tire

Abstract

This tire provides improved handling stability while maintaining good wet performance. [Solution] In a tire having a tread portion 1 that extends in the circumferential direction and forms an annular shape, the tread portion 1 has a groove portion 10 including a plurality of lug grooves 13 that extend in the tire width direction, and a projection 14 is formed on at least one side wall of at least one of the plurality of lug grooves 13, and the total area Sg1 (mm) when the groove portion 10 is viewed from the outside in the radial direction of the tire 2 ) and the sum of the areas of the projection 14 when viewed from the outer side in the radial direction of the tire, So1 (mm 2 The glass transition temperature Tg (°C) of the rubber composition constituting the tread portion 1 and the loss tangent tanδ of the rubber composition constituting the tread portion 1 at 0°C satisfy the relationship -4.0 ≤ (Sg1 / So1) × (tanδ / Tg) ≤ -0.05.

Description

[Technical Field]

[0001] The present invention relates to a tire having lug grooves extending in the tire width direction in the tread portion, and more particularly to a tire that improves handling stability while maintaining good wet performance. [Background technology]

[0002] In tires, to ensure wet performance, the tread is formed with multiple main grooves extending in the circumferential direction and multiple lug grooves extending in the width direction of the tire. In such tires, not only during braking and driving but also during normal driving, the circumferential force applied to the tread causes the side walls of the lug grooves extending in the width direction to deform in a way that causes them to collapse. When the side walls of the lug grooves collapse during driving, the handling stability decreases.

[0003] Therefore, in order to prevent such inconveniences, it has been proposed to provide protrusions on the side walls of the lug grooves to suppress deformation of the side walls of the lug grooves (see, for example, Patent Documents 1 to 3). By providing protrusions on the side walls of the lug grooves in this way, it is possible to suppress deformation that causes the side walls of the lug grooves to collapse during driving, thereby improving handling stability. However, when protrusions are provided in the lug grooves, there is a problem that drainage performance is reduced and wet performance at high speeds is impaired. In addition, in the case of all-season tires and snow tires, when the rubber of the tread hardens while driving on dry or wet roads at low temperatures, the adhesion to the road surface decreases, and the effect of suppressing the collapse of the side walls of the lug grooves by the protrusions may be impaired. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2004-351991 [Patent Document 2] Japanese Patent Publication No. 2016-88288 [Patent Document 3] Japanese Patent Publication No. 2016-107712 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The object of the present invention is to provide a tire that improves handling stability while maintaining good wet performance. [Means for solving the problem]

[0006] To achieve the above objective, the present invention provides a tire having a tread portion that extends in the circumferential direction of the tire and forms an annular shape, wherein the tread portion has a groove portion including a plurality of lug grooves that extend in the width direction of the tire, and a projection is formed on at least one side wall of at least one of the plurality of lug grooves, and the total area Sg1(mm²) of the groove portion when viewed from the outside in the radial direction of the tire 2 ) and the sum of the areas of the projections when viewed from the outer side in the radial direction of the tire, So1 (mm²) 2 The present invention is characterized in that the glass transition temperature Tg (°C) of the rubber composition constituting the tread portion and the loss tangent tanδ of the rubber composition constituting the tread portion at 0°C satisfy the relationship -4.0 ≤ (Sg1 / So1) × (tanδ / Tg) ≤ -0.05. [Effects of the Invention]

[0007] The inventors of the present invention conducted extensive research on the protrusions formed on the side walls of lug grooves and discovered that by optimizing the glass transition temperature Tg (°C) and the loss tangent tanδ at 0°C of the rubber composition constituting the tread portion according to the proportion of protrusions, it is possible to improve wet performance and handling stability in a balanced manner, leading to the present invention.

[0008] In other words, in the present invention, the tread portion has a groove portion including a plurality of lug grooves extending in the tire width direction, a projection is formed on at least one side wall of at least one of the plurality of lug grooves, and the total area Sg1(mm²) of the groove portion when viewed from the outside in the tire radial direction2 ) and the sum of the areas of the protrusions when viewed from the outside in the radial direction of the tire, So1(mm 2 ) and the glass transition temperature Tg (°C) of the rubber composition constituting the tread and the loss tangent tanδ of the rubber composition constituting the tread at 0°C satisfy the relationship -4.0 ≤ (Sg1 / So1) × (tanδ / Tg) ≤ -0.05, thereby improving handling stability while maintaining good wet performance. More specifically, when the value of So1 increases and the value of (Sg1 / So1) decreases, handling stability improves, but wet performance decreases, so the value of tanδ is increased based on the above relationship to compensate for this. Also, when the value of So1 decreases and the value of (Sg1 / So1) increases, wet performance improves, but handling stability decreases, so the value of Tg is increased based on the above relationship to compensate for this.

[0009] In the present invention, the sum of the areas of the lug grooves Sg2(mm²) is the area of ​​the lug grooves projected onto a plane perpendicular to the tread surface of the tread portion, passing through the groove width center position of each lug groove having a projection. 2 ) and the sum of the areas of the protrusions projected onto a plane perpendicular to the tread surface through the groove width center position of each lug groove having a protrusion So2(mm 2 It is preferable that the glass transition temperature Tg (°C) and the loss tangent tanδ satisfy the relationship -0.4 ≤ (Sg2 / So2) × (tanδ / Tg) ≤ -0.02. This makes it possible to improve handling stability while maintaining good wet performance. More specifically, when the value of So2 increases and the value of (Sg2 / So2) decreases, handling stability improves, but wet performance decreases, so the value of tanδ is increased based on the above relationship to compensate for this. Also, when the value of So2 decreases and the value of (Sg2 / So2) increases, wet performance improves, but handling stability decreases, so the value of Tg is increased based on the above relationship to compensate for this.

