pneumatic tires

Abstract

To provide a pneumatic tire excellent in total performance of low-fuel consumption performance, wet grip performance and steering stability.SOLUTION: Shoulder sipes 35 and 39 extending in a tire axis direction are provided in at least one of shoulder land parts 8 arranged at outermost sides in the tire axis direction in land parts 4. A tread width Wt and a groove depth D of a main groove satisfy the following formula (I), and lengths Ls of the shoulder sipes provided in the at least one of the shoulder land parts and the tread width Wt satisfy the following formula (II). A rubber composition for the shoulder land parts constituting the shoulder land parts includes four pts.mass or more of low-temperature plasticizer whose solidification temperature is -10°C or lower and three pts.mass or more of resin whose softening points are 60-120°C with respect to 100 pts.mass of rubber components.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Narrow-width (narrow tire section width), large-diameter (large tire outer diameter) pneumatic tires for passenger cars, in which the tire's internal pressure, section width (SW), and outer diameter (OD) satisfy a specific relationship, have been proposed as tires that reduce rolling resistance and achieve low fuel consumption.

[0003] Although methods for improving fuel economy from the compounding aspect, such as rubber compositions with reduced filler content, have been proposed, reducing the amount of filler to improve fuel economy generally tends to reduce wet grip performance, making it difficult to achieve both. Therefore, it is desired to improve fuel economy, wet grip performance, and steering stability in a balanced manner in pneumatic tires such as narrow-width, large-diameter tires. Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to solve the above problems and to provide a pneumatic tire that is excellent in overall performance, including fuel economy, wet grip performance, and steering stability. [Means for solving the problem]

[0005] The present invention is a pneumatic tire having a tread portion provided with three or more main grooves extending continuously in the tire circumferential direction and land portions separated by the main grooves, the main grooves include a pair of shoulder main grooves extending continuously in the tire circumferential direction at positions on both axially outer sides of the tire equator, and a center main groove extending continuously in the tire circumferential direction between the pair of shoulder main grooves, At least one of the shoulder land portions arranged on the outermost sides in the tire axial direction of the land portion is provided with a shoulder sipe extending in the tire axial direction, The tread width Wt and the groove depth D of the main groove satisfy the following formula (I), The length Ls of the shoulder sipe provided in at least one of the shoulder land portions and the tread width Wt satisfy the following formula (II), The shoulder land portion rubber composition is characterized in that it contains, per 100 parts by mass of a rubber component, 4 parts by mass or more of a low-temperature plasticizer having a solidification temperature of -10°C or less and 3 parts by mass or more of a resin having a softening point of 60 to 120°C. Regarding pneumatic tires.

number

[0006] The low-temperature plasticizer has a kinematic viscosity of 60 mm at 40°C. 2 / s or less is preferable. [Effects of the Invention]

[0007] According to the present invention, there is provided a pneumatic tire having a tread portion provided with three or more main grooves extending continuously in the tire circumferential direction and land portions separated by the main grooves, wherein the main grooves include a pair of shoulder main grooves extending continuously in the tire circumferential direction at positions on both axially outer sides of the tire equator, and a center main groove extending continuously in the tire circumferential direction between the pair of shoulder main grooves, at least one of the shoulder land portions arranged on the axially outermost side of the land portion is provided with a shoulder sipe extending in the tire axial direction, the tread width Wt, the groove depth D of the main groove, the shoulder sipe length Ls, and the tread width Wt satisfy a predetermined relationship, and the shoulder land portion uses a rubber composition comprising a low-temperature plasticizer with a specific freezing temperature and a resin with a specific softening point in a predetermined blend, thereby providing a pneumatic tire with excellent overall performance in terms of fuel economy, wet grip performance, and handling stability. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a development view of a tread portion of a pneumatic tire according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of the tread portion taken along line AA in FIG. [Figure 3] FIG. 2 is an enlarged view of the outer middle land portion of FIG. [Figure 4] 4(a) is a cross-sectional view of the first inclined portion taken along line BB in FIG. 3, and FIG. 4(b) is a cross-sectional view of the second inclined portion taken along line CC in FIG. [Figure 5] FIG. 2 is an enlarged view of the inner middle land portion of FIG. [Figure 6] FIG. 2 is an enlarged view of the outer shoulder land portion of FIG. 1. [Figure 7] FIG. 2 is an enlarged view of the inner shoulder land portion of FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention provides a pneumatic tire having a tread portion with three or more circumferentially continuous main grooves and land portions separated by the main grooves, the main grooves including a pair of shoulder main grooves extending circumferentially continuously at positions axially outboard of the tire equator and a center main groove extending circumferentially between the pair of shoulder main grooves, at least one of the axially outermost shoulder land portions is provided with a shoulder sipe extending in the tire axial direction, the tread width Wt and the groove depth D of the main groove satisfy formula (I), and the length Ls of the shoulder sipe in at least one of the shoulder land portions and the tread width Wt satisfy formula (II), and the shoulder land portion is formed using a rubber composition containing a low-temperature plasticizer with a specific freezing temperature and a resin with a specific softening point in a predetermined blend. This tire can provide a pneumatic tire with excellent overall performance in terms of fuel economy, wet grip performance, and handling stability.

[0010] The reason why such an effect is obtained is not clear, but is presumed to be as follows. Reducing the amount of filler to improve fuel economy typically results in a decline in wet grip performance. However, by using a rubber composition for the shoulder land portion that contains a well-balanced blend of a specific low-temperature plasticizer and resin, it is possible to improve wet grip performance without deteriorating fuel economy. Furthermore, while the incorporation of a low-temperature plasticizer tends to reduce thermal degradation, adopting a pattern that satisfies the above formulas (I) and (II) improves block rigidity, suppressing rubber deformation and heat accumulation. Adding a resin to improve wet grip performance increases the glass transition temperature (Tg), improving wet grip performance but tending to deteriorate fuel economy. On the other hand, adding a low-temperature plasticizer can improve wet grip performance while suppressing the increase in Tg, thereby suppressing the deterioration of fuel economy. Furthermore, while low-temperature plasticizers tend to reduce thermal degradation due to their small molecular weight, improving block rigidity with the above pattern is believed to suppress rubber deformation and reduce heat accumulation. Therefore, it is believed that the overall performance of fuel economy, wet grip performance, and handling stability is improved.

[0011] An embodiment of the present invention will now be described with reference to the drawings. Fig. 1 is a development view of a tread portion 2 of a pneumatic tire (hereinafter sometimes simply referred to as "tire") 1 of this embodiment. Fig. 2 is a cross-sectional view of the tread portion 2 of Fig. 1 taken along line AA. The pneumatic tire 1 of this embodiment is suitably used for passenger cars, for example.

[0012] The tread portion 2 of this embodiment has a tread pattern that specifies the orientation of the tire when mounted on a vehicle. The orientation of the tire when mounted on a vehicle is indicated by letters or marks on the sidewall (not shown), for example. In Fig. 1, the left side corresponds to the outer side of the vehicle, and the right side corresponds to the inner side of the vehicle.

[0013] By specifying the orientation for mounting on the vehicle, the tread portion 2 has an outer tread end Te1 located on the outer side of the vehicle when mounted on the vehicle, and an inner tread end Te2 located on the inner side of the vehicle when mounted on the vehicle.

[0014] Each tread end Te1, Te2 is the axially outermost contact point when the tire 1 is mounted on a standard rim (not shown), filled to a standard internal pressure, and in a standard state with no load, and is placed on a flat surface with a camber angle of 0 under a standard load.

[0015] A "genuine rim" is a rim that is defined for each tire by the standard system that includes the standard on which the tire is based. For example, 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."

[0016] "Normal internal pressure" is the air pressure specified for each tire by each standard in the standard system, including the standard 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," and for ETRTO, it is the "INFLATION PRESSURE."

[0017] "Normal load" is the load specified for each tire by each standard in the standard system, including the standard on which the tire is based. For JATMA, it is "maximum load capacity," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it is "LOAD CAPACITY."

[0018] The tread portion 2 of the tire 1 is provided with three or more main grooves 3 extending continuously in the tire circumferential direction, and land portions 4 separated by the main grooves 3.

[0019] Each main groove 3 extends, for example, linearly in the tire circumferential direction, but may also extend, for example, in a zigzag or wavy pattern.

[0020] The main grooves 3 include, for example, shoulder main grooves 5 provided on the outer tread edge Te1 side or the inner tread edge Te2 side, and a center main groove 6 provided closer to the tire equator C than the shoulder main grooves 5.

[0021] The shoulder main grooves 5 include, for example, an outer shoulder main groove 5A provided on the outer tread edge Te1 side and an inner shoulder main groove 5B provided on the inner tread edge Te2 side.

[0022] The center main groove 6 is provided, for example, between the outer shoulder main groove 5A and the inner shoulder main groove 5B. In this embodiment, for example, one center main groove 6 is provided on the tire equator C. For example, one center main groove 6 may be provided on the outer tread edge Te1 side and one on the inner tread edge Te2 side of the tire equator C.

