case where the sipe is not formed on the bottom of a shallow groove, and therefore, a snow column shear force can be increased. That is, snow performance can be improved.

[0090] The above technical features can be summarized as follows. That is, if only the simple blocks defined by the main grooves and the lateral grooves, which are "deep grooves," are formed on the tread, the tire will exhibit poor dry performance. Accordingly, replacing some "deep grooves" with "shallow grooves" will improve dry performance. On the other hand, snow performance will be reduced by a portion of the groove volume difference caused by replacing "lateral grooves" with "shallow grooves." To mitigate this reduction in snow performance, a "sipe" is additionally formed on the bottom of each "shallow groove." With this configuration, the tire can exhibit both excellent snow performance and excellent dry performance.

[0091] As described above, in this embodiment, the outer middle row 5D is formed only from composite blocks 21.

[0092] In this embodiment, each block 6 on the inner shoulder row 5A is simply divided by lateral grooves 4A, which are "deep grooves," and corrugated sipes 6a are formed on one surface of each block 6. In this manner, each block 10 on the outer shoulder row 5E is simply divided by lateral grooves 4F, which are "deep grooves," and corrugated sipes 10a are formed on one surface of each block 10.

[0093] Furthermore, in this embodiment, a "deep groove" is not formed on the inner middle row 5B. The lateral grooves 4B, which are "shallow grooves with sipes," are formed on the inner middle row 5B, and corrugated sipes 7b are formed on a surface of the inner middle row 5B. In the same way, a "deep groove" is not formed on the central row 5C. The lateral grooves 4C, which are "shallow grooves with sipes," are formed on the central row 5C, and corrugated sipes 8a are formed on a surface of the central row 5C.

[0094] In the first embodiment, each block 7 (see Fig. 1 and Fig. 2) on the inner middle row 5B is defined as a block defined by the inner main groove 3A, the first central main groove 3B, and two lateral grooves 4B, which are “shallow grooves with sipes.” In the first embodiment, each block 8 (see Fig. 1 and Fig. 2) on the central row 5C is defined as a block defined by the first central main groove 3B, the second central main groove 3C and two lateral grooves 4C which are “shallow grooves with sipes”.

[0095] However, by considering that the lateral groove 4B, 4C, which is a "shallow groove with sipes," has a smaller groove volume than a "deep groove," it can be considered that a rib that is not divided into blocks is continuously formed in each of the inner middle row 5B and the central row 5C. That is, the structure that satisfies the following three conditions can be defined as a "rib." This definition is also applicable to the third to seventh embodiments described later.

[0096] First, a “rib” is defined by two “main grooves” arranged adjacent to each other in the tire width direction.

[0097] Secondly, a “rib” is formed continuously in the tire circumferential direction or “shallow grooves” or “shallow grooves with sipes” are formed on a “rib”. Third, a “deep groove” is not formed on a “rib”.

[0098] In this embodiment, the lateral grooves 4B, 4C, which are "shallow grooves with sipes," are formed on the ribs (the inner middle row 5B and the center row 5C) at intervals in the tire circumferential direction, respectively. Corrugated sipes 7a are formed on the rib between every two adjacent lateral grooves 4B, and corrugated sipes 8a are formed on the rib between every two adjacent lateral grooves 4C.

[0099] It is preferred that the row composed only of "composite blocks" be the outer middle row 5D. The reason is as follows.

[0100] That is, generally due to camber of the tire 1 mounted on a vehicle, there is a tendency for a ground contact length at an inner side portion of the tread 2 in the tire width direction to become larger than that at an outer side portion of the tread 2 in the tire width direction. On the inner side portion in the tire width direction, where the ground contact length becomes larger than that on the outer side portion, it is desirable to give the highest priority to obtaining high rigidity. By forming a "rib" as defined above, the tire can ensure high rigidity. As a result, "composite blocks" that slightly reduce its rigidity but improve snow performance by an amount corresponding to the reduction in rigidity are formed on the outer side portion of the tread 2 in the tire width direction (outer center row 5D).

