AU2014388518A1

AU2014388518A1 - Pneumatic tire

Info

Publication number: AU2014388518A1
Application number: AU2014388518A
Authority: AU
Inventors: Kazuya Ishiguro
Original assignee: Yokohama Rubber Co Ltd
Current assignee: Yokohama Rubber Co Ltd
Priority date: 2014-03-28
Filing date: 2014-12-26
Publication date: 2016-11-17
Anticipated expiration: 2034-12-26
Also published as: JP2015189350A; JP5796655B1; CN106132729B; AU2014388518B2; WO2015145910A1; CN106132729A; DE112014006530T5; DE112014006530B4

Abstract

Provided is a pneumatic tire enabling an increase in noise performance while achieving both steering stability on dry road surface and driving performance on wet road surface. In a pneumatic tire (T) including a center land portion (13), an inner central land portion (14), an outer central land portion (15), an inner shoulder land portion (17), and an outer central land portion (18) which are separately formed by at least four main grooves (11), the pneumatic tire having a designated vehicle mount direction, the center land portion (13) is formed with center lug grooves (20) that open only to one of the main grooves (11) on the vehicle inner side, the inner central land portion (14) is formed with inner central lug grooves (21) that open only to another of the main grooves on the vehicle inner side, each of the lug grooves (20, 21) comprising a first inclination portion (20A, 21A) positioned on an opening end side and having a relatively large inclination angle and a second inclination portion (20B, 21B) positioned on a terminal side and having a relatively small inclination angle, and an inner central sipe (22) is formed at the terminal portion of each of the inner central lug grooves (21) terminating within the inner central land portion (14), wherein the relationships L1 > L2 and L3 > L4 are satisfied, where L1 is the length of the center lug groove (20), L2 is the length of the inner central lug groove (21), L3 is the sum of the length L2 and the length of the inner central sipe (22), and L4 is the width of the inner central land portion (14).

Description

WO 2015/145910 A1 PCT/JP2014/084486 PNEUMATIC TIRE Technical Field [0001]

The present invention relates to a pneumatic tire having at least four main grooves extending in a tire circumferential direction in a tread surface, and particularly relates to a pneumatic tire with improved noise performance while achieving both good steering stability performance on dry road surfaces and running performance on wet road surfaces.

Background Art [0002]

In recent years, with advances in road conditions and enhanced performance of vehicles, there is a strong demand for improvement of pneumatic tires in noise performance while achieving both good running performance on dry road surfaces (dry performance) and running performance on wet road surfaces (wet performance) when running at high speeds.

[0003]

Atypical method of improving wet performance is to ensuring drainage by forming main grooves extending in the tire circumferential direction as well as lug grooves and sipes extending in a tire width direction in the tread surface of tires. However, there is a problem in that it becomes difficult to ensure dry performance by such a method since the rigidity of land portions formed on the tread surface decreases, and moreover there is also a problem in that this decrease in rigidity simultaneously results in the deterioration of noise performance.

[0004]

Conventionally, as a measure to improve the noise performance while achieving both good dry performance and wet performance, it has been proposed that the shape and position of lug grooves be specified, while mounting direction of the tire on the vehicle be designated (for example, see Patent Document 1).

[0005]

In the structure of Patent Document 1, one type of lug grooves is made to communicate with two adjacent main grooves to ensure water drainage performance. However, because these lug grooves open in particular to the main groove located outward when mounted on a vehicle, noise performance is not sufficiently enhanced. Additionally, because these lug grooves form a row of blocks, tread rigidity decreases leading to dry performance being unable to be sufficiently ensured. This problem is able to be addressed by making these lug grooves not open to the main groove located 1 WO 2015/145910 A1 PCT/JP2014/084486 outward when mounted on a vehicle. However, such a simple modification results in the balance between the form of the lug grooves and the arrangement of the lug grooves being upset, and as a result the level of dry performance, wet performance, and noise performance becomes less than that obtained by the structure of Patent Document 1. Therefore, there is a demand for further improvement in the enhancement of noise performance while achieving both good dry performance and wet performance.

Citation List Patent Documents [0006]

Patent Document 1: Japanese Unexamined Patent Application Publication No. 2008-162390A

Summary of Invention Technical Problem [0007]

An object of the present invention is to provide a pneumatic tire with improved noise performance while achieving both good steering stability performance on dry road surfaces and running performance on wet road surfaces.

Solution to Problem [0008]

To achieve the objects described above, a pneumatic tire of the present invention is a pneumatic tire with a specified vehicle mounting direction provided with at least four main grooves extending in a tire circumferential direction in a tread surface, adjacent main grooves defining a plurality of circumferential land portions extending in the tire circumferential direction, and defining a shoulder land portion located outward in a tire width direction of the outermost main groove in the tire width direction on either side. The pneumatic tire comprises: a plurality of center lug grooves formed at intervals in the tire circumferential direction in the center land portion, which is the circumferential land portion located on a tire equator, each of the center lug grooves extending in the tire width direction communicating with the main groove on a vehicle inner side when mounted on a vehicle, and terminating within the center land portion without communicating with the main groove on a vehicle outer side when mounted on a vehicle; and a plurality of inner intermediate lug grooves formed at intervals in the tire circumferential direction in the inner intermediate land portion, which is the 2 WO 2015/145910 A1 PCT/JP2014/084486 circumferential land portion located to a side of the center land portion corresponding to the vehicle inner side when mounted on a vehicle, each of the inner intermediate lug grooves extend in the tire width direction communicating with the main groove on the vehicle inner side when mounted on a vehicle, and terminating within the inner intermediate land portion without communicating with the main groove on the vehicle outer side when mounted on a vehicle; wherein each of the center lug grooves and each of the inner intermediate lug grooves include a first inclined portion which is located proximal to an opening end and has a relatively great angle of inclination with respect to the tire circumferential direction and a second inclined portion which is located proximal to a terminating end and has a relatively low angle of inclination with respect to the tire circumferential direction; an inner intermediate sipe is formed at the terminating end of each of the inner intermediate lug grooves, the inner intermediate sipe extending in an extending direction of the second inclined portion of the corresponding inner intermediate lug groove and terminating within the inner intermediate land portion; and relationships LI > L2 and L3 > L4 are satisfied, where LI is a length of the center lug groove, L2 is a length of the inner intermediate lug groove, L3 is a sum of the length L2 and a length of the inner intermediate sipes, and L4 is a width of the inner intermediate land portion.