[0023] In this embodiment, the groove width W1 of each of the shoulder main grooves 5A and 5B and the groove width W2 of the center main groove 6 are, for example, Ground contact width TW 3.5 to 10.0% of the tread is desirable. Ground contact width TW is the distance in the tire axial direction between the outer tread edge Te1 and the inner tread edge Te2 of the tire 1 in the normal state.

[0024] In this embodiment, the inner shoulder main groove 5B has a groove width greater than that of the outer shoulder main groove 5A, for example, which improves the steering stability on dry roads and the wet performance in a well-balanced manner.

[0025] In this embodiment, the center main groove 6 has a groove width greater than that of the inner shoulder main groove 5B, for example, which allows water to be easily discharged near the tire equator C during wet driving, effectively suppressing hydroplaning.

[0026] By providing the above-mentioned main grooves 3, the land portion 4 is divided into, for example, a middle land portion 7 between the shoulder main groove 5 and the center main groove 6, and a shoulder land portion 8 on the axially outer side of the shoulder main groove 5.

[0027] The middle land portion 7 includes, for example, an outer middle land portion 7A between the outer shoulder main groove 5A and the center main groove 6, and an inner middle land portion 7B between the inner shoulder main groove 5B and the center main groove 6. The shoulder land portion 8 includes, for example, an outer shoulder land portion 8A between the outer shoulder main groove 5A and the axially outer end Po of the tread, and an inner shoulder land portion 8B between the inner shoulder main groove 5B and the axially inner end Pi of the tread.

[0028] An enlarged view of the outer middle land portion 7A is shown in Figure 3. As shown in Figure 3, the outer middle land portion 7A is provided with a through sipe 10 that crosses the entire width of the land portion. In this specification, the term "sipe" refers to a cut whose main portion is 1.5 mm or less in width, but also includes an embodiment in which the land portion has an opening whose width exceeds 1.5 mm on the tread side.

[0029] The through sipe 10 includes a first inclined portion 11 and a second inclined portion 12 in a plan view of the tread.

[0030] The first inclined portion 11 is inclined with respect to the tire axial direction. In this embodiment, the first inclined portion 11 is inclined, for example, toward one side in the tire circumferential direction (upward in FIG. 3 ) from the center main groove 6 and extends linearly. The angle θ1 of the first inclined portion 11 with respect to the tire axial direction is, for example, 20 to 30 degrees.

[0031] Figure 4(a) shows a cross-sectional view of the first inclined portion 11 taken along line BB in Figure 3. As shown in Figure 4(a), the first inclined portion 11 has, for example, a constant width from the tread surface 2s of the land portion to the bottom.

[0032] As shown in Fig. 3, the second inclined portion 12 is disposed, for example, closer to the outer tread edge Te1 than the first inclined portion 11 (as shown in Fig. 1, and the same applies hereinafter). The second inclined portion 12 is inclined in the opposite direction to the first inclined portion 11. The second inclined portion 12 of this embodiment extends linearly, for example, from the outer shoulder main groove 5A, inclining toward one side in the tire circumferential direction.

[0033] In this embodiment, the angle θ2 of the second inclined portion 12 with respect to the tire axial direction is preferably smaller than, for example, the angle θ1 of the first inclined portion 11 with respect to the tire axial direction. Specifically, the angle θ2 of the second inclined portion 12 with respect to the tire axial direction is, for example, 18 to 25 degrees.

[0034] Figure 4(b) shows a cross-sectional view of the second inclined portion 12 taken along line CC in Figure 3. As shown in Figure 4(b), the second inclined portion 12 includes, for example, a main body portion 16 that extends with a constant width and an opening 17 whose width increases between the main body portion 16 and the tread surface 2s of the land portion. Such a second inclined portion 12 helps to improve wet performance.

[0035] 3, the through sipe 10 includes a V-shaped portion 14 where the first inclined portion 11 and the second inclined portion 12 are connected in a plan view of the tread. In the through sipe 10 having such a V-shaped portion 14, when a lateral force acts on the land portion, the opposing sipe walls are in close contact with each other. This increases the apparent rigidity of the outer middle land portion 7A, thereby improving steering stability.

[0036] An apex 18 of the V-shaped portion 14 of the through sipe 10 is provided closer to the outer tread end Te1 than a center position 20 in the width direction of the outer middle land portion 7A.

[0037] In order to suppress uneven wear near the apex 18, it is desirable that the angle θ3 between the first inclined portion 11 and the second inclined portion 12 be an obtuse angle. Specifically, the angle θ3 is preferably 125° or more, more preferably 130° or more, and is preferably 140° or less, more preferably 135° or less.

[0038] In this embodiment, the outer middle land portion 7A is provided with outer middle lug sipes 24 that extend from the outer shoulder main groove 5A and terminate within the outer middle land portion 7A. The through sipes 10 and the outer middle lug sipes 24 are alternately arranged in the tire circumferential direction.

[0039] The outer middle lug sipe 24 includes, for example, a third inclined portion 25 and a fourth inclined portion 26.

[0040] The third inclined portion 25 extends from the axially inner end 24i of the outer middle lug sipe 24, inclining in the same direction as the first inclined portion 11 of the through sipe 10. In this embodiment, the third inclined portion 25 extends, for example, along the first inclined portion 11.

[0041] The third inclined portion 25 of this embodiment has, for example, a configuration similar to the cross-sectional shape (shown in FIG. 4(a) and the same applies hereinafter) of the first inclined portion 11. That is, it is desirable that the third inclined portion 25 be formed with a constant width from the tread surface to the bottom of the land portion (not shown).

[0042] The fourth inclined portion 26 is disposed, for example, between the third inclined portion 25 and the outer shoulder main groove 5A. The fourth inclined portion 26 is inclined in the opposite direction to the third inclined portion 25. In a preferred embodiment, the fourth inclined portion 26 of the present embodiment extends, for example, along the second inclined portion 12 of the through sipe 10.

[0043] The fourth inclined portion 26 has, for example, a configuration similar to the cross-sectional shape of the second inclined portion 12 of the through sipe 10 (shown in FIG. 4(b), and the same applies hereinafter). That is, the fourth inclined portion 26 includes, for example, a main body portion extending with a constant width and an opening portion (not shown) whose width increases between the main body portion and the tread surface of the land portion. Such a fourth inclined portion 26 helps to improve wet performance.

[0044] By connecting the third inclined portion 25 and the fourth inclined portion 26, the outer middle lug sipe 24 includes a portion that extends along the V-shaped portion 14 of the through sipe 10. When a lateral force acts on the land portion, the outer middle lug sipe 24 allows the opposing sipe walls to come into close contact with each other, further increasing the apparent rigidity of the outer middle land portion 7A.

[0045] An enlarged view of the inner middle land portion 7B is shown in Fig. 5. As shown in Fig. 5, a plurality of inner middle sipes 28 are provided in the inner middle land portion 7B.

[0046] The inner middle sipe 28 includes, for example, a central inclined portion 30, and a first side portion 31 and a second side portion 32 provided on both sides of the central inclined portion 30 in the tire axial direction.

[0047] The central inclined portion 30 extends linearly and is inclined with respect to the tire axial direction, for example, and exhibits an edge effect in the tire circumferential direction and the tire axial direction.

[0048] The central inclined portion 30 is preferably inclined, for example, in the opposite direction to the first inclined portion 11 (shown in FIG. 1) of the through sipe 10. Such a central inclined portion 30 helps to suppress tire drift.

[0049] The angle θ4 of the central inclined portion 30 with respect to the tire axial direction is preferably equal to or greater than 40°, more preferably equal to or greater than 45°, and is preferably equal to or less than 55°, more preferably equal to or less than 50°. Such a central inclined portion 30 exerts an edge effect in a well-balanced manner in the tire circumferential direction and the tire axial direction.

[0050] The central inclined portion 30 of this embodiment has, for example, the same cross-sectional shape as the first inclined portion 11. That is, it is desirable that the central inclined portion 30 be formed with a constant width from the tread surface to the bottom of the land portion (not shown). In such a central inclined portion 30, the opposing sipe wall surfaces are in close contact with each other when the tire contacts the ground. This increases the apparent rigidity of the inner middle land portion 7B, resulting in excellent steering stability.

[0051] The first side portion 31, for example, connects the center main groove 6 and the central inclined portion 30. The second side portion 32, for example, connects the inboard shoulder main groove 5B and the central inclined portion 30.

[0052] It is desirable that the first side portion 31 and the second side portion 32 each extend along the tire axial direction, thereby suppressing uneven wear near the end portion of the inner middle sipe 28.

[0053] The first side portion 31 and the second side portion 32 preferably each have a cross-sectional shape similar to that of the second inclined portion 12 of the through sipe 10. That is, the first side portion 31 and the second side portion 32 include, for example, a main portion extending with a constant width and an opening whose width increases between the main portion and the tread surface of the land portion (not shown). Such first side portion 31 and second side portion 32 help improve wet performance.

[0054] As shown in Figure 1, the inner middle sipe 28 is preferably smoothly connected to the through sipe 10 in the outer middle land portion 7A via the center main groove 6. "Smoothly connecting each sipe via the main groove" means that virtual sipes, which are virtual extensions of each sipe, intersect within the main groove. This sipe arrangement approximates the circumferential stiffness distribution of the outer middle land portion 7A and the inner middle land portion 7B, which helps, for example, to linearize steering response at the beginning of a turn.

