tire

Abstract

To provide a tire that can make both grip performance and low fuel consumption performance compatible.SOLUTION: A tire 1 comprises a tread part 2. The tread part 2 comprises a first rubber layer 3A constituting a grounding plane 2s, a second rubber layer 3B positioned inside in a tire radial direction of the first rubber layer 3A, and a third rubber layer 3C positioned inside in the tire radial direction of the second rubber layer 3B. A complex elastic modulus E*1 at 30°C of the first rubber layer 30A is 8.5 MPa or lower. A complex elastic modulus E*2 at 30°C of the second rubber layer 3B is 80%-90% of the complex elastic modulus E*1 of the first rubber layer 3A. A complex elastic modulus E*3 at 30°C of the third layer 3C is 35%-45% of the complex elastic modulus E*1 of the first rubber layer 3A. The first rubber layer 3A includes a first part 3a having a thickness t1 corresponding to 5%-25% of a tread thickness T and a second part 3b having a thickness t2 corresponding to 35%-55% of the tread thickness T.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Conventionally, tires having a tread portion composed of a plurality of rubber layers are known. Patent Document 1 below proposes a pneumatic tire having a tread portion including a first layer, a second layer, and a third layer, the rubber composition of which is specified. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-210044 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the tire of Patent Document 1, fuel economy performance tends to decrease when the thickness of the first rubber layer, which has a large impact on grip performance, is increased, and there has been a demand for further improvement in terms of achieving both the contradictory properties of grip performance and fuel economy performance.

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

[0006] The present invention is a tire having a tread portion, the tread portion comprising a first rubber layer constituting a ground contact surface, a second rubber layer located radially inward of the first rubber layer, and a third rubber layer located radially inward of the second rubber layer, the first rubber layer having a complex modulus E*1 at 30°C of 8.5 MPa or less, the second rubber layer having a complex modulus E*2 at 30°C of 80% to 90% of the complex modulus E*1 of the first rubber layer, the third rubber layer having a complex modulus E*3 at 30°C of 35% to 45% of the complex modulus E*1 of the first rubber layer, and the first rubber layer having a first portion having a thickness t1 of 5% to 25% of the tread thickness T and a second portion having a thickness t2 of 35% to 55% of the tread thickness T. Effect of the Invention

[0007] The tire of the present invention has the above-mentioned configuration, and thus can achieve both grip performance and low fuel consumption performance. [Brief description of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing one embodiment of a tread portion of a tire of the present invention. [Diagram 2] FIG. [Diagram 3] FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Fig. 1 is a tire meridian cross-sectional view showing a tread portion 2 of a tire 1 of this embodiment in a normal state. As shown in Fig. 1, the tire 1 of this embodiment has a tread portion 2. The tire 1 of this embodiment is suitably used as a pneumatic tire to be mounted on a passenger car or the like. Note that the tire 1 is not limited to a pneumatic tire for a passenger car, and can be applied to various tires such as a pneumatic tire for heavy loads, a pneumatic tire for a motorcycle, an airless tire, etc.

[0010] Here, "normal state" refers to a state in which, if the tire 1 is a pneumatic tire, the tire 1 is mounted on a normal rim, the internal pressure is adjusted to the normal pressure, and no load is applied. Unless otherwise specified below, the dimensions of each part of the tire 1 are values ​​measured in this normal state.

[0011] A "genuine rim" is a rim that is determined for each tire by a standard system that includes the standard on which tire 1 is based, for example, a "standard rim" for JATMA, a "design rim" for TRA, and a "measuring rim" for ETRTO. If there is no standard system that includes the standard on which tire 1 is based, a "genuine rim" is a rim that can be assembled and does not leak air, and that has the smallest rim diameter and the smallest rim width among the rims.

[0012] "Normal internal pressure" is the air pressure set for each tire by a standard system that includes the standard on which tire 1 is based, such as "maximum air pressure" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "INFLATION PRESSURE" for ETRTO. "Normal internal pressure" is the air pressure set for each tire by the manufacturer, etc., if there is no standard system that includes the standard on which tire 1 is based.

