pneumatic tires

Abstract

A pneumatic tire comprising a mounting direction predetermined with respect to a vehicle, the pneumatic tire comprising five land portions (30) in a tire width direction, the five land portions (30) being defined and formed by four circumferential main grooves (20) extending in a tire circumferential direction on a ground contact surface (10) of a tread portion (2), the five land portions (30) comprising a center land portion (31) on an equatorial plane of the tire (CL), a center outer side land portion (32) on a vehicle outer side of the center land portion (31), an outer side shoulder land portion (34) on the vehicle outer side of the center outer side land portion (32), form a central inner side web section (33) on a vehicle inner side of the central web section (31) and an inner side shoulder web section (35) on the vehicle inner side of the central inner side web section (33), wherein a web section width Wcc of the central web section (31) and a web section width Wco of the middle outer side web section (32) satisfies a ratio of 1.2 ≤ Wco / Wcc ≤ 1.4, the ground contact surface (10) of both the central outer side land portion (32) and the outer side shoulder land portion (34) protrudes to an outer side in a tire radial direction with respect to a reference profile, a projection amount Hco of the middle outer side web portion (32) and a projection amount Hso of the outer side shoulder web portion (34) satisfy a relationship of 1.2 ≤ Hso / Hco ≤ 2.0, and wherein the projection amount Hco of the central outer side web portion (32) is in a range of 0.2 mm ≤ Hco ≤ 0.4 mm.

Description

Technical field

[0001] The present invention relates to a pneumatic tire. State of the art

[0002] It is considered that in order to improve steering stability on dry road surfaces, the land portion width of a tread portion should be set wide to ensure tread rigidity. However, in this case, the ground contact pressure at the center in a width direction of a land portion decreases, and a ground contact length in a tire circumferential direction of the land portion is reduced in a ground contact area. Accordingly, an end portion is recessed inward in the ground contact length, and thus contact with the ground is deteriorated. As a result, steering stability performance on dry road surfaces may deteriorate. In addition, the ground contact pressure at the center in the width direction of the land portion decreases, and thus drainage performance deteriorates, and steering stability performance on wet road surfaces may also deteriorate.

[0003] In the prior art, for example, JP 2013-189121 A, JP 2016-002890 A and JP 2014-118123 A describe that the steering stability performance on dry road surfaces and the steering stability performance on wet road surfaces can be improved by configuring a land portion such that the center of a ground contact surface protrudes in a width direction.

[0004] DE 11 2014 005 018 T5 discloses a pneumatic tire provided with at least three circumferential grooves extending in a tire circumferential direction in a tread portion, and at least four ribs defined by the at least three circumferential grooves. These four ribs extend in the tire circumferential direction, and at least two ribs protrude outward in the tire radial direction. At the same time, a protrusion amount of the at least two ribs decreases (in order) from an inner side to an outer side in the tire width direction.

[0005] US 2014 / 0166169 A1 discloses a pneumatic tire comprising a tread portion divided into a central land portion by two main grooves extending continuously in the circumferential direction. The pneumatic tire further has a pair of center land portions and a pair of shoulder land portions.

[0006] Both the central web portion and the middle web portion have convex, radially outwardly directed projections with points. The shoulder web portions may be designed to have a similar profile to the central web portion and the two middle web portions.

[0007] DE 10 2015 212 995 A1 discloses a pneumatic tire comprising a tread portion having a plurality of straight main grooves and a plurality of land portions divided by the main grooves. The land portions protrude toward the outside from a base contour line of the tread portion in the radial direction of the tire.

[0008] An amount H2 of swelling of a floor section which, when correctly installed, is located on the inside of the vehicle, is greater than an amount H1 of swelling of the floor section located on the outside of the vehicle.

[0009] DE 10 2018 131 890 A1 discloses a pneumatic tire having a rubber material surface layer region comprising a first rubber material region formed from a first rubber material and a second rubber material region formed from a second rubber material. The rubber hardness of the second rubber material is higher than the rubber hardness of the first rubber material.

[0010] The first rubber material region is arranged on a first side in a tire width direction, and the second rubber material region is arranged on a second side in the tire width direction. An interface between the first rubber material region and the second rubber material region is located between a pair of main grooves located outermost in the tire width direction. An average tire outer diameter from a tire equatorial plane in the tire width direction toward the second side is larger than an average tire outer diameter from the tire equatorial plane in the tire width direction toward the first side. Brief description of the inventionTechnical problem

[0011] However, in recent years, there has been a need for further improvement of steering stability performance on dry road surfaces and steering stability performance on wet road surfaces due to the improvement of vehicle performance.

[0012] The present invention is made in view of the foregoing, and an object of the present invention is to provide a pneumatic tire capable of providing improved steering stability performance on dry road surfaces and improved steering stability performance on wet road surfaces. Solution to the problem

[0013] To solve the above-mentioned problem and to achieve the object, a pneumatic tire is provided having the features of independent claim 1. Advantageous embodiments are described in dependent claims 2 to 6.

[0014] According to the invention, the projection amount Hco of the middle outer side web portion is in a range of 0.2 mm ≤ Hco ≤ 0.4 mm.

[0015] Furthermore, in the pneumatic tire according to one aspect of the present invention, the protrusion amount Hso of the outer side shoulder land portion is preferably in a range of 0.3 mm ≤ Hso ≤ 0.6 mm.

[0016] According to the invention, the protrusion amount Hco of the middle outer side land portion and the protrusion amount Hso of the outer side shoulder land portion satisfy a relationship of 1.2 ≤ Hso / Hco ≤ 2.0.

[0017] Furthermore, in the pneumatic tire according to one aspect of the present invention, the ground contact surface of each of the center land portion and the inner side center land portion is preferably formed to protrude toward the outside in the tire radial direction with respect to a reference profile. A protrusion amount Hcc of the center land portion and the protrusion amount Hco of the outer side center land portion preferably satisfy a relationship of 0.9 ≤ Hcc / Hco ≤ 1.1. The protrusion amount Hcc of the center land portion and a protrusion amount Hci of the inner side center land portion preferably satisfy a relationship of 0.9 ≤ Hcc / Hci ≤ 1.1.

[0018] Furthermore, in the pneumatic tire according to one aspect of the present invention, it is preferable that no groove is provided on the ground contact surface of the center land portion when in contact with a ground. Grooves each including one end communicating with one of the circumferential main grooves located on an outer side in the tire width direction when in contact with a ground and the other end blindly terminating within each of the center outer side land portion and the center inner side land portion are preferably provided on the ground contact surface of each of the center outer side land portion and the center inner side land portion.

[0019] Furthermore, in the pneumatic tire according to one aspect of the present invention, the land portion width Wco of the outer side center land portion, a land portion width Wso of the outer side shoulder land portion, a land portion width Wci of the inner side center land portion, and a land portion width Wsi of the inner side shoulder land portion satisfy, with respect to the land portion width Wcc of the center land portion, the relationship 1.2 ≤ Wco / Wcc ≤ 1.4, preferably the relationship 1.4 ≤ Wso / Wcc ≤ 1.6, preferably the relationship 0.9 ≤ Wci / Wcc ≤ 1.1, preferably the relationship 1.4 ≤ Wsi / Wcc ≤ 1.6.