[0055] An enlarged view of the outer shoulder land portion 8A is shown in Figure 6. As shown in Figure 6, in the outer shoulder land portion 8A, for example, outer shoulder lateral grooves 34 and outer shoulder sipes 35 are provided alternately in the tire circumferential direction.

[0056] The outer shoulder lateral grooves 34 extend axially within the outer shoulder land portion 8A and terminate within the outer shoulder land portion 8A. This increases the axially inner rigidity of the outer shoulder land portion 8A, resulting in excellent handling stability. Furthermore, these outer shoulder lateral grooves 34 help reduce pumping noise by preventing air from flowing in from the outer shoulder main groove 5A.

[0057] The angle θ5 of the outer shoulder lateral groove 34 relative to the tire axial direction is preferably, for example, gradually increasing axially inward. Such outer shoulder lateral groove 34 can effectively guide water in the groove toward the outer tread edge Te1 during wet driving.

[0058] The outer shoulder sipe 35 extends, for example, from the outer shoulder main groove 5A axially outward in the tire and terminates within the outer shoulder land portion 8A.

[0059] The outer shoulder sipe 35 includes, for example, an inner portion 36 and an outer portion 37 .

[0060] The inner portion 36 communicates with the outer shoulder main groove 5A and extends axially along the tire. Such an inner portion 36 can suppress distortion of the contact patch between the inner end of the outer shoulder lateral groove 34 and the outer shoulder main groove 5A, thereby suppressing uneven wear.

[0061] The inner portion 36 preferably has a cross-sectional shape similar to that of the second inclined portion 12. That is, the inner portion 36 includes, for example, a main body portion extending with a constant width and an opening portion (not shown) whose width increases between the main body portion and the tread surface of the land portion. Such an inner portion 36 helps to improve wet performance.

[0062] For example, the outer portion 37 is continuous with the axially outer side of the inner portion 36. For example, the outer portion 37 terminates within the outer shoulder land portion 8A without reaching the outer tread edge Te1.

[0063] The outer portion 37 preferably has a cross-sectional shape similar to that of the first inclined portion 11. That is, the outer portion 37 is formed with a constant width from the tread surface to the bottom of the land portion (not shown), for example. Such an outer portion 37 helps to suppress uneven wear near the outer end of the outer shoulder sipe 35.

[0064] 1, it is desirable that the outer shoulder sipe 35 smoothly connect with the outer middle lug sipe 24 via the outer shoulder main groove 5A. Such a sipe arrangement helps to even out the progression of wear on the edges on both sides of the outer shoulder main groove 5A.

[0065] An enlarged view of the inner shoulder land portion 8B is shown in Figure 7. As shown in Figure 7, the inner shoulder land portion 8B has, for example, inner shoulder lateral grooves 38 and inner shoulder sipes 39 arranged alternately in the tire circumferential direction.

[0066] The inner shoulder lateral groove 38 has, for example, the same configuration as the outer shoulder lateral groove 34 (shown in FIG. 6). That is, the inner shoulder lateral groove 38 extends, for example, in the inner shoulder land portion 8B along the tire axial direction and terminates within the inner shoulder land portion 8B.

[0067] The inner shoulder sipe 39 includes, for example, an inner portion 40 and an outer portion 41 similar to the outer shoulder sipe 35 .

[0068] The inner portion 40 of the inboard shoulder sipe 39, for example, communicates with the inboard shoulder main groove 5B and extends along the tire axial direction. Moreover, it is desirable that the inner portion 40 of the inboard shoulder sipe 39 have a cross-sectional shape similar to that of the second inclined portion 12. That is, the inner portion 40 of the inboard shoulder sipe 39 includes, for example, a main body portion extending with a constant width and an opening portion (not shown) whose width increases between the main body portion and the tread surface of the land portion.

[0069] For example, the outer portion 41 of the inner shoulder sipe 39 is continuous with the inner portion 40 on the inner tread edge Te2 side. It is desirable that the outer portion 41 of the inner shoulder sipe 39 extends to the inner tread edge Te2. Such an inner shoulder sipe 39 helps to suppress distortion of the contact patch between the inner shoulder lateral grooves 38.

[0070] The outer portion 41 of the inner shoulder sipe 39 desirably has, for example, the same cross-sectional shape as the first inclined portion 11. That is, the outer portion 41 of the inner shoulder sipe 39 is formed, for example, with a constant width from the tread surface to the bottom of the land portion (not shown).

[0071] 1, it is desirable that the inner shoulder sipe 39 smoothly connects to the inner middle sipe 28 via the inner shoulder main groove 5B. Such a sipe arrangement helps to even out the progression of wear on the edges on both sides of the inner shoulder main groove 5B.

[0072] The pneumatic tire of the present invention has shoulder sipes extending in the tire axial direction on at least one of the shoulder land portions located at the outermost axial positions of the land portions, and the tire of Figures 1 and 2 has outer shoulder sipes 35 and inner shoulder sipes 39 on both the outer shoulder land portion 8A and the inner shoulder land portion 8B, respectively.

[0073] In the tire 1, the tread width Wt (mm) and the groove depth D (mm) of the main groove satisfy the following formula (I).

number

[0074] The tread width Wt of the tread portion 2 is the distance from one end to the other end in the axial direction of the tread. Po is the axially outer end of the tread, point Pi indicates the axially inner end of the tread, and the double arrow Wt indicates the axially outer end of the tread. PoFrom the axially inner edge of the tread Pi The groove depth D of the main groove (D1, D2, D3 in Figures 1 and 2) is the radial height from the bottom of the groove to the opening.

[0075] The groove depth D of the main grooves (in the tires of Figures 1 and 2, the groove depth D1 of the outer shoulder main groove 3, the groove depth D2 of the inner shoulder main groove 4, and the groove depth D3 of the center main groove 6) is preferably 3 to 12 mm, more preferably 4 to 10 mm, and even more preferably 5 to 8 mm, for example, in the case of a pneumatic tire for a passenger car. If it is equal to or greater than the lower limit, good drainage is obtained, and excellent wet performance tends to be obtained. If it is equal to or less than the upper limit, good rigidity is ensured, and excellent steering stability tends to be obtained.

[0076] The length Ls (mm) of the shoulder sipe provided in at least one of the shoulder land portions and the tread width Wt (mm) satisfy the following formula (II).

number

[0077] From the viewpoint of steering stability and the like, the length Ls of the shoulder sipe is, for example, preferably from 10 to 60 mm, more preferably from 2 to 50 mm, and even more preferably from 15 to 45 mm. The length Ls of the shoulder sipes is the length of each shoulder sipe in the axial direction of the tire, as shown in FIGS.

[0078] From the viewpoint of overall performance such as fuel economy, wet grip performance, and handling stability, the tread width Wt is, for example, preferably 140 to 250 mm, more preferably 150 to 220 mm, and even more preferably 160 to 200 mm.

[0079] From the viewpoint of overall performance such as fuel economy, wet grip performance, and steering stability, the tire outer diameter is, for example, preferably 600 to 700 mm, more preferably 610 to 690 mm, and even more preferably 630 to 680 mm. The tire outer diameter refers to the outer diameter of the tire when it is mounted on an applicable rim and no load is applied.

[0080] The shoulder land portion 8 is made of a rubber composition containing 100 parts by mass of rubber components, 4 parts by mass or more of a low-temperature plasticizer having a solidification temperature of -10°C or lower, and 3 parts by mass or more of a resin having a softening point of 60 to 120°C.

[0081] Examples of rubber components that can be used in the rubber composition include diene rubbers such as isoprene rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), and butyl rubber (IIR). Examples of isoprene rubbers include isoprene rubber (IR), epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, natural rubber (NR), deproteinized natural rubber (DPNR), highly purified natural rubber (UPNR), epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. These may be used alone or in combination of two or more. Among these, SBR and BR are preferred.

[0082] In the rubber composition, the content of SBR (total SBR content) in 100% by mass of the rubber component is preferably 30% by mass or more, more preferably 50% by mass or more, and even more preferably 70% by mass or more. The upper limit is preferably 95% by mass or less, more preferably 90% by mass or less. By keeping the content within the above range, good overall performance in terms of fuel economy, wet grip performance, and handling stability tends to be obtained.

[0083] From the viewpoints of fuel economy, wet grip performance, and handling stability, the SBR preferably contains a first styrene-butadiene rubber having a styrene content of 30% by mass or less and a second SBR having a styrene content of 35% by mass or more.

[0084] The first SBR has a styrene content of 30% by mass or less, preferably 28% by mass or less, and preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 20% by mass or more, and particularly preferably 25% by mass or more.

[0085] The vinyl content of the first SBR is preferably 20 mol% or more, more preferably 30 mol% or more, and even more preferably 40 mol% or more, and is preferably 80 mol% or less, more preferably 70 mol% or less.

[0086] The weight average molecular weight (Mw) of the first SBR is preferably 500,000 or more, more preferably 600,000 or more, and even more preferably 700,000 or more. On the other hand, the upper limit of Mw is not particularly limited, but is preferably 1,000,000 or less, more preferably 900,000 or less.