[0101] It is preferable that “composite blocks” are not formed on either the inner shoulder part in the tire width direction or the outer shoulder part in the tire width direction.

[0102] That is, to prevent aquaplaning on wet road surfaces, it is necessary to effectively drain water from the tread surface to the sides (outer sides) of a tire. Accordingly, it is desirable to improve drainage efficiency by forming a large number of "deep grooves" instead of grouping "composite blocks" on the inner shoulder portion in the tire width direction and on the outer shoulder portion in the tire width direction. (Third embodiment)

[0103] Referring to Fig.8, a tread 2 of a tire 1 according to a third embodiment differs from the tread 2 of the tire 1 according to the second embodiment only with regard to the configuration of the inner middle row 5B and the central row 5C.

[0104] On the inner middle row 5B, a lateral groove 4G, which is a "deep groove," and a lateral groove 4B, which is a "shallow groove with sipes," are alternately formed. Accordingly, the inner middle row 5B is formed of a plurality of composite blocks 22, each of which is divided by the lateral grooves 4G, which are "deep grooves" (see also Fig. 9A).

[0105] In the same way, on the central row 5C, a lateral groove 4H, which is a "deep groove," and a lateral groove 4C, which is a "shallow groove with slats," are alternately formed. Accordingly, the central row 5C is formed of a plurality of composite blocks 23, each of which is divided by the lateral grooves 4H, which are "deep grooves" (see also Fig. 9B). (Fourth embodiment)

[0106] Referring to Fig. 10, on a tread 2 of a tire 1 according to a fourth embodiment, an inner middle row 5B, a central row 5C and an outer middle row 5D are each formed from only “composite blocks”.

[0107] On the inner middle row 5B, two lateral grooves 4B, which are "shallow grooves with sipes," are formed between two lateral grooves 4G, which are "deep grooves." A composite block 24 is defined by an inner main groove 3A, a first central main groove 3B, and two lateral grooves 4G, which are "deep grooves" (see also Fig. 11A).

[0108] In the same way, on the central row 5C, two lateral grooves 4C, which are "shallow grooves with sipes," are formed between two lateral grooves 4H, which are "deep grooves." A composite block 25 is defined by a first central main groove 3B, a second central main groove 3C, and two lateral grooves 4H, which are "deep grooves" (see also Fig. 11B).

[0109] On the outer middle row 5D, two lateral grooves 4E, which are "shallow grooves with sipes," are formed between two lateral grooves 4D, which are "deep grooves." A composite block 26 is defined by a second central main groove 3C, an outer main groove 3C, and two lateral grooves 4D, which are "deep grooves" (see also Fig. 11C).

[0110] Unlike the second and third embodiments, in the fourth embodiment, each composite block 24, 25, 26 has two “shallow grooves with sipes” and therefore a surface of the block is divided into three subregions. (Other aspects of the second to fourth embodiments)

[0111] In the second to fourth embodiments, the tires each have four main grooves. However, in the second aspect of the present disclosure, it is sufficient for the tire to have at least three main grooves. When the tire has three main grooves, two rows of blocks or ribs are arranged between an inner shoulder row and an outer shoulder row. At least one row consists of two rows, and all blocks belonging to a row are formed of "composite blocks." The same applies to a tire with five or more main grooves.

[0112] Generally, vehicle tires are classified into vehicle tires in which a tire rotation direction is designated when a vehicle is traveling, and vehicle tires in which a tire rotation direction is not designated. The present disclosure is fundamentally applicable to both types of tires. However, in the second embodiment, for example, it is essential that all blocks belonging to the outer center row 5D be formed of "composite blocks 21." In such a case, it is a prerequisite that the tire rotation direction be designated. (Evaluation Test 2)

[0113] With regard to the tires of comparative examples 3 to 6 (see Fig.13) and the tires of Examples 2 to 4 were subjected to evaluation tests (snow performance tests and dry performance tests). The tires of Examples 2 to 4 are the tires of the second to fourth embodiments, respectively. The tires of Comparative Examples 3 to 6 are similar to the tires of Examples 2 to 4 in one respect: that each tire has four main grooves. However, the tires of Comparative Examples 3 to 6 differ from the tires of Examples 2 to 4 in the following respects.