[0020] Furthermore, in the pneumatic tire according to one aspect of the present invention, the ground contact surface of the inner side shoulder land portion is preferably formed to protrude toward the outside in the tire radial direction with respect to a reference profile. The protrusion amount Hso of the outer side shoulder land portion and the protrusion amount Hsi of the inner side shoulder land portion preferably satisfy a relationship of 0.9≤Hso / Hsi≤1.1. Advantageous effects of the invention

[0021] According to one embodiment of the present invention, the land portion width Wcc of the center land portion and the land portion width Wco of the center outer land portion satisfy the relationship Wcc < Wco, and in a region where the ground contact pressure on the vehicle outer side increases more than the center land portion during cornering, the ground contact surface of each of the center outer land portion and the outer side shoulder land portion is formed to protrude from the reference pattern to the outside in the tire radial direction, and thus the ground contact length of each of the center outer land portion and the outer side shoulder land portion can be ensured. As a result, the steering stability performance on dry road surfaces can be improved.Furthermore, the land portion width Wcc of the center land portion and the land portion width Wco of the outer side center land portion satisfy the relationship Wcc < Wco, and in a region where the ground contact pressure on the vehicle outer side increases more than the center land portion during cornering, the ground contact surface of each of the outer side center land portion and the outer side shoulder land portion is formed to protrude from the reference pattern toward the outer side in the tire radial direction. Thus, the ground contact pressure of each of the outer side center land portion and the outer side shoulder land portion can be increased.As a result, the water removal effect from the center portion in the tire width direction of both the center outer side land portion and the outer side shoulder land portion on both sides thereof in the tire width direction is improved, and the steering stability performance on wet road surfaces can be improved.In addition, by setting the protrusion amount Hso of the outer side shoulder land portion whose ground contact length in the ground contact area is reduced compared to the other one to be larger than the protrusion amount Hco of the center outer side land portion located adjacent to and inward from the outer side shoulder land portion in the tire width direction, a sudden decrease in the ground contact length between the center outer side land portion and the outer side shoulder land portion can be suppressed, and good contact with the ground can be achieved, which can contribute to improving the steering stability performance on dry road surfaces and the steering stability performance on wet road surfaces. As a result, the steering stability performance on dry road surfaces and the steering stability performance on wet road surfaces can be improved. Brief description of the drawings Fig. 1 is a meridian cross-sectional view of a pneumatic tire according to an embodiment of the present invention. Fig. 2 is a plan view of a tread portion of a pneumatic tire according to an embodiment of the present invention. Fig. 3 is a detailed view of a tread section of Fig. 1. Fig. 4 is a table showing the results of the performance evaluation test of pneumatic tires according to Examples of the present invention. Description of embodiments

[0022] Embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to these embodiments. Constituent elements of the embodiments include elements that can be easily replaced by a person skilled in the art or that are substantially identical. Furthermore, the majority of modified examples described in the embodiment can be combined as needed within the scope obvious to a person skilled in the art.

[0023] Fig. 1 is a meridian cross-sectional view of a pneumatic tire according to the present embodiment. Fig. 2 is a plan view of a tread portion of the pneumatic tire according to the present embodiment. Fig. 3 is a detailed view of a tread section of Fig. 1.

[0024] In the following description, the tire radial direction refers to a direction perpendicular to the rotational axis (not illustrated) of a pneumatic tire 1, the inner side in the tire radial direction refers to the side facing the rotational axis in the tire radial direction, and the outer side in the tire radial direction refers to the side facing away from the rotational axis in the tire radial direction. Furthermore, the tire circumferential direction refers to the circumferential direction with the rotational axis as the center axis. In addition, the tire width direction refers to a direction parallel to the rotational axis, the inner side in the tire width direction refers to a side toward the tire equatorial plane (tire equator line) CL in the tire width direction, and the outer side in the tire width direction refers to a side away from the tire equatorial plane CL in the tire width direction.The tire equatorial plane CL is a plane perpendicular to the rotational axis of the pneumatic tire 1 and passing through the tire width center of the pneumatic tire 1. In the tire equatorial plane CL, the tire width direction center line, which is the center position of the pneumatic tire 1 in the tire width direction, coincides with the tire width direction position. "Tire equator line" refers to a line lying on the tire equatorial plane CL and extending along the tire circumferential direction of the pneumatic tire 1. In the present embodiment, the tire equator line is denoted by the same reference symbol "CL" as the tire equatorial plane.

[0025] As in Fig. As illustrated in FIG. 1, the pneumatic tire 1 of the present embodiment includes a tread portion 2 and shoulder portions 3 on both sides of the tread portion 2, and from the respective shoulder portions 3, sidewall portions 4 and bead portions 5 are continuously arranged in this order. Furthermore, the pneumatic tire 1 includes a carcass layer 6, a belt layer 7, and a belt reinforcing layer 8.

[0026] The tread portion 2 is made of rubber material (tread rubber) and is exposed on the outermost side in the tire radial direction of the pneumatic tire 1; the outer peripheral surface thereof constitutes the contour of the pneumatic tire 1. The outer peripheral surface of the tread portion 2 is a surface that may mainly come into contact with a road surface during running and is configured as the ground contact surface 10.

[0027] The shoulder portions 3 are portions of the tread portion 2 located on both outer sides in the tire width direction. Furthermore, the sidewall portions 4 are exposed on the outermost sides of the pneumatic tire 1 in the tire width direction. Further, each of the bead portions 5 includes a bead core 15 and a bead filler 16. The bead core 15 is formed by winding a bead wire, which is a steel wire, into a ring shape. The bead filler 16 is a rubber material disposed in a space formed by folding back an end portion in the tire width direction of the carcass layer 6 at the position of the bead core 15.

[0028] The end portion in the tire width direction of the carcass layer 6 is folded back around a pair of the bead cores 15 to the outside in the tire width direction, and the carcass layer 6 is annularly stretched in the tire circumferential direction to form the frame of the tire. The carcass layer 6 is made of a plurality of coating rubber-coated carcass cords (not illustrated) juxtaposed at an angle with respect to the tire circumferential direction along the tire meridian direction. The carcass cords are made of organic fibers such as polyester, rayon, nylon, or the like. The carcass layer 6 is provided with at least one layer.

[0029] The belt layer 7 has a multi-layer structure in which at least two belts 7a, 7b are layered in the tread portion 2, with the belt layer 7 being arranged on the outer side in the tire radial direction, which is the outer periphery of the carcass layer 6 covering the carcass layer 6 in the tire circumferential direction. The belts 7a and 7b are formed by coating a plurality of cords (not illustrated) arranged side by side at a predetermined angle (e.g., 20° to 30°) with respect to the tire circumferential direction with a coating rubber. The cords are made of, for example, steel or organic fibers such as polyester, rayon, nylon, or the like. The overlapped belts 7a and 7b are arranged such that the cords intersect.

[0030] The belt reinforcing layer 8 is arranged on the outside of the belt layer 7 in the tire radial direction, that is, on its outer circumference, and covers the belt layer 7 in the tire circumferential direction. The belt reinforcing layer 8 is formed by a plurality of coating rubber-coated cords (not illustrated) arranged substantially parallel to the tire circumferential direction and adjacent to each other in the tire width direction. The cords are made of, for example, steel or organic fibers such as polyester, rayon, nylon, or the like, and the cord angle is within a range of ± 5° with respect to the tire circumferential direction. Fig. The belt reinforcing layer 8 illustrated in FIG. 1 is arranged to cover the entirety of the belt layer 7. The configuration of the belt reinforcing layer 8 is not limited to that described above. Although not explicitly illustrated in the drawings, a configuration may be adopted in which the belt reinforcing layer 8 is arranged to cover only the end portions in the tire width direction of the belt layer 7.Alternatively, a configuration may be adopted in which the belt reinforcing layer 8 includes two reinforcing layers, one of which is formed on the inner side in the tire radial direction so as to be longer in the tire width direction than the belt layer 7 and is arranged to cover the entirety of the belt layer 7, and the other of which is arranged on the outer side in the tire radial direction so as to cover only the end portions in the tire width direction of the belt layer 7. Alternatively, a configuration may be adopted in which the belt reinforcing layer 8 includes two reinforcing layers, each of the reinforcing layers being arranged to cover only the end portions in the tire width direction of the belt layer 7. In other words, the belt reinforcing layer 8 overlaps at least the end portions of the belt layer 7 in the tire width direction.In addition, the belt reinforcing layer 8 is arranged by winding a strip-shaped strip material, for example, with a width of 10 mm, in the tire circumferential direction.

[0031] Note that the internal structure of the pneumatic tire 1 described above is a typical example of the pneumatic tire 1; however, the internal structure is not limited thereto.

[0032] The pneumatic tire 1 of the present embodiment is a tire whose mounting direction is predetermined with respect to a vehicle. In other words, when the pneumatic tire 1 of the present embodiment is mounted on the vehicle, the orientation is predetermined with respect to the inside and outside of the vehicle in the tire width direction. The orientation marking is not illustrated in the drawings, but may be indicated, for example, by indicators provided on the sidewall portions 4. Therefore, when mounted on the vehicle, the side facing the outside of the vehicle is the "vehicle outside," and the side facing the inside of the vehicle is the "vehicle inside." Note that the vehicle outside and vehicle inside markings are not limited to the case where the tire is mounted on the vehicle.For example, in cases where the tire is mounted on a rim, the orientation of the rim with respect to the outside and inside of the vehicle in the tire width direction is predetermined. Thus, in cases where the pneumatic tire 1 is mounted on the rim, the orientation with respect to the outside and inside of the vehicle in the tire width direction is marked.