[0010] In this invention, the average value of the cross-sectional area of ​​the lug groove in a plane that passes through the centroid of each projection and is perpendicular to the extension direction of each lug groove, and is also perpendicular to the tread surface of the tread portion, is Sg3(mm2 ) and the average value So3 (mm of the cross-sectional area of the protrusions in a plane that is orthogonal to the extension direction of each lug groove and orthogonal to the tread surface of the tread portion, passing through the centroid of each protrusion 2 ) and the glass transition temperature Tg (°C) and the loss tangent tanδ preferably satisfy the relationship of -0.5 ≤ (Sg3 / So3) × (tanδ / Tg) ≤ -0.01. Thereby, while maintaining good wet performance, the handling stability can be improved. More specifically, when the value of So3 increases and the value of (Sg3 / So3) decreases, the handling stability is improved while the wet performance deteriorates. Therefore, in order to compensate for this, the value of tanδ is increased based on the above relational expression. Also, when the value of So3 decreases and the value of (Sg3 / So3) increases, the wet performance becomes good while the handling stability deteriorates. Therefore, in order to compensate for this, the value of Tg is increased based on the above relational expression.

[0011] In the present invention, in a tire having a mounting direction specified for a vehicle and a display portion for displaying the mounting direction, and the tread portion having an outer region located outside the vehicle with respect to the tire equator and an inner region located inside the vehicle with respect to the tire equator, the total area Sgα (mm of the groove portions included in the outer region when viewed from the outer side in the tire radial direction 2 ) and the total area Soα (mm of the protrusions included in the outer region when viewed from the outer side in the tire radial direction 2 ) and the total area Sgβ (mm of the groove portions included in the inner region when viewed from the outer side in the tire radial direction 2 ) and the total area Soβ (mm of the protrusions included in the inner region when viewed from the outer side in the tire radial direction 2 ) preferably satisfy the relationship of -17 ≤ Sgα / Soα - Sgβ / Soβ ≤ 17. Thereby, while maintaining good wet performance, the handling stability can be improved. Also, within the range allowed by the above relational expression, it is possible to adjust the contribution degrees to the wet performance or the handling stability of the outer region and the inner region.

[0012] In the present invention, it is preferable that the protrusions are provided on the groove walls on one side in the tire circumferential direction of the lug groove and the groove walls on the other side in the tire circumferential direction of the lug groove. That is, with respect to the rotation of the tire, the protrusions provided on the groove wall on one side (for example, the indentation side) in the tire circumferential direction of the lug groove and the protrusions provided on the groove wall on the other side (for example, the kicking-out side) in the tire circumferential direction of the lug groove are mixed, thereby effectively suppressing the collapse of the groove walls of the lug groove and enhancing the effect of improving the handling stability.

[0013] In the present invention, it is preferable that the depth D of the lug groove and the distance Da from the centroid of the protrusion to the groove bottom of the lug groove satisfy the relationship of 0.1 ≦ Da / D ≦ 0.7, and the groove width Gw of the lug groove and the height Ph of the protrusion satisfy the relationship of 1.4 ≦ Gw / Ph ≦ 3.3. Thereby, while minimizing the influence of the protrusions on the wet performance, the collapse of the side walls of the lug groove can be effectively suppressed and the effect of improving the handling stability can be enhanced.

[0014] In the present invention, it is preferable that the protrusions are provided in 50% or more of all the lug grooves formed in the tread portion. Thereby, the effect of improving the handling stability can be sufficiently obtained.

[0015] In the present invention, the tread portion has a plurality of main grooves extending in the tire circumferential direction, and a plurality of rows of land portions including a center land portion located on the tire equator and a shoulder land portion located on the outermost side in the tire width direction are partitioned by these main grooves. It is preferable that the number of lug grooves having protrusions in the shoulder land portion is 150% or more of the number of lug grooves having protrusions in the center land portion. Thereby, the effect of improving the handling stability can be enhanced.

[0016] The tire of the present invention is preferably a pneumatic tire, but may also be a non-pneumatic tire. In the case of a pneumatic tire, it can be filled with air, an inert gas such as nitrogen, or other gases inside.

[0017] In this invention, the area values ​​(Sg1, So1, Sg2, So2, Sg3, So3, Sgα, Soα, Sgβ, Soβ) are all measured within the contact area of ​​the tread when the tire is mounted on a standard rim and filled to the standard internal pressure (in the case of a pneumatic tire). The contact area in this invention is defined by the contact width in the axial direction of the tire that is formed when the tire is mounted on a standard rim, filled to the standard internal pressure (in the case of a pneumatic tire), placed vertically on a plane, and a standard load is applied. "Standard rim" refers to the rim specified for each tire in the standard system that includes the standard on which the tire is based. For example, it is the standard rim for JATMA, the "Design Rim" for TRA, or the "Measuring Rim" for ETRTO. "Standard internal pressure" refers to the air pressure corresponding to the maximum load capacity specified for each tire in the standard system that includes the standard on which the tire is based. "Regular load" is the load equivalent to 88% of the maximum load capacity specified for each tire in the standards system, including the standards on which the tire is based.

