tire

Abstract

To provide a tire which maintains a handling stability and can improve weight saving and a fuel consumption performance.SOLUTION: A belt layer 7 includes at least one belt ply 7A. The belt ply 7A has a minor axis SD and a major axis LD, and includes a single wire cord 9 in wich a ratio SD / LD between the minor axis SD and the major axis LD is less than 1.00, and a topping rubber 10 covering the single wire cord 9. The single wire cord 9 is arranged such that a direction of the minor axis SD is directed toward a thickness direction of the belt ply 7A. The topping rubber 10 has a complex elastic modulus (E*) of 7-20 MPa at a temperature of 70°C, an initial strain of 10%, an amplitude of a dynamic strain of ±1.0%, and a frequency of 10 Hz.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a tire using a flat single-wire cord. [Background technology]

[0002] BACKGROUND ART Tires have been proposed in which flat single-wire cords are used in belt plies (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-58515 Summary of the Invention [Problem to be solved by the invention]

[0004] In the belt ply, the topping rubber can be easily formed thinly while ensuring the cross-sectional area of ​​the belt cord, which contributes to weight reduction and improved fuel economy while maintaining the steering stability of the tire.

[0005] However, a reduction in the thickness of the topping rubber may result in excessive rigidity of the belt layer, which may affect ride comfort, and may also result in localized increases in strain in the topping rubber between the cords, which may affect durability.

[0006] The present invention has been devised in view of the above circumstances, and its main object is to provide a tire that has improved ride comfort and durability in a well-balanced manner while maintaining tire steering stability and fuel economy. [Means for solving the problem]

[0007] The present invention provides a tire having a belt layer disposed inside a tread portion, the belt layer including at least one belt ply, the belt ply including a single-wire cord having a minor diameter SD and a major diameter LD, with a ratio SD / LD of the minor diameter SD to the major diameter LD being less than 1.00, and a topping rubber covering the single-wire cord, the single-wire cord being disposed such that the minor diameter SD is oriented in the thickness direction of the belt ply, and the topping rubber having a complex modulus of elasticity (E*) of 7 to 20 MPa at a temperature of 70°C, an initial strain of 10%, a dynamic strain amplitude of ±1.0%, and a frequency of 10 Hz.

[0008] In the tire according to the present invention, the complex modulus (E*) is preferably 9 to 20 MPa.

[0009] In the tire according to the present invention, the minor diameter SD is preferably 0.15 to 0.42 mm.

[0010] In the tire according to the present invention, the minor diameter SD is preferably 0.15 to 0.35 mm.

[0011] In the tire according to the present invention, it is desirable that the ratio SD / LD of the single wire cord is 0.70 or less.

[0012] In the tire according to the present invention, it is desirable that the ratio SD / LD of the single wire cord is 0.50 or less.

[0013] In the tire according to the present invention, it is preferable that the belt layer includes a plurality of the belt plies.

[0014] In the tire according to the present invention, it is desirable that the distance (rubber thickness) D between the single cords among the plurality of belt plies is 0.30 to 1.05 mm.

[0015] In the tire according to the present invention, it is desirable that the difference D-SD between the distance D and the minor diameter SD is 0.20 to 0.45 mm.

[0016] In the tire according to the present invention, it is desirable that the tread portion has tread rubber having grooves formed on its outer surface, and the minimum rubber thickness from the bottom of the groove to the single-wire cord is 1.0 to 4.0 mm. [Effects of the Invention]

[0017] The tire of the present invention includes a belt ply including the flattened single-wire cord and the topping rubber, with the single-wire cord arranged so that the minor diameter SD is oriented in the thickness direction of the belt ply. This allows the thickness of the unvulcanized belt ply to be reduced while ensuring the cross-sectional area of ​​the belt cord. This reduces the tire's weight while maintaining the tire's steering stability, improving fuel economy. Furthermore, the complex modulus (E*) of the topping rubber is 7 MPa or more, thereby reducing strain in the topping rubber between the cords and improving the durability of the belt layer. Furthermore, the complex modulus (E*) of the topping rubber is 20 MPa or less, thereby increasing the flexibility of the belt layer and improving ride comfort. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a cross-sectional view showing one embodiment of a tire of the present invention. [Figure 2] 1 is a cross-sectional view of a belt ply of the present invention. [Figure 3] 1 is a cross-sectional view of a tread portion of a tire of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] An embodiment of the present invention will now be described with reference to the drawings. 1 shows a tire meridian cross section including a rotation axis of a tire 1 of this embodiment in a normal state. 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 and a non-pneumatic tire that does not have pressurized air filled inside the tire.

[0020] Here, "normal state" means, in the case where the tire 1 is a pneumatic tire, a state in which the tire 1 is mounted on a normal rim, adjusted to a normal internal 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.

