tire

Abstract

To provide a tire which improves total performance consisting of a low fuel consumption and an operation stability.SOLUTION: A contact area of a first layer 11 of a tread in a tire comprises: two or more circumferential grooves 13, 14, 15 which continuously extend in a tire circumferential direction; a pair of shoulder land parts 16, 17 arranged at both ends in a tire width direction and center land parts 18, 19; and a width direction groove and / or a width direction groove and a siping. Sr and Sce satisfy, when area of the whole land part is Sr and total area of the center land parts is Sce, the following expression (1): expression (1) 0.35≤Sce / Sr≤0.80. 30°CtanδBT and 30°CtanδSW satisfy, when loss tangent at 30°C of a rubber composition constituting a tread inner layer 12 is 30°CtanδBT, and loss tangent at 30°C of a rubber composition constituting a side wall of a side wall part 2 is 30°CtanδSW, the following expression (2): expression (2) 30°CtanδBT / 30°CtanδSW<1.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In recent years, as environmental regulations have become stricter, there has been an increasing demand for tires with excellent fuel efficiency. In particular, the tread, which contributes greatly to fuel efficiency, has a two-layer structure of a base tread and a cap tread, and attempts have been made to improve the fuel efficiency of the base tread, which is the internal component (i.e., to reduce heat generation). For example, a method has been proposed in which carbon black and silica are used in combination in the rubber composition that constitutes the base tread to achieve both low heat generation and reinforcement properties (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2003-12866 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, this method has the problem that the hardness of the rubber decreases, reducing the rigidity of the tire tread, thereby decreasing the driving stability.

[0005] An object of the present invention is to provide a tire which has improved overall performance in terms of fuel economy and driving stability. [Means for solving the problem]

[0006] As a result of intensive research into the above-mentioned problems, the inventors have found that in a tire having a tread portion consisting of two or more layers, a tire having improved overall performance in terms of fuel economy and handling stability can be obtained by setting the ratio of the center land portion to the total area of ​​the land portions of the first tread layer within a specified range, making the tan δ value of the rubber composition constituting the tread inner layer smaller than that of the rubber composition constituting the sidewall, and extending the ends of the tread inner layer to the sidewall, thereby completing the present invention.

[0007] That is, the present invention provides [1] A tire having a tread portion and a sidewall portion consisting of two or more layers, The tread portion consisting of two or more layers includes at least a tread first layer which is the outermost layer in the tire radial direction and a tread inner layer which is the inner layer in the tire radial direction, An end portion of the tread inner layer extends to a sidewall portion, and the tread inner layer is disposed inward in the tire width direction in the sidewall portion relative to the sidewall, The ground contact surface of the tread first layer has two or more circumferential grooves extending continuously in the circumferential direction of the tire, a pair of shoulder land portions separated by two circumferential grooves located at both ends in the tire width direction, a center land portion located between the pair of shoulder land portions, and a width groove or a width groove and a sipe, When the area of ​​the entire land portion is Sr and the total area of ​​the center land portion is Sce, Sr and Sce are expressed by the following formula (1): Formula (1) 0.35≦Sce / Sr≦0.80 Fulfilling The loss tangent at 30°C of the rubber composition constituting the tread inner layer is 30°C tanδ BT The loss tangent at 30° C. of the rubber composition constituting the sidewall of the sidewall portion is 30° C. tanδ SW When 30℃ tan δ BT and 30℃ tan δ SW But, the following formula (2) Equation (2) 30℃tanδ BT / 30℃tanδ SW <1 Meet the tires, [2] The tire according to the above [1], wherein the value of the right side of the formula (2) is 0.9. [3] The tire according to the above [1], wherein the value of the right side of the formula (2) is 0.8. [4] 30℃ tan δ BT and the Sr and the Sce are represented by the following formula (3): Equation (3) 30℃tanδ BT ×(Sce / Sr)≦0.15 The tire according to any one of the above items [1] to [3], [5] The tire according to the above [4], wherein the value of the right side of the formula (3) is 0.05. [6] The tire according to any one of the above [1] to [5], wherein the land width of one independent center land portion among the center land portions is at least twice the groove depth of at least one circumferential groove adjacent to the center land portion on the outer side in the tire width direction. [7] A tire according to any one of the above [1] to [6], wherein the central land portion has a sipe, the sipe extends to connect both edges of the central land portion in the width direction, and an angle θ between a straight line connecting both ends of the sipe of the central land portion in the width direction and the circumferential groove is in the range of 65 to 80 degrees. [8] When the circumferential length of the tire is La, the sum of the lengths of the edge components of the width direction of the width direction grooves Lb1 and the sum of the lengths of the edge components of the width direction of the sipes Lb2 is Lb, La and Lb are expressed by the following formula (4): Equation (4) 3≦Lb / La≦7 The tire according to the above [7], [9] In the tread surface of the tread first layer, when the contact area of ​​the tread surface is St, and the sum of the total area Sg1 of the circumferential grooves and the total area Sg2 of the widthwise grooves and the sipes is Sg, St and Sg are expressed by the following formula (5): Formula (5) 0.20≦Sg / St≦0.40 The tire according to any one of the above [1] to [8],

[10] The tire according to any one of the above [1] to [9], wherein the tire is a pneumatic tire for passenger cars. Regarding. Effect of the Invention

[0008] According to the present invention, it is possible to provide a pneumatic tire having improved overall performance including fuel economy and driving stability. [Brief description of the drawings]

[0009] [Figure 1] 1 is a tire meridian cross-sectional view showing an example of a tire according to the present disclosure. [Diagram 2] 1 is a tire meridian cross-sectional view showing an example of a tire according to the present disclosure. [Diagram 3] FIG. 2 is a tire meridian cross-sectional view showing an example of a tire of a comparative example. [Figure 4] FIG. 2 is a partial development view showing the tread pattern of the tire of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The tire disclosed herein is a tire having a tread portion and a sidewall portion each having two or more layers, the tread portion each having at least a tread first layer which is the outermost in the tire radial direction, and a tread inner layer which is the inner in the tire radial direction, an end portion of the tread inner layer extends to the sidewall portion, the tread inner layer is disposed inward in the tire width direction from the sidewall in the sidewall portion, the ground contact surface of the tread first layer has two or more circumferential grooves which extend continuously in the tire circumferential direction, a pair of shoulder land portions separated by the circumferential grooves which are located at both ends in the tire width direction, a center land portion located between the pair of shoulder land portions, and a width direction groove or a width direction groove and a sipe, and when the area of ​​the entire land portion is Sr and the total area of ​​the center land portion is Sce, Sr and Sce satisfy the formula (1), and the loss tangent at 30° C. of the rubber composition constituting the tread inner layer is 30° C. tanδ BT The loss tangent at 30° C. of the rubber composition constituting the sidewall of the sidewall portion is 30° C. tanδ SWWhen 30℃ tan δ BT and 30℃ tan δ SW is a tire that satisfies the above formula (2).

[0011] Without intending to be bound by theory, the mechanism by which the overall performance of fuel economy and driving stability is improved in the tire of the present disclosure is believed to be as follows: In other words, in the tire of the present disclosure, driving stability is achieved by optimizing the land portion rigidity by setting the ratio of the area (Sce) of the center land portion to the area (Sr) of the entire land portion of the tread within a predetermined range, while fuel economy is achieved by optimizing the 30°C tan δ of the rubber composition constituting the tread inner layer. BT The 30℃ tan δ of the rubber composition constituting the sidewall SW This is achieved by making the rolling resistance smaller than the rolling resistance of the inner tread layer and extending the end of the inner tread layer to the sidewall portion to increase the proportion of the inner tread layer with low rolling resistance. The improvement in handling stability and fuel efficiency achieved by these two means are mutually compatible, and as a result, it is believed that the overall performance of handling stability and fuel efficiency is improved.

[0012] The value of the right side of the formula (2) is preferably 0.9 or less, more preferably 0.8 or less, even more preferably 0.7 or less, and even more preferably 0.6 or less, which is believed to further improve fuel economy.

[0013] The 30°C tan δ BT It is preferable that the Sr and the Sce satisfy the formula (3), and it is more preferable that the value of the right side of the formula (3) is 0.05. It is considered that the overall performance of the driving stability and fuel economy is improved.

