AU2017402111A1

AU2017402111A1 - Pneumatic tire

Info

Publication number: AU2017402111A1
Application number: AU2017402111A
Authority: AU
Inventors: Masaya Mita
Original assignee: Yokohama Rubber Co Ltd
Current assignee: Yokohama Rubber Co Ltd
Priority date: 2017-03-07
Filing date: 2017-03-07
Publication date: 2018-10-11
Anticipated expiration: 2037-03-07
Also published as: DE112017007194T5; DE112017007194B4; AU2017402111B2; JP6256658B1; CN109311351B; KR102205523B1; WO2018163273A1; RU2699511C1; JPWO2018163273A1; CN109311351A; KR20190003661A

Abstract

The present invention is provided with: a center main groove provided in the ground-contact center part of a tread part; shoulder main grooves provided on the sides of the center main groove that are outward in the tire width direction; center land parts formed so as to be segmented by the center main groove and the shoulder main grooves; beveled parts provided at the open edges of the center groove on the center land part sides such that a plurality of bevels in which the position of the open edges is changed so as to be inclined in the tire circumferential direction are disposed along the tire circumferential direction; bent grooves provided in the center land parts, alongside, in the tire width direction, the open edges of the center main groove that have the beveled parts, and provided so as to bend along with the shape of the bevels of the beveled parts while extending along the tire circumference direction; and sub-grooves provided in the center land parts between the shoulder main grooves and the bent grooves so as to cross the tire circumference direction and extend toward the bent grooves 6, with one end that faces the bent grooves terminating inside the center land parts.

Description

Technical Field [0001]

The present invention relates to a pneumatic tire that can improve uneven wear resistance performance, while ensuring braking performance on wet road surfaces and preventing an appearance defect.

Background Art [0002]

In the related art, a pneumatic tire described in Patent Document 1, for example, is provided, in a tread portion, with at least four circumferential main grooves extending in the tire circumferential direction and a plurality of rib-like land portions that are formed being defined by the circumferential main grooves. Further, second land portions, which are defined by the circumferential main grooves disposed on the outermost side in the tire lateral direction and disposed on the inner side of the circumferential main grooves in the tire lateral direction, have a zigzag shape while extending in the tire circumferential direction, and are provided with zigzag narrow grooves that divide the second land portions in the tire lateral direction. According to the pneumatic tire described in Patent Document 1, since the second land portions are provided with the zigzag narrow grooves, there is an advantage that edge components of a tire contact surface are ensured, and the braking performance on wet road surfaces, that is, the wet performance of the tire is thus ensured.

Citation List Patent Literature [0003]

Patent Document 1: JP 4905599 B

Summary of Invention Technical Problems [0004]

However, since the zigzag narrow grooves have bent portions, there is a risk that the land portions may be damaged at a time of die release when forming the tire, and this may result in the occurrence of an appearance defect. In addition, since the zigzag narrow grooves have the bent portions, there is a risk that a difference in rigidity may occur in the vicinity of the zigzag narrow grooves, and this may result in the occurrence of uneven wear.

[0005]

In light of the foregoing, an object of the present invention is to provide a pneumatic tire capable of improving uneven wear resistance performance, while ensuring braking performance on wet road surfaces and preventing an appearance defect.

Solution to Problems [0006]

In order to solve the above-described problems and achieve the above-described object, a pneumatic tire of the present invention includes: a first main groove provided in a ground contact central portion of a tread portion to extend along a tire circumferential direction; a second main groove provided on an outer side of the first main groove in a tire lateral direction to extend along the tire circumferential direction; a land portion formed as a result of being defined by the first main groove and the second main groove and being continuous in the tire circumferential direction; a chamfered portion in which a plurality of chamfers are arranged along the tire circumferential direction, the plurality of chamfers being provided on an opening edge, on the land portion side, of the first main groove and causing a position of the opening edge to be changed diagonally with respect to the tire circumferential direction; a bent groove provided in the land portion, disposed side by side with the opening edge including the chamfered portion of the first main groove in the tire lateral direction, and provided to be bent in accordance with shapes of the chamfers of the chamfered portion while extending along the tire circumferential direction; and a subsidiary groove provided in the land portion between the second main groove and the bent groove and extending toward the bent groove in a direction intersecting with the tire circumferential direction, one end of the subsidiary groove being oriented toward the bent groove and terminated inside the land portion.

[0007]

According to this pneumatic tire, edge components of a tire contact surface are ensured by the bent groove, and a braking performance on wet road surfaces, that is, a wet performance of the tire is thus ensured. Further, by the bent groove being provided to be bent in accordance with the shapes of the chamfers of the chamfered portion provided on the opening edge of the first main groove, and also by the subsidiary groove being provided with the one end thereof being oriented toward the bent groove and terminated inside the land portion, when a die is released from the bent groove at the time of forming the tire, the bent groove is widened as a result of the land portion, which includes the bent groove, being deformed toward the chamfered portion side and the subsidiary groove side. As a result, releasability of the die is improved, and this prevents a situation in which the land portion is damaged at the time of die release, thereby enabling prevention of an appearance defect. Further, by the bent groove being provided to be bent in accordance with the shapes of the chamfers of the chamfered portion provided on the opening edge of the first main groove, and also by the subsidiary groove being provided with the one end thereof being oriented toward the bent groove and terminated inside the land portion, differences in rigidity in the land portion including the bent groove are reduced, thereby causing the ground contact pressure to be made uniform. As a result, an uneven wear resistance performance can be improved.

[0008]

Further, in the pneumatic tire of the present invention, a groove width Wa of the bent groove is formed to be in a range from 4% to 8% with respect to a dimension W of the land portion in the tire lateral direction.

[0009]

When the groove width Wa of the bent groove is less than 4% with respect to the dimension W of the land portion in the tire lateral direction, drainage properties of the bent groove decrease, and the contribution thereof to the braking performance on the wet road surfaces becomes smaller. On the other hand, when the groove width Wa of the bent groove is greater than 8% with respect to the dimension W of the land portion in the tire lateral direction, the rigidity of the land portion decreases, and an improvement effect on the uneven wear resistance performance becomes smaller. Therefore, in order to ensure the braking performance on the wet road surfaces, and at the same time, to improve the uneven wear resistance performance, the groove width Wa of the bent groove is preferably formed to be in the range from 4% to 8% with respect to the dimension W of the land portion in the tire lateral direction.

[0010]

Further, in the pneumatic tire of the present invention, a dimension Wb, in the tire lateral direction, from a center line of the bent groove to an edge of the chamfered portion in the land portion is formed to be in a range from 20% to 45% with respect to the dimension W of the land portion in the tire lateral direction.

[0011]

When the dimension Wb, in the tire lateral direction, from the center line of the bent groove to the edge of the chamfered portion in the land portion is less than 20% with respect to the dimension W of the land portion in the tire lateral direction, the bent groove becomes closer to the chamfered portion. As a result, the rigidity of the land portion decreases between the bent groove and the chamfered portion, and the improvement effect on the uneven wear resistance performance becomes smaller. On the other hand, when the dimension Wb, in the tire lateral direction, from the center line of the bent groove to the edge of the chamfered portion in the land portion is greater than 45% with respect to the dimension W of the land portion in the tire lateral direction, an area for disposing the subsidiary groove becomes narrower, and this makes it more difficult to ensure the length of the subsidiary groove. As a result, drainage properties of the subsidiary groove decrease, and the contribution thereof to the braking performance on the wet road surfaces becomes smaller. Therefore, in order to ensure the braking performance on the wet road surfaces, and at the same time, to improve the uneven wear resistance performance, the dimension Wb, in the tire lateral direction, from the center line of the bent groove to the edge of the chamfered portion in the land portion is preferably formed to be in the range from 20% to 45% with respect to the dimension W of the land portion in the tire lateral direction.

[0012]

Further, in the pneumatic tire of the present invention, a groove depth Ha of the bent groove is formed to be in a range from 30% to 55% with respect to a groove depth H of the first main groove.

[0013]

When the groove depth Ha of the bent groove is less than 30% with respect to the groove depth H of the first main groove, the drainage properties of the bent groove decrease, and the contribution thereof to the braking performance on the wet road surfaces becomes smaller. On the other hand, when the groove depth Ha of the bent groove is greater than 55% with respect to the groove depth H of the first main groove, the groove depth Ha of the bent groove becomes closer to the groove depth H of the first main groove, and the land portion becomes more likely to be damaged when the die is released from the bent groove at the time of forming the tire. As a result, the effect on preventing the appearance defect becomes smaller. Therefore, in order to ensure the braking performance on the wet road surfaces, and at the same time, to prevent the appearance defect, the groove depth Ha of the bent groove is preferably formed to be in the range from 30% to 55% with respect to the groove depth H of the first main groove.

[0014]

Further, in the pneumatic tire of the present invention, the chamfered portion is formed such that the chamfers include long sides and short sides, which are inclined with respect to the tire circumferential direction, and are formed in triangular shapes on the opening edge of the first main groove. The bent groove is formed to be bent while including first inclined portions, which are long and inclined in the tire circumferential direction along the long sides of the chamfers, and second inclined portions, which are short and inclined in the tire circumferential direction along the short sides of the chamfers. An angle a of the first inclined portion with respect to the tire circumferential direction is formed to be in a range from 2° to 7°, and an angle β of the second inclined portion with respect to the tire circumferential direction is formed to be in a range from 20° to 60°.

[0015]

When the angle a of the first inclined portion with respect to the tire circumferential direction is less than 2°, or when the angle β of the second inclined portion with respect to the tire circumferential direction is less than 20°, the bent groove becomes closer to the tire circumferential direction, and an edge effect thereof is reduced. As a result, the contribution of the bent groove to the braking performance on the wet road surfaces becomes smaller. On the other hand, when the angle a of the first inclined portion with respect to the tire circumferential direction exceeds 7°, or when the angle β of the second inclined portion with respect to the tire circumferential direction exceeds 60°, bend of the bent groove becomes excessive, and corner portions thereof become closer to acute angles. As a result, the rigidity of the land portion decreases, and the improvement effect on the uneven wear resistance performance becomes smaller. Further, when the die is released from the bent groove at the time of forming the tire, the land portion becomes more likely to be damaged, thus the effect on preventing the appearance defect becomes smaller. Therefore, in order to improve the uneven wear resistance performance, and at the same time, to prevent the appearance defect while ensuring the braking performance on the wet road surfaces, it is preferable that the angle a of the first inclined portion with respect to the tire circumferential direction be formed to be in the range from 2° to 7°, and the angle β of the second inclined portion with respect to the tire circumferential direction be formed to be in the range from 20° to 60°. [0016]

Further, in the pneumatic tire of the present invention, a dimension Wc of the chamfered portion in the tire lateral direction is formed to be in a range from 4% to 15% with respect to the dimension W of the land portion in the tire lateral direction.

[0017]

When the dimension Wc of the chamfered portion in the tire lateral direction is less than 4% with respect to the dimension W of the land portion in the tire lateral direction, drainage properties of the first main groove decrease, and the contribution thereof to the braking performance on the wet road surfaces becomes smaller. On the other hand, when the dimension Wc of the chamfered portion in the tire lateral direction exceeds 15% with respect to the dimension W of the land portion in the tire lateral direction, the chamfers are cut out in the land portion to a greater extent. As a result, the rigidity of the land portion decreases, and the improvement effect on the uneven wear resistance performance becomes smaller. Therefore, in order to ensure the braking performance on the wet road surfaces, and at the same time, to improve the uneven wear resistance performance, the dimension Wc of the chamfered portion in the tire lateral direction is preferably formed to be in the range from 4% to 15% with respect to the dimension W of the land portion in the tire lateral direction.

[0018]

Further, in the pneumatic tire of the present invention, a dimension Hb of the chamfered portion in a tire radial direction is formed to be in a range from 30% to 60% with respect to the groove depth H of the first main groove.

[0019]

When the dimension Hb of the chamfered portion in the tire radial direction is less than 30% with respect to the groove depth H of the first main groove, the drainage properties of the first main groove decrease, and the contribution thereof to the braking performance on the wet road surfaces becomes smaller. On the other hand, when the dimension Hb of the chamfered portion in the tire radial direction exceeds 60% with respect to the groove depth H of the first main groove, the rigidity of the land portion decreases, and the improvement effect on the uneven wear resistance performance becomes smaller. Therefore, in order to ensure the braking performance on the wet road surfaces, and at the same time, to improve the uneven wear resistance performance, the dimension Hb of the chamfered portion in the tire radial direction is preferably formed to be in the range from 30% to 60% with respect to the groove depth H of the first main groove.

[0020]

Further, in the pneumatic tire of the present invention, in a section in which the chamfered portion and the bent groove face each other in the tire lateral direction, a dimension Wc, in the tire lateral direction, of the chamfers in the chamfered portion is formed to be equal to a bending range Wd, in the tire lateral direction, of the section of the bent groove that faces the chamfers in the tire lateral direction. A dimension La, in the tire circumferential direction, of a single chamfer in the chamfered portion is formed to be equal to a dimension Lb, in the tire circumferential direction, which is a single bending unit in the section of the bent groove that faces the single chamfer in the tire lateral direction.

[0021]

According to this pneumatic tire, by forming the dimension Wc of the chamfer in the tire lateral direction to be equal to the bending range Wd, in the tire lateral direction, of the section of the bent groove that faces the chamfer in the tire lateral direction, and forming the dimension La of the single chamfer in the tire circumferential direction to be equal to the dimension Lb, in the tire circumferential direction, of the single bending unit in the section of the bent groove that faces the single chamfer in the tire lateral direction, the shapes of edges of the chamfers become parallel with the bends of the bent groove, and differences in rigidity, in the tire circumferential direction, of the land portion disposed between the chamfers and the bent groove are made uniform. As a result, a significant effect on improving the uneven wear resistance performance can be obtained.

[0022]

Further, in the pneumatic tire of the present invention, a dimension We of the subsidiary groove in the tire lateral direction is formed to be in a range from 40% to 50% with respect to the dimension W of the land portion in the tire lateral direction.

[0023]

When the dimension We of the subsidiary groove in the tire lateral direction is less than 40% with respect to the dimension W of the land portion in the tire lateral direction, the drainage properties of the subsidiary groove decrease, and the contribution thereof to the braking performance on the wet road surfaces becomes smaller. On the other hand, when the dimension We of the subsidiary groove in the tire lateral direction exceeds 50% with respect to the dimension W of the land portion in the tire lateral direction, the rigidity of the land portions decreases, and the improvement effect on the uneven wear resistance performance becomes smaller. Therefore, in order to ensure the braking performance on the wet road surfaces, and at the same time, to improve the uneven wear resistance performance, the dimension We of the subsidiary groove in the tire lateral direction is preferably formed to be in the range from 40% to 50% with respect to the dimension W of the land portion in the tire lateral direction.

[0024]

Further, in the pneumatic tire of the present invention, each of the second main grooves are provided on both sides of the first main groove in the tire lateral direction, the land portions are formed as a result of being defined by the first main groove and each of the second main grooves on both the sides of the first main groove in the tire lateral direction, and the chamfered portions are provided on both the opening edges of the first main groove. The bent grooves are provided in each of the land portions, and the subsidiary grooves are provided in each of the land portions. When the pneumatic tire is mounted on a regular rim, inflated to a regular internal pressure, and loaded at 70% of a regular load, and in a state in which the tread portion is in contact with a flat ground surface on the ground, a groove opening area of the first main groove including the chamfered portions is formed to be larger than the groove opening area of the first main groove excluding the chamfered portions by a range from 15% to 20%.

[0025]

When the groove opening area of the first main groove including the chamfered portions is larger than the groove opening area of the first main groove excluding the chamfered portions by less than 15%, an edge effect of the chamfers decreases, and the contribution thereof to the braking performance on the wet road surfaces becomes smaller. On the other hand, when the groove opening area of the first main groove including the chamfered portions is larger than the groove opening area of the first main groove excluding the chamfered portions by more than 20%, the chamfers are cut out in the land portions to a greater extent. As a result, the rigidity of the land portions decreases, and the improvement effect on the uneven wear resistance performance becomes smaller. Therefore, in order to ensure the braking performance on the wet road surfaces, and at the same time, to improve the uneven wear resistance performance, the groove opening area of the first main groove including the chamfered portions is preferably formed to be larger than the groove opening area of the first main groove excluding the chamfered portions by the range from 15% to 20%.

[0026]

Further, in the pneumatic tire of the present invention, each of the second main grooves are provided on both the sides of the first main groove in the tire lateral direction, the land portions are formed as a result of being defined by the first main groove and each of the second main grooves on both the sides of the first main groove in the tire lateral direction, and the chamfered portions are provided on both the opening edges of the first main groove. The bent grooves are provided in each of the land portions, and the subsidiary grooves are provided in each of the land portions. In each of the chamfered portions disposed on the opening edges of the first main groove, the chamfers are continuously provided in the tire circumferential direction, and boundary portions, at which the chamfers are continuous with each other, are provided to be displaced with respect to each other, in the tire circumferential direction, on each of the opening edges of the first main groove.