[0114] In the tire of Comparative Example 3, with respect to all four main grooves, ribs, each of which is located between two adjacent main grooves, are continuously formed in the tire circumferential direction without being divided by lateral grooves. However, a plurality of shallow sipe grooves are formed at intervals on each rib, and corrugated sipes are formed on the rib between every two adjacent shallow sipe grooves. The tire of Comparative Example 3 does not have any composite block. Furthermore, as described previously, shallow sipe grooves minimally affect the integrity between portions of the rib on both sides of shallow sipe grooves.

[0115] In the tire of Comparative Example 4, all four main grooves are divided by lateral grooves, each of which has ridges located between two adjacent main grooves. Corrugated sipes are formed on each block. The tire of Comparative Example 4 has no composite blocks, and all blocks are formed from simple blocks, thus ensuring high independence for each block.

[0116] In the tire of Comparative Example 5, with respect to all four main grooves, rib ridges, each of which is located between two adjacent main grooves, are not divided by "lateral grooves." However, "shallow grooves" are formed on the rib at intervals, and corrugated sipes are formed on the rib between two adjacent "shallow grooves." The tire of Comparative Example 5 does not have any "composite block." Furthermore, as previously described, "shallow grooves" minimally affect the integrity between portions of the rib on both sides of the "shallow grooves."

[0117] In the tire of Comparative Example 6, with respect to all four main grooves, "composite blocks" are arranged between every other adjacent main groove. In each row, a simple "block" separated from the periphery by main grooves and lateral grooves and a "composite block" are repeatedly formed. In other words, in the tire of Comparative Example 6, when attention is paid to a specific row, simple blocks, each of which is sandwiched only by "lateral grooves," are included in the specific row, unlike a "composite block."

[0118] The tires of Examples 2 to 4 of the present disclosure and the tires of Comparative Examples 3 to 6, which fall outside the scope of the present disclosure, were mounted on a vehicle, and comparative tests described below were conducted. The tire sizes of the respective tires and the vehicles used in the tests were as follows. Tire size: 225 / 50 R 17Vehicle used: Audi A4 (2000cc, FF Sedan)

[0119] In the snow performance test, each tire was mounted on a vehicle, and the vehicle drove on a snowy road surface while performing acceleration, braking, turning, and lane changes. Then, steering stability performance was evaluated through a sensor test performed by a driver. The evaluation was performed by expressing the result of the tire of Comparative Example 3 as a reference number out of 100. In Table 2, the larger the reference number, the more excellent the tire's snow steering stability performance.

[0120] In the dry performance test, each tire was mounted on a vehicle, and the vehicle drove on a dry road surface while performing acceleration, braking, turning, and lane changes. Then, steering stability performance was evaluated through a sensor test performed by a driver. The evaluation was performed by expressing the result of the tire of Comparative Example 3 as a reference number out of 100. In Table 2, the larger the reference number, the more excellent the tire's dry steering stability performance. [Table 2] Example 2 Example 3 Example 4 Snow performance 103 101 101 Drying performance 102 102 103 Comparison example 3 Comparison example 4 Comparison example 5 Comparison example 6 Snow performance 100 102 96 101 Drying performance 100 96 102 98

[0121] With respect to the tires of Examples 2 to 4, both snow performance and dry performance were higher than those of the tires of Comparative Example 3. The result indicates that the pneumatic tire of the present disclosure can exhibit both excellent snow performance and excellent dry performance.

[0122] On the other hand, all of Comparative Examples 4 to 6 are inferior to the tire of Comparative Example 3 in both snow performance and dry performance. That is, the tires of Comparative Examples 4 and 6 are inferior to Comparative Example 3 in terms of dry performance. The tire of Comparative Example 5 is inferior to the tire of Comparative Example 3 in terms of snow performance.

