Pneumatic tire

Abstract

To provide a pneumatic tire which can achieve low fuel consumption performance and noise performance.SOLUTION: A pneumatic tire 1 includes a tread part 2, a pair of side wall parts 3, a pair of bead parts 4, a carcass 6 extending between the pair of bead parts 4, and inner rubber 10 extending between the pair of bead parts 4 in the inner side of the carcass 6. The inner rubber 10 includes: a first portion 11 having at a first thickness t1 and extending in the tread part 2; and a pair of second portions 12 having a second thickness t2 and extending in the pair of side wall parts 3. The first thickness t1 is 1.5 to 3.5 times thicker than the second thickness t2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Various pneumatic tires capable of reducing road noise have been proposed in the past. For example, Patent Document 1 below proposes a pneumatic tire that reduces road noise while minimizing the impact on rolling resistance by providing fillers that extend radially inward from the belt end along the carcass to suppress vibration at the belt end. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-170968 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in recent years, with the spread of electric vehicles and the like, the standards required for fuel efficiency and noise performance of pneumatic tires have increased, and further improvements have been desired for the pneumatic tire of Patent Document 1.

[0005] The present invention has been devised in view of the above circumstances, and has as its main object to provide a pneumatic tire that can achieve both low fuel consumption performance and low noise performance. [Means for solving the problem]

[0006] The present invention is a pneumatic tire including a tread portion, a pair of sidewall portions, a pair of bead portions, a carcass extending between the pair of bead portions, and an inner rubber extending inside the carcass between the pair of bead portions, wherein the inner rubber includes a first portion extending through the tread portion at a first thickness and a pair of second portions extending through the pair of sidewall portions at a second thickness, and the first thickness is 1.5 to 3.5 times the second thickness. [Effects of the Invention]

[0007] The pneumatic tire of the present invention has the above-described configuration, and thus can achieve both low fuel consumption performance and noise performance. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing an embodiment of a pneumatic tire of the present invention. [Figure 2] FIG. 2 is an enlarged cross-sectional view of a tread portion. [Figure 3] 2 is a cross-sectional schematic view of a carcass and a belt layer at the tire equator. FIG. [Figure 4] FIG. 3 is a cross-sectional schematic view of a carcass and a belt layer at an outer end of a first belt ply. [Figure 5] FIG. 10 is an enlarged cross-sectional view of an inner rubber according to a second embodiment. [Figure 6] FIG. 10 is an enlarged cross-sectional view of an inner rubber of the third embodiment. [Figure 7] FIG. 10 is an enlarged cross-sectional view of an inner rubber of the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. 1 is a tire meridian cross-sectional view including a rotation axis showing a pneumatic tire 1 of this embodiment in a normal state. Here, the "normal state" refers to a state in which the pneumatic tire 1 is mounted on a normal rim, and is adjusted to a normal internal pressure and is unloaded. Unless otherwise specified below, the dimensions of each part of the pneumatic tire 1 are values ​​measured in this normal state.

[0010] If there is a standard system including the standard on which the pneumatic tire 1 is based, a "genuine rim" is a rim defined for each tire by that standard, for example, a "standard rim" for JATMA, a "design rim" for TRA, or a "measuring rim" for ETRTO. If there is no standard system including the standard on which the pneumatic tire 1 is based, a "genuine rim" is a rim with the smallest rim diameter and the smallest rim width among rims that can be assembled and do not cause air leakage.

[0011] "Normal internal pressure" is the air pressure set for each tire by a standard set by the JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for the TRA, and the "INFLATION PRESSURE" for the ETRTO. If there is no standard set that includes the standard set by the pneumatic tire 1, "normal internal pressure" is the air pressure set for each tire by the manufacturer, etc.

[0012] As shown in FIG. 1 , the pneumatic tire 1 of this embodiment includes a tread portion 2, a pair of sidewall portions 3, and a pair of bead portions 4. The bead portions 4 have, for example, an annularly extending bead core 5. The bead core 5 is formed, for example, from steel wire. The pneumatic tire 1 of this embodiment is suitable for use as a passenger vehicle tire. The pneumatic tire 1 is not limited to passenger vehicle tires, and can be applied to various types of tires, such as heavy-duty tires, motorcycle tires, and industrial vehicle tires.

[0013] The tread portion 2 of this embodiment has a first tread edge Te1, a second tread edge Te2, and a contact patch 2s extending between the first tread edge Te1 and the second tread edge Te2. Here, the first tread edge Te1 and the second tread edge Te2 are each the axially outermost contact points when the pneumatic tire 1 in a normal state is loaded with 70% of a normal load and contacts the ground on a flat surface with a camber angle of 0°.

[0014] "Normal load" is the load determined for each tire by a standard system that includes the standards on which the pneumatic tire 1 is based, if such a system exists; for example, it is "maximum load capacity" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "LOAD CAPACITY" for ETRTO. If there is no standard system that includes the standards on which the pneumatic tire 1 is based, "normal load" is the load determined for each tire by the manufacturer or the like as the maximum load that can be applied when using the pneumatic tire 1.

[0015] The contact patch 2s has a tire equator C, which is the axial center position between the first tread edge Te1 and the second tread edge Te2. That is, the tire equator C is the axial center position between the first tread edge Te1 and the second tread edge Te2 on the contact patch 2s. The axial distance from the first tread edge Te1 to the second tread edge Te2 is the tread width TW.

[0016] In this embodiment, the pair of sidewall portions 3 each include a sidewall outer surface 3s extending radially inward from the first tread edge Te1 and the second tread edge Te2. The sidewall outer surface 3s is a smooth, continuous surface except for locally uneven portions, and together with the contact patch 2s, constitutes a tire profile surface.

[0017] The sidewall outer surface 3s preferably includes a tire maximum width position 3p, which is the outermost position in the tire axial direction. The axial distance at the tire maximum width position 3p is the tire maximum width SW.

[0018] The pneumatic tire 1 of this embodiment includes a carcass 6 extending between a pair of bead portions 4, and an inner rubber 10 extending between the pair of bead portions 4 inside the carcass 6. The inner rubber 10 of this embodiment forms the tire cavity surface 1i.