Advantageous Effect of Invention [0009]

In the present invention, as described above, since each lug groove (center lug groove and inner intermediate lug groove) formed in the center land portion and the inner intermediate land portion opens to the main groove on the vehicle inner side when mounted on a vehicle, and does not open to the main groove on the vehicle outer side when mounted on a vehicle, the pumping sound and pattern noise during running are radiated toward the vehicle inner side, so external noise can be reduced. Additionally, the lug grooves (center lug grooves and inner intermediate lug grooves) are constituted by the first inclined portions and the second inclined portions, and the angles of inclination with respect to the tire circumferential direction of the opening end sides are greater than the angles of inclination with respect to the tire circumferential direction of the terminating end portion sides. As a result, water drainage performance can be improved. Furthermore, the inner intermediate sipe extends from the terminating end portion of the inner intermediate lug groove. As a result, in a configurations such as that described above in which one end of the inner intermediate lug groove terminates within the land portion to ensure noise performance, wet performance is secured by the inner intermediate sipe. In 3 WO 2015/145910 A1 PCT/JP2014/084486 particular, by setting the size relationship of the lengths LI to L4 to that described above, the balance between dry performance, wet performance, and noise performance is improved and all of these performances are achieved at a high degree.

[0010]

In the present invention, in the center land portion and the inner intermediate land portion, the section of a corner portion formed by the main groove and the center lug groove or inner intermediate lug groove where the angle of inclination of the first inclined portion is acute is preferably chamfered. Such a chamfered portion facilitates the flow of water in the lug grooves, thus enabling water drainage performance to be further improved. Additionally, uneven wear can be suppressed.

[0011]

In such configurations, the depth of the chamfer is preferably greater than the effective groove depth and less than the depth of the main groove. Setting the depth of the chamfer to such a depth allows superior water drainage performance to be maintained up until the terminal stage of wear.

[0012]

The present invention also preferably comprises: a plurality of outer intermediate lug grooves formed at intervals in the tire circumferential direction in the outer intermediate land portion, which is the circumferential land portion located on a side corresponding to the vehicle outer side when mounted on a vehicle, each of the outer intermediate lug grooves extending in the tire width direction communicating with the main groove on the vehicle inner side when mounted on a vehicle and terminating within the outer intermediate land portion without communicating with the main groove on the vehicle outer side when mounted on a vehicle; and a plurality of outer shoulder lug grooves formed at intervals in the tire circumferential direction in the outer shoulder land portion, which is the shoulder land portion on the side corresponding to the vehicle outer side when mounted on a vehicle, each of the outer shoulder lug grooves extending in the tire width direction communicating with the main groove on the vehicle inner side when mounted on a vehicle and terminating within the outer shoulder land portion. With this configuration, the lug grooves (the outer intermediate lug grooves and the outer shoulder lug grooves) are disposed in the land portions (the outer intermediate land portion and the outer shoulder land portion) on the side corresponding to the vehicle outer side of the tire equator when mounted on a vehicle. As a result, water drainage performance can be improved. Additionally, by the lug grooves (outer intermediate lug grooves and the outer shoulder lug grooves) opening only to the main groove on 4 WO 2015/145910 A1 PCT/JP2014/084486 the vehicle inner side when mounted on a vehicle, a reduction in noise performance is prevented.

[0013]

The present invention also preferably comprises: a plurality of inner shoulder lateral grooves formed at intervals in the tire circumferential direction in the inner shoulder land portion, which is the shoulder land portion on the side corresponding to the vehicle inner side when mounted on a vehicle, each of the inner shoulder lateral grooves extending in the tire width direction without communicating with the main groove on the vehicle outer side when mounted on a vehicle; and inner shoulder sipes extending from terminating end portions of the inner shoulder lateral grooves in an extending direction of the inner shoulder lateral grooves and connecting to the main groove on the vehicle outer side when mounted on a vehicle. With this configuration, the inner shoulder lateral grooves allow for increased water drainage performance, and because the inner shoulder lateral grooves do not open to the main groove on the side corresponding the vehicle outer side when mounted on a vehicle, no reduction in noise performance is caused. Additionally, instead of the inner shoulder lateral grooves opening to the main groove on the side corresponding to the vehicle outer side when mounted on a vehicle, the inner shoulder sipes are provided. As a result, the water drainage performance can be further increased with no reduction in noise performance.

[0014]

The present invention also preferably comprises: a plurality of outer shoulder lateral grooves formed at intervals in the tire circumferential direction in the outer shoulder land portion, which is the shoulder land portion on the side corresponding to the vehicle outer side when mounted on a vehicle, each of the outer shoulder lateral grooves extending in the tire width direction without communicating with the main groove on the vehicle inner side when mounted on a vehicle. This configuration allows water drainage performance to be further improved. Additionally, because the outer shoulder lateral grooves do not communicate with the main groove, even if noise (air column resonance) caused by the main groove occurs, the noise is not radiated to the exterior of the vehicle via the outer shoulder lateral grooves, thus preventing a reduction in noise performance.

[0015]

The present invention also preferably comprises: a plurality of outer shoulder sipes formed at intervals in the tire circumferential direction in the outer shoulder land portion, which is the shoulder land portion on the side corresponding to the vehicle outer side when mounted on a 5 WO 2015/145910 A1 PCT/JP2014/084486 vehicle, each of the outer shoulder sipes extending in the tire width direction without communicating with the main groove on the vehicle inner side when mounted on a vehicle and terminating within the outer shoulder land portion, wherein the outer shoulder sipes have a shape including a bent portion. By the sipe having a bent portion, the rigidity of the outer shoulder land portion is prevented from being excessively reduced. Additionally, an edge effect can be obtained via the sipe, thus allowing water drainage performance and dry performance to be further improved.

[0016]

The present invention also preferably comprises: a plurality of dimples in outer end regions of the shoulder land portions in the tire width direction. With this configuration, running resistance can be reduced and fuel economy improved when the vehicle is running.

Brief Description of Drawings [0017] FIG. 1 is a meridian cross-sectional view of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a front view illustrating a tread surface of the pneumatic tire according to an embodiment of the present invention. FIG. 3 is an explanatory view illustrating an enlarged portion of a tread surface of the pneumatic tire according to an embodiment of the present invention. FIG. 4 is a perspective view illustrating an enlarged chamfered portion of the pneumatic tire according to an embodiment of the present invention. FIG. 5 is an explanatory view illustrating the structure of an outer shoulder sipe of the pneumatic tire according to an embodiment of the present invention.

Description of Embodiment [0018] A configuration of the present invention will be described below in detail with reference to the accompanying drawings.