[0013] The tread portion 2 of this embodiment has a contact surface 2s extending between a pair of tread ends Te. Here, when the tire 1 is a pneumatic tire, the pair of tread ends Te are the axially outermost contact points when the pneumatic tire in a normal state is loaded with 70% of the normal load and contacts a flat surface with a camber angle of 0°. The axial distance between the pair of tread ends Te is the contact width TW. The axial center position between the pair of tread ends Te is the tire equator C.

[0014] "Normal load" is the load determined for each tire by a standard system that includes the standard on which tire 1 is based, such as "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. "Normal load" is the load determined for each tire by the manufacturer, etc., if there is no standard system that includes the standard on which tire 1 is based.

[0015] The tread portion 2 of this embodiment includes a plurality of rubber layers 3. The plurality of rubber layers 3 include a first rubber layer 3A constituting the ground contact surface 2s, a second rubber layer 3B located on the inner side in the tire radial direction of the first rubber layer 3A, and a third rubber layer 3C located on the inner side in the tire radial direction of the second rubber layer 3B. Such a tread portion 2 helps to achieve both grip performance and low fuel consumption performance by making the properties of the plurality of rubber layers 3 different.

[0016] The complex modulus E*1 of the first rubber layer 3A at 30°C is preferably 8.5 MPa or less. Such a first rubber layer 3A can exhibit good heat generation properties and can improve grip performance such as braking performance on wet road surfaces. The first rubber layer 3A also helps to solve the problem of improving performance on snow. The complex modulus E*1 of the first rubber layer 3A is preferably 6.0 MPa or more from the viewpoint of steering stability performance on dry road surfaces.

[0017] Here, the complex modulus is a value measured by taking a sample of length 20 mm × width 4 mm × thickness 1 mm from each rubber layer 3 and measuring it using a dynamic viscoelasticity measuring device (Iplexer series manufactured by GARO) under the following conditions in accordance with the provisions of JIS-K6394. The sample was taken so that its length was in the tire circumferential direction, its width was in the tire axial direction, and its thickness was in the tire radial direction. Initial strain: 5% Dynamic distortion: 1% Frequency: 10Hz Deformation mode: Stretch Measurement temperature: 30℃

[0018] The complex modulus E*2 of the second rubber layer 3B at 30° C. is preferably 80% to 90% of the complex modulus E*1 of the first rubber layer 3A. Such a second rubber layer 3B can suppress heat generation more effectively than the first rubber layer 3A, thereby improving fuel economy performance.

[0019] The complex modulus E*3 of the third rubber layer 3C at 30° C. is preferably 35% to 45% of the complex modulus E*1 of the first rubber layer 3A. Such a third rubber layer 3C can suppress heat generation more than the first rubber layer 3A and the second rubber layer 3B in the radially inner region of the tire where heat is likely to accumulate, thereby improving fuel economy performance.

[0020] Fig. 2 is a schematic diagram of the tread portion 2. As shown in Fig. 1 and Fig. 2, the first rubber layer 3A includes a first portion 3a having a thickness t1 that is 5% to 25% of the tread thickness T, and a second portion 3b having a thickness t2 that is 35% to 55% of the tread thickness T.

[0021] In such a tread portion 2, the first portion 3a is disposed at a position that significantly affects fuel economy, and the second portion 3b is disposed at a position that significantly affects grip performance, so that the grip performance and fuel economy, which are mutually contradictory, can be achieved at a high level. Therefore, the tire 1 of the present embodiment can achieve both grip performance and fuel economy.

[0022] In a more preferred embodiment, the first rubber layer 3A includes a third portion 3c disposed between the first portion 3a and the second portion 3b. The third portion 3c gradually increases in thickness from the thickness t1 of the first portion 3a of the first rubber layer 3A to the thickness t2 of the second portion 3b. Such a third portion 3c can alleviate stress changes at the boundary between the first portion 3a and the second portion 3b, thereby solving the problem of improving durability.