[0018] In this invention, the loss tangent tanδ is measured in accordance with JIS-K6394 using a dynamic viscoelasticity measuring device under the conditions of a frequency of 20 Hz, static strain of 10%, dynamic strain of ±0.5%, and temperature of 0°C. The glass transition temperature Tg is measured in accordance with JIS-K6240 using differential scanning calorimetry (DSC) to measure a thermogram at a heating rate of 20°C / min, and is detected as the temperature at the midpoint of the transition region. If there are multiple transition regions in the thermogram, the midpoint of the largest transition region is taken as the glass transition temperature Tg of the rubber composition. Furthermore, if the tread portion has a multilayer structure, the maximum value of the loss tangent tanδ is adopted, and the minimum value of the glass transition temperature Tg is adopted. [Brief explanation of the drawing]

[0019] [Figure 1] This is a meridian cross-sectional view showing a pneumatic tire according to an embodiment of the present invention. [Figure 2] Figure 1 is an unfolded diagram showing the tread pattern of a pneumatic tire. [Figure 3] This is a longitudinal cross-sectional view showing a lug groove with a protrusion. [Figure 4] This is an explanatory diagram illustrating the method for measuring the total area of ​​the lug grooves Sg2 and the total area of ​​the protrusions So2. [Figure 5] This is a cross-sectional view showing a lug groove with a protrusion. [Figure 6] This is an explanatory diagram illustrating the measurement method for the average cross-sectional area Sg3 of the lug groove and the average cross-sectional area So3 of the protrusions. [Figure 7] This is a cross-sectional view showing a lug groove with a protrusion. [Figure 8] This is a cross-sectional view showing a lug groove with a protrusion. [Figure 9] This is an exploded view showing the tread pattern of a pneumatic tire according to another embodiment of the present invention. [Figure 10] This is an exploded view showing the tread pattern of a pneumatic tire according to yet another embodiment of the present invention. [Figure 11] This is an exploded view showing the tread pattern of a pneumatic tire according to yet another embodiment of the present invention. [Figure 12] This is an exploded view showing the tread pattern of a pneumatic tire according to yet another embodiment of the present invention. [Figure 13] This is an exploded view showing the tread pattern of a pneumatic tire according to yet another embodiment of the present invention. [Modes for carrying out the invention]

[0020] The configuration of the present invention will be described in detail below with reference to the attached drawings. Figures 1 to 8 show a pneumatic tire according to an embodiment of the present invention.

[0021] As shown in Figure 1, the pneumatic tire of this embodiment comprises a tread portion 1 that extends in the circumferential direction of the tire and forms an annular shape, a pair of sidewall portions 2, 2 arranged on both sides of the tread portion 1, and a pair of bead portions 3, 3 arranged radially inward of these sidewall portions 2.

[0022] A carcass layer 4 is mounted between a pair of bead sections 3, 3. This carcass layer 4 includes multiple reinforcing cords extending in the radial direction of the tire, which are folded back from the inside to the outside of the tire around the bead core 5 located in each bead section 3. A bead filler 6 made of a rubber composition with a triangular cross-section is placed on the outer circumference of the bead core 5.

[0023] On the other hand, multiple belt layers 7 are embedded on the outer circumference of the carcass layer 4 in the tread portion 1. These belt layers 7 include multiple reinforcing cords that are inclined with respect to the tire circumferential direction, and the reinforcing cords are arranged to intersect each other between layers. In the belt layers 7, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set to, for example, a range of 10° to 40°. Steel cords are preferably used as the reinforcing cords of the belt layers 7. On the outer circumference of the belt layers 7, at least one belt cover layer 8 is arranged, in which the reinforcing cords are arranged at an angle of, for example, 5° or less with respect to the tire circumferential direction, for the purpose of improving high-speed durability. Organic fiber cords such as nylon or aramid are preferably used as the reinforcing cords of the belt cover layer 8.

[0024] The above-described tire internal structure is a typical example for pneumatic tires, but is not limited to this. In addition, a tread rubber layer R1 is placed outside the belt layer 7 and belt cover layer 8 in the tread section 1, a side rubber layer R2 is placed outside the carcass layer 4 in the sidewall section 2, and a rim cushion rubber layer R3 is placed outside the carcass layer 4 in the bead section 3.

[0025] As shown in Figure 2, the tread portion 1 has four main grooves 11 extending in the circumferential direction of the tire. These main grooves 11 divide the tread portion 1 into five rows of land portions 12. The five rows of land portions 12 include a center land portion 12A located on the tire equator CL, a pair of intermediate land portions 12B, 12B located on both sides of the center land portion 12A, and a pair of shoulder land portions 12C, 12C located on the outermost side in the tire width direction. Each of the shoulder land portions 12C has multiple lug grooves 13 extending in the tire width direction, spaced apart in the circumferential direction of the tire. The groove portion 10 formed in the tread portion 1 encompasses the main grooves 11 and the lug grooves 13. The lug grooves 13 may be formed in the center land portion 12A or the intermediate land portions 12B. The lug grooves 13 may divide each land portion 12, or they may terminate inside each land portion 12. However, it is preferable that the lug groove 13 has a length of 30% or more of the width of each land portion 12 and that its angle with respect to the tire circumferential direction is 60° or more. In addition, the groove width of the lug groove 13 must be 1.6 mm or more, preferably in the range of 2.0 mm to 4.0 mm, and the groove depth must be 2.0 mm or more. Each lug groove 13 has a pair of side walls 13a, 13b that face each other.