[0027]

When the boundary portions, across which the chamfers are continuous with each other, are provided to be aligned with each other, in the tire circumferential direction, on each of the opening edges of the first main groove, the chamfers are not present, in the tire circumferential direction, in the sections in which the boundaries are aligned with each other. As a result, the drainage performance decreases in those sections, and the contribution to the braking performance on the wet road surfaces becomes smaller, thereby causing a hydroplaning resistance performance to also decrease. Therefore, by the boundary portions, across which the chamfers are continuous with each other, being provided to be displaced with respect to each other, in the tire circumferential direction, on each of the opening edges of the first main groove, the chamfers are always present in the tire circumferential direction. Thus, the braking performance on the wet road surfaces can be ensured.

[0028]

Further, in the pneumatic tire of the present invention, the second main grooves are provided on each outer sides of the two first main grooves in the tire lateral direction, the land portions are formed as a result of being defined by the first main grooves and the second main grooves on the outer sides of the first main grooves in the tire lateral direction, and the chamfered portions are only provided on the opening edges on the outer sides of the first main grooves in the tire lateral direction. The bent grooves are provided in the land portions, and the subsidiary grooves are provided in the land portions. When the pneumatic tire is mounted on a regular rim, inflated to a regular internal pressure, and loaded at 70% of a regular load, and in a state in which the tread portion is in contact with a flat ground surface on the ground, a groove opening area of the first main grooves including the chamfered portions is formed to be larger than the groove opening area of the first main grooves excluding the chamfered portions by a range from 8% to 13%.

[0029]

When the groove opening area of the first main grooves including the chamfered portions is larger than the groove opening area of the first main grooves excluding the chamfered portions by less than 8%, the edge effect of the chamfers decreases, and the contribution thereof to the braking performance on the wet road surfaces becomes smaller. On the other hand, when the groove opening area of the first main grooves including the chamfered portions is larger than the groove opening area of the first main grooves excluding the chamfered portions by more than 13%, the chamfers are cut out in the land portions to a greater extent. As a result, the rigidity of the land portions decreases, and the improvement effect on the uneven wear resistance performance becomes smaller. Therefore, in order to ensure the braking performance on the wet road surfaces, and at the same time, to improve the uneven wear resistance performance, the groove opening area of the first main grooves including the chamfered portions is preferably formed to be larger than the groove opening area of the first main grooves excluding the chamfered portions by the range from 8% to 13%.

[0030]

Further, in the pneumatic tire of the present invention, a rubber hardness of a rubber material forming a tread surface of the tread portion is preferably set to be in a range from 62 to 68 at a temperature of 20°C.

[0031]

When the rubber hardness is less than 62, the rubber strength decreases, and the uneven wear resistance tends to decrease. On the other hand, when the rubber hardness exceeds 68, the rubber flexibility decreases, and the braking performance on the wet road surfaces tends to decrease. Thus, the rubber hardness of the rubber material forming the tread surface is preferably in the range from 62 to 68.

[0032]

Further, in the pneumatic tire of the present invention, a tan δ of the rubber material forming the tread surface of the tread portion is preferably set to be in a range from 0.60 to 0.80 at a temperature of 0°C.

[0033]

When the tan δ is less than 0.60, the wet performance, that is, the braking performance on the wet road surfaces tends to decrease. On the other hand, when the tan δ exceeds 0.8, the rubber strength decreases, and the land portions tend to become more likely to be damaged as a result of die release at the time of forming the tire. Thus, the tan δ of the rubber material forming the tread surface is preferably in the range from 0.60 to 0.80 at the temperature of 0°C. [0034]

Further, in the pneumatic tire of the present invention, in a meridian cross-section, an actual profile line in the land portion, which is formed as a result of being defined by the first main groove and the second main groove, is formed to project further to the outer side in the tire radial direction than an imaginary profile line that passes through an edge end on an inner side of the second main groove in the tire lateral direction and being in contact with the tread surface, and each of edge ends on each side of the first main groove adjacent to the second main groove in the tire lateral direction and being in contact with the tread surface.

[0035]

According to this type of pneumatic tire, by the actual profile line projecting further to the outer side in the tire radial direction than the imaginary profile line in the land portion, a ground contact length of the tire circumferential direction in a ground contact region can be increased compared to a case in which the imaginary profile line is applied. In other words, the ground contact region can be increased in the tire circumferential direction. As a result of this, contact with the ground is improved, and the braking performance on the wet road surfaces can thus be improved. In addition, as a result of the improved contact with the ground, the uneven wear resistance performance can be improved.

Advantageous Effects of Invention [0036]

A pneumatic tire according to the present invention can improve uneven wear resistance performance, while ensuring braking performance on wet road surfaces and preventing an appearance defect.

Brief Description of Drawings [0037]

FIG. 1 is a plan view of a tread portion of a pneumatic tire according to a first embodiment of the present invention.

FIGS. 2A and 2B are an enlarged plan view (FIG. 2A) and a cross-sectional view (FIG. 2B) of a portion of the tread portion of the pneumatic tire according to the first embodiment of the present invention.

FIG. 3 is an enlarged plan view of a portion of the tread portion of another example of the pneumatic tire according to the first embodiment of the present invention.

FIG. 4 is an enlarged plan view of a portion of the tread portion of the pneumatic tire according to the first embodiment of the present invention.

FIG. 5 is an explanatory diagram of imaginary profile lines of the tread portion of the pneumatic tire according to the first embodiment of the present invention.

FIG. 6 is a plan view of the tread portion of a pneumatic tire according to a second embodiment of the present invention.

FIGS. 7A and 7B are an enlarged plan view (FIG. 7A) and a cross-sectional view (FIG. 7B) of a portion of the tread portion of the pneumatic tire according to the second embodiment of the present invention.

FIG. 8 is an enlarged plan view of a portion of the tread portion of another example of the pneumatic tire according to the second embodiment of the present invention.

FIG. 9 is an enlarged plan view of a portion of the tread portion of the pneumatic tire according to the second embodiment of the present invention.

FIG. 10 is an explanatory diagram of imaginary profile lines of the tread portion of the pneumatic tire according to the second embodiment of the present invention.

FIG. 11 is a table showing the results of performance tests of pneumatic tires according to Examples of the present invention.

FIG. 12 is a table showing the results of performance tests of pneumatic tires according to Examples of the present invention.

FIG. 13 is a table showing the results of performance tests of pneumatic tires according to Examples of the present invention.

FIG. 14 is a table showing the results of performance tests of pneumatic tires according to Examples of the present invention.

FIG. 15 is a table showing the results of performance tests of pneumatic tires according to Examples of the present invention.

FIG. 16 is a table showing the results of performance tests of pneumatic tires according to Examples of the present invention.

Description of Embodiments [0038]

Embodiments of the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited by the embodiments. Additionally, constituents of the embodiments include elements that can be replaced and easily made by those skilled in the art or elements substantially the same as the constituents of the embodiments. Furthermore, the modified examples described in the embodiments can be combined as desired within the scope apparent to those skilled in the art.

[0039]

First Embodiment

FIG. 1 is a plan view of a tread portion of a pneumatic tire according to the present embodiment. FIGS. 2A and 2B are an enlarged plan view (FIG. 2A) and a cross-sectional view (FIG. 2B) of a portion of the tread portion of the pneumatic tire according to the present embodiment. FIG. 3 is an enlarged plan view of a portion of the tread portion of another example of the pneumatic tire according to the present embodiment. FIG. 4 is an enlarged plan view of a portion of the tread portion of the pneumatic tire according to the present embodiment. FIG. 5 is an explanatory diagram of imaginary profile lines of the tread portion of the pneumatic tire according to the present embodiment.

[0040]

Hereinafter, a tire circumferential direction refers to the circumferential direction with a rotation axis (not illustrated) of a pneumatic tire 1 as the center axis. Further, a “tire lateral direction” refers to the direction parallel with the rotation axis, an “inner side in the tire lateral direction” refers to the side toward a tire equatorial plane (tire equator line) CL in the tire lateral direction, and an “outer side in the tire lateral direction” refers to the side away from the tire equatorial plane CL in the tire lateral direction. Furthermore, a “tire radial direction” refers to the direction orthogonal to the rotation axis, an “inner side in the tire radial direction” refers to the side toward the rotation axis in the tire radial direction, and an “outer side in the tire radial direction” refers to the side away from the rotation axis in the tire radial direction. A tire equatorial plane CL is the plane orthogonal to the rotation axis that passes through the center of the tire width of the pneumatic tire 1. A “tire equator line” refers to a line along the tire circumferential direction of the pneumatic tire 1 that lies on the tire equatorial plane CL. In the present embodiment, the tire equator line and the tire equatorial plane are denoted by the same reference sign “CL.” [0041]

As illustrated in FIG. 1, the pneumatic tire 1 of the present embodiment includes a tread portion 2. The tread portion 2, which is formed from a rubber material, is exposed on the outermost side in the tire radial direction of the pneumatic tire 1, and the surface thereof constitutes the profile of the pneumatic tire 1 as a tread surface 2a.

[0042]

The tread surface 2a of the tread portion 2 includes a plurality of circumferential main grooves (main grooves) 3 (three in the present embodiment) that extend along the tire circumferential direction and are provided side by side in the tire lateral direction. In the present embodiment, the circumferential main groove 3 disposed at the center in the tire lateral direction is a center main groove (first main groove) 3A, and the circumferential main grooves 3 disposed on the outer sides, in the tire lateral direction, of the center main groove 3A are shoulder main grooves (second main grooves) 3B. Note that the circumferential groove 3 has a groove width from 5 mm to 20 mm and a groove depth (dimension from an opening position of the tread surface 2a to the groove bottom) from 5 mm to 15 mm.

[0043]

The center main groove 3 A of the circumferential main grooves 3 is disposed in a ground contact central portion of a ground contact region. The ground contact central portion is a region in the vicinity of the tire equatorial plane CL. The center main groove 3A, which is the circumferential main groove 3 disposed in the ground contact central portion in the present embodiment, is the circumferential main groove 3 disposed closest to the tire equatorial plane CL, and is disposed on the tire equatorial plane CL.

[0044]

Note that the ground contact region is a region where the tread surface 2a of the tread portion 2 of the pneumatic tire 1 comes into contact with a dry and flat road surface, when the pneumatic tire 1 is mounted on a regular rim, inflated to a regular internal pressure, and loaded with 70% of a regular load. Here, the regular rim refers to a standard rim defined by the Japan Automobile Tyre Manufacturers Association Inc. (JATMA), a design rim defined by the Tire and Rim Association, Inc. (TRA), or a measuring rim defined by the European Tyre and Rim Technical Organisation (ETRTO). Further, the “regular internal pressure” refers to a “maximum air pressure” defined by JATMA, a maximum value given in “Tire Load Limits at Various Cold Inflation Pressures” defined by TRA, or “Inflation Pressures” defined by ETRTO. Further, the “regular load” refers to a “maximum load capacity” defined by JATMA, the maximum value given in “Tire Load Limits at Various Cold Inflation Pressures” defined by TRA, and a “Load Capacity” defined by ETRTO.

[0045]

The tread surface 2a of the tread portion 2 includes a plurality of land portions 4 (four in the present embodiment) formed as a result of being defined by the circumferential main grooves 3 in the tire lateral direction. Then, in the present embodiment, two of the rib-like land portions 4, which are formed as a result of being defined by the center main groove 3 A and each of the shoulder main grooves 3B disposed on both the outer sides, in the tire lateral direction, of the center main groove 3A, are center land portions 4A. Further, each of the rib-like land portions 4 that are disposed on the outer side, in the tire lateral direction, of each of the shoulder main grooves 3B are shoulder land portions 4B.

[0046]

In such a pneumatic tire 1, the center main groove 3 A is provided with chamfered portions 5 that are disposed on opening edges of the center land portions 4A on the shoulder main groove 3B sides of the center main grooves 3A. In the chamfered portions 5, a plurality of chamfers 5A, which cause the positions of the opening edges to be changed diagonally with respect to the tire circumferential direction, are arranged along the tire circumferential direction. Since the center main groove 3A of the present embodiment is provided with the shoulder main grooves 3B on both the outer sides thereof in the tire lateral direction and also with the center land portions 4A on both the outer sides thereof in the tire lateral direction, the chamfered portions 5 are provided on the opening edges on both the sides of the center main groove 3A. As illustrated in FIG. 2B, the chamfers 5A are formed by cutting out, in a triangular shape, corner portions of the opening edges of the center main groove 3 A in the tread surface 2a of the center land portions 4A, and as illustrated in FIG. 2A and FIG. 3, the chamfers 5 A are formed as triangular recessed portions in a plan view. Specifically, the chamfers 5 A are each formed in a triangular shape on the opening edges of the center main groove 3 A, while each including a long side 5a and a short side 5b that have different lengths from each other and that are inclined with respect to the tire circumferential direction. Note that, although not illustrated in the drawings, the chamfers 5A may each be formed in the triangular shape on the opening edges of the center main groove 3 A, while each including two sides that have the same length and that are inclined with respect to the tire circumferential direction. Therefore, due to the chamfered portions 5, the center main groove 3A includes edge portions that are inclined with respect to the tire circumferential direction. Then, since each of the chamfered portions 5, which are provided on the opening edges of the center main groove 3 A on both the sides thereof in the tire lateral direction, is provided with the chamfers 5A that are inverted with respect to each other, an opening of the center main groove 3 A is formed to have a zigzag shape in which lightning shapes are continuously formed as a result of straight lines being bent many times along the tire circumferential direction. Further, as illustrated in FIG. 2A, the chamfers 5 A may be provided continuously in the tire circumferential direction, or as illustrated in FIG. 3, the chamfers 5A may be provided at intervals 5B in the tire circumferential direction.

[0047]

Further, in the pneumatic tire 1 of the present embodiment, bent grooves 6 and subsidiary grooves 7 are formed in the center land portions 4A that are formed as a result of being defined by the center main groove 3 A and the shoulder main grooves 3B.

[0048]

The bent grooves 6 are disposed side by side, in the tire lateral direction, with the opening edges including the chamfered portions 5 of the center main groove 3A, and are provided to extend along the tire circumferential direction. The bent grooves 6 are formed to be bent by being inclined in accordance with the shapes of the chamfers 5 A of the chamfered portions 5. Specifically, as illustrated in FIG. 2A and FIG. 3, the bent grooves 6 are formed to be bent to include first inclined portions 6a, which are long and inclined in the tire circumferential direction along the long sides 5a of the chamfers 5A, and second inclined portions 6b, which are short and inclined in the tire circumferential direction along the short sides 5b of the chamfers 5A. Then, since the bent grooves 6 are provided along the tire circumferential direction in accordance with the triangular shapes of the chamfers 5A, the bent grooves 6 are each formed in a zigzag shape in which lightning shapes are continuously formed as a result of straight lines being bent many times along the tire circumferential direction. Note that, in the pneumatic tire 1 illustrated in FIG. 3, since the chamfers 5A are provided at the intervals 5B, in the tire circumferential direction, on the opening edges of the center main groove 3 A extending in the tire circumferential direction, the bent grooves 6 include intermediate portions 6c that are not inclined and that extend in the tire circumferential direction. By those bent grooves 6, the center land portions 4A are divided into first center land portions 4Aa on the center main groove 3 A side and second center land portions 4Ab on the shoulder main groove 3B sides. Note that the bent groove 6 has a groove width that is 1.5 mm or greater and that is less than that of the circumferential main groove 3, and a groove depth that is less than that of the circumferential main groove 3.

[0049]

The subsidiary grooves 7 are provided between the shoulder main grooves 3B and the bent grooves 6 and are formed to intersect with the tire circumferential direction. As illustrated in FIG. 2A and FIG. 3, first ends 7a of the subsidiary grooves 7 extend toward the bent grooves 6, and are provided to be terminated inside the center land portions 4A (second center land portions 4Ab) such that a gap is provided between the first ends 7a and the bent grooves

6. Specifically, the first ends 7a of the subsidiary grooves 7 are provided to be oriented toward the second inclined portions 6b which are short and largely bent portion of the bent grooves 6. Further, second ends 7b of the subsidiary grooves 7 extend toward the shoulder main grooves 3B and are provided communicating with the shoulder main grooves 3B. Note that, although not illustrated in the drawings, the second ends 7b of the subsidiary grooves 7 may be provided to be terminated inside the center land portions 4A (second center land portions 4Ab) such that a gap is provided between the second ends 7b and the shoulder main grooves 3B. Note that the subsidiary groove 7 has a groove width that is 1.5 mm or greater and that is less than that of the circumferential main groove 3, and a groove depth that is less than that of the circumferential main groove 3.

[0050]

In this way, the pneumatic tire 1 of the present embodiment includes: the center main groove (first main groove) 3 A that is provided in the ground contact central portion of the tread portion 2 to extend along the tire circumferential direction; the shoulder main grooves (second main grooves) 3B that are provided on the outer sides of the center main groove 3A in the tire lateral direction to extend along the tire circumferential direction; the center land portions 4A that are formed as a result of being defined by the center main groove 3A and the shoulder main grooves 3B and that are formed to be continuous in the tire circumferential direction; the chamfered portions 5 in which the plurality of chamfers 5A are arranged in the tire circumferential direction, the plurality of chamfers 5 A being provided on the opening edges, on the center land portion 4A side, of the center main groove 3 A and causing the positions of the opening edges to be changed diagonally with respect to the tire circumferential direction; the bent grooves 6 that are provided in the center land portions 4A, which are disposed side by side, in the tire lateral direction, with the opening edges including the chamfered portions 5 of the center main groove 3A, and that are provided to be bent in accordance with the shapes of the chamfers 5A of the chamfered portions 5 while extending in the tire circumferential direction; and the subsidiary grooves 7 that are provided in the center land portions 4A between the shoulder main grooves 3B and the bent grooves 6 and that extend toward the bent grooves 6 in a direction intersecting with the tire circumferential direction, the first ends 7a being oriented toward the bent grooves 6 and terminated inside the center land portions 4A.