[0019] The inner rubber 10 of this embodiment includes a first portion 11 extending through the tread portion 2 at a first thickness t1, and a pair of second portions 12 extending through the pair of sidewall portions 3 at a second thickness t2. Here, the first thickness t1 and the second thickness t2 refer to the thickness from the inner surface 6i of the carcass 6 to the tire cavity surface 1i, and do not include a topping rubber 6g of a carcass ply 6A, which will be described later.

[0020] The first thickness t1 of this embodiment is greater than the second thickness t2. It is desirable that the first thickness t1 be greater than the second thickness t2 over the entire circumference of the tire. Such an inner rubber 10 can achieve the same vibration-reducing effect as increasing the thickness of the tread rubber 2G, which will be described later, with a small increase in weight. Furthermore, since an increase in the weight of the inner side of the carcass 6 has little effect on rolling resistance, the pneumatic tire 1 of this embodiment can improve noise performance while maintaining good fuel economy performance.

[0021] Here, the first thickness t1 being greater than the second thickness t2 means that the average value of the first thickness t1 is greater than the average value of the second thickness t2. The average value of the first thickness t1 corresponds to the value obtained by dividing the cross-sectional area of ​​the first portion 11 in the tire meridian cross section by the length of the first portion 11 along the tire cavity surface 1i. The same applies to the average value of the second thickness t2. Hereinafter, in this specification, the "first thickness t1" refers to the average value of the first thickness t1, and the "second thickness t2" refers to the average value of the second thickness t2.

[0022] The first thickness t1 is preferably 1.5 times or more the second thickness t2. By making the first thickness t1 1.5 times or more the second thickness t2, vibration of the tread portion 2 can be effectively suppressed, and the noise performance of the pneumatic tire 1 can be improved. From this perspective, the first thickness t1 is more preferably 1.75 times or more the second thickness t2, and even more preferably 1.9 times or more.

[0023] The first thickness t1 is preferably 3.5 times or less the second thickness t2. By making the first thickness t1 3.5 times or less the second thickness t2, an excessive increase in weight can be suppressed, and good fuel economy performance can be maintained for the pneumatic tire 1. From this viewpoint, the first thickness t1 is more preferably 2.7 times or less the second thickness t2, and even more preferably 2.2 times or less.

[0024] For these reasons, the first thickness t1 is preferably 1.5 to 3.5 times the second thickness t2, more preferably 1.75 to 2.7 times, and even more preferably 1.9 to 2.2 times. The combination of the upper and lower limits of these numerical ranges can be selected arbitrarily.

[0025] Such an inner rubber 10 can achieve both the effect of suppressing vibration and the effect of suppressing weight increase, so the pneumatic tire 1 of this embodiment can achieve both low fuel consumption performance and noise performance.

[0026] In a more preferred embodiment, the first thickness t1 is preferably 2.0 mm or greater. By making the first thickness t1 2.0 mm or greater, it is possible to effectively suppress vibrations in the tread portion 2 and improve the noise performance of the pneumatic tire 1. From this perspective, the first thickness t1 is more preferably 2.5 mm or greater, and even more preferably 2.8 mm or greater.

[0027] The first thickness t1 is preferably 4.5 mm or less. By setting the first thickness t1 to 4.5 mm or less, an excessive increase in weight can be suppressed, and good fuel economy performance can be maintained for the pneumatic tire 1. From this viewpoint, the first thickness t1 is more preferably 4.0 mm or less, and even more preferably 3.5 mm or less.

[0028] For these reasons, the first thickness t1 is preferably 2.0 to 4.5 mm, more preferably 2.5 to 4.0 mm, and even more preferably 2.8 to 3.5 mm. The combination of the upper and lower limits of these numerical ranges can be selected arbitrarily.

[0029] The second thickness t2 is preferably 0.5 mm or more. When the second thickness t2 is 0.5 mm or more, good air impermeability can be maintained, which helps to improve the durability performance of the pneumatic tire 1. From this perspective, the second thickness t2 is more preferably 0.7 mm or more, and even more preferably 1.0 mm or more.

[0030] The second thickness t2 is preferably 2.0 mm or less. By making the second thickness t2 2.0 mm or less, it is possible to suppress an excessive increase in weight and maintain good fuel economy performance of the pneumatic tire 1. From this viewpoint, the average value of the second thickness t2 is more preferably 1.8 mm or less, and even more preferably 1.5 mm or less.

[0031] For these reasons, the second thickness t2 is preferably 0.5 to 2.0 mm, more preferably 0.7 to 1.8 mm, and even more preferably 1.0 to 1.5 mm. The combination of the upper and lower limits of these numerical ranges can be selected arbitrarily.

[0032] Fig. 2 is an enlarged cross-sectional view of the tread portion 2. As shown in Fig. 2, the tread portion 2 of this embodiment includes a tread rubber 2G that forms the contact surface 2s. The tread portion 2 includes, for example, a cap rubber 2A that forms the contact surface 2s, and a base rubber 2B that is disposed radially inward of the cap rubber 2A.

[0033] The tread portion 2 is not limited to this embodiment, and may be made of, for example, one layer of rubber material, or three or more layers of rubber material. When the tread portion 2 is made of multiple rubber materials, the tread rubber 2G is the rubber material that makes up the contact surface 2s, for example, the cap rubber 2A.

[0034] The loss tangent tanδ1 at 70° C. of the rubber material constituting the first portion 11 is preferably equal to or greater than the loss tangent tanδ2 at 70° C. of the rubber material constituting the second portion 12. Such a first portion 11 helps to suppress vibration of the tread portion 2, and can improve the noise performance of the pneumatic tire 1.

[0035] Hereinafter, in this specification, "loss tangent tanδ1 of the first portion 11" means the loss tangent tanδ1 of the rubber material constituting the first portion 11 at 70°C, and "loss tangent tanδ2 of the second portion 12" means the loss tangent tanδ2 of the rubber material constituting the second portion 12 at 70°C.