[0019]

In FIG. 1, the mounting direction of a pneumatic tire T with respect to a vehicle is designated, IN represents the side corresponding to the vehicle inner side when mounted on the vehicle (hereinafter, referred to as the vehicle inner side), OUT represents the side corresponding to the vehicle outer side when mounted on the vehicle (hereinafter, referred to as the vehicle outer side), and CL represents the tire equator. The pneumatic tire T includes a tread portion 1, side wall portions 2, and bead portions 3. A carcass layer 4 extends between the left-right pair of bead 6 WO 2015/145910 A1 PCT/JP2014/084486 portions 3. The carcass layer 4 includes a plurality of reinforcing cords extending in a tire radial direction, and is folded back around a bead core 5 disposed in each bead portion 3 from a tire inner side to a tire outer side. Additionally, bead fillers 6 are disposed on the periphery of the bead cores 5, and each bead filler 6 is enveloped by a main body portion and a folded back portion of the carcass layer 4. In the tread portion 1, a plurality of belt layers 7, 8 (two layers in FIG. 1) are embedded on the outer circumferential side of the carcass layer 4. Each belt layer 7, 8 includes a plurality of reinforcing cords inclined with respect to the tire circumferential direction, the direction of the reinforcing cords of the different layers intersecting with each other. In the belt layers 7, 8, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set in the range, for example, of 10° to 40°. In addition, a belt reinforcing layer 9 is disposed on the outer circumferential side of the belt layers 7, 8. The belt reinforcing layer 9 includes organic fiber cords oriented in the tire circumferential direction. In the belt reinforcing layer 9, the angle of the organic fiber cords with respect to the tire circumferential direction is set, for example, to from 0 ° to 5°.

[0020]

The present invention may be applied to such a general pneumatic tire, however, the cross-sectional structure thereof is not limited to the basic structure described above.

[0021]

As illustrated in FIG. 2, a plurality (four in FIG. 2) of main grooves 11 extending in the tire circumferential direction is provided in the outer surface of the tread portion 1, in other words, in a tread surface 10, of the pneumatic tire according to the present invention. The groove width of the main grooves 11 is, for example, from 5 mm to 10 mm, and the groove depth is, for example, from 7 mm to 9 mm. A plurality (three in FIG. 2) of circumferential land portions 12 extends in the tire circumferential direction. Each circumferential land portion 12 is defined by adjacent main grooves 11. Of the circumferential land portions 12, the land portion located on the tire equator is referred to as a center land portion 13, the land portion located on the vehicle inner side of the center land portion 13 is referred to as an inner intermediate land portion 14, and the land portion located on the vehicle outer side of the center land portion 13 is referred to as the outer intermediate land portion 15. Additionally, on both sides of the tire equator CL in the tire width direction, shoulder land portions 16 are defined by the outer sides in the tire width direction of the outermost main grooves 11 in the tire width direction. Of the shoulder land portions 16, the land portion located on the vehicle inner side is referred to as an inner shoulder land portion 17, and the land portion located on the vehicle outer side is referred to as 7 WO 2015/145910 A1 PCT/JP2014/084486 an outer shoulder land portion 18. Of the plurality of circumferential land portions 12, in the center land portion 13 and the inner intermediate land portion 14, a plurality of lug grooves 19 is formed at intervals in the tire circumferential direction. Each lug groove 19 extends in the tire width direction, communicating with the main groove 11 on the vehicle inner side, and terminates within the circumferential land portion 12 without communicating with the main groove 11 on the vehicle outer side. The lug grooves 19 formed in the center land portion 13 are referred to as center lug grooves 20, and the lug grooves 19 formed in the inner intermediate land portion 14 are referred to as inner intermediate lug grooves 21. The groove width of the lug grooves 19 (the center lug grooves 20 and the inner intermediate lug grooves 21) is, for example, from 2 mm to 4 mm, and the groove depth is less than that of the main grooves 11, for example from 4 mm to 7 mm [0022]

As illustrated in the enlarged view of FIG. 3, a first inclined portion 20A of the center lug groove 20 proximal to the opening end and a second inclined portion 20B proximal to the terminating end have different angles of inclination with respect to the tire circumferential direction. The angle of inclination Ola with respect to the tire circumferential direction of the first inclined portion 20A of the center lug groove 20 and the angle of inclination 01b with respect to the tire circumferential direction of the second inclined portion 20B of the center lug groove 20 have the relationship: Ola > 01b. In other words, the center lug groove 20 is constituted by the first inclined portion 20A located proximal to the opening end with a relatively greater angle of inclination with respect to the tire circumferential direction and the second inclined portion 20B located proximal to the terminating end with a relatively low angle of inclination. In a similar manner, the inner intermediate lug groove 21 includes a first inclined portion 21A proximal to the opening end and a second inclined portion 21B proximal to the terminating end with different angles of inclination with respect to the tire circumferential direction. The angle of inclination 92a with respect to the tire circumferential direction of the first inclined portion 21A of the inner intermediate lug groove 21 and the angle of inclination 92b with respect to the tire circumferential direction of the second inclined portion 2 IB of the inner intermediate lug groove 21 have the relationship: 92a > 92b. In other words, the inner intermediate lug groove 21 is constituted by the first inclined portion 21A located proximal to the opening end with a relatively greater angle of inclination with respect to the tire circumferential direction and the second inclined portion 2IB located proximal to the terminating end with a relatively low angle of inclination with respect to the tire circumferential direction.

[0023] 8 PCT/JP2014/084486 WO 2015/145910 A1

Note that in the lug grooves 19 (center lug grooves 20 and inner intermediate lug grooves 21), as illustrated in FIG. 3, the first inclined portions curve at a predetermined radius of curvature (rl, R2), and the second inclined portions curve at a predetermined radius of curvature (r2, R2), thus giving the lug grooves 19 a shape in which the first inclined portions and the second inclined portions are smoothly connected at a connecting portion with a predetermined radius of curvature. When center points of the opening ends of the lug grooves 19 (the center lug grooves 20 and the inner intermediate lug grooves 21) are taken as pi, PI, points of intersection between the center lines of the first inclined portions (with the radii of curvature rl, Rl) and the center lines of the second inclined portions (with the radii of curvature r2, R2) are taken as p2, P2, and the center points of the terminating end portions are taken as p3, P3, the angle of inclination Ola is the angle of a straight line joining the point pi and the point p2 with respect to the circumferential direction, the angle of inclination 02a is the angle of a straight line joining the point PI and the point P2 with respect to the circumferential direction, the angle of inclination 01b is the angle of a straight line joining the point p2 and the point p3 with respect to the circumferential direction, and the angle of inclination 02b is the angle of a straight line joining the point P2 and the point P3 with respect to the circumferential direction. Note that the center line and radius of curvature of the connecting portion that joins the first inclined portion and the second inclined portion are omitted from FIG. 3.

[0024]

At the terminating end portion of each inner intermediate lug groove 21, an inner intermediate sipe 22 is formed. The inner intermediate sipe 22 extends in the extending direction of the second inclined portion 2 IB of the inner intermediate lug groove 21 and terminates within the inner intermediate land portion 15. Note that in the present invention, a sipe (inner intermediate sipes 22 described above and inner shoulder sipes 27 and outer shoulder sipes 29 described below) refers to a fine groove with a width of from 0.5 mm to 1.0 mm and a depth of from 4 mm to 7 mm.