[0051]

According to this pneumatic tire 1, edge components of a tire contact surface are ensured by the bent grooves 6, and the braking performance on wet road surfaces, that is, the wet performance of the tire is thus ensured. In addition, by the bent grooves 6 being bent in accordance with the shapes of the chamfers 5A of the chamfered portions 5 provided on the opening edges of the center main groove 3A, and also by the subsidiary grooves 7 being provided with the first ends 7a that are oriented toward the bent grooves 6 and are terminated inside the center land portions 4A, when a die is released from the bent grooves 6 at the time of forming the tire, the bent grooves 6 are widened as a result of the center land portions 4A (first center land portions 4Aa, second center land portions 4Ab) that include the bent grooves 6 being deformed toward the chamfered portion 5 side and the subsidiary groove 7 side. As a result, releasability of the die is improved, and this prevents a situation in which the center land portion 4A is damaged at the time of die release, and can thus prevent an appearance defect from occurring. Further, by the bent grooves 6 being provided to be bent in accordance with the shapes of the chamfers 5A of the chamfered portions 5 provided on the opening edges of the center main groove 3A, and also by the subsidiary grooves 7 being provided with the first ends 7a that are oriented toward the bent grooves 6 and that are terminated inside the center land portions 4A, differences in rigidity in the center land portions 4A including the bent grooves 6 are reduced, thereby causing the ground contact pressure to be made uniform. As a result, the uneven wear resistance performance can be improved.

[0052]

Further, as illustrated in FIG. 2A and FIG. 3, in the pneumatic tire 1 of the present embodiment, a groove width (opening width) Wa of the bent groove 6 is preferably formed to be in a range from 4% to 8% with respect to a dimension W of the center land portion 4A in the tire lateral direction.

[0053]

When the groove width Wa of the bent groove 6 is less than 4% with respect to the dimension W of the center land portion 4A in the tire lateral direction, drainage properties of the bent groove 6 decrease, and the contribution thereof to the braking performance on the wet road surfaces becomes smaller. On the other hand, when the groove width Wa of the bent groove 6 is greater than 8% with respect to the dimension W of the center land portion 4A in the tire lateral direction, the rigidity of the center land portions 4A decreases, and an improvement effect on the uneven wear resistance performance becomes smaller. Therefore, in order to ensure the braking performance on the wet road surfaces, and at the same time, to improve the uneven wear resistance performance, the groove width Wa of the bent groove 6 is preferably formed to be in the range from 4% to 8% with respect to the dimension W of the center land portion 4A in the tire lateral direction. Note that, in order to obtain significant effects on both ensuring the braking performance on the wet road surfaces and improving the uneven wear resistance performance, the groove width Wa of the bent groove 6 is preferably formed to be in a range from 5% to 7% with respect to the dimension W of the center land portion 4A in the tire lateral direction.

[0054]

Further, as illustrated in FIG. 2A and FIG. 3, in the pneumatic tire 1 of the present embodiment, a dimension Wb, in the tire lateral direction, from a center line S of the bent groove 6 to an edge 5c of the chamfered portion 5 in the center land portion 4A is preferably formed to be in a range from 20% to 45% with respect to the dimension W of the center land portion 4A in the tire lateral direction.

[0055]

The center line S of the bent groove 6 is a straight line passing through the center of the groove width Wa of the bent groove 6. The edge 5c of the chamfered portion 5 in the center land portion 4A is an edge of a section of the tread surface 2a of the center land portion 4A, and the chamfer 5A of the chamfered portion 5 is cut out to the greatest extent at the edge 5c.

[0056]

When the dimension Wb, in the tire lateral direction, from the center line S of the bent groove 6 to the edge 5c of the chamfered portion 5 in the center land portion 4A is less than 20% with respect to the dimension W of the center land portion 4A in the tire lateral direction, the bent grooves 6 become closer to the chamfered portions 5. As a result, the rigidity of the center land portions 4A decreases between the bent grooves 6 and the chamfered portions 5, and the improvement effect on the uneven wear resistance performance becomes smaller. On the other hand, when the dimension Wb, in the tire lateral direction, from the center line S of the bent groove 6 to the edge 5c of the chamfered portion 5 in the center land portion 4A is greater than 45% with respect to the dimension W of the center land portion 4A in the tire lateral direction, areas for disposing the subsidiary grooves 7 become narrower, and this makes it more difficult to ensure the length of the subsidiary grooves 7. As a result, the drainage properties of the subsidiary grooves 7 decrease, and the contribution thereof to the braking performance on the wet road surfaces becomes smaller. Therefore, in order to ensure the braking performance on the wet road surfaces, and at the same time, to improve the uneven wear resistance performance, the dimension Wb, in the tire lateral direction, from the center line S of the bent groove 6 to the edge 5 c of the chamfered portion 5 in the center land portion 4A is preferably formed to be in the range from 20% to 45% with respect to the dimension W of the center land portion 4A in the tire lateral direction. Note that, in order to obtain significant effects in terms of both ensuring the braking performance on the wet road surfaces and improving the uneven wear resistance performance, the dimension Wb, in the tire lateral direction, from the center line S of the bent groove 6 to the edge 5c of the chamfered portion 5 in the center land portion 4A is preferably formed to be in a range from 25% to 35% with respect to the dimension W of the center land portion 4A in the tire lateral direction.

[0057]

Further, as illustrated in FIG. 2B, in the pneumatic tire 1 of the present embodiment, a groove depth Ha of the bent groove 6 is preferably formed to be in a range from 30% to 55% with respect to a groove depth H of the center main groove 3A.

[0058]

When the groove depth Ha of the bent groove 6 is less than 30% with respect to the groove depth H of the center main groove 3A, the drainage properties of the bent grooves 6 decrease, and the contribution thereof to the braking performance on the wet road surfaces becomes smaller. On the other hand, when the groove depth Ha of the bent groove 6 is greater than 55% with respect to the groove depth H of the center main groove 3 A, the groove depth Ha of the bent groove 6 becomes closer to the groove depth H of the center main groove 3A, and the center land portions 4A are more likely to be damaged when the die is released from the bent grooves 6 at the time of forming the tire, thus reducing the effect of preventing the appearance defect. Therefore, in order to ensure the braking performance on the wet road surfaces, and at the same time, to prevent the appearance defect, the groove depth Ha of the bent groove 6 is preferably formed to be in the range from 30% to 55% with respect to the groove depth H of the center main groove 3A. Note that, in order to obtain significant effects on both ensuring the braking performance on the wet road surfaces and preventing the appearance defect, the groove depth Ha of the bent groove 6 is preferably formed to be in a range from 35% to 50% with respect to the groove depth H of the center main groove 3A.

[0059]

Further, as illustrated in FIG. 2A and FIG. 3, in the pneumatic tire 1 of the present embodiment, it is preferable that the chamfered portions 5 be formed such that the chamfers 5A are formed in the triangular shapes on the opening edges of the center main groove 3A while including the long sides 5a and the short sides 5b,which are inclined with respect to the tire circumferential direction, that the bent grooves 6 be formed to be bent while including the first inclined portions 6a, which are long and inclined in the tire circumferential direction along the long sides 5a of the chamfers 5A, and the second inclined portions 6b, which are short and inclined in the tire circumferential direction along the short sides 5b of the chamfers 5A, that an angle a of the first inclined portion 6a with respect to the tire circumferential direction be formed to be in a range from 2° to 7°, and that an angle β of the second inclined portion 6b with respect to the tire circumferential direction be formed to be in a range from 20° to 60°.

[0060]

When the angle a of the first inclined portion 6a with respect to the tire circumferential direction is less than 2°, or when the angle β of the second inclined portion 6b with respect to the tire circumferential direction is less than 20°, the bent grooves 6 become closer to the tire circumferential direction, and an edge effect thereof is reduced. As a result, the contribution of the bent groove 6 to the braking performance on the wet road surfaces becomes smaller. On the other hand, when the angle a of the first inclined portion 6a with respect to the tire circumferential direction exceeds 7°, or when the angle β of the second inclined portion 6b with respect to the tire circumferential direction exceeds 60°, the bend of the bent grooves 6 becomes excessive, and corner portions thereof become closer to acute angles. As a result, the rigidity of the center land portions 4A decreases, and the improvement effect on the uneven wear resistance performance becomes smaller. Further, when the die is released from the bent grooves 6 at the time of forming the tire, the center land portions

4A are more likely to be damaged, thus reducing the effect on preventing the appearance defect. Therefore, in order to improve the uneven wear resistance performance, and at the same time, to prevent the appearance defect while ensuring the braking performance on the wet road surfaces, it is preferable that the angle a of the first inclined portion 6a with respect to the tire circumferential direction be formed to be in the range from 2° to 7°, and the angle β of the second inclined portion 6b with respect to the tire circumferential direction be formed to be in the range from 20° to 60°. Note that, in order to obtain significant effects on all of improving the uneven wear resistance performance, ensuring the braking performance on the wet road surfaces and preventing the appearance defect, it is preferable that the angle a of the first inclined portion 6a with respect to the tire circumferential direction be formed to be in a range from 3° to 5°, and the angle β of the second inclined portion 6b with respect to the tire circumferential direction be formed to be in a range from 30° to 45°.

[0061]

Further, as illustrated in FIG. 2A and FIG. 3, in the pneumatic tire 1 of the present embodiment, a dimension Wc of the chamfered portion 5 in the tire lateral direction is preferably formed to be in a range from 4% to 15% with respect to the dimension W of the center land portion 4A in the tire lateral direction.

[0062]

When the dimension Wc of the chamfered portion 5 in the tire lateral direction is less than 4% with respect to the dimension W of the center land portion 4A in the tire lateral direction, the drainage properties of the center main groove 3A decrease, and the contribution thereof to the braking performance on the wet road surfaces becomes smaller. On the other hand, when the dimension Wc of the chamfered portion 5 in the tire lateral direction exceeds 15% with respect to the dimension W of the center land portion 4A in the tire lateral direction, the chamfers 5A are cut out in the center land portions 4A to a greater extent. As a result, the rigidity of the center land portions 4A decreases, and the improvement effect on the uneven wear resistance performance becomes smaller. Therefore, in order to ensure the braking performance on the wet road surfaces, and at the same time, to improve the uneven wear resistance performance, the dimension Wc of the chamfered portion 5 in the tire lateral direction is preferably formed to be in the range from 4% to 15% with respect to the dimension W of the center land portion 4A in the tire lateral direction. Note that, in order to obtain significant effects on both ensuring the braking performance on the wet road surfaces and improving the uneven wear resistance performance, the dimension Wc of the chamfered portion 5 in the tire lateral direction is preferably formed to be in a range from 6% to 8% with respect to the dimension W of the center land portion 4A in the tire lateral direction.

[0063]

Further, as illustrated in FIG. 2B, in the pneumatic tire 1 of the present embodiment, a dimension Hb of the chamfered portion 5 in the tire radial direction is preferably formed to be in a range from 30% to 60% with respect to the groove depth H of the center main groove 3 A.

[0064]

When the dimension Hb of the chamfered portion 5 in the tire radial direction is less than 30% with respect to the groove depth H of the center main groove 3A, the drainage properties of the center main groove 3 A decrease, and the contribution thereof to the braking performance on the wet road surfaces becomes smaller. On the other hand, when the dimension Hb of the chamfered portion 5 in the tire radial direction exceeds 60% with respect to the groove depth H of the center main groove 3A, the rigidity of the center land portions 4A decreases, and the improvement effect on the uneven wear resistance performance becomes smaller. Therefore, in order to ensure the braking performance on the wet road surfaces, and at the same time, to improve the uneven wear resistance performance, the dimension Hb of the chamfered portion 5 in the tire radial direction is preferably formed to be in the range from 30% to 60% with respect to the groove depth H of the center main groove 3A. Note that, in order to obtain significant effects on both ensuring the braking performance on the wet road surfaces and improving the uneven wear resistance performance, the dimension Hb of the chamfered portion 5 in the tire radial direction is preferably formed to be in a range from 40% to 55% with respect to the groove depth H of the center main groove 3 A.

[0065]

Further, as illustrated in FIG. 2A and FIG. 3, in the pneumatic tire 1 of the present embodiment, in sections in which the chamfered portions 5 and the bent grooves 6 face each other in the tire lateral direction, it is preferable that the dimension Wc of the chamfer 5A in the tire lateral direction be equal to a bending range Wd, in the tire lateral direction, of a section of the bent groove 6 that faces the chamfer 5A in the tire lateral direction, and that a dimension La, in the tire circumferential direction, of the single chamfer 5A of the chamfered portion 5 be equal to a dimension Lb, in the tire circumferential direction, which is the dimension of a single bending unit in a section of the bent groove 6 that faces the single chamfer 5A in the tire lateral direction.

[0066]

According to this pneumatic tire 1, by causing the dimension Wc of the chamfer 5A in the tire lateral direction to be formed to be equal to the bending range Wd, in the tire lateral direction, of the section of the bent groove 6 that faces the chamfer 5A in the tire lateral direction, and causing the dimension La of the chamfer 5A in the tire circumferential direction to be formed to be equal to the dimension Lb, in the tire circumferential direction, of the single bending unit in the section of the bent groove 6 that faces the chamfer 5 A in the tire lateral direction, the shapes of edges of the chamfers 5 A become parallel with the bends of the bent grooves 6, and differences in rigidity, in the tire circumferential direction, of the center land portions 4A disposed between the chamfers 5A and the bent grooves 6 are made uniform. As a result, a significant effect on improving the uneven wear resistance performance can be obtained. [0067]

Further, as illustrated in FIG. 2A and FIG. 3, in the pneumatic tire 1 of the present embodiment, a dimension We of the subsidiary groove 7 in the tire lateral direction is preferably formed to be in a range from 40% to 50% with respect to the dimension W of the center land portion 4A in the tire lateral direction.

[0068]

The dimension We of the subsidiary groove 7 in the tire lateral direction is a dimension in the tire lateral direction obtained when the subsidiary groove 7 is projected in the tire circumferential direction.

[0069]

When the dimension We of the subsidiary groove 7 in the tire lateral direction is less than 40% with respect to the dimension W of the center land portion 4A in the tire lateral direction, the drainage properties of the subsidiary groove 7 decrease, and the contribution thereof to the braking performance on the wet road surfaces becomes smaller. On the other hand, when the dimension We of the subsidiary groove 7 in the tire lateral direction exceeds 50% with respect to the dimension W of the center land portion 4A in the tire lateral direction, the rigidity of the center land portions 4A decreases, and the improvement effect on the uneven wear resistance performance becomes smaller. Therefore, in order to ensure the braking performance on the wet road surfaces, and at the same time, to improve the uneven wear resistance performance, the dimension We of the subsidiary groove 7 in the tire lateral direction is preferably formed to be in the range from 40% to 50% with respect to the dimension W of the center land portion 4A in the tire lateral direction. Note that, in order to obtain significant effects on both ensuring the braking performance on the wet road surfaces and improving the uneven wear resistance performance, the dimension We of the subsidiary groove 7 in the tire lateral direction is preferably formed to be in a range from 43%» to 46% with respect to the dimension W of the center land portion 4A in the tire lateral direction.

[0070]

Further, as illustrated in FIG. 2A and FIG. 3, in the pneumatic tire 1 of the present embodiment, the subsidiary groove 7 is preferably formed such that a shortest dimension Wf, between an end portion of the subsidiary groove 7 oriented toward the bent groove 6 and the bent groove 6, is formed to be in a range from 7%o to 20%» with respect to the dimension W of the center land portion 4A in the tire lateral direction.

[0071]

When the shortest dimension Wf, between the end portion of the subsidiary groove 7 oriented toward the bent groove 6 and the bent groove 6, is less than 7% with respect to the dimension W of the center land portion 4A in the tire lateral direction, the rigidity of the center land portions 4A decreases, and the improvement effect on the uneven wear resistance performance becomes smaller. On the other hand, when the shortest dimension Wf, between the end portion of the subsidiary groove 7 oriented toward the bent groove 6 and the bent groove 6, exceeds 20%» with respect to the dimension W of the center land portion 4A in the tire lateral direction, the rigidity of the center land portions 4A increases. As a result, when the die is released from the bent grooves 6 at the time of forming the tire, the center land portions 4A are more likely to be damaged, thus reducing the effect on preventing the appearance defect. Therefore, in order to prevent the appearance defect, and at the same time, to improve the uneven wear resistance performance, the shortest dimension Wf, between the end portion of the subsidiary groove 7 oriented toward the bent groove 6 and the bent groove 6, is preferably formed to be in the range from 7% to 20% with respect to the dimension W of the center land portion 4A in the tire lateral direction. Note that, in order to obtain significant effects on both preventing the appearance defect and improving the uneven wear resistance performance, the shortest dimension Wf, between the end portion of the subsidiary groove 7 oriented toward the bent groove 6 and the bent groove 6, is preferably formed to be in a range from 10%» to 15% with respect to the dimension W of the center land portion 4A in the tire lateral direction. Note that, in order to obtain the same effects, the shortest dimension Wf, between the end portion of the subsidiary groove 7 oriented toward the bent groove 6 and the bent groove 6, is preferably formed to be in a range from 2 mm to 5 mm, and more preferably formed to be in a range from 3 mm to 4 mm. [0072]

Further, as illustrated in FIGS. 1 to 3, in the pneumatic tire 1 of the present embodiment, the shoulder main grooves 3B are provided on each of the outer sides of the center main groove 3 A in the tire lateral direction, the center land portions 4A are formed as a result of being defined by the center main groove 3A and the shoulder main grooves 3B on both the outer sides of the center main groove 3 A in the tire lateral direction, the chamfered portions 5 are provided on both the opening edges of the center main groove 3A, the bent grooves 6 are provided in each of the center land portions 4A, and the subsidiary grooves 7 are provided in each of the center land portions 4A. When the pneumatic tire 1 is mounted on a regular rim, inflated to the regular internal pressure, and loaded at 70% of the regular load, and in a state in which the tread portion 2 is in contact with a flat ground surface on the ground, a groove opening area of the center main groove 3 A including the chamfered portions 5 is preferably formed to be larger than the groove opening area of the center main groove 3 A excluding the chamfered portions 5 by a range from 15% to 20%.