[0036] The loss tangent tanδ1 of the first portion 11 is desirably equal to or less than the loss tangent tanδA of the tread rubber 2G at 30°C. The measurement temperature is set to 30°C because the tread rubber 2G that forms the contact surface 2s is cooled by contact with the outside air. Such a first portion 11 can further reduce the effect on the rolling resistance in the tread portion 2, and is useful for improving the fuel efficiency performance of the pneumatic tire 1.

[0037] Here, in this specification, the loss tangent tanδ is a value measured using a dynamic viscoelasticity measuring device under the following conditions in accordance with the provisions of JIS-K6394. A rubber sample used to measure the loss tangent tanδ is, for example, taken from a vulcanized pneumatic tire 1, and is taken so that the longitudinal direction of the sample coincides with the circumferential direction of the pneumatic tire 1. Initial strain: 5% (when the measurement temperature is 30°C) or 10% (when the measurement temperature is 70°C) Dynamic strain amplitude: ±1% Frequency: 10Hz Deformation mode: tension Measurement temperature: 30℃ or 70℃

[0038] The loss tangent tanδ can be adjusted appropriately by adjusting the glass transition temperature Tg of the rubber composition and the types and amounts of various compounding agents. Specifically, the loss tangent tanδ can be increased by increasing the glass transition temperature Tg of the rubber composition, reducing the average particle size of reinforcing agents such as carbon and silica, increasing the compounding amount of reinforcing agents, reducing the amount of vulcanizing agents such as sulfur and accelerators, etc.

[0039] Here, when the first portion 11 is made of a single rubber material, the loss tangent tanδ1 of the first portion 11 is the loss tangent tanδ1 of that rubber material. When the first portion 11 is made of a plurality of rubber materials, the loss tangent tanδ1 of the first portion 11 is the average value calculated as a weighted average of the loss tangents tanδ1 of those rubber materials weighted by the cross-sectional area of ​​each rubber material. The same applies to the other loss tangents tanδ.

[0040] The loss tangent tanδ1 of the first portion 11 is preferably 1.0 times or more the loss tangent tanδ2 of the second portion 12. By making the loss tangent tanδ1 of the first portion 11 1.0 times or more the loss tangent tanδ2 of the second portion 12, it is possible to reliably achieve the vibration suppression effect of the tread portion 2. From this viewpoint, the loss tangent tanδ1 of the first portion 11 is more preferably 1.1 times or more the loss tangent tanδ2 of the second portion 12.

[0041] The loss tangent tanδ1 of the first portion 11 is preferably 2.0 times or less the loss tangent tanδ2 of the second portion 12. By making the loss tangent tanδ1 of the first portion 11 2.0 times or less the loss tangent tanδ2 of the second portion 12, it is possible to suppress damage such as peeling due to an excessive difference in physical properties and improve the durability performance of the pneumatic tire 1. From this perspective, the loss tangent tanδ1 of the first portion 11 is more preferably 1.5 times or less the loss tangent tanδ2 of the second portion 12.

[0042] For these reasons, the loss tangent tanδ1 of the first portion 11 is preferably 1.0 to 2.0 times, and more preferably 1.1 to 1.5 times, the loss tangent tanδ2 of the second portion 12. The combination of the upper and lower limits of these numerical ranges can be selected arbitrarily.

[0043] The loss tangent tanδ1 of the first portion 11 is preferably 0.3 times or more the loss tangent tanδA of the tread rubber 2G. By making the loss tangent tanδ1 of the first portion 11 0.3 times or more the loss tangent tanδA of the tread rubber 2G, it is possible to reduce the vibration of the tread portion 2 while maintaining the fuel efficiency performance of the pneumatic tire 1. From this perspective, the loss tangent tanδ1 of the first portion 11 is more preferably 0.4 times or more the loss tangent tanδA of the tread rubber 2G.

[0044] The loss tangent tanδ1 of the first portion 11 is preferably 0.8 times or less the loss tangent tanδA of the tread rubber 2G. By making the loss tangent tanδ1 of the first portion 11 0.8 times or less the loss tangent tanδA of the tread rubber 2G, it is possible to reduce vibration of the tread portion 2 while maintaining the steering stability performance of the pneumatic tire 1. From this viewpoint, the loss tangent tanδ1 of the first portion 11 is more preferably 0.7 times or less the loss tangent tanδA of the tread rubber 2G.

[0045] For these reasons, the loss tangent tanδ1 of the first portion 11 is preferably 0.3 to 0.8 times, and more preferably 0.4 to 0.7 times, the loss tangent tanδA of the tread rubber 2G. The combination of the upper and lower limit values ​​of these numerical ranges can be selected arbitrarily.

[0046] The first portion 11 is preferably formed from a rubber material having a loss tangent tanδ1 of 0.14 or more at 70°C. When the loss tangent tanδ1 of the first portion 11 is 0.14 or more, vibration of the tread portion 2 can be reliably suppressed and noise generation can be reduced. From this perspective, the loss tangent tanδ1 of the first portion 11 is more preferably 0.15 or more, and even more preferably 0.20 or more.

[0047] It is desirable that the loss tangent tanδ2 of the second portion 12 is equal to the loss tangent tanδ1 of the first portion 11. Such an inner rubber 10 allows the first portion 11 and the second portion 12 to be integrally formed, which helps to reduce the manufacturing cost of the pneumatic tire 1.

[0048] The loss tangent tanδA of the tread rubber 2G is preferably 0.30 or less. When the loss tangent tanδA of the tread rubber 2G is 0.30 or less, it is possible to reduce rolling resistance and improve the fuel economy performance of the pneumatic tire 1. From this viewpoint, the loss tangent tanδA of the tread rubber 2G is more preferably 0.25 or less, and even more preferably 0.20 or less.

[0049] When the tread portion 2 is composed of a cap rubber 2A and a base rubber 2B, the loss tangent tanδA of the tread rubber 2G at 30°C is the same as the loss tangent tanδA of the cap rubber 2A at 30°C. In this case, the loss tangent tanδB of the base rubber 2B at 70°C is preferably smaller than the loss tangent tanδA of the cap rubber 2A at 30°C. Such a tread portion 2 helps to improve fuel economy while maintaining good steering stability of the pneumatic tire 1.