[0087] In the rubber composition, the content of the first SBR is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 35% by mass or more, based on 100% by mass of the rubber component. The upper limit is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 65% ​​by mass or less.

[0088] The second SBR has a styrene content of 35% by mass or more, preferably 40% by mass or more, and preferably 70% by mass or less, more preferably 60% by mass or less, and even more preferably 50% by mass or less.

[0089] The vinyl content of the second SBR is preferably 10 mol% or more, more preferably 20 mol% or more, and even more preferably 30 mol% or more, and is preferably 60 mol% or less, and more preferably 50 mol% or less.

[0090] The weight average molecular weight (Mw) of the second SBR is preferably 700,000 or more, more preferably 800,000 or more, and even more preferably 900,000 or more. On the other hand, the upper limit of Mw is not particularly limited, but is preferably 1.5 million or less, more preferably 1.3 million or less.

[0091] In the rubber composition, the content of the second SBR is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, based on 100% by mass of the rubber component. The upper limit is preferably 50% by mass or less, and more preferably 40% by mass or less.

[0092] In this specification, the styrene content of SBR is 1 It is calculated by H-NMR measurement. The vinyl content is the vinyl content of the butadiene moiety (the number of vinyl group units in the butadiene structure), 1 The Mw can be calculated by H-NMR measurement. The Mw can be calculated by standard polystyrene conversion based on measurements obtained by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTPORE HZ-M manufactured by Tosoh Corporation).

[0093] The first SBR and second SBR can be prepared by appropriately setting the blending ratio of raw material monomers such as styrene and 1,3-butadiene and using known methods such as emulsion polymerization, solution polymerization, and anionic polymerization. These SBRs may be those in which the main chain and / or terminals of the rubber are modified with a modifying agent, or those that have been modified with a polyfunctional modifying agent such as tin tetrachloride or silicon tetrachloride to have a partially branched structure. Among these, it is preferable that the main chain and / or terminals of the first SBR and / or second SBR are modified with a modifying agent having a functional group that interacts with silica.

[0094] Examples of functional groups that interact with silica include amino groups, amide groups, alkoxysilyl groups, isocyanate groups, imino groups, imidazole groups, urea groups, ether groups, carbonyl groups, oxycarbonyl groups, sulfide groups, disulfide groups, sulfonyl groups, sulfinyl groups, thiocarbonyl groups, ammonium groups, imide groups, hydrazo groups, azo groups, diazo groups, carboxyl groups, nitrile groups, pyridyl groups, alkoxy groups, hydrocarbon groups, hydroxyl groups, oxy groups, and epoxy groups. These functional groups may have a substituent. Among these, primary, secondary, and tertiary amino groups (particularly, glycidylamino groups), epoxy groups, hydroxyl groups, alkoxy groups (preferably alkoxy groups having 1 to 6 carbon atoms), alkoxysilyl groups (preferably alkoxysilyl groups having 1 to 6 carbon atoms), and hydrocarbon groups are preferred.

[0095] The modified SBR having a functional group that interacts with silica is preferably an SBR (S-modified SBR) modified with a compound (modifier) ​​represented by the following formula:

[0096] [ka]

[0097] In the above formula, R 1 , R 2 and R 3R may be the same or different and represent an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group (-COOH), a mercapto group (-SH), or a derivative thereof. 4 and R 5 are the same or different and represent a hydrogen atom or an alkyl group. 4 and R 5 may bond to form a ring structure together with the nitrogen atom, and n represents an integer.

[0098] As the S-modified SBR, an SBR in which the polymerization terminals (active terminals) of a solution-polymerized styrene-butadiene rubber (S-SBR) have been modified with a compound represented by the above formula (S-modified S-SBR (such as the modified SBR described in JP 2010-111753 A)) is preferably used.

[0099] R 1 , R 2 and R 3 is preferably an alkoxy group (preferably an alkoxy group having 1 to 8 carbon atoms, more preferably an alkoxy group having 1 to 4 carbon atoms). 4 and R 5 is preferably an alkyl group (preferably an alkyl group having 1 to 3 carbon atoms). n is preferably 1 to 5, more preferably 2 to 4, and even more preferably 3. In addition, R 4 and R 5 When the groups bond to form a ring structure together with the nitrogen atom, the ring is preferably a 4- to 8-membered ring. The alkoxy group also includes a cycloalkoxy group (such as a cyclohexyloxy group) and an aryloxy group (such as a phenoxy group or a benzyloxy group).

[0100] Specific examples of the compound represented by the above formula (the modifying agent) include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, and 3-diethylaminopropyltriethoxysilane. Of these, 3-dimethylaminopropyltrimethoxysilane, 3-dimethylaminopropyltriethoxysilane, and 3-diethylaminopropyltrimethoxysilane are preferred. These may be used alone or in combination of two or more.

[0101] As the modified SBR having a functional group that interacts with silica, SBR modified with a compound (modifier) ​​represented by the following formula can also be suitably used.

[0102] [ka]

[0103] In the above formula, R may be the same or different and represent a monovalent hydrocarbon group having 1 to 30 carbon atoms. 2 is expressed by the following formula:

[0104] [ka]

[0105] (In the formula, R 11 and R 12 R may be the same or different and represent a divalent hydrocarbon group. 13 represents a cyclic ether group. 3 is expressed by the following formula:

[0106] [ka]

[0107] (In the formula, R 21 represents an alkylene group or alkylarylene group having 2 to 10 carbon atoms. 22 represents a hydrogen atom or a methyl group. 23 represents an alkoxy group or aryloxy group having 1 to 10 carbon atoms. t is an integer of 2 to 20. a, b, and c represent the number of repetitions of each repeating unit.

[0108] As the SBR modified with the compound (modifier) ​​represented by the above formula, SBR in which the polymerization terminal (active terminal) of solution-polymerized SBR (S-SBR) has been modified with the compound represented by the above formula is preferably used.

[0109] R may be the same or different and represent a monovalent hydrocarbon group having 1 to 30 carbon atoms, which may be linear, branched, or cyclic, and examples thereof include an aliphatic hydrocarbon group having 1 to 30 carbon atoms, an alicyclic hydrocarbon group having 3 to 30 carbon atoms, and an aromatic hydrocarbon group having 6 to 30 carbon atoms. Of these, an aliphatic hydrocarbon group having 1 to 30 carbon atoms is preferred, an aliphatic hydrocarbon group having 1 to 20 carbon atoms is more preferred, an aliphatic hydrocarbon group having 1 to 10 carbon atoms is even more preferred, and an aliphatic hydrocarbon group having 1 to 3 carbon atoms is particularly preferred. Preferred examples of R include alkyl groups having the above carbon number, specifically methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, 2-ethylhexyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, octadecyl, etc. Of these, methyl is particularly preferred.

[0110] X 2 R in 11 and R 12are the same or different and represent divalent hydrocarbon groups, examples of which include branched or unbranched alkylene groups having 1 to 30 carbon atoms, branched or unbranched alkenylene groups having 2 to 30 carbon atoms, branched or unbranched alkynylene groups having 2 to 30 carbon atoms, and arylene groups having 6 to 30 carbon atoms. Of these, branched or unbranched alkylene groups having 1 to 30 carbon atoms are preferred, more preferably branched or unbranched alkylene groups having 1 to 15 carbon atoms, even more preferably branched or unbranched alkylene groups having 1 to 5 carbon atoms, and particularly preferably unbranched alkylene groups having 1 to 3 carbon atoms. R 11 and R 12 Preferred examples of include alkylene groups having the above carbon numbers, specifically methylene, ethylene, propylene, isopropylene, butylene, isobutylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, tridecylene, tetradecylene, pentadecylene, hexadecylene, heptadecylene, octadecylene, etc. Among these, methylene, ethylene, and propylene groups are particularly preferred.

[0111] X 2 R in 13 represents a cyclic ether group. Examples of the cyclic ether group include cyclic ether groups having one ether bond, such as oxirane group, oxetane group, oxolane group, oxane group, oxepane group, oxocane group, oxonane group, oxecane group, oxete group, and oxole group; cyclic ether groups having two ether bonds, such as dioxolane group, dioxane group, dioxepane group, and dioxecane group; and cyclic ether groups having three ether bonds, such as trioxane group. Among these, cyclic ether groups having one ether bond and 2 to 7 carbon atoms are preferred, cyclic ether groups having one ether bond and 2 to 5 carbon atoms are more preferred, and oxirane groups are even more preferred. Furthermore, it is preferable that the cyclic ether group does not have an unsaturated bond in the ring skeleton. Furthermore, hydrogen atoms of the cyclic ether group may be substituted with the monovalent hydrocarbon group described above.

[0112] X 3R in 21 represents an alkylene group or alkylarylene group having 2 to 10 carbon atoms, and among these, a branched or unbranched alkylene group having 2 to 8 carbon atoms is preferred, a branched or unbranched alkylene group having 2 to 6 carbon atoms is more preferred, a branched or unbranched alkylene group having 2 to 4 carbon atoms is even more preferred, and a branched or unbranched alkylene group having 3 carbon atoms is particularly preferred. 21 Preferred examples of include alkylene groups having the above carbon numbers, specifically ethylene, propylene, isopropylene, butylene, isobutylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, etc. Among these, ethylene, propylene, isopropylene, butylene, and isobutylene groups are particularly preferred, with propylene and isopropylene groups being most preferred.