[0033] The ground contact surface 10 of the tread portion 2 is configured such that four circumferential main grooves 20 extending continuously in the tire circumferential direction and around the entire circumference of the tire are formed side by side in the tire width direction.

[0034] The main circumferential grooves 20 are each a groove required to display wear indicators specified by JATMA and including a groove width of 3.0 mm or more and a groove depth of 6.0 mm or more.

[0035] Note that the groove width, sipe width, and land portion width described below are measured as the maximum values of dimensions in the tire width direction from both groove opening ends opened on the ground contact surface 10 when the pneumatic tire 1 is mounted on a predetermined rim, inflated to the predetermined internal pressure, and in an unloaded state (predetermined load = 0). In a configuration in which recess portions and chamfered portions are formed in the groove opening edge, the groove width is measured with the groove opening end regarded as the outer edge of the recess portions and the chamfered portions, and is measured including the recess portions and the chamfered portions.The groove depth and the sipe depth are measured as the maximum values of the dimensions from the ground contact surface 10 to the groove bottom when the pneumatic tire 1 is mounted on a given rim and inflated to the given internal pressure and is in an unloaded state (given load = 0).

[0036] "Specified rim" means a "standard rim" as defined by the Japan Automobile Tire Manufacturers Association (JATMA), a "design rim" as defined by the Tire and Rim Association (TRA), or a "measuring rim" as defined by the European Tire and Rim Technical Organization (ETRTO). Furthermore, "specified internal pressure" refers to the "maximum air pressure" as defined by JATMA, the maximum value in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" as defined by TRA, or "INFLATION PRESSURES" as defined by ETRTO.Furthermore, “specified load” refers to a “maximum load capacity” as defined by JATMA, the maximum value in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” as defined by TRA or “LOAD CAPACITY” as defined by ETRTO.

[0037] The circumferential main grooves 20 are arranged such that two circumferential main grooves are provided on the outer side in the tire width direction with the equatorial plane of the tire CL as a boundary. Further, on the vehicle outer side, the circumferential main groove 20 near the equatorial plane of the tire CL is referred to as an outer side center main groove 21, and the circumferential main groove 20 on the outer side in the tire width direction of the outer side center main groove 21 is referred to as an outer side shoulder main groove 23. On the vehicle inner side, the circumferential main groove 20 near the equatorial plane of the tire CL is referred to as an inner side center main groove 22, and the circumferential main groove 20 on the outer side in the tire width direction of the inner side center main groove 22 is referred to as an inner side shoulder main groove 24.

[0038] In the present embodiment, the circumferential main groove 20 is configured such that the outer side center main groove 21 extending in the tire circumferential direction is formed in a zigzag shape bent at a certain pitch on both sides in the tire width direction. The inner side center main groove 22, the outer side shoulder main groove 23, and the inner side shoulder main groove 24 of the other circumferential main grooves are formed in a linear shape in the tire circumferential direction. Triangular chamfered portions, each having a long portion and a short portion, are formed on the ground contact surface 10 adjacent to each other in the tire circumferential direction at the groove opening end of the outer side center main groove 21.The long portions and the short portions of the chamfered portions are arranged point-symmetrically at both groove opening ends, and thus the outer side center main groove 21 is formed in a zigzag shape.

[0039] Further, five land portions 30 aligned side by side in the tire width direction are defined and formed by the four circumferential main grooves 20 (21, 22, 23, 24) on the ground contact surface 10 of the tread portion 2. Furthermore, the land portion 30 formed on the equatorial plane of the tire CL between the outer side center main groove 21 and the inner side center main groove 22 is referred to as a center land portion 31. The land portion 30 formed between the outer side center main groove 21 and the outer side shoulder main groove 23 on the vehicle outer side is referred to as an outer side center land portion 32. The land portion 30 formed on the outer side in the tire width direction of the outer side shoulder main groove 23 is referred to as an outer side shoulder land portion 34.The land portion 30 formed on the vehicle inner side between the inner side center main groove 22 and the inner side shoulder main groove 24 is referred to as an inner side center land portion 33. The land portion 30 formed on the outer side in the tire width direction of the inner side shoulder main groove 24 is referred to as an inner side shoulder land portion 35. The outer side shoulder main groove 23 and the inner side shoulder main groove 24 are respectively located at ground contact edges T.

[0040] The ground contact edges T are each two outermost edges of a ground contact area in the tire width direction. Fig. 2, the ground contact edges T are depicted as being continuous in the tire circumferential direction. The ground contact area is an area where the ground contact surface 10 of the tread portion 2 of the pneumatic tire 1 comes into contact with a dry, flat road surface when the pneumatic tire 1 is mounted on a specified rim, inflated to the specified internal pressure, and loaded with 70% of the specified load.

[0041] The center land portion 31 is provided with only sipes 41 formed on the ground contact surface 10. Each of the sipes 41 includes one end communicating with the inner side center main groove 22, extends toward the tire equatorial plane CL side (toward the inner side in the tire width direction), and includes the other end blindly terminating within the ground contact surface 10 of the center land portion 31. A plurality of sipes 41 are provided at intervals in the tire circumferential direction. The sipe 41 has the sipe having a sipe width in a range of 0.6 mm or more to 1.8 mm or less; and a sipe depth in a range of 3.0 mm or more to 7.0 mm or less. The sipe 41 is closed when the ground contact surface 10 is brought into contact with the ground.The sipe 41 ensures tread rigidity and contributes to improving steering stability performance on dry road surfaces compared to a configuration in which a plurality of lug grooves are arranged in the tire circumferential direction in the center land portion 31. Furthermore, the inclination angle of the sipe 41 is in a range of 45 degrees or more to 80 degrees or less with respect to the tire circumferential direction. By ensuring the inclination angle of 45 degrees or more, the sipe 41 contributes to suppressing the occurrence of chipping wear. By ensuring the inclination angle of 80 degrees or less, the sipe 41 contributes to improving steering stability performance on wet road surfaces due to edge effects.

[0042] The sipe 41 is preferably configured such that a dimension L1 in the tire width direction and a land portion width Wcc of the center land portion 31 have a relationship of 0.30≤L1 / Wcc≤0.60. The land portion width Wcc of the center land portion 31 is the dimension in the tire width direction of the ground contact surface 10 excluding the chamfered portions of the circumferential main grooves 20, and is also referred to as a ground contact width that can actually come into contact with a road surface. Hereinafter, the land portion widths of the other land portions are defined in the same way. With 0.30≤L1 / Wcc, the sipe 41 ensures the water removal effect and contributes to improving steering stability performance on wet road surfaces. With L1 / Wcc ≤ 0.60, the sipe 41 ensures the rigidity of the center web section 31 and contributes to the steering stability performance on dry road surfaces.

[0043] The middle outer side land portion 32 is provided only with lug grooves 51 and sipes 42 formed on the ground contact surface 10.

[0044] Each of the lug grooves 51 includes one end communicating with the outer side shoulder main groove 23, extends toward the inner side in the tire width direction, and includes the other end blindly terminating within the ground contact surface 10 of the outer side center land portion 32. The lug groove 51 is formed in a long shape extending mainly in the tire width direction, and is provided with a bent portion at the other end and formed in a short shape extending mainly in the tire circumferential direction. A plurality of lug grooves 51 are provided at intervals in the tire circumferential direction. A sipe (not illustrated) is formed in the groove bottom along the longitudinal direction of the lug groove 51, and a chamfer is formed on the ground contact surface 10 side of the sipe. Thus, the lug groove 51 is formed in the configuration described above.The chamfer may be arranged on both sides in the sipe width of the sipe or only on one side in the sipe width. The sipe of the lug groove 51 has a sipe width in a range of 0.3 mm or more to 1.5 mm or less and a sipe depth from the ground contact surface 10 in a range of 3.3 mm or more to 4.5 mm or less. The depth of the chamfer of the sipe depth of the lug groove 51 is in a range of 1.0 mm or more to 3.0 mm or less, and the width of the chamfer is in a range of 1.5 mm or more to 4.5 mm or less. Only the sipe of the lug groove 51 is closed when the ground contact surface 10 is brought into contact with the ground.