[0014] The width of one of the central land portions is preferably at least twice the groove depth of at least one circumferential groove adjacent to the central land portion on the outer side in the tire width direction. This is believed to increase the rigidity of the land portion and thus provide better steering stability.

[0015] The central land portion has a sipe, the sipe extends to connect both edges of the central land portion in the width direction, and the angle θ between a straight line connecting both ends of the sipe of the central land portion in the width direction and the circumferential groove is preferably in the range of 65 to 80 degrees. Since the water film within the contact patch width can be scraped off at the time of kicking off, it is considered that the wet grip performance when driving on a wet road surface can be improved.

[0016] When the circumferential length of the tire is La, the sum of the total length of the edge components of the width direction of the width direction grooves Lb1 and the total length of the edge components of the width direction of the sipes Lb2 is Lb, it is preferable that La and Lb satisfy the formula (4). It is believed that the steering stability of the tire on dry road surfaces and wet road surfaces can be sufficiently improved by optimizing the lengths of the edge components of the width direction of the width direction grooves and sipes.

[0017] In the tread surface of the tread first layer, when the ground contact area of ​​the tread surface is St, and the sum of the total area Sg1 of the circumferential grooves and the total area Sg2 of the widthwise grooves and the sipes is Sg, it is preferable that St and Sg satisfy the above formula (5). It is believed that it is possible to ensure drainage performance while maintaining rolling resistance, and maintain braking performance on wet road surfaces.

[0018] The tire is preferably a pneumatic tire for a passenger vehicle, in which case the effects of the present disclosure can be fully utilized.

[0019] [tire] Hereinafter, a tire according to the present disclosure will be described with reference to the drawings as appropriate. Note that the tire according to the present disclosure is not limited to the following embodiments.

[0020] FIG. 1 is a tire meridian cross-sectional view of an example of a tire of the present disclosure. The tire includes a tread portion 1, a sidewall portion 2, a clinch 3, and a carcass 4. The tread portion 1 includes a tread first layer 11 that is the outermost in the tire radial direction, and a tread inner layer 12 that is the innermost in the tire radial direction. The end portion (12E) of the tread inner layer 12 extends to the sidewall portion at a height position (H1) that is 20 / 40 of the tire section height (HT), and is disposed inward in the tire width direction from the sidewall. The upper end (3E) of the clinch 3 remains at a position (H2) that is 10 / 40 of the tire section height (HT). Here, HT, H1, and H2 are values ​​measured by assembling one of the two obtained by dividing the tire in half by a plane including the tire meridian on a regular rim.

[0021] Fig. 2 is a tire meridian cross-sectional view of an example of a tire of the present disclosure, similar to Fig. 1, but differs from Fig. 1 in that the end (12E) of the tread inner layer 12 extends to the sidewall portion at a height position (H1) of 14 / 40 of the tire section height (HT), and the upper end (3E) of the clinch 3 extends to a position (H2) of 24 / 40 of the tire section height (HT). The tread inner layer and the clinch are disposed in the sidewall portion with the carcass 4 interposed therebetween.

[0022] 3 is a meridian cross-sectional view of a tire of a comparative example to the tire of the present disclosure, in which the end (12E) of the tread inner layer 12 is at a height position (H1) of 36 / 40 of the tire section height (HT) and does not reach the sidewall part. The upper end (3E) of the clinch 3 remains at a position (H2) of 10 / 40 of the tire section height (HT).

[0023] 4 is a partial development view showing an example of a tread pattern of a tire disclosed herein. A tread pattern with a specified orientation for mounting on a vehicle is formed on the tread portion 1. The tread pattern of the tread portion 1 is formed in an asymmetric shape with respect to the tire equator C.

[0024] The tread portion 1 has an outer tread edge To and an inner tread edge Ti. The outer tread edge To is located on the outer side of the vehicle (on the right side in Figs. 1 and 4) when the tire is mounted on the vehicle. The inner tread edge Ti is located on the inner side of the vehicle (on the left side in Figs. 1 and 4) when the tire is mounted on the vehicle.

[0025] Each tread edge To, Ti is the outermost contact position in the tire width direction W (left and right direction in Figs. 1 and 4; hereafter simply referred to as width direction W) when a tire in a normal state is loaded with a normal load and touches the ground on a flat surface with a camber angle of 0 degrees. The normal state refers to a state in which the tire is mounted on a normal rim, inflated to a normal internal pressure, and no load is applied. In this specification, unless otherwise specified, the dimensions of each part of the tire (such as the tire cross-sectional width Wt) are values ​​measured in the normal state. In the normal state, the distance in the width direction W between the outer tread edge To and the inner tread edge Ti is defined as the tread width TW.

[0026] A "genuine rim" is a rim that is determined for each tire by the standard system that includes the standards on which the tire is based. In the case of JATMA, it is called a "standard rim," in the case of TRA, it is called a "Design Rim," and in the case of ETRTO, it is called a "Measuring Rim."

[0027] "Normal internal pressure" is the air pressure set for each tire by each standard in the standard system on which the tire is based. For JATMA, it is the "maximum air pressure." For TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." For ETRTO, it is the "INFLATION PRESSURE."

[0028] "Normal load" is the load that each standard specifies for each tire in the system of standards on which the tire is based. For JATMA, it is the "maximum load capacity." For TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." For ETRTO, it is the "LOAD CAPACITY."

[0029] The tire of the present disclosure is a tire having a tread portion and a sidewall portion each having two or more layers, and the tread portion each having two or more layers includes at least a first tread layer that is the outermost in the tire radial direction and an inner tread layer that is the innermost in the tire radial direction. The tire of FIG. 1 and FIG. 2 includes a tread portion 1, a sidewall portion 2, a clinch 3, and a carcass 4, and the tread portion 1 includes a first tread layer 11 that is the outermost in the tire radial direction and an inner tread layer 12 that is the innermost in the tire radial direction. The tread portion 1 may further include one or more layers in addition to the first tread layer 11 and the inner tread layer 12. In that case, the inner tread layer 12 may be arranged in any layer as long as it is arranged on the inner side of the first tread layer 11 in the tire radial direction, but in some embodiments, it is preferable to arrange it as the innermost layer that is the innermost in the tire radial direction.

[0030] In the tire of the present disclosure, the end of the tread inner layer extends to the sidewall portion, and the tread inner layer is disposed inward in the tire width direction from the sidewall in the sidewall portion. Such a configuration is preferable from the viewpoint of fuel efficiency. Here, "the end of the tread inner layer extends to the sidewall portion" means that the height of the end of the tread inner layer in the tire cross-sectional height is lower than the height of the upper end of the sidewall, as shown in Figures 1 and 2. From the viewpoint of fuel efficiency, the height of the end of the tread inner layer is preferably 33 / 40 or less of the tire cross-sectional height (HT), more preferably 32 / 40 or less, even more preferably 28 / 40 or less, even more preferably 24 / 40 or less, and even more preferably 20 / 40 or less.

[0031] In the tire of the present disclosure, the contact surface of the tread first layer has two or more circumferential grooves extending continuously in the circumferential direction of the tire, and land portions separated by the circumferential grooves, the land portions being a pair of shoulder land portions separated by two circumferential grooves located at both ends in the tire width direction and a center land portion located between the pair of shoulder land portions, and width grooves or width grooves and sipes.

[0032] In Fig. 4, three circumferential grooves 13, 14, and 15 are provided. However, the number of circumferential grooves is not particularly limited, and may be, for example, 2 to 5. In addition, in the present disclosure, the circumferential grooves 13, 14, and 15 extend linearly along the tire circumferential direction, but are not limited to such an embodiment, and may extend, for example, in a wave-like, sinusoidal, zigzag, or other shape along the tire circumferential direction.

[0033] The groove width of each of the circumferential grooves 13, 14, and 15 can be determined arbitrarily according to convention. In order to provide sufficient drainage performance while maintaining the pattern rigidity of the tread portion 1, the groove width of each of the circumferential grooves 13, 14, and 15 is preferably, for example, about 2.5% to 5% of the tread width TW. The groove depth of each of the circumferential grooves 13, 14, and 15 is not particularly limited, but is preferably 5.0 to 12.0 mm, more preferably 6.0 to 11.0 mm, and further preferably 7.0 to 10.0 mm.