[0073]

When the groove opening area of the center main groove 3 A including the chamfered portions 5 is larger than the groove opening area of the center main groove 3 A excluding the chamfered portions 5 by less than 15%, the edge effect of the chamfers 5A decreases, and the contribution thereof to the braking performance on the wet road surfaces becomes smaller. On the other hand, when the groove opening area of the center main groove 3 A including the chamfered portions 5 is larger than the groove opening area of the center main groove 3 A excluding the chamfered portions 5 by more than 20%, the chamfers 5A are cut out in the center land portions 4A to a greater extent. As a result, the rigidity of the center land portions 4A decreases, and the improvement effect on the uneven wear resistance performance becomes smaller. Therefore, in order to ensure the braking performance on the wet road surfaces, and at the same time, to improve the uneven wear resistance performance, the groove opening area of the center main groove 3A including the chamfered portions 5 Is preferably formed to be larger than the groove opening area of the center main groove 3 A excluding the chamfered portions 5 by the range from 15% to 20%. Note that, in order to obtain significant effects on both ensuring the braking performance on the wet road surfaces and improving the uneven wear resistance performance, the groove opening area of the center main groove 3 A including the chamfered portions 5 is preferably formed to be larger than the groove opening area of the center main groove 3 A excluding the chamfered portions 5 by a range from 17% to 19%.

[0074]

Further, as illustrated in FIG. 2A, in the pneumatic tire 1 of the present embodiment, the shoulder main grooves 3B are provided on each of the outer sides of the center main groove 3 A in the tire lateral direction, the center land portions 4A are formed as a result of being defined by the center main groove 3 A and the shoulder main grooves 3B on both the outer sides of the center main groove 3A in the tire lateral direction, the chamfered portions 5 are provided on both the opening edges of the center main groove 3 A, the bent grooves 6 are provided in each of the center land portions 4A, and the subsidiary grooves 7 are provided in each of the center land portions 4A. In such a pneumatic tire 1, it is preferable that, in each of the chamfered portions 5 provided on both the opening edges of the center main groove 3 A, the chamfers 5 A be provided continuously in the tire circumferential direction, and boundary portions A, across which the chamfers 5 A are continuous with each other, be provided to be displaced with respect to each other, in the tire circumferential direction, on each of the opening edges of the center main groove 3 A.

[0075]

When the boundary portions A, across which the chamfers 5A are continuous with each other, are provided to be aligned with each other in the tire circumferential direction, on each of the opening edges of the center main groove 3 A, the chamfers 5 A are not present, in the tire circumferential direction, in the sections in which the boundary portions A are aligned with each other. As a result, the drainage performance decreases in those sections, and the contribution to the braking performance on the wet road surfaces becomes smaller, thereby causing the hydroplaning resistance performance to also decrease. Therefore, by the boundary portions A, across which the chamfers 5A are continuous with each other, being provided to be displaced with respect to each other, in the tire circumferential direction, on each of the opening edges of the center main groove 3 A, the chamfers 5A are always present in the tire circumferential direction, and the braking performance on the wet road surfaces can thus be ensured.

[0076]

Incidentally, in the present embodiment, in each of the shoulder land portions 4B, a circumferential narrow groove 8 is formed that extends in the tire circumferential direction along each of the shoulder main grooves 3B. The shoulder land portions 4B are each divided by this circumferential narrow groove 8 into a first shoulder land portion 4Ba on the shoulder main groove 3B side and a second shoulder land portion 4Bb on the outermost side in tire lateral direction. Note that the circumferential narrow groove 8 has a groove width that is 1.5 mm or greater and that is less than that of the circumferential main groove 3, and a groove depth that is less than that of the circumferential main groove 3. [0077]

Further, in each of the shoulder land portions 4B, shoulder subsidiary grooves 9 are formed that intersect with the tire circumferential direction in the second shoulder land portion 4Bb. First ends of the shoulder subsidiary grooves 9 penetrate the circumferential narrow groove 8 and are terminated inside the first shoulder land portion 4Ba. Second ends of the shoulder subsidiary grooves are provided to extend toward the outer side of the tread surface 2a in the tire lateral direction. Note that the shoulder subsidiary groove 9 has a groove width that is 1.5 mm or greater and that is less than that of the circumferential main groove 3, and a groove depth that is less than that of the circumferential main groove 3. .

[0078]

Further, in each of the shoulder land portions 4B, shoulder narrow grooves 10 are formed that intersect with the tire circumferential direction in the second shoulder land portion 4Bb. First ends of the shoulder narrow grooves are communicated with the circumferential narrow groove 8, and second ends of the shoulder narrow grooves 10 are provided to extend toward the outer side of the tread surface 2a in the tire lateral direction Note that the shoulder narrow groove 10 is formed, as a so-called sipe, to be in range from 0.4 mm to

1.2 mm.

[0079]

Incidentally, as illustrated in FIG. 4 and FIG. 5, in the pneumatic tire 1 of the present embodiment, in a meridian cross-section, an actual profile line LB in each of the center land portions 4A, which are formed as a result of being defined by the center main groove 3A and the shoulder main grooves 3B, is preferably formed to project further to the outer side in the tire radial direction than an imaginary profile line LA, which passes through edge ends 3Ba that are on the inner sides of the shoulder main grooves 3B in the tire lateral direction and are in contact with the tread surface 2a, and each of edge ends 3Aa and 3 Aa that are on both sides of the center main groove 3 A adjacent to the shoulder main grooves 3B in the tire lateral direction and that are in contact with the tread surface 2a.

[0080]

As described above, in the meridian cross-section, the imaginary profile line LA is an arc that passes through the edge ends 3Ba that are on the inner sides of the shoulder main grooves 3B in the tire lateral direction and that are in contact with the tread surface 2a, and each of the edge ends 3 Aa and 3Aa that are on both sides of the center main groove 3A adjacent to the shoulder main grooves 3B in the tire lateral direction and that are in contact with the tread surface 2a, and that has a radius of curvature whose center point is positioned on the inner side of the tread surface 2a in the tire radial direction. Further, the imaginary profile line LA may have the center point on the tire equatorial plane CL. Further, the actual profile line LB is an arc that passes through the edge ends 3 Ba that are on the inner sides of the shoulder main grooves 3B in the tire lateral direction and that are in contact with the tread surface 2a, and the edge ends 3Aa that are on the shoulder main groove 3B side of the center main groove 3 A adjacent to the shoulder main grooves 3B and that are in contact with the tread surface 2a, and that has a center point positioned on the inner side of the tread surface 2a in the tire radial direction.

[0081]

According to this type of pneumatic tire 1, by the actual profile line LB projecting further to the outer side in the tire radial direction than the imaginary profile line LA in the center land portions 4A, a ground contact length of the tire circumferential direction in the ground contact region can be increased compared with a case in which the imaginary profile line LA is applied. In other words, the ground contact region can be increased in the tire circumferential direction. As a result of this, contact with the ground is improved, and the braking performance on the wet road surfaces can thus be improved. In addition, as a result of the improved contact with the ground, the uneven wear resistance performance can be improved. Further, by the actual profile line LB being formed to project further to the outer side in the tire radial direction than the imaginary profile line LA in the center land portions 4A provided on both sides in the tire lateral direction with the tire equatorial plane CL interposed therebetween, the above-described effects can be significantly obtained.

[0082]

Further, when the pneumatic tire 1 is mounted on a regular rim, inflated to the regular internal pressure, and loaded at 70% of the regular load, a maximum projection amount Ga, in the center land portions 4A, of the actual profile line LB that projects further to the outer side in the tire radial direction than the imaginary profile line LA is preferably from 0.1 mm to 0.5 mm.

[0083]

When the maximum projection amount Ga in the center land portions 4A is less than 0.1 mm, the projection amount of the center land portions 4A is reduced, and the contact with the ground becomes more difficult to be improved. On the other hand, when the maximum projection amount Ga in the center land portions 4A exceeds 0.5 mm, the projection amount of the center land portions 4A becomes excessive, and the ground contact length in a central section of the land portions is excessively increased. This causes uneven wear of a kind in which the central section of the land portions wears away at an early stage. Thus, in order to improve both the braking performance on the wet road surfaces and the uneven wear resistance performance, the maximum projection amount Ga, in the center land portions 4A, to the outer side in the tire radial direction is preferably from 0.1 mm to 0.5 mm.

[0084]

Note that, as illustrated in FIG. 5, in the pneumatic tire 1 of the present embodiment, in the meridian cross-section, profile lines of the shoulder land portions 4B provided on the outer sides of the shoulder main grooves 3B in the tire lateral direction are preferably formed on and matching with an imaginary profile line LA’ that passes through ground contact edges T and the edge ends 3Ba and 3Bb that are on both the sides of the shoulder main grooves 3B in the tire lateral direction and that are in contact with the tread surface 2a, and that is continuous with the imaginary profile line LA. In other words, the land portions that project further to the outer side in the tire radial direction than the imaginary profile line LA are only the center land portions 4A, which are provided further toward the tire equatorial plane CL side than the shoulder main grooves 3B. By the bent grooves 6 being provided, in the circumferential direction, in the center land portions 4A that are formed as a result of being defined by the center main groove 3A and the shoulder main grooves 3B, the contact with the ground in the central region of each of the center land portions 4A tends to decrease. Further, the center land portions 4A provided closer to the tire equatorial plane CL tend to have a lower ground contact pressure than the shoulder land portions 4B. Accordingly, the land portions that project further to the outer side in the tire radial direction than the imaginary profile line LA are preferably only the center land portions 4A, which are provided further toward the tire equatorial plane CL side than the shoulder main grooves 3B.

[0085]

Here, “ground contact edges T” refer to both outermost edges in the tire lateral direction of a region where the tread surface 2a of the tread portion 2 of the pneumatic tire 1 contacts the road surface, when the pneumatic tire 1 is mounted on a regular rim, inflated to the regular internal pressure, and loaded at the regular load. The ground contact edges T are continuous in the tire circumferential direction.

[0086]

Incidentally, in the present embodiment, a rubber material forming the tread surface 2a of the tread portion 2 preferably has a rubber hardness (JIS-A hardness compliant with JIS-K6253 under the condition of 20°C) ranging from 62 to 68, When the rubber hardness is less than 62, the rubber strength decreases, and uneven wear resistance tends to decrease. On the other hand, when the rubber hardness exceeds 68, the rubber flexibility decreases, and the braking performance on the wet road surfaces tends to decrease. Thus, the rubber hardness of the rubber material forming the tread surface 2a is preferably in the range from 62 to 68.

[0087]

Further, the rubber material forming the tread surface 2a of the tread portion 2 preferably has tan δ (tangent loss) ranging from 0.60 to 0.80. When the tan δ is less than 0.60, the wet performance, that is, the braking performance on the wet road surfaces tends to decrease. On the other hand, when the tan δ exceeds 0.80, the rubber strength decreases, and the land portions tend to become more likely to be damaged as a result of the die release at the time of forming the tire. Thus, the tan δ of the rubber material forming the tread surface 2a is preferably in the range from 0.60 to 0.80 at a temperature of 0°C.

[0088]

Second Embodiment

FIG. 6 is a plan view of the tread portion of a pneumatic tire according to a present embodiment. FIGS. 7A and 7B are an enlarged plan view (FIG. 7A) and a cross-sectional view (FIG. 7B) of a portion of the tread portion of the pneumatic tire according to the present embodiment. FIG. 8 is an enlarged plan view of a portion of the tread portion of another example of the pneumatic tire according to the present embodiment. FIG. 9 is an enlarged cross-sectional view of a portion of the tread portion of the pneumatic tire according to the present embodiment. FIG. 10 is an explanatory diagram of imaginary profile lines of the tread portion of the pneumatic tire according to the present embodiment.

[0089]

Hereinafter, the tire circumferential direction refers to the circumferential direction with a rotation axis (not illustrated) of a pneumatic tire 11 as the center axis. Further, the “tire lateral direction” refers to the direction parallel with the rotation axis. The “inner side in the tire lateral direction” refers to the side toward the tire equatorial plane (tire equator line) CL in the tire lateral direction. The “outer side in the tire lateral direction” refers to the side away from the tire equatorial plane CL in the tire lateral direction. Furthermore, the “tire radial direction” refers to the direction orthogonal to the rotation axis. The “inner side in the tire radial direction” refers to the side toward the rotation axis in the tire radial direction. The “outer side in the tire radial direction” refers to the side away from the rotation axis in the tire radial direction. The tire equatorial plane CL is the plane orthogonal to the rotation axis that passes through the center of the tire width of the pneumatic tire 11. The “tire equator line” refers to the line along the tire circumferential direction of the pneumatic tire 11 that lies on the tire equatorial plane CL. In the present embodiment, the tire equator line and the tire equatorial plane are denoted by the same reference sign “CL.” [0090]

As illustrated in FIG. 6, the pneumatic tire 11 of the present embodiment includes the tread portion 2. The tread portion 2, which is formed from a rubber material, is exposed on the outermost side in the tire radial direction of the pneumatic tire 11, and the surface thereof constitutes the profile of the pneumatic tire 11 as the tread surface 2a.

[0091]

The tread surface 2a of the tread portion 2 includes the plurality of circumferential main grooves (main grooves) 3 (four in the present embodiment) that extend along the tire circumferential direction and are disposed side by side in the tire lateral direction. Then, in the present embodiment, the two circumferential main grooves 3 that have the tire equatorial plane CL interposed therebetween and that are disposed in a central section in the tire lateral direction are the center main grooves (first main grooves) 3 A, and each of the circumferential main grooves 3 disposed on the outer sides, in the tire lateral direction, of the center main grooves 3 A are the shoulder main grooves (second main grooves) 3B. Note that the circumferential main groove 3 has a groove width from 5 mm to 20 mm, and a groove depth (dimension from the opening position of the tread surface 2a to the groove bottom) from 5 mm to 15 mm.

[0092]

The center main grooves 3 A of the circumferential main grooves 3 are each disposed in the ground contact central portion of the ground contact region. The ground contact central portion is the region in the vicinity of the tire equatorial plane CL, and the center main grooves 3A, which are the circumferential main grooves 3 disposed in the ground contact central portion in the present embodiment, are the circumferential main grooves 3 disposed adjacent to the tire equatorial plane CL.

[0093]

Note that the ground contact region is the region where the tread surface 2a of the tread portion 2 of the pneumatic tire 11 comes into contact with a dry and flat road surface, when the pneumatic tire 11 is mounted on a regular rim, inflated to the regular internal pressure, and loaded at 70% of the regular load. The regular rim refers to the standard rim defined by JATMA, the design rim defined by TRA, or the measuring rim defined by ETRTO. Further, the “regular internal pressure” refers to the “maximum air pressure” defined by JATMA, the maximum value given in “Tire Load Limits at Various Cold Inflation Pressures” defined by TRA, or “Inflation Pressures” defined by ETRTO. Further, the “regular load” refers to the “maximum load capacity” defined by JATMA, the maximum value given in “Tire Load Limits at Various Cold Inflation Pressures” defined by TRA, and the “Load Capacity” defined by ETRTO.

[0094]

The tread surface 2a of the tread portion 2 includes a plurality of land portions 41 (five in the present embodiment) that are formed as a result of being defined by the circumferential main grooves 3 in the tire lateral direction. Then, in the present embodiment, one of the rib-like land portions 41 that is formed as a result of being defined between each of the center main grooves 3 A is a center land portion 41 A. Further, two of the rib-like land portions 4, which are formed as a result of being defined by the center main grooves 3 A and the shoulder main grooves 3B that are disposed on the outer sides of the center main grooves 3A in the tire lateral direction, are middle land portions 41B. Further, the rib-like land portions 41, which are disposed on the outer side of each of the shoulder main grooves 3B in the tire lateral direction, are shoulder land portions 41C.