[0026] As shown in Figures 3 and 5, in the shoulder land portion 12C, a projection 14 is formed on one side wall 13b of the lug groove 13, projecting toward the other side wall 13a. Note that if a lug groove 13 is formed in the center land portion 12A or the intermediate land portion 12B, the projection 14 may also be provided on the lug groove 13 formed in the center land portion 12A or the intermediate land portion 12B.

[0027] In the above-described pneumatic tire, the total area Sg1(mm²) of the groove portion 10 including the lug groove 13 when viewed from the outer side in the radial direction of the tire. 2 ) and the sum of the areas of the projection 14 when viewed from the outer side in the radial direction of the tire, So1 (mm 2The relationship between the glass transition temperature Tg (°C) of the rubber composition constituting the tread rubber layer R1 of the tread portion 1 and the loss tangent tanδ of the rubber composition constituting the tread rubber layer R1 of the tread portion 1 at 0°C satisfies -4.0 ≤ (Sg1 / So1) × (tanδ / Tg) ≤ -0.05. The total area Sg1 of the groove portion 10 and the total area So1 of the protrusions 14 are the sum of the areas measured over the entire circumference of the tire in the contact area defined between a pair of contact ends E, E.

[0028] As described above, the total area Sg1(mm²) of the groove 10 when viewed from the outside in the radial direction of the tire. 2 ) and the sum of the areas of the projection 14 when viewed from the outer side in the radial direction of the tire, So1 (mm 2 ) and the glass transition temperature Tg (°C) of the rubber composition constituting the tread portion 1 and the loss tangent tanδ of the rubber composition constituting the tread portion 1 at 0°C satisfy the relationship -4.0 ≤ (Sg1 / So1) × (tanδ / Tg) ≤ -0.05, thereby improving handling stability while maintaining good wet performance. In other words, when the value of So1 increases and the value of (Sg1 / So1) decreases, handling stability improves, but wet performance decreases, so to compensate for this, the value of tanδ is increased based on the above relationship. The loss tangent tanδ at 0°C is an index that correlates with wet performance when driving on a wet road surface at high speeds. Also, when the value of So1 decreases and the value of (Sg1 / So1) increases, wet performance improves, but handling stability decreases, so to compensate for this, the value of Tg is increased based on the above relationship. The glass transition temperature Tg is an index that correlates with handling stability when driving on a dry road surface under normal conditions.

[0029] Here, if the value of (Sg1 / So1)×(tanδ / Tg) falls outside the above range, the effect of improving wet performance and handling stability in a balanced manner becomes insufficient. Preferably, the relationship -2.3≦(Sg1 / So1)×(tanδ / Tg)≦-0.3 is satisfied, and more preferably, the relationship -1.8≦(Sg1 / So1)×(tanδ / Tg)≦-0.4 is satisfied. It is desirable that the value of Sg1 / So1 is in the range of 18 to 80, the glass transition temperature Tg (°C) is in the range of -70°C to -20°C, and the loss tangent tanδ at 0°C is in the range of 0.6 to 1.2. For example, when Sg1 / So1=38.5, Tg=-30°C, and tanδ=1.0, then (Sg1 / So1)×(tanδ / Tg)=-1.3.

[0030] In the above-described pneumatic tire, as shown in Figure 4, when we assume a plane P1 that passes through the center position of the groove width of each lug groove 13 having a projection 14 and is perpendicular to the tread surface S of the tread portion 1, the sum of the areas of the lug grooves 13 projected toward the plane P1 in the groove width direction (the dashed line portion in Figure 3) is Sg2 (mm²). 2 ) and the sum of the areas of the projections 14 projected toward the surface P1 in the groove width direction (dashed line area in Figure 3) So2 (mm²) 2 The glass transition temperature Tg (°C) of the rubber composition constituting the tread rubber layer R1 of the tread portion 1 and the loss tangent tanδ of the rubber composition constituting the tread rubber layer R1 of the tread portion 1 should satisfy the relationship -0.4 ≤ (Sg2 / So2) × (tanδ / Tg) ≤ -0.02. The total area Sg2 of the lug grooves 13 and the total area So2 of the protrusions 14 are the sum of the areas measured in the contact region defined between a pair of contact ends E, E, but lug grooves 13 without protrusions 14 are excluded.

[0031] As described above, the sum of the areas of the lug grooves 13 projected onto the plane P1 perpendicular to the tread surface S of the tread portion 1, passing through the groove width center position of each lug groove 13 having a projection 14, is Sg2 (mm²). 2 ) and the sum of the areas of the projections 14 projected onto the plane P1 perpendicular to the tread surface S of the tread portion 1, passing through the groove width center position of each lug groove 13 having projections 14, So2 (mm 2) and the glass transition temperature Tg (°C) and the loss tangent tanδ satisfy the relationship -0.4 ≤ (Sg2 / So2) × (tanδ / Tg) ≤ -0.02, thereby improving handling stability while maintaining good wet performance. In other words, when the value of So2 increases and the value of (Sg2 / So2) decreases, handling stability improves, but wet performance decreases, so the value of tanδ is increased based on the above relationship to compensate for this. Also, when the value of So2 decreases and the value of (Sg2 / So2) increases, wet performance improves, but handling stability decreases, so the value of Tg is increased based on the above relationship to compensate for this.

[0032] If the value of (Sg2 / SO2) × (tanδ / Tg) falls outside the above range, the effect of improving wet performance and handling stability in a balanced way will be insufficient. Ideally, the value of Sg2 / SO2 should be in the range of 2.5 to 20. For example, when Sg2 / SO2 = 4.1, Tg = -30, and tanδ = 1.0, then (Sg2 / SO2) × (tanδ / Tg) = -0.14.