[0025]

In such an arrangement of the circumferential land portions 12 and the lug grooves 19, when the length of the center lug grooves 20 is taken as LI, the length of the inner intermediate lug grooves 21 is taken as L2, the sum of the length L2 of the inner intermediate lug grooves 21 and the length of the inner intermediate sipes 22 extending from the terminating end portions of the inner intermediate lug grooves 21 is taken as L3, and the width of the inner intermediate land portion 14 is taken as L4, the lengths LI to L4 satisf the relationships: LI > L2 and L3 > L4. Note that the lengths LI to L3, as illustrated in FIG. 3, are lengths measured along the center line of 9 PCT/JP2014/084486 WO 2015/145910 A1 the lug grooves 19, and length L4 is the length of the inner intermediate land portion 14 in the tire width direction.

[0026]

In the tread surface 10 configured as such, the lug grooves 19 open only to the main grooves 11 on the vehicle inner side, and do not open to the main grooves 11 on the vehicle outer side. As a result, the pumping sound and pattern noise during running is radiated toward the vehicle inner side. Accordingly, the external noise is reduced, and the noise performance can be removed. Additionally, the lug grooves 19 (center lug grooves 20 and inner intermediate lug grooves 21) are constituted by the first inclined portions 20A, 21A and the second inclined portions 20B, 21B, and the angles of inclination (Θ1Α, Θ2Α) with respect to the tire circumferential direction of the opening end sides are greater than the angles of inclination (Θ1Β, Θ2Β) with respect to the tire circumferential direction of the terminating end portion sides. As a result, the flow of water in the lug grooves 19 can be facilitated and water drainage performance can be improved. Furthermore, the inner intermediate sipe 22 extends from the terminating end portion of the inner intermediate lug groove 21. Asa result, in a configurations such as that described above in which one end of the inner intermediate lug groove 21 terminates within the land portion to ensure noise performance, wet performance is secured by the inner intermediate sipe 22. Additionally, by setting the size relationship of the lengths LI to L4 to that described above, the balance between dry performance, wet performance, and noise performance is improved and all of these performances are achieved at a high degree.

[0027]

Here, if grooves with a shape different from that of the lug grooves 19 described above (center lug grooves 20 and inner intermediate lug grooves 21), for example, grooves extending in the tire width direction and communicating with both the main groove 11 on the vehicle inner side and the main groove 11 on the vehicle outer side, are formed in the circumferential land portions 12, although the flow of rainwater and the like is improved and the wet performance is improved, the pumping sound and the pattern noise during running is also radiated to the vehicle outer side, so external noise cannot be reduced. Additionally, the circumferential land portions 12 are divided in the circumferential direction, so the rigidity of the circumferential land portions 12 is reduced, and the dry performance deteriorated.

[0028]

If the angles of inclination Ola, 01b, 02a, 02b have a size relationship different from that described above, the flow of water in the lug grooves 19 is not facilitated as in configurations in which the size relationship described above is satisfied, and thus the effect of improving water drainage performance is not obtained. The angles of 10 WO 2015/145910 A1 PCT/JP2014/084486 inclination Ola, Θlb, 02a, 02b only need to satisfy the size relationship described above. Additionally, for example, the angle of inclination Ola is preferably set in the range of 10° to 30°, the angle of inclination 01b is preferably set in the range of 40° to 70°, the angle of inclination 02a is preferably set in the range of 10° to 30°, and the angle of inclination 02b is preferably set in the range of 40° to 70°. Setting the angles of inclination in such ranges is advantageous in improving the water drainage performance.

[0029]

When the lengths LI to L4 have a size relationship different from that described above, dry performance, wet performance, and noise performance are unable to be improved in a well-balanced manner. Specifically, when the length LI is less than the length L2, dry performance is unable to be improved. When the length L3 is less than the length L4, wet performance is unable to be improved. The lengths LI to L4 only need to satisfy the size relationship described above. Additionally, for example, the length LI is preferably set in the range of 25 mm to 35 mm, the length L2 is preferably set in the range of 15 mm to 20 mm, the length L3 is preferably set in the range of 25 mm to 35 mm, and the length L4 is preferably set in the range of 20 mm to 25 mm. Setting the lengths in such ranges is advantageous in improving dry performance, wet performance, and noise performance in a well-balanced manner.

[0030]

As illustrated in FIG. 4, in the circumferential land portions 12 (the center land portion 13 and the inner intermediate land portion 14), the section of a comer portion 23 formed by the main groove 11 and the lug groove 19 (center lug groove 20 or inner intermediate lug groove 21) where the angle of inclination of the first inclined portion is acute is preferably chamfered. Such a chamfered portion renders the connecting portion between the main groove 11 and the center lug groove 20 or the inner intermediate lug groove 21 smooth. As a result, water drainage performance can be further improved and uneven wear can be suppressed.

[0031]

In such configurations, the depth of the chamfer is preferably greater than the effective groove depth and less than the depth of the main groove. Setting the depth of the chamfer to such a depth allows superior water drainage performance to be maintained up until the terminal stage of wear. Note that effective depth is the depth of the main groove minus the height of a wear indicator, and specifically is the depth of the main groove minus 1.6 mm. When the depth of the chamfer is less than the effective groove depth, the chamfer does not remain up until the terminal stage of 11 WO 2015/145910 A1 PCT/JP2014/084486 wear, and thus superior water drainage performance cannot be maintained up until the terminal stage of wear.

[0032]

In configurations in which chamfering is performed, the volume removed by chamfering (the volume of the triangular pyramid drawn in dotted lines in the drawing) is preferably in a range of 6 mm3 to 8 mm3, for example. This is advantageous in improving water drainage properties and suppressing uneven wear.

[0033]

In the outer intermediate land portion 15, a plurality of outer intermediate lug grooves 24 is preferably formed at intervals in the tire width direction. Each outer intermediate lug groove 24 extends in the tire width direction communicating with the main groove 11 located on the vehicle inner side, and terminates within the outer intermediate land portion 15 without communicating with the main groove 11 located on the vehicle outer side. Additionally, in the outer shoulder land portion 18, a plurality of outer shoulder lug grooves 25 is preferably formed at intervals in the tire width direction. Each outer shoulder lug groove 25 extends in the tire width direction communicating with the main groove 11 located on the vehicle inner side, and terminates within the outer shoulder land portion 18. By providing the outer intermediate lug grooves 24 and the outer shoulder lug grooves 25 in such a manner, lug grooves 19 (the outer intermediate lug grooves 24 and the outer shoulder lug grooves 25) are disposed in the land portion on the vehicle outer side of the tire equator (the outer intermediate land portion 15 and the outer shoulder land portion 18). As a result, water drainage performance can be improved. Additionally, by the lug grooves 19 (outer intermediate lug grooves 24 and the outer shoulder lug grooves 25) opening only to the main groove 11 on the vehicle inner side, a reduction in noise performance is prevented.

[0034]

In the inner shoulder land portion 17, a plurality of inner shoulder lateral grooves 26 is preferably formed at intervals in the tire circumferential direction.