[0095]

In such a pneumatic tire 11, the center main grooves 3 A are provided with the chamfered portions 5, which are disposed on opening edges of the middle land portions 4IB on the shoulder main groove 3B side of the center main grooves 3 A. In the chamfered portions 5, the plurality of chamfers 5 A, which cause the positions of the opening edges to be changed diagonally with respect to the tire circumferential direction, are arranged along the tire circumferential direction. Since the center main grooves 3 A of the present embodiment are provided with the shoulder main grooves 3B on the outer sides thereof in the tire lateral direction, and also with the middle land portions 41B on the outer sides thereof in the tire lateral direction, the chamfered portions 5 are only provided on the opening edges of the outer sides of the center main grooves 3 A in the tire lateral direction. As illustrated in FIG. 7B, the chamfers 5A are formed by cutting out, in a triangular shape, the corner portions of the opening edges of the center main grooves 3 A in the tread surface 2a of the middle land portions 4IB, and as illustrated in FIG. 7A and FIG. 8, the chamfers 5 A are formed as the triangular recessed portions in a plan view. Specifically, the chamfers 5A are each formed in a triangular shape on the opening edges of the center main grooves 3A, while each including the long side 5 a and the short side 5b that have different lengths from each other and that are inclined with respect to the tire circumferential direction. Note that, although not illustrated in the drawings, the chamfers 5 A may each be formed in the triangular shape on the opening edges of the center main grooves 3A, while each including two sides that have the same length and that are inclined with respect to the tire circumferential direction. Therefore, due to the chamfered portions 5, the center main grooves 3A include the edge portions that are inclined with respect to the tire circumferential direction. Further, as illustrated in FIG. 7A, the chamfers 5A may be provided continuously in the tire circumferential direction, or as illustrated in FIG. 8, the chamfers 5A may be provided at the intervals 5B in the tire circumferential direction.

[0096]

Further, in the pneumatic tire 11 of the present embodiment, the bent grooves 6 and the subsidiary grooves 7 are formed in the middle land portions 41B that are formed as a result of being defined by the center main grooves 3 A and the shoulder main grooves 3B.

[0097]

The bent grooves 6 are disposed side by side, in the tire lateral direction, with the opening edges including the chamfered portions 5 of the center main grooves 3A, and are provided to extend along the tire circumferential direction. The bent grooves 6 are formed to be bent, as a result of being inclined in accordance with the shapes of the chamfers 5 A of the chamfered portions 5. Specifically, as illustrated in FIG. 7Aand FIG. 8, the bent grooves 6 are formed to be bent to include the first inclined portions 6a, which are long and inclined in the tire circumferential direction along the long sides 5a of the chamfers, and the second inclined portions 6b, which are short and inclined in the tire circumferential direction along the short sides 5b of the chamfers 5 A. Then, since the bent grooves 6 are provided along the tire circumferential direction in accordance with the triangular shapes of the chamfers 5A, the bent grooves 6 are each formed in a zigzag shape in which lightning shapes are continuously formed as a result of straight lines being bent many times along the tire circumferential direction. Note that, in the pneumatic tire 1 illustrated in FIG. 8, since the chamfers 5A are provided at the intervals 5B, in the tire circumferential direction, on the opening edges of the center main grooves 3 A extending in the tire circumferential direction, the bent grooves 6 include the intermediate portions 6c that are not inclined and that extend in the tire circumferential direction. By those bent grooves 6, the middle land portions 41B are divided into first middle land portions 41Ba on the center main groove 3 A side and second middle portions 41Bb on the shoulder main groove 3B side. Note that the bent groove 6 has a groove width that is 1.5 mm or greater and that is less than that of the circumferential main groove 3, and a groove depth that is less than that of the circumferential main groove 3.

[0098]

The subsidiary grooves 7 are provided between the shoulder main grooves 3B and the bent grooves 6 and are formed to intersect with the tire circumferential direction. As illustrated in FIG. 7A and FIG. 8, the first ends 7a of the subsidiary grooves 7 extend toward the bent grooves 6, and are provided to be terminated inside the middle land portions 41B (second middle land portions 41Bb) such that a gap is provided between the first ends 7a and the bent grooves 6. Specifically, the first ends 7a of the subsidiary grooves 7 are provided to be oriented toward the second inclined portions 6b which are short and largely bent portion of the bent grooves 6. Further, the second ends 7b of the subsidiary grooves 7 extend toward the shoulder main grooves 3B and are provided communicating with the shoulder main grooves 3B. Note that, although not illustrated in the drawings, the second ends 7b of the subsidiary grooves 7 may be provided to be terminated inside the middle land portions 41B (second middle land portions 41Bb) such that a gap is provided between the second ends 7b and the shoulder main grooves 3B. Note that the subsidiary groove 7 has a groove width that is 1.5 mm or greater and that is less than that of the circumferential main groove 3, and a groove depth that is less than that of the circumferential main groove 3.

[0099]

In this way, the pneumatic tire 11 of the present embodiment includes: the center main grooves (first main grooves) 3 A that are provided in the ground contact central portion of the tread portion 2 to extend along the tire circumferential direction; the shoulder main grooves (second main grooves) 3B that are provided on the outer sides of the center main grooves 3 A in the tire lateral direction to extend along the tire circumferential direction; the middle land portions 41B that are formed as a result of being defined by the center main grooves 3 A and the shoulder main grooves 3B and that are formed to be continuous in the tire circumferential direction; the chamfered portions 5 in which the plurality of chamfers 5A are arranged in the tire circumferential direction, the plurality of chamfers 5 A being provided on the opening edges, on the middle land portion 41B side, of the center main grooves 3 A and causing the positions of the opening edges to be changed diagonally with respect to the tire circumferential direction; the bent grooves 6 that are provided in the middle land portions 4IB, disposed side by side, in the tire lateral direction, with the opening edges including the chamfered portions 5 of the center main grooves 3 A, and that are provided to be bent in accordance with the shapes of the chamfers 5A of the chamfered portions 5 while extending in the tire circumferential direction; and the subsidiary grooves 7 that are provided in the middle land portions 4IB between the shoulder main grooves 3B and the bent grooves 6 and extend toward the bent grooves 6 in the direction intersecting with the tire circumferential direction, the first ends 7a being oriented toward the bent grooves 6 and terminated inside the middle land portions 41B.

[0100]

According to this pneumatic tire 11, the edge components of the tire contact surface are ensured by the bent grooves 6, and the braking performance on the wet road surfaces, that is, the wet performance of the tire is thus ensured. Further, by the bent grooves 6 being bent in accordance with the shapes of the chamfers 5 A of the chamfered portions 5 provided on the opening edges of the center main grooves 3A, and also by the subsidiary grooves 7 being provided with the first ends 7a that are oriented toward the bent grooves 6 and are terminated inside the middle land portions 4IB, when the die is released from the bent grooves 6 at the time of forming the tire, the bent grooves 6 are widened as a result of the middle land portions 41B (first middle land portions 41 Ba, second middle land portions 41Bb) that include the bent grooves 6 being deformed toward the chamfered portion 5 side and the subsidiary groove 7 side. As a result, the releasability of the die is improved, and this prevents a situation in which the middle land portions 41B are damaged at the time of the die release, and can thus prevent the appearance defect from occurring. Further, by the bent grooves 6 being bent in accordance with the shapes of the chamfers 5A of the chamfered portions 5 provided on the opening edges of the center main grooves 3A, and also by the subsidiary grooves 7 being provided with the first ends 7a that are oriented toward the bent grooves 6 and that are terminated inside the middle land portions 4IB, differences in rigidity in the middle land portions 41B including the bent grooves 6 are reduced, thereby causing the ground contact pressure to be made uniform. As a result, the uneven wear resistance performance can be improved.

[0101]

Further, as illustrated in FIG. 7A and FIG. 8, in the pneumatic tire 11 of the present embodiment, the groove width (opening width) Wa of the bent groove 6 is preferably formed to be in a range from 4% to 8% with respect to the dimension W of the middle land portion 41B in the tire lateral direction. [0102]

When the groove width Wa of the bent groove 6 is less than 4% with respect to the dimension W of the middle land portion 41B in the tire lateral direction, the drainage properties of the bent grooves 6 decrease, and the contribution thereof to the braking performance on the wet road surfaces becomes smaller. On the other hand, when the groove width Wa of the bent groove 6 is greater than 8% with respect to the dimension W of the middle land portion 41B in the tire lateral direction, the rigidity of the middle land portions 41B decreases, and the improvement effect on the uneven wear resistance performance becomes smaller. Therefore, in order to ensure the braking performance on the wet road surfaces, and at the same time, to improve the uneven wear resistance performance, the groove width Wa of the bent groove 6 is preferably formed to be in the range from 4% to 8% with respect to the dimension W of the middle land portion 41B in the tire lateral direction. Note that, in order to obtain significant effects on both ensuring the braking performance on the wet road surfaces and improving the uneven wear resistance performance, the groove width Wa of the bent groove 6 is preferably formed to be in a range from 5% to 7% with respect to the dimension W of the middle land portion 41B in the tire lateral direction.

[0103]

Further, as illustrated in FIG. 7A and FIG. 8, in the pneumatic tire 11 of the present embodiment, the dimension Wb, in the tire lateral direction, from the center line S of the bent groove 6 to the edge 5c of the chamfered portion 5 in the middle land portion 41B is preferably formed to be in a range from 20% to 45% with respect to the dimension W of the middle land portion 41B in the tire lateral direction.

[0104]

The center line S of the bent groove 6 is the straight line passing through the center of the groove width Wa of the bent groove 6. The edge 5C in the middle land portion 41B of the chamfered portion 5 is an edge of a section of the tread surface 2a of the middle land portion 4 IB, and the chamfer 5 A of the chamfered portion 5 is cut out to the greatest extent at the edge 5 c.

[0105]

When the dimension Wb, in the tire lateral direction, from the center line S of the bent groove 6 to the edge 5 c of the chamfered portion 5 in the middle land portion 41B is less than 20% with respect to the dimension W of the middle land portion 41B in the tire lateral direction, the bent grooves 6 become closer to the chamfered portions 5. As a result, the rigidity of the middle land portions 41B decreases between the bent grooves 6 and the chamfered portions 5, and the improvement effect on the uneven wear resistance performance becomes smaller. On the other hand, when the dimension Wb, in the tire lateral direction, from the center line S of the bent groove 6 to the edge 5c of the chamfered portion 5 in the middle land portion 41B is greater than 45% with respect to the dimension W of the middle land portion 41B in the tire lateral direction, the areas for disposing the subsidiary grooves 7 become narrower, and this makes it more difficult to ensure the length of the subsidiary grooves 7. As a result, the drainage properties of the subsidiary grooves 7 decrease, and the contribution thereof to the braking performance on the wet road surfaces becomes smaller. Therefore, in order to ensure the braking performance on the wet road surfaces, and at the same time, to improve the uneven wear resistance performance, the dimension Wb, in the tire lateral direction, from the center line S of the bent groove 6 to the edge 5c of the chamfered portion 5 in the middle land portion 41B is preferably formed to be in the range from 20% to 45% with respect to the dimension W of the middle land portion 41B in the tire lateral direction. Note that, in order to obtain significant effects on both ensuring the braking performance on the wet road surfaces and improving the uneven wear resistance performance, the dimension Wb, in the tire lateral direction, from the center line S of the bent groove 6 to the edge 5c of the chamfered portion 5 in the middle land portion 41B is preferably formed to be in a range from 25% to 35% with respect to the dimension W of the middle land portion 41B in the tire lateral direction.

[0106]

Further, as illustrated in FIG. 7B, in the pneumatic tire 11 of the present embodiment, the groove depth Ha of the bent groove 6 is preferably formed to be in a range from 30% to 55% with respect to the groove depth H of the center main groove 3A.

[0107]

When the groove depth Ha of the bent groove 6 is less than 30% with respect to the groove depth H of the center main groove 3 A, the drainage properties of the bent groove 6 decrease, and the contribution thereof to the braking performance on the wet road surfaces becomes smaller. On the other hand, when the groove depth Ha of the bent groove 6 is greater than 55% with respect to the groove depth H of the center main groove 3A, the groove depth Ha of the bent groove 6 becomes closer to the groove depth H of the center main groove 3A, and the middle land portions 41B are more likely to be damaged when the die is released from the bent grooves 6 at the time of forming the tire, thus reducing the effect on preventing the appearance defect. Therefore, in order to ensure the braking performance on the wet road surfaces, and at the same time, to prevent the appearance defect, the groove depth Ha of the bent groove 6 is preferably formed to be in the range from 30% to 55% with respect to the groove depth H of the center main groove 3A. Note that, in order to obtain significant effects on both ensuring the braking performance on the wet road surfaces and preventing the appearance defect, the groove depth Ha of the bent groove 6 is preferably formed to be in a range from 35% to 50% with respect to the groove depth H of the center main groove 3A.

[0108]

Further, as illustrated in FIG. 7A and FIG. 8, in the pneumatic tire 11 of the present embodiment, it is preferable that the chamfered portions 5 be formed such that the chamfers 5A are formed in the triangular shapes on the opening edges of the center main grooves 3 A while including the long sides 5 a and the short sides 5b, which are inclined with respect to the tire circumferential direction, that the bent grooves 6 be formed to be bent while including the first inclined portions 6a, which are long and inclined in the tire circumferential direction along the long sides 5a of the chamfers 5A, and the second inclined portions 6b, which are short and inclined in the tire circumferential direction along the short sides 5b of the chamfers 5A, that the angle a of the first inclined portion 6a with respect to the tire circumferential direction be formed to be in a range from 2° to 7°, and that the angle β of the second inclined portion 6b with respect to the tire circumferential direction be formed to be in a range from 20° to 60°.

[0109]

When the angle a of the first inclined portion 6a with respect to the tire circumferential direction is less than 2°, or when the angle β of the second inclined portion with respect to the tire circumferential direction is less than 20°, the bent grooves 6 become closer to the tire circumferential direction, and the edge effect thereof is reduced. As a result, the contribution of the bent grooves 6 to the braking performance on the wet road surfaces becomes smaller. On the other hand, when the angle a of the first inclined portion 6a with respect to the tire circumferential direction exceeds 7°, or when the angle β of the second inclined portion 6b with respect to the tire circumferential direction exceeds 60°, the bend of the bent grooves 6 becomes excessive, and the corner portions thereof become closer to acute angles. As a result, the rigidity of the middle land portions 4IB decreases, and the improvement effect on the uneven wear resistance performance becomes smaller. Further, when the die is released from the bent grooves 6 at the time of forming the tire, the center land portions 4A are more likely to be damaged, thus reducing the effect on preventing the appearance defect. Therefore, in order to improve the uneven wear resistance performance, and at the same time, to prevent the appearance defect while ensuring the braking performance on the wet road surfaces, it is preferable that the angle a of the first inclined portion 6a with respect to the tire circumferential direction be formed to be in the range from 2° to 7°, and the angle β of the second inclined portion 6b with respect to the tire circumferential direction be formed to be in the range from 20° to 60°. Note that, in order to obtain significant effects on all of improving the uneven wear resistance performance, ensuring the braking performance on the wet road surfaces and preventing the appearance defect, it is preferable that the angle a of the first inclined portion 6a with respect to the tire circumferential direction be formed to be in a range from 3° to 5°, and the angle β of the second inclined portion 6b with respect to the tire circumferential direction be formed to be in a range from 30° to 45°.

[0110]

Further, as illustrated in FIG. 7A and FIG. 8, in the pneumatic tire 11 of the present embodiment, the dimension Wc of the chamfered portion 5 in the tire lateral direction is preferably formed to be in a range from 4% to 15% with respect to the dimension W of the middle land portion 41B in the tire lateral direction.

When the dimension Wc of the chamfered portion 5 in the tire lateral direction is less than 4% with respect to the dimension W of the middle land portion 41B in the tire lateral direction, the drainage properties of the center main grooves 3 A decrease, and the contribution thereof to the braking performance on the wet road surfaces becomes smaller. On the other hand, when the dimension Wc of the chamfered portion 5 in the tire lateral direction exceeds 15% with respect to the dimension W of the middle land portion 4 IB in the tire lateral direction, the chamfers 5 A are cut out in the middle land portions 41B to a greater extent. As a result, the rigidity of the middle land portions 4 IB decreases, and the improvement effect on the uneven wear resistance performance becomes smaller. Therefore, in order to ensure the braking performance on the wet road surfaces, and at the same time, to improve the uneven wear resistance performance, the dimension Wc of the chamfered portion 5 in the tire lateral direction is preferably formed to be in the range from 4% to 15% with respect to the dimension W of the middle land portion 41B in the tire lateral direction. Note that, in order to obtain significant effects on both ensuring the braking performance on the wet road surfaces and improving the uneven wear resistance performance, the dimension Wc of the chamfered portion 5 in the tire lateral direction is preferably formed to be in a range from 6% to 8% with respect to the dimension W of the middle land portion 41B in the tire lateral direction.

[0112]

Further, as illustrated in FIG. 7B, in the pneumatic tire 11 of the present embodiment, the dimension Hb of the chamfered portion 5 in the tire radial direction is preferably formed to be in a range from 30% to 60% with respect to the groove depth H of the center main groove 3A.