[0021] A "genuine rim" is a rim that is defined for each tire by the standard system that includes the standard on which tire 1 is based, such as a "standard rim" for JATMA, a "design rim" for TRA, or a "measuring rim" for ETRTO.

[0022] "Normal internal pressure" is the air pressure specified for each tire by each standard in the standard system, including the standard on which tire 1 is based. In the case of JATMA, it is the "maximum air pressure," in the case of TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and in the case of ETRTO, it is the "INFLATION PRESSURE."

[0023] As shown in FIG. 1, the tire 1 of this embodiment has a toroidal carcass 6 extending from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, and a belt layer 7 disposed radially outside the carcass 6 and inside the tread portion 2.

[0024] The tread portion 2 includes a tread rubber 2A.

[0025] The carcass 6 includes at least one carcass ply 6A, one carcass ply 6A in this embodiment. The carcass ply 6A includes carcass cords (not shown) arranged at an angle of 75 to 90 degrees with respect to the tire circumferential direction, for example. The carcass cords may be made of organic fiber cords such as aromatic polyamide or rayon.

[0026] The carcass ply 6A includes, for example, a main body portion 6a that extends from the tread portion 2 through the sidewall portion 3 to the bead cores 5 of the bead portions 4, and a turned-up portion 6b that is continuous with the main body portion 6a and is turned up around the bead cores 5 from the inside to the outside in the tire axial direction. Between the main body portion 6a and the turned-up portion 6b of the carcass ply 6A, for example, a bead apex rubber 8 that extends from the bead cores 5 to the outside in the tire radial direction is disposed.

[0027] The belt layer 7 includes at least one belt ply 7A, 7B, and in this embodiment, two belt plies 7A, 7B. The two belt plies 7A, 7B include, for example, a first belt ply 7A located on the radially inner side of the tire and a second belt ply 7B located on the outer side of the first belt ply 7A. Such a belt layer 7 can increase the rigidity of the tread portion 2 and improve the durability performance of the tire 1. The belt layer 7 may be composed of three or more belt plies.

[0028] Fig. 2 is an enlarged cross-sectional view of the belt layer 7. Fig. 2 illustrates the belt ply 7A, but the belt ply 7B can also have a similar structure. As shown in Fig. 2, at least one of the belt plies 7A and 7B of this embodiment includes belt cords 9 for reinforcing the tread portion 2 and a topping rubber 10 that covers the belt cords 9. The belt cords 9 and topping rubber 10 included in the belt ply 7A will be described below, but the same applies to the belt cords 9 and topping rubber 10 included in the belt ply 7B.

[0029] The belt cord 9 is made of a single-wire cord 11 that does not have a twisted structure. In this embodiment, a steel single-wire cord 11 is used as the belt cord 9. The material of the belt cord 9 is not limited to steel, and may be other metals, etc.

[0030] The single-wire cord 11 has a minor diameter SD and a major diameter LD, and the ratio SD / LD of the minor diameter SD to the major diameter LD is less than 1.00. That is, the cross section of the belt cord 9 is formed to have a flattened shape. The cross-sectional shape of the single-wire cord 11 is not particularly limited as long as the flattened shape is maintained. For example, the cross-sectional shape of the single-wire cord 11 may be an ellipse or an oval shape with a part of the edge being linear.

[0031] The single-wire cord 11 is arranged so that the direction of the minor diameter SD is oriented in the thickness direction of the belt ply 7A. This reduces the thickness of the belt ply 7A while maintaining the cross-sectional area of ​​the belt cord 9. Therefore, the tire 1 can be made lighter and have improved fuel economy while maintaining the steering stability and durability of the tire 1. The orientation of the single-wire cord 11 is substantially maintained before and after vulcanization.

[0032] The complex modulus of elasticity (E*) of the topping rubber 10 after vulcanization is preferably 7 to 20 MPa.

[0033] Here, the complex modulus (E*) of the topping rubber 10 is a value measured in accordance with the provisions of JIS-K6394 using a dynamic viscoelasticity measuring device (Iplexer series) manufactured by GABO under the following conditions. Initial strain: 10% Dynamic strain amplitude: ±1% Frequency: 10Hz Deformation mode: tension Measurement temperature: 70℃

[0034] When the complex elastic modulus (E*) of the topping rubber 10 is 7 MPa or more, distortion of the topping rubber 10 between the cords is suppressed, improving the durability performance of the belt layer 7. Furthermore, when the complex elastic modulus (E*) of the topping rubber 10 is 20 MPa or less, the flexibility of the belt layer 7 is increased, improving the ride comfort performance.

[0035] From the above viewpoint, the more desirable range of the complex modulus of elasticity (E*) of the topping rubber 10 is 9 to 12 MPa.