[0050] The loss tangent tanδB of the base rubber 2B is preferably 0.21 or less. A loss tangent tanδB of the base rubber 2B of 0.21 or less suppresses heat generation in the tread portion 2 during running and helps maintain good fuel economy performance of the pneumatic tire 1. From this perspective, the loss tangent tanδB of the base rubber 2B is more preferably 0.20 or less.

[0051] The complex modulus E*A of the tread rubber 2G at 30°C is preferably 7.8 MPa or more. If the complex modulus E*A of the tread rubber 2G is 7.8 MPa or more, it helps to suppress vibration of the tread portion 2 and improve the noise performance of the pneumatic tire 1. From this perspective, the complex modulus E*A of the tread rubber 2G is more preferably 8.0 MPa or more, and even more preferably 9.0 MPa or more. Note that when the tread rubber 2G is made up of multiple rubber materials, the complex modulus E*A is based on the rubber materials that make up the contact surface 2s.

[0052] Here, in this specification, the complex modulus E* is a value measured using a dynamic viscoelasticity measuring device under the following conditions in accordance with the provisions of JIS-K6394. A rubber sample used to measure the complex modulus E* is, for example, taken from a vulcanized pneumatic tire 1, and is taken so that the longitudinal direction of the sample coincides with the circumferential direction of the pneumatic tire 1. Initial strain: 5% Dynamic strain amplitude: ±1% Frequency: 10Hz Deformation mode: tension Measurement temperature: 30℃

[0053] The complex modulus E* can be adjusted appropriately by adjusting the glass transition temperature Tg of the rubber composition and the types and amounts of various compounding agents. Specifically, the complex modulus E* can be increased by increasing the glass transition temperature Tg of the rubber composition, reducing the average particle size of reinforcing agents such as carbon and silica, increasing the compounding amount of reinforcing agents, reducing the total amount of plasticizers, increasing the amount of vulcanizing agents such as sulfur and accelerators, etc.

[0054] As shown in Figures 1 and 2, the tread portion 2 of this embodiment includes a belt layer 7 arranged radially outward of the carcass 6, and a band layer 8 arranged radially outward of the belt layer 7.

[0055] The carcass 6 includes at least one carcass ply 6A, one carcass ply in this embodiment, in which carcass cords 6c (shown in FIG. 3) are arranged. The carcass ply 6A includes, for example, a main body portion 6a and a turned-up portion 6b. The main body portion 6a extends, for example, between the two bead portions 4. The turned-up portion 6b is continuous with the main body portion 6a and is turned up around the bead core 5 from the axially inner side to the axially outer side of the tire.

[0056] Fig. 3 is a cross-sectional schematic diagram of the carcass 6 and the belt layer 7 at the tire equator C. As shown in Fig. 3, the carcass ply 6A preferably includes a plurality of carcass cords 6c and a topping rubber 6g covering the carcass cords 6c. The carcass cords 6c are preferably organic fiber cords made of, for example, aramid or rayon. The carcass cords 6c are preferably arranged at an angle of 70 to 90° with respect to the tire equator C.

[0057] The loss tangent tanδC of the topping rubber 6g of the carcass ply 6A at 70°C is preferably 0.16 or less. When the loss tangent tanδC of the topping rubber 6g of the carcass ply 6A is 0.16 or less, heat generation in the carcass ply 6A can be suppressed, and the pneumatic tire 1 can achieve both low fuel consumption performance and durability performance during high-speed running. From this perspective, the loss tangent tanδC of the topping rubber 6g of the carcass ply 6A is more preferably 0.15 or less.

[0058] From the viewpoint of improving the noise performance of the pneumatic tire 1, it is desirable to make the loss tangent tanδ1 of the first portion 11 larger than the loss tangent tanδC of the topping rubber 6g of the carcass ply 6A.

[0059] 2 and 3, the belt layer 7 includes, for example, a first belt ply 7A adjacent to the carcass 6 and a second belt ply 7B disposed radially outward of the first belt ply 7A. Each of the first belt ply 7A and the second belt ply 7B in this embodiment includes a plurality of belt cords 7c arranged at an angle of 15 to 45° with respect to the tire equator C, and a topping rubber 7g covering the belt cords 7c.

[0060] The belt cords 7c of the first belt ply 7A and the belt cords 7c of the second belt ply 7B are preferably inclined in opposite directions relative to the tire circumferential direction. Such a belt layer 7 can effectively reinforce the tread portion 2.

[0061] The loss tangent tanδD of the topping rubber 7g of the first belt ply 7A at 70°C is preferably 0.16 or less. When the loss tangent tanδD of the topping rubber 7g of the first belt ply 7A is 0.16 or less, heat generation in the first belt ply 7A can be suppressed, and both fuel economy performance and durability performance during high-speed running of the pneumatic tire 1 can be achieved. From this perspective, the loss tangent tanδD of the topping rubber 7g of the first belt ply 7A is more preferably 0.15 or less.

[0062] From the viewpoint of improving the noise performance of the pneumatic tire 1, it is desirable to make the loss tangent tanδ1 of the first portion 11 larger than the loss tangent tanδD of the topping rubber 7g of the first belt ply 7A.

[0063] The loss tangent tanδE of the topping rubber 7g of the second belt ply 7B at 70°C is preferably 0.16 or less. When the loss tangent tanδE of the topping rubber 7g of the second belt ply 7B is 0.16 or less, heat generation in the second belt ply 7B can be suppressed, and both fuel economy performance and durability performance during high-speed running of the pneumatic tire 1 can be achieved. From this perspective, the loss tangent tanδE of the topping rubber 7g of the second belt ply 7B is more preferably 0.15 or less.

[0064] From the viewpoint of improving the noise performance of the pneumatic tire 1, it is desirable to make the loss tangent tanδ1 of the first portion 11 larger than the loss tangent tanδE of the topping rubber 7g of the second belt ply 7B.