[0034] In this disclosure, the term "shoulder land portion" refers to a pair of land portions formed between the circumferential groove located on the outermost side in the width direction W from the tire equator C and each tread edge To, Ti. In Fig. 4, there are provided an outer shoulder land portion 16 formed between the circumferential groove 14 located on the outermost side when mounted on a vehicle and the outer tread edge To, and an inner shoulder land portion 17 formed between the circumferential groove 13 located on the innermost side when mounted on a vehicle and the inner tread edge Ti.

[0035] In Fig. 4, the shoulder land portions 16, 17 are provided with a plurality of shoulder width direction grooves 21, 22 extending in a direction transverse to the shoulder land portions 16, 17. The plurality of shoulder width direction grooves 21, 22 are provided in each of the pair of shoulder land portions 16, 17. In this specification, the shoulder width direction groove provided in the outer shoulder land portion 16 is referred to as the outer shoulder width direction groove 21. Also, the shoulder width direction groove provided in the inner shoulder land portion 17 is referred to as the inner shoulder width direction groove 22.

[0036] In the present disclosure, the "center land portion" refers to all land portions sandwiched between the pair of shoulder land portions. In Fig. 4, there are provided an outer center land portion 18 formed between a circumferential groove 15 provided along the tire equator C and a circumferential groove 14 positioned on the outermost side when mounted on a vehicle, and an inner center land portion 19 formed between a circumferential groove 15 provided along the tire equator C and a circumferential groove 13 positioned on the innermost side when mounted on a vehicle, but the number of center land portions is not particularly limited and may be, for example, one to five.

[0037] In Fig. 4, the center land portions 18, 19 are provided with a plurality of center width direction grooves 25, 26 extending in a direction transverse to the center land portions 18, 19, and a plurality of center sipes 27, 28. The plurality of center width direction grooves 25, 26 and the plurality of center sipes 27, 28 are provided in each of the center land portions 18, 19. In this specification, the center width direction groove and center sipe provided in the outer center land portion 18 are referred to as the outer center width direction groove 25 and the outer center sipe 27, respectively. Also, the center width direction groove and center sipe provided in the inner center land portion 19 are referred to as the inner center width direction groove 26 and the inner center sipe 28, respectively.

[0038] The width of each of the widthwise grooves 21, 22, 25, 26 is preferably about 2.5% to 5% of the tread width TW. The depth of each of the widthwise grooves 21, 22, 25, 26 is not particularly limited, but is preferably 5.0 to 12.0 mm, more preferably 6.0 to 11.0 mm, and even more preferably 7.0 to 10.0 mm. In this specification, the term "sipe" refers to a thin cut having a width of 2.0 mm or less, preferably 0.5 to 1.5 mm.

[0039] The shoulder land portions 16, 17 may be provided with shoulder narrow grooves extending in the tire circumferential direction (not shown). By providing such shoulder narrow grooves, the edge components in the tire circumferential direction are increased, improving the cornering performance. In addition, the rigidity of the shoulder land portions 16, 17 in the tire circumferential direction is highly secured, improving the running performance on dry roads. The shoulder narrow grooves are not limited to extending linearly along the tire circumferential direction, and may extend in a wavy, sinusoidal, or zigzag shape along the tire circumferential direction. The groove width of the shoulder narrow groove is preferably 1.0% to 2.0% of the tread width TW, for example. The groove depth of the shoulder narrow groove is preferably 0.40 to 0.60 times the groove depth of the deepest part of the circumferential grooves 13, 14, and 15, for example.

[0040] The tire of the present disclosure is characterized in that, when the area of ​​all the land portions is Sr and the total area of ​​the center land portions is Sce, Sr and Sce satisfy the following formula (1). Formula (1) 0.35≦Sce / Sr≦0.80

[0041] The value (Sce / Sr) of formula (1) is preferably 0.38 or more, more preferably 0.40 or more, even more preferably 0.42 or more, even more preferably 0.44 or more, and even more preferably 0.45 or more. The value (Sce / Sr) of formula (1) is preferably 0.75 or less, more preferably 0.70 or less. By setting the ratio of the total area of ​​the center land portion to the area of ​​the entire tire land portion within the above range, the volume of the center land portion can be increased, and the land portion rigidity can be increased, thereby obtaining better steering stability.

[0042] In this specification, the area Sr of the entire land portion and the total area Sce of the center land portion are calculated from the ground contact shape of the tread surface when the tread is pressed against a flat surface under normal load. Neither Sr nor Sce includes grooves or sipes. In this specification, the ground contact shape is obtained by, for example, applying ink to the tread portion 1 after mounting the tire on a normal rim and maintaining the normal internal pressure, and pressing the tire perpendicularly against cardboard or the like under normal load (camber angle is 0°) to transfer the ink applied to the tread portion 1.

[0043] In the tire of the present disclosure, the loss tangent at 30° C. of the rubber composition constituting the tread inner layer is 30° C. tanδ BT The loss tangent at 30° C. of the rubber composition constituting the sidewall of the sidewall portion is 30° C. tanδ SW When 30℃ tan δ BT and 30℃ tan δ SW is characterized in that the following formula (2) is satisfied. Equation (2) 30℃tanδ BT / 30℃tanδ SW <1

[0044] Such a configuration is preferable from the viewpoint of fuel efficiency. BT / 30℃tanδ SW ) is preferably 0.95 or less, more preferably 0.90 or less, even more preferably 0.85 or less, and even more preferably 0.80 or less. BT is preferably 0.07 or more, more preferably 0.08 or more, and even more preferably 0.09 or more, and is preferably 0.15 or less, more preferably 0.14 or less, and even more preferably 0.13 or less. SW is preferably 0.10 or more, more preferably 0.11 or more, and even more preferably 0.12 or more, and is preferably 0.18 or less, more preferably 0.17 or less, and even more preferably 0.16 or less.

[0045] Here, 30° C. tan δ is the loss tangent measured on a vulcanized rubber test piece using a viscoelasticity spectrometer VES under the conditions of a temperature of 30° C., a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of 2%.

[0046] <Formula (3)> The tire of the present disclosure has the above-mentioned 30° C. tan δ BT It is preferable that the Sr and the Sce satisfy the following formula (3). Equation (3) 30℃tanδ BT ×(Sce / Sr)≦0.15

[0047] Such a configuration is preferable from the viewpoint of improving the overall performance of the steering stability and fuel economy. BT × (Sce / Sr) is preferably 0.10 or less, more preferably 0.08 or less, even more preferably 0.06 or less, and even more preferably 0.05 or less.

[0048] <Land width of center land portion and groove depth of adjacent circumferential groove> In the tire of the present disclosure, from the viewpoint of increasing the land portion rigidity and obtaining excellent steering stability, the land portion width of one independent center land portion is preferably at least twice the groove depth of at least one circumferential groove adjacent to the tire width direction outer side, more preferably at least 2.5 times, and even more preferably at least 3 times. The land portion width is not particularly limited, but is preferably at least 10 mm, more preferably at least 15 mm, and even more preferably at least 20 mm, and is preferably at most 60 mm, more preferably at most 50 mm, and even more preferably at most 40 mm. The groove depth is not particularly limited, but is preferably at least 5.0 mm, more preferably at least 6.0 mm, and even more preferably at least 7.0 mm, and is preferably at most 12.0 mm, more preferably at most 11.0 mm, and even more preferably at most 10.0 mm. In this specification, the land portion width and the groove depth are both measured in a normal state.