[0036] In this embodiment, the minor diameter SD of the single-wire cord 11 is preferably 0.15 to 0.42 mm. When the minor diameter SD is 0.15 mm or more, bending, breakage, etc. of the single-wire cord 11 during the manufacturing process of the belt ply 7A can be easily suppressed. Also, the cross-sectional area of ​​the single-wire cord 11 can be easily ensured, and the durability of the tire 1 can be easily improved. On the other hand, when the minor diameter SD is 0.42 mm or less, the thickness of the belt ply 7A can be suppressed, and therefore the weight of the tire 1 can be reduced and fuel economy performance can be improved.

[0037] From the above viewpoint, the minor diameter SD of the single-wire cord 11 is more preferably in the range of 0.20 to 0.35 mm.

[0038] In this embodiment, the ratio SD / LD of the single-wire cord 11 is preferably 0.70 or less. When the ratio SD / LD is 0.70 or less, the thickness of the belt ply 7A is suppressed, thereby reducing the weight of the tire 1 and improving fuel economy.

[0039] From the above viewpoint, the ratio SD / LD of the single-wire cord 11 is more preferably in the range of 0.50 or less.

[0040] In this embodiment, the distance D between the solid cords 11 in the belt plies 7A and 7B is preferably 0.30 to 1.05 mm. As shown in Fig. 2, the distance D is defined as the shortest distance between the solid cords 11 in the belt plies 7A and 7B, i.e., the thickness of the topping rubber 10 interposed therebetween.

[0041] When the distance D is 0.30 mm or more, the ride comfort performance and noise performance can be easily improved. On the other hand, when the distance D is 1.05 mm or less, the weight of the tire 1 can be easily reduced, and the fuel economy performance can be easily improved.

[0042] From the above viewpoint, the distance D is more preferably in the range of 0.50 to 0.80 mm.

[0043] The difference D-SD between the distance D and the minor diameter SD of the solid-wire cord 11 is preferably 0.20 to 0.45 mm. When the difference D-SD is 0.20 mm or more, ride comfort and noise performance are easily improved. On the other hand, when the difference D-SD is 0.45 mm or less, fuel economy performance is easily improved.

[0044] From the above viewpoint, the difference D-SD is more preferably in the range of 0.25 to 0.40 mm.

[0045] 3 shows an enlarged view of a part of the tread portion 2. Grooves 21 are formed on the outer surface 2a of the tread portion 2.

[0046] The minimum rubber thickness T from the bottom 22 of the groove 21 to the single-wire cord 11 is preferably 1.0 to 4.0 mm. When the minimum rubber thickness T is 1.0 mm or more, ride comfort and noise performance are easily improved, and damage to the tread portion 2 is suppressed. When the minimum rubber thickness T is 4.0 mm or less, the weight of the tire 1 can be easily reduced, and fuel economy performance is easily improved. In addition, the rigidity of the tread portion 2 can be easily increased, and steering stability performance is improved.

[0047] From the above viewpoint, the more desirable range of the minimum rubber thickness T of the single-wire cord 11 is 2.0 to 3.0 mm.

[0048] 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]

[0049] A 195 / 65R15 tire having the tire meridian cross section shown in Figure 1 was prototyped based on the specifications in Table 1. Using the prototype tires, handling stability, ride comfort, durability, and fuel economy were evaluated. The test methods for each prototype tire are as follows:

[0050] <Handling stability> A test driver rode in a front-wheel drive compact passenger car (engine displacement: 2000cc) fitted with prototype tires on all wheels, and the car was driven on a dry asphalt test course, where the characteristics related to steering response, rigidity, grip, etc. were evaluated by the driver's senses. The evaluation was based on a score of 100 for Comparative Example 1, with the higher the score, the better the performance.

[0051] <Ride comfort> A test driver rode in the test vehicle with the prototype tires mounted on all wheels, and the vehicle was driven around the test course, and the ride comfort was evaluated by the driver's sensory evaluation. The evaluation was based on a score of 100 for Comparative Example 1, with the higher the score, the better the ride comfort.

[0052] <Durability> The prototype tire was mounted on a bench durability tester, and the distance traveled until the tire broke was measured. The results were expressed as an index, with Comparative Example 1 being set at 100, and a larger index indicates a longer travel distance and better durability.

[0053] <Fuel efficiency> The prototype tire was mounted on a rolling resistance tester, and the rolling resistance was measured when the tire was run at an internal pressure of 230 kPa, a load of 3.43 kN, and a speed of 80 km / h. The results were expressed as an index, with Comparative Example 1 being set at 100, and a larger index indicates lower rolling resistance and better fuel economy.

[0054] The test results are shown in Table 1. For example, the overall performance of each example can be determined by summing up the numerical values ​​indicating each performance for each example (the same applies to Table 2 and onwards). [Table 1]

[0055] As is clear from Table 1, it was confirmed that the tires of the examples had significantly improved steering stability, ride comfort, durability and fuel economy in a well-balanced manner compared to Comparative Examples 1 to 4.