[0033] In the above-described pneumatic tire, as shown in Figure 6, assuming a plane P2 that passes through the centroid X of each projection 14 and is perpendicular to the extension direction of each lug groove 13, and is also perpendicular to the tread surface S of the tread portion 1, the average value of the cross-sectional area of ​​the lug groove 13 in plane P2 is Sg3(mm²). 2 ) and the average value of the cross-sectional area of ​​the projection 14 in the plane P2 So3(mm 2The relationship between the glass transition temperature Tg (°C) of the rubber composition constituting the tread rubber layer R1 of the tread portion 1 and the loss tangent tanδ of the rubber composition constituting the tread rubber layer R1 of the tread portion 1 should satisfy -0.5 ≤ (Sg3 / So3) × (tanδ / Tg) ≤ -0.01. The average value Sg3 of the cross-sectional area of ​​the lug groove 13 and the average value So3 of the cross-sectional area of ​​the projection 14 are the average values ​​of the cross-sectional areas measured in the contact area defined between a pair of contact ends E, E, but lug grooves 13 without projections 14 are excluded. The cross-sectional area of ​​the lug groove 13 is the cross-sectional area of ​​the internal space of the lug groove 13 (including the projection 14) demarcated by the imaginary line L1 of the tread surface S of the tread portion 1, and the cross-sectional area of ​​the projection 14 is the cross-sectional area of ​​the portion that protrudes into the lug groove 13 from the imaginary line L2 of the side wall 13b (or side wall 13a) of the lug groove 13.

[0034] As described above, the average value of the cross-sectional area of ​​the lug groove 13 in a plane P2 that passes through the centroid X of each projection 14 and is perpendicular to the extension direction of each lug groove 13, and is also perpendicular to the tread surface S of the tread portion 1 is Sg3 (mm²). 2 ) and the average value of the cross-sectional area of ​​the projection 14 in a plane P2 that passes through the centroid X of each projection 14 and is perpendicular to the extension direction of each lug groove 13 and perpendicular to the tread surface S of the tread portion 1, So3 (mm 2 ) and the glass transition temperature Tg (°C) and the loss tangent tanδ satisfy the relationship -0.5 ≤ (Sg3 / So3) × (tanδ / Tg) ≤ -0.01, thereby improving handling stability while maintaining good wet performance. In other words, when the value of So3 increases and the value of (Sg3 / So3) decreases, handling stability improves, but wet performance decreases, so the value of tanδ is increased based on the above relationship to compensate for this. Also, when the value of So3 decreases and the value of (Sg3 / So3) increases, wet performance improves, but handling stability decreases, so the value of Tg is increased based on the above relationship to compensate for this.

[0035] If the value of (Sg3 / SO3) × (tanδ / Tg) falls outside the above range, the effect of improving wet performance and handling stability in a balanced way will be insufficient. Ideally, the value of Sg3 / SO3 should be in the range of 2 to 10. For example, when Sg3 / SO3 = 5.6, Tg = -30℃, and tanδ = 1.0, then (Sg3 / SO3) × (tanδ / Tg) = -0.19.

[0036] In the above-described pneumatic tire, as shown in Figure 7, when a virtual line L2 is defined on the side wall 13b of the lug groove 13 and a measurement line L3 is defined that passes through the centroid X of the projection 14 and is perpendicular to the virtual line L2, the groove width Gw of the lug groove 13 is the distance from the virtual line L2 to the side wall 13a as measured on the measurement line L3, and the height Ph of the projection 14 is the distance from the virtual line L2 to the maximum protruding position of the projection 14 as measured on the measurement line L3. Furthermore, it is desirable that the relationship between the groove width Gw of the lug groove 13 and the height Ph of the projection 14 satisfies 1.4 ≤ Gw / Ph ≤ 3.3. This minimizes the influence of the projection 14 on wet performance while effectively suppressing the collapse of the side walls 13a and 13b of the lug groove 13, thereby improving handling stability. Here, if Gw / Ph is less than 1.4, the improvement in wet performance decreases, and conversely, if it is greater than 3.3, the improvement in handling stability decreases. The groove width Gw of the lug groove 13 is set to, for example, 1.6 mm or more, preferably in the range of 2.0 mm to 4.0 mm. The height Ph of the projection 14 is set to, for example, in the range of 0.2 mm to 2.0 mm.

[0037] In the above-described pneumatic tire, as shown in Figure 8, it is desirable that the depth D of the lug groove 13 and the distance Da from the centroid X of the projection 14 to the bottom of the lug groove 13 satisfy the relationship 0.1 ≤ Da / D ≤ 0.7. This minimizes the influence of the projection 14 on wet performance while effectively suppressing the collapse of the side walls 13a and 13b of the lug groove 13, thereby improving handling stability. Here, if Da / D is less than 0.1, the improvement in handling stability decreases, and conversely, if it is greater than 0.7, the improvement in wet performance decreases. Note that if the bottom of the lug groove 13 has undulations, the depth D of the lug groove 13 and the distance Da from the centroid X of the projection 14 to the bottom of the lug groove 13 are measured from the deepest part of the lug groove 13.