[0049] <Angle θ between the sipes in the center land area and the circumferential groove> In the tire of the present disclosure, the center land portion has sipes, the sipes extend so as to connect both edges of the center land portion in the width direction, and the angle θ between the straight line connecting both ends of the sipes of the center land portion in the width direction and the circumferential main groove is preferably in the range of 65 to 80 degrees. For example, in FIG. 4, the center land portions 18, 19 have sipes 27, 28, and these sipes 27, 28 extend so as to connect both edges of the center land portions 18, 19 in the width direction W. Here, the angle between the straight line connecting both ends of the sipe 27 in the width direction W and the circumferential groove 14, or the angle between the straight line connecting both ends of the sipe 28 in the width direction W and the circumferential groove 13 (both θ) is preferably in the range of 65 to 80 degrees. In this case, the water film can be scraped out in the center land portions 18, 19, and the braking performance on wet road surfaces can be improved. In this specification, the angle θ is calculated from the ground contact shape when the tread is pressed against a flat surface under a normal load in a normal state.

[0050] <Formula (4)> In the tire of the present disclosure, when the circumferential length of the tire is La, and the sum of the lengths of the widthwise edge components of the widthwise grooves, Lb1, and the sum of the lengths of the widthwise edge components of the sipes, Lb2, is Lb, it is preferable that La and Lb satisfy the following formula (4). Equation (4) 3≦Lb / La≦7

[0051] From the viewpoint of handling stability, the value (Lb / La) of formula (4) is preferably 3.5 or more, more preferably 4.0 or more, and even more preferably 4.5 or more. The value (Lb / La) of formula (4) is preferably 6.5 or less, more preferably 6.0 or less, and even more preferably 5.5 or less.

[0052] 4, the circumferential length of the tire is La, the sum of the lengths of the edge components of the widthwise grooves 21, 22, 25, 26 in the width direction W corresponds to Lb1, the sum of the lengths of the edge components of the sipes 27, 28 in the width direction W corresponds to Lb2, and the sum of Lb1 and Lb2 corresponds to Lb. By setting the relationship between the edge component lengths of the widthwise grooves 21, 22, 25, 26 and the sipes 27, 28 and the circumferential length La of the tire within the above range, the deformation of the tread portion 1 can be set within a predetermined range, and the area of ​​the land portions 16, 17, 18, 19 of the tread portion 1 can be secured to be greater than or equal to a predetermined value, thereby improving steering stability.

[0053] In addition, the "length of the edge component in the width direction W" of the widthwise grooves 21, 22, 25, 26 and the sipes 27, 28 refers to the projected length in the width direction W of the widthwise grooves 21, 22, 25, 26 and the sipes 27, 28 (the widthwise component of the widthwise component and the circumferential component).

[0054] Furthermore, the ratio Lb1 / La of the circumferential length La of the tire to the sum Lb1 of the lengths of the edge components in the width direction W of the widthwise grooves 21, 22, 25, 26 is preferably 2.0 to 6.5, more preferably 2.2 to 6.3, and more preferably 2.5 to 6.0. By setting the relationship between the sum Lb1 of the lengths of the edge components in the width direction W of the widthwise grooves 21, 22, 25, 26 and the circumferential length La of the tire in the above range, the steering stability can be further improved.

[0055] In addition, the sum Lb of the lengths of the edge components of the widthwise grooves 21, 22 in the shoulder land portions 16, 17 in the width direction W sh and the sum Lb of the lengths of the edge components of the width direction W of the width direction grooves 25, 26 in the center land portions 18, 19 ce 1 and the sum Lb of the edge components of the sipes 27, 28 in the width direction W in the center land portions 18, 19 ce Sum of 2 Lb ce Relative to Lb sh / Lb ce But, Lb sh / Lb ce< 1. In this case, the edge components in the shoulder land portions 16, 17 are reduced, and the rigidity of the shoulder land portions 16, 17 is increased. This suppresses wear of the shoulder land portions 16, 17, and improves steering stability.

[0056] In this specification, La, Lb, Lb1 and Lb2 are all measured in a normal state.

[0057] <Formula (5)> In the tire of the present disclosure, when the contact area of ​​the tread surface is St and the sum of the total area Sg1 of the circumferential grooves and the total area Sg2 of the widthwise grooves and the sipes is Sg, it is preferable that St and Sg satisfy the following formula (5). Formula (5) 0.20≦Sg / St≦0.40

[0058] The value (Sg / St) of formula (5) is preferably 0.23 or more, more preferably 0.25 or more, and even more preferably 0.27 or more. The value (Sg / St) of formula (5) is preferably 0.37 or less, more preferably 0.35 or less, and even more preferably 0.33 or less.

[0059] Sg1 / St is preferably 0.13 or more, more preferably 0.14 or more, and even more preferably 0.15 or more. Sg1 / St is preferably 0.20 or less, more preferably 0.19 or less, and even more preferably 0.18 or less.

[0060] Sg2 / St is preferably 0.10 or more, more preferably 0.11 or more, and even more preferably 0.12 or more. Sg1 / St is preferably 0.17 or less, more preferably 0.16 or less, and even more preferably 0.15 or less.

[0061] By setting the value (Sg / St) of formula (5) in the above range, the land portion rigidity of the tread can be increased. If the value (Sg / St) of formula (5) is less than the above range, the proportion of the land portion becomes too high, so drainage and grip tend to decrease. On the other hand, if the value (Sg / St) of formula (5) exceeds the above range, sufficient land portion rigidity of the tread cannot be obtained, so steering stability tends to decrease.

[0062] In this specification, the "contact area (St) of the tread surface" is calculated from the contact shape of the tread surface when the tread is pressed against a flat surface under a normal load in a normal state. St is the total area including the grooves and sipes. The total area Sg1 of the circumferential grooves and the total area Sg2 of the widthwise grooves and sipes are also calculated from the contact shape of the tread surface when the tread is pressed against a flat surface under a normal load in a normal state. Sg is the sum of Sg1 and Sg2.

[0063] <Layout of inner tread layer and clinch> In the tire of the present disclosure, the height of the end of the tread inner layer at the tire cross-sectional height (HT) is higher than the height of the upper end of the clinch, or if it is lower than the height of the upper end of the clinch, the tread inner layer is preferably disposed on the inner side of the clinch in the tire width direction with a carcass between the clinch and the tread inner layer. Although there is a large difference in rubber hardness between the tread inner layer and the clinch, such a configuration prevents the tread inner layer and the clinch from coming into contact with each other, thereby preventing deterioration of durability. For example, in FIG. 1, the height of the end (12E) of the tread inner layer 12 is higher than the height of the upper end (3E) of the clinch, and in FIG. 2, the height of the end (12E) of the tread inner layer 12 is lower than the height of the upper end (3E) of the clinch 3, but the tread inner layer 12 and the clinch 3 are disposed in the sidewall portion with a carcass 4 between them, so they are not in contact with each other.

[0064] [Rubber composition] The rubber composition constituting the tire of the present disclosure can be manufactured by a conventional method in the tire industry. In particular, the 30°C tan δ value of the rubber composition constituting the tread inner layer of the tire of the present disclosure is smaller than the 30°C tan δ value of the rubber composition constituting the sidewall, and such adjustment can be performed by a conventional method in the tire industry.

[0065] Specifically, the value of 30°C tan δ can be adjusted by the type and amount of chemicals (particularly rubber components, fillers, softeners, sulfur, vulcanization accelerators, and silane coupling agents) compounded in the rubber composition. For example, 30°C tan δ tends to be smaller when a rubber component with fewer unsaturated bonds is used, a softener with high compatibility with the rubber component is used, a modified rubber is used, silica is used as a filler, the amount of oil as a plasticizer is reduced, the amount of sulfur is increased, the amount of vulcanization accelerator is increased, or the amount of silane coupling agent is increased. Therefore, those skilled in the art can adjust the value of 30°C tan δ as appropriate according to the target value.

[0066] Hereinafter, chemicals that can be used in the rubber composition constituting the tire of the present disclosure, particularly in the rubber composition constituting the tread first layer, the tread inner layer or the sidewall, will be described.

[0067] <Rubber component> The rubber composition according to the present disclosure preferably contains, as a rubber component, at least one selected from the group consisting of isoprene-based rubber, styrene-butadiene rubber (SBR), and butadiene rubber (BR), more preferably contains SBR, and even more preferably contains SBR and BR. The rubber component may consist of only SBR and BR.