[0113] X 3 In R 22 represents a hydrogen atom or a methyl group, and is particularly preferably a hydrogen atom.

[0114] X 3 In R 23 represents an alkoxy group or aryloxy group having 1 to 10 carbon atoms, and among these, a branched or unbranched alkoxy group having 1 to 8 carbon atoms is preferred, a branched or unbranched alkoxy group having 1 to 6 carbon atoms is more preferred, and a branched or unbranched alkoxy group having 1 to 4 carbon atoms is even more preferred. 23 Preferred examples of include alkoxy groups having the above carbon numbers, specifically methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, pentyloxy, hexyloxy, heptyloxy, octyloxy, etc. Of these, methoxy, ethoxy, propoxy, and butoxy are particularly preferred, and methoxy is most preferred.

[0115] X 3 In the formula, t is an integer of 2 to 20, and an integer of 2 to 8 is particularly preferred.

[0116] The method for modifying SBR with a modifier can be a conventional method, for example, by contacting styrene-butadiene rubber with the compound. Specifically, there is a method in which, after preparing SBR by solution polymerization, a predetermined amount of the compound is added to the rubber solution, and the polymerization terminals (active terminals) of the SBR are reacted with the modifier.

[0117] As the SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used.

[0118] In the rubber composition, the BR content in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more. The upper limit is preferably 50% by mass or less, more preferably 35% by mass or less, and even more preferably 25% by mass or less. Within the above range, good fuel economy, wear resistance, etc. tend to be ensured.

[0119] Examples of BR that can be used include high-cis content BR, low-cis content BR, and BR containing syndiotactic polybutadiene crystals. These may be used alone or in combination of two or more.

[0120] The cis content of BR is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 98% by mass or more, with no particular upper limit. Within the above range, better effects tend to be obtained. The cis content of BR can be measured by infrared absorption spectroscopy.

[0121] The BR may be either unmodified BR or modified BR, and examples of the modified BR include modified BR modified with the above-mentioned modifying agents.

[0122] As the BR, for example, products from Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Corporation, etc. can be used.

[0123] The low-temperature plasticizer has a solidification temperature of −10° C. or lower, preferably −15° C. or lower. On the other hand, the lower limit is preferably −100° C. or higher, more preferably −50° C. or higher, and even more preferably −30° C. or higher. When the solidification temperature is within the above range, good overall performance in terms of fuel economy, wet grip performance, and handling stability tends to be obtained. In the present invention, the solidification temperature is a value measured by the following method. The sample was sealed in an aluminum cell, and the aluminum cell was inserted into the sample holder of a differential scanning calorimeter (DSC-60A, manufactured by Shimadzu Corporation). The sample holder was then heated to 150°C at a rate of 10°C / min under a nitrogen atmosphere while observing the endothermic peak, which was taken as the freezing point.

[0124] In the rubber composition, the content of the low-temperature plasticizer is 4 parts by mass or more, preferably 5 parts by mass or more, and more preferably 6 parts by mass or more, per 100 parts by mass of the rubber component. This tends to provide good overall performance in terms of fuel economy, wet grip performance, and handling stability. While there is no particular upper limit, the content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less.

[0125] The kinematic viscosity of the low-temperature plasticizer at 40°C is preferably 60 mm 2 / s or less, preferably 50 mm 2 / s or less, more preferably 45 mm 2 / s or less. By setting it to the upper limit or less, it is possible to improve wet grip performance without deteriorating fuel economy. The lower limit is not particularly limited, but is preferably 5 mm 2 / s or more, preferably 10 mm 2 / s or more. The kinematic viscosity is a value measured at 40°C in accordance with JIS K2283-2000.

[0126] Examples of the low-temperature plasticizer include oils. Examples of the oil include process oils, vegetable oils, and mixtures thereof. Examples of the process oil include paraffin-based process oils, aromatic process oils, and naphthenic process oils. Examples of the vegetable oil include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. These may be used alone or in combination of two or more. Among these, process oils are preferred.

[0127] As the oil, for example, products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Orisoi Co., Ltd., H&R Co., Ltd., Toyokuni Oil Mills Co., Ltd., Showa Shell Sekiyu KK, Fuji Kosan Co., Ltd., etc. can be used.

[0128] As the low-temperature plasticizer, for example, compounds such as phosphate esters, phthalate esters, aliphatic polybasic acid esters, trimellitate esters, acetate esters, and ricinoleate esters, or mixtures thereof, can be suitably used. These may be used alone or in combination of two or more. Among these, phosphate esters, phthalate esters, and aliphatic polybasic acid esters are preferred, and aliphatic polybasic acid esters are more preferred.

[0129] As the phosphate ester, known phosphate ester-based plasticizers such as mono-, di-, or triesters of phosphoric acid with a monoalcohol having 1 to 12 carbon atoms or its (poly)oxyalkylene adduct can be used. Specific examples include tris(2-ethylhexyl) phosphate, trimethyl phosphate, triethyl phosphate, tributyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, and 2-ethylhexyl diphenyl phosphate.

[0130] As the phthalate ester, a known phthalate ester-based plasticizer can be used, such as a diester of phthalic acid with an alcohol having about 1 to 13 carbon atoms. Specific examples include bis(2-ethylhexyl) phthalate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diisodecyl phthalate, butyl benzyl phthalate, diisononyl phthalate, and ethyl phthalyl ethyl glycolate.

[0131] Examples of the aliphatic polybasic acid ester include aliphatic dibasic acid esters and aliphatic tribasic acid esters. Of these, aliphatic dibasic acid esters such as adipate esters, azelaate esters, sebacate esters, maleate esters, and fumarate esters are preferred.

[0132] Among these aliphatic dibasic acid esters, the compounds represented by the following formula can be preferably used. [ka] [In the formula, R 11 represents a divalent saturated or unsaturated hydrocarbon group. 12 and R 13 are the same or different and are branched or unbranched alkyl groups, or -(R 14 -O) n -R 15 (n R 14 are the same or different and represent a branched or unbranched alkylene group. 15 represents a branched or unbranched alkyl group. n represents an integer. represents a group represented by the formula:

[0133] R 11The divalent saturated or unsaturated hydrocarbon group may be branched or unbranched, and examples thereof include an alkylene group, an alkenylene group, an arylene group, etc. The saturated or unsaturated hydrocarbon group preferably has 1 to 10 carbon atoms, and more preferably 2 to 6 carbon atoms. Specific examples of the alkylene group include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, and a decylene group. Examples of the alkenylene group include a vinylene group, a 1-propenylene group, and a 2-propenylene group. Examples of the arylene group include a phenylene group, a tolylene group, and a xylylene group.

[0134] R 12 and R 13 With regard to the above, the number of carbon atoms in the branched or unbranched alkyl group is preferably 1 to 15, more preferably 4 to 10. Specific examples include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group.

[0135] R 12 and 13 No-(R 14 -O) n -R 15 For the group represented by R 14 The branched or unbranched alkylene group preferably has 1 to 3 carbon atoms. 15 The number of carbon atoms in the branched or unbranched alkyl group is preferably 1 to 10, more preferably 2 to 6. Specific examples of the alkylene group and the alkyl group include those similar to those mentioned above. The integer n is preferably 1 to 10, more preferably 1 to 5, and even more preferably 1 to 3.

[0136] Suitable examples of the aliphatic dibasic acid esters represented by the above formula include the -(R 14 -O) n -R 15and bis(alkoxyalkoxyalkyl)adipates having a group represented by the following formula: Other examples include di-n-butyl adipate, diisobutyl adipate, etc. These may be used alone or in combination of two or more.

[0137] As the trimellitic acid ester, a known trimellitic acid ester-based plasticizer can be used, such as a triester of trimellitic acid and a saturated aliphatic alcohol having 8 to 13 carbon atoms. Specific examples include tri-2-ethylhexyl trimellitate, tri-n-octyl trimellitate, tridecyl trimellitate, triisodecyl trimellitate, and di-n-octyl-n-decyl trimellitate.

[0138] As the acetate ester, known acetate ester-based plasticizers such as esters of acetic acid and mono- or polyglycerin can be used. Specific examples include glyceryl triacetate, 2-ethylhexyl acetate, and polyglycerin acetate esters having a degree of polymerization of 2 to 4 and an acetylation rate of 50 to 100%.

[0139] Examples of ricinoleic acid esters include known ricinoleic acid ester-based plasticizers, such as alkyl acetylricinoleates (alkyl group: carbon number 1 to 10) such as methyl acetylricinoleate and butyl acetylricinoleate.

[0140] The low-temperature plasticizer may contain other components in addition to the above compounds, such as known plasticizers other than the above compounds, and polyalkylene glycol alkyl ethers such as diethylene glycol monobutyl ether.

[0141] The content of the above compound in 100% by mass of the low-temperature plasticizer is preferably 80% by mass or more, more preferably 90% by mass or more, and may be 100% by mass.