[0Π3]

When the dimension Hb of the chamfered portion 5 in the tire radial direction is less than 30% with respect to the groove depth H of the center main groove 3 A, the drainage properties of the center main grooves 3 A decrease, and the contribution thereof to the braking performance on the wet road surfaces becomes smaller. On the other hand, when the dimension Hb of the chamfered portion 5 in the tire radial direction exceeds 60% with respect to the groove depth H of the center main groove 3A, the rigidity of the middle land portions 41B decreases, and the improvement effect on the uneven wear resistance performance becomes smaller. Therefore, in order to ensure the braking performance on the wet road surfaces, and at the same time, to improve the uneven wear resistance performance, the dimension Hb of the chamfered portion 5 in the tire radial direction is preferably formed to be in the range from 30% to 60% with respect to the groove depth H of the center main groove 3 A. Note that, in order to obtain significant effects on both ensuring the braking performance on the wet road surfaces and improving the uneven wear resistance performance, the dimension Hb of the chamfered portion 5 in the tire radial direction is preferably formed to be in a range from 40% to 55% with respect to the groove depth H of the center main groove 3 A.

[0114]

Further, as illustrated in FIG. 7A and FIG. 8, in the pneumatic tire 11 of the present embodiment, in the sections in which the chamfered portions 5 and the bent grooves 6 face each other in the tire lateral direction, it is preferable that the dimension Wc of the chamfer 5A in the tire lateral direction be equal to the bending range Wd, in the tire lateral direction, of the section of the bent groove 6 that faces the chamfer 5 A in the tire lateral direction, and the dimension La, in the tire circumferential direction, of the single chamfer 5A of the chamfered portion 5 be equal to the dimension Lb, in the tire circumferential direction, which is the dimension of the single bending unit in the section of the bent groove 6 that faces the single chamfer 5 A in the tire lateral direction.

[0115]

According to this pneumatic tire 11, by causing the dimension Wc of the chamfer 5A in the tire lateral direction to be formed to be equal to the bending range Wd, in the tire lateral direction, of the section of the bent groove 6 that faces the chamfer 5A in the tire lateral direction, and causing the dimension La of the chamfer 5A in the tire circumferential direction to be formed to be equal to the dimension Lb, in the tire circumferential direction, of the single bending unit in the section of the bent groove 6 that faces the chamfer 5A in the tire lateral direction, the shapes of the edges of the chamfers 5 A become parallel with the bends of the bent grooves 6, and differences in rigidity, in the tire circumferential direction, of the middle land portions 41B disposed between the chamfers 5 A and the bent grooves 6 are made uniform. As a result, a significant effect on improving the uneven wear resistance performance can be obtained. [0116]

Further, as illustrated in FIG. 7A and FIG. 8, in the pneumatic tire 11 of the present embodiment, the dimension We of the subsidiary groove 7 in the tire lateral direction is preferably formed to be in a range from 40% to 50% with respect to the dimension W of the middle land portion 41B in the tire lateral direction.

[0117]

The dimension We of the subsidiary groove 7 in the tire lateral direction is the dimension in the tire lateral direction obtained when the subsidiary groove 7 is projected in the tire circumferential direction.

[0118]

When the dimension We of the subsidiary groove 7 in the tire lateral direction is less than 40% with respect to the dimension W of the middle land portion 41B in the tire lateral direction, the drainage properties of the subsidiary groove 7 decrease, and the contribution thereof to the braking performance on the wet road surfaces becomes smaller. On the other hand, when the dimension We of the subsidiary groove 7 in the tire lateral direction exceeds 50% with respect to the dimension W of the middle land portion 41B in the tire lateral direction, the rigidity of the middle land portions 41B decreases, and the improvement effect on the uneven wear resistance performance becomes smaller. Therefore, in order to ensure the braking performance on the wet road surfaces, and at the same time, to improve the uneven wear resistance performance, the dimension We of the subsidiary groove 7 in the tire lateral direction is preferably formed to be in the range from 40% to 50% with respect to the dimension W of the middle land portion 41B in the tire lateral direction. Note that, in order to obtain significant effects on both ensuring the braking performance on the wet road surfaces and improving the uneven wear resistance performance, the dimension We of the subsidiary groove 7 in the tire lateral direction is preferably formed to be in a range from 43% to 46% with respect to the dimension W of the middle land portion 41B in the tire lateral direction. [0119]

Further, as illustrated in FIG. 7A and FIG. 8, in the pneumatic tire 11 of the present embodiment, it is preferable that the subsidiary groove 7 is preferably formed such that the shortest dimension Wf between the end portion of the subsidiary groove 7 oriented toward the bent groove 6 and the bent groove 6 is formed to be in a range from 7% to 20% with respect to the dimension W of the middle land portion 41B in the tire lateral direction.

[0120]

When the shortest dimension Wf, between the end portion of the subsidiary groove 7 oriented toward the bent groove 6 and the bent groove 6, is less than 7% with respect to the dimension W of the middle land portion 41B in the tire lateral direction, the rigidity of the middle land portions 41B decreases, and the improvement effect on the uneven wear resistance performance becomes smaller. On the other hand, when the shortest dimension Wf, between the end portion of the subsidiary groove 7 oriented toward the bent groove 6 and the bent groove 6, exceeds 20% with respect to the dimension W of the middle land portion 41B in the tire lateral direction, the rigidity of the middle land portions 41B increases. As a result, when the die is released from the bent grooves 6 at the time of forming the tire, the middle land portions 4IB are more likely to be damaged, thus reducing the effect on preventing the appearance defect. Therefore, in order to prevent the appearance defect, and at the same time, to improve the uneven wear resistance performance, the shortest dimension Wf, between the end portion of the subsidiary groove 7 oriented toward the bent groove 6 and the bent groove 6, is preferably formed to be in the range from 7% to 20% with respect to the dimension W of the middle land portion 41B in the tire lateral direction. Note that, in order to obtain significant effects on both preventing the appearance defect and improving the uneven wear resistance performance, the shortest dimension Wf, between the end portion of the subsidiary groove 7 oriented toward the bent groove 6 and the bent groove 6, is preferably formed to be in a range from 10% to 15% with respect to the dimension W of the middle land portion 41B in the tire lateral direction. Note that, in order to obtain the same effects, the shortest dimension Wf, between the end portion of the subsidiary groove 7 oriented toward the bent groove 6 and the bent groove 6, is preferably formed to be in a range from 2 mm to 5 mm, and more preferably formed to be in a range from 3 mm to 4 mm. [0121]

Further, as illustrated in FIGS. 6 to 8, in the pneumatic tire 11 of the present embodiment, the shoulder main grooves 3B are provided on the outer side of each of the two center main grooves 3 A in the tire lateral direction, the middle land portions 41B are formed as a result of being defined by the center main grooves 3 A and the shoulder main grooves 3B on the outer side of each of the center main grooves 3 A in the tire lateral direction, the chamfered portions 5 are only provided on the opening edges on the outer sides of the center main grooves 3 A in the tire lateral direction, the bent grooves 6 are provided in each of the middle land portions 4IB, and the subsidiary grooves 7 are provided in each of the middle land portions 41B. When the pneumatic tire 11 is mounted on a regular rim, inflated to the regular internal pressure, and loaded at 70% of the regular load, and in a state in which the tread portion 2 is in contact with a flat surface on the ground, the groove opening area of the center main grooves 3 A including the chamfered portions 5 is preferably formed to be larger than the groove opening area of the center main grooves 3A excluding the chamfered portions 5 by a range from 8% to 13%.

[0122]

When the groove opening area of the center main grooves 3 A including the chamfered portions 5 is larger than the groove opening area of the center main grooves 3 A excluding the chamfered portions 5 by less than 15%, the edge effect of the chamfers 5A decreases, and the contribution thereof to the braking performance on the wet road surfaces becomes smaller. On the other hand, when the groove opening area of the center main grooves 3A including the chamfered portions 5 is larger than the groove opening area of the center main grooves 3A excluding the chamfered portions 5 by more than 20%, the chamfers 5 A are cut out in the middle land portions 41B to a greater extent. As a result, the rigidity of the middle land portions 4A decreases, and the improvement effect on the uneven wear resistance performance becomes smaller. Therefore, in order to ensure the braking performance on the wet road surfaces, and at the same time, to improve the uneven wear resistance performance, the groove opening area of the center main grooves 3 A including the chamfered portions 5 is preferably formed to be larger than the groove opening area of the center main grooves 3 A excluding the chamfered portions 5 by the range from 8%> to 13%. Note that, in order to obtain significant effects on both ensuring the braking performance on the wet road surfaces and improving the uneven wear resistance performance, the groove opening area of the center main grooves 3 A including the chamfered portions 5 is preferably formed to be larger than the groove opening area of the center main grooves 3 A excluding the chamfered portions 5 by a range from 9% to 11%.

[0123]

Incidentally, in the present embodiment, in each of the shoulder land portions 41C, the circumferential narrow groove 8 is formed that extends in the tire circumferential direction along each of the shoulder main grooves 3B. The shoulder land portions 41C each is divided by this circumferential narrow groove 8 into a first shoulder land portion 41Ca on the shoulder main groove 3B side and a second shoulder land portion 41 Cb on the outermost side in tire lateral direction. Note that the circumferential narrow groove 8 has a groove width that is 1.5 mm or greater and that is less than that of the circumferential main groove 3, and a groove depth that is less than that of the circumferential main groove 3.

[0124]

Further, in each of the shoulder land portions 41C, the shoulder subsidiary grooves 9 are formed that intersect with the tire circumferential direction in the second shoulder land portion 41Cb. The first ends of the shoulder subsidiary grooves 9 penetrate the circumferential narrow groove 8 and are terminated inside the first shoulder land portion 41Ca. The second ends of the shoulder subsidiary grooves 9 are provided to extend toward the outer side of the tread surface 2a in the tire lateral direction. Note that the shoulder subsidiary groove 9 has a groove width that is 1.5 mm or greater and that is less than that of the circumferential main groove 3, and a groove depth that is less than that of the circumferential main groove 3.

[0125]

Further, in each of the shoulder land portions 41C, shoulder narrow grooves 10 are formed that intersect with the tire circumferential direction in the second shoulder land portion 41 Cb. The first ends of the shoulder narrow grooves 10 are communicated with the circumferential narrow groove 8, and the second ends of the shoulder narrow grooves 10 are provided to extend toward the outer side of the tread surface 2a in the tire lateral direction. Note that the shoulder narrow groove 10 is formed, as the so-called sipe, to be in range from 0.4 mm to 1.2 mm.

[0126]

Incidentally, as illustrated in FIG.9 and FIG. 10, in the pneumatic tire 11 of the present embodiment, in a meridian cross-section, the actual profile line LB in the middle land portions 41B, which are formed as a result of being defined by the center main grooves 3A and the shoulder main grooves 3B, is preferably formed to project further to the outer side in the tire radial direction than the imaginary profile line LA, which passes through the edge ends 3Ba that are on the inner side of the shoulder main grooves 3B in the tire lateral direction and that are in contact with the tread surface 2a, and each of the edge ends 3Aa and 3Aa that are on both the sides of the center main grooves 3 A adjacent to the shoulder main grooves 3B in the tire lateral direction and that are in contact with the tread surface 2a.

[0127]

As described above, in the meridian cross-section, the imaginary profile line LA is the arc that passes through the edge ends 3Ba that are on the inner side of the shoulder main grooves 3B in the tire lateral direction and that are in contact with the tread surface 2a, and each of the edge ends 3 Aa and 3Aa that are on both the sides of the center main grooves 3 A adjacent to the shoulder main grooves 3B in the tire lateral direction and that are in contact with the tread surface 2a, and that has the radius of curvature whose center point is positioned on the inner side of the tread surface 2a in the tire radial direction. Further, the imaginary profile line LA may have the center point on the tire equatorial plane CL. Further, the actual profile line LB is an arc that passes through the edge ends 3Ba that are on the inner side of the shoulder main grooves 3B in the tire lateral direction and that are in contact with the tread surface 2a, and the edge ends 3Aa that are on the shoulder main groove 3B side of the center main grooves 3 A adjacent to the shoulder main grooves 3B and that are be in contact with the tread surface 2a, and that has the center point positioned on the inner side of the tread surface 2a in the tire radial direction. [0128]

According to this type of pneumatic tire 11, by the actual profile line LB projecting further to the outer side in the tire radial direction than the imaginary profile line LA in the middle land portions 4 IB, the ground contact length of the tire circumferential direction in the ground contact region can be increased compared with the case in which the imaginary profile line LA is applied. In other words, the ground contact region can be increased in the tire circumferential direction. As a result of this, the contact with the ground is improved, and the braking performance on the wet road surfaces can thus be improved. In addition, as a result of the improved contact with the ground, the uneven wear resistance performance can be improved. Further, by the actual profile line LB being formed to project further to the outer side in the tire radial direction than the imaginary profile line LA in the middle land portions 41B provided on both the sides in the tire lateral direction with the tire equatorial plane CL interposed therebetween, the above-described effects can be significantly obtained.

[0129]

Further, when the pneumatic tire 11 is mounted on a regular rim, inflated to the regular internal pressure, and loaded at 70% of the regular load, the maximum projection amount Ga, in the middle land portions 4 IB, of the actual profile line LB that projects further to the outer side in the tire radial direction than the imaginary profile line LA is preferably from 0.1 mm to 0.5 mm.

[0130]

When the maximum projection amount Ga in the middle land portions 41B is less than 0.1 mm, the projection amount of the center land portions 41B is reduced, and the contact with the ground becomes more difficult to be improved. On the other hand, when the maximum projection amount Ga in the middle land portions 41B exceeds 0.5 mm, the projection amount of the middle land portions 41B becomes excessive, and the ground contact length in the central section of the land portions is excessively increased. This causes the uneven wear of the kind in which the central section of the land portions wears away at an early stage. Thus, in order to improve both the braking performance on the wet road surfaces and the uneven wear resistance performance, the maximum projection amount Ga, to the outer side in the tire radial direction, in the middle land portions 41B is preferably from 0.1 mm to 0.5 mm.

[0131]

Further, as illustrated in FIG. 9 and FIG. 10, in the pneumatic tire 11 of the present embodiment, in the meridian cross-section, an actual profile line LD in the center land portions 41 A, which are formed as a result of being defined by each of the center main grooves 3 A, is preferably formed to project further to the outer side in the tire radial direction than the imaginary profile line LA that passes through each of the edge ends 3Aa and 3Aa that are on both the sides of the center main grooves 3 A in the tire lateral direction and that are in contact with the tread surface 2a.

[0132]

According to this type of pneumatic tire 11, by the actual profile line LD projecting further to the outer side in the tire radial direction than the imaginary profile line LA in the center land portion 41 A, the ground contact length of the tire circumferential direction in the ground contact region can be increased compared with the case in which the imaginary profile line LA is applied. In other words, the ground contact region can be increased in the tire circumferential direction. As a result of this, the contact with the ground is improved, and the braking performance on the wet road surfaces can thus be improved. In addition, as a result of the improved contact with the ground, the uneven wear resistance performance can be improved.

[0133]

Further, when the pneumatic tire 11 is mounted on a regular rim, inflated to the regular internal pressure, and loaded at 70% of the regular load, a maximum projection amount Gc, in the center land portion 41 A, of the actual profile line LD that projects further to the outer side in the tire radial direction than the imaginary profile line LA is preferably from 0.1 mm to 0.5 mm.

[0134]

When the maximum projection amount Gc in the center land portion 41A is less than 0.1 mm, the projection amount of the center land portion 41A is reduced, and the contact with the ground becomes more difficult to be improved. On the other hand, when the maximum projection amount Gc in the center land portion 41A exceeds 0.5 mm, the projection amount of the center land portion 41A becomes excessive, and the ground contact length in the central section of the land portions is excessively increased. This causes the uneven wear of the kind in which the central section of the land portions wears away at an early stage. Thus, in order to improve both the braking performance on the wet road surfaces and the uneven wear resistance performance, the maximum projection amount Gc, to the outer side in the tire radial direction, in the center land portion 41A is preferably from 0.1 mm to 0.5 mm.

[0135]

Note that, as illustrated in FIG. 10, in the pneumatic tire 11 of the present embodiment, in the meridian cross-section, profile lines of the shoulder land portions 41C provided on the outer sides of the shoulder main grooves 3B in the tire lateral direction are preferably formed on and matching with the imaginary profile line LA’ that passes through the ground contact edges T and the edge ends 3Ba and 3Bb that are on both the sides of the shoulder main grooves 3B in the tire lateral direction and that are in contact with the tread surface 2 a, and that is continuous with the imaginary profile line LA. In other words, the land portions that project further to the outer side in the tire radial direction than the imaginary profile line LA are the middle land portions 41B provided further toward the tire equatorial plane CL side than the shoulder main grooves 3B, or alternatively further include the center land portion 41 A. By the bent grooves 6 being provided, in the circumferential direction, in the middle land portions 41B that are formed as a result of being defined by the center main grooves 31A and the shoulder main grooves 3 IB, the contact with the ground in the vicinity of the center of each of the middle land portions 41B tends to decrease. Further, the middle land portions 41B provided closer to the tire equatorial plane CL tend to have a lower ground contact pressure than the shoulder land portions 41C. Accordingly, the land portions that project further to the outer side in the tire radial direction than the imaginary profile line LA are preferably the middle land portions 41B provided further toward the tire equatorial plane CL side than the shoulder main grooves 3B, or alternatively further include the center land portion 41 A.