[0038] Figures 9 to 13 show tread patterns of pneumatic tires according to other embodiments of the present invention. In particular, the embodiments shown in Figures 9 to 11 are pneumatic tires in which the mounting direction of the front and back sides of the tire when mounted on a vehicle is specified. In Figures 9 to 11, IN is the inside of the vehicle when mounted on a vehicle, and OUT is the outside of the vehicle when mounted on a vehicle. The tread portion 1 has an outer region Ao located outside the vehicle relative to the tire equator CL, and an inner region Ai located inside the vehicle relative to the tire equator CL. When the mounting direction relative to the vehicle is specified, for example, a display portion 2A indicating the mounting direction relative to the vehicle is formed on at least the sidewall portion 2 on the outside of the vehicle. The display portion 2A displays, for example, "OUTSIDE" along the tire circumferential direction on the outside of the vehicle, and for example, "INSIDE" along the tire circumferential direction on the inside of the vehicle.

[0039] In Figure 9, the total area Sgα (mm²) of the groove 10 included in the outer region Ao, when viewed from the outer side in the radial direction of the tire, is shown. 2 ) and the sum of the areas of the protrusions 14 included in the outer region Ao when viewed from the outer side in the radial direction of the tire, Soα (mm 2 ) and the sum of the areas of the grooves 10 included in the inner region Ai when viewed from the outside in the radial direction of the tire, Sgβ(mm 2 ) and the sum of the areas of the protrusions 14 included in the inner region Ai when viewed from the outer side in the radial direction of the tire, Soβ(mm 2The relationship -17≦Sgα / Soα-Sgβ / Soβ≦17 is satisfied. This makes it possible to improve handling stability while maintaining good wet performance. Furthermore, within the range permitted by the above relationship, it is possible to adjust the contribution of the outer region Ao and the inner region Ai to wet performance or handling stability. In Figure 9, by relatively reducing the sum of the areas Soβ when the protrusions 14 included in the inner region Ai are viewed from the outside in the radial direction of the tire, and relatively increasing the sum of the areas Soα when the protrusions 14 included in the outer region Ao are viewed from the outside in the radial direction of the tire, the wet performance based on the inner region Ai is improved while the handling stability based on the outer region Ao is improved. When adopting this trend, it is desirable to satisfy the relationship -17≦Sgα / Soα-Sgβ / Soβ≦0, more preferably -13≦Sgα / Soα-Sgβ / Soβ≦-2.

[0040] In the embodiments shown in Figures 10 and 11, the projections 14 are provided on one groove wall 13a and the other groove wall 13b of the lug groove 13 in the tire circumferential direction. More specifically, in Figure 10, the projections 14 included in the inner region Ai are located on one groove wall 13a of the lug groove 13 in the tire circumferential direction, and the projections 14 included in the outer region Ao are located on the other groove wall 13b of the lug groove 13 in the tire circumferential direction. In Figure 11, the projections 14 included in the inner region Ai are located on one groove wall 13a of the lug groove 13 in the tire circumferential direction, and the projections 14 included in the outer region Ao are located on both groove walls 13a and 13b of the lug groove 13 facing each other. In other words, when the tire rotates, the protrusions 14 provided on the groove wall 13a on one side of the lug groove 13 in the tire circumferential direction (for example, the side that is pressed down) and the protrusions 14 provided on the groove wall 13b on the other side of the lug groove 13 in the tire circumferential direction (for example, the side that is pushed out) are mixed together, which effectively suppresses the collapse of the groove walls 13a and 13b of the lug groove 13 and enhances the effect of improving steering stability. In particular, when the protrusions 14 are arranged on both groove walls 13a and 13b of the lug groove 13 facing each other, the protrusions 14 can effectively suppress the collapse of the side walls 13a and 13b of the lug groove 13 even if the lug groove 13 is not straight or if the blocks of the land portion 12 are deformed in a twisting manner.

[0041] In the embodiment shown in Figure 12, multiple lug grooves 13 and multiple protrusions 14 arranged within each lug groove 13 are formed not only on the pair of shoulder land sections 12C but also on the center land section 12A. In the embodiment shown in Figure 13, multiple lug grooves 13 and multiple protrusions 14 arranged within each lug groove 13 are formed not only on the pair of shoulder land sections 12C but also on the pair of intermediate land sections 12B. Even with this configuration, it is possible to improve handling stability while maintaining good wet performance.

[0042] In the pneumatic tire described above, the protrusions 14 are preferably formed in 50% or more, more preferably 80% or more, and more preferably 95% or more of the lug grooves 13 formed in the tread portion 1. This allows for a sufficient improvement in handling stability. The above specification refers to the ratio of the placement of protrusions 14 to the lug grooves 13 arranged throughout the tread portion 1, including the center land portion 12A, the intermediate land portion 12B, and the shoulder land portion 12C. The desired effect can also be obtained if the protrusions 14 are placed only in the center land portion 12A, only in the intermediate land portion 12B, or only in the shoulder land portion 12C.

[0043] In the above-described pneumatic tire, the tread portion 1 has multiple main grooves 11 extending in the circumferential direction of the tire, and these main grooves 11 divide the tire into multiple rows of land portions 12, including the center land portion 12A located on the tire equator CL and the shoulder land portion 12C located on the outermost side in the tire width direction. In this case, the number of lug grooves 13 with protrusions 14 in one row of shoulder land portion 12C should be 150% or more of the number of lug grooves 13 with protrusions 14 in one row of center land portion 12A. This allows for a sufficient improvement in handling stability. [Examples]

[0044] In a pneumatic tire with a tire size of 205 / 55R16, comprising a tread section, a pair of sidewall sections, and a pair of bead sections, conventional, comparative examples 1-4 and examples 1-19 were manufactured, each differing in the specifications of the protrusions provided on the side walls of the lug grooves formed in the tread section and the physical properties of the rubber composition constituting the tread section.