Each inner shoulder lateral groove 26 extends in the tire width direction without communicating with the main groove 11 located on the vehicle outer side. Additionally, the inner shoulder sipes 27 are preferably provided extending from terminating end portions of the inner shoulder lateral grooves 26 in the extending direction of the inner shoulder lateral grooves 26 and connecting to the main groove 11 located on the vehicle outer side. With this configuration, the inner shoulder lateral grooves 26 allow for increased water drainage performance, and because the inner shoulder lateral grooves 27 do not open to the main groove 11 on the vehicle outer side, no reduction in noise performance is caused. Additionally, instead of the 12 WO 2015/145910 A1 PCT/JP2014/084486 inner shoulder lateral grooves 26 opening to the main groove 11 on the vehicle outer side, the inner shoulder sipes 27 are provided. As a result, the water drainage performance can be further increased with no reduction in noise performance.

[0035]

In the outer shoulder land portion 18, a plurality of outer shoulder lateral grooves 28 is preferably formed at intervals in the tire circumferential direction.

Each outer shoulder lateral groove 28 extends in the tire width direction without communicating with the main groove 11 located on the vehicle inner side. This allows water drainage performance to be further improved. Additionally, because the outer side shoulder lug grooves 28 do not communicate with the main groove 11, air column resonance caused by the main grooves 11 can be prevented from being radiated to the vehicle outer side via the outer side shoulder lug grooves 28.

[0036]

Note that the outer end portions of the inner shoulder lateral grooves 26 and the outer shoulder lateral grooves 28 in the tire width direction may terminate within the shoulder land portion 16. However, as illustrated in FIG. 2, the outer end portions preferably extend to outward from the shoulder land portion 16 in the tire width direction rather than terminating within the shoulder land portion 16. This allows water drainage performance to be further improved.

[0037]

In the outer shoulder land portion 18, a plurality of outer shoulder sipes 29 is preferably formed at intervals in the tire circumferential direction. Each outer shoulder sipe 29 extends in the tire width direction without communicating with the main groove 11 located on the vehicle inner side and terminating within the outer shoulder land portion 18. In such configurations, the shape of the outer shoulder sipe 20 is preferably one with a bent portion rather than a rectilinear form. By the sipe having a bent portion, the rigidity of the outer shoulder land portion is prevented from being excessively reduced. Additionally, an edge effect can be obtained via the sipe, thus allowing water drainage performance and dry performance to be further improved.

[0038]

In particular, as illustrated in FIG. 5, the shape of the outer shoulder sipe 29 is preferably rectilinear at a portion 29A proximal to the tread surface (upper side of the drawing) and preferably a zigzag shape at a portion 29B proximal to the groove bottom (lower side of the drawing). With such a configuration, in the latter stages of wear when the rigidity of the land portions are reduced more so than the early stages of wear, the zigzag shaped sipes, which are less likely to decreases in rigidity than rectilinear shaped sipes, appear at the tread surface and exhibit this resistance. As a 13 WO 2015/145910 A1 PCT/JP2014/084486 result, rigidity of the land portions can be effectively maintained. Note that in FIG. 5, to facilitate understanding of the structure of the outer shoulder sipe 29, the outer shoulder sipe 29 is drawn in a solid line, the outer shoulder land portion 18 (a portion thereof) is drawn in a dot-dash line, and an additional line (dashed line) is drawn to facilitate understanding of the positional relationship between the portion 29A proximal to the tread surface and the portion 29B (in particular the groove bottom portion) proximal to the groove bottom of the outer shoulder sipes 29.

[0039]

In the embodiment illustrated in FIG. 2, a circumferential narrow groove 30 may be formed in the outer shoulder land portion 18. The circumferential narrow groove 30 has a groove width of from 2 mm to 3 mm and a groove depth of from 4 mm to 6 mm. Both the groove depth and the groove width of the circumferential narrow groove 30 are less than those of the main grooves 11 but greater than that of the sipes. The circumferential narrow groove 30 is preferably disposed outward in the tire width direction of the terminating end portion of the outer shoulder lug grooves 25 and inward in the tire width direction of the end portion of the outer shoulder lateral grooves 28 and the outer shoulder sipes 29 proximal to the tire equator CL. Additionally, the circumferential narrow groove 30 preferably does not communicate with the outer shoulder lug grooves 25, the outer shoulder lateral grooves 28, and the outer shoulder sipes 29. This configuration allows water drainage performance to be improved while suppressing a reduction in rigidity in the land portion of the like that would result if a main groove 11 was provided. Additionally, because the circumferential narrow groove 30 does not communicate with the outer shoulder lug grooves 25, the outer shoulder lateral grooves 28, and the outer shoulder sipes 29, if air column resonance is caused by the circumferential narrow groove 30, this is prevented from being radiated to the vehicle outer side, thus preventing a deterioration in noise performance.

[0040]

Provided at least four main grooves 11 are formed, there is no particular limitation on the number of main grooves 11, as with the embodiment illustrated in FIG. 2, preferably four main grooves 11 are provided due to the relationship between water drainage performance of the grooves and the rigidity of the tread surface. In other words, preferably, three circumferential land portions 12 and one shoulder land portion 16 on each side in the tire width direction (a total of two shoulder land portions 13) are defined.

[0041]

The width of the circumferential land portions 12 may be uniform or, as with the embodiment illustrated in FIG. 2, may be different. Specifically, when the width 14 WO 2015/145910 A1 PCT/JP2014/084486 of the center land portion 13 is taken as Wl, the width of the inner intermediate land portion 14 is taken as W2 (= L4), and the width of the outer intermediate land portion 15 is taken as W3, the relationship between the widths Wl to W2 satisfies: Wl > W2 >W3.

[0042] A plurality of dimples 32 is preferably disposed in an end region 31 to the outer side of the shoulder land portion 18 in the tire width direction. With this configuration, running resistance can be reduced and fuel economy improved when the vehicle is running.

Examples [0043]

Seventeen types of pneumatic tires with a tire size of 215/60R17 96H corresponding to Conventional Example 1, Comparative Examples 1 to 3, and Working Examples 1 to 13 were manufactured having the cross-sectional shape illustrated in FIG. 1. The pneumatic tires were based on the tread pattern illustrated in FIG. 2 and were set as indicated in Tables 1, 2 for the following categories: center lug groove: shape (open/not open to main groove on vehicle inner side/outer side), angle of inclination 91a, 91b, length LI, presence of chamfer on corner formed by center lug groove, chamfer depth (effective groove depth ratio); inner intermediate lug groove and inner intermediate sipe: configuration (presence of groove and/or sipe), shape (open/not open to main groove on vehicle inner side/outer side), angle of inclination 92a, 92b, length L2, L3, presence of chamfer on corner formed by the inner intermediate lug groove, chamfer depth (effective groove depth ratio); inner intermediate land portion: width L4; outer intermediate lug groove: shape (open/not open to main groove on vehicle inner side/outer side); outer shoulder lug groove: shape (open/not open to main groove/circumferential narrow groove on vehicle inner side); outer shoulder lateral groove: shape (open/not open to circumferential narrow groove); inner shoulder lateral groove: presence, shape (open/not open to main groove on vehicle outer side); inner shoulder sipe: presence, shape (open/not open to main groove on vehicle outer side); outer shoulder sipe: presence, shape.