[0136]

Here, the “ground contact edges T” refer to both the outermost edges in the tire lateral direction of the region where the tread surface 2a of the tread portion 2 of the pneumatic tire 11 contacts the road surface, when the pneumatic tire 11 is mounted on a regular rim, inflated to the regular internal pressure, and loaded at the regular load. The ground contact edges T are continuous in the tire circumferential direction.

[0137]

Incidentally, in the present embodiment, the rubber material forming the tread surface 2a of the tread portion 2 preferably has the rubber hardness (JIS-A hardness compliant with JIS-K6253 under the condition of 20°C) ranging from 62 to 68. When the rubber hardness is less than 62, the rubber strength decreases, and the uneven wear resistance tends to decrease. On the other hand, when the rubber hardness exceeds 68, the rubber flexibility decreases, and the braking performance on the wet road surfaces tends to decrease. Thus, the rubber hardness of the rubber material forming the tread surface 2a is preferably in the range from 62 to 68.

[0138]

Further, the rubber material forming the tread surface 2a of the tread portion 2 preferably has the tan δ (tangent loss) ranging from 0.60 to 0.80.

When the tan δ is less than 0.60, the wet performance, that is, the braking performance on the wet road surfaces, tends to decrease. On the other hand, when the tan δ exceeds 0.8, the rubber strength decreases, and the land portions tend to become more likely to be damaged as a result of the die release at the time of forming the tire. Thus, the tan δ of the rubber material forming the tread surface 2a is preferably in the range from 0.60 to 0.80 at the temperature of 0°C.

Examples [0139]

In the Examples, performance tests for the braking performance on the wet road surfaces, the uneven wear resistance performance, and vulcanization defects (appearance defects) were performed on a plurality of types of test tires of different conditions (see FIGS. 11 to 16).

[0140]

In those performance tests, a pneumatic tire of the form illustrated in FIG. 1 and FIGS. 2A and 2B and corresponding to the above-described first embodiment with the tire size of 195/65R15 was used as a test tire 1. This test tire 1 was assembled on a regular rim of 15x6J, inflated to the regular internal pressure (200 kPa), and mounted on a test vehicle (1400 cc, front engine front wheel drive vehicle). Further, a pneumatic tire of the form illustrated in FIG. 6 and FIGS. 7A and 7B and corresponding to the above-described second embodiment with the tire size of 215/45R17 was used as a test tire 2. This test tire 2 was assembled on a regular rim of 17><7J, inflated to the regular internal pressure (200 kPa), and mounted on a test vehicle (1400 cc, front engine front wheel drive vehicle).

[0141]

The braking performance on the wet road surfaces was evaluated by measuring the braking distance of the above-described test vehicle from a speed of 100 km/h on a wet road surface test course with a water depth of 1 mm. The measurement results are expressed as index values and evaluated with Conventional Examples 1 and 2 being assigned as the reference (100). In this evaluation, larger values are preferable.

[0142]

The uneven wear resistance performance was evaluated by performing a visual check on wear conditions after driving the above-described test vehicle on a dry road test course at an average speed of 80 km/h for 10000 km. Then, the measurement results are expressed as index values and evaluated with Conventional Examples 1 and 2 being assigned as the reference (100). In this evaluation, larger values are preferable.

[0143]

The vulcanization defects were evaluated by vulcanizing 200 units of the test tires 1 and 2, and performing a visual check on appearance defects such as damage and cracks in the land portions. Then, the measurement results are expressed as index values and evaluated with Conventional Examples 1 and 2 being assigned as the reference (100). In this evaluation, larger values are preferable.

[0144]

In the Examples illustrated in FIGS. 11 to 13, the test tires 1 were used that were based on the pneumatic tire of the form illustrated in FIG. 1 and FIGS. 2A and 2B. Compared with the pneumatic tire of the form illustrated in FIG. 1 and FIGS. 2A and 2B, in a pneumatic tire of Conventional Example 1, the first main groove was not provided with the chamfered portions, and straight line grooves extending in the tire circumferential direction were provided in place of the bent grooves. Compared with the pneumatic tire of the form illustrated in FIG. 1 and FIGS. 2A and 2B, in a pneumatic tire of Comparative Example 1, the first main groove was not provided with the chamfered portions. Meanwhile, pneumatic tires of Examples 1 to 40 were pneumatic tires of the form illustrated in FIG. 1 and FIGS. 2A and 2B, in which the first main groove was provided with the chamfered portions, and the bent grooves and the subsidiary grooves were provided.

[0145]

As shown by the test results in FIGS. 11 to 13, the pneumatic tires of Examples 1 to 40 have improved uneven wear resistance performance and vulcanization defects (appearance defects) while ensuring the braking performance on the wet road surfaces.

[0146]

In the Examples illustrated in FIGS. 14 to 16, the test tires 2 were used that were based on the pneumatic tire of the form illustrated in FIG. 6 and FIGS. 7A and 7B. Compared with the pneumatic tire of the form illustrated in FIG. 6 and FIGS. 7A and 7B, in a pneumatic tire of Conventional Example 2, the first main grooves were not provided with the chamfered portions, and straight line grooves extending in the tire circumferential direction were provided in place of the bent grooves. Compared with the pneumatic tire of the form illustrated in FIG. 6 and FIGS. 7A and 7B, in a pneumatic tire of Comparative Example 2, the first main grooves were not provided with the chamfered portions. Meanwhile, pneumatic tires of Examples 41 to 79 were pneumatic tires of the form illustrated in FIG. 6 and FIGS. 7A and 7B, in which the first main grooves were provided with the chamfered portions, and the bent grooves and the subsidiary grooves were provided.

[0147]

As shown by the test results in FIGS. 14 to 16, the pneumatic tires of Examples 41 to 79 have improved uneven wear resistance performance and vulcanization defects (appearance defects) while ensuring the braking performance on the wet road surfaces.

Reference Signs List [0148]

Pneumatic tire

Tread portion

2a Tread surface

3A Center main groove (first main groove)

3B Shoulder main groove (second main groove)

4A Center land portion (land portion)

Chamfered portion

5A Chamfer

5a Long side

5b Short side c Edge

Bent groove

6a First inclined portion 6b Second inclined portion

Subsidiary groove 5 7a First end

7b Second end A Boundary S Center line 11 Pneumatic tire

41B Middle land portion (land portion)

Claims

Claims [Claim 1]

A pneumatic tire comprising:

a first main groove provided in a ground contact central portion of a tread portion to extend along a tire circumferential direction;

a second main groove provided on an outer side of the first main groove in a tire lateral direction to extend along the tire circumferential direction;

a land portion formed as a result of being defined by the first main groove and the second main groove and being continuous in the tire circumferential direction;

a chamfered portion in which a plurality of chamfers are arranged along the tire circumferential direction, the plurality of chamfers being provided on an opening edge, on the land portion side, of the first main groove and causing a position of the opening edge to be changed diagonally with respect to the tire circumferential direction; .

a bent groove provided in the land portion, disposed side by side with the opening edge comprising the chamfered portion of the first main groove in the tire lateral direction, and provided to be bent in accordance with shapes of the chamfers of the chamfered portion while extending along the tire circumferential direction; and a subsidiary groove provided in the land portion between the second main groove and the bent groove and extending toward the bent groove in a direction intersecting with the tire circumferential direction, one end of the subsidiary groove being oriented toward the bent groove and terminated inside the land portion.
[Claim 2]

The pneumatic tire according to claim 1, wherein a groove width Wa of the bent groove is formed to be in a range from 4% to 8% with respect to a dimension W of the land portion in the tire lateral direction.
[Claim 3]

The pneumatic tire according to claim 1 or 2, wherein a dimension Wb, in the tire lateral direction, from a center line of the bent groove to an edge of the chamfered portion in the land portion is formed to be in a range from 20% to 45% with respect to the dimension W of the land portion in the tire lateral direction.
[Claim 4]

The pneumatic tire according to any one of claims 1 to 3, wherein a groove depth Ha of the bent groove is formed to be in a range from 30% to 55% with respect to a groove depth H of the first main groove.
[Claim 5]

The pneumatic tire according to any one of claims 1 to 4, wherein the chamfered portion is formed such that the chamfers comprise long sides and short sides, which are inclined with respect to the tire circumferential direction, and are formed in triangular shapes on the opening edge of the first main groove, the bent groove is formed to be bent and, comprising first inclined portions, which are long and inclined in the tire circumferential direction along the long sides of the chamfers, and second inclined portions, which are short and inclined in the tire circumferential direction along the short sides of the chamfers, an angle a of the first inclined portion with respect to the tire circumferential direction is formed to be in a range from 2° to 7°, and an angle β of the second inclined portion with respect to the tire circumferential direction is formed to be in a range from 20° to 60°.
[Claim 6]

The pneumatic tire according to any one of claims 1 to 5, wherein a dimension Wc of the chamfered portion in the tire lateral direction is formed to be in a range from 4% to 15% with respect to the dimension W of the land portion in the tire lateral direction.
[Claim 7]

The pneumatic tire according to any one of claims 1 to 6, wherein a dimension Hb of the chamfered portion in a tire radial direction is formed to be in a range from 30% to 60% with respect to the groove depth H of the first main groove.
[Claim 8]

The pneumatic tire according to any one of claims 1 to 7, wherein, in a section in which the chamfered portion and the bent groove face each other in the tire lateral direction, a dimension Wc, in the tire lateral direction, of the chamfers in the chamfered portion is formed to be equal to a bending range Wd, in the tire lateral direction, of the section of the bent groove that faces the chamfers in the tire lateral direction, and a dimension La, in the tire circumferential direction, of a single chamfer in the chamfered portion is formed to be equal to a dimension Lb, in the tire circumferential direction, which is a single bending unit in the section of the bent groove that faces the single chamfer in the tire lateral direction.
[Claim 9]

The pneumatic tire according to any one of claims 1 to 8, wherein a dimension We of the subsidiary groove in the tire lateral direction is formed to be in a range from 40% to 50% with respect to the dimension W of the land portion in the tire lateral direction.
[Claim 10]

The pneumatic tire according to any one of claims 1 to 9, wherein each of the second main grooves are provided on both sides of the first main groove in the tire lateral direction, the land portions are formed as a result of being defined by the first main groove and each of the second main grooves on both the sides of the first main groove in the tire lateral direction, the chamfered portions are provided on both the opening edges of the first main groove, the bent grooves are provided in each of the land portions, the subsidiary grooves are provided in each of the land portions, and when the pneumatic tire is mounted on a regular rim, inflated to a regular internal pressure, and loaded at 70% of a regular load, and in a state in which the tread portion is in contact with a flat ground surface on the ground, a groove opening area of the first main groove comprising the chamfered portions is formed to be larger than the groove opening area of the first main groove excluding the chamfered portions by a range from 15% to 20%.
[Claim 11]

The pneumatic tire according to any one of claims 1 to 10, wherein each of the second main grooves are provided on both the sides of the first main groove in the tire lateral direction, the land portions are formed as a result of being defined by the first main groove and each of the second main grooves on both the sides of the first main groove in the tire lateral direction, the chamfered portions are provided on both the opening edges of the first main groove, the bent grooves are provided in each of the land portions, the subsidiary grooves are provided in each of the land portions, and in each of the chamfered portions disposed on the opening edges of the first main groove, the chamfers are continuously provided in the tire circumferential direction, and boundary portions, at which the chamfers are continuous with each other, are provided to be displaced with respect to each other, in the tire circumferential direction, on each of the opening edges of the first main groove.
[Claim 12]

The pneumatic tire according to any one of claims 1 to 9, wherein the second main grooves are provided on each outer sides of the two first main grooves in the tire lateral direction, the land portions are formed as a result of being defined by the first main grooves and the second main grooves on the outer sides of the first main grooves in the tire lateral direction, the chamfered portions are only provided on the opening edges on the outer sides of the first main grooves in the tire lateral direction, the bent grooves are provided in the land portions, the subsidiary grooves are provided in the land portions, and when the pneumatic tire is mounted on a regular rim, inflated to a regular internal pressure, and loaded at 70% of a regular load, and in a state in which the tread portion is in contact with a flat ground surface on the ground, a groove opening area of the first main grooves comprising the chamfered portions is formed to be larger than the groove opening area of the first main grooves excluding the chamfered portions by a range from 8% to 13%.
[Claim 13]

The pneumatic tire according to any one of claims 1 to 12, wherein a rubber hardness of a rubber material forming a tread surface of the tread portion is set to be in a range from 62 to 68 at a temperature of 20°C.
[Claim 14]

The pneumatic tire according to any one of claims 1 to 13, wherein a tan δ of the rubber material forming the tread surface of the tread portion is set to be in a range from 0.60 to 0.80 at a temperature of 0°C.

[Claim 15]

The pneumatic tire according to any one of claims 1 to 14, wherein, in a meridian cross-section, an actual profile line in the land portion, which is formed as a result of being defined by the first main groove and the second main groove, is formed to project further to the outer side in the tire radial direction than an imaginary profile line that passes through an edge end on an inner side of the second main groove in the tire lateral direction and being in contact with the tread surface, and each of edge ends on each side of the first main groove adjacent to the second main groove in the tire lateral direction being in contact with the tread surface.

1/16

TIRE

CIRCUMFERENTIAL

DIRECTION

TIRE LATERAL DIRECTION <->

4Bb 4(4B)

4Ba 4Ab 4(4A) ) j (4(4A) 4Ab 4Ba 4Bb 4(4B) 4Aa ί 4Aa

FIG. 1

2/16

FIG. 2A

TIRE LATERAL DIRECTION / <-►

TIRE

CIRCUMFERENTIAL

DIRECTION

Γ“ I X\ QQ rlo. ZD

A

TIRE

RADIAL

DIRECTION

3/16

TIRE LATERAL DIRECTION ⁴-> !

TIRE

CIRCUMFERENTIAL

DIRECTION

Wd

4Ab 4(4A) 4Aa 4Aa 4(4A) 4Ab

FIG. 3

4/16

TIRE LATERAL DIRECTION

TIRE

RADIAL

DIRECTION

FIG. 4

5/16

TIRE LATERAL DIRECTION

4--------------.......................>

FIG. 5

6/16

TIRE LATERAL DIRECTION

1/16

FIG. 7A

TIRE LATERAL DIRECTION <->

TIRE

CIRCUMFERENTIAL

DIRECTION

FIG. 7B

TIRE

RADIAL

DIRECTION

4K41B)

Hb H

41(41 A)

SA

8/16

TIRE LATERAL DIRECTION

41(41 A)

TIRE

CIRCUMFERENTIAL

DIRECTION

V

41 Bb 4K41B) 41 Ba

FIG. 8

9/16

TIRE LATERAL DIRECTION

4->

TIRE

RADIAL

DIRECTION

41(4113}

FIG. 9

10/16

TIRE LATERAL DIRECTION

FIG. 10

11/16

Example 12 Yes Yes CO £ 1-0 27 to 33 LO Ν’ r^- to LO r- 60 Equal Equal 40 LO Displaced co 0.55 No 109 d CN o Example 11 03 Yes Yes | CO 27 to 33 LO o- r- to IO h- 30 Equal Equal 40 IO Displaced co 0.55 o 2 N- d co d CN d Example 10 CO Yes Yes I LO 27 to 33 45 LO LO 15 d co co 3 cr LU Equal 40 LO Displaced co 0.55 No CO d CN d CN d X Example S Yes Yes co £ LO 27 to 33 to O' LO IO Ν’ o co Equal i Equal d O- to Displaced co 0.55 No 107 I 103 | 102 Example 8 Yes Yes 03 £ LO 27 to 33 45 h- 60 j -rt- o CO Equal | Equal 40 LO Displaced co 0.55 No CO o V CN d x— CN d Example 7 Yes Yes Yes | LO 27 to 33 45 CN 20 | 30 Equal Equal d X)* to Displaced co 0.55 o 2 h*- d CO d co d Example 6 Yes Yes CO to 27 to 33 55 CN d CN 30 Equal Equal d LO Ό ω o 25 CL ω Q χ-* co 0.55 jd co o CN O V“ co d Example 5 Yes Yes co £ LO 27 to 33 o co ΓΝ o CN 'rt- d co CO 3 cr LU Equal 40 to Displaced co 0.55 No 106 | 104 co d Example 4 Yes Yes CO £ to : 27 to 42 o co CN O CN O' o co Equal Equal 40 to Displaced x— to 0.55 No CD d x~* | 105 co d Example 3 CO CO ω > co to 26 to 31 o co CN d CN tJ- 30 Equal Equal d rt- LO Displaced V co 0.55 co d | 103 co o Example 2 Yes Yes CO £ CO 26 to 31 o co CN d CN d co Equal Equal 40 LO Displaced co 0.55 o X co d co o | 103 Example 1 Yes Yes CO O' 26 to 31 o co CN O CN N- o co Equal Equal 40 LO Displaced co 0.55 No LO O co d | 103 Comparative Example 1 o 2: Yes 03 £ 26 to 31 CD co CN d CN 1 • 40 1 1 co 0,55 No 103 | 103 LO CD Conventional Example 1 o 2 o 2 co Φ 25 30 - 1 1 1 40 s 0.55 No 100 o o d d Presence of chamfered portion in first main groove Presence of bent groove (When there is no bent groove, straight line groove is present) | Presence of subsidiary groove | Relationship between bent groove Wa and land portion W {%) Relationship between bent groove center line Wb and land portion W (%) Relationship between bent groove Ha and first main groove H {%) | Angle a (’) of bent groove | Angle β (°) of bent groove Relationship between chamfered portion Wc and land portion W (%) Relationship between chamfered portion Hb and first main groove H (%) Relationship between chamfered portion Wc and bent groove Wd (Equal or different) Relationship between chamfered portion La and bent groove Lb (Equal or different) Relationship between subsidiary groove We and land portion W (%) | Difference in groove areas (%) Arrangement of chamfers in chamfered portion Rubber hardness of rubber material of tread surface Tan 6 of rubber material of tread surface Projection of actual profile LA of shoulder land portion Braking performance on wet road surfaces | Wear resistance performance | Vulcanization defects