[0045] The lug groove 51 is preferably configured such that a dimension L2 in the tire width direction and a land portion width Wco of the center outer side land portion 32 have a relationship of 0.65≤L2 / Wco≤0.85. With 0.65≤L2 / Wco, the lug groove 51 ensures the water removal effect and contributes to improving steering stability performance on wet road surfaces. With L2 / Wco≤0.85, the lug groove 51 ensures the rigidity of the center outer side land portion 32 and contributes to steering stability performance on dry road surfaces.In particular, the lug grooves 51 are arranged on an edge portion of the outer side center land portion 32 located on the outer side in the tire width direction (on the ground contact edge T side) where the contribution to the water removal effect is high, and thus the lug grooves 51 significantly contribute to improving the steering stability performance on wet road surfaces.

[0046] Each of the sipes 42 is individually arranged between blind-ended end portions of the lug grooves 51, which are adjacent to each other in the tire circumferential direction, and extends mainly in the tire circumferential direction. The sipe 42 does not communicate with the lug groove 51 and the circumferential main groove 20, and both ends of the sipe 42 blindly terminate within the ground contact surface 10 of the outer side center land portion 32. The sipe 42 extends parallel to the long portion of the chamfered portion of the outer side center main groove 21. The sipe 42 has a sipe width in a range of 0.6 mm or more to 1.8 mm or less; and a sipe depth in a range of 3.0 mm or more to 7.0 mm or less. The sipe 42 is closed when the ground contact surface 10 is brought into contact with the ground.As described above, in the lug grooves 51 having the dimension L2 in the tire width direction and arranged between the blind-ended end portions of the lug grooves 51, the sipes 42 are appropriately arranged with respect to the lug grooves 51 and the circumferential main grooves 20. As a result, the center outer side land portion 32 has uniform rigidity, which contributes to the steering stability performance on dry road surfaces.

[0047] The central inner side land portion 33 is provided only with lug grooves 52 and sipes 43 formed in the ground contact surface 10.

[0048] Each of the lug grooves 52 includes one end communicating with the inner side shoulder main groove 24, extends toward the inner side in the tire width direction, and includes the other end blindly terminating within the ground contact surface 10 of the inner side center land portion 33. The lug groove 52 is formed in a long shape extending mainly in the tire width direction. A plurality of lug grooves 52 are provided at intervals in the tire circumferential direction. A sipe (not illustrated) is formed in the groove bottom along the longitudinal direction of the lug groove 52, and a chamfer is formed on the ground contact surface 10 side of the sipe. Thus, the lug groove 52 is formed in the configuration described above. The chamfer may be arranged on both sides in the sipe width of the sipe or only on one side in the sipe width.The sipe of the lug groove 52 has a sipe width in a range of 0.3 mm or more to 1.5 mm or less, and a sipe depth from the ground contact surface 10 in a range of 3.3 mm or more to 4.5 mm or less. The depth of the chamfer of the sipe depth of the lug groove 51 is in a range of 1.0 mm or more to 3.0 mm or less, and the width of the chamfer is in a range of 1.5 mm or more to 4.5 mm or less. Only the sipe of the lug groove 51 is closed when the ground contact surface 10 is brought into contact with the ground.

[0049] The lug groove 52 is preferably configured such that a dimension L3 in the tire width direction and a land portion width Wci of the center inner side land portion 33 have a relationship of 0.60 ≤ L3 / Wci ≤ 0.70. With 0.60 ≤ L3 / Wci, the lug groove 52 ensures the water removal effect and contributes to improving steering stability performance on wet road surfaces. With L3 / Wci ≤ 0.70, the lug groove 52 ensures the rigidity of the center inner side land portion 33 and contributes to steering stability performance on dry road surfaces.

[0050] Each of the sipes 43 includes one end communicating with the inside center main groove 22, extends outward in the tire width direction, and includes the other end blindly terminating within the ground contact surface 10 of the inside center land portion 33. A plurality of sipes 43 are provided at intervals in the tire circumferential direction. The sipe 43 has a sipe width in a range of 0.6 mm or more to 1.8 mm or less; and a sipe depth in a range of 3.0 mm or more to 7.0 mm or less. The sipe 43 is closed when the ground contact surface 10 is brought into contact with the ground. The sipes 43 are arranged alternately with respect to the lug grooves 52 in the tire circumferential direction.As a result, compared to a configuration in which only the lug grooves or the sipes are arranged in the tire circumferential direction, a water removal effect is ensured, which contributes to improving steering stability performance on wet road surfaces. Furthermore, the rigidity balance of the center inner side land portion 33 is ensured, which contributes to improving steering stability performance on dry road surfaces.Specifically, the lug grooves 52 are arranged on an edge portion of the center inner land portion 33 located on the outer side in the tire width direction (located on the ground contact edge T side), where the contribution to the water removal effect is high, and the sipes 43 are arranged on an edge portion of the center inner land portion 33 located on the inner side in the tire width direction (located on the tire equatorial plane CL side), where the contribution to improving rigidity is high. Therefore, a relative balance between the steering stability performance on wet road surfaces and the steering stability performance on dry road surfaces can be effectively improved.

[0051] The sipe 43 is preferably configured such that a dimension L4 in the tire width direction and the land portion width Wci of the center inner side land portion 33 have a relationship of 0.20 ≤ L4 / Wci ≤ 0.25. With 0.20 ≤ L4 / Wci, the sipe 43 ensures the water removal effect and contributes to improving steering stability performance on wet road surfaces. With L4 / Wci ≤ 0.25, the sipe 43 ensures the rigidity of the center inner side land portion 33 and contributes to steering stability performance on dry road surfaces.

[0052] Note that the sipes 43 and the lug grooves 52 are arranged so as not to overlap each other when viewed in the tire circumferential direction. Specifically, a dimension D2 in the tire width direction between a blind end of the sipe 43 and a blind end of the lug groove 52 is preferably within a range of 0.05≤D2 / Wci≤0.20 with respect to the land portion width Wci of the center inner side land portion 33. As a result, compared with a configuration in which the sipes 43 and the lug grooves 52 overlap each other when viewed in the tire circumferential direction, the rigidity of the center inner side land portion 33 is ensured, which contributes to improving steering stability performance on dry road surfaces.

[0053] Furthermore, the sipe 43 of the inner side center land portion 33 and the sipe 41 of the center land portion 31 are inclined in an identical direction with respect to the tire circumferential direction. Moreover, the sipe 43 and the sipe 41 extend toward each other along the extension lines, and respective ends thereof communicating with the inner side center main groove 22 oppose each other across the inner side center main groove 22. As a result, the sipe 43 and the sipe 41 ensure the water removal effect and contribute to improving the steering stability performance on wet road surfaces.

[0054] The outer side shoulder land portion 34 is provided only with lug grooves 53 and sipes 44 formed in the ground contact surface 10.

[0055] Each of the lug grooves 53 extends from the outer side in the tire width direction to intersect with the ground contact edge T and extends toward the inner side in the tire width direction. An extension end of the lug groove 53 terminates blindly within the ground contact surface 10 of the outer side shoulder land portion 34 without communicating with the outer side shoulder main groove 23. A plurality of lug grooves 53 are provided at intervals in the tire circumferential direction. The lug groove 53 has a groove width in a range of 1.5 mm or more to 4.5 mm or less; and a groove depth in a range of 55% or more to 80% or less of a groove depth of the outer side shoulder main groove 23.

[0056] The lug groove 53 is preferably configured such that a dimension L5 from the ground contact edge T to the inner side in the tire width direction and a land portion width Wso of the outer side shoulder land portion 34 have a relationship of 0.50 ≤ L5 / Wso ≤ 0.85. With 0.50 ≤ L5 / Wso, the lug groove 53 ensures the water removal effect and contributes to improving steering stability performance on wet road surfaces. With L5 / Wso ≤ 0.85, the lug groove 53 ensures the rigidity of the outer side shoulder land portion 34 and contributes to steering stability performance on dry road surfaces. The land portion width Wso of the outer side shoulder land portion 34 is the dimension in the tire width direction between an edge portion of the outer side shoulder main groove 23 arranged on the outer side in the tire width direction and the ground contact edge T on the vehicle outer side.