[0123] In the tire of Comparative Example 4, all blocks are each formed from a single block, so the tire has low rigidity. Accordingly, the tire of Comparative Example 4 is expected to exhibit poor dry performance. In the tire of Comparative Example 6, some blocks are formed as "composite blocks," so the tire has better dry performance than the tire of Comparative Example 4. However, when compared with the tires of Examples 2 to 4, the tire of Comparative Example 6 has inferior dry performance. That is, in all the tires of Examples 2 to 4, all blocks belonging to a row are formed as "composite blocks."

[0124] In the tire of Comparative Example 5, although a "shallow groove" is formed on each ridge between every two adjacent main grooves of all main grooves, no blocks are formed by dividing the row by lateral grooves. Therefore, it can be noted that the tread surface has high rigidity and also high dry performance. On the other hand, the snow performance of the tread surface is reduced by an amount corresponding to the absence of the blocks formed by dividing the row. Accordingly, from the perspective of the behavior of both snow performance and dry performance, the tire of Comparative Example 5 is inferior to the tires of Examples 2 to 4. (Fifth embodiment)

[0125] Referring to Fig.13, a tread 2 of a tire 5 according to a fifth embodiment has the following two technical features compared with the tires of the second to fourth embodiments.

[0126] The first technical features are that lateral grooves 4B, which are “shallow grooves with sipes”, and sipes 7b are formed on an inner middle row 5B, but “deep grooves” are not formed on the inner middle row 5B (see also Fig. 14A). In other words, the inner middle row 5B is formed of a rib that is continuously formed without being divided by "deep grooves."

[0127] A second technical feature is that a lateral groove 4E, which is a "shallow groove with sipes," and a lateral groove 4D, which is a "deep groove," are alternately formed on an outer center row 5D. In other words, the outer center row 5D is formed only from composite blocks 27 grouped in a row in the tire circumferential direction (see also Fig. 14B). A lateral groove 4E, which is a “shallow groove with sipes,” and a plurality of sipes 9a are formed on the individual composite block 27.

[0128] As other configurations, although lateral grooves 4A and lateral grooves 4F, both of which are "deep grooves," are formed on each of the inner shoulder rows 5A and 5E, "shallow grooves with sipes" are not formed on the inner shoulder row 5A and the outer shoulder row 5E. Accordingly, the inner shoulder row 5A and the outer shoulder row 5E are formed from blocks 6 and blocks 10, each of which is not a "composite block," and corrugated sipes 6a and corrugated sipes 10a are formed on the individual blocks 6 and the individual blocks 10, respectively. In the same manner as the inner middle row 5B, lateral grooves 4C formed from "shallow grooves with sipes" are formed on the central row 5C, but "deep grooves" are not formed. The central row 5C is formed of a rib extending continuously in the tire circumferential direction.

[0129] Regarding the first technical features, in general, due to camber of the tire 1 when the tire 1 is mounted on a vehicle, there is a tendency for a ground contact length to become larger at an inner side portion of the tread 2 in the tire width direction than at an outer side portion of the tread 2 in the tire width direction. On the inner side portion in the tire width direction, where the ground contact length becomes larger than that on the outer side portion, it is desirable to give the highest priority to obtaining high rigidity. Accordingly, the inner center row 5B is formed of a rib continuously formed over the entire circumference of the tire.

[0130] As a result of adopting the first technical feature, the outer middle row 5D is formed of composite blocks 27, which slightly decrease the stiffness thereof, but can improve snow performance as the second technical feature by an amount corresponding to the reduction in stiffness. (Sixth Embodiment)

[0131] Referring to Fig. 15, a tread 2 of a tire 1 according to a sixth embodiment differs from the tread 2 of the tire 1 in the fifth embodiment only in a point that the configuration of a center row 5C and the configuration of an outer middle row 5D are exchanged with each other.