[0045] In the Conventional Example, Comparative Examples 1-4, and Examples 1-19, the ratio of the total groove area Sg1 to the total protrusion area So1 (Sg1 / So1), the ratio of the total lug groove area Sg2 to the total protrusion area So2 (Sg2 / So2), the ratio of the average cross-sectional area Sg3 to the average cross-sectional area So3 (Sg3 / So3), the glass transition temperature Tg of the rubber composition constituting the tread, the loss tangent tanδ of the rubber composition constituting the tread at 0°C ((Sg1 / So1) × (tanδ / Tg)), (Sg2 / So2) × (tanδ / Tg), (Sg3 / So3) × (tanδ / Tg), (Sgα / Soα) - (Sgβ / Soβ)), the presence or absence of bidirectional protrusions, Da / D, Gw / Ph, and the percentage of lug grooves with protrusions were set as shown in Tables 1 and 2. The Conventional Example is an example without protrusions.

[0046] These test tires were evaluated for wet performance and handling stability using the test methods described below, and the results are shown in Tables 1 and 2.

[0047] Wet performance: Each test tire was mounted on a 16x6.5J rim wheel and fitted to a 2000cc test vehicle. The tire pressure was set to 230kPa, and braking was performed on a test course consisting of a wet surface with a water depth of 1mm from a speed of 80km / h, with the braking distance measured. The evaluation results were shown as an index using the reciprocal of the measured value, with the conventional example set to 100. A higher index value indicates better wet performance.

[0048] Stability: Each test tire was mounted on a 16x6.5J rim wheel and fitted to a 2000cc test vehicle. The tire pressure was set to 230kPa, and subjective evaluations were conducted by test drivers on a test course consisting of dry asphalt. The evaluation results are shown as an index, with the conventional example set to 100. A higher index value indicates better handling stability.

[0049] [Table 1]

[0050] [Table 2]

[0051] As can be seen from Tables 1 and 2, the tires of Examples 1 to 19 were able to improve handling stability while maintaining good wet performance compared to conventional examples. On the other hand, the tires of Comparative Examples 1 and 3 showed a decrease in wet performance because the value of (Sg1 / So1) × (tanδ / Tg) was too large. On the other hand, the tires of Comparative Examples 2 and 4 did not show sufficient improvement in handling stability because the value of (Sg1 / So1) × (tanδ / Tg) was too small.

[0052] This disclosure encompasses the following inventions [1] to [8]. The invention [1] relates to a tire having a tread portion that extends in the circumferential direction of the tire and forms an annular shape, wherein the tread portion has a groove portion including a plurality of lug grooves that extend in the width direction of the tire, and a projection is formed on at least one side wall of at least one of the plurality of lug grooves, and the total area Sg1 (mm²) of the groove portion when viewed from the outside in the radial direction of the tire 2 ) and the sum of the areas of the projections when viewed from the outer side in the radial direction of the tire, So1 (mm²) 2 The tire is characterized in that the glass transition temperature Tg (°C) of the rubber composition constituting the tread portion and the loss tangent tanδ of the rubber composition constituting the tread portion at 0°C satisfy the relationship -4.0 ≤ (Sg1 / So1) × (tanδ / Tg) ≤ -0.05. The invention [2] relates to the sum of the areas of the lug grooves Sg2 (mm²) projected onto a plane perpendicular to the tread surface of the tread portion, passing through the groove width center position of each lug groove having the projection. 2 ) and the sum of the areas of the protrusions projected onto a plane perpendicular to the tread surface of the tread portion, passing through the groove width center position of each lug groove having the protrusions, So2(mm 2 The tire is characterized in that the glass transition temperature Tg (°C) and the loss tangent tanδ satisfy the relationship -0.4 ≤ (Sg² / SO²) × (tanδ / Tg) ≤ -0.02, as described in invention [1]. The invention [3] provides the average value of the cross-sectional area of ​​the lug groove in a plane that passes through the centroid of each projection and is perpendicular to the extension direction of each lug groove and perpendicular to the tread surface of the tread portion, Sg3(mm 2 ) and the average value of the cross-sectional area of ​​the protrusion in a plane that passes through the centroid of each protrusion, is perpendicular to the extension direction of each lug groove, and is perpendicular to the tread surface of the tread portion So3(mm 2 The tire is characterized in that the glass transition temperature Tg (°C) and the loss tangent tanδ satisfy the relationship -0.5 ≤ (Sg3 / So3) × (tanδ / Tg) ≤ -0.01, as described in Invention [1] or [2]. The invention [4] provides a tire having a display unit that specifies and indicates the mounting direction to a vehicle, and the tread portion having an outer region located outside the vehicle relative to the tire equator and an inner region located inside the vehicle relative to the tire equator, The sum of the areas of the grooves included in the outer region when viewed from the outer side in the radial direction of the tire, Sgα (mm²) 2 ) and the sum of the areas of the protrusions included in the outer region when viewed from the outside in the radial direction of the tire, Soα (mm 2 ) and the sum of the areas of the grooves included in the inner region when viewed from the outside in the radial direction of the tire, Sgβ(mm 2 ) and the sum of the areas of the protrusions included in the inner region when viewed from the outside in the radial direction of the tire, Soβ(mm 2 The tire is characterized in that ) satisfies the relationship -17≦Sgα / Soα-Sgβ / Soβ≦17 as described in any of the inventions [1] to [3]. Invention [5] is a tire according to any one of Inventions [1] to [4], characterized in that the projection is provided on one groove wall in the tire circumferential direction of the lug groove and on the other groove wall in the tire circumferential direction of the lug groove. Invention [6] is a tire according to any one of Inventions [1] to [5], characterized in that the depth D of the lug groove and the distance Da from the centroid of the projection to the bottom of the lug groove satisfy the relationship 0.1 ≤ Da / D ≤ 0.7, and the groove width Gw of the lug groove and the height Ph of the projection satisfy the relationship 1.4 ≤ Gw / Ph ≤ 3.3. Invention [7] is a tire according to any one of Inventions [1] to [6], characterized in that the protrusions are provided in 50% or more of the lug grooves of all the lug grooves formed in the tread portion. Invention [8] is a tire according to any one of Inventions [1] to [7], characterized in that the tread portion has a plurality of main grooves extending in the circumferential direction of the tire, and these main grooves divide a plurality of rows of land portions, including a center land portion located on the tire equator and a shoulder land portion located on the outermost side in the tire width direction, and the number of lug grooves having protrusions in the shoulder land portion is 150% or more of the number of lug grooves having protrusions in the center land portion. [Explanation of Symbols]