[0044] 15 WO 2015/145910 A1 PCT/JP2014/084486

Note that Conventional Example 1 had no inner intermediate sipes provided, the intermediate lug grooves opened to the main grooves also on the vehicle outer side, the intermediate land portions formed a row of blocks, and was provided with (rectilinear) sipes with an end portion on the vehicle outer side that does not open to the main groove on the vehicle outer side and an end portion on the vehicle inner side that terminates within the inner shoulder land portion, instead of inner shoulder lateral grooves. Additionally, Comparative Examples 1 to 3 and Working Examples 1 to 13 had a configuration in which, as illustrated in FIG 2, the end portions on the outer side in the tire width direction of the inner shoulder lateral grooves and outer shoulder lateral grooves extend to the outer side in the tire width direction of the shoulder land portions rather than terminating within the shoulder land portions and the outer shoulder sipes have one end which does not communicate with the circumferential narrow groove and another end that terminates within the outer shoulder land portion.

[0045]

In the tables, in the row "chamfer depth (effective groove depth ratio", "110%" for Working Example 7 means that the chamfer depth was greater than the effective groove depth and equal to the main groove depth. In the tables, in the row "shape" for "outer shoulder sipe", "2D" means a rectilinear sipe and "3D" means a sipe, as illustrated in FIG. 5, with a rectilinear shape proximal to the tread surface and a zigzag shape proximal to the groove bottom.

[0046]

These 17 types of pneumatic tires were evaluated for noise performance, dry performance, wet performance, and fuel economy performance by the evaluation methods described below, and the results are also shown in Tables 1, 2.

[0047]

Noise performance

Each type of test tire was assembled on wheels having a rim size of 17x6.5J, inflated to an air pressure of 230 kPa, mounted on a test vehicle (front wheel drive vehicle) having an engine displacement of 2.4 L. The pass-by noise was measured in accordance with a measuring method based on the EEC/ECE tire noise regulations, which correspond to the European pass-by noise regulations. The evaluation results were expressed as an index value using the inverse of the measurement value, with Conventional Example 1 being assigned a reference index value of 100. A greater index value indicates lower pass-by noise and better noise performance.

[0048]

Dry performance

Each type of test tire was assembled on wheels having a rim size of 17 x 6.5 J, inflated to an air pressure of 230 kPa, and mounted on a test vehicle (front wheel drive 16 WO 2015/145910 A1 PCT/JP2014/084486 vehicle) having an engine displacement of 2.4 L. The time required for the test driver to complete a slalom run was measured, the slalom test course being a 175 m long dry asphalt road surface with pylons placed 35 m apart. The evaluation results were expressed as an index value using the inverse of the measurement value, with 5 Conventional Example 1 being assigned a reference index value of 100. A larger index value indicates shorter required time and superior dry performance.

[0049]

Wet performance

Each type of test tire was assembled on wheels having a rim size of 17x6.5 J, 10 inflated to an air pressure of 230 kPa, and mounted on a test vehicle (front wheel drive vehicle) having an engine displacement of 2.4 L. The time required for the test driver to complete a slalom run was measured, the slalom test course being a 175 m long asphalt road surface covered with 2 mm to 3 mm of water with pylons placed 35 m apart. The evaluation results were expressed as an index value using the inverse 15 of the measurement value, with Conventional Example 1 being assigned a reference index value of 100. A larger index value indicates shorter required time and superior wet performance.

[0050]

Fuel economy performance 20 Each type of test tire was assembled on wheels with a rim size of 17x6.5J, inflated to an air pressure of 230 kPa, and mounted on a test vehicle (front wheel drive vehicle) having an engine displacement of 2.4 L. The fuel economy (distance travelled per volume unit of fuel) was measured after driving for 1 hour at a speed of 100 km/h. Evaluation results were expressed as index values, with Conventional 25 Example 1 being assigned a reference index value of 100. Larger index values indicate superior fuel economy performance.

[0051] [TABLE 1-1] Conventional Example 1 Working Example 1 Comparative Example 1 Center lug groove Open to main groove on vehicle inner side Open Open Open Open to main groove on vehicle outer side Not open Not open Not open Inclination angle 01a° 45 45 30 01b° 30 30 45 Length LI mm 30 30 30 17 WO 2015/145910 A1 PCT/JP2014/084486

Presence of chamfer Absent Present Present Chamfer depth (effective % groove depth ratio) - 100 100 Inner intermediate lug groove and inner intermediate sipe Configuration Groove only Groove and sipe Groove and sipe Open to main groove on vehicle inner side Open Open Open Open to main groove on vehicle outer side Open Not open Not open Inclination angle 92a ° 50 50 30 02b ° 50 30 50 Length L2 mm 25 15 15 L3 mm - 35 35 Presence of chamfer Absent Present Present Chamfer depth (effective % groove depth ratio) - 100 100 Inner intermediate land portion Width L4 mm 20 20 20 Outer intermediate lug groove Open to main groove on vehicle inner side Open Open Open Open to main groove on vehicle outer side Not open Not open Not open Outer shoulder lug groove Open to main groove on vehicle inner side Not open Open Open Open to circumferential narrow groove Not open Not open Not open Outer shoulder lateral groove Open to circumferential narrow groove Not open Not open Not open Inner shoulder lateral groove Presence Absent (sipe) Present Present Open to main groove on vehicle outer side - Not open Not open 18 WO 2015/145910 A1

Inner shoulder sipe Presence - Present Present Open to main groove on vehicle outer side - Open Open Outer shoulder sipe Presence Present Present Present Shape 2D 3D 3D Presence of dimples Presence Absent Present Present Noise Index performance value 100 103 103 Dry Index performance value 100 103 90 Wet Index performance value 100 103 103 Fuel economy Index performance value 100 103 103 [TABLE 1-2] Comparative Example 2 Comparative Example 3 Working Example 2 Center lug groove Open to main groove on vehicle inner side Open Open Open Open to main groove on vehicle outer side Not open Not open Not open Inclination angle 01a° 45 45 40 01b° 30 30 25 Length LI mm 30 10 30 Presence of chamfer Present Present Present Chamfer depth % (effective groove depth ratio) 100 100 100 Inner intermediate lug groove and inner intermediate sipe Configuration Groove only Groove and sipe Groove and sipe Open to main groove on vehicle inner side Open Open Open PCT/JP2014/084486 19 WO 2015/145910 A1