[0142] Examples of the low-temperature plasticizer include tris(2-ethylhexyl)phosphate (TOP, freezing temperature -70°C or lower), bis(2-ethylhexyl)sebacate (DOS, freezing temperature -62°C), bis(2-ethylhexyl)phthalate (DOP, freezing temperature -51°C), and bis[2-(2-butoxyethoxyethyl)ethyl]adipate (BXA, freezing temperature -19°C).

[0143] The rubber composition contains a resin having a softening point of 60 to 120°C. The lower limit of the softening point is preferably 70° C. or higher, more preferably 75° C. or higher. The upper limit is preferably 110° C. or lower, more preferably 100° C. or lower, and even more preferably 95° C. or lower. By keeping the softening point within the above range, good overall performance in terms of fuel economy, wet grip performance, and handling stability tends to be obtained. In this specification, the softening point is 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 tester.

[0144] In the rubber composition, the content of the resin is 3 parts by mass or more, preferably 4 parts by mass or more, and more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component. The content is preferably 30 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 10 parts by mass or less, and particularly preferably 7 parts by mass or less. When the content is within the above range, good overall performance in terms of fuel economy, wet grip performance, and handling stability tends to be obtained.

[0145] The resin can be any resin having the above softening point, such as coumarone-indene resin, α-methylstyrene resin, terpene resin, alkylphenol resin, etc. Among these, α-methylstyrene resin and coumarone-indene resin are preferred from the viewpoint of overall performance such as low fuel consumption, wet grip performance, and steering stability.

[0146] Coumarone-indene resin is a resin containing coumarone and indene as monomer components that make up the skeleton (main chain) of the resin. Other monomer components contained in the skeleton besides coumarone and indene include styrene, α-methylstyrene, methylindene, and vinyltoluene.

[0147] Examples of the α-methylstyrene resin include an α-methylstyrene homopolymer and a copolymer of α-methylstyrene and styrene.

[0148] Examples of terpene resins include polyterpenes, terpene phenols, aromatic modified terpene resins, and resins obtained by hydrogenating these resins. Polyterpene is a resin obtained by polymerizing terpene compounds. Terpene compounds are (C5H8) n The hydrocarbons and their oxygen-containing derivatives are represented by the following composition: monoterpenes (C 10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpenes (C 20 H 32 ), and examples thereof include α-pinene, β-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, and γ-terpineol.

[0149] Examples of polyterpenes include terpene resins such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, and β-pinene / limonene resin, which are made from the above-mentioned terpene compounds. Examples of terpene phenols include resins obtained by copolymerizing the above-mentioned terpene compounds with phenolic compounds, specifically resins obtained by condensing the above-mentioned terpene compounds, phenolic compounds, and formalin. Examples of phenolic compounds include phenol, bisphenol A, cresol, and xylenol. Examples of aromatic-modified terpene resins include resins obtained by modifying terpene resins with aromatic compounds. Examples of aromatic compounds include, but are not limited to, phenolic compounds such as phenol, alkylphenol, alkoxyphenol, and unsaturated hydrocarbon group-containing phenol; naphthol compounds such as naphthol, alkylnaphthol, alkoxynaphthol, and unsaturated hydrocarbon group-containing naphthol; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene, and unsaturated hydrocarbon group-containing styrene; coumarone, indene, and the like.

[0150] The alkylphenol resin is not particularly limited, and examples thereof include alkylphenol-aldehyde condensation resins obtained by reacting alkylphenol with aldehydes such as formaldehyde, acetaldehyde, and furfural in the presence of an acid or alkali catalyst; alkylphenol-alkyne condensation resins obtained by reacting alkylphenol with alkynes such as acetylene; and modified alkylphenol resins obtained by modifying these resins with compounds such as cashew oil, tall oil, linseed oil, various animal and vegetable oils, unsaturated fatty acids, rosin, alkylbenzene resins, aniline, and melamine. Among these, alkylphenol-alkyne condensation resins are preferred, and alkylphenol-acetylene condensation resins are particularly preferred, from the viewpoint of the effects of the present invention.

[0151] Examples of alkylphenols constituting the alkylphenol resin include cresol, xylenol, t-butylphenol, octylphenol, nonylphenol, etc. Among these, phenols having a branched alkyl group such as t-butylphenol are preferred, and t-butylphenol is particularly preferred.

[0152] The rubber composition preferably contains a filler such as carbon black, silica, calcium carbonate, talc, alumina, clay, aluminum hydroxide, mica, etc. Among these, carbon black and silica are preferred from the viewpoint of overall performance such as fuel economy, wet grip performance, and handling stability.

[0153] In the rubber composition, the carbon black content 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, per 100 parts by mass of the rubber component. The content is preferably 50 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less. By keeping the content within the above range, good overall performance in terms of fuel economy, wet grip performance, and handling stability tends to be obtained.

[0154] The nitrogen adsorption specific surface area (N2SA) of carbon black is preferably 50 m from the viewpoint of wet grip performance and handling stability. 2 / g or more, more preferably 80m 2 / g or more, more preferably 100m 2 The upper limit is not particularly limited, but from the viewpoint of fuel economy, dispersibility, etc., it is preferably 250 m 2 / g or less, more preferably 150m 2 / g or less, more preferably 130m 2 / g or less. The N2SA of carbon black is determined according to JIS K 6217-2:2001.

[0155] The carbon black is not particularly limited, but examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available products that can be used include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin-Nichika Carbon Co., Ltd., Columbia Carbon Co., Ltd., and the like. These may be used alone, or two or more types may be used in combination.

[0156] In the rubber composition, the content of silica is preferably 30 parts by mass or more, more preferably 45 parts by mass or more, and even more preferably 55 parts by mass or more, per 100 parts by mass of the rubber component, from the viewpoints of wet grip performance and handling stability. From the viewpoints of fuel economy, dispersibility, etc., the content is preferably 150 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 80 parts by mass or less.

[0157] The nitrogen adsorption specific surface area (N2SA) of the silica is preferably 80 m 2 / g or more, more preferably 115m 2 / g or more, more preferably 150m 2 By making it equal to or greater than the lower limit, good wet grip performance and handling stability tend to be obtained. 2 / g or less, more preferably 250m 2 / g or less, more preferably 2000m 2 By making the content below the upper limit, good fuel economy and silica dispersibility tend to be obtained. The N2SA of silica is a value measured by the BET method in accordance with ASTM D3037-93.

[0158] The silica is not particularly limited, and for example, dry process silica (anhydrous silica) or wet process silica (hydrated silica) can be used, but wet process silica (hydrated silica) is preferred because it has a large number of silanol groups. Commercially available products include those from Degussa, Tosoh Silica Co., Ltd., Solvay Japan Co., Ltd., Tokuyama Corporation, etc. These may be used alone or in combination of two or more types.

[0159] When the rubber composition contains silica, it is preferable that the rubber composition contains a silane coupling agent together with the silica. The silane coupling agent can be any silane coupling agent that has been conventionally used in combination with silica in the rubber industry, and is not particularly limited. Examples of the silane coupling agent include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxy ...4-trimethoxysilylbutyl)disulfide, bis(4-triethoxysilylbutyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, bis(4-triethoxysilylbutyl)trisulfide, bis(4-triethoxysilylbutyl)trisulf sulfide-based compounds such as 2-triethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based compounds such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and Momentive's NXT and NXT-Z; vinyl-based compounds such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based compounds such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based compounds such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Commercially available products include those from Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., and Dow Corning Toray Co., Ltd. These may be used alone or in combination of two or more. Of these, sulfide-based and mercapto-based products are preferred.

[0160] When the rubber composition contains a silane coupling agent, the content thereof is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, per 100 parts by mass of silica. By making the content equal to or greater than the lower limit, the effect of compounding the silane coupling agent tends to be obtained. Also, the content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less. By making the content equal to or less than the upper limit, the effect commensurate with the compounding amount tends to be obtained, and good processability during kneading tends to be obtained.

[0161] The rubber composition preferably contains sulfur (a sulfur vulcanizing agent). Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, etc., which are commonly used in the rubber industry. Commercially available products include those from Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, Nippon Kanzuri Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. These may be used alone or in combination of two or more.

[0162] In the rubber composition, the amount of sulfur (sulfur vulcanizing agent) per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, and even more preferably 1.0 part by mass or more. The upper limit is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, and even more preferably 2.5 parts by mass or less.

[0163] The rubber composition preferably contains a vulcanization accelerator. Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide (DM(2,2'-dibenzothiazolyl disulfide)), and N-cyclohexyl-2-benzothiazyl sulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); Examples of suitable vulcanization accelerators include sulfenamide-based vulcanization accelerators such as hexyl-2-benzothiazole sulfenamide, Nt-butyl-2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, di-orthotolylguanidine, and orthotolylbiguanidine. These may be used alone or in combination of two or more. Among these, sulfenamide-based and guanidine-based vulcanization accelerators are preferred.

[0164] In the rubber composition, the content of the vulcanization accelerator is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, per 100 parts by mass of the rubber component, from the viewpoint of vulcanization characteristics, etc. The content is preferably 8.0 parts by mass or less, more preferably 5.0 parts by mass or less, and even more preferably 3.0 parts by mass or less.