[0132] To be more specific, in this embodiment, on a central row 5C, a lateral groove 4H, which is a “deep groove,” and a lateral groove 4C, which is a “shallow groove with sipes,” are alternately formed, and the central row 5C is formed only of composite blocks 28 (see also Fig. 16B). On the other hand, on an outer middle row 5D, lateral grooves 4E, which are "shallow grooves with sipes," and sipes 9a are formed, but "deep grooves" are not formed. The outer middle row 5D is formed of a rib substantially equal to the rib forming the central row 5C in the fifth embodiment (see also Fig. 16C).

[0133] In this embodiment, in the same manner as in the fifth embodiment, the inner middle row 5B is formed of a rib (see also Fig. 16A). (Seventh Embodiment)

[0134] Referring to Fig. 17 to Fig. 18C, a tread 2 of a tire 1 according to the seventh embodiment differs from the tread 2 of the tire 1 of the fifth and sixth embodiments in that both a center row 5C and an outer middle row 5D are formed of only composite blocks 28, 29, respectively. (Other modifications of the fifth to seventh embodiments)

[0135] In the fifth to seventh embodiments, the tires have four main grooves. However, in the third aspect of the present disclosure, it is sufficient for the tire to have at least three main grooves. When the tire has three main grooves, two rows of blocks or ribs are arranged between an inner shoulder row 5A and an outer shoulder row 5B. With respect to two rows, the rib positioned between a pair of (two) main grooves positioned on an inner side in a state where the tire is mounted on a vehicle is not divided into blocks by lateral grooves, and sipes are formed on a surface of the rib, or shallow grooves with sipes having the sipes on a groove bottom are formed on the rib. All blocks belonging to the row between outer main grooves are formed of "composite blocks."

[0136] When the tire has five or more main grooves, a rib positioned between a pair of (two) main grooves positioned on an innermost side in a state where the tire is mounted on the vehicle is not divided into blocks by lateral grooves, and sipes are formed on a surface of the rib, or shallow grooves with sipes that have sipes on a groove bottom are formed on the rib. Furthermore, in at least one region between other pairs of central main rows, all the blocks belonging to the region are formed of "composite blocks." (Evaluation Test 3)

[0137] With regard to the tire of Comparative Example 7 ( Fig. 19) and the tires of Examples 5 to 7 were subjected to evaluation tests (a snow performance test, a dry performance test, and a dry braking test). The tires of Examples 5 to 7 are the tires of the fifth to sixth embodiments, respectively.

[0138] The tires of Comparative Example 7 share the same configuration with the tires of Examples 5 to 7 (fifth to seventh embodiments) except that the tire has four main grooves. However, the tire of Comparative Example 7 differs from the tires of Examples 5 to 7 in the following points.

[0139] In the tire of Comparative Example 7, with respect to all four main grooves, a continuous rib is not formed in each region defined between two adjacent main grooves. In the tires of Examples 5 to 7 (fifth to seventh embodiments), at least the inner center row 5B is formed of a rib. The rib is not divided into blocks by deep grooves, and sipes or shallow grooves with sipes are formed on a surface of the rib. By disposing such a groove on an inner side portion in the tire width direction, which has a large ground contact length, dry performance and dry braking performance are improved. On the other hand, in the tire of Comparative Example 7, a continuous rib ridge is not disposed on an inner side portion in the tire width direction or on other portions.

[0140] In this evaluation test, the tire size and vehicle used are essentially the same as those used in the aforementioned "Evaluation Test 2." The contents of the snow performance test and the dry performance test are also essentially the same as those of the snow performance test and the dry performance test in the aforementioned "Evolution Test 2" (a result of the tire of Comparative Example 7 is expressed as a reference number out of 100).