FIG. 11

12/16

Example 26 Yes Yes Yes I LO 27 to 33 45 Γ-— to to 20 43 Equal Equal LO r— Displaced to LO LO eS 0 105 0 0 Example 25 Yes Yes (Λ ω > LO 27 to 33 LO xf Γ'- 55 I CN 43 Equal Equal to r- Displaced <5 0.55 No CN O CN O co 0 'C— Example ! 24 | Yes Yes co LO 27 to 33 45 σ 70 I <O Xt Equal Equal in xr jx- Displaced co to to 0 No <23 O O Example I 23 ] Yes Yes CA £ LO 27 to 33 45 = <=> I-* co XT Equai Equai lo r— Ό Φ U ra CX <A Q s 0.55 No to <23 CO <23 Example 22 Yes Yes Yes | lo 27 to 33 o co r- LO to Ϊ— 43 Equal ra cr LU 45 Γ- Displaced V CO 0.55 No 105 5 O <2> Example 21 Yes Yes CA LO 27 to 33 LO CXI ϊ*- LO LO h- 43 Equal ra rs cr LU LO xj* r— CJ <u o ra ex <a O to 0.55 0 Z CO 0 CN O CO 0 Example 20 Yes CA £ CA £ to 10 to 18 to r— 55 I r— 43 Equal *ra cr LU lo O’ h- Displaced co 0.55 0 z r^- 0 O | 103 Example 19 Yes Yes Yes ) o 27 to 33 to r- I 55 I L- 43 Equal Equal to xT f*- Ό CD O 0. ca O to 0.55 0 z 00 <=> T™ O | 103 Example 18 Yes <A 2 CA CN 27 to 33 45 r— 55 | r— CO xT Equai Equai to xi· i-· Displaced to 0.55 No i-- C2> | 105 CO 0 V™ Example 17 Yes Yes CA £ IO 27 to 33 LO Μ r- LO LO h- CO Equal Equal lo Displaced to 0.55 0 cr> 0 0 CN 0 Example 16 Yes CA CD > CA £ «Ο 27 to 33 45 h- 55 j h- co xj- Equal Equal lo xr 0 CN Displaced to 0.55 No 0 0 <23 T CN <23 Example 15 Yes Yes Yes | LO 27 to 33 45 r-. IO LO r- 43 Equal ra 23 cr LU LO XT LO Displaced to 0.55 No CO O CN C23 | 103 Example 14 Yes Yes Yes | LO 27 to 33 to IO to r- 43 Equal Equal OS to | Displaced co 0.55 No 109 O | 103 Example 13 Yes Yes Yes | LO 27 to 33 45 r·*-- to to t» CO xf Equal Equal 0 xf- to Displaced' co 0.55 No CO 0 CN O v· CN O Presence of chamfered portion in first main groove Presence of bent groove (When there is no bent groove, straight line groove is present) | Presence of subsidiary groove Relationship between bent groove Wa and land portion W {%) Relationship between bent groove center line Wb and land portion W (%) | Relationship between bent groove Ha j and first main groove H (%) ! Angle a (°) of bent groove j Angle β (°) of bent groove Relationship between chamfered portion Wc and land portion W (%) Relationship between chamfered portion Hb and first main groove H (%) Relationship between chamfered portion Wc and bent groove Wd (Equal or different) Relationship between chamfered portion La and bent groove Lb (Equal or different) Relationship between subsidiary groove We and land portion W (%) | Difference in groove areas (%) Arrangement of chamfers in chamfered portion Rubber hardness of rubber material of tread surface Tan δ of rubber materia! of tread surface Projection of actual profile LA of shoulder land portion Braking performance on wet road surfaces I Wear resistance performance I Vulcanization defects

FIG. 12

13/16

Example 40 Yes Yes to £ LO 27 to 33 45 Γ- LO to Γ-— 43 Equal Equal LO xf 30 Displaced CO 0.55 Yes r^- o x— 103 CD Example 39 Yes Yes to 2 LO 27 to 33 LO Γ·’— 55 I r~- CO xf* Equal CO 3 CF L±J ⁴⁵ o co Not displaced co 0.85 No Ο o V CD CD Example 38 Yes Yes co ? LO 27 to 33 LO xj- ί- 55 I 43 Equal Equai 45 I 30 Not displaced co 0.8 No CO CD CD ν’ CD x— Example 37 Yes Yes co £ LO 27 to 33 45 u- 55 I CO XT Equal Equal to XF o co Not displaced co 0.6 No CD CD CD CD Example 36 Yes Yes Yes I IO 27 to 33 LO r- 55 | r— 43 Equal Equal 45 cd co Not displaced .... 89 | 0.55 No 104 to CD 5 Example 35 Yes Yes Yes | LO 27 to 33 45 I 55 | r— CO xt Equal Equal 45 CD CO Not displaced CM CO 0.55 o z: in o CM CD 5 Φ Cu £Z χΤ ra °° X LU Yes Yes to £ LO 27 to 33 45 r- LO LO r- co Equal Equal tn CD <O Not displaced 69 0.55 a z to o CO o o Example 33 Yes Yes co LO CO to o CM 45 r- 55 l r- 43 Equal Equal LO xf CD CO Not displaced CO 0.55 o z: in CD CD CD Example 32 Yes CO Yes | LO 27 to 33 45 t-W LO LO CO Xj· j Equal Equal LO XJ* I 30 i Displaced co 0.55 o 2 m CD CM CD CD Example 31 Yes Yes Yes | LO 27 to 33 45 r- LO LO r·^ CO xf Equal Equal to xF o Displaced E 0.55 o a: CM CD xf CD | 102 Example 30 Yes Yes co Φ > LO 27 to 33 LO xt t·*- 55 I h- ⁴³ Equal CO σ LU LO LO i'·’ Displaced CD 0.55 o 105 O | 102 Example 29 Yes Yes Yes j LO : 27 to 33 45 r— 55 j P— 43 CO cr UJ Equal LO CO h Ό Φ O Cl co o CO SS‘0 o z: 102 | 102 CD Example 28 Yes Yes Yes j LO 27 to 33 45 Γ*** io to 65 TS d cr LU Equal LO F- Displaced CO 0.55 No 105 CD x— E Example 27 Yes Yes Yes | LO 27 to 33 LO LO LO LO CM Equal Equal LO xr r- Displaced V CO 0.55 o z: CM CD x— | 103 | 103 Presence of chamfered portion in first main groove Presence of bent groove (When there is no bent groove, straight line groove is present) | Presence of subsidiary groove | Relationship between bent groove Wa and land portion W (%) Γ Relationship between bent groove | center line Wb and land portion W {%) Relationship between bent groove Ha and first main groove H (%) j Angle σ (°) of bent groove | j Angle β(’) of bent groove | Relationship between chamfered portion Wc and land portion W (%) Relationship between chamfered portion Hb and first main groove H (%) Relationship between chamfered portion Wc and bent groove Wd (Equal or different) Relationship between chamfered portion La and bent groove Lb (Equal or different) Relationship between subsidiary groove We and land portion W (%) | Difference in groove areas (%) Arrangement of chamfers in chamfered portion Rubber hardness of rubber material of tread surface Tan δ of rubber material of tread surface Projection of actual profile LA of shoulder land portion Braking performance on wet road surfaces | Wear resistance performance | Vulcanization defects

FIG. 13

14/16

Example 52 Yes Yes Yes I lo 27 to 33 45 Γ'-'· 55 I t-· 1 09 Equal Equal 1 40 CO s 0.55 o 2 CD CD CN CD Example 51 Yes Yes ω £ to 27 to 33 45 1 55 I r— o co Equal Equal cd nJ- co x— CO 0.55 No r- o CO CD CN O Example 50 Yes Yes to 2 LO 27 to 33 45 r- 1 55 J to 30 Equal Equal 40 co <s to to o o 2 co CD I 102 CN CD Example 49 Yes Yes cn £ ID 27 to 33 to N- 1 55 1 30 Equal Equal 40 co CO 0.55 No CD | 103 CN θ Example 48 £ Yes £ to 27 to 33 45 Γ— cd co nr CD co Equal Equal 40 co 5 0.55 o 2 OD CD CN O | 102 Example 47 Yes Yes to £ LO 27 to 33 45 CN o CN Ν^- 30 Equal Equal o *nr co co 0.55 O 2 h— CD | 103 | 103 Example 46 Yes Yes Yes | to 27 to 33 55 CN 1 20 ’Ν' o co Equal Equai 40 co to 0.55 No oo CD | 102 1.........103 Example 45 Yes Yes Yes | LO 27 to 33 o co CN θ CN nt· 30 Equal «3 Σ3 cr LU cd nr oo co 0.55 No CO CD •c* nt O CO CD x— Example 44 Yes Yes cn LO 27 to 42 30 CN 1 20 1 nt 30 «5 3 σ LU Equal o nr oo co 0.55 No CO O to CD x— OO CD Example 43 Yes Yes (Λ £ LO 26 to 31 cd CO CN o CN nr o co Equal Equai o nT oo co 0.55 No CO CD | 103 | 103 ih X LU Yes Yes Yes I oo 26 to 31 cd CO CN cd CN nf cd co rtJ C3 Ul «J ZJ C3* LU 40 oo co 0,55 No OO CD CO CD x— CO o Example 41 Yes Yes Yes I n· 26 to 31 o co CN o CN nJ- 30 Equal Equal o nr co CO 0.55 No 105 | 103 | 103 Comparative Example 2 o 2 Yes CO £ n]· 26 to 31 30 CN cd CN 1 t cd nt I co LO LO cd o 2 CO o CO CD LO O Conventional Example 2 No No I SSA nt 25 30 1 t 1 1 CD nt r co 0.55 No CD CD P ioo I ioo Presence of chamfered portion in first main groove Presence of bent groove (When there is no bent groove, straight line groove is present) [Presence of subsidiary groove | Relationship between bent groove Wa and land portion W (%) IRelationship between bent groove (center line Wb and land portion W (%) Relationship between bent groove Ha and first main groove H (%) O > o o cn C <D JD O σ O <3> cn sz <r [Angle p (°) of bent groove [Relationship between chamfered portion Wc and land portion W (%) IRelationship between chamfered portion Hb and first main groove H (%) Relationship between chamfered portion Wc and bent groove Wd (Equa! or different) Relationship between chamfered portion La and bent groove Lb (Equai or different) Relationship between subsidiary groove We and land portion W (%) [Difference in groove areas (%) Rubber hardness of rubber material of tread surface Tan 5 of rubber material of tread surface Projection of actual profile LA of middle land portion Braking performance on wet road (surfaces jWear resistance performance [Vulcanization defects

FIG. 14

15/16

Example j 66 Yes | Yes Yes I tn 27 to 33 to •M· h- 55 I o 04 43 Equal Equal tn Xt* era r-* to 0.55 Q ZZ 105 V o s Example 65 Yes Yes I sax in 27 to 33 45 h— 55 I 04 43 Equal Equal 45 era V to 0.55 O 2 102 OJ era co era Example 64 Yes Yes Yes I LO 27 to 33 to o 1 ⁷⁰ 1 h- CO Equal Equal in O' o to 0.55 No era V S o Example 63 CO £ Yes (Λ £ LO 27 to 33 45 - era r— 43 Equal Equal 45 era CD 0.55 o o in era V co era Example 62 Yes Yes Yes | IO 27 to 33 o to h- 55 | r— 43 to ra cr LLf Equal 45 o <s 0.55 No 105 <ra o era Example 61 Yes Yes CO £ io 27 to 33 25 r- 55 | h— 43 Equal Equal LO O’ era to 0,55 o CO o V— 04 era | 103 Example 60 Yes Yes 60 £ LO 10 to 18 to IO to CO *4* Equal Equal 45 era s 0.55 No 107 o | 103 Example 59 Yes Yes Yes | O 27 to 33 45 55 | b- CO -cj* Equal Equal 45 era to 0.55 No 108 era CO o Example 58 Yes Yes CM 27 to 33 to O' h- 55 ] CO 'tf' Equal Equal 45 era to SS’O o ί'·'- o tn o co «ra v— Example 57 Yes Yes Yes | LO 27 to 33 to ’’T r·' Γ 55 1 r— CO Equal j Equal in O' CD to 0.55 No 109 era | 102 Example 56 Yes Yes Yes | to 27 to 33 tn 55 ! r— CO Equal ra ra cr □J 45 CO to 0.55 No era V era era OJ O v— Example 55 Yes Yes 60 to 27 to 33 to r— | 55 | 43 Equal Equal LO O' co CO 0.55 No 108 | 102 | 103 Example 54 Yes Yes Yes | io 27 to 33 45 r— to to 43 Equal Equal 50 co co 0.55 o 2: 03 era CD CO «ra V Example j 53 | Yes Yes ω to 27 to 33 45 55 43 ra 23 O* LU Equal era oo to 0.55 o 2: 108 OJ o CM era Presence of chamfered portion in first main groove Presence of bent groove (When there is no bent groove, straight line groove is present) | Presence of subsidiary groove | Relationship between bent groove Wa and land portion W (%) Relationship between bent groove center line Wb and land portion W {%) Relationship between bent groove Ha and first main groove H (%) ) Angle cr (°) of bent groove ( | Angle β (°) of bent groove | Relationship between chamfered portion Wc and land portion W (%) Relationship between chamfered portion Hb and first main groove H (%) Relationship between chamfered portion Wc and bent groove Wd (Equal or different) Relationship between chamfered portion La and bent groove Lb (Equal or different) Relationship between subsidiary groove We and land portion W (%) I Difference in groove areas {%) Rubber hardness of rubber material of tread surface Tan δ of rubber material of tread surface Projection of actual profile LA of middle land portion Braking performance on wet road surfaces | Wear resistance performance | Vulcanization defects

FIG. 15

16/16

Example 79 Yes Yes w >- io CO co o CM 45 p— 55 1 P- co Equal 03 3 cr LU LO ·<· m T~ tO 0.55 Yes P- o M- <3 5 Example 78 Yes Yes ω £ in 27 to 33 45 P— n n P- 5 Equal *nj 3 cr LU n O’ n to 0.85 No <3 CM CD CD CD Example 77 Yes Yes ω in 27 to 33 45 P«W 55 P— 43 Equal Equal in -d- in to 0.8 No CO cd CM CD CD Example 76 Yes Yes co £ m 27 to 33 in p- in in P— 43 Equal Equal in «r in to 0.6 o Z 106 I 102 s Example 75 Yes Yes Yes j in CO co o p- CM 45 P- 55 j P-. CO 03 3 CP LU CO 3 cr LU 45 n co to 0.55 No 104 | 104 CD Example 74 Yes Yes co £ tn 27 to 33 45 P-- n n r— 43 Equal Equal 45 m CM to 0.55 o 105 | 103 CD Example 73 Yes Yes co ? n 27 to 33 n P- n n p- CO •'Cf Equal Equal tn *Cp in <J3 to SS'O No 103 WH I s Example 72 Yes Yes co £ m 27 to 33 n O’ P* in in P- 43 Equai Equal 45 in to 0.55 No in o | 102 CD Example 71 Yes C?> to £ m 27 to 33 m O’ p- 1 55 I P- CO Equal Equal n •rt* in to m in cd o CM θ 'T CD CM CD Example 70 Yes Yes to 2 m 27 to 33 n o- P- 1 ss | P- co ^p Equal Equal in n cd v· s 0.55 o z 105 O CM O Example 69 Yes Yes Yes in 27 to 33 45 P- n n P— 43 Equal Equal 35 CD to 0.55 o z 102 | 102 T“ <3 Example 68 Yes Yes CO tn 27 to 33 45 P·— 55 ) P^ in to Equal Equal 45 CD to m tn o o z 105 CD O Example 67 Yes £ co £ in 27 to 33 n •<5p P- in n P- 25 Equal Equai tn ««3· CD to SS'O No CM O CO O CO o j Presence of chamfered portion in first I main groove Presence of bent groove (When there is no bent groove, straight line groove is present) | Presence of subsidiary groove j Relationship between bent groove Wa and land portion W (%) Relationship between bent groove center line Wb and land portion W (%) Relationship between bent groove Ha and first main groove H (%) | Angie a (°) of bent groove | Angie β (°) of bent groove Relationship between chamfered portion Wc and land portion W (%) Relationship between chamfered portion Hb and first main groove H (%) Relationship between chamfered portion Wc and bent groove Wd (Equal or different) Relationship between chamfered portion La and bent groove Lb (Equal or different) Relationship between subsidiary groove¹ We and land portion W (%) | Difference in groove areas (%) Rubber hardness of rubber material of tread surface Tan 5 of rubber material of tread surface Projection of actual profile LA of middle land portion Braking performance on wet road surfaces j Wear resistance performance I Vulcanization defects

FIG. 16