[0056] A tire of size 195 / 65R15 having the tire meridian cross section shown in Figure 1 was prototyped based on the specifications in Table 2. Durability and fuel economy performance were evaluated using the prototype tires. The test method for each prototype tire is as follows.

[0057] <Durability> Durability was evaluated using the same method as above. The results are expressed as an index, with Example 6 being 100, and a larger index indicates a longer running distance and better durability.

[0058] <Fuel efficiency> The rolling resistance was measured using the same method as above. The results are expressed as an index, with Example 12 being 100, and the larger the index, the smaller the rolling resistance and the better the fuel economy performance.

[0059] The test results are shown in Table 2. [Table 2]

[0060] A tire of size 195 / 65R15 having the tire meridian cross section shown in Figure 1 was prototyped based on the specifications in Table 3. Using the prototype tires, ride comfort performance and fuel economy performance were evaluated. The test method for each prototype tire is as follows.

[0061] <Ride comfort> The ride comfort performance was evaluated in the same manner as above. The results are expressed as an index, with Example 13 being 100, and the larger the index, the better the ride comfort performance.

[0062] <Fuel efficiency> The fuel economy performance was evaluated in the same manner as above. The results are expressed as an index with Example 18 being 100, with a larger index indicating better fuel economy performance.

[0063] The test results are shown in Table 3. [Table 3]

[0064] A tire of size 195 / 65R15 having the tire meridian cross section shown in Figure 1 was prototyped based on the specifications in Table 4. Using the prototype tires, ride comfort performance and fuel economy performance were evaluated. The test method for each prototype tire is as follows.

[0065] <Ride comfort> The ride comfort performance was evaluated in the same manner as above. The results are expressed as an index, with Example 19 being 100, and the larger the index, the better the ride comfort performance.

[0066] <Fuel efficiency> The fuel economy performance was evaluated in the same manner as above. The results are expressed as an index with Example 24 being 100, with a larger index indicating better fuel economy performance.

[0067] The test results are shown in Table 4. [Table 4]

[0068] A tire of size 195 / 65R15 having the tire meridian cross section shown in Figure 1 was prototyped based on the specifications in Table 5. Using the prototype tires, ride comfort performance and fuel economy performance were evaluated. The test method for each prototype tire is as follows.

[0069] <Ride comfort> The ride comfort performance was evaluated in the same manner as above. The results are expressed as an index with Example 25 being 100, with a larger index indicating better ride comfort performance.

[0070] <Fuel efficiency> The fuel economy performance was evaluated in the same manner as above. The results are expressed as an index with Example 30 being 100, with a larger index indicating better fuel economy performance.

[0071] The test results are shown in Table 5. [Table 5] [Explanation of symbols]

[0072] 1 tire 2 Tread section 2A Tread rubber 2a Outer surface 7 Belt Layer 7A Belt Ply 7B belt ply 10 Topping Rubber 11 Single-wire cord 21 Groove 22 bottom D distance LD long diameter SD short diameter T Minimum rubber thickness

Claims

1. A tire having a belt layer disposed inside the tread portion, The belt layer includes a plurality of belt plies, The belt ply includes a single-wire cord having a minor diameter SD and a major diameter LD, and not having a twisted structure, in which a ratio SD / LD of the minor diameter SD to the major diameter LD is less than 1.00, and a topping rubber covering the single-wire cord, The single-wire cord is arranged such that the direction of the minor diameter SD is oriented in the thickness direction of the belt ply, The topping rubber has a complex modulus of elasticity (E*) of 7 to 20 MPa at a temperature of 70°C, an initial strain of 10%, a dynamic strain amplitude of ±1.0%, and a frequency of 10 Hz; a distance (rubber thickness) D between the single cords among the plurality of belt plies is 0.30 to 1.05 mm; a difference (D-SD) between the distance (D) and the minor diameter (SD) is 0.20 to 0.45 mm; The tread portion has a tread rubber having grooves formed on an outer surface thereof, the minimum rubber thickness from the bottom of the groove to the single cord is 1.0 to 4.0 mm; No reinforcing cord is present on the outer side of the belt layer in the tire radial direction. tire.

2. 2. The tire of claim 1, wherein the complex modulus (E*) is 9 to 20 MPa.

3. 3. The tire according to claim 1, wherein the minor diameter SD is 0.15 to 0.42 mm.

4. 4. The tire according to claim 3, wherein the minor diameter SD is 0.15 to 0.35 mm.

5. 5. The tire according to claim 1, wherein the ratio SD / LD of the single-wire cord is 0.70 or less.

6. The tire according to claim 5, wherein the ratio SD / LD of the single cord is 0.50 or less.

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