[0141] In the dry braking test, the respective tires were mounted on a vehicle, and the braking distance required to stop the vehicle after ABS braking was applied at 100 km / h on a dry road surface was measured. The evaluation was performed by expressing the result of the tire of Comparative Example 7 as a reference number out of 100. In Table 3, the larger the reference number, the better the tire's dry braking performance. [Table 3] Example 5 Example 6 Example 9 Comparison example 7 Snow performance 100 100 104 100 Drying performance 104 104 103 100 Dry braking performance 106 106 103 100

[0142] With attention paid to dry performance and dry braking performance, in all of the tires of Examples 5 to 7, with respect to the inner side portion in the tire width direction, where a basic contact length in the tire circumferential direction becomes the longest when camber is taken into consideration, the inner center row 5B is formed of a rib. The rib is not divided into blocks by "deep grooves," and sipes or shallow grooves with sipes are formed on a surface of the rib, thus providing high rigidity. Furthermore, the sipes or shallow grooves with sipes formed on the surface of the rib can increase the grip force.That is, by forming the rib ridge with high rigidity and high adhesion force on the inner side part in the tire width direction where the ground contact length is large, the pneumatic tire can obtain high movement performance and braking performance on a dry road surface.

[0143] On the other hand, the tire of Comparative Example 7 has the configuration in which the inner center row 5B on the inner side portion in the tire width direction is formed of blocks with high independence from each other, each of which is divided by lateral grooves. Accordingly, the dry performance and dry braking performance of the tire of Comparative Example 7 are expected to be inferior to those of the tires of Examples 5 to 7.

[0144] In the tires of Examples 5, 6, two rows of continuous ribs are formed, and therefore, the tires of Examples 5, 6 are expected to have high dry performance and high dry braking performance compared with the tire of Example 7 in which only one row of ribs is formed, due to this difference in the number of rows of continuous ribs.

[0145] When attention is drawn to the snow performance, in the tire of Example 7, both the center row 5C and the outer middle row 5D are formed of the composite blocks 28, 29. On the other hand, in the tires of Examples 5, 6 and the tire of Comparative Example 7, only either the center row 5C or the outer middle row 5D is formed of the composite blocks, so the number of composite blocks is smaller than the number of composite blocks in the tire of Example 7. Accordingly, it is considered that snow performance of the tires of Examples 5, 6 and the tires of Comparative Example 7 is inferior to snow performance of the tire of Example 7.

[0146] As previously described, composite blocks have a beneficial effect of enabling a tire to exhibit both excellent snow performance and excellent dry performance. In the tires of Examples 5 and 6 with a relatively small number of composite blocks, the beneficial effect of improving dry performance due to the composite blocks is expected to be reduced by an amount corresponding to the number of composite blocks. However, in the tires of Examples 5 and 6, the ribs are formed in two rows, and therefore, dry performance is improved. As a result, the dry performance of the tires of Examples 5 and 6 as a whole is superior to the dry performance of the tire of Comparative Example 7.

[0147] In the tires of Examples 5 to 7, both "waved sipes" and "shallow grooves with sipes" are formed on one rib ridge surface. However, it is estimated that substantially the same advantageous effects can be achieved even if only one of "waved sipes" or "shallow grooves with sipes" is formed on the rib ridge surface, or even if straight sipes are formed on the rib ridge surface instead of the waved sipes.