[0065] In this embodiment, the loss tangent tanδE of the topping rubber 7g of the second belt ply 7B is equal to the loss tangent tanδD of the topping rubber 7g of the first belt ply 7A. In such a belt layer 7, the materials forming the first belt ply 7A and the second belt ply 7B can be uniformly managed, and the manufacturing cost of the pneumatic tire 1 can be reduced.

[0066] 2, it is desirable that the axially outer end 7b of the second belt ply 7B is positioned axially more inward than the axially outer end 7a of the first belt ply 7A on each side of the tire equator C. As a result, the axial length of the second belt ply 7B is shorter than the axial length of the first belt ply 7A.

[0067] Such a belt layer 7 can reinforce the tread portion 2 while preventing the second belt ply 7B from becoming excessively large, and is therefore useful for achieving both low fuel consumption performance and noise performance for the pneumatic tire 1.

[0068] Fig. 4 is a cross-sectional schematic diagram of the carcass 6 and the belt layer 7 at the outer end 7a of the first belt ply 7A. As shown in Fig. 3 and Fig. 4, a first distance L1 between the carcass cord 6c and the belt cord 7c at the tire equator C is preferably longer than a second distance L2 between the carcass cord 6c and the belt cord 7c at the outer end 7a of the first belt ply 7A. Here, the first distance L1 and the second distance L2 are the shortest distances between the carcass cord 6c and the belt cord 7c in the tire radial direction, respectively.

[0069] Such a tread portion 2 can suppress the transmission of vibrations input from the road surface to the carcass cords 6c, thereby improving the noise performance of the pneumatic tire 1. Furthermore, by making the first distance L1 larger than the second distance L2, the first thickness t1 of the first portion 11 of the inner rubber 10 at the tire equator C can be reduced, thereby improving the fuel efficiency performance of the pneumatic tire 1.

[0070] The first distance L1 is preferably 1.2 times or more the second distance L2. By making the first distance L1 1.2 times or more the second distance L2, it is possible to reliably suppress the transmission of vibrations from the road surface to the carcass cords 6c. From this perspective, the first distance L1 is more preferably 1.3 times or more the second distance L2, and even more preferably 1.4 times or more.

[0071] The first distance L1 is preferably 2.5 times or less the second distance L2. By making the first distance L1 2.5 times or less the second distance L2, it is possible to reliably suppress the transmission of vibrations from the road surface to the carcass cords 6c. From this perspective, the first distance L1 is more preferably 2.3 times or less the second distance L2, and even more preferably 2.1 times or less.

[0072] For these reasons, the first distance L1 is preferably 1.2 to 2.5 times the second distance L2, more preferably 1.3 to 2.3 times, and even more preferably 1.4 to 2.1 times. The combination of the upper and lower limits of these numerical ranges can be selected arbitrarily.

[0073] 2, the band layer 8 is composed of at least one band ply 8A, one band ply in this embodiment. Although not shown, the band ply 8A includes, for example, a band cord arranged at an angle of 5° or less with respect to the tire equator C, and a topping rubber covering the band cord. The band layer 8 in this embodiment is arranged so as to cover the entire belt layer 7.

[0074] The loss tangent tanδF of the topping rubber of the band ply 8A at 70°C is preferably 0.16 or less. When the loss tangent tanδF of the topping rubber of the band ply 8A is 0.16 or less, heat generation in the band ply 8A can be suppressed, and both fuel economy performance and durability performance during high-speed running of the pneumatic tire 1 can be achieved. From this perspective, the loss tangent tanδF of the topping rubber of the band ply 8A is more preferably 0.15 or less.

[0075] From the viewpoint of improving the noise performance of the pneumatic tire 1, it is desirable to make the loss tangent tanδ1 of the first portion 11 larger than the loss tangent tanδF of the topping rubber of the band ply 8A.

[0076] The inner rubber 10 is preferably made of an air-impermeable rubber material. Examples of such rubber materials include butyl-based or halogenated butyl-based rubber materials. In the inner rubber 10 of this embodiment, the first portion 11 and the second portion 12 are made of the same rubber material.

[0077] The first portion 11 of the inner rubber 10 of this embodiment includes a pair of end portions 11A on the outer sides in the tire axial direction. It is desirable that the first thickness t1 of each of the pair of end portions 11A continuously decreases toward the outer end 11a of the first portion 11 in the tire axial direction. In other words, the position where the decrease in the first thickness t1 ends corresponds to the outer end 11a of the first portion 11 in the tire axial direction in this embodiment. Such a first portion 11 helps to suppress stress concentration at the outer end 11a and improve the durability performance of the pneumatic tire 1.

[0078] The axially outer end 11a of the first portion 11 of the inner rubber 10 is preferably located at the same axial position as the outer end 7b of the second belt ply 7B, or is located axially inward of the outer end 7b of the second belt ply 7B and within 10 mm in the tire axial direction. In such an inner rubber 10, the end 11A of the first portion 11 is located radially inward of the second belt ply 7B, so that changes in rigidity at the end 11A can be absorbed by the belt layer 7.

[0079] The first portion 11 extends at a constant first thickness t1 between the pair of end portions 11A. Such a first portion 11 can suppress vibration of the tread portion 2 while suppressing excessive weight increase, thereby achieving both fuel economy and noise performance of the pneumatic tire 1. Here, the constant first thickness t1 means that the difference between the maximum and minimum thickness values ​​is 5% or less of the maximum value.

[0080] The tread portion 2 includes, for example, a plurality of circumferential grooves 20 extending continuously in the tire circumferential direction. The plurality of circumferential grooves 20 include at least one crown groove 20A (two in this embodiment) extending to a position close to the tire equator C, and at least one shoulder groove 20B (one on each side of the tire equator C in this embodiment) extending outward in the tire axial direction from the crown groove 20A.

[0081] The axially outer end 11a of the first portion 11 of the inner rubber 10 is preferably located axially outward of the axially outermost shoulder groove 20B. In the first portion 11 of this embodiment, the entire end 11A is located axially outward of the axially outermost shoulder groove 20B. In such an inner rubber 10, the portion where the circumferential grooves 20 are provided is the first portion 11, so that vibration of the tread portion 2 caused by the circumferential grooves 20 can be efficiently suppressed.