[0057] Each of the sipes 44 includes one end communicating with the outer side shoulder main groove 23, extends to the outside in the tire width direction, and includes the other end blindly terminating within the ground contact surface 10 of the outer side shoulder land portion 34 without intersecting with the ground contact edge T. A plurality of the sipes 44 are arranged at intervals in the tire circumferential direction. The sipe 44 has a sipe width in a range of 0.6 mm or more to 1.8 mm or less; and a sipe depth in a range of 3.0 mm or more to 7.0 mm or less. The sipe 44 is closed when the ground contact surface 10 is brought into contact with the ground. The sipes 44 are arranged alternately with respect to the lug grooves 53 in the tire circumferential direction.As a result, compared to a configuration in which only the lug grooves or the sipes are arranged in the tire circumferential direction, a water removal effect is ensured, which contributes to improving steering stability performance on wet road surfaces. Furthermore, the rigidity balance of the outer side shoulder land portion 34 is ensured, which contributes to improving steering stability performance on dry road surfaces.

[0058] The sipe 44 is preferably configured such that a dimension L6 in the tire width direction and the land portion width Wso of the outer side shoulder land portion 34 have a relationship of 0.50 ≤ L6 / Wso ≤ 0.85. With 0.50 ≤ L6 / Wso, the sipe 44 ensures the water removal effect and contributes to improving steering stability performance on wet road surfaces. With L6 / Wso ≤ 0.85, the sipe 44 ensures the rigidity of the outer side shoulder land portion 34 and contributes to steering stability performance on dry road surfaces.

[0059] Furthermore, the sipes 44 and the lug grooves 53 are arranged to overlap each other when viewed in the tire circumferential direction. Specifically, dimensions D3 in the tire width direction between respective blind ends of the sipe 44 and the lug groove 53 that overlap each other are preferably in a range of 0.50≤D3 / Wso≤0.70 with respect to the land portion width Wso of the outer side shoulder land portion 34. As a result, compared with a configuration in which the sipes 44 and the lug grooves 53 do not overlap each other when viewed in the tire circumferential direction, a water removal effect is ensured, which contributes to improving steering stability performance on wet road surfaces.

[0060] Only a narrow circumferential groove 61, lug grooves 54 and sipes 45 are formed in the inner side shoulder land section 35.

[0061] The circumferential narrow groove 61 is a narrow groove extending in the tire circumferential direction and continuously formed in the entire circumference of the tire. The circumferential narrow groove 61 has a groove width in a range of 0.8 mm or more to 3.0 mm or less and a groove depth in a range of 0.8 mm or more to 3.0 mm or less. The inner side shoulder land portion 35 is divided by the circumferential narrow groove 61 into an inner land portion 351 located on the inner side shoulder main groove 24 side and on the inner side in the tire width direction; and an outer land portion 352 located on the ground contact edge T side and on the outer side in the tire width direction.

[0062] A dimension D4 in the tire width direction from an edge portion of the narrow circumferential groove 61 located on the outer side in the tire width direction to the ground contact edge T on the vehicle inner side; and a land portion width Wsi of the inner side shoulder land portion 35 preferably have a ratio of 0.55 ≤ D4 / Wsi ≤ 0.85. As a result, in the inner side shoulder land portion 35, the position of the narrow circumferential groove 61 is fixed in the tire width direction, and the narrow circumferential groove 61 appropriately exerts a water removal effect and contributes to improving steering stability performance on wet road surfaces.In addition, the narrow circumferential groove 61 in the inner side shoulder land portion 35 adjusts land portion widths of the inner land portion 351 and the outer land portion 352, provides appropriate rigidity of the inner land portion 351 and the outer land portion 352, and thus contributes to improving the steering stability performance on dry road surfaces.

[0063] Each of the lug grooves 54 extends from the outer side in the tire width direction to intersect with the ground contact edge T and extends toward the inner side in the tire width direction. An extension end of the lug groove 54 blindly terminates within the ground contact surface 10 of the inner side shoulder land portion 35 without communicating with the inner side shoulder main groove 24. The lug groove 54 penetrates the narrow circumferential groove 61 and has a blind end present within the ground contact surface 10 of the inner side land portion 351. A plurality of lug grooves 54 are provided at intervals in the tire circumferential direction. The lug groove 54 has a groove width in a range of 1.5 mm or more to 4.5 mm or less; and a groove depth in a range of 55% or more to 80% or less of a groove depth of the inner side shoulder main groove 24.

[0064] The lug groove 54 is preferably configured such that a dimension L7 from the ground contact edge T to the inner side in the tire width direction and the land portion width Wsi of the inner side shoulder land portion 35 have a relationship of 0.60 ≤ L7 / Wsi ≤ 0.85. With 0.60 ≤ L7 / Wsi, the lug groove 54 ensures the water removal effect and contributes to improving steering stability performance on wet road surfaces. With L7 / Wsi ≤ 0.85, the lug groove 54 ensures the rigidity of the inner side shoulder land portion 35, particularly the rigidity of the inner land portion 351, and contributes to steering stability performance on dry road surfaces. The land portion width Wsi of the inner side shoulder land portion 35 is the dimension in the tire width direction between an edge portion of the inner side shoulder main groove 24 arranged on the outer side in the tire width direction and the ground contact edge T on the vehicle inner side.

[0065] Each of the sipes 45 includes one end communicating with the inner side shoulder main groove 24, extends to the outside in the tire width direction, and includes the other end blindly ending within the ground contact surface 10 of the inner side shoulder land portion 35 without intersecting with the ground contact edge T. The sipe 45 penetrates the circumferential narrow groove 61 and has a blind end present within the ground contact surface 10 of the outer side land portion 352. A plurality of sipes 45 are provided at intervals in the tire circumferential direction. The sipe 45 has a sipe width in a range of 0.6 mm or more to 1.8 mm or less; and a sipe depth in a range of 3.0 mm or more to 7.0 mm or less. The sipe 45 is closed when the ground contact surface 10 is brought into contact with the ground.The sipes 45 are arranged alternately with respect to the lug grooves 53 in the tire circumferential direction. As a result, compared to a configuration in which only the lug grooves or the sipes are arranged in the tire circumferential direction, a water removal effect is ensured, which contributes to improving steering stability performance on wet road surfaces. Furthermore, the rigidity balance of the inner side shoulder land portion 35 is ensured, which contributes to improving steering stability performance on dry road surfaces.

[0066] The sipe 45 is preferably configured such that a dimension L8 in the tire width direction and the land portion width Wsi of the inner side shoulder land portion 35 have a relationship of 0.70 ≤ L8 / Wsi ≤ 0.90. With 0.70 ≤ L8 / Wsi, the sipe 45 ensures the water removal effect and contributes to improving steering stability performance on wet road surfaces. With L8 / Wsi ≤ 0.90, the sipe 45 ensures the rigidity of the inner side shoulder land portion 35, particularly the rigidity of the outer side land portion 352, and contributes to steering stability performance on dry road surfaces.

[0067] Furthermore, the sipes 45 and the lug grooves 54 are arranged to overlap each other when viewed in the tire circumferential direction. As a result, compared to a configuration in which the sipes 45 and the lug grooves 54 do not overlap each other when viewed in the tire circumferential direction, a water removal effect is ensured, which contributes to improving steering stability performance on wet road surfaces.

[0068] In the pneumatic tire 1 of the present embodiment described above, the land portion width Wcc of the center land portion 31 and the land portion width Wco of the center outer side land portion 32 satisfy a relationship of Wcc < Wco. Furthermore, in the pneumatic tire 1 of the present embodiment, the ground contact surface 10 of each of the center outer side land portion 32 and the outer side shoulder land portion 34 is formed to protrude toward the outside in the tire radial direction with respect to a reference pattern, and a protrusion amount Hco of the center outer side land portion 32 and a protrusion amount Hso of the outer side shoulder land portion 34 satisfy a relationship of Hco < Hso.

[0069] Here is how in Fig. As illustrated in FIG. 3, a reference profile PRco of the outer side center land portion 32 is an arc in a meridian cross-sectional view in an unloaded state (specified load = 0) in which the pneumatic tire 1 is mounted on a specified rim and inflated to the specified internal pressure. The arc passes through three points of the respective groove opening ends P1o, P2o of the outer side center main groove 21 and a groove opening end P3o on the inner side in the tire width direction of the outer side shoulder main groove 23.Furthermore, in the land portion width Wco of the outer-side center land portion 32, which is a dimension in the tire width direction between the groove opening end P2o on the outer side in the tire width direction of the outer-side center main groove 21 and the groove opening end P3o on the inner side in the tire width direction of the outer-side shoulder main groove 23, the ground contact surface 10 of the outer-side center land portion 32 protrudes toward the outer side in the tire radial direction from the respective groove opening ends P2o, P3o to the center portion in the tire width direction while being formed in a gradually curved line (or arc). In other words, namely, the protrusion amount Hco of the outer-side center land portion 32 is a protrusion difference from the reference profile PRco with respect to the respective groove opening ends P2o, P3o, which are end portions of the land portion width Wco in the tire width direction.