[0068] (SBR) There is no particular limitation on the SBR, and examples thereof include solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), and modified SBRs thereof (modified S-SBR, modified E-SBR). Modified SBRs include SBRs whose ends and / or main chains are modified, and modified SBRs (condensates, those having a branched structure, etc.) coupled with tin, silicon compounds, etc. Among these, S-SBR and modified SBR are preferred. Furthermore, hydrogenated products of these SBRs (hydrogenated SBR), etc. can also be used. These SBRs may be used alone or in combination of two or more.

[0069] Examples of S-SBR that can be used in the present disclosure include S-SBR manufactured and sold by JSR Corporation, Sumitomo Chemical Co., Ltd., Ube Industries, Ltd., Asahi Kasei Corporation, ZS Elastomers Co., Ltd., and the like.

[0070] From the viewpoints of wet grip performance and abrasion resistance, the styrene content of SBR is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more. From the viewpoints of temperature dependency of grip performance and blow resistance, the styrene content is preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less. In this specification, the styrene content of SBR is 1 It is calculated by H-NMR measurement.

[0071] The vinyl content of SBR is preferably 10 mol% or more, more preferably 15 mol% or more, and even more preferably 20 mol% or more, from the viewpoints of ensuring reactivity with silica, wet grip performance, rubber strength, and abrasion resistance. Also, the vinyl content of SBR is preferably 70 mol% or less, more preferably 65 mol% or less, and even more preferably 60 mol% or less, from the viewpoints of preventing an increase in temperature dependency, breaking elongation, and abrasion resistance. In this specification, the vinyl content of SBR (amount of 1,2-bonded butadiene units) is measured by infrared absorption spectroscopy.

[0072] From the viewpoint of wet grip performance, the weight average molecular weight (Mw) of SBR is preferably 200,000 or more, more preferably 250,000 or more, and even more preferably 300,000 or more. From the viewpoint of crosslinking uniformity, the weight average molecular weight is preferably 2,000,000 or less, more preferably 1,800,000 or less, and even more preferably 1,500,000 or less. In this specification, the weight average molecular weight of SBR can be calculated in terms of standard polystyrene based on the measured value by gel permeation chromatography (GPC) (for example, GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTIPORE HZ-M manufactured by Tosoh Corporation).

[0073] In the case where SBR is contained, the content in 100% by mass of the rubber component is preferably 30% by mass or more, more preferably 35% by mass or more, and even more preferably 40% by mass or more, from the viewpoint of the effects of the present disclosure. The content of SBR is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less.

[0074] (BR) The BR is not particularly limited, and examples of the BR that can be used include those commonly used in the tire industry, such as BR with a cis 1,4 bond content (cis content) of less than 50% (low cis BR), BR with a cis 1,4 bond content of 90% or more (high cis BR), rare earth butadiene rubber (rare earth BR) synthesized using a rare earth catalyst, BR containing syndiotactic polybutadiene crystals (SPB-containing BR), and modified BR (high cis modified BR, low cis modified BR). These BRs may be used alone or in combination of two or more.

[0075] The modified BR is obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and includes those in which the terminals of the modified BR molecule are bonded with tin-carbon bonds (tin-modified BR), butadiene rubber having a condensed alkoxysilane compound at the active terminal of the butadiene rubber (silica-modified BR), etc. Examples of such modified BR include tin-modified BR and silica-modified BR manufactured and sold by ZS Elastomer Co., Ltd.

[0076] From the viewpoint of wear resistance, the weight average molecular weight (Mw) of BR is preferably 300,000 or more, more preferably 350,000 or more, and even more preferably 400,000 or more. From the viewpoint of crosslinking uniformity, it is preferably 2,000,000 or less, and more preferably 1,000,000 or less. The weight average molecular weight of BR can be determined by standard polystyrene conversion based on the measured value obtained by gel permeation chromatography (GPC) (for example, GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTIPORE HZ-M manufactured by Tosoh Corporation).

[0077] When BR is contained, the content in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, from the viewpoint of the effects of the present disclosure. The content of BR is preferably 70% by mass or less, more preferably 65% ​​by mass or less, and even more preferably 60% by mass or less.

[0078] (Isoprene rubber) As the isoprene-based rubber, for example, isoprene rubber (IR) and natural rubber, which are common in the tire industry, can be used. In addition to unmodified natural rubber (NR), natural rubber also includes modified natural rubber such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), high-purity natural rubber, and grafted natural rubber. These isoprene-based rubbers may be used alone or in combination of two or more.

[0079] The NR is not particularly limited, and any NR commonly used in the tire industry can be used, such as SIR20, RSS#3, and TSR20.

[0080] When an isoprene-based rubber is contained, the content thereof in 100% by mass of the rubber component is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less, from the viewpoint of the present disclosure. In addition, when an isoprene-based rubber is contained, the lower limit of the content is not particularly limited, and may be 0% by mass.

[0081] (Other rubber components) The rubber component according to the present disclosure may contain rubber components other than the isoprene-based rubber, SBR, and BR. As the other rubber components, crosslinkable rubber components generally used in the tire industry can be used, such as styrene-isoprene-butadiene copolymer rubber (SIBR), styrene-isobutylene-styrene block copolymer (SIBS), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), hydrogenated nitrile rubber (HNBR), butyl rubber (IIR), ethylene propylene rubber, polynorbornene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), hydrin rubber, and the like. These other rubber components may be used alone or in combination of two or more. The content of the other rubber in the rubber component may be 0% by mass.

[0082] <Filler> The rubber composition according to the present disclosure preferably contains silica as a filler, and more preferably contains carbon black and silica.

[0083] (Carbon Black) As the carbon black, any carbon black commonly used in the tire industry can be appropriately used, such as N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. These carbon blacks may be used alone or in combination of two or more kinds.

[0084] From the perspective of reinforcement, the nitrogen adsorption specific surface area (N2SA) of carbon black is 80m 2 / g or more is preferable, and 90m 2 / g or more is more preferable, and 100m 2 From the viewpoints of fuel economy and processability, N2SA is more preferably 200m 2 / g or less is preferable, and 170m 2 / g or less is more preferable, and 155m 2 The N2SA of carbon black is a value measured in accordance with JIS K 6217-2 "Basic properties of carbon black for rubber - Part 2: Determination of specific surface area - Nitrogen adsorption method - Single point method".

[0085] When carbon black is contained, the content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more from the viewpoint of abrasion resistance and wet grip performance, and is preferably 50 parts by mass or less, more preferably 35 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 10 parts by mass or less from the viewpoint of fuel economy.

[0086] (silica) The silica is not particularly limited, and can be, for example, silica prepared by a dry method (anhydrous silica), silica prepared by a wet method (hydrated silica), or other silica commonly used in the tire industry. Among them, hydrated silica prepared by a wet method is preferred because it contains a large number of silanol groups. These silicas can be used alone or in combination of two or more.

[0087] The nitrogen adsorption specific surface area (N2SA) of silica is set at 140m from the viewpoints of fuel efficiency and wear resistance. 2 / g or more is preferable, and 170m 2 From the viewpoints of fuel efficiency and processability, it is more preferable that the tensile strength is 350 m 2 / g or less is preferable, and 300m 2 / g or less is more preferable, and 250m 2 / g or less is more preferable. In this specification, the N2SA of silica is a value measured by the BET method in accordance with ASTM D3037-93.

[0088] When silica is contained, the content per 100 parts by mass of the rubber component is preferably 20 parts by mass or more, more preferably 40 parts by mass or more, even more preferably 50 parts by mass or more, and particularly preferably 60 parts by mass or more, from the viewpoint of wet grip performance, and is preferably 130 parts by mass or less, more preferably 120 parts by mass or less, and even more preferably 110 parts by mass or less, from the viewpoint of abrasion resistance.

[0089] The total content of silica and carbon black per 100 parts by mass of the rubber component is preferably 40 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 60 parts by mass or more from the viewpoint of abrasion resistance, and is preferably 160 parts by mass or less, more preferably 140 parts by mass or less, and even more preferably 120 parts by mass or less from the viewpoint of fuel economy and elongation at break.

[0090] The proportion of silica to the total content of silica and carbon black is preferably 60 mass % or more, more preferably 70 mass % or more, further preferably 80 mass % or more, and particularly preferably 85 mass % or more.