[0082] As shown in FIG. 1, it is desirable that the maximum groove depth d (mm) of the crown groove 20A closest to the tire equator C satisfies the following formula (1).

number

[0083] Such a tread portion 2 has shallow crown grooves 20A, and therefore is excellent in responsiveness to inputs from the road surface, thereby improving the steering stability and fuel economy of the pneumatic tire 1. Furthermore, in this tread portion 2, the first portion 11 of the inner rubber 10 can suppress an increase in vibration that accompanies shallower crown grooves 20A, and the pneumatic tire 1 can maintain good noise performance.

[0084] Here, the crown groove 20A closest to the tire equator C is determined based on the average value of the distance in the tire axial direction between the tire equator C and the center line of the crown groove 20A. For example, when a crown groove 20A is located on the tire equator C, the crown groove 20A closest to the tire equator C corresponds to the crown groove 20A. When a pair of crown grooves 20A are located at equal distances on either side of the tire equator C, these two crown grooves 20A correspond to the crown groove 20A closest to the tire equator C.

[0085] The tread width TW is preferably 70% or more of the tire maximum width SW. By making the tread width TW 70% or more of the tire maximum width SW, it is possible to prevent the weight of the tread portion 2 from becoming excessively small, thereby improving the noise performance of the pneumatic tire 1. From this perspective, the tread width TW is more preferably 72% or more of the tire maximum width SW.

[0086] The tread width TW is preferably 80% or less of the tire maximum width SW. By making the tread width TW 80% or less of the tire maximum width SW, it is possible to prevent the weight of the tread portion 2 from becoming excessively large, thereby improving the fuel efficiency performance of the pneumatic tire 1. From this perspective, the tread width TW is more preferably 78% or less of the tire maximum width SW.

[0087] For these reasons, the tread width TW is preferably 70% to 80% of the maximum tire width SW, and more preferably 72% to 78%. The combination of the upper and lower limits of these numerical ranges can be selected arbitrarily.

[0088] It is desirable that the rubber thickness from the outer surface 8s of the band layer 8 of the tread portion 2 to the contact surface 2s gradually decrease from the tire equator C to the first tread edge Te1 and the second tread edge Te2. Such a tread portion 2 can suppress excessive weight increase and improve the fuel economy performance of the pneumatic tire 1.

[0089] The rubber thickness of the tread portion 2 includes, for example, a first rubber thickness T1 at the tire equator C, a second rubber thickness T2 at a first position 2a axially outward of the tire equator C, and a third rubber thickness T3 at a second position 2b axially outward of the first position 2a. The first position 2a is, for example, a position 40% of the tread half width TW / 2 away from the tire equator C toward the first tread edge Te1. The second position 2b is, for example, a position 80% of the tread half width TW / 2 away from the tire equator C toward the first tread edge Te1. Here, the tread half width TW / 2 is the axial distance from the tire equator C to the first tread edge Te1.

[0090] The first rubber thickness T1 is preferably 8.0 mm or more. By making the first rubber thickness T1 8.0 mm or more, it is possible to suppress vibration of the tread portion 2 and improve the noise performance of the pneumatic tire 1. From this viewpoint, the first rubber thickness T1 is more preferably 8.5 mm or more, and even more preferably 9.0 mm or more.

[0091] The first rubber thickness T1 is preferably 15.0 mm or less. By setting the first rubber thickness T1 to 15.0 mm or less, an excessive weight increase can be suppressed and the fuel economy performance of the pneumatic tire 1 can be improved. From this viewpoint, the first rubber thickness T1 is more preferably 14.0 mm or less, and even more preferably 12.5 mm or less.

[0092] For these reasons, the first rubber thickness T1 is preferably 8.0 to 15.0 mm, more preferably 8.5 to 14.0 mm, and even more preferably 9.0 to 12.5 mm. The combination of the upper and lower limits of these numerical ranges can be selected arbitrarily.

[0093] The second rubber thickness T2 is preferably smaller than the first rubber thickness T1. Such a tread portion 2 can suppress an excessive increase in weight and improve the fuel economy performance of the pneumatic tire 1.

[0094] The difference (T1-T2) between the first rubber thickness T1 and the second rubber thickness T2 is preferably 1.0 mm or less. By having the difference (T1-T2) be 1.0 mm or less, it is possible to suppress the occurrence of vibration due to excessive thickness changes and improve the noise performance of the pneumatic tire 1. From this perspective, the difference (T1-T2) is more preferably 0.5 mm or less, and even more preferably 0.3 mm or less.

[0095] The third rubber thickness T3 is preferably smaller than the second rubber thickness T2. In the tread portion 2 of this embodiment, the rubber thickness gradually decreases from the first rubber thickness T1 to the third rubber thickness T3. Such a tread portion 2 can suppress excessive weight increase and improve the fuel efficiency performance of the pneumatic tire 1.

[0096] The difference (T2-T3) between the second rubber thickness T2 and the third rubber thickness T3 is preferably 1.0 mm or more. By making the difference (T2-T3) 1.0 mm or more, it is possible to reliably suppress an excessive increase in weight and improve the fuel economy performance of the pneumatic tire 1. From this viewpoint, the difference (T2-T3) is more preferably 1.2 mm or more, and even more preferably 1.5 mm or more.

[0097] The difference (T2-T3) between the second rubber thickness T2 and the third rubber thickness T3 is preferably 3.0 mm or less. By having the difference (T2-T3) be 3.0 mm or less, it is possible to suppress the generation of vibration due to excessive changes and improve the noise performance of the pneumatic tire 1. From this perspective, the difference (T2-T3) is more preferably 2.8 mm or less, and even more preferably 2.5 mm or less.

[0098] For these reasons, the difference (T2-T3) between the second rubber thickness T2 and the third rubber thickness T3 is preferably 1.0 to 3.0 mm, more preferably 1.2 to 2.8 mm, and even more preferably 1.5 to 2.5 mm. The combination of the upper and lower limits of these numerical ranges can be selected arbitrarily.