Open to main groove on vehicle outer side Not open Not open Not open Inclination angle 92a ° 50 50 45 02b ° 30 30 25 Length L2 mm 25 13 15 L3 mm - 18 35 Presence of chamfer Present Present Present Chamfer depth % (effective groove depth ratio) 100 100 100 Inner intermediate land portion Width L4 mm 20 20 20 Outer intermediate lug groove Open to main groove on vehicle inner side Open Open Open Open to main groove on vehicle outer side Not open Not open Not open Outer shoulder lug groove Open to main groove on vehicle inner side Open Open Open Open to circumferential narrow groove Not open Not open Not open Outer shoulder lateral groove Open to circumferential narrow groove Not open Not open Not open Inner shoulder lateral groove Presence Present Present Present Open to main groove on vehicle outer side Not open Not open Not open Inner shoulder sipe Presence Present Present Present Open to main groove on vehicle outer side Open Open Open Outer shoulder sipe Presence Present Present Present Shape 3D 3D 3D PCT/JP2014/084486 20 WO 2015/145910 A1

Presence of dimples Presence Present Present Present Noise Index performance value 95 100 104 Dry performance Index value 100 100 102 Wet performance Index value 100 90 103 Fuel economy Index performance value 103 103 103 [TABLE 1-3]

Working Working Working Example Example Example 3 4 5 Center lug groove Open to main groove on vehicle inner side Open Open Open Open to main groove on Not Not Not vehicle outer side open open open Inclination angle 01a° 50 45 45 01b° 35 30 30 Length LI mm 30 25 35 Presence of chamfer Present Present Present Chamfer depth (effective % groove depth ratio) 100 100 100 Inner intermediate Configuration Groove Groove Groove lug groove and and sipe and sipe and sipe inner intermediate sipe Open to main groove on vehicle inner side Open Open Open Open to main groove on Not Not Not vehicle outer side open open open Inclination angle 02a ° 55 50 50 02b ° 35 30 30 Length L2 mm 15 10 20 L3 mm 35 30 40 Presence of chamfer Present Present Present PCT/JP2014/084486 21 PCT/JP2014/084486

Chamfer depth (effective % groove depth ratio) 100 100 100 Inner intermediate land portion Width L4 mm 20 20 20 Outer intermediate lug groove Open to main groove on vehicle inner side Open Open Open Open to main groove on vehicle outer side Not open Not open Not open Outer shoulder lug groove Open to main groove on vehicle inner side Open Open Open Open to circumferential narrow groove Not open Not open Not open Outer shoulder lateral groove Open to circumferential narrow groove Not open Not open Not open Inner shoulder lateral groove Presence Present Present Present Open to main groove on vehicle outer side Not open Not open Not open Inner shoulder sipe Presence Present Present Present Open to main groove on vehicle outer side Open Open Open Outer shoulder sipe Presence Present Present Present Shape 3D 3D 3D Presence of dimples Presence Present Present Present Noise performance Index value 102 104 102 Dry performance Index value 104 104 102 Wet performance Index value 103 102 104 Fuel economy Index value performance 103 103 103 [0052] [TABLE 2-1] Working Working Working Working Example Example Example Example 6 7 8 9 Center lug groove Open to main groove on vehicle inner side Open Open Open Open WO 2015/145910 A1 22 WO 2015/145910 A1

Open to main groove on vehicle outer side Not open Not open Not open Not open Inclination angle 01a ° 45 45 45 45 01b ° 30 30 30 30 Length LI mm 30 30 30 30 Presence of chamfer Absent Present Present Present Chamfer depth % (effective groove depth ratio) - 50 110 100 Inner intermediate lug groove and inner intermediate sipe Configuration Groove and sipe Groove and sipe Groove and sipe Groove and sipe Open to main groove on vehicle inner side Open Open Open Open Open to main groove on vehicle outer side Not open Not open Not open Not open Inclination angle 02a ° 50 50 50 50 02b ° 30 30 30 30 Length L2 mm 15 15 15 15 L3 mm 35 35 35 35 Presence of chamfer Absent Present Present Present Chamfer depth % (effective groove depth ratio) - 50 110 100 Inner intermediate land portion Width L4 mm 20 20 20 20 Outer intermediate lug groove Open to main groove on vehicle inner side Open Open Open Open Open to main groove on vehicle outer side Not open Not open Not open Open Outer shoulder lug groove Open to main groove on vehicle inner side Open Open Open Open PCT/JP2014/084486 23 PCT/JP2014/084486

Open to circumferential narrow groove Not open Not open Not open Not open Outer shoulder lateral groove Open to circumferential narrow groove Not open Not open Not open Not open Inner shoulder lateral groove Presence Present Present Present Present Open to main groove on vehicle outer side Not open Not open Not open Not open Inner shoulder sipe Presence Present Present Present Present Open to main groove on vehicle outer side Open Open Open Open Outer shoulder sipe Presence Present Present Present Present Shape 3D 3D 3D 3D Presence of dimples Presence Absent Present Present Present Noise Index performance value 104 104 102 95 Dry Index performance value 103 103 103 95 Wet Index performance value 102 102 104 110 Fuel economy Index performance value 103 103 103 103 [TABLE 2-2]

Working Example 10 Working Example 11 Working Example 12 Working Example 13 Center lug groove Open to main groove on vehicle inner side Open Open Open Open Open to main groove on vehicle outer side Not open Not open Not open Not open Inclination angle Ola ° 45 45 45 45 01b ° 30 30 30 30 WO 2015/145910 A1 24 WO 2015/145910 A1

Length LI mm 30 30 30 30 Presence of chamfer Present Present Present Present Chamfer depth % (effective groove depth ratio) 100 100 100 100 Inner intermediate lug groove and inner intermediate sipe Configuration Groove and sipe Groove and sipe Groove and sipe Groove and sipe Open to main groove on vehicle inner side Open Open Open Open Open to main groove on vehicle outer side Not open Not open Not open Not open Inclination angle 92a ° 50 50 50 50 02b ° 30 30 30 30 Length L2 mm 15 15 15 15 L3 mm 35 35 35 35 Presence of chamfer Present Present Present Present Chamfer depth % (effective groove depth ratio) 100 100 100 100 Inner intermediate land portion Width L4 mm 20 20 20 20 Outer intermediate lug groove Open to main groove on vehicle inner side Open Open Open Open Open to main groove on vehicle outer side Not open Not open Not open Not open Outer shoulder lug groove Open to main groove on vehicle inner side Open Open Open Open Open to circumferential narrow groove Open Not open Not open Not open Outer shoulder lateral groove Open to circumferential narrow groove Not open Open Not open Not open PCT/JP2014/084486 25 WO 2015/145910 A1

Inner shoulder lateral groove Presence Present Present Present Present Open to main groove on vehicle outer side Not open Not open Open Not open Inner shoulder sipe Presence Present Present Absent Present Open to main groove on vehicle outer side Open Open - Open Outer shoulder sipe Presence Present Present Present Present Shape 3D 3D 3D 2D Presence of dimples Presence Present Present Present Present Noise Index performance value 95 97 97 103 Dry Index performance value 95 97 97 102 Wet Index performance value 110 105 105 102 Fuel economy Index performance value 103 103 103 103 PCT/JP2014/084486 [0053]

As can be seen from Table 1, Working Examples 1 to 13 had improved noise performance, dry performance, wet performance, and yearly installment performance 5 compared with Conventional Example 1.