[0091] (Other fillers) As fillers other than silica and carbon black, those which have been generally used in the tire industry, such as aluminum hydroxide, calcium carbonate, alumina, clay, and talc, can be used.

[0092] (Silane coupling agent) Silica is preferably used in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and any silane coupling agent conventionally used in combination with silica in the tire industry can be used. Examples of the silane coupling agent include the following mercapto-based silane coupling agents; sulfide-based silane coupling agents such as bis(3-triethoxysilylpropyl) disulfide and bis(3-triethoxysilylpropyl) tetrasulfide; vinyl-based silane coupling agents such as vinyl triethoxysilane and vinyl trimethoxysilane; amino-based silane coupling agents such as 3-aminopropyl triethoxysilane, 3-aminopropyl trimethoxysilane and 3-(2-aminoethyl) aminopropyl triethoxysilane; glycidoxy-based silane coupling agents such as γ-glycidoxypropyl triethoxysilane and γ-glycidoxypropyl trimethoxysilane; nitro-based silane coupling agents such as 3-nitropropyl trimethoxysilane and 3-nitropropyl triethoxysilane; and chloro-based silane coupling agents such as 3-chloropropyl trimethoxysilane and 3-chloropropyl triethoxysilane. Among them, sulfide-based silane coupling agents and / or mercapto-based silane coupling agents are preferred, and mercapto-based silane coupling agents are more preferred. These silane coupling agents may be used alone or in combination of two or more.

[0093] The mercapto-based silane coupling agent is preferably a compound represented by the following formula (7) and / or a compound containing a bonding unit A represented by the following formula (8) and a bonding unit B represented by the following formula (9). [ka] (In the formula, R 101 , R 102 , and R 103 are each independently an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or -O-(R 111 -O) z -R 112 (z R 111 each independently represents a divalent hydrocarbon group having 1 to 30 carbon atoms; R112 represents an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, or an aralkyl group having 7 to 30 carbon atoms; z represents an integer of 1 to 30; 104 represents an alkylene having 1 to 6 carbon atoms. [ka] [ka] (wherein x represents an integer of 0 or more; y represents an integer of 1 or more; R 201 represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, or an alkynyl group having 2 to 30 carbon atoms, which may be substituted by a hydroxyl or carboxyl group; R 202 represents an alkylene having 1 to 30 carbon atoms, an alkenylene having 2 to 30 carbon atoms, or an alkynylene having 2 to 30 carbon atoms; 201 and R 202 may form a ring structure.)

[0094] Examples of the compound represented by formula (7) include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and the compound represented by the following formula (10) (Si363 manufactured by Evonik Degussa), and the compound represented by the following formula (10) can be preferably used. These may be used alone or in combination of two or more kinds. [ka]

[0095] Examples of compounds containing a bond unit A represented by formula (8) and a bond unit B represented by formula (9) include those manufactured and sold by Momentive, Inc. These may be used alone or in combination of two or more.

[0096] The content of silane coupling agent with respect to 100 parts by mass of silica (when multiple silane coupling agents are used, the total amount of all of them) is preferably 1.0 parts by mass or more, more preferably 3.0 parts by mass or more, and even more preferably 5.0 parts by mass or more, from the viewpoint of increasing the dispersibility of silica.Furthermore, from the viewpoint of cost and processability, it is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 12 parts by mass or less.

[0097] As the filler, in addition to carbon black and silica, other fillers may be used. Such fillers are not particularly limited, and any fillers generally used in this field, such as aluminum hydroxide, alumina (aluminum oxide), calcium carbonate, magnesium sulfate, talc, clay, etc., may be used. These fillers may be used alone or in combination of two or more.

[0098] <Other compounding agents> In addition to the above-mentioned components, the rubber composition according to the present disclosure may appropriately contain compounding agents commonly used in the tire industry, such as softeners, waxes, processing aids, stearic acid, zinc oxide, antioxidants, vulcanizing agents, and vulcanization accelerators.

[0099] (Softener) The rubber composition according to the present disclosure preferably contains a softener. Examples of the softener include resin, oil, liquid rubber, and ester-based plasticizer. The softener may be used alone or in combination of two or more kinds.

[0100] The resin is not particularly limited, but examples thereof include petroleum resins, terpene resins, rosin resins, phenol resins, etc., which are commonly used in the tire industry. The resins may be used alone or in combination of two or more kinds.

[0101] Examples of the petroleum resin include C5 petroleum resin, aromatic petroleum resin, C5C9 petroleum resin, etc. The petroleum resin may be used alone or in combination of two or more kinds.

[0102] C5 petroleum resin refers to a resin obtained by polymerizing a C5 fraction. Examples of C5 fractions include petroleum fractions having 4 to 5 carbon atoms, such as cyclopentadiene, pentene, pentadiene, and isoprene. As a C5 petroleum resin, dicyclopentadiene resin (DCPD resin) is preferably used.

[0103] The aromatic petroleum resin refers to a resin obtained by polymerizing a C9 fraction, and may be a hydrogenated or modified resin. Examples of the C9 fraction include petroleum fractions having 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, indene, and methylindene. Specific examples of aromatic petroleum resins that can be suitably used include coumarone-indene resins, coumarone resins, indene resins, and aromatic vinyl resins. As the aromatic vinyl resin, a homopolymer of α-methylstyrene or styrene or a copolymer of α-methylstyrene and styrene is preferred, and a copolymer of α-methylstyrene and styrene is more preferred, because they are economical, easy to process, and have excellent heat generation properties. As the aromatic vinyl resin, for example, commercially available products from Kraton, Eastman Chemical, etc. can be used.

[0104] The C5C9 petroleum resin refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and may be a hydrogenated or modified resin. Examples of the C5 fraction and the C9 fraction include the petroleum fractions mentioned above. As the C5C9 petroleum resin, for example, those commercially available from Tosoh Corporation, LUHUA, etc. can be used.

[0105] Examples of the terpene resin include polyterpene resins consisting of at least one selected from terpene compounds such as α-pinene, β-pinene, limonene, and dipentene; aromatic modified terpene resins made from the terpene compounds and aromatic compounds; terpene phenolic resins made from terpene compounds and phenolic compounds; and terpene resins obtained by subjecting these terpene resins to hydrogenation treatment (hydrogenated terpene resins). Examples of aromatic compounds that are raw materials for aromatic modified terpene resins include styrene, α-methylstyrene, vinyltoluene, and divinyltoluene. Examples of phenolic compounds that are raw materials for terpene phenolic resins include phenol, bisphenol A, cresol, and xylenol. The terpene resins may be used alone or in combination of two or more.

[0106] The rosin-based resin is not particularly limited, but examples thereof include natural resin rosin, and rosin-modified resins obtained by modifying natural resin rosin through hydrogenation, disproportionation, dimerization, esterification, etc. The rosin-based resins may be used alone or in combination of two or more kinds.

[0107] The phenol-based resin is not particularly limited, but examples thereof include phenol-formaldehyde resin, alkylphenol-formaldehyde resin, alkylphenol-acetylene resin, oil-modified phenol-formaldehyde resin, etc. The phenol-based resin may be used alone or in combination of two or more kinds.

[0108] From the viewpoint of wet grip performance, the softening point of the resin is preferably 60° C. or higher, and more preferably 65° C. or higher. From the viewpoint of processability and improving the dispersibility of the rubber component and the filler, the softening point is preferably 150° C. or lower, more preferably 140° C. or lower, and even more preferably 130° C. or lower. In this specification, the softening point may be defined as the temperature at which the ball drops when the softening point specified in JIS K 6220-1:2001 is measured using a ring and ball softening point measuring device.

[0109] When a resin is contained, the content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more from the viewpoint of wet grip performance, and is preferably 60 parts by mass or less, more preferably 40 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 15 parts by mass or less from the viewpoint of suppressing heat buildup.

[0110] Examples of the oil include process oil, vegetable oil, and animal oil. Examples of the process oil include paraffin-based process oil, naphthenic process oil, and aromatic process oil. In addition, as an environmental measure, process oil with a low content of polycyclic aromatic compound (PCA) compounds can be used. Examples of the low PCA content process oil include light extract solvate (MES), treated distillate aromatic extract (TDAE), and heavy naphthenic oil. One type of oil may be used alone, or two or more types may be used in combination.