[0023] Fig. 3 is a schematic diagram of the contact patch 2s. As shown in Fig. 3, the contact patch 2s of this embodiment has a large contact length in the tire circumferential direction of the crown region in the vicinity of the tire equator C. Since the contact patch 2s has a large contact area of ​​the crown region, the crown region has a large effect on grip performance such as braking performance on wet road surfaces.

[0024] The shoulder contact length Ls of the ground contact surface 2s at 80% of the ground contact width TW is preferably 65% ​​to 95% of the crown contact length Lc at the tire equator C. By making the shoulder contact length Ls 65% or more of the crown contact length Lc, compressive strain in the shoulder region under load can be alleviated and heat generation in the shoulder region, which is prone to heat generation and has a large impact on fuel economy, can be suppressed, which helps to improve fuel economy. By making the shoulder contact length Ls 95% or less of the crown contact length Lc, the ground contact area of ​​the crown region can be reliably increased, which helps to improve grip performance.

[0025] 1 and 2, the first portion 3a of this embodiment is located on both sides of the second portion 3b in the tire axial direction. In such a tread portion 2, the vicinity of the tire equator C, which has a large effect on grip performance, can be the second portion 3b, and both sides thereof, which have a large effect on fuel economy performance, can be the first portions 3a, thereby achieving both grip performance and fuel economy performance.

[0026] The first portion 3a is preferably located axially outboard of 35% to 45% of the contact width TW from the tire equator C. Such a first portion 3a can increase the contribution of the second rubber layer 3B to the shoulder region, which has a significant effect on fuel economy performance, and can improve fuel economy performance.

[0027] The width w1 of the first portion 3a in the tire axial direction is preferably 5% to 20% of the contact width TW. When the width w1 of the first portion 3a is 5% or more of the contact width TW, the shoulder region that has a large effect on fuel economy performance can be reliably made into the first portion 3a. When the width w1 of the first portion 3a is 20% or less of the contact width TW, even if the first portion 3a is lost due to wear, the first rubber layer 3A can remain in the second portion 3b, and excellent grip performance can be maintained. Note that the first portion 3a may extend, for example, to the outside in the tire axial direction beyond the tread end Te.

[0028] The width w2 of the second portion 3b in the tire axial direction is preferably 70% to 90% of the contact width TW. When the width w2 of the second portion 3b is 70% or more of the contact width TW, the contribution of the first rubber layer 3A can be increased in the crown region, which has a large effect on grip performance, and grip performance can be improved. When the width w2 of the second portion 3b is 90% or less of the contact width TW, the contribution of the second rubber layer 3B can be increased in the shoulder region, which has a large effect on fuel economy, and fuel economy can be improved.

[0029] As shown in Fig. 1 and Fig. 3, the tread portion 2 has at least one circumferential groove 4 extending in the circumferential direction of the tire, four in this embodiment. The groove depth d of the circumferential groove 4 is preferably 5.5 to 8.5 mm. When the groove depth d of the circumferential groove 4 is 5.5 mm or more, excellent drainage is exhibited when traveling on wet roads, and wet performance can be improved. When the groove depth d of the circumferential groove 4 is 8.5 mm or less, the tread thickness T of the tread portion 2 can be reduced, which helps to reduce the weight of the tread portion 2 and improve fuel efficiency.

[0030] The groove bottom 4a of the circumferential groove 4 is located, for example, in the third rubber layer 3C. Such a tread portion 2 can further reduce the tread thickness T, and can improve fuel efficiency. The position of the groove bottom 4a of the circumferential groove 4 is not limited to this embodiment, and may be located, for example, in the second rubber layer 3B. In this case, the tread portion 2 can maintain good grip performance even when the circumferential groove 4 is worn down to the point where it disappears.

[0031] The loss tangent tanδ1 of the first rubber layer 3A at 30° C. is preferably 0.20 to 0.25. When the loss tangent tanδ1 of the first rubber layer 3A is 0.20 or more, the first rubber layer 3A can exhibit good heat generation properties and can achieve both grip performance such as braking performance on wet roads and performance on snow. When the loss tangent tanδ1 of the first rubber layer 3A is 0.25 or less, excessive heat generation is suppressed, which helps to improve fuel efficiency.