[0054]

Comparative Example 1, in which the size relationships between the angles of inclination Ola, 01b, 02a, 02b of the center lug groove and the inner intermediate lug groove were reversed, had worse water drainage performance than Conventional 10 Example 1. Comparative Example 2, in which inner intermediate sipes were not provided (in other words an example the same as Comparative Example 1 except that the inner intermediate lug grooves did not open to the main groove on the vehicle outer side), had better noise performance but worse wet performance than Conventional Example 1. Comparative Example 3, in which the size relationship of 26 WO 2015/145910 A1 PCT/JP2014/084486 the lengths LI to L4 was reversed, had worse dry performance and wet performance than Conventional Example 1.

Reference Signs List [0055] 1 Tread portion 2 Sidewall portion 3 Bead portion 4 Carcass layer 5 Bead core 6 Bead filler 7, 8 Belt layer 9 Belt reinforcing layer 10 Tread surface 11 Main groove 12 Circumferential land portion 13 Center land portion 14 Inner intermediate land portion 15 Outer intermediate land portion 16 Shoulder land portion 17 Inner shoulder land portion 18 Outer shoulder land portion 19 Lug groove 20 Center lug groove 20A First inclined portion 20B Second inclined portion 21 Inner intermediate lug groove 21AFirst inclined portion 2IB Second inclined portion 22 Inner intermediate sipe 23 Corner portion 24 Outer intermediate lug groove 25 Outer shoulder lug groove 26 Inner shoulder lateral groove 27 Outer shoulder sipe 28 Outer shoulder lateral groove 29 Outer shoulder sipe 30 Circumferential narrow groove 27 5 WO 2015/145910 A1 PCT/JP2014/084486 31 End region 32 Dimple CL Tire equator 28

Claims

Claims

1. A pneumatic tire with a specified vehicle mounting direction provided with at least four main grooves extending in a tire circumferential direction in a tread surface, adjacent main grooves defining a plurality of circumferential land portions extending in the tire circumferential direction, and defining a shoulder land portion located outward in a tire width direction of the outermost main groove in the tire width direction on either side, the pneumatic tire comprising: a plurality of center lug grooves formed at intervals in the tire circumferential direction in a center land portion, which is the circumferential land portion located on a tire equator, each of the center grooves extending in the tire width direction communicating with the main groove on a vehicle inner side when mounted on a vehicle, and terminating within the center land portion without communicating with the main groove on a vehicle outer side when mounted on a vehicle; a plurality of inner intermediate lug grooves formed at intervals in the tire circumferential direction in an inner intermediate land portion, which is the circumferential land portion located on a side corresponding to the vehicle inner side when mounted on a vehicle, each of the inner intermediate lug grooves extend in the tire width direction communicating with the main groove on the vehicle inner side when mounted on a vehicle, and terminating within the inner intermediate land portion without communicating with the main groove on the vehicle outer side when mounted on a vehicle; wherein each of the center lug grooves and each of the inner intermediate lug grooves include a first inclined portion which is located proximal to an opening end and has a relatively great angle of inclination with respect to the tire circumferential direction and a second inclined portion which is located proximal to a terminating end and has a relatively low angle of inclination with respect to the tire circumferential direction; an inner intermediate sipe is formed at the terminating end of each of the inner intermediate lug grooves, the inner intermediate sipe extending in an extending direction of the second inclined portion of the corresponding inner intermediate lug groove and terminating within the inner intermediate land portion; and relationships LI > L2 and L3 > L4 are satisfied, where LI is a length of the center lug groove, L2 is a length of the inner intermediate lug groove, L3 is a sum of the length L2 and a length of the inner intermediate sipes, and L4 is a width of the inner intermediate land portion.
2. The pneumatic tire according to claim 1, wherein in the center land portion and in the inner intermediate land portion, a section of a comer portion formed by the main groove and the center lug groove or the inner intermediate lug groove where an angle of inclination of the first inclined portion is acute is chamfered.
3. The pneumatic tire according to claim 2, wherein the chamfers have depth that is greater than an effective groove depth and less than a depth of the main grooves.
4. The pneumatic tire according to any one of claims 1 to 3, further comprising: a plurality of outer intermediate lug grooves formed at intervals in the tire circumferential direction in an outer intermediate land portion, which is the circumferential land portion located on a side corresponding to the vehicle outer side when mounted on a vehicle, each of the outer intermediate lug grooves extending in the tire width direction communicating with the main groove on the vehicle inner side when mounted on a vehicle and terminating within the outer intermediate land portion without communicating with the main groove on the vehicle outer side when mounted on a vehicle; and a plurality of outer shoulder lug grooves formed at intervals in the tire circumferential direction in an outer shoulder land portion, which is the shoulder land portion on the side corresponding to the vehicle outer side when mounted on a vehicle, each of the outer shoulder lug grooves extending in the tire width direction communicating with the main groove on the vehicle inner side when mounted on a vehicle and terminating within the outer shoulder land portion.
5. The pneumatic tire according to any one of claims 1 to 4, further comprising: a plurality of inner shoulder lateral grooves formed at intervals in the tire circumferential direction in an inner shoulder land portion, which is the shoulder land portion on the side corresponding to the vehicle inner side when mounted on a vehicle, each of the inner shoulder lateral grooves extending in the tire width direction without communicating with the main groove on the vehicle outer side when mounted on a vehicle; and inner shoulder sipes extending from terminating end portions of the inner shoulder lateral grooves in an extending direction of the inner shoulder lateral grooves and connecting to the main groove on the vehicle outer side when mounted on a vehicle.
6. The pneumatic tire according to any one of claims 1 to 5, further comprising: a plurality of outer shoulder lateral grooves formed at intervals in the tire circumferential direction in an outer shoulder land portion, which is the shoulder land portion on a side corresponding to the vehicle outer side when mounted on a vehicle, each of the outer shoulder lateral grooves extending in the tire width direction without communicating with the main groove on the vehicle inner side when mounted on a vehicle.
7. The pneumatic tire according to any one of claims 1 to 6, further comprising: a plurality of outer shoulder sipes formed at intervals in the tire circumferential direction in an outer shoulder land portion, which is the shoulder land portion on a side corresponding to the vehicle outer side when mounted on a vehicle, each of the outer shoulder sipes extending in the tire width direction without communicating with the main groove on the vehicle inner side when mounted on a vehicle and terminating within the outer shoulder land portion, wherein the outer shoulder sipes have a shape including a bent portion.
8. The pneumatic tire according to any one of claims 1 to 7, further comprising: a plurality of dimples in outer end regions of the shoulder land portions in the tire width direction.