[0111] When oil is contained, the content per 100 parts by mass of the rubber component is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more from the viewpoint of processability. Also, from the viewpoint of abrasion resistance, the content is preferably 60 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less. In this specification, the content of oil includes the amount of oil contained in the oil-extended rubber.

[0112] The liquid rubber is not particularly limited as long as it is a polymer that is in a liquid state at room temperature (25° C.), and examples thereof include liquid butadiene rubber (liquid BR), liquid styrene butadiene rubber (liquid SBR), liquid isoprene rubber (liquid IR), liquid styrene isoprene rubber (liquid SIR), liquid farnesene rubber, etc. These liquid rubbers may be used alone or in combination of two or more kinds.

[0113] When the liquid rubber is contained, the content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, and particularly preferably 5 parts by mass or more. The content of the liquid rubber is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 20 parts by mass or less.

[0114] Examples of ester-based plasticizers include dibutyl adipate (DBA), diisobutyl adipate (DIBA), dioctyl adipate (DOA), di-2-ethylhexyl azelate (DOZ), dibutyl sebacate (DBS), diisononyl adipate (DINA), diethyl phthalate (DEP), dioctyl phthalate (DOP), diundecyl phthalate (DUP), dibutyl phthalate (DBP), dioctyl sebacate (DOS), tributyl phosphate (TBP), trioctyl phosphate (TOP), triethyl phosphate (TEP), trimethyl phosphate (TMP), thymidine triphosphate (TTP), tricresyl phosphate (TCP), trixylenyl phosphate (TXP), etc. These ester-based plasticizers may be used alone or in combination of two or more.

[0115] When an ester plasticizer is contained, the content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, and particularly preferably 5 parts by mass or more. The content of the ester plasticizer is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 20 parts by mass or less.

[0116] The content of the softener per 100 parts by mass of the rubber component (the total amount when multiple softeners are used in combination) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more from the viewpoint of wet grip performance, and is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, even more preferably 50 parts by mass or less, and particularly preferably 40 parts by mass or less from the viewpoint of processability.

[0117] (wax) When the wax is contained, the content thereof per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, from the viewpoint of weather resistance of the rubber, and is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less, from the viewpoint of preventing whitening of the tire due to bloom.

[0118] (Processing aids) Examples of the processing aid include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, mixtures of fatty acid metal salts and fatty acid amides, etc. These processing aids may be used alone or in combination of two or more. Examples of the processing aids that can be used include those commercially available from Schill+Seilacher, Performance Additives, etc.

[0119] When a processing aid is contained, the content thereof per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, from the viewpoint of improving processability, and is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, from the viewpoints of abrasion resistance and breaking strength.

[0120] (Anti-aging agent) The antiaging agent is not particularly limited, but examples thereof include amine-based, quinoline-based, quinone-based, phenol-based, and imidazole-based compounds, and carbamic acid metal salts, and the like. Phenylenediamine-based antiaging agents such as N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, and N-cyclohexyl-N'-phenyl-p-phenylenediamine, and quinoline-based antiaging agents such as 2,2,4-trimethyl-1,2-dihydroquinoline polymer and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline are preferred. These antiaging agents may be used alone or in combination of two or more.

[0121] When an antioxidant is contained, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, from the viewpoint of ozone crack resistance of the rubber, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, from the viewpoint of abrasion resistance and wet grip performance.

[0122] (Stearic acid) When stearic acid is contained, the content thereof per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, from the viewpoint of processability, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, from the viewpoint of vulcanization speed.

[0123] (Zinc Oxide) When zinc oxide is contained, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, from the viewpoint of processability, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, from the viewpoint of abrasion resistance.

[0124] (Vulcanizing agent) As the vulcanizing agent, sulfur is preferably used, and examples of the sulfur that can be used include powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur.

[0125] When sulfur is contained as a vulcanizing agent, the content per 100 parts by mass of the rubber component is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, from the viewpoint of ensuring sufficient vulcanization reaction. Also, from the viewpoint of preventing deterioration, the content is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, and even more preferably 3.0 parts by mass or less. Note that, when oil-containing sulfur is used as a vulcanizing agent, the content of the vulcanizing agent is the total content of the pure sulfur contained in the oil-containing sulfur.

[0126] Examples of vulcanizing agents other than sulfur include alkylphenol-sulfur chloride condensates, sodium 1,6-hexamethylene-dithiosulfate dihydrate, 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, etc. As these vulcanizing agents other than sulfur, commercially available products from Taoka Chemical Co., Ltd., Lanxess Co., Ltd., Flexis, etc. can be used.

[0127] (Vulcanization accelerator) Examples of the vulcanization accelerator include sulfenamide-based, thiazole-based, thiuram-based, thiourea-based, guanidine-based, dithiocarbamic acid-based, aldehyde-amine-based or aldehyde-ammonia-based, imidazoline-based, and xanthate-based vulcanization accelerators. These vulcanization accelerators may be used alone or in combination of two or more. Among them, one or more vulcanization accelerators selected from the group consisting of sulfenamide-based, guanidine-based, and thiazole-based vulcanization accelerators are preferred.

[0128] Examples of sulfenamide vulcanization accelerators include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolylsulfenamide (DCBS), etc. Among them, N-cyclohexyl-2-benzothiazolylsulfenamide (CBS) is preferred.

[0129] Examples of the guanidine vulcanization accelerator include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatechol borate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, 1,3-di-o-cumenyl-2-propionylguanidine, etc. Among them, 1,3-diphenylguanidine (DPG) is preferable.

[0130] Examples of the thiazole-based vulcanization accelerator include 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, etc. Among these, 2-mercaptobenzothiazole is preferred.

[0131] When a vulcanization accelerator is contained, the content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 2 parts by mass or more. The content per 100 parts by mass of the rubber component is preferably 8 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 6 parts by mass or less. By setting the content of the vulcanization accelerator within the above range, breaking strength and elongation tend to be secured.

[0132] [Manufacturing] The rubber composition according to the present disclosure can be produced by a known method, for example, by kneading the above-mentioned components using a rubber kneading device such as an open roll or an internal kneader (such as a Banbury mixer or kneader).

[0133] The kneading step includes, for example, a base kneading step in which compounding ingredients and additives other than the vulcanizing agent and the vulcanization accelerator are kneaded, and a final kneading (F kneading) step in which the vulcanizing agent and the vulcanization accelerator are added to the kneaded product obtained in the base kneading step and kneaded. Furthermore, the base kneading step can be divided into a plurality of steps as desired.

[0134] The kneading conditions are not particularly limited, but examples thereof include a method in which in the base kneading step, kneading is performed for 3 to 10 minutes at a discharge temperature of 150 to 170° C., and in the final kneading step, kneading is performed for 1 to 5 minutes at 70 to 110° C. The vulcanization conditions are not particularly limited, but examples thereof include a method in which vulcanization is performed for 10 to 30 minutes at 150 to 200° C.

[0135] The tire of the present disclosure composed of the rubber composition can be manufactured by a normal method using the rubber composition. That is, an unvulcanized rubber composition obtained by blending the above-mentioned components with a rubber component as necessary is extruded into the shape of a first tread layer, a tread inner layer, or a sidewall, laminated together with other tire components on a tire building machine, and molded by a normal method to form an unvulcanized tire, and the unvulcanized tire is heated and pressurized in a vulcanizer to manufacture a tire.

[0136] [Application] The rubber composition can be used for various tire treads, such as passenger car tires, truck and bus tires, motorcycle tires, high performance tires, all-season tires, summer tires, and winter tires such as studless tires. Among them, at least one of passenger car tires and summer tires is preferable. EXAMPLES

[0137] The present disclosure will be specifically described below based on examples, but the present disclosure is not limited to these examples.