[0099] Here, the first rubber thickness T1, the second rubber thickness T2, and the third rubber thickness T3 each refer to the thickness from the outer surface 8s of the band layer 8 to the ground contact surface 2s, and are thicknesses that do not include the topping rubber of the band ply 8A.

[0100] In the above-described embodiment, the first portion 11 and the second portion 12 of the inner rubber 10 are formed from a single rubber material, but the inner rubber 10 is not limited to this form and may, for example, be formed from multiple rubber materials.

[0101] Figure 5 is an enlarged cross-sectional view of the inner rubber 10 of the second embodiment. The same elements as those in the above-mentioned embodiment are given the same reference numerals, and their description will be omitted. As shown in Figure 5, the first portion 11 of the inner rubber 10 of the second embodiment includes an inner liner layer 16 made of an air-impermeable rubber material, and an additional layer 17 disposed between the inner liner layer 16 and the carcass 6.

[0102] The additional layer 17 of the second embodiment is made of a rubber material different from that of the inner liner layer 16. The additional layer 17 may be made of, for example, an air-permeable rubber material. Such an inner rubber 10 has a wide variety of materials to choose from for the additional layer 17, and is suitable for achieving various performances at low cost.

[0103] The additional layer 17 may be made of, for example, a rubber material having a loss tangent tanδ at 70°C greater than that of the inner liner layer 16. In this case, the loss tangent tanδ1 of the first portion 11 is the average value obtained by weighting the loss tangent tanδ of the inner liner layer 16 and the loss tangent tanδ of the additional layer 17 by the cross-sectional area. The loss tangent tanδ2 of the second portion 12 corresponds to the loss tangent tanδ of the inner liner layer 16. Such an additional layer 17 can more reliably reduce vibrations in the tread portion 2, and can improve the noise performance of the pneumatic tire 1.

[0104] Figure 6 is an enlarged cross-sectional view of the inner rubber 10 of the third embodiment. The same elements as those in the above-mentioned embodiments are given the same reference numerals, and their description will be omitted. As shown in Figure 6, the additional layer 17 may be disposed, for example, on the radially inner side of the inner liner layer 16. In this case, the additional layer 17 forms part of the tire cavity surface 1i. Like the inner rubber 10 of the second embodiment, the inner rubber 10 of the third embodiment also has a wide variety of material options for the additional layer 17, making it suitable for achieving a variety of performances at low cost.

[0105] As shown in Figures 5 and 6, even when the first portion 11 of the inner rubber 10 includes an additional layer 17, the first thickness t1 is the thickness from the inner surface 6i of the carcass 6 in the tread portion 2 to the tire cavity surface 1i, and is the thickness excluding the topping rubber 6g of the carcass ply 6A.

[0106] Figure 7 is an enlarged cross-sectional view of the inner rubber 10 of the fourth embodiment. The same elements as those of the above-mentioned embodiments are given the same reference numerals, and their explanation will be omitted. As shown in Figure 7, the second part 12 of the inner rubber 10 of the fourth embodiment includes an inner liner layer 16 made of an air-impermeable rubber material, and an intermediate layer 18 disposed between the inner liner layer 16 and the carcass 6.

[0107] The intermediate layer 18 of the fourth embodiment is made of a rubber material different from that of the inner liner layer 16. The intermediate layer 18 may be made of the same rubber material as the additional layer 17 (shown in FIGS. 3 and 4), for example, or may be made of a rubber material different from that of the additional layer 17. Such an inner rubber 10 allows for a wide variety of material options for the intermediate layer 18 and is suitable for achieving a variety of performances at low cost.

[0108] The intermediate layer 18 overlaps with the band layer 8 in the tire axial direction, for example. The intermediate layer 18 of the fourth embodiment overlaps with the belt layer 7 in the tire axial direction. The intermediate layer 18 may be continuous with the first portion 11 of the inner rubber 10, for example. The intermediate layer 18 desirably overlaps with the turned-up portion 6b of the carcass 6 in the tire radial direction. Such an intermediate layer 18 helps to suppress vibration of the sidewall portion 3, and can improve the noise performance of the pneumatic tire 1.

[0109] Even when the second portion 12 of the inner rubber 10 includes an intermediate layer 18, the second thickness t2 is the thickness from the inner surface 6i of the carcass 6 in the sidewall portion 3 to the tire inner cavity surface 1i, and is the thickness excluding the topping rubber 6g of the carcass ply 6A.

[0110] Although a particularly preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment and can be modified and practiced in various ways. [Example]

[0111] Pneumatic tires having the basic structure shown in Figure 1 were prototyped based on the specifications in Tables 1 and 2. Each prototype test tire was tested for fuel economy and noise performance. The common specifications and test methods for each test tire are as follows:

[0112] <Common specifications> Tire size: 195 / 65R15 91S Rim: 15 x 6.0J Maximum tire width: 211mm Tire pressure: Front 250kPa / Rear 240kPa Test vehicle: 1800cc hybrid vehicle

[0113] <Low fuel consumption performance> The rolling resistance of each test tire, adjusted to the front tire pressure, was measured using a rolling resistance tester. The results were expressed as an index, where the reciprocal of the measured rolling resistance was set at 100 for the comparative example, and the larger the index, the smaller the rolling resistance and the better the fuel economy.

[0114] <Noise performance> A test vehicle fitted with test tires on all wheels was driven at a speed of 60 km / h on a road noise measurement road (rough asphalt road), and the interior noise (noise below 500 Hz) was measured. The results were expressed as an index, where the reciprocal of the interior noise was set at 100 for the comparative example, and the larger the index value, the lower the interior noise and the better the noise performance.

[0115] The test results are shown in Tables 1-2. [Table 1]

[0116] [Table 2]

[0117] The test results confirmed that the pneumatic tires of the examples were superior to the comparative example in both fuel economy and noise performance, and also in overall performance evaluated as the sum of fuel economy and noise performance. Therefore, it was confirmed that the pneumatic tires of the examples achieved both fuel economy and noise performance.

[0118] [Note] The present invention is as follows.