[0070] Furthermore, a reference profile PRso of the outer side shoulder land portion 34 is an arc in a meridian cross-sectional view in an unloaded state (specified load = 0) in which the pneumatic tire 1 is mounted on a specified rim and inflated to the specified internal pressure. The arc passes through three points of the groove opening end P3o and a groove opening end P4o of the outer side shoulder main groove 23 and the ground contact edge T on the vehicle outer side.Furthermore, in the land portion width Wso of the outer side shoulder land portion 34, which is a dimension in the tire width direction between the groove opening end P4o on the outer side in the tire width direction of the outer side shoulder main groove 23 and the ground contact edge T on the vehicle outer side, the ground contact surface 10 of the outer side shoulder land portion 34 protrudes toward the outer side in the tire radial direction from the groove opening end P4o and the ground contact edge T on the vehicle outer side to the center portion in the tire width direction while being formed in a gradually curved line (or arc). In other words, namely, the protrusion amount Hso of the outer side shoulder land portion 34 is a protrusion difference from the reference profile PRso with respect to the groove opening end P4o, which is an end portion of the land portion width Wso in the tire width direction, and the ground contact edge T on the vehicle outer side.

[0071] Therefore, according to the pneumatic tire 1, the land portion width Wcc of the center land portion 31 and the land portion width Wco of the center outer side land portion 32 satisfy the relationship Wcc < Wco, and in a region where the ground contact pressure on the vehicle outer side increases more during cornering than the center land portion 31, the ground contact surface 10 of each of the center outer side land portion 32 and the outer side shoulder land portion 34 is formed to protrude from the reference pattern to the outer side in the tire radial direction PRco, PRso, and thus the ground contact length of each of the center portion in the tire width direction of each of the center outer side land portion 32 and the outer side shoulder land portion 34 can be ensured. The ground contact length is the dimension in the tire circumferential direction in the above-described ground contact range.As a result, the steering stability performance on dry road surfaces can be maintained. Furthermore, the land portion width Wcc of the center land portion 31 and the land portion width Wco of the center outer side land portion 32 satisfy the relationship Wcc < Wco, and in a region where the ground contact pressure on the vehicle outer side increases more than the center land portion 31 during cornering, the ground contact surface 10 of each of the center outer side land portion 32 and the outer side shoulder land portion 34 is formed to protrude from the reference profile PRco, PRso to the outer side in the tire radial direction. Thus, the ground contact pressure at the center portion in the tire width direction of each of the center outer side land portion 32 and the outer side shoulder land portion 34 can be increased.As a result, the water removal effect from the center portion in the tire width direction of both the center outer side land portion 32 and the outer side shoulder land portion 34 on both sides thereof in the tire width direction is improved, and the steering stability performance on wet road surfaces can be improved.Furthermore, by setting the protrusion amount Hso of the outer side shoulder land portion 34, whose ground contact length in the ground contact area is reduced compared to the other, to be larger than the protrusion amount Hco of the center outer side land portion 32 located adjacent to and inward from the outer side shoulder land portion 34 in the tire width direction, a sudden decrease in the ground contact length between the center outer side land portion 32 and the outer side shoulder land portion 34 can be suppressed, and good contact with the ground can be achieved, which can contribute to improving the steering stability performance on dry road surfaces and the steering stability performance on wet road surfaces. As a result, the steering stability performance on dry road surfaces and the steering stability performance on wet road surfaces can be improved.

[0072] In addition, in the pneumatic tire 1 of the present embodiment, the protrusion amount Hco of the outer side center land portion 32 is in a range of 0.2 mm ≤ Hco ≤ 0.4 mm.

[0073] According to the pneumatic tire 1, by setting the protrusion amount Hco of the center outer side land portion 32 to 0.2 mm or more, the ground contact pressure at the center portion in the tire width direction of the center outer side land portion 32 is brought close to the ground contact pressure on both sides thereof in the tire width direction. On the other hand, by setting the protrusion amount Hco of the center outer side land portion 32 to 0.4 mm or less, an excessive decrease in the ground contact pressure on both sides of the center outer side land portion 32 in the tire width direction is suppressed. As a result, the center outer side land portion 32 can provide good contact with the ground, and the gripping force with the road surface can be increased. Accordingly, the steering stability performance on dry road surfaces and the steering stability performance on wet road surfaces can be improved.

[0074] Further, in the pneumatic tire 1 of the present embodiment, the protrusion amount Hso of the outer side shoulder land portion 34 is preferably in a range of 0.3 mm ≤ Hso ≤ 0.6 mm.

[0075] According to the pneumatic tire 1, by setting the protrusion amount Hso of the outer side shoulder land portion 34 to 0.3 mm or more, the ground contact pressure at the center portion in the tire width direction of the outer side shoulder land portion 34 can be brought close to the ground contact pressure on both sides thereof in the tire width direction. On the other hand, by setting the protrusion amount Hso of the outer side shoulder land portion 34 to 0.6 mm or less, an excessive decrease in the ground contact pressure on both sides of the outer side shoulder land portion 34 in the tire width direction can be suppressed. As a result, the outer side shoulder land portion 34 can provide good contact with the ground, and the gripping force with the road surface can be increased. Accordingly, the steering stability performance on dry road surfaces and the steering stability performance on wet road surfaces can be improved.

[0076] In addition, in the pneumatic tire 1 of the present embodiment, the protrusion amount Hco of the outer side center land portion 32 and the protrusion amount Hso of the outer side shoulder land portion 34 satisfy a relationship of 1.2 ≤ Hso / Hco ≤ 2.0.

[0077] According to the pneumatic tire 1, the balance between the ground contact pressure at the center outer side land portion 32 and the ground contact pressure at the outer side shoulder land portion 34 is ensured, and the center outer side land portion 32 and the outer side shoulder land portion 34 can provide good contact with the ground. In a region where the ground contact pressure on the vehicle outer side increases more than on the center land portion 31 during cornering, the gripping force on the road surface can be increased. Accordingly, the steering stability performance on dry road surfaces and the steering stability performance on wet road surfaces can be improved.

[0078] Furthermore, in the pneumatic tire 1 of the present embodiment, the ground contact surface 10 of each of the center land portion 31 and the inner side center land portion 33 is formed to be outward in the tire radial direction with respect to a reference profile PRcc, PRci. A protrusion amount Hcc of the center land portion 31 and the protrusion amount Hco of the outer side center land portion 32 preferably satisfy a relationship of 0.9≤Hcc / Hco≤1.1, and the protrusion amount Hcc of the center land portion 31 and the protrusion amount Hci of the inner side center land portion 33 preferably satisfy a relationship of 0.9≤Hcc / Hci≤1.1.

[0079] Here is how in Fig. As illustrated in FIG. 3, the reference profile PRcc of the center land portion 31 is an arc in a meridian cross-sectional view in an unloaded state (specified load = 0) in which the pneumatic tire 1 is mounted on a specified rim and inflated to the specified internal pressure. The arc passes through three points of the respective groove opening ends P1o, P2o of the outer side center main groove 21 and a groove opening end P1i on the inner side in the tire width direction of the inner side center main groove 22, or the arc passes through three points of the groove opening end P1i and a groove opening end P2i of the inner side center main groove 22 and the groove opening end P2i on the inner side in the tire width direction of the outer side center main groove 21.Furthermore, in the land portion width Wcc of the center land portion 31, which is a dimension in the tire width direction between the groove opening end P1o on the inner side in the tire width direction of the outer side center main groove 21 and the groove opening end P1i on the inner side in the tire width direction of the inner side center main groove 22, the ground contact surface 10 of the center land portion 31 protrudes toward the outer side in the tire radial direction from the respective groove opening ends P1o, P1i to the center portion in the tire width direction while being formed in a gradually curved line (or arc). In other words, the protrusion amount Hcc of the center land portion 31 is a protrusion difference from the reference profile PRcc with respect to the respective groove opening ends P1o, P1i, which are end portions of the land portion width Wcc in the tire width direction.