[0032] Here, the loss tangent is a value measured in the same manner as the above-mentioned complex modulus. That is, the loss tangent is a value measured by taking a sample of 20 mm in length × 4 mm in width × 1 mm in thickness from each rubber layer 3, and measuring it using a dynamic viscoelasticity measuring device (Iplexer series manufactured by GARO) under the following conditions in accordance with the provisions of JIS-K6394. The sample was taken so that its length was in the tire circumferential direction, its width was in the tire axial direction, and its thickness was in the tire radial direction. Initial strain: 5% Dynamic distortion: 1% Frequency: 10Hz Deformation mode: Stretch Measurement temperature: 30℃

[0033] In this embodiment, the loss tangent tanδ2 of the second rubber layer 3B at 30° C. is smaller than the loss tangent tanδ1 of the first rubber layer 3A. Such a second rubber layer 3B can suppress heat generation more effectively than the first rubber layer 3A, thereby improving fuel economy performance.

[0034] The loss tangent tanδ2 of the second rubber layer 3B is preferably 60% to 80% of the loss tangent tanδ1 of the first rubber layer 3A. When the loss tangent tanδ2 of the second rubber layer 3B is 60% or more of the loss tangent tanδ1 of the first rubber layer 3A, good grip performance can be maintained even when the second rubber layer 3B becomes the ground contact surface 2s due to wear. When the loss tangent tanδ2 of the second rubber layer 3B is 80% or less of the loss tangent tanδ1 of the first rubber layer 3A, heat generation under load can be suppressed and fuel economy can be improved.

[0035] 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 in various ways. EXAMPLES

[0036] A prototype tire with the basic structure shown in Figure 1 was produced based on the specifications in Table 1. Using the prototype tire, fuel economy and grip performance tests were conducted, and the overall performance, which is the sum of these performances, was evaluated. The main common specifications and test methods are as follows:

[0037] <Common specifications> Tire size: 255 / 50R20 109V XL Rim size: 20×8.0J Test vehicle: Large SUV

[0038] <Low fuel consumption performance> The prototype tire was mounted on a rolling resistance tester, the air pressure was adjusted to 250 kPa, and the rolling resistance was measured under the condition of a load of 8.09 kN. The results are expressed as an index with Comparative Example 1 being 100, and the larger the index value, the smaller the rolling resistance and the more excellent the fuel efficiency performance.

[0039] <Grip performance> A test driver rode in a test vehicle equipped with the prototype tire, and a braking test was conducted on a wet road surface. In addition, the braking distance on a wet road surface was measured using the prototype tire when it was 70% worn. The results were expressed as an index with the unworn Comparative Example 1 being set at 100, and the higher the index, the shorter the braking distance and the better the grip performance.

[0040] The test results are shown in Table 1. [Table 1]

[0041] As a result of the test, it was confirmed that the tires of the embodiment had superior overall performance, which was evaluated by combining fuel efficiency performance, grip performance, and grip performance at 70% wear, compared to the comparative example, and achieved both grip performance and fuel efficiency performance.

[0042] [Note] The present invention is as follows.

[0043] [Invention 1] A tire having a tread portion, the tread portion includes a first rubber layer constituting a contact surface, a second rubber layer located radially inward of the first rubber layer, and a third rubber layer located radially inward of the second rubber layer, The complex modulus E*1 of the first rubber layer at 30° C. is 8.5 MPa or less, The complex modulus E*2 of the second rubber layer at 30° C. is 80% to 90% of the complex modulus E*1 of the first rubber layer, A complex modulus E*3 of the third rubber layer at 30° C. is 35% to 45% of the complex modulus E*1 of the first rubber layer, The first rubber layer includes a first portion having a thickness t1 of 5% to 25% of the tread thickness T, and a second portion having a thickness t2 of 35% to 55% of the tread thickness T. tire.