Claims

[1] Pneumatic tires (1) comprising: four main grooves (3A-3D) formed on a tread (2) such that the four main grooves (3A-3D) extend in a tire circumferential direction (Y); a plurality of lateral grooves (4A-4F) formed on the tread (2); and five block rows (5A-5E), each comprising a plurality of blocks (6, 7, 8, 9, 10) each defined by the main grooves (3A-3D) and a pair of lateral grooves (4A-4F) arranged adjacent to each other in the tire circumferential direction (Y), the blocks (6, 7, 8, 9, 10) being grouped in a row (5A-5E) in the tire circumferential direction (Y), wherein a mounting posture of a pneumatic tire (1) with respect to a vehicle body is indicated in a tire width direction (X), where the main grooves (3A-3D) have: an inner main groove (3A) positioned on an innermost side in the tire width direction (X) in a state where the tire (1) is mounted on the vehicle; an outer main groove (3D) positioned on an outermost side in the tire width direction (X) in a state where the tire (1) is mounted on the vehicle; a first central main groove (3B) arranged adjacent to an outer side of the inner main groove (3A) in the tire width direction (X); and a second central main groove (3C) arranged adjacent to an inner side of the outer main groove (3D) in the tire width direction (X), where the block rows (5A-5E) have: an inner shoulder row (5A) positioned within the inner main groove (3A) in the tire width direction (X); an outer shoulder row (5E) positioned outside the outer main groove (3D) in the tire width direction (X); an inner middle row (5B) positioned between the inner main groove (3A) and the first central main groove (3B); an outer middle row (5D) positioned between the outer main groove (3D) and the second central main groove (3C); and a central row (5C) positioned between the first central main groove (3B) and the second central main groove (3C), wherein a groove width (GWb) of the first central main groove (3B) and a groove width (GWc) of the second central main groove (3C) is greater than a groove width (GWa) of the inner main groove (3A) and a groove width (GWd) of the outer main groove (3D), wherein the lateral groove (4A) comprises a plurality of first lateral grooves (4A) formed at intervals in the tire circumferential direction (Y) so as to define blocks (6) belonging to the inner shoulder row (5A), wherein a first raised part (16) connecting the block pairs (6) belonging to the inner shoulder row (5A) is formed in every second of the first lateral grooves (4A) on the inner main groove side, a depth (GD1') of the first lateral groove (4A) in the first raised part (16) is less than a depth (GD1) of the first lateral groove (4A) in other parts, and the first raised part (16) does not extend into the inner main groove (3A) in the tire width direction (X), wherein a second raised part (17) is formed on the outer main groove (3D) to connect an outer side surface of the block (9) belonging to the outer middle row (5D) and an inner side surface of the block (10) belonging to the outer shoulder row (5E), and a depth (GD0') of the outer main groove (3D) in the second raised part (17) is less than a depth (GD0) of the outer main groove (3D) in other parts, and wherein a plurality of second slits (10b) communicating with each other in the tire circumferential direction (Y) are formed in the block (10) belonging to the outer shoulder row (5E). [2] A pneumatic tire (1) according to claim 1, wherein the depth (GD1') of the first lateral groove (4A) in the first raised part (16) is set to 0.4 to 0.6 times inclusive as large as the depth (GD1) of the first lateral groove (4A) in other parts. [3] A pneumatic tire (1) according to claim 1 or 2, wherein the depth (GD0') of the outer main groove (3D) in the second raised part (17) is set to 0.5 to 0.7 times inclusive as large as the depth (GD0) of the outer main groove (3D) in other parts. [4] A pneumatic tire (1) according to any one of claims 1 to 3, wherein the lateral groove (4F) comprises a plurality of second lateral grooves (4F) formed at intervals in the tire width direction (X) so as to define the blocks (10) belonging to the outer shoulder row (5E), and wherein the second lateral groove (4F) extends in the tire width direction (X) beyond an outer ground contact edge (GEo) of the tread (2) in the tire width direction (X). [5] The pneumatic tire (1) according to claim 4, wherein the lateral groove (4D, 4E) comprises a plurality of third lateral grooves (4D, 4E) formed at intervals in the tire width direction (X) so as to define the blocks (9) belonging to the outer center row (5D), and wherein the second lateral groove (4F) and the third lateral groove (4D, 4E) are grouped in a state in which the second lateral groove (4F) and the third lateral groove (4D, 4E) are positionally aligned with each other so as to communicate with each other from the second center main groove (3C) to the outer ground contact edge (GEo) in the tire width direction (X). [6] A pneumatic tire (1) according to any one of claims 1 to 5, wherein a plurality of first slits (6c, 6d, 6e) grouped in a staggered manner in the tire circumferential direction (Y) are formed on the block (6) belonging to the inner shoulder row (5A).

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