[0080] Furthermore, the reference profile PRci of the inner side center land portion 33 is an arc in a meridian cross-sectional view in an unloaded state (specified load = 0) in which the pneumatic tire 1 is mounted on a specified rim and inflated to the specified internal pressure. The arc passes through three points of the respective groove opening ends P1i, P2i of the inner side center main groove 22 and a groove opening end P3i on the inner side in the tire width direction of the inner side shoulder main groove 24.Furthermore, in the land portion width Wci of the inner-side center land portion 33, which is a dimension in the tire width direction between the groove opening end P2i on the outer side in the tire width direction of the inner-side center main groove 22 and the groove opening end P3i on the inner side in the tire width direction of the inner-side shoulder main groove 24, the ground contact surface 10 of the inner-side center land portion 33 protrudes toward the outer side in the tire radial direction from the respective groove opening ends P2i, P3i to the center portion in the tire width direction while being formed in a gradually curved line (or arc). In other words, namely, the protrusion amount Hci of the inner-side center land portion 33 is a protrusion difference from the reference profile PRci with respect to the respective groove opening ends P2i, P3i, which are end portions of the land portion width Wci in the tire width direction.

[0081] Accordingly, according to the pneumatic tire 1, the ground contact surface 10 of each of the center land portion 31 and the center inner side land portion 33 is also formed to protrude from the reference profile PRcc, PRci toward the outside in the tire radial direction, and thus the ground contact length at the center portion in the tire width direction of each of the center land portion 31 and the center inner side land portion 33 can be ensured. As a result, the steering stability performance on dry road surfaces can be improved. In addition, the ground contact surface 10 of each of the center land portion 31 and the center inner side land portion 33 is formed to protrude from the reference profile PRcc, PRci toward the outside in the tire radial direction, and thus the ground contact pressure at the center portion in the tire width direction of each of the center land portion 31 and the center inner side land portion 33 can be increased.Thus, the water removal effect from the center portion in the tire width direction of each of the center land portion 31 and the center inner side land portion 33 on both sides thereof in the tire width direction is improved, and the steering stability performance on wet road surfaces can be improved. As a result, the steering stability performance on dry road surfaces and the steering stability performance on wet road surfaces can be improved. In addition, the protrusion amount Hcc of the center land portion 31 and the protrusion amount Hco of the center outer side land portion 32 satisfy the relationship 0.9≤Hcc / Hco≤1.1, and the protrusion amount Hcc of the center land portion 31 and a protrusion amount Hci of the center inner side land portion 33 satisfy the relationship 0.9≤Hcc / Hci≤1.1.Accordingly, the ground contact pressure can be prevented from varying excessively in the center land portion 31, the center outer side land portion 32, and the center inner side land portion 33. The center land portion 31, the center outer side land portion 32, and the center inner side land portion 33 provide good contact with the ground. Thus, the gripping force with the road surface can be increased, and the steering stability performance on dry road surfaces and the steering stability performance on wet road surfaces can be improved.

[0082] Furthermore, in the pneumatic tire 1 of the present embodiment, it is preferable that no groove is provided on the ground contact surface 10 of the center land portion 31 when it is in contact with the ground. Grooves (the lug grooves 51, 52) each having one end communicating with the circumferential main groove 20 on the outer side in the tire width direction (the outer side shoulder main groove 23 or the inner side shoulder main groove 24) and the other end blindly terminating within the outer side center land portion 32 or the inner side center land portion 33 are preferably provided on the ground contact surface 10 of both the outer side center land portion 32 and the inner side center land portion 33 when they are in contact with the ground.

[0083] According to the pneumatic tire 1, no groove is present on the ground contact surface 10 of the center land portion 31 when it is in contact with the ground. Thus, the center land portion 31 ensures the rigidity of the land portion and provides good contact with the ground. As a result, the grip force with the road surface can be increased and the steering stability performance on dry road surfaces can be improved.In addition, grooves (the lug grooves 51, 52), each having one end communicating with the circumferential main groove 20 on the outer side in the tire width direction (the outer side shoulder main groove 23 or the inner side shoulder main groove 24) and the other end blindly terminating within the center outer side land portion 32 or the center inner side land portion 33, are provided on the ground contact surface 10 of both the center outer side land portion 32 and the center inner side land portion 33. Thus, the rigidity is prevented from decreasing while ensuring the water removal effect. As a result, the steering stability performance on dry road surfaces can be improved while maintaining the steering stability performance on wet road surfaces.

[0084] Furthermore, in the pneumatic tire 1 of the present embodiment, the land portion width Wco of the outer side center land portion 32, the land portion width Wso of the outer side shoulder land portion 34, the land portion width Wci of the inner side center land portion 33, and the land portion width Wsi of the inner side shoulder land portion 35 satisfy the relationships 1.2 ≤ Wco / Wcc ≤ 1.4; 1.4 ≤ Wso / Wcc ≤ 1.6; 0.9 ≤ Wci / Wcc ≤ 1.1; 1.4 ≤ Wsi / Wcc ≤ 1.6 with respect to the land portion width Wcc of the center land portion 31.

[0085] According to the pneumatic tire 1, the land portion width Wco of the outer side center land portion 32 is formed to be 1.2 times to 1.4 times as large as the land portion width Wcc of the center land portion 31. The land portion width Wso of the outer side shoulder land portion 34 is formed to be 1.4 times to 1.6 times as large as the land portion width Wcc of the center land portion 31. The land portion width Wci of the inner side center land portion 33 is formed to be equal to the land portion width Wcc of the center land portion 31. The land portion width Wsi of the inner side shoulder land portion 35 is formed to be 1.4 times to 1.6 times as large as the land portion width Wcc of the center land portion 31.As a result, the gripping force with the road surface can be fully well balanced in the tire width direction of the ground contact area, and the steering stability performance on dry road surfaces and the steering stability performance on wet road surfaces can be improved.

[0086] Further, in the pneumatic tire 1 of the present embodiment, the ground contact surface 10 of the inner side shoulder land portion 35 is formed to protrude toward the outside in the tire radial direction with respect to a reference profile PRsi, and the protrusion amount Hso of the outer side shoulder land portion 34 and a protrusion amount Hsi of the inner side shoulder land portion 35 preferably satisfy a relationship of 0.9 ≤ Hso / Hsi ≤ 1.1.

[0087] Here is how in Fig. As illustrated in Figure 3, the reference profile PRsi of the inner side shoulder land portion 35 is an arc in a meridian cross-sectional view in an unloaded state (specified load = 0) in which the pneumatic tire 1 is mounted on a specified rim and inflated to the specified internal pressure. The arc passes through three points of the respective groove opening ends P3i, P4i of the inner side shoulder main groove 24 and the ground contact edge T on the vehicle inner side.Furthermore, in the land portion width Wsi of the inner side shoulder land portion 35, which is a dimension in the tire width direction between the groove opening end P4i on the outer side in the tire width direction of the inner side shoulder main groove 24 and the ground contact edge T on the vehicle inner side, the ground contact surface 10 of the inner side shoulder land portion 35 protrudes toward the outer side in the tire radial direction from the groove opening end P4i and the ground contact edge T on the vehicle inner side to the center portion in the tire width direction while being formed in a gradually curved line (or arc). In other words, the protrusion amount Hsi of the inner side shoulder land portion 35 is a protrusion difference from the reference profile PRsi with respect to the groove opening end P4i, which is an end portion of the land portion width Wsi in the tire width direction, and the ground contact edge T on the vehicle inner side.

[0088] Accordingly, according to the pneumatic tire 1, the ground contact surface 10 of the inner side shoulder land portion 35 is also formed to protrude from the reference profile PRsi to the outer side in the tire radial direction, and thus the ground contact length at the tire width direction center portion of the inner side shoulder land portion 35 can be ensured. As a result, the steering stability performance on dry road surfaces can be improved. In addition, the ground contact surface 10 of the inner side shoulder land portion 35 is also formed to protrude from the reference profile PRsi to the outer side in the tire radial direction, and thus the ground contact pressure at the tire width direction center portion of the inner side shoulder land portion 35 can be increased.Thus, the water removal effect from the center portion in the tire width direction of the inner side shoulder land portion 35 to both sides thereof in the tire width direction is improved, and the steering stability performance on wet road surfaces can be improved. As a result, the steering stability performance on dry road surfaces and the steering stability performance on wet road surfaces can be improved. In addition, the protrusion amount Hso of the outer side shoulder land portion 34 and the protrusion amount Hsi of the inner side shoulder land portion 35 satisfy the relationship 0.9≤Hso / Hsi≤1.1. Accordingly, the ground contact pressure can be prevented from varying excessively in the outer side shoulder land portion 34 and the inner side shoulder land portion 35. The outer side shoulder land portion 34 and the inner side shoulder land portion 35 provide good contact with the ground.Thus, the gripping force can be increased with the road surface and the steering stability performance on dry road surfaces and the steering stability performance on wet road surfaces can be improved. Examples

[0089] In examples according to an embodiment of the present invention, performance tests are conducted on steering stability performance on dry road surfaces (dry performance) and steering stability performance on wet road surfaces (wet performance) on a plurality of types of pneumatic tires under different conditions (see Fig. 4).