[0044] [Invention 2] The tire according to the present invention 1, wherein the first portion is located on both sides of the second portion in the tire axial direction.

[0045] [Invention 3] The tire according to invention 1 or 2, wherein the first portion is positioned axially outboard of 35% to 45% of the contact width TW from the tire equator.

[0046] [Invention 4] The tire according to any one of claims 1 to 3, wherein the axial width w2 of the second portion is 70% to 90% of the contact width TW.

[0047] [Invention 5] The tire according to any one of inventions 1 to 4, wherein the shoulder contact length Ls at a position that is 80% of the contact width TW of the contact patch is 65% to 95% of the crown contact length Lc at the tire equator.

[0048] [Invention 6] The tread portion has at least one circumferential groove extending in a circumferential direction of the tire, The tire according to any one of Inventions 1 to 5, wherein the circumferential groove has a groove depth of 5.5 to 8.5 mm.

[0049] [Invention 7] 7. The tire according to claim 6, wherein a groove bottom of the circumferential groove is located in the third rubber layer.

[0050] [Invention 8] The tire according to any one of claims 1 to 7, wherein the loss tangent tan δ1 of the first rubber layer at 30° C. is 0.20 to 0.25.

[0051] [The present invention 9] The tire according to present invention 8, wherein a loss tangent tan δ2 at 30° C. of the second rubber layer is smaller than the loss tangent tan δ1 of the first rubber layer.

[0052] [The present invention 10] 10. The tire according to claim 9, wherein the loss tangent tan δ2 of the second rubber layer is 60% to 80% of the loss tangent tan δ1 of the first rubber layer. [Explanation of symbols]

[0053] 1 Tire 2 Tread section 3A First Rubber Layer 3B Second rubber layer 3C 3rd rubber layer 3a Part 1 3b 2nd part

Claims

1. A tire having a tread portion, the tread portion includes a first rubber layer constituting a ground contact surface, a second rubber layer located inward in a tire radial direction of the first rubber layer, and a third rubber layer located inward in a tire radial direction of the second rubber layer, The complex modulus E*1 of the first rubber layer at 30° C. is 8.5 MPa or less, a complex elastic modulus E*2 at 30° C. of the second rubber layer is 80% to 90% of the complex elastic modulus E*1 of the first rubber layer, a complex elastic modulus E*3 at 30° C. of the third rubber layer is 35% to 45% of the complex elastic modulus E*1 of the first rubber layer, The first rubber layer includes a first portion having a thickness t1 that is 5% to 25% of a tread thickness T, and a second portion having a thickness t2 that is 35% to 55% of the tread thickness T. tire.

2. The tire according to claim 1 , wherein the first portion is located on both sides of the second portion in the tire axial direction.

3. The tire according to claim 1, wherein the first portion is positioned axially outboard of 35% to 45% of a contact width TW from the tire equator.

4. The tire according to claim 1, wherein the axial width w2 of the second portion is 70% to 90% of the contact width TW.

5. 2. The tire according to claim 1, wherein the shoulder contact length Ls at a position that is 80% of the contact width TW of the contact patch is 65% to 95% of the crown contact length Lc at the tire equator.

6. The tread portion has at least one circumferential groove extending in a circumferential direction of the tire, 2. The tire according to claim 1, wherein the circumferential groove has a groove depth of 5.5 to 8.5 mm.

7. The tire according to claim 6 , wherein a groove bottom of the circumferential groove is located in the third rubber layer.

8. The tire according to any one of claims 1 to 7, wherein a loss tangent tan δ1 at 30°C of the first rubber layer is 0.20 to 0.

25.

9. The tire according to claim 8 , wherein a loss tangent tan δ2 at 30° C. of the second rubber layer is smaller than the loss tangent tan δ1 of the first rubber layer.

10. The tire according to claim 9, wherein the loss tangent tan δ2 of the second rubber layer is 60% to 80% of the loss tangent tan δ1 of the first rubber layer.

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