[0165] The rubber composition may contain a wax. The wax is not particularly limited, and examples thereof include petroleum waxes such as paraffin wax and microcrystalline wax; natural waxes such as vegetable wax and animal wax; and synthetic waxes such as polymers of ethylene, propylene, etc. Commercially available products available from Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Seiko Chemical Co., Ltd., etc. may be used. These may be used alone or in combination of two or more. Of these, petroleum waxes are preferred, and paraffin wax is more preferred.

[0166] In the rubber composition, the wax content is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 10 parts by mass or less, more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component.

[0167] The rubber composition may contain an antioxidant. The antioxidant is not particularly limited, and examples thereof include naphthylamine-based antioxidants such as phenyl-α-naphthylamine; diphenylamine-based antioxidants such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, and N,N'-di-2-naphthyl-p-phenylene Examples of suitable antioxidants include p-phenylenediamine antioxidants such as diamines; quinoline antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol-based antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. Commercially available products include those from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., and Flexis. These antioxidants may be used alone or in combination of two or more. Among these, p-phenylenediamine antioxidants (more preferably, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) are preferred.

[0168] In the rubber composition, the content of the antioxidant per 100 parts by mass of the rubber component is preferably 0.3 parts by mass or more, more preferably 1 part by mass or more, and is preferably 7 parts by mass or less, more preferably 6 parts by mass or less, and even more preferably 5 parts by mass or less.

[0169] The rubber composition may also contain a fatty acid, in particular stearic acid. As the stearic acid, conventionally known ones can be used, for example, products from NOF Corporation, NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc. can be used.

[0170] In the rubber composition, the amount of the fatty acid is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, per 100 parts by mass of the rubber component, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less.

[0171] The rubber composition may contain zinc oxide. As the zinc oxide, conventionally known products can be used, for example, products from Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. can be used.

[0172] In the rubber composition, the amount of zinc oxide is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, per 100 parts by mass of the rubber component, and is preferably 5 parts by mass or less, more preferably 4 parts by mass or less.

[0173] In addition to the above components, the rubber composition may contain additives that are generally used in the tire industry, such as surfactants.

[0174] The rubber composition can be produced by a known method, for example, by kneading the components using a rubber kneading device such as an open roll, a Banbury mixer, or a kneader, followed by vulcanization.

[0175] As for kneading conditions, in the base kneading step in which additives other than the crosslinking agent (vulcanizing agent) and vulcanization accelerator are kneaded, the kneading temperature is usually 100 to 180°C, preferably 120 to 170°C. In the finish kneading step in which the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is usually 120°C or lower, preferably 85 to 110°C. Furthermore, the composition kneaded with the vulcanizing agent and vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 140 to 190°C, preferably 150 to 185°C.

[0176] For example, tire 1 is manufactured by a conventional method using a vulcanized rubber composition obtained by vulcanizing an unvulcanized rubber composition. That is, the unvulcanized rubber composition containing the above-mentioned various components is extruded to fit the shape of each tire component (for example, a tread with shoulder land portions formed), and then molded together with other tire components in a tire building machine by a conventional method to form an unvulcanized tire. Tire 1 is obtained by heating and pressurizing this unvulcanized tire in the vulcanizer.

[0177] The tire 1 is suitably used as a passenger car tire, a truck / bus tire, a motorcycle tire, a racing tire, etc., and is particularly suitably used as a passenger car tire.

[0178] Although the pneumatic tire of the present invention has been described in detail above, the present invention is not limited to the specific embodiment described above, and can be modified and practiced in various ways. [Example]

[0179] Pneumatic tires of size 175 / 65R17 with the basic tread pattern shown in Figure 1 were prototyped. Each test tire was tested for fuel economy, wet grip performance, and handling stability. The common specifications and test methods for each test tire are as follows. The test results are shown in each table. The reference comparative examples in Tables 2 and 4 are Comparative Examples 1-1 and 2-1, respectively. Rim: 18x5JJ Tire pressure: 260kPa Test vehicle: 2400cc, front-wheel drive Test tire mounting position: All wheels

[0180] The compositions of rubbers A to H and L to S used in the tread rubber are shown in Tables 1 and 3. The various chemicals shown in Tables 1 and 3 are as follows. SBR1: SBR1 prepared in Production Example 1 below SBR2: SBR2 prepared in Production Example 2 below BR: BR150B (cis content 98% by mass) manufactured by Ube Industries, Ltd. Silica: Ultrasil VN3 (N2SA175m) manufactured by Evonik Degussa 2 / g) Carbon black: Diablack I (N2SA114m) manufactured by Mitsubishi Chemical Corporation 2 / g) Silane coupling agent: Si69 (bis(3-triethoxysilylpropyl)tetrasulfide) manufactured by Evonik Degussa Plasticizer 1: Diana Process AH-24 (aromatic process oil, solidification temperature 5°C, kinematic viscosity at 40°C 2000mmHg) manufactured by Idemitsu Kosan Co., Ltd. 2 / s) Plasticizer 2: Process oil PW-32 (paraffinic process oil, solidification temperature -18°C, kinematic viscosity at 40°C 30mm) manufactured by Idemitsu Kosan Co., Ltd. 2 / s) Plasticizer 3: DOS (bis(2-ethylhexyl) sebacate) manufactured by Daihachi Chemical Co., Ltd., solidification temperature -62°C, kinematic viscosity at 40°C 10 mm 2 / s) Plasticizer 4: TOP (tris(2-ethylhexyl phosphate) manufactured by Daihachi Chemical Co., Ltd., freezing temperature -70°C or less, kinematic viscosity at 40°C 12 mm 2 / s) Resin 1: SYLVARES SA85 (α-methylstyrene-based resin (copolymer of α-methylstyrene and styrene), softening point 85°C) manufactured by Arizona Chemical Co. Resin 2: NOVARES C30 (coumarone-indene resin, softening point 30°C) manufactured by Rutgers Chemicals Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd. Antioxidant: Nocrac 6C (N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Stearic acid: NOF Corporation's "Tsubaki" stearic acid Zinc oxide: Three types of zinc oxide manufactured by Hakusui Tech Co., Ltd. Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Co., Ltd. Vulcanization accelerator 1: Noccela NS (Nt-butyl-2-benzothiazylsulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Noccelaer D (N,N'-diphenylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0181] <Preparation of terminal modifying agent> Under a nitrogen atmosphere, 23.6 g of 3-(N,N-dimethylamino)propyltrimethoxysilane (3-dimethylaminopropyltrimethoxysilane) (manufactured by AZMAX Corporation) was placed in a 100 ml measuring flask, and anhydrous hexane (manufactured by Kanto Chemical Co., Ltd.) was added to bring the total volume to 100 ml.

[0182] <Production Example 1> A 30-L pressure vessel thoroughly purged with nitrogen was charged with 18 L of n-hexane, 540 g of styrene (Kanto Chemical Co., Inc.), 1460 g of butadiene, and 17 mmol of tetramethylethylenediamine, and the mixture was heated to 40°C. Next, 10.5 mL of butyllithium was added, and the mixture was heated to 50°C and stirred for 3 hours. Next, 3.5 mL of a 0.4 mol / L silicon tetrachloride / hexane solution was added, and the mixture was stirred for 30 minutes. Next, 30 mL of the above-mentioned terminal modifier was added, and the mixture was stirred for 30 minutes. 2 mL of methanol (Kanto Chemical Co., Inc.) in which 0.2 g of 2,6-tert-butyl-p-cresol (Ouchi Shinko Chemical Industry Co., Ltd.) had been dissolved was added to the reaction solution, and the reaction solution was then placed in a stainless steel vessel containing 18 L of methanol to recover the aggregates. The resulting aggregates were dried under reduced pressure for 24 hours to obtain SBR1. The styrene content of the resulting SBR1 was 28% by mass. The Mw was 717,000 and the vinyl content was 60 mol %.

[0183] <Production Example 2> An autoclave equipped with a stirrer was charged with 6,000 g of cyclohexane, 150 g of styrene, 450 g of 1,3-butadiene, and tetramethylethylenediamine equivalent to 1.5 times the molar amount of n-butyllithium used, followed by the addition of 9.5 mmol of n-butyllithium to initiate polymerization at 50°C. Twenty minutes after the start of polymerization, a mixture of 60 g of styrene and 340 g of 1,3-butadiene was added continuously over 60 minutes. The maximum temperature during the polymerization reaction was 70°C. After the addition was completed, the polymerization reaction was continued for another 40 minutes. After confirming that the polymerization conversion rate had reached 100%, a small amount of the polymerization solution was sampled. The sampled small amount of polymerization solution was added with excess methanol to stop the reaction, and then air-dried to obtain the polymer, which was used as a sample for gel permeation chromatography analysis. Immediately after sampling a small amount of the polymerization solution, a 10% toluene solution of polyorganosiloxane A (a compound represented by the formula below, which can be synthesized by the method described in Vol. 28 of Experimental Chemistry Lectures, 4th Edition, edited by the Chemical Society of Japan, and its references) was added in an amount equivalent to 0.03 times the molar amount of n-butyllithium used. After 30 minutes of reaction, methanol was added as a polymerization terminator in an amount equivalent to 2 times the molar amount of n-butyllithium used to obtain a polymerization solution containing conjugated diene rubber I. 0.2 parts by mass of Irganox 1520 (manufactured by Ciba-Geigy) was added as an antioxidant per 100 parts by mass of rubber to the polymerization solution. The polymerization solvent was then removed by steam stripping, and the mixture was vacuum dried at 60°C for 24 hours to obtain solid SBR2. The styrene content of the resulting SBR2 was 42% by mass. The Mw was approximately 1 million, and the vinyl content was 32 mol%.