[0090] In the performance evaluation tests, pneumatic tires, which are test tires with a nominal size of 225 / 50R17 98W specified by JATMA, are mounted on specified rims with a rim size of 17 × 75 J, inflated to an internal pressure of 230 kPa, and mounted on all front and rear wheels of a sedan-type test vehicle.

[0091] As an evaluation method for steering stability performance on dry road surfaces, the test vehicle is driven on a dry road test track, and the dedicated test driver performs sensation-based evaluations of braking and driving performance, lane-changing performance, cornering performance, and the like. The evaluation results are expressed as index values, with the prior art example evaluated as a reference value (100). In this evaluation, higher index values indicate better steering stability performance on dry road surfaces.

[0092] As an evaluation method for steering stability performance on wet road surfaces, the test vehicle is driven on a wet road test track, and the dedicated test driver performs sensation-based evaluations of braking and driving performance, lane-changing performance, cornering performance, and the like. The evaluation results are expressed as index values, with the prior art example evaluated as a reference value (100). In this evaluation, higher values indicate better steering stability performance on wet road surfaces.

[0093] In Fig. 4, each of the pneumatic tires of the prior art example and Examples 1 to 15 has a mounting direction predetermined with respect to a vehicle. Examples 1 to 9 are comparative examples not according to the present invention. Five land portions are defined and formed in the tire width direction by four circumferential main grooves extending in the tire circumferential direction on the ground contact surface of the tread portion, and thus the tire includes a center land portion on the tire equatorial plane, an outer-side center land portion on the vehicle outer side of the center land portion, an outer-side shoulder land portion on the vehicle outer side of the outer-side center land portion, an inner-side center land portion on the vehicle inner side of the center land portion, and an inner-side shoulder land portion on the vehicle inner side of the inner-side center land portion.

[0094] In the pneumatic tire of the prior art example, the ground contact surface of each of the land portions is located on the reference pattern, and the width of each of the land portions is the same. On the other hand, each of the pneumatic tires of Examples 1 to 15 is configured such that the land portion width Wcc of the center land portion and the land portion width Wco of the outer side center land portion satisfy the relationship Wcc < Wco, so that the ground contact surface of each of the outer side center land portion and the outer side shoulder land portion is formed to protrude toward the outside in the tire radial direction with respect to the reference pattern, and such that the protrusion amount Hco of the outer side center land portion and the protrusion amount Hso of the outer side shoulder land portion satisfy the relationship Hcc < Hso.

[0095] As the test results in Fig.4, the pneumatic tires of Comparative Examples 1 to 9 and Examples 10 to 15 not according to the invention have improved steering stability performance on dry road surfaces and improved steering stability performance on wet road surfaces. List of reference symbols 1 pneumatic tire 2 Tread section 3 shoulder section 4 side wall section 5 bead section 6 carcass layers 7 belt layer 7a, 7b Belt 8 Belt reinforcement layer 10 Ground contact surface 15 bead core 16 bead fillers 20 main circumferential groove 21 Outer center main groove 22 Inside center main groove 23 Outer shoulder main groove 24 inside shoulder main groove 30 footbridge section 31 Central bridge section 32 Middle outer side web section 33 Middle inside web section 34 Outer shoulder bar section 35 inside shoulder bar section 351 inner web section 352 outer web section 41, 42, 43, 44, 45 slat 51, 52, 53, 54 lug groove 61 Narrow circumferential groove CL Equatorial plane of the tire Hcc projection amount of center web section Hci projection amount of middle inner side web section Hco projection amount of middle outer side web section Hsi projection amount of inner shoulder web section Hso projection amount of outer side shoulder web section P1o, P2o Groove opening end of outer side center main groove P1i, P2i Groove opening end of inside center main groove P3o, P4o Groove opening end of outer side shoulder main groove P3i, P4i Groove opening end of inside shoulder main groove PRcc reference profile of central web section PRco reference profile of middle outer side web section PRso reference profile of outer shoulder web section PRci reference profile of middle inner web section PRsi reference profile of inner shoulder web section T Ground contact edge Wcc web section width of middle web section Wco web section width of middle outer side web section Wso web section width of outer side shoulder web section Wci web section width of middle inside web section Wsi web section width of inner shoulder web section

Claims

[1] A pneumatic tire comprising a mounting direction predetermined with respect to a vehicle, the pneumatic tire comprising five land portions (30) in a tire width direction, the five land portions (30) being defined and formed by four circumferential main grooves (20) extending in a tire circumferential direction on a ground contact surface (10) of a tread portion (2), the five land portions (30) including a center land portion (31) on an equatorial plane of the tire (CL), a center outer side land portion (32) on a vehicle outer side of the center land portion (31), an outer side shoulder land portion (34) on the vehicle outer side of the center outer side land portion (32), form a central inner side web section (33) on a vehicle inner side of the central web section (31) and an inner side shoulder web section (35) on the vehicle inner side of the central inner side web section (33), wherein a web section width Wcc of the central web section (31) and a web section width Wco of the middle outer side web section (32) satisfies a ratio of 1.2 ≤ Wco / Wcc ≤ 1.4, the ground contact surface (10) of both the central outer side land portion (32) and the outer side shoulder land portion (34) protrudes to an outer side in a tire radial direction with respect to a reference profile, a projection amount Hco of the middle outer side web portion (32) and a projection amount Hso of the outer side shoulder web portion (34) satisfy a relationship of 1.2 ≤ Hso / Hco ≤ 2.0, and wherein the projection amount Hco of the central outer side web portion (32) is in a range of 0.2 mm ≤ Hco ≤ 0.4 mm. [2] A pneumatic tire according to claim 1, wherein the protrusion amount Hso of the outer side shoulder land portion (34) is in a range of 0.3 mm ≤ Hso ≤ 0.6 mm. [3] A pneumatic tire according to claim 1 or 2, wherein the ground contact surface (10) of each of the center land portion (31) and the center inner side land portion (33) is formed to protrude toward the outside in the tire radial direction with respect to a reference profile, a projection amount Hcc of the central web portion (31) and the projection amount Hco of the central outer side web portion (32) satisfy a relationship of 0.9 ≤ Hcc / Hco ≤ 1.1, and the projection amount Hcc of the central web portion (31) and a projection amount Hci of the central inner side web portion (33) satisfy a relationship of 0.9 ≤ Hcc / Hci ≤ 1.

1. [4] A pneumatic tire according to any one of claims 1 to 3, wherein no groove is present on the ground contact surface (10) of the center web portion (31), when it is in contact with a floor, and Grooves each comprising one end communicating with one of the circumferential main grooves (20) located on an outer side in the tire width direction when in contact with a ground and the other end blindly terminating within each of the center outer side land portion (32) and the center inner side land portion (33) are provided on the ground contact surface (10) of each of the center outer side land portion (32) and the center inner side land portion (33). [5] A pneumatic tire according to any one of claims 1 to 4, wherein a land portion width Wso of the outer side shoulder land portion (34), a land portion width Wci of the central inner side land portion (33), and a land portion width Wsi of the inner side shoulder land portion (35) satisfy the relationships 1.4 ≤ Wso / Wcc ≤ 1.6, 0.9 ≤ Wci / Wcc ≤ 1.1, 1.4 ≤ Wsi / Wcc ≤ 1.6 with respect to the land portion width Wcc of the central land portion (31). [6] The pneumatic tire according to any one of claims 1 to 5, wherein the ground contact surface (10) of the inner side shoulder land portion (35) is formed to protrude toward the outside in the tire radial direction with respect to a reference profile, and the protrusion amount Hso of the outer side shoulder land portion (34) and a protrusion amount Hsi of the inner side shoulder land portion (35) satisfy a relationship of 0.9 ≤ Hso / Hsi ≤ 1.1.

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