[0138] <Various chemicals> The various chemicals used in the examples and comparative examples are listed below. SBR1: HPR850 manufactured by JSR Corporation (styrene content: 27.5% by mass, vinyl content: 59.0% by mass, non-oil extended product) SBR2: SPRINTAN SLR6430 manufactured by TRINSEO (styrene content: 40% by mass, vinyl content: 24% by mass, Mw: 1.46 million, oil-extended product: contains 37.5 parts by mass of TDAE oil per 100 parts by mass of solids) BR1: UBEPOL BR (registered trademark) 150B manufactured by Ube Industries, Ltd. (cis content: 97%, Mw: 440,000) BR2: ASAPRENE N103 manufactured by Asahi Kasei Corporation (cis content: 38% by mass, Mw: 550,000) Carbon black: Diablack N220 (N2SA: 115m) manufactured by Mitsubishi Chemical Corporation 2 / g) Silica: ULTRASIL® VN3 (N2SA: 175 m) manufactured by Evonic 2 / g) Silane coupling agent 1: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonic Silane coupling agent 2: NXT-Z45 manufactured by Momentive (mercapto-based silane coupling agent: copolymer of bonding unit A (55 mol%) and bonding unit B (45 mol%)) Oil: H&R VIVATEC 500 (TDAE oil) Anti-aging agent: Antigen 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd. Stearic acid: Beads of stearic acid camellia manufactured by NOF Corporation Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Resin: Sylvatraxx 4401 manufactured by Kraton (copolymer of α-methylstyrene and styrene, softening point: 85°C) Sulfur: HK-200-5 (5% oil sulfur) manufactured by Hosoi Chemical Industry Co., Ltd. Vulcanization accelerator 1: Noccela CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Noccelaer D (DPG, 1,3-diphenylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0139] <Production of test vulcanized rubber sheets and test tires> According to the composition shown in Table 1, the chemicals other than sulfur and vulcanization accelerator were kneaded for 4 minutes at a discharge temperature of 160°C using a 1.7L closed Banbury mixer to obtain a kneaded product. Next, sulfur and vulcanization accelerator were added to the kneaded product obtained using an open roll, and the mixture was kneaded for 4 minutes to obtain an unvulcanized rubber composition. Furthermore, the unvulcanized rubber composition obtained was press-vulcanized for 12 minutes under the condition of 170°C to obtain a vulcanized rubber sheet for testing.

[0140] The unvulcanized rubber composition thus obtained was extruded to have the shape of the first tread layer, the inner tread layer, or the sidewall shown in Table 2, and then laminated together with other members to produce a raw tire. Next, in the vulcanization process, the tire was press molded at 170°C for 20 minutes to produce a test tire of 195 / 65R15 size. Here, in Table 2, the values ​​of Sce, Sr, θ, Sg (Sg1, Sg2) and St are values ​​measured from the ground contact shape when the tread is pressed against a flat surface under a normal load as described above, and the land width of the center land portion, the groove depth of the circumferential groove adjacent to the center land portion on the outer side in the tire width direction, La and Lb (Lb1, Lb2) are values ​​measured in the normal state as described above. Also, HT, H1 and H2 are values ​​measured by assembling one of the two obtained by dividing the tire in half at a plane including the tire meridian on a normal rim as described above.

[0141] <Evaluation> The evaluation method is as follows: The performance target value in the examples is a total performance index of 200 or more, which is the sum of the fuel economy index and the driving stability index.

[0142] (Measurement of tan δ) The loss tangent (30°C tan δ) of the test vulcanized rubber sheet was measured using a viscoelasticity spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.) under conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of 2%.

[0143] (low fuel consumption) The rolling resistance of each test tire was measured using a rolling resistance tester when it was run with a rim (15x6JJ), internal pressure (230kPa), load (3.43kN), and speed (80km / h), and was expressed as an index (rolling resistance index) with the standard comparative example (Comparative Example 1) taken as 100. A higher index indicates lower rolling resistance and better fuel economy.

[0144] (Handling stability) Each test tire was fitted to all wheels of a vehicle (a domestically produced FF vehicle with an engine displacement of 2000cc) and the vehicle was driven around a test course with a dry asphalt surface, and the lap time was measured. The driving stability was expressed as an index using the formula below. The higher the index, the better the driving stability. The reference tire was a commercially available tire of the same tire size with a rolling resistance performance labeling of AA or higher, and had a lap time that was faster (slower) than those of the examples and comparative examples. Steering stability=[(Lap time of reference tire−Lap time of test tire) / (Lap time of reference tire−Lap time of Comparative Example 1 tire)]×100

[0145] [Table 1]

[0146] [Table 2]

[0147] The results in Table 2 show that the tires of the examples show superior values ​​for the overall performance index, which is the sum of the fuel economy index and the handling stability index, compared to the tires of the comparative example, and that the overall performance of fuel economy and handling stability has been improved. [Explanation of symbols]

[0148] 1 Tread section 2 Sidewall 3. Clinch 3E Top of the clinch 4. Carcass 11 First tread layer 12 Tread inner layer 12E End of inner tread layer 13, 14, 15 Circumferential groove 16 Outer shoulder land area 17 Inner shoulder land area 18 Outer center land area 19 Inner Center Land Section 21 Outer shoulder width direction groove 22 Inner shoulder width direction groove 25 Outer center width groove 26 Inner center width groove 27 Outer center sipe 28 Inner center sipe C Tire Equator HT Tire section height To outer tread edge Ti inner tread edge TW tread width W Tire width direction Wt Tire section width

Claims

1. A tire having a tread portion and a sidewall portion each having two or more layers, The tread portion consisting of two or more layers includes at least a tread first layer which is outermost in the tire radial direction and a tread inner layer which is inner in the tire radial direction, An end portion of the tread inner layer extends to a sidewall portion, and the tread inner layer is disposed inward in the tire width direction in the sidewall portion relative to the sidewall, The ground contact surface of the tread first layer has two or more circumferential grooves extending continuously in the circumferential direction of the tire, a pair of shoulder land portions separated by two circumferential grooves located at both ends in the tire width direction, a center land portion located between the pair of shoulder land portions, and a width groove or a width groove and a sipe, When the area of ​​the entire land portion is Sr and the total area of ​​the center land portion is Sce, Sr and Sce are expressed by the following formula (1): Formula (1) 0.35≦Sce / Sr≦0.80 Fulfilling The loss tangent at 30° C. of the rubber composition constituting the tread inner layer is 30° C. tan δ BT The loss tangent at 30° C. of the rubber composition constituting the sidewall of the sidewall portion is 30° C. tan δ SW When the temperature is 30° C., tan δ BT and 30°C tan δ SW is expressed by the following formula (2): tanδ at 30°C of formula (2) BT / tanδ at 30°C SW < 1 Fulfilling The 30° C. tan δ BT , the Sr, and the Sce satisfy the following formula (3): Formula (3) 30°C tan δ BT × (Sce / Sr)≦0.05 Meet the tires.

2. The tire according to claim 1 , wherein the value of the right side of the formula (2) is 0.

9.

3. The tire according to claim 1 , wherein the value of the right side of the formula (2) is 0.

8.

4. The tire according to any one of claims 1 to 3, wherein the land width of one independent center land portion among the center land portions is at least twice the groove depth of at least one circumferential groove adjacent to the center land portion on the outer side in the tire width direction.

5. The tire according to any one of claims 1 to 4, wherein the central land portion has a sipe, the sipe extends to connect both edges of the central land portion in the width direction, and an angle θ between a straight line connecting both ends of the sipe of the central land portion in the width direction and the circumferential groove is in the range of 65 to 80 degrees.

6. When the circumferential length of the tire is La, the sum of the length Lb1 of the edge components of the width direction of the width direction grooves and the length Lb2 of the edge components of the width direction of the sipes is Lb, La and Lb are expressed by the following formula (4): Formula (4) 3≦Lb / La≦7 The tire according to claim 5, wherein

7. In the tread surface of the tread first layer, when a ground contact area of ​​the tread surface is St, and a sum of a total area Sg1 of the circumferential grooves and a total area Sg2 of the widthwise grooves and the sipes is Sg, St and Sg are expressed by the following formula (5): Formula (5) 0.20≦Sg / St≦0.40 The tire according to any one of claims 1 to 6, which satisfies the above.

8. The tire according to any one of claims 1 to 7, wherein the tire is a pneumatic tire for passenger cars.

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