[0184] [ka]

[0185] <Fuel efficiency> Using a rolling resistance tester, the rolling resistance of a test tire was measured when it was run on a rim (18x5JJ), with an internal pressure (260kPa), a load (3.43kN), and at a speed (80km / h), and the low rolling resistance was expressed as an index. The higher the index, the better the fuel efficiency. The index is calculated using the following formula: (Fuel efficiency) = (Low rolling resistance of the tire of the reference comparative example) / (Low rolling resistance of the tire of each compound) × 100

[0186] <Wet grip performance> The test vehicle was driven on an asphalt road with a radius of 100m, where a puddle of water 5mm deep and 20m long was placed, and the lateral acceleration (lateral G) of the front wheels was measured. The results are the average lateral G at speeds of 50-80km / h, and are expressed as an index with the reference comparative example being 100. The higher the value, the better the wet grip performance.

[0187] <Handling stability> The test vehicle was driven on an asphalt circuit course and the handling stability was evaluated by the driver. The results were scored based on a standard comparative example being 100, with a higher score indicating better handling stability.

[0188] [Table 1]

[0189] [Table 2]

[0190] [Table 3]

[0191] [Table 4] [Explanation of symbols]

[0192] 2 Tread section 3 Main groove 4 Land 8 Shoulder Land Area 8A Outer shoulder land area 8B inner shoulder land area 34 Outer shoulder groove 35 outer shoulder sipe 38 Inner shoulder groove 39 Inner shoulder sipe Wt Tread width D Main groove depth D1 Outer shoulder main groove depth D2 Inner shoulder main groove depth D3 Center main groove depth Ls Shoulder sipe length Ls1 Length of outer shoulder sipe 35 Ls2 Length of inner shoulder sipe 39 Te1 outer tread edge Te2 Inner tread edge Po Tread axially outer end Pi tread axially inner edge

Claims

1. A pneumatic tire having a tread portion provided with three or more main grooves extending continuously in the tire circumferential direction and land portions separated by the main grooves, the main grooves include a pair of shoulder main grooves extending continuously in the tire circumferential direction at positions on both axially outer sides of the tire equator, and a center main groove extending continuously in the tire circumferential direction between the pair of shoulder main grooves, At least one of the shoulder land portions arranged on the outermost sides in the tire axial direction of the land portion is provided with a shoulder sipe extending in the tire axial direction, The tread width Wt and the groove depth D of the main groove satisfy the following formula (I), The length Ls of the shoulder sipe provided in at least one of the shoulder land portions and the tread width Wt satisfy the following formula (II), The shoulder land portion rubber composition is characterized in that it contains, per 100 parts by mass of a rubber component, 4 parts by mass or more of a low-temperature plasticizer having a solidification temperature of −10° C. or less, 3 parts by mass or more of a resin having a softening point of 60 to 120° C., 1 to 50 parts by mass of carbon black, and 30 to 150 parts by mass of silica. Pneumatic tires. [Equation 1] (The tread width Wt is the distance from one axial end to the other axial end of the tread. The groove depth D of the main groove is the radial height from the groove bottom to the opening.)

2. A pneumatic tire having a tread portion provided with three or more main grooves extending continuously in the tire circumferential direction and land portions separated by the main grooves, the main grooves include a pair of shoulder main grooves extending continuously in the tire circumferential direction at positions on both axially outer sides of the tire equator, and a center main groove extending continuously in the tire circumferential direction between the pair of shoulder main grooves, At least one of the shoulder land portions arranged on the outermost sides in the tire axial direction of the land portion is provided with a shoulder sipe extending in the tire axial direction, The tread width Wt and the groove depth D of the main groove satisfy the following formula (I), The length Ls of the shoulder sipe provided in at least one of the shoulder land portions and the tread width Wt satisfy the following formula (II), The rubber composition for the shoulder land portion, which constitutes the shoulder land portion, contains, per 100 parts by mass of a rubber component, 4 parts by mass or more of a low-temperature plasticizer having a solidification temperature of −10° C. or less and 3 parts by mass or more of a resin having a softening point of 60 to 120° C.; The tire outer diameter is 600 to 700 mm. Pneumatic tires. [Equation 2] (The tread width Wt is the distance from one axial end to the other axial end of the tread. The groove depth D of the main groove is the radial height from the groove bottom to the opening.)

3. A pneumatic tire having a tread portion provided with three or more main grooves extending continuously in the tire circumferential direction and land portions separated by the main grooves, the main grooves include a pair of shoulder main grooves extending continuously in the tire circumferential direction at positions on both axially outer sides of the tire equator, and a center main groove extending continuously in the tire circumferential direction between the pair of shoulder main grooves, At least one of the shoulder land portions arranged on the outermost sides in the tire axial direction of the land portion is provided with a shoulder sipe extending in the tire axial direction, The tread width Wt and the groove depth D of the main groove satisfy the following formula (I), The length Ls of the shoulder sipe provided in at least one of the shoulder land portions and the tread width Wt satisfy the following formula (II), The shoulder land portion rubber composition is characterized in that it contains, per 100 parts by mass of a rubber component, 4 parts by mass or more of a low-temperature plasticizer having a solidification temperature of −10° C. or less and 3 to 30 parts by mass of a resin having a softening point of 60 to 120° C. Pneumatic tires. [Equation 3] (The tread width Wt is the distance from one axial end to the other axial end of the tread. The groove depth D of the main groove is the radial height from the groove bottom to the opening.)

4. A pneumatic tire having a tread portion provided with three or more main grooves extending continuously in the tire circumferential direction and land portions separated by the main grooves, the main grooves include a pair of shoulder main grooves extending continuously in the tire circumferential direction at positions on both axially outer sides of the tire equator, and a center main groove extending continuously in the tire circumferential direction between the pair of shoulder main grooves, At least one of the shoulder land portions arranged on the outermost sides in the tire axial direction of the land portion is provided with a shoulder sipe extending in the tire axial direction, The tread width Wt and the groove depth D of the main groove satisfy the following formula (I), The length Ls of the shoulder sipe provided in at least one of the shoulder land portions and the tread width Wt satisfy the following formula (II), The rubber composition for the shoulder land portion, which constitutes the shoulder land portion, contains, per 100 parts by mass of a rubber component, 4 parts by mass or more of a low-temperature plasticizer having a solidification temperature of −10° C. or less and 3 parts by mass or more of a resin having a softening point of 60 to 120° C.; The rubber component is characterized in that the content of styrene-butadiene rubber is 30 to 95% by mass and the content of butadiene rubber is 5 to 50% by mass, based on 100% by mass of the rubber component. Pneumatic tires. [Equation 4] (The tread width Wt is the distance from one axial end to the other axial end of the tread. The groove depth D of the main groove is the radial height from the groove bottom to the opening.)

5. A pneumatic tire having a tread portion provided with three or more main grooves extending continuously in the tire circumferential direction and land portions separated by the main grooves, the main grooves include a pair of shoulder main grooves extending continuously in the tire circumferential direction at positions on both axially outer sides of the tire equator, and a center main groove extending continuously in the tire circumferential direction between the pair of shoulder main grooves, At least one of the shoulder land portions arranged on the outermost sides in the tire axial direction of the land portion is provided with a shoulder sipe extending in the tire axial direction, The tread width Wt and the groove depth D of the main groove satisfy the following formula (I), The length Ls of the shoulder sipe provided in at least one of the shoulder land portions and the tread width Wt satisfy the following formula (II), The rubber composition for the shoulder land portion, which constitutes the shoulder land portion, contains, per 100 parts by mass of a rubber component, 4 parts by mass or more of a low-temperature plasticizer having a solidification temperature of −10° C. or less and 3 parts by mass or more of a resin having a softening point of 60 to 120° C.; The rubber component is characterized in that it contains a first styrene-butadiene rubber having a styrene content of 30% by mass or less and a second styrene-butadiene rubber having a styrene content of 35% by mass or more. Pneumatic tires. [Equation 5] (The tread width Wt is the distance from one axial end to the other axial end of the tread. The groove depth D of the main groove is the radial height from the groove bottom to the opening.)

6. The low-temperature plasticizer has a kinematic viscosity of 60 mm at 40°C. ２ The pneumatic tire according to any one of claims 1 to 5, wherein the flexural modulus is 1 / s or less.

7. The pneumatic tire according to any one of claims 1 to 6, wherein the shoulder sipes are inner shoulder sipes.

8. 10≦Wt / 2D≦25 and 15≦Ls / Wt×100≦25 are satisfied, The pneumatic tire according to any one of claims 1 to 6, wherein the shoulder sipes are inner shoulder sipes.

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