[0053] 1. Tread section 2 Sidewall section 3. Bead section 10 grooves 11 Main groove 12,12A,12B,12C Land part 13 lug grooves 14 protrusions

Claims

1. In a tire having a tread portion that extends in the circumferential direction and forms an annular shape, the tread portion has a groove portion including a plurality of lug grooves extending in the tire width direction, a projection is formed on at least one side wall of at least one of the plurality of lug grooves, and the total area Sg1 (mm²) of the groove portion when viewed from the outside in the radial direction of the tire is such that 2 ) and the sum of the areas of the projections when viewed from the outside in the radial direction of the tire So1 (mm 2 A tire characterized in that the glass transition temperature Tg (°C) of the rubber composition constituting the tread portion and the loss tangent tanδ of the rubber composition constituting the tread portion at 0°C satisfy the relationship -4.0 ≤ (Sg1 / So1) × (tanδ / Tg) ≤ -0.

05.

2. Sg2 (mm²) is the sum of the areas of the lug grooves projected onto a plane perpendicular to the tread surface of the tread portion, passing through the center position of the groove width of each lug groove having the projection. 2 ) and the sum of the areas of the protrusions projected onto a plane perpendicular to the tread surface of the tread portion, passing through the groove width center position of each lug groove having the protrusions So2 (mm 2 The tire according to claim 1, characterized in that the glass transition temperature Tg (°C) and the loss tangent tanδ satisfy the relationship -0.4 ≤ (Sg² / So²) × (tanδ / Tg) ≤ -0.

02.

3. The average value of the cross-sectional area of ​​the lug groove in a plane that passes through the centroid of each protrusion, is perpendicular to the extension direction of each lug groove, and is perpendicular to the tread surface of the tread portion, Sg3 (mm²) 2 ) and the average value of the cross-sectional area of ​​the protrusion in a plane that passes through the centroid of each protrusion, is perpendicular to the extension direction of each lug groove, and is perpendicular to the tread surface of the tread portion So3 (mm 2 The tire according to claim 1 or 2, characterized in that the glass transition temperature Tg (°C) and the loss tangent tanδ satisfy the relationship -0.5 ≤ (Sg3 / So3) × (tanδ / Tg) ≤ -0.

01.

4. A tire having a designated mounting direction for a vehicle and a display unit that indicates the mounting direction, wherein the tread portion has an outer region located outside the vehicle relative to the tire equator and an inner region located inside the vehicle relative to the tire equator, The total area Sgα (mm 2 ) of the groove portions included in the outer region as viewed from the outer side in the tire radial direction, the total area Soα (mm 2 ) of the protrusion portions included in the outer region as viewed from the outer side in the tire radial direction, the total area Sgβ (mm 2 ) of the groove portions included in the inner region as viewed from the outer side in the tire radial direction, and the total area Soβ (mm 2 ) of the protrusion portions included in the inner region as viewed from the outer side in the tire radial direction satisfy the relationship of -17 ≦ Sgα / Soα - Sgβ / Soβ ≦ 17. The tire according to claim 1 or 2, characterized in that.

5. The tire according to claim 1 or 2, characterized in that the projection is provided on one groove wall in the tire circumferential direction of the lug groove and on the other groove wall in the tire circumferential direction of the lug groove.

6. The tire according to claim 1 or 2, characterized in that the depth D of the lug groove and the distance Da from the centroid of the projection to the bottom of the lug groove satisfy the relationship 0.1 ≤ Da / D ≤ 0.7, and the groove width Gw of the lug groove and the height Ph of the projection satisfy the relationship 1.4 ≤ Gw / Ph ≤ 3.

3.

7. The tire according to claim 1 or 2, characterized in that the protrusions are provided in 50% or more of the lug grooves of all the lug grooves formed in the tread portion.

8. The tire according to claim 1 or 2, characterized in that the tread portion has a plurality of main grooves extending in the circumferential direction of the tire, and these main grooves divide a plurality of land portions, including a center land portion located on the tire equator and a shoulder land portion located on the outermost side in the tire width direction, and the number of lug grooves having protrusions in the shoulder land portion is 150% or more of the number of lug grooves having protrusions in the center land portion.

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