[0119] [Invention 1] A pneumatic tire, A tread portion; A pair of sidewall portions; a pair of bead portions; a carcass extending between the pair of bead portions; an inner rubber extending between the pair of bead portions on the inner side of the carcass, the inner rubber includes a first portion extending through the tread portion at a first thickness and a pair of second portions extending through the pair of sidewall portions at a second thickness, The first thickness is 1.5 to 3.5 times the second thickness. Pneumatic tires.

[0120] [Invention 2] the tread portion includes a first tread edge, a second tread edge, and a contact surface extending between the first tread edge and the second tread edge, the pair of sidewall portions each include a sidewall outer surface extending radially inward from the first tread edge and the second tread edge, the sidewall outer surface includes a maximum tire width position which is the outermost position in the tire axial direction, The pneumatic tire according to invention 1, wherein a tread width TW, which is the distance in the tire axial direction from the first tread edge to the second tread edge, is 70% to 80% of a tire maximum width SW, which is the distance in the tire axial direction at the tire maximum width position.

[0121] [Invention 3] the tread portion includes a plurality of circumferential grooves extending continuously in the tire circumferential direction, the plurality of circumferential grooves includes a crown groove closest to the tire equator, 3. The pneumatic tire according to claim 2, wherein the maximum groove depth d (mm) of the crown groove satisfies the following formula (1):

number

[0122] [Invention 4] 4. The pneumatic tire according to claim 2 or 3, wherein the rubber thickness of the tread portion gradually decreases from the tire equator toward the first tread end and the second tread end.

[0123] [Invention 5] 5. The pneumatic tire according to any one of claims 1 to 4, wherein the first thickness is 2.0 to 4.5 mm.

[0124] [Invention 6] 6. The pneumatic tire according to any one of claims 1 to 5, wherein the first portion is formed of rubber having a loss tangent tanδ1 at 70°C of 0.14 or more.

[0125] [Invention 7] the tread portion includes a belt layer disposed on the outer side of the carcass in the tire radial direction, the belt layer includes a first belt ply and a second belt ply disposed outward of the first belt ply in the tire radial direction, On each side of the tire equator, an axially outer end of the second belt ply is located axially more inward than an axially outer end of the first belt ply, The pneumatic tire according to any one of claims 1 to 6, wherein an axially outer end of the first portion of the inner rubber is located at the same position in the tire axial direction as the outer end of the second belt ply, or is located axially inward of the outer end of the second belt ply and within 10 mm in the tire axial direction.

[0126] [Invention 8] The carcass includes at least one carcass ply in which carcass cords are arranged, the first belt ply includes a plurality of belt cords arranged at an angle with respect to the tire equator, A pneumatic tire according to Invention 7, wherein a first distance, which is the shortest distance in the tire radial direction between the carcass cord and the belt cord at the tire equator, is longer than a second distance, which is the shortest distance in the tire radial direction between the carcass cord and the belt cord at the outer end of the first belt ply.

[0127] [Invention 9] 9. The pneumatic tire according to invention 8, wherein the first distance is 1.2 to 2.5 times the second distance. [Explanation of symbols]

[0128] 1 pneumatic tire 2 Tread section 3 Sidewall 4 Bead section 6. Carcass 10 Inner rubber 11 Part 1 12 Part 2

Claims

1. A pneumatic tire, A tread portion; A pair of sidewall portions; a pair of bead portions; a carcass extending between the pair of bead portions; an inner rubber extending between the pair of bead portions on the inner side of the carcass, the inner rubber includes a first portion extending through the tread portion at a first thickness and a pair of second portions extending through the pair of sidewall portions at a second thickness, The first thickness is 1.5 to 3.5 times the second thickness. Pneumatic tires.

2. the tread portion includes a first tread edge, a second tread edge, and a contact surface extending between the first tread edge and the second tread edge, the pair of sidewall portions each include a sidewall outer surface extending radially inward from the first tread edge and the second tread edge, the sidewall outer surface includes a maximum tire width position which is the outermost position in the tire axial direction, 2. The pneumatic tire according to claim 1, wherein a tread width TW, which is the distance in the tire axial direction from the first tread edge to the second tread edge, is 70% to 80% of a tire maximum width SW, which is the distance in the tire axial direction at the tire maximum width position.

3. the tread portion includes a plurality of circumferential grooves extending continuously in the tire circumferential direction, the plurality of circumferential grooves includes a crown groove closest to the tire equator, The pneumatic tire according to claim 2 , wherein the maximum groove depth d (mm) of the crown groove satisfies the following formula (1): [Equation 1] where: d: Maximum groove depth of crown groove (mm) SW: Maximum tire width (mm)

4. The pneumatic tire according to claim 2 , wherein the rubber thickness of the tread portion gradually decreases from the tire equator toward the first tread edge and the second tread edge.

5. The pneumatic tire according to claim 1, wherein the first thickness is 2.0 to 4.5 mm.

6. The pneumatic tire according to claim 1 , wherein the first portion is formed from a rubber material having a loss tangent tanδ1 at 70° C. of 0.14 or more.

7. the tread portion includes a belt layer disposed on the outer side of the carcass in the tire radial direction, the belt layer includes a first belt ply and a second belt ply disposed outward of the first belt ply in the tire radial direction, On each side of the tire equator, an axially outer end of the second belt ply is located axially more inward than an axially outer end of the first belt ply, 7. The pneumatic tire according to claim 1, wherein an axially outer end of the first portion of the inner rubber is located at the same position in the tire axial direction as the outer end of the second belt ply, or is located axially inward of the outer end of the second belt ply and within 10 mm in the tire axial direction.

8. The carcass includes at least one carcass ply in which carcass cords are arranged, the first belt ply includes a plurality of belt cords arranged at an angle with respect to the tire equator, 8. The pneumatic tire according to claim 7, wherein a first distance that is the shortest distance in the tire radial direction between the carcass cord and the belt cord at the tire equator is greater than a second distance that is the shortest distance in the tire radial direction between the carcass cord and the belt cord at the outer end of the first belt ply.

9. The pneumatic tire according to claim 8, wherein the first distance is 1.2 to 2.5 times the second distance.

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